7,942 research outputs found

    Transcatheter Tricuspid Valve Intervention The Next Frontier∗

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    パリ詩篇(フランス国立図書館所蔵の写本 Fonds latin, 8824)に 収録されている古英語で書かれた散文と韻文による詩篇の翻訳について

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    ウェセックスのアルフレッド王の作とされる古英語散文の詩篇と10世紀に書かれた作者不詳の韻文の詩編を比較し、どのような方法で翻訳が行われているのか、詩篇の解釈にどれほど準拠しているのか、解釈の焦点をどこに合わせているのか、について論じる。特に韻文の詩篇の文体的および修辞的特徴について考察する

    Distributional fixed point equations for island nucleation in one dimension: a retrospective approach for capture zone scaling

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    The distributions of inter-island gaps and captures zones for islands nucleated on a one-dimensional substrate during submonolayer deposition are considered using a novel retrospective view. This provides an alternative perspective on why scaling occurs in this continuously evolving system. Distributional fixed point equations for the gaps are derived both with and without a mean field approximation for nearest neighbour gap size correlation. Solutions to the equations show that correct consideration of fragmentation bias justifies the mean field approach which can be extended to provide closed-from equations for the capture zones. Our results compare favourably to Monte Carlo data for both point and extended islands using a range of critical island size i=0,1,2,3i=0,1,2,3. We also find satisfactory agreement with theoretical models based on more traditional fragmentation theory approaches.Comment: 9 pages, 7 figures and 1 tabl

    Oocyte size, egg index, and body lipid content in relation to body size in the solitary bee Megachile rotundata

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    Females of solitary, nest-provisioning bees have relatively low fecundity, but produce large eggs as part of their overall strategy of investing substantially in each offspring. In intraspecific comparisons of several species of solitary, nest-provisioning bees and wasps, the size of the mature eggs produced increases with female body size. We further examined oocyte size–body size correlations in the solitary bee Megachile rotundata (F.), an important crop pollinator. We hypothesized that larger females carry larger basal oocytes (i.e., those next in line to be oviposited) but that body size–oocyte size correlations would be absent soon after emergence, before their first eggs fully matured. Because egg production is likely affected by the quantity of stored lipids carried over from the bees’ immature stages, we also tested the hypothesis that female body size is correlated with the body lipid content at adult emergence, the time during which oocyte growth accelerates. We found significant correlations of body size with oocyte size variables chosen to reflect: (1) the magnitude of the investment in the next egg to be laid (i.e., the length and volume of the basal oocyte) and (2) the longer term potential to produce mature oocytes (i.e., the summed lengths and volumes of the three largest oocytes in each female). Positive correlations existed throughout the nesting season, even during the first week following adult emergence. The ability to produce and carry larger oocytes may be linked to larger females starting the nesting season with greater lipid stores (which we document here) or to greater space within the abdomen of larger females. Compared to other species of solitary bees, M. rotundata appears to have (1) smaller oocytes than solitary nest-provisioning bees in general, (2) comparable oocyte sizes relative to congeners, and (3) larger oocytes than related brood parasitic megachilids

    The random phase approximation applied to ice

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    Standard density functionals without van der Waals interactions yield an unsatisfactory description of ice phases, specifically, high density phases occurring under pressure are too unstable compared to the common low density phase Ih_h observed at ambient conditions. Although the description is improved by using functionals that include van der Waals interactions, the errors in relative volumes remain sizable. Here we assess the random phase approximation (RPA) for the correlation energy and compare our results to experimental data as well as diffusion Monte Carlo data for ice. The RPA yields a very balanced description for all considered phases, approaching the accuracy of diffusion Monte Carlo in relative energies and volumes. This opens a route towards a concise description of molecular water phases on surfaces and in cavities

    The Pre-Appointment Experience of Supreme Court Justices

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    Benjamin H. Barton’s recent article, An Empirical Study of Supreme Court Justice Pre-Appointment Experience, makes a significant contribution to the growing body of work that compares and contrasts the professional and educational backgrounds of the current members of the Roberts Court with their predecessors. I share Professor Barton’s concerns

    Limit curve theorems in Lorentzian geometry

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    The subject of limit curve theorems in Lorentzian geometry is reviewed. A general limit curve theorem is formulated which includes the case of converging curves with endpoints and the case in which the limit points assigned since the beginning are one, two or at most denumerable. Some applications are considered. It is proved that in chronological spacetimes, strong causality is either everywhere verified or everywhere violated on maximizing lightlike segments with open domain. As a consequence, if in a chronological spacetime two distinct lightlike lines intersect each other then strong causality holds at their points. Finally, it is proved that two distinct components of the chronology violating set have disjoint closures or there is a lightlike line passing through each point of the intersection of the corresponding boundaries.Comment: 25 pages, 1 figure. v2: Misprints fixed, matches published versio

    Mean curvature flow and quasilocal mass for two-surfaces in Hamiltonian General Relativity

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    A family of quasilocal mass definitions that includes as special cases the Hawking mass and the Brown-York ``rest mass'' energy is derived for spacelike 2-surfaces in spacetime. The definitions involve an integral of powers of the norm of the spacetime mean curvature vector of the 2-surface, whose properties are connected with apparent horizons. In particular, for any spacelike 2-surface, the direction of mean curvature is orthogonal (dual in the normal space) to a unique normal direction in which the 2-surface has vanishing expansion in spacetime. The quasilocal mass definitions are obtained by an analysis of boundary terms arising in the gravitational ADM Hamiltonian on hypersurfaces with a spacelike 2-surface boundary, using a geometric time-flow chosen proportional to the dualized mean curvature vector field at the boundary surface. A similar analysis is made choosing a geometric rotational flow given in terms of the twist covector of the dual pair of mean curvature vector fields, which leads to a family of quasilocal angular momentum definitions involving the squared norm of the twist. The large sphere limit of these definitions is shown to yield the ADM mass and angular momentum in asymptotically flat spacetimes, while at apparent horizons a quasilocal version of the Gibbons-Penrose inequality is derived. Finally, some results concerning positivity are proved for the quasilocal masses, motivated by consideration of spacelike mean curvature flow of 2-surfaces in spacetime.Comment: Revised version, includes an analysis of null flows with applications to mass and angular momentum for apparent horizon

    Unsteady flow around a Rectangular Cylinder

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    This paper describes an investigation into the unsteady flow behaviour around a rectangular cylinder using particle image velocimetry (PIV). Instantaneous and average velocity fields were obtained from PIV images. Analysis of the structures observed in the instantaneous velocity fields reveals the presence of small scale (Kelvin-Helmholtz) vortex structures in the shear layer that separates at the leading edge of the rectangular cylinder, and evidence of von Karman vortex shedding was observed in the wake region

    The effect on survival of early detection of breast cancer in South Australia

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    Early detection of breast cancer is an important public health policy. Programs of regular screening examinations have been widely established in an attempt to detect the disease when the primary tumour diameter is small. In South Australia, BreastScreen SA suggests that women between the ages of 50 and 70 years be screened every 24 months. Our aim in this paper is to make assessments of various screening procedures by using statistical models with parameters estimated exclusively from South Australian data. We establish a relationship between primary tumour diameter and ultimate survival time. We estimate an advantage of 2.9 (.7) years in median survival time for those women detected with the disease by BreastScreen SA, compared with an unscreened population. We construct a computer model from which we determine the consequences of using a 12 month screening interval, and also the effect of beginning screening at the age of 40 rather than the current conventional commencement age of 50 years
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