Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
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Item Biphasic oxidation reactions promoted by amphiphilic catalysts based on red mud residue(Applied Catalysis B: Environmental, 2014-01) Tristão, J. C.; Oliveira, A. A. S.; Teixeira, I. F.; Christofani, Taís; Guimarães, I. R.; Moura, F. C. C.Biphasic oxidation reactions of organic contaminants with H2O2 were promoted by amphiphilic catalysts prepared from red mud residue and carbon nanostructures. Contaminants oxidation is especially important for petroleum treatment, since S and N compounds are extremely unwanted mainly due to environmental issues. Also, government regulations around the levels of these pollutants in fuels are becoming increasingly strict. The amphiphilic catalysts were tested in oxidation of different model molecules: Sudan IV lipophilic dye, tiophene, dibenzothiophene and quinoline and showed very good removal, reaching 100% of contaminants oxidation. The amphiphilic catalysts act in two steps of biphasic oxidation: (i) favor the formation of a reversible emulsion between the organic contaminated phase and the aqueous oxidized phase and (ii) catalyze Fenton reaction. After reaction, the emulsion can be easily separated by a magnetic process into two phases: decontaminated organic phase and aqueous phase with oxidized contaminants.Item Mathematical analysis of a model for plant invasion mediated by allelopathy(Ecological Complexity, 2014-06) Fassoni, A. C.; Martins, M. L.Exotic plants threaten the biodiversity of natural habitats and the integrity of agricultural systems throughout the World. Therefore, understanding, predicting and controlling plant invasions became issues of great practical importance. In the present paper, a model for plant invasion based on allelopathic suppression is proposed and studied through analytical methods and numerical integration. Employing linear stability analysis the conditions for plant coexistence as well as one species extinction were determined for the spatially homogeneous system. These conditions demonstrate the advantage conferred to the alien plant by its phytotoxin. It was shown that the system exhibits bistability between two distinct fixed points, either associated to species coexistence or to the extinction of one species. Numerical simulation is also included to support such results. Further, the invasion spreading starting from a single, spatially localized initial focus was investigated by numerical integration of the model's equations. As obtained for the spatially homogeneous system, at strong interspecific competition the outcome is the extinction of one plant species. In contrast, at low interspecific competition, the rule is the coexistence between the invader and native plants. So, under weak competition alien species can invade, but genetic diversity can be sustained.