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71.
A new strategy for the combinatorial synthesis of new materials has been developed through the consecutive application of an Ugi 4CC reaction and a ring-opening metathesis polymerization (ROMP) reaction. Norbornenyl aldehydes and carboxylic acids could be used in the Ugi MCR to give highly diverse monomers that were converted to the corresponding polymers by exposure to the second-generation Grubbs' catalyst. These polymers have structural features reminiscent of polypeptides and the process could be extended to the preparation of chiral materials. 相似文献
72.
D. Khalil A. Makhoute A. Maquet G. Rahali M. Zitane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):287-295
The dynamics of laser-assisted elastic collisions in
helium is studied using the second-order Born approximation.
Detailed calculations of the scattering amplitudes are performed
by using the Sturmian basis expansion. Differential cross sections
for elastic scattering with the net absorption/emission of up to
two photons are calculated for collision energies of 5 eV, 10 eV,
and 20 eV. We discuss the influence of the low-energy electrons on
the differential cross section (DCS) as a function of the
scattering angle for selected choices of the laser frequency and
the number of photons exchanged between the external field and
electron-helium system. 相似文献
73.
A linear and nonlinear study has been made of cylindrical interface, carrying a uniform surface charge in the presence of a finite rate of charge relaxation, is investigated by using multiple scales method. The linear stability flow is analyzed by deriving a dispersion relation for the growth waves, and solving it analytically and numerically to find marginal stability curves. We investigate the electric charge relaxation effects on the stability of the flow by considering various limiting cases. We also examine the effects of finite charge relaxation times in axisymmetric and nonaxisymmetric modes. In the nonlinear approach, it is shown that the evolution of the amplitude is governed by a Ginzburg–Landau equation. There is also obtained a nonlinear modified Schrödinger equation describing the evolution of wave packets for small charge relaxation time. Further, the classic Schrödinger equation is obtained when the influence of relaxation time charge is neglected. On the other hand, the complex amplitude of quasi-monochromatic standing waves near the cutoff wavenumber is governed by a similarly type of nonlinear Schrödinger equation in which the roles of time and space are interchanged. This equation makes it possible to estimate the nonlinear effect on the cutoff wavenumber. The nonlinear theory, when used to investigate the stability of charged liquid jet, appears accurately to predict a new unstable regions. The effects of the surface charge and charge relaxation on the stability are identified. The various stability criteria are discussed both analytically and numerically and the stability diagrams are obtained. 相似文献
74.
M. Alshikh Khalil G. Vitrant P. Raimond P. A. Chollet F. Kajzar 《Optics Communications》1999,170(4-6):281-284
We report on the fabrication and characterization of composite planar waveguides for frequency doubling. Modal dispersion phase matching is obtained for TM0 fundamental and (TM1, TM2) harmonic wavelength. The experimental conversion efficiency was η=0.45% with an SH wavelength of 0.516 μm for TM0ω–TM22ω mode conversion. The phase-matching condition can be fulfilled by adjusting the diffusion time of ion-exchange and the thickness of the polymer layer. 相似文献
75.
76.
Christos Lampropoulos Theocharis C. Stamatatos Khalil A. Abboud George Christou 《Polyhedron》2009,28(9-10):1958-1964
The use of a convenient source of MnIII ions, namely the [Mn(OR)(O2CR′)2]n (R = H, Me, and R′ = Me, But) family of 1-D coordination polymers, afforded two new enneanuclear and decanuclear molecular clusters, homometallic [Mn9O7(O2CBut)13(MeCN)2] (3) and heterometallic [Mn10?xFex(OMe)20(O2CMe)10] (x < 10) (4), respectively. Compound 3 was synthesized by a solvent-induced structural transformation, whereas complex 4 resulted from the reaction of [Mn(OH)(O2CMe)2]n with an FeIII source. The core of 3 comprises two [Mn4O2]8+ butterfly units and a [Mn3O]7+ triangular unit fused together by sharing one Mn atom. Magnetic susceptibility measurements of 3 revealed dominant antiferromagnetic interactions within the molecule, and a ground state of S = 1 with many low-lying excited states. Complex 4 is a mixed FeIII/MnIII single-strand molecular wheel, which forms 3D nanotubular stacks arranged in a zig–zag fashion. The described work suggests that the [Mn(OR)(O2CR′)2]n compounds represent excellent starting materials for MnIII carboxylate cluster chemistry. 相似文献
77.
A novel titania sol-gel coating, including tetrabutyl orthototitanat (TBOT) as initial alkoxide, triethanolamine (TEA) as stabilizer, nitric acid as acid catalyst, and polyethylene glycol (PEG, 6000) as binder was prepared for the first time on an anodized aluminium wire and subsequently applied to headspace solid phase microextraction (HS-SPME) of benzene, toluene, ethylbenzene and xylenes (BTEX) with gas chromatography flame ionization detection (GC-FID). The analytical characteristics of the proposed porous titania sol-gel derived TBOT/PEG/TEA (41.6:16.0:42.4) fiber were comparable with reported fibers. The extraction temperature, extraction time, effect of salt addition, desorption temperature and desorption time were optimized. Under the optimized conditions and for all BTEX components, the linearity was from 20 to 800 μg L−1, the RSD was below 8.2% and limit of detections (LODs) were between 5.4 and 14.8 μg L−1. The recovery values were from 86.7% to 94.2% in water samples. The proposed HS-SPME-GC-FID method was successfully applied for the analysis of BTEX compounds from petrochemical wastewater samples. 相似文献
78.
A. Makhoute D. Khalil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):77-82
We study electron-atom scattering in the presence of a
laser field with elliptic polarization. We discuss the dependence
of the differential cross sections for the cases of circular and
linear polarizations as a function of scattering angle.
Interesting typical signatures of the phase between the two
components of the circular polarization of the laser field appear
in the differential cross section. 相似文献
79.
S. K. Shakshooki L. Szirtes A. Azrak M. Ahmed S. Khalil 《Journal of Radioanalytical and Nuclear Chemistry》1989,132(1):49-58
Solid amorphous Zr-, Ti- and ZrxTi(1–x) phosphates (where x=0.10, 0.33, 0.66, and 0.90) in various sodium forms were contacted with an excess of solid oxalic acid dihydrate to its molten state for a given time. The oxalic acid was removed by extraction and the residue was washed with redistilled water. As a result of this, crystalline forms of Zr-, Ti-, and ZrxTi(1–x) phosphates were obtained. Using various sodium forms of the initial samples, higher rate of crystallisation resulted than that found in case of hydrogen forms of initial samples. 相似文献
80.
Gani Issayev Khalil Djebbi Goutham Kukkadapu Marco Mehl Scott W. Wagnon William J. Pitz Aamir Farooq 《Proceedings of the Combustion Institute》2021,38(1):641-649
Distillate fuels contain significant proportions of naphtheno-aromatic components and tetralin is a suitable surrogate component to represent this molecular moiety. The presence of aromatic and naphthyl rings makes kinetic modeling of tetralin very challenging. Primary radicals formed during the oxidation of tetralin can be aryl, benzylic or paraffinic in nature. Using available information on reaction paths and rate constants of naphthenes and alkyl-aromatics, a kinetic model of tetralin has been developed in the current study with emphasis on low-temperature chemistry and high-pressure conditions. Due to the lack of high-level quantum chemical calculations on reaction pathways of tetralin, analogous rates from ab-initio studies on benzylic and paraffinic radicals have been adopted here. Some modifications to the reaction rate rules are incorporated to account for the unique characteristics of tetralin's molecular structure. Important reaction channels have been identified using reaction path and brute force sensitivity analyses. In order to investigate the model performance at low temperatures, new experiments are carried out in a rapid compression machine on blends of tetralin and 3-methylpentane. Blending of low-reactivity tetralin with a high-reactivity alkane allowed the investigation of tetralin ignition at very low temperatures (665 – 856 K). The kinetic model developed in the current study is found to predict the current experiments and literature data adequately. The new model will aid in high-fidelity surrogate predictions at engine-relevant conditions. 相似文献