990 resultados para Linear Series


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Abstract Primary cytomegalovirus (CMV) infection is rare in immunocompetent adults, even rarer in elderly patients. Little is known about the severity of symptoms and the clinical course in this patient group. In children and younger adults, CMV mostly presents as an asymptomatic disease or a self-limiting mild mononucleosis-like syndrome. We describe the clinical course of an unusually severe primary CMV infection in a 69-y-old otherwise healthy man, as well as 6 other severe cases in immunocompetent adults at our institution, and compare them to adult cases from the literature. CMV primary infection and antiviral treatment should be considered in immunocompetent elderly persons presenting with a severe mononucleosis-like syndrome.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

BACKGROUND: Trigeminal neuralgia (TN) related to multiple sclerosis (MS) is more difficult to manage pharmacologically and surgically. OBJECTIVE: This article aims to evaluate the safety and efficacy of Gamma Knife surgery (GKS) in this special group of patients. METHODS: Between July 1992 and November 2010, 43 cases with more than 1 year of follow-up were operated with GKS for TN related to MS and prospectively evaluated in the Timone University Hospital, Marseille, France. Radiosurgery using the Gamma Knife (model B or C or Perfexion) was performed. A single 4-mm isocenter was positioned at a median distance of 8 mm (range 5.7-14.7) anterior to the emergence of the nerve. A median maximum dose of 85 Gy (range 75-90) was delivered. RESULTS: The median follow-up period was 53.8 months (12-157.1). Thirty-nine patients (90.7%) were initially pain free. Their actuarial probability of remaining pain free without medication at 6 months, 1, 3, 5 and 10 years was 87.2, 71.8, 43.1, 38.3 and 20.5%, respectively, and remained stable till 12 years. The hypoesthesia actuarial rate at 6 months, 1 and 2 years was 11.5, 11.5 and 16%, and remained stable till 12 years. CONCLUSIONS: GKS proved safe and effective in this special group of patients.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We present a simple randomized procedure for the prediction of a binary sequence. The algorithm uses ideas from recent developments of the theory of the prediction of individual sequences. We show that if thesequence is a realization of a stationary and ergodic random process then the average number of mistakes converges, almost surely, to that of the optimum, given by the Bayes predictor.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We develop a mathematical programming approach for the classicalPSPACE - hard restless bandit problem in stochastic optimization.We introduce a hierarchy of n (where n is the number of bandits)increasingly stronger linear programming relaxations, the lastof which is exact and corresponds to the (exponential size)formulation of the problem as a Markov decision chain, while theother relaxations provide bounds and are efficiently computed. Wealso propose a priority-index heuristic scheduling policy fromthe solution to the first-order relaxation, where the indices aredefined in terms of optimal dual variables. In this way wepropose a policy and a suboptimality guarantee. We report resultsof computational experiments that suggest that the proposedheuristic policy is nearly optimal. Moreover, the second-orderrelaxation is found to provide strong bounds on the optimalvalue.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

PRINCIPLES: Interstitial pregnancy represents 2% of ectopic pregnancies, but it is a highly morbid condition with a 2.5% of maternal mortality. Its diagnostic and therapeutic management remains controversial. The aim of this review is to describe the management of interstitial pregnancy in our institution between 2001 and 2011 and to define some general rules for the clinical practice. METHODS: Single institution retrospective study. RESULTS: Eleven women were treated for interstitial pregnancy. The median age was 33 years and the median gestity was 4. Seven patients had a history of gynaecological surgery and four interstitial pregnancies followed in vitro fertilisation. The diagnosis was made at a median gestational age of seven weeks with a median beta-HCG level of 5,838 U/l. Six of the eleven patients received an initial treatment with intracornual methotrexate, three with intramuscular methotrexate and two with surgery. The median time to beta-HCG resolution was 58 days. Three of the eleven patients needed a second line treatment: two after intramuscular methotrexate and one after intracornual methotrexate. Six patients had further pregnancies and delivered by caesarean section. CONCLUSIONS: A high prevalence of previous ectopic pregnancies, gynaecological surgery and of pregnancies resulting from in vitro fertilisation was observed. The earliness of the diagnosis was the factor that allowed a conservative treatment in most cases. Beta-HCG level follow up was fundamental in allowing a second line therapy but beta-HCG can persist over a long period of time and this must be taken into account due to its possible psychological impact. Intracornual methotrexate seems to be more efficacious than intramuscular methotrexate in our series.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

It is well accepted that people resist evidence that contradicts their beliefs.Moreover, despite their training, many scientists reject results that are inconsistent withtheir theories. This phenomenon is discussed in relation to the field of judgment anddecision making by describing four case studies. These concern findings that clinical judgment is less predictive than actuarial models; simple methods have proven superiorto more theoretically correct methods in times series forecasting; equal weighting ofvariables is often more accurate than using differential weights; and decisions cansometimes be improved by discarding relevant information. All findings relate to theapparently difficult-to-accept idea that simple models can predict complex phenomenabetter than complex ones. It is true that there is a scientific market place for ideas.However, like its economic counterpart, it is subject to inefficiencies (e.g., thinness,asymmetric information, and speculative bubbles). Unfortunately, the market is only correct in the long-run. The road to enlightenment is bumpy.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Research on judgment and decision making presents a confusing picture of human abilities. For example, much research has emphasized the dysfunctional aspects of judgmental heuristics, and yet, other findings suggest that these can be highly effective. A further line of research has modeled judgment as resulting from as if linear models. This paper illuminates the distinctions in these approaches by providing a common analytical framework based on the central theoretical premise that understanding human performance requires specifying how characteristics of the decision rules people use interact with the demands of the tasks they face. Our work synthesizes the analytical tools of lens model research with novel methodology developed to specify the effectiveness of heuristics in different environments and allows direct comparisons between the different approaches. We illustrate with both theoretical analyses and simulations. We further link our results to the empirical literature by a meta-analysis of lens model studies and estimate both human andheuristic performance in the same tasks. Our results highlight the trade-off betweenlinear models and heuristics. Whereas the former are cognitively demanding, the latterare simple to use. However, they require knowledge and thus maps of when andwhich heuristic to employ.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

O tema da Programação Linear, com as suas particularizações do Problema dos Transportes e do Problema da Afectação de Recursos, é hoje estudado em cursos diversos onde uma disciplina de Investigação Operacional esteja presente. Trata-se, em última análise, de um problema de cálculo de extremos condicionados, seja de máximo ou de mínimo, que apresenta características muito particulares e de grande elegância simbólica. Também os Problemas dos Transportes e da Afectação de Recursos se podem resolver como problemas de Programação Linear, através do Algoritmo Simplex, embora seja preferível o recurso a algoritmos próprios, de muitíssimo maior simplicidade: o Algoritmo dos Transportes e o Algoritmo Húngaro, respectivamente. De molde a facilitar a compreensão do que realmente está em jogo, consideram-se aqui dois casos de determinação de extremos e de extremos condicionados, mas ao nível do final do ensino secundário.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A eficácia da cobertura vegetal morta no controle da erosão pode ser avaliada através de dois indicadores principais: a porcentagem de cobertura do solo pelos resíduos culturais e sua persistência sobre a superfície ao longo do tempo. O preparo do solo, por sua vez, pode exercer influência significativa sobre esses indicadores. O trabalho foi realizado no campo, no município de Eldorado do Sul, Depressão Central do Rio Grande do Sul. Avaliou-se a persistência da cobertura vegetal morta durante um período de pousio, que foi de maio de 1989 a abril de 1990, em sucessão à cultura da soja. Os resíduos dessa cultura foram manejados sem preparo, por escarificação e por gradagem. A porcentagem de cobertura do solo pelos resíduos culturais foi quantificada pelo método fotográfico e pelo da transeção linear. A cultura da soja produziu cobertura vegetal morta em pequena quantidade e de baixa durabilidade. A distribuição dos resíduos na superfície, sem preparo do solo, foi o tratamento que possibilitou melhor correlação (R²) entre os índices de cobertura obtidos pelos dois métodos testados. Nas áreas sob gradagem ou escarificação do solo, os índices de cobertura obtidos pelo método fotográfico foram superiores aos da transeção linear, enquanto, na área sem preparo do solo, houve similaridade entre os resultados dos dois métodos.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This work proposes novel network analysis techniques for multivariate time series.We define the network of a multivariate time series as a graph where verticesdenote the components of the process and edges denote non zero long run partialcorrelations. We then introduce a two step LASSO procedure, called NETS, toestimate high dimensional sparse Long Run Partial Correlation networks. This approachis based on a VAR approximation of the process and allows to decomposethe long run linkages into the contribution of the dynamic and contemporaneousdependence relations of the system. The large sample properties of the estimatorare analysed and we establish conditions for consistent selection and estimation ofthe non zero long run partial correlations. The methodology is illustrated with anapplication to a panel of U.S. bluechips.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

To an odd irreducible 2-dimensional complex linear representation of the absolute Galois group of the field Q of rational numbers, a modular form of weight 1 is associated (modulo Artin's conjecture on the L-series of the representation in the icosahedral case). In addition, linear liftings of 2-dimensional projective Galois representations are related to solutions of certain Galois embedding problems. In this paper we present some recent results on the existence of liftings of projective representations and on the explicit resolution of embedding problems associated to orthogonal Galois representations, and explain how these results can be used to construct modular forms.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

PURPOSE: Recently, a 76-gene prognostic signature able to predict distant metastases in lymph node-negative (N(-)) breast cancer patients was reported. The aims of this study conducted by TRANSBIG were to independently validate these results and to compare the outcome with clinical risk assessment. EXPERIMENTAL DESIGN: Gene expression profiling of frozen samples from 198 N(-) systemically untreated patients was done at the Bordet Institute, blinded to clinical data and independent of Veridex. Genomic risk was defined by Veridex, blinded to clinical data. Survival analyses, done by an independent statistician, were done with the genomic risk and adjusted for the clinical risk, defined by Adjuvant! Online. RESULTS: The actual 5- and 10-year time to distant metastasis were 98% (88-100%) and 94% (83-98%), respectively, for the good profile group and 76% (68-82%) and 73% (65-79%), respectively, for the poor profile group. The actual 5- and 10-year overall survival were 98% (88-100%) and 87% (73-94%), respectively, for the good profile group and 84% (77-89%) and 72% (63-78%), respectively, for the poor profile group. We observed a strong time dependence of this signature, leading to an adjusted hazard ratio of 13.58 (1.85-99.63) and 8.20 (1.10-60.90) at 5 years and 5.11 (1.57-16.67) and 2.55 (1.07-6.10) at 10 years for time to distant metastasis and overall survival, respectively. CONCLUSION: This independent validation confirmed the performance of the 76-gene signature and adds to the growing evidence that gene expression signatures are of clinical relevance, especially for identifying patients at high risk of early distant metastases.