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71.
Claudio C. Silveira Paulo Cesar S. Santos Samuel R. Mendes Antonio L. Braga 《Journal of organometallic chemistry》2008,693(26):3787-3790
A general method for the synthesis of vinylic chalcogenides by nucleophilic and Ni-catalyzed vinylic substitution on vinylic halides by phenyl chalcogenolates is described. The reactions were regio and stereoselective for the nickel catalyzed substitution, and mixture of isomers was observed for some examples in the thermal process in DMF. 相似文献
72.
L. C. Mendes R. E. R. Abrigo V. D. Ramos P. S. C. Pereira 《Journal of Thermal Analysis and Calorimetry》2010,99(2):545-549
The influence of PC melt flow rate (MFR) on phase behavior, thermal and rheological properties of catalysed and non-catalysed
poly(ethylene terephthalate)/polycarbonate (PET/PC) (80/20 wt%) reactive blending were investigated. Two types of PC named
PC1 and PC2 with MFR 3.1 and 10.8 g/10 min, respectively, were used. Each PC and the catalyst showed significant influence
on calorimetric properties, thermal stability and WAXS patterns of the blends. Regarding to TG/DTG, the blends degraded in
two steps which were attributed to PET rich phase and PC one and permit to infer that a partially miscible blends were produced. 相似文献
73.
Miguel A. T. Walter Aline A. Q. Abdu Luís Fernando Figueira da Silva Joo Luiz F. Azevedo 《国际流体数值方法杂志》2005,49(9):999-1014
The compressible gas flows of interest to aerospace applications often involve situations where shock and expansion waves are present. Decreasing the characteristic dimension of the computational cells in the vicinity of shock waves improves the quality of the computed flows. This reduction in size may be accomplished by the use of mesh adaption procedures. In this paper an analysis is presented of an adaptive mesh scheme developed for an unstructured mesh finite volume upwind computer code. This scheme is tailored to refine or coarsen the computational mesh where gradients of the flow properties are respectively high or low. The refinement and coarsening procedures are applied to the classical gas dynamic problems of the stabilization of shock waves by solid bodies. In particular, situations where oblique shock waves interact with an expansion fan and where bow shocks arise around solid bodies are considered. The effectiveness of the scheme in reducing the computational time, while increasing the solution accuracy, is assessed. It is shown that the refinement procedure alone leads to a number of computational cells which is 20% larger than when alternate passes of refinement and coarsening are used. Accordingly, a reduction of computational time of the same order of magnitude is obtained. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
74.
Heck reactions between iodobenzene and methyl acrylate were carried out in monoglyme and diglyme as solvents, using different ligands and palladium sources, and good to high yields were obtained in the production of (E)‐substituted olefins. The ionic liquid BmimCl was successfully utilized as pre‐ligand to substitute triphenylphosphine. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
75.
Aline Bonami Sandrine Grellier Mohammad Kacim 《Transactions of the American Mathematical Society》2008,360(3):1377-1390
We extend to multilinear Hankel operators the fact that some truncations of bounded Hankel operators are still bounded. We prove and use a continuity property of bilinear Hilbert transforms on products of Lipschitz spaces and Hardy spaces.
76.
Isolda C. Mendes Fernanda B. Costa Geraldo M. de Lima José D. Ardisson Isabel Garcia-Santos Alfonso Castiñeiras Heloisa Beraldo 《Polyhedron》2009,28(6):1179-1185
Reaction of tin tetrachloride with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives gave [Sn(2Am4DH)Cl3] (1), [Sn(2Am4Me)Cl3] (2), [Sn(2Am4Et)Cl3] (3) and [Sn(2Am4Ph)Cl3] (4) as products, in which an anionic thiosemicarbazone coordinates to the metal centre along with three chloride ions. The crystal structures of 1 and 2 were determined. The thiosemicarbazones were moderately active against Candida albicans and Pseudomonas aeruginosa. Upon coordination to tin(IV) the antimicrobial activity of the thiosemicarbazones increases. The studied compounds proved to be toxic to Artemia salina, suggesting that they could present cytotoxic activity against solid tumors. 相似文献
77.
Johanna Méndez Arias Anelize de Oliveira Moraes Luiz Felipe Amarante Modesto Aline Machado de Castro Nei Pereira Jr 《Applied biochemistry and biotechnology》2017,181(2):593-603
Poly(ethylene glycol) (PEG 4000) and bovine serum albumin (BSA) were investigated with the purpose of evaluating their influence on enzymatic hydrolysis of sugarcane bagasse. Effects of these supplements were assayed for different enzymatic cocktails (Trichoderma harzianum and Penicillium funiculosum) that acted on lignocellulosic material submitted to different pretreatment methods with varying solid (25 and 100 g/L) and protein (7.5 and 20 mg/g cellulose) loadings. The highest levels of glucose release were achieved using partially delignified cellulignin as substrate, along with the T. harzianum cocktail: increases of 14 and 18 % for 25 g/L solid loadings and of 33 and 43 % for 100 g/L solid loadings were reached for BSA and PEG supplementation, respectively. Addition of these supplements could maintain hydrolysis yield even for higher solid loadings, but for higher enzymatic cocktail protein loadings, increases in glucose release were not observed. Results indicate that synergism might occur among these additives and cellulase and xylanases. The use of these supplements, besides depending on factors such as pretreatment method of sugarcane bagasse, enzymatic cocktails composition, and solid and protein loadings, may not always lead to positive effects on the hydrolysis of lignocellulosic material, making it necessary further statistical studies, according to process conditions. 相似文献
78.
This paper presents a comparative study between a carbon molecular sieve (CMS) membrane and a commercial CMS adsorbent; these materials are suited for selective gas permeation and adsorption-based gas separations, respectively. The purpose of this analysis is to better understand the mass transport mechanism in CMS membranes and how it is related to the material's structure. The structural characterization based on the adsorption of CO2 at 0 °C revealed that the adsorbent has a greater micropore volume, a smaller mean pore width and a micropore size distribution shifted to the left, when compared to the membrane. This translates into a lower adsorption capacity of the membrane towards N2, Ar, CO2 and O2 at 29.5 °C and 0–7 bar. The adsorption kinetics were also studied and the pressure-dependence of the apparent time constants established; different models were used to predict the experimental results, emphasizing the very important role of the ultramicroporosity on the properties of the materials. The CMS membrane exhibited a pore blockage effect when permeating O2 and CO2. Further morphologic characterization was performed by SEM, X-ray diffraction and mercury porosimetry. 相似文献
79.
Signori AM Santos Kde O Eising R Albuquerque BL Giacomelli FC Domingos JB 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17772-17779
A new and straightforward method for screening highly catalytically active silver nanoparticle-polymer composites derived from branched polyethyleneimine (PEI) is reported. The one-step systematic derivatization of the PEI scaffold with alkyl (butyl or octyl) and ethanolic groups led to a structural diversity correlated to the stabilization of silver nanoparticles and catalysis. Analysis of PEI derivative libraries identified a silver nanoparticle-polymer composite that was able to efficiently catalyze the p-nitrophenol reduction by NaBH(4) in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 0.57 s(-1) m(-2) L. Carried out in the presence of excess NaBH(4), the catalytic reaction was observed to follow pseudo-first-order kinetics and the apparent rate constant was linearly dependent on the total surface area of the silver nanoparticles (Ag-NPs), indicating that catalysis takes place on the surface of the nanoparticles. All reaction kinetics presented induction periods, which were dependent on the concentration of substrates, the total surface of the nanoparticles, and the polymer composition. All data indicated that this induction time is related to the resistance to substrate diffusion through the polymer support. Hydrophobic effects are also assumed to play an important role in the catalysis, through an increase in the local substrate concentration. 相似文献
80.
Aline Machado de Castro Kelly Cristina Nascimento Rodrigues Pedro Juliana Cunha da Cruz Marcela Costa Ferreira Selma Gomes Ferreira Leite Nei Pereira 《Applied biochemistry and biotechnology》2010,162(7):2111-2122
Sugarcane bagasse is an agroindustrial residue generated in large amounts in Brazil. This biomass can be used for the production
of cellulases, aiming at their use in second-generation processes for bioethanol production. Therefore, this work reports
the ability of a fungal strain, Trichoderma harzianum IOC-4038, to produce cellulases on a novel material, xylan free and cellulose rich, generated from sugarcane bagasse, named
partially delignified cellulignin. The extract produced by T. harzianum under submerged conditions reached 745, 97, and 559 U L−1 of β-glucosidase, FPase, and endoglucanase activities, respectively. The partial characterization of this enzyme complex
indicated, using a dual analysis, that the optimal pH values for the biocatalysis ranged from 4.9 to 5.2 and optimal temperatures
were between 47 and 54 °C, depending on the activity studied. Thermal stability analyses revealed no significant decrease
in activity at 37 °C during 23 h of incubation. When compared to model strains, Aspergillus niger ATCC-16404 and Trichoderma reesei RutC30, T. harzianum fermentation was faster and its extract showed a better balanced enzyme complex, with adequate characteristics for its application
in simultaneous saccharification and fermentation processes. 相似文献