Hypovitaminosis A: cofactor of deleterious clinic outcome in human being

Importante foco de atenção em Saúde Pública tem sido a avaliação de determinados micronutrientes no ser humano, em especial aqueles que se encontram associados à vulnerabilidade orgânica, conseqüente ao desiquilíbrio ou à deficiência desses micronutrientes. Entre os micronutrientes, a hipovitaminose A tem sido objeto de realce devido à significante prevalência em populações de países em desenvolvimento. Este artigo aborda a Vitamina A, enfocando seu metabolismo e as repercussões deletérias, decorrentes de sua deficiência sobre o organismo, suas manifestações no ciclo gravidopuerperal, e sua interação em situações clínicas, específicas.An important focus of attention in Public Health has been micronutrient deficiency in human being because of the enhanced vulnerability of individuals to the effects of micronutrient deficiency or imbalance. Among all micronutrients deficiencies, vitamin A has been one of the most important public health problems, affecting a large percentage of people in developing countries. This article focus on a review of vitamin A metabolism, deleterious repercussions and association with several clinical and obstetrics conditions. It highlights hypovitaminosis A as cofactor of deleterious clinic outcome in human being

DFT Study of Hydrogen-Assisted Dissociation of CO by HCO, COH, and HCOH Formation on Fe(100)

DFT calculations using the GGA-PBE exchange correlation functional were used to investigate the effect of the hydrogen in the assisted CO dissociation on the Fe(100) surface. The formation mechanisms of the primary products CH, OH, CH2, and H2O involved in the Fischer-Tropsch synthesis have been studied. Three different routes were investigated passing through the HCO, COH, or HCOH intermediates. The energy barriers of the reactions were estimated using the nudged elastic band method (NEB). The energy profiles of assisted and double-assisted dissociations of CO are presented. The formation energies of HCO, COH, and HCOH intermediates are estimated to be endothermic with activation energies of 0.90, 1.07, and 2.13 eV, respectively. The formation of CH2 is energetically more favorable with the global reaction energy estimated to be -1.10 eV. The other CH, OH, and H2O intermediates have also endothermic formation energies with respect to the Fe(100)/(CO + H) system. The chemical bonding of the adsorbed intermediates and reactants was analyzed based on the population analysis, electron localization function, and pseudodifferential charge density. A comparison with direct CO dissociation leads to the conclusion that hydrogen-assisted processes constitute viable routes for CO dissociation on Fe (100) and alkanes formation.Fil: Amaya Roncancio, Sebastian. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Linares, Daniel Humberto. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Duarte, Hélio A.. Universidade Federal de Minas Gerais; BrasilFil: Sapag, Manuel Karim. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin