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31.
Ziyafaddin H. Asadov Khuraman A. Mammadova Gulnara A. Ahmadova Saida F. Ahmadbayova 《Journal of Dispersion Science and Technology》2013,34(7):1022-1028
The influence of counterions on the surface properties of N-lauryl diisopropanolamine surfactants is delineated using conductometry and surface tension measurements. Twelve types of organic counterions have been studied: C1–C12 monocarboxylic acids anions. The surface properties of the synthesized surfactants, including surface tension, critical micelle concentration (CMC), effectiveness (πCMC), efficiency (pC20), maximum surface excess (Γmax), minimum surface area (Amin), Gibbs energy of micellization (ΔGmic), and adsorption (ΔGad) processes in the aqueous. The biodegradability of the prepared surfactants was tested in river water using the die-away method. Petroleum-collecting and petroleum-dispersing capacities of the synthesized compounds on the surface of water of varying mineralization degree have been studied. 相似文献
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Density functional theory (DFT) method with B3LYP functional and 6-311++G(d,p) basis set has been used to predict the geometries, relative stabilities, electronic structures and bonding analysis of Mixed AlmBn?mH n 2? and CmBn?mH n 2?m (n = 6, 10, 12 and m = 1, 2) clusters; being compared to the BnH n 2? ones. Therefore, the DFT results suggest that the replacing of boron by aluminium or carbon is governed by Natural net charges following Gimar’s and Williams’s rules. The AlmBn?mH n 2? structures are relatively distorted compared to those of BnH n 2? and CmBn?mH n 2?m . In AlmBn?mH n 2? structures Al atoms prefer the adjacent sites, however for the C2Bn?2Hn cluster cages, the carbon atoms are positioned at diametrically opposed sites. The large HOMO–LUMO gaps show that the predicted clusters have chemical stabilities, principally, those of AlmBn?mH n 2? ones, which are not experimentally isolated. The optimized geometries obtained through boron substitution by Al and C lead to compactness and to contracted structures, respectively, where B–B bonds are the shortest in mono- and di-carbaboranes. 相似文献
33.
Highly correlated ab initio methods were used in order to generate the potential energy curves and spin-orbit couplings of electronic ground and excited states of PS and PS(+). We also computed those of the bound parts of the electronic states of the PS(-) anion. We used standard coupled cluster CCSD(T) level with augmented correlation-consistent basis sets, internally contacted multi-reference configuration interaction, and the newly developed CCSD(T)-F12 methods in connection with the explicitly correlated basis sets. Core-valence correction and scalar relativistic effects were examined. Our data consist of a set of spectroscopic parameters (equilibrium geometries, harmonic vibrational frequencies, rotational constants, spin-orbit, and spin-spin constants), adiabatic ionization energies, and electron affinities. For the low laying electronic states, our calculations are consistent with previous works whereas the high excited states present rather different shapes. Based on these new computations, the earlier ultraviolet bands of PS and PS(+) were reassigned. For PS(-) and in addition to the already known anionic three bound electronic states (i.e., X(3)Σ(-), (1)Δ, and 1(1)Σ(+)), our calculations show that the (1)Σ(-), (3)Σ(+), and the (3)Δ states are energetically below their quartet parent neutral state (a(4)Π). The depletion of the J = 3 component of PS(-)((3)Δ) will mainly occur via weak interactions with the electron continuum wave. 相似文献
34.
Saida Mnasri Néji Besbes Najoua Frini-Srasra Ezzeddine Srasra 《Comptes Rendus Chimie》2012,15(5):437-443
The purified Tunisian clay G and the commercialized American clay W were pillared with zirconium, aluminum and mixed pillars zirconium–aluminum, cerium–zirconium, cerium–aluminum, and cerium–zirconium–aluminum. These different clays were used in the synthesis of 2,2-dimethyl-1,3-dioxolane 3 by acetalyzation of acetone 2 with ethylene glycol 1 under autogenously pressure and without solvent. Results indicate that the yield of product 3 depends of the nature and the acidity of the clay used and the time of reaction. 相似文献
35.
Finite volume methods for dam-break flows over erodible sediment beds require a monotone numerical flux. In the present study we present a new flux-limiter scheme based on the Lax–Wendroff method coupled with a non-homogeneous Riemann solver and a flux limiter function. The non-homogeneous Riemann solver consists of a predictor stage for the discretization of gradient terms and a corrector stage for the treatment of source terms. The proposed method satisfy the conservation property such that the discretization of the flux gradients and the source terms are well-balanced in the numerical solution of suspended sediment models. The flux-limiter method provides accurate results avoiding numerical oscillations and numerical dissipation in the approximated solutions. Several standard test examples are considered to verify the performance and the accuracy of the proposed method. 相似文献
36.
Scott?McCulloughEmail author Saida?Sultanic 《Integral Equations and Operator Theory》2012,72(4):449-482
This note presents a commutant lifting theorem (CLT) of Agler type for the annulus \({\mathbb A}\) . Here the relevant set of test functions are the minimal inner functions on \({\mathbb A}\) —those analytic functions on \({\mathbb A}\) which are unimodular on the boundary and have exactly two zeros in \({\mathbb A}\) —and the model space is determined by a distinguished member of the Sarason family of kernels over \({\mathbb A}\) . The ideas and constructions borrow freely from the CLT of Ball et al. (Indiana Univ Math J 48(2):653–675, 1999) and Archer (Unitary dilations of commuting contractions. PhD thesis, University of Newcastle, 2004) for the polydisc, and Ambrozie and Eschmeier (A commutant lifting theorem on analytic polyhedra. Topological algebras, their applications, and related topics, 83108, Banach Center Publications, vol 67. Polish Academy of Sciences, Warsaw, 2005) for the ball in \({\mathbb C^n}\) , as well as generalizations of the de Branges–Rovnyak construction like found in Agler (On the representation of certain holomorphic functions defined on a polydisc. Topics in operator theory: Ernst D. Hellinger memorial volume, operator theory: advances and applications, vol 48. Birkhäuser, Basel, pp 47–66, 1990) and Ambrozie et al. (J Oper Theory 47(2):287–302, 2002). It offers a template for extending the result in McCullough and Sultanic (Complex Anal Oper Theory 1(4):581–620, 2007) to infinitely many test functions. Among the needed new ingredients is the formulation of the factorization implicit in the statement of the results in Ball et al. (Indiana Univ Math J 48(2):653–675, 1999) and Archer (Unitary dilations of commuting contractions. PhD thesis, University of Newcastle, 2004) and McCullough and Sultanic (Complex Anal Oper Theory 1(4):581–620, 2007) in terms of certain functional Hilbert spaces of Hilbert space valued functions. 相似文献
37.
Kharroubi M Balme S Henn F Giuntini JC Belarbi H Haouzi A 《Journal of colloid and interface science》2009,329(2):339-345
Dehydration of a series of homoionic alkali-exchanged montmorillonites is studied at different treatment temperatures by means of thermogravimetric analysis. More specifically, we investigate the last stages of dehydration when the number of adsorbed water molecules corresponds, at maximum, to a monolayer. Weight losses are measured at several constant temperatures as a function of time. Application of Van't Hoff's law yields the dehydration enthalpy. Trends and data similar to those reported from other experimental conditions are found. Comparison with X-ray data and with the dissociation enthalpy of alkali cation/water complexes shows that dehydration of weakly hydrated homoionic alkali montmorillonites results from the competition between opposite energy contributions due to (i) the cation solvation, (ii) the hydration of the silicate interlayer surface, and (iii) the structural swelling. So, depending on the balance between these various energy contributions, different behaviors are observed according to the nature of the alkali cations. 相似文献
38.
Bensaid Ilhem Atik Bekkara Fawzia El Haci Imad Abdelhamid Belarbi Karima Beddou Fawzia Bekhechi Chahrazed 《Natural product research》2018,32(4):481-485
In an extensive search for bioactive compounds from plant sources, the quantitative and qualitative characterisation of the compounds present in Cynoglossum cheirifolium extracts was studied. Total phenolic and flavonoid contents were determined by spectrophotometric techniques. In vitro antioxidant and radical scavenging profiling was determined through DPPH? scavenging activity and Ferric reducing antioxidant power (FRAP). Our study showed that leaves produce more phenolic compounds, followed by flowering aerial part. The butanolic fraction obtained from leaves extract exhibited the highest total phenolics (78.65 ± 3.58 mg GAE/g DW) and flavonoids (22.15 ± 4.66 mg CE/g DW). In contrast, this fraction displayed the highest DPPH? scavenging ability with IC50 values of 0.06 ± 0.003 mg/mL. The RP-HPLC-PDA analysis of phenolic compounds from leaves of C. cheirifolium lets to identify: rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid, syringic acid, sinapic acid and rutin. The obtained results indicate that this plant represent a valuable source of natural antioxidants. 相似文献
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The aim of this work is to develop a well‐balanced finite‐volume method for the accurate numerical solution of the equations governing suspended sediment and bed load transport in two‐dimensional shallow‐water flows. The modelling system consists of three coupled model components: (i) the shallow‐water equations for the hydrodynamical model; (ii) a transport equation for the dispersion of suspended sediments; and (iii) an Exner equation for the morphodynamics. These coupled models form a hyperbolic system of conservation laws with source terms. The proposed finite‐volume method consists of a predictor stage for the discretization of gradient terms and a corrector stage for the treatment of source terms. The gradient fluxes are discretized using a modified Roe's scheme using the sign of the Jacobian matrix in the coupled system. A well‐balanced discretization is used for the treatment of source terms. In this paper, we also employ an adaptive procedure in the finite‐volume method by monitoring the concentration of suspended sediments in the computational domain during its transport process. The method uses unstructured meshes and incorporates upwinded numerical fluxes and slope limiters to provide sharp resolution of steep sediment concentrations and bed load gradients that may form in the approximate solutions. Details are given on the implementation of the method, and numerical results are presented for two idealized test cases, which demonstrate the accuracy and robustness of the method and its applicability in predicting dam‐break flows over erodible sediment beds. The method is also applied to a sediment transport problem in the Nador lagoon.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献