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561.
Magnetic nanoparticles (MNPs) Fe3O4-immobilized guanidine (Fe3O4 MNPs-guanidine) have been used as an efficient catalyst for the preparation of spiro[pyrazoloquinoline-oxindoles] and spiro[chromenopyrazolo-oxindoles] by four-component reactions of phenylhydrazine or hydrazine hydrate, isatins, ketoesters and naphthylamine or 2-naphthol under reflux condition in ethanol. This method provides several advantages including mild reaction conditions, the applicability to a wide range of substrates, the reusability of the catalyst and low catalyst loading.  相似文献   
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A 2‐dimensional hydrodynamic finite volume model has been proposed for simultaneous simulation of free surface and saturated porous media. The governing equations of the former are 2‐dimensional averaged in a unit width of Navier‐Stokes, whereas that of the latter are Darcy law. An efficient, simple, and stable algorithm has been proposed to track the surface elevation in Cartesian coordinate system by which the water elevation in each computational column has been computed along with the other pressure unknowns simultaneously. The surface position has not been considered to remain in a specific layer so the number of cells in each column have been variably adjusted in accordance with the water surface elevation. Performance of the coupled model has been validated against a range of hydrodynamic problems including propagation of linear short wave, seepage test, tidal oscillation in a lagoon system, gravity current, and saltwater intrusion. Comparison between numerical results, analytical solutions, and experimental data demonstrates that the model represents well the interacting surface water and ground water flow and solute transport processes.  相似文献   
564.
Large‐scale torsional actuation occurs in twisted fibers and yarns as a result of volume change induced electrochemically, thermally, photonically, and other means. A quantitative relationship between torsional actuation (stroke and torque) and volume change is here introduced. The analysis is based on experimental investigation of the effects of fiber diameter and inserted twist on the torsional stroke and torque measured when heating and cooling nylon 6 fibers over the temperature range of 26–62 °C. The results show that the torsional stroke depends only on the amount of twist inserted into the fiber and is independent of fiber diameter. The torque generated is larger in fibers with more inserted twist and with larger diameters. These results are successfully modeled using a single‐helix approximation of the twisted fiber structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1278–1286  相似文献   
565.
The effect of water molecule adsorption on the surface of (5,0) zigzag boron nitride nanotube was studied by density functional theory calculations. Geometrical optimizations were carried out at the B3LYP/6-31+G* level of theory. Six different configurations of water molecule(s) adsorption process including monomer (1WB and 1WN), dimer (2WB, 2WNN, and 2WBN), and trimer (3WB) clusters were obtained. The strengths of interactions were analyzed by the equilibrium geometries, binding energies, and charge transfer. The natural bonding analysis was also performed to investigate electronic properties. The results reveal that the adsorption of water is more favorable as the water cluster size increases.  相似文献   
566.
A rapid, highly efficient and mild green synthesis of 5,5‐diphenylhydantoin derivatives was achieved from the reaction of symmetrical or unsymmetrical benzil derivatives with urea in the presence of ethanolic KOH under ultrasound irradiation. This simple method affords 5,5‐diphenylhydantoin derivatives at room temperature in short reaction time with high yield and purity. This study aimed to overcome the limitations and drawbacks of the reported methods such as tedious work‐up, low yield and long reaction time.  相似文献   
567.
<正>A wide variety of aldoximes and ketoximes were regenerated to corresponding carbonyl compounds with Al(NO_3)_3·9H_2O in presence of catalytic amounts of NaBr in CH_2Cl_2 at room temperature.  相似文献   
568.
A new thiomorpholine-functionalized nanoporous mesopore Mobil Composition of Matter No. 41 (MCM-41), abbreviated as TMMCM-41, was synthesized and applied as a sensing material in construction of a cadmium carbon paste electrode. The electrode composition of 20.1%wt TMMCM-41, 54.0% graphite powder, 25.9% paraffin oil showed the stable potential response to Cd2+ ions with the Nernstian slope of 28.6 mV decade?1 (±1.8 mV decade?1) over a wide linear concentration range of 10?6 to 10?2?mol L?1 with a detection limit of 6?×?10?7 mol L?1. The electrode has fast response time and long-term stability (more than 4 months). The proposed electrode was used to determine the concentration of cadmium in tap water contaminated by this metal and cadmium electroplating waste water samples.  相似文献   
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