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排序方式: 共有263条查询结果,搜索用时 15 毫秒
51.
Lombardo G Amoddeo A Hamdi R Ayeb H Barberi R 《The European physical journal. E, Soft matter》2012,35(5):32-6
Thermotropic nematic materials relax strong distortions by lowering the nematic order: the uniaxial symmetry is broken and is locally replaced by biaxial domains. We investigated the dynamics of the nematic order near a boundary surface of an asymmetric π-cell submitted to an external electric field, close to the electric order reconstruction threshold. An unexpected phenomenon is observed close, but below the threshold: the biaxial order spreads on the surface inducing a consequent bulk topological behaviour equivalent to the splay-bend fast transition allowed by order reconstruction at higher voltage. 相似文献
52.
Hamdi M. Hassaneen Ahmed M. Farag Ahmad S. Shawali Mohamed S. Algharib 《Journal of heterocyclic chemistry》1987,24(3):577-580
The regioselectivity of the cycloadditions of α,β-unsaturated nitrilimine derived from N-phenylcinnamo-hydrazidoyl chloride 2 to C = Se, C = S and C = C double bonds of the resonance stabilized selenocyanate and thiocyanate anions, enol tautomer of dibenzoylmethane and benzalacetophenone was investigated. The results indicate that the reactions studied are dipole-LUMO-dipolarophile-HOMO controlled and that the larger orbital coefficient in the LUMO of N-phenylcinnamonitrilimine is on the carbon atom bearing the styryl group. The structures of the cycloadducts were assigned and confirmed on the basis of their elemental analyses and spectra. 相似文献
53.
Functional Analysis and Its Applications - Using a change of basis in the algebra of symmetric functions, we compute the moments of the Hermitian Jacobi process. After a careful arrangement of... 相似文献
54.
Microwave-assisted synthesis of calix[4]resorcinarenes by cyclocondensation of various aldehydes and resorcinol catalysed by 12-tungstophosphoric acid type Keggin (H3PW12O40·13H2O) or concentrated HCl is described. Excellent isolated yields (up to 90%) were attained within short reaction times (typically, 3-5 min) when the reaction was performed under microwaves irradiation. 相似文献
55.
A novel quadridentate, N2O2 type Schiff base, synthesized from 1,4‐bis‐(o‐aminophenoxy)butane and 2‐hydroxynaphthalin‐1‐carbaldehyde, forms stable complexes with transition metal ions such as Co(II), Cu(II) and Ni(II) in DMF. Microanalytical data, elemental analysis, magnetic measurements, UV‐visible and IR‐spectra as well as conductance measurements were used to confirm the structures. Electrochemical measurements show that metal complexes undergo quasi‐reversible one‐electron redox processes. The voltammetric results also revealed that the CuL complex has the highest electron transfer rate indicating that both the Cu(II) and Cu(I) forms appear in a similar planar configuration, so the electron transfer does not require larger reorganization of the complex. 相似文献
56.
Transport in Porous Media - Compositional simulation is typically used to study subsurface displacement processes that involve complex physics. Such processes are highly nonlinear and they occur at... 相似文献
57.
H. Hamdi R. Abderrahim F. Meganem 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(1):32-36
Formation of inclusion complex between benzidine diammonium dipicrate and β-cyclodextrin with stoichiometry 1:2 (guest–host) has been established by UV, 1H NMR, 13C NMR, IR spectra and powder X-ray diffractometry. 1H NMR studies are used to confirm the inclusion and to provide information on the geometry of dipicrate inside the cavity of β-cyclodextrin. 相似文献
58.
Ha-Thi MH Souchon V Hamdi A Métivier R Alain V Nakatani K Lacroix PG Genêt JP Michelet V Leray I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):9056-9065
The design of a new class of fluorophores is presented. Some push-pull chromophores (D-pi-A) containing polyphenylethynyl units and a phosphane oxide moiety were efficiently prepared from common intermediates. Straightforward syntheses gave novel one-armed, rod-shaped and three-armed, star-shaped fluorophores. The optical properties of the resulting star-shaped derivatives were evaluated, showed high fluorescence quantum yields, and their excitation induces very efficient charge redistribution. Moreover, thanks to their push-pull character, the molecules exhibited significant second-order NLO properties with good transparency, up to 67x10(-30) esu at 1907 nm, with an absorption lambdamax at 369 nm. The effect of the donor group and of the number of phenylethynyl arms have been studied in this work. 相似文献
59.
Tarek Hamdi 《Complex Analysis and Operator Theory》2018,12(7):1697-1705
The present paper provides a proof of \(i^*(\mathbb {C}P+\mathbb {C}(I-P); \mathbb {C}Q+\mathbb {C}(I-Q))=-\chi _{{ orb}}(P,Q)\) for two projections P, Q without any extra assumptions. An analytic approach is adopted to the proof, based on a subordination result for the liberation process of symmetries associated with P, Q. 相似文献
60.
Naceur Hamdi Feten Bouabdallah Antonio Romerosa Rached Benhassen 《Comptes Rendus Chimie》2010,13(10):1261-1268
A new family of coumarin derivatives (4a–i) containing a chalcone moiety was synthesized by condensation of 3-acetyl-4-difluoro boryloxycoumarin (2) with aryl and heteroaryl aldehydes with piperidine in chloroform. Resulting compounds were characterized by IR, 13C, 1H NMR and UV visible spectroscopy. Compound 3-((2E)-3-(3,4,5-Trimethoxy-phenyl)prop-2-enoyl)-2(H)-chromen-2-one (4g) was characterized by single crystal X-ray diffraction. The antioxidant and antibacterial activities of the obtained compounds 4a-i was evaluated. The biological activity found for these compounds is discussed against their structural features, physical and chemical properties. 相似文献