998 resultados para 1.3-MU-M


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Extracellular β-1,3-glucanase was produced by Trichoderma harzianum Rifai cultivated in the Agaricus blazei (Agaricus brasiliensis) extract as a substrate in submerged fermentation. A 22-central composite factorial design was developed using the time of culture (x1/day) and Agaricus blazei extract concentration (x2/(g/L)) as variables, and the results were analyzed using response surface methodology (RSM). The results showed that the Agaricus blazei extract concentration was the most important variable in the production of β-1,3-glucanase, and the maximum β-1,3-glucanase activity (0.77 U/mL) was obtained in one day of cultivation. The β-glucan present in the cell wall of Agaricus blazei mushroom proved to be a good substrate for inducing the production of specific β-1,3-glucanase by Trichoderma harzianum Rifai.

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The present paper is a comprehensive study concerning Fe K-edge X-ray absorption spectroscopy (XAS) measurements, which were performed to characterize the local structure of (1 - x)Pb(Fe2/3W1/3)O 3-xPbTiO3 samples as a function of temperature and PbTiO3 content. Results obtained by the fits of extended X-ray absorption fine structure consist with rhombohedral symmetry for Pb(Fe 2/3W1/3)O3 composition at temperatures lower than room temperature. This result is in apparent disagreement with X-ray and neutron diffraction characterization which have been reported. This apparent disagreement is related to the fact that XAS probes the short-range order, whereas X-ray diffraction provides structural information about the average structure. Moreover, as the PbTiO3 content increases, a disorder has been detected at local structure of the FeO6 octahedron. Analysis of X-ray absorption near edge structure spectra did not show modifications in intensity nor energy of transitions. © 2013 American Institute of Physics.

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Presenta la organizacion de los trabajos, resumen de los debates y conclusiones de la reunion del CEGAN que se convoco a fin de servir de foco preparatorio para la Conferencia Extraordinaria de la CEPAL, celebrada en Mexico entre el 19 y el 23 de enero de 1987, y cuyo tema principal se refiere a estrategias y politicas nacionales e internacionales conducentes a la recuperacion y al desarrollo de los paises de la region.

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Pós-graduação em Fisiopatologia em Clínica Médica - FMB

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Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Pós-graduação em Ciência e Tecnologia de Materiais - FC

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1,3-propanediol is a high-value specialty chemical which has many industrial applications. Its main use is the production of the polymer polypropylene terephthalate, a thermoplastic used in the textile and automobile industries. The interest in 1,3-propanediol production from glycerol bio-conversion has increased after the employment of biodiesel by various countries, being produced by chemical synthesis from petroleum intermediates or biotechnologically by microbial fermentation. Glycerol is an abundant low-cost byproduct from biodiesel refineries, and it is the only substrate that can be naturally or enzymatically converted to 1,3-propanediol by microbial fermentation. In this review, information on 1,3-propanediol's importance, production and purification are presented, along with results from recent research on glycerol microbial conversion to 1,3-propanediol. The bio-production of this intermediate compound from glycerol is very attractive both economically and environmentally, since it allows the replacement of fossil fuels by renewable resources.

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Oxidation states of transition metal cations in spinels-type oxides are sometimes extremely difficult to determine by conventional spectroscopic methods. One of the most complex cases occurs when there are different cations, each one with several possible oxidation states, as in the case of the magnetoresistant Mn(2-x)V(1+x)O4 (x=0, 1/3 and 1) spinel-type family. In this contribution we describe the determination of the oxidation state of manganese and vanadium in Mn(2-x)V(1+x)O4 (x=0, 1/3,1) spinel-type compounds by analyzing XANES and high-resolution K beta X-ray fluorescence spectra. The ionic models found are Mn22+V4+O4, Mn5/32+V4/33.5+O4 and Mn2+V23+O4. Combination of the present results with previous data provided a reliable cation distribution model. For these spinels, single magnetic electron paramagnetic resonance (EPR) lines are observed at 480 K showing the interaction among the different magnetic ions. The analysis of the EPR parameters show that g-values and relative intensities are highly influenced by the concentration and the high-spin state of Mn2+. EPR broadening linewidth is explained in terms of the bottleneck effect, which is due to the presence of the fast relaxing V3+ ion instead of the weak Mn2+ (S state) coupled to the lattice. The EPR results, at high temperature, are well explained assuming the oxidation states of the magnetic ions obtained by the other spectroscopic techniques. (c) 2013 Elsevier Inc. All rights reserved.

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Oxidation state and coordination of transition metal cations seems to be hard to assess when considering multiple cations, each one with different possible oxidation states. In fact, this is the case of the spineltype double oxides family. High resolution K beta X-ray fluorescence spectra were measured in Mn(2-x)V(1+4)O4 (x=0 and 1/3) spinels-type double oxides in order to determine the oxidation state and coordination of V and Mn cations. The relative intensity of radiative Auger effect KM2,3M4,5 to the total intensity and the integral absolute difference value were used as reference parameters for the characterization of Mn oxidation states. The coordination of Mn ions was inferred by the intensity of the K beta(5) line. In the case of V compounds, it was used as the intensity of the line K beta' relative to the total area of K beta region. The obtained results were further compared with X-ray absorption spectra analysis, showing good agreements regarding the oxidation state characterization. However, there were found some discrepancies in coordination, due to customary oversimplifications in the K beta(5) line origin. The obtained results might represent valuable and useful data for chemical scopes of characterizing spineltype oxides family. (C) 2013 Elsevier Ltd. All rights reserved.