15,482 research outputs found

    The Ritter-Kolb Catalogue and its Impact on Research into CVs, LMXBs and related Objects

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    In the first part of this paper, the Ritter-Kolb catalogue (RKcat for short), its history and a few examples of its application to research in the field of cataclysmic variables are briefly described. In a second part we look forward to possible future applications of RKcat for the study of cataclysmic variables, low-mass X-ray binaries and related objects. Last but not least we also briefly comment on the future of the RKcat service itself

    Vision to reality: From Robert R. Wilson's frontier to Leon M. Lederman's Fermilab

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    This paper examines the roles of vision and leadership in creating and directing Fermi National Accelerator Laboratory from the late 1960s through the 1980s. The story divides into two administrations having different problems and accomplishments, that of Robert R. Wilson (1967-1978), which saw the transformation from cornfield to frontier physics facility, and that of Leon Max Lederman (1979-1989), in which the laboratory evolved into one of the world's major high-energy facilities. Lederman's pragmatic vision of a user-based experimental community helped him to convert the pioneering facility that Wilson had built frugally into a laboratory with a stable scientific, cultural, and funding environment

    Regulation of 92-kD gelatinase release in HL-60 leukemia cells

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    Matrix metalloproteinase 9 (MMP-9), also known as 92-kD type IV collagenase/gelatinase, is believed to play a critical role in tumor invasion and metastasis. Here, we report that MMP-9 was constitutively released from the human promyelocytic cell line HL-60 as determined by zymographic analysis. Tumor necrosis factor-alpha (TNF-alpha) enhanced the enzyme release threefold to fourfold and the protein kinase C (PKC) activator and differentiation inducer 12-O-tetradecanoylphorbol-13- acetate (TPA) eightfold to ninefold. Gelatinase induction by TNF-alpha and TPA was inhibited by actinomycin D or cycloheximide, indicating that de novo protein synthesis was required. Neutralizing monoclonal antibodies to TNF-alpha (anti-TNF-alpha) decreased the basal MMP-9 release of these cells. In addition, these antibodies also significantly interfered with the TPA-induced enzyme release. Agents that inhibit TNF-alpha expression in HL-60 cells, such as pentoxifylline and dexamethasone, completely abrogated both the constitutive and TPA-evoked MMP-9 release. Diethyldithiocarbamate, which is known to stimulate TNF-alpha production in HL-60 cells, exerted a positive effect on MMP-9 release in untreated cells but was inhibitory in TPA-treated HL-60 cells. The PKC inhibitor staurosporine at low concentrations (100 ng/mL) caused a significant augmentation of MMP-9 release in untreated cultures that was blocked by the addition of anti-TNF-alpha. High concentrations (2 mumol/L) of staurosporine completely abolished the extracellular enzyme activity both in untreated and TPA-stimulated cells. These results suggest, that TNF- alpha is required for basal and PKC-mediated MMP-9 release in HL-60 leukemia cells. Thus, MMP-9 secretion may be regulated by TNF-alpha not only in a paracrine but also in an autocrine fashion. This may potentiate the matrix degradative capacity of immature leukemic cells in the processes of bone marrow egress and the evasion of these cells into peripheral tissue

    Cosmic Microwave Background Observations as a Way to Discriminate Among Inflation Models

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    The upcoming satellite missions MAP and Planck will measure the spectrum of fluctuations in the Cosmic Microwave Background with unprecedented accuracy. We discuss the prospect of using these observations to distinguish among proposed models of inflationary cosmology.Comment: To appear in the proceedings of the XXXIIIrd Rencontres de Moriond, "Fundamental Parameters in Cosmology", 17-24 January, Les Arcs, France. 6 Pages, 2 figures, uses moriond.st

    Non-critical String Cosmologies

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    Non-critical String Cosmologies are offered as an alternative to Standard Big Bang Cosmology. The new features encompassed within the dilaton dependent non-critical terms affect the dynamics of the Universe\'s evolution in an unconventional manner being in agreement with the cosmological data. Non-criticality is responsible for a late transition to acceleration at redshifts z=0.2. The role of the uncoupled rolling dilaton to relic abundance calculations is discussed. The uncoupled rolling dilaton dilutes the neutralino relic densities in supersymmetric theories by factors of ten, relaxing considerably the severe WMAP Dark Matter constraints, while at the same time leaves almost unaffected the baryon density in agreement with primordial Nucleosynthesis.Comment: 16 pages, 7 figures, conference tal

    A Note on Gravitational Baryogenesis

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    The coupling between Ricci scalar curvature and the baryon number current dynamically breaks CPT in an expanding universe and leads to baryon asymmetry. We study the effect of time dependence of equation of state parameter of the FRW universe on this asymmetry.Comment: 10 pages, accepted for publication in Physical Review

    Multicomponent solution in modified theory of gravity in the early universe

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    We study the modified theory of gravity in Friedmann Robertson Walker universe composed of several perfect fluids. We consider the power law inflation and determine the equation of state parameters in terms of the parameters of modified gravity's Lagrangian in the early universe. We also discuss briefly the gravitational baryogenesis in this model.Comment: 9 pages, accepted for publication in Physical Review

    Bulk viscosity of a gas of neutrinos and coupled scalar particles, in the era of recombination

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    Bulk viscosity may serve to damp sound waves in a system of neutrinos coupled to very light scalar particles, in the era after normal neutrino decoupling but before recombination. We calculate the bulk viscosity parameter in a minimal scheme involving the coupling of the two systems. We add some remarks on the bulk viscosity of a system of fully ionized hydrogen plus photons.Comment: 6 pages, 4 figure
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