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排序方式: 共有75条查询结果,搜索用时 500 毫秒
1.
Nadir Arada Paulo Correia Adélia Sequeira 《Numerical Methods for Partial Differential Equations》2007,23(6):1468-1500
This article is concerned with the equations governing the steady motion of a viscoelastic incompressible second‐order fluid in a bounded domain. A new proof of existence and uniqueness of strong solutions is given. In addition, using appropriate finite element methods to approximate a coupled equivalent problem, sharp error estimates are obtained using a fixed point argument. The method is applied to the two‐dimensional lid‐driven cavity problem, at low Reynolds number and in a certain range of values of the viscoelastic parameters, to analyze the combined effects of inertia and viscoelasticity on the flow. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
2.
Jonathan S. Dordick K. C. Backman R. Balakrishnan R. Brent M. S. Ptashne L. P. Casson S. A. Goff A. L. Goldberg P. A. Cornelius R. M. Hochstrasser N. R. Kallenbach H. Rubin G. J. Todaro H. A. De Boer J. C. Delgoffe M. Lobmann N. ZyGraich L. Gehrke T. Kunkel A. Paau S. G. Platt L. Sequeira M. A. Palladino H. G. Roman D. Hultmark T. T. Rasmusan H. Steiner 《Applied biochemistry and biotechnology》1990,26(1):107-113
Protein engineering and site-directed mutagenesis is becoming immensely important in both fundamental studies and commercial applications involving proteins and enzymes in biocatalysis. Protein engineering has become a powerful tool to help biochemists and molecular enzymologists elucidate structure-function relationships in enzymic active sites, to understand the intricacies of protein folding and denaturation, and to alter the selectivity of enzymatic catalysis. Commercial applications of engineered enzymes are being developed to increase protein stability, widen or narrow substrate specificity, and to develop novel approaches for use of enzymes in organic synthesis, drug design, and clinical applications. In addition to protein engineering, novel expression systems have been designed to prepare large quantities of genetically engineered proteins. Recent US patents and scientific literature on protein engineering, site-directed mutagenesis, and protein expression systems related to protein engineering are surveyed. Patent abstracts are summarized individually and a list of literature references are given. 相似文献
3.
Margaret Sequeira Dermot Diamond Antoine Daridon Jan Lichtenberg Sabeth Verpoorte N. F. de Rooij 《Trends in analytical chemistry : TRAC》2002,21(12):816-827
Progress in the development of a micro-fluidic system for colorimetric monitoring of ammonia in drinking and wastewater is described. The ultimate goal is to have a miniaturised instrument that can produce accurate, reliable measurements, is easy to operate, has minimal power consumption, and can operate autonomously for a year. In this study, the indophenol reaction is incorporated into a simple, reliable analytical micro-fluidic system. Absorbance measurements for the blue ammonia-indophenol complex formed in the micro-fluidic system are shown. A key issue is the limiting stability of hypochlorite, a reagent used in the assay. The effects of hypochlorite concentration and impurities on the stability of hypochlorite are investigated and discussed. Decomposition is shown to be very dependent on the presence of heavy-metal impurities. With low levels of these catalytic metals and careful storage, hypochlorite has been shown to be stable for over a year. 相似文献
4.
Maria Jo?o Carrilho Plancha Carmen Mireya Rangel César Augusto Correia de Sequeira 《Journal of Solid State Electrochemistry》2012,16(2):665-671
The (PEO)4ZnCl2 electrolyte (PEO, polyethylene oxide) was studied in view of its potential application in a solid-state rechargeable zinc
cell. The electrochemical stability window was established, and decomposition voltage values between 3.19 (20 °C) and 1.44 V
(150 °C) were estimated. Cyclic voltammetry studies using a Pt/(PEO)4ZnCl2/Pt cell indicated reversibility of the Zn2+/Zn couple at the electrode/electrolyte interface. Laboratory cells Zn(−)/(PEO)4ZnCl2/Nb2O5(+) were assembled and studied at 55 °C, under various discharge current densities. Results of cell discharge profiles, capacity
values, charge–discharge cycles and cell stabilities are reported. 相似文献
5.
We consider optimal control problems of systems governed by stationary, incompressible generalized Navier–Stokes equations with shear dependent viscosity in a two-dimensional or three-dimensional domain. We study a general class of viscosity functions with shear-thinning and shear-thickening behavior. We prove an existence result for such class of optimal control problems. 相似文献
6.
This work is concerned with the study of steady flows of an incompressible viscoelastic fluid of Oldroyd type, with viscosity depending on the second invariant of the rate of deformation tensor in an exterior domain. We establish a result of existence and uniqueness of strong solutions for sufficiently small data and give estimates relating these solutions to those of the corresponding generalized Newtonian fluid. 相似文献
7.
Luís G. Dias Cédric Sequeira Ana C.A. Veloso Mara E.B.C. Sousa António M. Peres 《Analytica chimica acta》2014
Overconsumption of sugar-sweetened beverages may increase the risk of health problems and so, the evaluation of their glycemic load and fructose-intolerance level is essential since it may allow establishing possible relations between physiologic effects of sugar-rich beverages and health. In this work, an electronic tongue was used to accurately classify beverages according to glycemic load (low, medium or high load) as well to their adequacy for people suffering from fructose malabsorption syndrome (tolerable or not): 100% of correct classifications (leave-one-out cross-validation) using linear discriminant models based on potentiomentric signals selected by a meta-heuristic simulated annealing algorithm. These results may be partially explained by the electronic tongue’s capability to mimic the human sweetness perception and total acid flavor of beverages, which can be related with glycemic load and fructose-intolerance index. Finally, the E-tongue was also applied to quantify, accurately, healthy and sensory indexes using multiple linear regression models (leave-one-out cross-validation: Radj > 0.99) in the following dynamic ranges: 4.7 < glycemic load ≤ 30; 0.4 < fructose intolerance index ≤ 1.5; 32 < sweetness perception < 155; 1.3 < total acid flavor, g L−1 < 8.3; and, 5.8 < well-balanced flavor ≤ 74. So, the proposed electronic tongue could be used as a practical, fast, low-cost and green tool for beverage’s healthy and sensory evaluation. 相似文献
8.
Kinetic studies of the electrochemical generation of Ag(II) and Co(III) ions and the catalytic oxidation of isopropanol in acidic media are presented. Its mediated and non-mediated electrooxidation up to carbon dioxide is considered. 相似文献
9.
Results of a detailed crystallographic study of the structural phase transitions in LiKSO4, carried out using single crystal neutron diffraction at ambient and below-ambient temperatures (300–100 K), are presented. The study indicates two clear phase transitions at 205 K (from space group P63 to space group P31c), at 189 K (to space group Cc) and a third transition at about 130 K in the cooling cycle. The corresponding temperatures are 250 K, 200 K and 138 K in the heating cycle. The existence of twins, mixed phases, and extremely sluggish kinetics for the various phase transitions, as well as the structural details of the various phases in this mixed salt, can explain the apparent inconsistencies in the results of several experimental investigations reported in the literature. 相似文献
10.
C. A. C. Sequeira D. M. F. Santos P. S. D. Brito 《Russian Journal of Electrochemistry》2008,44(7):852-856
The electrocatalysis of the oxygen reduction reaction by lanthanum-strontium manganate La0.5Sr0.5MnO3 (LSM) has been studied by cyclic voltammetry using the rotating ring-disc electrode technique (RRDE) in alkaline medium.
From the ring-disc data and other kinetic parameters it was concluded that the oxygen reduction occurs by dissociative chemisorption
at low overpotentials. At higher overpotentials, the formation of hydrogen peroxide (HO2− in this case) on the electrocatalyst has been observed. The apparent exchange current density for oxygen reduction on LSM
has been found to be 2 × 10−7 A cm−2, while the corresponding Tafel slope is 0.100 V per decade. The possible reaction mechanism for electroreduction of oxygen
on this oxide catalyst has been discussed.
Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 7, pp. 919–923.
The text was submitted by the authors in English. 相似文献