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排序方式: 共有229条查询结果,搜索用时 906 毫秒
21.
Saied M. Soliman Assem Barakat Hazem A. Ghabbour 《Journal of Coordination Chemistry》2017,70(8):1339-1356
A new highly distorted hexacoordinated silver(I) complex [AgL2NO3] with 2-(bis(methylthio)methylene)-1-phenylbutane-1,3-dione (L) as ligand is synthesized and characterized using elemental analysis, FTIR, NMR, and X-ray single-crystal structure analysis. The ligand (L) and the nitrate group act as bidentate ligands. The geometry around the silver ion has an intermediate configuration between a trigonal prism (TP) and an octahedron (OCT). Continuous shape measure (CShM) analysis indicated a closer configuration to TP than OCT. Experimentally and theoretically, the Ag–S bonds are shorter than any of the Ag–O bonds, indicating a stronger interaction between Ag+ (soft metal) and S-atom as a softer site than oxygen. Natural bond orbital (NBO) analyses showed higher interaction energies between the S-atom lone pairs and the Ag–antibonding NBO (8.61–31.39 kcal/mol) than LP(O)→Ag (3.48–11.46 kcal/mol). The acceptor antibonding NBO of the Ag atom has mainly s-orbital character. The Ag atom has a natural charge of +0.7579 e at the experimental structure, suggesting that negative charge was transferred from the ligand (0.0666 e) and nitrate (0.1090 e) to the Ag ion. Using Hirshfeld surface analysis, the important intermolecular interactions between molecular units within the crystal lattice of the ligand and its Ag-complex were analyzed and compared. 相似文献
22.
Bulk superconducting samples of type Tl0.5Pb0.5Sr1.6Ba0.4CaCu2−x
Ru
x
O7−δ, (Tl, Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were prepared by the conventional one-step solid-state reaction technique. The prepared samples were investigated
using X-ray powder diffraction, electrical resistivity and electron paramagnetic resonance (EPR) measurements. Enhancement
of the phase formation, superconducting transition temperature T
c and hole carriers concentration P was observed up to x = 0.075. For x > 0.075, a reverse trend was observed. EPR spectra were measured at different temperatures (120–290 K) for all prepared samples.
The number of spins N participating in the resonance and the paramagnetic susceptibility χ were calculated as a function of both Ru-content and
temperature. N and χ increased as the Ru-content increased. A linear relationship between logN and 1/T was established, from which the activation energy E
a was calculated as a function of the Ru-content. The temperature dependence of χ was fitted according to Curie–Weiss type
of magnetic behavior. Curie constant C, Curie temperature θ, the effective magnetic moment μ and the electronic specific heat γ were estimated as a function of the Ru-content. 相似文献
23.
Use of some organic dyes in gamma irradiation dose determination 总被引:1,自引:0,他引:1
In the present work, the radiation-induced color bleaching of Remazol brilliant blue (RBB), Wegocet orange (WO), Methyl green
(Me G) and Thioflavine S (Th S) dyes solutions was studied. Solutions of these dyes in different solvents were found to obey
Beer’s law within certain concentration levels. The % color bleaching occurring in different dye solutions on using different
gamma irradiation doses was determined and the data obtained showed the existence of good linear relationships among them
in the four dye systems used. The linear sections lines were used as calibration curves for evaluating unknown gamma irradiation
doses. From the obtained results, it was concluded that RBB in water, WO in ethanol, Me G in butanol and Th S in 60% ethanol–water
mixture could be used for dose evaluation within the dose ranges 5–25 kGy for RBB, 20–90 kGy for WO, 10–70 kGy for Me G and
5–160 kGy for Th S. The sensitivity of the systems towards gamma radiations has been also reported. 相似文献
24.
Patra D Barakat C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1823-1828
Hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroburate, modified the properties of aqueous surfactant solutions associated with curcumin. Because of potential pharmaceutical applications as an antioxidant, anti-inflammatory and anti-carcinogenic agent, curcumin has received ample attention as potential drug. The interaction of curcumin with various charged aqueous surfactant solutions showed it exists in deprotonated enol form in surfactant solutions. The nitro and hydroxyl groups of o-nitrophenol interact with the carbonyl and hydroxyl groups of the enol form of curcumin by forming ground state complex through hydrogen bonds and offered interesting information about the nature of the interactions between the aqueous surfactant solutions and curcumin depending on charge of head group of the surfactant. IL[bmin][BF4] encouraged early formation of micelle in case of cationic and anionic aqueous surfactant solutions, but slightly prolonged micelle formation in the case of neutral aqueous surfactant solution. However, for curcumin IL [bmin][BF4] favored strong association (7-fold increase) with neutral surfactant solution, marginally supported association with anionic surfactant solution and discouraged (~2-fold decrease) association with cationic surfactant solution. 相似文献
25.
H.M. Barakat 《Journal of the Egyptian Mathematical Society》2011,19(1-2):28-32
In the first part of this review article some recent developments of maximal correlation coefficient, introduced by Gebelein (1941) [7], and its applications in various areas of statistics are discussed. The second part is devoted to find the distributions providing the maximal correlation coefficient between generalized order statistics (gos) and dual generalized order statistics (dgos), which are introduced by Kamps (1995) [8] and Burkschat et al. (2003) [4], respectively. Finally, in the third part, general theorems are presented, which give simple non-parametric criterion for the asymptotic independence between the different elements of gos, as well as dgos. 相似文献
26.
Exact solutions for vibrational levels of diatomic molecules via the Morse potential are obtained by means of the asymptotic
iteration method. It is shown that the numerical results for the energy eigenvalues of7Li2 are all in excellent agreement with those obtained before. Without any loss of generality, other states and other diatomic
molecules could be treated in a similar way. 相似文献
27.
Graft copolymers of nylon-6 and acrylonitrile have been prepared by the direct grafting technique. Carrying out the liquid phase direct irradiation grafting in air in the presence of a redox salt made the technique more efficient. The effects of reaction parameters (such as total dose, solvent type and composition) and monomer concentration on the mutual grafting in the liquid and vapour phases were studied. The results indicate that, if all reaction parameters were fixed, the vapour phase technique gives rise to lower grafting yield than the liquid phase method. 相似文献
28.
29.
Richard Barakat 《Stochastic Processes and their Applications》1978,8(1):77-85
The average frequency with which a trigonometric sum having linearly independent frequencies achieves a given value in a specified time interval was solved by Kac in the form of a double integral. In the present paper, Kac's solution is generalized by allowing the amplitudes of the sinusoidal terms to be statistically independent random variables possessing compact probability density functions. The average frequency is expressed as a Fourier cosine series. Representative numerical calculations are shown. The asymptotic form of the average frequency is also discussed. 相似文献
30.