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131.
A closure approximation for nematic liquid crystals based on the canonical distribution subspace theory 总被引:2,自引:0,他引:2
A closure approximation for nematic polymers is presented. It approximates the fourth rank order tensor in terms of lower
rank tensors, and is derived in the framework of the canonical distribution subspace theory. This approach requires a choice
of the class of distributions: Here the set of Bingham distributions is chosen, as already introduced by Chaubal and Leal
(1998). The closure is written in a generic frame of reference, and in an explicit form, so that it can be easily implemented.
Such formulation also permits studying the closure approximation with continuation tools, which rather completely describe
the system dynamics. The predictions can then be compared with those obtained with the exact model. The shear flow is considered
as a test, since this flow condition appears to be the most demanding for closure approximations for nematic polymers.
Received: 30 November 1999/Accepted: 30 November 1999 相似文献
132.
133.
Camille Houle Dr. Paul R. Savoie Clotilde Davies Damien Jardel Prof. Pier Alexandre Champagne Dr. Brigitte Bibal Prof. Jean-François Paquin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10620-10625
We describe the first thiourea-catalyzed C−F bond activation. The use of a thiourea catalyst and Ti(OiPr)4 as a fluoride scavenger allows the amination of benzylic fluorides to proceed in moderate to excellent yields. Preliminary results with S- and O-based nucleophiles are also presented. DFT calculations reveal the importance of hydrogen bonds between the catalyst and the fluorine atom of the substrate to lower the activation energy during the transition state. 相似文献
134.
Pier Franco Marino Gemma Caterina Maria Rossi Giuseppe Campagna Decio Capobianco Ciro Costagliola 《Molecules (Basel, Switzerland)》2020,25(23)
The aim of the present study was to evaluate the effects of supplementation with a fixed combination of citicoline 500 mg, homotaurine 50 mg, and vitamin E 12 mg (CIT/HOMO/VITE) on contrast sensitivity and visual-related quality of life in patients with primary open-angle glaucoma (POAG) in mild stage. This was a multicenter, observational, cross-over, short-term, pilot study on POAG patients with stable controlled intraocular pressure (IOP). Patients were randomly assigned to Group 1 (current topical therapy for 4 months and then current topical therapy plus CIT/HOMO/VITE for 4 months) or Group 2 (CIT/HOMO/VITE in addition to current topical therapy for 4 months and then topical therapy alone for 4 months). Best-corrected visual acuity, IOP, visual field, and the Spaeth/Richman contrast sensitivity (SPARCS) test score were recorded at baseline and after 4 and 8 months. The Glaucoma Quality of Life-15 (GQL-15) questionnaire was administered at each check time. Forty-four patients were assigned to Group 1 and 65 to Group 2. Over the follow-up period, there were no significant changes in IOP or visual field findings, whereas SPARCS and GQL-15 findings significantly varied from baseline, both being improved in subjects treated with CIT/HOMO/VITE fixed combination. These results demonstrate that a daily intake of a fixed combination of citicoline, homotaurine, and vitamin E in addition to the topical medical treatment significantly increased the total score of the contrast sensitivity test and the quality of life in patients with POAG. 相似文献
135.
Pier Vittorio Ceccherini 《Results in Mathematics》1997,32(3-4):221-233
136.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis Angela Maria Bernard Pier Paolo Piras 《Journal of heterocyclic chemistry》1997,34(4):1283-1290
The reaction between N1-acylacetamidrazones 1 and enol ether 2 is described. Depending on the reaction conditions and on the substitution pattern of amidrazones 2-acylhydrazino-4-methyl-6-trifluoro-methylpyridines 3 and/or 2-acylhydrazino-6-methyl-4-trifluoromethylpyridines 4 were obtained. 相似文献
137.
We prove a stability theorem for the eigenvalues of general non-negative self-adjoint linear operators with compact resolvents and by applying it we prove a sharp stability result for the dependence of the eigenvalues of second order uniformly elliptic linear operators with homogeneous Neumann boundary conditions upon domain perturbation. 相似文献
138.
Violetta Cecchetti Arnaldo Fravolini Fausto Schiaffella Oriana Tabarrini Weicheng Zhou Pier Giuseppe Pagella 《Journal of heterocyclic chemistry》1992,29(2):375-382
The synthesis of 1,4-benzothiazine-2-carboxylic acid 1-oxides as agents which mimic quinolone antibacterial, are described. The key step includes intramolecular cyclization of phenylsulfinyl acrylates 17 and 18 which are prepared in six steps from 11. None of new target compounds showed interesting antibacterial activity in vitro against the tested strains. 相似文献
139.
Different isoelectric buffers are analysed theoretically, taking into account a fundamental parameter, i.e., the ratio between intrinsic buffering power and conductivity (R=β/λ). For a model ampholyte, the above parameter is analysed both as a function of the pI and the pKb–pKa values. For natural pH gradients, the variation of R, connected with approaching the isoelectric point, is evaluated. A case of oligo-protic ampholytes is also considered. 相似文献
140.
Alberto Caprara Matteo Fischetti Paolo Toth Daniele Vigo Pier Luigi Guida 《Mathematical Programming》1997,79(1-3):125-141
Crew management is concerned with building the work schedules of crews needed to cover a planned timetable. This is a well-known
problem in Operations Research and has been historically associated with airlines and mass-transit companies. More recently,
railway applications have also come on the scene, especially in Europe. In practice, the overall crew management problem is
decomposed into two subproblems, called crew scheduling and crew rostering. In this paper, we give an outline of different
ways of modeling the two subproblems and possible solution methods. Two main solution approaches are illustrated for real-world
applications. In particular we discuss in some detail the solution techniques currently adopted at the Italian railway company,
Ferrovie dello Stato SpA, for solving crew scheduling and rostering problems. 相似文献