16,093 research outputs found

    In vivo contact stresses at the radiocarpal joint using a finite element method of the complete wrist joint

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    A small number of cadaveric studies have been carried out looking at the force transmission through the radiocarpal joint. In this study subject specific finite element models were created of the whole wrist joint using measured biomechanical data to capture the forces acting on the wrist with the hand generating a maximum gripping force

    A multinomial quadrivariate D-vine copula mixed model for meta-analysis of diagnostic studies in the presence of non-evaluable subjects

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    Diagnostic test accuracy studies observe the result of a gold standard procedure that defines the presence or absence of a disease and the result of a diagnostic test. They typically report the number of true positives, false positives, true negatives and false negatives. However, diagnostic test outcomes can also be either non-evaluable positives or non-evaluable negatives. We propose a novel model for the meta-analysis of diagnostic studies in the presence of non-evaluable outcomes, which assumes independent multinomial distributions for the true and non-evaluable positives, and, the true and non-evaluable negatives, conditional on the latent sensitivity, specificity, probability of non-evaluable positives and probability of non-evaluable negatives in each study. For the random effects distribution of the latent proportions, we employ a drawable vine copula that can successively model the dependence in the joint tails. Our methodology is demonstrated with an extensive simulation study and applied to data from diagnostic accuracy studies of coronary computed tomography angiography for the detection of coronary artery disease. The comparison of our method with the existing approaches yields findings in the real data application that change the current conclusions

    Distributed lag models for hydrological data

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    The distributed lag model (DLM), used most prominently in air pollution studies, finds application wherever the effect of a covariate is delayed and distributed through time. We explore the use of modified formulations of DLMs to provide flexible varying-coeficient models with smoothness constraints, applicable in any setting in which lagged covariates are regressed on a time-dependent response. The models are applied to simulated flow and rainfall data and to flow data from a Scottish mountain river, with particular emphasis on approximating the relationship between environmental covariates and flow regimes in order to detect the influence of unobserved processes. It was found that under certain rainfall conditions some of the variability in the influence of rainfall on flow arises through a complex interaction between antecedent ground wetness and the time-delay in rainfall. The models are able to identify subtle changes in rainfall response, particularly in the location of peak influence in the lag structure and offer a computationally attractive approach for fitting DLMs

    Bridging the Climate Information Gap: A Framework for Engaging Knowledge Brokers and Decision Makers in State Climate Assessments

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    Large-scale analyses like the National Climate Assessment (NCA) contain a wealth of information critical to national and regional responses to climate change but tend to be insufficiently detailed for action at state or local levels. Many states now engage in assessment processes to meet information needs for local authorities. The goals of state climate assessments (SCAs) should be to provide relevant, actionable information to state and local authorities, and to generate primary sources, build networks and inform stakeholders. To communicate local climate impacts to decision makers, SCAs should express credibility, salience and legitimacy. They can provide information (e.g., case studies, data sets) and connect stakeholders to the NCA and its process. Based on our experience in the Vermont Climate Assessment (VCA), we present a framework to engage decision makers in SCAs using a fluid network of scientific experts and knowledge brokers to conduct subject area prioritization, data analysis and writing. The VCA addressed economic, environmental and social impacts of climate change at local scales to increase resiliency and manage risk. Knowledge brokers communicated VCA findings through their own stakeholder networks. We include a qualitative impact evaluation, and believe our framework for interaction among scientists, knowledge brokers and stakeholders to be an effective structure for SCAs and a transformative experience for students

    Decidability Results for Multi-objective Stochastic Games

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    We study stochastic two-player turn-based games in which the objective of one player is to ensure several infinite-horizon total reward objectives, while the other player attempts to spoil at least one of the objectives. The games have previously been shown not to be determined, and an approximation algorithm for computing a Pareto curve has been given. The major drawback of the existing algorithm is that it needs to compute Pareto curves for finite horizon objectives (for increasing length of the horizon), and the size of these Pareto curves can grow unboundedly, even when the infinite-horizon Pareto curve is small. By adapting existing results, we first give an algorithm that computes the Pareto curve for determined games. Then, as the main result of the paper, we show that for the natural class of stopping games and when there are two reward objectives, the problem of deciding whether a player can ensure satisfaction of the objectives with given thresholds is decidable. The result relies on intricate and novel proof which shows that the Pareto curves contain only finitely many points. As a consequence, we get that the two-objective discounted-reward problem for unrestricted class of stochastic games is decidable.Comment: 35 page

    Equilibrium structure and bonding of small iron-carbon clusters

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    The equilibrium geometries, binding energies, and electronic structure of neutral FeC n (n≤3) clusters have been calculated self‐consistently using ab initio molecular orbital theory. The exchange and correlation contributions to the total energy were computed using both the density functional method (with and without nonlocal correction) as well as the Hartree–Fock–Möller–Plesset theory. All levels of theory predict the equilibrium geometries to be cyclic. The binding energies, bond lengths, and the Mulliken charges obtained from both methods of calculations are also in agreement. The results are compared with recent mobility and photoelectron spectroscopy experiments

    Size reconstructibility of graphs

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    The deck of a graph GG is given by the multiset of (unlabelled) subgraphs {Gv:vV(G)}\{G-v:v\in V(G)\}. The subgraphs GvG-v are referred to as the cards of GG. Brown and Fenner recently showed that, for n29n\geq29, the number of edges of a graph GG can be computed from any deck missing 2 cards. We show that, for sufficiently large nn, the number of edges can be computed from any deck missing at most 120n\frac1{20}\sqrt{n} cards.Comment: 15 page