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31.
Mustapha Hellou Thi Diep Phuong Bach 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2011,11(3):135-147
The purpose of this study is to calculate Stokes flow structures in relation to flow rate distribution in a junction of four
orthogonal channels. Particular attention was paid to the existence of recirculation flow inside the channels for low Reynolds
numbers. The presence of this recirculation flow may be observed, but only when the flow rate is relatively low in at least
one of the branches. 相似文献
32.
Mustapha?Azreg-A?nou 《General Relativity and Gravitation》2010,42(6):1427-1456
We investigate the generic properties of static, spherically symmetric, asymptotically flat solutions to the field equations
describing gravity minimally coupled to a nonlinear self-gravitating real scalar field. Five corollaries and a theorem on
selection criteria for two- and one-parametric solutions are proven and conditions for obtaining particle-like solutions,
black holes or naked singularities are derived. A series of exact solutions in closed forms including different black holes,
naked singularities and particle-like solutions, all of which obey the weak energy condition at spatial infinity, are provided.
Two further corollaries elaborate on the behavior of solutions at spatial infinity, critical mass, mass density, pressure
and energy conditions. 相似文献
33.
The aim of this work is the study of the Cauchy problem for a large class of linear operators, non-necessarily kowalevskian, with shrinking argument. We prove the well posedness of this problem in the space of analytic functions with respect to time and Gevrey class with respect to spatial variable. Our tools are based on formal norms of Leray and Waelbroeck [J. Leray, L. Waelbroeck, Norme formelle d'une fonction composée (Préliminaire à l'étude des systèmes non linéaires, hyperboliques non stricts), in: Colloque de Liège, CBRM, 1964, pp. 145-152. [23]], already used in [Cl. Wagschal, Le problème de Goursat non linéaire, J. Math. Pure Appl. 58 (1979) 309-337; D. Gourdin, M. Mechab, Solution globale d'un problème de Cauchy linéaire, J. Funct. Anal. 202 (2003) 123-146]. 相似文献
34.
Gas‐phase copper and silver complexes with phosphorothioate and phosphorodithioate pesticides investigated using electrospray ionization mass spectrometry
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Efforts to improve agricultural productivity have led to a growing dependency on organophosphorus pesticides. Phosphorothioate and phosphorodithioate pesticides are organophosphorus pesticide subclasses with widespread application for the control of insects feeding on vegetables and fruits. However, even low doses of these pesticides can cause neurological problems in humans; thus, their determination and monitoring in agricultural foodstuffs is important for human health. Phosphorothioate and phosphorodithioate pesticides may be poorly ionized during electrospray, adversely affecting limits of detection. These pesticides can form complexes with Cu2+ and Ag+, however, potentially improving ionization. In the present work, we used electrospray ionization/mass spectrometry (ESI/MS) to study fenitrothion, parathion, diazinon, and malathion coordination complexes with silver and copper ions. Stable 1 : 1 and 1 : 2 metal/pesticide complexes were detected. Mass spectra acquired from pesticide solutions containing Ag+ or Cu2+ showed a significant increase in signal‐to‐background ratio over those acquired from solutions containing only the pesticides, with Ag+ improving detection more effectively than Cu2+. Addition of Ag+ to a pesticide solution improved the limit of detection by ten times. The relative affinity of each pesticide for Ag+ was related to complex stability, following the order diazinon > malathion > fenitrothion > parathion. The formation of Ag+–pesticide complexes can significantly improve the detection of phosphorothioate and phosphorodithioate pesticides using ESI/MS. The technique could potentially be used in reactive desorption electrospray ionization/mass spectrometry to detect phosphorothioate and phosphorodithioate pesticides on fruit and vegetable skins. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
35.
Mostafa Hossein Beyki Hassan Alijani Yousef Fazli 《Research on Chemical Intermediates》2017,43(11):6245-6257
An efficient adsorption system was developed for removal of hazardous Direct Blue 71 as a sample azo dye. The γ-Fe2O3@CuO adsorption system was synthesized based on a sol–gel combustion route and characterized by energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, vibrating-sample magnetometry (VSM), and field-emission scanning electron microscopy (FESEM) techniques. The response surface methodology with Box–Behnken design was used to evaluate the effects of pH, shaking time, and adsorbent dose on dye adsorption. The results showed that solution pH was the parameter with greatest effect on dye adsorption. Adsorption equilibrium was reached quickly, within 8 min. Study of isotherms revealed adsorption capacity of 45.7 mg g?1 according to the Freundlich model. Sorbent regeneration could be performed using methanol–NaOH (0.1 mol L?1) solution. 相似文献
36.
In this work a facile hydrothermal route has been employed to prepare a multiwall carbon nanotube wrapped in a chelating resin. 8-Hydroxyquinoline and p-formaldehyde were used as monomer and linker for polymer synthesis. The prepared composite was employed as an efficient adsorbent for lead adsorption and preconcentration from various matrices. Effective parameters on lead adsorption have been optimized by central composite design. Results showed that equilibrium adsorption was obtained at pH = 4, with a shacking time of 15 min and adsorbent dosage of 15 mg. Isotherm study showed that the sorbent has adsorbent capacity of 250 mg g?1; moreover, the process followed a Langmuir isotherm model. Thermodynamic investigation confirmed that lead adsorption is spontaneous, as well as follows endothermic path. 相似文献
37.
We study a collisionless kinetic equation describing density distribution function of the position and velocity of particles moving in a slab with finite thickness and with a partly diffusive boundary reflection. In particular, we deal with existence of an invariant density and with the convergence to the equilibrium. We also study the long time behavior of densities when the equilibrium does not exists. 相似文献
38.
Abdelmounaim Safer Mustapha Rahmouni François Carreaux Ludovic Paquin Olivier Lozach Laurent Meijer Jean Pierre Bazureau 《Chemical Papers》2011,65(3):332-337
A series of nine 5-arylidenerhodanine derivatives was prepared in good yields and purity without the use of a solvent or catalyst
under microwave-assisted condensation with some substituted isatins. All 5-arylidenerhodanines were evaluated as possible
inhibitors of the CK1α/β, CDK5/p25, and GSK-3α/β kinases. None of them showed substantive inhibitory activity against these kinases when evaluated at the concentration of
10 μM. 相似文献
39.
Gerber I Oubenali M Bacsa R Durand J Gonçalves A Pereira MF Jolibois F Perrin L Poteau R Serp P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(41):11467-11477
The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or carboxylic groups. At room temperature, this reaction takes place on the most reactive carbon atoms. At higher temperatures a different mechanism would operate, as evidenced by the difference in activation energies. Experimental data can be partially related to first-principles calculations, showing a multistep functionalization mechanism. The theoretical aspects of the present article have led us to propose the most efficient pathway leading to carboxylic acid functional groups on the surface. Starting from mono-vacancies, it ends up with the synergistic formation of dangling -COOH groups and the enlargement of the vacancies. 相似文献
40.
Bourdolle A Allali M Mulatier JC Le Guennic B Zwier JM Baldeck PL Bünzli JC Andraud C Lamarque L Maury O 《Inorganic chemistry》2011,50(11):4987-4999
Two europium complexes with bis(bipyridine) azamacrocyclic ligands featuring pendant arms with or without π-conjugated donor groups are synthesized and fully characterized by theoretical calculations and NMR spectroscopy. Their photophysical properties, including two-photon absorption, are investigated in water and in various organic solvents. The nonfunctionalized ligand gives highly water-stable europium complexes featuring bright luminescence properties but poor two-photon absorption cross sections. On the other hand, the europium complex with an extended conjugated antenna ligand presents a two-photon absorption cross section of 45 GM at 720 nm but is poorly luminescent in water. A detailed solvent-dependent photophysical study indicates that this luminescence quenching is not due to the direct coordination of O-H vibrators to the metal center but to the increase of nonradiative processes in a protic solvent induced by an internal isomerization equilibrium. 相似文献