7,617 research outputs found

    Model-independent assessment of current direct searches for spin-dependent dark matter

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    I evaluate the current results of spin-dependent weakly interacting massive particle (WIMP) searches within a model-independent framework, showing the most restrictive limits to date derive from the combination of xenon and sodium iodide experiments. The extension of this analysis to the case of positive signal experiments is elaborated.Comment: 4 pages, 4 figures, revised and accepted for publication on Phys. Rev. Let

    Cow, farm, and herd management factors in the dry period associated with raised somatic cell counts in early lactation

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    This study investigated cow characteristics, farm facilities, and herd management strategies during the dry period to examine their joint influence on somatic cell counts (SCC) in early lactation. Data from 52 commercial dairy farms throughout England and Wales were collected over a 2-yr period. For the purpose of analysis, cows were separated into those housed for the dry period (6,419 cow-dry periods) and those at pasture (7,425 cow-dry periods). Bayesian multilevel models were specified with 2 response variables: ln SCC (continuous) and SCC >199,000 cells/mL (binary), both within 30 d of calving. Cow factors associated with an increased SCC after calving were parity, an SCC >199,000 cells/mL in the 60 d before drying off, increasing milk yield 0 to 30 d before drying off, and reduced DIM after calving at the time of SCC estimation. Herd management factors associated with an increased SCC after calving included procedures at drying off, aspects of bedding management, stocking density, and method of pasture grazing. Posterior predictions were used for model assessment, and these indicated that model fit was generally good. The research demonstrated that specific dry-period management strategies have an important influence on SCC in early lactation

    Impact of imperfect test sensitivity on determining risk factors : the case of bovine tuberculosis

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    Background Imperfect diagnostic testing reduces the power to detect significant predictors in classical cross-sectional studies. Assuming that the misclassification in diagnosis is random this can be dealt with by increasing the sample size of a study. However, the effects of imperfect tests in longitudinal data analyses are not as straightforward to anticipate, especially if the outcome of the test influences behaviour. The aim of this paper is to investigate the impact of imperfect test sensitivity on the determination of predictor variables in a longitudinal study. Methodology/Principal Findings To deal with imperfect test sensitivity affecting the response variable, we transformed the observed response variable into a set of possible temporal patterns of true disease status, whose prior probability was a function of the test sensitivity. We fitted a Bayesian discrete time survival model using an MCMC algorithm that treats the true response patterns as unknown parameters in the model. We applied our approach to epidemiological data of bovine tuberculosis outbreaks in England and investigated the effect of reduced test sensitivity in the determination of risk factors for the disease. We found that reduced test sensitivity led to changes to the collection of risk factors associated with the probability of an outbreak that were chosen in the ‘best’ model and to an increase in the uncertainty surrounding the parameter estimates for a model with a fixed set of risk factors that were associated with the response variable. Conclusions/Significance We propose a novel algorithm to fit discrete survival models for longitudinal data where values of the response variable are uncertain. When analysing longitudinal data, uncertainty surrounding the response variable will affect the significance of the predictors and should therefore be accounted for either at the design stage by increasing the sample size or at the post analysis stage by conducting appropriate sensitivity analyses

    Ludii -- The Ludemic General Game System

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    While current General Game Playing (GGP) systems facilitate useful research in Artificial Intelligence (AI) for game-playing, they are often somewhat specialised and computationally inefficient. In this paper, we describe the "ludemic" general game system Ludii, which has the potential to provide an efficient tool for AI researchers as well as game designers, historians, educators and practitioners in related fields. Ludii defines games as structures of ludemes -- high-level, easily understandable game concepts -- which allows for concise and human-understandable game descriptions. We formally describe Ludii and outline its main benefits: generality, extensibility, understandability and efficiency. Experimentally, Ludii outperforms one of the most efficient Game Description Language (GDL) reasoners, based on a propositional network, in all games available in the Tiltyard GGP repository. Moreover, Ludii is also competitive in terms of performance with the more recently proposed Regular Boardgames (RBG) system, and has various advantages in qualitative aspects such as generality.Comment: Accepted at ECAI 202

    Quantum oscillations and a non-trivial Berry phase in the noncentrosymmetric superconductor BiPd

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    We report the measurements of de Haas-van Alphen (dHvA) oscillations in the noncentrosymmetric superconductor BiPd. Several pieces of a complex multi-sheet Fermi surface are identified, including a small pocket (frequency 40 T) which is three dimensional and anisotropic. From the temperature dependence of the amplitude of the oscillations, the cyclotron effective mass is (0.180.18 ±\pm 0.1) mem_e. Further analysis showed a non-trivial π\pi-Berry phase is associated with the 40 T pocket, which strongly supports the presence of topological states in bulk BiPd and may result in topological superconductivity due to the proximity coupling to other bands.Comment: 5 pages, 3 figure

    Discovery of Griffiths phase in itinerant magnetic semiconductor Fe_{1-x}Co_xS_2

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    Critical points that can be suppressed to zero temperature are interesting because quantum fluctuations have been shown to dramatically alter electron gas properties. Here, the metal formed by Co doping the paramagnetic insulator FeS2_2, Fe1x_{1-x}Cox_xS2_2, is demonstrated to order ferromagnetically at x>xc=0.01±0.005x>x_c=0.01\pm0.005 where we observe unusual transport, magnetic, and thermodynamic properties. We show that this magnetic semiconductor undergoes a percolative magnetic transition with distinct similarities to the Griffiths phase, including singular behavior at xcx_c and zero temperature.Comment: 10 pages, 4 figure

    Associations between physical activity and depressive symptoms by weight status among adults with type 2 diabetes: Results from diabetes miles-Australia

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    © 2017 Human Kinetics, Inc. Background: To examine associations between physical activity (PA) and depressive symptoms among adults with type 2 diabetes mellitus (Type 2 DM), and whether associations varied according to weight status. Methods: Diabetes MILES-Australia is a national survey of adults with diabetes, focused on behavioral and psychosocial issues. Data from 705 respondents with Type 2 DM were analyzed, including: demographic and clinical characteristics, PA (IPAQ-SF), depressive symptoms (PHQ-9), and BMI (self-reported height and weight). Data analysis was performed using ANCOVA. Results: Respondents were aged 59 ± 8 years; 50% women. PA was negatively associated with depressive symptoms for the overall sample (?p 2= 0.04,P < .001) and all weight categories separately: healthy (?p 2 0.11 P = .041,), overweight (?p 2= 0.04, P = .025) and obese (?p 2 = 0.03, P = .007). For people who were healthy (BMI 18.5 to 24.9) or overweight (BMI 25 to 29.9), high amounts of PA were significantly associated with fewer depressive symptoms; for adults who were obese (BMI ? 30) however, both moderate and high amounts were associated with fewer depressive symptoms. Conclusions: PA is associated with fewer depressive symptoms among adults with Type 2DM, however the amount of PA associated with fewer depressive symptoms varies according to weight status. Lower amounts of PA might be required for people who are obese to achieve meaningful reductions in depressive symptoms compared with those who are healthy weight or overweight. Further research is needed to establish the direction of the relationship between PA and depressive symptoms

    The Físchlár digital video system: a digital library of broadcast TV programmes

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    Físchlár is a system for recording, indexing, browsing and playback of broadcast TV programmes which has been operational on our University campus for almost 18 months. In this paper we give a brief overview of how the system operates, how TV programmes are organised for browse/playback and a short report on the system usage by over 900 users in our University
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