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41.
Rachid Rahouadj Jean-Franois Ganghoffer Christian Cunat 《Mechanics Research Communications》2003,30(2):119-123
In the first part of this contribution, the Lie-symmetries of the principle of least action associated to the constitutive equations of the DNLR formalism of relaxation have been presented. We examine in this second part the continuous symmetries corresponding to the simple case of stress relaxation under isothermal conditions. The well-known principle of time/temperature equivalence is discussed in terms of variational symmetry for the Jacobi’s action functional, and connected to the Onsager’s relation near the thermodynamic equilibrium. 相似文献
42.
Enrique Alvarez-Manzaneda Rachid ChahbounEsteban Alvarez Ramón Alvarez-ManzanedaPedro E. Muñoz Fermín JiménezHanane Bouanou 《Tetrahedron letters》2011,52(31):4017-4020
The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon-carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds. 相似文献
43.
Nunes SP Karunakaran M Pradeep N Behzad AR Hooghan B Sougrat R He H Peinemann KV 《Langmuir : the ACS journal of surfaces and colloids》2011,27(16):10184-10190
The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values. 相似文献
44.
A library of novel, lipid-modified derivatives of ascorbic acid was shown to exhibit highly attractive properties as surfactants, emulsifiers, oil soluble antioxidants, and highly effective gelators in organic solvents and especially water. In these systems, intermolecular hydrogen bonding and van der Waals forces act synergistically to induce gelation as confirmed by spectroscopic studies. The morphology of the formed gel has been characterized by scanning electron microscopy. 相似文献
45.
Samira El Moumen Rachid EllaiaRajae Aboulaich 《Applied mathematics and computation》2011,218(7):3265-3276
In this paper we present a new hybrid method, called the SASP method. The purpose of this method is the hybridization of the simulated annealing (SA) with the descent method, where we estimate the gradient using simultaneous perturbation. Firstly, the new hybrid method finds a local minimum using the descent method, then SA is executed in order to escape from the currently discovered local minimum to a better one, from which the descent method restarts a new local search, and so on until convergence.The new hybrid method can be widely applied to a class of global optimization problems for continuous functions with constraints. Experiments on 30 benchmark functions, including high dimensional functions, show that the new method is able to find near optimal solutions efficiently. In addition, its performance as a viable optimization method is demonstrated by comparing it with other existing algorithms. Numerical results improve the robustness and efficiency of the method presented. 相似文献
46.
Schneebeli ST Kamenetska M Cheng Z Skouta R Friesner RA Venkataraman L Breslow R 《Journal of the American Chemical Society》2011,133(7):2136-2139
Understanding electron transport across π-π-stacked systems will help to answer fundamental questions about biochemical redox processes and benefit the design of new materials and molecular devices. Herein we employed the STM break-junction technique to measure the single-molecule conductance of multiple π-π-stacked aromatic rings. We studied electron transport through up to four stacked benzene rings held together in an eclipsed fashion via a paracyclophane scaffold. We found that the strained hydrocarbons studied herein couple directly to gold electrodes during the measurements; hence, we did not require any heteroatom binding groups as electrical contacts. Density functional theory-based calculations suggest that the gold atoms of the electrodes bind to two neighboring carbon atoms of the outermost cyclophane benzene rings in η(2) fashion. Our measurements show an exponential decay of the conductance with an increasing number of stacked benzene rings, indicating a nonresonant tunneling mechanism. Furthermore, STM tip-substrate displacement data provide additional evidence that the electrodes bind to the outermost benzene rings of the π-π-stacked molecular wires. 相似文献
47.
Mercey G Verdelet T Saint-André G Gillon E Wagner A Baati R Jean L Nachon F Renard PY 《Chemical communications (Cambridge, England)》2011,47(18):5295-5297
Nerve agents are highly toxic organophosphorus compounds with strong inhibition potency against acetylcholinesterase (AChE). Herein, we describe two first extremely promising uncharged reactivators for poisoned human AChE with a superior or similar in vitro ability to reactivate the enzyme as compared to that of HI-6, obidoxime, TMB-4 and HL?-7. 相似文献
48.
Hicham Benaissa El‐Hassan Benkhira Rachid Fakhar Abdelhadi Hachlaf 《Mathematical Methods in the Applied Sciences》2019,42(4):1292-1311
We consider here a mathematical model describing the bilateral frictional contact between a thermo‐piezoelectric body and a thermally conductive foundation. We model the behavior of the material with a linear thermo‐electro‐elastic constitutive law. The process is assumed to be quasistatic and the contact is modeled with a nonlocal version of Coulomb's dry friction law, in which the frictional heat generated in the process, is taken into account. We drive a variational formulation of the problem and establish the existence of its weak solution. 相似文献
49.
Abdelkrim El-Ghayoury Laurent Douce Raymond Ziessel Rachid Seghrouchni Antoine Skoulios 《Liquid crystals》1996,21(1):143-146
5,5'-[(4-Hexadecyloxyphenyl)ethynyl]-2,2'-bipyridine was synthesized by a palladium(O) cross-coupling reaction. Its thermotropic liquid crystalline behaviour was analysed using differential scanning calorimetry, polarizing microscopy, and X-ray diffraction. Three enantiotropic tilted smectic phases were identified upon heating: SF, SI, and SC. 相似文献
50.
The purpose of this paper is to state sufficient conditions for the existence of linear feedback laws which render the equilibrium solution of a composite partially linear stochastic system (the linear part of which is deterministic) exponentially stable in mean square. 相似文献