Defects in hydrogenated amorphous silicon-carbon alloy films prepared by glow discharge decomposition and sputtering

金沢大学理工研究域電子情報通信学系Properties of hydrogenated amorphous silicon-carbon alloy (a-Si 1-xCx: H) films prepared by radio frequency (rf) glow discharge decomposition and rf sputtering have been investigated by means of electron spin resonance (ESR), infrared absorption, optical absorption, and photoconductivity measurements. Although the number of C-H per C atom [C-H]/[C] is larger than that of Si-H per Si atom [Si-H]/[Si], the ESR spin density increases greatly with the C content. The increase in the density of dangling bonds may be related to the fact that the number of H atoms in gathered phase increases with an increase in x. ESR measurements also give useful information about the preferential formation of C or Si dangling bonds and the atomic distribution of Si and C through a compositional dependence of the g value. A remarkable feature for a-Si1-xCx: H film is that the presence of C atoms in the amorphous network makes the Si-H bond in a-Si 1-xCx: H more stable than that in a-Si:H

Stone-Wales Transformation Paths in Fullerene C60

The mechanisms of formation of a metastable defect isomer of fullerene C60 due to the Stone-Wales transformation are theoretically studied. It is demonstrated that the paths of the "dynamic" Stone-Wales transformation at a high sufficient for overcoming potential barriers) temperature can differ from the two "adiabatic" transformation paths discussed in the literature. This behavior is due to the presence of a great near-flat segment of the potential-energy surface in the neighborhood of metastable states. Besides, the sequence of rupture and formation of interatomic bonds is other than that in the case of the adiabatictransformation.Comment: 10 pages, 6 figure

Energy Landscape and Global Optimization for a Frustrated Model Protein

The three-color (BLN) 69-residue model protein was designed to exhibit frustrated folding. We investigate the energy landscape of this protein using disconnectivity graphs and compare it to a Go model, which is designed to reduce the frustration by removing all non-native attractive interactions. Finding the global minimum on a frustrated energy landscape is a good test of global optimization techniques, and we present calculations evaluating the performance of basin-hopping and genetic algorithms for this system.Comparisons are made with the widely studied 46-residue BLN protein.We show that the energy landscape of the 69-residue BLN protein contains several deep funnels, each of which corresponds to a different β-barrel structure

Light-induced creation of defects and related phenomena in silicon-based amorphous semiconductors.

金沢大学理工研究域電子情報通信学系Light-induced creation of defects and their annealing process were studied by ESR, photoconductivity and photoluminescence measurements for a-Si//1// minus //xN//x:H and a-Si//1// minus //xC//x:H films besides a-Si:H films with various spin densities and H contents. The results show that the degradation of the photoconductivity and the photoluminescence is mainly attributed to creation of dangling bonds due to bond breaking

Use of a polyphasic approach including MALDI-TOF MS for identification of Aspergillus section Flavi strains isolated from food commodities in Brazil

Brazil is one the largest producers and exporters of food commodities in the world. The evaluation of fungi capable of spoilage and the production mycotoxins in these commodities is an important issue that can be of help in bioeconomic development. The present work aimed to identify fungi of the genus Aspergillus section Flavi isolated from different food commodities in Brazil. Thirty-five fungal isolates belonging to the section Flavi were identified and characterised. Different classic phenotypic and genotypic methodologies were used, as well as a novel approach based on proteomic profiles produced by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Type or reference strains for each taxonomic group were included in this study. Three isolates that presented discordant identification patterns were further analysed using the internal transcribed spacer (ITS) region and calmodulin gene sequences. The data obtained from the phenotypic and spectral analyses divide the isolates into three groups, corresponding to taxa closely related to Aspergillus flavus, Aspergillus parasiticus, and Aspergillus tamarii. Final polyphasic fungal identification was achieved by joining data from molecular analyses, classical morphology, and biochemical and proteomic profiles generated by MALDI-TOF MS.Acknowledgments are due to FAPEMIG - Fundacao de Amparo a Pesquisa do Estado de Minas Gerais (Brazil) for financial support. F. C. da Silva extends thanks to CAPES - Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (Brazil) for the PhD grant. C. Santos and N. Lima thank CAPES for the financial support as international visiting professors in the Post-Graduate Programme in Agricultural Microbiology, Federal University of Lavras, Lavras (MG), Brazil