7,744 research outputs found

    Binary spinning black hole Hamiltonian in canonical center-of-mass and rest-frame coordinates through higher post-Newtonian order

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    The recently constructed Hamiltonians for spinless binary black holes through third post-Newtonian order and for spinning ones through formal second post-Newtonian order, where the spins are counted of zero post-Newtonian order, are transformed into fully canonical center-of-mass and rest-frame variables. The mixture terms in the Hamiltonians between center-of-mass and rest-frame variables are in accordance with the relation between the total linear momentum and the center-of-mass velocity as demanded by global Lorentz invariance. The various generating functions for the center-of-mass and rest-frame canonical variables are explicitly given in terms of the single-particle canonical variables. The no-interaction theorem does not apply because the world-line condition of Lorentz covariant position variables is not imposed.Comment: 18 pages, no figure

    Expedient and Monotone Learning Rules

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    This paper considers learning rules for environments in which little prior and feedback information is available to the decision-maker. Two properties of such learning rules, absolute expediency and monotonicity, are studied. The paper provides some necessary and some sufficient conditions for these properties. A number of examples show that there is quite a large variety of learning rules which have these properties. It is also shown that all learning rules that have these properties are, in some sense, related to replicator dynamics of evolutionary game theory.Absolute expediency, monotonicity, learning rule, decision making

    Shock-wave therapy of gastric outlet syndrome caused by a gallstone

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    A patient with gastric outlet syndrome (Bouveret's syndrome) caused by a large gallstone impacted in the duodenal bulb was successfully treated by extracorporeal shock-wave lithotripsy. Thus, open abdominal surgery could be avoided. For disintegration of the stone, three consecutive lithotripsy procedures were necessary. Thereafter, stone fragments could be extracted endoscopically. Extracorporeal shock-wave lithotripsy could become a non-surgical alternative in patients with obstruction of the duodenum caused by a gallstone

    Binary spinning black hole Hamiltonian in canonical center-of-mass and rest-frame coordinates through higher post-Newtonian order

    Full text link
    The recently constructed Hamiltonians for spinless binary black holes through third post-Newtonian order and for spinning ones through formal second post-Newtonian order, where the spins are counted of zero post-Newtonian order, are transformed into fully canonical center-of-mass and rest-frame variables. The mixture terms in the Hamiltonians between center-of-mass and rest-frame variables are in accordance with the relation between the total linear momentum and the center-of-mass velocity as demanded by global Lorentz invariance. The various generating functions for the center-of-mass and rest-frame canonical variables are explicitly given in terms of the single-particle canonical variables. The no-interaction theorem does not apply because the world-line condition of Lorentz covariant position variables is not imposed.Comment: 18 pages, no figure

    How Many Bucks in a Bang: On the Estimation of the Economic Costs of Conflict

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    The estimation of the costs of conflict is currently receiving a lot of attention in the literature. This paper aims to give a thorough overview of the existing literature, first by addressing the history of case studies that address conflict costs and second by looking at the existing body of cross-country analyses for conflict costs. In addition to the existing cross-country literature, a number of studies that only concern themselves with particular elements of conflict costs are included as well. In the end, this paper combines the insights from these previous analyses to explore how much room there is to further improve the existing studies. Specific recommendations are given how to proceed with the development of the field of conflict cost measurement.Conflict, costs of conflict, case studies

    Does Security Play a Role in European Development Aid Policy?

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    In this Policy Briefing we address the question of whether there is a coherent and consistent policy when it comes to giving development aid. While one would theoretically argue that aid provision should be based on objective criteria set out to optimize governments' behavior or people's welfare, we find that this is not the case. While specific countries may be optimizing their objectives in international aidgiving, the cumulative effect, particularly when it comes to European policy is incoherent and inconsistent. Coordinating development policy at the European level could alleviate this problem.

    How Many Bucks in a Bang: On the Estimation of the Economic Costs of Conflict

    Get PDF
    The estimation of the costs of conflict is currently receiving a lot of attention in the literature. This paper aims to give a thorough overview of the existing literature, first by addressing the history of case studies that address conflict costs and second by looking at the existing body of cross-country analyses for conflict costs. In addition to the existing cross-country literature, a number of studies that only concern themselves with particular elements of conflict costs are included as well. In the end, this paper combines the insights from these previous analyses to explore how much room there is to further improve the existing studies. Specific recommendations are given how to proceed with the development of the field of conflict cost measurement.Conflict, costs of conflict, case studies

    Fast T2 Mapping with Improved Accuracy Using Undersampled Spin-echo MRI and Model-based Reconstructions with a Generating Function

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    A model-based reconstruction technique for accelerated T2 mapping with improved accuracy is proposed using undersampled Cartesian spin-echo MRI data. The technique employs an advanced signal model for T2 relaxation that accounts for contributions from indirect echoes in a train of multiple spin echoes. An iterative solution of the nonlinear inverse reconstruction problem directly estimates spin-density and T2 maps from undersampled raw data. The algorithm is validated for simulated data as well as phantom and human brain MRI at 3 T. The performance of the advanced model is compared to conventional pixel-based fitting of echo-time images from fully sampled data. The proposed method yields more accurate T2 values than the mono-exponential model and allows for undersampling factors of at least 6. Although limitations are observed for very long T2 relaxation times, respective reconstruction problems may be overcome by a gradient dampening approach. The analytical gradient of the utilized cost function is included as Appendix.Comment: 10 pages, 7 figure
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