82,820 research outputs found

    Nucleon-nucleon potentials in phase-space representation

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    A phase-space representation of nuclear interactions, which depends on the distance r\vec{r} and relative momentum p\vec{p} of the nucleons, is presented. A method is developed that permits to extract the interaction V(r,p)V(\vec{r},\vec{p}) from antisymmetrized matrix elements given in a spherical basis with angular momentum quantum numbers, either in momentum or coordinate space representation. This representation visualizes in an intuitive way the non-local behavior introduced by cutoffs in momentum space or renormalization procedures that are used to adapt the interaction to low momentum many-body Hilbert spaces, as done in the unitary correlation operator method or with the similarity renormalization group. It allows to develop intuition about the various interactions and illustrates how the softened interactions reduce the short-range repulsion in favor of non-locality or momentum dependence while keeping the scattering phase shifts invariant. It also reveals that these effective interactions can have undesired complicated momentum dependencies at momenta around and above the Fermi momentum. Properties, similarities and differences of the phase-space representations of the Argonne and the N3LO chiral potential, and their UCOM and SRG derivatives are discussed

    Robotic observations of the most eccentric spectroscopic binary in the sky

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    The visual A component of the Gliese 586AB system is a double-lined spectroscopic binary consisting of two cool stars with the exceptional orbital eccentricity of 0.976. Such an extremely eccentric system may be important for our understanding of low-mass binary formation. We present a total of 598 high-resolution echelle spectra from our robotic facility STELLA from 2006-2012 which we used to compute orbital elements of unprecedented accuracy. The orbit constrains the eccentricity to 0.97608+/-0.00004 and the orbital period to 889.8195+/-0.0003d. The masses of the two components are 0.87+/-0.05 Msun and 0.58+/-0.03 Msun if the inclination is 5+/-1.5degr as determined from adaptive-optics images, that is good to only 6% due to the error of the inclination although the minimum masses reached a precision of 0.3%. The flux ratio Aa:Ab in the optical is betwee n 30:1 in Johnson-B and 11:1 in I. Radial velocities of the visual B-component (K0-1V) appear constant to within 130 m/s over six years. Sinusoidal modulations of Teff of Aa with an amplitude of apprx 55 K are seen with the orbital period. Component Aa appears warmest at periastron and coolest at apastron, indicating atmospheric changes induced by the high orbital eccentricity. No light variations larger than approximately 4 mmag are detected for A, while a photometric period of 8.5+/-0.2 d with an amplitude of 7 mmag is discovered for the active star B, which we interpret to be its rotation period. We estimate an orbital period of approx 50,000 yr for the AB system. The most likely age of the AB system is >=2 Gyr, while the activity of the B component, if it were a single star, would imply 0.5 Gyr. Both Aa and B are matched with single-star evolutionary tracks of their respective mass

    From nucleon-nucleon interaction matrix elements in momentum space to an operator representation

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    Starting from the matrix elements of the nucleon-nucleon interaction in momentum space we present a method to derive an operator representation with a minimal set of operators that is required to provide an optimal description of the partial waves with low angular momentum. As a first application we use this method to obtain an operator representation for the Argonne potential transformed by means of the unitary correlation operator method and discuss the necessity of including momentum dependent operators. The resulting operator representation leads to the same results as the original momentum space matrix elements when applied to the two-nucleon system and various light nuclei. For applications in fermionic and antisymmetrized molecular dynamics, where an operator representation of a soft but realistic effective interaction is indispensable, a simplified version using a reduced set of operators is given

    A program to evaluate dye lasers as high power, pulsed, visible light sources

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    Spectral emission of visible from Q switched dye laser

    Cathodoluminescence of enstatite from chondritic and achondritic meteorites and its selenological implications Technical report, 1 Sep. 1967 - 1 Jul. 1968

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    Cathodoluminescence of enstatite from chondritic and achondritic meteorites and selenological implication

    The Effects of Market Survey Rates, Job Evaluation and Job Gender on Job Pay

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    The present study investigates the effects of current pay, market surveys, job evaluation points, job gender, and rater sex on pay rates for jobs. 406 compensation administrators assigned new pay rates to nine jobs in one of two matched job sets: either all predominantly female, or all predominantly male. The two sets were matched on all quantitative data (current rate, market rate, and job evaluation points), but varied in terms of job titles and descriptions. Multiple analyses of variance and regression analyses were performed to determine whether job gender had a significant effect on assigned pay rates, holding other factors constant. Regardless of the analysis employed, no evidence of gender bias was found. Limitations and suggestions for future research are offered

    Some monetary facts

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    This article describes three long-run monetary facts derived by examining data for 110 countries over a 30-year period, using three definitions of a country's money supply and two subsamples of countries: (1) Growth rates of the money supply and the general price level are highly correlated for all three money definitions, for the full sample of countries, and for both subsamples. (2) The growth rates of money and real output are not correlated, except for a subsample of countries in the Organisation for Economic Co-operation and Development, where these growth rates are positively correlated. (3) The rate of inflation and the growth rate of real output are essentially uncorrelated. ; Reprinted in Quarterly Review, Fall 2001 (v. 25, no. 4)Money supply ; Monetary theory

    Correlations in hot and dense quark matter

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    We present a relativistic three-body equation to investigate three-quark clusters in hot and dense quark matter. To derive such an equation we use the Dyson equation approach. The equation systematically includes the Pauli blocking factors as well as the self energy corrections of quarks. Special relativity is realized through the light front form. Presently we use a zero-range force and investigate the Mott transition.Comment: 6 pages, 4 figure, Few-Body Systems style file

    Spatial control of irreversible protein aggregation

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    Liquid cellular compartments spatially segregate from the cytoplasm and can regulate aberrant protein aggregation, a process linked to several medical conditions, including Alzheimer's and Parkinson's diseases. Yet the mechanisms by which these droplet-like compartments affect protein aggregation remain unknown. Here, we combine kinetic theory of protein aggregation and liquid-liquid phase separation to study the spatial control of irreversible protein aggregation in the presence of liquid compartments. We find that, even for weak interactions between the compartment constituents and the aggregating monomers, aggregates are strongly enriched inside the liquid compartment relative to the surrounding cytoplasm. We show that this enrichment is caused by a positive feedback mechanism of aggregate nucleation and growth which is mediated by a flux maintaining the phase equilibrium between the compartment and the cytoplasm. Our model predicts that the compartment volume that maximizes aggregate enrichment in the compartment is determined by the reaction orders of aggregate nucleation. The underlying mechanism of aggregate enrichment could be used to confine cytotoxic protein aggregates inside droplet-like compartments suggesting potential new avenues against aberrant protein aggregation. Our findings could also represent a common mechanism for the spatial control of irreversible chemical reactions in general
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