排序方式: 共有62条查询结果,搜索用时 15 毫秒
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Nesrine Dammak Olfa Ouledltaief Nadim Fakhfakh Mourad Benzina 《Surface and interface analysis : SIA》2014,46(7):457-464
Tunisian bentonites were used to prepare three modified clays: two organoclays by intercalating respectively didodecyldimethylammoniumbromide (DDMAC) and hexadecyltrimethylammoniumbromide (HDTMAC), and synthesis of NaX zeolite. The X‐ray diffraction, infrared and thermogravimetric analyses enabled us to differentiate between the structures obtained. Clay materials systems were used as adsorbent for the investigation of the adsorption isotherms and saturation capacity of O‐xylene, a toxic volatile organic compound, by gravimetric method at three different temperatures 20, 30, and 40 °C. The absolute values of the volatile organic compound adsorbed amounts in the intercalated clays (604 mg g?1) were higher than for the zeolite (296 mg g?1). The adsorption isotherms were analysed by the Freundlich and Langmuir equations. The latter was found to describe better the equilibrium adsorption data. Mass transfer coefficient of O‐xylene is evaluated using uptake curve method, and all values are in the order of 10?2 s?1. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Spectro-ellipsometric studies of activated sol-gel thin films to detect Cu ions in aqueous solutions
Othman Belhadj Miled Cédric Boissière Jacques Livage 《Journal of Physics and Chemistry of Solids》2006,67(8):1775-1780
Thickness, refractive index n and extinction coefficient k of eriochrome cyanine R (ECR) dye doped mesostructured silica film (ECRMSSF) dip-coated on silicon wafers without prior removal of surfactant have been determined in the visible range of the spectrum by spectroscopic-ellipsometry (SE). ECRMSSF was used as sensing detection layer of Cu2+ in aqueous solutions of known pH. The dependence of optical parameters on the pH range of the aqueous phase (pH=6-8) was investigated. The detection reversibility of ECRMSSF was demonstrated. An electron paramagnetic resonance spectrum demonstrated the complexation of Cu2+ by the entrapped ECR. 相似文献
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Horoshenkov KV Khan A Bécot FX Jaouen L Sgard F Renault A Amirouche N Pompoli F Prodi N Bonfiglio P Pispola G Asdrubali F Hübelt J Atalla N Amédin CK Lauriks W Boeckx L 《The Journal of the Acoustical Society of America》2007,122(1):345-353
This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex acoustic impedance at normal incidence and plane wave absorption coefficient which are determined using the standard impedance tube method. The paper provides detailed procedures related to sample preparation and installation and it discusses the dispersion in the acoustical material property observed between individual material samples and laboratories. The importance of the boundary conditions, homogeneity of the porous material structure, and stability of the adopted signal processing method are highlighted. 相似文献
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Youssef Arfaoui Salah Kouass Nesrine Salah Azaiez Ben Akacha Abderrahmen Guesmi 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):o353-o355
In the title compound, C11H21N2O5P, one of the two carbazate N atoms is involved in the C=N double bond and the H atom of the second N atom is engaged in an intramolecular hydrogen bond with an O atom from the dimethylphosphorin‐2‐yl group, which is in an uncommon cis position with respect to the carbamate group. The cohesion of the crystal structure is also reinforced by weak intermolecular hydrogen bonds. Density functional theory (DFT) calculations at the B3LYP/6‐311++g(2d,2p) level revealed the lowest energy structure to have a Z configuration at the C=N bond, which is consistent with the configuration found in the X‐ray crystal structure, as well as a less stable E counterpart which lies 2.0 kcal mol−1 higher in potential energy. Correlations between the experimental and computational studies are discussed. 相似文献
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The Team Orienteering Problem (TOP) is a particular vehicle routing problem in which the aim is to maximize the profit gained from visiting customers without exceeding a travel cost/time limit. This paper proposes a new and fast evaluation process for TOP based on an interval graph model and a Particle Swarm Optimization inspired Algorithm (PSOiA) to solve the problem. Experiments conducted on the standard benchmark of TOP clearly show that our algorithm outperforms the existing solving methods. PSOiA reached a relative error of 0.0005% whereas the best known relative error in the literature is 0.0394%. Our algorithm detects all but one of the best known solutions. Moreover, a strict improvement was found for one instance of the benchmark and a new set of larger instances was introduced. 相似文献
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In this paper, we study the solvability of the Steklov problem Δpu=|u|p−2u in Ω, on ∂Ω, under assumptions on the asymptotic behaviour of the quotients f(x,s)/|s|p−2s and pF(x,s)/|s|p which extends the classical results with Dirichlet boundary conditions that for a.e. x∈∂Ω, the limits at the infinity of these quotients lie between the first two eigenvalues. 相似文献
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Tahar Belhadj 《Tetrahedron letters》2005,46(47):8117-8120
The addition of 3-methylindolylmagnesium bromide to tetra-O-benzyl-α-d-gluconothionolactone yields the expected indole N-gluconothioamide as its hemiorthothioamide tautomer. The thiol function is alkylated to yield the corresponding orthothioamide, a 1′-alkylthio-substituted N-glycoside. Alternatively, the 1′-alkylthio-N-glycoside can be accessed from the corresponding indole N-gluconamide via a boron trifluoride-etherate mediated orthoesterification with ethanethiol. Radical reduction of the orthothioamide yields the N-glycosides in 2:1 stereoselectivity in favor of the β-N-glycoside, while reduction via the oxonium ion leads to an improved 6:1 selectivity. 相似文献
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Lazim H Josephsen J Ben Hassen A Belhadj O Limam F 《Applied biochemistry and biotechnology》2005,125(3):189-199
Various strains of Escherichia coli, isolated from different patients, were screened for type II restriction endonuclease activity. In 1 out of 23 patients,
a type II restriction endonuclease activity was found. The restriction endonuclease designated Eco1524I was purified to near
homogeneity, based on hydroxyapatite and heparin sepharose chromatography. Eco1524I exhibited endonuclease restriction activity
in the pH range from 6.0 to 10.0 (maximum level at pH 8.0) and required Mg2+ as divalent cation. The enzyme was stable till temperature 55°C and pH range from 6.0 to 10.0. Eco1524I recognized the sequence
6-bp palindromic 5′AGG↑CCT 3′, producing blunt end and is found to be an isoschizomer of Stu I. 相似文献