3,945 research outputs found

    Overview of Issues Surrounding Strangeness in the Nucleon

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    The calculation of the strangeness content of the nucleon and its experimental verification is a fundamental step in establishing non-perturbative QCD as the correct theory describing the structure of hadrons. It holds a role in QCD analogous to the correct calculation of the Lamb shift in QED. We review the latest developments in the vector and scalar matrix elements of the strange quarks in the proton, where there has recently been considerable progress.Comment: Invited presentation at the 10th Conference on the Intersection of Nuclear and Particle Physics, San Diego, May 26-May 30, 200

    The Content of Several Measures of Social Desirability

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    The question of whether to remove socially desirable responding (SDR) variance from self-report personality inventories, or to treat it as a facet of personality, has been the center of a debate spanning the last 25 years (Furnham, 1986). Recently, this controversy again came to the forefront of the literature via an exchange between a group of researchers (Block, 1990; Edwards, 1990; Nicholson & Hogan, 1990; Walsh, 1990). The essence of this debate is whether the correlation between a SDR scale and a personality scale indicated that the personality scale is contaminated by SDR bias, or if it merely indicates that there is content overlap between the two types of scales

    The STAR W Spin Physics Program with (s)\sqrt(s) = 500 GeV Polarized pp Collisions at RHIC

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    Production of W bosons in longitudinally polarized pp collisions provides an excellent tool to probe the flavor-dependence of sea quark polarizations in the polarized proton. Current status and future plans for the W physics program with the STAR detector at RHIC are presented along with remarks concerning our knowledge of the nature and origin of the partonic sea.Comment: Talk given at the Tenth Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2009), 26-31 May 2009, San Diego CA, USA; 4 pages, 3 figure

    Frequencies of infaunal invertebrates related to water content of Chesapeake Bay sediments

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    The following relationship was investigated for a total of 44 stations, using sequential (linear) multiregression analysis: A = f (D, S a , S., C, M , S , W) where A = the frequency of an infauna! invertebrate species, D : water depth at the station, Sa = per cent sand, Si =percent silt, C = per cent clay, Mz = mean grain size, S o = sediment Sorting Coefficient, and W = water content. Three animals were chosen for the dependent variable: Ensis directus, Nephtys incisa, and Retusa canaliculata. Results of the least-squares search procedure indicate that if the water content is carefully determined this variable always appears as one of the most important, when the independent variables are considered in combinations of two or three at a time. The implication is that water content, a mass property of the sediment that reflects the interrelationships of mean grain size, sorting, grain packing, and mineralogy, is a highly useful environmental variable that should be measured in studies that attempt to establish animal-sediment relationships

    R-evolution: Improving perturbative QCD

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    Perturbative QCD results in the MSbar scheme can be dramatically improved by switching to a scheme that accounts for the dominant power law dependence on the factorization scale in the operator product expansion. We introduce the ``MSR scheme'' which achieves this in a Lorentz and gauge invariant way. The MSR scheme has a very simple relation to MSbar, and can be easily used to reanalyze MSbar results. Results in MSR depend on a cutoff parameter R, in addition to the mu of MSbar. R variations can be used to independently estimate i) the size of power corrections, and ii) higher order perturbative corrections (much like mu in MSbar). We give two examples at three-loop order, the ratio of mass splittings in the B*-B and D*-D systems, and the Ellis-Jaffe sum rule as a function of momentum transfer Q in deep inelastic scattering. Comparing to data, the perturbative MSR results work well even for Q ~ 1 GeV, and the size of power corrections is reduced compared to those in MSbar.Comment: 4 pages, 3 figures, axis label for Fig.2 fixe

    AN ECONOMIC ANALYSIS OF THE NORTH DAKOTA CATTLE INDUSTRY

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    The analysis was conducted to evaluate the impacts of both the Federal Agricultural Improvement and Reform Act of 1996 (FAIR) and the cattle cycle on the livestock enterprises. The North Dakota Representative Farm and Ranch Model, which uses the Food and Agricultural Policy Research Institute price projections as an input, was developed and used for this analysis. Net farm income and farm debt-to-asset ratios for the average and large beef cattle farms were analyzed. The U.S. cattle industry has been characterized by cyclical variations in production and prices. It appears that the current cattle cycle is in the final stages of expansion. Cattle numbers continued to increase during 1995, but at a slow rate. Industry estimates are that the bottom of cattle prices will occur in late 1996 or 1997. Price recovery is projected to start sometime in 1998 as inventory numbers decline. Prices are forecast to rise through 2002. Net farm income for the representative beef cattle farms is projected to follow the cattle cycle with the lowest net incomes during 1997- 1999. Net farm income for most representative beef cattle farms recovers by 2002-2003. The debt-to-asset ratios for the representative beef cattle farms will likely rise throughout the forecast period. FAPRI Note: Figures are not included in the machine readable copy--contact the authors for more information.livestock, representative farms, cattle cycle, Production Economics,

    GW method with the self-consistent Sternheimer equation

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    We propose a novel approach to quasiparticle GW calculations which does not require the computation of unoccupied electronic states. In our approach the screened Coulomb interaction is evaluated by solving self-consistent linear-response Sternheimer equations, and the noninteracting Green's function is evaluated by solving inhomogeneous linear systems. The frequency-dependence of the screened Coulomb interaction is explicitly taken into account. In order to avoid the singularities of the screened Coulomb interaction the calculations are performed along the imaginary axis, and the results are analytically continued to the real axis through Pade' approximants. As a proof of concept we implemented the proposed methodology within the empirical pseudopotential formalism and we validated our implementation using silicon as a test case. We examine the advantages and limitations of our method and describe promising future directions.Comment: 18 pages, 6 figure

    Spin squeezing of high-spin, spatially extended quantum fields

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    Investigations of spin squeezing in ensembles of quantum particles have been limited primarily to a subspace of spin fluctuations and a single spatial mode in high-spin and spatially extended ensembles. Here, we show that a wider range of spin-squeezing is attainable in ensembles of high-spin atoms, characterized by sub-quantum-limited fluctuations in several independent planes of spin-fluctuation observables. Further, considering the quantum dynamics of an f=1f=1 ferromagnetic spinor Bose-Einstein condensate, we demonstrate theoretically that a high degree of spin squeezing is attained in multiple spatial modes of a spatially extended quantum field, and that such squeezing can be extracted from spatially resolved measurements of magnetization and nematicity, i.e.\ the vector and quadrupole magnetic moments, of the quantum gas. Taking into account several experimental limitations, we predict that the variance of the atomic magnetization and nematicity may be reduced as far as 20 dB below the standard quantum limits.Comment: 18 pages, 5 figure

    Impulsivity, Impulsive and Reflective Processes and the Development of Alcohol Use and Misuse in Adolescents and Young Adults

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    This paper contrasts dual-process and personality approaches in the prediction of addictive behaviors and related risk behaviors. In dual-process models, behavior is described as the joint outcome of qualitatively different “impulsive” (or associative) and “reflective” processes. There are important individual differences regarding both types of processes, and the relative strength of both in a specific situation is influenced by prior behavior and state variables (e.g., fatigue, alcohol use). From this perspective, a specific behavior (e.g., alcohol misuse) can be predicted by the combined indices of the behavior-related impulsive processes (e.g., associations with alcohol), and reflective processes, including the ability to refrain from a motivationally salient action. Personality approaches have reported that general traits such as impulsivity predict addictive behaviors. Here we contrast these two approaches, with supplementary analyses on four datasets. We hypothesized that trait impulsivity can predict specific risky behaviors, but that its predictive power disappears once specific behavior-related associations, indicators of executive functioning, and their interaction are entered into the equation. In all four studies the observed interaction between specific associations and executive control (EC) was robust: trait impulsivity did not diminish the prediction of alcohol use by the interaction. Trait impulsivity was not always related to alcohol use, and when it was, the predictive power disappeared after entering the interaction between behavior-specific associations and EC in one study, but not in the other. These findings are interpreted in relation to the validity of the measurements used, which leads to a more refined hypothesis

    Role of laminin carbohydrates on cellular interactions

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    Role of laminin carbohydrates on cellular interactions. Laminins, a family of large multidomain glycoproteins of the basal lamina, have been implicated in the development and maintenance of cellular and tissue organization. Considerable interest has arisen concerning the ways in which laminin carries out its biological functions. Previously these biologic responses have been primarily attributed to the peptide sequences of laminin, however, newer studies suggest that laminin carbohydrates may also participate in such cellular activities. Recently, a subpopulation of laminin molecules purified from EHS sarcoma by lectin affinity chromatography has been shown to contain about 25 to 30% carbohydrate. Most of the carbohydrates present are complex-type asparagine-linked oligosaccharides encompassing many different structures, some of which are unique to laminin. To date, the biological function of the carbohydrates of laminin remains somewhat unclear. They do not appear to be needed for heparin binding or to enhance proteinase stability, however, current evidence suggests they are important in cellular spreading and neurite outgrowth. It is our hypothesis that the covalently-linked carbohydrate moieties of laminin will ultimately prove to be involved in information transfer to responsive cells. It is the purpose of this review to delineate current concepts of the structure and function of this unique glycoprotein's sugar chains
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