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21.
Stephanie A. Grimmel Tiago Q. Teodoro Lucas Visscher 《International journal of quantum chemistry》2020,120(21):e26111
Frozen density embedding (FDE) theory is one of the major techniques aiming to bring modeling of extended chemical systems into the realm of high accuracy calculations. To improve its accuracy it is of interest to develop kinetic energy density functional approximations specifically for FDE applications. In the study reported here we focused on optimizing parameters of a generalized gradient approximation-like kinetic energy functional with the purpose of better describing electron excitation energies. We found that our optimized parametrizations, named excPBE and excPBE-3 (as these are derived from a Perdew-Burke-Ernzerhof-like parametrization), could not yield improvements over available functionals when applied on a test set of systems designed to probe solvatochromic shifts. Moreover, as several different functionals yielded very similar errors to the simple local-density approximation (LDA), it is questionable whether it is worthwhile to go beyond the LDA in this context. 相似文献
22.
Gonalo A. O. Tiago Inês A. S. Matias Ana P. C. Ribeiro Luísa M. D. R. S. Martins 《Molecules (Basel, Switzerland)》2020,25(24)
In this review, the roles of room temperature ionic liquids (RTILs) and RTIL based solvent systems as proposed alternatives for conventional organic electrolyte solutions are described. Ionic liquids are introduced as well as the relevant properties for their use in electrochemistry (reduction of ohmic losses), such as diffusive molecular motion and ionic conductivity. We have restricted ourselves to provide a survey on the latest, most representative developments and progress made in the use of ionic liquids as electrolytes, in particular achieved by the cyclic voltammetry technique. Thus, the present review comprises literature from 2015 onward covering the different aspects of RTILs, from the knowledge of these media to the use of their properties for electrochemical processes. Out of the scope of this review are heat transfer applications, medical or biological applications, and multiphasic reactions. 相似文献
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de Carvalho Tiago Cristiano Rony Gonçalves Luiz Fernando Tonon Durval José 《Nonlinear dynamics》2020,101(1):719-739
The aim of this paper is to study the qualitative dynamics of a piecewise smooth system modeling the intermittent treatment of the human immunodeficiency virus. Typical singularities and closed orbits are observable, and we quantitatively explore the dynamics around those singularities and closed orbits. Moreover, we conclude that this protocol always will be successful since the trajectory passing through any initial condition converges to one of these distinguished orbits. Our formal mathematical results corroborate the real-world observation, where the virus is not eliminated, but the number of infected cells is controlled around a specific value.
相似文献25.
Lorena M. A. Silva Elenilson G. A. Filho Sérgio S. Thomasi Bianca F. Silva Antonio G. Ferreira Tiago Venâncio 《Magnetic resonance in chemistry : MRC》2013,51(9):541-548
The informal (and/or illegal) e‐commerce of pharmaceutical formulations causes problems that governmental health agencies find hard to control, one of which concerns formulas sold as natural products. The purpose of this work was to explore the advantages and limitations of DOSY and HPLC–UV–SPE–NMR. These techniques were used to identify the components of a formula illegally marketed in Brazil as an herbal medicine possessing anti‐inflammatory and analgesic properties. DOSY was able to detect the major components present at higher concentrations. Complete characterization was achieved using HPLC–UV–SPE–NMR, and 1D and 2D NMR analyses enabled the identification of known synthetic drugs. These were ranitidine and a mixture of orphenadrine citrate, piroxicam, and dexamethasone, which are co‐formulated in a remedy called Rheumazim that is used to relieve severe pain, but it is prohibited in Brazil because of a lack of sufficient pharmacokinetic and pharmacodynamic information. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Tiago P. Filomena Miguel A. Lejeune 《Journal of Optimization Theory and Applications》2014,161(1):308-329
We consider a probabilistic portfolio optimization model including fixed and proportional transaction costs. We derive a deterministic equivalent of the probabilistic model for fat-tailed portfolio returns. We develop a method which finds provably near-optimal solutions in minimal amount of time for industry-sized (up to 2000 assets) problems. To solve the mixed-integer nonlinear programming (MINLP) deterministic formulation equivalent to the stochastic problem, we design a mathematical programming-based warm-start heuristic. The tests show the computational efficiency of the heuristic which is more than an order of magnitude faster than Cplex in finding high-quality solutions. 相似文献
28.
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
29.
Claudio A. Buzzi Tiago de Carvalho Marco A. Teixeira 《Journal de Mathématiques Pures et Appliquées》2014
This paper is concerned with a codimension analysis of a two-fold singularity of piecewise smooth planar vector fields, when it behaves itself like a center of smooth vector fields (also called nondegenerate Σ-center). We prove that any nondegenerate Σ-center is Σ -equivalent to a particular normal form Z0. Given a positive integer number k we explicitly construct families of piecewise smooth vector fields emerging from Z0 that have k hyperbolic limit cycles bifurcating from the nondegenerate Σ -center of Z0 (the same holds for k=∞). Moreover, we also exhibit families of piecewise smooth vector fields of codimension k emerging from Z0. As a consequence we prove that Z0 has infinite codimension. 相似文献
30.
A new methodology for the determination of the fluorescence quantum yield of dyes adsorbed onto microcrystalline cellulose is presented and applied to rhodamine 101, cresyl violet and auramine O. It is based on a previously reported method by Ruetten and Thomas (J. Phys. Chem., 1998, 102, 598-606), which is not applicable to the dyes used in the present study. It uses ground-state diffuse reflectance spectra obtained with and without filters, which prevents the luminescence of the dye from reaching the integrating sphere and the photodetector. New equations are presented here, correcting for the fluorescence emission of the dye, which depends on the detector sensitivity. Cut-on filters, which have a transmittance close to unity in the absorption region, and close to zero in the emission region, of the dye are used to obtain corrected reflectance spectra. The influence of the substrate was also taken into account. This methodology may be applied to other probes and surfaces or emissions of a different nature (i.e., phosphorescence or delayed fluorescence), and constitutes a very simple and general procedure to solve the important problem of luminescence quantum yield determination of probes adsorbed onto solid powdered surfaces. 相似文献