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排序方式: 共有246条查询结果,搜索用时 156 毫秒
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Ahmed Oueslati Imen Abdelhedi Régis Mercier Eric Drockenmuller Hatem Ben Romdhane 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4650-4656
Photoresponsive polyamides containing main‐chain pentamethylated norbornadiene (NBD) moieties are obtained in quantitative yields via the Yamazaki–Higashi reaction between a pentamethylated NBD dicarboxylic acid and a series of aromatic diamines. Chemical structures are confirmed by 1H and 13C NMR and weight average molar masses measured by SEC are in the range of 21,500–28,600 g mol?1 with chain dispersities close to 2. Physical properties are investigated by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, and viscosimetry. All obtained polyamides are amorphous with glass transition temperatures ranging from 68 to 124 °C. They are soluble at room temperature in common organic solvents and exhibit good thermal stabilities with Td10 values ranging from 175 to 276 °C. The photochemical isomerization of the NBD moiety into quadricyclane (QC) is studied by UV/vis spectroscopy after sunlight irradiation of polymer films. For all polyamides, a first‐order kinetic rate is observed for the conversion of NBD to QC. The thermal release of the stored energy associated to the reverse transformation of QC groups into NBD ones is about 90–95 kJ mol?1 as measured by DSC of the irradiated polymer films. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4650–4656 相似文献
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The Weinstein transform satisfies some uncertainty principles similar to the Euclidean Fourier transform. A generalization
and a variant of Cowling-Price theorem, Miyachi’s theorem, Beurling’s theorem, and Donoho-Stark’s uncertainty principle are
obtained for the Weinstein transform. 相似文献
76.
Sonia Besbes Hatem Mhiri Georges Le Palec Philippe Bournot 《Heat and Mass Transfer》2003,39(8-9):675-686
The turbulent interaction between two opposed plane jets separated by a distance H is experimentally studied by using a PIV
(Particle Image Velocimetry) method and numerically investigated by means of a finite volume code. Two turbulence models have
been tested: the standard k-ɛ model and a second-order model. The validation of the numerical study was performed by comparing
the results with experimental data obtained for the case of two interacting opposed jets at ambient temperature (isothermal
case). The effect of the angle of inclination of the jets is studied. Conclusions of the validation are then used to study
the interaction between two jets, one being maintained at ambient temperature whereas the other is heated. Results show that
the stagnation point moves towards the heated jet. It is shown that the heating induces a stabilizing effect on the flow. 相似文献
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In this paper, we consider the sum of two bounded linear operators defined on a Banach space and we present some new and quite general conditions to investigate their essential spectra. 相似文献
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Hatem A. Abdel‐Aziz Khalid A. Al‐Rashood Kamal Eldin H. ElTahir Hany S. Ibrahim 《中国化学会会志》2011,58(7):863-868
A series of 3,4‐bis‐chalcone‐N‐arylpyrazoles 3a‐h was prepared conveniently from diacetyl pyrazoles 2a,b . All reactions were carried out under conventional thermal heating and/or microwave irradiation. The structure of the latter functionally pyrazoles was confirmed under the bases of their IR, mass, 1H NMR and 13C NMR. The X‐ray diffraction of compound 3e not only confirmed the chemical structure of 3a‐h , but also showed the E configuration of their chalcone moieties. Treatment of compound 3e with phenyl hydrazine in presence of acetic acid afforded the tri‐pyrazle 4 . The anti‐inflammatory activity of the newly synthesized compounds was investigated. Some of these compounds showed a moderate activity when compared with indomethacin as a reference drug. The combination between chalcone and pyrazole moieties revealed a variable effect in anti‐inflammatory activity. 相似文献
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Ismail Warad Maha Al-Ali Belkheir Hammouti Taibi Ben Hadda Rami Shareiah Mohamed Rzaigui 《Research on Chemical Intermediates》2013,39(6):2451-2461
A novel di-μ-chloro-bis[chloro(4,7-dimethyl-1,10-phenanthroline)cadmium(II)] dimer complex has been prepared by reacting CdCl2·2.5H2O with 4,7-dimethyl-1,10-phenanthroline (dmphen) ligand. The complex was characterized on the basis of elemental analysis, FAB-MS, IR, UV–visible, 1H, and 13C NMR spectroscopy, TG/DTA, and X-ray single-crystal diffraction studies. The Cd(II) ions in [CdCl2(C14H12N2)]2 are coordinated to three Cl atoms with the centrosymmetric dimer bridged through the Cl atoms and two N atoms in a slightly distorted square-pyramidal disposition. Several hydrogen bonds formed between the terminal Cl atoms and H-Me/H-Ph groups may stabilize the structure in the dimer form. 相似文献
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