25,569 research outputs found

    ROSAT observations of two 'cooling flow' EMSS Galaxies

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    We present ROSAT observations of two luminous L~10^44 erg/s EMSS galaxies, MS1019+5139 and MS1209+3917, previously classified as 'cooling flow' galaxies. MS1019+5139 does not appear to be spatially extended (<13 kpc) while its spectrum is well fit by a power law with Gamma = 1.73 +0.19-0.18; X-ray variability on a timescale of ~ years is also clearly detected. MS1209+3917 shows no evidence of spatial extension (<50 kpc) but it shows variability, while its spectrum can be fit with thermal bremsstrahlung emission (kT=1.8 +0.9-0.4 keV) or a power law model (Gamma = 2.50 +0.44-0.42, but with excess photoelectric absorption above the Galactic value). All the above argue against thermal emission from a group of galaxies or a galaxy but in favour of an AGN (possibly BL Lac) interpretation. We conclude that no 'normal' galaxies with high X-ray luminosities have yet been detected in the EMSS survey that could be significant contributors to the X-ray background.Comment: 6 pages, LaTeX, 6 postscript figures included, to appear in MNRA

    Local-time asymmetries in the Venus thermosphere

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    Our current understanding of the global structure and dynamics of the Venus thermosphere is embodied in models such as the Venus Thermospheric General Circulation Model (VTGCM) and empirical composition models such as VIRA and VTS3. We have completed an analysis of ultraviolet images of Venus at 130 nm acquired by the Pioneer Venus Orbiter Ultraviolet Spectrometer (PVOUVS). We have examined 97 images spanning the 10-year period between 1980 and 1990, and have developed a technique for global radiative transfer modeling with which we create synthetic models of each image analyzed. We have developed a hypothesis for understanding the persistent local-time asymmetry observed as a signature of vertically propagating internal gravity waves interacting with the thermospheric SS-AS circulation. This hypothesis is presented

    Black hole pair creation and the stability of flat space

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    We extend the Gross-Perry-Yaffe approach of hot flat space instability to Minkowski space. This is done by a saddle point approximation of the partition function in a Schwarzschild wormhole background which is coincident with an eternal black hole. The appearance of an instability in the whole manifold is here interpreted as a black hole pair creation.Comment: 11 pages,RevTeX4, 2 figures. Accepted for publication in Int. J. Mod. Phys.

    Adaptive grid methods for Q-tensor theory of liquid crystals : a one-dimensional feasibility study

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    This paper illustrates the use of moving mesh methods for solving partial differential equation (PDE) problems in Q-tensor theory of liquid crystals. We present the results of an initial study using a simple one-dimensional test problem which illustrates the feasibility of applying adaptive grid techniques in such situations. We describe how the grids are computed using an equidistribution principle, and investigate the comparative accuracy of adaptive and uniform grid strategies, both theoretically and via numerical examples

    Developing and applying an integrated modular design methodology within a SME

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    Modularity within a product can bring advantages to the design process by facilitating enhanced design reuse, reduced lead times, decreased cost and higher levels of quality. While the benefits of modularity are becoming increasingly better known, at present it is usually left to the designers themselves to introduce modularity into products. Studies into modularity have shown that byimplementing 'formal' methods, further benefits can be made in terms of time, cost, quality and performance. Current approaches that have been proposed for the formal development of modular design methodologies fail to accurately represent knowledge that is inherently produced during design projects and fail to consider design from the different viewpoints of the development process. This work, built on previous work on modularity and design for reuse, aims to develop an integrated design methodology that will optimise the modules created through the design process and allow for modularity to be 'built-in' to product development from the initial stages. The methodology andassociated tools have been developed to provide an easy-to-use approach to modularity that has support for design rationales and company knowledge that aid in effective design decision making. The methodology, named GeMoCURE, provides an integrated total solution to modular design based on reuse of proven physical and knowledge modules. Its incremental nature allows for the optimalstructure to be maintained as the design progresses. A special focus has been on the application of this approach for Small to Medium Enterprises (SMEs), which are typically challenged by a lack of design human resources and expertise

    Results of the Mariner 6 and 7 Mars occultation experiments

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    Final profiles of temperature, pressure, and electron density on Mars were obtained for the Mariner 6 and 7 entry and exit cases, and results are presented for both the lower atmosphere and ionosphere. The results of an analysis of the systematic and formal errors introduced at each stage of the data-reduction process are also included. At all four occulation points, the lapse rate of temperature was subdadiabatic up to altitudes in excess of 20 km. A pronounced temperature inversion was present above the surface at the Mariner 6 exit point. All four profiles exhibit a sharp, superadiabatic drop in temperature at high altitudes, with temperatures falling below the frost point of CO2. These results give a strong indication of frozen CO2 in the middle atmosphere of Mars

    Use of Most Bothersome Symptom as a Coprimary Endpoint in Migraine Clinical Trials: A Post-Hoc Analysis of the Pivotal ZOTRIP Randomized, Controlled Trial.

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    ObjectiveTo better understand the utility of using pain freedom and most bothersome headache-associated symptom (MBS) freedom as co-primary endpoints in clinical trials of acute migraine interventions.BackgroundAdhesive dermally applied microarray (ADAM) is an investigational system for intracutaneous drug administration. The recently completed pivotal Phase 2b/3 study (ZOTRIP), evaluating ADAM zolmitriptan for the treatment of acute moderate to severe migraine, was one of the first large studies to incorporate MBS freedom and pain freedom as co-primary endpoints per recently issued guidance by the US Food and Drug Administration. In this trial, the proportion of patients treated with ADAM zolmitriptan 3.8 mg, who were pain-free and MBS-free at 2 hours post-dose, was significantly higher than for placebo.MethodsWe undertook a post-hoc analysis of data from the ZOTRIP trial to examine how the outcomes from this trial compare to what might have been achieved using the conventional co-primary endpoints of pain relief, nausea, photophobia, and phonophobia.ResultsOf the 159 patients treated with ADAM zolmitriptan 3.8Ā mg or placebo, prospectively designated MBS were photophobia (nā€‰=ā€‰79), phonophobia (nā€‰=ā€‰43), and nausea (nā€‰=ā€‰37). Two-hour pain free rates in those with photophobia as the MBS were 36% for ADAM zolmitriptan 3.8 mg and 14% for placebo (Pā€‰=ā€‰.02). Corresponding rates for those with phonophobia as the MBS were 14% and 41% (Pā€‰=ā€‰.05). For those whose MBS was nausea, corresponding values were 56% and 16%, respectively (Pā€‰=ā€‰.01). Two-hour freedom from the MBS for active drug vs placebo were 67% vs 35% (Pā€‰&lt;ā€‰.01) for photophobia, 55% vs 43% (Pā€‰=ā€‰.45) for phonophobia, and 89% vs 58% for nausea (Pā€‰=ā€‰.04). MBS freedom but not pain freedom was achieved in 28%. Only 1 patient (1%) achieved pain freedom, but not MBS freedom. The proportion with both pain and MBS freedom was highest (56%) among those whose MBS was nausea.ConclusionIn this study, the use of MBS was feasible and seemed to compare favorably to the previously required 4 co-primary endpoints

    Topology and Bistability in liquid crystal devices

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    We study nematic liquid crystal configurations in a prototype bistable device - the Post Aligned Bistable Nematic (PABN) cell. Working within the Oseen-Frank continuum model, we describe the liquid crystal configuration by a unit-vector field, in a model version of the PABN cell. Firstly, we identify four distinct topologies in this geometry. We explicitly construct trial configurations with these topologies which are used as initial conditions for a numerical solver, based on the finite-element method. The morphologies and energetics of the corresponding numerical solutions qualitatively agree with experimental observations and suggest a topological mechanism for bistability in the PABN cell geometry

    Exploring Contractor Renormalization: Tests on the 2-D Heisenberg Antiferromagnet and Some New Perspectives

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    Contractor Renormalization (CORE) is a numerical renormalization method for Hamiltonian systems that has found applications in particle and condensed matter physics. There have been few studies, however, on further understanding of what exactly it does and its convergence properties. The current work has two main objectives. First, we wish to investigate the convergence of the cluster expansion for a two-dimensional Heisenberg Antiferromagnet(HAF). This is important because the linked cluster expansion used to evaluate this formula non-perturbatively is not controlled by a small parameter. Here we present a study of three different blocking schemes which reveals some surprises and in particular, leads us to suggest a scheme for defining successive terms in the cluster expansion. Our second goal is to present some new perspectives on CORE in light of recent developments to make it accessible to more researchers, including those in Quantum Information Science. We make some comparison to entanglement-based approaches and discuss how it may be possible to improve or generalize the method.Comment: Completely revised version accepted by Phy Rev B; 13 pages with added material on entropy in COR

    Effects of weak anchoring on C1 and C2 chevron structures

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    We present a theoretical study of the effect of weak anchoring on the transition between C1 and C2 chevron structures in smectic C liquid crystals. We employ a continuum theory which allows for variable cone, azimuthal and layer tilt angles. Equilibrium profiles for the director cone and azimuthal angles in the C1 and C2 states are calculated from the standard Euler-Lagrange minimisation of the total energy of the system. By comparing the total energies of the C1 and C2 states we can determine the globally stable chevron profile and calculate the critical temperature for the C1-C2 transition, which depends on anchoring strength and pretilt angle variations
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