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排序方式: 共有331条查询结果,搜索用时 31 毫秒
291.
Eliana Alves Nuno Santos Tânia Melo Elisabete Maciel M. Luísa Dória Maria A. F. Faustino João P. C. Tomé Maria G. P. M. S. Neves José A. S. Cavaleiro Ângela Cunha Luisa A. Helguero Pedro Domingues Adelaide Almeida M. Rosário M. Domingues 《Rapid communications in mass spectrometry : RCM》2013,27(23):2717-2728
292.
Patricia Bogalhos Lucente Fregolente Gláucia Maria F. Pinto Maria Regina Wolf-Maciel Rubens Maciel Filho 《Applied biochemistry and biotechnology》2010,160(7):1879-1887
Distilled glycerides are obtained through distillation of the system mono-diglycerides which is produced from the esterification
reaction between a triglyceride with glycerol. In this work, monoglycerides (MG) and diglycerides (DG) are produced through
lipase-catalyzed glycerolysis of soybean oil using Candida antarctica B in a solvent-free system. To separate the products of the reaction in order to obtain essentially MG and an oil of DG,
it is necessary to use a suitable process in order to preserve the stability of the components and to keep the products free
of inappropriate solvents. So, after 24 h of enzymatic reaction, the mixture of acylglycerols and fatty acids was distilled
into a centrifugal molecular distiller, since it provides a free solvent and lower temperature environment to increase the
desired product concentration. Starting from a material with 25.06% of triglycerides (TG), 46.63% of DG, 21.72% of MG, 5.38%
of free fatty acids (FFA), and 1.21% of glycerol, the MG purity in the distillate stream was 80% at evaporator temperature
(T
E) equal to 250 °C and feed flow rate (Q) equal to 10.0 mL/min. At these conditions, the MG recovery was 35%. The material collected in the residue stream presented
DG-enriched oil with TG unhydrolyzed, residual MG, and low acidity (29.83% of TG, 53.20% of DG, 15.64% of MG, and 1.33% of
FFA), which is suitable to replace TG oil in the human diet. 相似文献
293.
Ulisses Barres de Almeida Elisabete M. de Gouveia Dal Pino 《Brazilian Journal of Physics》2013,43(5-6):328-340
Gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. Cherenkov Telescope Array (CTA) is an international initiative to build the next-generation ground-based gamma-ray observatory which will have a factor of 5–10 improvement in sensitivity in the 100-GeV–10-TeV range and an extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the Northern and another in the Southern Hemisphere) for full sky coverage and will be operated as an open observatory. It will provide a deep insight into the non-thermal high-energy Universe. In this talk, we will briefly present the major design concepts of CTA as well as its vast science case. 相似文献
294.
Betânia H. Lunelli Rafael R. Andrade Daniel I. P. Atala Maria Regina Wolf Maciel Francisco Maugeri Filho Rubens Maciel Filho 《Applied biochemistry and biotechnology》2010,161(1-8):227-237
Lactic acid is an important product arising from the anaerobic fermentation of sugars. It is used in the pharmaceutical, cosmetic, chemical, and food industries as well as for biodegradable polymer and green solvent production. In this work, several bacterial strains were isolated from industrial ethanol fermentation, and the most efficient strain for lactic acid production was selected. The fermentation was conducted in a batch system under anaerobic conditions for 50 h at a temperature of 34 °C, a pH value of 5.0, and an initial sucrose concentration of 12 g/L using diluted sugarcane molasses. Throughout the process, pulses of molasses were added in order to avoid the cell growth inhibition due to high sugar concentration as well as increased lactic acid concentrations. At the end of the fermentation, about 90% of sucrose was consumed to produce lactic acid and cells. A kinetic model has been developed to simulate the batch lactic acid fermentation results. The data obtained from the fermentation were used for determining the kinetic parameters of the model. The developed model for lactic acid production, growth cell, and sugar consumption simulates the experimental data well. 相似文献
295.
296.
M. C. Maciel S. A. Santos G. N. Sottosanto 《Journal of Optimization Theory and Applications》2009,142(2):385-398
This work is concerned with differentiable constrained vector optimization problems. It focus on the intrinsic connection
between positive linearly dependent gradient sets and the distinct notions of regularity that come to play in this context.
The main aspect of this contribution is the development of regularity conditions, based on the positive linear dependence
or independence of gradient sets, for problems with general nonlinear constraints, without any convexity hypothesis. Being
easy to verify, these conditions might be useful to define termination criteria in the development of algorithms.
This work was supported by Fundación Antorchas, Grant 13900/4; by Southern National University, Grant UNS 24/L069; by Comahue
National University, Grant E060/04; by CNPq-Brazil (Grants 302412/2004-2, 473586/2005-5 and 303465/2007-7) and by FAPESP-Brazil
(06/53768-0). 相似文献
297.
Yuriko Nozawa Akira Kawashima Elisabete Hiromi Hashimoto Hajime Kato Ken-ichi Harada 《Journal of chromatography. A》2009,1216(18):3807-3811
In the advanced Marfey's method, the resolution between the diastereomers derivatized with 1-fluoro-2,4-dinitrophenyl-5-l-leucinamide (l-FDLA) and 1-fluoro-2,4-dinitrophenyl-5-d-leucinamide (d-FDLA) is reflected by the difference of hydrophobicity of the two functional groups at the asymmetric carbon. However, no effective method has been developed for the estimation of hydrophobicity so far. For this purpose, we introduced log D from the ACD Labs LogD and applied it to relatively simple primary amines, amino acids and secondary alcohols in the present study. It was found that the difference of the retention times (ΔtR) correlated with that of log D (Δlog D) for both diastereomers based on the obtained experimental results. Based on these results, the following procedure was proposed for the non-empirical determination of the absolute configuration of primary amines including amino acids and secondary alcohols: (1) estimate the hydrophobicity by the calculation of log D for the two substituent groups at the asymmetric carbon, (2) locate the trans-type arrangement of the two more hydrophobic substituents in the l-DLA derivative and judge the asymmetric carbon to be R or S in the trans-type that is eluted first, (3) derivatize the desired compound with l- or d-FDLA and analyze by LC/MS, and (4) compare the elution order with the prospective one and determine the absolute configuration at the asymmetric carbon. Furthermore, log D could also be used to predict the retention times of unavailable amino acids and small peptides, indicating that the combination of the advanced Marfey's method with log D would provide more reliable structural information on a mixture composed of amino acids and small peptides. The developed method is being applied to more complicated compounds. 相似文献
298.
Adriano Pinto Mariano Caliane Bastos Borba Costa Dejanira de Franceschi de Angelis Francisco Maugeri Filho Daniel Ibraim Pires Atala Maria Regina Wolf Maciel Rubens Maciel Filho 《Applied biochemistry and biotechnology》2009,159(2):366-381
In this work, the mathematical optimization of a continuous flash fermentation process for the production of biobutanol was
studied. The process consists of three interconnected units, as follows: fermentor, cell-retention system (tangential microfiltration),
and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The objective of the optimization
was to maximize butanol productivity for a desired substrate conversion. Two strategies were compared for the optimization
of the process. In one of them, the process was represented by a deterministic model with kinetic parameters determined experimentally
and, in the other, by a statistical model obtained using the factorial design technique combined with simulation. For both
strategies, the problem was written as a nonlinear programming problem and was solved with the sequential quadratic programming
technique. The results showed that despite the very similar solutions obtained with both strategies, the problems found with
the strategy using the deterministic model, such as lack of convergence and high computational time, make the use of the optimization
strategy with the statistical model, which showed to be robust and fast, more suitable for the flash fermentation process,
being recommended for real-time applications coupling optimization and control. 相似文献
299.
Jackson D. Megiatto Jr. Cristina G. Silva Elaine C. Ramires Elisabete Frollini 《Polymer Testing》2009,28(8):793-800
Thermoset phenolic composites reinforced with sisal fibers were prepared to optimize the cure step. In the present study, processing parameters such as pressure, temperature, and time interval were varied to control the vaporization of the water generated as a byproduct during the crosslinking reaction. These molecules can vaporize forming voids, which in turn affect the final material properties. The set of results on impact strength revealed that the application of higher pressure before the gel point of the phenolic matrix produced composites with better properties. The SEM images showed that the cure cycle corresponding to the application of higher values of molding pressure at the gel point of the phenolic resin led to the reduction of voids in the matrix. In addition, the increase in the molding pressure during the cure step increased the resin interdiffusion. Better filling of the fiber channels decreased the possibility of water molecules diffusing through the internal spaces of the fibers. These molecules then diffused mainly through the bulk of the thermoset matrix, which led to a decrease in the water diffusion coefficient (D) at all three temperatures (25, 55 and 70 °C) considered in the experiments. 相似文献
300.
Luís Gustavo Cofani dos Santos Elisabete A. De Nadai Fernandes Márcio Arruda Bacchi Gabriel Adrián Sarriés Lucimara Blumer Fernando Barbosa Júnior 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):493-496
Aiming at international competitiveness of the Brazilian dairy sector, new governmental policies were released to improve
quality and safety of bovine milk. In this context, it is important to quantify essential and toxic chemical elements. Here,
the composition of milk samples taken at 32 dairy farms in Minas Gerais State was assessed by instrumental neutron activation
analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS), besides the evaluation of usual quality parameters.
Significant differences were found for Ba, K, Na and fat content amongst dairy farms with diverse quality levels established
on basis of somatic cell and total bacterial count. 相似文献