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141.
Zhang G Marie P Maaloum M Muller P Benoit N Krafft MP 《Journal of the American Chemical Society》2005,127(29):10412-10419
The formation of large (approximately 20-35 nm) surface hemimicelles in monolayers of semifluorinated alkanes, C(n)F(2)(n)(+1)C(m)H(2)(m)(+1) (FnHm), observed after transfer onto silicon wafers, is a general phenomenon. F6H16 and F8H14 exclusively form highly monodisperse circular hemimicelles, organized in a hexagonal array. The other FnHm investigated form both circular and elongated hemimicelles. The longer FnHm is, the larger the area fraction of elongated micelles; both the hydrocarbon block (H-block) and the fluorocarbon block (F-block) affect this area fraction. The length of the elongated micelles increases with the total length of the diblocks. The diameter of the circular micelles increases with the length of the H-block but, unexpectedly, not with that of the F-block. Model calculations account for these observations. Close examination of the circular micelles showed that they generally present a pit or a tip at their center. The width of the elongated micelles is comparable to the radius of the circular micelles, suggesting that the latter arise from a partition of elongated micelles, followed by coalescence of the edges of the resulting fragments. The elongated micelles become shorter and fewer when surface pressure increases, further suggesting a conversion of elongated into circular micelles. This conversion is reversible. The surface pressure-molecular area isotherms do not present any feature that forebears the existence of hemimicelles. The obtaining of stable surface patterns from simple, "nonpolar" molecular fluorocarbon/hydrocarbon diblocks opens a new approach for producing featured nanostructures from organic templates. 相似文献
142.
Hydrated proteins undergo a dynamical transition around 200 K from glasslike to liquidlike motion. Molecular dynamics simulations have been used to study the temperature dependence of the dynamics of ribonuclease A in the hydrated crystal, a model dehydrated powder, and aqueous solution. Changes in the dynamics accompanying the transition throughout the protein have been quantified in terms of the mean-squared fluctuations (MSFs) of methyl hydrogen atoms on the 100 ps time scale. In solution at 300 K the MSFs span a broad distribution, consistent with NMR relaxation measurements. The MSF distribution in the hydrated crystal at 300 K is qualitatively similar to the solution result, except for a slight shift to lower values, and dehydration results in a dramatic shift of the MSFs to lower values. As the temperature is lowered, the whole distribution of methyl group fluctuations in the hydrated crystal shifts to lower values. Most of the methyl groups in the hydrated protein display a nonlinear temperature dependence with a dynamical transition at approximately 200 K, but most methyl groups do not undergo a transition in the dehydrated protein. We conclude that the dynamical transition occurs throughout most of the protein and that solvent is required for the transition. 相似文献
143.
M’hammed Badaoui Ali Nour Abdennasser Slimani Mounir Khaled Berrah 《Transport in Porous Media》2007,67(1):69-91
In this paper, the Thin Layer Method (TLM) is adapted for solving one-dimensional primary consolidation problems. It is also
combined with a stochastic formulation integrating Monte Carlo simulations to investigate primary consolidation of a random
heterogeneous soil profile. This latter is modeled as a set of superposed layers extending horizontally to infinity, and having
random properties. Spatial variability of soil properties is considered in the vertical direction only. Soil properties of
interest are elastic modulus and soil permeability, modeled herein as spatially random fields. Lognormal distribution is chosen
because it is suitable for strictly non-negative random variables, and enables analyzing the large variability of such properties.
The statistics regarding final settlement and its corresponding time are investigated by performing a parametric study, which
integrates the influence of variation coefficient of both elastic modulus and soil permeability, and vertical correlation
length. Obtained results indicate that heterogeneity significantly influences primary consolidation of the soil profile, generating
a quite different way of soil grain rearrangement and water pressure dissipation in comparison to the homogeneous case, and
causing a delay in the consolidation process. 相似文献
144.
The fungicide Flutriafol was mineralised on irradiation of its aqueous solution, in which anatase P25 was suspended, with a medium pressure mercury lamp under an air stream. The half-time of reaction, t1/2, i.e. the time at which the total organic carbon of the solution was halved, decreased in the series of P25 loaded with RuO2>Pt>Ag>MnO2. Heating P25 at 500°C for 3 h reduced t1/2 compared to bare, unheated P25. 相似文献
145.
Mounir Hajji Mohamed Faouzi Zid Ahmed Driss Tahar Jouini 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):i76-i78
A new non‐centrosymmetrical form of lithium molybdyl arsenate has been synthesized and grown as a single crystal. The structure of β‐LiMoO2(AsO4) is built up of corner‐sharing AsO4 tetrahedra and MoO6 octahedra which form a three‐dimensional framework containing tunnels running along the a axis, wherein the Li+ cations are located. This novel structure is compared with the compound LiMoO2(AsO4) of the same formula, and with those of AMO2(XO4) (A is Na, K, Rb or Pb, M is Mo or V, and X is P or As) and B(MoO2)2(XO4)2 (B is Ba, Pb or Sr). 相似文献
146.
In the present study, a simultaneous modelling, in transient regime and 3D, of the thermal and mass transfers inside a room of habitat (including its internal walls), heated by a hot water radiator, and the thermal and mass transfers inside the heating equipment is carried out. The adopted CFD code, at numerical simulations, is on a macroscopic scale. Comparing numerical values to the experimental quantities showed that the results of the used numerical code are satisfactory. 相似文献
147.
2,4‐Bis‐(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide (Lawesson's reagent) ( 1 ) reacted with 2‐hydrazino‐3‐methyl‐quinoxaline ( 2 ) to give [1,2,4,3]‐triazaphospholo[4,5‐a]quinoxaline derivative 3 . The Mannich reaction using different amines on compound 3 gave Mannich bases 4a–d . Also, compound 3 reacted with formaldehyde to give the corresponding 2‐hydroxymethyl derivative 5 , which upon reaction with thionyl chloride gave the corresponding chloromethyl derivative 6 . Treatment of compound 6 with some thiols yielded the corresponding sulfides 7a–d . Acylation of compound 3 gave acylated compounds 8a,b . Compound 9 , which was prepared through the reaction of compound 3 with ethyl cyanoacetate, was investigated as a starting material for the synthesis of some new heterocyclic systems 10–13 . Also, reaction of compound 9 with carbon disulfide and 2 equivalents of methyl iodide in a one‐pot reaction yielded the corresponding ketene‐S,S‐acetal 14 , which in turn reacted with bidentates to give some new heterocycles 15–17 . © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:520–529, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20473 相似文献
148.
Abbas Mohammed Nooredeen Saeed Ayman Ali Ali Mounir Ben Errachid Abdelhamid Zine Nadia Baraket Abdullatif Singh Baljit 《Journal of Solid State Electrochemistry》2019,23(4):1129-1144
Journal of Solid State Electrochemistry - Self-assembled monolayer (SAM) of cobalt teraaminophthalocyanine (CoTAPc) was developed on thioctic acid (TA) dithiol modified gold electrode and... 相似文献
149.
150.
Mounir Laroussi J. Reece Roth 《International Journal of Infrared and Millimeter Waves》1993,14(8):1601-1617
In monostatic radar applications it is the signal back to the source that is responsible for target detection. The back-scattering cross-section allows one to calculate the amount of power reflected back in the direction of incidence. In this paper, we develop theoretically and calculate computationally the back-scattering cross-section of a cylindrical column of magnetized plasma with a uniform number density. The effect of the plasma number density and of the collision frequency are investigated. 相似文献