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81.
Kazem Bitaghsir Fadafan Seyed Kamal Tabatabaei 《The European Physical Journal C - Particles and Fields》2014,74(4):1-11
Nuclear effects in deep inelastic scattering at low $x$ are phenomenologically described changing the typical dynamical and/or kinematical scales characterizing the free nucleon case. In a holographic approach, this rescaling is an analytical property of the computed structure function $F_2(x,Q^2)$ . This function is given by the sum of a conformal term and of a contribution due to quark confinement, depending on IR hard-wall parameter $z_0$ and on the mean square distances, related to a parameter $Q^\prime $ , among quarks and gluons in the target. The holographic structure function per nucleon in a nucleus $A$ is evaluated showing that a rescaling of the typical nucleon size, $z_0$ and $Q^\prime $ , due to nuclear binding, can be reabsorbed in a $Q^2$ -rescaling scheme. The difference between neutron and proton structure functions and the effects of the longitudinal structure functions can also be taken into account. The obtained theoretical results favorably compare with the experimental data. 相似文献
82.
Mohamed Hassan Magda A. Barsy Eman A. El Rady Abdullah Sulaiman Al-Ayed Mona Frempong Kamal U. Sadek 《Journal of heterocyclic chemistry》2024,61(4):543-549
An efficient synthesis of novel benzo[f]Chromeno[2,3-d]pyrimidine and unknown benzo[f]chromeno[2,3-d][1,2,4]triazolopyrimidine derivatives is described utilizing ethyl-2-amino-4-phenyl-4H-benzo[f]chromene-3-carboxylate as precursor via aza-Wittig reaction. The process proved to be simple, high-yielding, and efficient. 相似文献
83.
Kamal Jain 《Combinatorica》2001,21(1):39-60
We present a factor 2 approximation algorithm for finding a minimum-cost subgraph having at least a specified number of edges
in each cut. This class of problems includes, among others, the generalized Steiner network problem, which is also known as
the survivable network design problem. Our algorithm first solves the linear relaxation of this problem, and then iteratively
rounds off the solution. The key idea in rounding off is that in a basic solution of the LP relaxation, at least one edge
gets included at least to the extent of half. We include this edge into our integral solution and solve the residual problem.
Received March 6, 1998 相似文献
84.
The kinetics of H2O2 decomposition have been investigated using ZrO2 supported with transition metal ions including CuII, AgI, HgII, CoII, MnII, NiII and FeIII. At pH = 6.8, the reaction rate exhibits a first order dependence on the initial H2O2 concentration at low concentrations. The order of activity of the different catalysts is strongly dependent on the [H2O2]0 used. The reaction proceed via the formation of the peroxo-intermediate which has an inhibiting effect on the reaction rate. The rate increases with increasing pH, and attains a limiting rate at higher pH's. A reaction mechanism is proposed involving liberation of HO2 radicals from the peroxo-intermediate as the rate-determining step. 相似文献
85.
This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies. 相似文献
86.
87.
Kamal Sarabandi 《International Journal of Infrared and Millimeter Waves》1990,11(11):1303-1321
A periodic, corrugated, dielectric layer is simulated by an anisotropic dielectric layer of equal thickness. The tensor elements of the equivalent dielectric layer are given in terms of the permittivity of the dielectric material, the period of the surface corrugation, and the width of the corrugations. The validity of this technique is verified by comparing the reflection coefficient of the equivalent layer with that of the corresponding corrugated layer using the moment method. Employing a multiple layer approach, the technique is extended to handle periodic surfaces with arbitrary cross sections which can be used to design millimeter wave dielectric plate polarizers and absorbers. 相似文献
88.
Y. M. Temerk M. M. Kamal Z. A. Ahmed M. S. Ibrahim 《Fresenius' Journal of Analytical Chemistry》1990,336(7):589-592
Summary A differential pulse polarographic method has been applied to the determination of trace concentrations of polycytidylic acid (Poly-C) in absence and presence of metal ions. The applicability of differential pulse polarography for the trace determination of the investigated biological compound was examined with regard to the dependence of differential pulse current on various parameters such as pH, pulse amplitude, scan rate and drop time. The selectivity of this technique for the determination of binary and a ternary mixtures of poly-C and some metal ions has been also reported. Limits of detection and quantitation have been calculated for the differential pulse polarographic determination of the poly-C and various metal ions. The validity of this method is supported by the constancy of the ip/C values and a statistical analysis is included on calibration curve parameters and observed concentration. 相似文献
89.
The zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones gives functionalized cyclopentanols in good yield in the presence of a catalytic amount of mercury(II) chloride in N,N-dimethylformamide as solvent at room temperature. The reaction is regio- and stereo-selective producing 3,4-trans-diarylcyclopentanols selectively. 相似文献
90.
Tungstophosphoric acid catalyzed rapid and good yielding reactions of α,β-unsaturated aldehydes with arenethiols to give the corresponding 4-thioaryl-1,2,3,4-tetrahydro-1-benzothiopyrans (thiochromans) under solvent-free and room temperature conditions. 相似文献