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307 results on '"Wechsler S"'

1. Rain dance: the role of randomization in clinical trials

Author

Diniz JB, Fossaluza V, Pereira CAB, and Wechsler S

Subjects
Randomization, intentional allocation, clinical trials, current trends, biostatistics, Medicine
Abstract

Juliana Belo Diniz,1 Victor Fossaluza,2 Carlos Alberto de Bragança Pereira,1,2 Sergio Wechsler2 1Institute of Psychiatry, Clinics Hospital University of São Paulo Medical School, 2Department of Statistics, Institute of Mathematics and Statistics, University of São Paulo, São Paulo, Brazil Abstract: Randomized clinical trials are the gold standard for testing efficacy of treatment interventions. However, although randomization protects against deliberately biased samples, it does not guarantee random imbalances will not occur. Methods of intentional allocation that can overcome such deficiency of randomization have been developed, but are less frequently applied than randomization. Initially, we introduce a fictitious case example to revise and discuss the reasons of researchers' resistance to intentionally allocate instead of simply randomizing. We then introduce a real case example to evaluate the performance of an intentional protocol for allocation based on compositional data balance. A real case of allocation of 50 patients in two arms was compared with an optimal allocation of global instead of sequential arrivals. Performance was measured by a weighted average of Aitchison distances, between arms, of prognostic factors. To compare the intentional allocation with simple random allocation, 50,000 arrival orderings of 50 patients were simulated. To each one of the orders, both kinds of allocations into two arms were considered. Intentional allocation performed as well as optimal allocation in the case considered. In addition, out of the 50,000 simulated orders, 61% of them performed better with intentional allocation than random allocation. Hence, we conclude that intentional allocation should be encouraged in the design of future interventional clinical trials as a way to prevent unbalanced samples. Our sequential method is a viable alternative to overcome technical difficulties for study designs that require sequential inclusion of patients as it does not require prior knowledge about the total sample composition. Keywords: randomization, intentional allocation, clinical trials, current trends, biostatistics

Published
2016

2. Asymptomatic HLA-A*02:01-Restricted Epitopes from Herpes Simplex Virus Glycoprotein B Preferentially Recall Polyfunctional CD8+ T Cells from Seropositive Asymptomatic Individuals and Protect HLA Transgenic Mice against Ocular Herpes

Author

Dervillez, X., Qureshi, H., Chentoufi, A. A, Khan, A. A, Kritzer, E., Yu, D. C, Diaz, O. R, Gottimukkala, C., Kalantari, M., Villacres, M. C, Scarfone, V. M, McKinney, D. M, Sidney, J., Sette, A., Nesburn, A. B, Wechsler, S. L, and BenMohamed, L.

Published
2013

21. Active Learning

Author

Balasubramanian, V N, Ho, S S, Vovk, V, Balasubramanian, Vineeth N, Chakraborty, S, Wechsler, S, Panchanathan, S, Balasubramanian, V N, Ho, S S, Vovk, V, Balasubramanian, Vineeth N, Chakraborty, S, Wechsler, S, and Panchanathan, S

Abstract

In this chapter, we describe how the p-values derived from the conformal predictions framework can be used for active learning; that is, to select the informative examples from a data collection that can be used to train a classifier for best performance. We show the connection of this approach to information-theoretic methods, as well as show how the methodology can be generalized to multiple classifier models and information fusion settings.

Published
2014

24. Molecular cloning, chromosomal mapping, and characterization of the human cardiac-specific homeobox gene hCsx

Author

Turbay, D., Wechsler, S. B., Blanchard, K. M., and Izumo, S.

Subjects
Base Sequence, Sequence Homology, Amino Acid, Myocardium, Molecular Sequence Data, Genes, Homeobox, Chromosome Mapping, Gene Expression Regulation, Developmental, Hybrid Cells, Blotting, Northern, Polymerase Chain Reaction, Fetus, Karyotyping, Humans, Amino Acid Sequence, Cloning, Molecular, Sequence Analysis, In Situ Hybridization, Fluorescence, Research Article, DNA Primers
Abstract

BACKGROUND: Csx/Nkx2.5, a murine nonclustered homeobox gene expressed primarily in the heart, has significant sequence similarity to the Drosophila tinman gene. Tinman is essential for heart and gut formation in Drosophila. Targeted mutation in the mouse gene, Csx/Nkx2.5, arrests cardiac development during early embryonic stages, suggesting an evolutionary conservation in cardiogenesis. MATERIALS AND METHODS: We have isolated and characterized a human homolog, hCsx, from an adult cardiac cDNA library. Northern blotting and ribonuclease protection was used to define the pattern of expression during normal development and in disease states. Chromosomal localization of the gene was determined by somatic cell hybrid analysis and fluorescent in situ hybridization. RESULTS: The predicted amino acid sequence of hCsx has 87% overall homology to the murine gene with 100% identity in the homeodomain. The homeodomain sequence of hCsx is 95% identical to its Xenopus homolog, and 65% to tinman. hCsx mRNA was detected exclusively in the heart. hCsx transcript was detected at 12 weeks in human embryonic heart, the earliest time point examined, and was up-regulated 5-fold between 12 and 19 weeks. There was no significant alteration of hCsx message level in the myocardium of 14 patients with end stage heart failure compared to a normal control. The human gene mapped to the distal portion of chromosome 5, the 5q34-q35 region. This defines a new synteny region between human chromosome 5q and the t-locus of mouse chromosome 17, where the mouse Csx gene is located. CONCLUSIONS: hCsx, the human homolog of Drosophila tinman, is expressed in heart in a tissue restricted manner. Distal 5q trisomies produce several phenotypic abnormalities, including a high incidence of congenital heart disease. Isolation of the hCsx gene will allow further studies of mutations in this gene and their potential associations with some forms of congenital heart disease in humans.

Published
1996

32. ABC for kids.

Author

Campos, T. F. and Wechsler, S.

Subjects
*APPROXIMATION theory, *BAYESIAN analysis, *MAXIMUM likelihood statistics, *ALGORITHMS, *STATISTICAL sampling, *DISTRIBUTION (Probability theory), *GAMMA distributions
Abstract

This work aims to present a simple explanation about the ABC, Approximate Bayesian Computation or likelihood-free methods, a sampler algorithm class made to sampling from a posteriori distribution π(θ|x) in an independent way of the likelihood function. Along of this paper is to present a couple of ABC algorithms such as the ABC Rejection and the ABC MCMC. These algorithms are also applied to the beta model and to the normal-gamma model, in order to generate an univariate posterior distribution and a bivariate distribution, respectively. [ABSTRACT FROM AUTHOR]

Published
2012
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