73,782 research outputs found

    The diffuse neutrino flux from the inner Galaxy: constraints from very high energy gamma-ray observations

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    Recently, the MILAGRO collaboration reported on the detection of a diffuse multi-TeV emission from a region of the Galactic disk close to the inner Galaxy. The emission is in excess of what is predicted by conventional models for cosmic ray propagation, which are tuned to reproduce the spectrum of cosmic rays observed locally. By assuming that the excess detected by MILAGRO is of hadronic origin and that it is representative for the whole inner Galactic region, we estimate the expected diffuse flux of neutrinos from a region of the Galactic disk with coordinates −40∘<l<40∘-40^{\circ} < l < 40^{\circ}. Our estimate has to be considered as the maximal expected neutrino flux compatible with all the available gamma ray data, since any leptonic contribution to the observed gamma-ray emission would lower the neutrino flux. The diffuse flux of neutrinos, if close to the maximum allowed level, may be detected by a km3^3--scale detector located in the northern hemisphere. A detection would unambiguously reveal the hadronic origin of the diffuse gamma-ray emission.Comment: submitted to Astroparticle Physic

    A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)

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    A detailed analysis of the evolution of the properties of core-jet systems within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a power-law relationship between jet intensity and width that suggests for the typical jet, little if any energy is lost as it moves away from its core. Using VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be aligned with the the direction of emission on kiloparsec scales. We also found that this alignment improves as the jets move farther from their cores on projected scales as small as ~50-100 pc. This suggests that realignment of jets on these projected scales is relatively common. We typically find a modest amount of bending (a change in jet position angle of ~5 deg.) on these scales, suggesting that this realignment may typically occur relatively gradually.Comment: Accepted to ApJ, 20 pages, 8 figure

    Towards the development of a problem solver for the monitoring and control of instrumentation in a grid environment

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    This paper considers the issues involved in developing a generic problem solver to be used within a grid environment for the monitoring and control of instrumentation. The specific feature of such an environment is that the type of data to be processed, as well as the problem, is not always known in advance. Therefore, it is necessary to develop a problem solver architecture that addresses this issue. We propose to analyze the performance of the problem solving algorithms available within the WEKA toolkit and determine a decision tree of the best performing algorithm for a given type of data. For this purpose the algorithms have been tested using 51 datasets either drawn from publicly available repositories or generated in a grid-enabled environmen

    Investigation of long-lived eddies on Jupiter

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    Quasi-geostrophic, two layer models of the Jovian atmosphere are under development; these may be used to simulate eddy phemonena in the atmosphere and include tracer dynamics explicitly. The models permit the investigation of the dynamics of quasi-geostrophic eddies under more controlled conditions than are possible in the laboratory. They can also be used to predict the distribution and behavior of tracer species, and hence to discriminate between different models of the mechanisms forcing the eddies, provided suitable observations can be obtained. At the same time, observational strategies are being developed for the Near Infrared Mapping Spectrometer on the Galileo Orbiter, with the objective of obtaining composition measurements for comparison with the models. Maps of features at thermal infrared wavelengths near 5 micron and reflected sunlight maps as a function of wavelength and phase angle will be obtained. These should provide further useful information on the morphology, composition and microstructure of clouds within eddy features. Equilibrium chemistry models which incorporate advection may then be used to relate these results of the dynamical models and provide addtional means of classifying different types of eddies

    Finite volume corrections to pi-pi scattering

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    Lattice QCD studies of hadron-hadron interactions are performed by computing the energy levels of the system in a finite box. The shifts in energy levels proportional to inverse powers of the volume are related to scattering parameters in a model independent way. In addition, there are non-universal exponentially suppressed corrections that distort this relation. These terms are proportional to exp(-m_pi L) and become relevant as the chiral limit is approached. In this paper we report on a one-loop chiral perturbation theory calculation of the leading exponential corrections in the case of I=2 pi-pi scattering near threshold.Comment: 17 pages, 2 figures, 1 table. Version published in PR

    Eastern Range Extension of \u3ci\u3eLeptoglossus Occidentalis\u3c/i\u3e With a Key to Leptoglossus Species of America North of Mexico (Heteroptera: Coreidae)

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    Leptoglossus occidentalis is reported for the first time from Illinois and Michigan, and confirmed for Indiana. A key to the species of Leptoglossus occurring in America north of Mexico is presented

    Data mining and fusion

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    The DMSP/MFR total ozone and radiance data base

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    This report describes the entries in sufficient detail so that the data base might be useful to others. The characteristics of the MFR sensor are briefly discussed and a complete index to the data base tapes is given

    Transport of heat and mass in a two-phase mixture. From a continuous to a discontinuous description

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    We present a theory which describes the transport properties of the interfacial region with respect to heat and mass transfer. Postulating the local Gibbs relation for a continuous description inside the interfacial region, we derive the description of the Gibbs surface in terms of excess densities and fluxes along the surface. We introduce overall interfacial resistances and conductances as the coefficients in the force-flux relations for the Gibbs surface. We derive relations between the local resistivities for the continuous description inside the interfacial region and the overall resistances of the surface for transport between the two phases for a mixture. It is shown that interfacial resistances depend among other things on the enthalpy profile across the interface. Since this variation is substantial the coupling between heat and mass flow across the surface are also substantial. In particular, the surface puts up much more resistance to the heat and mass transfer then the homogeneous phases over a distance comparable to the thickness of the surface. This is the case not only for the pure heat conduction and diffusion but also for the cross effects like thermal diffusion. For the excess fluxes along the surface and the corresponding thermodynamic forces we derive expressions for excess conductances as integrals over the local conductivities along the surface. We also show that the curvature of the surface affects only the overall resistances for transport across the surface and not the excess conductivities along the surface.Comment: 25 pages, 2 figure
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