51 research outputs found

    Zinterhof Sequences in GRID-Based Numerical Integration

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    The appropriateness of Zinterhof sequences to be used in GRID-based QMC integration is discussed. Theoretical considerations as well as experimental investigations are conducted comparing and assessing different strategies for an efficient and reliable usage. The high robustness and ease of construction exhibited by those sequences qualifies them as excellent QMC point set candidates for heterogeneous environments like the GRID

    The luminosity function of field galaxies

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    Schmidt's method for construction of luminosity function of galaxies is generalized by taking into account the dependence of density of galaxies from the distance in the near Universe. The logarithmical luminosity function (LLF) of field galaxies depending on morphological type is constructed. We show that the LLF for all galaxies, and also separately for elliptical and lenticular galaxies can be presented by Schechter function in narrow area of absolute magnitudes. The LLF of spiral galaxies was presented by Schechter function for enough wide area of absolute magnitudes: . Spiral galaxies differ slightly by parameter . At transition from early spirals to the late spirals parameter in Schechter function is reduced. The reduction of mean luminosity of galaxies is observed at transition from elliptical galaxies to lenticular galaxies, to early spiral galaxies, and further, to late spiral galaxies, in a bright end, . The completeness and the average density of samples of galaxies of different morphological types are estimated. In the range the mean number density of all galaxies is equal 0.127 Mpc-3.Comment: 14 page, 8 figures, to appear in Astrophysic

    Characterizing the non-linear growth of large-scale structure in the Universe

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    The local Universe displays a rich hierarchical pattern of galaxy clusters and superclusters. The early Universe, however, was almost smooth, with only slight 'ripples' seen in the cosmic microwave background radiation. Models of the evolution of structure link these observations through the effect of gravity, because the small initially overdense fluctuations attract additional mass as the Universe expands. During the early stages, the ripples evolve independently, like linear waves on the surface of deep water. As the structures grow in mass, they interact with other in non-linear ways, more like waves breaking in shallow water. We have recently shown how cosmic structure can be characterized by phase correlations associated with these non-linear interactions, but hitherto there was no way to use that information to reach quantitative insights into the growth of structures. Here we report a method of revealing phase information, and quantify how this relates to the formation of a filaments, sheets and clusters of galaxies by non-linear collapse. We use a new statistic based on information entropy to separate linear from non-linear effects and thereby are able to disentangle those aspects of galaxy clustering that arise from initial conditions (the ripples) from the subsequent dynamical evolution.Comment: Accepted for publication in Nature. For high-resolution Figure 3, please see http://www.nottingham.ac.uk/~ppzpc/phases/n0colorphase.html, For the animations and the idea of this paper please see http://www.nottingham.ac.uk/~ppzpc/phases/index.htm

    Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

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    Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ18O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ18O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ18O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ18O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ18O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ18O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ18O values measured during tag recording time and corresponding δ18O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ18O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ18O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ18O signature acquisition, and associated variation, are clarified

    Quinpramine Ameliorates Rat Experimental Autoimmune Neuritis and Redistributes MHC Class II Molecules

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    Activation of inflammatory cells is central to the pathogenesis of autoimmune demyelinating diseases of the peripheral nervous system. The novel chimeric compound quinpramine—generated from imipramine and quinacrine—redistributes cholesterol rich membrane domains to intracellular compartments. We studied the immunological and clinical effects of quinpramine in myelin homogenate induced Lewis rat experimental autoimmune neuritis (EAN), a model system for acute human inflammatory neuropathies, such as the Guillain-Barré syndrome. EAN animals develop paresis of all limbs due to autoimmune inflammation of peripheral nerves. Quinpramine treatment ameliorated clinical disease severity of EAN and infiltration of macrophages into peripheral nerves. It reduced expression of MHC class II molecules on antigen presenting cells and antigen specific T cell proliferation both in vitro and in vivo. Quinpramine exerted its anti-proliferatory effect on antigen presenting cells, but not on responder T cells. Our data suggest that quinpramine represents a candidate pharmaceutical for inflammatory neuropathies

    Gravitational Lensing from a Spacetime Perspective

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    Numerical Hydrodynamics and Magnetohydrodynamics in General Relativity

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    SEARCHING for PLANET NINE with COADDED WISE and NEOWISE-REACTIVATION IMAGES

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    A distant, as yet unseen ninth planet has been invoked to explain various observations of the outer solar system. While such a "Planet Nine," if it exists, is most likely to be discovered via reflected light in the optical, it may emit much more strongly at 3-5 μm than simple blackbody predictions would suggest, depending on its atmospheric properties. As a result, Planet Nine may be detectable at 3.4 μm with the Wide-field Infrared Survey Explorer, but single exposures are too shallow except at relatively small distances ( au). We develop a method to search for Planet Nine far beyond the W1 single-exposure sensitivity, to distances as large as 800 au, using inertial coadds of W1 exposures binned into ∼1 day intervals. We apply our methodology to a ∼2000 square degree testbed sky region which overlaps a southern segment of Planet Nine's anticipated orbital path. We do not detect a plausible Planet Nine candidate, but are able to derive a detailed completeness curve, ruling out its presence within the parameter space searched at W1 < 16.66 (90% completeness). Our method uses all publicly available W1 imaging, spanning 2010 January to 2015 December, and will become more sensitive with future NEOWISE-Reactivation releases of additional W1 exposures. We anticipate that our method will be applicable to the entire high Galactic latitude sky, and we will extend our search to that full footprint in the near future
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