1,180 research outputs found

    Simulating Your Estate Transfer Alternatives (Input Form)

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    Spike-and-Slab Priors for Function Selection in Structured Additive Regression Models

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    Structured additive regression provides a general framework for complex Gaussian and non-Gaussian regression models, with predictors comprising arbitrary combinations of nonlinear functions and surfaces, spatial effects, varying coefficients, random effects and further regression terms. The large flexibility of structured additive regression makes function selection a challenging and important task, aiming at (1) selecting the relevant covariates, (2) choosing an appropriate and parsimonious representation of the impact of covariates on the predictor and (3) determining the required interactions. We propose a spike-and-slab prior structure for function selection that allows to include or exclude single coefficients as well as blocks of coefficients representing specific model terms. A novel multiplicative parameter expansion is required to obtain good mixing and convergence properties in a Markov chain Monte Carlo simulation approach and is shown to induce desirable shrinkage properties. In simulation studies and with (real) benchmark classification data, we investigate sensitivity to hyperparameter settings and compare performance to competitors. The flexibility and applicability of our approach are demonstrated in an additive piecewise exponential model with time-varying effects for right-censored survival times of intensive care patients with sepsis. Geoadditive and additive mixed logit model applications are discussed in an extensive appendix

    Fluctuations of radiation from a chaotic laser below threshold

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    Radiation from a chaotic cavity filled with gain medium is considered. A set of coupled equations describing the photon density and the population of gain medium is proposed and solved. The spectral distribution and fluctuations of the radiation are found. The full noise is a result of a competition between positive correlations of photons with equal frequencies (due to stimulated emission and chaotic scattering) which increase fluctuations, and a suppression due to interaction with a gain medium which leads to negative correlations between photons. The latter effect is responsible for a pronounced suppression of the photonic noise as compared to the linear theory predictions.Comment: 7 pages, 5 figures; expanded version, to appear in Phys. Rev.

    The TIGRE gamma-ray telescope

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    TIGRE is an advanced telescope for gamma-ray astronomy with a few arcmin resolution. From 0.3 to 10 MeV it is a Compton telescope. Above 1 MeV, its multi-layers of double sided silicon strip detectors allow for Compton recoil electron tracking and the unique determination for incident photon direction. From 10 to 100 MeV the tracking feature is utilized for gamma-ray pair event reconstruction. Here we present TIGRE energy resolutions, background simulations and the development of the electronics readout system

    Insufficient Reporting of Factors Associated with Exercise Referral Scheme Uptake, Attendance, and Adherence: A Systematic Review of Reviews

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    Background: Exercise Referral Schemes (ERS) are prescribed programmes aimed at tackling physical inactivity and associated non-communicable disease. Inconsistencies in reporting, recording and delivering ERS make it challenging to identify what works, why, and for whom. Methods: PRISMA guided this narrative review of reviews. Fifteen electronic databases were searched for systematic reviews of ERS. Reviewers applied inclusion criteria and quality assessed via the AMSTAR tool. Data on uptake, attendance and adherence were extracted. Results: Eleven reviews met the inclusion criteria. AMSTAR quality was medium. Definitions of uptake varied within reviews. Uptake ranged from 35%-81%. Groups reported as more likely to take up ERS included, (i) females and (ii) older adults. Attendance was defined variably but ranged from 12%-49%. Men were more likely to attend ERS. Effect of medical diagnosis upon uptake and attendance was inconsistent. Exercises prescribed were unreported and therefore, adherence to exercise prescriptions was unreported. The influence of theoretically-informed approaches on uptake, attendance and adherence was generally lacking, however, self-determination, peer support and supervision support were reported as influencing attendance. Conclusions: There was insufficient reporting across studies about uptake, attendance and adherence. Complex interventions like ERS require consistent definitions, recording and reporting of these key facets, but this is not evident from the existing literature

    Freezing by Monte Carlo Phase-Switch

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    We describe a Monte Carlo procedure which allows sampling of the disjoint configuration spaces associated with crystalline and fluid phases, within a single simulation. The method utilises biased sampling techniques to enhance the probabilities of gateway states (in each phase) which are such that a global switch (to the other phase) can be implemented. Equilibrium freezing-point parameters can be determined directly; statistical uncertainties prescribed transparently; and finite-size effects quantified systematically. The method is potentially quite general; we apply it to the freezing of hard spheres.Comment: 5 pages, 2 figure
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