Supplementation of soft drinks with metallic ions reduces dissolution of bovine enamel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Solid-phase extraction of metal ions from fuel ethanol with a nanostructured adsorbent

This work describes the synthesis and characterization of a new octakis[3-(2,2'-dipyridylamine)propyl]octasilsesquioxane (T8-Pr-DPA), and a study of the metal ion preconcentration in fuel ethanol. Batch and column experiments were conducted to investigate for the removal of heavy metal ions from fuel ethanol. The results showed that the Langmuir allowed to describe the sorption equilibrium data of the metal ions on T8-Pr-DPA in a satisfactory way. The following maximum adsorption capacities (in mmolg-1) were determined: 3.62 for Fe (III), 3.32 for Cr (III), 2.15 for Cu (II), 1.80 for Co (II), 1.62 for Pb (II), 1.32 for Ni (II) and 0.88 for Zn (II). The thermodynamic parameters for the adsorption process such as free energy of adsorption (δG), enthalpy of adsorption (δH) and entropy of adsorption (δS) were calculated. Thermodynamic parameters showed that the system has favorable enthalpic, Gibbs free energy, and entropic values. The sorption-desorption of the metal ions has made possible the development of a preconcentration and determination method of metal ions at trace level in fuel ethanol. The method of quantitative analysis for Fe, Cu, Ni and Zn in fuel ethanol by Flame AAS was validated. Several parameters have been taken into account and evaluated for the validation of method, namely: linearity, limit of detection, limit of quantification, and the relative standard deviation and accuracy. The accuracy of the method was assessed by testing analyte recovery in the fuel ethanol samples. © 2013 Elsevier B.V.

Reestructuración del transporte público en la Ciudad de México

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Tránsito y transporte en la Ciudad de México: el sistema de ejes viales

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Liberalización del transporte urbano en Santiago de Chile

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Regulación y subvención del transporte colectivo urbano: los argumentos a favor y en contra

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Transporte marítimo

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Modelos matemáticos para problemas de dimensionamento de lotes com restrições de capacidade e custos de transporte

In this paper, capacitated lot sizing problems in which the classical lot sizing decisions are made considering the transportation costs of the manufactured products were studied. These costs are related to the necessary number of pallets or trucks to pack and/or transport the products from the factory to the warehouse. Three extensions of a mixed integer linear programming model from the literature are considered, representing general cases that are commonly found in companies. These models are tested and evaluated using an optimization package, and a Lagrangian heuristic was developed for one of the extensions proposed.

La política de los países de América Latina y el Caribe en materia de transporte marítimo regular y la Convención de las NU sobre un Código de Conducta de las Conferencias Marítimas = Latin American and Caribbean liner shipping policies and the UN Convention on a Code of Conduct for Liner Conferences

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La evolución de las redes de transporte terrestre en América Latina

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El significado para América Latina del estandar de las Naciones Unidas sobre el intercambio electrónico de datos para administración, comercio y transporte (UN

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El transporte eléctrico urbano en América Latina: una breve reseña de su pasado, presente y perspectivas

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