Study of the interaction between hydrogen and carbon-based nanomaterials

Hydrogen is a promising energy carrier. Coupling hydrogen production to renewable energy sources would help alleviate the world\u27s dependence on fossil fuels. A hurdle that must be overcome for that scenario is the development of satisfactory hydrogen storage media. Theoretical work suggests that carbon-based nanomaterials are plausible candidates; The research objective of this work is to study the influence of hydrogen adsorption on the chemical and electronic properties of carbon-based nanomaterials (i.e., single-walled carbon nanotubes and C60). An atomic hydrogen source was constructed. Nanomaterials were exposed to atomic and/or molecular hydrogen, and the local chemical and electronic interaction was studied using Photoelectron Spectroscopy. Annealing of hydrogenated samples shows the reversibility of the adsorption of atomic hydrogen. The results obtained give detailed information about hydrogenation-induced chemical and electronic interactions, showing that Photoelectron Spectroscopy, with the atomic hydrogen source, is a powerful tool to investigate the hydrogen storage potential of carbon-based nanomaterials

ESTÁGIO SUPERVISIONADO E IDENTIDADE PROFISSIONAL EM SERVIÇO SOCIAL: DILEMAS E POTENCIALIDADES NO CONTEXTO CONTEMPORÂNEO

Resumo O presente trabalho traz como premissa a compreensão do Estágio Supervisionado em Serviço Social enquanto solo fértil para a construção da identidade profissional do assistente social. Objetiva problematizar como esse espaço contribui para moldar uma identidade profissional, e suas principais determinações contemporâneas. Com um levantamento bibliográfico/documental verifica-se como o Estágio se constitui em um espaço privilegiado de potencialidades e desafios. Dentre estes se apresenta a precarização dos espaços sócioocupacionais; a tendência a uma instrumentalização do Estágio; e proliferação dos estágios não-obrigatórios. Por outro lado, é ancorando-se no nosso Projeto Profissional que busca-se alternativas de enfrentamento dessa realidade

Characterization of a protease produced by a Trichoderma harzianum isolate which controls cocoa plant witches' broom disease

BACKGROUND: Several Trichoderma strains have been reported to be effective in controlling plant diseases, and the action of fungal hydrolytic enzymes has been considered as the main mechanism involved in the antagonistic process. However, although Trichoderma strains were found to impair development of Crinipellis perniciosa, the causal agent of cocoa plant witches' broom disease, no fungal strain is available for effective control of this disease. We have then undertaken a program of construction of hydrolytic enzyme-overproducing Trichoderma strains aiming improvement of the fungal antagonistic capacity. The protease of an indian Trichoderma isolate showing antagonistic activity against C. perniciosa was purified to homogeneity and characterized for its kinetic properties and action on the phytopathogen cell wall. RESULTS: A protease produced by the Trichoderma harzianum isolate 1051 was purified to homogeneity by precipitation with ammonium sulfate followed by hydrophobic chromatography. The molecular mass of this protease as determined by SDS-polyacrylamide gel electrophoresis was about 18.8 kDa. Its N-terminal amino acid sequence shares no homology with any other protease. The purified enzyme substantially affected the cell wall of the phytopathogen C. perniciosa. Western-blotting analysis showed that the enzyme was present in the culture supernatant 24 h after the Trichoderma started to grow in casein-containing liquid medium. CONCLUSIONS: The capacity of the Trichoderma harzianum protease to hydrolyze the cell wall of C. perniciosa indicates that this enzyme may be actually involved in the antagonistic process between the two fungi. This fact strongly suggest that hydrolytic enzyme over-producing transgenic fungi may show superior biocontrol capacity

Fast convergence delayed signal cancellation method for sequence component separation

Delayed Signal Cancellation (DSC) is one of the methods used to separate the negative and positive sequence components in unbalanced 34 systems. In this paper a DSC methodology with a fast convergence time is proposed and is shown that an improved separation of the positive and negative sequences is feasible. Experimental results are presented to demonstrate the performance of the proposed methodology

Vector control strategies to enable equal frequency operation of the modular multilevel matrix converter

The Modular Multilevel Matrix Converter (M3C) is an ac-to-ac converter suitable for high-power applications. The control of this converter is complex, mainly when the frequencies of the ac systems connected to the ports of the converter are close or equal, because the floating capacitors can present large voltage oscillations. Therefore, this paper proposes a new Vector Control System to enable the operation of the M3C when the input-output frequencies are equal. The effectiveness of the proposal is validated through simulations and experimental results conducted with a 27 power-cell prototype

Analysis of Renewable Energy Policies Related to Repowering the Wind Energy Sector: the Spanish Case

In countries that started early with wind energy, the old wind turbines were located in places where the wind is often very good. Since the best places in which the wind is concerned are occupied by old wind turbines (with lower capacity than the more recent ones) the trend is to start replacing old turbines with new ones. With repowering, the first generation of wind turbines can be replaced by modern multi-megawatt wind turbines. The aim of this article is to analyze energy policies in the Spanish energy sector in the repowering of wind farms from the viewpoint of the current situation of the wind energy sector. The approach presented in this article is meant to explain what have been the policies related to the repowering sector making a brief analysis of the spectrum of different stimulii that are demanded by the market analyzing also the future perspectives of the repowering sector by establishing the new opportunities based on the new published regulations