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51.
Schamel equation in an inhomogeneous magnetized sheared flow plasma with q-nonextensive trapped electrons 下载免费PDF全文
An investigation is carried out for understanding the properties of ion–acoustic(IA) solitary waves in an inhomogeneous magnetized electron-ion plasma with field-aligned sheared flow under the impact of q-nonextensive trapped electrons. The Schamel equation and its stationary solution in the form of solitary waves are obtained for this inhomogeneous plasma. It is shown that the amplitude of IA solitary waves increases with higher trapping efficiency(β), while the width remains almost the same. Further, it is found that the amplitude of the solitary waves decreases with enhanced normalized drift speed, shear flow parameter and the population of the energetic particles. The size of the nonlinear solitary structures is calculated to be a few hundred meters and it is pointed out that the present results are useful to understand the solar wind plasma. 相似文献
52.
Adeel Arsalan Iqbal Ahmad Syed Abid Ali Kiran Qadeer Shaukat Mahmud Fozia Humayun Anwar Ejaz Beg 《国际化学动力学杂志》2020,52(3):207-217
Cyanocobalamin (B12) is a photosensitive vitamin, and its photodegradation to hydroxocobalamin (B12b) in liposomes has been investigated. The values of apparent first-order rate constants (kobs) for the photodegradation of B12 in liposomes (nine preparations) are in the range of (0.52-2.24) × 10–3 min–1, compared to 3.21 × 10–3 min–1 for B12 in aqueous solution (pH 5.0). The entrapment efficiency of B12 in liposomes is 26.4-38.8%. The values of kobs show a linear relation with phosphatidylcholine (PC) content in liposomes, indicating the influence of PC in inhibiting the rate of photolysis of B12. The value of the bimolecular rate constant for photochemical interaction of B12 and PC is 0.32 M–1 min–1, indicating the stabilizing effect of PC on the photolysis of B12. The ratio of B12 stabilization in liposomal preparations is in the range 2-6 compared to that of the unentrapped vitamin The stabilization of B12 is mediated by a photoinduced charge-transfer B12-PC complex that leads to the reduction of B12 to B12r, which is then oxidized to B12b that has low susceptibility to photolysis. The extent of stabilization of B12 probably depends on the degree of interaction between the two compounds under the reaction conditions, indicated by the loss of B12 fluorescence. 相似文献
53.
A simpler analytical approach is employed to obtain energy integral equation for a pseudo‐particle in a pseudo‐potential, which admits double layer (DL) solutions for the non‐linear low‐frequency electrostatic perturbations in non‐uniform plasma consisting of electrons and two kinds of ions. One of the ion species has field‐aligned shear flow and electrons are superthermal kappa distributed. This theoretical model is applied to the upper ionospheric oxygen‐dominated plasma that has small concentration of protons along with upward flow of oxygen ions. Under suitable boundary conditions, both rarefactive (density dip) and compressive (density hump) DLs are obtained solving energy integral equation using the plasma parameters of ionosphere around altitude of 800 km. The amplitude and width of the DLs depend upon the scale lengths of density and temperature gradients as well as on the ratio of equilibrium densities of oxygen and hydrogen. 相似文献
54.
S. Nazir B. Amin A. Shaukat Y. Saeed 《Journal of Physics and Chemistry of Solids》2009,70(5):874-1965
First principles density functional calculations, using full potential linearized augmented plane wave (FP-LAPW) method, have been performed in order to investigate the structural, electronic and optical properties of CaxZn1−xO alloy in B1 (NaCl) phase. Dependence of structural parameters as well as the band gap values on the composition x have been analyzed in the range 0?x?1. Calculated electronic structure and the density of states of these alloys are discussed in terms of the contribution of Zn d, O p and Ca p and d states. Furthermore, optical properties such as complex dielectric constants ε(ω), refractive index including extinction coefficient k(ω), normal-incidence reflectivity R(ω), absorption coefficient α(ω) and optical conductivity σ(ω) are calculated and discussed in the incident photon energy range 0-45 eV. 相似文献
55.
A. Shaukat Y. Saeed N. Ikram H. Akbarzadeh 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):439-446
First principles calculations have been performed within the
framework of density functional theory to investigate the structural,
electronic and optical properties of all four possible B1, B2, B3 and B4
phases of CaS. Apart from the standard local density approximation (LDA) and
GGA (PBE), a more accurate nonempirical density functional generalized
gradient approximation (GGA), as proposed by Wu and Cohen [Phys. Rev. B 73,
235116 (2006)] for the exchange-correlation energy, EXC, has been
attempted in these calculations. Calculated electronic structure and the
density of states are analyzed in terms of the contribution of Ca d states
and S s and p states in determining the nature of the fundamental band gap
in various phases. Reflectivity, R (ω), the real and imaginary part
of the dielectric functions, ε(ω), have been
calculated for all the phases and the results have been discussed and
compared with the existing experimental data. 相似文献
56.
57.
Ahmed Shaukat Dr. Eduardo Anaya-Plaza Prof. Ngong Kodiah Beyeh Prof. Mauri A. Kostiainen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(11):e202104341
Supramolecular self-assembly of biomolecules provides a powerful bottom-up strategy to build functional nanostructures and materials. Among the different biomacromolecules, protein cages offer various advantages including uniform size, versatility, multi-modularity, and high stability. Additionally, protein cage crystals present confined microenvironments with well-defined dimensions. On the other hand, molecular hosts, such as cyclophanes, possess a defined cavity size and selective recognition of guest molecules. However, the successful combination of macrocycles and protein cages to achieve functional co-crystals has remained limited. In this study, we demonstrate electrostatic binding between cationic pillar[5]arenes and (apo)ferritin cages that results in porous and crystalline frameworks. The electrostatically assembled crystals present a face-centered cubic (FCC) lattice and have been characterized by means of small-angle X-ray scattering and cryo-TEM. These hierarchical structures result in a multiadsorbent framework capable of hosting both organic and inorganic pollutants, such as dyes and toxic metals, with potential application in water-remediation technologies. 相似文献
58.
By a uniform and simple Weyl invariant coupling of scale and matter fields, we construct theories that unify massless, massive, and partially massless excitations. Masses are related to tractor Weyl weights, and Breitenlohner–Freedman stability bounds in anti de Sitter amount to reality of these weights. The method relies on tractor calculus – mathematical machinery allowing Weyl invariance to be kept manifest at all stages. The equivalence between tractor and higher spin systems with arbitrary spins and masses is also considered. 相似文献
59.
The melt pool formation during the heating of titanium and steel surfaces by a moving CO2 laser beam is examined. The repetitive pulses are introduced in the simulations and the Marangoni effect in the melt pool is incorporated in the model study. The influence of laser scanning speed and the laser intensity parameter on the melt pool size is also considered. The enthalpy–porosity method is adopted to account for the phase change in the irradiated spot. It is found that the influence of laser scanning speed on the melt pool size is considerable, which is more pronounced for laser beam parameter β=1. The melt pool size is smaller for stainless steel as compared to that corresponding to titanium. 相似文献
60.
Full-potential linearized augmented plane wave plus local orbitals (FP-LAPW+lo) method within density functional theory (DFT) has been utilized to calculate structural, electronic and optical properties of Be-doped CdS, CdSe and CdTe compounds with the dopant concentration x in the range 0≤x≤1. For the contribution of exchange-correlation potential, we used Wu-Cohen generalized gradient approximation (GGA) to calculate structural parameters, whereas both Wu-Cohen and Engel-Vosko GGA have been applied to calculate electronic structure of the materials. Only a slight deviation from Vegard's law has been observed for the calculated lattice constants and bulk moduli of the alloys. Structural and chemical factors that affect the band-gap bowing of these semiconductor alloys have been estimated and discussed. Density of states curves and charge density maps have been calculated and analyzed. Lastly, optical properties of both binary and their related ternary alloys have been discussed in terms of the calculated dielectric function. The resultant optical parameters are compared with the available experimental data and other calculations. 相似文献