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81.
Ismail B. Onajobi Shabbir Hussain Kulsoom Javaid Obasola E. Fagade I. A. Oladosu 《Natural product research》2016,30(22):2507-2513
Two new 10-hydroxy-9(10H)-anthracenone, madagascenone A (1) and B (2), were isolated from the barks of Harungana madagascariensis Lam. The structures of the compounds were determined using 1D- and 2D-NMR and mass spectroscopic techniques. Both of the compounds showed an in vitro α-glucosidase inhibition with IC50 = 69.9 ± 4.21 and 122.3 ± 1.13 μM, respectively, more potent than the standard acarbose (IC50 = 840 ± 1.23 μM). 相似文献
82.
83.
We propose two new Lagrangian dual problems for chance-constrained stochastic programs based on relaxing nonanticipativity constraints. We compare the strength of the proposed dual bounds and demonstrate that they are superior to the bound obtained from the continuous relaxation of a standard mixed-integer programming (MIP) formulation. For a given dual solution, the associated Lagrangian relaxation bounds can be calculated by solving a set of single scenario subproblems and then solving a single knapsack problem. We also derive two new primal MIP formulations and demonstrate that for chance-constrained linear programs, the continuous relaxations of these formulations yield bounds equal to the proposed dual bounds. We propose a new heuristic method and two new exact algorithms based on these duals and formulations. The first exact algorithm applies to chance-constrained binary programs, and uses either of the proposed dual bounds in concert with cuts that eliminate solutions found by the subproblems. The second exact method is a branch-and-cut algorithm for solving either of the primal formulations. Our computational results indicate that the proposed dual bounds and heuristic solutions can be obtained efficiently, and the gaps between the best dual bounds and the heuristic solutions are small. 相似文献
84.
Meng-Che Tu Han-Yi Chen Yuxi Wang Shabbir M. Moochhala Palaniappan Alagappan Bo Liedberg 《Analytica chimica acta》2015
This article reports on carbon nanotube/manganese dioxide (CNT–MnO2) composites as electrochemical tags for non-enzymatic signal amplification in immunosensing. The synthesized CNT–MnO2 composites showed good electrochemical activity, electrical conductivity and stability. The electrochemical signal of CNT–MnO2 composites coated glassy carbon electrode (GCE) increased by nearly two orders of magnitude compared to bare GCE in hydrogen peroxide (H2O2) environment. CNT–MnO2 composite was subsequently validated as electrochemical tags for sensitive detection of α-fetoprotein (AFP), a tumor marker for diagnosing hepatocellular carcinoma. The electrochemical immunosensor demonstrated a linear response on a log-scale for AFP concentrations ranging from 0.2 to 100 ng mL−1. The limit of detection (LOD) was estimated to be 40 pg mL−1 (S/N = 3) in PBS buffer. Further measurements using AFP spiked plasma samples revealed the applicability of fabricated CNT–MnO2 composites for clinical and diagnostic applications. 相似文献
85.
We present the design of fluoro derivatives of B(10)H(14) and Li@B(10)H(14) baskets. A synergistic effect of conical push and inward pull (reported independently in previous lithium nonlinear optical (NLO) complexes) has been explored in these derivatives to achieve a robustly large NLO response and a higher vertical ionization potential. Li@1,3,6,9-F(4)B(10)H(10), Li@6,9-F(2)B(10)H(12), and Li@2,4,6,9-F(4)B(10)H(10) exhibit first hyperpolarizability (β(0)) values as large as 181?624, 133?199, and 32?314 au; their vertical ionization potentials are 6.45, 6.30, and 6.78 eV, respectively. These values are significantly higher than those previously reported in Li-doped fluorocarbon chains at the same MP2/6-31+G* level of theory (Xu, H. L.; Li, Z. R.; Wu, D.; Wang, B. Q.; Li, Y.; Gu, F. L.; Aoki, Y. J. Am. Chem. Soc. 2007, 129, 2967). They also exceed those from our earlier designed Li@B(10)H(14) basket (Muhammad, S.; Xu, H. L.; Liao, Y.; Kan, Y. H.; Su , Z. M. J. Am. Chem. Soc. 2009, 131, 2967). In addition, new quantum chemical calculations of enthalpies of reaction (Δ(r)H°) at 298 K for B(10)H(14) and its lithium/fluoro derivatives highlight the changes in their thermodynamical aspects. The calculated enthalpies of lithiation reactions are -10.04, -11.29, and -13.18 kcal/mol for B(10)H(14), 6,9-F(2)B(10)H(12), and 2,4-F(2)B(10)H(12), respectively, demonstrating a higher probability of fluoro decaboranes for reaction with lithium. The obtained results not only explain the effect of position and number dependence of substituted fluoro atom(s) in B(10)H(14) and Li@B(10)H(14) but also elucidate a synergistic behavior to polarize a lithium excess electron for high NLO responses and vertical ionization potentials. 相似文献
86.
Hassan Waqas Muhammad Saad Salman Asim Riaz Naeem Riaz Saima Shabbir 《Crystal Research and Technology》2015,50(5):379-388
Two facile and efficient methods, to synthesize zinc oxide (ZnO) particles with different morphologies, have been reported here. Thermal decomposition route yielded micron sized irregular shaped ZnO particles. While co‐precipitation method rendered transparent flakes which then transformed to hexagonal discs with relatively more uniform size and shape. These hexagonal discs were further converted to the cone type morphology when hexamethylenetetramine was added in the precursor solution. However, spherical type ZnO nanoparticles were obtained by incorporating polyvinyl alcohol during co‐precipitation strategy. XRD confirmed the formation of wurtzite structure in all the samples. FTIR spectroscopy revealed the presence of ZnO characteristic peaks. Moreover, 3‐D directional growths and the presence of UV‐Vis broadband multi‐absorption peaks, and green to orange photoluminescence emissions confirmed the potential application of the synthesized ZnO particles in various piezoelectric and luminescence applications.
87.
We consider probabilistically constrained linear programs with general distributions for the uncertain parameters. These problems
involve non-convex feasible sets. We develop a branch-and-bound algorithm that searches for a global optimal solution to this
problem by successively partitioning the non-convex feasible region and by using bounds on the objective function to fathom
inferior partition elements. This basic algorithm is enhanced by domain reduction and cutting plane strategies to reduce the
size of the partition elements and hence tighten bounds. The proposed branch-reduce-cut algorithm exploits the monotonicity properties inherent in the problem, and requires solving linear programming subproblems.
We provide convergence proofs for the algorithm. Some illustrative numerical results involving problems with discrete distributions
are presented. 相似文献
88.
Stuart P. Kitney Fei Cheng Shabbir Khan Christopher N. Hope William McNab 《Liquid crystals》2013,40(8):1027-1033
We report a ligand-free Pd/Si3N4 catalysed Suzuki–Miyaura aryl–aryl cross-coupling reaction using mixtures of water-miscible solvents, such as dimethoxyethane, ethanol and isopropanol with water and several bases, such as sodium carbonate and potassium phosphate. The reaction time and catalyst concentration were optimised and the heterogeneous nature of the reaction was investigated. The optimised reaction conditions were used to synthesise a standard liquid crystal using environmentally friendly solvents and a Pd/Si3N4 catalyst. This reaction is scalable to produce larger quantities. 相似文献
89.
Ashfaque H. Bokhari Tasawar Hayat Wasiq Hussain Ghulam Shabbir 《International Journal of Theoretical Physics》1995,34(3):411-415
In this paper we use iterative methods to generate series solutions of the gravitational field equations in a cosmological model with heat flow. 相似文献
90.
Dr. Dong‐Lai Wang Dr. Hong‐Liang Xu Prof. Zhong‐Min Su Dr. Shabbir Muhammad Dr. Dong‐Yan Hou 《Chemphyschem》2012,13(5):1232-1239
Drying‐tube‐shaped single‐walled carbon nanotubes (SWCNTs) with multiple carbon ad‐dimer (CD) defects are obtained from armchair (n,n,m) SWCNTs (n=4, 5, 6, 7, 8; m=7, 13). According to the isolated‐pentagon rule (IPR) the drying‐tube‐shaped SWCNTs are unstable non‐IPR species, and their hydrogenated, fluorinated, and chlorinated derivatives are investigated. Interestingly, chemisorptions of hydrogen, fluorine, and chlorine atoms on the drying tube‐shaped SWCNTs are exothermic processes. Compared to the reaction energies for binding of H, F, and Cl atoms to perfect and Stone–Wales‐defective armchair (5,5) nanotubes, binding of F with the multiply CD defective SWCNTs is stronger than with perfect and Stone–Wales‐defective nanotubes. The reaction energy for per F2 addition is between 85 and 88 kcal mol?1 more negative than that per H2 addition. Electronic structure analysis of their energy gaps shows that the CD defects have a tendency to decrease the energy gap from 1.98–2.52 to 0.80–1.17 eV. After hydrogenation, fluorination, and chlorination, the energy gaps of the drying‐tube‐shaped SWCNTs with multiple CD defects are substantially increased to 1.65–3.85 eV. Furthermore, analyses of thermodynamic stability and nucleus‐independent chemical shifts (NICS) are performed to analyze the stability of these molecules. 相似文献