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81.
We investigate the propagation regions of electromagnetic plane waves with negative phase velocity in the ergosphere of static charged black strings. For such a propagation, some conditions for negative phase velocity are established that depend on the metric components and the choice of the octant. We conclude that these conditions remain unaffected by the negative values of the cosmological constant. 相似文献
82.
We take the collapsing radiative fluid to investigate the dynamical instability with cylindrical symmetry. We match the interior and exterior cylindrical geometries. Dynamical instability is explored at radiative and non-radiative perturbations. We conclude that the dynamical instability of the collapsing cylinder depends on the critical value γ < 1 for both radiative and nonradiative perturbations. 相似文献
83.
We discuss the propagation of electromagnetic plane waves with negative phase velocity in regular black holes. For this purpose, we consider the Bardeen model as a nonlinear magnetic monopole and the Bardeen model coupled to nonlinear electrodynamics with a cosmological constant. It turns out that the region outside the event horizon of each regular black hole does not support negative phase velocity propagation, while its possibility in the region inside the event horizon is discussed. 相似文献
84.
Shahed Sharif 《Mathematische Annalen》2012,354(3):1029-1047
The period of a curve is the smallest positive degree of Galois-invariant divisor classes. The index is the smallest positive degree of rational divisors. We construct examples of genus one curves with prescribed period and index over a given global field, as long as the characteristic of the field does not divide the period. 相似文献
85.
Following the scheme developed by Misner and Sharp, we discuss the dynamics of gravitational collapse. For this purpose, an
interior cylindrically symmetric spacetime is matched to an exterior charged static cylindrically symmetric spacetime using
the Darmois matching conditions. Dynamical equations are obtained with matter dissipating in the form of shear viscosity.
The effect of charge and dissipative quantities over the cylindrical collapse are studied. Finally, we show that homogeneity
in energy density and conformal flatness of spacetime are necessary and sufficient for each other. 相似文献
86.
M. Ijaz Khan Tasawar Hayat Sumaira Qayyum Muhammad Imran Khan A. Alsaedi 《Physics letters. A》2018,382(34):2343-2353
Here a novel applications of entropy generation optimization is presented for nonlinear Sisko nanomaterial flow by rotating stretchable disk. Flow is examined in the absence of magnetohydrodynamics and Joule heating. Total irreversibility rate (entropy generation rate) is investigated for different flow parameters. Heat source/sink and viscous dissipation effects are considered. Impacts of Brownian motion and thermophoresis on irreversibility have been analyzed. Governing flow equations comprise momentum, energy and nanoparticle concentration. Von Karman's similarity variables are implemented for reduction of PDEs into ODEs. Homotopy analysis technique for series solutions is implemented. Attention is given to the irreversibility. The impacts of different flow parameters on velocity, nanoparticle concentration, temperature and irreversibility rate are graphically presented. From obtained results it is examined that irreversibility rate enhances for larger estimation of Brinkman number and diffusion. Furthermore it is also examined that temperature and nanoparticle concentration show contrast behavior through Prandtl number and Brownian motion. 相似文献
87.
88.
Ramu Meesala Mohd Nizam Mordi Sharif Mahsufi Mansor Mohd Mustaqim Rosli 《Molecular Crystals and Liquid Crystals》2014,605(1):125-134
An efficient method is described for the synthesis of 9-phenyl-9H-pyrido[3,4-b]indole and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole by employing a catalytic amount of CuI (10 mole%) without any ligand. The single crystal of 9-phenyl-9H-pyrido[3,4-b]indole was produced by crystallization from hexane and ethyl acetate mixture that was investigated by single X-ray diffraction (XRD). The compound crystallizes in monoclinic P21/c space group with unit cell dimensions a = 11.3132(5) Å, b = 12.0061(5) Å, c = 9.2498(4) Å, α = 90°, β = 103.187(3)°, γ = 90°. 1H and 13C NMR, IR, and mass spectroscopic methods of the compounds are also discussed. 相似文献
89.
Sharif Ahmad Syed Marghoob Ashraf Fehmida Naqvi Shakuntala Yadav Fahmina Zafar 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1409-1419
To improve the physico‐mechanical and chemical resistance properties, lower the curing temperature of annona squamosa and pongamia glabra seeds oils based polyesteramides [ASPEA, PGPEA], as well as to convert the non‐edible seed oils into value added products, their respective alumina‐incorporated polyesteramides resins [Al‐ASPEA, Al‐PGPEA] have been synthesized. The resins and their coatings have been tested for their chemical, physico mechanical and chemical/corrosion resistance properties. These properties were compared among the prepared resins and with that of previously reported alumina filled linseed polyesteramide [Al‐LPEA]. It was observed that Al‐PGPEA‐71, which has the highest amount of oleic acid chains, shows the best physico‐mechanical and chemical resistance properties. 相似文献
90.
Muhammad Sharif Anahit Pews-Davtyan Jan Lukas Susann Pohlers Arndt Rolfs Peter Langer Matthias Beller 《Tetrahedron》2014
The Suzuki–Miyaura coupling reaction was applied for the synthesis of biologically relevant derivatives of known mucolytic agents Bromhexine and Ambroxol. Using commercially available electron-rich and electron-poor arylboronic acids the desired products are obtained in moderate to high yields (42–81%). 相似文献