654 research outputs found
Factors influencing transfusion-associated HLA sensitization in patients bridged to heart transplantation using ventricular assist device.
BackgroundBridging heart failure patients with mechanical ventricular assist devices (VAD) enables access to transplantation. However, VAD is associated with increased risk for anti-HLA antibodies associated with rejection of subsequent allografts. Factors determining alloantibody formation in these patients remain undefined.MethodsWe performed a single-center retrospective cohort study of 164 patients undergoing heart transplantation from 2014 to 2017. Medical records including use of VAD, transfused blood products, anti-HLA antibody testing, crossmatch, and time to transplant were evaluated.ResultsPatients received an average of 13.8 red blood cell and 1.9 single-donor platelet units associated with VAD. There was a 28.7% increase in the incidence of anti-HLA antibodies after VAD. Development of anti-HLA antibodies did not correlate with volume or type of blood products, but with pre-VAD HLA sensitization status; relative risk of new alloantibodies in patients with pre-VAD antibodies was 3.5-fold higher than those without prior antibodies (P = .008). Development of new anti-HLA antibodies was associated with an increased time to transplant (169 vs 330 days, P = .013).ConclusionsOur findings indicate that the presence of anti-HLA antibodies pre-VAD was the most significant risk factor for developing additional antibodies post-VAD, suggesting that a subset of patients may be predisposed to alloantibody formation
How Good are Our Measures? Investigating the Appropriate Use of Factor Analysis for Survey Instruments
Background: Evaluation work frequently utilizes factor analysis to establish the dimensionality, reliability, and stability of surveys. However, survey data is typically ordinal, violating the assumptions of most statistical methods, and thus is often factor-analyzed inappropriately. Purpose: This study illustrates the salient analytical decisions for factor-analyzing ordinal survey data appropriately and demonstrates the repercussions of inappropriate analyses. Setting: The data used for this study are drawn from an evaluation of the efficacy of a drama-based approach to teaching Shakespeare in elementary and middle school. Intervention: Not applicable. Research Design: Survey research. Data Collection and Analysis: Four factor analytic methods were compared: a traditional exploratory factor analysis (EFA), a full-information EFA, and two EFAs within the confirmatory factor analysis framework (E/CFA) conducted according to the Jöreskog method and the Gugiu method. Findings: Methods appropriate for ordinal data produce better models, the E/CFAs outperform the EFAs, and the Gugiu method demonstrates greater model interpretability and stability than the Jöreskog method. These results suggest that the Gugiu E/CFA may be the preferable factor analytic method for use with ordinal data. Practical applications of these findings are discussed. Keywords: factor analysis; ordinal data; E/CFA; survey research
Evaluación del Programa de Abasto Social de Leche a cargo de Liconsa S.A. de C.V. desde un enfoque de derechos humanos
El derecho humano a la alimentación es resultado de declaraciones, tratados y leyes, que busca obligar a los estados para que adopten medidas para garantizar la alimentación para erradicar la pobreza extrema y el hambre. Sin embargo, sigue persistiendo la desnutrición y la falta de acceso a la alimentación, lo que implica una violación grave del derecho fundamental de toda persona. Este trabajo reporta la necesidad de reformular el Programa de Abasto Social de Leche a cargo de Liconsa, S.A. de C.V. a partir de una perspectiva de derecho humano a la alimentación y las recomendaciones para realizarlo
Nonrelativistic hydrogen type stability problems on nonparabolic 3-manifolds
We extend classical Euclidean stability theorems corresponding to the
nonrelativistic Hamiltonians of ions with one electron to the setting of non
parabolic Riemannian 3-manifolds.Comment: 20 pages; to appear in Annales Henri Poincar
Linkage disequilibrium fine mapping of quantitative trait loci: A simulation study
Recently, the use of linkage disequilibrium (LD) to locate genes which
affect quantitative traits (QTL) has received an increasing
interest, but the plausibility of fine mapping using linkage
disequilibrium techniques for QTL has not been well studied. The main
objectives of this work were to (1) measure the extent and pattern of
LD between a putative QTL and nearby markers in finite populations and
(2) investigate the usefulness of LD in fine mapping QTL in simulated
populations using a dense map of multiallelic or biallelic marker
loci. The test of association between a marker and QTL and the power
of the test were calculated based on single-marker regression
analysis. The results show the presence of substantial linkage
disequilibrium with closely linked marker loci after 100 to 200
generations of random mating. Although the power to test the
association with a frequent QTL of large effect was satisfactory, the
power was low for the QTL with a small effect and/or low
frequency. More powerful, multi-locus methods may be required to map
low frequent QTL with small genetic effects, as well as combining both
linkage and linkage disequilibrium information. The results also
showed that multiallelic markers are more useful than biallelic
markers to detect linkage disequilibrium and association at an equal
distance
Using the Very Short Form of the Children’s Behavior Questionnaire for Spanish-Speaking Populations in Low- and Middle-Income Countries: A Psychometric Analysis of Dichotomized Variables
While the psychometric properties of the Spanish version of the Very Short Form of the Children’s Behavior Questionnaire (CBQ-VSF) have been assessed in the US and Europe in samples composed of middle- and high-income parents with high levels of education, no studies have tested the instrument in low-income Spanish-speaking populations living in low- and middle- income countries. To fill this gap, our cross-sectional study assessed the psychometric properties of the Spanish version of the CBQ-VSF version in a sample of 315 low-income and low-educated parents with preschool children living in the Caribbean Region of Colombia. While our findings revealed problems that were similar to those identified in previous assessments of the CBQ-VSF Spanish version, they also showed unique problems related to the sociodemographic characteristics of our sample, containing many individuals with a low income and low educational level. Most of the participants gave extreme responses, resulting in a notable kurtosis and skewness of the data. This article describes how we addressed these problems by dichotomizing the variables into binary categories. Additionally, it demonstrates that merely translating the CBQ-VSF is insufficient to be able to capture many of the underlying latent constructs associated with low-income and low-educated Latino/Hispanic populations
Prevalent Behavior of Strongly Order Preserving Semiflows
Classical results in the theory of monotone semiflows give sufficient
conditions for the generic solution to converge toward an equilibrium or
towards the set of equilibria (quasiconvergence). In this paper, we provide new
formulations of these results in terms of the measure-theoretic notion of
prevalence. For monotone reaction-diffusion systems with Neumann boundary
conditions on convex domains, we show that the set of continuous initial data
corresponding to solutions that converge to a spatially homogeneous equilibrium
is prevalent. We also extend a previous generic convergence result to allow its
use on Sobolev spaces. Careful attention is given to the measurability of the
various sets involved.Comment: 18 page
A remark on an overdetermined problem in Riemannian Geometry
Let be a Riemannian manifold with a distinguished point and
assume that the geodesic distance from is an isoparametric function.
Let be a bounded domain, with , and consider
the problem in with on ,
where is the -Laplacian of . We prove that if the normal
derivative of along the boundary of is a
function of satisfying suitable conditions, then must be a
geodesic ball. In particular, our result applies to open balls of
equipped with a rotationally symmetric metric of the form
, where is the standard metric of the sphere.Comment: 8 pages. This paper has been written for possible publication in a
special volume dedicated to the conference "Geometric Properties for
Parabolic and Elliptic PDE's. 4th Italian-Japanese Workshop", organized in
Palinuro in May 201
Green's function for the Hodge Laplacian on some classes of Riemannian and Lorentzian symmetric spaces
We compute the Green's function for the Hodge Laplacian on the symmetric
spaces M\times\Sigma, where M is a simply connected n-dimensional Riemannian or
Lorentzian manifold of constant curvature and \Sigma is a simply connected
Riemannian surface of constant curvature. Our approach is based on a
generalization to the case of differential forms of the method of spherical
means and on the use of Riesz distributions on manifolds. The radial part of
the Green's function is governed by a fourth order analogue of the Heun
equation.Comment: 18 page
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