20,411 research outputs found

    ENVIRONMENTAL AND ECONOMIC ACCOUNTING FOR THE GERMAN AGRICULTURAL SECTOR

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    How can we estimate the negative externalities of agriculture at the national level, and attribute these to specific production activities and outputs? The paper presents a method that calculates the mass flow in the whole agricultural sector including inputs from other sectors, and that allows to analyse resource use and emissions, e.g. of greenhouse gases. Data inputs are the German economic accounts for agriculture, farm structural survey and market statistics, as well as environmental statistics. In the framework of the German agricultural sector model RAUMIS, material flows within the agricultural sector are described, as well as inputs from other German sectors and imports. Through a processanalytical approach, all information is integrated and matrices of resource use and emissions for all agricultural production activities are generated. A monetary allocation is used to identify the respective activities that are responsible for emissions, including indirect emissions in upstream sectors. Related to the market output, cumulative emissions per unit of output can be computed. Results for the period from 1995 to 2007 show the trend of resource uses and emissions for the national average values of important commodities such as milk and meat.SEEA, Input-Output Analysis, agriculture, resource use, trade, emissions, carbon footprint, Livestock Production/Industries, Resource /Energy Economics and Policy,

    Role of QCD compositeness in the production of scalar and tensor mesons through single-photon annihilation e+eγγS(T)e^+ e^- \to \gamma^* \to \gamma S(T)

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    We study the exclusive production of scalar S=0++S = 0^{++} and tensor T=2++T = 2^{++} mesons through single-photon annihilation e+eγγS(T)e^+ e^- \to \gamma^* \to \gamma S(T). Using QCD compositeness of the involved hadrons considered as quark-antiquark systems, the prediction for the scaling of the differential cross sections of these processes is dσ/dt1/s3d\sigma/dt \sim 1/s^3 at large ss. We further derive the scaling of the γγS\gamma^\ast \to \gamma S and γγT\gamma^\ast \to \gamma T transition form factors: FγγS(s)1/sF_{\gamma^\ast\gamma S}(s) \sim 1/s and FγγT(s)1/s2F_{\gamma^\ast\gamma T}(s) \sim 1/s^2. Results for the respective cross sections of the scalar and tensor meson production are presented. Note, when scalar and tensor mesons are considered as tetraquark systems of two tightly bound color diquarks, corresponding to them transition form factors and differential cross sections have the same falloffs as in case of quark-antiquark picture. For other tetraquark or two-hadron molecules configurations the transition form factors FγγS(T)(s)F_{\gamma^\ast\gamma S(T)}(s) and the differential cross section dσ/dtd\sigma/dt have additional 1/s1/s and 1/s21/s^2 falloffs, respectively.Comment: 7 page

    Direct Detection of Leptophilic Dark Matter in a Model with Radiative Neutrino Masses

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    We consider an electro-weak scale model for Dark Matter (DM) and radiative neutrino mass generation. Despite the leptophilic nature of DM with no direct couplings to quarks and gluons, scattering with nuclei is induced at the 1-loop level through photon exchange. Effectively, there are charge-charge, dipole-charge and dipole-dipole interactions. We investigate the parameter space consistent with constraints from neutrino masses and mixing, charged lepton-flavour violation, perturbativity, and the thermal production of the correct DM abundance, and calculate the expected event rate in DM direct detection experiments. We show that current data from XENON100 start to constrain certain regions of the allowed parameter space, whereas future data from XENON1T has the potential to significantly probe the model.Comment: 24 pages, 8 figures, 2 tables, discussion of large theta13 added, version to appear in PR

    Interstitial stem cells in Hydra

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    Resummed effective action in the world-line formalism

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    Using the world-line method we resum the scalar one-loop effective action. This is based on an exact expression for the one-loop action obtained for a background potential and a Taylor expansion of the potential up to quadratic order in x-space. We thus reproduce results of Masso and Rota very economically. An alternative resummation scheme is suggested using ``center of mass'' based loops which is equivalent under the assumption of vanishing third and higher derivatives in the Taylor expansion but leads to simplified expressions. In an appendix some general issues concerning the relation between world-line integrals with fixed end points versus integrals with fixed center are clarified. We finally note that this method is also very valuable for gauge field effective actions where it is based on the Euler--Heisenberg type resummation.Comment: 15 page

    Low-metallicity star formation: Relative impact of metals and magnetic fields

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    Low-metallicity star formation poses a central problem of cosmology, as it determines the characteristic mass scale and distribution for the first and second generations of stars forming in our Universe. Here, we present a comprehensive investigation assessing the relative impact of metals and magnetic fields, which may both be present during low-metallicity star formation. We show that the presence of magnetic fields generated via the small-scale dynamo stabilises the protostellar disc and provides some degree of support against fragmentation. In the absence of magnetic fields, the fragmentation timescale in our model decreases by a factor of ~10 at the transition from Z=0 to Z>0, with subsequently only a weak dependence on metallicity. Similarly, the accretion timescale of the cluster is set by the large-scale dynamics rather than the local thermodynamics. In the presence of magnetic fields, the primordial disc can become completely stable, therefore forming only one central fragment. At Z>0, the number of fragments is somewhat reduced in the presence of magnetic fields, though the shape of the mass spectrum is not strongly affected in the limits of the statistical uncertainties. The fragmentation timescale, however, increases by roughly a factor of 3 in the presence of magnetic fields. Indeed, our results indicate comparable fragmentation timescales in primordial runs without magnetic fields and Z>0 runs with magnetic fields.Comment: MNRAS in pres
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