33,605 research outputs found

    A reusable prepositioned ATP reaction chamber

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    Luminescence biometer detects presence of life by means of light-emitting chemical reaction of luciferin and luciferase with adenosine triphosphate (ATP) that occurs in all living cells. Amount of light in reaction chamber is measured to determine presence and extent of life

    Gas-rich dwarf galaxies in dense and sparse environments

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    Dwarf irregular galaxies (generically labelled Im for the present purposes) pose an enigma to students of galaxy evolution. In nearby groups and the Virgo cluster, Im galaxies are at least as abundant as spiral galaxies, and their low surface brightnesses and high gas-to-stars ratios suggest that (at least in the stochastic self-propagating star formation scenario) there should be significant numbers of HI clouds with masses approaching 10(exp 8) solar mass which have undergone very little or no star formation. To date, however, no clouds with so little star formation that they would not be recognized as Im galaxies on high-quality photographic plates have been identified. There have been suggestions that such dwarfs may be tidally disrupted in regions of high galactic density, but may be prevalent in low density regions. We offer data from three parallel programs relevant to this issue. (1) A large number of Im galaxies throughout the Local Supercluster have been mapped in the HI spectral line using the Arecibo Radiotelescope, and we can establish the frequency with which HI disks much more extended than their optically visible portions are found. (2) Our extensive mapping of spiral and dwarf galaxies in the Virgo cluster allows us to set stringent limits on the density of star-free Hi clouds in that cluster. (3) We have conducted a sampling of the void in the distribution of galaxies toward the super galactic pole, optimized for finding low-mass HI clouds at redshifts out to approximately 2000 km/s

    Ethylenebisdithiocarbamates and ethylenethiourea: possible human health hazards.

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    Humans are exposed to ethylenebisdithiocarbamates (EBDCs) from environmental sources. Exposure to EBDCs is chronic for workers in a variety of industries, where EBDCs are used for their properties as slimicides, vulcanization accelerators, antioxidants, and scavengers in waste-water treatment. EBDCs, and particularly the EBDC metabolite ethylenethiourea, have clearly defined, important toxic effects in various animal species, and there is reason to suspect they are carcinogenic in humans. In the absence of definitive information regarding human risk, further studies need to be done. In the interim, regular surveillance of workers with high levels of exposure to EBDCs, with specific attention to markers of thyroid and hepatic pathology, should be considered

    Correlation Statistics of Irregular and Spiral Galaxies Mapped in HI

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    Several measures of galaxy size and mass obtained from the neutral hydrogen mapping of 70 dwarf irregular galaxies presented in Paper I (Hoffman et al. 1996) are compared statistically to those for the set of all available HI-mapped dwarfs and HI-mapped spirals distributed within the same spatial volume to investigate variations in Tully-Fisher relations and in surface densities as functions of galaxy size and luminosity or mass. Some ambiguities due to the ``non-commutativity'' of the correlations among the variables are addressed and linear regressions of logarithms of blue luminosity, HI and optical radii, velocity profile half-width incorporating rotation and random motions, HI mass, and indicative dynamical mass are presented and analyzed. The surface density of HI is almost constant along the sequence of size/mass/luminosity while surface density of blue luminosity increases with galaxy size. For quantities not involving HI we find no evidence for a ``break'' between dwarfs and spirals, but we do find some curvature in velocity vs. radius and in the Tully-Fisher relation. There is an indication for a difference in the correlations involving HI mass or radius between dwarfs alone and spirals alone, in the sense that irregulars have somewhat more HI mass or slightly larger HI radii than spirals at a given blue luminosity, optical radius, or velocity profile width.Comment: AASTeX, to appear in ApJ, 26 pages + 3 tables + 12 figure

    Light detection instrument Patent

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    Detection instrument for light emitted from ATP biochemical reactio

    On Multiple Zeta Values of Even Arguments

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    For k <= n, let E(2n,k) be the sum of all multiple zeta values with even arguments whose weight is 2n and whose depth is k. Of course E(2n,1) is the value of the Riemann zeta function at 2n, and it is well known that E(2n,2) = (3/4)E(2n,1). Recently Z. Shen and T. Cai gave formulas for E(2n,3) and E(2n,4). We give two formulas form E(2n,k), both valid for arbitrary k <=n, one of which generalizes the Shen-Cai results; by comparing the two we obtain a Bernoulli-number identity. We also give explicit generating functions for the numbers E(2n,k) and for the analogous numbers E*(2n,k) defined using multiple zeta-star values of even arguments.Comment: DESY number added; misprints fixed; reference added. Second revision (2016): New result on multiple zeta-star values adde

    IGB grid: User's manual (A turbomachinery grid generation code)

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    A grid generation code called IGB is presented for use in computational investigations of turbomachinery flowfields. It contains a combination of algebraic and elliptic techniques coded for use on an interactive graphics workstation. The instructions for use and a test case are included

    Entropy of gas and dark matter in galaxy clusters

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    On the basis of a large scale 'adiabatic', namely non-radiative and non-dissipative, cosmological smooth particle hydrodynamic simulation we compare the entropy profiles of the gas and the dark matter (DM) in galaxy clusters. The quantity K_g = T_g \rho_g^{-2/3} provides a measure for the entropy of the intra-cluster gas. By analogy with the thermodynamic variables of the gas the velocity dispersion of the DM is associated with a formal temperature and thereby K_DM = \sigma_DM^2 \rho_DM^{-2/3} is defined. This DM entropy is related to the DM phase space density by K_DM \propto Q_DM^{-2/3}. In accord with other studies the DM phase space density follows a power law behaviour, Q_DM \propto r^{-1.82}, which corresponds to K_DM \propto r^{1.21}. The simulated intra-cluster gas has a flat entropy core within (0.8 \pm 0.4) R_s, where R_s is the NFW scale radius. The outer profile follows the DM behaviour, K_g \propto r^{1.21}, in close agreement with X-ray observations. Upon scaling the DM and gas densities by their mean cosmological values we find that outside the entropy core a constant ratio of K_g / K_{DM} = 0.71 \pm 0.18 prevails. By extending the definition of the gas temperature to include also the bulk kinetic energy the ratio of the DM and gas extended entropy is found to be unity for r > 0.8 R_s. The constant ratio of the gas thermal entropy to that of the DM implies that observations of the intra-cluster gas can provide an almost direct probe of the DM.Comment: 7 pages, 8 figures, accepted for publication in MNRAS, web page of the The Marenostrum Numerical Cosmology Project : http://astro.ft.uam.es/~marenostrum
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