After characterization of preferred conditions for Helicobacter pylori survival in the sessile state, it was observed that the bacterium transforms from spiral to coccoid under mild circumstances, whereas under extreme ones it is unable to undergo shape modification. This strongly supports the view that transformation into the coccoid form is an active, biologically led process, switched on by the bacterium as a protection mechanism.
Part of the reason for rejecting aquatic environments as possible vectors for the transmission of Helicobacter pylori has been the preference of this microorganism to inhabit the human stomach and hence use a direct oral-oral route for transmission. On the other hand, most enteric bacterial pathogens are well known for being able to use water as an environmental reservoir. In this work, we have exposed 13 strains of seven different Helicobacter spp. (both gastric and enterohepatic) to water and tracked their survival by standard plating methods and membrane integrity assessment. The influence of different plating media and temperatures and the presence of light on recovery was also assessed. There was good correlation between cultivability and membrane integrity results (Pearson's correlation coefficient ؍ 0.916), confirming that the culture method could reliably estimate differences in survival among different Helicobacter spp. The species that survived the longest in water was H. pylori (>96 h in the dark at 25°C), whereas H. felis appeared to be the most sensitive to water (<6 h). A hierarchical cluster analysis demonstrated that there was no relationship between the enterohepatic nature of Helicobacter spp. and an increased time of survival in water. This work assesses for the first time the survival of multiple Helicobacter spp., such has H. mustelae, H. muridarum, H. felis, H. canadensis, H. pullorum, and H. canis, in water under several conditions and concludes that the roles of water in transmission between hosts are likely to be similar for all these species, whether enterohepatic or not.
ResumoO objetivo do presente estudo foi avaliar se a autoeficácia funciona como variável mediadora na relação entre a sobrecarga de trabalho e as dimensões de burnout. Participaram da pesquisa 982 professores de escolas públicas e privadas. Foram utilizados como instrumentos de pesquisa o questionário para avaliação da síndrome de burnout, versão para professores, a escala geral de autoeficácia e a subescala de sobrecarga laboral da organizational Stress Questionnaire. Os resultados obtidos por meio da análise de regressão linear confirmaram a hipótese de que a autoeficácia desempenha um papel mediador entre a sobrecarga de trabalho e as dimensões de burnout. O resultado aponta para a importância de intervenções que contemplem o desenvolvimento da autoeficácia em professores como medida de prevenção ou reabilitação da síndrome de burnout. Palavras-chave: síndrome de burnout; sobrecarga laboral; autoeficácia, professores; mediação.The mediational role of self-efficacy in the relation between workload and burnout' dimensions in teachers AbstractThe objective of this study was to evaluate if self-efficacy can be a mediating variable in the relationship between workload and the dimensions of burnout. The research involved 982 teachers from public and private schools. The Questionnaire for the assessment of burnout Syndrome was used as research instrument, a version for teachers, the General Scale of Self-efficacy and the Subscale of Workload the Organizational Stress Questionnaire. The results obtained by means of linear regression analysis confirmed the hypothesis that self-efficacy plays a mediating role between workload and the dimensions of burnout. The result demonstrates the importance of interventions directed to the development of self-efficacy in teachers as a measure of prevention or rehabilitation of the burnout syndrome. Keywords: burnout syndrome; mediation; teachers; self-efficacy; workload.El papel mediador de la autoeficacia en la relación entre la sobrecarga de trabajo y las dimensiones de burnout en profesores ResumenEl objetivo del estudio fue evaluar si la autoeficacia funciona como variable mediadora en la relación entre la sobrecarga de trabajo y las dimensiones de burnout. Participaron 982 profesores de escuelas públicas y privadas. Se utilizaron como herramientas el Cuestionario para Evaluación del Síndrome de burnout, versión para profesores, la Escala General de Autoeficacia y la Sub--escala de Sobrecarga Laboral de la Organizational Stress Questionnaire. Los resultados obtenidos mediante el análisis de regresión linear confirmaron la hipótesis de que la autoeficacia ejerce un papel mediador entre la sobrecarga de trabajo y las dimensiones de burnout. El resultado muestra la importancia de intervenciones que contemplen el desarrollo de la autoeficacia en profesores, como medida de prevención o rehabilitación del Síndrome burnout. Palabras-clave: síndrome de burnout; sobrecarga laboral; autoeficacia; profesores; mediación. IntroduçãoA Organização Internacional do Trabalho (OIT, 2012) aponta ...
Histogram-valued variables are a particular kind of variables studied in Symbolic Data Analysis where to each entity under analysis corresponds a distribution that may be represented by a histogram or by a quantile function. Linear regression models for this type of data are necessarily more complex than a simple generalization of the classical model: the parameters cannot be negative; still the linear relation between the variables must be allowed to be either direct or inverse. In this work, we propose a new linear regression model for histogram-valued variables that solves this problem, named Distribution and Symmetric Distribution Regression Model. To determine the parameters of this model, it is necessary to solve a quadratic optimization problem, subject to non-negativity constraints on the unknowns; the error measure between the predicted and observed distributions uses the Mallows distance. As in classical analysis, the model is associated with a goodness-of-fit measure whose values range between 0 and 1. Using the proposed model, applications with real and simulated data are presented.
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