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Sample records for 4he accumulation rate

  1. Electron screening and stellar rates in the {sup 3}He({sup 3}He,2p){sup 4}He and {sup 3}He(d,p){sup 4}He fusion reactions

    SciTech Connect

    Messahel, L.; Ouichaoui, S.; Belhout, A.; Fouka, M.; Trabelsi, A.

    2008-05-12

    The astrophysical S(E) factor experimental data available over the energy region E (C.M.)<1.0 MeV for the {sup 3}He({sup 3}He,2p){sup 4}He and {sup 3}He(d,p){sup 4}He fusion reactions are analyzed using a polynomial expression and the R-Matrix formalism, respectively. The reaction thermonuclear rates for bare nuclei are determined and compared to previous ones after a precise assessment of the electron screening factors. New level parameter values are deduced for the {sup 5}Li nucleus.

  2. Zircon 4He/3He thermochronometry

    NASA Astrophysics Data System (ADS)

    Tripathy-Lang, Alka; Fox, Matthew; Shuster, David L.

    2015-10-01

    Multiple thermochronometric methods are often required to constrain time-continuous rock exhumation for studying tectonic processes or development of km-scale topography at Earth's surface. Here, we explore 4He/3He thermochronometry of zircon as a method for constraining continuous time-temperature (t-T) paths of individual samples through a temperature range that is complementary to methods such as 40Ar/39Ar thermochronometry of K-feldspar and 4He/3He thermochronometry of apatite. For different cooling rates and diffusion domain size, the temperature sensitivity of zircon 4He/3He thermochronometry ranges from slightly less than 100 °C to slightly greater than 250 °C; a typical sample provides continuous thermal constraints over ∼100 °C within that range. Outside these temperatures, 4He in zircon will either be quantitatively retained or completely lost by volume diffusion. As proof-of-concept, we present stepwise release 4He/3He spectra and associated U and Th concentration maps measured by laser ablation ICP-MS analysis of individual crystal aliquots of Fish Canyon Tuff (FCT) zircon and of a more complex setting in the Sierra Nevada batholith that experienced reheating from a proximal basaltic intrusion, the Little Devil's Postpile (LDP). The FCT zircon 4He/3He release spectra are consistent with a 4He spatial distribution dominated by alpha-ejection from crystal surfaces. The spatial distributions of U and Th measured in the same crystals do not substantially influence 4He/3He release spectra that are predicted for the known thermal history, even when incorporating spatially variable diffusivity due to accumulation of radiation damage. Conversely, the LDP 4He/3He release spectra are strongly influenced by the observed parent nuclide zonation. A three-dimensional (3D) numerical model of 4He production and diffusion, which incorporates crystal geometry, U and Th zonation, and spatially variable He diffusion kinetics, substantially improves the fit between

  3. Rate Coefficient for the (4)Heμ + CH4 Reaction at 500 K: Comparison between Theory and Experiment.

    PubMed

    Arseneau, Donald J; Fleming, Donald G; Li, Yongle; Li, Jun; Suleimanov, Yury V; Guo, Hua

    2016-03-01

    The rate constant for the H atom abstraction reaction from methane by the muonic helium atom, Heμ + CH4 → HeμH + CH3, is reported at 500 K and compared with theory, providing an important test of both the potential energy surface (PES) and reaction rate theory for the prototypical polyatomic CH5 reaction system. The theory used to characterize this reaction includes both variational transition-state (CVT/μOMT) theory (VTST) and ring polymer molecular dynamics (RPMD) calculations on a recently developed PES, which are compared as well with earlier calculations on different PESs for the H, D, and Mu + CH4 reactions, the latter, in particular, providing for a variation in atomic mass by a factor of 36. Though rigorous quantum calculations have been carried out for the H + CH4 reaction, these have not yet been extended to the isotopologues of this reaction (in contrast to H3), so it is important to provide tests of less rigorous theories in comparison with kinetic isotope effects measured by experiment. In this regard, the agreement between the VTST and RPMD calculations and experiment for the rate constant of the Heμ + CH4 reaction at 500 K is excellent, within 10% in both cases, which overlaps with experimental error. PMID:26484648

  4. Radiogenic 4He as a conservative tracer in buried-valley aquifers

    USGS Publications Warehouse

    Van Der Hoven, S. J.; Wright, R.E.; Carstens, D.A.; Hackley, Keith C.

    2005-01-01

    [1] The accumulation of 4He in groundwater can be a powerful tool in hydrogeologic investigations. However, the use of 4He often suffers from disagreement or uncertainty related to in situ and external sources of 4He. In situ sources are quantified by several methods, while external sources are often treated as calibration parameters in modeling. We present data from direct laboratory measurements of 4He release from sediments and field data of dissolved 4He in the Mahomet Aquifer, a well-studied buried-valley aquifer in central Illinois. The laboratory-derived accumulation rates (0.13-0.91 ??cm3 STP kgwater-1 yr-1) are 1-2 orders of magnitude greater than the accumulation rates based on the U and Th concentrations of the sediments (0.004-0.009 ??cm3 STP kgwater-1 yr -1). The direct measurement of accumulation rates are more consistent with dissolved concentrations of 4He in the groundwater. We suggest that the direct measurement method is applicable in a variety of hydrogeologic settings. The patterns of accumulation of 4He are consistent with the conceptual model of flow in the aquifer based on hydraulic and geochemical evidence and show areas where in situ production and external sources of 4He are dominant. In the southwestern part of the study area, Ne concentrations are less than atmospheric solubility, indicating gases have been lost from the groundwater. Available evidence indicates that the gases are lost as groundwater passes by pockets of CH4 in glacial deposits overlying the aquifer. However, the external flux from the underlying bedrock appears to dominate the accumulation of radiogenic 4He in the aquifer in the southwestern part of the study area, and the loss or gain of helium as groundwater passes through the overlying sediments is minor in comparison. Copyright 2005 by the American Geophysical Union.

  5. Experiments with solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.

    2010-08-01

    The possibility of supersolid behavior in 4He was predicted many years ago, but negative experiments in the 1970’s removed motivation for further experimental efforts to explore the possibility until the work of Goodkind’s group renewed attention. Kim and Chan found unambiguous evidence for a period shift in a torsional oscillator filled with solid 4He and this observation and its interpretation have created substantial interest in the study of solid 4He. Here, recent work with an experimental design that allows for superfluid 4He to be in direct contact with solid 4He off the melting curve will be discussed and evidence for the flow of helium atoms through a cell filled with solid 4He, caused by an applied chemical potential difference will be briefly reviewed.

  6. Aspects of 4He II

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.

    1981-10-01

    Some recent assertions concerning Fröhlich's form for the second-order reduce density matrix for 4He II are shown to be incorrect, based on work by McMillan and Whitlock et al. An ansatz to replace the Beliaev ansatz is advanced, which leads directly to Fröhlich's form.

  7. Coulomb sum rule for {sup 4}He

    SciTech Connect

    J. Carlson; J. Jourdan; R. Schiavilla; I. Sick

    2002-10-01

    We determine the Coulomb sum for {sup 4}He using world data on {sup 4}He(e, e') and compare the results to calculations based on realistic interactions and including two-body components in the nuclear charge operator. We find good agreement between theory and experiment using free-nucleon form factors. The apparent reduction of the in-medium G{sub ep} implied by IA-interpretation of the L/T-ratios measured in {sup 4}He(e,e'p) and {sup 4}He([vec]e, e'p) is not confirmed.

  8. Crystallization of 4He in aerogel via mass flow from surrounding solid 4He

    NASA Astrophysics Data System (ADS)

    Matsuda, H.; Ochi, A.; Isozaki, R.; Minami, S.; Nomura, R.; Pollanen, J.; Halperin, W. P.; Okuda, Y.

    2016-07-01

    The phase boundary between the quantum solid and the liquid phases of 4He is strongly modified in a porous material. However the phase diagram at very low temperatures remains unexplored. We have used a variable-volume experimental cell with optical access to visualize the crystallization of 4He in silica aerogels with independent control of the pressure and temperature. The onset of crystallization was investigated in two aerogel samples with differing porosity both by pressurization at constant temperature and by cooling at constant pressure. With isothermal pressurization we have established a low-temperature phase diagram for each aerogel, and we find that the equilibrium crystallization pressure is reduced with increasing aerogel porosity. Crystals also began to grow in the aerogel on cooling at fixed pressure below an onset temperature Tgrow. We found that below this temperature the crystallization rate increased with decreasing temperature. The aerogel in our cell was surrounded by bulk crystals of 4He , and surprisingly Tgrow was found to be widely distributed when the surrounding bulk crystals were repressurized. In this experimental arrangement, crystallization within the aerogel on cooling requires mass flow from these exterior bulk crystals and is strongly influenced by the disordered structure at the interface between the bulk solid and the helium within the aerogel.

  9. {sup 4}He microscopic optical model potential

    SciTech Connect

    Guo Hairui; Liang Haiying; Han Yinlu; Shen Qingbiao; Xu Yongli

    2011-06-15

    The {sup 4}He microscopic optical model potential is obtained by Green's function method through nuclear matter approximation and local density approximation based on the effective Skyrme interaction. The microscopic optical model potential is analyzed and utilized to calculate the reaction cross sections and elastic scattering angular distributions for the target nuclei in the mass range 12{<=}A{<=}209 with incident {sup 4}He energy up to 400 MeV. The theoretical results are compared with the experimental data.

  10. Exploration of Vacancies in Solid 4^He

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Ceperley, David

    2006-03-01

    Experiments by Kim and Chan [1] have renewed interest in the understanding of supersolids and whether mechanisms exist in solid ^4He to allow for supersolid-like effects. Ground state vacancies would lead to bose condensation and superfluidity. Using Path Integral Monte Carlo we examine vacancy formation energies, vacancy-vacancy interactions and the effect of vacancies on supersolid behavior in solid ^4He. [1] E. Kim and M. H. Chan, Science 305, 1941 (2004).

  11. Formation of the weakly bound muonic molecule (4Heμt) 01 2 + in the three-body (tμ) 1 s +4He +4He collision

    NASA Astrophysics Data System (ADS)

    Czapliński, Wilhelm; Rybski, Michał

    2016-02-01

    Formation of the weakly bound muonic molecule (4Heμt) 01 2 + in the excited rotational-vibrational state (J , ν) = (0 , 1) due to the three-body collision (tμ) 1 s +4He +4He is considered for the first time. It is assumed that the process occurs in T-4He gaseous mixture in thermal equilibrium containing thermalized muonic tritium atoms. The corresponding reaction rate is calculated in the frame of the distorted wave Born approximation (DWBA) method using the dipole approximation for the interaction of tμ +4He system with the incoming helium atom. The obtained formation rate (normalized to helium density equal to the liquid hydrogen density) increases with temperature from 7.8 ṡ106 s-1 for 1000 K to 4.8 ṡ107 s-1 for 3000 K.

  12. Generalized Rotational Susceptibility Studies of Solid 4He

    NASA Astrophysics Data System (ADS)

    Gadagkar, V.; Pratt, E. J.; Hunt, B.; Yamashita, M.; Graf, M. J.; Balatsky, A. V.; Davis, J. C.

    2012-11-01

    Using a novel SQUID-based torsional oscillator (TO) technique to achieve increased sensitivity and dynamic range, we studied TO's containing solid 4He. Below ˜250 mK, the TO resonance frequency f increases and its dissipation D passes through a maximum as first reported by Kim and Chan. To achieve unbiased analysis of such 4He rotational dynamics, we implemented a new approach based upon the generalized rotational susceptibility χ{4He}^{ - 1}(ω,T). Upon cooling, we found that equilibration times within f( T) and D( T) exhibit a complex synchronized ultraslow evolution toward equilibrium indicative of glassy freezing of crystal disorder conformations which strongly influence the rotational dynamics. We explored a more specific χ{4He}^{ -1}(ω,tau(T)) with τ( T) representing a relaxation rate for inertially active microscopic excitations. In such models, the characteristic temperature T ∗ at which df/ dT and D pass simultaneously through a maximum occurs when the TO angular frequency ω and the relaxation rate are matched: ωτ( T ∗)=1. Then, by introducing the free inertial decay (FID) technique to solid 4He TO studies, we carried out a comprehensive map of f( T, V) and D( T, V) where V is the maximum TO rim velocity. These data indicated that the same microscopic excitations controlling the TO motions are generated independently by thermal and mechanical stimulation of the crystal. Moreover, a measure for their relaxation times τ( T, V) diverges smoothly everywhere without exhibiting a critical temperature or velocity, as expected in ωτ=1 models. Finally, following the observations of Day and Beamish, we showed that the combined temperature-velocity dependence of the TO response is indistinguishable from the combined temperature-strain dependence of the 4He shear modulus. Together, these observations imply that ultra-slow equilibration of crystal disorder conformations controls the rotational dynamics and, for any given disorder conformation, the

  13. Continental degassing of 4He by surficial discharge of deep groundwater

    NASA Astrophysics Data System (ADS)

    Aggarwal, Pradeep K.; Matsumoto, Takuya; Sturchio, Neil C.; Chang, Hung K.; Gastmans, Didier; Araguas-Araguas, Luis J.; Jiang, Wei; Lu, Zheng-Tian; Mueller, Peter; Yokochi, Reika; Purtschert, Roland; Torgersen, Thomas

    2015-01-01

    Radiogenic 4He is produced by the decay of uranium and thorium in the Earth's mantle and crust. From here, it is degassed to the atmosphere and eventually escapes to space. Assuming that all of the 4He produced is degassed, about 70% of the total 4He degassed from Earth comes from the continental crust. However, the outgoing flux of crustal 4He has not been directly measured at the Earth's surface and the migration pathways are poorly understood. Here we present measurements of helium isotopes and the long-lived cosmogenic radio-isotope 81Kr in the deep, continental-scale Guarani aquifer in Brazil and show that crustal 4He reaches the atmosphere primarily by the surficial discharge of deep groundwater. We estimate that 4He in Guarani groundwater discharge accounts for about 20% of the assumed global flux from continental crust, and that other large aquifers may account for about 33%. Old groundwater ages suggest that 4He in the Guarani aquifer accumulates over half- to one-million-year timescales. We conclude that 4He degassing from the continents is regulated by groundwater discharge, rather than episodic tectonic events, and suggest that the assumed steady state between crustal production and degassing of 4He, and its resulting atmospheric residence time, should be re-examined.

  14. sup 4 He- sup 4 He elastic scattering and variational wave functions

    SciTech Connect

    Usmani, A.A.; Ahmad, I. ); Usmani, Q.N. )

    1992-01-01

    We calculate differential cross sections for {sup 4}He-{sup 4}He elastic scattering at 4.32 GeV/{ital c} in the framework of Glauber multiple scattering theory using correlated variational wave functions as given by the two-nucleon Urbana {ital v}{sub 14} potential and the spin-isospin averaged Melfleit-Tjon force {ital V}. These wave functions are found to give fairly satisfactory results.

  15. 4He crystals in superfluid under zero gravity.

    PubMed

    Takahashi, Takuya; Nomura, Ryuji; Okuda, Yuichi

    2012-03-01

    The response of 4He crystals to the rapid reduction of gravity down to practically zero in a superfluid was investigated visually, utilizing the parabolic flight of a jet plane. At a high temperature of 1.6 K, the shape of 4He crystals in the bcc phase did not change with a reduction of gravity during a parabolic period of 20 s, due to the low crystallization rate. At lower temperatures, such as 0.63 K, where the crystallization rate is sufficiently high, the shape of 4He crystals in the hcp phase changed significantly, relaxing to a quasiequilibrium shape under zero gravity, where the c facet became enlarged and the a facet emerged on the surface. The crystal did not detach from the sample cell wall at any time because the adhesive force manifested as partial wetting to the wall was sufficiently strong. Some crystals removed from the wall by an acoustic wave pulse were found to float and drift in the superfluid for approximately 4.2 s under zero gravity, although most of them were quickly reattached to the wall. PMID:22587030

  16. Dry dilution refrigerator with 4He-1 K-loop

    NASA Astrophysics Data System (ADS)

    Uhlig, Kurt

    2015-03-01

    In this article we summarize experimental work on cryogen-free 3He/4He dilution refrigerators which, in addition to the dilution refrigeration circuit, are equipped with a 4He-1 K-stage. This type of DR becomes worth considering when high cooling capacities are needed at T ∼ 1 K to cool cold amplifiers and heat sink cables. In our application, the motivation for the construction of this type of cryostat was to do experiments on superconducting quantum circuits for quantum information technology and quantum simulations. In other work, DRs with 1 K-stage were proposed for astro-physical cryostats. For neutron scattering research, a top-loading cryogen-free DR with 1 K-stage was built which was equipped with a standard commercial dilution refrigeration insert. Cooling powers of up to 100 mW have been reached with our 1 K-stage, but higher refrigeration powers were achieved with more powerful pulse tube cryocoolers and higher 4He circulation rates in the 1 K-loop. Several different versions of a 1 K-loop have been tested in combination with a dilution refrigeration circuit. The lowest temperature of our DR was 4.3 mK.

  17. The Annealing Process in Solid 4He

    NASA Astrophysics Data System (ADS)

    Rittner, Ann Sophie C.; Reppy, John D.

    2007-09-01

    We have used a torsional oscillator with square cross section and a resonance frequency of 185 Hz to confirm the nonclassical rotational inertia (NCRI) discovered by Kim and Chan (Nature 427:225, 2004; Science 305:1941, 2004). We have also found a strong correlation between the NCRI signal and a high dissipation Q -1 of 4×10-6 of the oscillation above the transition temperature. Here, we present preliminary results of the annealing process in 4He at a pressure of 26 bar. When holding the temperature constant above 1 K we have observed a immediate rise in the period and a slow decay of the dissipation. The equilibrium value of Q -1 decreases with increasing temperature.

  18. Tortuosity of 4He Films on Aerogel

    SciTech Connect

    Ashton, C. E.; Golov, A. I.; Mulders, N.

    2006-09-07

    A torsional oscillator has been used to study the flow of liquid 4He through silica aerogel. The tortuosity and dissipation of the flow in the fractal aerogel environment has been measured, for both capillary condensed films and a fully saturated cell. The scaling of tortuosity as a function of filling fraction has been investigated. We compare the results of our 88%-porous aerogel to a 92%-porous sample where a transverse sound technique was used. Our more sensitive technique has reduced the scatter in both the frequency and dissipation data. Like in the previous transverse sound experiment, we find tortuosity as a function of filling fraction to scale with an exponent of {approx} -1.1. Further experiments are planned, to find the dependence of the exponent on the fractal dimension and porosity of aerogel.

  19. Positive ion induced solidification of 4He.

    PubMed

    Moroshkin, P; Lebedev, V; Weis, A

    2009-03-20

    We have observed bulk solidification of 4He induced by nucleation on positive alkali ions in pressurized superfluid helium. The ions are extracted into the liquid from alkali-doped solid He by a static electric field. The experiments prove the existence of charged particles in a solid structure composed of doped He that was recently shown to coexist with superfluid helium below the He solidification pressure. This supports our earlier suggestion that the Coulomb interaction of positive ions surrounded by a solid He shell (snowballs) and electrons trapped in spherical cavities (electron bubbles), together with surface tension, is responsible for the stability of that structure against melting. We have determined the density of charges in the sample by two independent methods. PMID:19392211

  20. Superfluid 4He dynamics beyond quasiparticle excitations

    NASA Astrophysics Data System (ADS)

    Beauvois, K.; Campbell, C. E.; Dawidowski, J.; Fâk, B.; Godfrin, H.; Krotscheck, E.; Lauter, H.-J.; Lichtenegger, T.; Ollivier, J.; Sultan, A.

    2016-07-01

    The dynamics of superfluid 4He at and above the Landau quasiparticle regime is investigated by high-precision inelastic neutron scattering measurements of the dynamic structure factor. A highly structured response is observed above the familiar phonon-maxon-roton spectrum, characterized by sharp thresholds for phonon-phonon, maxon-roton, and roton-roton coupling processes. The experimental dynamic structure factor is compared to the calculation of the same physical quantity by a dynamic many-body theory including three-phonon processes self-consistently. The theory is found to provide a quantitative description of the dynamics of the correlated bosons for energies up to about three times that of the Landau quasiparticles.

  1. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2002-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the areally Integrated snow accumulation and the net ice discharge of the ice sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.

  2. Astrophysical S factors of radiative {sup 3}He{sup 4}He, {sup 3}H{sup 4}He, and {sup 2}H{sup 4}He capture

    SciTech Connect

    Dubovichenko, S. B.

    2010-09-15

    The possibility of describing the astrophysical S factors for radiative {sup 3}He{sup 4}He capture at energies of up to 15 keV and radiative {sup 3}H{sup 4}He and {sup 2}H{sup 4}He capture at energies of up 5 keV is considered on the basis of the potential cluster model involving forbidden states.

  3. Microscopic characterization of overpressurized superfluid 4He

    NASA Astrophysics Data System (ADS)

    Rossi, M.; Vitali, E.; Reatto, L.; Galli, D. E.

    2012-01-01

    We have studied static and dynamical properties of superfluid 4He at T=0 K in the pressure range from -6 up to 87 atm well above freezing into the metastable region. Zero temperature properties have been obtained with the exact shadow path integral ground state (SPIGS) method. Information about dynamic structure factors at different pressures have been obtained from imaginary time correlation functions via the genetic inversion via falsification of theories (GIFT) method. In the full pressure range sharp roton excitations are always present in the spectral functions. The roton energy decreases at higher pressures in good agreement with experimental data also in the metastable region. The roton energies have essentially a linear trend with pressure, going from about 7.4 K near freezing to about 4.3 K at about 87 atm. The pressure at which the linear trend would extrapolate to a zero roton energy turns out to be about 170 atm. At T=0 K, no sign of metastable glass phase has been found; the disordered systems studied at pressures above about 87 atm readily start homogeneous nucleation processes. Our results in the metastable phase for the condensate fractions and roton gaps differ remarkably from previous ones obtained via a diffusion Monte Carlo study.

  4. Deeply Virtual Compton Scattering off 4He

    NASA Astrophysics Data System (ADS)

    Joosten, Sylvester; CLAS Collaboration

    2015-10-01

    The European Muon Collaboration (EMC) observed the first signs of a modification of the partonic structure of the nucleon when present in a nuclear medium. The precise nature of these effects, as well as their underlying cause, is yet to be determined. The generalized parton distribution (GPD) framework provides a powerful tool to study the partonic structure of nucleons inside a nucleus. Hard exclusive leptoproduction of a real photon off a nucleon, deeply virtual Compton scattering (DVCS), is presently considered the cleanest experimental access to the GPDs, through the Compton form factors (CFFs). This is especially the case for scattering off the spin-zero helium nucleus, where only a single CFF contributes to the process. The real and imaginary parts of this CFF can be constrained through the beam-spin asymmetry (BSA). We will present the first measurements of the DVCS process off 4He using the CEBAF 6 GeV polarized electron beam and the CLAS detector at JLab. The CLAS detector was supplemented with an inner electromagnetic calorimeter for photons produced at small angles, as well as a radial time projection chamber (RTPC) to detect low-energy recoil nuclei. This setup allowed for a clean measurement of the BSA in both the coherent and incoherent channels.

  5. Search for dislocation free 4He crystals

    NASA Astrophysics Data System (ADS)

    Souris, Fabien; Fefferman, Andrew; Haziot, Ariel; Beamish, John; Balibar, Sebastien

    2014-03-01

    The elastic anomaly of 4He crystals is known to be a consequence of the motion of their dislocations. We have built an acoustic cell in order to grow and study crystals with the smallest possible density of dislocations. It has a polished inner surface to avoid pinning sites for the liquid-solid interface. Piezoelectric transducers are placed outside the cell volume, in order to drive and detect acoustical resonances through built-in copper membranes. We expect dislocation free crystals to behave rather differently from the usual ones (1,2). For example, they should not show any anomalous softening. Preliminary results show that crystals grown in this particular cell have longer dislocation lengths than in those studied in previous experiments (1,2). Centimeter long dislocations should resonate below 20 kHz. 1- A. Haziot et al., Phys. Rev. Lett. 110, 035301 (2013), Phys. Rev. B 87, 060509(R) (2013), and Phys. Rev. B 88, 014106 (2013). 2- A. D. Fefferman et al., submitted to Phys. Rev. B, Nov. 2013. ERC Grant AdG247258 SUPERSOLID and NSERC Canada.

  6. Measurements of diffuse and specular scattering of sup 4 He atoms from sup 4 He films

    SciTech Connect

    Mukherjee, S.

    1989-01-01

    We have observed scattering of {sup 4}He atomic beams from films of {sup 4}He on glass and mica substrates. The specular reflection coefficient, or reflectivity, R(k,{theta}) was measured as a function of the angle of incidence {theta} and the wavevector k of the incident atoms, and the thickness of the film. The film thickness d varied from 45 {angstrom} to macroscopic values. In contrast to previous experiments on scattering from 10 cm deep liquid, we observed not only the expected specular reflection, but also isotropic diffuse scattering. To explain the diffuse signal, we assume that most of the incident atoms are converted into phonons, rotons and ripplons at the surface of the film. The phonons and rotons are scattered at the substrate, and subsequently evaporate an isotropic distribution of atoms.

  7. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2001-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.

  8. Compression-Driven Mass Flow in Bulk Solid 4He

    NASA Astrophysics Data System (ADS)

    Cheng, Zhi Gang; Beamish, John

    2016-07-01

    Mass flow has been observed in solid 4He coexisting with superfluid confined in Vycor, but its physical mechanism remains an open question. Here we report observations of flow in experiments in which Vycor has been eliminated, allowing us to study the intrinsic flow in solid 4He without the complications introduced by the presence of superfluid and the associated solid-liquid interfaces. By growing crystals with 3He concentration as low as x3=5 ×10-12, we also avoided the low temperature flow suppression observed in previous experiments and found that the flow rate continued to increase down to at least 28 mK without saturation. In addition, 3He concentrations of 120 ppb, which suppressed most of the low temperature flow in previous experiments, had no effect in our samples. The larger 3He concentrations needed to block the bulk solid flow suggest that the mass flow involves a larger area, such as disordered liquid layer on solid surface and grain boundaries.

  9. Compression-Driven Mass Flow in Bulk Solid ^{4}He.

    PubMed

    Cheng, Zhi Gang; Beamish, John

    2016-07-01

    Mass flow has been observed in solid ^{4}He coexisting with superfluid confined in Vycor, but its physical mechanism remains an open question. Here we report observations of flow in experiments in which Vycor has been eliminated, allowing us to study the intrinsic flow in solid ^{4}He without the complications introduced by the presence of superfluid and the associated solid-liquid interfaces. By growing crystals with ^{3}He concentration as low as x_{3}=5×10^{-12}, we also avoided the low temperature flow suppression observed in previous experiments and found that the flow rate continued to increase down to at least 28 mK without saturation. In addition, ^{3}He concentrations of 120 ppb, which suppressed most of the low temperature flow in previous experiments, had no effect in our samples. The larger ^{3}He concentrations needed to block the bulk solid flow suggest that the mass flow involves a larger area, such as disordered liquid layer on solid surface and grain boundaries. PMID:27447513

  10. Lattice Relaxation of 4He with 3He Impurities: NMR Studies

    NASA Astrophysics Data System (ADS)

    Candela, D.; Huan, C.; Kim, S. S.; Yin, L.; Xia, J. S.; Sullivan, N. S.

    2014-12-01

    Measurements of the 3He nuclear spin relaxation times of dilute 3He impurities in solid 4He have been used to explore the unusual dynamics of solid 4He at low temperatures. The 3He impurities move through the lattice by quantum mechanical exchange with neighboring 4He atoms. Because of the larger zero point motion of the 3He atoms, there is an appreciable lattice distortion that accompanies the tunneling 3 He atom and the tunneling motion depends on the elastic properties of the 4He lattice. This motion modulates the 3He-3He nuclear dipole- dipole interactions and thus determines the NMR relaxation rates. We compare the observed temperature dependence of the NMR relaxation rates with that expected from the measurements of the shear modulus by Syshchenko et al. [Phys. Rev. Lett. 104, 195301 (2009)].

  11. Distortion of bulk-ion distribution function due to nuclear elastic scattering and its effect on T(d,n){sup 4}He reaction rate coefficient in neutral-beam-injected deuterium-tritium plasmas

    SciTech Connect

    Matsuura, H.; Nakao, Y.

    2007-05-15

    An effect of nuclear elastic scattering on the rate coefficient of fusion reaction between field deuteron and triton in the presence of neutral beam injection heating is studied. Without assuming a Maxwellian for bulk-ion distribution function, the Boltzmann-Fokker-Planck (BFP) equations for field (bulk) deuteron, field (bulk) triton, {alpha}-particle, and beam deuteron are simultaneously solved in an ITER-like deuterium-tritium thermonuclear plasma [R. Aymar, Fusion Eng. Des. 55, 107 (2001)]. The BFP calculation shows that enhancement of the reaction rate coefficient due to knock-on tail formation in fuel-ion distribution functions becomes appreciable, especially in the case of low-density operations.

  12. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-11-01

    The authors combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of silicon. They obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, the authors study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  13. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  14. Mass accumulation rates in Asia during the Cenozoic

    NASA Astrophysics Data System (ADS)

    Métivier, François; Gaudemer, Yves; Tapponnier, Paul; Klein, Michel

    1999-05-01

    This work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in Asia since the beginning of the Cenozoic, ~ 66 Ma. The estimates were derived from isopach maps, cross-sections and drill holes or stratigraphic columns assuming regional similarity of the strata. Average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods: Palaeocene ( ~ 66-58 Ma), Eocene ( ~ 58-37 Ma), Oligocene( ~ 37-30 and 30-24 Ma), Miocene ( ~ 24-17, 17-11 and 11-5 Ma), Pliocene ( ~ 5-2 Ma) and Quaternary ( ~ 2-0 Ma). These rates shed new light on the geological history of Asia since the onset of the collision of India with Asia ( ~ 50 Ma). The overall average accumulation rates curve for Asian sedimentary basins since the beginning of the Tertiary shows an exponential form with slow accumulation rates (less than 0.5 x 10^6 km^3 Myr^- 1) until the beginning of the Oligocene, more than 15 Myr after the onset of the collision. From the Oligocene onwards rates increase quickly in an exponential manner, reaching their maximum values in the Quaternary (more than 1.5 x 10^6 km^3 Myr^- 1). From these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the India-Eurasia collision history. At smaller scales one may distinguish between independent histories at the subcontinental and basin scales. This permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of Asia during the Cenozoic.

  15. Accumulation rates of airborne heavy metals in wetlands

    USGS Publications Warehouse

    Souch, C.J.; Filippelli, G.M.; Dollar, N.; Perkins, S.; Mastalerz, Maria

    2002-01-01

    Accumulation rates of heavy metals (Cd, Cr, Cu, Mn, Pb, and Zn) retained in wetland sediments in northwest Indiana-downwind of the Chicago-Gary-Hammond industrial area-are quantified to assess anthropogenic influences on atmospheric fluxes. Metal concentrations for 22 sediment cores are determined by ICP-AES after ashing and strong acid extraction. Relations between organic content and metal concentrations at depth are used to separate natural and anthropogenic sources. Accumulation rates over the lifetime of the wetlands (???4500 years) have averaged 0.2 (Cd), 1.4 (Cu), 1.7 (Cr), 13.4 (Mn), 4.8 (Pb), and 18.7 (Zn) mg m-2 y-1. Rates for the last 100 years have increased on average by factors of 6 (Cd), 8 (Cu), 10 (Mn), 15 (Pb), and 30 (Zn), remaining effectively constant for Cr. Where the wetlands have been drained, metals have been lost from the sediments, owing to changes in organic content and local hydrochemistry (exposure to acidic rainfall). Sediment-based accumulation rates at the undrained sites are higher, though generally consistent, with measured and modeled atmospheric fluxes documented by short-term studies conducted over the last three decades. The fraction of the total metals in the wetlands estimated to be of anthropogenic origin ranges from approximately 3% for Cr, up to approximately 35% for Pb, and 70% for Zn. This historic legacy of contamination must be considered in land management decisions, particularly when wetlands are drained.

  16. Superclimb of Dislocations in Solid 4He

    NASA Astrophysics Data System (ADS)

    Kuklov, Anatoly

    2011-03-01

    Edge dislocation with superfluid core can perform superclimb -- non-conservative motion (climb) assisted by superflow along its core. Such dislocation, with Burgers vector along the C-axis, has been found in ab initio simulations of hcp solid 4. Uniform network of superclimbing dislocations can induce isochoric compressibility which is finite (in contrast to ideal solid where it vanishes) and, practically, independent of the network density. Here N is total number of atoms and is chemical potential. Such giant response has been observed by Ray and Hallock during superfluid flow events through solid He4. Study of superclimbing dislocation within the model of Granato-Lücke string, subjected to Peierls potential and to vanishing bias by , has found that exhibits wide peak in the intermediate range of temperatures (T) - above some determined by Peierls energy and below above which superfluidity of the core essentially vanishes. Non-Luttinger type behavior characterized by K scaling as some power χ of dislocation length is observed in the wide peak region. Biasing superclimbing dislocation by finite μ (due to a contact with liquid through vycor electrodes,) can induce core roughening caused by thermally assisted tunneling of jog-antijog pairs through the barrier produced by combination of Peierls potential and the bias. The threshold for this effect scales as with some power a~ 1.7. The roughening is found to be hysteretic below some temperature Thyst , with TR determining temperature of thermal roughening, He exhibits strong and narrow resonant peak leading to a dip in the core superfluid sound velocity. This mechanism is proposed as an explanation for a strong and narrow dip observed in critical superflow rate. It is found that the dip characteristics are sensitive to the bias by μ and, therefore, this can be used as a test for the proposed mechanism. It is also predicted that the dip depth at given μc ~ 1 /La should be periodic in χ with the period T . This

  17. Sound velocity of liquid 4He in aerogel

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Arai, Osamu; Okuda, Yuichi; Tajiri, Koji

    2000-07-01

    The sound velocity and attenuation of liquid 4He in 93.7% and 94.6% porosity aerogels were measured for a frequency of 10 MHz. The sound velocity in 93.7% aerogel was larger than that in bulk 4He, whereas that in 94.6% was smaller. A model of the aerogel- 4He composite gave satisfactory agreement with the dependence of the sound velocity on the temperature and the aerogel density. This shows that the normal fluid is clamped to aerogel strands, although the viscous penetration depth is comparable to the typical size of a void in the aerogel.

  18. Solid 4He probed by both torsional oscillator and ultrasound

    NASA Astrophysics Data System (ADS)

    Kojima, Harry; Iwasa, Izumi; Goodkind, John

    2013-03-01

    The interpretation of observed anomalous increases in the frequencies of torsional oscillators (TO) containing solid 4He confined in Vycor nanopores as evidence for emergence of a supersolid phase has been met recently by conflicting experiments. Yet questions remain on the origin of the observed TO anomalies in bulk solid 4He samples. To search for the origin, we are carrying out simultaneous measurements of 10 MHz longitudinal ultrasound and TOs (250 ~ 1100 Hz) on identical solid 4He samples. Temperature dependence of velocity and attenuation of ultrasound and that of amplitude and frequency of TO are measured. At the temperatures, where TO anomalies occur, anomalies in sound velocity and attenuation also appear. When solid 4He is doped with 20 ppm 3He, the tempeature of TO anomaly tracks that of ultrasound. Interpretation of these observations in terms of the motion of dislocation lines will be presented. Research supported by NSF.

  19. Creep in solid 4He at temperatures below 1 K

    NASA Astrophysics Data System (ADS)

    Zhuchkov, V. A.; Lisunov, A. A.; Maidanov, V. A.; Neoneta, A. S.; Rubanskyi, V. Yu.; Rubets, S. P.; Rudavskii, E. Ya.; Smirnov, S. N.

    2015-03-01

    Creep in solid 4He at temperatures of ˜100-1000 mK is studied experimentally by detecting the flow of helium through a frozen porous membrane under a constant external force. Creep curves are measured for different temperatures and mechanical stresses. This method has made it possible to detect low creep rates in helium down to the lowest temperatures in these experiments. It is found that throughout this temperature range, creep is thermally activated and the activation energy decreases with falling temperature and increasing mechanical stress. An analysis shows that for temperatures above ≈500 mK, Nabarro-Herring diffusive creep takes place in solid helium with mass transfer by self diffusion of atoms and a counterflow of vacancies. The experimental data have been used to obtain the self-diffusion coefficient as a function of temperature for different stresses. At temperatures below ≈500 mK creep takes place at a very low flow rate (˜10-13 cm/s) and a very low activation energy (˜0.5-0.7 K), while the creep mechanism remains unclear.

  20. A comparison of groundwater dating with 81Kr, 36Cl and 4He in four wells of the Great Artesian Basin, Australia

    NASA Astrophysics Data System (ADS)

    Lehmann, B. E.; Love, A.; Purtschert, R.; Collon, P.; Loosli, H. H.; Kutschera, W.; Beyerle, U.; Aeschbach-Hertig, W.; Kipfer, R.; Frape, S. K.; Herczeg, A.; Moran, J.; Tolstikhin, I. N.; Gröning, M.

    2003-06-01

    reasonable initial 36Cl/Cl ratio of 125×10 -15, which is consistent with other studies in this part of the GAB, it is then possible to determine ( Ci, Ca) parameter sets for all four samples and consequently to simulate the Cl and the 36Cl evolution with time. Strong evidence that the whole procedure is adequate comes from: (i) a comparison of Ci with the calculated noble gas recharge temperatures (NGRT) indicating that a higher NGRT is related to higher input chloride concentrations Ci (because of higher evapotranspiration) and (ii) a comparison of Ca with the measured 4He concentration confirming the idea that both chloride and helium are added to the groundwater in parallel. It turns out that the four samples fall into two groups: (i) for two of the samples (Raspberry Creek and Oodnadatta) initial 36Cl concentrations are high and 36Cl dating based on radioactive decay is possible. The 4He accumulation rate for these two samples is low (0.2×10 -10 cm 3 STP 4He/(cm 3 water yr)); (ii) for the other two samples (Duck Hole and Watson Creek) the initial 36Cl concentration is low and therefore subsurface processes dominate resulting in almost constant 36Cl concentrations with time; 36Cl groundwater dating is not possible. The 4He accumulation rate for these two samples is about 10 times higher (1.9×10 -10 cm 3 STP 4He/(cm 3 water yr)). 129I concentrations are interpreted as a simple mixing between an atmospheric and a subsurface source.

  1. Correlation of Excess Enthalpy and ^4He Production: a Review

    NASA Astrophysics Data System (ADS)

    Miles, M. H.

    2004-03-01

    Three different sets of experiments conducted in the Navy Laboratory (NAWCWD) at China Lake, California (1990-1994) clearly established that helium-4 is the main fusion product in the Pd/D_2O+LiOD electrolysis system(P.A. Mosier-Boss, S.R. Chubb, M. Fleischmann, M. Imam, M. H. Miles, S. Szpak, TR 1862, SPAWAR Systems Center, San Diego; see http://www.lenr-canr.org/acrobat/MosierBossthermaland.pdf). A correlation between excess enthalpy and excess helium-4 was measured in 18 out of 21 experiments. The observation of no excess enthalpy was correlated with no excess helium in 12 out of 12 experiments. Thus 30 out of 33 experiments agree with the hypothesis that the excess enthalpy produced in cold fusion studies is correlated with helium-4 production: d+darrow ^4He + 23.8 MeV. Furthermore, the measured rate of helium-4 production was always in the appropriate range of 10^1^0 to 10^1^2 atoms per second per watt of excess power.

  2. Vortex emission from quantum turbulence in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Nago, Y.; Nishijima, A.; Kubo, H.; Ogawa, T.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

    2013-01-01

    An oscillating object can stretch quantized vortices attached to it in superfluids due to the relative superflow, steadily generating quantum turbulence, even in the zero-temperature limit. We report the emission and propagation of quantized vortices from quantum turbulence generated in superfluid 4He at low temperatures. A vortex-free vibrating wire enables us to detect the first collision of vortex rings and therefore to measure the time-of-flight of a vortex emitted from a generator to a detector. The detection times from the start of turbulence generation exhibit an exponential distribution, suggesting that the detection is a Poisson process. Vortices are emitted continuously, but each vortex has a random flight velocity and direction. We estimated the nondetection time and mean detection period from the distribution for two flight distances. By estimating the flight velocity, we find that only vortices with velocities lower than the detector velocity can be detected, even if the sizes of the emitted vortices are smaller than the wire thickness or the vibration amplitude. The ratio of the detection rate as a function of vortex velocity suggests anisotropic emission of vortices from the quantum turbulence.

  3. Death rates reflect accumulating brain damage in arthropods.

    PubMed

    Fonseca, Duane B; Brancato, Carolina L; Prior, Andrew E; Shelton, Peter M J; Sheehy, Matt R J

    2005-09-22

    We present the results of the first quantitative, whole-lifespan study of the relationship between age-specific neurolipofuscin concentration and natural mortality rate in any organism. In a convenient laboratory animal, the African migratory locust, Locusta migratoria, we find an unusual delayed-onset neurolipofuscin accumulation pattern that is highly correlated with exponentially accelerating age-specific Gompertz-Makeham death rates in both males (r=0.93, p=0.0064) and females (r=0.97, p=0.0052). We then test the conservation of this association by aggregating the locust results with available population-specific data for a range of other terrestrial, freshwater, marine, tropical and temperate arthropods whose longevities span three orders of magnitude. This synthesis shows that the strong association between neurolipofuscin deposition and natural mortality is a phylogenetically and environmentally widespread phenomenon (r=0.96, p < 0.0001). These results highlight neurolipofuscin as a unique and outstanding integral biomarker of ageing. They also offer compelling evidence for the proposal that, in vital organs like the brain, either the accumulation of toxic garbage in the form of lipofuscin itself, or the particular molecular reactions underlying lipofuscinogenesis, including free-radical damage, are the primary events in senescence. PMID:16191601

  4. A flight experiment to determine GPS photochemical contamination accumulation rates

    NASA Technical Reports Server (NTRS)

    Tribble, A. C.; Haffner, J. W.

    1990-01-01

    It was recently suggested that photochemically deposited contamination, originating from volatiles outgassed by a spacecraft, may be responsible for the anomalous degradation in power seen on the GPS Block 1 vehicles. In an attempt to confirm, or deny, the photochemical deposition rates predicted, a study was undertaken to design a flight experiment to be incorporated on the GPS vehicles currently in production. The objective was to develop an inexpensive, light weight instrument package that would give information on the contamination levels within a few months of launch. Three types of apparatus were studied, Quartz Crystal Microbalances, (QCM's), modified solar cells, and calorimeters. A calorimeter was selected due primarily to its impact on the production schedule of the GPS vehicles. An analysis of the sensitivity of the final design is compared to the predicted contamination accumulation rates in order to determine how long after launch it will take the experiment to show the effects of photochemical contamination.

  5. Heat Capacity of Dilute 3He-4He Monolayer Films

    NASA Astrophysics Data System (ADS)

    Morishita, Masashi

    2016-05-01

    The heat capacities of a small amount of 3He dissolved in monolayer 4He films are measured to clarify natures of monolayer 4He films. With increasing areal density, the measured heat capacities gradually increase and subsequently gradually decrease. With further increase in areal density, the measured heat capacity rapidly decreases to zero over a very narrow areal density range near that of the sqrt{3} × sqrt{3} phase. These slightly complex areal-density variations and dependence on 3He concentration are discussed from the viewpoint of the known properties of 4He films. The behaviors can be explained. However, the expected two-dimensional gas-liquid or gas-solid coexistence is not observed in this study.

  6. Surface Waves on the Superfluids ^3He and ^4He

    NASA Astrophysics Data System (ADS)

    Manninen, M. S.; Ranni, A.; Rysti, J.; Todoshchenko, I. A.; Tuoriniemi, J. T.

    2016-06-01

    Free surface waves were examined both in superfluids ^3He and ^4He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in ^3He is one of the first of its kind, but in ^4He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning T< 100 mK for ^4He and T˜ 100 μ K for ^3He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.

  7. Surface Waves on the Superfluids ^3 He and ^4 He

    NASA Astrophysics Data System (ADS)

    Manninen, M. S.; Ranni, A.; Rysti, J.; Todoshchenko, I. A.; Tuoriniemi, J. T.

    2016-04-01

    Free surface waves were examined both in superfluids ^3 He and ^4 He with the premise that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work in ^3 He is one of the first of its kind, but in ^4 He, it was possible to produce a much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning T< 100 mK for ^4 He and T˜ 100 μ K for ^3 He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.

  8. A Summary of Mass Flux Measurements in Solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.; Ray, M. W.; Vekhov, Y.

    2012-11-01

    Here we provide a summary and brief review of some of the work done with solid 4He at the University of Massachusetts Amherst below a sample pressure of 28 bar. The motivation for the work has been to attempt to pass 4He atoms through solid 4He without directly applying mechanical pressure to the solid itself. The specific technique chosen is limited to pressures near the melting curve and was initially designed to provide a yes/no answer to the question of whether or not it might be possible to observe such a mass flux. The thermo-mechanical effect and direct mass injection have been separately used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid 4He, which is in the hcp region of the phase diagram. The thermo-mechanical effect is a more versatile approach. And, in a particular symmetric application it is designed to provide a mass flux with little or no net increase in the density of the solid. Our observations, off but near the melting curve, have included: (1) the presence of an increasing DC flux of atoms through the solid-filled cell with decreasing temperature below ≈650 mK and no flux above this temperature; (2) the presence of a flux minimum and flux instability in the vicinity of 75-80 mK, with a flux increase at lower temperatures; (3) the temperature dependence of the flux above 100 mK and the dependence of the flux on the net driving chemical potential difference provide interesting insights on the possible mechanism that leads to the flux above 100 mK. The most recent data suggest that whatever is responsible for the flux in solid 4He, at least for T>100 mK, may be an example of a Bosonic Luttinger liquid.

  9. Transverse beam asymmetries from $^4$He and hydrogen targets

    SciTech Connect

    Lisa Kaufman

    2007-07-01

    The HAPPEX Collaboration at Jefferson Lab has measured the transverse beam spin asymmetries ($A_T$) for elastic electron scattering from proton and $^4$He targets. The experiment was conducted using a vertically polarized electron beam of energy ~3 GeV at $Q^2$ ~0.1 GeV$^2$ and a scattering angle $\\theta_{lab}$ ~6$^{\\circ}$. The preliminary results are reported here. The $^4$He measurement is non-neglible; therefore, it will be necessary to make measurements of $A_T$ for future parity-violating experiments using nuclear targets

  10. Photodisintegration of $^4$He into p+t

    SciTech Connect

    R. Nasseripour, B.L. Berman, N. Benmouna, Y. Ilieva, J.-M. Laget

    2009-10-01

    The two-body photodisintegration of $^4$He into a proton and a triton has been studied using the CEBAF Large-Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung-tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid $^4$He target. This is the first measurement of the photodisintegration of $^4$He above 0.4 GeV. The differential cross sections for the $\\gamma$$^4$He$\\to pt$ reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by J.-M. Laget. At 0.6-1.2 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. These results reinforce the conclusion of our previous study of the three-body breakup of $^3$He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV .

  11. Transverse Ultrasound Measurements in 4He Single Crystals

    NASA Astrophysics Data System (ADS)

    Syshchenko, O.; Beamish, J.

    2008-02-01

    Recently, Kim and Chan (Science 305:1941, 2004; Phys. Rev. Lett. 97:115302, 2006) have reported an anomalous decoupling transition of solid 4He in a torsional oscillator measurement, and interpret their results as evidence for non-classical rotational inertia and a possible supersolid phase of 4He. The detailed nature and properties of such a “supersolid” state in 4He are still far from being clear, although there are clues from experiments involving 3He impurities, different sample cell geometries, annealing effects and grain boundary flow. Defects produced during crystal growth or deformation (e.g. dislocations) may affect supersolidity, or even produce it, and they are expected to have significant impact on the elastic properties of the solid. The supersolid fraction could also decouple from the lattice and produce a decrease in the transverse sound speed. We have begun the experiments in this laboratory to study such effects, measuring the velocity and attenuation of transverse ultrasound at 10 MHz in 4He single crystals grown at constant pressure.

  12. Small Multielectron Bubbles in Bulk Superfluid 4He

    SciTech Connect

    Lehtovaara, Lauri; Eloranta, Jussi

    2006-09-07

    A computational method for describing multielectron bubbles in bulk superfluid helium (4He) is described. The developed method can be used to study their stability and spectroscopic properties in both singlet and triplet manifolds. Our initial results indicate meta-stability of the spherical two-electron bubble in its singlet ground state.

  13. Study of states in 14C via the 10Be(4He,4He)10Be reaction

    NASA Astrophysics Data System (ADS)

    Malcolm, J. D.; Freer, M.; Ashwood, N. I.; Curtis, N.; Munoz-Britton, T.; Wheldon, C.; Ziman, V. A.; Catford, W. N.; Brown, S.; Wilson, G.; Soic, N.; Bardayan, D.; Pain, S. D.; Achouri, N. L.; Chipps, K.; Crzywacz-Jones, K.

    2012-09-01

    A study of the 10Be(4He,4He)10Be reaction has been performed at 10Be beam energies of 25.0, 27.0, 29.0, 32.0, 34.0, 38.0, 40.0, 42.0, 44.0 and 46.0 MeV. The measurements were to explore possible molecular rotational bands in 14C. Three states at excitation energies of Ex = 18.8, 19.76 and 20.66 MeV have been measured and their spins have been determined to be 5-, 5- and 6+, respectively.

  14. Maximum supercoolign in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point

    SciTech Connect

    Sinha, D.N.; Hoffer, J.K.

    1984-01-01

    Measurements of supercooling in liquid /sup 3/He-/sup 4/He mixtures near the tricritical point are presented. The reduced temperature range 0.001 < epsilon identical to (1 - T/T/sub t/) < 0.01 was investigated for three different rates of cooling using a pressure-quench technique. For epsilon < 0.012, the maximum supercooling was found to be a function of the cooling rate. Comparisons with data in organic binary mixtures are given.

  15. Rate of tree carbon accumulation increases continuously with tree size.

    PubMed

    Stephenson, N L; Das, A J; Condit, R; Russo, S E; Baker, P J; Beckman, N G; Coomes, D A; Lines, E R; Morris, W K; Rüger, N; Alvarez, E; Blundo, C; Bunyavejchewin, S; Chuyong, G; Davies, S J; Duque, A; Ewango, C N; Flores, O; Franklin, J F; Grau, H R; Hao, Z; Harmon, M E; Hubbell, S P; Kenfack, D; Lin, Y; Makana, J-R; Malizia, A; Malizia, L R; Pabst, R J; Pongpattananurak, N; Su, S-H; Sun, I-F; Tan, S; Thomas, D; van Mantgem, P J; Wang, X; Wiser, S K; Zavala, M A

    2014-03-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence. PMID:24429523

  16. Rate of tree carbon accumulation increases continuously with tree size

    USGS Publications Warehouse

    Stephenson, N.L.; Das, A.J.; Condit, R.; Russo, S.E.; Baker, P.J.; Beckman, N.G.; Coomes, D.A.; Lines, E.R.; Morris, W.K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S.J.; Duque, Á.; Ewango, C.N.; Flores, O.; Franklin, J.F.; Grau, H.R.; Hao, Z.; Harmon, M.E.; Hubbell, S.P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L.R.; Pabst, R.J.; Pongpattananurak, N.; Su, S.-H.; Sun, I-F.; Tan, S.; Thomas, D.; van Mantgem, P.J.; Wang, X.; Wiser, S.K.; Zavala, M.A.

    2014-01-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage—increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to understand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  17. Rate of tree carbon accumulation increases continuously with tree size

    NASA Astrophysics Data System (ADS)

    Stephenson, N. L.; Das, A. J.; Condit, R.; Russo, S. E.; Baker, P. J.; Beckman, N. G.; Coomes, D. A.; Lines, E. R.; Morris, W. K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S. J.; Duque, Á.; Ewango, C. N.; Flores, O.; Franklin, J. F.; Grau, H. R.; Hao, Z.; Harmon, M. E.; Hubbell, S. P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L. R.; Pabst, R. J.; Pongpattananurak, N.; Su, S.-H.; Sun, I.-F.; Tan, S.; Thomas, D.; van Mantgem, P. J.; Wang, X.; Wiser, S. K.; Zavala, M. A.

    2014-03-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  18. Sodium dimers on the surface of liquid {sup 4}He

    SciTech Connect

    Ancilotto, F.; DeToffol, G.; Toigo, F.

    1995-12-01

    We have studied the structure of a sodium dimer interacting with liquid {sup 4}He. We calculated the equilibrium configuration and binding energy of a Na{sub 2} molecule solvated in a bulk liquid {sup 4}He ``bubble`` and near the liquid-vapor interface ``dimple`` by using a density-functional approach. We find that the solvated molecule is a metastable state, while the the lowest energy bound state occurs when the molecule lies flat on the surface of the liquid. The binding energy for the ``erect`` dimer is only {similar_to}1 K higher than the flat dimer, with no potential energy barrier between the two orientations, implying relatively free rotations of the molecule on the surface. The small effects of the liquid environment on the vibrational properties of the dimer are investigated.

  19. Overview on Solid 4He and the Issue of Supersolidity

    NASA Astrophysics Data System (ADS)

    Chan, M. H. W.; Hallock, R. B.; Reatto, L.

    2013-09-01

    Here we provide an overview of the status of the field of solid 4He with a focus on the recent theoretical and experimental activities stimulated by the 2004 experiments of Kim and Chan. The overview attempts to place the experimental and theoretical work in context, to respect the historical flow of the field and discuss our present understanding of the question of supersolidity in 4He. The possibility of supersolidity in cold atoms and in other systems is also addressed. Special issues of the Journal of Low Temperature Physics (168(3/4), 2012; 169(3/4), 2012), in addition to this issue, have been devoted to this subject and this overview is meant to accompany those issues of the journal.

  20. Bose-Einstein condensation in liquid 4He under pressure

    SciTech Connect

    Glyde, Henry R; Omar Diallo, Souleymane; Azuah, Richard T; Kirichek, Oleg; Taylor, Jon W.

    2011-01-01

    We present neutron scattering measurements of Bose-Einstein condensation, the atomic momen- tum distribution and Final State effects in liquid 4He under pressure. The condensate fraction at low temperature is found to decrease from n0 = 7.25 0.75% at SVP (p 0) to n0 = 3.2 0.75% at pressure p = 24 bar. This indicates an n0 = 3.0% in the liquid at the liquid/solid co-existence line (p = 25.3 bar). The atomic momentum distribution n(k) has high occupation of low k states and differs significantly from a Gaussian (e.g. a classical n(k)). Both n(k) and the Final state function broaden with increasing pressure, reflecting the increased localization of the 4He in space under increased pressure.

  1. NOVEL CONCEPTS FOR ISOTOPIC SEPARATION OF 3HE/4HE

    SciTech Connect

    Roy, L.; Nigg, H.; Watson, H.

    2012-09-04

    The research outlined below established theoretical proof-of-concept using ab initio calculations that {sup 3}He can be separated from {sup 4}He by taking advantage of weak van der Waals interactions with other higher molecular weight rare gases such as xenon. To the best of our knowledge, this is the only suggested method that exploits the physical differences of the isotopes using a chemical interaction.

  2. The Nature of the Glassy Phase in 4He Crystals

    NASA Astrophysics Data System (ADS)

    Antsygina, T. N.; Poltavskaya, M. I.; Chishko, K. A.

    2015-08-01

    A model of a close-packed polytype with a random stacking fault structure is used to interpret the anomalies of the thermodynamic properties of the disordered (glassy) phase in solid HCP 4He in the so-called supersolid state. The temperature dependence of the phonon pressure is calculated theoretically, and compared to experimental data. A quantitative agreement between the theory and the experiment is achieved.

  3. Hyperspherical coupled channel calculations of energy and structure of (4)He-(4)He-Li(+) and its isotopic combinations.

    PubMed

    Liu, Min-Min; Wu, Meng-Shan; Han, Hui-Li; Shi, Ting-Yun

    2016-07-21

    The ground state vibrational energy and spatial features of (4)He-(4)He-Li(+) and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li(+)-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained. PMID:27448884

  4. Hyperspherical coupled channel calculations of energy and structure of 4He-4He-Li+ and its isotopic combinations

    NASA Astrophysics Data System (ADS)

    Liu, Min-min; Wu, Meng-Shan; Han, Hui-li; Shi, Ting-yun

    2016-07-01

    The ground state vibrational energy and spatial features of 4He-4He-Li+ and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li+-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained.

  5. Production of {sup 4}He and tritium from Be in the COBRA-1A2 irradiation

    SciTech Connect

    Greenwood, L.R.

    1998-03-01

    The production of {sup 4}He and tritium has been calculated for beryllium irradiated in the COBRA-1A2 experiment in the Experimental Breeder Reactor II. Reaction rates were based on adjusted neutron spectra determined from reactor dosimetry measurements at three different elevations in the region of the beryllium capsules. Equations are given so that gas production can be calculated for any specific capsule elevation.

  6. Solidification of 4He clusters adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Markić, L. Vranješ; Stipanović, P.; Bešlić, I.; Zillich, R. E.

    2016-07-01

    We determined the ground state of He4N clusters adsorbed on one side of graphene for selected cluster sizes in the range from N =20 to N =127 . For all investigated clusters variational and diffusion Monte Carlo simulations were performed at T =0 K, and in addition for a selected subset finite temperature path integral Monte Carlo. At T =0 K the liquid or solid character of each cluster was investigated by restricting the phase using corresponding importance sampling trial-wave functions. The 4He-graphene interaction was modeled as a sum of individual 4He-C interactions, where both isotropic and anisotropic models were tested; also the effect of the substrate-mediated McLachlan interaction was investigated. We have found homogeneous crystallization in models of anisotropic interactions, starting from clusters with N =26 atoms in simulations without the McLachlan interaction, and between N =37 and 61 when it is included. The atoms become increasingly delocalized as one moves from the center of the cluster to the perimeter, evidenced by the Lindemann parameter. On the other hand, in the case of the isotropic interaction model, a liquidlike structure is more favorable for all considered cluster sizes. We use a liquid-drop model to extrapolate the energy per particle to the N →∞ limit, and the results are compared with the values obtained in studies of bulk 4He on graphene. Low-temperature path integral Monte Carlo simulations are in agreement with ground-state results.

  7. Vacancy distribution in a rotating solid 4He

    NASA Astrophysics Data System (ADS)

    Pushkarov, D. I.

    2012-03-01

    Vacancy distribution is considered in a rotating solid 4He immersed in a superfluid helium-II. Vacancies are considered as a quasiparticle gas of vacancions with a gap dispersion law. It is shown that the radial distribution depends on Poisson's ratio and practically not on Young's modulus. The treatment is based on a nonlinear theory unifying the elasticity theory equations and a Boltzmann-type transport equation valid for arbitrary angular velocities. The situation simulates, in a sense, the Kim and Chan rotational experiments where nonclassical inertia was observed. The model cannot be applied to solid 3He. We do not presuppose in this work any supersolid fraction.

  8. Classical Rotational Inertia of Solid {sup 4}He

    SciTech Connect

    Dash, J.G.; Wettlaufer, J.S.

    2005-06-17

    The observation of reduced rotational inertia in a cell containing solid {sup 4}He has been interpreted as evidence for superfluidity of the solid. We propose an alternative explanation: slippage of the solid, due to grain boundary premelting between the solid and dense adsorbed layers at the container wall. We calculate the range of film thickness, and determine the viscosity that will account for the missing rotational inertia. Grain boundary premelting also explains inertial anomalies in an earlier study of solid helium in porous glass and indicates that the liquid is partially superfluid.

  9. Deeply Virtual Compton Scattering off ^4He nucleus

    NASA Astrophysics Data System (ADS)

    El Alaoui, Ahmed

    2010-02-01

    The recently developed formalism of generalized parton distributions (GPDs) provides a theoretical tool to reveal the internal structure of the nucleon. These objects can be obtained via Deeply Virtual Compton Scattering (DVCS) processes. They contain informations on the transverse spatial position and the longitudinal momentum of quarks inside the nucleon and they also give access to the contribution of the quark orbital angular momentum to the nucleon. In contrast to many DVCS experiments using a proton target, only few experiments are devoted to study GPDs in a nuclear target which is important because it allows to address medium modification of bound nucleon GPDs compared to free nucleon GPDs. One of the goals of the new EG6 experiment at Thomas Jefferson Laboratory is to extract the real and imaginary parts of the ^4He Compton form factor (HA(xB,t)) from measurement of beam spin asymmetries by scattering a polarized 6 GeV electron beam off a ^4He pressurized gaz target. Details on the experiment will be presented here. )

  10. Nickel accumulation by Streptanthus polygaloides (Brassicaceae) reduces floral visitation rate.

    PubMed

    Meindl, George A; Ashman, Tia-Lynn

    2014-02-01

    Hyperaccumulation is the phenomenon whereby plants take up and sequester in high concentrations elements that generally are excluded from above-ground tissues. It largely is unknown whether the metals taken up by these plants are transferred to floral rewards (i.e., nectar and pollen) and, if so, whether floral visitation is affected. We grew Streptanthus polygaloides, a nickel (Ni) hyperaccumulator, in short-term Ni supplemented soils and control soils to determine whether Ni is accumulated in floral rewards and whether floral visitation is affected by growth in Ni-rich soils. We found that while supplementation of soils with Ni did not alter floral morphology or reward quantity (i.e., anther size or nectar volume), Ni did accumulate in the nectar and pollen-filled anthers-providing the first demonstration that Ni is accumulated in pollinator rewards. Further, S. polygaloides grown in Ni-supplemented soils received fewer visits per flower per hour from both bees and flies (both naïve to Ni-rich floral resources in the study area) relative to plants grown in control soils, although the probability a plant was visited initially was unaffected by Ni treatment. Our findings show that while Ni-rich floral rewards decrease floral visitation, floral visitors are not completely deterred, so some floral visitors may collect and ingest potentially toxic resources from metal-hyperaccumulating plants. In addition to broadening our understanding of the effects of metal accumulation on ecological interactions in natural populations, these results have implications for the use of insect-pollinated plants in phytoremediation. PMID:24477333

  11. Capillary Condensation of Liquid 4He in Aerogel on Cooling Through {lambda} Point

    SciTech Connect

    Miyashita, W.; Yoneyama, K.; Kato, H.; Nomura, R.; Okuda, Y.

    2006-09-07

    Capillary condensation of liquid 4He in silica aerogel with a 90% porosity was investigated visually. The initial condition of the experiment was such that liquid 4He was present in the sample cell but not in the aerogel. This situation was realized by introducing the liquid into the cell at a fast rate to avoid liquefaction in the aerogel. The free surface of the liquid rose up in the cell with filling and eventually reached the bottom of the aerogel. Then, the aerogel absorbed the liquid by capillary condensation. The height of the liquid in the aerogel rose with time t roughly as t1/2 in the normal fluid phase. This behavior was consistent with the Washburn model. When the system was cooled through the {lambda} point during the condensation, the liquid height started to rise faster in the superfluid phase with a constant velocity of about 0.3 mm/sec. The dynamics of capillary condensation was strongly dependent on whether the liquid 4He was in the normal or the superfluid phase.

  12. Spin polarization effects in the /sup 3/H(d,n)/sup 4/He fusion reaction

    SciTech Connect

    Conzett, H.E.; Rioux, C.

    1985-06-01

    A recent investigation has shown that the /sup 3/H(d,n)/sup 4/He fusion reaction rate could be enhanced by a factor of 3/2 if the fusion plasma consisted of both polarized deuterons and tritons, forming exclusively the channel-spin S = 3/2, J = 3/2/sup +/ state. This result follows simply from the statistical weights of the quartet S = 3/2 and doublet S = 1/2 initial states, with the assumption of the single J = 3/2/sup +/ reaction amplitude. Since, with a small but nonzero J = 1/2/sup +/ amplitude, the maximum enhancement of the reaction occurs at the peak of the J = 3/2/sup +/ resonance, corresponding to a deuteron lab energy of 107 keV, it is of obvious interest to know what the enhancement would be at the lower energies that are typical of fusion plasmas. We are able to address this question by extending earlier calculations which gave the values of all of the spin-polarization observables at this J = 3/2/sup +/ resonance in both the /sup 3/H(d,n)/sup 4/He and the /sup 3/He(d,p)/sup 4/He reactions.

  13. Superfluidity, BEC, and dimensions of liquid 4He in nanopores

    NASA Astrophysics Data System (ADS)

    Markić, L. Vranješ; Glyde, H. R.

    2015-08-01

    We present path integral Monte Carlo (PIMC) calculations of the superfluid fraction, ρS/ρ , and the one-body density matrix (OBDM) [Bose-Einstein condensation (BEC)] of liquid 4He confined in nanopores. Liquid 4He in nanopores represents a dense Bose liquid at reduced dimension and in disorder. The goal is to determine the effective dimensions of the liquid in the pores. It is to test whether observed properties, such as a very low onset temperature for superflow, Tc, can be predicted by a standard, static PIMC ρS/ρ . We simulate a cylinder of liquid of diameter dL surrounded by 5 Å of inert solid 4He in a nanopore of diameter d ; d =dL+10 Å . We find a PIMC ρS(T ) /ρ and OBDM that scales as a 1D fluid Luttinger liquid at extremely small liquid pore diameters only, dL=6 Å . At this dL, the liquid fills the pore in a 1D line at the center of the pore and there is no PIMC superflow. In the range 8 ≤dL≤22 Å the PIMC ρS(T ) /ρ scales as a 2D liquid. In this dL range the liquid fills the pores in 2D-like cylindrical layers. The crossover from no superflow at d =16 Å to superflow at d ≥18 Å agrees with experiment. There is a crossover to 3D scaling at larger dL≃22 Å . In the range 8 ≤dL≤22 Å , the Tc predicted using the Kosterlitz-Thouless 2D scaling criterion of the OBDM agrees well with that obtained from ρS(T ) /ρ . These results suggest that the superflow observed in small pore media is standard static superflow with the low Tc arising from its 2D character. An operational onset temperature, TBEC, for BEC can be defined as the temperature at which there is a crossover from exponential to algebraic decay in the OBDM. This definition leads to a TBEC≥Tc as observed in larger pore media.

  14. Quantized Vortex State in hcp Solid 4He

    NASA Astrophysics Data System (ADS)

    Kubota, Minoru

    2012-11-01

    The quantized vortex state appearing in the recently discovered new states in hcp 4He since their discovery (Kim and Chan, Nature, 427:225-227, 2004; Science, 305:1941, 2004) is discussed. Special attention is given to evidence for the vortex state as the vortex fluid (VF) state (Anderson, Nat. Phys., 3:160-162, 2007; Phys. Rev. Lett., 100:215301, 2008; Penzev et al., Phys. Rev. Lett., 101:065301, 2008; Nemirovskii et al., arXiv:0907.0330, 2009) and its transition into the supersolid (SS) state (Shimizu et al., arXiv:0903.1326, 2009; Kubota et al., J. Low Temp. Phys., 158:572-577, 2010; J. Low Temp. Phys., 162:483-491, 2011). Its features are described. The historical explanations (Reatto and Chester, Phys. Rev., 155(1):88-100, 1967; Chester, Phys. Rev. A, 2(1):256-258, 1970; Andreev and Lifshitz, JETP Lett., 29:1107-1113, 1969; Leggett, Phys. Rev. Lett., 25(22), 1543-1546, 1970; Matsuda and Tsuneto, Prog. Theor. Phys., 46:411-436, 1970) for the SS state in quantum solids such as solid 4He were based on the idea of Bose Einstein Condensation (BEC) of the imperfections such as vacancies, interstitials and other possible excitations in the quantum solids which are expected because of the large zero-point motions. The SS state was proposed as a new state of matter in which real space ordering of the lattice structure of the solid coexists with the momentum space ordering of superfluidity. A new type of superconductors, since the discovery of the cuprate high T c superconductors, HTSCs (Bednorz and Mueller, Z. Phys., 64:189, 1986), has been shown to share a feature with the vortex state, involving the VF and vortex solid states. The high T c s of these materials are being discussed in connection to the large fluctuations associated with some other phase transitions like the antiferromagnetic transition in addition to that of the low dimensionality. The supersolidity in the hcp solid 4He, in contrast to the new superconductors which have multiple degrees of freedom of

  15. Non-relativistic approximations to the pion production operator in 4He(p, n π+) 4He

    NASA Astrophysics Data System (ADS)

    Greben, J. M.; Woloshyn, R. M.

    1980-01-01

    Various non-relativistic pion production operators are applied in the study of the 4He(p, nπ +) 4He process. We compare their predictions with fully covariant calculations of the external emission graphs both for pseudovector and pseudoscalar coupling. It is found that the non-relativistic pion production operators cannot reproduce the relativistic results quantitatively, in particular for the pseudoscalar case. The simple static pion production operator gives agreement with the relativistic pseudovector results to within a factor three or four. Adding recoil terms to this static operator has a significant effect on the cross section but does not improve the agreement with the relativistic results. The implications of PCAC and the soft-pion theorem for the relativistic calculation are studied. The uncertainty in the cross section in the soft-pion approach is found to be considerably smaller than the difference between pseudovector and pseudoscalar results or between the relativistic pseudovector result and its non-relativistic approximations.

  16. Theoretical modeling of electron mobility in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Aitken, Frédéric; Bonifaci, Nelly; von Haeften, Klaus; Eloranta, Jussi

    2016-07-01

    The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid 4He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ions are briefly discussed.

  17. Theoretical modeling of electron mobility in superfluid (4)He.

    PubMed

    Aitken, Frédéric; Bonifaci, Nelly; von Haeften, Klaus; Eloranta, Jussi

    2016-07-28

    The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid (4)He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ions are briefly discussed. PMID:27475346

  18. cap alpha. /sup 4/He elastic scattering at high energies

    SciTech Connect

    Usmani, A.A.; Ahmad, I.; Usmani, Q.N.

    1989-03-01

    Differential cross sections for ..cap alpha.. /sup 4/He elastic scattering have been calculated at incident ..cap alpha..-particle momenta of 4.32, 5.07, and 7.0 GeV/c within the framework of Glauber multiple scattering theory. The full Glauber amplitude has been calculated using the Monte Carlo method for evaluating multidimensional integrals. We found that, in general, the more realistic double-Gaussian model for the density brings theory closer to experiment as compared to the generally used single-Gaussian model in some momentum transfer regions. Our results with the double-Gaussian model and an acceptable set of NN parameters are in fairly good agreement with the experimental data at 4.32 and 5.07 GeV/c.

  19. Dislocation Structure and Mobility in hcp 4He

    NASA Astrophysics Data System (ADS)

    Landinez Borda, Edgar Josué; Cai, Wei; de Koning, Maurice

    2016-07-01

    Using path-integral Monte Carlo simulations, we assess the core structure and mobility of the screw and edge basal-plane dislocations in hcp 4He. Our findings provide key insights into recent interpretations of giant plasticity and mass flow junction experiments. First, both dislocations are dissociated into nonsuperfluid Shockley partial dislocations separated by ribbons of stacking fault, suggesting that they are unlikely to act as one-dimensional channels that may display Lüttinger-liquid-like behavior. Second, the centroid positions of the partial cores are found to fluctuate substantially, even in the absence of applied shear stresses. This implies that the lattice resistance to motion of the partial dislocations is negligible, consistent with the recent experimental observations of giant plasticity. Further results indicate that both the structure of the partial cores and the zero-point fluctuations play a role in this extreme mobility.

  20. Dislocation Structure and Mobility in hcp ^{4}He.

    PubMed

    Landinez Borda, Edgar Josué; Cai, Wei; de Koning, Maurice

    2016-07-22

    Using path-integral Monte Carlo simulations, we assess the core structure and mobility of the screw and edge basal-plane dislocations in hcp ^{4}He. Our findings provide key insights into recent interpretations of giant plasticity and mass flow junction experiments. First, both dislocations are dissociated into nonsuperfluid Shockley partial dislocations separated by ribbons of stacking fault, suggesting that they are unlikely to act as one-dimensional channels that may display Lüttinger-liquid-like behavior. Second, the centroid positions of the partial cores are found to fluctuate substantially, even in the absence of applied shear stresses. This implies that the lattice resistance to motion of the partial dislocations is negligible, consistent with the recent experimental observations of giant plasticity. Further results indicate that both the structure of the partial cores and the zero-point fluctuations play a role in this extreme mobility. PMID:27494477

  1. Σ production from targets of ^4He and ^13C

    NASA Astrophysics Data System (ADS)

    Chrien, R. E.

    1996-10-01

    One of the abiding issues in hypernuclear research has been the question of the formation of nuclear bound states incorporating the Σ-hyperon. The recent increases in beam intensity at the Brookhaven AGS have enabled us to obtain a high statistics study on the production of Σ-hyperons on a ^4He target. Earlier research using stopped kaons at KEK indicated the presence of structure in the (K^-,π^-) reaction, and led to the postulate of a Σ bound state. That structure has now been definitely confirmed in the in-flight kaon experiment at the LESB2 beam line and Moby-Dick spectrometer. An improved measurement of the binding energy of the presumed state will be reported, together with a production cross section. In addition, both (K^-,π^-) and (K^-,π^+) reactions on ^13C have been studied and will be compared to similar measurements on ^9Be.

  2. Observation of melting of solid 4He by sound wave

    NASA Astrophysics Data System (ADS)

    Okuda, Y.; Yamazaki, S.; Yoshida, T.; Fujii, H.; Matsumoto, K.

    1999-03-01

    We have observed the crystal melting, or the depletion of the solid/liquid interface where the strong pulsed sound beam was passing. The crystal was produced around 0.8 K with the atomically rough horizontal surface sitting in the middle of the sample cell. The interface was very mobile which was confirmed by an easy excitation of the crystallization/melting wave. When the received signal through the interface was monitored as a function of the input power, a sudden saturation of the received signal was observed at some power. For well above that power, the melting of the interface was visible through a video camera for both the cases of the sound emission from fluid-side and solid-side. This would be the first observation of sound induced melting of solid 4He.

  3. Metastable Helium Molecules as Tracers in Superfluid {sup 4}He

    SciTech Connect

    Guo, W.; Wright, J. D.; Cahn, S. B.; Nikkel, J. A.; McKinsey, D. N.

    2009-06-12

    Metastable helium molecules generated in a discharge near a sharp tungsten tip immersed in superfluid {sup 4}He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He{sub 2}* molecules is produced. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the first excited vibrational level of the triplet ground state. Subsequent imaging of the tagged molecules with an expanded 925 nm probe laser pulse allows us to measure the flow velocity of the jet. The techniques we developed provide new tools in quantitatively studying the normal fluid flow in superfluid helium.

  4. Metastable helium molecules as tracers in superfluid 4He.

    PubMed

    Guo, W; Wright, J D; Cahn, S B; Nikkel, J A; McKinsey, D N

    2009-06-12

    Metastable helium molecules generated in a discharge near a sharp tungsten tip immersed in superfluid 4He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He(2*) molecules is produced. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the first excited vibrational level of the triplet ground state. Subsequent imaging of the tagged molecules with an expanded 925 nm probe laser pulse allows us to measure the flow velocity of the jet. The techniques we developed provide new tools in quantitatively studying the normal fluid flow in superfluid helium. PMID:19658945

  5. The spectra of mixed 3He-4He droplets.

    PubMed

    Fantoni, S; Guardiola, R; Navarro, J; Zuker, A

    2005-08-01

    The diffusion Monte Carlo technique is used to calculate and analyze the excitation spectrum of 3He atoms bound to a cluster of 4He atoms by using a previously determined optimum filling of single-fermion orbits with well-defined orbital angular momentum L, spin S, and parity quantum numbers. The study concentrates on the energies and shapes of the three kinds of states for which the fermionic part of the wave function is a single Slater determinant: maximum L or maximum S states within a given orbit, and fully polarized clusters. The picture that emerges is that of systems with strong shell effects, whose binding and excitation energies are essentially determined by averages over configuration at fixed number of particles and spin, i.e., by the monopole properties of an effective Hamiltonian. PMID:16108665

  6. Quantum Tunneling of ^3 He in Solid ^4 He: A New Analysis

    NASA Astrophysics Data System (ADS)

    Huan, C.; Kim, S. S.; Candela, D.; Sullivan, N. S.

    2016-06-01

    We discuss the analysis of the experimental values of the nuclear spin-lattice and spin-spin relaxation times for the tunneling of ^3 He as isotopic impurities in solid ^4 He. These two relaxation times cannot be described quantitatively using a unique correlation time although it is often presented as such in the literature. In this paper, we discuss how to distinguish the high-frequency portion of the spectral densities that determine the spin-lattice relaxation rates from the low-frequency components which determine the spin-spin relaxation rates.

  7. Formation of 3He droplets in dilute 3He-4He solid solutions

    NASA Astrophysics Data System (ADS)

    Huan, Chao; Candela, Don; Kim, Sung; Yin, Liang; Xia, Jiang-Sheng; Sullivan, Neil

    2015-03-01

    We review the different stages of the formation of 3He droplets in dilute solid 3He-4He solutions. The studies are interesting because the phase separation in isotopic helium mixtures is a first-order transition with a conserved order parameter. The rate of growth of the droplets as observed in NMR studies is compared with the rates expected for homogeneous nucleation followed by a period of coarsening known as Ostwald ripening. Work suported by the National Science Foundation - DMR-1303599 and DMR- 1157490 (National High Magnetic Field Laboratory).

  8. Excitations of Superfluid ^4He at Wavevectors Beyond the Roton

    NASA Astrophysics Data System (ADS)

    Glyde, Henry; Sakhel, Asaad

    2002-03-01

    We present a Quantum Field Theoretical Model that reproduces the basic features of the temperature dependence of the dynamic structure factor S(Q,ω) of ^4He as observed in the inelastic-neutron scattering data taken at ISIS( J. V. Pierce, R. T. Azuah, B. F, A. R. Sakhel, H. R. Glyde, W. G. Stirling, J. Phys: Cond. Matter, 13(2001) 4421., UK. A range of the wavevectors Q beyond the roton (Q > 2.0 Åis considered. The model is able to reproduce the decrease in the intensity of the single-particle excitation peak with increase of T in the range 0.6 <= T <= 2.1 K. Also, it reproduces the second peak at higher energy representing the single excitation intensity lying in the two excitation band. The model is based on the formulation of S(Q,ω) of Gavoret and Nozières( J. Gavoret and P. Nozières, Ann. Phys., 28, 349-399 (1964). In this formulation, the dynamic susceptibility is separated into a singular part involving the condensate and a regular part involving states above the condensate \\chi = \\chiS + \\chi_R. Here \\chiS = n n_0(T) Λ G Λ, Λ is a vertex, G the renormalized single particle Green's function, n the density of ^4He at SVP and n_0(T) the condensate fraction as a function of T. \\chi_R(Q,ω) involves both a single particle-hole and a multiparticle component. All vertices and interactions are assumed T-independent, and only n0 changes with T. Also, the roton width is accounted for by a momentum (k) and temperature dependent width of the Landau-Khalatnikov form (H. R. Glyde, Excitations in Liquid and Solid helium), Oxford, Clarendron Press, (1994)..

  9. Coherent Propagation of Elementary Excitations in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Goodkind, John M.; Ho, Pei-Chun

    1998-03-01

    We have measured the interaction of heat pulses and acoustic pulses propagating along orthogonal paths in solid ^4He with small amounts of ^3He impurities. The interaction is revealed as a variation of the acoustic attenuation, alpha, and velocity, v, as a function of the delay between launching of the heat pulses and the acoustic pulses. alpha and v pass through extreema at delay times corresponding to the relative propagation velocities of the acoustic waves and the excitations created by the heat pulses. The propagation velocities of the various excitations, determined in this way, are between 50 and 150 m/sec and they increase with decreasing temperature. There are two distinct peaks and a long tail at temperatures above about 500 mK indicating that more than one mode is propagating. The peak effect occurs at a different delay time for alpha than for v at temperatures near the attenuation peak (PC HO, I. P. Bindloss, and J. M. Goodkind, J. Low Temp. Phys., November 1997), providing further evidence for more than one type of propagating mode. The sign of the effect reverses as T is decreased and the change of alpha is of opposite sign to that expected from the equilibrium T dependence of alpha. We will discuss the relation of this phenomenon to previous indications of propagating modes in solid ^4He (G.A. Lengua and J. M. Goodkind, J. Low Temp. Phys., 79), 251 (1990)and to the possible Bose-Einstein condensation (PC HO, I. P. Bindloss, and J. M. Goodkind, J. Low Temp. Phys., November 1997).

  10. Giant isochoric compressibility of solid 4He: The bistability of superclimbing dislocations

    NASA Astrophysics Data System (ADS)

    Kuklov, A. B.

    2015-10-01

    A significant accumulation of matter in solid 4He observed during a superflow event, dubbed the giant isochoric compressibility (or the syringe effect), is discussed within the model of dislocations with superfluid core. It is shown that solid 4He in contact with a superfluid reservoir can develop a bistability with respect to the syringe fraction, with the threshold for the bias by chemical potential determined by a typical free length of dislocations with superfluid core. The main implications of this effect are hysteresis and strongly nonlinear dynamical behavior leading to growth, proliferation, and possibly exiting from a crystal of superclimbing dislocations. Three major channels for such dynamics are identified: (i) injection and inflation of the prismatic loops from the boundary, (ii) Bardeen-Herring generation of the loops in the bulk, and (iii) helical instability of the screw dislocations. It is argued that the syringe instability may have already been observed in the experiments on the superflow through solid Helium-4. Several testable predictions for the time and the bias dependencies of the dynamics are suggested.

  11. Annual Greenland accumulation rates (2009-2012) from airborne snow radar

    NASA Astrophysics Data System (ADS)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joesph R.; Tedesco, Marco; Leuschen, Carl; Gogineni, Prasad

    2016-08-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  12. Annual Greenland Accumulation Rates (2009-2012) from Airborne Snow Radar

    NASA Technical Reports Server (NTRS)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joseph R.; Tedesco, Marco; Leuschen, Carl; Gogineni, Prasad

    2016-01-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 gigahertz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semi-automated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 percent. A comparison of the radarderived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and longterm mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR - Modele Atmospherique Regional for Greenland and vicinity) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  13. Elevated rates of organic carbon, nitrogen, and phosphorus accumulation in a highly impacted mangrove wetland

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Eyre, Bradley D.; Santos, Isaac R.; Machado, Wilson; Luiz-Silva, Wanilson; Smoak, Joseph M.; Breithaupt, Joshua L.; Ketterer, Michael E.; Sanders, Luciana; Marotta, Humberto; Silva-Filho, Emmanoel

    2014-04-01

    The effect of nutrient enrichment on mangrove sediment accretion and carbon accumulation rates is poorly understood. Here we quantify sediment accretion through radionuclide tracers to determine organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) accumulation rates during the previous 60 years in both a nutrient-enriched and a pristine mangrove forest within the same geomorphological region of southeastern Brazil. The forest receiving high nutrient loads has accumulated OC, TN, and TP at rates that are fourfold, twofold, and eightfold respectively, higher than those from the undisturbed mangrove. Organic carbon and TN stable isotopes (δ13C and δ15N) reflect an increased presence of organic matter (OM) originating with either phytoplankton, benthic algae, or another allochthonous source within the more rapidly accumulated sediments of the impacted mangrove. This suggests that the accumulation rate of OM in eutrophic mangrove systems may be enhanced through the addition of autochthonous and allochthonous nonmangrove material.

  14. Incorporating 3-D parent nuclide zonation for apatite 4He/3He thermochronometry: An example from the Appalachian Mountains

    NASA Astrophysics Data System (ADS)

    Fox, Matthew; McKeon, Ryan E.; Shuster, David L.

    2014-11-01

    ability to constrain km-scale exhumation with apatite 4He/3He thermochronometry is well established and the technique has been applied to a range of tectonic and geomorphic problems. However, multiple sources of uncertainty in specific crystal characteristics limit the applicability of the method, especially when geologic problems require identifying small perturbations in a cooling path. Here we present new 4He/3He thermochronometric data from the Appalachian Mountains, which indicate significant parent nuclide zonation in an apatite crystal. Using LA-ICPMS measurements of U and Th in the same crystal, we design a 3-D model of the crystal to explore the effects of intracrystal variability in radiation damage accumulation. We describe a numerical approach to solve the 3-D production-diffusion equation. Using our numerical model and a previously determined time temperature path for this part of the Appalachians, we find excellent agreement between predicted and observed 4He/3He spectra. Our results confirm this time-temperature path and highlight that for complex U and Th zonation patterns, 3-D numerical models are required to infer an accurate time-temperature history. In addition, our results provide independent and novel evidence for a radiation damage control on diffusivity. The ability to exploit intracrystal differences in 4He diffusivity [i.e., temperature sensitivity) greatly increases the potential to infer complex thermal histories.

  15. Magnetic-field-assisted atomic polarization spectroscopy of 4 He

    NASA Astrophysics Data System (ADS)

    Li, Sheng; Wang, Haidong; Wu, Teng; Peng, Xiang; Guo, Hong; Cream Team

    2016-05-01

    Atomic polarization spectroscopy (PS) is a high resolution sub-Doppler atomic spectroscopic technique with free modulation. It is always desirable to obtain a PS signal with zero background as it can provide a more preferable laser frequency stabilization performance. There are many factors that can affect the PS signal background, i.e., the laser power, the laser polarization and the magnetic field. Here, we demonstrate a method for observing and analyzing the effects on the PS signal of 4 He under different magnetic fields. At the beginning, under nearly zero magnetic field, the large asymmetrical PS signal background has been observed and cannot be eliminated by only optically adjusting. Then, we find that the PS signal profile can be changed and controlled by varying the magnetic field with transverse or longitudinal direction and different intensity. The optimized PS signal with symmetrical dispersive profile and zero background is obtained when the magnetic field is chosen and controlled in the transverse direction and more than 20000nT intensity. Similar phenomenon cannot be observed under the longitudinal magnetic field. A theoretical model is also presented, which explains and agrees well with our experimental results.

  16. Stress induced roughening of superclimbing dislocation in solid 4He

    NASA Astrophysics Data System (ADS)

    Aleinikava, Darya; Kuklov, Anatoly

    2011-03-01

    We investigate numerically superclimb of dislocation in solid 4 He biased by externally imposed chemical potential μ . The effective action takes into account quantum phase slips in the core superfluid as well as the core displacement in Peierls potential within the Granato-Lücke string model. The bias produces stress on the core and this can result in dislocation roughening. Such roughening is characterized by hysteretic behavior at temperatures (T) below some threshold Thyst . At T >Thyst strongresonantpeaksdevelopinthedislocationdifferentialresponse . Thesepeaksexhibitperiodicbehaviorvs μ, with the period determined by Peierls potential and dislocation length. We explain these effects by thermally assisted tunneling of jog-antijog pairs across the barrier created by Peierls potential and the bias. Since superclimbing is controlled by core superflow, speed of sound along the superfluid core exhibits dip-like features at the peak positions. We propose that this effect is seen in the mass transport experiment. We acknowledge support by NSF, grants PHY1005527 and PHY0653135,and by CUNY, grant 63071-00 41.

  17. Critical behavior of liquid {sup 4}He at negative pressures

    SciTech Connect

    Campbell, C.E.; Folk, R.; Krotscheck, E.

    1996-10-01

    The authors examine the equation of state of liquid {sup 4}He at negative pressures close to the spinodal density {rho}{sub s} where the hydrodynamic speed of sound vanishes. The non-analytic behavior of the equation of state and the speed of sound in the vicinity of the spinodal density are calculated in two and in three dimensions; they find for the speed of sound the non-analytic behavior mc{sub s}{sup 2} {approximately} ({rho}-{rho}{sub s}){sup 2/5} in three dimensions and mc{sub s}{sup 2} {approximately} [({rho}-{rho}{sub s})/{vert_bar}ln({rho}-{rho}{sub s}){vert_bar}]{sup 1/2} in two dimensions. The authors then examine the low density regime numerically, using a semianalytic microscopic theory. It is found that non-analytic exponents are visible only in a negligible density regime around the spinodal point. Estimates for the spinodal densities, and the range of critical fluctations are provided.

  18. 4He Thermophysical Properties: New Ab Initio Calculations

    PubMed Central

    Hurly, John J.; Mehl, James B.

    2007-01-01

    Since 2000, atomic physicists have reduced the uncertainty of the helium-helium “ab initio” potential; for example, from approximately 0.6 % to 0.1 % at 4 bohr, and from 0.8 % to 0.1 % at 5.6 bohr. These results led us to: (1) construct a new inter-atomic potential ϕ07, (2) recalculate values of the second virial coefficient, the viscosity, and the thermal conductivity of 4He from 1 K to 10,000 K, and (3), analyze the uncertainties of the thermophysical properties that propagate from the uncertainty of ϕ07 and from the Born-Oppenheimer approximation of the electron-nucleon quantum mechanical system. We correct minor errors in a previous publication [J. J. Hurly and M. R. Moldover, J. Res. Nat. Inst. Standards Technol. 105, 667 (2000)] and compare our results with selected data published after 2000. The ab initio results tabulated here can serve as standards for the measurement of thermophysical properties. PMID:27110456

  19. Pseudopotential theory of interacting roton pairs in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Bedell, K.; Pines, D.; Zawadowski, A.

    1984-01-01

    A configuration-space pseudopotential, which is closely related to that used by Aldrich and Pines to describe the effective interaction between background particles in 3He and 4He, is constructed and used to calculate the roton-roton scattering amplitude. From that amplitude we obtain a theory that is completely congruent with the roton-liquid theory of Bedell, Pines, and Fomin. We calculate two-roton bound states, roton-liquid parameters, and roton lifetimes, as well as information about the hybridization of the two-roton bound state with excitations of higher and lower energy. Excellent agreement between theory and experiment is obtained for the l=2 bound state at zero pair momentum, the roton lifetime, the roton contribution to the normal-fluid viscosity and the normal-fluid density, and the temperature variation of the roton energy. The effective roton-roton coupling parameters at large pair momentum are found to be an order of magnitude larger than those for small or vanishing pair momentum. At SVP we find that a substantial number of two-roton bound states of varying symmetry exist for pair momentum up to ~ 3 Å -1; at standard pressure, however the roton-roton interaction for momenta ~ 1 Å -1 is found to become repulsive, so that both the l=2 bound state at zero pair momentum and bound states at intermediate momenta are predicted to disappear under pressure.

  20. Spatial variation in rates of carbon and nitrogen accumulation in a boreal bog

    SciTech Connect

    Ohlson, M.; Oekland, R.H.

    1998-12-01

    Although previous studies hint at the occurrence of substantial spatial variation in the accumulation rates of C and N in bogs, the extent to which rates may vary on high-resolution spatial and temporal scales is not known. A main reason for the lack of knowledge is that it is problematic to determine the precise age of peat at a given depth. The authors determined rates of carbon and nitrogen accumulation in the uppermost decimeters of a bog ecosystem using the pine method, which enables accurate dating of surface peat layers. They combined accumulation data with numerical and geostatistical analyses of the recent vegetation to establish the relationship between bog vegetation and rate of peat accumulation. Use of a laser technique for spatial positioning of 151 age-determined peat cores within a 20 x 20 m plot made it possible to give the first tine-scaled account of spatial and temporal variation in rates of mass, carbon, and nitrogen accumulation during the last century. Rates of C and N accumulation were highly variable at all spatial scales studied. For example, after {approximately}125 yr of peat growth, C and N accumulation varied by factors of five and four, respectively, from 25 to 125 g/dm{sup 2} for C, and from 0.7 to 2.6 g/dm{sup 2} for N. It takes 40 yr of peat accumulation before significant amounts of C are lost through decay. Hummocks built up by Sphagnum fuscum and S. rubellum were able to maintain average rates of C accumulation that exceed 2 g{center_dot}dm{sup {minus}2}{center_dot} yr{sup {minus}1} during 50 yr of growth. The authors argue that data on spatial variation in rates of C accumulation are necessary to understand the role of boreal peatlands in the greenhouse effect and global climate.

  1. 4He behavior in calcite filling viewed by (U-Th)/He dating, 4He diffusion and crystallographic studies

    NASA Astrophysics Data System (ADS)

    Cros, Alexandre; Gautheron, Cécile; Pagel, Maurice; Berthet, Patrick; Tassan-Got, Laurent; Douville, Eric; Pinna-Jamme, Rosella; Sarda, Philippe

    2014-01-01

    Fault-filling calcite crystals sampled from the Eocene/Oligocene Gondrecourt graben, Paris Basin, Eastern France, have been studied in order to test the potentiality of calcite (U-Th)/He dating, based on recognized He retention behavior in crystal lattice at surface temperature (Copeland et al., 2007). The samples have been selected because of their relatively old Eocene to Oligocene precipitation age and cold thermal history (<40 °C since precipitation). They were sorted into three main tectonic and morphological groups in order of precipitation, including (1) micro-fracture calcites, (2) breccia and associated geodic calcites, and (3) vein and associated geodic calcites. (U-Th)/He dating of 63 calcite fragments yields ages dispersed from 0.2 ± 0.02 to 35.8 ± 2.7 Ma, as well as two older dates of 117 ± 10 and 205 ± 28 Ma (1σ). These He ages correlate with grain chemistry, such as Sr, ΣREE concentrations or (La/Yb)N ratios, likely reflecting parent fluid evolution. Only the oldest He ages, which correspond to the most recently precipitated crystals, have preserved the total 4He budget since precipitation. To better understand both the age dispersion and why calcites precipitated earlier show younger ages, 4He diffusion experiments have been conducted on 10 Gondrecourt calcite fragments from 3 samples with He ages of ∼0.2-6 Ma. Additionally, a crystallographic investigation by X-ray diffraction (XRD) performed on similar samples reveals that crystal structure evolves with increasing temperature, beginning with micro-cracks and cleavage opening. These XRD results shed light on the (U-Th)/He data, indicating that, in fault-filling calcite, He retention is controlled by multiple diffusion domains (MDD) with various sizes, and therefore, evolves through time with strong consequences on (U-Th)/He age. We thus interpret the Gondrecourt calcite (U-Th)/He age scatter as a consequence of the production of defects due to successive calcite crystallization phases

  2. Systematics of pure and doped 4He clusters

    NASA Astrophysics Data System (ADS)

    Chin, S. A.; Krotscheck, E.

    1995-10-01

    Optimized variational calculations have been carried out for pure and doped clusters of 4He atoms up to a cluster size of N=1000 particles. For small cluster sizes with less than or equal to 112 particles, where comparisions with existing diffusion Monte Carlo results are possible, we find excellent agreement for the ground-state energy, correlation, and structure functions. For larger clusters our ground-state energies extrapolate smoothly toward a bulk limit of -7.2 K with a surface energy of 0.272 K Å-2. The resulting ground-state densities show unmistakable oscillations, confirming our earlier conclusions based on diffusion Monte Carlo studies. The present study of large clusters allows us to bridge the gap between finite systems and the bulk limit. Specifically, we show how the bulk limit of collective energies is reached as well as how the bulk Feynman spectrum is reproduced in the S-wave component of the dynamic structure function in large droplets. By plotting the collective excitation energy of higher multipole modes as a function of an effective wave number k=√scrl(scrl+1)/R, we show that the resulting spectrum can be directly compared with experimental excitation energies determined for plane liquid surfaces and films. By summing up to scrl=50 partial wave components, we show that the full dynamic structure function simultaneously displays the phonon-roton and the ripplon excitation spectrum. In the case of helium droplets doped with impurities such as rare gas atoms or the SF6 molecule, we show that the dipole collective mode becomes unstable with increased droplet size, strongly indicating that these impurities are delocalized inside large droplets. The microscopic character of the instability is revealed in the excitation functions and transition densities of the dipole mode. The introduction of impurities also profoundly alters the dynamic structure function, severely ``fragments'' the Feynman spectrum, and obliterates landmark structures such

  3. Thermal properties of {sup 4}He surfaces and interfaces

    SciTech Connect

    Clements, B.E.; Krotscheck, E. |; Tymczak, C.J.

    1997-05-01

    A first-principle quantum statistical mechanical theory is used to study the properties of thick liquid {sup 4}He films absorbed to the weakly binding substrates: Li, Na, and Cs. Values for the liquid-gas and solid-liquid surface energies are determined. By fitting, at long wavelengths, the film`s lowest energy mode with the standard expression for the ripplon energy, which depends on the liquid-gas surface energy, the authors obtain excellent agreement with the liquid-vacuum surface energy from recent experiments and also the one previously extracted from quantum liquid droplet calculations. The full spectrum of excitations for wave vectors less than 0.50 {Angstrom}{sup {minus}1} is calculated using a dynamical correlated basis function theory developed in earlier work, which includes multi-phonon scattering processes. Particle currents and transition densities are used to elucidate the nature of the excitations. At a coverage of 0.40 {Angstrom}{sup {minus}2}, the lowest mode shows no significant substrate dependence, and is recognized as being a ripplon propagating in the liquid film at the liquid-gas surface. A new effect is observed for the Cs substrate; the second lowest mode is qualitatively different than found on the other substrates and is identified as interfacial ripplon. In the other substrates the second mode is a volume mode altered somewhat by the high density inner liquid layers. The linewidths of these modes are also calculated. The dynamic excitations provide the input for the thermodynamic theory and the effects on the free energy, heat capacity, and thermal surface broadening of these films are studied as function of the nature of the excitations, the number of modes, and variations in the substrate potentials.

  4. Precision prediction for the big-bang abundance of primordial 4He

    NASA Astrophysics Data System (ADS)

    Lopez, Robert E.; Turner, Michael S.

    1999-05-01

    Within the standard models of particle physics and cosmology we have calculated the big-bang prediction for the primordial abundance of 4He to a theoretical uncertainty of less than 0.1% (δYP<+/-0.0002), improving the current theoretical precision by a factor of 10. At this accuracy the uncertainty in the abundance is dominated by the experimental uncertainty in the neutron mean lifetime, τn=885.4+/-2.0 sec. The following physical effects were included in the calculation: the zero and finite-temperature radiative, Coulomb and finite-nucleon-mass corrections to the weak rates; order-α quantum-electrodynamic correction to the plasma density, electron mass, and neutrino temperature; and incomplete neutrino decoupling. New results for the finite-temperature radiative correction and the QED plasma correction were used. In addition, we wrote a new and independent nucleosynthesis code designed to control numerical errors to be less than 0.1% . Our predictions for the 4He abundance are presented in the form of an accurate fitting formula. Summarizing our work in one number, YP(η=5×10-10)=0.2462+/-0.0004 (expt) +/-<0.0002 (theory). Further, the baryon density inferred from the Burles-Tytler determination of the primordial D abundance, ΩBh2=0.019+/-0.001, leads to the prediction YP=0.2464+/-0.0005 (D/H) +/-<0.0002 (theory) +/-0.0005 (expt). This ``prediction'' and an accurate measurement of the primeval 4He abundance will allow an important consistency test of primordial nucleosynthesis.

  5. The rate of aging: the rate of deficit accumulation does not change over the adult life span.

    PubMed

    Mitnitski, Arnold; Rockwood, Kenneth

    2016-02-01

    People age at different rates. We have proposed that rates of aging can be quantified by the rate at which individuals accumulate health deficits. Earlier estimates, using cross-sectional analyses suggested that deficits accumulated exponentially, at an annual rate of 3.5%. Here, we estimate the rate of deficit accumulation using longitudinal data from the Canadian National Population Health Survey. By analyzing age-specific trajectories of deficit accumulation in people aged 20 years and over (n = 13,668) followed biannually for 16 years, we found that the longitudinal average annual rate of deficit accumulation was 4.5% (±0.75%). This estimate was notably stable during the adult life span. The corresponding average doubling time in the number of deficits was 15.4 (95% CI 14.82-16.03) years, roughly 30% less than we had reported from the cross-sectional analysis. Earlier work also established that the average number of deficits accumulated by individuals (N), equals the product of the intensity of environmental stresses (λ) causing damage to the organism, by the average recovery time (W). At the individual level, changes in deficit accumulation can be attributed to both changes in environmental stresses and changes in recovery time. By contrast, at the population level, changes in the number of deficits are proportional to the changes in recovery time. In consequence, we propose here that the average recovery time, W doubles approximately every 15.4 years, independently of age. Such changes quantify the increase of vulnerability to stressors as people age that gives rise to increasing risk of frailty, disability and death. That deficit accumulation will, on average, double twice between ages 50 and 80 highlights the importance of health in middle age on late life outcomes. PMID:25972341

  6. Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

    EPA Science Inventory

    Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

  7. Using transplants to measure accumulation rates of epiphytic bryophytes in forests of western Oregon

    USGS Publications Warehouse

    Rosso, A.L.; Muir, Patricia S.; Rambo, T.

    2001-01-01

    We sought a simple and effective transplant method that could be used to measure biomass accumulation rates of epiphytic bryophytes. Trials were carried out in the Pseudotsuga menziesii-dominated forests of western Oregon. We tested multiple transplant methods over a 13-month period while comparing accumulation rates of Antitrichia curtipendula (Hedw.) Brid. and Isothecium myosuroides Brid. among an old-growth stand, a young stand, and a recent clearcut. In our study area, Antitrichia is considered to be an old-growth associate while Isothecium is a more ubiquitous species. Methods tested included containment in net bags, containment in hairnets, and directly tying mats to substrates. Three sizes of transplants were tested with both natural and inert artificial substrates. Transplants of approximately five g enclosed in plastic net bags and tied to either natural or artificial substrates worked well for our purposes. Only minor differences were found in mean accumulation rates between the old growth and young stand, though variation in accumulation rates was higher in the old growth. Neither species appeared capable of surviving in the clearcut. Antitrichia accumulated biomass 60% faster in the canopy than in the understory on average. Antitrichia also accumulated at a faster rate than Isothecium, with mean 13-month biomass increases of 11.8 and 3.7% respectively for 5 g transplants in the understory. Our results suggest that Antitrichia's association with old growth may be due more to dispersal or establishment limitations than to a decreased ability to grow in young stands.

  8. Rapid glacial erosion at 1.8 Ma revealed by 4He/3He thermochronometry.

    PubMed

    Shuster, David L; Ehlers, Todd A; Rusmoren, Margaret E; Farley, Kenneth A

    2005-12-01

    Alpine glaciation and river incision control the topography of mountain ranges, but their relative contributions have been debated for years. Apatite 4He/3He thermochronometry tightly constrains the timing and rate of glacial erosion within one of the largest valleys in the southern Coast Mountains of British Columbia, Canada. Five proximate samples require accelerated denudation of the Klinaklini Valley initiating 1.8 +/- 0.2 million years ago (Ma). At least 2 kilometers of overlying rock were removed from the valley at >/=5 millimeters per year, indicating that glacial valley deepening proceeded >/=6 times as fast as erosion rates before approximately 1.8 Ma. This intense erosion may be related to a global transition to enhanced climate instability approximately 1.9 Ma. PMID:16339442

  9. Annual Greenland accumulation rates (2009-2012) from airborne Snow Radar

    NASA Astrophysics Data System (ADS)

    Koenig, L. S.; Ivanoff, A.; Alexander, P. M.; MacGregor, J. A.; Fettweis, X.; Panzer, B.; Paden, J. D.; Forster, R. R.; Das, I.; McConnell, J.; Tedesco, M.; Leuschen, C.; Gogineni, P.

    2015-12-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet (GrIS) through increasing surface melt, emphasizing the need to closely monitor surface mass balance (SMB) in order to improve sea-level rise predictions. Here, we quantify accumulation rates, the largest component of GrIS SMB, at a higher spatial resolution than currently available, using Snow Radar stratigraphy. We use a semi-automated method to derive annual-net accumulation rates from airborne Snow Radar data collected by NASA's Operation IceBridge from 2009 to 2012. An initial comparison of the accumulation rates from the Snow Radar and the outputs of a regional climate model (MAR) shows that, in general, the radar-derived accumulation matches closely with MAR in the interior of the ice sheet but MAR estimates are high over the southeast GrIS. Comparing the radar-derived accumulation with contemporaneous ice cores reveals that the radar captures the annual and long-term mean. The radar-derived accumulation rates resolve large-scale patterns across the GrIS with uncertainties of up to 11 %, attributed mostly to uncertainty in the snow/firn density profile.

  10. Topographic control and accumulation rate of some Holocene coral reefs: south Florida and Dry Tortugas

    USGS Publications Warehouse

    Shinn, E.A.; Hudson, J.H.; Halley, R.B.; Lidz, B.H.

    1977-01-01

    Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.

  11. Radiocarbon dating, chronologic framework, and changes in accumulation rates of holocene estuarine sediments from Chesapeake Bay

    USGS Publications Warehouse

    Colman, Steven M.; Baucom, P.C.; Bratton, J.F.; Cronin, T. M.; McGeehin, J.P.; Willard, D.; Zimmerman, A.R.; Vogt, P.R.

    2002-01-01

    Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelarator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210 Pb and 137 Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

  12. IMPACT OF PARTICLE AGGLOMERATION ON ACCUMULATION RATES IN THE GLASS DISCHARGE RISER OF HLW MELTER

    SciTech Connect

    Matyas, Josef; Jansik, Danielle P.; Owen, Antionette T.; Rodriguez, Carmen P.; Lang, Jesse B.; Kruger, Albert A.

    2013-08-05

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with X-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, and on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185±155 µm, and produced >3 mm thick layer after 120 h at 850 °C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.

  13. Impact Of Particle Agglomeration On Accumulation Rates In The Glass Discharge Riser Of HLW Melter

    SciTech Connect

    Kruger, A. A.; Rodriguez, C. A.; Matyas, J.; Owen, A. T.; Jansik, D. P.; Lang, J. B.

    2012-11-12

    The major factor limiting waste loading in continuous high-level radioactive waste (HLW) melters is an accumulation of particles in the glass discharge riser during a frequent and periodic idling of more than 20 days. An excessive accumulation can produce robust layers a few centimeters thick, which may clog the riser, preventing molten glass from being poured into canisters. Since the accumulation rate is driven by the size of particles we investigated with x-ray microtomography, scanning electron microscopy, and image analysis the impact of spinel forming components, noble metals, and alumina on the size, concentration, and spatial distribution of particles, and on the accumulation rate. Increased concentrations of Fe and Ni in the baseline glass resulted in the formation of large agglomerates that grew over the time to an average size of ~185+-155 {mu}m, and produced >3 mm thick layer after 120 h at 850 deg C. The noble metals decreased the particle size, and therefore significantly slowed down the accumulation rate. Addition of alumina resulted in the formation of a network of spinel dendrites which prevented accumulation of particles into compact layers.

  14. Accumulation Rate of Microbial Biomass at Two Permeable Reactive Barrier Sites

    NASA Astrophysics Data System (ADS)

    Wilkin, R.; Sewell, G.; Puls, R.

    2001-12-01

    Accumulation of mineral precipitates and microbial biomass are key factors that impact the long term performance of in situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero valent iron reactivity and permeability. Results are presented from solid phase and groundwater monitoring studies conducted at two Permeable Reactive Barrier sites, U.S. Coast Guard Support Center (Elizabeth City, North Carolina) and the Denver Federal Center (Lakewood, Colorado). At both sites barrier installations have been in place for approximately five years. Over this period, consistent patterns of spatially heterogeneous microbial biomass accumulation are observed at these sites. The iron-aquifer interface witnesses the greatest accumulation of microbial biomass and mineral precipitates. There accumulation rates are a factor of 3 to 10 times greater than midwall or downgradient regions. Estimates of porosity loss due to mineral and biomass buildup range from about 1 to 5 percent per year of the initial available volume. Phospholipid fatty acid profiles indicate that the PRB biomass is dominated by biomarkers indicative of anaerobic sulfate reducing or iron reducing bacteria. This result is in agreement with acid volatile sulfide concentrations that strongly correlate with biomass concentrations. Upgradient groundwater chemistry and flow rate appear to be the main factors that control the rate (and type) of mineral precipitate formation as well as the rate of biomass accumulation. Notice, this is an abstract of a proposed presentation and does not necessarily reflect EPA policy.

  15. Production of {sup 4}He, {sup 3}He, and tritium from Be irradiated in FFTF-MOTA-2B

    SciTech Connect

    Greenwood, L.R.

    1998-03-01

    The production of {sup 4}He, {sup 3}He, and tritium has been calculated for beryllium irradiated in the Materials Open Test Assembly (MOTA)-2B experiment in the Fast Flux Test Facility (FFTF). Reaction rates were based on adjusted neutron spectra determined from reactor dosimetry measurements at seven different elevations in the irradiation assembly. Equations are given so that gas production, dpa, and neutron fluences can be calculated for any specific elevation in the MOTA-2B assembly.

  16. Incorporation of radiometric tracers in peat and implications for estimating accumulation rates.

    PubMed

    Hansson, Sophia V; Kaste, James M; Olid, Carolina; Bindler, Richard

    2014-09-15

    Accurate dating of peat accumulation is essential for quantitatively reconstructing past changes in atmospheric metal deposition and carbon burial. By analyzing fallout radionuclides (210)Pb, (137)Cs, (241)Am, and (7)Be, and total Pb and Hg in 5 cores from two Swedish peatlands we addressed the consequence of estimating accumulation rates due to downwashing of atmospherically supplied elements within peat. The detection of (7)Be down to 18-20 cm for some cores, and the broad vertical distribution of (241)Am without a well-defined peak, suggest some downward transport by percolating rainwater and smearing of atmospherically deposited elements in the uppermost peat layers. Application of the CRS age-depth model leads to unrealistic peat mass accumulation rates (400-600 g m(-2) yr(-1)), and inaccurate estimates of past Pb and Hg deposition rates and trends, based on comparisons to deposition monitoring data (forest moss biomonitoring and wet deposition). After applying a newly proposed IP-CRS model that assumes a potential downward transport of (210)Pb through the uppermost peat layers, recent peat accumulation rates (200-300 g m(-2) yr(-1)) comparable to published values were obtained. Furthermore, the rates and temporal trends in Pb and Hg accumulation correspond more closely to monitoring data, although some off-set is still evident. We suggest that downwashing can be successfully traced using (7)Be, and if this information is incorporated into age-depth models, better calibration of peat records with monitoring data and better quantitative estimates of peat accumulation and past deposition are possible, although more work is needed to characterize how downwashing may vary between seasons or years. PMID:24946030

  17. Rates and environmental controls of aeolian dust accumulation, Athabasca River Valley, Canadian Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.; Wolfe, Stephen A.

    2010-09-01

    Despite an abundance of sedimentary archives of mineral dust (i.e. loess) accumulations from cold, humid environments, the absence of contemporary process investigations limits paleoenvironmental interpretations in these settings. Dust accumulations measured at Jasper Lake, a seasonally-filled reach of the glacially-fed Athabasca River in the Canadian Rocky Mountains, are some of the highest contemporary rates recorded to date. High deposition rates, including a maximum of 27,632 kg ha -1 month -1, occur during river low-flow periods, but even the lowest deposition rates, occurring during bankfull periods, exceed other contemporary rates of deposition. High rates of dust deposition may be attributed to geomorphic and climatic controls affecting sediment supply, availability and transport, and biologic factors affecting accumulation. Localized confinement of the Jasper River by tributary river alluvial fans has caused channel expansion upstream, and formation of the shallow depositional basin known as Jasper Lake. This localized sedimentary basin, coupled with large seasonal water level fluctuations and suitably high wind speeds, favors seasonal dust production. In addition, a dense source-proximal coniferous forest stand encourages high dust accumulation, via increased aerodynamic roughness and airflow deceleration. The forest stand also appears to act as an efficient dust filter, with the interception and storage of dust by the forest canopy playing a significant role with regards to secondary fallout and sediment accumulation. Overall, these results provide new insights on the environmental controls of dust entrainment and accumulation in cold, humid settings, and help clarify controls on the formation of Holocene river-sourced loess deposits.

  18. Spatial Accumulation-Rate Pattern Inferred from Radar Internal Layers and Point Measurements of Velocity and Accumulation near Taylor Mouth, Victoria Land

    NASA Astrophysics Data System (ADS)

    Waddington, E. D.; Neumann, T. A.; Morse, D. L.; Marshall, H.

    2002-12-01

    Internal layers in ice sheets, as measured by ice-penetrating radar, are most likely isochrones. The depth to a shallow internal layer is proportional to the local accumulation rate. However, low-frequency radars often do not record very shallow layers. High-frequency radars (GPR) record shallow layers, but cannot detect the deeper layers that reflect longer-term patterns of climate. Older, deeper layers are also influenced to an increasing degree by accumulated strain due to ice flow, and by the upstream accumulation rate. For this Geophysical Inverse Problem, our Forward Model is a steady-state ice-flow model with measured ice-sheet surface topography, ice thickness, and flowband width, which tracks particles to create modelled internal layers. Ice motion is driven by the input flux into the upper end of the flowband, and by the accumulation pattern along the flowband. To solve the Inverse Problem, our observations comprise depth of an internal layer, and point measurements of accumulation rate and surface velocity. Associated uncertainties are also required. We use Least-Squares or Singular-Value Decomposition to solve for model parameters (input ice flux, piece-wise linear accumulation-rate profile, and layer age) that minimize the mismatch between the data and the model estimates of the data. If the layer age and its uncertainty are known independently, they can also be used. Variable weights can be assigned to each type of data. The data-resolution matrix shows that, for shallow layers, we can resolve high-wavenumber variations in accumulation rate. For deeper layers, we resolve spatial averages of accumulation rates. We apply the model to a flowband at Taylor Mouth between Taylor Dome and Taylor Glacier. The model finds more variation in the inferred accumulation-rate profile than in the depth-profile of an internal layer. The new accumulation-rate profile produces an improved chronology for an ice core collected along the flowline.

  19. Anisotropic superfluidity of (4)He on a C36 fullerene molecule.

    PubMed

    Park, Sungjin; Kim, Byeongjoon; Kwon, Yongkyung

    2015-09-14

    We have performed path-integral Monte Carlo calculations to study the adsorption of (4)He atoms on two different C36 isomers with the D6h and the D2d symmetries. The radial (4)He density distributions reveal layer-by-layer growth with the first layer being located at a distance of ∼5.5 Å from the C36 molecular center and the second layer at ∼8.3 Å. From the angular density profiles of (4)He, we find different quantum states as the number of (4)He adatoms N varies. For N = 20, we observe commensurate solid structures on both D6h and D2d isomers, where each of 8 hexagon and 12 pentagon centers of the fullerene surfaces is occupied by a single (4)He atom. The second-layer promotion starts beyond N = 38 on both isomers, where a compressible incommensurate structure is observed on the D6h isomer and another commensurate structure on D2d. Between N = 20 and N = 38, the (4)He monolayer on D6h shows several distinct rings of delocalized (4)He atoms along with strongly anisotropic superfluid responses at low temperatures, while isotropic but weak superfluid responses are observed in the (4)He layer on D2d. PMID:26374039

  20. Quantum effects in the sorption kinetics of 4He by mesoporous materials

    NASA Astrophysics Data System (ADS)

    Dolbin, A. V.; Khlistyuck, M. V.; Esel'son, V. B.; Gavrilko, V. G.; Vinnikov, N. A.; Basnukaeva, R. M.; Danchuk, V. V.

    2016-02-01

    Sorption and desorption of 4He by a mesoporous silicate material MCM-41 was studied in the temperature range of 1.5-290 K. It was shown that for T = 25-290 K the thermal activation mechanism is dominant in the sorption kinetics of 4He atoms by an MCM-41 sample. Its activation energy was estimated as Ea ≈ 164.8 K. For T = 12-23 K, the diffusion of 4He atoms in the MCM-41 was practically independent of temperature, which typically occurs when the tunnelling mechanism of diffusion dominates over the thermally activated one. A change in the mobility of 4He atoms in MCM-41 channels was observed at T = 6-12 K, which may be indicative of the formation upon cooling (or decay upon heating) of a 4He monolayer and subsequent multilayers on the inner surfaces of the channels. Below 6 K, the diffusion coefficients of 4He are only weakly temperature dependent, which may be attributed to the behavior of quantum 4He liquid in the MCM-41 channels covered with several layers of 4He atoms.

  1. Anisotropic superfluidity of {sup 4}He on a C{sub 36} fullerene molecule

    SciTech Connect

    Park, Sungjin; Kim, Byeongjoon; Kwon, Yongkyung

    2015-09-14

    We have performed path-integral Monte Carlo calculations to study the adsorption of {sup 4}He atoms on two different C{sub 36} isomers with the D{sub 6h} and the D{sub 2d} symmetries. The radial {sup 4}He density distributions reveal layer-by-layer growth with the first layer being located at a distance of ∼5.5 Å from the C{sub 36} molecular center and the second layer at ∼8.3 Å. From the angular density profiles of {sup 4}He, we find different quantum states as the number of {sup 4}He adatoms N varies. For N = 20, we observe commensurate solid structures on both D{sub 6h} and D{sub 2d} isomers, where each of 8 hexagon and 12 pentagon centers of the fullerene surfaces is occupied by a single {sup 4}He atom. The second-layer promotion starts beyond N = 38 on both isomers, where a compressible incommensurate structure is observed on the D{sub 6h} isomer and another commensurate structure on D{sub 2d}. Between N = 20 and N = 38, the {sup 4}He monolayer on D{sub 6h} shows several distinct rings of delocalized {sup 4}He atoms along with strongly anisotropic superfluid responses at low temperatures, while isotropic but weak superfluid responses are observed in the {sup 4}He layer on D{sub 2d}.

  2. High Rates of Species Accumulation in Animals with Bioluminescent Courtship Displays.

    PubMed

    Ellis, Emily A; Oakley, Todd H

    2016-07-25

    One of the great mysteries of evolutionary biology is why closely related lineages accumulate species at different rates. Theory predicts that populations undergoing strong sexual selection will more quickly differentiate because of increased potential for genetic isolation [1-6]. Whether or not these population genetic processes translate to more species at macroevolutionary scales remains contentious [7]. Here we show that lineages with bioluminescent courtship, almost certainly a sexually selected trait, have more species and faster rates of species accumulation than their non-luminous relatives. In each of ten distantly related animal lineages from insects, crustaceans, annelid worms, and fishes, we find more species in lineages with bioluminescent courtship compared to their sister groups. Furthermore, we find under a Yule model that lineages with bioluminescent courtship displays have significantly higher rates of species accumulation compared to a larger clade that includes them plus non-luminous relatives. In contrast, we do not find more species or higher rates in lineages that use bioluminescence for defense, a function presumably not under sexual selection. These results document an association between the origin of bioluminescent courtship and increased accumulation of species, supporting theory predicting sexual selection increases rates of speciation at macroevolutionary scales to influence global patterns of biodiversity. PMID:27345160

  3. A direct measurement of the 6Li(n,t)4He cross section at sub-thermal neutron energy

    NASA Astrophysics Data System (ADS)

    Yue, A.; Dewey, M.; Gilliam, D.; Nico, J.; Greene, G.; Laptev, A.

    2014-09-01

    The thermal neutron capture cross section for the 6Li(n,t)4He reaction is an important neutron cross section standard. Yet few measurements of it have been performed and the ENDF/B-VII recommended value of (938 . 5 +/- 1 . 3) b is based heavily on measurements performed at higher energies. The first absolute, direct measurement of the 6Li(n,t)4He cross section at sub-thermal neutron energy has been performed at the NIST Center for Neutron Research. An alpha-gamma counter was used to measure the absolute neutron fluence of a monoenergetic neutron beam to sub-0.1% precision. The alpha-gamma counter used a thick, totally absorbing target of 10B-enriched boron carbide. The rate of absorbed neutrons was determined by counting the 478 keV 10B(n, γ)7Li gamma rays with calibrated high-purity germanium detectors. Simultaneously, the absolute rate of neutron-induced charged particles was measured for three thin 6Li targets of known density with a defined solid-angle counter. Using the known density of the 6Li targets and measurements of the rate of charged particles from the 6Li targets, the fluence of the neutron beam, and the energy of the neutron beam, we determine the 6Li(n,t)4He cross section at En = 3 . 3 meV to 0.3% uncertainty.

  4. Nuclear georeactor origin of oceanic basalt 3He/4He, evidence, and implications

    PubMed Central

    Herndon, J. Marvin

    2003-01-01

    Nuclear georeactor numerical simulation results yield substantial 3He and 4He production and 3He/4He ratios relative to air (RA) that encompass the entire 2-SD (2σ) confidence level range of tabulated measured 3He/4He ratios of basalts from along the global spreading ridge system. Georeactor-produced 3He/4He ratios are related to the extent of actinide fuel consumption at time of production and are high near the end of the georeactor lifetime. Georeactor numerical simulation results and the observed high 3He/4He ratios measured in Icelandic and Hawaiian oceanic basalts indicate that the demise of the georeactor is approaching. Within the present level of uncertainty, one cannot say precisely when georeactor demise will occur, whether in the next century, in a million years, or in a billion years from now. PMID:12615991

  5. Investigation of the reaction D(4He, γ)6Li at ultralow energies

    NASA Astrophysics Data System (ADS)

    Burkatovskaya, Yu. B.; Bystritsky, V. M.; Dudkin, G. N.; Krylov, A. R.; Lysakov, A. S.; Gazi, S.; Huran, J.; Nechaev, B. A.; Padalko, V. N.; Sadovsky, A. B.; Tuleushev, Yu. G.; Filipowicz, M.; Philippov, A. V.

    2016-03-01

    The cross section of the reaction D(4He, γ)6Li with titanium and zirconium deuterides as targets is measured for incident 4He+ ion energies of 30 and 36 keV, respectively. The ion beam is generated by a Hall pulsed plasma accelerator. For the first time, upper limits on the cross section of the reaction D(4He, γ)6Li at ultralow energies are imposed (at 90% confidence level): σ ≤ 1.2 × 10-35 cm2 for the TiD2 target and E(4He+) = 30 keV, and σ ≤ 7 × 10-36 cm2 for the ZrD2 target and E(4He+) = 36 keV

  6. Ab initio many-body calculations of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions.

    PubMed

    Navrátil, Petr; Quaglioni, Sofia

    2012-01-27

    We apply the ab initio no-core shell model combined with the resonating-group method approach to calculate the cross sections of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions. These are important reactions for the big bang nucleosynthesis and the future of energy generation on Earth. Starting from a selected similarity-transformed chiral nucleon-nucleon interaction that accurately describes two-nucleon data, we performed many-body calculations that predict the S factor of both reactions. Virtual three-body breakup effects are obtained by including excited pseudostates of the deuteron in the calculation. Our results are in satisfactory agreement with experimental data and pave the way for microscopic investigations of polarization and electron-screening effects, of the (3)H(d,γn)(4)He bremsstrahlung and other reactions relevant to fusion research. PMID:22400830

  7. Holocene Carbon Accumulation Rates in the SPRUCE Bog Prior to Warming and Elevated CO2 Treatment

    NASA Astrophysics Data System (ADS)

    McFarlane, K. J.; Iversen, C. M.; Phillips, J. R.; Brice, D. J.; Hanson, P. J.

    2015-12-01

    In the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) experiment warming and elevated CO2 treatments are being applied to an ombrotrophic spruce bog: the S1 Bog (S1) at Marcell Experimental Forest in northern Minnesota. To provide a historical context for recent and expected experimentally-induced changes in the bog's belowground carbon balance, we reconstructed historical carbon accumulation rates in peat using radiocarbon from 19 peat cores collected from randomly distributed SPRUCE plots. This unusually high number of cores allows us to assess spatial variability in age-depth profiles and accumulation rates across the SPRUCE study area within S1. This data, along with recent C flux measurements, show that the bog has been accumulating carbon for at least 12,0000 years and has continued to be a sink for atmospheric carbon of approximately 150 g C m-2 yr-1 in recent decades. Early Holocene accumulation rates are similar to those reported for other northern peatlands (approximately 25 g C m-2 yr-1), but apparent carbon accumulation decreased substantially around 3,000 years ago (to 5-15 g C m-2 yr-1) and stayed low until the last century. This decrease is considerably larger than that reported for other peatlands and is therefore unlikely to result only from cooling during the Holocene or bog succession. Although no charcoal has been found in peat at this site, evidence from a neighboring bog indicates a considerable amount of peat formed during this period was consumed by fire and it is possible that smoldering fires consumed peat, resulting in low apparent accumulation rates. Past droughts may have also contributed to observed trends by lowering the acrotelm/catotelm boundary, allowing for enhanced aerobic peat decomposition. This work provides important background information on spatial variability and carbon biogeochemistry that will aid in interpretation of climate change simulation experiments at S1.

  8. Nutritive Value and Herbage Accumulation Rates of Pasture Sown to Grass, Legume, and Chicory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Planting pastures to mixtures of forages may benefit herbage production; however, wide fluctuations in botanical composition could cause unstable nutritive value. A grazing study was conducted to examine how forage mixture complexity influenced nutritive value and accumulation rate during spring, su...

  9. Human epididymis protein 4 (HE4) in laboratory medicine and an algorithm in renal disorders.

    PubMed

    Kappelmayer, János; Antal-Szalmás, Péter; Nagy, Béla

    2015-01-01

    Over the past three decades, cancer antigen (CA) 125 has been utilized for monitoring women who were treated for ovarian cancer. However, this tumor marker showed several limitations such as false elevation in benign pelvic diseases and, in turn, no alterations in ovarian tumors at early stages with a relatively high ratio. For more than ten years, the human epididymis protein 4 (HE4) has become available for the routine laboratory repertoire, showing a higher sensitivity and specificity compared to that of CA125 in ovarian malignancies, but also in other types of tumors based on recently accumulated clinical data. Despite its remarkable diagnostic characteristics, in certain cases, the evaluation of HE4 results may be problematic when patients suffer from additional conditions that may alter HE4 level. Besides the direct effects of age and smoking, menopause status and decreased renal function also show a substantial impact on HE4 values, which should be considered in each patient. For this purpose, we attempted to create a new formula and an algorithm that may be helpful to predict the probability of the presence of ovarian tumor by using the concentrations of HE4 and CA125. PMID:25127713

  10. Microscopic description of {sup 4}He + {sup 4}He elastic scattering over the energy range E=100-280 MeV

    SciTech Connect

    El-Azab Farid, M.

    2006-12-15

    Analysis of the differential cross sections for {sup 4}He +{sup 4}He elastic scattering is performed within the framework of the double-folding optical model. Two appropriate effective nucleon-nucleon interactions are employed to generate the {alpha}-{alpha} folded real potentials. The obtained potentials in conjunction with phenomenological Woods-Saxon (WS) derivative imaginary potentials are used to investigate six sets of the elastic scattering data through the energy range 100-280 MeV. Successful reproduction of the data is obtained by both considered interactions. In addition, real phenomenological potentials expressed in a squared WS form are successfully used to reproduce these data.

  11. T(T,2n)4He and 3He(3He,2p)4He: The Reaction Mechanism from Solar Energies to 10 MeV

    NASA Astrophysics Data System (ADS)

    Bacher, A. D.; Brune, C. R.; Sayre, D. B.; Hale, G. M.; Frenje, J. A.; Gatu Johnson, M.

    2016-03-01

    We have studied the energy dependence of the reaction mechanism of the T(t,2n)4He reaction at stellar energies and of its charge symmetric analog reaction 3He(3He,2p)4He at energies up 10 MeV. We find that the reaction mechanism changes dramatically over this energy range in part due to the interference of the two identical fermions in the three-body final state. This contribution is dedicated to the memory of Tom Tombrello, my Ph.D. advisor at Cal Tech, who died in 2014.

  12. Distinct mutation accumulation rates among tissues determine the variation in cancer risk

    PubMed Central

    Hao, Dapeng; Wang, Li; Di, Li-jun

    2016-01-01

    Cancer is believed to be a result of accumulated mutations. However, this concept has not been fully confirmed owing to the impossibility of tracking down the ancestral somatic cell. We sought to verify the concept by exploring the correlation between cancer risk and mutation accumulation among different tissues. We hypothesized that the detected mutations through bulk tumor sequencing are commonly shared in majority, if not all, of tumor cells and are therefore largely a reflection of the mutations accumulated in the ancestral cell that gives rise to tumor. We collected a comprehensive list of mutation frequencies revealed by bulk tumor sequencing, and investigated its correlation with cancer risk to mirror the correlation between mutation accumulation and cancer risk. This revealed an approximate 1:1 relationship between mutation frequency and cancer risk in 41 different cancer types based on the sequencing data of 5,542 patients. The correlation strongly suggests that variation in cancer risk among tissues is mainly attributable to distinct mutation accumulation rates. Moreover, the correlation establishes a baseline to evaluate the effect of non-mutagenic carcinogens on cancer risk. Finally, our mathematic modeling provides a reasonable explanation to reinforce that cancer risk is predominantly determined by the first rate-limiting mutation. PMID:26785814

  13. Distinct mutation accumulation rates among tissues determine the variation in cancer risk.

    PubMed

    Hao, Dapeng; Wang, Li; Di, Li-jun

    2016-01-01

    Cancer is believed to be a result of accumulated mutations. However, this concept has not been fully confirmed owing to the impossibility of tracking down the ancestral somatic cell. We sought to verify the concept by exploring the correlation between cancer risk and mutation accumulation among different tissues. We hypothesized that the detected mutations through bulk tumor sequencing are commonly shared in majority, if not all, of tumor cells and are therefore largely a reflection of the mutations accumulated in the ancestral cell that gives rise to tumor. We collected a comprehensive list of mutation frequencies revealed by bulk tumor sequencing, and investigated its correlation with cancer risk to mirror the correlation between mutation accumulation and cancer risk. This revealed an approximate 1:1 relationship between mutation frequency and cancer risk in 41 different cancer types based on the sequencing data of 5,542 patients. The correlation strongly suggests that variation in cancer risk among tissues is mainly attributable to distinct mutation accumulation rates. Moreover, the correlation establishes a baseline to evaluate the effect of non-mutagenic carcinogens on cancer risk. Finally, our mathematic modeling provides a reasonable explanation to reinforce that cancer risk is predominantly determined by the first rate-limiting mutation. PMID:26785814

  14. Accumulation-rate history at Siple Dome, West Antarctica, using bubble number-density

    NASA Astrophysics Data System (ADS)

    Spencer, M.; Dennison, A.; Alley, R. B.; Fitzpatrick, J. J.; Fegyveresi, J. M.

    2012-12-01

    Past allowable accumulation rate/temperature combinations at Siple Dome, West Antarctica, are estimated from the measured number-density of bubbles in ice core samples. Mass density increase and grain growth in polar firn both are controlled by temperature and accumulation rate, and their integrated effects are recorded in the number-density of bubbles as the firn changes to ice [1]. Accumulation-rate estimates from measured bubble number-density and additional constraints from numerical modeling of firn densification at Siple Dome are consistent with 1-D ice-flow model results that have little change in the thickness of the ice sheet in the central Ross Embayment of West Antarctica since the last glacial maximum [2]. Using methods developed to analyze late-Holocene bubble number-density samples from the West Antarctic Ice Sheet Divide Ice Core Project [3], Siple Dome bubble number-densities show an early-Holocene high in accumulation rate followed by an approximately 10% reduction in accumulation rate between 11.33 ka and 1.863 ka. [1] Spencer, M.K., R.B. Alley and J.J. Fitzpatrick. Developing a bubble number-density paleoclimatic indicator for glacier ice, J. Glaciol. 52(178), 358-364 (2006). [2] E.D. Waddington et al., Decoding the dipstick: thickness of Siple Dome, West Antarctica, at the last glacial maximum, Geology 33(4), 281-284 (2005). [3] J.M. Fegyveresi, et al., Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates, J. Glaciol., 57(204) , 629 - 638 (2011).

  15. Rates of β-amyloid accumulation are independent of hippocampal neurodegeneration

    PubMed Central

    Wiste, Heather J.; Knopman, David S.; Vemuri, Prashanthi; Mielke, Michelle M.; Weigand, Stephen D.; Senjem, Matthew L.; Gunter, Jeffrey L.; Lowe, Val; Gregg, Brian E.; Pankratz, Vernon S.; Petersen, Ronald C.

    2014-01-01

    Objective: To test the hypotheses predicted in a hypothetical model of Alzheimer disease (AD) biomarkers that rates of β-amyloid (Aβ) accumulation on PET imaging are not related to hippocampal neurodegeneration whereas rates of neurodegenerative brain atrophy depend on the presence of both amyloid and neurodegeneration in a population-based sample. Methods: A total of 252 cognitively normal (CN) participants from the Mayo Clinic Study of Aging had 2 or more serial visits with both amyloid PET and MRI. Subjects were classified into 4 groups based on baseline positive/negative amyloid PET (A+ or A−) and baseline hippocampal volume (N+ or N−). We compared rates of amyloid accumulation and rates of brain atrophy among the 4 groups. Results: At baseline, 148 (59%) were amyloid negative and neurodegeneration negative (A−N−), 29 (12%) amyloid negative and neurodegeneration positive (A−N+), 56 (22%) amyloid positive and neurodegeneration negative (A+N−), and 19 (8%) amyloid positive and neurodegeneration positive (A+N+). High rates of Aβ accumulation were found in those with abnormal amyloid at baseline and were not influenced by hippocampal neurodegeneration at baseline. In contrast, rates of brain atrophy were greatest in A+N+. Conclusions: We describe a 2-feature biomarker approach to classifying elderly CN subjects that is complementary to the National Institute on Aging–Alzheimer's Association preclinical staging criteria. Our results support 2 key concepts in a model of the temporal evolution of AD biomarkers. First, the rate of Aβ accumulation is not influenced by neurodegeneration and thus may be a biologically independent process. Second, Aβ pathophysiology increases or catalyzes neurodegeneration. PMID:24706010

  16. Hydroacoustic and spatial analysis of sediment fluxes and accumulation rates in two Virginia reservoirs, USA.

    PubMed

    Clark, E V; Odhiambo, B K; Yoon, S; Pilati, L

    2015-06-01

    Watershed sediment fluxes and reservoir sediment accumulation rates were analyzed in two contrasting reservoir systems in central and western Virginia. Lake Pelham, located in the Piedmont geologic province, is a human-impacted reservoir with a watershed dominated by agricultural, residential and industrial land uses. Conversely, Lake Moomaw has a largely undeveloped watershed characterized by very steep slopes and forested land use located in the Valley and Ridge province. The Revised Universal Soil Loss Equation (RUSLE) and sediment delivery ratios (SDRs) were used to estimate soil losses in the two watersheds. Bathymetric and sediment accumulation surveys of the two reservoirs were also conducted using a multi-frequency hydroacoustic surveying system. The RUSLE/SDR erosion model estimates 2150 kg ha(-1) year(-1) for Lake Pelham and 2720 kg ha(-1) year(-1) for Lake Moomaw, a 410 and 13 % increase from assumed pristine (100 % forested) land use for the respective basins. Mean sediment accumulation rates of 1.51 and 0.60 cm year(-1) were estimated from the hydroacoustic survey of Lake Pelham and Lake Moomaw, respectively. Overall, Lake Moomaw has relatively low sediment accumulation rates; however, the reservoir is vulnerable to increases in sediment fluxes with further human development due to the steep slopes and highly erodible colluvial soils that characterize the basin. Higher erosion and sediment accumulation rates in Lake Pelham are most likely reflecting the impact of human development on sedimentation processes, where the loss of vegetal buffers and increase in impervious surfaces exacerbates both the surficial soil losses as well as intrinsic stream sediment production leading to the current annual reservoir capacity loss of 0.4 %. PMID:25563837

  17. Interlayer correlation between two 4He monolayers adsorbed on both sides of α -graphyne

    NASA Astrophysics Data System (ADS)

    Ahn, Jeonghwan; Park, Sungjin; Lee, Hoonkyung; Kwon, Yongkyung

    2015-07-01

    Path-integral Monte Carlo calculations have been performed to study the 4He adsorption on both sides of a single α -graphyne sheet. For investigation of the interlayer correlation between the upper and the lower monolayers of 4He adatoms, the 4He-substrate interaction is described by the sum of the 4He-C interatomic pair potentials for which we use both Lennard-Jones and Yukawa-6 anisotropic potentials. When the lower 4He layer is a C4 /3 commensurate solid, the upper-layer 4He atoms are found to form a kagome lattice structure at a Mott-insulating density of 0.0706 Å-2 and a commensurate solid at an areal density of 0.0941 Å-2 for both substrate potentials. The correlation between upper- and lower-layer pseudospins, which were introduced in Kwon et al. [Phys. Rev. B 88, 201403(R) (2013)], 10.1103/PhysRevB.88.201403 for two degenerate configurations of three 4He atoms in a hexagonal cell, depends on the substrate potential used; with the substrate potential based on the anisotropic Yukawa-6 pair potentials, the Ising pseudospins of both 4He layers are found to be antiparallel to each other whereas the parallel and antiparallel pseudospin alignments between the two 4He layers are nearly degenerate with the Lennard-Jones potentials. This is attributed to the difference in the interlayer distance, which is ˜4 Å with the Yukawa-6 substrate potential but as large as ˜4.8 Å with the Lennard-Jones potential.

  18. Viscosity of liquid {sup 4}He and quantum of circulation: Are they related?

    SciTech Connect

    L’vov, Victor S. E-mail: skrbek@fzu.cz; Skrbek, Ladislav E-mail: skrbek@fzu.cz; Sreenivasan, Katepalli R. E-mail: skrbek@fzu.cz

    2014-04-15

    In the vicinity of the superfluid transition in liquid {sup 4}He, we explore the relation between two apparently unrelated physical quantities—the kinematic viscosity, ν, in the normal state and the quantum of circulation, κ, in the superfluid state. The model developed here leads to the simple relationship ν ≈ κ/6, and links the classical and quantum flow properties of liquid {sup 4}He. We critically examine available data relevant to this relation and find that the prediction holds well at the saturated vapor pressure. Additionally, we predict the kinematic viscosity for liquid {sup 4}He along the λ-line at negative pressures.

  19. Triple oxygen isotopic composition of the high-3He/4He mantle

    NASA Astrophysics Data System (ADS)

    Starkey, N. A.; Jackson, C. R. M.; Greenwood, R. C.; Parman, S.; Franchi, I. A.; Jackson, M.; Fitton, J. G.; Stuart, F. M.; Kurz, M.; Larsen, L. M.

    2016-03-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.

  20. Soil carbon stocks and their rates of accumulation and loss in a boreal forest landscape

    USGS Publications Warehouse

    Rapalee, G.; Trumbore, S.E.; Davidson, E.A.; Harden, J.W.; Veldhuis, H.

    1998-01-01

    Boreal forests and wetlands are thought to be significant carbon sinks, and they could become net C sources as the Earth warms. Most of the C of boreal forest ecosystems is stored in the moss layer and in the soil. The objective of this study was to estimate soil C stocks (including moss layers) and rates of accumulation and loss for a 733 km2 area of the BOReal Ecosystem-Atmosphere Study site in northern Manitoba, using data from smaller-scale intensive field studies. A simple process-based model developed from measurements of soil C inventories and radiocarbon was used to relate soil C storage and dynamics to soil drainage and forest stand age. Soil C stocks covary with soil drainage class, with the largest C stocks occurring in poorly drained sites. Estimated rates of soil C accumulation or loss are sensitive to the estimated decomposition constants for the large pool of deep soil C, and improved understanding of deep soil C decomposition is needed. While the upper moss layers regrow and accumulate C after fires, the deep C dynamics vary across the landscape, from a small net sink to a significant source. Estimated net soil C accumulation, averaged for the entire 733 km2 area, was 20 g C m-2 yr-1 (28 g C m-2 yr-1 accumulation in surface mosses offset by 8 g C m-2 yr-1 lost from deep C pools) in a year with no fire. Most of the C accumulated in poorly and very poorly drained soils (peatlands and wetlands). Burning of the moss layer in only 1% of uplands would offset the C stored in the remaining 99% of the area. Significant interannual variability in C storage is expected because of the irregular occurrence of fire in space and time. The effects of climate change and management on fire frequency and on decomposition of immense deep soil C stocks are key to understanding future C budgets in boreal forests.

  1. Rate of production, dissolution and accumulation of biogenic solids in the ocean

    NASA Technical Reports Server (NTRS)

    Arrhenius, G.

    1988-01-01

    The equatorial current system, by its response to global circulation changes, provides a unique recording mechanism for long range climatic oscillations. A permanent record of the changes in rate of upwelling and organic production is generated in the equatorial deep sea sediments, particularly by such biogenic components which are unaffected by secondary dissolution. In order to determine the rates of accumulation of various sedimentary components, a reliable differential measurement of age of the strata must be obtained. Various approaches to this problem are reviewed, and sources of error discussed. Secondary dissolution of calcium carbonate introduces a substantial and variable difference between the dissolution-modified, and hence a priori unknown, rate of deposition on one hand and the rate of accumulation, derivable from the observed concentration, on the other. The cause and magnitude of these variations are of importance, particularly since some current dating schemes are based on assumed constancy in the rate of accumulation of this and, in some cases, also all other sedimentary components. The concepts used in rate evaluation are discussed with emphasis on the difference between the state of dissolution, an observable property of the sediment, and the rate of dissolution, a parameter that requires deduction of the carbonate fraction dissolved, and of the time differential. As a most likely cause of the enhanced state of dissolution of the interglacial carbonate sediments is proposed the lowered rates of biogenic production and deposition, which cause longer exposure of the carbonate microfossils to corrosion in the bioturbated surface layer of the sediment. Historical perspective is included in the discussion in view of the dedication of the Symposium to Hans Pettersson, the leader of the Swedish Deep Sea Expedition 1947-1948, an undertaking that opened a new era in deep sea research and planetary dynamics.

  2. The distribution of the heavy metal accumulation rate in the biomass of three Daphnia species

    SciTech Connect

    Gajula, V.K.; Hovorka, J.; Stuchlik, E.

    1995-12-31

    The difference in the accumulation rate of a mixture of heavy metals in aquatic organisms is of considerable interest because of its importance in the prediction of the effect of pollutants in aquatic systems. In this study the authors are making an effort to evaluate the accumulation patterns of pollutants in aquatic organisms by establishing a relation between the level of an accumulated mixture of heavy metals (Cd, Zn, Pb, As, Hg) in individuals of Daphnia magna, Daphnia pulicaria and Daphnia galeata and its dry weight with respect to the form of heavy metals in the aquatic environment. One age group of Daphnia species (10 day old) were exposed to 5 ppb, 10 ppb and 20 ppb of the mixture of heavy metals for 24 hours in three different experiments. In the first experiment the mixture of heavy metals was present exclusively in labelled algae (Scendesmus actus), in the second in an aquatic medium with non labelled algae, and in the third experiment the mixture of heavy metals was dissolved in the aquatic medium only without the addition of algae. The concentration of the heavy metal mixture in individuals of D.magna; D.pulicaria and D.galeata was determined using atomic absorption spectrometry. Results were statistically evaluated and the rate of accumulation and influence of various heavy metals in the biomass of three Daphnia species is discussed.

  3. Kaonic 3He and 4He X-ray measurements in SIDDHARTA

    NASA Astrophysics Data System (ADS)

    Ishiwatari, Tomoichi; Bazzi, M.; Beer, G.; Berucci, C.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Clozza, A.; Corradi, G.; Curceanu (Petrascu), C.; d'Uffizi, A.; Fiorini, C.; Ghio, F.; Girolami, B.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Lucherini, V.; Marton, J.; Okada, S.; Pietreanu, D.; Piscicchia, K.; Poli Lener, M.; Ponta, T.; Quaglia, R.; Rizzo, A.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Wünschek, B.; Zmeskal, J.

    2012-05-01

    The SIDDHARTA experiment measured the kaonic 3He and 4He 3 d →2 p X-ray transitions using gaseous targets for the first time. The strong-interaction shift both of the kaonic 3He and 4He 2 p states was determined with a precision of a few eV. The shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70's and 80's, while it is consistent with the recent result of the KEK E570 experiment, as well as the theoretical calculated values. Therefore, the problem on kaonic helium (the "kaonic helium puzzle") was definitely solved. The first observation of the kaonic 3He X-rays was also achieved in the SIDDHARTA experiment. The shift both of kaonic 3He and 4He was found to be as small as a few eV.

  4. Kaonic 3He and 4He X-ray measurements in SIDDHARTA

    NASA Astrophysics Data System (ADS)

    Ishiwatari, Tomoichi; Bazzi, M.; Beer, G.; Berucci, C.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Clozza, A.; Corradi, G.; Curceanu (Petrascu), C.; d'Uffizi, A.; Fiorini, C.; Ghio, F.; Girolami, B.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Lucherini, V.; Marton, J.; Okada, S.; Pietreanu, D.; Piscicchia, K.; Poli Lener, M.; Ponta, T.; Quaglia, R.; Rizzo, A.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Wünschek, B.; Zmeskal, J.

    The SIDDHARTA experiment measured the kaonic 3He and 4He 3d →2p X-ray transitions using gaseous targets for the first time. The strong-interaction shift both of the kaonic 3He and 4He 2p states was determined with a precision of a few eV. The shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70's and 80's, while it is consistent with the recent result of the KEK E570 experiment, as well as the theoretical calculated values. Therefore, the problem on kaonic helium (the "kaonic helium puzzle") was definitely solved. The first observation of the kaonic 3He X-rays was also achieved in the SIDDHARTA experiment. The shift both of kaonic 3He and 4He was found to be as small as a few eV.

  5. Proposal for measurement of 4He II condensate - A reply to recent criticisms

    NASA Astrophysics Data System (ADS)

    Cummings, F. W.; Hyland, G. J.; Rowlands, G.

    1981-11-01

    Recent criticisms of a method to measure the temperature-dependent condensate fraction in 4He II, proposed by the authors some time ago, are assessed and found to be insufficient to discredit our procedure.

  6. Synthesis of passive microwave and radar altimeter data for estimating accumulation rates of polar snow

    NASA Technical Reports Server (NTRS)

    Davis, Curt H.

    1993-01-01

    In this paper, we compare dry-snow extinction coefficients derived from radar altimeter data with brightness temperature data from passive microwave measurements over a portion of the East Antarctic plateau. The comparison between the extinction coefficients and the brightness temperatures shows a strong negative correlation, where the correlation coefficients ranged from -0.87 to -0.95. The extinction coefficient of the dry polar snow decreases with increasing surface elevation, while the average brightness temperature increases with surface elevation. Our analysis shows that the observed trends are related to geographic variations in scattering coefficient of snow, which in turn are controlled by variations in surface temperature and snow accumulation rate. By combining information present in the extinction coefficient and brightness temperature data sets, we develop a model that can be used to obtain quantitative estimates of the accumulation rate of dry polar snow.

  7. The Triple Oxygen Isotopic Composition of High 3He/4He Mantle

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Parman, S. W.; Starkey, N.; Greenwood, R.; Franchi, I.; Jackson, M. G.; Fitton, J. G.; Stewart, F. M.; Larsen, L. M.

    2015-12-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes [1]. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the ∆17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 x SEM) ‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (~5 ‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that oxygen remains coupled to the more incompatible elements during melt production and migration and that the intermediate δ18O value is a feature of the mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source. [1] S

  8. Balancing sample accumulation and DNA degradation rates to optimize noninvasive genetic sampling of sympatric carnivores.

    PubMed

    Lonsinger, Robert C; Gese, Eric M; Dempsey, Steven J; Kluever, Bryan M; Johnson, Timothy R; Waits, Lisette P

    2015-07-01

    Noninvasive genetic sampling, or noninvasive DNA sampling (NDS), can be an effective monitoring approach for elusive, wide-ranging species at low densities. However, few studies have attempted to maximize sampling efficiency. We present a model for combining sample accumulation and DNA degradation to identify the most efficient (i.e. minimal cost per successful sample) NDS temporal design for capture-recapture analyses. We use scat accumulation and faecal DNA degradation rates for two sympatric carnivores, kit fox (Vulpes macrotis) and coyote (Canis latrans) across two seasons (summer and winter) in Utah, USA, to demonstrate implementation of this approach. We estimated scat accumulation rates by clearing and surveying transects for scats. We evaluated mitochondrial (mtDNA) and nuclear (nDNA) DNA amplification success for faecal DNA samples under natural field conditions for 20 fresh scats/species/season from <1-112 days. Mean accumulation rates were nearly three times greater for coyotes (0.076 scats/km/day) than foxes (0.029 scats/km/day) across seasons. Across species and seasons, mtDNA amplification success was ≥95% through day 21. Fox nDNA amplification success was ≥70% through day 21 across seasons. Coyote nDNA success was ≥70% through day 21 in winter, but declined to <50% by day 7 in summer. We identified a common temporal sampling frame of approximately 14 days that allowed species to be monitored simultaneously, further reducing time, survey effort and costs. Our results suggest that when conducting repeated surveys for capture-recapture analyses, overall cost-efficiency for NDS may be improved with a temporal design that balances field and laboratory costs along with deposition and degradation rates. PMID:25454561

  9. Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

    NASA Astrophysics Data System (ADS)

    Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

    2015-12-01

    Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.

  10. Organic Carbon, Nitrogen and Phosphorus Accumulation Rates in the Soils of the Everglades Mangrove Ecotone

    NASA Astrophysics Data System (ADS)

    Smoak, J. M.; Breithaupt, J. L.; Sanders, C. J.

    2015-12-01

    One of the fundamental questions with regard to coastal ecotones relates to their role in the transformation, transport and storage of biogeochemically important constituents and how that role may be altered by climate change. Coastal wetlands provide a range of valuable ecosystem services including sequestering organic carbon (OC) and nutrients in their soils at rates greater than terrestrial ecosystems on a per area basis. As such the Everglades mangrove ecotone, the largest contiguous mangrove forest in North America, is a biogeochemical "hotspot" at the interface of freshwater marsh and the Gulf of Mexico. Over the last one hundred years this region has been impacted by a reduction in freshwater flow and a sea-level rise (SLR) of 2.3 mm/yr which combined to cause a landward shift in the ecotone. This creates an ideal setting to examine climate induced alterations in the mangrove-ecotone biogeochemical cycle. The ability of the Everglades mangrove forest to keep pace with SLR depends largely on the rate of organic matter accumulation as that accumulation is a key contributor to accretion. However, the basic threat from SLR can be exacerbated in some areas by accelerating organic matter mineralization due to increasing salinity. The increase in salinity supplies sulfate which functions as a terminal electron acceptor that soil microbes can utilize to enhance mineralization in the brackish ecotone regions of coastal wetlands. To investigate these processes, we measured mangrove forest soil accretion, OC, N and P accumulation rates over the most recent 10, 50 and 100 year periods (via 210Pb dating) from the Gulf of Mexico to the upper freshwater reaches of the mangrove forest within Everglades National Park. Lower organic carbon accumulation rates compared to the rest of the system were found in the ecotone region most susceptible to enhanced organic matter mineralization.

  11. Effect of confinement on phase-separation and superfluid transition in ^3 He-^4 He mixtures

    NASA Astrophysics Data System (ADS)

    Shenoy, V. B.; Saam, W. F.

    1996-03-01

    We derive the phase diagram of ^3 He - ^4 He mixtures confined between parallel plates within phenomelogical Landau theory. The analyses focus on the effect of the separation between the plates and the magnitude of surface field ( which is a measure of preference for ^4He rich phase) on phase-separation and superfluid transition in the confined mixtures. Connection to recent experiments on He mixtures in aerogel is made.

  12. Polarization of3He and3He-4He mixtures with the castaing-nozieres method

    NASA Astrophysics Data System (ADS)

    van Woerkens, C. M. C. M.; Remeijer, P.; Steel, S. C.; Jochemsen, R.; Frossati, G.

    1996-01-01

    We describe experiments employing a strongly improved technique to prepare highly polarized3He and3He-4He mixtures. The polarization is obtained with the rapid melting method. A novel design cell using Vespel SP-1 (a sintered form of polyimide) can reach relative volume changes of 17%, which is required to decompress a completely solid3He-4He mixture to a completely liquid state at 23 bar.

  13. New Phenomenon of the Hysteresis of 4He in Vycor Glass

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Xu, Xiaonong; Yan, Yong; A, L. Thomson; D, F. Brewer; S, Haynes; N, Sharma

    1992-02-01

    The low temperature part of hysteresis curves of the freezing and melting processes of 4He in vycor glass with the lowest temperature 0.4K were measured, as the pressure ranged from 36.45 to 55.18 (105 Pa). Some novel characteristics of these curves were observed in such high temperature and pressure range. They may result from the existence of superfluid 4He.

  14. Iunconsistencies in Accumulation Rates of Black Sea Sediments Inferred from Records of Laminae and 210Pb

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Anderson, R. F.

    1992-04-01

    Recently-published estimates for the age of the unit 1-unit 2 contact in Black Sea sediments based on accelerator mass spectrometry (AMS) 14C measurements [Jones, 1990; Calvert et al., 1991] appear to be older than those based on the previously published chronology based on lamina couplets [Degens et al., 1980; Hay, 1988] by a factor of 2 to 3. To help reconcile the differences, we compare sediment accumulation rates based on the 210Pb method with estimates based on lamina counts for two cores from the Black Sea abyssal plain. Accumulation rates estimated using the 210Pb technique have varied little over the last 150 years from the averages of 55 and 50 g m-2 yr-1 at stations in the western and eastern basins, respectively. These values are about a factor of 2 lower than accumulation rates derived by counting lamina couplets over the dated intervals. Close examination of the laminae suggests that the discrepancy exists both because it is difficult to count the very fine laminae and because a complete couplet is not deposited every year. In order to provide a useful stratigraphic horizon for future investigators studying sedimentary records of the Black Sea, we estimate the age of a distinct black marker horizon which can be easily identified across the entire abyssal plain to be 150±8 years (deposited in 1838±8 A.D.).

  15. A high-temperature supersolid of 4He in a one-dimensional periodic potential

    DOE PAGESBeta

    Olsen, Raina J

    2015-01-01

    The search for robust experimental proof of supersolidity has encountered many complicating factors, such as temperature dependent changes in the mechanical properties of solid 4He which mimic the signature of superfluid flow. As a result, the physical existence and true nature of this unique state of matter are still under debate. Here we consider 4He stabilized by a one-dimensional periodic potential whose lattice spacing is similar to the length scale of the 4He-4He interaction. We use the Bogoliubov transformation to calculate the excitation spectrum, finding that when interactions between nearest or next-nearest neighbors are attractive, there is a finite positivemore » gap in energy between the delocalized ground state and the lowest energy excitations which, under certain conditions, is significantly larger than both the melting temperature and the lambda temperature. This means that it should be possible to observe a supersolid at a high enough temperature that superfluidity in bulk liquid 4He or changes in the mechanical properties of bulk solid 4He do not obscure it. The properties of experimentally achievable materials which could support this type of supersolid are also discussed.« less

  16. Accumulation rates of Th-230, Pa-231, and some transition metals on the Bermuda Rise

    USGS Publications Warehouse

    Bacon, M.P.; Rosholt, J.N.

    1982-01-01

    Measurements of 238U, 234U, 230Th, 232Th, 231Pa, Mn, Fe, Co, Ni, Cu, and Zn were made on 23 samples from core GPC-5, a 29-m giant piston core from a water depth of 4583 m on the northeastern Bermuda Rise (33??41.2???N, 57??36.9???W). This area is characterized by rapid deposition of sediment transported by abyssal currents. Unsupported 230Th and 231Pa are present throughout the core but, because of large variations in the sedimentation rate, show marked departures from exponential decay with depth. The trend with depth of the 231Paex 230Thex ratio is consistent with the average accumulation rate of 36 cm/1000 y reported earlier on the basis of radiocarbon dating and CaCO3 stratigraphy. When expressed on a carbonate-free basis, concentrations of Mn, Co, Ni, Cu, Zn, 230Thex, and 231Paex all show cyclic variations positively correlated with those of CaCO3. The correlations can be explained by a model in which all of these constituents, including CaCO3, are supplied to the sediments from the water column at a constant rate. Concentration variations are controlled mainly by varying inputs of terrigenous detritus, with low inputs occurring during interglacials and high inputs during glacials. Relationships between the metal and 230Thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column. The results, in ??g/cm2-1000 y, are: 4300 ?? 1100 for Mn, 46 ?? 16 for Ni and 76 ?? 26 for Cu. These rates are somewhat larger than ocean-wide averages estimated by other methods, and the absolute rate of 230Th accumulation in GPC-5 averages about nine times higher than production in the overlying water column. This part of the Bermuda Rise and similar bottom-current deposits may act as important accumulators of elements scavenged from seawater. ?? 1982.

  17. Accumulation rate and mixing of shelf sediments in the Monterey Bay National Marine Sanctuary

    USGS Publications Warehouse

    Lewis, R.C.; Coale, K.H.; Edwards, B.D.; Marot, M.; Douglas, J.N.; Burton, E.J.

    2002-01-01

    The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm-2 yr-1 and range from 0.42 g cm-2 yr-1 to 0.12 g cm-2 yr-1. Accumulation rates were highest at mid-shelf water depths (60-100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5-13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column. ?? 2002 Elsevier Science B.V. All rights reserved.

  18. Sediment mixing and accumulation rate effects on radionuclide depth profiles in Hudson estuary sediments

    SciTech Connect

    Olsen, C.R.; Simpson, H.J.; Peng, T.; Bopp, R.F.; Trier, R.M.

    1981-11-20

    Measured anthropogenic radionuclide profiles in sediment cores from the Hudson River estuary were compared with profiles computed by using known input histories of radionuclides to the estuary and mixing coefficients which decreased exponentially with depth in the sediment. Observed /sup 134/Cs sediment depth profiles were used in the mixing rate computation because reactor releases were the only significant source for this nuclide, whereas the inputs of /sup 137/Cs and /sup 239.240/Pu to the estuary were complicated by runoff or erosion in upstream areas, in addition to direct fallout from precipitation. Our estimates for the rates of surface sediment mixing in the low salinity reach of the estuary range from 0.25 to 1 cm/sup 2//yr, or less. In some areas of the harbor adjacent to New York City, were fine-particle accumulation rates are generally >3 cm/yr, and often as high as 10 to 20 cm/yr, sediment mixing rates as high as 10 cm/sup 2//yr would have little effect on radionuclide peak distributions. Consequently, anthropogenic radionuclide maximum activities in subsurface sediments of the Hudson appear to be useful as time-stratigraphic reference levels, which can be correlated with periods of maximum radionuclide inputs for estimating rates and patterns of sediment accumulation.

  19. Elementary Excitations in Solid and Liquid 4He at the Melting Pressure

    NASA Astrophysics Data System (ADS)

    Todoshchenko, I. A.; Alles, H.; Junes, H. J.; Manninen, M. S.; Parshin, A. Y.; Tsepelin, V.

    2008-02-01

    Recent discovery of a nonclassical rotational inertia (NCRI) in solid 4He below 0.2 K by Kim and Chan has revived great interest in the problem of supersolidity and initiated intensive study on the properties of solid 4He. A direct proof that the onset of NCRI corresponds to the supersolid transition would be the observation of a corresponding drop of the entropy of solid 4He below the transition temperature. We have measured the melting pressure of ultrapure 4He in the temperature range from 0.01 to 0.45 K with several single crystals grown at different pressures and with the accuracy of 0.5 μbar. In addition, supplementary measurements of the pressure in liquid 4He at constant volume have been performed, which allowed us to eliminate the contribution of the temperature-dependent properties of the pressure gauge from the measured melting pressure data. With the correction to the temperature-dependent sensitivity of the pressure gauge, the variation of the melting pressure of 4He below 320 mK obeys the pure T 4 law due to phonons with the accuracy of 0.5 μbar, and no sign of the transition is seen (Todoshchenko et al. in JETP Lett. 85:454, 2007). This sets the upper limit of ˜5ṡ10-8 R for a possible excess entropy in high-quality 4He crystals below 320 mK. At higher temperatures the contribution from rotons in the superfluid 4He has been observed. The thermal expansion coefficient of the superfluid 4He has been measured in the range from 0.01 to 0.7 K with the accuracy of ˜10-7 1/K, or by two orders of magnitude better than in previous measurements. The roton contributions to the melting pressure and to the pressure in liquid at a constant volume are consistent and yield the value of 6.8 K for the roton gap, which is very close to the values obtained with other methods. As no contribution due to weakly interacting vacancies to the melting pressure of 4He has been observed, the lower limit of about 5.5 K for their activation energy can be set.

  20. Trojan horse particle invariance studied with the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He reactions

    SciTech Connect

    Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Bertulani, C.; Mukhamedzhanov, A.; Blokhintsev, L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Kiss, G. G.; Li, C.; Tumino, A.

    2011-04-15

    The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree {sup 3}He({sup 6}Li,{alpha}{alpha})H and {sup 3}He({sup 7}Li,{alpha}{alpha}){sup 2}H reactions. The cross sections for the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of {sup 3}He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases.

  1. Carbon accumulation rate of peatland in the High Arctic, Svalbard: Implications for carbon sequestration

    NASA Astrophysics Data System (ADS)

    Nakatsubo, Takayuki; Uchida, Masaki; Sasaki, Akiko; Kondo, Miyuki; Yoshitake, Shinpei; Kanda, Hiroshi

    2015-06-01

    Moss tundra that accumulates a thick peat layer is one of the most important ecosystems in the High Arctic, Svalbard. The importance of this ecosystem for carbon sequestration was estimated from the apparent rates of carbon accumulation based on the 14C age and amount of peat in the active layer. The study site at Stuphallet, Brøgger Peninsula, northwestern Svalbard was covered with a thick peat layer dominated by moss species such as Calliergon richardsonii, Paludella squarrosa, Tomenthypnum nitens, and Warnstorfia exannulata. The average thickness of the active layer (brown moss and peat) was approximately 28 cm in 1 August 2011. The calibrated (cal) age of peat from the bottom of the active layer (20-30 cm below the peatland surface) ranged from 81 to 701 cal yr BP (median value of 2σ range). Based on the total carbon (4.5-9.2 kg C m-2), the apparent rate of carbon accumulation in the active layer was 9.0-19.2 (g C m-2 yr-1), which is similar to or greater than the net ecosystem production or net primary production reported for other vegetation types in this area. Our data suggest that moss tundra plays an important role in carbon sequestration in this area.

  2. Vibrational effects in a weakly-interacting quantum solvent: The CO molecule in 4He gas and in 4He droplets

    NASA Astrophysics Data System (ADS)

    Paesani, F.; Gianturco, F. A.

    2002-06-01

    The coupling between the intermolecular motion and the internal vibrational coordinate in the He-CO system is computed at the post-Hartree-Fock level using the DFT+DISP model already employed by us for similar systems and reviewed here in the main text. The quality of the computation of such weak effects is compared with other, earlier model calculations and then used for the evaluation of the vibrational relaxation cross sections of the CO molecule diluted in 4He gas. A further assessment of the vibrational coupling is carried out by computing, with a stochastic approach that employs the Diffusion Monte Carlo method, the effects on the vibrational frequency of the CO impurity from its immersion in 4He droplets of variable size. Both sets of results are analyzed and discussed to gauge the reliability of the computed coupling vis-a-vis one of those suggested by earlier calculations. This study provides further evidence on the difficulty of quantitatively obtaining from calculations the extremely small effects connected with molecular vibrational features in this system and caused by the weak interaction between the title molecule and a quantum solvent like 4He.

  3. Systems Level Regulation of Rhythmic Growth Rate and Biomass Accumulation in Grasses

    SciTech Connect

    Kay, Steve A.

    2013-05-02

    Several breakthroughs have been recently made in our understanding of plant growth and biomass accumulation. It was found that plant growth is rhythmically controlled throughout the day by the circadian clock through a complex interplay of light and phytohormone signaling pathways. While plants such as the C4 energy crop sorghum (Sorghum bicolor (L.) Moench) and possibly the C3 grass (Brachypodium distachyon) also exhibit daily rhythms in growth rate, the molecular details of its regulation remain to be explored. A better understanding of diurnally regulated growth behavior in grasses may lead to species-specific mechanisms highly relevant to future strategies to optimize energy crop biomass yield. Here we propose to devise a systems approach to identify, in parallel, regulatory hubs associated with rhythmic growth in C3 and C4 plants. We propose to use rhythmicity in daily growth patterns to drive the discovery of regulatory network modules controlling biomass accumulation.

  4. Measurements on the melting curve of ^4He down to 10 mK

    NASA Astrophysics Data System (ADS)

    Alles, Harry

    2007-03-01

    Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and Chan has initiated an intensive study on the properties of solid ^4He. As Kim and Chan have interpreted their observation as the evidence of supersolid behavior, we have decided to measure very accurately the melting curve of ^4He because, as the slope of the melting curve is proportional to the difference in the entropy of the liquid and solid phases, there should be an anomaly at the possible supersolid transition. We have measured the melting curve of ^4He with the accuracy of about 0.5 microbar with ^4He crystals which had various concentration of defects. All our samples showed only the expected T^4 dependence due to phonons without any sign of the supersolid transition in the temperature range of 80400 mK. Below 80 mK we observed a small deviation from T^4 dependence which, however, cannot be attributed to the supersolid transition because our recent measurements with the cell containing liquid sample only suggest that this deviation is by the temperature variation of properties of BeCu membrane of our capacitive pressure gauge. In addition to our published data with ^4He of natural purity [Phys. Rev. Lett. 97, 165302 (2006)] we also report our recent measurements of the melting curve with ultra pure ^4He (0.3 ppb of ^3He impurities). In these measurements we followed optically the shape of the sample crystals which had very good quality.

  5. LATE CENOZOIC INCREASE IN ACCUMULATION RATES OF TERRESTRIAL SEDIMENT: How Might Climate Change Have Affected Erosion Rates?

    NASA Astrophysics Data System (ADS)

    Molnar, Peter

    2004-05-01

    Accumulation rates of terrestrial sediment have increased in the past few million years both on and adjacent to continents, although not everywhere. Apparently, erosion has increased in elevated terrain regardless of when last tectonically active or what the present-day climate. In many regions, sediment coarsened abruptly in late Pliocene time. Sparser data suggest increased sedimentation rates at 15 Ma, approximately when oxygen isotopes in benthic foraminifera imply high-latitude cooling. If climate change effected accelerated erosion, understanding how it did so remains the challenge. Some obvious candidates, such as lowered sea level leading to erosion of continental shelves or increased glaciation, account for increased sedimentation in some, but not all, areas. Perhaps stable climates that varied slowly allowed geomorphic processes to maintain a state of equilibrium with little erosion until 34 Ma, when large oscillations in climate with periods of 20,00040,000 years developed and denied the landscape the chance to reach equilibrium.

  6. [Dynamics simulation on plant growth, N accumulation and utilization of processing tomato at different N fertilization rates].

    PubMed

    Wang, Xin; Ma, Fu-Yu; Diao, Ming; Fan, Huam; Cui, Jing; Jia, Biao; He, Hai-Bing; Liu, Qi

    2014-04-01

    Three field experiments were conducted to simulate the dynamics of aboveground biomass, N accumulation and utilization of drip-irrigated processing tomatoes at different N fertilization rates (0, 75, 150, 300, 450, or 600 kg x hm(-2)). The results showed that Logistic models best described the changes in aboveground biomass, N accumulation, and utilization of accumulated N efficiency with the physiological development time (PDT). Rapid accumulation of N began about 4-6 d (PDT) earlier than the rapid accumulation of aboveground biomass. The momentary utilization rate of N (NMUR) increased after emergence, reached a single peak, and then decreased. The N accumulation, aboveground biomass and yield were highest in the 300 kg x hm(-2) treatment. The quadratic model indicated that application rate of 349 to 382 kg N x hm(-2) was optimum for drip-irrigated processing tomatoes in northern Xinjiang. PMID:25011297

  7. An integral method to estimate the moment accumulation rate on the Creeping Section of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Tong, Xiaopeng; Sandwell, David T.; Smith-Konter, Bridget

    2015-10-01

    Moment accumulation rate (also referred to as moment deficit rate) is a fundamental quantity for evaluating seismic hazard. The conventional approach for evaluating moment accumulation rate of creeping faults is to invert for the slip distribution from geodetic measurements, although even with perfect data these slip-rate inversions are non-unique. In this study, we show that the slip-rate versus depth inversion is not needed because moment accumulation rate can be estimated directly from surface geodetic data. We propose an integral approach that uses dense geodetic observations from Interferometric Synthetic Aperture Radar (InSAR) and the Global Positioning System (GPS) to constrain the moment accumulation rate. The moment accumulation rate is related to the integral of the product of the along-strike velocity and the distance from the fault. We demonstrate our methods by studying the Creeping Section of the San Andreas fault observed by GPS and radar interferometry onboard the ERS and ALOS satellites. Along-strike variation of the moment accumulation rate is derived in order to investigate the degree of partial locking of the Creeping Section. The central Creeping Segment has a moment accumulation rate of 0.25-3.1 × 1015 Nm yr-1 km-1. The upper and lower bounds of the moment accumulation rates are derived based on the statistics of the noise. Our best-fitting model indicates that the central portion of the Creeping Section is accumulating seismic moment at rates that are about 5 per cent to 23 per cent of the fully locked Carrizo segment that will eventually be released seismically. A cumulative moment budget calculation with the historical earthquake catalogue (M > 5.5) since 1857 shows that the net moment deficit at present is equivalent to a Mw 6.3 earthquake.

  8. On the origin of (4)He and (40)Ar in natural gold

    NASA Technical Reports Server (NTRS)

    Eugster, O.; Hofmann, B.; Niedermann, S.; Thalmann, CH.

    1993-01-01

    In a first report on our investigations of noble gases in native gold we demonstrated that placer gold contains an excess of radiogenic (4)He and (40)Ar relative to the concentrations expected from in situ decay of U, Th, and K, respectively, during the geologic age of about 30 Ma of the samples. We also showed that the U/Th-(4)He age of 36 Ma of vein-type gold from the Southern Alps agrees with its K-Ar formation age derived from associated muscovite and biotite. We now studied the question of the origin of the (4)He and (40)Ar excesses of placer gold. We conclude that gold contains two components of noble gases, a low-temperature component from fluid inclusions or phases which release noble gases at less than 800 C and a high-temperature component released when gold melts (1064 C). In some samples extremely high U and K concentrations or an unreasonably high formation age would be required to explain the observed (4)He abundances. Thus, trapped (4)He and (40)Ar must be present in gold.

  9. Theoretical Basis for Anomalous Heat and ^4He in Deuterium-Metal Systems

    NASA Astrophysics Data System (ADS)

    Chubb, Scott; Chubb, Talbot

    2000-03-01

    Because electromagnetic (E.M.) forces have infinite range, reactions exist in which the degrees of freedom associated with nuclear- and atomic- scales are coupled. Although such non-separable reactions are possible in conventional D+D fusion, they rarely occur because the relevant E.M.-induced reaction (D+Darrow ^4He) violates the rules of energy-momentum conservation (EMC) at-a-point, except when a high momentum (HM) gamma ray is emitted. When D^+ and ^4He^+^+ occupy ion band states with low concentration, however, different forms of E.M. coupling become possible in which EMC is violated locally but conserved globally and D+Darrow ^4He reactions occur without HM particles(http: //www.aps.org/meet/CENT99/BAPS/abs/S9500.html). Using a generalized KKR-Multiple-Scattering theory, we have formulated Generalized Kadanoff-Baym Equations ( D.C. Langreth and J.W. Wilkins, Phys. Rev. B 6), 3189 (1972). that describe the associated non-local heat and ^4He release from the resulting coupling between nuclear interactions, D^+ and ^4He^+^+ ion band states, and electrons.

  10. Anomalous Elasticity of 4He Films at the Quantum Phase Transition

    NASA Astrophysics Data System (ADS)

    Shirahama, Keiya; Takahashi, Daisuke; Kogure, Takayuki; Yoshimura, Hitomi; Higashino, Rama

    4 He films on solid substrates exhibit a quantum phase transition between localized (nonsuperfluid) and superfluid states by changing coverage n. We have made torsional oscillator (TO) studies for 4He films adsorbed on nanoporous glasses. A TO with localized films showed an apparent ''supersolid'' behavior, an increase in TO frequency f with broad peak in Q-1. Combining with FEM analyses for TO's with different designs, we conclude that the behavior results from the softening of adsorbed 4He films at high temperatures. The features in f and Q-1 are fitted well to a Debye-like activation with a distributed energy gap Δ, so the elasticity is accounted by thermal excitation of localized atoms to an ''extended'' state. As the critical coverage nc approaches the gap decreases to zero with a powerlaw Δ ~(n -nc) 1 . 2 . Assuming that the 4He chemical potential μ (n) is located in the middle of the gap, we can estimate the elastic constant κ-1 =n2 ∂μ / ∂n . The elasticity agrees with shear moduli of 4He films obtained from the FEM analysis within factor of three. The energetics proposed from the elastic behavior naturally explains other properties of He films adsorbed on disordered substrates.

  11. Control of the wetting properties of ^{4}He crystals in superfluid.

    PubMed

    Takahashi, T; Minezaki, H; Suzuki, A; Obara, K; Itaka, K; Nomura, R; Okuda, Y

    2016-05-01

    To investigate whether it is possible to control the wetting of ^{4}He crystals on a wall in superfluid, the contact angles of ^{4}He crystals were measured on rough and smooth walls at very low temperatures. A rough wall was prepared in a simple manner in which a commercially available coating agent for car mirrors, which makes the glass surface superhydrophobic, was used to coat a glass plate. The contact angles of ^{4}He crystals were increased by approximately 10^{∘} on the rough wall coated with the agent. Therefore, the increase in the repellency of ^{4}He crystals in superfluid was demonstrated to be possible on a very rough surface. The enhancement of the contact angles and a scanning electron microscopy image of the coated surface both suggest that a Cassie-Baxter state of ^{4}He crystals was realized on the surface; the crystals did not have full contact with the wall, but entrapped superfluid was present beneath the crystals in the hollow parts of the rough wall. PMID:27300963

  12. Van der Waals correlation between two 4He monolayers on the opposite sides of graphene

    NASA Astrophysics Data System (ADS)

    Kwon, Yongkyung

    2015-06-01

    Path-integral Monte Carlo calculations have been performed to study the correlation between two 4He monolayers adsorbed on opposite sides of a graphene sheet. Here, the 4He-substrate interaction is described by the pairwise sum of the 4He-C interatomic potentials. We employ two different anisotropic 4He-C pair potentials proposed to fit the helium scattering data on a graphite surface, namely, a 6-12 Lennard-Jones potential and a Yukawa-6 potential. With the Lennard-Jones substrate potential, we do not observe any noticeable correlation between two oppositeside 4He monolayers, which is consistent with the prediction of the previous theoretical studies based on the same substrate potential. When the Yukawa-6 substrate potential is used, however, two incommensurate triangular solids, which are realized at the first-layer completion density of 0.12 Å -2, are found to favor an AA stacking order, two triangular lattices on top of each other, over an AB stacking. Finally, the effects of this interlayer correlation on the formation of stable mobile vacancies are discussed.

  13. Torsional oscillator studies for possible supersolidity in two-dimensional 4He solid

    NASA Astrophysics Data System (ADS)

    Shibayama, Y.; Fukuyama, H.; Shirahama, K.

    2009-02-01

    The origin of "supersolidity" of solid 4He, which was reported by Kim and Chan, has not yet been clarified. Although Bose-Einstein condensation of zero-point vacancies (ZPVs) was initially considered to be a possible origin, recent studies imply that crystal imperfections in the solid samples are strongly associated with the observed supersolid behaviors. In two-dimensional (2D) 3He system on graphite, on the other hand, a novel phase due to quantum hopping of ZPVs has been found. This suggests that ZPVs form also in 2D 4He solid systems and their quantum hopping results in superfluidity of ZPVs, namely, supersolidity. In order to search for the possible 2D supersolid state, we perform torsional oscillator studies for 4He films adsorbed on graphite. At the 4He coverage of 18.7 nm-2 a positive frequency shift was observed below 300 mK. The size of the shift decreases with increasing the oscillation velocity. This behavior closely resembles to the supersolid behavior of bulk solid 4He.

  14. Control of the wetting properties of 4He crystals in superfluid

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Minezaki, H.; Suzuki, A.; Obara, K.; Itaka, K.; Nomura, R.; Okuda, Y.

    2016-05-01

    To investigate whether it is possible to control the wetting of 4He crystals on a wall in superfluid, the contact angles of 4He crystals were measured on rough and smooth walls at very low temperatures. A rough wall was prepared in a simple manner in which a commercially available coating agent for car mirrors, which makes the glass surface superhydrophobic, was used to coat a glass plate. The contact angles of 4He crystals were increased by approximately 10° on the rough wall coated with the agent. Therefore, the increase in the repellency of 4He crystals in superfluid was demonstrated to be possible on a very rough surface. The enhancement of the contact angles and a scanning electron microscopy image of the coated surface both suggest that a Cassie-Baxter state of 4He crystals was realized on the surface; the crystals did not have full contact with the wall, but entrapped superfluid was present beneath the crystals in the hollow parts of the rough wall.

  15. Accumulation rates of biogenous silica and terrigenous detritus in late Miocene-early Pliocene Santa Maria basin, California

    SciTech Connect

    Ramiriz, P.C.

    1988-03-01

    The upper-Miocene-lower Pliocene laminated to massive diatomaceous strata of the Santa Maria basin encompass portions of the Monterey and overlying conformable to nonconformable Sisquoc Formations and record the continued accumulation of admixed siliceous (mostly diatoms) and terrigenous (silt and clay) components in a Neogene borderland basin. Lithologies, which vary from diatomite to diatomaceous mudstone, are the result of fluctuations in slope-accumulating silica and terrigenous debris. Bulk accumulation rates, as well as silica and terrigenous component accumulation rates, were calculated for four measured sections using accurate stratal thicknesses, absolute ages, rock compositions, and bulk densities. Bulk accumulation rates range from less than 20 to greater than 70 mg/cm/sup 2//year and are comparable to bulk accumulation rates in the present-day Santa Barbara basin and Gulf o f California. Silica accumulation rates (20-30 mg/cm/sup 2//year) suggest that sedimentation took place beneath productive waters and they exceed those encountered in other high-productivity oceanic areas, such as the Bering Sea and Peruvian coastal waters. Relatively high terrigenous accumulation rates (18-35 mg/cm/sup 2//year) reflect the dilution of these high-productivity waters by continentally derived detritus. Comparison of calculated accumulation rates with rates determined for similarly aged strata of the Santa Barbara basin reveals that silica and terrigenous debris were accumulating at higher rates within the Santa Maria basin. These differences are due to the complex interplay of tectonics and oceanographics and to the proximity of the basins relative to the strandline.

  16. Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

    USGS Publications Warehouse

    Roberts, H.M.; Muhs, D.R.; Wintle, A.G.; Duller, G.A.T.; Bettis, E. Arthur, III

    2003-01-01

    A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35-50 ??m quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil's Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr-much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values. ?? 2003 Elsevier Science (USA). All rights reserved.

  17. Rapid Changes on Sediment Accumulation Rates within Submarine Canyons Caused By Bottom Trawling Activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Masque, P.; Martin, J.; Paradis, S.; Juan, X.; Toro, M.; Palanques, A.

    2014-12-01

    The physical disturbance of the marine sedimentary environments by commercial bottom trawling is a matter of concern. The direct physical effects of this fishing technique include scraping and ploughing of the seabed and increases of the near-bottom water turbidity by sediment resuspension. However, the quantification of the sediment that has been resuspended by this anthropogenic activity over years and has been ultimately exported across the margin remains largely unaddressed. The analysis of sediment accumulation rates from sediment cores collected along the axes of several submarine canyons in the Catalan margin (northwestern Mediterranean) has allowed to estimate the contribution of this anthropogenic activity to the present-day sediment dynamics. 210Pb chronologies, occasionally supported by 137Cs dating, indicate a rapid increase of sediment accumulation rates since the 1970s, in coincidence with a strong impulse in the industrialization of the trawling fleets of this region. Such increase has been associated to the enhanced delivery of sediment resuspended by trawlers from the shelves and upper slope regions towards the canyon's interior, and to the rapid technical development at that time, in terms of engine power and gear size. This change has been observed in La Fonera (or Palamós) Canyon at depths greater than 1700 m, while in other canyons it is restricted to shallower regions (~1000 m in depth) closer to fishing grounds. Two sampling sites from La Fonera and Foix submarine canyons that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied several years after the first chronological analyses. These two new cores reveal a second and more rapid increase of sediment accumulation rates in both canyons occurring circa 2002 and accounting for about 2 cm/y. This second change at the beginning of the XXI century has been attributed to a preferential displacement of the trawling fleet towards slope fishing grounds surrounding submarine

  18. Ages and Accumulation Rates of the Martian Polar Layered Deposits Estimated from Orbital Tuning

    NASA Astrophysics Data System (ADS)

    Sori, M.; Bailey, E. A.; Perron, J.; Huybers, P. J.; Aharonson, O.; Limaye, A.

    2013-12-01

    Layers of dusty water ice in the polar caps of Mars have been hypothesized to record climate changes driven by variation of the planet's orbit and spin axis, but the time interval over which the polar layered deposits (PLDs) formed is unknown, and an orbital influence has not been conclusively demonstrated. We performed orbital tuning of reconstructed PLD stratigraphic sequences in an attempt to constrain the accumulation interval and test for the presence of an orbital signal. Our procedure uses dynamic time warping (DTW) to search for a match between two time series - the polar insolation history and brightness or topographic information in the PLDs - and then assesses the significance of potential matches using a Monte Carlo procedure. We selected 30 images of the northern PLDs from the Mars Orbiter Camera (MOC) aboard the Mars Global Surveyor spacecraft and used Mars Orbiter Laser Altimeter profiles to transform each image into a record of image brightness as a function of vertical depth. To constrain the PLD age and accumulation rate, we tuned each image record to Martian insolation records for varying time intervals. If a particular insolation interval produced the strongest match to an image, and if the match became weaker as the image was tuned to progressively longer or shorter intervals, we chose the best-fitting interval as an estimated accumulation time for that PLD sequence, and used the depth range to estimate a corresponding PLD accumulation rate. We also tuned the insolation records to synthetic records containing no orbital influence to test whether the image matches were spurious. Of the 30 MOC images analyzed, 16 produce insolation intervals that we consider strong matches. These images yield an average deposition rate of 0.5 × 0.2 mm/yr for the northern PLDs. The images represent only a fraction of the entire stratigraphy; extrapolating that deposition rate farther back in time yields an age of ~4 Ma for the entire PLD sequence present in the

  19. Green's function theory for the Cheng-Schick model of 3He-4He mixtures

    NASA Astrophysics Data System (ADS)

    Siemann, R. P.; Boukahil, A.; Huber, D. L.

    2014-08-01

    In this paper, we outline a theory for the thermodynamic properties of 3He-4He mixtures in the neighborhood of the critical line and the tricritical point (TCP). The theory utilizes the Cheng-Schick (CS) lattice gas model where both the 3He and 4He atoms are treated as quantum particles on a lattice. The analysis is based on Green's function approach. Results are presented for the ordering susceptibility and the thermal averages of the occupation numbers of 3He and 4He atoms. We derive a self-consistent equation for the ordering susceptibility and use it to calculate the critical line and locate the TCP. Our findings are compared with the predictions obtained from high temperature series expansions, mean field theory and the random phase approximation (RPA).

  20. Study of Supersolidity and Shear Modulus Anomaly of 4He in a Triple Compound Oscillator

    NASA Astrophysics Data System (ADS)

    Mi, Xiao; Mueller, Erich J.; Reppy, John D.

    2012-12-01

    The recently discovered shear modulus anomaly in solid 4He bears a strong similarity to the phenomenon of supersolidity in solid 4He and can lead to the period shift and dissipative signals in torsional oscillator experiments that are nearly identical to the classic NCRI signals observed by Kim and Chan. In the experiments described here, we attempt to isolate the effects of these two phenomena on the resonance periods of torsion oscillators. We have constructed a triple compound oscillator with distinct normal modes. We are able to demonstrate that, for this oscillator, the period shifts observed below 200 mK have their primary origin in the temperature dependence of the shear modulus of the solid 4He sample rather than the formation of a supersolid state.

  1. Upper bound on parity-violating neutron spin rotation in {sup 4}He

    SciTech Connect

    Snow, W. M.; Luo, D.; Walbridge, S. B.; Crawford, B. E.; Gan, K.; Micherdzinska, A. M.; Opper, A. K.; Heckel, B. R.; Swanson, H. E.; Sharapov, E. I.; Zhumabekova, V.

    2011-02-15

    We report an upper bound on parity-violating neutron spin rotation in {sup 4}He. This experiment is the most sensitive search for neutron-weak optical activity yet performed and represents a significant advance in precision in comparison to past measurements in heavy nuclei. The experiment was performed at the NG-6 slow-neutron beamline at the National Institute of Standards and Technology (NIST) Center for Neutron Research. Our result for the neutron spin rotation angle per unit length in {sup 4}He is d{phi}/dz=[+1.7{+-}9.1(stat.){+-}1.4(sys.)]x10{sup -7} rad/m. The statistical uncertainty is smaller than current estimates of the range of possible values of d{phi}/dz in n+{sup 4}He.

  2. Explosion of electron bubbles attached to quantized vortices in liquid {sup 4}He

    SciTech Connect

    Pi, Marti; Mayol, Ricardo; Hernando, Alberto; Barranco, Manuel; Ancilotto, Francesco

    2007-06-28

    Electron bubbles in superfluid {sup 4}He have been recently observed in low-temperature cavitation measurements under experimental conditions where quantized vortices are also present in the liquid, and which might be attached to the bubbles. We have calculated, within density functional theory, the structure and energetics of electron bubbles pinned to linear vortices in liquid {sup 4}He at low temperature, and the pressure at which such structures become mechanically unstable. Our results are in semiquantitative agreement with the experiments. We discuss dynamical effects not included in the theoretical model used in the present calculations, and which could explain some discrepancies between our results and the experimental data.

  3. Kosterlitz-Thouless Transition in 4He Films Adsorbed to Rough Calcium Fluoride

    SciTech Connect

    Luhman, D. R.; Hallock, R. B.

    2006-09-07

    Previous measurements in our lab have shown that the onset of superfluidity at the KT transition, typically seen as a sharp change in the frequency of a smooth-surface quartz crystal microbalance, becomes less identifiable in the presence of increasing surface roughness or disorder, while the peak in the dissipation is unchanged. Using a series of microbalances coated with increasingly rough CaF2, we have extended our measurements to lower 4He film coverages and thus lower temperatures. We find at lower 4He coverages that the presence of disorder on the substrate has a diminished effect on the frequency shift.

  4. High-sensitivity measurement of 3He-4He isotopic ratios for ultracold neutron experiments

    NASA Astrophysics Data System (ADS)

    Mumm, H. P.; Huber, M. G.; Bauder, W.; Abrams, N.; Deibel, C. M.; Huffer, C. R.; Huffman, P. R.; Schelhammer, K. W.; Janssens, R.; Jiang, C. L.; Scott, R. H.; Pardo, R. C.; Rehm, K. E.; Vondrasek, R.; Swank, C. M.; O'Shaughnessy, C. M.; Paul, M.; Yang, L.

    2016-06-01

    Research efforts ranging from studies of solid helium to searches for a neutron electric dipole moment require isotopically purified helium with a ratio of 3He to 4He at levels below that which can be measured using traditional mass spectroscopy techniques. We demonstrate an approach to such a measurement using accelerator mass spectroscopy, reaching the 10-14 level of sensitivity, several orders of magnitude more sensitive than other techniques. Measurements of 3He/4He in samples relevant to the measurement of the neutron lifetime indicate the need for substantial corrections. We also argue that there is a clear path forward to sensitivity increases of at least another order of magnitude.

  5. Field studies using the oyster Crassostrea virginica to determine mercury accumulation and depuration rates

    SciTech Connect

    Palmer, S.J.; Presley, B.J.; Powell, E.N. ); Taylor, R.J. )

    1993-09-01

    Mercury as an environmental hazard, especially with regard to human health, has been of concern since the Minamata disaster. From 1966 to 1970 a chlor-alkali plant in Point Comfort, Texas released mercury-enriched wastewater (up to 29.9 kgHg/day) into Lavaca Bay (TWQB 1977). Since 1970 the Texas Department of Health (TDH) has periodically closed and then re-opened portions of Lavaca Bay to the harvesting of crabs and finfish based on their levels (<>0.5 ppm Hg wet weight) of mercury. A 1988 closure remains in effect as of this writing. Mercury contamination in Lavaca Bay organisms thus continues to be a problem 22 years after the chlor-alkali plant ceased releasing mercury into the bay. The goal of the following research was to better understand the behavior of mercury in Lavaca Bay. Oysters have been widely used as indicator species in metal pollution studies. Most such programs have focused on the concentrations of metals in oysters from different geographic areas. This study, however, investigated the rate and amount of mercury a [open quotes]clean[close quotes] oyster would accumulate when transplanted to a contaminated estuary and the rate of mercury depuration by contaminated oysters placed in a clean environment. The oysters were additionally analyzed for Ba, Cu, Fe, P, and Zn to test for the possible involvement of these metals in mercury accumulation and depuration. 17 refs., 3 figs., 2 tabs.

  6. Distributions and accumulation rates of polycyclic aromatic hydrocarbons in the northern Gulf of Mexico sediments.

    PubMed

    Adhikari, Puspa L; Maiti, Kanchan; Overton, Edward B; Rosenheim, Brad E; Marx, Brian D

    2016-05-01

    Sediment samples collected from shelf, slope and interior basin of the northern Gulf of Mexico during 2011-2013, 1-3 years after the Deepwater Horizon (DWH) oil spill, were utilized to characterize PAH pollution history, in this region. Results indicate that the concentrations of surface ΣPAH43 and their accumulation rates vary between 44 and 160 ng g(-1) and 6-55 ng cm(-2) y(-1), respectively. ΣPAH43 concentration profiles, accumulation rates and Δ(14)C values are significantly altered only for the sediments in the immediate vicinity of the DWH wellhead. This shows that the impact of DWH oil input on deep-sea sediments was generally limited to the area close to the spill site. Further, the PAHs source diagnostic analyses suggest a noticeable change in PAHs composition from higher to lower molecular weight dominance which reflects a change in source of PAHs in the past three years, back to the background composition. Results indicate low to moderate levels of PAH pollution in this region at present, which are unlikely to cause adverse effects on benthic communities. PMID:26895564

  7. Complex Wind-Induced Variations of Surface Snow Accumulation Rates over East Antarctica

    NASA Astrophysics Data System (ADS)

    Das, I.; Scambos, T. A.; Koenig, L.; van den Broeke, M.; Lenaerts, J.

    2015-12-01

    Accurate quantification of surface snow-accumulation over Antarctica is important for mass balance estimates and climate studies based on ice core records. Using airborne radar, lidar and thresholds of surface slope, modeled surface mass balance (SMB) and wind fields, we have predicted continent-wide distribution of wind-scour zones over Antarctica. These zones are located over relatively steep ice surfaces formed by ice flow over bedrock topography. Near-surface winds accelerate over these steeper slopes and erode and sublimate the snow. This results in numerous localized regions (typically ≤ 200 km2) with reduced or negative surface accumulation. Although small zones of re-deposition occur at the base of the steeper slope areas, the redeposited mass is small relative to the ablation loss. Total losses from wind-scour and wind-glaze areas amounts to tens of gigatons annually. Near the coast, winds often blow significant amounts of surface snow from these zones into the ocean. Large uncertainties remain in SMB estimates over East Antarctica as climate models do not adequately represent the small-scale physical processes that lead to mass loss or redistribution over the wind-scour zones. In this study, we also use Operation IceBridge's snow radar data to provide evidence for a gradual ablation of ~16-18 m of firn (~200 years of accumulation) from wind-scour zones over the upper Recovery Ice Stream catchment. The maximum ablation rates observed in this region are ~ -54 kg m-2 a-1 (-54 mm water equivalent a-1). Our airborne radio echo-sounding analysis show snow redeposition downslope of the wind-scour zones is <10% of the cumulative mass loss. Our study shows that the local mass loss is dominated by sublimation to water vapor rather than wind-transport of snow.

  8. Finding the Missing γ in D+Darrow ^4He Cold Fusion Excess Heat:

    NASA Astrophysics Data System (ADS)

    Chubb, Scott

    2002-03-01

    The source of Cold Fusion (CF)Excess Heat is a novel form of D+Darrow ^4He reaction in which no high energy γ rays are emitted (http:// www.aps.org/meet/MAR01/baps/abs/S7640003.html) . An important source of confusion concerning this point is the apparent lack of consensus about known effects associated even with the conventional D+Darrow^4He+γ reaction. In fact, although little information about D+Darrow ^4He+γ appears in the conventional fusion literature, the photo-dissociation reaction ^4He+γarrowD+D not only has been widely studied but is known to occur through a quadrupolar (E2) transition in which the two particle wave function associated with the D-nuclei is required to preserve Bose symmetry, in the far field regions, where the Electromagnetic Interaction EMI is dominant. Also in this reaction coupling occurs between strong and EMI's that invalidates the separability requirements that are present in the remaining D+D fusion reactions. These facts lend credibility to the notion that coherent many-body effects, involving D-exchange can alter the reaction in such a way that γ ray emission is not required.

  9. The ABC Effect in the Double-Pionic Fusion to 4He.

    NASA Astrophysics Data System (ADS)

    Pricking, A.

    2010-04-01

    The double-pionic fusion to 4He was measured exclusively and kinematically complete with the WASA 4π detector at COSY for the reactions dd →4Heπ0π0 and dd →4Heπ+π- . The measurements were performed over the full energy region, where the so-called ABC effect was observed previously in inclusive measurements. Whereas the latter exhibit not only a low-mass enhancement - the ABC-effect - in the 4He missing mass spectrum but also a prominent high-mass enhancement, we observe only a very strong low-mass enhancement and no pronounced high mass enhancement. This is in contrast to theoretical predictions based on t-channel ∆∆ excitation. Also the energy dependence of the observed total cross section does not fit to such predictions. Both features, however, agree very well with the observations in the most basic double-pionic fusion process in the isoscalar channel pn → dπ0π0.

  10. Electron screening in the {sup 3}He(d,p){sup 4}He reaction

    SciTech Connect

    Barker, F. C.

    2007-02-15

    A reanalysis of data for the {sup 3}He(d,p){sup 4}He reaction obtained using the Trojan-horse method, together with data from a direct measurement, leads to an electron-screening potential that is not consistent with the adiabatic limit, but it is consistent with a previous value from different data.

  11. A non-perturbative approach to freezing of superfuid 4He in density functional theory

    NASA Astrophysics Data System (ADS)

    Minoguchi, T.; Galli, De; Rossi, M.; Yoshimori, A.

    2012-12-01

    Freezing of various classical liquids is successfully described by density functional theory (DFT). On the other hand, so far no report has been published that DFT describes the freezing of superfuid 4He correctly. In fact, DFT gives too stable solid phase and the superfuid phase does not exist at finite positive pressures within a second order perturbation. In this paper we try a non-perturbative version of DFT, that is modified weighted density approximation (MWDA) to go beyond second order perturbation for the freezing of superfuid 4He. Via an exact zero temperature quantum Monte-Carlo (QMC) method we have computed the equation of state and the compressibility of superfuid 4He. By utilizing a recently introduced analytic continuation method (the GIFT method), we have obtained also density response functions at different densities from QMC imaginary time correlation functions. Contrary to second order perturbation, by employing these QMC data as DFT input we find a too stable superfuid phase, preventing freezing around the experimentally observed freezing pressure. We find the same pathological behavior by using another model energy functional of superfuid 4He (Orsay-Trento model). We conclude that the straightforward MWDA calculation gives such a poor result when liquid-gas transition is present.

  12. Third sound and stability of 3He-4He mixture films

    SciTech Connect

    Anderson, R. H.; Krotscheck, E.; Miller, M. D.

    2006-09-07

    We study third sound and the interaction between 3He adatoms in two thin 3He-4He mixture films from a first-principles, microscopic theory. Utilizing the variational, hypernetted-chain Euler-Lagrange (HNC-EL) theory as applied to inhomogeneous boson systems, we calculate chemical potentials for both the 4He superfluid film and the physisorbed 3He. Numerical density derivatives of the chemical potentials lead to the sought-after third sound speeds that clearly reflect a layered structure of at least seven oscillations. In this paper, we report third sound on model substrates: Nuclepore, and sodium. We find that the effect of the 3He depends sensitively on the particular 4He film coverage. Our most important result is that, with the addition of 3He, the third sound speed can either increase or decrease. In fact, in some regimes, the added 3He destabilizes the film and can drive ''layering transitions'', leading to fairly complicated geometric structures of the film in which the outermost layer is predicted to consist of phase-separated regions of 3He and 4He.

  13. Search for anisotropy in the Debye-Waller factor of HCP solid (4)He.

    PubMed

    Barnes, Ashleigh L; Hinde, Robert J

    2016-02-28

    The properties of hexagonal close packed (hcp) solid (4)He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid (4)He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp (4)He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp (4)He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm(3), and is found to be in good qualitative agreement with experimental data. PMID:26931710

  14. The Quest for Bose-Einstein Condensation in Solid 4He

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.; Azuah, R. T.; Glyde, H. R.

    2011-03-01

    Ever since the seminal torsional oscillator (TO) measurements of Kim and Chan which suggested the existence of a phase transition in solid 4He, from normal to a `supersolid' state below a critical temperature T c = 200 mK, there has been an unprecedented amount of excitement and research activity aimed at better understanding this phase. Despite much work, this remarkable phase has yet to be independently confirmed by conventional scattering techniques, such as neutron scattering. We have carried out a series of neutron scattering measurements, which we here review, aimed at observing Bose-Einstein condensation (BEC) in solid 4He at temperatures below T c . In bulk liquid 4He, the appearance of BEC below T λ signals the onset of superfluidity. The observation of a condensate fraction in the solid would provide an unambiguous confirmation for `supersolidity'. Although, our measurements have not yet revealed a non-zero condensate fraction or algebraic off diagonal long-range order n 0 in solid 4He down to 65 mK, i.e. n 0=(0±0.3)%, our search for BEC and its corollaries continues with improved instrumentation.

  15. Search for supersolid 4He in neutron scattering experiments at ISIS

    NASA Astrophysics Data System (ADS)

    Kirichek, O.

    2009-02-01

    The observation of a non-classical rotation inertia (NCRI) fraction in bulk solid 4He by M. Chan and E. Kim [1, 2] attracted significant interest as a possible manifestation of supersolid state of matter. Despite numerous experimental and theoretical studies inspired by this observation, an explicit explanation for this phenomenon is still missing. Neutron scattering experiments on solid helium may help to shed light on the physical grounds of NCRI and answer the question on whether this phenomenon could be caused by Bose-Einstein Condensation. In this paper we are going to discuss the results obtained in experiments involving neutron scattering on solid 4He. Microscopic quantitative data such as mean kinetic energy, mean square momentum and mean square displacement of helium atoms as well as the lattice parameter have been obtained for the first time for solid 4He in temperature range 70mK - 500 mK. No change was seen in the single atom kinetic energy (within statistical error better than 1%) as well as change in the lattice parameter (within 0.03%). The mean square displacement did not change in the region of expected supersolid transition either. All these results suggest that the NCRI transition is quite different from the superfluid transition in liquid 4He.

  16. Equilibrium shape of 4He crystal under zero gravity below 200 mK

    PubMed Central

    Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

    2015-01-01

    Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. 4He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of 4He. We report the relaxation processes of macroscopic 4He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened 4He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff’s origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained. PMID:26601315

  17. ^4 He Crystals in Reduced Gravity Obtained by Parabolic Flights of a Jet Plane

    NASA Astrophysics Data System (ADS)

    Takahashi, Takuya; Nomura, Ryuji; Okuda, Yuichi

    2016-03-01

    ^4 He crystals usually sink to the bottom of the container in a superfluid and are deformed into a flat shape by gravity when their size is much larger than the capillary length of 1 mm. When gravity is reduced to zero, the capillary length diverges and the gravity-flattened crystals are expected to relax into an equilibrium crystal shape determined by the interfacial free energy at low enough temperatures where the relaxation time is very short. We performed a reduced gravity experiment on ^4 He crystals at ultralow temperatures by developing a specially designed ^3 He-^4 He dilution refrigerator compatible with the experimental restrictions in a small jet plane. ^4 He crystals relaxed to the equilibrium crystal shape below 600 mK during a reduced gravity period of 20 s produced by a parabolic flight. The equilibrium crystal shape, however, was metastable in most cases, governed by the boundary conditions imposed by the wall. Utilizing acoustic radiation pressure, we deformed the crystal enough to allow it to escape from the metastable shape below 150 mK. After this large deformation, the crystal relaxed to a shape completely different from its initial shape, showing three types of facets, viz., c-, a-, and s-facets, which was concluded to be the lowest energy equilibrium shape.

  18. Search for anisotropy in the Debye-Waller factor of HCP solid 4He

    NASA Astrophysics Data System (ADS)

    Barnes, Ashleigh L.; Hinde, Robert J.

    2016-02-01

    The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

  19. Equilibrium shape of (4)He crystal under zero gravity below 200 mK.

    PubMed

    Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

    2015-10-01

    Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. (4)He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of (4)He. We report the relaxation processes of macroscopic (4)He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened (4)He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff's origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained. PMID:26601315

  20. Phase-space analysis of convection in a /sup 3/He - superfluid /sup 4/He solution

    SciTech Connect

    Haucke, H.; Maeno, Y.

    1982-01-01

    Observations have been made on thermal convection below 1K in a dilute solution of /sup 3/He in superfluid /sup 4/He contained in a cylindrical cell of aspect ratio GAMMA = 1.20. Complicated oscillatory phenomena were observed with a high degree of reproducibility using two temperature sensors. Phase-space analysis suggests a description in terms of strange-attractor dynamics.

  1. Bounding the rate of moment deficit accumulation along the Tohoku segment using GEONET GPS data

    NASA Astrophysics Data System (ADS)

    Segall, P.; Johnson, K. M.; Miyazaki, S.

    2011-12-01

    Geodetic estimates of strain accumulation compared to the rate of past moment release provide important input to earthquake hazard forecasts. Prior to the March 2011 Tohoku earthquake a number of studies investigated plate coupling along the Japan Trench in NE Japan using GEONET GPS data. Most of these assumed an elastic back-slip framework, and regularized the underdetermined inverse problem by minimizing some norm of the back-slip rate. All studies apparently smoothed to zero coupling at the trench and therefore infer the highest coupling just offshore. In contrast, we estimate rigorous bounds on the maximum and minimum permissible rates of moment deficit (MDR) accumulation, not a ``favored'' model according to some ad hoc regularization, using methods of Johnson et al [1994] and Murray and Segall [2002]. Given a domain of interest (the Tohoku rupture segment) and Green's functions G relating slip to data, we solve the following optimization problem for back-slip rate m: {minimize}\\ || G m - d ||22 \\ {subject to} \\ A m = M0 \\ \\ {and} \\ \\ 0 ≤ mi ≤ vplate, where A = [1,1, ... 1], such that A m yields the (normalized) moment-rate. on the model domain. Preliminary results find that || G m - d ||22 exhibits a broad minimum over a factor of 2 in MDR. For the minimum MDR the locked zone is just offshore, while the plate-boundary near the trench slips at the plate rate. At the maximum MDR the locked zone is much larger, including the entire fault near the trench. This clearly demonstrates that the shallow fault is completely in the null-space for onshore data, and that there is at least a factor of two uncertainty in MDR. We will present results employing a bootstrap procedure that is independent of an assumed error distribution in the GPS data. We also extend the method to include viscoelastic earthquake cycle effects, including time-dependence due both to past earthquakes and steady backslip. In these models, fault locking near the trench induces flow which

  2. Lieb-Liniger-like model of quantum solvation in CO-4HeN clusters

    NASA Astrophysics Data System (ADS)

    Farrelly, D.; Iñarrea, M.; Lanchares, V.; Salas, J. P.

    2016-05-01

    Small 4He clusters doped with various molecules allow for the study of "quantum solvation" as a function of cluster size. A peculiarity of quantum solvation is that, as the number of 4He atoms is increased from N = 1, the solvent appears to decouple from the molecule which, in turn, appears to undergo free rotation. This is generally taken to signify the onset of "microscopic superfluidity." Currently, little is known about the quantum mechanics of the decoupling mechanism, mainly because the system is a quantum (N + 1)-body problem in three dimensions which makes computations difficult. Here, a one-dimensional model is studied in which the 4He atoms are confined to revolve on a ring and encircle a rotating CO molecule. The Lanczos algorithm is used to investigate the eigenvalue spectrum as the number of 4He atoms is varied. Substantial solvent decoupling is observed for as few as N = 5 4He atoms. Examination of the Hamiltonian matrix, which has an almost block diagonal structure, reveals increasingly weak inter-block (solvent-molecule) coupling as the number of 4He atoms is increased. In the absence of a dopant molecule the system is similar to a Lieb-Liniger (LL) gas and we find a relatively rapid transition to the LL limit as N is increased. In essence, the molecule initially—for very small N—provides a central, if relatively weak, attraction to organize the cluster; as more 4He atoms are added, the repulsive interactions between the identical bosons start to dominate as the solvation ring (shell) becomes more crowded which causes the molecule to start to decouple. For low N, the molecule pins the atoms in place relative to itself; as N increases the atom-atom repulsion starts to dominate the Hamiltonian and the molecule decouples. We conclude that, while the notion of superfluidity is a useful and correct description of the decoupling process, a molecular viewpoint provides complementary insights into the quantum mechanism of the transition from a molecular

  3. Lieb-Liniger-like model of quantum solvation in CO-(4)HeN clusters.

    PubMed

    Farrelly, D; Iñarrea, M; Lanchares, V; Salas, J P

    2016-05-28

    Small (4)He clusters doped with various molecules allow for the study of "quantum solvation" as a function of cluster size. A peculiarity of quantum solvation is that, as the number of (4)He atoms is increased from N = 1, the solvent appears to decouple from the molecule which, in turn, appears to undergo free rotation. This is generally taken to signify the onset of "microscopic superfluidity." Currently, little is known about the quantum mechanics of the decoupling mechanism, mainly because the system is a quantum (N + 1)-body problem in three dimensions which makes computations difficult. Here, a one-dimensional model is studied in which the (4)He atoms are confined to revolve on a ring and encircle a rotating CO molecule. The Lanczos algorithm is used to investigate the eigenvalue spectrum as the number of (4)He atoms is varied. Substantial solvent decoupling is observed for as few as N = 5 (4)He atoms. Examination of the Hamiltonian matrix, which has an almost block diagonal structure, reveals increasingly weak inter-block (solvent-molecule) coupling as the number of (4)He atoms is increased. In the absence of a dopant molecule the system is similar to a Lieb-Liniger (LL) gas and we find a relatively rapid transition to the LL limit as N is increased. In essence, the molecule initially-for very small N-provides a central, if relatively weak, attraction to organize the cluster; as more (4)He atoms are added, the repulsive interactions between the identical bosons start to dominate as the solvation ring (shell) becomes more crowded which causes the molecule to start to decouple. For low N, the molecule pins the atoms in place relative to itself; as N increases the atom-atom repulsion starts to dominate the Hamiltonian and the molecule decouples. We conclude that, while the notion of superfluidity is a useful and correct description of the decoupling process, a molecular viewpoint provides complementary insights into the quantum mechanism of the transition from a

  4. Search for supersolidity in solid 4He using multiple-mode torsional oscillators

    PubMed Central

    Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

    2016-01-01

    In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941–1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853–856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state. PMID:27222579

  5. Search for supersolidity in solid 4He using multiple-mode torsional oscillators.

    PubMed

    Eyal, Anna; Mi, Xiao; Talanov, Artem V; Reppy, John D

    2016-06-01

    In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid (4)He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941-1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid (4)He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the (4)He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853-856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid (4)He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the (4)He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state. PMID:27222579

  6. Search for supersolidity in solid 4He using multiple-mode torsional oscillators

    NASA Astrophysics Data System (ADS)

    Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

    2016-06-01

    In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941–1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853–856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state.

  7. Radiation-damage-controlled He diffusion and 4He/3He spectra in apatite: an example of mutually consistent results from the Grand Canyon (Invited)

    NASA Astrophysics Data System (ADS)

    Farley, K. A.; Flowers, R. M.

    2009-12-01

    Recent work indicates that He diffusion from apatite is impeded by the accumulation of radiation damage from actinide decay. Supporting evidence includes laboratory diffusion measurements as well as (U-Th)/He dates positively correlated with effective uranium (eU) concentration in certain geologic situations. Here we investigate whether the radiation damage effect can be identified in 4He concentration profiles, as it must be if the system behaves as we anticipate. Apatites from nearby igneous basement samples in the Upper Gorge of the Grand Canyon showing a strong date-eU correlation were proton irradiated, step-heated, and analyzed for 4He/3He spectra. The low eU apatites with younger He dates yielded nearly flat spectra, while the high eU apatites with older He dates yielded highly rounded spectra (see Figure). This implies that the higher eU apatites were partially retaining He while the lower eU apatites were still acting as an open system. Using the RDAAM kinetic model (Flowers et al. 2009) and local geologic constraints we confirm that this behavior is consistent with the observed differences in date and eU, providing compelling evidence that both the He dates and the 4He profiles are sensitive to radiation damage accumulation. Equally importantly, the combination of multiple samples with differing eU and thus differing 4He/3He spectra yields remarkably tight constraints on the time-temperature path experienced by these rocks, from ~90oC down to < 30oC.

  8. Verification of International Space Station Component Leak Rates by Helium Accumulation Method

    NASA Technical Reports Server (NTRS)

    Underwood, Steve D.; Smith, Sherry L.

    2003-01-01

    Discovery of leakage on several International Space Station U.S. Laboratory Module ammonia system quick disconnects (QDs) led to the need for a process to quantify total leakage without removing the QDs from the system. An innovative solution was proposed allowing quantitative leak rate measurement at ambient external pressure without QD removal. The method utilizes a helium mass spectrometer configured in the detector probe mode to determine helium leak rates inside a containment hood installed on the test component. The method was validated through extensive developmental testing. Test results showed the method was viable, accurate and repeatable for a wide range of leak rates. The accumulation method has been accepted by NASA and is currently being used by Boeing Huntsville, Boeing Kennedy Space Center and Boeing Johnson Space Center to test welds and valves and will be used by Alenia to test the Cupola. The method has been used in place of more expensive vacuum chamber testing which requires removing the test component from the system.

  9. Recent accumulation rates of an Alpine glacier derived from repeated airborne GPR and firn cores

    NASA Astrophysics Data System (ADS)

    Sold, Leo; Huss, Matthias; Eichler, Anja; Schwikowski, Margit; Hoelzle, Martin

    2014-05-01

    The topmost areas of glaciers contain a valuable record of their past accumulation rates. The water equivalent of annual firn layers can be used to initiate or extend existing time series of local mass balance and, ultimately, to consolidate the knowledge on the response of glaciers to changing climatic conditions. Measurements of the thickness and density of firn layers typically involve drilling in remote areas and core analysis and are thus expensive in terms of time and effort. Here, we discuss measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using two in-situ firn cores and airborne Ground-Penetrating Radar (GPR). The firn cores were analysed regarding their density, major ions and deuterium concentration. The ammonium (NH4+) concentration is known to show seasonality due to a higher source activity and pronounced vertical transportation in the atmosphere in summer. The deuterium concentration serves as a proxy for air temperature during precipitation formation. Together, they provide depth and dating of annual summer surfaces. GPR has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Airborne surveys allow measurements to be taken in remote and inaccessible areas. However, to transfer information from the GPR pulse travel time to the depth domain, the dielectric permittivity of the material is required, that changes with density of the firn. We observed a good agreement of the GPR signal with pronounced changes in the density profile, ice layers and peak contents of major ions. This underlines the high potential of GPR for detecting firn layers. However, not all peak-densities and thick ice layers represent a former glacier summer surface but can also be due to melting and refreezing during winter. We show that up to four years of annual

  10. Comparisons of 210Pb and pollen methods for determining rates of estuarine sediment accumulation

    USGS Publications Warehouse

    Brush, G.S.; Martin, E.A.; DeFries, R.S.; Rice, C.A.

    1982-01-01

    Comparisons of sedimentation rates obtained by 210Pb and pollen analyses of 1-m cores collected throughout the Potomac Estuary show good agreement in the majority of cores that can be analyzed by both methods. Most of the discrepancy between the methods can be explained by the analytical precision of the 210Pb method and by the exactness with which time horizons can be identified and dated for the pollen method. X-radiographs of the cores and the distinctness of the pollen horizons preclude significant displacement by reworking and/or mixing of sediments. Differences between the methods are greatest where uncertainties exist in assigning a rate by one or both methods (i.e., 210Pb trends and/or "possible" horizon assignments). Both methods show the same relative rates, with greater sediment accumulation more common in the upper and middle estuary and less toward the mouth. The results indicate that geochronologic studies of estuarine sediments should be preceded by careful observation of sedimentary structures, preferably by X-radiography, to evaluate the extent of mixing of the sediments. Time horizons, whether paleontologic or isotopic, are generally blurred where mixing has occurred, precluding precise identification. Whenever possible, two methods should be used for dating sediments because a rate, albeit erroneous, can be obtained isotopically in sediments that are mixed; accurate sedimentation rates are also difficult to determine where the time boundary is a zone rather than a horizon, where the historical record does not provide a precise date for the pollen horizon, or where scouring has removed some of the sediment above a dated pollen horizon. ?? 1982.

  11. Testing the U-Th/4He dating method on carbonates I. Helium diffusion

    NASA Astrophysics Data System (ADS)

    Pinti, D. L.; Ghaleb, B. G.; Sano, Y.; Blanchette, S.; Mathouchanh, E.; Takahata, N.

    2012-12-01

    Corals and other carbonates, such as speleothems, are important climatic-change proxies which need to be precisely dated for paleoclimatic reconstructions. Yet, U-Th disequilibrium method is applicable up to ca. 500 ka old carbonates. Calcite is difficult to date precisely by U-Pb method because of the low U amounts often found and difficulties in correcting for the common lead. Radiogenic 4He produced by decay of 238U and 235U incorporated into carbonates is a potential chronometer of Quaternary, and possibly Tertiary, corals and speleothems. However, several limitations exist for this method, related to the few data on the He diffusion [1] and on the alpha recoil effect in carbonate minerals. We decided to measure 4He by step heating in carbonate samples dated previously by U-Th disequilibrium: a coral (Scleractinia) from Cape Verde dated at 125 ka; a stalagmite from Patagonia dated at 128 ka; and two hydrothermal travertines from the Ziz Valley in Morocco with ages ≥ 500 ka. A one cm3 of each sample was cut by saw, crushed, washed and sieved to 80-100μm and 100-125μm fractions. Crushed samples (0.5 to 1 gram) were loaded in a vacuum crucible and 4He extracted by step heating. Previous step heating experiments on a sub-Arctic flowstone suggested that 4He is mainly released between 400 and 600°C [2]. However, the first coral sample heated at 100°C steps, showed a release pattern profile with 4He mainly released between 200 and 400°C. Measured 4He amount of 2.05 x 10-8 (±0.03% 1σ) ccSTP/g and U content of 2.7 ppm yield a U-4He age of 62.5 ka, lower than that obtained by U-Th disequilibrium. Data were not precise enough to calculate diffusion parameters using the Arrhenius diagram. The second step-heating pyrolysis of the coral using 50°C-steps indicated that all 4He is released between 250 and 350°C. The measured 4He amount was 2.27 x 10-8 (±0.04% 1σ) ccSTP/g, yielding an age of 83 ka, again lower compared to that obtained by U-Th disequilibrium. The

  12. Sexual difference in polychlorinated biphenyl accumulation rates of walleye (Stizostedion vitreum)

    USGS Publications Warehouse

    Madenjian, Charles P.; Noguchi, George E.; Haas, Robert C.; Schrouder, Kathrin S.

    1998-01-01

    Adult male walleye (Stizostedion vitreum) exhibited significantly higher polychlorinated biphenyl (PCB) concentrations than similarly aged female walleye from Saginaw Bay (Lake Huron). To explain this difference, we tested the following three hypotheses: (i) females showed a considerably greater reduction in PCB concentration immediately following spawning than males, (ii) females grew at a faster rate and therefore exhibited lower PCB concentrations than males, and (iii) males spent more time in the Saginaw River system than females, and therefore received a greater exposure to PCBs. The first hypothesis was tested by comparing PCB concentration in gonadal tissue with whole-body concentration, the second hypothesis was tested via bioenergetics modeling, and we used mark-recapture data from the Saginaw Bay walleye fishery to address the third hypothesis. The only plausible explanation for the observed difference in PCB accumulation rate was that males spent substantially more time in the highly contaminated Saginaw River system than females, and therefore were exposed to greater environmental concentrations of PCBs. Based on the results of our study, we strongly recommend a stratified random sampling design for monitoring PCB concentration in Saginaw Bay walleye, with fixed numbers of females and males sampled each year.

  13. Constraints on the Recent Rate of Lunar Regolith Accumulation from Diviner Observations

    NASA Technical Reports Server (NTRS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.

    2012-01-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances pre dicted to be covered by continuous ejecta. However, most of these sur faces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrar ed observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperat ures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highla nds), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth . Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differen ces in the thickness of accumulated regolith. However, away from youn g craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculat ed H values for young craters show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42, abstract 2437). This method could, in principle, be extended to other

  14. Target Selection Signals Influence Perceptual Decisions by Modulating the Onset and Rate of Evidence Accumulation.

    PubMed

    Loughnane, Gerard M; Newman, Daniel P; Bellgrove, Mark A; Lalor, Edmund C; Kelly, Simon P; O'Connell, Redmond G

    2016-02-22

    Computational and neurophysiological research has highlighted neural processes that accumulate sensory evidence for perceptual decisions [1]. These processes have been studied in the context of highly simplified perceptual discrimination paradigms in which the physical evidence appears at times and locations that are either entirely predictable or exogenously cued (e.g., by the onset of the stimulus itself). Yet, we are rarely afforded such certainty in everyday life. For example, when driving along a busy motorway, we must continually monitor the movements of surrounding vehicles for events that call for a lane change. In such scenarios, it is unknown which of the continuously present information sources will become relevant or when. Although it is well established that evidence integration provides an effective mechanism for countering the impact of noise [2], the question of how this mechanism is implemented in the face of uncertain evidence onsets has yet to be answered. Here, we show that when monitoring two potential sources of information for evidence occurring unpredictably in both time and space, the human brain employs discrete, early target selection signals that significantly modulate the onset and rate of neural evidence accumulation, and thereby the timing and accuracy of perceptual reports. These selection signals share many of the key characteristics of the N2pc component highlighted in the literature on visual search [3, 4] yet are present even in the absence of distractors and under situations of low temporal and spatial uncertainty. These data provide novel insights into how target selection supports decision making in uncertain environments. PMID:26853360

  15. Critical Casimir force in 4He films: confirmation of finite-size scaling.

    PubMed

    Ganshin, A; Scheidemantel, S; Garcia, R; Chan, M H W

    2006-08-18

    We present new capacitance measurements of critical Casimir force-induced thinning of 4He films near the superfluid transition, focused on the region below Tlambda where the effect is the greatest. 4He films of 238, 285, and 340 A thickness are adsorbed on atomically smooth, N-doped silicon substrates. The Casimir force scaling function theta, deduced from the thinning of these three films, collapses onto a single universal curve, attaining a minimum theta=-1.30+/-0.03 at x=td1/nu=-9.7+/-0.8 A1/nu. The collapse confirms the finite-size scaling origin of the dip in the film thickness. Separately, we also confirm the presence down to 2.13 K of the Goldstone or surface fluctuation force, which makes the superfluid film approximately 2 A thinner than the normal film. PMID:17026241

  16. Dislocation densities and lengths in solid 4He from elasticity measurements

    NASA Astrophysics Data System (ADS)

    Haziot, Ariel; Fefferman, Andrew D.; Beamish, John R.; Balibar, Sébastien

    2013-02-01

    Measurements on solid 4He show large softening of the shear modulus due to dislocations, behavior which has been described as giant plasticity. Dislocation networks may also be responsible for the unusual behavior seen in torsional oscillator and flow experiments. However, previous estimates of dislocation densities vary by many orders of magnitude, even in single crystals grown under similar conditions. By measuring the temperature and frequency dependencies of the elastic dissipation, we have determined dislocation densities and network lengths in 4He single crystals, both in coexistence with liquid and at higher pressures, and in polycrystals grown at constant density. In all cases, dislocation lengths are much longer and the networks are less connected than previous estimates. Even in polycrystals, the dislocation network is far too sparse to explain the torsional oscillator results in terms of superfluidity in a dislocation network.

  17. Apatite 4He/3He and (U-Th)/He evidence for an ancient Grand Canyon.

    PubMed

    Flowers, R M; Farley, K A

    2012-12-21

    The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite (4)He/(3)He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. (4)He/(3)He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma. PMID:23196906

  18. No Effect of Steady Rotation on Solid ^4He in a Torsional Oscillator

    NASA Astrophysics Data System (ADS)

    Fear, M. J.; Walmsley, P. M.; Zmeev, D. E.; Mäkinen, J. T.; Golov, A. I.

    2016-05-01

    We have measured the response of a torsional oscillator containing polycrystalline hcp solid 4He to applied steady rotation in an attempt to verify the observations of several other groups that were initially interpreted as evidence for macroscopic quantum effects. The geometry of the cell was that of a simple annulus, with a fill line of relatively narrow diameter in the centre of the torsion rod. Varying the angular velocity of rotation up to 2 rad s^{-1} showed that there were no step-like features in the resonant frequency or dissipation of the oscillator and no history dependence, even though we achieved the sensitivity required to detect the various effects seen in earlier experiments on other rotating cryostats. All small changes during rotation were consistent with those occurring with an empty cell. We thus observed no effects on the samples of solid ^4He attributable to steady rotation.

  19. Superheat Limit of 4He and Its Quantum Deviation from Classical Behavior

    NASA Astrophysics Data System (ADS)

    Nishigaki, Kazu; Saji, Yoshiro

    1983-07-01

    The superheating of normal liquid 4He was investigated by means of continuous heating of liquid specimen in a small glass capillary over a temperature range 2.26 K to 4.88 K. The maximum superheating data obtained were compared with the prediction from the homogeneous nucleation theory and the data for various liquids in terms of the reduced coordinates. It is confirmed that the agreement between the homogeneous nucleation theory and experiment on 4He is satisfactory, and the scaled superheating depends parametrically on the quantum parameter \\varLambda*, i.e., the deviations of the data for quantum liquids from the classical behavior become pronounced as the parameter is increased.

  20. Apatite 4He/3He and (U-Th)/He Evidence for an Ancient Grand Canyon

    NASA Astrophysics Data System (ADS)

    Flowers, R. M.; Farley, K. A.

    2012-12-01

    The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite 4He/3He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. 4He/3He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma.

  1. A discussion of the dispersion curve of energy excitations in liquid 4He

    NASA Astrophysics Data System (ADS)

    Bogoyavlenskii, I. V.; Puchkov, A. V.; Skomorokhov, A. N.; Karnatsevich, L. V.

    2004-10-01

    An investigation of the dispersion of excitations in a quantum liquid, superfluid 4He, is carried out. An attempt is made to systematize the published experimental data that indicate a substantially different nature of excitations with wave vectors corresponding to different parts of the dispersion curve of liquid 4He. Neutron spectroscopy data are analyzed in relation to a certain physical hypothesis concerning the formation of such a spectrum, and it is found that the majority of the known experimental facts can be explained in framework of that hypothesis. Particular attention is paid to a comparison of the experimental data obtained on the DIN-2PI time-of-flight spectrometer (at the IBR-2 Reactor, Dubna) with the results obtained at foreign research centers.

  2. Charge-induced instability of the /sup 4/He solid-superfluid interface

    SciTech Connect

    Savignac, D.; Leiderer, P.

    1982-12-20

    The interface between crystalline and superfluid /sup 4/He, when charged with negative ions, is deformed as a result of melting and crystallization processes. As long as the electric field normal to the interface is below a critical value, the deformation is stable and reversible. Above the critical field a charge-induced instability of the crystal is observed, which resembles the electrohydrodynamic instability of liquid surfaces.

  3. Competition between thermal fluctuations and disorder in the crystallization of 4He in aerogel.

    PubMed

    Nomura, Ryuji; Osawa, Aiko; Mimori, Tomohiro; Ueno, Ken-ichi; Kato, Haruko; Okuda, Yuichi

    2008-10-24

    The dynamical transition in the crystallization of 4He in aerogel has been investigated by direct visualization and dynamical phase diagrams have been determined. The crystal-superfluid interface in aerogel advances via creep at high temperatures and avalanches at low temperatures. The transition temperature is higher at a higher interface velocity and lower in higher porosity aerogels. The transition is due to competition between thermal fluctuations and disorder for the crystallization process. PMID:18999765

  4. Electronically tunable fiber laser for optical pumping of {sup 3}He and {sup 4}He

    SciTech Connect

    Stephens, E.F.; Patrick, H.; Gilbert, S.L.

    1996-03-01

    We present in this paper a low threshold, highly stable, integrated fiber laser cavity that uses an electronically tunable internal Bragg grating. The fiber laser produced over 5 mW with a spectral width of about 5 GHz at 1083 nm. The laser was used to achieve 30{percent} polarization of the 2{sup 3}{ital S}{sub 1} metastable states of {sup 4}He in a weak rf discharge cell. {copyright} {ital 1996 American Institute of Physics.}

  5. Wave Turbulence in Superfluid {sup 4}He: Energy Cascades and Rogue Waves in the Laboratory

    SciTech Connect

    Efimov, V. B.; Ganshin, A. N.; McClintock, P. V. E.; Kolmakov, G. V.; Mezhov-Deglin, L. P.

    2008-11-13

    Recent work on second sound acoustic turbulence in superfluid {sup 4}He is reviewed. Observations of forward and inverse energy cascades are described. The onset of the inverse cascade occurs above a critical driving energy and it is accompanied by giant waves that constitute an acoustic analogue of the rogue waves that occasionally appear on the surface of the ocean. The theory of the phenomenon is outlined and shown to be in good agreement with the experiments.

  6. A new method for determining the 3He/4He ratio in the local interstellar medium

    NASA Astrophysics Data System (ADS)

    Lemoine, M.; Vidal-Madjar, A.; Ferlet, R.

    1993-06-01

    We propose here an original method for estimating the 3He/4 Heratio in the local diffuse interstellar medium at a low cost from an observational point of view. The main idea is to measure the shift in radial velocity of the 4He λ537Å and λ584Å lines due to the presence of 3He in the red wing of these lines, and to compare the observed shift to the shifts obtained through numerical simulations for different 3He/4He ratios. We performed such simulations in order to reveal the efficiency of this method, using typical astrophysical conditions and instrumental parameters corresponding to the Lyman-FUSE mission. We find that this method should yield the 3He/4He ratio with a 1 σ uncertainty ˜50% at a spectral resolving power R=30 000 and a signal-to-noise ratio S/N=50. This method thus appears more adapted to a forehand estimation of the interstellar 3He/4He ratio than the standard profile fitting method, which should yield a 1 σ uncertainty of 10% at R=30 000 and S/N ≃ 290 (Hurwitz & Bowyer, t985). Finally, our method should be able to settle the evolutionary status of 3He if 3He has been significantly enhanced or depleted in the last 4.6 Gyr. Combined with the measurement of the deuterium abundance on the same line of sight (already programmed on HST), this might yield very important constraint on Big-Bang nucleosynthesis consistency.

  7. Combination of a 3He/ 4He dilution refrigerator and an ESR spectrometer

    NASA Astrophysics Data System (ADS)

    von Spalden, Y.; Baberschke, K.

    1981-08-01

    We report the combination of a 3He/ 4He dilution refrigerator with ESR spectrometers of 1,3 and 9 GHz. Since only the sample is cooled down to Millikelvin, the microwave-frequency frequency setup can be changed very eaily during an experiment. The ESR intensities of a Au167 Er and a AuEr sample were used to calibrate the temperature of the sample.

  8. Primary populations of metastable antiprotonic (4)He and (3)He atoms.

    PubMed

    Hori, M; Eades, J; Hayano, R S; Ishikawa, T; Sakaguchi, J; Tasaki, T; Widmann, E; Yamaguchi, H; Torii, H A; Juhász, B; Horváth, D; Yamazaki, T

    2002-08-26

    Initial distributions of metastable antiprotonic (4)He and (3)He atoms over principal (n) and angular momentum (l) quantum numbers have been deduced using laser spectroscopy experiments. The regions n = 37-40 and n = 35-38 in the two atoms account for almost all of the observed fractions [(3.0 +/- 0.1)% and (2.4 +/- 0.1)%] of antiprotons captured into metastable states. PMID:12190401

  9. Selective adsorption of 4He on the NaCl(001) surface

    NASA Astrophysics Data System (ADS)

    Leung, W. Y.; Larese, J. Z.; Frankl, D. R.

    1984-01-01

    The diffraction of 4He nozzle beams at several energies from cleaved (001) surfaces of NaCl has been studied. Resonance features are identified and give binding energies of 4.1 ± 0.1, 1.5 ± 0.1 and 0.3 ± 0.15 meV. One feature suggests an energy of 5 meV, but this is unsubstantiated. The resonance signatures are in disagreement with elastic scattering theories.

  10. Observation of a Dislocation-Related Interfacial Friction Mechanism in Mobile Solid 4He

    NASA Astrophysics Data System (ADS)

    Eyal, Anna; Livne, Ethan; Polturak, Emil

    2016-04-01

    We report a study of the temperature and stress dependence of the friction associated with a relative motion of crystallites of solid 4He in contact with each other. A situation where such motion exists emerges spontaneously during a disordering of a single crystal contained inside an annular sample space of a torsional oscillator (TO). Under the torque applied by the oscillating walls of the TO these crystallites move relative to each other, generating measurable dissipation at their interface. We studied this friction between 0.5 and 1.8 K in solid samples grown from commercially pure 4He and from a 100 ppm 3He-4He mixture. The data were analyzed by modeling the TO as a driven harmonic oscillator. In this model, an analysis of the resonant frequency and amplitude of the TO yields the temperature dependence of the friction coefficient. By fitting the data to specific forms, we found that over our temperature range, the dominant friction mechanism associated with the interfacial motion of the crystallites results from climb of individual dislocations. The characteristic energy scale associated with this friction can be 3 or 6 K, depending on the sample. The motion of the solid in the presence of such friction can perhaps be described as the low limit of "slip-stick" motion.

  11. Superfluid Onset of 4He Nanotube Depending on a One-Dimensional Length

    NASA Astrophysics Data System (ADS)

    Matsushita, T.; Shinohara, A.; Hieda, M.; Wada, N.

    2016-05-01

    A 1D Bose fluid has been actually realized for the 4 He nanotubes formed in 1D nanochannels, and the superfluidity observed by a torsional oscillator. Dependence of the superfluid density on the channel diameter was qualitatively well explained by a theory that the superfluid onset temperature depends on an effective 1D length L_{eff} which is the ratio of the length to the circumference of the fluid nanotube. To examine this mechanism, we measured the superfluid of a new 4 He nanotube formed in the 1D channel with the diameter 3.1 nm and the length 10-20 \\upmu m, which is one order longer than that of the former channels. The observed superfluid is similar to that of the much smaller diameter, typically 2.2 or 1.8 nm, channel with the shorter length. This indicates that the superfluid onset observed for the present 4He nanotubes is determined by the finite effective 1D length L_{eff}, not by the channel diameter. In addition to this length dependence, dynamics at the 1D superfluid onset is indicated by a dissipation peak at 103 Hz measurement frequency.

  12. Observation of Non-Classical Rotational Inertia in Bulk Solid 4He

    NASA Astrophysics Data System (ADS)

    Kondo, Motoshi; Takada, Shunichi; Shibayama, Yoshiyuki; Shirahama, Keiya

    2007-09-01

    In recent torsional oscillator experiments by Kim and Chan (KC), a decrease of rotational inertia has been observed in solid 4He in porous materials (Kim, E., Chan, M.H.W. in Nature 427:225, 2004; J. Low Temp. Phys. 138:859, 2005) and in a bulk annular channel (Kim, E., Chan, M.H.W. in Science 305:1941, 2004). This observation strongly suggests the existence of “non-classical rotational inertia” (NCRI), i.e. superflow, in solid 4He. In order to study such a possible “supersolid” phase, we perform torsional oscillator experiments for cylindrical solid 4He samples. We have observed decreases in rotational inertia below 200 mK for two solid samples (pressures P=4.1 and 3.0 MPa). The observed NCRI fraction at 70 mK is 0.14%, which is about 1/3 of the fraction observed in the annulus by KC. Our observation is the first experimental confirmation of the possible supersolid finding by KC.

  13. New solar axion search using the CERN Axion Solar Telescope with 4He filling

    NASA Astrophysics Data System (ADS)

    Arik, M.; Aune, S.; Barth, K.; Belov, A.; Bräuninger, H.; Bremer, J.; Burwitz, V.; Cantatore, G.; Carmona, J. M.; Cetin, S. A.; Collar, J. I.; Da Riva, E.; Dafni, T.; Davenport, M.; Dermenev, A.; Eleftheriadis, C.; Elias, N.; Fanourakis, G.; Ferrer-Ribas, E.; Galán, J.; García, J. A.; Gardikiotis, A.; Garza, J. G.; Gazis, E. N.; Geralis, T.; Georgiopoulou, E.; Giomataris, I.; Gninenko, S.; Gómez Marzoa, M.; Hasinoff, M. D.; Hoffmann, D. H. H.; Iguaz, F. J.; Irastorza, I. G.; Jacoby, J.; Jakovčić, K.; Karuza, M.; Kavuk, M.; Krčmar, M.; Kuster, M.; Lakić, B.; Laurent, J. M.; Liolios, A.; Ljubičić, A.; Luzón, G.; Neff, S.; Niinikoski, T.; Nordt, A.; Ortega, I.; Papaevangelou, T.; Pivovaroff, M. J.; Raffelt, G.; Rodríguez, A.; Rosu, M.; Ruz, J.; Savvidis, I.; Shilon, I.; Solanki, S. K.; Stewart, L.; Tomás, A.; Vafeiadis, T.; Villar, J.; Vogel, J. K.; Yildiz, S. C.; Zioutas, K.; CAST Collaboration

    2015-07-01

    The CERN Axion Solar Telescope (CAST) searches for a →γ conversion in the 9 T magnetic field of a refurbished LHC test magnet that can be directed toward the Sun. Two parallel magnet bores can be filled with helium of adjustable pressure to match the x-ray refractive mass mγ to the axion search mass ma. After the vacuum phase (2003-2004), which is optimal for ma≲0.02 eV , we used 4He in 2005-2007 to cover the mass range of 0.02-0.39 eV and 3He in 2009-2011 to scan from 0.39 to 1.17 eV. After improving the detectors and shielding, we returned to 4He in 2012 to investigate a narrow ma range around 0.2 eV ("candidate setting" of our earlier search) and 0.39-0.42 eV, the upper axion mass range reachable with 4He, to "cross the axion line" for the KSVZ model. We have improved the limit on the axion-photon coupling to ga γ<1.47 ×10-10 GeV-1 (95% C.L.), depending on the pressure settings. Since 2013, we have returned to the vacuum and aim for a significant increase in sensitivity.

  14. Active Inspection of Nuclear Materials Using {sup 4}He Scintillation Detectors

    SciTech Connect

    Davatz, G.; Howard, A.; Chandra, R.; Gendotti, U.

    2011-12-13

    The detection of fissionable materials by neutron and high-energy photon active interrogation methods is explored using {sup 4}He scintillation detectors to search for prompt and delayed neutron signature. The low electron density of {sup 4}He in addition to its pulse shape discrimination capability allows strong rejection of gamma radiation. For the detection of the prompt neutron signatures, this capability is important as the signal produced by induced fission is accompanied by intense gamma radiation. The nanosecond time resolution of {sup 4}He scintillation detectors can be used for time-of-flight measurements aimed at determining the energy of the emitted neutrons. For delayed neutron detection, the insensitivity to the low energy neutrons present from non-signal reactions is inherent. Unlike detectors requiring a moderator, this technology can easily be collimated to reduce sensitivity to neutrons from outside the field of interest. The performance of the detectors for these applications is studied using GEANT4 computer modeling, based on measured detector parameters. A comparison is made with technologies typically used for these applications, i.e. heavily shielded organic scintillators for prompt neutron detection and Cd-lined {sup 3}He neutron detectors for the detection of delayed neutrons.

  15. Tracing nitrogen accumulation in decaying wood and examining its impact on wood decomposition rate

    NASA Astrophysics Data System (ADS)

    Rinne, Katja T.; Rajala, Tiina; Peltoniemi, Krista; Chen, Janet; Smolander, Aino; Mäkipää, Raisa

    2016-04-01

    Decomposition of dead wood, which is controlled primarily by fungi is important for ecosystem carbon cycle and has potentially a significant role in nitrogen fixation via diazotrophs. Nitrogen content has been found to increase with advancing wood decay in several studies; however, the importance of this increase to decay rate and the sources of external nitrogen remain unclear. Improved knowledge of the temporal dynamics of wood decomposition rate and nitrogen accumulation in wood as well as the drivers of the two processes would be important for carbon and nitrogen models dealing with ecosystem responses to climate change. To tackle these questions we applied several analytical methods on Norway spruce logs from Lapinjärvi, Finland. We incubated wood samples (density classes from I to V, n=49) in different temperatures (from 8.5oC to 41oC, n=7). After a common seven day pre-incubation period at 14.5oC, the bottles were incubated six days in their designated temperature prior to CO2 flux measurements with GC to determine the decomposition rate. N2 fixation was measured with acetylene reduction assay after further 48 hour incubation. In addition, fungal DNA, (MiSeq Illumina) δ15N and N% composition of wood for samples incubated at 14.5oC were determined. Radiocarbon method was applied to obtain age distribution for the density classes. The asymbiotic N2 fixation rate was clearly dependent on the stage of wood decay and increased from stage I to stage IV but was substantially reduced in stage V. CO2 production was highest in the intermediate decay stage (classes II-IV). Both N2 fixation and CO2 production were highly temperature sensitive having optima in temperature 25oC and 31oC, respectively. We calculated the variation of annual levels of respiration and N2 fixation per hectare for the study site, and used the latter data together with the 14C results to determine the amount of N2 accumulated in wood in time. The proportion of total nitrogen in wood

  16. On the Evolution of the Light Elements. I. D, 3He, and 4He

    NASA Astrophysics Data System (ADS)

    Fields, Brian D.

    1996-01-01

    The light elements D, 3He, 4He, and 7Li are produced in big bang nucleosynthesis and undergo changes in their abundances due to Galactic processing. Since one may observe most of these elements only in contemporary environments, knowledge of the intervening evolution is necessary for determining the observational constraints on primordial nucleosynthesis Chemical and stellar evolution model dependences in light element evolution are systematically investigated via a comparison of 1460 possible chemical evolution scenarios and a comparison of stellar nucleosynthesis yields, all of which have been selected to fit solar neighborhood C, N, 0, and Fe abundances as well as the observed local gas density and gas mass fraction. The light element evolution and solar system yields in these models are found to span a wide range, explicitly demonstrating the model dependence. The range of model dependence for D, 3He, and 4He solar abundances is calculated, and its sensitivity to the heavy element constraints is noted. The chemical evolution contribution to the uncertainty in the observed primordial light element abundances is estimated, and the effects of this uncertainty on big bang nucleosynthesis results are discussed. The predictions for the light elements are found to be correlated; the extent and physical origin of these correlations is discussed. D and 3He evolution is found to have significant model dependence; however, the dominant factor determining their solar and interstellar abundances is their primordial abundance. In addition, 3He is found to be very sensitive to the details of processing in low-mass stars. 4He yields are shown to be very model dependent. In particular, both the introduction of mass loss and the possibly very high 4He stellar yields in the poorly understood mass range of ˜8-12Msun can lead to large enhancement of 4He production and can lead to large slopes of ΔY/ΔN and ΔY/ΔO. It is found that the inclusion of secondary nitrogen leads to

  17. Accumulation rates of the heavy metals lead, mercury and cadmium in ombrotrophic peatlands in the west of Ireland

    NASA Astrophysics Data System (ADS)

    Coggins, A. M.; Jennings, S. G.; Ebinghaus, R.

    The vertical distributions of three heavy metals: Hg, Pb and Cd were determined in 3 cores sampled from two ombrotrophic bogs in the west of Ireland, one at Knockroe Co. Mayo, and the second at Letterfrack National Park, Co. Galway. Core chronologies were established using 210Pb dating techniques and were checked with fallout radionuclides from weapons testing. Variations were found in metal concentrations and cumulative inventories of each of the metals within each site and between the two sites. Maximum accumulation rates of the anthropogenically derived elements Hg, Pb, and Cd, were found in peat sediments dated between 1950 and 1970s at both sites. Pb and Hg accumulation rates are slightly lower than those found in similar studies from remote sites in Europe. Hg accumulation rates are fairly similar to those found in peatlands in America. Unlike the Pb and Hg concentration profiles, the Cd concentration profiles at the Letterfrack site were dominated by a surface enrichment, thought to be due to biological cycling of Cd in the peat. However Cd accumulation rates calculated at the Knockroe site are lower than those observed in Eastern Europe. Local meteorological conditions at the sites chosen for this study may account for the lower concentrations profiles observed when compared with some of the European studies. The similarity between the timing of the increase in metal accumulation rates in peat bogs in Northern America and this study could indicate that long range transportation of trace metals from Northern America may be occurring. Lead accumulations in the surface peat sediments (1993-1996) were between 1.5-3.0 mg m -2 yr -1 and 4-5 mg m -2 yr -1 at Knockroe and Letterfrack, respectively. Mercury accumulation rates for the same period at Knockroe were found to be between 6-11 μg m -2 yr -1, and between 19-24 μg m -2 yr -1 at Letterfrack. A greater variation in surface Cd accumulation rates was observed at both sites, with surface layer accumulation

  18. Impacts of timber harvesting on historic sediment accumulation rates in the Coos Bay estuary, Oregon

    NASA Astrophysics Data System (ADS)

    Mathabane, N.; Roering, J. J.

    2014-12-01

    The expansion and development of human infrastructure along the coastline of the Pacific Northwest has profound consequences for the habitability and general ecological health of coastal ecosystems. Coos County, one of the most economically critical regions of the Oregon Coast, experienced vigorous timber harvest activity in the aftermath of WWII that declined in the last several decades. This period of extractive land use may have drastically altered the sediment supply in the major catchments of the Coos and Millicoma Rivers and lead to variations in sediment flux into the Coos Bay estuary. Accurate sediment flux histories are critical data for deciphering the relative importance of climate and land use factors such as logging and road construction on sediment production. Reduction of root reinforcement following timber harvest increases the likelihood of shallow landsliding and debris flows. In addition, forest roads increase sediment production due to overland flow and entrainment of fine sediments on hydrologically connected roads. Although these processes have been documented in small watersheds, their compounded effect on estuaries and coastal settings has not been well documented. We use Pb-210 activities derived from sediment cores taken at various locations in the Coos Bay estuary to establish temporal variations in sediment accumulation rates (SARs). Our cores will also be analyzed to assess dissolved oxygen and other proxies for ecosystem functioning. By correlating these SARs with quantitative metrics for timber extraction rate such as board feet per year and qualitative evaluations from historical photos, we propose to document the cumulative effect of historic forest practices. The temporal resolution provided by this technique should allow us to link changes in estuarine sedimentation to changes in land use as well as climatic triggers such as storms. The conclusions of this study will add valuable information regarding the ultimate impact of

  19. Apatite 4He/3He thermochronometry evidence for an ancient Grand Canyon, Colorado Plateau, USA

    NASA Astrophysics Data System (ADS)

    Flowers, R. M.; Farley, K. A.

    2012-12-01

    The very existence of Grand Canyon inspires questions about why canyons are carved, how drainage systems and landscapes evolve, and how these processes relate to the elevation gain of plateaus. Yet when and why Grand Canyon was carved have been extraordinarily controversial for more than 150 years. Over the last several decades, the dominant view for the origin of the canyon is one of rapid incision at 5-6 Ma, when detritus derived from the upstream reaches of the Colorado River system appeared in Grand Wash Trough at the Colorado River's western exit from the Colorado Plateau. The absence of such diagnostic deposits prior to 6 Ma has been used to argue that Grand Canyon was not yet excavated (e.g., Karlstrom et al., 2008). However, a variety of data hint at a more ancient age for part or all of the canyon, and it has been proposed that a smaller drainage basin in largely carbonate lithologies could explain the absence of pre-6 Ma Colorado River clastics in Grand Wash Trough even if a significant Grand Canyon were present. Most recently, apatite (U-Th)/He (AHe) thermochronometry data from western Grand Canyon were used to infer excavation of this area to within several hundred meters of its modern depth by ca. 70 Ma (Wernicke, 2011), an interpretation in direct conflict with the young canyon model. The unexpected implications of the initial Grand Canyon AHe work motivated the apatite 4He/3He and U-Th zonation study presented here. Apatite 4He/3He thermochronometry provides information about the spatial distribution of radiogenic 4He in an apatite crystal that can better constrain a sample's cooling history. A key premise of AHe and 4He/3He spectra interpretation is that the He kinetic model used is accurate. We first investigate whether differing 4He/3He spectra for apatites of variable AHe date, radiation damage, and U-Th zonation from eastern Grand Canyon yield mutually consistent thermal history results using the RDAAM kinetic model, which must be true if the

  20. BIOACCUMULATION OF KEPONE BY SPOT ('LEIOSTOMUS XANTHURUS'): IMPORTANCE OF DIETARY ACCUMULATION AND INGESTION RATE

    EPA Science Inventory

    The relative extent of dietary accumulation and bioconcentration of Kepone by spot (Leiostomus xanthurus) was quantitatively evaluated at food rations of 4, 8, or 20% of the average wet weight of fish. 14C-Kepone was utilized to determine bioconcentration and dietary accumulation...

  1. Constraints on the recent rate of lunar regolith accumulation from Diviner observations

    NASA Astrophysics Data System (ADS)

    Ghent, R. R.; Hayne, P. O.; Bandfield, J. L.; Campbell, B. A.; Carter, L. M.; Allen, C.; Paige, D. A.

    2012-12-01

    Many large craters on the lunar nearside show radar CPR signatures consistent with the presence of blocky ejecta blankets, to distances predicted to be covered by continuous ejecta. However, most of these surfaces show limited enhancements in both derived rock abundance and rock-free regolith temperatures calculated from Diviner nighttime infrared observations. This indicates that the surface rocks are covered by a layer of thermally insulating regolith material. By matching the results of one-dimensional thermal models to Diviner nighttime temperatures, we have constrained the thermophysical properties of the upper regolith, and the thickness of regolith overlying proximal ejecta. We find that for all of the regions surveyed (all in the nearside highlands), the nighttime cooling curves are best fit by a density profile that varies exponentially with depth, consistent with a linear mixture of rocks and regolith fines, with increasing rock content with depth. Our results show significant spatial variations in the density e-folding depth, H, among young crater ejecta regions, indicating differences in the thickness of accumulated regolith. However, away from young craters, the average regional "equilibrium" value of H (Heq) is remarkably consistent, and is on the order of 5 cm. As expected, near-rim ejecta associated with young craters show lower values of H, indicating a high rock content in the shallow subsurface; for older craters, the average value of H approaches the regional value of Heq. Calculated H values for young craters (Giordano Bruno, Moore F, Byrgius A, Necho, Tycho, Jackson, King, and Copernicus) show a clear correlation with published ages, providing the first observational constraint on the recent rate of lunar regolith accumulation. In addition, this result may help to resolve the apparent discrepancy between ages calculated from small crater counts on melt ponds versus counts on continuous ejecta (e.g., King crater; Ashley et al., 2011, LPSC 42

  2. Shell-model description of the charge form factor and the first excited state in /sup 4/He

    SciTech Connect

    Bevelacqua, J.J.

    1982-09-01

    A /sup 4/He shell-model formalism, including two- and three-body forces, is used to calculate ground and first excited state properties. Inclusion of the three-body force improves the calculated ground state rms radius, ground state form factor, and position of the /sup 4/He first excited state.

  3. Estimating the groundwater residence time in eskers of the Amos region, northern Quebec by 3H-3He and (U-Th/4He) methods

    NASA Astrophysics Data System (ADS)

    Boucher, Christine; Berthot, Laureline; Pinti, Daniele Luigi; Larocque, Marie; Cloutier, Vincent; Blanchette, Daniel; Castro, Maria Clara; Hall, Chris M.

    2013-04-01

    -Mathieu-Berry esker and the Harricana moraine allowing calculation of vertical infiltration rates varying between 0.9 and 7.0 m/yr. A calibrated 4He production rate allows estimation of (U-Th/4He) groundwater residence times. The oldest waters are those from the fractured bedrock and display an age of 8000 years. Intermediate waters with ages varying from 50 to 800 yrs are likely the result of mixing between deeper fossil water and freshwater flowing through the eskers. Interestingly, the oldest ages recorded in the Saint Mathieu Berry esker are located in a fault zone.

  4. Use of correlated potential harmonic basis functions for the description of the {sup 4}He trimer and small clusters

    SciTech Connect

    Das, Tapan Kumar; Chakrabarti, Barnali; Canuto, Sylvio

    2011-04-28

    A correlated many-body basis function is used to describe the {sup 4}He trimer and small helium clusters ({sup 4}He{sub N}) with N= 4 - 9. A realistic helium dimer potential is adopted. The ground state results of the {sup 4}He dimer and trimer are in close agreement with earlier findings. But no evidence is found for the existence of Efimov state in the trimer for the actual {sup 4}He-{sup 4}He interaction. However, decreasing the potential strength we calculate several excited states of the trimer which exhibit Efimov character. We also solve for excited state energies of these clusters which are in good agreement with Monte Carlo hyperspherical description.

  5. Low-energy R -matrix fits for the 6Li(d ,α ) 4HeS factor

    NASA Astrophysics Data System (ADS)

    Grineviciute, J.; Lamia, L.; Mukhamedzhanov, A. M.; Spitaleri, C.; La Cognata, M.

    2015-01-01

    Background: Information about the 6Li(d ,α ) 4He reaction rates of astrophysical interest can be obtained by extrapolating direct data to lower energies, or by indirect methods. The indirect Trojan horse method, as well as various R -matrix and polynomial fits to direct data, estimate electron screening energies much larger than the adiabatic limit. Calculations that include the subthreshold resonance estimate smaller screening energies. Purpose: Obtain the 6Li(d,α ) 4He reaction R -matrix parameters and the bare astrophysical S factor for energies relevant to the stellar plasmas by fitting R -matrix formulas for the subthreshold resonances to the S -factor data above 60 keV. Methods: The bare S factor is calculated using the single- and the two-level R -matrix formulas for the closest to the threshold 0+ and 2+ subthreshold states at 22.2 ,20.2 , and 20.1 MeV. The electron screening potential U e is then obtained by fitting it as a single parameter to the low-energy data. The calculations are also done by fitting U e simultaneously with other parameters. Results: The low-energy S factor is dominated by the 2+ subthreshold resonance at 22.2 MeV. The influence of the other two subthreshold states is small. The resultant electron screening is smaller than the adiabatic value. The fits that neglect the electron screening above 60 keV produce a significantly smaller electron screening potential. The calculations show a large ambiguity associated with a choice of the initial channel radius. Conclusions: The R -matrix fits do not show a significantly larger Ue than predicted by the atomic physics models. The R -matrix best fit provides U e=149.5 eV and Sb(0 ) =21.7 MeV b.

  6. 210Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Delbono, I.; Barsanti, M.; Schirone, A.; Conte, F.; Delfanti, R.

    2016-08-01

    Nine sediment cores were collected between 2009 and 2012 in the inner continental shelf (Mediterranean Sea, Italy) mainly influenced by the Magra River, at water depths ranging from 11 to 64 m. Mass Accumulation Rates (MARs) were calculated through 210Pb analysed by Gamma spectrometry. Three different dating models (single and two-layer CF-CS, CRS) were applied to clay normalised 210Pbxs profiles and 137Cs was used to validate the 210Pb geochronology. The maximum MAR values (>2 g cm-2 yr-1) were found in the region adjacent to the Magra River mouth and outside the Gulf of La Spezia (0.9±0.1 g cm-2 yr-1 at St. 3-C6 and 4-C4). Results from 137Cs/210Pbxs ratios calculated in Surface Mixed Layers (SMLs) evidenced the coastal boundaries of the Magra River depositional area, which is very limited towards south. Differently, in the north-west sector, fine sediments are generally driven by the Ligurian Current and move towards north-west: at the deepest and most distant station from the River mouth, the MAR value is the lowest one in the study area. Few major Magra River floods occurred during the sediment core sampling period. By using the short-lived radioisotope 7Be as a tracer of river floods, a clear 7Be signature of 2009 flood is present at St. 1-SA1C. Finally, by analyzing the clay normalised 210Pbxs profiles, a decrease of its activity dating the years 1999 and 2000 is observed in four cores, corresponding to two major Magra River floods occurring in those years.

  7. Accumulate repeat accumulate codes

    NASA Technical Reports Server (NTRS)

    Abbasfar, Aliazam; Divsalar, Dariush; Yao, Kung

    2004-01-01

    In this paper we propose an innovative channel coding scheme called 'Accumulate Repeat Accumulate codes' (ARA). This class of codes can be viewed as serial turbo-like codes, or as a subclass of Low Density Parity Check (LDPC) codes, thus belief propagation can be used for iterative decoding of ARA codes on a graph. The structure of encoder for this class can be viewed as precoded Repeat Accumulate (RA) code or as precoded Irregular Repeat Accumulate (IRA) code, where simply an accumulator is chosen as a precoder. Thus ARA codes have simple, and very fast encoder structure when they representing LDPC codes. Based on density evolution for LDPC codes through some examples for ARA codes, we show that for maximum variable node degree 5 a minimum bit SNR as low as 0.08 dB from channel capacity for rate 1/2 can be achieved as the block size goes to infinity. Thus based on fixed low maximum variable node degree, its threshold outperforms not only the RA and IRA codes but also the best known LDPC codes with the dame maximum node degree. Furthermore by puncturing the accumulators any desired high rate codes close to code rate 1 can be obtained with thresholds that stay close to the channel capacity thresholds uniformly. Iterative decoding simulation results are provided. The ARA codes also have projected graph or protograph representation that allows for high speed decoder implementation.

  8. Geographic variability in organic carbon stock and accumulation rate in sediments of East and Southeast Asian seagrass meadows

    NASA Astrophysics Data System (ADS)

    Miyajima, Toshihiro; Hori, Masakazu; Hamaguchi, Masami; Shimabukuro, Hiromori; Adachi, Hiroshi; Yamano, Hiroya; Nakaoka, Masahiro

    2015-04-01

    Organic carbon (OC) stored in the sediments of seagrass meadows has been considered a globally significant OC reservoir. However, the sparsity and regional bias of studies on long-term OC accumulation in coastal sediments have limited reliable estimation of the capacity of seagrass meadows as a global OC sink. We evaluated the amount and accumulation rate of OC in sediment of seagrass meadows and adjacent areas in East and Southeast Asia. In temperate sites, the average OC concentration in the top 30 cm of sediment was higher in seagrass meadows (780-1080 mmol g-1) than in sediments without seagrass cover (52-430 mmol g-1). The average OC in the top 30 cm of subtropical and tropical seagrass meadow sediments ranged from 140 to 440 mmol g-1. Carbon isotope mass balancing suggested that the contribution of seagrass-derived carbon to OC stored in sediments was often relatively minor (temperate: 10-40%; subtropical: 35-82%; tropical: 4-34%) and correlated to the habitat type, being particularly low in estuarine habitats. Stock of OC in the top meter of sediment of all the studied meadows ranged from 38 to 120 Mg ha-1. The sediment accumulation rates were estimated by radiocarbon dating of six selected cores (0.32-1.34 mm yr-1). The long-term OC accumulation rates calculated from the sediment accumulation rate and the top 30 cm average OC concentration for the seagrass meadows (24-101 kg ha-1 yr-1) were considerably lower than the OC accumulation rates previously reported for Mediterranean Posidonia oceanica meadows (580 kg ha-1 yr-1 on average). Current estimates for the global carbon sink capacity of seagrass meadows, which rely largely on Mediterranean studies, may be considerable overestimations.

  9. Spatially Extended Avalanches in a Hysteretic Capillary Condensation System: Superfluid {sup {bold 4}}He in Nuclepore

    SciTech Connect

    Lilly, M.P.; Wootters, A.H.; Hallock, R.B.

    1996-11-01

    Capacitive studies of hysteretic capillary condensation of superfluid {sup 4}He in Nuclepore have shown that the initial draining of the pores occurs over a small range of the chemical potential with avalanches present as groups of pores drain. In the work reported here, the avalanches in this system are shown to be nonlocal events which involve pores distributed at low density across the entire sample. The nonlocal avalanche behavior is shown to be enabled by the presence of a superfluid film connection among the pores. {copyright} {ital 1996 The American Physical Society.}

  10. Candidate Resonant Tetraneutron State Populated by the 4He (8H3, 8Be) ) Reaction

    NASA Astrophysics Data System (ADS)

    Kisamori, K.; Shimoura, S.; Miya, H.; Michimasa, S.; Ota, S.; Assie, M.; Baba, H.; Baba, T.; Beaumel, D.; Dozono, M.; Fujii, T.; Fukuda, N.; Go, S.; Hammache, F.; Ideguchi, E.; Inabe, N.; Itoh, M.; Kameda, D.; Kawase, S.; Kawabata, T.; Kobayashi, M.; Kondo, Y.; Kubo, T.; Kubota, Y.; Kurata-Nishimura, M.; Lee, C. S.; Maeda, Y.; Matsubara, H.; Miki, K.; Nishi, T.; Noji, S.; Sakaguchi, S.; Sakai, H.; Sasamoto, Y.; Sasano, M.; Sato, H.; Shimizu, Y.; Stolz, A.; Suzuki, H.; Takaki, M.; Takeda, H.; Takeuchi, S.; Tamii, A.; Tang, L.; Tokieda, H.; Tsumura, M.; Uesaka, T.; Yako, K.; Yanagisawa, Y.; Yokoyama, R.; Yoshida, K.

    2016-02-01

    A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the double-charge-exchange reaction 4He (8H3, 8Be) at 186 MeV /u . The energy of the state is 0.83 ±0.65 (stat ) ±1.25 (syst ) MeV above the threshold of four-neutron decay with a significance level of 4.9 σ . Utilizing the large positive Q value of the (8He, 8Be) reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently.

  11. Inclusive proton polarization in. gamma. sup 3,4 He r arrow pX reactions

    SciTech Connect

    Zybalov, A.A.; Karasev, S.P.; Konovalov, O.G.; Marekhin, S.V.; Sorokin, P.V.; Storozhenko, Y.O.; Tenishev, A.E. )

    1989-05-01

    This paper presents the first measured data on the inclusive proton polarization in the interaction of photons with {sup 3}He and {sup 4}He nuclei. The proton energy (170 MeV) and emission angle (72{degree}) were chosen such that the proton yield from the meson photoproduction reaction on free nucleons should be kinematically forbidden, and the photon energy in the disintegration of the two-nucleon pair in the nucleus should be such that ensures an essential polarization of the proton from the deuteron photodisintegration. The measurements were performed using the Kharkov 2 GeV electron linac facilities. (AIP)

  12. Measurements of Vortex Line Density Generated by a Quartz Tuning Fork in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Jackson, M. J.; Kolosov, O.; Schmoranzer, D.; Skrbek, L.; Tsepelin, V.; Woods, A. J.

    2016-05-01

    We present proof-of-concept measurements of the vortex line density generated by a quartz tuning fork resonator probed by the attenuation of second sound in superfluid ^4He at 1.6 K. The force-velocity response of a quartz tuning fork operating at a frequency of 31 kHz exhibited the onset of extra damping at a velocity of 0.5 ms^{-1}. Attenuation of the 5th resonant mode of second sound was observed at the same velocity, indicating the production of vortex lines. Our measurements demonstrate that an increase of the drag coefficient corresponds to the development of quantum turbulence.

  13. Formation of a Mesa Shaped Phonon Pulse in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Adamenko, I. N.; Nemchenko, K. E.; Slipko, V. A.

    2010-05-01

    We present a theory for the formation of a mesa shaped phonon pulse in superfluid 4He. Starting from the hydrodynamic equations of superfluid helium, we obtain the system of equations which describe the evolution of strongly anisotropic phonon systems. Such systems can be created experimentally. The solution of the equations are simple waves, which correspond to second sound in the moving phonon pulse. Using these exact solutions, we describe the expansion of phonon pulses in superfluid helium at zero temperature. This theory gives an explanation for the mesa shape observed in the measured phonon angular distributions. Almost all dependencies of the mesa shape on the system parameters can be qualitatively understood.

  14. Communication: Nucleation of quantized vortex rings in {sup 4}He nanodroplets

    SciTech Connect

    Mateo, David; Leal, Antonio; Barranco, Manuel; Pi, Martí; Hernando, Alberto; Cargnoni, Fausto; Mella, Massimo; Zhang, Xiaohang; Drabbels, Marcel

    2014-04-07

    Whereas most of the phenomena associated with superfluidity have been observed in finite-size helium systems, the nucleation of quantized vortices has proven elusive. Here we show using time-dependent density functional simulations that the solvation of a Ba{sup +} ion created by photoionization of neutral Ba at the surface of a {sup 4}He nanodroplet leads to the nucleation of a quantized ring vortex. The vortex is nucleated on a 10 ps timescale at the equator of a solid-like solvation structure that forms around the Ba{sup +} ion. The process is expected to be quite general and very efficient under standard experimental conditions.

  15. Measurements of Superfluid 4He Flow Through Sub-15 nm Aperture Arrays

    SciTech Connect

    Hoffmann, J. A.; Hunt, B.; Wang, M.; Davis, J. C.; Black, C. T.

    2006-09-07

    We have constructed an experiment designed to study Josephson phenomena in 4He. Motivated by reports and our ideas for novel silicon nanofabrication techniques, we designed the experiment to study the possibility of a transition from stochastic to coherent phase slippage. Here we briefly describe the nanofabrication of sub-15 nm aperture arrays and show preliminary data. For temperatures below 2 K, these data show temperature dependence of the superfluid critical velocity through the weak link which is characteristic of phase-slip limited flow.

  16. Heat Capacity of Superfluid (sup 4)He in the Presence of a Heat Current Near T

    NASA Technical Reports Server (NTRS)

    Chui, Talso C. P.; Goodstein, David L.; Harter, Alexa W.; Mukhopadhyay, Ranjan

    1996-01-01

    The thermodynamic theory of superfluid helium in the presence of a heat current is presented. We show that there is a thermodynamic relation between the heat capacity and the expression ps(W), which describes the depression of the superfluid density with the counterflow velocity W. Using this relation we show that the heat capacity of superfluid super4He in the presence of a heat current diverges at a depressed lambda transition temperature, suggesting the possibility of a new second order phase transition where the superfluid wave function is not the order parameter.

  17. Superfluidity, Bose condensation and neutron scattering in liquid {sup 4}He

    SciTech Connect

    Silver, R.N.

    1997-04-01

    The relation between superfluidity and Bose condensation in {sup 4}He provides lessons that may be valuable in understanding the strongly correlated electron system of high {Tc} superconductivity. Direct observation of a Bose condensate in the superfluid by deep inelastic neutron scattering measurements has been attempted over many years. But the impulse approximation, which relates momentum distributions to neutron scattering structure functions, is broadened by final state effects. Nevertheless, the excellent quantitative agreement between ab initio quantum many body theory and high precision neutron experiments provides confidence in the connection between superfluidity and Bose condensation.

  18. Torsional oscillator and synchrotron x-ray experiments on solid {sup 4}He in aerogel.

    SciTech Connect

    Mulders, N.; West, J. T.; Chan, M. H. W.; Kodituwakku, C. N.; Burns, C. A.; Lurio, L. B.; Univ. of Delaware; Pennsylvania State Univ.; Western Michigan Univ.; Northern Illinois Univ.

    2008-01-01

    X-ray diffraction experiments show that solid {sup 4}He grown in aerogel is highly polycrystalline, with an hcp crystal structure (as in bulk) and a crystallite size of approximately 100 nm. In contrast to the expectation that the highly disordered solid will have a large supersolid fraction, torsional oscillator measurements show a behavior that is strikingly similar to high purity crystals grown from the superfluid phase. The low temperature supersolid fraction is only {approx}3 x 10{sup -4}, and the onset temperature is {approx}100 mK.

  19. Dynamics of the BCC-HCP transition of solid 4He

    NASA Astrophysics Data System (ADS)

    Fujii, Hirosuke; Okumura, Yuji; Matsumoto, Koichi; Okuda, Yuichi

    2000-07-01

    We are optically studying the phase transition from BCC to HCP of solid 4He (1.43 K) at melting pressure to investigate how the crystal changes its structure when it is in equilibrium with superfluid. When the temperature was changed slowly through the transition, new phase seeds were nucleated somewhere and those seeds grew in the superfluid phase. The interesting point is that growth of the new seeds is more favorable than the direct solid-solid Martensitic transition. Whereas at the transition of 1.78 K where the solid is in equilibrium with the normal fluid, the transition occurred as an ordinary Martensitic transition.

  20. Self-consistent continuum random-phase approximation calculations of {sup 4}He electromagnetic responses

    SciTech Connect

    De Donno, V.; Co', G.; Anguiano, M.; Lallena, A. M.

    2011-09-15

    We study the electromagnetic responses of {sup 4}He within the framework of the self-consistent continuum random-phase approximation theory. In this approach, the ground-state properties are described by a Hartree-Fock calculation. The single-particle basis constructed in this manner is used in the calculations of the continuum responses of the system. Finite-range interactions are considered in the calculations. We compare our results with photon-absorption cross sections and electron-scattering quasielastic data. From this comparison, and also from the comparison with the results of microscopic calculations, we deduce that our approach describes well the continuum excitation.

  1. Properties of 4He and 6Li with improved chiral EFT interactions

    NASA Astrophysics Data System (ADS)

    Maris, P.; Binder, S.; Calci, A.; Epelbaum, E.; Furnstahl, R. J.; Golak, J.; Hebeler, K.; Kamada, H.; Krebs, H.; Langhammer, J.; Liebig, S.; Meißner, U.-G.; Minossi, D.; Nogga, A.; Potter, H.; Roth, R.; Skibiński, R.; Topolnicki, K.; Vary, J. P.; Witala, H.

    2016-03-01

    We present recent results for 4He and 6Li obtained with improved NN interactions derived from chiral effective field theory up to N4LO. The many-body calculations are performed order-by-order in the chiral expansion. At N3LO and N4LO additional renormalization using the Similarity Renormalization Group is adopted to improve numerical convergence of the many-body calculations. We discuss results for the ground state energies, as well as the magnetic moment and the low-lying spectrum of 6Li.

  2. Pion absorption on {sup 3}He and {sup 4}He with emission of three energetic protons

    SciTech Connect

    LADS Collaboration

    1997-06-01

    Results from a 4{pi} solid angle measurement of the reactions {sup 3}He({pi}{sup +},ppp) and {sup 4}He({pi}{sup +},ppp)n at incident pion energies of T{sub {pi}{sup +}}=70, 118, 162, 239, and 330 MeV are presented. For {sup 3}He the total absorption cross sections and their decomposition into two-proton and three-proton components are evaluated; for {sup 4}He the three-proton absorption cross sections are given. The differential distributions of the three-proton multinucleon absorption mode of both nuclei are analyzed and compared to each other by making use of a complete set of variables. The data are investigated for signatures of initial and final state interactions: it is found that more than half of the three-proton yield cannot be accounted for by cascade mechanisms. The remaining strength shows dependence on the incident pion angular momentum, but also structures that are not explained by simple semiclassical models. {copyright} {ital 1997} {ital The American Physical Society}

  3. Study on the Turbulent Flow of Superfluid 4He Generated by a Vibrating Wire

    SciTech Connect

    Yano, H.; Handa, A.; Obara, K.; Ishikawa, O.; Hata, T.; Nakagawa, M.

    2006-09-07

    We have studied the flow of superfluid 4He generated by a vibrating wire. As the drive force increases, the velocity of the wire grows in the laminar-flow regime, until it suddenly drops at the onset of the turbulent-flow regime. As the drive force decreases, the turbulence disappears at a critical velocity. This result suggests that the vortices on the wire are confined within a finite size, even in turbulence. We have measured the critical velocity of seven vibrating wires, whose resonance frequencies range from 0.5 kHz to 9 kHz, at 1.4 K and found that the critical velocity is almost constant below an oscillation frequency of 2 kHz and increases above this frequency. We have also observed the response of a vibrating wire in superfluid 4He at a low temperature of 30 mK. We find that the resonance frequency jumps upward at the same moment as the entry of the flow to a turbulent state. The frequency jump may be caused by vortex dynamics such as expansion, entanglement, and reconnection occurring in the turbulence.

  4. Spin-polarized hydrogen adsorbed on the surface of superfluid {sup 4}He

    SciTech Connect

    Marín, J. M.; Boronat, J.; Markić, L. Vranješ

    2013-12-14

    The experimental realization of a thin layer of spin-polarized hydrogen H↓ adsorbed on top of the surface of superfluid {sup 4}He provides one of the best examples of a stable, nearly two-dimensional (2D) quantum Bose gas. We report a theoretical study of this system using quantum Monte Carlo methods in the limit of zero temperature. Using the full Hamiltonian of the system, composed of a superfluid {sup 4}He slab and the adsorbed H↓ layer, we calculate the main properties of its ground state using accurate models for the pair interatomic potentials. Comparing the results for the layer with the ones obtained for a strictly 2D setup, we analyze the departure from the 2D character when the density increases. Only when the coverage is rather small the use of a purely 2D model is justified. The condensate fraction of the layer is significantly larger than in 2D at the same surface density, being as large as 60% at the largest coverage studied.

  5. Excitations in a thin liquid {sup 4}He film from inelastic neutron scattering

    SciTech Connect

    Clements, B.E. |; Godfrin, H.; Krotscheck, E. |; Lauter, H.J.; Leiderer, P.; Passiouk, V. |; Tymczak, C.J.

    1996-05-01

    We perform a thorough analysis of the experimental dynamic structure function measured by inelastic neutron scattering for a low-temperature ({ital T}=0.65 K) four-layer liquid {sup 4}He film. The results are interpreted in light of recent theoretical calculations of the (nonvortex) excitations in thin liquid Bose films. The experimental system consists of four outer liquid layers, adsorbed to two solid inner {sup 4}He layers, which are themselves adsorbed to a graphite substrate. Relatively intense surface (ripplon) and bulklike modes are observed. The analysis of the experimental data gives strong evidence for still other modes and supports the long-standing theoretical predictions of layerlike modes (layer phonons) associated with excitations propagating primarily within the liquid layers comprising the film. The results of the analysis are consistent with the occurrence of level crossings between modes, and the existence of a layer modes for which the theory predicts will propagate in the vicinity of the solid-liquid interface. The theory and experiment agree on the detailed nature of the ripplon; its dispersion at low momenta, its fall off in intensity at intermediate momenta, and the level crossings at high momentum. Similar to experiment, the theory yields an intense mode in the maxon-roton region which is intrepreted as the formation of the bulklike excitation. {copyright} {ital 1996 The American Physical Society.}

  6. Ab initio many-body calculations of nucleon-4He scattering with three-nucleon forces

    DOE PAGESBeta

    Hupin, Guillaume; Langhammer, Joachim; Navratil, Petr; Quaglioni, Sofia; Calci, Angelo; Roth, Robert

    2013-11-27

    We extend the ab initio no-core shell model/resonating-group method to include three-nucleon (3N) interactions for the description of nucleon-nucleus collisions. We outline the formalism, give algebraic expressions for the 3N-force integration kernels, and discuss computational aspects of two alternative implementations. The extended theoretical framework is then applied to nucleon-4He elastic scattering using similarity-renormalization-group (SRG)-evolved nucleon-nucleon plus 3N potentials derived from chiral effective field theory. We analyze the convergence properties of the calculated phase shifts and explore their dependence upon the SRG evolution parameter. We include up to six excited states of the 4He target and find significant effects from themore » inclusion of the chiral 3N force, e.g., it enhances the spin-orbit splitting between the 3/2– and 1/2– resonances and leads to an improved agreement with the phase shifts obtained from an accurate R-matrix analysis of the five-nucleon experimental data. As a result, we find remarkably good agreement with measured differential cross sections at various energies below the d+3H threshold, while analyzing powers manifest larger deviations from experiment for certain energies and angles.« less

  7. Depression of the Superfluid Transition Temperature in 4He by a Heat Flow

    NASA Astrophysics Data System (ADS)

    Yin, Liang; Lin, Peng; Qi, Xin

    2014-11-01

    The depression of the superfluid transition temperature Tλ in 4He by a heat flow Q is studied. A small sealed cell with a capillary is introduced and a stable and flat superfluid transition temperature plateau is easily obtained by controlling the temperature of the variable-temperature platform and the bottom chamber of the sealed cell. Owing to the depression effect of the superfluid transition temperature by the heat flow, the heat flow through the capillary is changed by the temperature control to obtain multiple temperature plateaus of different heat flows. The thermometer self-heating effect, the residual heat leak of the 4.2 K environment, the temperature difference on the He II liquid column, the Kapiza thermal resistance between the liquid helium and the copper surface of the sealed cell, the temperature gradient of the sealed cell, the static pressure of the He II liquid column and other factors have influence on the depression effect and the influence is analyzed in detail. Twenty experiments of the depression of the superfluid transition temperature in 4He by heat flow are made with four sealed cells in one year. The formula of the superfluid transition temperature pressured by the heat flow is Tλ (Q) = -0.00000103Q + 2.1769108, and covers the range 229 <= Q <= 6462 μW/cm2.

  8. Unusual behavior of 3He-4He mixtures in connected OD boxes

    NASA Astrophysics Data System (ADS)

    Kimball, M. O.; Gasparini, F. M.

    2009-02-01

    We report on measurements of the specific heat of 3He-4He mixtures confined to boxes connected with fill channels 1 μm wide and 19 nm high. These data were meant as a study of mixtures to test universality of finite-size scaling along the lambda-line. We find instead that the mixtures have very unusual behavior relative to mixtures studied in geometries for 2D and 1D crossover. These latter data can be scaled successfully as long as one does not include data for pure 4He. In contrast, the 0D crossover data do not scale on either side of the bulk transition temperature Tλ and have rather different overall behavior: They show a dramatically larger temperature shift of the specific heat maximum Cmax relative to data for 2D and ID, the value of the specific heat at Tλ is substantially smaller than that observed for the other dimensionalities, and the value of Cmax exceeds the magnitude of the bulk specific heat at the same temperature. This overall behavior is so unusual that it suggests there is a role being played by the connecting channels even though the liquid within them remains in the normal state over the temperature range in which the specific heat is measured.

  9. Observations of Vortex Emissions from Superfluid 4He Turbulence at High Temperatures

    NASA Astrophysics Data System (ADS)

    Oda, S.; Wakasa, Y.; Kubo, H.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

    2014-04-01

    An immersed object with high velocity oscillations causes quantum turbulence in superfluid 4He, even at very low temperatures. The continuously generated turbulence may emit vortex rings from a turbulent region. In the present work, we report vortex emissions from quantum turbulence in superfluid 4He at high temperatures, by using three vibrating wires as a turbulence generator and vortex detectors. Two detector wires were mounted beside a generator wire: one in parallel and the other in perpendicular to the oscillation direction of the generator. The detection times of vortex rings represent an exponential distribution with a delay time t 0 and a mean detection period t 1. The delay time includes the generation time of a fully developed turbulence and the time-of-flight of a vortex ring. At high temperatures, vortices are dissipated by relative motion between a normal fluid component and the vortices, resulting that only large vortex rings are reachable to the detectors. Using this method, we detected vortex rings with a diameter of 100 μm, comparable to a peak-to-peak vibration amplitude of 104 μm of the generator. The large vortices observed here are emitted anisotropically from the generator. The emissions parallel to the vibrating direction are much less than those perpendicular to the direction.

  10. Missing Lead and High 3He/4He in Ancient Sulfides Associated with Continental Crust Formation

    PubMed Central

    Huang, Shichun; Lee, Cin-Ty A.; Yin, Qing-Zhu

    2014-01-01

    Major terrestrial reservoirs have Pb isotopes more radiogenic than the bulk silicate Earth. This requires a missing unradiogenic Pb reservoir, which has been argued to reside in the lower continental crust or dissolved in the core. Chalcophile element studies indicate that continent formation requires the formation of sulfide-bearing mafic cumulates in arcs. Because Pb, but not U, partitions into sulfides, we show that continent formation must have simultaneously generated time-integrated unradiogenic Pb reservoirs composed of sulfide-bearing cumulates, now recycled back into the mantle or stored deep in the continental lithosphere. The generation of such cumulates could also lead to coupled He-Pb isotopic systematics because 4He is also produced during U-Th-Pb decay. Here, we show that He may be soluble in sulfide melts, such that sulfide-bearing cumulates would be enriched in both Pb and He relative to U and Th, “freezing” in He and Pb isotopes of the ambient mantle at the time of sulfide formation. This implies that ancient sulfide-bearing cumulates would be characterized by unradiogenic Pb and He isotopes (high-3He/4He). These primitive signatures are usually attributed to primordial, undifferentiated mantle, but in this case, they are the very imprint of mantle differentiation via continent formation. PMID:24937103

  11. Experiments on the rapid mechanical expansion of liquid 4He through its superfluid transition.

    PubMed

    Efimov, V B; Griffiths, O J; Hendry, P C; Kolmakov, G V; McClintock, P V E; Skrbek, L

    2006-11-01

    Phenomena following a rapid mechanical quench of liquid 4He from its normal to its superfluid phase are reported and discussed. The mechanical expansion apparatus is an improved version of that described previously. It uses a double-cell geometry to effect a partial separation of the sample from the convolutions of the bellows that form the outer wall of the cell. Consistent with earlier work, no evidence is found for the production of quantized vortices via the Kibble-Zurek (KZ) mechanism. Although the expansion is complete within 15ms , the second-sound velocity and attenuation continue to increase for a further approximately 60ms ; correspondingly the temperature decreases. Subsequently, the temperature rises again toward its final value as the second-sound velocity and attenuation decrease. It is shown that this unexpected behavior is apparently associated with a large-amplitude second-sound oscillation produced by the expansion, and it is suggested that the observed vortices are created by the normal fluid-superfluid counterflow that constitutes the second-sound wave. If production of large-amplitude second sound is inherent to the mechanical expansion of liquid 4He through the superfluid transition, as appears to be the case for final temperatures more than 3mK from the lambda transition, the phenomenon sets a lower bound on the density of KZ vortices that can be detected in this type of experiment. PMID:17279991

  12. Marine debris accumulation in the Northwestern Hawaiian Islands: an examination of rates and processes.

    PubMed

    Dameron, Oliver J; Parke, Michael; Albins, Mark A; Brainard, Russell

    2007-04-01

    Large amounts of derelict fishing gear accumulate and cause damage to shallow coral reefs of the Northwestern Hawaiian Islands (NWHI). To facilitate maintenance of reefs cleaned during 1996-2005 removal efforts, we identify likely high-density debris areas by assessing reef characteristics (depth, benthic habitat type, and energy regime) that influence sub-regional debris accumulation. Previously cleaned backreef and lagoonal reefs at two NWHI locations were resurveyed for accumulated debris using two survey methods. Accumulated debris densities and weights were found to be greater in lagoonal reef areas. Sample weight-based debris densities are extrapolated to similar habitats throughout the NWHI using a spatial 'net habitat' dataset created by generalizing IKONOS satellite derivatives for depth and habitat classification. Prediction accuracy for this dataset is tested using historical debris point data. Annual NWHI debris accumulation is estimated to be 52.0 metric tonnes. For planning purposes, individual NWHI atolls/reefs are allotted a proportion of this total. PMID:17217968

  13. On determining ice accumulation rates in the past 40,000 years using in situ cosmogenic C-14

    NASA Technical Reports Server (NTRS)

    Lal, D.; Jull, A. J. T.

    1990-01-01

    Radiocarbon is produced in situ in ice by nuclear spallations of oxygen by cosmic ray neutrons. As the firn accumulates, it acquires a predictable concentration of in situ C-14, inversely proportional to the rate of accumulation. Most of this production occurs when the amount of overlying ice is less than (2-3) Lambda, where lambda is the absorption mean free path for cosmic radiation in ice, about 150 g/sq cm, i.e. within the top 10 m. In most accumulation areas, this is firn. In situ produced C-14 is added to the firn as it accumulates, and is not expected to be lost by diffusion. During the firn-ice transition, atmospheric CO2 is trapped, adding (C-14)02 to the ice. The signature of in situ C-14 is however not obliterated since about 60 percent of in situ C-14 is instantly oxidized to (C-14)O in the ice. The results available to date are discussed, and it is proposed that this in situ (C-14)O can be used to determine ice accumulation rates back to 40,000 yrs in the past.

  14. Recent rates of carbon accumulation in montane fens ofYosemite National Park, California, U.S.A.

    USGS Publications Warehouse

    Drexler, Judith; Fuller, Christopher C.; Orlando, James; Moore, Peggy E.

    2016-01-01

    Little is known about recent rates of carbon storage in montane peatlands, particularly in the western United States. Here we report on recent rates of carbon accumulation (past 50 to 100 years) in montane groundwater-fed peatlands (fens) of Yosemite National Park in central California, U.S.A. Peat cores were collected at three sites ranging in elevation from 2070 to 2500 m. Core sections were analyzed for bulk density, % organic carbon, and 210Pb activities for dating purposes. Organic carbon densities ranged from 0.026 to 0.065 g C cm-3. Mean vertical accretion rates estimated using210Pb over the 50-year period from ∼1960 to 2011 and the 100-year period from ∼1910 to 2011 were 0.28 (standard deviation = ±0.09) and 0.18 (±-0.04) cm yr-1, respectively. Mean carbon accumulation rates over the 50- and 100-year periods were 95.4 (±25.4) and 74.7 (±17.2) g C m-2 yr-1, respectively. Such rates are similar to recent rates of carbon accumulation in rich fens in western Canada, but more studies are needed to definitively establish both the similarities and differences in peat formation between boreal and temperate montane fens.

  15. Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean

    USGS Publications Warehouse

    Grantz, A.; Phillips, R.L.; Mullen, M.W.; Starratt, S.W.; Jones, Glenn A.; Naidu, A.S.; Finney, B.P.

    1996-01-01

    Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010??120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of ???10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr. Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and ??13C values of -27 to - 25??? in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and ??13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures. The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be

  16. Communication: Unraveling the {sup 4}He droplet-mediated soft-landing from ab initio-assisted and time-resolved density functional simulations: Au@{sup 4}He{sub 300}/TiO{sub 2}(110)

    SciTech Connect

    Lara-Castells, María Pilar de Aguirre, Néstor F.; Stoll, Hermann; Mitrushchenkov, Alexander O.; Mateo, David; Pi, Martí

    2015-04-07

    An ab-initio-based methodological scheme for He-surface interactions and zero-temperature time-dependent density functional theory for superfluid {sup 4}He droplets motion are combined to follow the short-time collision dynamics of the Au@{sup 4}He{sub 300} system with the TiO{sub 2}(110) surface. This composite approach demonstrates the {sup 4}He droplet-assisted sticking of the metal species to the surface at low landing energy (below 0.15 eV/atom), thus providing the first theoretical evidence of the experimentally observed {sup 4}He droplet-mediated soft-landing deposition of metal nanoparticles on solid surfaces [Mozhayskiy et al., J. Chem. Phys. 127, 094701 (2007) and Loginov et al., J. Phys. Chem. A 115, 7199 (2011)].

  17. ACCUMULATION RATE OF MICROBIAL BIOMASS AT TWO PERMEABLE REACTIVE BARRIER SITES

    EPA Science Inventory

    Accumulation of mineral precipitates and microbial biomass are key factors that impact the long-term performance of in-situ Permeable Reactive Barriers for treating contaminated groundwater. Both processes can impact remedial performance by decreasing zero-valent iron reactivity...

  18. Laboratory Determination of Molybdenum Accumulation Rates as a Measure of Hypoxic Conditions

    EPA Science Inventory

    Redox sensitive metals, such as molybdenum (Mo), are enriched in reducing sediments due to authigenic fixation in anoxic interstitial waters of sediments. This study tested whether the process of fixation and accumulation of Mo in sediments could provide a geochemical indicator o...

  19. Peat Accumulation in the Everglades (USA) during the Past 4000 Years: Rates, Drivers, and Sources of Error

    NASA Astrophysics Data System (ADS)

    Glaser, P. H.; Volin, J. C.; Givnish, T. J.; Hansen, B. C.; Stricker, C. A.

    2012-12-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. AMS-14C dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands

  20. Carbon and sediment accumulation in the Everglades (USA) during the past 4000 years: Rates, drivers, and sources of error

    NASA Astrophysics Data System (ADS)

    Glaser, Paul H.; Volin, John C.; Givnish, Thomas J.; Hansen, Barbara C. S.; Stricker, Craig A.

    2012-09-01

    Tropical and subtropical wetlands are considered to be globally important sources of greenhouse gases, but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida in order to assess these problems and determine the factors that could govern carbon accumulation in this large subtropical wetland. Accelerator mass spectroscopy dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion (0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands.

  1. Carbon and sediment accumulation in the Everglades (USA) during the past 4000 years: rates, drivers, and sources of error

    USGS Publications Warehouse

    Glaser, Paul H.; Volin, John C.; Givnish, Thomas J.; Hansen, Barbara C. S.; Stricker, Craig A.

    2012-01-01

    Tropical and sub-tropical wetlands are considered to be globally important sources for greenhouse gases but their capacity to store carbon is presumably limited by warm soil temperatures and high rates of decomposition. Unfortunately, these assumptions can be difficult to test across long timescales because the chronology, cumulative mass, and completeness of a sedimentary profile are often difficult to establish. We therefore made a detailed analysis of a core from the principal drainage outlet of the Everglades of South Florida, to assess these problems and determine the factors that could govern carbon accumulation in this large sub-tropical wetland. Accelerator mass spectroscopy dating provided direct evidence for both hard-water and open-system sources of dating errors, whereas cumulative mass varied depending upon the type of method used. Radiocarbon dates of gastropod shells, nevertheless, seemed to provide a reliable chronology for this core once the hard-water error was quantified and subtracted. Long-term accumulation rates were then calculated to be 12.1 g m-2 yr-1 for carbon, which is less than half the average rate reported for northern and tropical peatlands. Moreover, accumulation rates remained slow and relatively steady for both organic and inorganic strata, and the slow rate of sediment accretion ( 0.2 mm yr-1) tracked the correspondingly slow rise in sea level (0.35 mm yr-1 ) reported for South Florida over the past 4000 years. These results suggest that sea level and the local geologic setting may impose long-term constraints on rates of sediment and carbon accumulation in the Everglades and other wetlands.

  2. Constraining mass accumulation rates across the Cretaceous-Paleogene boundary clay layer using extraterrestrial helium-3

    NASA Astrophysics Data System (ADS)

    Giron, M.; Sepulveda, J.; Mukhopadhyay, S.; Alegret, L.; Summons, R. E.

    2012-12-01

    The extended duration of the negative δ13C excursion observed in marine carbonates spanning the Cretaceous-Paleogene (K-Pg) mass extinction event has lead to two main hypothesized post-extinction models ("Strangelove" and "Living Ocean";[1, 2]) for the status of marine primary productivity and the global carbon cycle. However, these models are largely inconsistent with recent paleontological and geochemical evidence suggesting heterogeneous changes in marine productivity and carbon export [3, 4]. While the analysis of lipid biomarkers in the cosmopolitan boundary clay layer allows us to assess changes in primary production by non-calcifying organisms in the immediate aftermath of the mass extinction [4], our poor understanding of the deposition of the clay layer precludes a more detailed reconstruction of short-term variations in marine ecosystem resilience. Here, we present data on extraterrestrial 3He derived from interplanetary dust particles used as a constant flux proxy to constrain fluctuations in mass accumulation rates (MARs) [5] and the duration of the boundary clay deposition in three classic and expanded K-Pg boundary sections: El Kef (Tunisia), Caravaca (Spain), and Kulstirenden (Denmark). Our results from different depositional environments indicate average durations for the sedimentation of the clay layer that are comparable (~10 kyr) to other localities [5], thus confirming its globally brief deposition. Early Paleogene MARs vary among locations when compared to background Late Cretaceous values and do not strictly follow carbonate content as traditionally assumed, thus suggesting variable depositional conditions at different locations. Changes in sediment MARs across the K-Pg will be used to calculate MARs of algal- and bacterial-derived biomarkers, as well as benthic foraminifera, in order to assess the timing and global nature of the recovery of marine primary production and carbon export. 1. Hsu, K.J., He, Q., Mckenzie, J.A., Weissert, H

  3. Dynamic structure factor of liquid 4He across the normal-superfluid transition

    NASA Astrophysics Data System (ADS)

    Ferré, G.; Boronat, J.

    2016-03-01

    We have carried out a microscopic study of the dynamic structure factor of liquid 4He across the normal-superfluid transition temperature using the path integral Monte Carlo method. The ill-posed problem of the inverse Laplace transform, from the imaginary-time intermediate scattering function to the dynamic response, is tackled by stochastic optimization. Our results show a quasiparticle peak and a small and broad multiphonon contribution. In spite of the lack of strength in the collective peaks, we clearly identify the rapid dropping of the roton peak amplitude when crossing the transition temperature Tλ. Other properties such as the static structure factor, static response, and one-phonon contribution to the response are also calculated at different temperatures. The changes of the phonon-roton spectrum with the temperature are also studied. An overall agreement with available experimental data is achieved.

  4. Development of Experiments to Measure D and 4He Charge Radii with Elastic Electron Scattering Method

    NASA Astrophysics Data System (ADS)

    Saudi, Sheikh

    Charge radii are one of the important physical characteristics to understand the electromagnetic structure of nuclei. For light nuclei, they are playing a more critical role to better understand the nucleon-nucleon interaction and test the existing models for bound states. Recent measurements of proton radius, done with muonic hydrogen spectroscopy, showed about 7 standard deviation lower than previous experimental results. This discrepancy triggered the so called "Proton Radius Puzzle" in physics world. Several groups are preparing to perform new experiments to extract the proton radius with better precision and model independent methods. It is equally important to perform new experiments for light nuclei, like deuteron (D) and helium-4 (4He), to verify the existing results for their radii. In this thesis work, we have developed an experimental method based on coincidence detection of the scattered electrons and recoiled light nuclei to measure the charge radii of deuteron and helium-4 with high accuracy.

  5. {sup 3}He+{sup 4}He {yields} {sup 7}Be astrophysical S factor

    SciTech Connect

    Brown, T. A. D.; Bordeanu, C.; Snover, K. A.; Storm, D. W.; Melconian, D.; Sallaska, A. L.; Sjue, S. K. L.; Triambak, S.

    2007-11-15

    We present precision measurements of the {sup 3}He+{sup 4}He {yields} {sup 7}Be reaction in the range E{sub c.m.}=0.33 to 1.23 MeV using a small gas cell and detection of both prompt {gamma} rays and {sup 7}Be activity. Our prompt and activity measurements are in good agreement within the experimental uncertainty of several percent. We find S(0)=0.595{+-}0.018 keV b from fits of the Kajino theory to our data. We compare our results with published measurements, and we discuss the consequences for Big Bang Nucleosynthesis and for solar neutrino flux calculations.

  6. A predictive theory for elastic scattering and recoil of protons from 4He

    DOE PAGESBeta

    Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr

    2014-12-08

    Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as α particles) are calculated directly by solving the Schrodinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe the concentrations and depth profiles ofmore » either hydrogen or helium. Furthermore, we compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among data sets and can be used to predict these cross sections when measurements are not available.« less

  7. Predictive theory for elastic scattering and recoil of protons from 4He

    NASA Astrophysics Data System (ADS)

    Hupin, Guillaume; Quaglioni, Sofia; Navrátil, Petr

    2014-12-01

    Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as α particles) are calculated directly by solving the Schrödinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe the concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among data sets and can be used to predict these cross sections when measurements are not available.

  8. A Continuous 4He Refrigerator for Use in a Superfluid Helium Bath

    SciTech Connect

    Wang, Suwen; Avaloff, D.; Nissen, J. A.; Stricker, D. A.; Lipa, J. A.

    2006-09-07

    In cryogenic applications in space, the base temperature, Tmin of the helium bath in the dewar is typically determined by the design of the porous plug and the associated plumbing. For certain experiments, the required operating temperature of the instrument is lower than the bath temperature. In the laboratory, temperatures below 1.2 K require very large pumps or the use of 3He systems. We have demonstrated a modified 4He refrigerator with a continuous fill from a superfluid helium bath with a base temperature more than 0.5 K below the bath temperature. We describe the operation as well as the mechanism of such a refrigerator. For operation in space the refrigerator would need to be equipped with a porous plug to retain the fluid.

  9. Experimental study of nanofluidics and phase transitions of normal and superfluid 4He

    NASA Astrophysics Data System (ADS)

    Velasco, Angel Enriques

    This thesis addresses the experimental results of two different research topics. The first is the experimental work of pressure driven flows in the smallest, single nanotubes ever investigated. The nanotube boundary conditions and slip lengths from argon, nitrogen, water, and helium experiments were analyzed and compared to macroscopic boundary conditions. The second research topic discusses the work on ellipsometric and quartz microbalance measurements of the 2D superfluid phase diagram of 4He on alkali substrates. Ellipsometric results of sodium on HOPG provide the first evidence of the existence of the 2D critical point on an intermediate strength substrate. Pressure driven flows through single nanopores and microtubes were measured with a calibrated mass spectrometer with pressure drops up to 30 Atm. The nanopores were between 30 nm to 600 nm in diameter and etched in mica and PET membranes of several microns thickness. Microtubes several inches long of fused quartz and nickel material were tested with diameters between 1.8 micron and 25 micron. For 4He and argon gas we observed the flow transition between the free molecular and continuum regimes at 293 K and 77 K. No discrepancy between the macroscopic theory and the 30 nm nanopore data was found. Because of the exceptionally low viscosity of gaseous helium the laminar-turbulent transition could also be observed within these submicron channels. The small viscosity of 4He was too small to dampen inertial effects at a Reynolds number of 2000. In addition to single phase gas flows, our experimental technique also allows us to investigate flows in which the nano or micro scale pipe is either partially or completely filled with liquids. The position of the intrinsic liquid/vapor interface was important for understanding this type of flow. Strong evaporation and cooling at the liquid-vapor interface can lead to freezing for conventional fluids such as nitrogen and water, which in turn leads to complex intermittent

  10. Dynamics of {sup 3}He impurities in {sup 4}He films

    SciTech Connect

    Clements, B.E. |; Krotscheck, E. |; Saarela, M.

    1995-08-01

    Using a microscopic variational theory the authors calculate the binding energy of {sup 3}He impurities in films of {sup 4}He absorbed to a graphite substrate. Without adjustable parameters, they obtain excellent agreement with the experimental binding energies for the ground state of the {sup 3}He impurity. To calculate excited states, they then introduce a time-dependent variational wave function. In that way, the impurity acquires a hydrodynamic effective mass for its motion parallel to the surface due to hydrodynamic backflow. Excited states have a finite lifetime. When these effects are included, both the energy of the first excited state of the impurity, and the effective mass of the ground state, also agree well with experimental data.

  11. Relaxation dynamics of spindodal decomposition in superfluid ^3He-^4He mixtures

    NASA Astrophysics Data System (ADS)

    Chay, Terrence Y.; Goldenfeld, Nigel; Bauer, Gregory H.; Ceperley, David M.

    1998-03-01

    We study the dynamics of the Hohenberg-Nelson system(P.C. Hohenberg and David R. Halperin, Phys. Rev. B 20):2665 (1979). for ^3He-^4He mixtures after a quench using a mesoscopic cell dynamical systems (CDS) model. The spinodal region is characterized by maximal growth at a single nonzero wave vector which scales with time. Because CDS exploits universality to avoid taking Δ x and Δ t to infinitesimals, rapid simulations are possible on large systems making it an ideal way to find such scaling behavior. Using thermodynamic properties obtained from experiement and exactly calculated from path integral monte carlo studies, one can obtain the workable CDS phenomenological parameters to do time evolution studies of large-scale mixtures.

  12. Nuclear Transparency with the gamma + n -> pi- + p Process in 4He

    SciTech Connect

    Dipangkar Dutta; Feng Xiong; Lingyan Zhu; John Arrington; Todd Averett; Elizabeth Beise; John Calarco; Ting Chang; Jian-Ping Chen; Eugene Chudakov; Marius Coman; Benjamin Clasie; Christopher Crawford; Sonja Dieterich; Frank Dohrmann; Kevin Fissum; Salvatore Frullani; Haiyan Gao; Ronald Gilman; Charles Glashausser; Javier Gomez; Kawtar Hafidi; Jens-Ole Hansen; Douglas Higinbotham; R.J. Holt; Cornelis De Jager; Xiaochao Zheng; X. Jiang; Edward Kinney; Kevin Kramer; Gerfried Kumbartzki; John LeRose; Nilanga Liyanage; David Mack; Pete Markowitz; Kathy McCormick; Zein-Eddine Meziani; Robert Michaels; J. Mitchell; Sirish Nanda; David Potterveld; Ronald Ransome; Paul Reimer; Bodo Reitz; Arunava Saha; Elaine Schulte; Charles Seely; Simon Sirca; Steffen Strauch; Vincent Sulkosky; Branislav Vlahovic; Lawrence Weinstein; Krishni Wijesooriya; Claude Williamson; Bogdan Wojtsekhowski; Hong XIANG; Wang Xu; J. Zeng

    2003-08-01

    We have measured the nuclear transparency of the fundamental process {gamma} n {yields} {pi}{sup -} p in {sup 4}He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6 to 4.5 GeV and at {theta}{sub cm}{sup {pi}} = 70{sup o} and 90{sup o}. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations which include the quantum chromodynamics phenomenon of color transparency.

  13. Polarization Transfer in 4He(e-vector,e[prime]p-vector)3H

    SciTech Connect

    Michael Paolone

    2007-10-01

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the 4He(e-vector,e[prime]p-vector)3H reaction at a Q2 of 0.8 (GeV/c)2 and 1.3 (GeV/c)2 with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c)2 from both Mainz and Jefferson Lab, in which the measured ratio of polarization-transfer coefficients differs from a fully relativistic DWIA calculation. Preliminary results hint at a possible unexpected Q2 dependence in the polarization transfer coefficient ratio. Final analysis will help constrain FSI models

  14. A two-stage 3He- 4He fridge for bolometric photometry

    NASA Astrophysics Data System (ADS)

    Maiani, T.; de Bernardis, P.; De Petris, M.; Granata, S.; Masi, S.; Orlando, A.; Aquilini, E.; Cardoni, P.; Martinis, L.; Scaramuzzi, F.

    1999-09-01

    We describe the design, construction and performance of a double stage 3He- 4He refrigerator, built to cool down a multiband bolometric photometer at the MITO telescope. The fridge was optimized to work without external pumps, with the main cryostat providing a 4.2 K thermostat at sea level and a 4.0 K one at high mountain pressure conditions. The measured ultimate temperature of the fridge is 290 mK, with a hold time of 81 h. The external heat input on the cold flange is ˜35 μW, with the main bath at 4.0 K. The recycle time is 8 h with a heat input on the thermostat during recycling of ˜6800 J. The cryostat can operate without any relevant changes to performance tilted down to 50° from the vertical position, as needed at the telescope focal plane.

  15. Disappearance of Roton Propagation in Superfluid {sup 4}He at T{sub {lambda}}

    SciTech Connect

    Svensson, E.C.; Montfrooij, W.; de Schepper, I.M.

    1996-11-01

    Using neutron scattering, we determine the dynamic structure factor {ital S}({ital q},{nu}) of liquid {sup 4}He for the roton wave number {ital q}=2.0{sup {minus}1} as a function of frequency {nu} at constant density 0.1715 gcm{sup {minus}3} and for ten temperatures in the range 1.08{le}{ital T}{le}2.00 K, primarily near the superfluid transition temperature {ital T}{sub {lambda}}=1.9202 K. The {lambda} transition is marked by a complete softening of the roton mode and a rapid decrease in lifetime. This change is continuous with temperature, and we find no evidence for a new mode appearing as one enters the superfluid phase, as has been proposed on the basis of theoretical considerations. {copyright} {ital 1996 The American Physical Society.}

  16. Response functions of imaging plates to photons, electrons and {sup 4}He particles

    SciTech Connect

    Bonnet, T.; Denis-Petit, D.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Aléonard, M. M.

    2013-10-15

    Imaging plates from Fuji (BAS-SR, MS, and TR types) are phosphor films routinely used in ultra high intensity laser experiments. However, few data are available on the absolute IP response functions to ionizing particles. We have previously measured and modeled the IP response functions to protons. We focus here on the determination of the responses to photons, electrons, and {sup 4}He particles. The response functions are obtained on an energy range going from a few tens of keV to a few tens of MeV and are compared to available data. The IP sensitivities to the different ionizing particles demonstrate a quenching effect depending on the particle stopping power.

  17. Critical Scaling Properties at the Superfluid Transition of {sup 4}He in Aerogel

    SciTech Connect

    Nikolaou, Marios; Wallin, Mats; Weber, Hans

    2006-12-01

    We study the superfluid transition of {sup 4}He in aerogel by Monte Carlo simulations and finite size scaling analysis. Aerogel is a highly porous silica glass, which we model by a diffusion limited cluster aggregation model. The superfluid is modeled by a three dimensional XY model, with excluded bonds to sites on the aerogel cluster. We obtain the correlation length exponent {nu}=0.73{+-}0.02, in reasonable agreement with experiments and with previous simulations. For the heat capacity exponent {alpha}, both experiments and previous simulations suggest deviations from the Josephson hyperscaling relation {alpha}=2-d{nu}. In contrast, our Monte Carlo results support hyperscaling with {alpha}=-0.2{+-}0.05. We suggest a reinterpretation of the experiments, which avoids scaling violations and is consistent with our simulation results.

  18. Heat capacity of {sup 4}He in Vycor near the critical coverage

    SciTech Connect

    Van Keuls, F.W.; Crowell, P.A.; Reppy, J.D.

    1993-04-01

    The authors report heat capacity measurements of {sup 4}He films in Vycor near the critical coverage. The goal of these studies is to determine whether the low temperature phase at coverages below the onset of superfluidity is a glass or an insulator with a gap. The data cover a temperature range of 5 mK to 600 mK. At the lowest temperatures, a CMN DC-SQUID thermometer is used. This thermometer contains 3 mg of CMN to minimize its heat capacity. The sensitivity at 10 mK is better than 500 pK/{radical}Hz. The CMN powder is mixed with a Ag sinter to improve thermal conductivity. The resistance thermometers mounted on the cell are found to be reliable down to 14 mK.

  19. Russell Donnelly's last legacy: Pursuing grid turbulence in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Ihas, Gary; Yang, Jihee

    2015-11-01

    Quantum turbulence, a tangle of quantized vortex lines in a superfluid, may hold significant keys to understanding all types of turbulence. Russell Donnelly pioneered this line of research, beginning with studies of grid turbulence probed by second sound. The apparatus built by Russell and his students, with significant up-grades, is now being used at the University of Florida to continue his work on decaying grid turbulence in superfluid 4He. The Oregon work used a 1cm wide square channel, while the Florida work has been in both 1 cm and 5 cm square channels. The larger channel allows detailed study of the increase in eddy size before saturation at the channel walls during the decay process. Power law fits of the turbulence decay in time allow comparison with theory, work intended to be Russell Donnelly's last experiment. Supported in part by US NSF #1007937.

  20. Studies of the 4He Nucleus in the (e,e'p) Reaction

    SciTech Connect

    Bodo Reitz

    2003-10-01

    Jefferson Lab experiment E97-111 measured the unseparated cross section for the (e,e'p) reaction on {sup 4}He at recoil momenta up to 530 {approx} MeV/c. In the plane-wave impulse approximation, many calculations predict a sharp minimum in the cross section for recoil momenta around 450 {approx} MeV/c and show that its location is sensitive to the short-range part of the internucleon potential. However, reaction dynamic effects such as final-state interactions and meson-exchange currents can obscure such a minimum. To distinguish and study these effects data were taken at several different kinematics. The preliminary results of the experiment are presented and compared to recent model calculations.

  1. Selective-adsorption line shapes in the scattering of 4He by LiF(001)

    NASA Astrophysics Data System (ADS)

    Wesner, David A.; Frankl, Daniel R.

    1981-08-01

    Selective-adsorption line shapes were experimentally studied in 17-meV 4He-atom scattering from a LiF(001) crystalline surface. The specular and several diffracted beams were measured for a variety of incidence conditions. Specular line shapes obey the three rules put forth by Wolfe and Weare. The specular and diffracted-beam line shapes obey the rules formulated recently by Celli, Garcia, and Hutchison in all cases except for the specular Wolfe-Weare rule-2 case. In this case the mixed-extrema structure predicted by Wolfe and Weare is seen. This line shape is very sensitive to surface temperature and age, confirming a recent prediction of Wolfe and Weare concerning inelastic effects on the selective-adsorption line shapes.

  2. Probing Liquid ^4He with Quartz Tuning Forks Using a Novel Multifrequency Lock-in Technique

    NASA Astrophysics Data System (ADS)

    Bradley, D. I.; Haley, R. P.; Kafanov, S.; Noble, M. T.; Pickett, G. R.; Tsepelin, V.; Vonka, J.; Wilcox, T.

    2016-09-01

    We report on a novel technique to measure quartz tuning forks, and possibly other vibrating objects, in a quantum fluid using a multifrequency lock-in amplifier. The multifrequency technique allows to measure the resonance curve of a vibrating object much faster than a conventional single frequency lock-in amplifier technique. Forks with resonance frequencies of 12 kHz and 16 kHz were excited and measured electro-mechanically either at a single frequency or at up to 40 different frequencies simultaneously around the same mechanical mode. The response of each fork was identical for both methods and validates the use of the multifrequency lock-in technique to probe properties of liquid helium at low fork velocities. Using both methods we measured the resonance frequency and drag of two 25-μ m-wide quartz tuning forks immersed in liquid ^4He in the temperature range from 4.2 K to 1.5 K at saturated vapour pressure. The damping and shift of resonance frequency experienced by both tuning forks at low velocities are well described by hydrodynamic contributions in the framework of the two-fluid model. The sensitivity of the 25-μ m-wide tuning forks is larger compared to similar 75-μ m-wide forks and in combination with the faster multifrequency lock-in technique could be used to improve thermometry in liquid ^4He. The multifrequency technique could also be used for studies of the onset of non-linear phenomena such as quantum turbulence and cavitation in superfluids.

  3. Probing Liquid ^4 He with Quartz Tuning Forks Using a Novel Multifrequency Lock-in Technique

    NASA Astrophysics Data System (ADS)

    Bradley, D. I.; Haley, R. P.; Kafanov, S.; Noble, M. T.; Pickett, G. R.; Tsepelin, V.; Vonka, J.; Wilcox, T.

    2016-06-01

    We report on a novel technique to measure quartz tuning forks, and possibly other vibrating objects, in a quantum fluid using a multifrequency lock-in amplifier. The multifrequency technique allows to measure the resonance curve of a vibrating object much faster than a conventional single frequency lock-in amplifier technique. Forks with resonance frequencies of 12 kHz and 16 kHz were excited and measured electro-mechanically either at a single frequency or at up to 40 different frequencies simultaneously around the same mechanical mode. The response of each fork was identical for both methods and validates the use of the multifrequency lock-in technique to probe properties of liquid helium at low fork velocities. Using both methods we measured the resonance frequency and drag of two 25-μ m-wide quartz tuning forks immersed in liquid ^4 He in the temperature range from 4.2 K to 1.5 K at saturated vapour pressure. The damping and shift of resonance frequency experienced by both tuning forks at low velocities are well described by hydrodynamic contributions in the framework of the two-fluid model. The sensitivity of the 25-μ m-wide tuning forks is larger compared to similar 75-μ m-wide forks and in combination with the faster multifrequency lock-in technique could be used to improve thermometry in liquid ^4 He. The multifrequency technique could also be used for studies of the onset of non-linear phenomena such as quantum turbulence and cavitation in superfluids.

  4. Distinguishing 3He and 4He with the Electron Proton Telescope (EPT) on Solar Orbiter

    NASA Astrophysics Data System (ADS)

    Boden, S.; Kulkarni, S. R.; Steinhagen, J.; Tammen, J.; Martin-Garcia, C.; Wimmer-Schweingruber, R. F.; Boettcher, S. I.; Seimetz, L.; Ravanbakhsh, A.; Elftmann, R.; Schuster, B.; Kulemzin, A.; Kolbe, S.; Mahesh, Y.; Knieriem, V.; Yu, J.; Kohler, J.; Panitzsch, L.; Terasa, C.; Boehm, E.; Rodriguez-Pacheco, J.; Prieto, M.; Gomez-Herrero, R.

    2015-12-01

    The Electron Proton Telescope (EPT) is one of the sensors of the Energetic Particle Detector (EPD) for the Solar Orbiter mission, which will provide key measurements to address particle acceleration at and near the Sun. The EPD suite consists of four different sensors (STEP, SIS, EPT and HET) which together will resolve the energetic particle spectrum from 2 keV to 20 MeV for electrons, 3 keV to 100 MeV for protons and circa 100 keV/nuc to 100 MeV/nuc for heavier ions.EPT itself is primarily designed to cleanly separate and measure electrons in the energy range from 20 - 400 keV and protons from 20 - 7000 keV. To achieve this, EPT uses two back-to-back solid state detectors with a magnet system to deflect electrons on one side and a Polyimide foil to stop protons below ~400 keV on the other side. The two detectors then serve as each other's anti-coincidence. Additionally this setup also allows us to measure penetrating particles with deposited energies in the 1 MeV to 40 MeV range. Looking at the ratio of deposited energy in the two detectors versus total deposited energy allows us to differentiate between protons and alpha particles. Distinguishing 3He from 4He will be challenging, but possible provided good knowledge of the instrument, high-fidelity modeling and a precise calibration of EPT. Here, we will present feasibility studies leading to a determination of the 3He / 4He ratio with EPT.

  5. Transport in ultradilute solutions of 3He in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Beck, D. H.; Pethick, C. J.

    2015-07-01

    We calculate the effect of a heat current on transporting 3He dissolved in superfluid 4He at ultralow concentration, as will be utilized in a proposed experimental search for the electric dipole moment of the neutron (nEDM). In this experiment, a phonon wind will be generated to drive (partly depolarized) 3He down a long pipe. In the regime of 3He concentrations ≲10-9 and temperatures ˜0.5 K, the phonons comprising the heat current are kept in a flowing local equilibrium by small angle phonon-phonon scattering, while they transfer momentum to the walls via the 4He first viscosity. On the other hand, the phonon wind drives the 3He out of local equilibrium via phonon-3He scattering. For temperatures below 0.5 K, both the phonon and 3He mean free paths can reach the centimeter scale, and we calculate the effects on the transport coefficients. We derive the relevant transport coefficients, the phonon thermal conductivity, and the 3He diffusion constants from the Boltzmann equation. We calculate the effect of scattering from the walls of the pipe and show that it may be characterized by the average distance from points inside the pipe to the walls. The temporal evolution of the spatial distribution of the 3He atoms is determined by the time dependent 3He diffusion equation, which describes the competition between advection by the phonon wind and 3He diffusion. As a consequence of the thermal diffusivity being small compared with the 3He diffusivity, the scale height of the final 3He distribution is much smaller than that of the temperature gradient. We present exact solutions of the time dependent temperature and 3He distributions in terms of a complete set of normal modes.

  6. Phonon-roton modes of liquid 4He beyond the roton in MCM-41

    SciTech Connect

    Azuah, Richard T; Omar Diallo, Souleymane; Adams, Mark A.; Kirichek, Oleg; Glyde, Henry R

    2013-01-01

    We present neutron scattering measurements of the phonon-roton (P-R) mode of superfluid 4He confined in 47 A MCM-41 at T = 0.5 K at wave vectors, Q, beyond the roton wave vector (QR = 1.92 A-1). Measurements beyond the roton require access to high wave vectors (up to Q = 4 A-1) with excellent energy resolution and high statistical precision. The present results show for the first time that at T = 0.5 K the P-R mode in MCM-41 extends out to wave-vector Q 3.6 A-1 with the same energy and zero width (within precision) as observed in bulk superfluid 4He. Layer modes in the roton region are also observed. Specifically, the P-R mode energy, !Q, increases with Q for Q > QR and reaches a plateau at a maximum energy !Q = 2 where is the roton energy, = 0.74 0.01 meV in MCM-41. This upper limit means the P-R mode decays to two rotons when its energy exceeds 2 . It also means that the P-R mode does not decay to two layers modes. If the P-R could decay to two layer modes, !Q would plateau at a lower energy, !Q = 2 L where L = 0.60 meV is the energy of the roton like minimum of the layer mode. The observation of the P-R mode with energy up to 2 shows that the P-R mode and the layer modes are independent modes with apparently little interaction between them.

  7. T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure.

    PubMed

    Lee, Eun-Young; Flynn, Michael R; Du, Guangwei; Lewis, Mechelle M; Fry, Rebecca; Herring, Amy H; Van Buren, Eric; Van Buren, Scott; Smeester, Lisa; Kong, Lan; Yang, Qing; Mailman, Richard B; Huang, Xuemei

    2015-08-01

    Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies. PMID:25953701

  8. T1 Relaxation Rate (R1) Indicates Nonlinear Mn Accumulation in Brain Tissue of Welders With Low-Level Exposure

    PubMed Central

    Lee, Eun-Young; Flynn, Michael R.; Du, Guangwei; Lewis, Mechelle M.; Fry, Rebecca; Herring, Amy H.; Van Buren, Eric; Van Buren, Scott; Smeester, Lisa; Kong, Lan; Yang, Qing; Mailman, Richard B.; Huang, Xuemei

    2015-01-01

    Although the essential element manganese (Mn) is neurotoxic at high doses, the effects of lower exposure are unclear. MRI T1-weighted (TIW) imaging has been used to estimate brain Mn exposure via the pallidal index (PI), defined as the T1W intensity ratio in the globus pallidus (GP) versus frontal white matter (FWM). PI may not, however, be sensitive to Mn in GP because Mn also may accumulate in FWM. This study explored: (1) whether T1 relaxation rate (R1) could quantify brain Mn accumulation more sensitively; and (2) the dose-response relationship between estimated Mn exposure and T1 relaxation rate (R1). Thirty-five active welders and 30 controls were studied. Occupational questionnaires were used to estimate hours welding in the past 90 days (HrsW) and lifetime measures of Mn exposure. T1W imaging and T1-measurement were utilized to generate PI and R1 values in brain regions of interest (ROIs). PI did not show a significant association with any measure of Mn and/or welding-related exposure. Conversely, in several ROIs, R1 showed a nonlinear relationship to HrsW, with R1 signal increasing only after a critical exposure was reached. The GP had the greatest rate of Mn accumulation. Welders with higher exposure showed significantly higher R1 compared either with controls or with welders with lower exposure. Our data are additional evidence that Mn accumulation can be assessed more sensitively by R1 than by PI. Moreover, the nonlinear relationship between welding exposure and Mn brain accumulation should be considered in future studies and policies. PMID:25953701

  9. Search for sup 3 H, sub 3 He, and sub 4 He in D sub 2 -loaded titanium

    SciTech Connect

    Clarke, W.B.; Clarke, R.M. )

    1992-03-01

    In this paper a search is described for {sup 3}He, {sup 4}He, and tritium produced when D{sub 2} is absorbed by titanium sponge, or released when titanium deuteride is heated. The D{sub 2} is prepared from pre-nuclear-era D{sub 2}O, which has a tritium/deuterium (T/D) ratio of 1.8 {times} 10{sup {minus}15}. Two reservoirs of titanium sponge in a vacuum system attached to the inlet line of a mass spectrometer are heated to allow rapid transfer of D{sub 2} from one sponge to the other. Significant amounts of {sup 3}He and {sup 4}He are released only after the deuterium content is increased to reach TiD{sub 1.5} in one sponge. Then {sup 3}He and {sup 4}He are decreased as the D{sub 2} is transferred back and forth. When the titanium is loaded to a composition of TiD{sub 2.0}, {sup 3}He and {sup 4}He increase during the next two transfers, then decrease. When the D{sub 2} is replaced by H{sub 2}, then D{sub 2}-H{sub 2} (1:1), {sup 3}He and {sup 4}He decrease steadily, indicating that the transfer process causes partial release of {sup 3}He and {sup 4}He trapped in the titanium.

  10. Project Hotspot: Linear accumulation rates of late Cenozoic basalt at Kimama, Idaho, and implications for crustal strain and subsidence rates of the central Snake River Plain

    NASA Astrophysics Data System (ADS)

    Rodgers, D. W.; Potter, K. E.; Shervais, J. W.; Champion, D. E.; Duncan, R. A.

    2013-12-01

    Project Hotspot's Kimama drill hole on the Snake River Plain, Idaho recovered a 1912 m thick section of basalt core that ranges in age from ~700 ka to at least 6.14 Ma, based on five 40Ar/39Ar analyses and twenty paleomagnetic age assignments. Fifty-four flow groups comprising 510 individual flows were defined, yielding an average recurrence interval of ~11,400 years between flows. Age-depth analysis indicate that, over thicknesses >150 m and age spans >500 k.y., accumulation rates were constant at 30 m/100 k.y. The existence and persistence of this linear accumulation rate for greater than 5 m.y. documents an external tectonic control on eruption dynamics. One conceptual model relates accumulation rates to horizontal crustal strain, such that far-field extension rate controls the periodicity of dikes that feed basalt flows. In this model, each of the 54 flow groups would have a deep-seated, relatively wide (1-10m) dike that branches upward into a network of narrow (10-100 cm) dikes feeding individual lava flows. Assuming an east-west lateral lava flow extent of up to 50 km, the Kimama data record a steady-state crustal strain rate of 10-9 to 10-10 y-1. This rate is comparable to modern, decadal strain rates measured with GPS in the adjacent Basin & Range province, but exceeds decadal strain rates of zero measured in the eastern Snake River Plain. Linear accumulation rates also provide insight into basalt subsidence history. In this model, the middle-upper crust subsides due to the added weight of lava flows, the added weight of mid-crustal sills/dikes, and thermal contraction in the wake of the Yellowstone hot spot. Isostatic compensation would occur in the (nearly) molten lower crust. Assuming constant surface elevation and a basalt density of 2.6 g/cm3, the lava flow weight would account for 87% of the burial through time, yielding a steady-state "tectonic" subsidence rate of 4 m/100 k.y. attributed to the driving forces of mid-crustal injection and/or thermal

  11. Kinetics of the reaction of the heaviest hydrogen atom with H2, the 4Heμ + H2 → 4HeμH + H reaction: experiments, accurate quantal calculations, and variational transition state theory, including kinetic isotope effects for a factor of 36.1 in isotopic mass.

    PubMed

    Fleming, Donald G; Arseneau, Donald J; Sukhorukov, Oleksandr; Brewer, Jess H; Mielke, Steven L; Truhlar, Donald G; Schatz, George C; Garrett, Bruce C; Peterson, Kirk A

    2011-11-14

    The neutral muonic helium atom (4)Heμ, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation (μSR) measurements of the chemical reaction rate constant of (4)Heμ with molecular hydrogen, (4)Heμ + H(2) → (4)HeμH + H, at temperatures of 295.5, 405, and 500 K, as well as a μSR measurement of the hyperfine coupling constant of muonic He at high pressures. The experimental rate constants, k(Heμ), are compared with the predictions of accurate quantum mechanical (QM) dynamics calculations carried out on a well converged Born-Huang (BH) potential energy surface, based on complete configuration interaction calculations and including a Born-Oppenheimer diagonal correction. At the two highest measured temperatures the agreement between the quantum theory and experiment is good to excellent, well within experimental uncertainties that include an estimate of possible systematic error, but at 295.5 K the quantum calculations for k(Heμ) are below the experimental value by 2.1 times the experimental uncertainty estimates. Possible reasons for this discrepancy are discussed. Variational transition state theory calculations with multidimensional tunneling have also been carried out for k(Heμ) on the BH surface, and they agree with the accurate QM rate constants to within 30% over a wider temperature range of 200-1000 K. Comparisons between theory and experiment are also presented for the rate constants for both the D + H(2) and Mu + H(2) reactions in a novel study of kinetic isotope effects for the H + H(2) reactions over a factor of 36.1 in isotopic mass of the atomic reactant. PMID:22088068

  12. Accumulation rates or percentages? How to quantify Sporormiella and other coprophilous fungal spores to detect late Quaternary megafaunal extinction events

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2013-10-01

    Spores of coprophilous fungi, and in particular those of Sporormiella, are a routinely used proxy for detecting late Quaternary herbivore extinction events in sedimentary records. Spore abundance is typically quantified as a percentage of the total, or dryland, pollen sum. Although this is a quick method that does not require the development of site-specific age-depth models, it relies on stable pollen accumulation rates and is therefore highly sensitive to changes in vegetation. This may lead to incorrect placement of extinction events in sedimentary records, particularly when they occur contemporaneously with major climatic/vegetation transitions. We suggest that the preferred method of quantification should be accumulation rate, and that pollen abundance data should also be presented, particularly for periods of major vegetation change. This approach provides a more reliable record of past herbivore abundance independent of vegetation change, allowing extinction events to be more accurately placed in stratigraphic sequences.

  13. Characterization of helium diffusion behavior from continuous heating experiments: Sample screening and identification of multiple 4He components

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Idleman, B. D.; Zeitler, P. K.

    2015-12-01

    Old, slowly cooled apatites often yield overdispersed helium ages due to factors such as parent zonation, He implantation, radiation damage, crystal defects, and fluid inclusions. Careful mineral selection and many replicate analyses can mitigate the impact of some of these effects. However, this approach adds unnecessary costs in time and resources when dating well-behaved apatites and is generally ineffective at identifying the root cause of age dispersion and providing suitable age corrections for poorly behaved samples. We assess a new technique utilizing static-gas measurement during continuous heating as a means to rapidly screen apatite samples. In about the time required for a conventional total-gas analysis, this method can discriminate between samples showing the volume-diffusion behavior expected for apatite and those showing anomalous release patterns, inconsistent with their use in thermochronologic applications. This method may also have the potential to quantify and discriminate between the radiogenic and extraneous 4He fractions released by a sample. Continuously heated samples that outgas by volume diffusion during a linear heating schedule should produce a characteristic sigmoidal 4He fractional loss profile, with the exact shape and position of these profiles (in loss vs. heating time space) controlled by sample kinetics, grain size, and heating rate. Secondary factors such as sample zoning and alpha-loss distribution have a relatively minor impact on such profiles. Well-behaved examples such as the Durango standard and other apatites with good age reproducibility show the expected smooth, sigmoidal gas release with complete exhaustion by temperatures predicted for volume diffusion using typical apatite kinetics (e.g., by ~900˚C for linear heating at 20˚C/minute). In contrast, "bad actor" samples that do not replicate well show significant degrees of helium release deferred to higher temperatures. We report on screening results for a range of

  14. On the Effect of Ramp Rate in Damage Accumulation of the CPV Die-Attach: Preprint

    SciTech Connect

    Bosco, N. S.; Silverman, T. J.; Kurtz, S. R.

    2012-06-01

    It is commonly understood that thermal cycling at high temperature ramp rates may activate unrepresentative failure mechanisms. Increasing the temperature ramp rate of thermal cycling, however, could dramatically reduce the test time required to achieve an equivalent amount of thermal fatigue damage, thereby reducing overall test time. Therefore, the effect of temperature ramp rate on physical damage in the CPV die-attach is investigated. Finite Element Model (FEM) simulations of thermal fatigue and thermal cycling experiments are made to determine if the amount of damage calculated results in a corresponding amount of physical damage measured to the die-attach for a variety of fast temperature ramp rates. Preliminary experimental results are in good agreement with simulations and reinforce the potential of increasing temperature ramp rates. Characterization of the microstructure and resulting fatigue crack in the die-attach suggest a similar failure mechanism across all ramp rates tested.

  15. tetra neutron system studied by exothermic double-charge exchange reaction 4He(8He, 8Be)4n

    NASA Astrophysics Data System (ADS)

    Kisamori, Keiichi; Sharaq06 Collaboration

    2014-09-01

    A possible existence of the tetra-neutron system as a resonance state is still an open and fascinating question, while theoretical papers using ab-initio calculation suggests that the bound tetra-neutron does not exist. We have performed a missing-mass spectroscopy of the 4n system via the exothermic double-charge exchange reaction 4He(8He,8Be)4n. The experiment was carried out at the RIBF at RIKEN using the SHARAQ spectrometer and the liquid He target system. Since the secondary beam, 8He at 190A MeV, has a large internal energy, it is possible to produce the 4n system in small momentum transfers of less than 20 MeV/c. In the present analysis, a new analytical framework to treat multi-particles under high beam rate condition (2 MHz) was developed for good statistics. At the SHARAQ spectrometer, 8Be can be identified by measuring the invariant mass of the coincident two-alpha particle with a good signal-to-noise ratio. About several tens of candidate events are obtained above the 4n threshold. We will show the preliminary result of missing-msss spectrum and discuss the shape of spectrum.

  16. Study of astrophysically important resonant states in 26Si by the 28Si(4He,6He)26Si reaction

    NASA Astrophysics Data System (ADS)

    Kwon, Young Kwan; Lee, C. S.; Moon, J. Y.; Lee, J. H.; Kim, J. Y.; Kubono, S.; Iwasa, N.; Inafiki, K.; Yamaguchi, H.; He, J. J.; Saito, A.; Wakabayashi, Y.; Fukijawa, H.; Amadio, G.; Khiem, L. H.; Tanaka, M.; Chen, A.; Kato, S.

    PoS(NIC-IX)024 , b, H. Yamaguchia, J. J. Hea , A. Saitoa , Y. Wakabayashia, H. Fujikawaa, G. The emission of 1.809 MeV gamma-ray from the first excited state of 26 Mg followed by beta- decay of 26 Al in its ground state (denoted as 26 Alg.s. ) has been identified by gamma-ray telescopes such the Compton Gamma-Ray Observatory (CGRO) [1]. To resolve controversy over the pos- sible sources of the observational 1.809 MeV gamma-rays, one needs accurate knowledge of the production rate of 26 Al. The 25 Al(p,γ)26Si reaction which is the competition reaction for produc- tion of 26 Alg.s. is one of the important subjects to be investigated. In this work, the astrophysically important 26 Si states above the proton threshold were studied via the 28 Si(4 He,6 He)26 Si reaction. We have preformed an angular distribution measurement using the high resolution QDD spectro- graph (PA) at Center for Nuclear Study (CNS), University of Tokyo. The experimental results and data analysis will be presented.

  17. Accumulate-Repeat-Accumulate-Accumulate-Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Sam; Thorpe, Jeremy

    2004-01-01

    Inspired by recently proposed Accumulate-Repeat-Accumulate (ARA) codes [15], in this paper we propose a channel coding scheme called Accumulate-Repeat-Accumulate-Accumulate (ARAA) codes. These codes can be seen as serial turbo-like codes or as a subclass of Low Density Parity Check (LDPC) codes, and they have a projected graph or protograph representation; this allows for a high-speed iterative decoder implementation using belief propagation. An ARAA code can be viewed as a precoded Repeat-and-Accumulate (RA) code with puncturing in concatenation with another accumulator, where simply an accumulator is chosen as the precoder; thus ARAA codes have a very fast encoder structure. Using density evolution on their associated protographs, we find examples of rate-lJ2 ARAA codes with maximum variable node degree 4 for which a minimum bit-SNR as low as 0.21 dB from the channel capacity limit can be achieved as the block size goes to infinity. Such a low threshold cannot be achieved by RA or Irregular RA (IRA) or unstructured irregular LDPC codes with the same constraint on the maximum variable node degree. Furthermore by puncturing the accumulators we can construct families of higher rate ARAA codes with thresholds that stay close to their respective channel capacity thresholds uniformly. Iterative decoding simulation results show comparable performance with the best-known LDPC codes but with very low error floor even at moderate block sizes.

  18. Slip rate of the Calico fault: Implications for anomalous geodetic strain accumulation across the Eastern California shear zone

    NASA Astrophysics Data System (ADS)

    Oskin, M.; Perg, L.; Blumentritt, D.; Mukhopadhyay, S.; Iriondo, A.

    2004-12-01

    Recent earthquake activity and high geodetically derived fault-slip rates across the Eastern California shear zone motivate comparisons with long-term geologic deformation rates to test for transient strain accumulation. We report new geologic slip-rate results from a transect at 34.8° N across the central Mojave Desert where six dextral faults (Helendale, Lenwood, Camp Rock, Calico, Pisgah-Bullion, and Ludlow) accommodate all late Quaternary right-lateral displacement. High-resolution LIDAR topography data have been successfully acquired across all six faults as part of a project to measure a complete budget of long-term geologic fault slip rates. Field investigations of the northern Rodman Mountains conducted with the aid of the new topography data identified several surfaces dextrally offset by the Calico fault. A preliminary slip rate of 1.3±0.3 mm/yr is calculated from an 800± 200 m offset of alluvial fan deposits containing clasts of the ca. 600 ka Pipkin basalt flow. Cosmogenic surface exposure age dating of offset geomorphic surfaces and refined Ar/Ar dating of the basalt flow, in progress, will provide multiple constraints of this fault slip rate. The slip rate of the Calico fault is more than twice that of the Blackwater fault, located on strike with the Calico fault in the northwest Mojave Desert. This discrepancy supports that strain is transferred away from the Calico fault and other adjacent northwest-striking dextral faults onto domino-style rotating blocks bounded by sinistral faults in the Fort Irwin region. A newly identified active thrust fault and fault-related fold bounding the northern Rodman mountains accommodates shortening east of the Calico fault that may be caused by space problems at the intersection of these conjugate fault systems. Overall, slip rate on the Calico fault, together with existing paleoseismic histories on adjacent faults, does not account for more than 5 mm/yr of strain accumulation across the Eastern California shear

  19. Processes and Rates of Sediment and Wood Accumulation in Headwater Streams of the Oregon Coast Range, U.S.A.

    NASA Astrophysics Data System (ADS)

    May, C. L.; Gresswell, R. E.

    2001-12-01

    Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow in unlogged basins in the central Oregon Coast Range. Changes in sediment and wood storage were quantified for 13 streams that ranged from 4 to 135 years post-disturbance. The volume of wood in the channel was strongly correlated with the time since the previous debris flow, and the accumulation rate was linear. The pattern of sediment accumulation was non-linear and appeared to increase as the storage capacity of the channel increased through time. Wood recruited from the local hillslopes and riparian areas functioned to store the majority sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for a longer period of time. With an adequate supply of wood, low-order channels have the potential for storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

  20. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.; Schläppi, M.; Santibañez, P.; Rivera, A.; Casassa, G.

    2012-12-01

    Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000 to 2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16´40´´ S, 73°21´14´´ W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16% ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4 to 7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  1. Rotational cooling efficiency upon molecular ionization: the case of Li{_2(a^3Σ_u^+)} and Li{_2^+(X^2Σ_g^+)} interacting with ^4He

    NASA Astrophysics Data System (ADS)

    Wernli, M.; Bodo, E.; Gianturco, F. A.

    2007-11-01

    The low-temperature (up to about 100 K) collisional (de)excitation cross sections are computed using the full coupled-channel (CC) quantum dynamics for both Li2 and Li2+ molecular targets in collision with ^4He. The interaction forces are obtained from fairly accurate ab initio calculations and the corresponding pseudo-rates are also computed. The results show surprising similarities between sizes of inelastic flux distributions within final states in both systems and the findings are connected with the structural change in the molecular rotor features when the neutral species is replaced by its ionic counterpart.

  2. Copper dimer interactions on a thermomechanical superfluid {sup 4}He fountain

    SciTech Connect

    Popov, Evgeny; Eloranta, Jussi

    2015-05-28

    Laser induced fluorescence imaging and frequency domain excitation spectroscopy of the copper dimer (B{sup 1}Σ{sub g}{sup +}←X{sup 1}Σ{sub u}{sup +}) in thermomechanical helium fountain at 1.7 K are demonstrated. The dimers penetrate into the fountain provided that their average propagation velocity is ca. 15 m/s. This energy threshold is interpreted in terms of an imperfect fountain liquid-gas interface, which acts as a trap for low velocity dimers. Orsay-Trento density functional theory calculations for superfluid {sup 4}He are used to characterize the dynamics of the dimer solvation process into the fountain. The dimers first accelerate towards the fountain surface and once the surface layer is crossed, they penetrate into the liquid and further slow down to Landau critical velocity by creating a vortex ring. Theoretical lineshape calculations support the assignment of the experimentally observed bands to Cu{sub 2} solvated in the bulk liquid. The vibronic progressions are decomposed of a zero-phonon line and two types of phonon bands, which correlate with solvent cavity interface compression (t < 200 fs) and expansion (200 < t < 500 fs) driven by the electronic excitation. The presented experimental method allows to perform molecular spectroscopy in bulk superfluid helium where the temperature and pressure can be varied.

  3. One-Dimensional Liquid ^{4}He: Dynamical Properties beyond Luttinger-Liquid Theory.

    PubMed

    Bertaina, G; Motta, M; Rossi, M; Vitali, E; Galli, D E

    2016-04-01

    We compute the zero-temperature dynamical structure factor of one-dimensional liquid ^{4}He by means of state-of-the-art quantum Monte Carlo and analytic continuation techniques. By increasing the density, the dynamical structure factor reveals a transition from a highly compressible critical liquid to a quasisolid regime. In the low-energy limit, the dynamical structure factor can be described by the quantum hydrodynamic Luttinger-liquid theory, with a Luttinger parameter spanning all possible values by increasing the density. At higher energies, our approach provides quantitative results beyond the Luttinger-liquid theory. In particular, as the density increases, the interplay between dimensionality and interaction makes the dynamical structure factor manifest a pseudo-particle-hole continuum typical of fermionic systems. At the low-energy boundary of such a region and moderate densities, we find consistency, within statistical uncertainties, with predictions of a power-law structure by the recently developed nonlinear Luttinger-liquid theory. In the quasisolid regime, we observe a novel behavior at intermediate momenta, which can be described by new analytical relations that we derive for the hard-rods model. PMID:27081985

  4. Improvement of the Spatial Amplitude Isotropy of a ^4He Magnetometer Using a Modulated Pumping Beam

    NASA Astrophysics Data System (ADS)

    Chéron, B.; Gilles, H.; Hamel, J.; Moreau, O.; Noël, E.

    1997-08-01

    Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a ^4He magnetometer developed in our Laboratory. Les magnétomètres à pompage optique sont des magnétomètres scalaires. Contrairement aux magnétomètres vectoriels, ils mesurent le module du champ magnétique quelle que soit l'orientation du capteur dans l'espace. Cependant, pour certaines orientations du magnétomètre par rapport à la direction du champ à mesurer, l'amplitude du signal de résonance s'annule et la mesure devient impossible. Dans cet article, nous présentons une solution simple pour réduire l'anisotropie spatiale d'amplitude et nous l'appliquons à un magnétomètre à hélium-4 développé dans notre Laboratoire.

  5. Interaction of Ions, Atoms and Small Molecules with Quantized Vortex Lines in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Eloranta, Jussi; Matteo, David; Williams, Gary

    2015-03-01

    The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3+,He* (3 S), He2*(3Σu) and e-) with quantized rectilinear vortex lines in superfluid 4He is calculated using density functional methods at 0 K. The technique yields the impurity radius as well as the vortex line core parameter. The core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or from the trapping potential fitting is smaller than previously suggested but is compatible with a re-analysis of the Rayfield-Reif experiment. All of the impurities have significant binding energies to the vortex lines below 1 K where the thermally assisted escape process becomes very inefficient. Even at higher temperatures the trapping times, especially for larger clusters, are sufficiently long that the observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or thermally assisted escape. A new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He*. Work supported by the NSF, Grants CHE-1262306 and DMR-1205734, and the Interdisciplinary Research Institute for the Sciences.

  6. Medium Modifications from {sup 4}He(e-vector,e'p-vector){sup 3}H

    SciTech Connect

    Malace, S.; Paolone, M.; Strauch, S.

    2008-10-13

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the {sup 4}He(e-vector,e'p-vector){sup 3}H reaction at a Q{sup 2} of 0.8 (GeV/c){sup 2} and 1.3 (GeV/c){sup 2} with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c){sup 2} from both Mainz and Jefferson Lab. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring either the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model or strong charge-exchange final-state interactions. The measured induced polarizations agree well with the fully relativistic calculation and indicate that these strong final-state interactions may not be applicable.

  7. Development of low temperature solid state detectors for ultra-cold neutrons within superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baker, C. A.; Balashov, S. N.; Green, K.; van der Grinten, M. G. D.; Iaydjiev, P. S.; Ivanov, S. N.; Pendlebury, J. M.; Shiers, D. B.; Tucker, M. A. H.; Yoshiki, H.; Geltenbort, P.

    2003-04-01

    As part of an R&D programme for the development of a next-generation experiment to measure the neutron electric dipole moment, in which ultra-cold neutrons (UCN) are produced and stored in superfluid 4He (superthermal source), we have developed cryogenic detectors of UCN that can operate in situ within the superfluid. Surface barrier detectors and PIN diode detectors have been tested and proven to work well at temperatures as low as 80 mK. When combined with a layer of 6LiF which converts neutrons to charged particles, these detectors form a reliable UCN detection system which has been tested in liquid helium down to 430 mK. The detectors have operated within superfluid helium for periods of up to 30 days with no signs of degradation. The development of this detection system has enabled us to measure the flux of UCN from a superthermal UCN source with no intervening transmission windows which can attenuate the flux. The addition of thin films of magnetically aligned iron also enables these detectors to be used in situ for neutron spin-polarisation analysis.

  8. Operator evolution for ab initio electric dipole transitions of 4He

    DOE PAGESBeta

    Schuster, Micah D.; Quaglioni, Sofia; Johnson, Calvin W.; Jurgenson, Eric D.; Navartil, Petr

    2015-07-24

    A goal of nuclear theory is to make quantitative predictions of low-energy nuclear observables starting from accurate microscopic internucleon forces. A major element of such an effort is applying unitary transformations to soften the nuclear Hamiltonian and hence accelerate the convergence of ab initio calculations as a function of the model space size. The consistent simultaneous transformation of external operators, however, has been overlooked in applications of the theory, particularly for nonscalar transitions. We study the evolution of the electric dipole operator in the framework of the similarity renormalization group method and apply the renormalized matrix elements to the calculationmore » of the 4He total photoabsorption cross section and electric dipole polarizability. All observables are calculated within the ab initio no-core shell model. Furthermore, we find that, although seemingly small, the effects of evolved operators on the photoabsorption cross section are comparable in magnitude to the correction produced by including the chiral three-nucleon force and cannot be neglected.« less

  9. 4He+n+n continuum within an ab initio framework

    DOE PAGESBeta

    Romero-Redondo, Carolina; Quaglioni, Sofia; Navratil, Petr; Hupin, Guillaume

    2014-07-16

    In this study, the low-lying continuum spectrum of the 6He nucleus is investigated for the first time within an ab initio framework that encompasses the 4He+n+n three-cluster dynamics characterizing its lowest decay channel. This is achieved through an extension of the no-core shell model combined with the resonating-group method, in which energy-independent nonlocal interactions among three nuclear fragments can be calculated microscopically, starting from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with three-body scattering boundary conditions by means of the hyperspherical-harmonics method on a Lagrange mesh. Using amore » soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we find the known Jπ = 2+ resonance as well as a result consistent with a new low-lying second 2+ resonance recently observed at GANIL at ~2.6 MeV above the He6 ground state. We also find resonances in the 2–, 1+, and 0– channels, while no low-lying resonances are present in the 0+ and 1– channels.« less

  10. Operator evolution for ab initio electric dipole transitions of 4 He

    NASA Astrophysics Data System (ADS)

    Schuster, Micah; Quaglioni, Sofia; Johnson, Calvin; Jurgenson, Eric; Navratil, Petr

    2015-04-01

    A goal of nuclear theory is to make quantitative predictions of low-energy nuclear observables starting from accurate microscopicinternucleon forces. Modern effective interaction theory, applying unitary transformations to soften the nuclear Hamiltonian and hence accelerate the convergence of ab initio calculations as a function of the model space size, is a major element of such an effort. The consistent simultaneous transformation of external operators, however, has been overlooked in applications of the theory, particularly for non-scalar transitions. We study the evolution of the electric dipole operator in the framework of the similarity-renormalization group method and apply the renormalized matrix elements to the calculation of the 4 He total photo absorption cross section and electric dipole polarizability. All observables are calculated within the ab initio no-core shell model. We find that, although seemingly small, the effects of induced operators on the photo absorption cross section are comparable in magnitude to the correction produced by including the three-nucleon force and cannot be neglected. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. One-Dimensional Liquid 4He: Dynamical Properties beyond Luttinger-Liquid Theory

    NASA Astrophysics Data System (ADS)

    Bertaina, G.; Motta, M.; Rossi, M.; Vitali, E.; Galli, D. E.

    2016-04-01

    We compute the zero-temperature dynamical structure factor of one-dimensional liquid 4He by means of state-of-the-art quantum Monte Carlo and analytic continuation techniques. By increasing the density, the dynamical structure factor reveals a transition from a highly compressible critical liquid to a quasisolid regime. In the low-energy limit, the dynamical structure factor can be described by the quantum hydrodynamic Luttinger-liquid theory, with a Luttinger parameter spanning all possible values by increasing the density. At higher energies, our approach provides quantitative results beyond the Luttinger-liquid theory. In particular, as the density increases, the interplay between dimensionality and interaction makes the dynamical structure factor manifest a pseudo-particle-hole continuum typical of fermionic systems. At the low-energy boundary of such a region and moderate densities, we find consistency, within statistical uncertainties, with predictions of a power-law structure by the recently developed nonlinear Luttinger-liquid theory. In the quasisolid regime, we observe a novel behavior at intermediate momenta, which can be described by new analytical relations that we derive for the hard-rods model.

  12. Theory of deep inelastic neutron scattering. II. Application to normal and superfluid 4He

    NASA Astrophysics Data System (ADS)

    Silver, Richard N.

    1989-03-01

    The hard-core perturbation theory (HCPT) predictions for high-momentum-transfer neutron scattering from liquid 4He are numerically evaluated. The input to the calculations are Monte Carlo and variational momentum distributions, the radial distribution function, and the Jeffreys-Wentzel-Kramers-Brillouin phase shifts for the He potential. Consistent with the ω2 sum rule, the Gaussian width of the dynamic structure function S(Q,ω) is the same in HCPT and in the impulse approximation (IA). However, where the IA predicts structure in S(Q,ω) below Tλ due to the Bose condensate, HCPT predicts that S(Q,ω) is smoothed by final-state broadening. The final-state effects are negligible for the normal fluid above Tλ. The approach to the IA at high Q is shown to be O(logQ) for the He-He potential, which implies that S(Q,ω) satisfies approximate Y scaling and that final-state broadening is significant for all feasible experiments. Extensions of HCPT to lower Q and to other systems are qualitatively discussed. The problem of extracting momentum distributions in quantum fluids and solids from high-Q neutron scattering is addressed.

  13. Theory of deep inelastic neutron scattering. II. Application to normal and superfluid /sup 4/He

    SciTech Connect

    Silver, R.N.

    1989-03-01

    The hard-core perturbation theory (HCPT) predictions for high-momentum-transfer neutron scattering from liquid /sup 4/He are numerically evaluated. The input to the calculations are Monte Carlo and variational momentum distributions, the radial distribution function, and the Jeffreys-Wentzel-Kramers-Brillouin phase shifts for the He potential. Consistent with the ..omega../sup 2/ sum rule, the Gaussian width of the dynamic structure function S(Q,..omega..) is the same in HCPT and in the impulse approximation (IA). However, where the IA predicts structure in S(Q,..omega..) below T/sub lambda/ due to the Bose condensate, HCPT predicts that S(Q,..omega..) is smoothed by final-state broadening. The final-state effects are negligible for the normal fluid above T/sub lambda/. The approach to the IA at high Q is shown to be O(logQ) for the He-He potential, which implies that S(Q,..omega..) satisfies approximate Y scaling and that final-state broadening is significant for all feasible experiments. Extensions of HCPT to lower Q and to other systems are qualitatively discussed. The problem of extracting momentum distributions in quantum fluids and solids from high-Q neutron scattering is addressed.

  14. Time-of-Flight Measurements of Vortices Emitted from Quantum Turbulence in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Kubo, H.; Nago, Y.; Nishijima, A.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

    2013-06-01

    An oscillating obstacle generates quantum turbulence in superfluids, when vortices remained attached to obstacle surfaces or vortex rings collided with it during oscillation. Turbulence provides a source of vortices; however, the characteristics of these vortices are not clear. In the present work, we report the flight of vortices emitted from quantum turbulence in superfluid 4He at low temperatures, using vibrating wires as a generator and a detector of vortices. A vortex-free vibrating wire can detect only the first colliding vortex ring, though it will be refreshed after low vibration and be able to detect a vortex ring again. By measuring a period from the start of turbulence generation to the vortex detection repeatedly, we find an exponential distribution of time-of-flights with a non-detection period t 0 and a mean detection period t 1, suggesting a Poisson process. Both periods t 0 and t 1 increase with increasing distance between a generator and a detector. A vortex flight velocity estimated from period t 0 suggests that the sizes of the emitted vortex rings distribute to a range smaller than a generator thickness or a generator vibration amplitude. Vortices are emitted radially from a turbulence region, at least in the direction of oscillator vibration.

  15. Generation and detection of vortex rings in superfluid 4He at very low temperature

    NASA Astrophysics Data System (ADS)

    Yano, H.; Nishijima, A.; Yamamoto, S.; Ogawa, T.; Nago, Y.; Obara, K.; Ishikawa, O.; Tsubota, M.; Hata, T.

    2012-12-01

    Motions of vortices are fundamental characteristics of quantum turbulence. These motions are expected to be governed only by quantized circulations in superfluids at the zero temperature limit. In the present paper, we report the motions of vortex rings emitted from a quantum turbulence in superfluid 4He, by detecting vortex rings using a vortex-free vibrating wire as a detector. The time of flights of vortex rings are distributed, because vortex rings are emitted in any direction from a turbulent region and the detector can respond only to a reachable vortex ring. By measuring time-of-flights many times, we find an exponential distribution of time-of-flights with a non-detection period, which corresponds to the fastest time of flights of vortex rings. For a larger generation power of vortex rings, a distribution of time-of-flights still shows a single exponential distribution, but a non-detection period becomes shorter. This result implies that sizes of emitted vortex rings are distributed dependently on the generation power of turbulence. The observed exponential distributions are confirmed by numerical simulations of the dynamics of vortex rings.

  16. Third Sound Generation in Superfluid 4He Films Adsorbed on Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Iaia, Vito; Menachekanian, Emin; Williams, Gary

    2014-03-01

    A technique is developed for generating third sound in superfluid 4He films coating the surface of multiwall carbon nanotubes. Third sound is a thickness and temperature wave of the helium film, and in our case we detect the temperature oscillations with a carbon resistance bolometer. The nanotubes are packed in an annular resonator that is vibrated with a mechanical shaker assembly consisting of a permanent magnet mounted on springs, and surrounded by a superconducting coil. The coil is driven with an oscillating current, vibrating the cell at that frequency. Sweeping the drive frequency over the range 100-200 Hz excites the resonant third sound mode of the cell, seen as a high-Q signal in the FFT analysis of the bolometer signal. A problem with our original cell was that the mechanical drive would also shake the dilution refrigerator cooling the cell to low temperatures, and increasing the drive would start to heat up the refrigerator and the cell, which were rigidly coupled together. A new configuration now suspends the cell as a pendulum on a string, with thermal contact made by copper wires. Piezo sensor measurements show this reduces the vibration reaching the refrigerator by two orders of magnitude, which should allow measurements at lower temperatures.

  17. Third Sound in Superfluid 4He Films Adsorbed on Packed Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Menachekanian, Emin

    Third sound is studied for superfluid films of 4He adsorbed on multiwall carbon nanotubes packed into an annular resonator. The third sound is generated with mechanical oscillation of the cell, and detected with carbon bolometers. A filling curve at temperatures near 250 mK shows oscillations in the third sound velocity, with maxima at the completion of the 4th and 5th atomic layers. Sharp changes in the Q factor of the third sound are found at partial layer fillings. Temperature sweeps at a number of fill points show strong broadening effects on the Kosterlitz-Thouless (KT) transition, and rapidly increasing dissipation, in qualitative agreement with the predictions of Machta and Guyer. At the 4th layer completion there is a sudden reduction of the transition temperature TKT , and then a recovery back to linear variation with fill, although the slope is considerably smaller than the KT prediction. These effects might be related to changes in the gas-liquid coexistence regions.

  18. Photon scattering from 12C and 4He nuclei near the Δ(1232) resonance

    NASA Astrophysics Data System (ADS)

    Igarashi, R.; Bergstrom, J. C.; Caplan, H. S.; Doss, K. G. E.; Hallin, E. L.; Skopik, D. M.; Delli Carpini, D.; Booth, E. C.; McIntyre, E. K.; Miller, J. P.; Lucas, M. A.; MacGibbon, B. E.; Nathan, A. M.; Wells, D.

    1995-08-01

    Angular distributions for photon scattering from 12C and 4He have been measured using continuous wave bremsstrahlung from the Saskatchewan Accelerator Laboratory pulse stretcher ring. Data for carbon were taken at 158.8, 195.2, 197.2, 247.2, and 290.2 MeV end-point energies, and for helium were taken at an end-point energy of 158.8 MeV. A large NaI(Tl) gamma ray spectrometer with 1.7% resolution was used to detect the scattered photons at laboratory scattering angles ranging from 20° to 150°. The excellent energy resolution of the NaI detector allowed a separation of elastic from inelastic photon scattering for the first time at these energies. The angular distributions for elastic scattering are in only fair agreement with delta-hole theory and theory based on the optical theorem at forward angles, and completely disagree with theory at backward angles. Measured cross sections for inelastic scattering leading to the 4.43 MeV state in carbon are small compared to the elastic scattering at forward angles, but are dominant at backward angles. This experiment is the first to separate elastic from inelastic photon scattering at these energies.

  19. Investigation of Grid Turbulence in Superfluid 4He with Improved Measurement Technique

    NASA Astrophysics Data System (ADS)

    Yang, Jihee; Ihas, Gary G.

    Quantum turbulence(QT), a tangle of quantized vorticity in a macroscopically correlated quantum fluid, can have many analogous aspects to classical turbulence. Understanding QT can give us insights into classical turbulence as well as fluids in general. We generate QT by pulling a grid through a 4.6 cm x 4.6 cm cross-section channel in superfluid 4He. Second sound, a temperature/entropy wave, is used to monitor vorticity, ω. A resonant technique with high (3000) Q increases greatly the sensitivity of the measurement, but it requires a phase and amplitude locked tracking system which adheres to the resonant peak independent of frequency shifts. According to theories, the vorticity decays as ω ~ t- 11 / 10 or ω ~ t- 17 / 14 when the energy containing eddies are growing. When they saturate at the channel size, the vorticity begins decaying as ω ~ t3/2. These different decaying regions are examined in this large channel and compared to previous experiments that have been performed in 1 cm2 square channels. US NSF DMR#1007937.

  20. The reflection of low energy phonons at the free surface of liquid4He. II. Experiment

    NASA Astrophysics Data System (ADS)

    Baddar, H.; Edwards, D. O.

    1996-09-01

    Using a heater and bolometer as source and detector, the reflection of a pulsed beam of phonons at the free surface of liquid4He at ˜ 0.05 K has been measured for angles of incidence between 30 ° and 80 °. The energy distribution of the incident beam was obtained from the theory of phonon decay in the accompanying paper (I). The average incident phonon energy was ˜ 0.3 K, corresponding to an effective beam temperature of about 0.1 K. Both heater and bolometer were made from graphite resistor board with a layer of poly aniline fibers to increase the absorptivity for rotons. The angular distribution of the phonons from the heater is quite broad, approximately (cosn π+cosm θ)/2 with n ≈ 0.65 and m ≈ 3.4. However, the receiver response has a broad component with n ≈ 2.2 and an extraordinarily narrow one with m ≈ 106. In agreement with the theory in I, the reflection appears to be specular within the accuracy of the experiment. The reflection coefficient is unity within the experimental error; the weighted mean value is 1.001±0.025. During the experiment, the free surface became contaminated with ˜ 0.034 of a monolayer of3He, but no effect from the3He impurity was observed.

  1. Polarization Induced Spin Wave Damping in Spin Polarized Liquid 3He 4He

    NASA Astrophysics Data System (ADS)

    Perisanu, Sorin; Vermeulen, Gerard

    2007-08-01

    We have measured the temperature and polarization dependence of Silin spin wave spectra in a saturated 3He 4He mixture with a concentration of 9.4% at a pressure of 8 bars. The mixture has been cooled and polarized by a Leiden dilution refrigerator to temperatures in the range 10 15 mK and polarizations as high as 9.2% corresponding to 3.4 times the equilibrium polarization of 2.7% in the external magnetic field of 11.36 T. The analysis takes into account the dipolar interactions and results in the relaxation time τ ⊥ and spin diffusion constant D ⊥ . We find that τ ⊥ and D ⊥ are proportional to 1/(T2+mathcal{A}2T_{a0}2) where T is the temperature, mathcal{A} is the polarization enhancement factor and T a0 is the anisotropy temperature for the mixture at equilibrium in the external field. Our result T a0=3.66±0.14 mK is 30% higher than the theoretical prediction for very dilute mixtures and is evidence for the existence of polarization induced relaxation of transverse spin currents.

  2. First-principles modeling of quantum nuclear effects and atomic interactions in solid 4He at high pressure

    NASA Astrophysics Data System (ADS)

    Cazorla, Claudio; Boronat, Jordi

    2015-01-01

    We present a first-principles computational study of solid 4He at T =0 K and pressures up to ˜160 GPa. Our computational strategy consists in using van der Waals density functional theory (DFT-vdW) to describe the electronic degrees of freedom in this material, and the diffusion Monte Carlo (DMC) method to solve the Schrödinger equation describing the behavior of the quantum nuclei. For this, we construct an analytical interaction function based on the pairwise Aziz potential that closely matches the volume variation of the cohesive energy calculated with DFT-vdW in dense helium. Interestingly, we find that the kinetic energy of solid 4He does not increase appreciably with compression for P ≥85 GPa. Also, we show that the Lindemann ratio in dense solid 4He amounts to 0.10 almost independently of pressure. The reliability of customary quasiharmonic DFT (QH DFT) approaches in describing quantum nuclear effects in solids is also studied. We find that QH DFT simulations, although provide a reasonable equation of state in agreement with experiments, are not able to reproduce correctly these critical effects in compressed 4He. In particular, we disclose huge discrepancies of at least ˜50 % in the calculated 4He kinetic energies using both the QH DFT and present DFT-DMC methods.

  3. Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica).

    PubMed

    Caiazzo, Laura; Becagli, Silvia; Frosini, Daniele; Giardi, Fabio; Severi, Mirko; Traversi, Rita; Udisti, Roberto

    2016-04-15

    Five snow pits and five firn cores were sampled during the 2003-2004 Italian Antarctic Campaign at Talos Dome (East Antarctica), where a deep ice core (TALDICE, TALos Dome Ice CorE, 1650m depth) was drilled in 2005-2008 and analyzed for ionic content. Particular attention is spent in applying decontamination procedures to the firn cores, as core sections were stored for approximately 10years before analysis. By considering the snow pit samples to be unperturbed, the comparison with firn core samples from the same location shows that ammonium, nitrate and MSA are affected by storage post-depositional losses. All the other measured ions are confirmed to be irreversibly deposited in the snow layer. The removal of the most external layers (few centimeters) from the firn core sections is proved to be an effective decontamination procedure. High-resolution profiles of seasonal markers (nitrate, sulfate and MSA) allow a reliable stratigraphic dating and a seasonal characterization of the samples. The calculated mean accumulation-rate values range from 70 to 85mmw.e.year(-1), in the period 2003-1973 with small differences between two sectors: 70-74mmw.e.year(-1) in the NNE sector (spanning 2003-1996years) and 81-92mmw.e.year(-1) in the SSW sector (spanning 2003-1980years). This evidence is interpreted as a coupled effect of wind-driven redistribution processes in accumulation/ablation areas. Statistical treatment applied to the concentration values of the snow pits and firn cores samples collected in different points reveals a larger temporal variability than spatial one both in terms of concentration of chemical markers and annual accumulation. The low spatial variability of the accumulation rate and chemical composition measured in the five sites demonstrates that the TALDICE ice core paleo-environmental and paleo-climatic stratigraphies can be considered as reliably representative for the Talos Dome area. PMID:26849319

  4. A closer look at the Neogene erosion and accumulation rate increase

    NASA Astrophysics Data System (ADS)

    Willenbring, J.; von Blanckenburg, F.

    2008-12-01

    Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

  5. Measurements of the strong-interaction widths of the kaonic 3He and 4He 2p levels

    NASA Astrophysics Data System (ADS)

    SIDDHARTA Collaboration; Bazzi, M.; Beer, G.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Curceanu (Petrascu), C.; d'Uffizi, A.; Fiorini, C.; Frizzi, T.; Ghio, F.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Longoni, A.; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Wünschek, B.; Widmann, E.; Zmeskal, J.

    2012-07-01

    The kaonic 3He and 4He X-rays emitted in the 3d→2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Γ2p(He3)=6±6(stat.)±7 (syst.) eV, and Γ2p(He4)=14±8 (stat.)±5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55±34 eV determined by the experiments performed in the 70's and 80's, while the width of kaonic 3He was determined for the first time.

  6. Search of Superfluidity of Solid 4He in a Porous Vycor Glass by Means of the Ultrasound Technique

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Fukazawa, S.; Taniguchi, J.; Suzuki, M.; Shirahama, K.

    2006-09-01

    Kim and Chan have reported that solid 4He shows a reduction of the rotational moment of inertia below 0.2 K, which suggests an onset of superfluidity. Ultrasound should be sensitive to mass decoupling caused by superfluidity. If a superfluid component exists, the sound velocity of a porous material filled with solid 4He could increase. We have carried out ultrasonic measurements for a porous Vycor glass filled with solid 4He. Since the reported "critical velocity" is very low, we have adopted a continuous wave resonance technique which realizes the oscillating velocity less than 1 × 10-7 m/s. The resolution of the sound velocity is 10-5 for small oscillating velocities, and is enough to detect the expected mass decoupling. Although the present experimental conditions are rather limited, no signature of supersolid has been observed.

  7. Sediment accumulation rates in Conowingo Reservoir as determined by man-made and natural radionuclides

    SciTech Connect

    McLean, R.I.; Domotor, S.L. ); Summers, J.K.; Wilson, H. ); Olsen, C.R.; Larsen, I.L. )

    1991-05-01

    The Susquehanna River is the major contributor to sediment loadings in the Chesapeake Bay. Because many environmental contaminants are associated with suspended particulates, the degree of particle retention within the reservoirs of the lower Susquehanna River is an important consideration in evaluating contaminant loadings to the Chesapeake Bay. Profiles of weapons-test Cs-137, nuclear power plant-related Cs-134 and Cs-137, and naturally-derived Pb-210 were used to estimate rates of sediment accretion in the Conowingo Reservoir,an impoundmment of the Susquehanna River along the Maryland-Pennsylvania border. Net accretion rates ranged from about 2 cm yr{sup {minus}1} downstream of a nuclear power plant cooling discharge to a high of about 7 cm yr{sup {minus}1} at the mount of an incoming creek. Slight, but consistent, increases in the annual rate of accretion since the creation of the reservoir in 1928 are apparent. The current net average annual sediment load retained by the reservoir is estimated to be 0.4 {times} 10{sup 6} to 1.5 {times} 10{sup 6} metric tons yr{sup {minus}1}. The retained sediment load represents about 8-23% of the long-time average sediment input to the reservoir.

  8. Kaonic 3He and 4He measurements in the SIDDHARTA experiment at the DAΦNE collider

    NASA Astrophysics Data System (ADS)

    Tatsuno, H.; Bazzi, M.; Beer, G.; Bombelli, L.; Bragadireanu, A. M.; Cargnelli, M.; Curceanu (Petrascu), C.; d'Uffizi, A.; Fiorini, C.; Frizzi, T.; Ghio, F.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Longoni, A.; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Widmann, E.; Wünschek, B.; Zmeskal, J.

    2012-12-01

    The SIDDHARTA collaboration measured kaonic 3He and 4He 3d → 2p X-rays with gaseous targets at the DAΦNE e+e- collider. The 2p-state strong-interaction shifts and widths were precisely determined by using 144 high-resolution silicon drift detectors. The shift of K-4He is in good agreement with theoretical calculations and consistent with the recent experimental result of KEK-PS E570. The shift of K-3He is also determined for the first time. The newly determined widths are in agreement with optical model calculations.

  9. Mass Flux Stability in the Presence of Temperature Excursions and Perturbations in Solid ^3 He-^4 He Mixtures

    NASA Astrophysics Data System (ADS)

    Vekhov, Ye.; Hallock, R. B.

    2016-03-01

    The DC superfluid ^4 He mass flux through a cell filled with solid ^4 He diluted by ppm amounts of ^3 He is susceptible to flux changes when perturbations of the solid sample are imposed. We report on the details of the reproducibility of the flux following excursions in temperature and cryostat helium transfer-induced apparatus vibration, particularly including excursions to temperatures above which the flux is immeasurably small. And we report on behavior following an annealing, partial melting, and re-freezing of the sample at temperatures and pressures close to and on the melting curve.

  10. Mass Flux Stability at the T_d Conductance Transition in Solid ^3He-^4He Mixtures

    NASA Astrophysics Data System (ADS)

    Vekhov, Yegor; Hallock, R. B.

    2016-05-01

    Measurements of the ^4He mass flux through a cell filled with solid ^3He-^4He mixtures in the ^3He concentration range 0.17-220 ppm have demonstrated a reversible dramatic decrease in the flux on cooling through a concentration-dependent temperature T_d, close to the mixture phase separation temperature. For low ^3He concentrations, the flux change transition is complete within 2 mK. We report on the stability of the flux for fixed temperatures in this transition region.

  11. Pole approximation validation in the study of the {sup 6}Li(d,{alpha}){sup 4}He reaction

    SciTech Connect

    Pizzone, R. G.; Kiss, G. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Li, C.; Tumino, A.

    2010-11-24

    The Trojan Horse Method (THM) was applied to the {sup 3}He+{sup 6}Li interaction in order to investigate the quasi-free {sup 6}Li(d,{alpha}){sup 4}He reaction. The experiment was performed at 17 MeV at the Cyclotron Institute of the Czech Academy of Science. The extracted {sup 6}Li(d,{alpha}){sup 4}He quasi-free cross-section was compared with the behavior of direct data. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM above the Coulomb barrier.

  12. Multinucleon pion absorption on {sup 4}He into the pppn final state

    SciTech Connect

    Lehmann, A.; Backenstoss, G.; Koehler, J.; Kroedel, M.; Weyer, H.J.; Wildi, M.; Hoffart, A.; Trezeciak, R.; Ullrich, H.; Gram, P.A.; Breuer, H.; Gregory, N.K.; Mateos, A.O.; Redwine, R.P.; Rowntree, D.; Simicevic, N.; Wilson, K.E.; Kyle, G.; Wang, M.; Wang, M.H.; Dooling, T.; Klein, A.; Lehmann, A.; Doebbeling, H.; Hoffart, A.; Ingram, C.H.; Koch, K.; Kotlinski, B.; Michaelian, K.; Sennhauser, U.; Weyer, H.J.; Androic, D.; Bosnar, D.; Furic, M.; Petkovic, T.; Planinic, M.

    1997-10-01

    Results from a 4{pi} solid angle measurement of the reaction {pi}{sup +4}He{r_arrow}pppn at incident pion energies of T{sub {pi}{sup +}}= 70, 118, 162, 239, and 330 MeV are presented. Integrated cross sections are given for the reactions where three nucleons participate, leading to energetic (ppp) or (ppn) final states, and for states where four nucleons are involved (pppn). The two three-nucleon absorption modes were investigated in particular, and an energy dependent isospin ratio of the cross sections of {sigma}{sub ppn}/ {sigma}{sub ppp}=3.6{plus_minus}1.3, 2.6 {plus_minus}0.5, 1.8{plus_minus}0.3, 1.4{plus_minus} 0.2, and 1.8{plus_minus}0.6 was determined from 70 to 330 MeV. The differential cross sections were described by a complete set of eight independent variables and compared to simple cascade and phase space models. From this analysis the contributions from initial state interactions to the multinucleon absorption cross sections were found to be more important at higher pion energies, while those from final state interactions are stronger at lower energies. However, both mechanisms combined were found to account for not more than one-third of the total pppn multinucleon yield. The remaining strength is reasonably well reproduced by phase space models, but shows a dependence on the incident pion{close_quote}s orbital angular momentum. The isospin structure of the (ppp) and (ppn) final states is not understood, nor are some structures in their distributions. The four-nucleon yield (pppn) was found to be weak (1{endash}8{percent} of the total absorption cross section) and shows no evidence for a {open_quotes}double- {Delta}{close_quotes} excitation. {copyright} {ital 1997} {ital The American Physical Society}

  13. Second-sound studies of coflow and counterflow of superfluid {sup 4}He in channels

    SciTech Connect

    Varga, Emil; Skrbek, L.; Babuin, Simone

    2015-06-15

    We report a comprehensive study of turbulent superfluid {sup 4}He flow through a channel of square cross section. We study for the first time two distinct flow configurations with the same apparatus: coflow (normal and superfluid components move in the same direction), and counterflow (normal and superfluid components move in opposite directions). We realise also a variation of counterflow with the same relative velocity, but where the superfluid component moves while there is no net flow of the normal component through the channel, i.e., pure superflow. We use the second-sound attenuation technique to measure the density of quantised vortex lines in the temperature range 1.2 K ≲ T ≲ T{sub λ} ≈ 2.18 K and for flow velocities from about 1 mm/s up to almost 1 m/s in fully developed turbulence. We find that both the steady-state and temporal decay of the turbulence significantly differ in the three flow configurations, yielding an interesting insight into two-fluid hydrodynamics. In both pure superflow and counterflow, the same scaling of vortex line density with counterflow velocity is observed, L∝V{sub cf}{sup 2}, with a pronounced temperature dependence; in coflow instead, the vortex line density scales with velocity as L ∝ V{sup 3/2} and is temperature independent; we provide theoretical explanations for these observations. Further, we develop a new promising technique to use different second-sound resonant modes to probe the spatial distribution of quantised vortices in the direction perpendicular to the flow. Preliminary measurements indicate that coflow is less homogeneous than counterflow/superflow, with a denser concentration of vortices between the centre of the channel and its walls.

  14. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid {sup 4}He

    SciTech Connect

    Mateo, David; Eloranta, Jussi; Williams, Gary A.

    2015-02-14

    The interaction of a number of impurities (H{sub 2}, Ag, Cu, Ag{sub 2}, Cu{sub 2}, Li, He{sub 3}{sup +}, He{sup *} ({sup 3}S), He{sub 2}{sup ∗} ({sup 3}Σ{sub u}), and e{sup −}) with quantized rectilinear vortex lines in superfluid {sup 4}He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He{sup *}.

  15. Effect of self-alkalization on nitrite accumulation in a high-rate denitrification system: Performance, microflora and enzymatic activities.

    PubMed

    Li, Wei; Shan, Xiao-Yu; Wang, Zhi-Yao; Lin, Xiao-Yu; Li, Chen-Xu; Cai, Chao-Yang; Abbas, Ghulam; Zhang, Meng; Shen, Li-Dong; Hu, Zhi-Qiang; Zhao, He-Ping; Zheng, Ping

    2016-01-01

    The self-alkalization of denitrifying automatic circulation (DAC) reactor resulted in a large increase of pH up to 9.20 and caused a tremendous accumulation of nitrite up to 451.1 ± 49.0 mgN L(-1) at nitrate loading rate (NLR) from 35 kgN m(-3) d(-1) to 55 kgN m(-3) d(-1). The nitrite accumulation was greatly relieved even at the same NLR once the pH was maintained at 7.6 ± 0.2 in the system. Enzymatic assays indicated that the long-term bacterial exposure to high pH significantly inhibited the activity of copper type nitrite reductase (NirK) rather than the cytochrome cd1 type nitrite reductase (NirS). The terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that the dominant denitrifying bacteria shifted from the NirS-containing Thauear sp. 27 to the NirK-containing Hyphomicrobium nitrativorans strain NL23 during the self-alkalization. The significant nitrite accumulation in the high-rate denitrification system could be therefore, due to the inhibition of Cu-containing NirK by high pH from the self-alkalization. The results suggest that the NirK-containing H. nitrativorans strain NL23 could be an ideal functional bacterium for the conversion of nitrate to nitrite, i.e. denitritation, which could be combined with anaerobic ammonium oxidation (Anammox) to develop a new process for nitrogen removal from wastewater. PMID:26595097

  16. Rate of denitrification and the accumulation of intermediates in a denitrifying bioreactor

    NASA Astrophysics Data System (ADS)

    Parsignault, D. R.; Gursky, H.; Kellogg, E. M.; Matilsky, T.; Murray, S.; Schreier, E.; Tananbaum, H.; Giacconi, R.; Brinkman, A. C.

    2012-12-01

    Denitrifying bioreactors (DNBRs) are an emerging mechanism to mitigate the impact of excess reactive nitrogen by harnessing the activity of ubiquitous denitrifying soil microbes. DNBRs fundamentally consist of an organic carbon energy source sufficiently saturated to develop anaerobic conditions and support heterotrophic reduction of nitrate to dinitrogen. Although recent research has well established achievable nitrate removal in DNBRs upwards of 90%, few studies experimentally determine the fate of nitrogen in these systems. This study differentiates between denitrification to inert nitrogen gas, which permanently removes reactive nitrogen from an enriched ecosystem, and transformation of nitrate to another bioavailable form (such as N2O or NOX, powerful greenhouse gases). Previous research has failed to make this distinction and as both are perceived as a reduction in nitrate concentration at the outlet, the utility of DNBRs in reducing downstream reactive nitrogen has not been sufficiently established. In order to quantify the rate of nitrate removal and the products produced, dissolved gas samples are collected from the DNBR with passive diffusion gas samplers while the influent and effluent nitrate concentration and chemical oxygen demand are monitored in real time with spectrometer probes. Nitrate removal is compared with the denitrification rate and the ratio of dinitrogen to nitrous oxide is reported. Denitrification is quantified from the proportion of nitrogen gas products produced from the nitrate pool, indicated by the negative congruence of the regression of 15N enrichment in the nitrate pool and temporal depletion in the gaseous products. The proportion of nitrous oxide to dinitrogen is examined with respect to saturation and redox potential. This research informs the interpretation of previous studies as well as advises the focus of long-term system level monitoring that will provide further information on the design and application of DNBRs to

  17. Understanding the rates of nonpolar organic chemical accumulation into passive samplers deployed in the environment: Guidance for passive sampler deployments.

    PubMed

    Apell, Jennifer N; Tcaciuc, A Patricia; Gschwend, Philip M

    2016-07-01

    Polymeric passive samplers have become a common method for estimating freely dissolved concentrations in environmental media. However, this approach has not yet been adopted by investigators conducting remedial investigations of contaminated environmental sites. Successful adoption of this sampling methodology relies on an understanding of how passive samplers accumulate chemical mass as well as developing guidance for the design and deployment of passive samplers. Herein, we outline the development of a simple mathematical relationship of the environmental, polymer, and chemical properties that control the uptake rate. This relationship, called a timescale, is then used to illustrate how each property controls the rate of equilibration in samplers deployed in the water or in the sediment. Guidance is also given on how to use the timescales to select an appropriate polymer, deployment time, and suite of performance reference compounds. Integr Environ Assess Manag 2016;12:486-492. © 2015 SETAC. PMID:26426907

  18. Estimation of uptake rate constants for PCB congeners accumulated by semipermeable membrane devices and brown treat (Salmo trutta)

    USGS Publications Warehouse

    Meadows, J.C.; Echols, K.R.; Huckins, J.N.; Borsuk, F.A.; Carline, R.F.; Tillitt, D.E.

    1998-01-01

    The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMD to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB- contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and dissolved concentrations averaged 4.9 and 3.7 ??g/L, respectively, during the exposure. Total concentrations of PCBs in fish rose from 0.06 to 118.3 ??g/g during the 28-day exposure, while concentrations in the SPMD rose from 0.03 to 203.4 ??g/ g. Uptake rate constants (k1) estimated for SPMDs and brown trout were very similar, with k1 values for SPMDs ranging from one to two times those of the fish. The pattern of congener uptake by the fish and SPMDs was also similar. The rates of uptake generally increased or decreased with increasing K(ow), depending on the assumption of presence or absence of TOC.The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMB to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB-contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and

  19. L-series X-ray yields of kaonic 3He and 4He atoms in gaseous targets

    NASA Astrophysics Data System (ADS)

    Bazzi, M.; Beer, G.; Berucci, C.; Bragadireanu, A. M.; Cargnelli, M.; Curceanu, C.; d'Uffizi, A.; Fiorini, C.; Ghio, F.; Guaraldo, C.; Hayano, R. S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Sandri, P. Levi; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Quaglia, R.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D. L.; Sirghi, F.; Tatsuno, H.; Vazquez Doce, O.; Wünschek, B.; Widmann, E.; Zmeskal, J.

    2014-05-01

    The SIDDHARTA experiment measured X-rays from kaonic helium atoms using, for the first time, gaseous 3He and 4He targets. Clear patterns of the L-series X-rays of kaonic 3He and 4He atoms were observed. By using accurate Monte Carlo simulations, the absolute yields of these X-ray transitions were determined to be Y(3 d → 2 p) = 25.0{-5.8/+6.7}% for 3He (0.96 g/l), Y(3 d → 2 p) = 23.1{-4.2/+6.0}% for 4He (1.65 g/l), and Y(3 d → 2 p) = 17.2{-9.5/+2.6}% for 4He (2.15g/l). In addition, the yields Y ( nd → 2 p), with n > 3 were also determined. The measured yields provide valuable information for understanding the cascade processes of kaonic helium atoms as a function of the target density.

  20. Near-threshold search for the isospin-forbidden d+darrow^4He+π^0 reaction.

    NASA Astrophysics Data System (ADS)

    Stephenson, E. J.; Allgower, C.; Bacher, A. D.; Doskow, J.; Lavelle, C.; Nann, H.; Olmsted, J.; Rinckel, T.; Pickar, M. A.; Pancella, P. V.; Smith, A.; Spinka, H. M.; Rapaport, J.

    2002-10-01

    We will discuss our search at 228.5 MeV for the isospin-forbidden ddarrow^4Heπ^0 reaction, which constrains charge symmetry breaking contributions from the down-up quark mass difference and electromagnetic effects. The forward-going ^4He nuclei, which lie inside a θ_lab=1.2^rc cone, are separated from the deuteron beam in a 6^rc bending magnet and captured and identified in a magnetic channel. Separation of ^4Heπ^0 events depends on a reconstruction of the pion missing mass from channel position and time of flight in order to distinquish them from double radiative capture ^4Heγγ events. Two detector systems observe d+d elastic scattering at θ_c.m.=9.1^rc and 90^rc as a monitor of the luminosity ( ˜ 2× 10^31 /cm^2/s) given by the circulating IUCF Cooler beam and a cold D2 jet target. The d+d cross sections are scaled from p+d elastic cross sections by observing both during a run with a molecular HD target. Following two d+d commissioning runs, production began in early June 2002 and is planned to continue in July.

  1. Energy spectra of single neutrons and charged particles emitted following the absorption of stopped negative pions in 4He

    NASA Astrophysics Data System (ADS)

    Cernigoi, C.; Gabrielli, I.; Grion, N.; Pauli, G.; Saitta, B.; Ricci, R. A.; Boccaccio, P.; Viesti, G.

    1981-02-01

    Energy spectra have been measured of single neutrons, protons and deuterons emitted following the capture at rest of negative pions in 4He. The neutron energy spectrum has been measured with an energy resolution of 4% at 90 MeV. The absolute number of stopped pions has been measured.

  2. Prediction of stable C7 /12 and metastable C4 /7 commensurate solid phases for 4He on graphite

    NASA Astrophysics Data System (ADS)

    Ahn, Jeonghwan; Lee, Hoonkyung; Kwon, Yongkyung

    2016-02-01

    Using a substrate potential described by a pairwise sum of empirical 4He-C interatomic potentials, we have performed path-integral Monte Carlo calculations for 4He adatoms on graphite. It is found that a second-layer commensurate structure is not stable above an incommensurate first-layer triangular solid. This is consistent with the conclusion of the previous theoretical study of Corboz et al. [Phys. Rev. B 78, 245414 (2008), 10.1103/PhysRevB.78.245414] that was based on a laterally averaged one-dimensional potential. On the other hand, we observe a new stable C7 /12 commensurate solid in the first 4He layer at the areal density of 0.111 Å-2, which is close to the second-layer promotion density. This high-density commensurate solid exhibits a √{12 }×√{12 } structure registered to the graphite surface that is not disrupted by the development of the second 4He layer. Furthermore, a second-layer 4/7 commensurate structure relative to the first-layer C7 /12 solid is found to be at least metastable, opening the possibility of two-dimensional supersolidity.

  3. Correlated wave functions and hyperfine splittings of the 2 s state of muonic sup 3,4 He atoms

    SciTech Connect

    Chen, M. )

    1992-02-01

    The correlated wave functions of the 2{ital s} state, (1{ital s}){sub {ital e}}(2{ital s}){sub {mu}} of muonic {sup 4}He and {sup 3}He atoms are calculated by the variational approach, employing an improved set of the Hylleraas-type basis functions to study the 2{ital s} state of muonic He atoms. The energy and radial expectation values are calculated. Our proposed wave functions for the muonic {sup 4}He and {sup 3}He atoms are good enough to describe the electron and muon at small, intermediate, and large values of radial coordinates. The hyperfine splittings of the (1{ital s}){sub {ital e}}(2{ital s}){sub {mu}} muonic {sup 4}He and {sup 3}He atoms are also presented. Including relativistic, QED, and other corrections up to {ital O}({alpha}{sup 2}), we arrive at the values {Delta}{nu}= 4287.01{plus minus}0.10 and 4052.64{plus minus}0.10 MHz for the total hyperfine splittings of the 2{ital s} state of muonic {sup 4}He and {sup 3}He atoms, respectively.

  4. A finite-temperature density functional study of electron self-trapping in 3He and 4He.

    PubMed

    Jin, Dafei; Guo, Wei

    2012-06-28

    We introduce a compact finite-temperature density functional model to study electron self-trapping in both liquid and vapor (3)He and (4)He. This model can quantitatively reproduce the most essential thermodynamic properties of (3)He and (4)He along their liquid-vapor coexistence lines. The structures and energetics of self-trapped electron bubbles on the 1S ground state and 1P excited state are particularly investigated. Our results show that 1S and 1P bubbles exist in liquid at any temperature, whereas 1S bubbles exist in vapor only above 1.6 K in (3)He and above 2.8 K in (4)He, 1P bubbles exist in vapor only above 2.5 K in (3)He and 4.0 K in (4)He. An initially spherical 1P bubble is unstable against deformation towards a peanut shape. In liquid, a peanut-shaped 1P bubble is held from fission by surface tension until reaching the liquid-vapor critical point, whereas in vapor it always splits into two smaller bubbles. The existence of 1P bubbles in finite-temperature liquid helium and their fission instability in helium vapor reveal interesting physics in this system. PMID:22755590

  5. Spectroscopic information of 6Li from elastic scattering of deuterons, 3He and 4He by 6Li

    NASA Astrophysics Data System (ADS)

    Amar, A.

    2014-07-01

    The elastic scattering of deuterons, 3He and 4He on 6Li at different incident energies have been analyzed in the framework of the optical model (OM) using ECIS88 as well as SPI GENOA codes. The optical potential parameters were extracted in the phenomenological treatment. A good agreement between theoretical and experimental differential cross-sections was obtained in whole angular range. Parameters for real part of potential have been also calculated microscopically with double-folding model for the d, 3He and 4He scattering, respectively, using DFPOT code. The elastic transfer mechanism has been studied by coupled reaction channel (CRC) method using FRESCO code. Spectroscopic amplitudes of 6Li ≡ t + 3He and 6Li ≡ α + d configurations have been extracted from d, 3He and 4He scattering on 6Li at wide energy range. A comparison between spectroscopic amplitudes obtained from deuteron and α elastically scattering from 6Li has been made. The extracted spectroscopic amplitudes of 6Li ≡ 4He + d(SF = SA2) from 6Li(d, 6Li)d and 6Li(α, 6Li)α are not the same as expected theoretically.

  6. Influences of sediment geochemistry on metal accumulation rates and toxicity in the aquatic oligochaete Tubifex tubifex.

    PubMed

    Méndez-Fernández, Leire; De Jonge, Maarten; Bervoets, Lieven

    2014-12-01

    Metal bioaccumulation and toxicity in the aquatic oligochaete Tubifex tubifex exposed to three metal-contaminated field-sediments was studied in order to assess whether sediment-geochemistry (AVS, TOC) plays a major role in influencing these parameters, and to assess if the biodynamic concept can be used to explain observed effects in T. tubifex tissue residues and/or toxicity. An active autotomy promotion was observed in three studied sediments at different time points and reproduction impairment could be inferred in T. tubifex exposed to two of the tested sites after 28 days. The present study showed that sediment metal concentration and tissue residues followed significant regression models for four essential metals (Cu, Co, Ni and Zn) and one non-essential metal (Pb). Organic content normalization for As also showed a significant relationship with As tissue residue. Porewater was also revealed to be an important source of metal uptake for essential metals (e.g. Cu, Ni and Zn) and for As, but AVS content was not relevant for metal uptake in T. tubifex in studied sediments. Under the biodynamic concept, it was shown that influx rate from food (IF, sediment ingestion) in T. tubifex, in a range of sediment geochemistry, was able to predict metal bioaccumulation, especially of the essential metals Cu, Ni and Zn, and for the non-essential metal Pb. Additionally, IF appeared to be a better predictor for metal bioaccumulation in T. tubifex compared to sediment geochemistry normalization. PMID:25456225

  7. Biogenic silica fluxes and accumulation rates in the Gulf of California

    SciTech Connect

    Thunell, R.C.; Pride, C.J.; Tappa, E. ); Muller-Karger, F.E. )

    1994-04-01

    The Gulf of California, though small in size, plays an important role in the global silica cycle. The seasonal pattern of biogenic silica flux in the gulf is closely related to that of phytoplankton biomass levels and is controlled by changes in weather and hydrographic conditions. The highest opal fluxes ([approximately] 0.35 g[center dot]m[sup [minus]2][center dot]d[sup [minus]1]) occur during winter and spring, and they are comparable to those measured in some of the most productive ecosystems of the world. Approximately 15%-25% of the biogenic silica produced in surface waters is preserved in gulf sediments, a figure significantly higher than the average global ocean preservation rate. However, the flux of opal at 500 m water depth is less than 25% of that being produced at the surface, suggesting that most of the recycling of biogenic silica in the Gulf of California occurs in the upper water column. 28 refs., 3 figs.

  8. Magma accumulation rates and thermal histories of plutons of the Sierra Nevada batholith, CA

    NASA Astrophysics Data System (ADS)

    Davis, Jesse W.; Coleman, Drew S.; Gracely, John T.; Gaschnig, Richard; Stearns, Michael

    2012-03-01

    Zircon U-Pb geochronology results indicate that the John Muir Intrusive Suite of the central Sierra Nevada batholith, California, was assembled over a period of at least 12 Ma between 96 and 84 Ma. Bulk mineral thermochronology (U-Pb zircon and titanite, 40Ar/39Ar hornblende and biotite) of rocks from multiple plutons comprising the Muir suite indicates rapid cooling through titanite and hornblende closure following intrusion and subsequent slow cooling through biotite closure. Assembly of intrusive suites in the Sierra Nevada and elsewhere over millions of years favors growth by incremental intrusion. Estimated long-term pluton assembly rates for the John Muir Intrusive Suite are on the order of 0.001 km3 a-1 which is inconsistent with the rapid magma fluxes that are necessary to form large-volume magma chambers capable of producing caldera-forming eruptions. If large shallow crustal magma chambers do not typically develop during assembly of large zoned intrusive suites, it is doubtful that the intrusive suites represent cumulates left behind following caldera-forming eruptions.

  9. Using Cyclic Variations Of Early Pliocene Diatom Assemblages To Determine Sediment Accumulation Rates In The ANDRILL AND-1B Core

    NASA Astrophysics Data System (ADS)

    Konfirst, M. A.; Scherer, R. P.; Monien, D.; Kuhn, G.; Winter, D.; Sjunneskog, C. M.

    2009-12-01

    In the 2006-2007 Antarctic field season, the ANDRILL MIS project recovered a 1,285m record of Miocene through Plio-Pleistocene sediments near Ross Island in the Ross Sea region of Antarctica. Diatom biostratigraphy, radiometric dating and magnetostratigraphy were used in conjunction with the evaluation of glacial surfaces of erosion (GSEs) to produce a well-constrained age model for the core. However, within the Plio-Pleistocene interval (the upper ~620m), the ANDRILL record also included 13 discrete intervals composed of nearly pure diatomite, the longest of which is over 80m thick. The lack of GSEs during periods of high diatom accumulation has created limitations in assigning ages to specific core depths within the diatomite intervals. In this study, data were collected on abundance of key diatom species present within 290 samples from the long Early Pliocene diatomite unit (DU XI- 363.37-459.24 mbsf) as well as ~15m of diatom-rich mudstone immediately overlying it. We analyzed diatom records at high resolution (as high as ca. 600 year sample interval, according to the chronostratigraphic correlations established by this study). This approximately 100m section was then subdivided into five units based on major diatom assemblage shifts and changes in both geochemical properties and clast abundance counts (Pompilio et al., 2007). Cyclic changes in relative diatom abundance were identified within each unit using characteristic species and matched to variations in the oxygen isotope record (Lisiecki & Raymo, 2005) using the chronostratigraphic framework established by Naish et al. (2007), which included the assignment of an oxygen isotope age to specific core depths. Additionally, the core ages provided by the correlation of diatom abundance with the isotope record allowed the calculation of sediment accumulation rates through the interval. The results presented here provide a further refinement to the ANDRILL age model and allow interpretation of the interaction

  10. The helium flux from the continents and ubiquity of low-3He/4He recycled crust and lithosphere

    NASA Astrophysics Data System (ADS)

    Day, James M. D.; Barry, Peter H.; Hilton, David R.; Burgess, Ray; Pearson, D. Graham; Taylor, Lawrence A.

    2015-03-01

    New helium isotope and trace-element abundance data are reported for pyroxenites and eclogites from South Africa, Siberia, and the Beni Bousera Massif, Morocco that are widely interpreted to form from recycled oceanic crustal protoliths. The first He isotope data are also presented for Archaean peridotites from the Kaapvaal (South Africa), Slave (Canada), and Siberian cratons, along with recently emplaced off-craton peridotite xenoliths from Kilbourne Hole, San Carlos (USA) and Vitim (Siberia), to complement existing 3He/4He values obtained for continental and oceanic peridotites. Helium isotope compositions of peridotite xenoliths vary from 7.3 to 9.6 RA in recently (<10 kyr) emplaced xenoliths, to 0.05 RA in olivine from cratonic peridotite xenoliths of the 1179 Ma Premier kimberlite, South Africa. The helium isotope compositions of the peridotites can be explained through progressive sampling of 4He produced from radiogenic decay of U and Th in the mineral lattice in the older emplaced peridotite xenoliths. Ingrowth of 4He is consistent with generally higher 4He concentrations measured in olivine from older emplaced peridotite xenoliths relative to those from younger peridotite xenoliths. Collectively, the new data are consistent with pervasive open-system behaviour of He in peridotite xenoliths from cratons, mobile belts and tectonically-active regions. However, there is probable bias in the estimate of the helium isotope composition of the continental lithospheric mantle (6.1 ± 2.1 RA), since previously published databases were largely derived from peridotite xenoliths from non-cratonic lithosphere, or phenocrysts/xenocrysts obtained within continental intraplate alkaline volcanics that contain a contribution from asthenospheric sources. Using the new He isotope data for cratonic peridotites and assuming that significant portions (>50%) of the Archaean and Proterozoic continental lithospheric mantle are stable and unaffected by melt or fluid infiltration on

  11. Biomass Accumulation Rates of Amazonian Secondary Forest and Biomass of Old-Growth Forests from Landsat Time Series and GLAS

    NASA Astrophysics Data System (ADS)

    Helmer, E.; Lefsky, M. A.; Roberts, D.

    2009-12-01

    We estimate the age of humid lowland tropical forests in Rondônia, Brazil, from a somewhat densely spaced time series of Landsat images (1975-2003) with an automated procedure, the Threshold Age Mapping Algorithm (TAMA), first described here. We then estimate a landscape-level rate of aboveground woody biomass accumulation of secondary forest by combining forest age mapping with biomass estimates from the Geoscience Laser Altimeter System (GLAS). Though highly variable, the estimated average biomass accumulation rate of 8.4 Mg ha-1 yr-1 agrees well with ground-based studies for young secondary forests in the region. In isolating the lowland forests, we map land cover and general types of old-growth forests with decision tree classification of Landsat imagery and elevation data. We then estimate aboveground live biomass for seven classes of old-growth forest. TAMA is simple, fast, and self-calibrating. By not using between-date band or index differences or trends, it requires neither image normalization nor atmospheric correction. In addition, it uses an approach to map forest cover for the self-calibrations that is novel to forest mapping with satellite imagery; it maps humid secondary forest that is difficult to distinguish from old-growth forest in single-date imagery; it does not assume that forest age equals time since disturbance; and it incorporates Landsat Multispectral Scanner (MSS) imagery. Variations on the work that we present here can be applied to other forested landscapes. Applications that use image time series will be helped by the free distribution of coregistered Landsat imagery, which began in December 2008, and of the Ice Cloud and land Elevation Satellite (ICESat) Vegetation Product, which simplifies the use of GLAS data. Finally, we demonstrate here for the first time how the optical imagery of fine spatial resolution that is viewable on Google Earth provides a new source of reference data for remote sensing applications related to land cover

  12. Accumulation of Cd by the marine sponge Halichondria panicea pallas: Effects upon filtration rate and its relevance for biomonitoring

    SciTech Connect

    Olesen, T.M.E.; Weeks, J.M. )

    1994-05-01

    The marine demosponge Halichondria panicea Pallas, is a cosmopolitan species occurring in coastal waters with varied conditions of light, current, salinity and turbidity. H. panicea has a leuconoid structure and is composed of siliceous spicules and spongin fibers. Sponges are important members of many shallow water marine benthic communities, but comparatively little is known of their trace metal biology. Sponge architecture is constructed around a system of water canals and the physiology of the sponge is largely dependent on the currents of water flowing through their bodies. The volume of water pumped by a sponge is remarkable, ca. 100-1200 ml h[sup [minus]1] g[sup [minus]1]. This large volume of water passing through the body of a sponge means that most cells are in direct contact with the external medium. Many sponges are able to accumulate trace metals and are highly tolerant of such pollutants. This has led to the proposal that a [open quotes]sponge watch[close quotes] program be initiated supplementary to the existing [open quotes]mussel watch[close quotes] program. In view of the large volume of water passing through the bodies of sponges such as H. panicea, the suitability of this species as a biomonitoring organism was further investigated. This study describes the accumulation strategy of the demosponge H. panicea exposed to dissolved cadmium (Cd) and the effect of Cd upon sponge filtration rate.

  13. Using beryllium-10 to test the validity of past accumulation rate reconstruction from water isotope records in East Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2014-08-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 ka in Antarctica. Inferring the variations of past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high resolution 10Be record covering a full climatic cycle over the period 269 to 355 kyr BP from MIS 9 to MIS 10 (Marine Isotope Stages). After correcting 10Be for the estimated effect of the paleomagnetic field, we deduce that the classical estimation of accumulation rate variations from records of water isotopes agrees, with a possible underestimation of 16%, with the uncertainty on the temperature reconstruction from water isotopes in Antarctic ice cores. This is within their uncertainty of -10 to +30%. Finally, we show that the relationship between temperature and accumulation rate is comparable when using ice core data and results from several AGCM simulations run on glacial-interglacial conditions despite a larger spread in model outputs. These results indicate that the thermodynamic law linking moisture content in the air and temperature, as implemented in the different models, leads to realistic results even in polar regions, at the end of the water distillation trajectory.

  14. Belowground carbon balance and carbon accumulation rate in the successional series of monsoon evergreen broad-leaved forest

    USGS Publications Warehouse

    Zhou, G.; Liu, S.; Tang, X.; Ouyang, X.; Zhang, Dongxiao; Liu, J.; Yan, J.; Zhou, C.; Luo, Y.; Guan, L.; Liu, Yajing

    2006-01-01

    The balance, accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper, based on long-term observations to the soil organic matter, input and standing biomass of litter and coarse woody debris, and dissolved organic carbon carried in the hydrological process of subtropical climax forest ecosystem - monsoon evergreen broad-leaved forest, and its two successional forests of natural restoration - coniferous and broad-leaved mixed forest and Pinus massoniana forest, as well as data of root biomass obtained once every five years and respiration measurement of soil, litter and coarse woody debris respiration for 1 year. The major results include: the belowground carbon pools of monsoon evergreen broad-leaved forest, coniferous and broad-leaved mixed forest, and Pinus massoniana forest are 23191 ?? 2538 g ?? m-2, 16889 ?? 1936 g ?? m-2 and 12680 ?? 1854 g ?? m-2, respectively, in 2002. Mean annual carbon accumulation rates of the three forest types during the 24a from 1978 to 2002 are 383 ?? 97 g ?? m-2 ?? a-1, 193 ?? 85 g ?? m-2 ?? a-1 and 213 ?? 86 g ?? m-2 ?? a-1, respectively. The belowground carbon pools in the three forest types keep increasing during the observation period, suggesting that belowground carbon pools are carbon sinks to the atmosphere. There are seasonal variations, namely, they are strong carbon sources from April to June, weak carbon sources from July to September; while they are strong carbon sinks from October to November, weak carbon sinks from December to March. ?? Science in China Press 2006.

  15. Kinetics of the Reaction of the Heaviest Hydrogen Atom with H2, the 4Heμ + H2 -> 4HeμΗ + H Reaction: Experiments, Accurate Quantal Calculations, and Variational Transition State Theory, including Kinetic Isotope Effects for a Factor of 36.1 in Isotopic Mass

    SciTech Connect

    Fleming, Donald G.; Arseneau, Donald J.; Sukhorukov, Oleksandr; Brewer, Jess H.; Mielke, Steven L.; Truhlar, Donald G.; Schatz, George C.; Garrett, Bruce C.; Peterson, Kirk A.

    2011-11-14

    The neutral muonic helium atom {sup 4}He{mu}, in which one of the electrons of He is replaced by a negative muon, may be effectively regarded as the heaviest isotope of the hydrogen atom, with a mass of 4.115 amu. We report details of the first muon spin rotation ({mu}SR) measurements of the chemical reaction rate constant of {sup 4}He{mu} with molecular hydrogen, {sup 4}He{mu} + H{sub 2} {yields} {sup 4}He{mu}H + H, at temperatures of 295.5, 405, and 500 K, as well as a {mu}SR measurement of the hyperfine coupling constant of muonic He at high pressures. The experimental rate constants, k{sub He{mu}}, are compared with the predictions of accurate quantum mechanical (QM) dynamics calculations carried out on a well converged Born-Huang (BH) potential energy surface, based on complete configuration interaction calculations and including a Born-Oppenheimer diagonal correction. At the two highest measured temperatures the agreement between the quantum theory and experiment is good to excellent, well within experimental uncertainties that include an estimate of possible systematic error, but at 295.5 K the quantum calculations for k{sub He{mu}} are below the experimental value by 2.1 times the experimental uncertainty estimates. Possible reasons for this discrepancy are discussed. Variational transition state theory calculations with multidimensional tunneling have also been carried out for k{sub He{mu}} on the BH surface, and they agree with the accurate QM rate constants to within 30% over a wider temperature range of 200-1000 K. Comparisons between theory and experiment are also presented for the rate constants for both the D + H{sub 2} and Mu + H{sub 2} reactions in a novel study of kinetic isotope effects for the H + H{sub 2} reactions over a factor of 36.1 in isotopic mass of the atomic reactant.

  16. Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids.

    PubMed

    Bell, James R; Alderson, Lynda; Izera, Daniela; Kruger, Tracey; Parker, Sue; Pickup, Jon; Shortall, Chris R; Taylor, Mark S; Verrier, Paul; Harrington, Richard

    2015-01-01

    Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12·2-m suction-traps throughout the year to collect migrating aphids. In 2014, the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatiotemporal analysis and the provision of the first British annotated checklist of aphids since 1964. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life-history traits. We then highlight emerging pests using accumulation patterns. Linear and nonlinear mixed-effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16 °C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. All 55 species studied had earlier first flight trends at rate of β = -0·611 ± SE 0·015 days year(-1). Of these species, 49% had earlier last flights, but the average species effect appeared relatively stationary (β = -0·010 ± SE 0·022 days year(-1)). Most species (85%) showed increasing duration of their flight season (β = 0·336 ± SE 0·026 days year(-1)), even though only 54% increased their log annual count (β = 0·002 ± SE <0·001 year(-1)). The ADD16 and NAO were shown to drive patterns in aphid phenology in a spatiotemporal context. Early in the year when the first aphids were migrating, the effect of the winter NAO was highly significant. Further into the year, ADD16 was a strong predictor. Latitude had a near linear effect on first flights, whereas longitude produced a generally less-clear effect on all responses. Aphids that are anholocyclic (permanently parthenogenetic) or are monoecious (non

  17. Long-term phenological trends, species accumulation rates, aphid traits and climate: five decades of change in migrating aphids

    PubMed Central

    Bell, James R; Alderson, Lynda; Izera, Daniela; Kruger, Tracey; Parker, Sue; Pickup, Jon; Shortall, Chris R; Taylor, Mark S; Verrier, Paul; Harrington, Richard

    2015-01-01

    1. Aphids represent a significant challenge to food production. The Rothamsted Insect Survey (RIS) runs a network of 12·2-m suction-traps throughout the year to collect migrating aphids. In 2014, the RIS celebrated its 50th anniversary. This paper marks that achievement with an extensive spatiotemporal analysis and the provision of the first British annotated checklist of aphids since 1964. 2. Our main aim was to elucidate mechanisms that advance aphid phenology under climate change and explain these using life-history traits. We then highlight emerging pests using accumulation patterns. 3. Linear and nonlinear mixed-effect models estimated the average rate of change per annum and effects of climate on annual counts, first and last flights and length of flight season since 1965. Two climate drivers were used: the accumulated day degrees above 16 °C (ADD16) indicated the potential for migration during the aphid season; the North Atlantic Oscillation (NAO) signalled the severity of the winter before migration took place. 4. All 55 species studied had earlier first flight trends at rate of β = −0·611 ± SE 0·015 days year−1. Of these species, 49% had earlier last flights, but the average species effect appeared relatively stationary (β = −0·010 ± SE 0·022 days year−1). Most species (85%) showed increasing duration of their flight season (β = 0·336 ± SE 0·026 days year−1), even though only 54% increased their log annual count (β = 0·002 ± SE <0·001 year−1). 5. The ADD16 and NAO were shown to drive patterns in aphid phenology in a spatiotemporal context. Early in the year when the first aphids were migrating, the effect of the winter NAO was highly significant. Further into the year, ADD16 was a strong predictor. Latitude had a near linear effect on first flights, whereas longitude produced a generally less-clear effect on all responses. Aphids that are anholocyclic (permanently parthenogenetic) or are monoecious (non-host-alternating) were

  18. Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

    NASA Astrophysics Data System (ADS)

    Karageorgis, A. P.; Kaberi, H.; Price, N. B.; Muir, G. K. P.; Pates, J. M.; Lykousis, V.

    2005-12-01

    Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from 210Pb and 137Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm -2 yr -1 (Axios and Aliakmon Rivers) and 0.414 g cm -2 yr -1 (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess 210Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from ˜1 cm in inshore stations to ˜2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or 'excess' metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.

  19. Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of {sup 4}He nanodroplets on surfaces: {sup 4}He/graphene

    SciTech Connect

    Lara-Castells, María Pilar de; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O.; Pi, Martí

    2014-10-21

    In this work we propose a general strategy to calculate accurate He–surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on {sup 4}He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of {sup 4}He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the {sup 4}He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

  20. Snow accumulation rate on Qomolangma (Mount Everest), Himalaya: synchroneity with sites across the Tibetan Plateau on 50-100 year timescales

    NASA Astrophysics Data System (ADS)

    Kaspari, Susan; Hooke, Roger Leb.; Mayewski, Paul Andrew; Kang, Shichang; Hou, Shugui; Qin, Dahe

    Annual-layer thickness data, spanning AD 1534-2001, from an ice core from East Rongbuk Col on Qomolangma (Mount Everest, Himalaya) yield an age-depth profile that deviates systematically from a constant accumulation-rate analytical model. The profile clearly shows that the mean accumulation rate has changed every 50-100 years. A numerical model was developed to determine the magnitude of these multi-decadal-scale rates. The model was used to obtain a time series of annual accumulation. The mean annual accumulation rate decreased from ˜0.8 m ice equivalent in the 1500s to ˜0.3 m in the mid-1800s. From ˜1880 to ˜1970 the rate increased. However, it has decreased since ˜1970. Comparison with six other records from the Himalaya and the Tibetan Plateau shows that the changes in accumulation in East Rongbuk Col are broadly consistent with a regional pattern over much of the Plateau. This suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area. However, a record from Dasuopu, only 125 km northwest of Qomolangma and 700 m higher than East Rongbuk Col, shows a maximum in accumulation during the 1800s, a time during which the East Rongbuk Col and Tibetan Plateau ice-core and tree-ring records show a minimum. This asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology.

  1. Simultaneous investigation of shear modulus and torsional resonance of solid 4He

    NASA Astrophysics Data System (ADS)

    Shin, Jaeho; Choi, Jaewon; Shirahama, Keiya; Kim, Eunseong

    2016-06-01

    We investigate the origin of a resonant period drop of a torsional oscillator (TO) containing solid 4He by inspecting its relation to a change in elastic modulus. To understand this relationship directly, we measure both phenomena simultaneously using a TO with a pair of concentric piezoelectric transducers inserted in its annulus. We confirm experimentally that both anomalies are directly related. Although the temperature, 3He concentration, and frequency dependence are essentially the same, a marked discrepancy in the drive amplitude dependence is observed. We find that this discrepancy originates from the anisotropic response of polycrystalline solid 4He connected with low-angle grain boundaries by studying the shear modulus parallel to and perpendicular to the driving direction.

  2. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2015-03-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS) 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum). After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr-1 instead of 3.95). This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a). Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an interglacial state, i

  3. Tensor analyzing powers T20(θ) and T22(θ) in the 2H(darrow,γ) 4He reaction

    NASA Astrophysics Data System (ADS)

    Seyler, R. G.; Weller, H. R.

    1985-05-01

    Reaction theory expressions are used to prove that the tensor analyzing powers T20(θ) and T22(θ) for the 2H(darrow,γ) 4He reaction are isotropic if the reaction is pure E2 and terms quadratic in channel-spin-2 matrix elements are neglected. Experimental departures from isotropy can be expected near θ-0°, 90°, and 189°.

  4. Quasifree Lambda, Sigma^0, and Sigma^- electroproduction from 1,2H, 3,4He, and Carbon

    SciTech Connect

    F. Dohrmann; A. Ahmidouch; C.S. Armstrong; J. Arrington; R. Asaturyan; S. Avery; K. Bailey; H. Bitao; H. Breuer; D.S. Brown; R. Carlini; J. Cha; N. Chant; E. Christy; A. Cochran; L. Cole; J. Crowder; S. Danagoulian; M. Elaasar; R. Ent; H. Fenker; Y. Fujii; L. Gan; K. Garrow; D.F. Geesaman; P. Gueye; K. Hafidi; W. Hinton; H. Juengst; C. Keppel; Y. Liang; J.H. Liu; A. Lung; D. Mack; P. Markowitz; J. Mitchell; T. Miyoshi; H. Mkrtchyan; S.K. Mtingwa; B. Mueller; G. Niculescu; I. Niculescu; D. Potterveld; B.A. Raue; P.E. Reimer; J. Reinhold; J. Roche; M. Sarsour; Y. Sato; R.E. Segel; A. Semenov; S. Stepanyan; V. Tadevosyan; S. Tajima; L. Tang; A. Uzzle; S. Wood; H. Yamaguchi; C. Yan; L. Yuan; B. Zeidman; M. Zeier; B. Zihlmann

    2007-07-30

    Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and Carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma hyperons were determined at Q^2= 0.35(GeV/c)^2 and W= 1.91GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.

  5. Motion of a helical vortex filament in superfluid 4He under the extrinsic form of the local induction approximation

    NASA Astrophysics Data System (ADS)

    Van Gorder, Robert A.

    2013-08-01

    Very recently, Shivamoggi ["Vortex motion in superfluid 4He: Reformulation in the extrinsic vortex-filament coordinate space," Phys. Rev. B 84, 012506 (2011)], 10.1103/PhysRevB.84.012506 studied the extrinsic form of the local induction approximation (LIA) for the motion of a Kelvin wave on a vortex filament in superfluid 4He, and obtained some results in a cubic approximation. Presently, we study the motion of helical vortex filaments in superfluid 4He under the exact fully nonlinear LIA considered in potential form by Van Gorder ["Fully nonlinear local induction equation describing the motion of a vortex filament in superfluid 4He," J. Fluid Mech. 707, 585 (2012)], 10.1017/jfm.2012.308 and obtained from the Biot-Savart law through the equations of Hall and Vinen ["The rotation of liquid helium II. I. Experiments on the propagation of second sound in uniformly rotating helium II," Proc. R. Soc. London, Ser. A 238, 204 (1956)], 10.1098/rspa.1956.0214 including superfluid friction terms. Nonlinear dispersion relations governing the helical Kelvin wave on such a vortex filament are derived in exact form, from which we may exactly calculate the phase and group velocity of the Kelvin wave. With this, we classify the motion of a helical Kelvin wave on a vortex filament under the LIA. The dispersion relations and results, which follow are exact in nature, in contrast to most results in the literature, which are usually numerical approximations. As such, our results accurately capture the qualitative behavior of the Kelvin waves under the LIA. Extensions to other frameworks are discussed.

  6. The structure of mixed {sup 3}He-{sup 4}He droplets doped with OCS: A density functional approach

    SciTech Connect

    Leal, Antonio; Mateo, David; Pi, Martí; Barranco, Manuel; Navarro, Jesús

    2013-11-07

    We have investigated the structure and energetics of mixed {sup 3}He-{sup 4}He droplets doped with a carbonyl sulfide molecule within a density functional approach considering a small but finite temperature of 0.1 K. The molecule is treated as an external field to which the helium droplet is attached. The energetics and appearance of these droplets are discussed for selected numbers of helium atoms, identifying the first magic numbers of the fermionic component.

  7. Exclusive measurements of mean pion multiplicities in 4He-nucleus reactions from 200 to 800 MeV/nucleon

    NASA Technical Reports Server (NTRS)

    L'Hote, D.; Alard, J. P.; Augerat, J.; Babinet, R.; Brochard, F.; Fodor, Z.; Fraysse, L.; Girard, J.; Gorodetzky, P.; Gosset, J.; Laspalles, C.; Lemaire, M. C.; Lucas, B.; Montarou, G.; Parizet, M. J.; Poitou, J.; Racca, C.; Schimmerling, W.; Tamain, J. C.; Terrien, Y.; Valero, J.; Cugnon, J.; Vandermeulen, J.

    1987-01-01

    Mean multiplicities of pi+ and pi- in 4He collisions with C, Cu, and Pb at 200, 600, and 800 MeV/u, and with C and Pb at 400 MeV/u have been measured using the large solid angle detector Diogene. The independence of pion multiplicity on projectile incident energy, target mass and proton multiplicity is studied in comparison with intra-nuclear cascade predictions. The discrepancy between experimental results and theory is pointed out and discussed.

  8. Background reduction system of {sup 4}He({sup 12}C,{sup 16}O)gamma at KUTL

    SciTech Connect

    Taniguchi, M.; Sagara, K.; Teranishi, T.; Fujita, K.; Iwabuchi, R.; Gotoh, T.; Nakano, K.; Oba, N.

    2010-06-01

    The C-alpha reaction is one of the most important reactions in astrophysics. At Kyushu University Tandem accelerator Laboratory (KUTL), a high detective efficiency measurement has been made by adopting inverse kinematics: {sup 12}C beam is injected on windowless {sup 4}He gas target. In this experiment, a powerful background reduction system is necessary. We describe the effectiveness of the background system consisting of recoil mass separator, a long time chopper, and new movable slits.

  9. Measurement of the sup 3 He( n ,. gamma. ) sup 4 He cross section at thermal neutron energies

    SciTech Connect

    Wolfs, F.L.H.; Freedman, S.J.; Nelson, J.E. ); Dewey, M.S.; Greene, G.L. )

    1989-12-18

    We have measured the cross section for radiative capture of thermal neutrons on {sup 3}He. The measured cross section of 54{plus minus}6 {mu}b is used to estimate the astrophysical {ital S} factor for the reaction {sup 3}He({ital p},{ital e}{sup +}{nu}){sup 4}He which gives rise to high-energy neutrinos from the Sun.

  10. Are high 3He/4He ratios in oceanic basalts an indicator of deep-mantle plume components?

    USGS Publications Warehouse

    Meibom, A.; Anderson, D.L.; Sleep, N.H.; Frei, R.; Chamberlain, C.P.; Hren, M.T.; Wooden, J.L.

    2003-01-01

    The existence of a primordial, undegassed lower mantle reservoir characterized by high concentration of 3He and high 3He/4He ratios is a cornerstone assumption in modern geochemistry. It has become standard practice to interpret high 3He/4He ratios in oceanic basalts as a signature of deep-rooted plumes. The unfiltered He isotope data set for oceanic spreading centers displays a wide, nearly Gaussian, distribution qualitatively similar to the Os isotope (187Os/188 Os) distribution of mantle-derived Os-rich alloys. We propose that both distributions are produced by shallow mantle processes involving mixing between different proportions of recycled, variably aged radiogenic and unradiogenic domains under varying degrees of partial melting. In the case of the Re-Os isotopic system, radiogenic mid-ocean ridge basalt (MORB)-rich and unradiogenic (depleted mantle residue) endmembers are constantly produced during partial melting events. In the case of the (U+Th)-He isotope system, effective capture of He-rich bubbles during growth of phenocryst olivine in crystallizing magma chambers provides one mechanism for 'freezing in' unradiogenic (i.e. high 3He/4He) He isotope ratios, while the higher than chondritic (U+Th)/He elemental ratio in the evolving and partially degassed MORB melt provides the radiogenic (i.e. low 3He/4He) endmember. If this scenario is correct, the use of He isotopic signatures as a fingerprint of plume components in oceanic basalts is not justified. Published by Elsevier Science B.V.

  11. Processes and rates of sediment and wood accumulation in headwater streams of the Oregon Coast Range, USA

    USGS Publications Warehouse

    May, Christine L.; Gresswell, Robert E.

    2003-01-01

    Channels that have been scoured to bedrock by debris flows provide unique opportunities to calculate the rate of sediment and wood accumulation in low-order streams, to understand the temporal succession of channel morphology following disturbance, and to make inferences about processes associated with input and transport of sediment. Dendrochronology was used to estimate the time since the previous debris flow and the time since the last stand-replacement fire in unlogged basins in the central Coast Range of Oregon. Debris flow activity increased 42 per cent above the background rate in the decades immediately following the last wildfire. Changes in wood and sediment storage were quantified for 13 streams that ranged from 4 to 144 years since the previous debris flow. The volume of wood and sediment in the channel, and the length of channel with exposed bedrock, were strongly correlated with the time since the previous debris flow. Wood increased the storage capacity of the channel and trapped the majority of the sediment in these steep headwater streams. In the absence of wood, channels that have been scoured to bedrock by a debris flow may lack the capacity to store sediment and could persist in a bedrock state for an extended period of time. With an adequate supply of wood, low-order channels have the potential of storing large volumes of sediment in the interval between debris flows and can function as one of the dominant storage reservoirs for sediment in mountainous terrain.

  12. Photodisintegration cross section of the reaction (4)He(γ,p)(3)H between 22 and 30 MeV.

    PubMed

    Raut, R; Tornow, W; Ahmed, M W; Crowell, A S; Kelley, J H; Rusev, G; Stave, S C; Tonchev, A P

    2012-01-27

    The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei. PMID:22400829

  13. Modern rates of glacial sediment accumulation along a 15° S-N transect in fjords from the Antarctic Peninsula to southern Chile

    NASA Astrophysics Data System (ADS)

    Boldt, Katherine V.; Nittrouer, Charles A.; Hallet, Bernard; Koppes, Michele N.; Forrest, Brittany K.; Wellner, Julia S.; Anderson, John B.

    2013-12-01

    of glacial erosion in temperate climates rank among the highest worldwide, and the sedimentary products of such erosion record climatic and tectonic signals in many glaciated settings, as well as temporal changes in glacier behavior. Glacial sediment yields are expected to decrease with increasing latitude because decreased temperature and meltwater production reduce glacial sliding, erosion, and sediment transfer; however, this expectation lacks a solid supportive database. Herein we present modern 210Pb-derived sediment accumulation rates on decadal to century time scales for 12 fjords spanning 15° of latitude from the Antarctic Peninsula to southern Chile and interpret the results in light of glacimarine sediment accumulation worldwide. 210Pb records from the Antarctic Peninsula show surprisingly steady sediment accumulation throughout the past century at rates of 1-7 mm yr-1, despite rapid warming and glacial retreat. Cores from the South Shetland Islands reveal accelerated sediment accumulation over the past few decades, likely due to changes in the thermal state of the glaciers in this region, which straddles the boundary between subpolar and temperate conditions. In Patagonia and Tierra del Fuego, sediment accumulates faster (11-24 mm yr-1), and previously collected seismic profiles show that rates reach meters per year close to the glacier termini. This increase in sediment accumulation rates with decreasing latitude reflects the gradient from subpolar to temperate climates and is consistent with glacial erosion being much faster in the temperate climate of southern Chile than in the polar climate of the Antarctic Peninsula.

  14. Export Production Fluctuations in the Eastern Equatorial Pacific during the Pliocene-Pleistocene: Reconstruction Using Barite Accumulation Rates

    NASA Astrophysics Data System (ADS)

    Paytan, A.; Ma, Z.; Ravelo, A. C.; Liu, Z.

    2014-12-01

    Over the last 5 million years, Earth has experienced a transition from warmer climates to cooler climates. It is not clear how these changes affected export productivity in the Equatorial Pacific (EEP) and what are the potential feedbacks between ocean productivity and climate? To address these questions we use barite accumulation rates to reconstruct export productivity in the eastern equatorial Pacific (ODP Site 849) and compare the record to sea surface temperature (SST) fluctuations and other productivity proxies over the past 5.3 Ma. We find that export productivity fluctuated considerably on multiple time scales. During the Pliocene between 4.5 and 3 Ma, export productivity was on average higher (~50 g C m-2 yr-1) than during the Pleistocene (~ 35 g C m-2 yr-1). In the Pleistocene a trend of decreasing export production occurred between 3 Ma and 1 Ma (from ~60 to ~20 g C m-2 yr-1) followed by an increase over the last million years. Our record reveal decoupling between export productivity and SST on long (million year) time scales as previously suggested. Throughout this time interval shorter orbital-scale large amplitude fluctuations (between 10 and 100 g C m-2 yr-1) in export productivity are observed and export production was generally higher during cold periods or during transitions. Results from this study suggest that in the EEP mechanisms that affect carbon export on orbital time scales differed from those operating on longer time scales.

  15. Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

    NASA Astrophysics Data System (ADS)

    Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

    2016-08-01

    Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

  16. Off-river waterbodies on tidal rivers: Human impact on rates of infilling and the accumulation of pollutants

    NASA Astrophysics Data System (ADS)

    Woodruff, Jonathan D.; Martini, Anna P.; Elzidani, Emhmed Z. H.; Naughton, Thomas J.; Kekacs, Daniel J.; MacDonald, Daniel G.

    2013-02-01

    Cut-off meanders, backwater ponds, and blocked valley coves are all common features along the tidal reaches of lowland rivers. While significant progress has been made to understand sediment dynamics in similar off-river environments above the head of tides, less is known about the processes driving transport and sedimentation within these systems when tidally influenced. To provide insight we combine sedimentological observations with flux analyses for a series of tidal off-river waterbodies along the Lower Connecticut River spanning the river's entire 100 km tidal reach. Sedimentation rates exhibit a clear seaward increase with growing tidal influence, and are an order of magnitude higher than accumulation rates obtained previously from neighboring marsh and subtidal environments. A simplified mass balance can relate time-series measurements of water level and suspended sediment concentration to observed trends in sedimentation, and support flood-dominated asymmetry in tidal sediment flux (i.e. tidal pumping) as the primary mechanism for enhanced trapping. Relatively steady rates of deposition are observed in off-river waterbodies over the last century, with little evidence of deposition dominated by extreme events. Suspended sediment concentrations rise significantly in the main tidal river with increasing river discharge, while tidal range is damped with rising freshwater flow. The net result is an optimal freshwater discharge for maximizing the tidal pumping of sediment from the main river into tidal off-river waterbodies, with more routine discharge events largely responsible for driving long-term trends in deposition. A sudden shift in lithology towards more inorganic, fluvial derived sediment is commonly observed towards the end of the 19th century, along with over an order of magnitude increase in the rate of deposition. The timing of the onset of rapid infilling occurs contemporaneous with the documented creation and/or deepening of tidal tie

  17. A novel method of determining accumulation rates during the last glacial period at Berkner Island, West Antarctica

    NASA Astrophysics Data System (ADS)

    Massam, Ashleigh; Sneed, Sharon; Mulvaney, Robert; Mayewski, Paul; Whitehouse, Pippa

    2015-04-01

    within the ice sheet - a particular issue in Antarctica where accumulation rates can be very low. In addition, this is the only study so far that is able to evaluate the empirical relationships used in modelled reconstructions of glacial conditions, by comparing modelled glaciological profiles with the profiles derived from the ultra-high resolution trace element analysis. The ultimate outcome of this research is the construction of a more robust age-depth profile which will enable better insight and comprehension of past climate conditions including palaeoaccumulation. The authors acknowledge funding from a NERC DTG studentship, with support from the Antarctic Science bursary, the WM Keck Foundation and the US National Science Foundation.

  18. Analysis of the scintillation mechanism in a pressurized 4He fast neutron detector using pulse shape fitting

    NASA Astrophysics Data System (ADS)

    Kelley, R. P.; Murer, D.; Ray, H.; Jordan, K. A.

    2015-03-01

    An empirical investigation of the scintillation mechanism in a pressurized 4He gas fast neutron detector was conducted using pulse shape fitting. Scintillation signals from neutron interactions were measured and averaged to produce a single generic neutron pulse shape from both a 252Cf spontaneous fission source and a (d,d) neutron generator. An expression for light output over time was then developed by treating the decay of helium excited states in the same manner as the decay of radioactive isotopes. This pulse shape expression was fitted to the measured neutron pulse shape using a least-squares optimization algorithm, allowing an empirical analysis of the mechanism of scintillation inside the 4He detector. A further understanding of this mechanism in the 4He detector will advance the use of this system as a neutron spectrometer. For 252Cf neutrons, the triplet and singlet time constants were found to be 970 ns and 686 ns, respectively. For neutrons from the (d,d) generator, the time constants were found to be 884 ns and 636 ns. Differences were noted in the magnitude of these parameters compared to previously published data, however the general relationships were noted to be the same and checked with expected trends from theory. Of the excited helium states produced from a 252Cf neutron interaction, 76% were found to be born as triplet states, similar to the result from the neutron generator of 71%. The two sources yielded similar pulse shapes despite having very different neutron energy spectra, validating the robustness of the fits across various neutron energies.

  19. Analysis of the scintillation mechanism in a pressurized {sup 4}He fast neutron detector using pulse shape fitting

    SciTech Connect

    Kelley, R.P. Ray, H.; Jordan, K.A.; Murer, D.

    2015-03-15

    An empirical investigation of the scintillation mechanism in a pressurized {sup 4}He gas fast neutron detector was conducted using pulse shape fitting. Scintillation signals from neutron interactions were measured and averaged to produce a single generic neutron pulse shape from both a {sup 252}Cf spontaneous fission source and a (d,d) neutron generator. An expression for light output over time was then developed by treating the decay of helium excited states in the same manner as the decay of radioactive isotopes. This pulse shape expression was fitted to the measured neutron pulse shape using a least-squares optimization algorithm, allowing an empirical analysis of the mechanism of scintillation inside the {sup 4}He detector. A further understanding of this mechanism in the {sup 4}He detector will advance the use of this system as a neutron spectrometer. For {sup 252}Cf neutrons, the triplet and singlet time constants were found to be 970 ns and 686 ns, respectively. For neutrons from the (d,d) generator, the time constants were found to be 884 ns and 636 ns. Differences were noted in the magnitude of these parameters compared to previously published data, however the general relationships were noted to be the same and checked with expected trends from theory. Of the excited helium states produced from a {sup 252}Cf neutron interaction, 76% were found to be born as triplet states, similar to the result from the neutron generator of 71%. The two sources yielded similar pulse shapes despite having very different neutron energy spectra, validating the robustness of the fits across various neutron energies.

  20. Mauna Loa lava accumulation rates at the Hilo drill site: Formation of lava deltas during a period of declining overall volcanic growth

    USGS Publications Warehouse

    Lipman, P.W.; Moore, J.G.

    1996-01-01

    Accumulation rates for lava flows erupted from Mauna Loa, as sampled in the uppermost 280 m of the Hilo drill hole, vary widely for short time intervals (several thousand years), but overall are broadly similar to those documented elsewhere on this volcano since 100 ka. Thickness variations and accumulation rates for Mauna Loa lavas at the Hilo drill site have been strongly affected by local paleotopography, including funneling and ponding between Mauna Kea and Kilauea. In addition, gentle submerged slopes of Mauna Kea in Hilo Bay have permitted large shoreline displacements by Mauna Loa flows. Ages of eruptive intervals have been determined from published isotopic data and from eustatic sea level curves modified to include the isostatic subsidence of the island of Hawaii at 2.2-2.6 mm/yr. Prior to 10 ka, rates of Mauna Loa lava accumulation at the drill site varied from 0.6 to 4.3 mm/yr for dateable intervals, with an overall rate of 1.8 mm/yr. Major eruptive pulses at about 1.3 and 10 ka, each probably representing a single long-lived eruption based on lack of weathering between flow units, increase the overall accumulation rate to 2.4 mm/yr. The higher rate since 10 ka reflects construction of thick near-shoreline lava deltas as postglacial sea levels rose rapidly. Large lava deltas form only along coastal segments where initially subaerial slopes have been submerged by the combined effects of eustatic sea level rise, isostatic subsidence, or spreading of volcano flanks. Overall accumulation of 239 m of lava at the drill site since 100-120 ka closely balances submergence of the Hilo area, suggesting that processes of coastal lava deposition have been modulated by rise in sea level. The Hilo accumulation rate is slightly higher than average rates of 1-2 mm/yr determined elsewhere along the Mauna Loa coast, based on rates of shoreline coverage and dated sea cliff and fault scarp exposures. Low rates of coastal lava accumulation since 100 ka, near or below the rate

  1. Forest dynamics and tip-up pools drive pulses of high carbon accumulation rates in a tropical peat dome in Borneo (Southeast Asia)

    NASA Astrophysics Data System (ADS)

    Dommain, René; Cobb, Alexander R.; Joosten, Hans; Glaser, Paul H.; Chua, Amy F. L.; Gandois, Laure; Kai, Fuu-Ming; Noren, Anders; Salim, Kamariah A.; Su'ut, N. Salihah H.; Harvey, Charles F.

    2015-04-01

    Peatlands of Southeast Asia store large pools of carbon but the mechanisms of peat accumulation in tropical forests remain to be resolved. Patch dynamics and forest disturbance have seldom been considered as drivers that can amplify or dampen rates of peat accumulation. Here we used a modified piston corer, noninvasive geophysical measurements, and geochemical and paleobotanical techniques to establish the effect of tree fall on carbon accumulation rates in a peat swamp forest dominated by Shorea albida in Brunei (Borneo). Carbon initially accumulated in a mangrove forest at over 300 g C m-2 yr-1 but declined to less than 50 g C m-2 yr-1 with the establishment of a peat swamp forest. A rapid accumulation pulse of 720-960 g C m-2 yr-1 occurred around 1080 years ago as a tip-up pool infilled. Tip-up pools are common in the peatlands of northwest Borneo where windthrow and lightning strikes produce tree falls at a rate of 4 trees ha-1 every decade. A simulation model indicates that tip-up pools, which are formed across the entire forested peat dome, produce local discontinuities in the peat deposit, when peat is removed to create a pool that is rapidly filled with younger material. The resulting discontinuities in peat age at the base and sides of pool deposits obscure linkages between carbon accumulation rates and climate and require new approaches for paleoenvironmental reconstructions. Our results suggest that carbon accumulation in tropical peat swamps may be based on fundamentally different peat-forming processes than those of northern peatlands.

  2. Precision measurement of the 3 d → 2 p x-ray energy in kaonic 4He

    NASA Astrophysics Data System (ADS)

    Okada, S.; Beer, G.; Bhang, H.; Cargnelli, M.; Chiba, J.; Choi, Seonho; Curceanu, C.; Fukuda, Y.; Hanaki, T.; Hayano, R. S.; Iio, M.; Ishikawa, T.; Ishimoto, S.; Ishiwatari, T.; Itahashi, K.; Iwai, M.; Iwasaki, M.; Juhász, B.; Kienle, P.; Marton, J.; Matsuda, Y.; Ohnishi, H.; Outa, H.; Sato, M.; Schmid, P.; Suzuki, S.; Suzuki, T.; Tatsuno, H.; Tomono, D.; Widmann, E.; Yamazaki, T.; Yim, H.; Zmeskal, J.

    2007-09-01

    We have measured the Balmer-series x-rays of kaonic 4He atoms using novel large-area silicon drift x-ray detectors in order to study the low-energy Kbar-nucleus strong interaction. The energy of the 3 d → 2 p transition was determined to be 6467 ± 3 (stat) ± 2 (syst) eV. The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment.

  3. Measurements of the T(t,2n)4He neutron spectrum at low reactant energies from inertial confinement implosions.

    PubMed

    Casey, D T; Frenje, J A; Gatu Johnson, M; Manuel, M J-E; Sinenian, N; Zylstra, A B; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Radha, P B; Meyerhofer, D D; Sangster, T C; McNabb, D P; Amendt, P A; Boyd, R N; Hatchett, S P; Quaglioni, S; Rygg, J R; Thompson, I J; Bacher, A D; Herrmann, H W; Kim, Y H

    2012-07-13

    Measurements of the neutron spectrum from the T(t,2n)4He (tt) reaction have been conducted using inertial confinement fusion implosions at the OMEGA laser facility. In these experiments, deuterium-tritium (DT) gas-filled capsules were imploded to study the tt reaction in thermonuclear plasmas at low reactant center-of-mass (c.m.) energies. In contrast to accelerator experiments at higher c.m. energies (above 100 keV), these results indicate a negligible n + 5He reaction channel at a c.m. energy of 23 keV. PMID:23030170

  4. Polarization transfer in the {sup 4}He({rvec e}, e'{rvec p}){sup 3}H reaction

    SciTech Connect

    Sonja Dieterich; et. al

    2001-02-15

    Polarization transfer in the {sup 4}He({rvec e}, e'{rvec p}){sup 3}H reaction at a Q{sup 2} of 0.4 (GeV/c){sup 2} was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.

  5. A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

    SciTech Connect

    S.P. Malace, M. Paolone, S. Strauch

    2011-01-01

    We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin independent charge-exchange term in the latter calculation.

  6. HCHO in a cold, quantum solvent: size and shape of its "bubbles" in (4)He droplets from stochastic simulations.

    PubMed

    Marinetti, F; Yurtsever, E; Gianturco, F A

    2010-09-16

    The full interaction between formaldehyde and (4)He atoms has been obtained from a first-principle calculation of the forces at play. In order to describe the nanoscopic features of HCHO being solvated in a quantum liquid, further Monte Carlo calculations for the system HCHO@He(N) with N up to 20 have been carried out. The energetics and structure of the systems, as N changes, are extensively analyzed, and the excluded volume ("bubble") created by the inner cage that surrounds the solvated molecule is described and discussed to provide molecular microsolvation details for the title system. PMID:20462179

  7. Lowest vibrational states of {sup 4}He{sup 3}He{sup +}: Non-Born-Oppenheimer calculations

    SciTech Connect

    Stanke, Monika; Bubin, Sergiy; Kedziera, Dariusz; Molski, Marcin; Adamowicz, Ludwik

    2007-11-15

    Very accurate quantum mechanical calculations of the first five vibrational states of the {sup 4}He{sup 3}He{sup +} molecular ion are reported. The calculations have been performed explicitly including the coupling of the electronic and nuclear motions [i.e., without assuming the Born-Oppenheimer (BO) approximation]. The nonrelativistic non-BO wave functions were used to calculate the {alpha}{sup 2} relativistic mass velocity, Darwin, and spin-spin interaction corrections. For the lowest vibrational transition, whose experimental energy is established with high precision, the calculated and the experimental results differ by only 0.16 cm{sup -1}.

  8. Variation of Accumulation Rates Over the Last Eight Centuries on the East Antarctic Plateau Derived from Volcanic Signals in Ice Cores

    NASA Technical Reports Server (NTRS)

    Anschuetz, H.; Sinisalo, A.; Isaksson, E.; McConnell, J. R.; Hamran, S.-E.; Bisiaux, M. M.; Pasteris, D.; Neumann, T. A.; Winther, J.-G.

    2011-01-01

    Volcanic signatures in ice-core records provide an excellent means to date the cores and obtain information about accumulation rates. From several ice cores it is thus possible to extract a spatio-temporal accumulation pattern. We show records of electrical conductivity and sulfur from firn cores from the Norwegian-USA scientific traverse during the International Polar Year 2007-2009 (IPY) through East Antarctica. Major volcanic eruptions are identified and used to assess century-scale accumulation changes. The largest changes seem to occur in the most recent decades with accumulation over the period 1963- 2007/08 being up to 25 % different from the long-term record. There is no clear overall trend, some sites show an increase in accumulation over the period 1963 to present while others show a decrease. Almost all of the sites above 3200 m above sea level (asl) suggest a decrease. These sites also show a significantly lower accumulation value than large-scale assessments both for the period 1963 to present and for the long-term mean at the respective drill sites. The spatial accumulation distribution is influenced mainly by elevation and distance to the ocean (continentality), as expected. Ground-penetrating radar data around the drill sites show a spatial variability within 10-20 % over several tens of kilometers, indicating that our drill sites are well representative for the area around them. Our results are important for large-scale assessments of Antarctic mass balance and model validation.

  9. Unified description of 6Li structure and deuterium-4He dynamics with chiral two- and three-nucleon forces

    DOE PAGESBeta

    Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr

    2015-05-29

    Here, we provide a unified ab initio description of the 6Li ground state and elastic scattering of deuterium (d) on 4He (α) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of 6Li. The calculation reproduces the empirical binding energy of 6Li, yielding an asymptotic D- to S-state ratio of the 6Li wave function in the d+α configuration of –0.027, in agreement with a determination from 6Li–4He elastic scattering, but overestimates the excitation energy of the 3+more » state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the 2H(α,γ)6Li radiative capture, responsible for the big-bang nucleosynthesis of 6Li.« less

  10. Unified description of ^{6}Li structure and deuterium-^{4}He dynamics with chiral two- and three-nucleon forces.

    PubMed

    Hupin, Guillaume; Quaglioni, Sofia; Navrátil, Petr

    2015-05-29

    We provide a unified ab initio description of the ^{6}Li ground state and elastic scattering of deuterium (d) on ^{4}He (α) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of ^{6}Li. The calculation reproduces the empirical binding energy of ^{6}Li, yielding an asymptotic D- to S-state ratio of the ^{6}Li wave function in the d+α configuration of -0.027, in agreement with a determination from ^{6}Li-^{4}He elastic scattering, but overestimates the excitation energy of the 3^{+} state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the ^{2}H(α,γ)^{6}Li radiative capture, responsible for the big-bang nucleosynthesis of ^{6}Li. PMID:26066431

  11. Studies of kinetic processes in a concentrated 3He-4He solution using an oscillating tuning fork

    NASA Astrophysics Data System (ADS)

    Bakhvalova, V. A.; Gritsenko, I. A.; Rudavskii, E. Ya.; Chagovets, V. K.; Sheshin, G. A.

    2015-07-01

    The dissipative processes causing the damping of quartz tuning fork vibrations in a solution of 15% 3He in 4He, are studied in a temperature range of 0.5-2.3 K. The resonance curves of the tuning forks are measured in the laminar flow region of the liquid, and their width is determined by the width of the dissipative processes. We examined tuning forks with a resonance frequency of 32 kHz, located inside a flask ("enclosed") and tuning forks without a flask ("unenclosed"). The results of the experiment are compared to existing theories. It was found that a significant contribution to the damping of tuning fork oscillations for a solution, as opposed to pure 4He, is from the second sound radiation, the contribution of which exceeds the input of viscous dissipation at low temperatures. The radiation of the first sound does not contribute to the damping of the oscillations of the "enclosed" fork due to the small size of the cell versus the wavelength. In the case of the "unenclosed" fork, the damping is determined by three processes: viscous dissipation and radiation of the first and second sounds.

  12. Frequency-dependent Study of Ultrapure Solid 4He by Using Rigid Double-pendulum Torsional Oscillator

    NASA Astrophysics Data System (ADS)

    Choi, Jaewon; Shin, Jaeho; Kim, Eunseong

    2015-03-01

    The physical origin of the period drop found in the torsional oscillator (TO) containing solid 4He was previously interpreted as the appearance of supersolidity. The current consensus is that the increase in the shear modulus leads to the period anomaly. Further studies show that the stiffening effect in TO can be amplified if a TO is not properly designed to be ``rigid.'' In this study, we designed a rigid double-pendulum TO. High purity solid 4He sample (0.6ppb) was grown by the block capillary method. The resonant period of TO starts to decrease from the empty cell data at 80mK. The ratio of the resonant period changes to the total mass loading are 3 . 8 ×10-5 and 2 . 6 ×10-4 for 1st and 2nd mode, respectively. Unlike recent experiment, we could not found a frequency-independent period drop. The upper bound for the putative supersolid fraction is less than 4 ×10-6 . The dissipation peak accompanied with the period drop was also analyzed with Cole-Cole plot and ωτ plot. We conclude that major contribution for the anomalous TO responses comes from the elastic effect.

  13. Two- and Three-Body Photodisintegration of ^4He at E_γ=150-250 MeV

    NASA Astrophysics Data System (ADS)

    Rice, B. J.; Canon, R. S.; Wulf, E. A.; Weller, H. R.; Keeter, K.; Kolb, N. R.; Mueller, C.; Pywell, R. E.; Retzlaff, G. R.; Skopik, D. M.; Feldman, G.

    1997-10-01

    The reactions ^4He(γ,dd) and ^4He(γ,npd) with E_γ=150-250 MeV have been studied using tagged and untagged bremsstrahlung γ rays from the electron accelerator at the Saskatchewan Accelerator Laboratory (SAL). Angular distributions and energy dependences of the cross sections have been measured at six angles from 45^circ to 141^circ in the center-of-mass frame. Preliminary results indicate that the (γ,dd) cross section is peaked near 45^circ and 135^circ with a minimum at 90^circ, consistent with an E2 angular distribution. This contradicts the suggestion by Silverman [1] that the distribution is peaked at 90^circ. Our preliminary absolute cross sections favor the lower values of previous reports (see references in [1]). In order to extract the amplitudes and phases of the contributing multipoles, a transition-matrix element analysis will be performed. Implications of these two- and three-body results for current few-body theories will be discussed. * Research supported in part by DOE grant DE-FG02-97ER41033. [1] B. H. Silverman et al., Phys. Rev. C 29, 35 (1984).

  14. Rates of post-fire vegetation recovery and fuel accumulation as a function of burn severity and time-since-burn in four western U.S. ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation recovery and fuel accumulation rates following wildfire are useful measures of ecosystem resilience, yet few studies have quantified these variables over 10 years post-fire. Conventional wisdom is that recovery time to pre-fire condition will be slower as a function of burn severity, as i...

  15. Low-3He/4He sublithospheric mantle source for the most magnesian magmas of the Karoo large igneous province

    NASA Astrophysics Data System (ADS)

    Heinonen, Jussi S.; Kurz, Mark D.

    2015-09-01

    The massive outpourings of Karoo and Ferrar continental flood basalts (CFBs) ∼180 Ma ago mark the initial Jurassic rifting stages of the Gondwana supercontinent. The origin and sources of these eruptions have been debated for decades, largely due to difficulties in defining their parental melt and mantle source characteristics. Recent findings of Fe- and Mg-rich dikes (depleted ferropicrite suite) from Vestfjella, western Dronning Maud Land, Antarctica, have shed light on the composition of the deep sub-Gondwanan mantle: these magmas have been connected to upper mantle sources presently sampled by the Southwest Indian Ocean mid-ocean ridge basalts (SWIR MORBs) or to high 3He/4He plume-entrained non-chondritic primitive mantle sources formed early in Earth's history. In an attempt to determine their He isotopic composition and relative contributions from magmatic, cosmogenic, and radiogenic He sources, we performed in-vacuo stepwise crushing and melting analyses of olivine mineral separates, some of which were abraded to remove the outer layer of the grains. The best estimate for the mantle isotopic composition is given by a sample with the highest amount of He released (>50%) during the first crushing step of an abraded coarse fraction. It has a 3He/4He of 7.03 ± 0.23 (2σ) times the atmospheric ratio (Ra), which is indistinguishable from those measured from SWIR MORBs (6.3-7.3 Ra; source 3He/4He ∼6.4-7.6 Ra at 180 Ma) and notably lower than in the most primitive lavas from the North Atlantic Igneous Province (up to 50 Ra), considered to represent the epitome magmas from non-chondritic primitive mantle sources. Previously published trace element and isotopic (Sr, Nd, and Pb) compositions do not suggest a direct genetic link to any modern hotspot of Indian or southern Atlantic Oceans. Although influence of a mantle plume cannot be ruled out, the high magma temperatures and SWIR MORB-like geochemistry of the suite are best explained by supercontinent insulation

  16. A 9000 year perspective on carbon accumulation rates under changing hydro-climate and vegetation conditions in a mountain peatland, northern Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Feurdean, Angelica; Panait, Andrei; Gałka, Mariusz; Diaconu, Andrei; Hutchinson, Simon; Mulch, Andreas; Tantau, Ioan; Hickler, Thomas

    2016-04-01

    Peatlands, in particular ombrogenous bogs, which entirely depend on water from precipitation, are sensitive to changes in the balance between precipitation and evapotranspiration; and therefore highly suitable for hydro-climatological reconstruction. Peatlands also represent a large carbon pool in the terrestrial biosphere. However, little is known about the C sequestration processes in mountain peatlands under various competing drivers of change (climate, vegetation, fire). We applied a multi-proxy approach (bulk density, loss on ignition, total organic carbon, testate amoebae, δ13C in Sphagnum, plant macrofossils, pollen and charcoal) to a peat sequence from a mountain ombrogenous bog (Tǎul Muced) to explore how changes in hydro-climate conditions, peat plant composition and fire have affected long-term physical peat properties and the rate of carbon accumulation over the last 9000 years. Carbon accumulation at this site ranged from 7 to 105 g C cm2 yr1 (mean 23 ± 14 g C cm2 yr_1). We found that high moisture availability (P-E) as inferred from testate amoebae and δ13C values in Sphagnum increased the carbon sink capacity of peatland. The strength of the relationship between the rate of carbon accumulation and climate appears particularly evident over the last millennium when high C accumulation rates correlated with the warm and wet conditions of the Medieval Climate Anomaly and lower C accumulation rates with the dry conditions of the Little Ice Age. We also found a significant positive correlation between the rate of C accumulation and changes in vegetation; rates were lowest (17 g C cm2 yr_1), during periods of mixed Sphagnum (primarily S. magellanicum and S. angustifolium) and vascular plant (Cyperaceae, Eriophorum vaginatum) growth and increased (31 g C cm2 yr_1) during the accumulation of Sphagnum peat, regardless the dominant Sphagnum species. We did not find indication of peatland fire during the investigated interval. Our study represents one of the

  17. Parity-Violating Electron Scattering from {sup 4}He and the Strange Electric Form Factor of the Nucleon

    SciTech Connect

    Aniol, K.A.; Margaziotis, D.J.; Armstrong, D.S.; Averett, T.; Finn, J.M.; Holmstrom, T.; Kelleher, A.; Moffit, B.; Sulkosky, V.; Benaoum, H.; Holmes, R.; Souder, P.A.; Bertin, P.Y.; Ferdi, C.

    2006-01-20

    We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 4}He at an average scattering angle <{theta}{sub lab}>=5.7 deg. and a four-momentum transfer Q{sup 2}=0.091 GeV{sup 2}. From these data, for the first time, the strange electric form factor of the nucleon G{sub E}{sup s} can be isolated. The measured asymmetry of A{sub PV}=(6.72{+-}0.84{sub (stat)}{+-}0.21{sub (syst)})x10{sup -6} yields a value of G{sub E}{sup s}=-0.038{+-}0.042{sub (stat)}{+-}0.010{sub (syst)}, consistent with zero.

  18. The influence of embedded atoms, molecules, and clusters on the lifetimes of electron bubbles in large 4He droplets

    NASA Astrophysics Data System (ADS)

    Fárník, Michal; Toennies, J. Peter

    2003-03-01

    The lifetimes of electrons injected into large (≈106atoms) superfluid 4He droplets have been measured in the presence of different prior embedded rare gas atoms, their clusters, and the molecules O2, H2O, and SF6. For the light rare gas atoms Ne and Ar the lifetimes of about 6ṡ10-2 s, found previously for pure droplets, are reduced to between 1-2ṡ10-2 s. Single molecules with large electron affinities, such as SF6 and O2 and small clusters of H2O lead to a significant increase in the lifetimes. In the case of Kr and Xe, larger clusters with n¯>14 are needed before the lifetimes increase. A simple model, which takes account of the energy levels occupied by the electrons in the corresponding molecules or the clusters, assumed to be solid, can qualitatively explain the observations.

  19. Polarization transfer in 4He(e,e'p)3H: is the ratio GEp/GMp modified in medium ?

    SciTech Connect

    Rocco Schiavilla

    2004-12-01

    Polarization observables in the {sup 4}He({rvec e}, e{prime} {rvec p}){sup 3}H reaction are calculated using accurate three- and four-nucleon bound-state wave functions, a realistic model for the nuclear electromagnetic current operator, and a treatment of final-state-interactions with an optical potential model constrained by p {sup 3}H elastic and charge-exchange cross section data. In contrast to earlier studies, no significant discrepancies are found between theory and experiment both for the ratio of transverse to longitudinal polarization transfers and for the induced polarization, when free-nucleon electromagnetic form factors are used in the current operator. The present results challenge the current interpretation of the experimental data in terms of medium-modified form factors.

  20. Determination of thicknesses and impurities of targets by measuring backscattered particles from 2 MeV 4He +-bombardment

    NASA Astrophysics Data System (ADS)

    Guoji, Xu; Yuhua, Zhao; Shengnan, Zheng; Yongchang, Xu

    1985-06-01

    The measurement of target thicknesses and impurity contents using backscattering, as well as the principle of this technique are briefly described. The targets are irradiated in a beam of 2 MeV 4He + ions. The backscattered ions are detected using a Si(Au) solid-state detector. Gold and calcium fluoride on thin carbon backing and selfsupporting silicon foils were determined from peak width measurements. Oxygen and tungsten impurities in a silicon target being prepared by vacuum evaporation from a tungsten boat were determined using the same method. The thickness of a thin aluminium deposit on thick tantalum backing was obtained from the energy shift of the tantalum peak between two spectra recorded with respectively the aluminium and the tantalum facing the ion beam. Copper contamination on the surface on an iron layer electroplated on copper foil was determined by comparison of the copper peak area with the iron peak height in the backscattering spectrum.

  1. Electric breakdown and ionization detection in normal liquid and superfluid 4He for the SNA nEDM experiment

    NASA Astrophysics Data System (ADS)

    Karcz, Maciej

    A new experiment to search for the neutron electric dipole moment (nEDM) is under construction at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The SNS nEDM experiment is a national collaboration spanning over 20 universities and laboratories with more than 100 physicists and engineers contributing to the research and development. The search for a nEDM is a precision test of time reversal symmetry in particle physics, in the absence of a discovery, the SNS nEDM experiment seeks to improve the present limit on the nEDM value by two orders of magnitude. A non-zero value of the nEDM would help to explain the asym- metry between matter and anti-matter in the universe by providing an additional source of charge conjugation and parity symmetry violation, a necessary ingredient in the theory of baryogenesis in the early universe. The nEDM experiment will measure the Larmor precession frequency of neutrons by detecting scintillation from neutron capture by a dilute concentration of 3He inside a bath of superfluid 4He. Neutron capture by 3He is spin-dependent and the magnetic moments of the neutron and the 3He nucleus are comparable. A direct measurement of the precession frequency of polarized 3He and scintillation from neutron capture allows for the relative precession frequencies of 3He and the neutron to be determined. The experiment will then look for changes in the relative precession of 3He and neutrons under the influence of strong electric fields. 3He has negligible EDM and therefore any deviation due to an applied electric field would be from a nEDM. The nEDM experiment will need to apply strong electric fields inside superfluid (SF) 4He and it was necessary to investigate the ability of SF 4He to sustain electric fields. An experiment to study electric breakdown in superfluid 4He was constructed at the Indiana University Center for Exploration of Energy and Matter (CEEM). The experiment studied the electric breakdown behavior of liquid

  2. Polarization Transfer in {sup 4}He(e-vector,e{sup '}p-vector){sup 3}H

    SciTech Connect

    Paolone, Michael

    2007-10-26

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the {sup 4}He(e-vector,e{sup '}p-vector){sup 3}H reaction at a Q{sup 2} of 0.8 (GeV/c){sup 2} and 1.3 (GeV/c){sup 2} with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c){sup 2} from both Mainz and Jefferson Lab, in which the measured ratio of polarization-transfer coefficients differs from a fully relativistic DWIA calculation. Preliminary results hint at a possible unexpected Q{sup 2} dependence in the polarization transfer coefficient ratio. Final analysis will help constrain FSI models.

  3. Direct measurement of {sup 4}He({sup 12}C, {sup 16}O){gamma} reaction near stellar energy

    SciTech Connect

    Fujita, K.; Sagara, K.; Teranishi, T.; Goto, T.; Iwabuchi, R.; Matsuda, S.; Oba, N.; Taniguchi, M.; Yamaguchi, H.

    2010-08-12

    A cross section measurement with a direct {sup 16}O detection method for the reaction energy from E{sub cm} = 2.4 down to 0.7 MeV is planned at Kyushu University Tandem Laboratory (KUTL). To perform the experiment successfully and to get the quantitative information of the cross section within the 10% error, we have newly developed several instruments in 2009, such as a blow-in type windowless gas target and movable slit system placed in the recoil mass separator. By using the windowless blow-in gas target, a pressure of 24 Torr was achieved. The effective thickness along the beam axis was measured by p+{sup 4}He scattering. Thanks to the movable slits installed in a recoil mass separator and the trajectory analysis, we found effective reduction of background conditions from the {sup 12}C beam.

  4. The 4He1H ratios in the chemical compositions of solar flare particles and the primordial solar nebula

    NASA Technical Reports Server (NTRS)

    Sakurai, K.

    1985-01-01

    The chemical abundances of solar flare particles are similar to those of galactic cosmic rays at their sources. In order to infer the 4He/1H ratio in the solar atmosphere, this ratio as observed in the interstellar gases was considered in addition to those which were contained of galactic cosmic rays and the stars classified as the early types. Since it is clear that the most of these ratios ever deduced for both of the Sun and solar flare particles are lower than those for the interstellar gases, this ratio suggests that hydrogens are relatively overabundant in the chemical abundances of the Sun and the primordial solar nebula as compared to those of the interstellar gases currently observed.

  5. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    SciTech Connect

    Gong, W.; Peng, X. Li, W.; Guo, H.

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  6. Frequency stabilization of a 1083 nm fiber laser to 4He transition lines with optical heterodyne saturation spectroscopies

    NASA Astrophysics Data System (ADS)

    Gong, W.; Peng, X.; Li, W.; Guo, H.

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  7. Acceptance Studies for 4He(e,e'p)X Reaction up to High Missing Energies and Momenta

    NASA Astrophysics Data System (ADS)

    Finton, Drew; Benmokhtar, Fatiha

    2014-03-01

    Data collected from the Helium-4 target in Hall A at Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, Virginia, was analyzed using the object-oriented data analysis software ROOT and used to create Missing Energy Spectra for Missing Momenta ranging from 150 MeV/c to 755 MeV/c for 4He(e,e'p)X reaction channels. Jefferson Lab is a continuous electron beam accelerator facility, and Hall A contains two high resolution spectrometers as well as the cryogenic Helium-4 target. Acceptance cuts were made to six measured variables to remove background noise, and then applied to produce a Missing Energy Spectrum showing two- and three-body break up channels as well as pion electro-production energy threshold. The analysis of these missing energy spectra will be used to understand the contributions of one-, two-, and three-body interactions.

  8. A Survey of Beam Asymmetries in Semi-exclusive Electron Scattering on {sup 4}He and {sup 12}C

    SciTech Connect

    Dan Protopopescu

    2002-12-01

    A study of the polarized electron beam asymmetry in semi-exclusive (e,e{prime}p) reactions on {sup 4}He and {sup 12}C over a large kinematic range has been performed. The beam asymmetry A{prime}{sub LT} is related to the imaginary part of the longitudinal-transverse interference and therefore it vanishes in reactions proceeding through a channel with a single dominant mechanism. In quasifree nucleon knockout, the helicity asymmetry provides an unambiguous signature for the interference between direct knockout and rescattering amplitudes. The data were taken in April-May 1999 using polarized beams of energies between 2.2 and 4.4 GeV, with the CEBAF Large Acceptance Spectrometer (CLAS) detector located in Hall B at the Jefferson Laboratory, VA. The measured asymmetries compare well with the theoretical predictions.

  9. Time-of-Flight Experiments of Vortex Rings Propagating from Turbulent Region of Superfluid 4He at High Temperature

    NASA Astrophysics Data System (ADS)

    Nago, Y.; Ogawa, T.; Obara, K.; Yano, H.; Ishikawa, O.; Hata, T.

    2011-02-01

    We report the time-of-flight of quantized vortex rings generated by a vibrating wire in superfluid 4He which contains normal fluid component. A cover box of vibrating wires and slow cooling of superfluid reduce the number of vortices attached to wire surfaces, enabling us to study vortex rings propagating from a turbulent region. Using two vibrating wires as a generator and a detector of vortices, the time-of-flight of vortices propagating a distance of 0.88 mm was measured at 1.25 K. We find that the time-of-flights distribute from 0.06 s to 27.4 s, much larger than the lifetimes of circular vortex rings limited in the size of a generator amplitude. These results imply that large vortex rings with non-circular shape or vortex tangles are created by the generator, propagating slowly and colliding with the detector before complete disappearance.

  10. Parity-Violating Electron Scattering from {sup 4}He and the Strange Electric Form Factor of the Nucleon

    SciTech Connect

    Aniol, Konrad; Armstrong, David; Averett, Todd; Benaoum, Hachemi; Bertin, Pierre; Burtin, Etienne; Cahoon, Jason; Cates, Gordon; Chang, C; Chao, Yu-Chiu; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Craver, Brandon; Cusanno, Francesco; Decowski, Piotr; Deepa, Deepa; Ferdi, Catherine; Feuerbach, Robert; Finn, John; Frullani, Salvatore; Fuoti, Kirsten; Garibaldi, Franco; Gilman, Ronald; Glamazdin, Oleksandr; Gorbenko, V; Grames, Joseph; Hansknecht, John; Higinbotham, Douglas; Holmes, Richard; Holmstrom, Timothy; Humensky, Thomas; Ibrahim, Hassan; Jager, Cornelis De; Jiang, Xiaodong; Kaufman, Lisa; Kelleher, Aidan; Kolarkar, Ameya; Kowalski, Stanley; Kumar, Krishna; Lambert, Daniel; Laviolette, Peter; LeRose, John; Lhuillier, David; Liyanage, Nilanga; Margaziotis, Demetrius; Mazouz, Malek; McCormick, Kathy; Meekins, David; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Monaghan, Peter; Camacho, Carlos Munoz; Nanda, Sirish; Nelyubin, Vladimir; Neyret, Damien; Paschke, Kent; Poelker, Benard; Pomatsalyuk, Roman; Qiang, Yi; Reitz, Bodo; Roche, Julie; Saha, Arunava; Singh, Jaideep; Snyder, Ryan; Souder, Paul; Subedi, Ramesh; Suleiman, Riad; Sulkosky, Vincent; Tobias, William; Urciuoli, Guido; Vacheret, Antonin; Voutier, Eric; Wang, Kebin; Wilson, R; Wojtsekhowski, Bogdan; Zheng, Xiaochao

    2005-06-01

    We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 4}He at an average scattering angle {theta}{sub lab} = 5.7 degrees and a four-momentum transfer Q{sup 2} = 0.091 GeV{sup 2}. From these data, for the first time, the strange electric form factor of the nucleon G{sub E}{sup s} can be isolated. The measured asymmetry of A{sub PV} = 6.72 {+-} 0.84 (stat) {+-} 0.21 (syst) parts per million yields a value of G{sub E}{sup s} = -0.038 {+-} 0.042 (stat) {+-} 0.010 (syst), consistent with zero.

  11. Frequency-dependent study of solid 4He contained in a rigid double-torus torsional oscillator

    NASA Astrophysics Data System (ADS)

    Choi, Jaewon; Shin, Jaeho; Kim, Eunseong

    2015-10-01

    The rigid double-torus torsional oscillator (TO) is constructed to reduce any elastic effects inherent to complicated TO structures, allowing explicit probing for a genuine supersolid signature. We investigated the frequency- and temperature-dependent response of the rigid double-torus TO containing solid 4He with 0.6-ppb 3He and 300-ppb 3He . We did not find evidence to support the frequency-independent contribution proposed to be a property of supersolid helium. The frequency-dependent contribution which comes from the simple elastic effect of solid helium coupled to the TO is essentially responsible for the entire response. The magnitude of the period drop is linearly proportional to f2, indicating that the responses observed in this TO are mostly caused by the overshoot of "soft" solid helium against the wall of the torus. Dissipation of the rigid TO is vastly suppressed compared to that of nonrigid TOs.

  12. Elucidating effects of atmospheric deposition and peat decomposition processes on mercury accumulation rates in a northern Minnesota peatland over last 10,000 cal years

    NASA Astrophysics Data System (ADS)

    Nater, E. A.; Furman, O.; Toner, B. M.; Sebestyen, S. D.; Tfaily, M. M.; Chanton, J.; Fissore, C.; McFarlane, K. J.; Hanson, P. J.; Iversen, C. M.; Kolka, R. K.

    2014-12-01

    Climate change has the potential to affect mercury (Hg), sulfur (S) and carbon (C) stores and cycling in northern peatland ecosystems (NPEs). SPRUCE (Spruce and Peatland Responses Under Climate and Environmental change) is an interdisciplinary study of the effects of elevated temperature and CO2 enrichment on NPEs. Peat cores (0-3.0 m) were collected from 16 large plots located on the S1 peatland (an ombrotrophic bog treed with Picea mariana and Larix laricina) in August, 2012 for baseline characterization before the experiment begins. Peat samples were analyzed at depth increments for total Hg, bulk density, humification indices, and elemental composition. Net Hg accumulation rates over the last 10,000 years were derived from Hg concentrations and peat accumulation rates based on peat depth chronology established using 14C and 13C dating of peat cores. Historic Hg deposition rates are being modeled from pre-industrial deposition rates in S1 scaled by regional lake sediment records. Effects of peatland processes and factors (hydrology, decomposition, redox chemistry, vegetative changes, microtopography) on the biogeochemistry of Hg, S, and other elements are being assessed by comparing observed elemental depth profiles with accumulation profiles predicted solely from atmospheric deposition. We are using principal component analyses and cluster analyses to elucidate relationships between humification indices, peat physical properties, and inorganic and organic geochemistry data to interpret the main processes controlling net Hg accumulation and elemental concentrations in surface and subsurface peat layers. These findings are critical to predicting how climate change will affect future accumulation of Hg as well as existing Hg stores in NPE, and for providing reference baselines for SPRUCE future investigations.

  13. Isotopic separation of sup 3 He/ sup 4 He from solar wind gases evolved from the lunar regolith

    SciTech Connect

    Wilkes, W.R. ); Wittenberg, L.J. )

    1992-01-01

    The potential benefits of {sup 3}He when utilized in a nuclear fusion reactor to provide clean, safe electricity in the 21st century for the world's inhabitants has been documented. Unfortunately, He is scarce on earth. Large quantities of {sup 3}He, perhaps a million tonnes, are embedded in the lunar regolith, presumably implanted by the solar wind together with other elements, notably {sup 4}He, H, C and N. Several studies have suggested processing the lunar regolith and recovering these valuable solar wind gases. Once released, these gases can be separated for use. The separation of helium isotopes is described in this paper. {sup 3}He constitutes only 400 at{center dot}ppm of lunar He, too dilute to separate economically by distillation alone. A superfluid'' separator is being considered to preconcentrate the {sup 3}He. The superfluid separator consists of a porous filter in a tube maintained at a temperature of 2.17 K or less. Although the {sup 4}He, which is superfluid below 2.17 K, flows readily through the filter, the He is blocked by the filter, and becomes enriched at the feed end. He can be enriched to about 10% in such a system. The enriched product from the superfluid separation serves as a feed to a distillation apparatus operating at a pressure of 9 kPa, with a boiler temperature of 2.4 K, and a condenser temperature of 1.6 K. Under constant flow conditions, a 99.9% enriched He product can be produced in this apparatus. The heat rejection load of the refrigeration equipment necessary to cool the separation operations would be conducted during the lunar nights.

  14. Isotopic separation of {sup 3}He/{sup 4}He from solar wind gases evolved from the lunar regolith

    SciTech Connect

    Wilkes, W.R.; Wittenberg, L.J.

    1992-09-01

    The potential benefits of {sup 3}He when utilized in a nuclear fusion reactor to provide clean, safe electricity in the 21st century for the world`s inhabitants has been documented. Unfortunately, He is scarce on earth. Large quantities of {sup 3}He, perhaps a million tonnes, are embedded in the lunar regolith, presumably implanted by the solar wind together with other elements, notably {sup 4}He, H, C and N. Several studies have suggested processing the lunar regolith and recovering these valuable solar wind gases. Once released, these gases can be separated for use. The separation of helium isotopes is described in this paper. {sup 3}He constitutes only 400 at{center_dot}ppm of lunar He, too dilute to separate economically by distillation alone. A ``superfluid`` separator is being considered to preconcentrate the {sup 3}He. The superfluid separator consists of a porous filter in a tube maintained at a temperature of 2.17 K or less. Although the {sup 4}He, which is superfluid below 2.17 K, flows readily through the filter, the He is blocked by the filter, and becomes enriched at the feed end. He can be enriched to about 10% in such a system. The enriched product from the superfluid separation serves as a feed to a distillation apparatus operating at a pressure of 9 kPa, with a boiler temperature of 2.4 K, and a condenser temperature of 1.6 K. Under constant flow conditions, a 99.9% enriched He product can be produced in this apparatus. The heat rejection load of the refrigeration equipment necessary to cool the separation operations would be conducted during the lunar nights.

  15. Comparison of the effectiveness of exposure to low LET helium particles (4He) and gamma rays (137Cs) on the disruption of cognitive performance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rats were exposed to either Helium (4He) particles (1000 MeV/n; 0.1 – 10 cGy; head-only) or Cesium 137Cs gamma rays (50 – 400 cGy; whole body) and the effects of irradiation on cognitive performance evaluated. The results indicated that exposure to doses of 4He particles as low as 0.1 cGy disrupted...

  16. Correlation of gold in siliceous sinters with 3He 4He in hot spring waters of Yellowstone National Park

    USGS Publications Warehouse

    Fournier, R.O.; Kennedy, B.M.; Aoki, M.; Thompson, J.M.

    1994-01-01

    temperatures may contain waters with different [H2S] and [Au]. The [H2S] in a subsurface reservoir water is difficult to assess on the basis of analyses of hot spring waters because of uncertainties about steam loss during fluid ascent. However, the same processes that result in low [H2S] in reservoir waters also tend to result in decreases in the ratio of 3He 4He(R) dissolved in that water. Values of R relative to this ratio in air (Ra) attain values > 15 in YNP thermal waters. To date, all of the thermal waters at YNP that have R Ra values <9 have been found to deposit sinters with relatively low gold concentrations. These include all of the thermal waters that discharge from 180-215??C reservoirs at Upper, Midway, and Lower Geyser Basins within the western part of the Yellowstone caldera, and thermal waters at Norris Geyser Basin, outside the Yellowstone caldera, where some of the waters flow directly to the surface from a reservoir where the temperature is about 300??C. A high 3He 4He ratio in thermal water discharged at the surface does not guarantee high gold concentrations in the sinter deposited by this water. Boiling with loss of steam (the gas phase takes a separate route to the surface) during rapid upflow from the shallowest reservoir to the surface decreases the [H2S] and total He dissolved in the residual liquid without appreciably changing the 3He 4He ratio. This is because the isotopic composition of the He of the initial bulk fluid is unchanged and there is too little time for much radiogenic 4He to build back into the liquid during this rapid ascent from the near-surface reservoir. However, if boiling with phase separation and loss of steam occurs deep in the system, the 3He 4He ratio in the residual liquid, now depleted in H2S and total He, will be susceptible to dilution with radiogenic 4He that is acquired during the longer residence time underground. Some or all of the Au that comes out of solution when an initial gold bisulfide complex breaks

  17. Variations in the accumulation, localization and rate of metabolization of selenium in mature Zea mays plants supplied with selenite or selenate.

    PubMed

    Longchamp, Mélanie; Castrec-Rouelle, Maryse; Biron, Philippe; Bariac, Thierry

    2015-09-01

    Quantification of selenium bioavailability from foods is a key challenge following the discovery of the antioxidant role of this micronutrient in human health. This study presents the uptake, accumulation and rate of metabolization in mature Zea mays plants grown in hydroponic solution supplemented with selenate or selenite. Selenium content was lower in plants supplemented with selenate and accumulated mainly in the leaves compared with selenite-treated plants where the selenium was retained in the roots. Selenite-treated grains accumulated more selenium. Selenate was metabolized less than selenite in whole plants, but in grains selenium was present exclusively as organic selenium compounds. For humans, the bioavailability of organic selenium was evaluated at 90% compared with only 50% for inorganic forms. Our results show that the potential for selenium bioavailability is increased with selenite treatment. PMID:25842318

  18. Three hen strains fed photoisomerized trans,trans CLA-rich soy oil exhibit different yolk accumulation rates and source-specific isomer deposition.

    PubMed

    Shinn, Sara E; Gilley, Alex D; Proctor, Andrew; Anthony, Nicholas B

    2015-04-01

    Most CLA chicken feeding trials used cis,trans (c,t) and trans,cis (t,c) CLA isomers to produce CLA-rich eggs, while reports of trans,trans (t,t) CLA enrichment in egg yolks are limited. The CLA yolk fatty acid profile changes and the 10-12 days of feeding needed for maximum CLA are well documented, but there is no information describing CLA accumulation during initial feed administration. In addition, no information on CLA accumulation rates in different hen strains is available. The aim of this study was to determine a mathematical model that described yolk CLA accumulation and depletion in three hen strains by using t,t CLA-rich soybean oil produced by photoisomerization. Diets of 30-week Leghorns, broilers, and jungle fowl were supplemented with 15% CLA-rich soy oil for 16 days, and eggs were collected for 32 days. Yolk fatty acid profiles were measured by GC-FID. CLA accumulation and depletion was modeled by both quadratic and piecewise regression analysis. A strong quadratic model was proposed, but it was not as effective as piecewise regression in describing CLA accumulation and depletion. Broiler hen eggs contained the greatest concentration of CLA at 3.2 mol/100 g egg yolk, then jungle fowl at 2.9 mol CLA, and Leghorns at 2.3 mol CLA. The t,t CLA isomer levels remained at 55% of total yolk CLA during CLA feeding. However, t-10,c-12 (t,c) CLA concentration increased slightly during CLA accumulation and was significantly greater than c-9,t-11 CLA. Jungle fowl had the smallest increase in yolk saturated fat with CLA yolk accumulation. PMID:25771890

  19. OSL-based lateral progradation and aeolian sediment accumulation rates for the Apalachicola Barrier Island Complex, North Gulf of Mexico, Florida

    NASA Astrophysics Data System (ADS)

    Rink, W. J.; López, G. I.

    2010-11-01

    Vertical sediment cores in five separate beach ridge complexes along the north-east Gulf of Mexico Coast were recovered and dated using optically stimulated luminescence (OSL) dating of quartz: these are located on Cape San Blas (CSB), Little St. George Island (LSGI), Richardson's Hammock (RH), St. Joseph Peninsula (SJP) and Saint Vincent Island (SVI). All of these landforms are coastal barrier systems situated along a 100 km stretch of the Florida Panhandle, U.S.A. Two samples were collected for dating from each core. Ridge accumulation rates (RAR) associated with lateral progradation were calculated from the dated samples. We also determined average sediment accumulation rates (ASAR) for two intervals within each sediment core. All OSL ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable. Moreover, all dated ridges were found to be in correct temporal sequence based on their geomorphic positions. Rapidly accreted sequences were found to be backed by St. Joseph Bay in the western region of the study area. More slowly accreted sequences were associated with the more eastern stretches of the study area backed by St. Vincent Sound and Apalachicola Bay. Our ASAR results are in accord with an Australian study of modern dune accumulation. Perhaps our most important finding is that in the barrier island environments of this north-eastern Gulf Coast region, aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place. This confirms our similar earlier observation on SVI (López and Rink, 2008). We find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges. Lateral progradation rates of ridge sequences were highly variable within the study area, ranging from 92 to 848 m/100 years, but we did find agreement

  20. A comparison of conventional /sup 60/Co testing and low dose-accumulation-rate exposure of metal-gate CMOS IC'S

    SciTech Connect

    Roeske, S.B.; Edwards, W.H.; Gammill, P.E.; Puariea, J.W.; Zipay, J.W.

    1984-12-01

    Data are presented for the CD4000 family of Hi-Rel, rad-hard, metal-gate CMOS ICs which show a much greater tolerance to low dose-rate ionizing radiation than that observed with ''conventional rate'' (approximately 10/sup 6/ rad(Si)/hr) /sup 60/Co testing. Data obtained using conventional rate /sup 60/Co irradiations followed by either a 24-hour, high-temperature (100/sup 0/C) anneal or a 65-day, room temperature anneal are in good agreement with data obtained by exposing similar parts at a low dose-accumulation rate (daily 17second, 5000 rad(Si) exposures) for 200 consecutive days. Graphs of thresholds, output drive, and propagation delay for both low doseaccumulation rate and conventional rate exposures are included.

  1. Comparison of annual accumulation rates derived from in situ and ground penetrating radar methods across Alaskan glaciers

    NASA Astrophysics Data System (ADS)

    McGrath, D.; Gusmeroli, A.; Oneel, S.; Sass, L. C.; Arendt, A. A.; Wolken, G. J.; Kienholz, C.; McNeil, C.

    2013-12-01

    Constraining annual snowfall accumulation in mountain glacier environments is essential for determining the annual mass balance of individual glaciers and predicting seasonal meltwater runoff to river and marine ecosystems. However, large spatial and elevation gradients, coupled with sparse point measurements preclude accurate quantification of this variable using traditional methods. Here, we report on an extensive field campaign conducted in March-May 2013 on key benchmark glaciers in Alaska, including Taku Glacier near Juneau, Scott Glacier near Cordova, both Eklutna and Wolverine Glacier near Anchorage and Gulkana Glacier in the interior Alaska Range. Over 50 km of 500 MHz common-offset ground penetrating radar (GPR) surveys were collected on each glacier, with an emphasis on capturing spatial variability in the accumulation zone. Frequent in situ observations were collected for comparison with the GPR, including probe depths, snow pits and shallow firn cores (~8 m). We report on spatial and elevation gradients across this suite of glaciers and across numerous climatic zones and discuss differences between GPR and in situ derived annual accumulation estimates. This comparison is an essential first step in order to effectively evaluate regional atmospheric re-analysis products.

  2. Construction of a Newly Designed Small-Size Mass Spectrometer for Helium Isotope Analysis: Toward the Continuous Monitoring of 3He/4He Ratios in Natural Fluids

    PubMed Central

    Bajo, Ken-ichi; Sumino, Hirochika; Toyoda, Michisato; Okazaki, Ryuji; Osawa, Takahito; Ishihara, Morio; Katakuse, Itsuo; Notsu, Kenji; Igarashi, George; Nagao, Keisuke

    2012-01-01

    The construction of a small-size, magnetic sector, single focusing mass spectrometer (He-MS) for the continuous, on-site monitoring of He isotope ratios (3He/4He) is described. The instrument is capable of measuring 4He/20Ne ratios dissolved in several different types of natural fluids of geochemical interest, such as groundwater and gas from hot springs, volcanoes and gas well fields. The ion optics of He-MS was designed using an ion trajectory simulation program “TRIO,” which permits the simultaneous measurement of 3He and 4He with a double collector system under a mass resolution power (M/ΔM) of >700. The presently attained specifications of He-MS are; (1) a mass resolving power of ca. 430, sufficient to separate 3He+ from interfering ions, HD+ and H3+, (2) ultra-high vacuum conditions down to 3×10−8 Pa, and (3) a sufficiently high sensitivity to permit amounts of 3He to be detected at levels as small as 10−13 cm3 STP (3×106 atoms). Long term stability for 3He/4He analysis was examined by measuring the 3He/4He standard gas (HESJ) and atmospheric He, resulting in ∼3% reproducibility and ≤5% experimental error for various amounts of atmospheric He from 0.3 to 2.3×10−6 cm3 STP introduced into the instrument. A dynamic range of measurable 3He/4He ratios with He-MS is greater than 103 which was determined by measuring various types of natural fluid samples from continental gas (with a low 3He/4He ratio down to 2×10−8) to volcanic gas (with a high 3He/4He ratio up to 3×10−5). The accuracy and precision of 3He/4He and 4He/20Ne ratios were evaluated by comparing the values with those measured using well established noble gas mass spectrometers (modified VG5400/MS-III and -IV) in our laboratory, and were found to be in good agreement within analytical errors. Usefulness of the selective extraction of He from water/gas using a high permeability of He through a silica glass wall at high temperature (700°C) is demonstrated. PMID:24349910

  3. Construction of a newly designed small-size mass spectrometer for helium isotope analysis: toward the continuous monitoring of (3)he/(4)he ratios in natural fluids.

    PubMed

    Bajo, Ken-Ichi; Sumino, Hirochika; Toyoda, Michisato; Okazaki, Ryuji; Osawa, Takahito; Ishihara, Morio; Katakuse, Itsuo; Notsu, Kenji; Igarashi, George; Nagao, Keisuke

    2012-01-01

    The construction of a small-size, magnetic sector, single focusing mass spectrometer (He-MS) for the continuous, on-site monitoring of He isotope ratios ((3)He/(4)He) is described. The instrument is capable of measuring (4)He/(20)Ne ratios dissolved in several different types of natural fluids of geochemical interest, such as groundwater and gas from hot springs, volcanoes and gas well fields. The ion optics of He-MS was designed using an ion trajectory simulation program "TRIO," which permits the simultaneous measurement of (3)He and (4)He with a double collector system under a mass resolution power (M/ΔM) of >700. The presently attained specifications of He-MS are; (1) a mass resolving power of ca. 430, sufficient to separate (3)He(+) from interfering ions, HD(+) and H3 (+), (2) ultra-high vacuum conditions down to 3×10(-8) Pa, and (3) a sufficiently high sensitivity to permit amounts of (3)He to be detected at levels as small as 10(-13) cm(3) STP (3×10(6) atoms). Long term stability for (3)He/(4)He analysis was examined by measuring the (3)He/(4)He standard gas (HESJ) and atmospheric He, resulting in ∼3% reproducibility and ≤5% experimental error for various amounts of atmospheric He from 0.3 to 2.3×10(-6) cm(3) STP introduced into the instrument. A dynamic range of measurable (3)He/(4)He ratios with He-MS is greater than 10(3) which was determined by measuring various types of natural fluid samples from continental gas (with a low (3)He/(4)He ratio down to 2×10(-8)) to volcanic gas (with a high (3)He/(4)He ratio up to 3×10(-5)). The accuracy and precision of (3)He/(4)He and (4)He/(20)Ne ratios were evaluated by comparing the values with those measured using well established noble gas mass spectrometers (modified VG5400/MS-III and -IV) in our laboratory, and were found to be in good agreement within analytical errors. Usefulness of the selective extraction of He from water/gas using a high permeability of He through a silica glass wall at high

  4. Sediment accumulation rates and high-resolution stratigraphy of recent fluvial suspension deposits in various fluvial settings, Morava River catchment area, Czech Republic

    NASA Astrophysics Data System (ADS)

    Sedláček, Jan; Bábek, Ondřej; Kielar, Ondřej

    2016-02-01

    We present a comprehensive study concerning sedimentary processes in fluvial sediment traps within the Morava River catchment area (Czech Republic) involving three dammed reservoirs, four meanders and oxbow lakes, and several natural floodplain sites. The objective of the study was to determine sediment accumulation rates (SAR), estimate erosion rates, calculating these using a combination of the 137Cs method and historical data. Another purpose of this study was to provide insight into changing erosion and accumulation rates over the last century. Extensive water course modifications were carried out in the Morava River catchment area during the twentieth century, which likely affected sedimentation rates along the river course. Other multiproxy stratigraphic methods (X-ray densitometry, magnetic susceptibility, and visible-light reflectance spectrometry) were applied to obtain additional information about sediment infill. Sediment stratigraphy revealed distinct distal-to-proximal patterns, especially in reservoirs. Granulometrically, silts and sandy silts prevailed in sediments. Oxbow lakes and meanders contained larger amounts of clay and organic matter, which is the main difference between them and reservoirs. Pronounced 137Cs peaks were recorded in all studied cores (maximum 377 Bq·kg- 1), thus indicating Chernobyl fallout from 1986 or older events. Calculated sediment accumulation rates were lowest in distal parts of reservoirs (0.13-0.58 cm/y) and floodplains (0.45-0.88 cm/y), moderately high rates were found in proximal parts of reservoirs and oxbow lakes (2.27-4.4 cm/y), and the highest rates in some oxbow lakes located near the river (6-8 cm/y). The frequency of the inundation still can be high in some natural areas as in the Litovelské Pomoraví protected area, whereas the decreasing frequency of the inundation in other modified parts can contribute to a lower sedimentation rate. The local effects such as difference between SARs in oxbow lakes and

  5. Increasing sediment accumulation rates in La Fonera (Palamós) submarine canyon axis and their relationship with bottom trawling activities

    NASA Astrophysics Data System (ADS)

    Puig, P.; Martín, J.; Masqué, P.; Palanques, A.

    2015-10-01

    Previous studies conducted in La Fonera (Palamós) submarine canyon (NW Mediterranean) found that trawling activities along the canyon flanks cause resuspension and transport of sediments toward the canyon axis. 210Pb chronology supported by 137Cs dating applied to a sediment core collected at 1750 m in 2002 suggested a doubling of the sediment accumulation rate since the 1970s, coincident with the rapid industrialization of the local trawling fleet. The same canyon area has been revisited a decade later, and new data are consistent with a sedimentary regime shift during the 1970s and also suggest that the accumulation rate during the last decade could be greater than expected, approaching ~2.4 cm yr-1 (compared to ~0.25 cm yr-1 pre-1970s). These results support the hypothesis that commercial bottom trawling can substantially affect sediment dynamics and budgets on continental margins, eventually initiating the formation of anthropogenic depocenters in submarine canyon environments.

  6. Missing-Mass Spectroscopy of the 4-Neutron System by Exothermic Double-Charge Exchange Reaction 4He(8He,8Be)4n

    NASA Astrophysics Data System (ADS)

    Kisamori, Keiichi; Shimoura, Susumu; Miya, Hiroyuki; Assie, Marlene; Baba, Hidetada; Baba, Tatsuo; Beaumel, Didier; Dozono, Masanori; Fujii, Toshihiko; Fukuda, Naoki; Go, Shintaro; Hammache, Fariouz; Ideguchi, Eiji; Inabe, Naohiro; Itoh, Masatoshi; Kameda, Daisuke; Kawase, Shoichiro; Kawabata, Takahiro; Kobayashi, Motoki; Kondo, Yosuke; Kubo, Toshiyuki; Kubota, Yuki; Kurata-Nishimura, Mizuki; Lee, CheongSoo; Maeda, Yukie; Matsubara, Hiroaki; Michimasa, Shin'ichiro; Miki, Kenjiro; Nishi, Takahiro; Noji, Shumpei; Ota, Shinsuke; Sakaguchi, Satoshi; Sakai, Hideyuki; Sasamoto, Yoshiko; Sasano, Masaki; Sato, Hiromi; Shimizu, Yohei; Stolz, Andreas; Suzuki, Hiroshi; Takaki, Motonobu; Takeda, Hiroyuki; Takeuchi, Satoshi; Tamii, Atsushi; Tang, Leung; Tokieda, Hiroshi; Tsumura, Miho; Uesaka, Tomohiro; Yako, Kentaro; Yanagisawa, Yoshiyuki; Yokoyama, Rin

    A possible existence of the tetra-neutron system as a resonance state is still an open and fascinating question, while theoretical papers using ab-initio calculation suggests that the bound tetra-neutron does not exist. We have performed a missing-mass spectroscopy of the 4n system via the exothermic double-charge exchange reaction 4He(8He,8Be)4n. The experiment was carried out at the RIBF at RIKEN using the SHARAQ spectrometer. Since the secondary beam, 8He at 190 A MeV, has a large internal energy, it is possible to produce the 4n system with small momentum transfers of less than 20 MeV/c. In the present analysis, a new analytical framework to treat multi-particles under high beam rate condition (2 MHz) was developed for good statistics. At the SHARAQ spectrometer, 8Be can be identified by measuring the invariant mass of the coincident two alpha particles with a good signal-to-noise ratio. About several tens of candidate events are obtained above the 4n threshold.

  7. Production of high energy and low flux protons using 2D(3He,p)4He for space detector calibrations

    NASA Astrophysics Data System (ADS)

    Wang, Y. Q.; Burward-Hoy, J. M.; Tesmer, J. R.

    2014-08-01

    In this report, we want to demonstrate that besides the conventional use for elemental analysis and depth profiling by ion beam analysis (IBA), particles generated through ion-solid interactions in IBA may find other novel and important applications. Specifically, we use Rutherford backscattered and nuclear reaction produced high energy proton particles to calibrate an energetic particle subsystem (called ZEP) of the Space and Atmospheric Burst Reporting System (SABRS) at Los Alamos National Laboratory (LANL). To simulate low radiation flux in the space, we have devised an experiment that uses an ultrathin (∼51.8 nm) self-support gold foil to scatter a proton beam from a 3 MV Tandem accelerator into the ZEP subsystem. Direct backscattering from the thin gold foil produces proton particles with tunable energies of 0.2-6.0 MeV and desired counting rates of <10 kHz. To extend the proton particle energy beyond the Tandem's limit of 6 MeV, a high Q-value nuclear reaction, 2D + 3He → p + 4He + 18.352 MeV, was used. This reaction allows us to obtain as high as 25.6 MeV proton particles on our 3 MV tandem accelerator, more than 4 times as high as the accelerator's maximum proton beam energy, and has greatly extended our proton energy range for this calibration activity. Preliminary ZEP subsystem calibration results are presented.

  8. How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate.

    PubMed

    Yang, HongKun; Meng, YaLi; Chen, BingLin; Zhang, XingYue; Wang, YouHua; Zhao, WenQing; Zhou, ZhiGuo

    2016-01-01

    Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen. PMID:27532007

  9. How Integrated Management Strategies Promote Protein Quality of Cotton Embryos: High Levels of Soil Available N, N Assimilation and Protein Accumulation Rate

    PubMed Central

    Yang, HongKun; Meng, YaLi; Chen, BingLin; Zhang, XingYue; Wang, YouHua; Zhao, WenQing; Zhou, ZhiGuo

    2016-01-01

    Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen. PMID:27532007

  10. In situ cosmogenic H-3, C-14, and Be-10 for determining the net accumulation and ablation rates of ice sheets

    NASA Technical Reports Server (NTRS)

    Lal, D.; Nishiizumi, K.; Arnold, J. R.

    1987-01-01

    The usefulness of the in situ cosmogenic H-3, C-14, and Be-10 produced by spallation of oxygen nuclei in ice, as tracers to determine net accumulation/ablation rates of ice sheets is explored. The application of the in situ H-3 and Be-10 is severely constrained because at deposition, ice contains appreciable amounts of these isotopes from the atmosphere. The case is much more favorable for C-14, which is not carried with wet precipitations; atmospheric C-14 gets mechanically trapped in the ice during deposition. It is pointed out that cosmogenic C-14 would probably exist as (C-14)O in ice. This seems to be supported by the published results of Fireman and Norris (1981). Considering their inherent amounts in the ice and the expected in situ production rates, conditions under which these isotopes can be used to study net accumulation and ablation rates are discussed. Available data on C-14 and Be-10 on polar ice from accumulation and ablation zones is also discussed. It is concluded that H-3 and C-14 should find wide applications in studying ice dynamics and Be-10 in very special circumstances.

  11. The (4)He(gamma,dd) reaction at E(gamma) = 150--250 MeV

    NASA Astrophysics Data System (ADS)

    Rice, Bryan Joseph

    1998-09-01

    We have performed a measurement of the cross section for the 4He(/gamma,d)2H reaction with Eγ=150[-]250 MeV at the Saskatchewan Accelerator Laboratory (SAL). The experiment was performed using bremsstrahlung γ rays produced by a 273 MeV electron beam. The target was liquid helium contained in a simple cryostat. Two detector arms consisting of plastic scintillator telescopes were utilized to detect both reaction particles in coincidence. We obtained relative and absolute cross sections at six angles in two energy bins (150-190 and 190-250 MeV). The angular distribution of the cross section shows peaking behavior at 90o in the center-of-mass frame. A Legendre polynomial fit to the data shows this distribution can be described by a sin2/theta angular distribution. This distribution suggests the presence of electric dipole or E1 radiation, but isospin selection rules and identical bosons in the exit channel forbid the dominant /Delta S=0 E1 transition. Performing a transition-matrix element (TME) analysis using only strictly allowed transitions, we found that the observed angular distribution could be described by the constructive interference of just two TME's: electric quadrupole (E2) s- and d-wave capture to the D-state of 4He. We performed a direct-capture calculation in order to determine if the D-state could contribute to such a high degree to the cross section. Our calculations, which used an optical model potential from elastic scattering data at lower energies, yielded the result that 90% of the cross section arises from capture to the D-state. The calculation, however, places all capture strength to the D-state into g-wave capture and, as a result, fails to reproduce the observed sin2/theta angular distribution. The lack of existing theoretical work for this system at these energies conspires to keep the mechanism for this angular distribution unclear, but we hope this result will motivate four-body theorists to extend their calculations to this energy

  12. Shallow Sediment Trace Metal Concentrations and Short-Term Accumulation Rates in the Neponset River Estuary, Massachusetts, USA

    NASA Astrophysics Data System (ADS)

    Spencer, J. R.; Zhu, J.; Olsen, C. R.

    2010-12-01

    The Neponset River estuary is a small estuary that drains into the Boston Harbor on the east coast of the United States. It is also a highly urbanized estuary and has a long history of urban development over 450 years. In July 2006, six sediment cores were collected in the Neponset River estuary to examine particle dynamics and sediment accumulation via radionuclide (Beryllium-7) dating, and to determine sediment metal concentrations (As, Cu, Pb, and Zn) via ED-XRF measurements. Measured sediment Be-7 profiles indicate various sedimentation environments, where sediment accumulation, resuspension or redeposition is likely to occur. High metal concentrations were often corresponding to high Be-7 inventories in sediment cores. Possible sources of trace metal contaminants in the water column include: storm water run-off, Combined Sewer Overflows (CSOs), a well-documented industrial pollution event that occurred upstream in the early to mid twentieth century, and the resuspension of sediment. Existing and future data will provide baseline information for quantifying the effects of the proposed and pending environmental restoration project, which includes the removal of the Baker Dam. The combined pre- and post-Dam removal data may then be used in cost-benefit analyses for other similar estuarine restoration projects.

  13. Fragmentation of {sup 7}Li relativistic nuclei on a proton into the {sup 3}H + {sup 4}He channel

    SciTech Connect

    Peresadko, N. G.; Alexandrov, Yu. A. Gerasimov, S. G.; Dronov, V. A.; Larionova, V. G.; Pisetskaya, A. V.; Tamm, E. I.; Fetisov, V. N.; Kharlamov, S. P.; Shesterkina, L. N.

    2010-11-15

    In a track nuclear photoemulsion exposed to a beam of {sup 7}Li nuclei accelerated to a momentum of 3 GeV/c per nucleon at the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna), 13 events in which {sup 7}Li nuclei interacting with protons break up into {sup 3}H and {sup 4}He fragments were detected among 3730 inelastic-interaction events. For this fragmentation channel, the cross section was found to be 8 {+-} 2 mb. The average value of the fragment total transverse momentum was 214 {+-} 5 MeV/c. This value exceeds markedly the average value of the transverse-momentum transfer in the coherent dissociation of {sup 7}Li nuclei on track-emulsion nuclei (166{+-}5MeV/c). The recoil-proton transverse momentum was on average 98% of the total proton momentum. The longitudinal-momentum distribution of protons was characterized by a variance of 16 MeV/c and a mean value of 37 {+-} 2MeV/c.

  14. Electron scattering from 4He and Ne clusters: determination of the cluster density from the electronic surface barrier potential

    NASA Astrophysics Data System (ADS)

    Martini, K.; Toennies, J. P.; Winkler, C.

    1991-03-01

    A monoenergetic beam of electrons is scattered from a beam of 4He clusters. The angular distribution of the scattered electronically excited atoms and clusters is measured by an open Venetian-blind multiplier, which is rotatable in the plane of both beams. The threshold electron energy for excitation of the clusters shows a shift to higher energies with respect to the atom component by between 0.6 and 1.1 eV depending on the cluster source temperature T0 ( P0 = 20 bar in all experiments). The observed potential shift Eb is attributed to the surface barrier for penetration of the electrons into the cluster. From the known dependence of Eb on density the core densities of the helium clusters is estimated to vary between n = 1.2 × 10 22 cm -3 and n = 2.2 × 10 22 cm -3 for T0 = 14.9 and 11 K, respectively. The latter values agree with those for bulk liquid helium. For Ne clusters, Eb = 0.7 ± 0.3 eV independent of the source conditions.

  15. Simultaneous measurements of the torsional oscillator and shear modulus of solid 4He diluted with various 3He concentration

    NASA Astrophysics Data System (ADS)

    Shin, Jaeho; Choi, Wonsuk; Choi, Jaewon; Jang, Seong; Shirahama, Keiya; Kim, Eunseong

    2013-03-01

    In 2004, Kim and Chan observed the non-classical rotational inertia (NCRI) of solid helium-4 by using a torsional oscillator (TO). Below 200mK, the resonance period of solid helium dropped, which was originally interpreted as the mass decoupling of the fraction of solid helium. Recently, anomalous increase in the shear modulus of solid helium was found and showed striking similarity in temperature, frequency, 3He concentration, and drive dependence to those of the NCRI. To understand the connection between the NCRI and the shear modulus anomaly, we simultaneously measure the change in the resonance frequency and the stiffness of solid helium below 200mK. The torsion cell contains a pair of the concentric piezoelectric transducers (PZT) which defines an annular channel for the simultaneous measurements. We will report the interference between the motion of the TO at resonance and AC motion of the PZT in solid 4He with different 3He concentration. We gratefully acknowledge the financial support by the National Research Foundation of Korea through the Creative Research Initiatives.

  16. Direct measurement of {sup 4}He({sup 12}C, {sup 16}O)gamma reaction at KUTL

    SciTech Connect

    Fujita, K.; Sagara, K.; Teranishi, T.; Goto, T.; Iwabuchi, R.; Matsuda, S.; Nakano, K.; Oba, N.; Taniguchi, M.; Yamaguchi, H.

    2010-06-01

    A {sup 12}C+{sup 4}He->{sup 16}O+gamma is regarded as the very important reaction to know the evolution of heavy stars. The cross section is, however, still unknown in spite of more than 40 years experiment in the world because of an existence of a resonance state of {sup 16}O at sub-threshold region. A cross section measurement with the direct detection of the produced {sup 16}O from E{sub cm} = 2.4 downto 0.7 MeV have been planned at Kyushu University Tandem Laboratory(KUTL). Detection of the {sup 16}O is the most possible method at low energy, since a detection efficiency of the {sup 16}O is very high.The new windowless blow-in gas target was developed to achieve the pressure of 24 Torr. Many movable slit were installed in a recoil mass separator, so that the backgrounds generated by the {sup 12}C beam was eliminated effectively. The results of recent experiments at E{sub cm} = 2.4 and 1.5 MeV are reported.

  17. A "high 4He/3He" mantle material detected under the East Pacific Rise (15°4'N)

    NASA Astrophysics Data System (ADS)

    Mougel, Berengere; Moreira, Manuel; Agranier, Arnaud

    2015-03-01

    We investigate in details helium isotope data reported in Mougel et al. (2014) for 14 basaltic samples collected on the East Pacific Rise by submersible (15°4'N) where the ridge interacts with the Mathematician seamounts. Samples locations are separated by only few hundred meters across a 15 km along-axis profile. The data reveal a strong geochemical variability that has never been observed at such high spatial resolution for helium isotope compositions. Moreover, they reveal an unusually high 4He/3He mantle component also characterized by unradiogenic lead, atypical in oceanic basalts. He-Pb systematics suggests a mixture between a nonradiogenic lead and radiogenic helium pyroxenitic component, recycled from the deep continental lithosphere and the ambient peridotitic mantle. The He isotope difference between these two end-members can be interpreted as a time evolution of two distinct mantle sources after a slight (U + Th)/3He fractionation, likely due to some ancient degassing during the formation of deep continental pyroxenites.

  18. High momentum transfer R{sub T,L} response functions for {sup 3,4}He.

    SciTech Connect

    Filippone, Bradley; Jones Woodward, Cathleen; Potterveld, David; Day, Donal; Beck, Douglas; Boyd, G.; Dodge, Gail; Sick, Ingo; McCarthy, James; Mougey, Jean; Chen, Jian-Ping; Morgenstern, Joseph; Jourdan, Juerg; Giovanetti, Kevin; Kemper, Kirby; Dennis, Lawrence; Smith, Lee; Chinitz, Leigh; Minehart, Ralph; Milner, Richard; Sealock, Richard; Walker, Richard; McKeown, Robert; Thornton, Stephen; Koh, T.; Lorenzon, Wolfgang; Meziani, Zein-Eddine; Meziani, Zein-Eddine

    1992-07-01

    The tantalizing problem of the 'quenching' of the Coulomb sum rule observed in medium weight nuclei is investigated in light nuclei at high momentum transfer. Inclusive electron scattering cross sections for {sup 3,4}He have been measured in the quasielastic region at electron energies between 0.9 GeV and 4.3 GeV, and scattering angles of 15deg and 85deg. Longitudinal (R{sub L}) and transverse (R{sub T}) response functions have been extracted using a Rosenbluth separation at constant vertical strokeq vectorvertical stroke of 1.050 (GeV/c). The ratio of the longitudinal to the transverse reduced response functions in the negative y region reaches unity. The experimental Coulomb sum rule although with large uncertainty and conversly to the case of medium weight nuclei, saturates at high momentum to the He nucleus total charge namely Z=2. (orig.). INDEX TERMS: coulomb excitation; differential cross sections; electron spectra; electrons; experimental data; gev range 01-10;

  19. Burst mode with ps- and fs-pulses: Influence on the removal rate, surface quality, and heat accumulation

    NASA Astrophysics Data System (ADS)

    Neuenschwander, B.; Kramer, Th.; Lauer, B.; Jaeggi, B.

    2015-03-01

    The burst mode for ps and fs pulses for steel and copper is investigated. It is found that the reduction of the energy in a single pulse (in the burst) represents the main factor for the often reported gain in the removal rate using the burst mode e.g. for steel no investigated burst sequence lead to a higher removal rate compared to single pulses at higher repetition rate. But for copper a situation was found where the burst mode leads to a real increase of the removal rate in the range of 20%. Further the burst mode offers the possibility to generate slightly melted flat surfaces with good optical properties in the case of steel. Temperature simulations indicate that the surface state during the burst mode could be responsible for the melting effect or the formation of cavities in clusters which reduces the surface quality.

  20. Accumulated occupational class and self-rated health. Can information on previous experience of class further our understanding of the social gradient in health?

    PubMed

    Kjellsson, Sara

    2013-03-01

    Previous research has shown a social gradient in health with better health for people in more advantaged positions in society. This research has mainly been on the relationship between current position and health, or social position in childhood and health, but less is known about the potential accumulative impact of positions held in adulthood. In this paper I use the economic activity histories from the Swedish Level of Living survey to examine the relationship between accumulated occupational class positions and health. Step-wise linear probability models are used to investigate how to best capture the potential association between class experience and self-rated health (SRH), and whether the effect of current class is modified when measures of accumulated class are included. I then further test the potentially lasting association between previous exposure to the health risk of working class by analysing only individuals currently in higher or intermediate level service class; the classes under least exposure. I find a positive association between accumulated experiences of working class and less than good SRH. Furthermore, even for employees currently in non-manual positions the risk for less than good SRH increases with each added year of previous experience within working class. This suggests that the social gradient can be both accumulative and lasting, and that more information on the mechanisms of health disparities can be found by taking detailed information on peoples' pasts into account. Although gender differences in health are not a focus in this paper, results also indicate that the influence of class experiences on health might differ between men and women. PMID:23422057

  1. Bare-nucleus astrophysical factor of the {sup 3}He(d,p){sup 4}He reaction via the 'Trojan horse' method

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Tumino, A.; Cherubini, S.; Lamia, L.; Musumarra, A.; Pizzone, R.G.; Rinollo, A.; Romano, S.; Typel, S.; Rolfs, C.; Schuermann, D.; Strieder, F.

    2005-12-15

    The {sup 3}He(d,p){sup 4}He reaction has been studied from E{sub c.m.}=600 keV down to astrophysical energies by means of the 'Trojan horse' method using the {sup 6}Li({sup 3}He,p{alpha}){sup 4}He three-body reaction at E{sub lab}=5 and 6 MeV. Coincidence spectra were measured in kinematic conditions favoring the quasifree {sup 3}He+{sup 2}H process. The bare astrophysical factor S{sub b}(E) for the {sup 3}He(d,p){sup 4}He reaction was extracted from the three-body cross section in the modified plane-wave Born approximation. Comparison with the S{sub b} extrapolation from the free two-body data is presented. The independent estimate of the screening potential as obtained with the present work seems to confirm the theoretical adiabatic limit.

  2. Mass accumulation rate changes in Chinese loess during MIS 2, and asynchrony with records from Greenland ice cores and North Pacific Ocean sediments during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Kang, Shugang; Roberts, Helen M.; Wang, Xulong; An, Zhisheng; Wang, Min

    2015-12-01

    Sensitivity-corrected quartz optically stimulated luminescence (OSL) dating methods have been widely accepted as a promising tool for the construction of late Pleistocene chronology and mass or dust accumulation rates (MARs or DARs) on the Chinese Loess Plateau (CLP). Many quartz OSL ages covering marine isotope stage (MIS) 2 (equal to L1-1 in Chinese loess) have been determined for individual sites within the CLP in the past decade. However, there is still a lack of detailed MAR or DAR reconstruction during MIS 2 across the whole of the CLP. Here, we present detailed MARs determined for eight sites with closely-spaced quartz OSL ages covering ∼MIS 2, and relative MARs suggested by a probability density analysis of 159 quartz OSL ages ranging from ∼30 to 10 ka ago, from 15 sites on the CLP. The results show enhanced dust accumulation during the Last Glacial Maximum (LGM), with particularly rapid dust accumulation from ∼23 to 19 ka ago (the late LGM). In contrast, MARs determined for the last deglaciation (from ∼19 to 12 ka ago) are low. The MAR changes during MIS 2 in Chinese loess are mainly controlled by the East Asian winter monsoon (EAWM) intensity, which is forced by Northern Hemisphere ice volume. The MAR changes also indicate that dust accumulation during MIS 2 is generally continuous at millennial time scales on the CLP. Comparison of Asian-sourced aeolian dust MARs in Chinese loess with those preserved in Greenland ice cores and North Pacific Ocean sediments indicates that rapid dust accumulation occurred from ∼26 to 23 ka ago (the early LGM) in Greenland ice cores and North Pacific Ocean sediments, suggesting a several kilo-year difference in timing when compared with the rapid dust accumulation during the late LGM in Chinese loess. This asynchronous timing in enhanced dust accumulation is probably related to both changes in the EAWM intensity and changes in the mean position of zone axis of the Westerly jet, both of which are greatly influenced

  3. Geologic ages and accumulation rates of basalt-flow groups and sedimentary interbeds in selected wells at the Idaho National Engineering Laboratory, Idaho

    SciTech Connect

    Anderson, S.R.; Liszewski, M.J.; Cecil, L.D.

    1997-01-01

    Geologic ages and accumulation rates, estimated from regressions, were used to evaluate measured ages and interpreted stratigraphic and structural relations of basalt and sediment in the unsaturated zone and the Snake River Plain aquifer at the Idaho National Engineering Laboratory (INEL) in eastern Idaho. Geologic ages and accumulation rates were estimated from standard linear regressions of 21 mean potassium-argon (K-Ar) ages, selected mean paleomagnetic ages, and cumulative depths of a composite stratigraphic section composed of complete intervals of basalt and sediment that were deposited in areas of past maximum subsidence. Accumulation rates also were estimated from regressions of stratigraphic intervals in three wells in and adjacent to an area of interpreted uplift at and near the Idaho Chemical Processing Plant (ICPP) and the Test Reactor Area (TRA) to allow a comparison of rates in areas of past uplift and subsidence. Estimated geologic ages range from about 200 thousand to 1.8 million years before present and are reasonable approximations for the interval of basalt and sediment above the effective base of the aquifer, based on reported uncertainties of corresponding measured ages. Estimated ages between 200 and 800 thousand years are within the range of reported uncertainties for all 15 K-Ar ages used in regressions and two out of three -argon ({sup 40}Ar/{sup 39}Ar) ages of duplicate argon samples. Two sets of estimated ages between 800 thousand and 1.8 million years are within the range of reported uncertainties for all seven K-Ar ages used in regressions, which include one shared age of about 800 thousand years. Two sets of ages were estimated for this interval because K-Ar ages make up two populations that agree with previous and revised ages of three paleomagnetic subchrons. The youngest set of ages is consistent with a K-Ar age from the effective base of the aquifer that agrees with previous ages of the Olduvai Normal-Polarity Subchron.

  4. A method for investigation of the D(4He, γ)6Li reaction in the Ultralow energy region under a high background

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Dudkin, G. N.; Krylov, A. R.; Gazi, S.; Huran, J.; Nechaev, B. A.; Padalko, V. N.; Sadovsky, A. B.; Tuleushev, Yu. Zh.; Filipowicz, M.; Philippov, A. V.

    2016-07-01

    The cosmological lithium problem, that is, a noticeable discrepancy between the predicted and observed abundances of lithium, is in conflict with the Standard Big Bang Nucleosynthesis model. For example, the abundance of 7Li is 2-4 times smaller than predicted by the Standard Big Bang Nucleosynthesis. As to the abundance of 6Li, recent more accurate optical investigations have yielded only the upper limit on the 6Li/7Li ratio, which makes the problem of 6Li abundance and accordingly of disagreement with the Standard Big Bang Nucleosynthesis predictions less acute. However, experimental study of the D(4He, γ)6Li reaction cross section is still of current importance because there is a theoretical approach predicting its anomalously large value in the region of energies below the Standard Big Bang Nucleosynthesis energy. The work is dedicated to the measurement of the cross section for the D(4He, γ)6Li reaction proceeding in zirconium deuteride at the incident 4He+ion energy of 36 keV. The experiment is performed at a pulsed Hall plasma accelerator with an energy spread of 20% FWHM. A method for direct measurement of the background from the reaction chain D(4He, 4He)D→D(D, n)3He→(n, γ) and/or (n, n‧γ) ending with activation of the surrounding material by neutrons is proposed and implemented in the work. An upper limit on the D(4He, γ)6Li reaction cross section σ≤7·10-36 cm2 at the 90% confidence level is obtained.

  5. Anomalously High Isotope Ratio 3He/4He and Tritium in Deuterium-Loaded Metal: Evidence for Nuclear Reaction in Metal Hydrides at Low Temperature

    NASA Astrophysics Data System (ADS)

    Jiang, Song-Sheng; He, Ming; Wu, Shao-Yong; Qi, Bu-Jia

    2012-01-01

    Anomalous 3He/4He ratios in deuterium-loaded titanium samples are observed to be about 1-4 × 10-1, much greater than the values (<=10-4) in natural objects. Control experiments with the deuterium-unloaded titanium sample and original industrial deuterium gas are also carried out, but no anomalous 3He/4He values are observed. In addition, anomalous tritium in deuterium-loaded titanium samples are also observed. To explain the excess 3He and tritium in the deuterium-loaded titanium samples, it is required that the deuteron-induced nuclear reaction occurs in the samples at low temperature.

  6. Theory for supersolid 4He : Vacancy condensation facilitated by a low-energy bound state of a vacancy and an interstitial

    NASA Astrophysics Data System (ADS)

    Dai, Xi; Ma, Michael; Zhang, Fu-Chun

    2005-10-01

    Although both vacancies and interstitials have relatively high activation energies in the normal solid, we propose that a lower energy bound state of a vacancy and an interstitial may facilitate vacancy condensation to give supersolidity in 4He . We use a phenomenological two-band boson lattice model to demonstrate this new mechanism and discuss the possible relevance to the recently observed superfluidlike, nonclassical rotational inertial experiments of Kim and Chan in solid 4He . Some of our results may also be applicable to trapped bosons in optical lattices.

  7. Analysis of ultratrace lithium and boron by neutron activation and mass-spectrometric measurement of 3He and 4He.

    PubMed

    Clarke, W B; Koekebakker, M; Barr, R D; Downing, R G; Fleming, R F

    1987-01-01

    A new technique for analysis of lithium and boron at ultratrace concentrations (less than 10(-8)g g-1) is described. The method consists of mass-spectrometric assay of 3He from decay of tritium produced by thermal-neutron reaction on 6Li, and 4He produced by thermal-neutron reaction on 10B. Two neutron-irradiation facilities were used: the McMaster reactor, which is 235U-enriched and light-water moderated; and a graphite-moderated thermal column attached to the 235U-enriched, heavy-water-moderated core at the National Bureau of Standards (NBS) reactor. In the McMaster irradiations, fast neutrons (greater than 0.2 MeV) induce the reactions 14N(n, 3H)12C, 12C(n, alpha)9Be, 16O(n, alpha)13C, and 14N(n, alpha)11B. These reactions become serious sources of error in samples such as human blood which have very low concentrations of lithium and boron, and high concentrations of nitrogen, carbon and oxygen. In the NBS thermal column, fast-neutron reactions are virtually absent, and only corrections for thermal-neutron capture by deuterium, and thermal-neutron (n, alpha) reactions on oxygen, sulfur, chlorine, potassium, and calcium need to be taken into account. Results are presented for various actual samples including human blood and its components, and some standard biological reference materials, to provide a realistic base for other workers to judge the reliability of the method. PMID:2822629

  8. Human epididymis protein 4 (HE4) plays a key role in ovarian cancer cell adhesion and motility

    SciTech Connect

    Lu, Renquan; Sun, Xinghui; Xiao, Ran; Zhou, Lei; Gao, Xiang; Guo, Lin

    2012-03-09

    Highlights: Black-Right-Pointing-Pointer We generated stable transduced HE4 overexpression and knockdown cells. Black-Right-Pointing-Pointer HE4 was associated with EOC cell adhesion and motility. Black-Right-Pointing-Pointer HE4 might have some effects on activation of EGFR-MAPK signaling pathway. Black-Right-Pointing-Pointer HE4 play an important role in EOC tumorigenicity. -- Abstract: Human epididymis protein 4 (HE4) is a novel and specific biomarker for epithelial ovarian cancer (EOC). We previously demonstrated that serum HE4 levels were significantly elevated in the majority of EOC patients but not in subjects with benign disease or healthy controls. However, the precise mechanism of HE4 protein function is unknown. In this study, we generated HE4-overexpressing SKOV3 cells and found that stably transduced cells promoted cell adhesion and migration. Knockdown of HE4 expression was achieved by stable transfection of SKOV3 cells with a construct encoding a short hairpin DNA directed against the HE4 gene. Correspondingly, the proliferation and spreading ability of HE4-expressed cells were inhibited by HE4 suppression. Mechanistically, impaired EGFR and Erk1/2 phosphorylation were observed in cells with HE4 knockdown. The phosphorylation was restored when the knockdown cells were cultured in conditioned medium containing HE4. Moreover, in vivo tumorigenicity showed that HE4 suppression markedly inhibited the growth of tumors. This suggests that expression of HE4 is associated with cancer cell adhesion, migration and tumor growth, which can be related to its effects on the EGFR-MAPK signaling pathway. Our results provide evidence of the cellular and molecular mechanisms that may underlie the motility-promoting role of HE4 in EOC progression. The role of HE4 as a target for gene-based therapy might be considered in future studies.

  9. Experimental investigation of the dynamics of a vibrating grid in superfluid 4He over a range of temperatures and pressures.

    PubMed

    Charalambous, D; Skrbek, L; Hendry, P C; McClintock, P V E; Vinen, W F

    2006-09-01

    In an earlier paper [Nichol, Phys. Rev. E, 70, 056307 (2004)] some of the present authors presented the results of an experimental study of the dynamics of a stretched grid driven into vibration at or near its resonant frequency in isotopically pure superfluid 4He over a range of pressures at a very low temperature, where the density of normal fluid is negligible. In this paper we present the results of a similar study, based on a different grid, but now including the temperature range where the normal fluid density is no longer insignificant. The new grid is very similar to the old one except for a small difference in the character of its surface roughness. In many respects the results at low temperature are similar to those for the old grid. At low amplitudes the results are somewhat history dependent, but in essence there is no damping greater than that in vacuo. At a critical amplitude corresponding to a velocity of about 50 mms(-1) there is a sudden and large increase in damping, which can be attributed to the generation of new vortex lines. Strange shifts in the resonant frequency at intermediate amplitudes observed with the old grid are no longer seen, however they must therefore have been associated with the different surface roughness, or perhaps were due simply to some artifact of the old grid, the details of which we are currently unable to determine. With the new grid we have studied both the damping at low amplitudes due to excitations of the normal fluid, and the dependence of the supercritical damping on temperature. We present evidence that in helium at low amplitudes there may be some enhancement in the effective mass of the grid in addition to that associated with potential flow of the helium. In some circumstances small satellite resonances are seen near the main fundamental grid resonance, which are attributed to coupling to some other oscillatory system within the experimental cell. PMID:17025743

  10. The null hypothesis: steady rates of erosion, weathering and sediment accumulation during Late Cenozoic mountain uplift and glaciation

    NASA Astrophysics Data System (ADS)

    Willenbring, J. K.; Jerolmack, D. J.

    2015-12-01

    At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from this equilibrium condition arise from the transient response of landscape denudation to climatic and tectonic perturbations, and may be long lived. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. To support this contention, we synthesize existing data for weathering fluxes, global sedimentation rates, sediment yields and tectonic motions. The records show a remarkable constancy in the pace of Earth-surface evolution over the last 10 million years. These findings provide strong support for the null hypothesis; that global rates of landscape change have remained constant over the last ten million years, despite global climate change and massive mountain building events. Two important implications are: (1) global climate change may not change global denudation rates, because the nature and sign of landscape responses are varied; and (2) tectonic and climatic perturbations are accommodated in the long term by changes in landscape form. This work undermines the hypothesis that increased weathering due to late Cenozoic mountain building or climate change was the primary agent for a decrease in global temperatures.

  11. Effects of feeding and organism loading rate on PCB accumulation by Lumbriculus variegatus in sediment bioaccumulation testing

    EPA Science Inventory

    Sediment bioaccumulation test methods published by USEPA and ASTM in 2000 specify that the Lumbriculus variegatus, a freshwater oligochaete, should not be fed during the 28-day exposure and recommends an organism loading rate of total organic carbon in sediment to organism dry we...

  12. Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Ikeda-Fukazawa, T.; Suwa, M.; Schwander, J.; Kameda, T.; Lundin, J.; Hori, A.; Motoyama, H.; Döring, M.; Leuenberger, M.

    2015-12-01

    Gases in ice cores are invaluable archives of past environmental changes (e.g., the past atmosphere). However, gas fractionation processes after bubble closure in the firn are poorly understood, although increasing evidence indicates preferential leakages of smaller molecules (e.g., neon, oxygen, and argon) from the closed bubbles through the ice matrix. These fractionation processes are believed to be responsible for the observed millennial δO2/N2 variations in ice cores, linking ice core chronologies with orbital parameters. In this study, we investigated high-resolution δAr/N2 of the GISP2 (Greenland Ice Sheet Project 2), NGRIP (North Greenland Ice Core Project), and Dome Fuji ice cores for the past few thousand years. We find that δAr/N2 at multidecadal resolution on the "gas-age scale" in the GISP2 ice core has a significant negative correlation with accumulation rate and a positive correlation with air contents over the past 6000 years, indicating that changes in overloading pressure induced δAr/N2 fractionation in the firn. Furthermore, the GISP2 temperature and accumulation rate for the last 4000 years have nearly equal effects on δAr/N2 with sensitivities of 0.72 ± 0.1 ‰ °C-1 and -0.58 ± 0.09 ‰ (0.01 m ice year-1)-1, respectively. To understand the fractionation processes, we applied a permeation model for two different processes of bubble pressure build-up in the firn, "pressure sensitive process" (e.g., microbubbles: 0.3-3 % of air contents) with a greater sensitivity to overloading pressures and "normal bubble process". The model indicates that δAr/N2 in the bubbles under the pressure sensitive process are negatively correlated with the accumulation rate due to changes in overloading pressure. On the other hand, the normal bubbles experience only limited depletion (< 0.5 ‰) in the firn. Colder temperatures in the firn induce more depletion in δAr/N2 through thicker firn. The pressure sensitive bubbles are so depleted in δAr/N2 at the

  13. Contributions of excited {sup 6}Li and {sup 7}Li nuclei to the production of {sup 4}He+{sup 2}H and {sup 4}He+{sup 3}H systems in {sup 16}O{sub p} collisions at a momentum of 3.25 GeV/c per nucleon

    SciTech Connect

    Olimov, K.; Glagolev, V. V.; Gulamov, K. G.; Lutpullaev, S. L.; Kurbanov, A. R.; Olimov, A. K.; Petrov, V. I.; Yuldashev, A. A.

    2013-07-15

    New experimental data on the cross sections for the yield of excited {sup 6}Li* and {sup 7}Li* nuclei and on their contributions to the production of {sup 4}He + {sup 2}H and {sup 4}He+{sup 3}H light dinuclear systems in {sup 16}O{sub p} collisions at a momentumof 3.25 A GeV/c per nucleon are presented.

  14. Soil weathering and accumulation rates of oxalate-extractable phases derived from alpine chronosequences of up to 1 Ma in age

    NASA Astrophysics Data System (ADS)

    Dahms, Dennis; Favilli, Filippo; Krebs, Rolf; Egli, Markus

    2012-05-01

    In this study we compare newly-developed chemical weathering data with previously published data from soils developed along two chronosequences of glacial deposits in the European Alps and the Rocky Mountains (Wind River Range, USA). By combining these chronosequences, we are able to present a comprehensive dataset that represents a time period of > 1 Ma. We describe weathering trends of important elements using a number of weathering indices (e.g., K + Ca/Ti ratio, the weathering 'index B' of Kronberg and Nesbitt (1981) and the open mass transport function). Further, we describe the accumulation of Al, Fe, Si and Mn oxyhydroxides (including partially organic phases) as a function of time, and derive the corresponding accumulation rates. We calculated pedogenetically formed oxyhydroxides using an approach based on immobile elements. Our study represents one of only a few studies that describe rates of soil chemical weathering over a period as long as ~ 1 Ma. Results show that rates of chemical weathering clearly decrease along the chronosequences with increasing age of the soils. We find weathering rates are nearly four orders of magnitude lower in the 1 Ma-old soils than in the young soils. Our results suggest that the older soils may be reaching a steady state for these chemical properties in their present environments. A power function best explains the measured time-trends of the 'index B' and (K + Ca)/Ti) ratios in the soils. The best time-trend model for pedogenic weakly- to poorly crystalline phases and the relative losses/gains (based on the open-system mass transport function) were obtained with an exponential decay model function. In terms of the soil system, the decreases in the accumulation rate of the oxyhydroxides appears to be influenced not only by the factor of time but by climate as well (increased precipitation at higher altitudes slows the decrease in weathering rate over time). Thus, our ~ 1 Ma chronosequences also become pedogenic gradients

  15. The {sup 3}He(e,e'p){sup 2}H and {sup 4}He(e,e'p){sup 3}H reactions at high momentum transfer

    SciTech Connect

    Ford, William P.; Schiavilla, Rocco; Van Orden, J. W.

    2014-03-01

    We present updated calculations for observables in the processes {sup 3}He(e,e'p){sup 2}H, {sup 4}He(e,e'p){sup 3}H and {sup 4}He(e-vector, e'p-vector){sup 3}H. This update entails the implementation of improved nucleon-nucleon (NN) amplitudes to describe final state interactions (FSI) within a Glauber approximation and includes full spin-isospin dependence in the profile operator. In addition, an optical potential, which has also been updated since previous work, is utilized to treat FSI for the {sup 4}He(e,e'p){sup 3}H and {sup 4}He(e-vector, e'p-vector){sup 3}H reactions. The calculations are compared with experimental data and show good agreement between theory and experiment. Comparisons are made between the various approximations in the Glauber treatment, including model dependence due to the NN scattering amplitudes, rescattering contributions, and spin dependence. We also analyze the validity of the Glauber approximation at the kinematics the data is available, by comparing to the results obtained with the optical potential.

  16. Probing the Repulsive Core of the Nucleon-Nucleon Interaction via the 4He(e,e`pN) Triple-Coincidence Reaction

    DOE PAGESBeta

    Korover, Igor; Muangma, Navaphon; Hen, Or; Shneor, Ran; Sulkosky, Vincent; Kelleher, Aidan; Gilad, Shalev; Higinbotham, Douglas; Piasetzky, Eliazer; Wood, Stephen; et al

    2014-07-01

    We studied simultaneously the 4He(e,e'p), 4He(e,e'pp), and 4He(e,e'pn) reactions at Q2=2 [GeV/c]2 and xB >1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail ofmore » the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.« less

  17. Search for the enhancement of the thermal expansion coefficient of superfluid 4HE Near T_Lambada by a heat current

    NASA Technical Reports Server (NTRS)

    Liu, Y.; Israelsson, U.; Larson, M.

    2001-01-01

    Presentation on the transition in 4He in the presence of a heat current (Q) provides an ideal system for the study of phase transitions under non-equlibrium, dynamical conditions. Many physical properties become nonlinear and Q-dependant near the transition temperature, T_Lambada.

  18. Probing the repulsive core of the nucleon-nucleon interaction via the (4)He(e,e'pN) triple-coincidence reaction.

    PubMed

    Korover, I; Muangma, N; Hen, O; Shneor, R; Sulkosky, V; Kelleher, A; Gilad, S; Higinbotham, D W; Piasetzky, E; Watson, J W; Wood, S A; Aguilera, P; Ahmed, Z; Albataineh, H; Allada, K; Anderson, B; Anez, D; Aniol, K; Annand, J; Armstrong, W; Arrington, J; Averett, T; Badman, T; Baghdasaryan, H; Bai, X; Beck, A; Beck, S; Bellini, V; Benmokhtar, F; Bertozzi, W; Bittner, J; Boeglin, W; Camsonne, A; Chen, C; Chen, J-P; Chirapatpimol, K; Cisbani, E; Dalton, M M; Daniel, A; Day, D; de Jager, C W; De Leo, R; Deconinck, W; Defurne, M; Flay, D; Fomin, N; Friend, M; Frullani, S; Fuchey, E; Garibaldi, F; Gaskell, D; Gilman, R; Glamazdin, O; Gu, C; Gueye, P; Hamilton, D; Hanretty, C; Hansen, J-O; Hashemi Shabestari, M; Holmstrom, T; Huang, M; Iqbal, S; Jin, G; Kalantarians, N; Kang, H; Khandaker, M; LeRose, J; Leckey, J; Lindgren, R; Long, E; Mammei, J; Margaziotis, D J; Markowitz, P; Marti Jimenez-Arguello, A; Meekins, D; Meziani, Z; Michaels, R; Mihovilovic, M; Monaghan, P; Munoz Camacho, C; Norum, B; Nuruzzaman; Pan, K; Phillips, S; Pomerantz, I; Posik, M; Punjabi, V; Qian, X; Qiang, Y; Qiu, X; Rakhman, A; Reimer, P E; Riordan, S; Ron, G; Rondon-Aramayo, O; Saha, A; Schulte, E; Selvy, L; Shahinyan, A; Sirca, S; Sjoegren, J; Slifer, K; Solvignon, P; Sparveris, N; Subedi, R; Tireman, W; Wang, D; Weinstein, L B; Wojtsekhowski, B; Yan, W; Yaron, I; Ye, Z; Zhan, X; Zhang, J; Zhang, Y; Zhao, B; Zhao, Z; Zheng, X; Zhu, P; Zielinski, R

    2014-07-11

    We studied simultaneously the (4)He(e,e'p), (4)He(e,e'pp), and (4)He(e,e'pn) reactions at Q(2)=2(GeV/c)(2) and x(B)>1, for an (e,e'p) missing-momentum range of 400 to 830  MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum, in a region where the nucleon-nucleon (NN) force is expected to change from predominantly tensor to repulsive. The abundance of neutron-proton pairs is reduced as the nucleon momentum increases beyond ∼500  MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum. Our data are compared with calculations of two-nucleon momentum distributions in (4)He and discussed in the context of probing the elusive repulsive component of the NN force. PMID:25062168

  19. Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation.

    PubMed

    Mauad, Cristiane R; Wagener, Angela de L R; Massone, Carlos G; Aniceto, Mayara da S; Lazzari, Letícia; Carreira, Renato S; Farias, Cássia de O

    2015-02-15

    Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement. PMID:25434473

  20. Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

    USGS Publications Warehouse

    Brown, Erik Thorson; Stallard, Robert F.; Larsen, Matthew C.; Raisbeck, Grant M.; Yiou, Francoise

    1995-01-01

    We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma −1, consistent with mass balance results. 

  1. Myotubes from Severely Obese Type 2 Diabetic Subjects Accumulate Less Lipids and Show Higher Lipolytic Rate than Myotubes from Severely Obese Non-Diabetic Subjects

    PubMed Central

    Bakke, Siril S.; Kase, Eili T.; Moro, Cedric; Stensrud, Camilla; Damlien, Lisbeth; Ludahl, Marianne O.; Sandbu, Rune; Solheim, Brita Marie; Rustan, Arild C.; Hjelmesæth, Jøran; Thoresen, G. Hege; Aas, Vigdis

    2015-01-01

    About 80% of patients with type 2 diabetes are classified as overweight. However, only about 1/3 of severely obese subjects have type 2 diabetes. This indicates that several severely obese individuals may possess certain characteristics that protect them against type 2 diabetes. We therefore hypothesized that this apparent paradox could be related to fundamental differences in skeletal muscle lipid handling. Energy metabolism and metabolic flexibility were examined in human myotubes derived from severely obese subjects without (BMI 44±7 kg/m2) and with type 2 diabetes (BMI 43±6 kg/m2). Lower insulin sensitivity was observed in myotubes from severely obese subjects with type 2 diabetes. Lipolysis rate was higher, and oleic acid accumulation, triacylglycerol content, and fatty acid adaptability were lower in myotubes from severely obese subjects with type 2 diabetes compared to severely obese non-diabetic subjects. There were no differences in lipid distribution and mRNA and protein expression of the lipases HSL and ATGL, the lipase cofactor CGI-58, or the lipid droplet proteins PLIN2 and PLIN3. Glucose and oleic acid oxidation were also similar in cells from the two groups. In conclusion, myotubes established from severely obese donors with established type 2 diabetes had lower ability for lipid accumulation and higher lipolysis rate than myotubes from severely obese donors without diabetes. This indicates that a difference in intramyocellular lipid turnover might be fundamental in evolving type 2 diabetes. PMID:25790476

  2. Examination of sludge accumulation rates and sludge characteristics for a decentralized community wastewater treatment systems with individual primary clarifier tanks located in Wardsville (Ontario, Canada).

    PubMed

    Lossing, Heather; Champagne, Pascale; McLellan, P James

    2010-01-01

    In conventional septic systems, settling and partial treatment via anaerobic digestion occurs in the septic tank. One of the byproducts of solids separation in the septic tank is a semi-liquid material known as septage, which must be periodically pumped out. Septage includes the liquid portion within the tank, as well as the sludge that settles at the bottom of the tank and the scum that floats to the surface of the liquid layer. A number of factors can influence septage characteristics, as well as the sludge and scum accumulation rates within the tank. This paper presents the results of a 2007 field sampling study conducted in Wardsville (Ontario, Canada). The field study examined 29 individual residential two-chamber septic tanks in a community serviced by a decentralized wastewater treatment system in operation for approximately 7 years without septage removal. The field investigation provided a comprehensive data set that allowed for statistical analysis of the data to assess the more critical factors influencing solids accumulation rates within each of the clarifier chambers. With this data, a number of predictive models were developed using water usage data for each residence as an explanatory variable. PMID:21123926

  3. Intracellular accumulation of AMP as a cause for the decline in rate of ethanol production by Saccharomyces cerevisiae during batch fermentation

    SciTech Connect

    Dombek, K.M.; Ingram, L.O.

    1988-01-01

    A general hypothesis is presented for the decline in the rate of ethanol production (per unit of cell protein) during batch fermentation. Inhibition of ethanol production is proposed to result from the intracellular accumulation of AMP during the transition from growth to the stationary phase. AMP acts as a competitive inhibitor of hexokinase with respect to ATP. When assayed in vitro in the presence of ATP and AMP concentration equivalent to those within cells at different stages of fermentation, hexokinase activity declined in parallel with the in vivo decline in the rate of ethanol production. The coupling of glycolytic flux and fermentation to cell growth via degradation products of RNA may be of evolutionary advantage for Saccharomyces cerevisiae. Such a coupling would reduce the exposure of nongrowing cells to potentially harmful concentrations of waste products from metabolism and would conserve nutrients for future growth under more favorable conditions.

  4. Accumulate-Repeat-Accumulate-Accumulate Codes

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Dolinar, Samuel; Thorpe, Jeremy

    2007-01-01

    Accumulate-repeat-accumulate-accumulate (ARAA) codes have been proposed, inspired by the recently proposed accumulate-repeat-accumulate (ARA) codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. ARAA codes can be regarded as serial turbolike codes or as a subclass of low-density parity-check (LDPC) codes, and, like ARA codes they have projected graph or protograph representations; these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The objective in proposing ARAA codes as a subclass of ARA codes was to enhance the error-floor performance of ARA codes while maintaining simple encoding structures and low maximum variable node degree.

  5. 186Os and 187Os enrichments and high-3He/4He sources in the Earth’s mantle: Evidence from Icelandic picrites

    NASA Astrophysics Data System (ADS)

    Brandon, Alan D.; Graham, David W.; Waight, Tod; Gautason, Bjarni

    2007-09-01

    Picrites from the neovolcanic zones in Iceland display a range in 187Os/ 188Os from 0.1297 to 0.1381 (γ Os = + 2.1 to +8.7) and uniform 186Os/ 188Os of 0.1198375 ± 32 (2 σ). The value for 186Os/ 188Os is within uncertainty of the present-day value for the primitive upper mantle of 0.1198398 ± 16. These Os isotope systematics are best explained by ancient recycled crust or melt enrichment in the mantle source region. If so, then the coupled enrichments displayed in 186Os/ 188Os and 187Os/ 188Os from lavas of other plume systems must result from an independent process, the most viable candidate at present remains core-mantle interaction. While some plumes with high 3He/ 4He, such as Hawaii, appear to have been subjected to detectable addition of Os (and possibly He) from the outer core, others such as Iceland do not. A positive correlation between 187Os/ 188Os and 3He/ 4He from 9.6 to 19 Ra in Iceland picrites is best modeled as mixtures of 1 Ga or older ancient recycled crust mixed with primitive mantle or incompletely degassed depleted mantle isolated since 1-1.5 Ga, which preserves the high 3He/ 4He of the depleted mantle at the time. These mixtures create a hybrid source region that subsequently mixes with the present-day convecting MORB mantle during ascent and melting. This multistage mixing scenario requires convective isolation in the deep mantle for hundreds of million years or more to maintain these compositionally distinct hybrid sources. The 3He/ 4He of lavas derived from the Iceland plume changed over time, from a maximum of 50 Ra at 60 Ma, to approximately 25-27 Ra at present. The changes are coupled with distinct compositional gaps between the different aged lavas when 3He/ 4He is plotted versus various geochemical parameters such as 143Nd/ 144Nd and La/Sm. These relationships can be interpreted as an increase in the proportion of ancient recycled crust in the upwelling plume over this time period. The positive correlation between 187Os/ 188Os and

  6. Asthenosphere-lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah

    NASA Astrophysics Data System (ADS)

    Konrad, Kevin; Graham, David W.; Thornber, Carl R.; Duncan, Robert A.; Kent, Adam J. R.; Al-Amri, Abdullah M.

    2016-04-01

    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed 3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (< 850 ka) and the northeasternmost of the volcanic fields. There is a remarkable homogeneity of 3He/4He trapped within most xenoliths, with a weighted mean of 7.54 ± 0.03 RA (2σ, n = 20). This homogeneity occurs over at least eight different xenolith types (including spinel lherzolite, amphibole clinopyroxenite, olivine websterite, clinopyroxenite and garnet websterite), and encompasses ten different volcanic centers within an area of ~ 2500 km2. The homogeneity is caused by volatile equilibration between the xenoliths and fluids derived from their host magma, as fluid inclusions are annealed during the infiltration of vapor-saturated magmas along crystalline grain boundaries. The notable exceptions are the anhydrous spinel lherzolites, which have a lower weighted mean 3He/4He of 6.8 ± 0.3 RA (2σ, n = 2), contain lower concentrations of trapped He, and have a distinctly depleted light rare earth element signature. 3He/4He values of ~ 6.8 RA are also commonly found in spinel lherzolites from harrats Ithnayn, Al Birk, and from Zabargad Island in the Red Sea. Olivine from non-xenolith-bearing lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting. Elevated 3He/4He in the western harrats has been observed only at Rahat (up to 11.8 RA; Murcia et al., 2013), a

  7. Role of heat accumulation in the multi-shot damage of silicon irradiated with femtosecond XUV pulses at a 1 MHz repetition rate.

    PubMed

    Sobierajski, Ryszard; Jacyna, Iwanna; Dłużewski, Piotr; Klepka, Marcin T; Klinger, Dorota; Pełka, Jerzy B; Burian, Tomáš; Hájková, Věra; Juha, Libor; Saksl, Karel; Vozda, Vojtěch; Makhotkin, Igor; Louis, Eric; Faatz, Bart; Tiedtke, Kai; Toleikis, Sven; Enkisch, Hartmut; Hermann, Martin; Strobel, Sebastian; Loch, Rolf A; Chalupsky, Jaromir

    2016-07-11

    The role played by heat accumulation in multi-shot damage of silicon was studied. Bulk silicon samples were exposed to intense XUV monochromatic radiation of a 13.5 nm wavelength in a series of 400 femtosecond pulses, repeated with a 1 MHz rate (pulse trains) at the FLASH facility in Hamburg. The observed surface morphological and structural modifications are formed as a result of sample surface melting. Modifications are threshold dependent on the mean fluence of the incident pulse train, with all threshold values in the range of approximately 36-40 mJ/cm2. Experimental data is supported by a theoretical model described by the heat diffusion equation. The threshold for reaching the melting temperature (45 mJ/cm2) and liquid state (54 mJ/cm2), estimated from this model, is in accordance with experimental values within measurement error. The model indicates a significant role of heat accumulation in surface modification processes. PMID:27410821

  8. Carbonic anhydrase activity and photosynthetic rate in the tree species Paulownia tomentosa Steud. Effect of dimethylsulfoxide treatment and zinc accumulation in leaves.

    PubMed

    Lazova, Galia N; Naidenova, Tsveta; Velinova, Katya

    2004-03-01

    The enzyme carbonic anhydrase (CA) (EC 4.2.1.1) catalyzes the reversible conversion of CO2 to HCO3- and has been shown to be involved in photosynthesis. The enzyme has been shown in animals, plants, eubacteria and viruses, but similar reports on the evidence for CA activity in tree plants does not be appear to be available. In the preliminary analyses of the work, the CA activity in leaf extracts from the tree species Paulownia tomentosa Steud. (introduced in Bulgaria) is described. A connection between CA activity and the rate of photosynthetic CO2 fixation is shown. In the second portion of the work, the effect of 10(-4) mol/L and 10(-2) mol/L dimethylsulfoxide (DMSO) on the zinc accumulation in leaves is demonstrated. It is suggested that CA activity is an indicator of the level of physiologically active zinc in leaves of P. tomentosa Steud. A connection between the process of zinc accumulation in leaves and the activity of the enzymes CA and glycolate oxidase (GO) (EC 1.1.3.1) is established. PMID:15077628

  9. Glaciation in the Late Noachian Icy Highlands: Ice accumulation, distribution, flow rates, basal melting, and top-down melting rates and patterns

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2015-02-01

    Geological evidence for extensive non-polar ice deposits of Amazonian age indicates that the current cold and dry climate of Mars has persisted for several billion years. The geological record and climate history of the Noachian, the earliest period of Mars history, is less certain, but abundant evidence for fluvial channels (valley networks) and lacustrine environments (open-basin lakes) has been interpreted to represent warm and wet conditions, including rainfall and runoff. Alternatively, recent atmospheric modeling results predict a "cold and icy" Late Noachian Mars in which moderate atmospheric pressure accompanied by a full water cycle produce an atmosphere where temperature declines with elevation following an adiabatic lapse rate, in contrast to the current situation on Mars, where temperature is almost completely determined by latitude. These results are formulated in the Late Noachian Icy Highlands (LNIH) model, in which these cold and icy conditions lead to the preferential deposition of snow and ice at high elevations, such as the southern uplands. What is the fate of this snow and ice and the nature of glaciation in such an environment? What are the prospects of melting of these deposits contributing to the observed fluvial and lacustrine deposits? To address these questions, we report on a glacial flow-modeling analysis using a Mars-adapted ice sheet model with LNIH climate conditions. The total surface/near-surface water inventory is poorly known for the Late Noachian, so we explore the LNIH model in a "supply-limited" scenario for a range of available water abundances and a range of Late Noachian geothermal fluxes. Our results predict that the Late Noachian icy highlands (above an equilibrium line altitude of approximately +1 km) were characterized by extensive ice sheets of the order of hundreds of meters thick. Due to extremely cold conditions, the ice-flow velocities in general were very low, less than a few mm/yr, and the regional ice

  10. The influence of structural features of marine humic substances on the accumulation rates of cadmium by a blue mussel Mytilus edulis

    SciTech Connect

    Pempkowiak, J.; Kozuch, J. ); Southon, T. )

    1994-01-01

    Laboratory experiments revealed that both concentration and origin of humic substances (HS) influence the accumulation rates of cadmium by the blue mussel Mytilus edulis. In the concentration of humic substances typical of seawater, the increase is about 60% and 100%, respectively, for aquatic and sedimentary humic substances. The phenomenon was attributed to the stimulation of cadmium uptake due to complexing properties of the substances toward cadmium. Complexing capacity of sedimentary humic substances was found to be 0.57 [mu]g/mg HS, that of aquatic substances 0.41 [mu]g/mg HS. Cross Polarization Magic Angle Spinning (CP/MAS) [sup 13]C NMR of the investigated humic substances revealed differences in the spectra at about 175, 100, 55 and 32 ppm. This was attributed to the varying content of oxygen containing functional groups involved in formation of complexes with metal ions. 8 refs., 4 figs., 3 tabs.

  11. Biomass accumulation rates of Amazonian secondary forest and biomass of old-growth forests from Landsat time series and the Geoscience Laser Altimeter System

    NASA Astrophysics Data System (ADS)

    Helmer, Eileen H.; Lefsky, Michael A.; Roberts, Dar A.

    2009-01-01

    We estimate the age of humid lowland tropical forests in Rondônia, Brazil, from a somewhat densely spaced time series of Landsat images (1975-2003) with an automated procedure, the Threshold Age Mapping Algorithm (TAMA), first described here. We then estimate a landscape-level rate of aboveground woody biomass accumulation of secondary forest by combining forest age mapping with biomass estimates from the Geoscience Laser Altimeter System (GLAS). Though highly variable, the estimated average biomass accumulation rate of 8.4 Mg ha-1 yr-1 agrees well with ground-based studies for young secondary forests in the region. In isolating the lowland forests, we map land cover and general types of old-growth forests with decision tree classification of Landsat imagery and elevation data. We then estimate aboveground live biomass for seven classes of old-growth forest. TAMA is simple, fast, and self-calibrating. By not using between-date band or index differences or trends, it requires neither image normalization nor atmospheric correction. In addition, it uses an approach to map forest cover for the self-calibrations that is novel to forest mapping with satellite imagery; it maps humid secondary forest that is difficult to distinguish from old-growth forest in single-date imagery; it does not assume that forest age equals time since disturbance; and it incorporates Landsat Multispectral Scanner imagery. Variations on the work that we present here can be applied to other forested landscapes. Applications that use image time series will be helped by the free distribution of coregistered Landsat imagery, which began in December 2008, and of the Ice Cloud and land Elevation Satellite Vegetation Product, which simplifies the use of GLAS data. Finally, we demonstrate here for the first time how the optical imagery of fine spatial resolution that is viewable on Google Earth provides a new source of reference data for remote sensing applications related to land cover.

  12. Biogeochemical cycling in an organic-rich coastal marine basin. 9. Sources and accumulation rates of vascular plant-derived organic material

    SciTech Connect

    Haddad, R.I.; Martens, C.S. )

    1987-11-01

    The sources, degradation and burial of vascular plant debris deposited over the past several decades in the lagoonal sediments of Cape Lookout Bight, North Carolina, are quantified using alkaline cupric oxide lignin oxidation product (LOP) analysis. Non-woody angiosperms, accounting for 92 {plus minus} 32% of the recognizable sedimentary vascular plant debris, are calculated to contribute 23 {plus minus} 17% of the total organic carbon buried over the past decade. When combined with a previously established sedimentary organic carbon budget for this site a vascular plant derived carbon burial rate of 26 {plus minus}20 mole C m{sup {minus}2} yr{sup {minus}1} is calculated for this same time interval. The refractory nature and invariant depth distributions of the lignin oxidation products (LOP), when coupled with evidence for constant degradation rates of metabolizable materials, indicate that sediment accumulation at this site has been a steady state process with respect to source and burial of organic carbon since its conversion from an inner-continental shelf to a lagoonal environment during the late 1960's. Thus systematic down-core decreases in labile organic matter result from early diagenetic processes rather than input rate variations.

  13. Systematic Vibration Studies on a Cryogen-Free ^3 He/^4 He Dilution Refrigerator for X-ray Spectroscopy at Storage Rings

    NASA Astrophysics Data System (ADS)

    Scholz, P. A.; Kraft-Bermuth, S.; Andrianov, V.

    2016-01-01

    High-precision X-ray spectroscopy of highly charged ions at storage rings provides a sensitive test of quantum electrodynamics in strong Coulomb fields. To increase the precision of such experiments, silicon microcalorimeters have already been applied successfully. To minimize the interruption of beam times due to maintenance, a new cryogen-free ^3 He/^4 He dilution refrigerator has been designed and is under commissioning. However, in cryogen-free systems microphonic noise due to vibrations contributes considerably to the overall noise and may limit the detector energy resolution. Therefore, we report on systematic vibration studies on a cryogen-free ^3 He/^4 He dilution refrigerator which is specially adapted for experiments at storage rings.

  14. The 2014 effusive eruption at Stromboli volcano (Italy): Inferences from soil CO2 flux and 3He/4He ratio in thermal waters

    NASA Astrophysics Data System (ADS)

    Rizzo, Andrea Luca; Federico, Cinzia; Inguaggiato, Salvatore; Sollami, Aldo; Tantillo, Mariano; Vita, Fabio; Bellomo, Sergio; Longo, Manfredi; Grassa, Fausto; Liuzzo, Marco

    2015-04-01

    A new eruption started at Stromboli on 6 August 2014, which had been preceded by 2 months of increased Strombolian activity and several lava overflows from the craters. The eruption was characterized by a lava effusion in Sciara del Fuoco from a fracture at 650 m above sea level that lasted until 13-17 November. Here we present the first geochemical observations of this eruption, based on the soil CO2 flux in the summit area and on 3He/4He ratios in the thermal waters near Stromboli village. We infer that this eruption was triggered by the gradual replenishment of the feeding system by a CO2- and 3He-rich magma at the end of 2013 and after June 2014, suggested by the increase in 3He/4He ratio before eruption, which reached its highest value since 2007. We thus infer that this eruption was unusual, and we finally speculate on the evolutionary scenario of posteruption.

  15. 40Ar/39Ar and (U-Th)/He - 4He/3He geochronology of landscape evolution and channel iron deposit genesis at Lynn Peak, Western Australia

    NASA Astrophysics Data System (ADS)

    Vasconcelos, Paulo M.; Heim, Jonathan A.; Farley, Kenneth A.; Monteiro, Hevelyn; Waltenberg, Kathryn

    2013-09-01

    (U-Th)/He geochronology of authigenic goethite cements from the Lynn Peak channel iron deposit (CID), Hamersley Province, Western Australia, reveals a history of mineral precipitation ranging from ca. 33 to 14 Ma. Massive goethites from nearby weathering profiles at Roy Hill North, a possible source of detrital material during the aggradation of the Lynn Peak channels, yield (U-Th)/He results as old as ca. 64 Ma. The combination of (U-Th)/He geochronology with incremental outgassing 4He/3He studies on proton-irradiated samples reveals that Lynn Peak goethites host radiogenic 4He in low retentivity (LRD) and high retentivity (HRD) domains and that the HRDs account for most of the sample mass and have lost very little of their original 4He over geologic time. Such high retentivity is especially notable given the goethites were collected from the surface, where they were subject to significant heating by solar irradiation. Minor contamination by detrital fragments of potentially 4He-rich primary phases (e.g., rutile, ilmenite, zircon) occurs in some samples. Fortunately, the 4He/3He method permits characterization of this extraneous 4He component, which is small (<10 wt.% of the total 4He in the goethite) and can be corrected out in estimating the goethite formation age. These results indicate that the Lynn Peak channel was already aggraded and undergoing goethite cementation by ca. 33 Ma. The history of aggradation and channel cementation independently measured through 40Ar/39Ar geochronology is consistent with that obtained from the (U-Th)/He and 4He/3He record. Laser incremental-heating 40Ar/39Ar geochronology of detrital and authigenic Mn oxides, primarily cryptomelane (KMn8O16·xH2O), from the same locality in the Lynn Peak channel reveals that detrital oxides are older than ca. 44 Ma (and as old as ca. 65 Ma) and authigenic oxides are younger than ca. 35 Ma and as young as ca. 16 Ma. Authigenic cryptomelane precipitation and channel cementation occurred

  16. Solving the Large Discrepancy Between Inclusive and Exclusive Measurements of the 8Li + 4He → 11B + n Reaction Cross Section at Astrophysical Energies

    NASA Astrophysics Data System (ADS)

    La Cognata, M.; Del Zoppo, A.; Alba, R.; Cherubini, S.; Colonna, N.; Di Pietro, A.; Figuera, P.; Gulino, M.; Lamia, L.; Musumarra, A.; Pellegriti, M. G.; Pizzone, R. G.; Rolfs, C.; Romano, S.; Spitaleri, C.; Tumino, A.

    2009-12-01

    A solution of the large discrepancy existing between inclusive and exclusive measurements of the 8Li + 4He → 11B + n reaction cross section at E cm < 3 MeV is evaluated. This problem has profound astrophysical relevance for this reaction is of great interest in big bang and r-process nucleosynthesis. By means of a novel technique, a comprehensive study of all existing 8Li + 4He → 11B + n cross section data is carried out, setting up a consistent picture in which all the inclusive measurements provide the reliable value of the cross section. New unambiguous signatures of the strong branch pattern non-uniformities, near the threshold of higher 11B excited levels, are presented and their possible origin, in terms of the cluster structure of the involved excited states of 11B and 12Bnuclei, is discussed.

  17. Systematic Vibration Studies on a Cryogen-Free ^3He/^4He Dilution Refrigerator for X-ray Spectroscopy at Storage Rings

    NASA Astrophysics Data System (ADS)

    Scholz, P. A.; Kraft-Bermuth, S.; Andrianov, V.

    2016-08-01

    High-precision X-ray spectroscopy of highly charged ions at storage rings provides a sensitive test of quantum electrodynamics in strong Coulomb fields. To increase the precision of such experiments, silicon microcalorimeters have already been applied successfully. To minimize the interruption of beam times due to maintenance, a new cryogen-free ^3He/^4He dilution refrigerator has been designed and is under commissioning. However, in cryogen-free systems microphonic noise due to vibrations contributes considerably to the overall noise and may limit the detector energy resolution. Therefore, we report on systematic vibration studies on a cryogen-free ^3He/^4He dilution refrigerator which is specially adapted for experiments at storage rings.

  18. Effect of the variation of the Higgs vacuum expectation value upon the deuterium binding energy and primordial abundances of D and 4He

    NASA Astrophysics Data System (ADS)

    Mosquera, M. E.; Civitarese, O.

    2010-09-01

    Aims: We calculate the constraints on the time variation of the Higgs vacuum expectation value from Big Bang Nucleosynthesis. Methods: Starting from the calculation of the deuterium binding-energy, as a function of the pion-mass and using the NN-Reid 93 potential, we calculate the abundances of primordial D and 4He by modifying Kawano's code. The Higgs vacuum expectation value (v) and the baryon to photon ratio (ηB) enter the calculation as free parameters. By using the observational data of D and 4He, we set constraints on ηB and on the variation of v, relative to a constant value of ΛQCD. Results: Results are consistent with null variation in v and ɛD for the early universe, within 6σ. Conclusions: We obtained a linear dependence of ɛD upon v and found that the best-fit-value of the variation of v is null within 6σ.

  19. Tensor analyzing powers T/sub 20/(theta) and T/sub 22/(theta) in the /sup 2/H(darrow,. gamma. ) /sup 4/He reaction

    SciTech Connect

    Seyler, R.G.; Weller, H.R.

    1985-05-01

    Reaction theory expressions are used to prove that the tensor analyzing powers T/sub 20/(theta) and T/sub 22/(theta) for the /sup 2/H(darrow,..gamma..) /sup 4/He reaction are isotropic if the reaction is pure E2 and terms quadratic in channel-spin-2 matrix elements are neglected. Experimental departures from isotropy can be expected near theta-0/sup 0/, 90/sup 0/, and 189/sup 0/.

  20. Comparative study of dose distributions and cell survival fractions for 1H, 4He, 12C and 16O beams using Geant4 and Microdosimetric Kinetic model

    NASA Astrophysics Data System (ADS)

    Burigo, Lucas; Pshenichnov, Igor; Mishustin, Igor; Bleicher, Marcus

    2015-04-01

    Depth and radial dose profiles for therapeutic 1H, 4He, 12C and 16O beams are calculated using the Geant4-based Monte Carlo model for Heavy-Ion Therapy (MCHIT). 4He and 16O ions are presented as alternative options to 1H and 12C broadly used for ion-beam cancer therapy. Biological dose profiles and survival fractions of cells are estimated using the modified Microdosimetric Kinetic model. Depth distributions of cell survival of healthy tissues, assuming 10% and 50% survival of tumor cells, are calculated for 6 cm SOBPs at two tumor depths and for different tissues radiosensitivities. It is found that the optimal ion choice depends on (i) depth of the tumor, (ii) dose levels and (iii) the contrast of radiosensitivities of tumor and surrounding healthy tissues. Our results indicate that 12C and 16O ions are more appropriate to spare healthy tissues in the case of a more radioresistant tumor at moderate depths. On the other hand, a sensitive tumor surrounded by more resistant tissues can be better treated with 1H and 4He ions. In general, 4He beam is found to be a good candidate for therapy. It better spares healthy tissues in all considered cases compared to 1H. Besides, the dose conformation is improved for deep-seated tumors compared to 1H, and the damage to surrounding healthy tissues is reduced compared to heavier ions due to the lower impact of nuclear fragmentation. No definite advantages of 16O with respect to 12C ions are found in this study.