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排序方式: 共有118条查询结果,搜索用时 187 毫秒
1.
Sofiane Ben Hamouda Quang Trong Nguyen Pierre Schaetzel 《European Polymer Journal》2006,42(11):2994-3005
Ethylene/ethane sorption characteristics were determined for dry Pebax™ (poly(amide 12-block-tetramethylenoxide) copolymer)/AgBF4 membranes by using an electronic microbalance. The membranes containing 0.7 and 22 wt.% AgBF4 showed a dual-mode sorption isotherm. The ethane isotherms for all the membranes were of the Henry-type, which is the normal sorption for gases in rubbery polymers. The abnormal presence of Langmuir sorption sites only for ethylene in the rubbery copolymer, never reported sofar, is attributed to the silver-based specific complexation sites. The silver salt which dissolved in limited amounts in the rubbery copolymer had a much smaller Langmuir sorption capacity than the salt that crystallized in the copolymer. The sorption kinetics indicate that the crystallized salt did adsorb slowly ethylene according to a zeroth-order kinetics, but not ethane. The gas uptake kinetics resulting from a step of the pressure surrounding the copolymer exhibited one stage for ethane but two stages for ethylene. For the latter, there was first a fast Fickian sorption stage, then a drift of the zeroth-order sorption of ethylene on salt crystals, which contributes for a large part to the total uptake. The zeroth-order sorption suggests that the sorbed ethylene amount in the second-stage is independent of the crystal-surface coverage. The value of the Fickian diffusion coefficient calculated by fitting the kinetics with a solution of the second Fick’s law was 5 × 10−12 m2/s for both ethylene (the first stage) and ethane, and is typical for small organic compounds in a rubbery material. 相似文献
2.
Layer-by-layer fabrication and characterization of DNA-wrapped single-walled carbon nanotube particles 总被引:2,自引:0,他引:2
Carbon nanotubes have been proposed as support materials for numerous applications, including the development of DNA sensors. One of the challenges is the immobilization of DNA or other biological molecules on the sidewall of carbon nanotubes. This paper introduces a new fabrication of DNA-carbon nanotubes particles using the layer-by-layer (LBL) technique on single-walled carbon nanotubes (SWCNTs). Poly(diallyldimethylammonium) (PDDA), a positively charged polyelectrolyte, and DNA as a negatively charged counterpart macromolecule are alternatively deposited on the water-soluble oxidized SWCNTs. Pure DNA/PDDA/SWCNTs particles can be prepared and separated by simple unltracentrifugation. The characterization of DNA/PDDA/SWCNTs particles was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). An electrode modified by the DNA/PDDA/SWCNTs particles shows a dramatic change of the electrochemical signal in solutions of tris(2,2'-bipyridyl)ruthenium(II) ((Ru(bpy)(3)2+) as a reporting redox probe. A preliminary application of the DNA-modified carbon nanotubes in the development of DNA sensors used in the investigation of DNA damage by nitric oxide is presented. 相似文献
3.
The spin coherent state path integral describing the dynamics of a two-level system interacting with electromagnetic wave of circular polarization is considered. The propagator is first written in the standard form by replacing the spin by a unit vector aligned along the polar and azimuthal directions. Then it is determined exactly using a simple transformations. Thus, the exact energy spectra with corresponding wave functions are deduced. 相似文献
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6.
Ahmed Mekki Kamel Khimeche Abdallah Dahmani 《The Journal of chemical thermodynamics》2010,42(8):1050-1055
A differential scanning calorimetry (d.s.c.) was used to determine binary (solid + liquid) phase equilibria (SLE) for four binary mixtures, viz. (n-nitrosodiphenylamine + diphenylamine), (2-nitrodiphenylamine + ethyl centralite), (2,4-dinitro-N-ethylaniline + methyl centralite), and (2,4-diphenylamine + 4,4′-dinitroethylcentralite). These compounds are used as stabilizers in gun powders and propellants. Results obtained with this technique are compared with those correlated by NRTL and ideal models. It was found out that all the systems are simple eutectic systems and deviations between experimental and predicted SLE results were observed. 相似文献
7.
Boumediene Abdellaoui Sofiane E. H. Miri Ireneo Peral Tarik M. Touaoula 《NoDEA : Nonlinear Differential Equations and Applications》2014,21(4):453-490
In this paper we deal with the following quasilinear parabolic problem $$\left\{\begin{array}{l@{\quad}l} (u^\theta)_t - \Delta_p {u} = \lambda \frac{u^{p - 1}}{|x|^{p}} + u^q + f,\,\, u \geq 0 \quad {\rm in} \;\;\Omega \times (0, T),\\ u(x, t) = 0 \quad\qquad\qquad\qquad\qquad\qquad\qquad {\rm on}\; \partial \Omega \times(0, T),\\ u(x, 0) = u_0(x), \,\,\, \qquad\qquad\qquad\qquad\qquad x \in\; \Omega,\end{array}\right.$$ where θ is either 1 or (p ? 1), \({N \geq 3, \,\Omega \subset \mathcal{IR}^N}\) is either a bounded regular domain containing the origin or \({\Omega \equiv \mathcal{IR}^N}\) , 1 < p < N, q > 0 and u 0 ≥ 0, f ≥ 0 with suitable hypotheses. The aim of this work is to get natural conditions to show the existence or the nonexistence of nonnegative solutions. In the case of nonexistence result, we analyze blow-up phenomena for approximated problems in connection with the classical Harnack inequality, in the Moser sense, more precisely in connection with a strong maximum principle. We also study when finite time extinction (1 < p < 2) and finite speed propagation (p > 2) occur related to the reaction power. 相似文献
8.
Zied Zarai Houda Gharsallah Adnane Hammami Hafedh Mejdoub Sofiane Bezzine Youssef-Talel Gargouri 《Applied biochemistry and biotechnology》2012,168(4):877-886
In order to report pharmacological characterization of marine snail (Hexaplex trunculus) hepatopancreatic phospholipase A2 (mSDPLA2), we have talked for the first time the antimicrobial activity against different pathogenic bacterial strains, anti-chlamydial activity as well as its cytotoxic activity against McCoy cell lines. mSDPLA2, showed a high level of activity towards Gram-positive bacteria as Staphylococcus aureus and Staphylococcus epidermidis. Whereas Gram-negative bacteria, unfortunately, exhibited a higher resistance, mSDPLA2 was also found to have a strong cytotoxic activity, causing significant morphological alterations of the McCoy cell lines surfaces and to be a hinder to the proliferation. Moreover, mSDPLA2 proved to have a very potent anti-chlamydial activity. Over 95?% inhibition of chlamydial inclusions were obtained at a concentration of 10???g/ml of mSDPLA2 after 24?h postinfection. Interestingly, at a concentration of 10???g/ml of mSDPLA2, the proliferation of McCoy cells was not affected. Approximately 50?% inhibition of cell growth was obtained with a concentration of 37???g/mL of mSDPLA2. mSDPLA2 could be considered as an excellent candidate for the development of a new anti-infective agent. This enzyme showed significant antimicrobial activities. 相似文献
9.
Belkacem Manser Idir Belaidi Abderrachid Hamrani Sofiane Khelladi Farid Bakir 《Comptes Rendus Mecanique》2019,347(2):141-165
A wisely chosen geometry of micro textures with the favorable relative motion of lubricated surfaces in contacts can enhance tribological characteristics. In this paper, a computational investigation related to the combined influence of bearing surface texturing and journal misalignment on the performances of hydrodynamic journal bearings is reported. To this end, a numerical analysis is performed to test three texture shapes: square “SQ”, cylindrical “CY”, and triangular “TR”, and shaft misalignment variation in angle and degree. The Reynolds equation of a thin viscous film is solved using a finite differences scheme and a mass conservation algorithm (JFO boundary conditions), taking into account the presence of textures on both full film and cavitation regions. Preliminary results are compared with benchmark data and are consistent with a positive enhancement in misaligned bearing performances (load carrying capacity and friction). The results suggest that the micro-step bearing mechanism is a key parameter, where the micro-pressure recovery action present in dimples located at the second angular part of the bearing (from 180° to 360°) can compensate for the loss on performances caused by shaft misalignment, while the micro-pressure drop effect at the full film region causes poor performances. Considering the right arrangement of textures on the contact surface, their contours geometries can have a significant impact on the performance of misaligned journal bearings, particularly at high eccentricity ratios, high misalignment degrees and when the misalignment angle α approaches to or . 相似文献
10.
The aim of this work is to establish the existence of multi-peak solutions for the following class of quasilinear problems where \(\epsilon\) is a positive parameter, \(N\geq2\), \(V\), \(f\) are continuous functions satisfying some technical conditions and \(\phi\) is a \(C^{1}\)-function.
相似文献
$$ - \mbox{div} \bigl(\epsilon^{2}\phi\bigl(\epsilon|\nabla u|\bigr)\nabla u \bigr) + V(x)\phi\bigl(\vert u\vert\bigr)u = f(u)\quad\mbox{in } \mathbb{R}^{N}, $$