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71.
This paper investigates the effect of non-uniform temperature gradient and magnetic field on Marangoni convection in a horizontal fluid layer heated from below and cooled from above with a constant heat flux. A linear stability analysis is performed. The influence of various parameters on the convection onset is analyzed. Six non-uniform basic temperature profiles are considered, and some general conclusions about their desta- bilizing effects are presented. 相似文献
72.
Leli Deswita Roslinda Nazar Anuar Ishak Rokiah Ahmad Ioan Pop 《Heat and Mass Transfer》2010,46(8-9):1013-1018
The effects of suction/injection on steady laminar mixed convection boundary layer flow over a permeable horizontal surface of a wedge in a viscous and incompressible fluid is considered in this paper. The similarity solutions of the governing boundary layer equations are obtained for some values of the suction/injection parameter f 0, the constant exponent m of the wall temperature as well as the mixed convection parameter λ. The resulting system of nonlinear ordinary differential equations is solved numerically for both assisting and opposing flow regimes using an implicit finite-difference scheme known as the Keller-box method. Numerical results for the reduced skin friction coefficient, the local Nusselt number, and the velocity and temperature profiles are obtained for various values of parameters considered. Dual solutions are found to exist for the case of opposing flow. 相似文献
73.
Nazar Savytskyy 《Physics letters. A》2008,372(11):1851-1855
We show that using the concept of the two-dimensional level number N⊥ one can experimentally study of the nodal domains in a three-dimensional (3D) microwave chaotic rough billiard with the translational symmetry. Nodal domains are regions where a wave function has a definite sign. We found the dependence of the number of nodal domains ℵN⊥ lying on the cross-sectional planes of the cavity on the two-dimensional level number N⊥. We demonstrate that in the limit N⊥→∞ the least squares fit of the experimental data reveals the asymptotic ratio ℵN⊥/N⊥?0.059±0.029 that is close to the theoretical prediction ℵN⊥/N⊥?0.062. This result is in good agreement with the predictions of percolation theory. 相似文献
74.
Waqar Azeem Peter John Muhammad Faizan Nazar Muhammad Ashfaq Islam Ullah Khan Shahzad Sharif Atif Riaz 《Journal of solution chemistry》2018,47(6):1048-1059
Core–shell architecture of surfactant micelles can act to shield active drug molecules from the adverse environmental conditions and enhance their bioavailability. In the present study the molecular interactions of a fixed dose combination (FDC) containing ofloxacin (OFX) and ornidazole (ORN), with cetyltrimethylammonium bromide (CTAB, a quaternary ammonium surfactant) were investigated under normal physiological pH (pH 7.4?±?0.1). The impact of the cationic micelle on the spectral and physiochemical properties of the FDC components OFX and ORN was systematically examined by electronic spectroscopy. Micellar liquid chromatography and differential spectral methods were used to optimize analysis of the magnitude of binding constants and related Gibbs energies. The results suggest the potential solubilization of drugs in the external part of the micelles, which may prove to be more helpful for their controlled release. These outcomes have been verified by the binding capacities of drug–CTAB combinational system that may be helpful to customize the uptake of drug molecules in cells. 相似文献
75.
The infrared chemiluminescence technique has been used to obtain k(V′, R′, T′) (V′, R′, Tt? are product vibrational, rotational and translational energies) for the reactions (i) H + ClNO → HCl + NO (energy-release Etot′ = 68.5 kcal mole?1) and (ii) H + CII → HCl + I (Etot′ = 55.8 kcal mole?1). Reaction (i) exhibits inefficient conversion of energy-release into vibration in the new bond, characteristic of a light attacking atom reacting on a repulsive energy-surface. Reaction (ii) has a bimodal HCl product-energy-distribution suggesting that 18% of the reaction proceeds by direct attack at the Cl end of CII to yield low V′ and R′, and 82% by indirect reaction from the 1 end to give high V′ and R′. 相似文献
76.
Synthesis,spectroscopic characterization,and computed optical analysis of green fluorescent cyclohexenone derivatives
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Muhammad Faizan Nazar Amir Badshah Asif Mahmood Muhammad Naveed Zafar Muhammad Ramzan Saeed Ashraf Janjua Muhammad Asam Raza Riaz Hussain 《Journal of Physical Organic Chemistry》2016,29(3):152-160
Cyclohexenone containing chalcones core is one important class of materials, which exhibit high nonlinear optical (NLO) responses and good crystallizability. The present study reports the successful development of six new fluorescent cyclohexenone derivatives (CDs) via conventional Robinson annulation method. The molecular structures of these newly synthesized CDs were confirmed by using various analytical techniques such as 1H NMR, 13C NMR, FTIR, EIMS, UV–Vis spectroscopy and single crystal X‐ray diffraction. The crystallographic data revealed that the spatial structure of the representative CD (4BE) belongs to monoclinic, P21/c space group. The results from luminescence studies show that the CDs molecules apparently emit intense green light at room temperature in aqueous media. The relative polarity and molecular chemical stability of the CDs molecules were predicted by measuring the molecular electrostatic potential and frontier molecular orbital energy. In addition, the UV–Vis spectra, transition character and electronic structures of these CDs were computed by using quantum chemical methodology. It was interesting to note that the values of computed and experimental electronic transitions (λmax) were in good agreement and these CDs display high hyperpolarizability (β) values. The present work will be helpful for systematical understanding of the structures and the optical properties of CDs for studying the structure–activity relationship that will suggest their potential application in photonic devices. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
77.
M. N. Zafar M. F. Nazar S. H. Sumrra Gul-E-Saba A. Yasmin A. H. Atif 《Russian Journal of Coordination Chemistry》2016,42(4):225-251
This review provides a broad overview of the literature related to the importance of ligands in homogeneous catalysis. In particular, it describes the types of nitrogen donor ligands that have typically been used for homogeneous catalysis. We surveyed the important transition metal homogenous catalysts explicitly from 2011 up to early 2014 and summarize their comparative catalytic activities. Generally, the main factors observed are the ligand structure, electron donor property and steric bulk which can affect the catalytic activity. Electron count and inductive effect can also influence the efficiency of homogeneous catalyst. 相似文献
78.
Strategic synthesis of SBA-15 nanorods 总被引:1,自引:0,他引:1
A simple synthesis of homogeneously sized, ordered mesoporous silica nanorods (SBA-15), spanning about 10 porous channels in width and ranging from 300 to 600 nm in length is reported. 相似文献
79.
A heterogeneous polyvinylpolypyrrolidone supported Brønsted acidic catalyst ([PVPP-BS]HSO4) was used to synthesize butyrate in this paper. The prepared catalysts were characterized by FT-IR, TG, and FESEM and their catalytic activity in butyric acid esterification with benzyl alcohol was investigated. The influencing factors such as the amount of catalyst, reaction temperature, and reaction time were carefully studied. Under the optimized condition with the butyric acid to benzyl alcohol mole ratio of 1: 1.2 and the reaction temperature of 130°C, the yield of benzyl butyrate reached 96.8 % within 4 h in the presence of 8 mass % of catalyst. Moreover, the catalyst could be reused six times without noticeable drop in activity. This catalyst was also used to synthesize other kinds of butyrates achieving the butyrate yield above 90 %. 相似文献
80.