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401.
Dina Murtinho M. Elisa Silva Serra A.M.d’A. Rocha Gonsalves 《Tetrahedron: Asymmetry》2010,21(1):62-68
Derivatives of (+)-camphoric acid were prepared by a short and simple synthetic sequence and proved to be excellent ligands for the enantioselective ethylation of benzaldehyde with diethylzinc, with ees of up to 96% being obtained. The most efficient ligand was tested with several aromatic aldehydes and ees of up to 99% were observed. Structural features of the ligands are determinant for achieving high enantioselectivities. 相似文献
402.
Niina Aaltonen Juha R. Savinainen Casandra Riera Ribas Jani Rönkkö Anne Kuusisto Jani Korhonen Dina Navia-Paldanius Jukka Häyrinen Piia Takabe Heikki Käsnänen Tatu Pantsar Tuomo Laitinen Marko Lehtonen Sanna Pasonen-Seppänen Antti Poso Tapio Nevalainen Jarmo T. Laitinen 《Chemistry & biology》2013,20(3):379-390
403.
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
404.
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
405.
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
406.
The ability of nanoparticles to manipulate the molecules and their structures has revolutionized the conventional drug delivery system. The chitosan nanoparticles, because of their biodegradability, biocompatibility, better stability, low toxicity, simple and mild preparation methods, offer a valuable tool to novel drug delivery systems in the present scenario. Besides ionotropic gelation method, other methods such as microemulsion method, emulsification solvent diffusion method, polyelectrolyte complex method, emulsification cross-linking method, complex coacervation method and solvent evaporation method are also in use. The chitosan nanoparticles have also been reported to have key applications in parentral drug delivery, per-oral administration of drugs, in non-viral gene delivery, in vaccine delivery, in ocular drug delivery, in electrodeposition, in brain targeting drug delivery, in stability improvement, in mucosal drug delivery in controlled drug delivery of drugs, in tissue engineering and in the effective delivery of insulin. The present review describes origin and properties of chitosan and its nanoparticles along with the different methods of its preparation and the various areas of novel drug delivery where it has got its application. 相似文献
407.
Dina Scarpi 《Tetrahedron》2006,62(7):1575-1582
Dipeptide isostere 5, belonging to the class of 9-exo BTKa, was synthesised starting from R,R-tartaric acid and 4-nitro-1-(3-nitrophenyl)butan-1-one. The nine-membered lactam showed interesting structural features and was inserted in a 5-residue model peptide. The conformational properties of this modified peptide have been studied by NMR and molecular modelling, indicating that compound 5 acted as a reverse turn inducer. 相似文献
408.
Chitosan/carboxymethyl cashew gum polyelectrolyte complexes were synthesized using different proportions of chitosan (CH) and carboxymethyl cashew gum (CMCG). The optimum CH:CMCG ratio was 25:75, which produced highest product yield. Polyelectrolyte (PEC) samples were characterized by thermogravimetric analysis and FT-IR spectroscopy. Parameters such as initial and maximal degradation temperatures and activation energy (Ea) were determined. Activation energies follows the order CMCG > CH > PECs samples. Infrared analysis from residual products after heating at 280 °C in different times indicated that cleavage of the glycosidic bond and formation of unsaturated products occurred. 相似文献
409.
410.