Non-conventional vortex configurations in a mesoscopic flat disk

The influence of superficial defects on the vortex configurations of a thin superconducting disk is investigated within the time dependent Ginzburg-Landau formalism. The free energy, magnetization, vorticity, and the Cooper pair density are calculated for both metastable and stable vortex configurations and different number of defects on its surface in the presence of an external magnetic field applied perpendicular to the disk area. We show that the competition between the confinement geometry and the geometric position of the defects leads to non-conventional vortex configurations which are not compatible with the symmetry of the sample geometry.

Adsorption of polyelectrolytes onto oppositely charged cylindrical macroions

In this work we investigate the adsorption of polyelectrolyte chains onto uniformly charged cylindrical macroions by means of the Metropolis Monte Carlo simulations and weighted histogram analysis method. Adopting a simplified model for macromolecules and treating the electrolytic solution in the Debye-Hückel level, conformational properties of the adsorbed chain, such as the radius of gyration and the thickness of the adsorbed layer, are provided as a function of ionic strength and macroion charge density. By analysis of the free energy profile as a function of the radius of gyration it was possible to identify first-order-like transitions between adsorbed and desorbed states and obtain a macroion charge density dependence of the critical ionic strength in good agreement with experiments. © 2013 AIP Publishing LLC.

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.

Linear arrangement of metallic and superconducting defects in a thin superconducting sample

The vortex matter in a superconducting disk with a linear configuration of metallic and superconducting defects is studied. Effects associated to the pinning (anti-pinning) force of the metallic (superconducting) defect on the vortex configuration and on the thermodynamic critical fields are analyzed in the framework of the Ginzburg Landau theory. We calculate the loop of the magnetization, vorticity and free energy curves as a function of the magnetic field for a thin disk. Due to vortex-defect attraction for a metallic defect (repulsion for a superconducting defect), the vortices always (never) are found to be sitting on the defect position. © 2013.

Analyzing the effect of homogeneous frustration in protein folding

The energy landscape theory has been an invaluable theoretical framework in the understanding of biological processes such as protein folding, oligomerization, and functional transitions. According to the theory, the energy landscape of protein folding is funneled toward the native state, a conformational state that is consistent with the principle of minimal frustration. It has been accepted that real proteins are selected through natural evolution, satisfying the minimum frustration criterion. However, there is evidence that a low degree of frustration accelerates folding. We examined the interplay between topological and energetic protein frustration. We employed a Cα structure-based model for simulations with a controlled nonspecific energetic frustration added to the potential energy function. Thermodynamics and kinetics of a group of 19 proteins are completely characterized as a function of increasing level of energetic frustration. We observed two well-separated groups of proteins: one group where a little frustration enhances folding rates to an optimal value and another where any energetic frustration slows down folding. Protein energetic frustration regimes and their mechanisms are explained by the role of non-native contact interactions in different folding scenarios. These findings strongly correlate with the protein free-energy folding barrier and the absolute contact order parameters. These computational results are corroborated by principal component analysis and partial least square techniques. One simple theoretical model is proposed as a useful tool for experimentalists to predict the limits of improvements in real proteins. © 2013 Wiley Periodicals, Inc.

The application of a surface response methodology in the solar/UV-induced degradation of dairy wastewater using immobilized ZnO as a semiconductor

An Advanced Oxidation Process (AOPs) was carried out in this study with the use of immobilized ZnO and solar/UV as an energy source to degrade dairy wastewater. The semibatch reactor system consisted of metal plate of 800 × 250 mm and a glass tank. The reaction time was of 3 h for 3 L of dairy wastewater. Experiments were performed based on a surface response methodology in order to optimize the photocatalytic process. Degradation was measured in percentage terms by total organic carbon (TOC). The entry variables were ZnO coating thickness and pH, using three levels of each variable. The optimized results showed a TOC degradation of 31.7%. Optimal parameters were metal-plate coating of 100 m of ZnO and pH of 8.0. Since solar/UV is a constant and free energy source in most tropical countries, this process tends to suggest an interesting contribution in dairy wastewater treatment, especially as a pretreatment and the optimal conditions to guarantee a better efficiency of the process. © 2013 Gisella R. Lamas Samanamud et al.

Estudo do efeito da adição de frustração no enovelamento de proteínas utilizando modelos baseados em estruturas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise conformacional dos petídeos protonectina e protonectina (1-6), isolados e em associação, em mistura TFE-água

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Regimes de frustração ótima em enovelamento de proteínas com modelos baseado em estrutura

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

Aplicação do eletrocapilaridade na manipulação de microgotas

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

Análise comparativa da viabilidade econômica da utilização de coletores solar para aquecimento de água

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Aplicações de secagem para o aproveitamento de resíduos da banana, visando sua aplicação na indústria

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelo estatístico de rede de resistores para o estudo de processos de condução em nanocompósitos poliméricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da solubilidade de apatitas em meios de interesse biológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese e caracterização de híbridos inorgânico-orgânicos funcionalizados com tiouréia e 2,2’-dipiridilamina: aplicação em adsorção de íons metálicos, pré-concentração e catálise

Pós-graduação em Ciência dos Materiais - FEIS