3,503 research outputs found

    The Implications of Galaxy Formation Models for the TeV Observations of Current Detectors

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    This paper represents a step toward constraining galaxy formation models via TeV gamm a ray observations. We use semi-analytic models of galaxy formation to predict a spectral distribution for the intergalactic infrared photon field, which in turn yields information about the absorption of TeV gamma rays from extra-galactic sources. By making predictions for integral flux observations at >200 GeV for several known EGRE T sources, we directly compare our models with current observational upper limits obtained by Whipple. In addition, our predictions may offer a guide to the observing programs for the current population of TeV gamma ray observatories.Comment: 6 pages, 11 figures, to appear in the proceedings of the 6th TeV Workshop at Snowbird, U

    A preliminary longitudinal study of white matter alteration in cocaine use disorder subjects

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    Background Previous diffusion tensor imaging (DTI) studies have consistently shown that subjects with cocaine use disorder (CocUD) had altered white matter microstructure in the corpus callosum. It is believed that these alterations are due to preexisting factors, chronic cocaine use, or both. However, there is no published longitudinal DTI study on human cocaine users yet which could shed light on the relationship between cocaine use and DTI findings. Methods This study used a longitudinal design and DTI to test if the white matter microstructure shows quicker alteration in CocUD subjects than controls. DTI data were acquired from eleven CocUD subjects who participated a treatment study and eleven non-drug-using controls at baseline (Scan 1) and after ten weeks (Scan 2). The baseline fractional anisotropy (FA), a general measure of white matter microstucture, and the change in FA (ΔFA, equals Scan 1 FA minus Scan 2 FA) were both compared between groups. Results The two groups did not show a difference in FA at baseline. The CocUD subjects had significantly greater ΔFA than the controls in the left splenium of the corpus callosum. In CocUD subjects, greater ΔFA in this region was associated with shorter lifetime cocaine use and greater number of positive cocaine urine samples collected during the treatment. Conclusion The finding in the left splenium is consistent with previous animal studies and provide indirect evidence about the effects of chronic cocaine use on white matter alterations. The subject sample size is small, therefore the results should be treated as preliminary

    A Call for the Structured Physicist Report

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    Introduction: The field of diagnostic radiology continues to struggle with the clinical adoption of the structured interpretive report, with many radiologists preferring a semistructured, free-text dictation style to a more rigid, highly structured approach that some professional leaders have promoted [1]. Although structured reporting compliance in the radiologist community has been difficult to achieve, diagnostic radiologists have been thinking about and discussing this important issue for many years; it is also a part of the ACR’s Imaging 3.0_ campaign [2]. In the breast imaging community, the well-established BI-RADS_ recommendations produce a very structured report, with a discussion of interpretive findings culminating in a numeric BI-RADS score ranging from 0 to 6 [3]. Unlike some interpretive radiology reports, which can be ambiguous in terms of the next course of action, the BI-RADS scale is not only a diagnostic scale but also prescriptive of what the necessary follow-up should be

    The Chain Lakes Massif and its Contact With a Cambrian Ophiolite and a Caradocian Granite

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    Guidebook for field trips in southern and west-central Maine, October 13, 14 and 15, 1989: New England Intercollegiate Geological Conference 81st annual meeting: Trip B-

    ALMA observations of feeding and feedback in nearby Seyfert galaxies: an AGN-driven outflow in NGC 1433

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    We report ALMA observations of CO(3-2) emission in the Seyfert 2 double-barred galaxy NGC1433, at the unprecedented spatial resolution of 0.5"=24 pc. Our aim is to probe AGN feeding and feedback phenomena through the morphology and dynamics of the gas inside the central kpc. The CO map, which covers the whole nuclear region (nuclear bar and ring), reveals a nuclear gaseous spiral structure, inside the nuclear ring encircling the nuclear stellar bar. This gaseous spiral is well correlated with the dusty spiral seen in Hubble Space Telescope images. The nuclear spiral winds up in a pseudo-ring at 200 pc radius, which might correspond to the inner ILR. Continuum emission is detected at 0.87 mm only at the very centre, and its origin is more likely thermal dust emission than non-thermal emission from the AGN. It might correspond to the molecular torus expected to exist in this Seyfert 2 galaxy. The HCN(4-3) and HCO+(4-3) lines were observed simultaneously, but only upper limits are derived, with a ratio to the CO(3-2) line lower than 1/60 at 3sigma, indicating a relatively low abundance of very dense gas. The kinematics of the gas over the nuclear disk reveal rather regular rotation only slightly perturbed by streaming motions due to the spiral; the primary and secondary bars are too closely aligned with the galaxy major or minor axis to leave a signature in the projected velocities. Near the nucleus, there is an intense high-velocity CO emission feature redshifted to 200 km/s (if located in the plane), with a blue-shifted counterpart, at 2" (100 pc) from the centre. While the CO spectra are quite narrow in the centre, this wide component is interpreted as an outflow involving a molecular mass of 3.6 10^6 Mo and a flow rate 7 Mo/yr. The flow could be in part driven by the central star formation, but is mainly boosted by the AGN through its wind or radio jets.Comment: 11 pages, 9 figures, Accepted in Astronomy and Astrophysic

    Modulation of ecosystem services by animal personalities

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    Conservationists rarely consider the roles individuals, with their own unique behavior, physiology, and genome, play in shaping ecosystem processes and consequently ecosystem services, but this is changing. An ongoing surge in research on animal personalities (that is, behavioral differences among individuals that are consistent over time and across contexts) is exposing the ecological roles of individuals to scientific scrutiny. Here, we present four broad examples of ecosystem services that are likely to be shaped by personalities: (1) pollination and seed dispersal, (2) regulation of pest species, (3) ecotourism, and (4) maintenance of soil quality. Although researchers have suggested diverse links between animal personality and ecosystem function, very few have examined this association. We outline a four-step process for quantifying and validating these linkages, leading to application for conservation practitioners, and conclude by recommending that accounting for behavioral variation should be incorporated into the management of ecosystem services
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