367 research outputs found

    Introduction to papers on astrostatistics

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    We are pleased to present a Special Section on Statistics and Astronomy in this issue of the The Annals of Applied Statistics. Astronomy is an observational rather than experimental science; as a result, astronomical data sets both small and large present particularly challenging problems to analysts who must make the best of whatever the sky offers their instruments. The resulting statistical problems have enormous diversity. In one problem, one may have to carefully quantify uncertainty in a hard-won, sparse data set; in another, the sheer volume of data may forbid a formally optimal analysis, requiring judicious balancing of model sophistication, approximations, and clever algorithms. Often the data bear a complex relationship to the underlying phenomenon producing them, much in the manner of inverse problems.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS234 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Bayesian Analysis of the (Generalized) Chaplygin Gas and Cosmological Constant Models using the 157 gold SNe Ia Data

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    The generalized Chaplygin gas model (GCGM) contains 5 free parameters, here, they are constrained through the type Ia supernovae data, i.e., the ``gold sample'' of 157 supernovae data. Negative and large positive values for α\alpha are taken into account. The analysis is made by employing the Bayesian statistics and the prediction for each parameter is obtained by marginalizing on the remained ones. This procedure leads to the following predictions: α=−0.75−0.24+4.04\alpha = - 0.75^{+4.04}_{-0.24}, H0=65.00−1.75+1.77H_0=65.00^{+1.77}_{-1.75}, Ωk0=−0.77−5.94+1.14\Omega_{k0} = - 0.77^{+1.14}_{-5.94}, Ωm0=0.00−0.00+1.95\Omega_{m0} = 0.00^{+1.95}_{-0.00}, Ωc0=1.36−0.85+5.36\Omega_{c0} = 1.36^{+5.36}_{-0.85}, Aˉ=1.000−0.534+0.000\bar A = 1.000^{+0.000}_{-0.534}. Through the same analysis the specific case of the ordinary Chaplygin gas model (CGM), for which α=1\alpha = 1, is studied. In this case, there are now four free parameters and the predictions for them are: H0=65.01−1.71+1.81H_0 = 65.01^{+1.81}_{-1.71}, Ωk0=−2.73−0.97+1.53\Omega_{k0} = - 2.73^{+1.53}_{-0.97}, Ωm0=0.00−0.00+1.22\Omega_{m0} = 0.00^{+1.22}_{-0.00}, Ωc0=1.34−0.70+0.94\Omega_{c0} = 1.34^{+0.94}_{-0.70}, Aˉ=1.000−0.270+0.000\bar A = 1.000^{+0.000}_{-0.270}. To complete the analysis the Λ\LambdaCDM, with its three free parameters, is considered. For all these models, particular cases are considered where one or two parameters are fixed. The age of the Universe, the deceleration parameter and the moment the Universe begins to accelerate are also evaluated. The quartessence scenario, is favoured. A closed (and in some cases a flat) and accelerating Universe is also preferred. The CGM case α=1\alpha = 1 is far from been ruled out, and it is even preferred in some particular cases. In most of the cases the Λ\LambdaCDM is disfavoured with respect to GCGM and CGM.Comment: 23 pages, LaTeX 2e, 6 tables, 38 EPS figures, uses graphic

    Bayesian Constraints on theta_{13} from Solar and KamLAND Neutrino Data

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    We present the results of a Bayesian analysis of solar and KamLAND neutrino data in the framework of three-neutrino mixing. We adopt two approaches for the prior probability distribution of the oscillation parameters Delta m^2_{21}, sin^2 theta_{12}, sin^2 theta_{13}: 1) a traditional flat uninformative prior; 2) an informative prior which describes the limits on sin^2 theta_{13} obtained in atmospheric and long-baseline accelerator and reactor neutrino experiments. In both approaches, we present the allowed regions in the sin^2 theta_{13} - Delta m^2_{21} and sin^2 theta_{12} - sin^2 theta_{13} planes, as well as the marginal posterior probability distribution of sin^2 theta_{13}. We confirm the 1.2 sigma hint of theta_{13} > 0 found in hep-ph/0806.2649 from the analysis of solar and KamLAND neutrino data. We found that the statistical significance of the hint is reduced to about 0.8 sigma by the constraints on sin^2 theta_{13} coming from atmospheric and long-baseline accelerator and reactor neutrino data, in agreement with arXiv:0808.2016.Comment: 21 pages. Final version published in Phys. Rev. D 80 (2009) 05300

    Social networks in medical practice

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    The number of social network users is rising meteorically, a trend that also includes health-care workers. Even though social networking can serve educational functions and is an effective means of communicating medical resources, it is associated with a variety of important challenges. Misuse of social networks by health-care workers can have dire consequences, ranging from seemingly simple issues such as affecting the doctor’s reputation to serious legal matters. Maintaining professionalism and preserving the concepts of confidentiality and privacy is essential. In this review we will analyze some of the dilemmas that have been brought about by the use of social networks in the healthcare environment, as well as existing guidelines on the matter

    Heavy metal contamination in sediments of an artificial reservoir impacted by long-term mining activity in the Almad\ue9n mercury district (Spain)

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    Sediments from the Castilseras reservoir, located downstream on the Valdeazogues River in the Almad\ue9n mercury district, were collected to assess the potential contamination status related to metals(oids) associated with river sediment inputs from several decommissioned mines. Metals(oids) concentrations in the reservoir sediments were investigated using different physical and chemical techniques. The results were analyzed by principal component analysis (PCA) to explain the correlations between the sets of variables. The degree of contamination was evaluated using the enrichment factor (EF) and the geoaccumulation index (Igeo). PCA revealed that the silty fraction is the main metals(oids) carrier in the sediments. Among the potentially harmful elements, there is a group (Al, Cr, Cu, Fe, Mn, Ni, and Zn) that cannot be strictly correlated to the mining activity since their concentrations depend on the lithological and edaphological characteristics of the materials. In contrast, As, Co, Hg, Pb, and S showed significant enrichment and contamination, thus suggesting relevant contributions from the decommissioned mines through fluvial sediment inputs. As far as Hg and S are concerned, the high enrichment levels pose a question concerning the potential environmental risk of transfer of the organic forms of Hg (mainly methylmercury) from the bottom sediments to the aquatic food chain
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