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251.
Masood Parvez Saeed Anwar Amin Badshah Bashir Ahmad Abdul Majeed Muhammad Ashfaq 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):159-160
The crystal structure of the title compound, [Sn4(C4H9)8(C10H6NO4)4O2], contains centrosymmetric dimers. It contains a central Sn2O2 core with the O atoms bonded to two dibutylbis(N‐phthaloylglycinato)tin units. The Sn atoms of the core are six‐coordinate in a skew trapezoidal bipyramidal geometry, while the exocyclic Sn atoms are essentially five‐coordinate in a distorted trigonal geometry. The Sn—C distances lie in a narrow range of 2.120 (5)–2.138 (4) Å. 相似文献
252.
Effect of fluence and ambient environment on the surface and structural modification of femtosecond laser irradiated Ti 下载免费PDF全文
Umm-i-Kalsoom Shazia Bashir Nisar Ali M Shahid Rafique Wolfgang Husinsky Chandra S R Nathala Sergey V Makarov Narjis Begum 《中国物理 B》2016,25(1):18101-018101
Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures(commonly reffered to as, laser induced periodic surface structures, LIPSS). The purpose of the present investigations is to explore the effect of fsec laser fluence and ambient environments(Vacuum O_2) on the formation of LIPSS and conical structures on the Ti surface. The surface morphology was investigated by scanning electron microscope(SEM). The ablation threshold with single and multiple(N = 100) shots and the existence of an incubation effect was demonstrated by SEM investigations for both the vacuum and the O_2 environment. The phase analysis and chemical composition of the exposed targets were performed by x-ray diffraction(XRD) and energy dispersive x-ray spectroscopy(EDS), respectively. SEM investigations reveal the formation of LIPSS(nano micro). FFT d-spacing calculations illustrate the dependence of periodicity on the fluence and ambient environment. The periodicity of nano-scale LIPSS is higher in the case of irradiation under vacuum conditions as compared to O_2. Furthermore, the O2 environment reduces the ablation threshold. XRD data reveal that for the O_2 environment, new phases(oxides of Ti) are formed. EDS analysis exhibits that after irradiation under vacuum conditions, the percentage of impurity element(Al) is reduced. The irradiation in the O_2 environment results in 15% atomic diffusion of oxygen. 相似文献
253.
An efficient three-component protocol was developed for the one-pot synthesis of 1,2,3-triazoles from natural product based acids and phenols, using CuSO4–sodium ascorbate catalyst system. The method is general and showed considerable synthetic advantage giving products in excellent yields with a wide substrate scope. 相似文献
254.
255.
The new Ca2CoNbO6 double perovskites has been synthesized by solid-state reaction and its crystal structure has been refined using X-ray powder diffraction data. Rietveld fit to the diffraction data shows that the compound is monoclinically distorted and adopts space group P21/n. The cell parameters are: a = 5.4797(1) Å, b = 5.6051(1) Å, c = 7.8119(2) Å, β = 89.96(1)°. The Co and Nb are found to be distributed over the six coordinated octahedral sites in rock salt arrangement. However, nearly identical ionic radii of Co and Nb lead to severe degree of anti-site disorder (31%). The refined Co–O and Nb–O bond lengths are 1.9788(2) Å and 2.0642(2) Å respectively. 相似文献
256.
In this study, the surface morphology and structure of dentin after ablation by ultra-short pulses were evaluated using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM). The dentin specimens examined were irradiated by a chirped-pulse-amplification (CPA) Ti:sapphire laser (800 nm) and the optimal conditions for producing various nanostructures were determined. Based on the ESEM results, it was possible to identify an energy density range as the ablation threshold for dentin. The laser-induced damage was characterized over the fluence range 1.3-2.1 J/cm2. The results demonstrate that by selecting suitable parameters one can obtain efficient dentin surface preparation without evidence of thermal damage, i.e., with minimized heat affected zones and reduced collateral damage, the latter being normally characterized by formation of microcracks, grain growth and recrystallization in the heat affected zones. 相似文献
257.
In this paper, we investigate the topological structure of solution sets for stochastic evolution inclusions in Hilbert spaces when the semigroup is compact as well as noncompact. It is shown that the solution set is nonempty, compact, and an Rδ-set, which means that the solution set may not be a singleton but, from the point of view of algebraic topology, it is equivalent to a point, in the sense that it has the same homology group as one-point space. As applications of the obtained results, an example is given. 相似文献
258.
Dynamics of a stochastic chemostat competition model with plasmid-bearing and plasmid-free organisms 下载免费PDF全文
Miaomiao Gao Daqing Jiang Tasawar Hayat Ahmed Alsaedi Bashir Ahmad 《Journal of Applied Analysis & Computation》2020,10(4):1464-1481
In this paper, we consider a chemostat model of competition between plasmid-bearing and plasmid-free organisms, perturbed by white noise. Firstly, we prove the existence and uniqueness of the global positive solution. Then by constructing suitable Lyapunov functions, we establish sufficient conditions for the existence of a unique ergodic stationary distribution. Furthermore, conditions for extinction of plasmid-bearing organisms are obtained. Theoretical analysis indicates that large noise intensity $\sigma_{2}^{2}$ is detrimental to the survival of plasmid-bearing organisms and is not conducive to the commercial production of genetically altered organisms. Finally, numerical simulations are presented to illustrate the results. 相似文献
259.
Bashir Ahmad 《Journal of Applied Mathematics and Computing》2010,34(1-2):385-391
In this paper, we prove the existence of solutions for an anti-periodic boundary value problem of fractional differential equations of order q∈(2,3]. The contraction mapping principle and Krasnoselskii’s fixed point theorem are applied to establish the results. 相似文献
260.