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Search Results: 1 - 10 of 9252 matches for " Silvia emiko Shimakura "
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Bayesian analysis for a class of beta mixed models
Wagner Hugo Bonat,Paulo Justiniano Ribeiro Jr,Silvia emiko Shimakura
Statistics , 2014,
Abstract: Generalized linear mixed models (GLMM) encompass large class of statistical models, with a vast range of applications areas. GLMM extends the linear mixed models allowing for different types of response variable. Three most common data types are continuous, counts and binary and standard distributions for these types of response variables are Gaussian, Poisson and Binomial, respectively. Despite that flexibility, there are situations where the response variable is continuous, but bounded, such as rates, percentages, indexes and proportions. In such situations the usual GLMM's are not adequate because bounds are ignored and the beta distribution can be used. Likelihood and Bayesian inference for beta mixed models are not straightforward demanding a computational overhead. Recently, a new algorithm for Bayesian inference called INLA (Integrated Nested Laplace Approximation) was proposed.INLA allows computation of many Bayesian GLMMs in a reasonable amount time allowing extensive comparison among models. We explore Bayesian inference for beta mixed models by INLA. We discuss the choice of prior distributions, sensitivity analysis and model selection measures through a real data set. The results obtained from INLA are compared with those obtained by an MCMC algorithm and likelihood analysis. We analyze data from an study on a life quality index of industry workers collected according to a hierarchical sampling scheme. Results show that the INLA approach is suitable and faster to fit the proposed beta mixed models producing results similar to alternative algorithms and with easier handling of modeling alternatives. Sensitivity analysis, measures of goodness of fit and model choice are discussed.
The Gamma-count distribution in the analysis of experimental underdispersed data
Walmes Marques Zeviani,Paulo Justiniano Ribeiro Jr.,Wagner Hugo Bonat,Silvia Emiko Shimakura,Joel Augusti Muniz
Statistics , 2013, DOI: 10.1080/02664763.2014.922168
Abstract: Event counts are response variables with non-negative integer values representing the number of times that an event occurs within a fixed domain such as a time interval, a geographical area or a cell of a contingency table. Analysis of counts by Gaussian regression models ignores the discreteness, asymmetry and heterocedasticity and is inefficient, providing unrealistic standard errors or possibily negative predictions of the expected number of events. The Poisson regression is the standard model for count data with underlying assumptions on the generating process which may be implausible in many applications. Statisticians have long recognized the limitation of imposing equidispersion under the Poisson regression model. A typical situation is when the conditional variance exceeds the conditional mean, in which case models allowing for overdispersion are routinely used. Less reported is the case of underdispersion with fewer modelling alternatives and assessments available in the literature. One of such alternatives, the Gamma-count model, is adopted here in the analysis of an agronomic experiment designed to investigate the effect of levels of defoliation on different phenological states upon the number of cotton bolls. Results show improvements over the Poisson model and the semiparametric quasi-Poisson model in capturing the observed variability in the data. Estimating rather than assuming the underlying variance process lead to important insights into the process.
Proposta sobre uso de dados de receitas de antimicrobianos retidas: a experiência EUREQA
Camargo, Eduardo Celso Gerbi;Kiffer, Carlos Roberto Veiga;Pignatari, Antonio Carlos Campos;Shimakura, Silvia Emiko;Ribeiro Jr, Paulo Justiniano;Monteiro, Antonio Miguel Vieira;
Cadernos de Saúde Pública , 2012, DOI: 10.1590/S0102-311X2012000500017
Abstract: this study demonstrates that the use of information from medical prescriptions is essential for understanding the dynamics of community bacterial resistance. the resulting analysis can also influence and help establish more adequate public health policies on the control and optimization of antimicrobial use. the article demonstrates the use of a logical model developed by the eureqa project for acquisition, classification, interpretation, and analysis of data from prescriptions for oral antimicrobial use.
A geographical population analysis of dental trauma in school-children aged 12 and 15 in the city of Curitiba-Brazil
Max L Carvalho, Samuel J Moysés, Roberto E Bueno, Silvia Shimakura, Simone T Moysés
BMC Health Services Research , 2010, DOI: 10.1186/1472-6963-10-203
Abstract: Geostatistical analysis of the database and thematic maps were generated showing the distribution of dental trauma cases according to Curitiba's Health Districts and other variables of interest. Dental trauma spatial variation was assessed using a generalized additive model in order to identify and control the individual risk-factors and thus determine whether spatial variation is constant or not throughout the Health Districts and the place of residence of individuals. In addition, an analysis was made of the coverage of dental trauma cases taking the spatial distribution of Curitiba's primary healthcare centres.The overall prevalence of dental trauma was 37.1%, with 53.1% in males and 46.7% in females. The spatial analysis confirms the hypothesis that there is significant variation in the occurrence of dental trauma, considering the place of residence in the population studied (Monte Carlo test, p = 0,006). Furthermore, 28.7% of cases had no coverage by the primary healthcare centres.The effect of the place of residence was highly significant in relation to the response variable. The delimitation of areas, as a basis for case density, enables the qualification of geographical territories where actions can be planned based on priority criteria. Promotion, control and rehabilitation actions, applied in regions of higher prevalence of dental trauma, can be more effective and efficient, thus providing healthcare refinement.In recent years the complexity of dental trauma epidemiology has been highlighted in the specialized literature, with successive reports of its increasing prevalence [1,2]. Although it is not consensus that it represents a public health problem, given that its impact on the individual level is often not self-perceived, many are those who advocate that actions to prevent and control this problem in communities cannot be postponed [3-8].Epidemiologically, there are many geographical and population aspects that can be related to traumatic injuries [9-1
Distribui??o espacial do risco: modelagem da mortalidade infantil em Porto Alegre, Rio Grande do Sul, Brasil
Shimakura, Silvia E.;Carvalho, Marilia Sá;Aerts, Denise R. G. C.;Flores, Rui;
Cadernos de Saúde Pública , 2001, DOI: 10.1590/S0102-311X2001000500025
Abstract: estimation and mapping of risk profiles are the main concerns of epidemiology. this paper analyzes spatial distribution of infant mortality cases as compared to live-born controls from porto alegre, rio grande do sul. the modeling framework adopted in this research work is a spatial point process. under this structure, a risk measure which continuously varies over the study region is defined and estimated using generalized additive model methods. this approach has the advantage of allowing for risk factors that are simple and easy to interpret. the procedure also allows the construction of tolerance contours which help identify areas of significantly high/low risk and an overall test for the null hypothesis of constant risk over the region. application of this method to infant mortality data showed a highly significant spatial variation in risk for neonatal mortality data and non-significant results for post-neonatal mortality data.
Distribui o espacial do risco: modelagem da mortalidade infantil em Porto Alegre, Rio Grande do Sul, Brasil
Shimakura Silvia E.,Carvalho Marilia Sá,Aerts Denise R. G. C.,Flores Rui
Cadernos de Saúde Pública , 2001,
Abstract: Estima o e mapeamento de perfis de risco s o interesses da Epidemiologia. Neste trabalho, é analisada a distribui o espacial de casos de mortalidade infantil, comparados a controles de nascidos vivos amostrados do Sistema de Informa es sobre Nascidos Vivos da cidade de Porto Alegre, Rio Grande do Sul, Brasil. A modelagem adotada neste trabalho baseia-se em um processo pontual espacial, na qual se define uma medida de risco que varia continuamente sobre a regi o de estudo e estimada por meio de métodos de modelos aditivos generalizados. Essa abordagem possui a vantagem de permitir a incorpora o, no modelo, de efeitos de determinantes individuais e ecológicos de risco sob forma simples e de fácil interpreta o. Também permite a constru o de contornos de tolerancia que auxiliam na identifica o de áreas de alto/baixo risco e de um teste global da hipótese nula de risco constante relativa à regi o. A aplica o do método aos dados de mortalidade infantil mostrou varia o espacial no risco altamente significativa para mortalidade neonatal e n o significativa para mortalidade pós-neonatal.
Invasive aspergillosis in hematopoietic stem cell transplant recipients: a retrospective analysis
Carvalho-Dias, Viviane Maria Hessel;Sola, Caroline Bonamin Santos;Cunha, Clóvis Arns da;Shimakura, Sílvia Emiko;Pasquini, Ricardo;Queiroz-Telles, Flávio de;
Brazilian Journal of Infectious Diseases , 2008, DOI: 10.1590/S1413-86702008000500008
Abstract: invasive aspergillosis (ia) currently is an important cause of mortality in subjects undergoing hematopoietic stem cell transplants (hsct) and is also an important cause of opportunistic respiratory and disseminated infections in other types of immunocompromised patients. we examined the medical records of 24 cases of proven and probable invasive aspergillosis (ia) at the hospital de clinicas of the federal university of parana, brazil, from january 1996 to october 2006. during this period occurred a mean of 2.2 cases per year or 3.0 cases per 100 hstc transplants. there was a significant relationship between structural changes in the bone marrow transplant (bmt) unit and the occurrence of ia cases (p=0.034, relative risk (rr) = 2.47). approximately 83% of the patients died due to invasive fungal infection within 60 days of follow up. some factors tended to be associated with mortality, but these associations were not significant. these included corticosteroid use, neutropenia (<100 cells/mm3) at diagnosis, patients that needed to change antifungal therapy because of toxicity of the initial first-line regimen and disseminated disease. these factors should be monitored in bmt units to help prevent ia. physicians should be aware of the risk factors for developing invasive fungal infections and try to reduce or eliminate them. however, once this invasive disease begins, appropriate diagnostic and treatment measures must be implemented as soon as possible in order to prevent the high mortality rates associated with this condition.
The Automorphism Group of the Vertex Operator Algebra $V_L^+$ for an even lattice $L$ without roots
Hiroki Shimakura
Mathematics , 2003,
Abstract: The automorphism group of the vertex operator algebra $V_L^+$ is studied by using its action on isomorphism classes of irreducible $V_L^+$-modules. In particular, the shape of the automorphism group of $V_L^+$ is determined when $L$ is isomorphic to an even unimodular lattice without roots, $\sqrt2R$ for an irreducible root lattice $R$ of type $ADE$ and the Barnes-Wall lattice of rank 16.
An $E_8$-approach to the moonshine vertex operator algebra
Hiroki Shimakura
Mathematics , 2010, DOI: 10.1112/jlms/jdq078
Abstract: In this article, we study the moonshine vertex operator algebra starting with the tensor product of three copies of the vertex operator algebra $V_{\sqrt2E_8}^+$, and describe it by the quadratic space over $\F_2$ associated to $V_{\sqrt2E_8}^+$. Using quadratic spaces and orthogonal groups, we show the transitivity of the automorphism group of the moonshine vertex operator algebra on the set of all full vertex operator subalgebras isomorphic to the tensor product of three copies of $V_{\sqrt2E_8}^+$, and determine the stabilizer of such a vertex operator subalgebra. Our approach is a vertex operator algebra analogue of "An $E_8$-approach to the Leech lattice and the Conway group" by Lepowsky and Meurman. Moreover, we find new analogies among the moonshine vertex operator algebra, the Leech lattice and the extended binary Golay code.
Decompositions of the Moonshine Module with respect to subVOAs associated to codes over $\Z_{2k}$
Hiroki Shimakura
Mathematics , 2001,
Abstract: In this paper, we give decompositions of the moonshine module $V^{\natural}$ with respect to subVOAs associated to extremal Type II codes over $Z_{2k}$ for an integer $k\ge2$. Those subVOAs are isomorphic to the tensor product of 24 copies of the charge conjugation orbifold VOA. Using such decompositions, we obtain some elements of type 4A (k odd) and 2B (k even) of the Monster simple group Aut$(V^{\natural})$.
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