456 research outputs found

    Zeroing in on more photons and gluons

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    We discuss radiation zeros that are found in gauge tree amplitudes for processes involving multi-photon emission. Previous results are clarified by examples and by further elaboration. The conditions under which such amplitude zeros occur are identical in form to those for the single-photon zeros, and all radiated photons must travel parallel to each other. Any other neutral particle likewise must be massless (e.g. gluon) and travel in that common direction. The relevance to questions like gluon jet identification and computational checks is considered. We use examples to show how certain multi-photon amplitudes evade the zeros, and to demonstrate the connection to a more general result, the decoupling of an external electromagnetic plane wave in the ``null zone". Brief comments are made about zeros associated with other gauge-boson emission.Comment: 26 page

    Amplitude Zeros in Radiative Decays of Scalar Particles

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    We study amplitude zeros in radiative decay processes with a photon or a gluon emission of all possible scalar particles(e.g. scalar leptoquarks) which may interact with the usual fermions in models beyond the standard model. For the decays with a photon emission, the amplitudes clearly exhibit the factorization property and the differential decay rates vanish at specific values of a certain variable which are determined only by the electric charges of the particles involved and independent of the particle masses and the various couplings. For the decays with a gluon emission, even though the zeros are washed away, the differential decay rates still have distinct minima. The branching ratios as a function of leptoquark masses are presented for the scalar leptoquark decays. We also comment on the decays of vector particles into two fermions and a photon.Comment: Revtex, 17 pages + 6 figures (available upon request), Preprint, OITS559. Several typos with tex file were correcte

    Women, anger, and aggression an interpretative phenomenological analysis

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    This study reports a qualitative phenomenological investigation of anger and anger-related aggression in the context of the lives of individual women. Semistructured interviews with five women are analyzed using interpretative phenomenological analysis. This inductive approach aims to capture the richness and complexity of the lived experience of emotional life. In particular, it draws attention to the context-dependent and relational dimension of angry feelings and aggressive behavior. Three analytic themes are presented here: the subjective experience of anger, which includes the perceptual confusion and bodily change felt by the women when angry, crying, and the presence of multiple emotions; the forms and contexts of aggression, paying particular attention to the range of aggressive strategies used; and anger as moral judgment, in particular perceptions of injustice and unfairness. The authors conclude by examining the analytic observations in light of phenomenological thinking

    Association between composition of the human gastrointestinal microbiome and development of fatty liver with choline deficiency

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    Background & Aims: Nonalcoholic fatty liver disease affects up to 30% of the US population, but the mechanisms underlying this condition are incompletely understood. We investigated how diet standardization and choline deficiency influence the composition of the microbial community in the human gastrointestinal tract and the development of fatty liver under conditions of choline deficiency. Methods: We performed a 2-month inpatient study of 15 female subjects who were placed on well-controlled diets in which choline levels were manipulated. We used 454-FLX pyrosequencing of 16S ribosomal RNA bacterial genes to characterize microbiota in stool samples collected over the course of the study. Results: The compositions of the gastrointestinal microbial communities changed with choline levels of diets; each individual's microbiome remained distinct for the duration of the experiment, even though all subjects were fed identical diets. Variations between subjects in levels of Gammaproteobacteria and Erysipelotrichi were directly associated with changes in liver fat in each subject during choline depletion. Levels of these bacteria, change in amount of liver fat, and a single nucleotide polymorphism that affects choline were combined into a model that accurately predicted the degree to which subjects developed fatty liver on a choline-deficient diet. Conclusions: Host factors and gastrointestinal bacteria each respond to dietary choline deficiency, although the gut microbiota remains distinct in each individual. We identified bacterial biomarkers of fatty liver that result from choline deficiency, adding to the accumulating evidence that gastrointestinal microbes have a role in metabolic disorders

    Investigation of the Neutron Form Factors by Inclusive Quasi-Elastic Scattering of Polarized Electrons off Polarized 3^{3}He: A Theoretical Overview

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    The theory of quasi-elastic inclusive scattering of polarized leptons off polarized 3^3He is critically reviewed and the origin of different expressions for the polarized nuclear response function appearing in the literature is explained. The sensitivity of the longitudinal asymmetry upon the neutron form factors is thoroughly investigated and the role played by the polarization angle for minimizing the proton contribution is illustrated.Comment: Phys. Rev C in press; 9 figs. (available upon request

    Einstein, incompleteness, and the epistemic view of quantum states

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    Does the quantum state represent reality or our knowledge of reality? In making this distinction precise, we are led to a novel classification of hidden variable models of quantum theory. Indeed, representatives of each class can be found among existing constructions for two-dimensional Hilbert spaces. Our approach also provides a fruitful new perspective on arguments for the nonlocality and incompleteness of quantum theory. Specifically, we show that for models wherein the quantum state has the status of something real, the failure of locality can be established through an argument considerably more straightforward than Bell's theorem. The historical significance of this result becomes evident when one recognizes that the same reasoning is present in Einstein's preferred argument for incompleteness, which dates back to 1935. This fact suggests that Einstein was seeking not just any completion of quantum theory, but one wherein quantum states are solely representative of our knowledge. Our hypothesis is supported by an analysis of Einstein's attempts to clarify his views on quantum theory and the circumstance of his otherwise puzzling abandonment of an even simpler argument for incompleteness from 1927.Comment: 18 pages, 8 figures, 1 recipe for cupcakes; comments welcom

    An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud

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    The local correlation between far-infrared (FIR) emission and radio-continuum (RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc. The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is shown to be greatest in the most active star forming regions with a power law slope of ~1.14 indicating that the RC emission increases faster than the FIR emission. The slope of the other regions and the SMC are much flatter and in the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the regions which range from 0.5 to 0.95. The thermal fraction of the RC emission alone can provide the expected FIR/RC correlation. The results are consistent with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s appear to escape the SMC so readily, the results here may not provide support for coupling between the local gas density and the magnetic field intensity.Comment: 19 pages, 7 Figure

    Realistic Model of the Nucleon Spectral Function in Few- and Many- Nucleon Systems

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    By analysing the high momentum features of the nucleon momentum distribution in light and complex nuclei, it is argued that the basic two-nucleon configurations generating the structure of the nucleon Spectral Function at high values of the nucleon momentum and removal energy, can be properly described by a factorised ansatz for the nuclear wave function, which leads to a nucleon Spectral Function in the form of a convolution integral involving the momentum distributions describing the relative and center-of-mass motion of a correlated nucleon-nucleon pair embedded in the medium. The Spectral Functions of 3He^3He and infinite nuclear matter resulting from the convolution formula and from many-body calculations are compared, and a very good agreement in a wide range of values of nucleon momentum and removal energy is found. Applications of the model to the analysis of inclusive and exclusive processes are presented, illustrating those features of the cross section which are sensitive to that part of the Spectral Function which is governed by short-range and tensor nucleon-nucleon correlations.Comment: 40 pages Latex , 16 ps figures available from the above e-mail address or from [email protected]

    Mitogen-induced stimulation and suppression of erythroid burst promoting activity production by human mononuclear cells

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    Exposure of human peripheral blood mononuclear cells or highly enriched monocytes to various plant lectins substantially alters their production of erythroid burst promoting activity (BPA). Neither unstimulated, nor mitogen stimulated, enriched T lymphocytes produced demonstrable BPA. Each of the lectins tested resulted in a different pattern of alteration of BPA production by mononuclear cells. Increasing concentrations of phytohaemagglutinin (PHA) caused a progressive increase in BPA production up to a plateau level at concentrations above 0·25–0·5 Μ1/ml. Concanavalin A (Con A) at concentrations of 0·05–0·1 Μg/ml stimulated BPA production, but Con A concentrations > 1 Μg/ml never augmented BPA production by mononuclear cells. Pokeweed mitogen inhibited BPA production by mononuclear cells in a concentration-dependent manner. Since PHA and Con A can bind to and stimulate both monocytes/macrophages and T lymphocytes, some production of BPA by stimulated T cells in the presence of monocytes cannot be ruled out. Earlier studies demonstrated that T cells augment monocyte production of BPA. Thus, monocyte–T cell interactions, as well as activation of monocytes and perhaps lymphocytes, play an important role in regulation of BPA production in vitro .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73808/1/j.1365-2141.1983.tb01232.x.pd
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