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21.
N-Alkyl-oxaziridines react in the presence of a nucleophile as an oxygenating agent; in the absence of a nucleophile, an isomerization reaction is observed. This study describes the synthesis of two new dihydroisoquinoline oxaziridines and their reactivity in an acid-promoted reaction in the presence and absence of sulfides. 相似文献
22.
Walid Mabrouk Ridha Lafi Jean Franois Fauvarque Amor Hafiane Cyrille Sollogoub 《先进技术聚合物》2021,32(1):304-314
The purpose of this work is to study the desalination of brackish water using a new ion exchange membrane, made from sulfochlorated polyethersulfone (Cl‐PES), and crosslinked using aminated polyethersulfone (NH2‐PES) as a crosslinking reagent. This membrane, named ClNH2 membrane, has been obtained by reaction between Cl‐PES with 1.3 SO2Cl groups per monomer unit and 0.2 equivalent amount of NH2‐PES. ClNH2 membrane has been characterized in terms of contact angle, transport number, intrinsic conductivity, and water uptake (as a function of temperature). Electrodialysis performances of the newly synthetized membranes have been measured using an electrodialysis cell at a laboratory scale and compared to commercial membranes. All the experiments have been performed using synthetic brackish water solutions prepared from sodium chloride salts with different concentrations (varying from 0.5 to 5.0 g/L). The concentration of different water samples obtained has been found to be below the amount recommended by the World Health Organization (WHO) for drinking water. 相似文献
23.
J. Gummel Y. Corvis J. Jestin J. M’Hamdi L. Barré 《The European physical journal. Special topics》2009,167(1):171-176
Presence of suspended particles such as asphaltene in crude oils
could significantly affect the production by means of deposition in porous
media especially near the well bore. We investigate this phenomenon using
the ability of Small Angle Neutron Scattering technique to probe directly
the asphaltene adsorption process in a porous medium at the nanometer length
scale under flow conditions. A device based on a quartz tube filled with SiC
particles constitute the porous medium in which an asphaltene solution in a
mixture of good (toluene)/bad (heptane) solvent is injected under
controlled flow. The contrast matching technique enables to match the porous
medium scattering contributions and to measure the signal of the deposit.
Such a device can be used for curves surface measurements on a setup
originally designed for bulk studies and permit thus the direct comparison
with measurements on flat surfaces (neutron reflectivity) and indirect
adsorption measurements (adsorption isotherm). We show here that asphaltene
in good solvent leads to a monolayer whereas addition of bad solvent results
in a multilayer growth which is consistent with the deposition behaviour
described in the literature. 相似文献
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25.
This Note deals with the boundary null-controllability of linear diffusion–reaction equations in a 2D bounded domain. We transform the determination of the sought HUM boundary control into the minimization of a continuous and strictly convex functional. In the case of a rectangular domain where the diffusion tensor is represented by a diagonal matrix, we establish a procedure based on the inner product method that uses a complete orthonormal family of Sturm–Liouville's eigenfunctions to express explicitly the sought control. 相似文献
26.
Hamdi Raïssi 《Comptes Rendus Mathematique》2011,349(21-22):1203-1206
This Note is devoted to the test of instantaneous linear Granger causality when the errors are dependent but uncorrelated. The assumptions are weak and include a large set of dynamics as for instance the GARCH processes. We show that the standard Wald test for testing instantaneous linear Granger causality is not valid in our framework. As a consequence Wald tests which are valid in our framework are proposed. 相似文献
27.
Anion complexation. A ditriphenylphosphonium calix[4]arene derivative as a novel receptor for anions
A novel anionic receptor 2 consisting of a calix[4]arene bearing two alkytriphenylphosphonium has been prepared by two different procedures. The complexation occurred at the phosphonium sites probably due to electrostatic and/or π-anion forces. 相似文献
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30.
Ridha Kossai Bedri Emir Jacques Simonet Guy Mousset 《Journal of Electroanalytical Chemistry》1989,270(1-2)
Sulphonamides may lead, in the course of their cathodic cleavage, to intermediate amino radicals. These radicals may be reduced or trapped rapidly by nitrones added “ in situ ”. The method allows (by means of ESR spectral analysis) elements for establishing cleavage mechanisms to be obtained. 相似文献