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267 results on '"Portnoy, S."'

1. The Bunching and Monotonicity Properties of Families of Probability Distributions

Author

Portnoy, S., Torrado, N., and Veerman, J. J. P.

Subjects
Mathematics - Statistics Theory, 60E15, 62E99
Abstract

Measuring the concentration of random variables is a fundamental concept in probability and statistics. Here, we explore a type of concentration measure for continuous random variables with bounded support and use it to provide a notion of stochastic order by concentration. We give an application to the Beta family of distributions, and specifically to the one-parameter subfamily with constant mean. This leads to using U.S. household income data to fit generalized Beta distributions and offers a new measure of income concentration., Comment: 19 pages, 4 figures

Published
2024

5. MRI characterization of hemodynamic patterns of human fetuses with cyanotic congenital heart disease

Author

Sun, L., primary, van Amerom, J. F. P., additional, Marini, D., additional, Portnoy, S., additional, Lee, F.‐T., additional, Saini, B. S., additional, Lim, J. M., additional, Aguet, J., additional, Jaeggi, E., additional, Kingdom, J. C., additional, Macgowan, C. K., additional, Miller, S. P., additional, Huang, G., additional, and Seed, M., additional

Published
2021
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20. Feasibility study - vitamin d loading determination by ftir-atr

Author

Simana, E., Simian, R., Portnoy, S., Jaffe, A., and Dekel, B.

Abstract

Purpose: The aim of the present study was to develop a simple and accurate way to measure vitamin D levels. Vitamin D nowadays is measured by a variety of methods which their common drawbacks are expensive equipment and the need for high trained technical staff. In this research we measured vitamin D levels by means of Fourier transform infra red method in conjugation with the evanescent wave spectroscopy technique, in order to develop a simpler vitamin D measurement method. Methods: Blood samples were collected from patients with vitamin D deficiency at five intervals before and up to 16 days after they took a dose of 200,000 IU vitamin D 3. Samples were measured by the conventional bio-chemical method and by the evanescent wave spectroscopy means. Results: Correlation was found between the vitamin D levels measured by the traditional method and by the evanescent wave spectroscopy technique. The absorption lines occurred prominently in the IR spectral regions of the Amide I (&1650 cm -1),Amide II (&1530 cm -1) and the (&3400 cm -1) absorption band which is attributed to the hydroxyl group indicated by the O-H stretch. In addition, the examination of the blood samples using the evanescent wave spectroscopy with clustering techniques facilitated the discrimination between vitamin D deficiency and normal vitamin D levels. Practical relevance: This study demonstrates the potential of using the Fourier transform infra red method in conjugation with the evanescent wave spectroscopy techniquecoupled with multivariate analysis as a non-expensive, rapid and accurate alternative to the routine methodologies.

Published
2015

29. Specification tests in mixed effects models

Author

Meintanis, S.G. Portnoy, S.

Abstract

Two methods are proposed for testing the error distribution in mixed effects models, where J measurements are taken on each of I individuals. The test statistics involve empirical characteristic functions resulting from estimation of the mixed effects. One method is designed for J large and is justified by asymptotic results when J→∞. The other is appropriate for moderately small J, and appears to be a simpler alternative method achieving the near n consistency of the procedure of Hall and Yao (2003). This method is based on a novel use of piecewise linear approximations to characteristic functions along a grid, and its computation may be simplified using complex arithmetic. Theoretical and computational issues are addressed while Monte Carlo results show that the new procedures compare favorably with classical methods. © 2011 Elsevier B.V.

Published
2011

31. Hereditary breast and ovarian cancer.

Author

Lyubchenko, L. N., primary, Bateneva, E. I., additional, Abramov, I. S., additional, Emelyanova, M. A., additional, Budik, Yu. A., additional, Tyulyandina, A. S., additional, Krokhina, O. V., additional, Vorotnikov, I. K., additional, Sobolevskyj, V. A., additional, Nasedkina, T. V., additional, and Portnoy, S. M., additional

Published
2015
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32. Course of soft tissue injuries in the transtibial amputation residuum

Author

Portnoy, S., Siev-Ner, I., Yizhar, Z., Shabshin, N., Seelen, H.A.M., Oomens, C.W.J., Gefen, A., and Soft Tissue Biomech. & Tissue Eng.

Subjects
body regions, SDG 3 - Good Health and Well-being
Abstract

A transtibial amputation (ITA) prosthetic user has to deal with daily complications associated with his artificial limb. Though highly progressed, technologically and functionally, the TTA prosthesis is far from ideally replacing an intact limb, mainly due to unique inherent anatomy. After a long and complicated fitting process, the prosthetic limb is often a source of gait abnormalities, limb pain and soft tissue breakdown. While commercial prosthetic accessories and aids are plentiful, tools that analyze the mechanical conditions in the soft tissues of the residual limb during load-bearing are scarce. Therefore, clinicians are not well-equipped with tools that are able to quantify the effectiveness of socket rectification and the use of aids, e.g. liners and thigh corset. In this review we will discuss TTA aetiology and elaborate on the prostheses that are most commonly used today. We will also review gait characteristic and its associated complications. Mainly, we will discuss socket limb interaction and methods for quantifying the internal mechanical conditions in the residual limb for the purpose of preventing deep tissue injuries.

Published
2009

49. In vitro detection of apoptosis using oscillating and pulsed gradient diffusion magnetic resonance imaging.

Author

Portnoy, S., Fichtner, N. D., Dziegielewski, C., Stanisz, M. P., and Stanisz, G. J.

Abstract

Cellular apoptosis, a common pathway towards tumor regression, is induced by many radiotherapy and chemotherapy regimens. Imaging methods that can detect apoptosis may be able to assess treatment response earlier than typical tumor volume measurements. In this paper, a wide range of diffusion experiments and a simple model of diffusion in tissues were used to probe the microstructural effects of apoptosis. Experiments were conducted on acute myeloid leukemia cell pellets, where apoptosis was induced by treatment with the chemotherapeutic agent cisplatin. Seventy-two hours following cisplatin treatment, pulsed and oscillating gradient diffusion measurements were utilized to assess effects across a broad range of structural scales. The presence of apoptosis, which was histologically confirmed by TUNEL (terminal deoxynucleotidyl transferase UTP nick end labelling) staining, significantly changed diffusion properties. To describe these changes, the data were fit to the parallel plane model, which characterizes the effects of restricted diffusion in terms of three parameters: d, the restricted size, Dfree, the intrinsic, free diffusion coefficient of the solvent, and Drest, the long time or 'restricted' diffusion coefficient. Apoptotic samples exhibited significant decreases in parameters d and Dfree and a significant increase in Drest. These changes appear consistent with the established morphological effects of apoptosis. In particular, the decrease in d may be a result of the combined effects of cell shrinkage, nuclear fragmentation and membrane blebbing, the decrease in Dfree may relate to cytosolic condensation, while the increase in Drest can be attributed to increased membrane permeability and extracellular volume fraction. By non-invasively detecting apoptosis, the methods reported in this study have the potential to improve upon current MRI methods for monitoring therapeutic response. Furthermore, these methods may offer sufficient specificity to differentiate between apoptosis and other modes of cell death, such as oncosis or necrosis. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2014
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