16,096 research outputs found

    Diets of shags Phalacrocorax aristotelis and cormorants P. carbo in Norway and possible implications for gadoid stock recruitment

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    The diets of shags and cormorants were studied in Norway through analyses of regurgitated pellets. Although this method has many limitations, indications were that both species rely heavily on small gadoids (Gadidae) and sand eels (Ammodytidae) for food throughout their range, but also eat other fish species when available. There was considerable dietary overlap between species, despite a tendency for cormorants to eat larger fish and more benthic items than shags. Predation by shags and cormorants could be a factor limiting the recruitment of cod and saithe into what are now severely reduced, but commercially important stocks in the Norwegian and Barents Seas

    Ab-initio No-Core Gamow Shell Model calculations with realistic interactions

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    No-Core Gamow Shell Model (NCGSM) is applied for the first time to study selected well-bound and unbound states of helium isotopes. This model is formulated on the complex energy plane and, by using a complete Berggren ensemble, treats bound, resonant, and scattering states on equal footing. We use the Density Matrix Renormalization Group method to solve the many-body Schr\"{o}dinger equation. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for 3^3H and 4^4He nuclei. We also performed {\textit ab initio} NCGSM calculations for the unstable nucleus 5^5He and determined the ground state energy and decay width, starting from a realistic N3^3LO chiral interaction.Comment: 17 pages, 14 figures. Revised version. Discussion on microscopic overlap functions, SFs and ANCs is added. Added references. Accepted for publication at PR

    Band Mapping in One-Step Photoemission Theory: Multi-Bloch-Wave Structure of Final States and Interference Effects

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    A novel Bloch-waves based one-step theory of photoemission is developed within the augmented plane wave formalism. Implications of multi-Bloch-wave structure of photoelectron final states for band mapping are established. Interference between Bloch components of initial and final states leads to prominent spectral features with characteristic frequency dispersion experimentally observed in VSe_2 and TiTe_2. Interference effects together with a non-free-electron nature of final states strongly limit the applicability of the common direct transitions band mapping approach, making the tool of one-step analysis indispensable.Comment: 4 jpg figure

    Optically Pumped NMR Measurements of the Electron Spin Polarization in GaAs Quantum Wells near Landau Level Filling Factor nu=1/3

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    The Knight shift of Ga-71 nuclei is measured in two different electron-doped multiple quantum well samples using optically pumped NMR. These data are the first direct measurements of the electron spin polarization, P(nu,T)=/max, near nu=1/3. The P(T) data at nu=1/3 probe the neutral spin-flip excitations of a fractional quantum Hall ferromagnet. In addition, the saturated P(nu) drops on either side of nu=1/3, even in a Btot=12 Tesla field. The observed depolarization is quite small, consistent with an average of about 0.1 spin-flips per quasihole (or quasiparticle), a value which does not appear to be explicable by the current theoretical understanding of the FQHE near nu=1/3.Comment: 4 pages (REVTEX), 5 eps figures embedded in text; minor changes, published versio

    Nonsequential positive-operator-valued measurements on entangled mixed states do not always violate a Bell inequality

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    We present a local-hidden-variable model for positive-operator-valued measurements (an LHVPOV model) on a class of entangled generalized Werner states, thus demonstrating that such measurements do not always violate a Bell-type inequality. We also show that, in general, if the state ρ\rho' can be obtained from ρ\rho with certainty by local quantum operations without classical communication then an LHVPOV model for the state ρ\rho implies the existence of such a model for ρ\rho'.Comment: 4 pages, no figures. Title changed to accord with Phys. Rev. A version. Journal reference adde

    The Impact of Advanced Biofuels on Aviation Emissions and Operations in the U.S.

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    We analyze the economic and emissions impacts on U.S. commercial aviation of the Federal Aviation Administration’s renewable jet fuel goal when met using advanced fermentation (AF) fuel from perennial grasses. These fuels have recently been certified for use in aircraft and could potentially provide greater environmental benefits than aviation biofuels approved previously. Due to uncertainties in the commercialization of AF technologies, we consider a range of assumptions concerning capital costs, energy conversion efficiencies and product slates. In 2030, estimates of the implicit subsidy required to induce consumption of AF jet fuel range from 0.45to0.45 to 20.85 per gallon. These correspond to a reference jet fuel price of 3.23pergallonandAFjetfuelcostsrangingfrom4.01to3.23 per gallon and AF jet fuel costs ranging from 4.01 to 24.41 per gallon. In all cases, as renewable jet fuel represents around 1.4% of total fuel consumed by commercial aviation, the goal has a small impact on aviation operations and emissions relative to a case without the renewable jet fuel target, and emissions continue to grow relative to those in 2005. Costs per metric ton of carbon dioxide equivalent abated by using biofuels range from 42to42 to 652.This work is funded by the U.S. Federal Aviation Administration (FAA) and Defense Logistics Agency Energy (DLA Energy) through Project 47 of the Partnership for Air Transportation Noise and Emissions Reduction (PARTNER). The Joint Program on the Science and Policy of Global Change is funded by the U.S. Department of Energy and a consortium of government and industrial sponsors (for the complete list see http://globalchange.mit.edu/sponsors/all)

    WHO International Pilot Study of Schizophrenia

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    The results are described of a transcultural psychiatric study of schizophrenia undertaken by WHO in nine countries. The study proved that such a collaboration was feasible, that it was possible to develop research procedures for international use, and that similar types of schizophrenia could be found in each of the countries involved. One thousand two hundred and two patients were studied and over 2 million items of information obtaine
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