313 research outputs found
A general class of zero-or-one inflated beta regression models
This paper proposes a general class of regression models for continuous
proportions when the data contain zeros or ones. The proposed class of models
assumes that the response variable has a mixed continuous-discrete distribution
with probability mass at zero or one. The beta distribution is used to describe
the continuous component of the model, since its density has a wide range of
different shapes depending on the values of the two parameters that index the
distribution. We use a suitable parameterization of the beta law in terms of
its mean and a precision parameter. The parameters of the mixture distribution
are modeled as functions of regression parameters. We provide inference,
diagnostic, and model selection tools for this class of models. A practical
application that employs real data is presented.Comment: 21 pages, 3 figures, 5 tables. Computational Statistics and Data
Analysis, 17 October 2011, ISSN 0167-9473
(http://www.sciencedirect.com/science/article/pii/S0167947311003628
Predictors of combined cognitive and physical decline
OBJECTIVES: To determine the incidence and correlates of combined declines in cognitive and physical performance. DESIGN: Cohort study of community-dwelling older women with moderate to severe disability. SETTING: The community surrounding Baltimore, Maryland. PARTICIPANTS: Participants in the Women's Health and Aging Study I with Mini-Mental State Examination (MMSE) score or 24 or greater and walking speed greater than 0.4 m/s at baseline. MEASUREMENTS: Cognitive decline was defined as an MMSE score less than 24 and physical decline as a walking speed of 0.4 m/s or less in at least one of the three annual follow-up visits. Participants were stratified into groups based on cognitive or physical decline or both. Group characteristics were compared, and results were adjusted for age, race, education, and significant covariates. RESULTS: Of 558 women that met the baseline MMSE and walking speed inclusion criteria, 21% developed physical decline, 12% developed cognitive decline, and 11% experienced combined cognitive and physical decline. After adjustment, physical decline was associated with age, nonwhite race, former smoking, baseline walking speed, and instrumental activities of daily living (IADL) impairment. Cognitive decline was associated with age and baseline MMSE score. Combined decline was associated with age, baseline walking speed, MMSE score, IADL impairment, as well as current smoking (odds ratio (OR)=5.66, 95% confidence interval (CI)=1.49-21.54) and hemoglobin level (OR=0.68, 95% CI=0.47-0.98). CONCLUSION: Potential predictors of cognitive and physical performance decline were identified. The association between smoking and lower hemoglobin levels and combined cognitive and physical decline may represent potentially modifiable risk factors and should be confirmed in future studie
Généralisation du diagramme de Voronoï et placement de formes géométriques complexes dans un nuage de points.
La gĂ©omĂ©trie algorithmique est une discipline en pleine expansion dont l'objet est la conception d'algorithmes rĂ©solvant des problĂšmes gĂ©omĂ©triques. De tels algorithmes sont trĂšs utiles notamment dans l'ingĂ©nierie, l'industrie et le multimĂ©dia. Pour ĂȘtre performant, il est frĂ©quent qu'un algorithme gĂ©omĂ©trique utilise des structures de donnĂ©es spĂ©cialisĂ©es.Nous nous sommes intĂ©ressĂ©s Ă une telle structure : le diagramme de VoronoĂŻ et avons proposĂ© une gĂ©nĂ©ralisation de celui-ci. Ladite gĂ©nĂ©ralisation rĂ©sulte d'une extension du prĂ©dicat du disque vide (prĂ©dicat propre Ă toute rĂ©gion de VoronoĂŻ) Ă une union de disques. Nous avons analysĂ© les rĂ©gions basĂ©es sur le prĂ©dicat Ă©tendu et avons proposĂ© des mĂ©thodes pour les calculer par ordinateur.Par ailleurs, nous nous sommes intĂ©ressĂ©s aux problĂšmes de placement de formes , thĂšme rĂ©current en gĂ©omĂ©trie algorithmique. Nous avons introduit un formalisme universel pour de tels problĂšmes et avons, pour la premiĂšre fois, proposĂ© une mĂ©thode de rĂ©solution gĂ©nĂ©rique, en ce sens qu'elle est apte Ă rĂ©soudre divers problĂšmes de placement suivant un mĂȘme algorithme.Nos travaux prĂ©sentent, d'une part, l'avantage d'Ă©largir le champ d'application de structures de donnĂ©es basĂ©es sur VoronoĂŻ. D'autre part, ils facilitent de maniĂšre gĂ©nĂ©rale l'utilisation de la gĂ©omĂ©trie algorithmique, en unifiant dĂ©finitions et algorithmes associĂ©s aux problĂšmes de placement de formes.Computational geometry is an active branch of computer science whose goal is the design of efficient algorithms solving geometric problems. Such algorithms are useful in domains like engineering, industry and multimedia. In order to be efficient, algorithms often use special data structures.In this thesis we focused on such a structure: the Voronoi diagram. We proposed a new generalized diagram. We have proceeded by extending the empty disk predicate (satisfied by every Voronoi region) to an arbitrary union of disks. We have analyzed the new plane regions based on the extended predicate, and we designed algorithms for computing them.Then, we have considered another topic, which is related to the first one: shape placement problems. Such problems have been studied repeatedly by researchers in computational geometry. We introduced new notations along with a global framework for such problems. We proposed, for the first time a generic method, which is able to solve various placement problems using a single algorithm.Thus, our work extend the scope of Voronoi based data structures. It also simplifies the practical usage of placement techniques by unifying the associated definitions and algorithms.MULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF
Interplay of disorder and magnetic field in the superconducting vortex state
We calculate the density of states of an inhomogeneous superconductor in a
magnetic field where the positions of vortices are distributed completely at
random. We consider both the cases of s-wave and d-wave pairing. For both
pairing symmetries either the presence of disorder or increasing the density of
vortices enhances the low energy density of states. In the s-wave case the gap
is filled and the density of states is a power law at low energies. In the
d-wave case the density of states is finite at zero energy and it rises
linearly at very low energies in the Dirac isotropic case
(\alpha_D=t/\Delta_0=1, where t is the hopping integral and \Delta_0 is the
amplitude of the order parameter). For slightly higher energies the density of
states crosses over to a quadratic behavior. As the Dirac anisotropy increases
(as \Delta_0 decreases with respect to the hopping term) the linear region
decreases in width. Neglecting this small region the density of states
interpolates between quadratic and back to linear as \alpha_D increases. The
low energy states are strongly peaked near the vortex cores.Comment: 12 REVTeX pages, 15 figure
Formation of Large-Scale Semi-Organized Structures in Turbulent Convection
A new mean-field theory of turbulent convection is developed. This theory
predicts the convective wind instability in a shear-free turbulent convection
which causes formation of large-scale semi-organized fluid motions in the form
of cells or rolls. Spatial characteristics of these motions, such as the
minimum size of the growing perturbations and the size of perturbations with
the maximum growth rate, are determined. This study predicts also the existence
of the convective shear instability in a sheared turbulent convection which
results in generation of convective shear waves with a nonzero hydrodynamic
helicity. Increase of shear promotes excitation of the convective shear
instability. Applications of the obtained results to the atmospheric turbulent
convection and the laboratory experiments on turbulent convection are
discussed. This theory can be applied also for the describing a mesogranular
turbulent convection in astrophysics.Comment: 16 pages, 10 figures, REVTEX4, PHYSICAL REVIEW E, v. 67, in press
(2003
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Genome-wide association study of kidney function decline in individuals of European descent.
Genome-wide association studies (GWASs) have identified multiple loci associated with cross-sectional eGFR, but a systematic genetic analysis of kidney function decline over time is missing. Here we conducted a GWAS meta-analysis among 63,558 participants of European descent, initially from 16 cohorts with serial kidney function measurements within the CKDGen Consortium, followed by independent replication among additional participants from 13 cohorts. In stage 1 GWAS meta-analysis, single-nucleotide polymorphisms (SNPs) at MEOX2, GALNT11, IL1RAP, NPPA, HPCAL1, and CDH23 showed the strongest associations for at least one trait, in addition to the known UMOD locus, which showed genome-wide significance with an annual change in eGFR. In stage 2 meta-analysis, the significant association at UMOD was replicated. Associations at GALNT11 with Rapid Decline (annual eGFR decline of 3âml/min per 1.73âm(2) or more), and CDH23 with eGFR change among those with CKD showed significant suggestive evidence of replication. Combined stage 1 and 2 meta-analyses showed significance for UMOD, GALNT11, and CDH23. Morpholino knockdowns of galnt11 and cdh23 in zebrafish embryos each had signs of severe edema 72âh after gentamicin treatment compared with controls, but no gross morphological renal abnormalities before gentamicin administration. Thus, our results suggest a role in the deterioration of kidney function for the loci GALNT11 and CDH23, and show that the UMOD locus is significantly associated with kidney function decline.Kidney International advance online publication, 10 December 2014; doi:10.1038/ki.2014.361
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
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