7,415 research outputs found

    A catalogue of velocities in the cluster of galaxies Abell 85

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    We present a catalogue of velocities for 551 galaxies (and give the coordinates of 39 stars misclassified as galaxies in our photometric plate catalogue) in a region covering about 100'×\times100' (0.94×\times0.94 Mpc for an average redshift of 0.0555, assuming H∘_\circ=50 km s−1^{-1} Mpc−1^{-1}) in the direction of the rich cluster Abell 85. This catalogue includes previously published redshifts by Beers et al. (1991) and Malumuth et al. (1992), together with our 367 new measurements. A total of 305 galaxies have velocities in the interval 13350-20000 km s−1^{-1}, and will be considered as members of the cluster. Abell 85 therefore becomes one of the clusters with the highest number of measured redshifts; its optical properties are being investigated in a companion paper.Comment: Accepted for publication in A&AS, Table 4 available in electronic form onl

    Zeolite phi: a physical mixture of chabazite and offretite

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    Zeolite Phi is synthesized by two methods reported previously. Results from X-ray powder diffraction and scanning electron microscopy suggest that the materials are physical mixtures of chabazite and offretite; one sample has a small amount of phillipsite. The X-ray powder diffraction data from these samples, and those reported previously, are indexed and their unit-cell parameters compare well to those obtained from a physical mixture of chabazite and offretite. These samples show multiple particle morphologies that are indicative of physical mixtures. Zeolite Phi is concluded to be a physical mixture of chabazite and offretite and we suggest that the use of the name zeolite Phi be discontinued

    Security policy refinement using data integration: a position paper.

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    In spite of the wide adoption of policy-based approaches for security management, and many existing treatments of policy verification and analysis, relatively little attention has been paid to policy refinement: the problem of deriving lower-level, runnable policies from higher-level policies, policy goals, and specifications. In this paper we present our initial ideas on this task, using and adapting concepts from data integration. We take a view of policies as governing the performance of an action on a target by a subject, possibly with certain conditions. Transformation rules are applied to these components of a policy in a structured way, in order to translate the policy into more refined terms; the transformation rules we use are similar to those of global-as-view database schema mappings, or to extensions thereof. We illustrate our ideas with an example. Copyright 2009 ACM

    Complex stimulus control in humans: Merging functional and equivalence classes

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    This dissertation investigated the merging of functional and equivalence classes produced by training responding to either simple or conditional discriminations. Experiment 1 targeted the acquisition of three three-member equivalence classes featuring class-specific reinforcers and three three-member functional classes each controlling the occurrence of a nonsense vocal response. Four female college students completed testing for the targeted stimulus classes. Two subjects demonstrated class-consistent emergent responding, but only one of them maintained class-consistent responding across repeated testing. This student withdrew from the experiment before class merging was arranged. Experiment 2 simplified and expedited the procedures for producing independent emergent classes. Four female college students demonstrated class-consistent responding for three three-member equivalence classes and three two-member functional classes. Classes merged successfully after subjects completed training relating each equivalence class to a functional class via one simple or conditional discrimination. Subsequently, each merged class was expanded by training one additional simple or conditional discrimination

    Linearized stability analysis of gravastars in noncommutative geometry

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    In this work, we find exact gravastar solutions in the context of noncommutative geometry, and explore their physical properties and characteristics. The energy density of these geometries is a smeared and particle-like gravitational source, where the mass is diffused throughout a region of linear dimension (α)\sqrt{(\alpha)} due to the intrinsic uncertainty encoded in the coordinate commutator. These solutions are then matched to an exterior Schwarzschild spacetime. We further explore the dynamical stability of the transition layer of these gravastars, for the specific case of β=M2/α<1.9\beta=M^2/\alpha<1.9, where M is the black hole mass, to linearized spherically symmetric radial perturbations about static equilibrium solutions. It is found that large stability regions exist and, in particular, located sufficiently close to where the event horizon is expected to form.Comment: 6 pages, 3 figure
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