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101.
102.
Polyphenol microspheres were prepared by template polymerization of phenol in the presence of horseradish peroxidase as bio‐enzyme catalyst and aqueous 1,4‐dioxane as solvent. The morphology of polyphenol microspheres thus obtained was observed with a scanning electron microscope. Further, polyphenol microspheres as obtained were loaded with palladium to generate polyphenol microsphere‐supported Pd complex. Resultant Pd complex catalyst supported by polyphenol microspheres was characterized by means of Fourier transformation infrared spectrometry, X‐ray diffraction, X‐ray photoelectron spectroscopy and scanning electron microscopy, and its thermal stability was examined. Moreover, the catalytic activity of polyphenol microsphere‐supported Pd catalyst as synthesized for the Heck reactions of acrylic acid with aryl iodides was evaluated. Results indicate that the polyphenol microsphere as obtained has a diameter of about 500 nm. Polyphenol microsphere‐supported Pd catalyst, as synthesized, at a dosage of 0.37 mol% Pd, possesses good catalytic activity for the Heck reactions of acrylic acid with aryl iodides in air at a low temperature of 50°C, and it also exhibits catalytic activity for bromide and activated chlorobenzene. The polyphenol microsphere‐supported Pd complex has good thermal stability, and it can be readily separated and reused; the yield of the reaction of iodobenzene with acrylic acid remains at 82% after five recycle runs, showing promising potential as a catalyst for Heck reactions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
103.
Jiawang Nie 《Mathematical Programming》2013,142(1-2):485-510
Consider the optimization problem of minimizing a polynomial function subject to polynomial constraints. A typical approach for solving it globally is applying Lasserre’s hierarchy of semidefinite relaxations, based on either Putinar’s or Schmüdgen’s Positivstellensatz. A practical question in applications is: how to certify its convergence and get minimizers? In this paper, we propose flat truncation as a certificate for this purpose. Assume the set of global minimizers is nonempty and finite. Our main results are: (1) Putinar type Lasserre’s hierarchy has finite convergence if and only if flat truncation holds, under some generic assumptions; the same conclusion holds for the Schmüdgen type one under weaker assumptions. (2) Flat truncation is asymptotically satisfied for Putinar type Lasserre’s hierarchy if the archimedean condition holds; the same conclusion holds for the Schmüdgen type one if the feasible set is compact. (3) We show that flat truncation can be used as a certificate to check exactness of standard SOS relaxations and Jacobian SDP relaxations. 相似文献
104.
105.
Xiaoyu Zhou Caiqiao Xiong Shuo Zhang Ning Zhang Zongxiu Nie 《Journal of the American Society for Mass Spectrometry》2013,24(5):794-800
In this article, we investigated the nonlinear resonance effect in the Paul trap with a superimposed hexapole field, which was assumed as a perturbation to the quadrupole field. On the basis of the Poincare-Lighthill-Kuo (PLK) perturbation method, ion motional equation, known as nonlinear Mathieu equation (NME) was expressed as the addition of approximation equations in terms of perturbation order. We discussed the frequency characteristics of ion axial-radial (z-r) coupled motion in the nonlinear field, derived the expressions of ion trajectories and nonlinear resonance conditions, and found that the mechanism of nonlinear resonance is similar to the normal resonance. The frequency spectrum of ion motion in nonlinear field includes not only the natural frequency series but also nonlinear introduced frequency series, which provide the driving force for the nonlinear resonance. The nonlinear field and the nonlinear effects are inevitable in practical ion trap experiments. Our method provides better understanding of these nonlinear effects and would be helpful for the instrumentation for ion trap mass spectrometers. 相似文献
106.
A new fluorescent probe with a long-wavelength emission and multiple hydrogen bond sites for guanine, 3-(4-chloro-6-p-nitrophenoxy-1,3,5-triazinylamino)-7-dimethylamino-2-methylphenazine (CNTDP), was designed and synthesized by using cyanuric chloride as a molecular scaffold, neutral red as a fluorophore and p-nitrophenol as an assistant unit. The recognition behavior of CNTDP for guanine and its spectroscopic properties in different solvents were investigated. It was found that the probe's fluorescence can be selectively quenched by guanine instead of thymine, indicating that fully complementary hydrogen bonding plays a key role in such a recognition process. In addition, the fluorescence quenching mechanism of the probe by guanine and the electronic effects of neutral red, triazine ring and p-nitrophenol moieties on the fluorescence of the whole molecule were also discussed. 相似文献
107.
QING XiangDong WU HaiLong NIE ChongChong LI Yong YAN XiuFang ZHANG XiHua YIN XiaoLi YU RuQin 《中国科学:化学(英文版)》2013,56(11):1641-1650
This work presents a novel application of second-order calibration based on self-weighted alternating trilinear decomposition(SWATLD)algorithm for analyzing the HPLC-DAD data.The proposed method makes it possible to simultaneously determine teflubenzuron,hexaflumuron,flufenoxuron,chlorfluazuron,diflubenzuron and benzoylurea in different fruit samples,i.e.pear,apple and banana,in the selected time region of chromatogram.The concentration,elution time and spectral information of these benzoylurea insecticides are selectively extracted from complex matrices even in the presence of unknown interferences.The root-mean-square error of prediction(RMSEP)and figures of merit,including sensitivity(SEN),selectivity(SEL)and limit of detection(LOD)are employed to access the performance of the method.The LODs obtained for these insecticides are within the range 0.017–0.26 ppm in pears,0.039–0.33 ppm in apples,0.041–0.44 ppm in bananas,respectively.Such a chemometrics-based protocol holds great potential to be extended as a promising alternative for more practical applications in food safety and quality monitoring. 相似文献
108.
Imidazole, 1,2,4-triazole, indole, and benzotriazole undergo conjugate additions with α, β-unsaturated carbonyl compounds in the presence of anhydrous potassium phosphate at ambient temperature to afford the corresponding Michael adducts in excellent yields. 相似文献
109.
Zhi-bin Zhang Wen-bin Nie Qin Li Guo-xuan Xiong Xiao-hong Cao Yun-hai Liu 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):361-368
Carboxyl-rich hydrothermal carbon spheres were prepared by simply heating pristine hydrothermal carbon spheres (HCSs) at lower temperature in air, and the textural properties were characterized using Boehm titrations, scanning electron microscopy, Fourier transform infrared spectrometer (FT-IR) and elemental-analysis. The result of Boehm titrations indicated that the content of carboxyl groups on HCSs increased significantly from 0.53 to 3.81 mmol/g after heat-treatment at 300 °C, which was also confirmed by FT-IR and EA qualitatively. The ability of heat-treated HCSs has been explored for the removal and recovery of uranium from aqueous solutions, and the influences of different experimental parameters, such as heat-treatment temperature, contact time and ionic strength, on adsorption were investigated. The U(VI) sorption capacity of HCSs increased from 55.0 to 179.95 mg/g after heat-treatment at 300 °C for 5 h. Selective adsorption studies showed that the heat-treated HCSs could selectively remove U(VI), and the selectivity coefficients were improved after heat-treatment in the presence of co-existing ions, Na(I), Ni(II), Sr(II), Mn(II), Mg(II) and Zn(II). The adsorbent HCSs could be effectively regenerated by 0.05 mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.0 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 5.0 g heat-treated HCSs. In addition, a reaction mechanism for newly generating carboxyl groups on pristine HCSs surface during heat-treatment process and uranyl ion interaction with carboxyl-rich hydrothermal carbon spheres were also supposed. 相似文献
110.
Liang Qu Lu-Jing Ren Juan Li Guan-Nan Sun Li-Na Sun Xiao-Jun Ji Zhi-Kui Nie He Huang 《Applied biochemistry and biotechnology》2013,171(7):1865-1876
Growth and fermentation characteristics, biomass composition, lipid characterization and metabolic profiling analysis of two different Schizochytrium sp. strains, the original strain and the industrial adaptive strain, were investigated in the fed-batch fermentation process. The final cell biomass, total lipids content, docosahexanoic acid (DHA) content and DHA productivity of the adaptive strain were much higher than those of the original strain. The metabolic distinctions which extensively existed between these two strains were revealed by the score plot of principal component analysis. In addition, potential biomarkers responsible for discriminating different strains were identified as myo-inositol, histidine, alanine, asparagine, cysteine, and oxalic acid. These findings provided new insights into the industrial strain screening and further improvement of DHA production by Schizochytrium sp. 相似文献