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991.
The ring‐opening polymerization of propylene oxide catalyzed by double metal complex (DMC) is carried out in continuous micro‐reactor (C‐MR). It is found that the monomer conversion at the C‐MR outlet is usually 100% within 2 min of average residence time, which means that the polymerization rate in the C‐MR is faster than that in a traditional semi‐continuous tank reactor. However, the induction period still exists in the polymerization in C‐MR, but can be shortened by increasing the reaction temperature or the micro‐reactor length. The mechanism of monomer coordination and ring opening on DMC during the induction period is confirmed by the 1H NMR analysis of the samples obtained under very short average residence time. The molecular weight distribution (MWD) of product from C‐MR is generally narrow, which indicates that the process still maintain the characteristics of the “living” polymerization. That is, there is a very high rate ratio of chain transfer to chain propagation provided by the DMC catalyst. However, with the same average residence time, the MWD of product from the longer C‐MR is broader, which can be attributed to the increase of the chain propagation rate caused by rise of pressure. 相似文献
992.
The graphene nanopowder for electro-catalytic oxidation of dopamine and uric acid in the presence of ascorbic acid has been investigated by cyclic voltammetry,linear polarization and chronoamperometry.The graphene nanopowder modified electrode was prepared using the drop coating method,which displayed excellent electrocatalytic activity towards the oxidation of dopamine and uric acid compared with the bare glassy carbon electrode in phosphate buffer solution at pH=7.0.Linear responses for dopamine and uric acid were obtained in the ranges of3.3μmol/L to 249.1μmol/L and 6.7μmol/L to 386.3μmol/L with detection limits of 1.5μmol/L and 2.7μmol/L(S/N=3),respectively.The response time was less than 2 s in case of dopamine and 3 s in case of uric acid,respectively.The results demonstrated that the graphene nanopowder had potential for detecting dopamine and uric acid. 相似文献
993.
R. Lach M. M. Bućko K. Haberko M. Szumera R. Gajerski 《Journal of Thermal Analysis and Calorimetry》2013,112(2):727-730
Co-precipitation of alumina/YAG precursor from aluminum and yttrium nitrates solution with ammonium carbonate results in dawsonite (NH4Al(OH)2CO3). Its crystallographic parameters differ from the compound precipitated without the yttrium additive. It indicates that yttrium ions become incorporated into the dawsonite structure. The DSC/TG and X-ray measurements show decomposition of dawsonite at elevated temperature resulting in γ-Al2O3 which transforms to δ and θ modifications at still higher temperatures. The full transformation to α-Al2O3 and YAG occurs at temperatures higher than 1,230 °C. 相似文献
994.
Lablanquie P Penent F Palaudoux J Andric L Selles P Carniato S Bučar K Zitnik M Huttula M Eland JH Shigemasa E Soejima K Hikosaka Y Suzuki IH Nakano M Ito K 《Physical review letters》2011,106(6):063003
The formation of hollow molecules (with a completely empty K shell in one constituent atom) through single-photon core double ionization has been demonstrated using a sensitive magnetic bottle experimental technique combined with synchrotron radiation. Detailed properties are presented such as the spectroscopy, formation, and decay dynamics of the N(2)(2+) K(-2) main and satellite states and the strong chemical shifts of double K holes on an oxygen atom in CO, CO2, and O2 molecules. 相似文献
995.
In this paper, we introduce a new implicit iterative algorithm for finding a common element of a countable family of continuous pseudocontractions in a uniformly smooth Banach space. We obtain some strong convergence theorems under suitable conditions. Our results extend the recent results announced by many others. 相似文献
996.
997.
Guo Ping LI Wei Ren XU Xian Jie LIN Cheng Bu LIU 《中国化学快报》2006,17(3):423-426
Nitrones are useful in the preparation of many interesting compounds such as amino aldehydes, aminosugars, aza sugars, amino acids, aminoalcohols, peptide isosteres and nucleoside analogs. Nitrones are generally prepared by the condensation reactions of c… 相似文献
998.
An LD-pumped Nd:YVO4 passively Q-switched by V:YAG and intracavity frequency doubled by LBO red pulse laser at 671 nm was presented. With 1.6 W incident pump power, average output power of 53 mW, pulse duration (FWHM) of 29.5 ns, pulse repetition rate of 37.2 kHz, peak power of 48.3 W and single-pulse energy of 1.43 μJ were obtained. The stability of pulse energy and repetition rate was better than 3% for 4 h. 相似文献
999.
1000.
模糊积分变换与模糊Choquet积分的一致连续性 总被引:2,自引:0,他引:2
在一般非负单调函数空间 m[0 ,a]上引入模糊积分变换与距离的概念 ,证明了这种模糊积分变换与模糊 Choquet积分在 m[0 ,a]上关于这种距离是一致连续的 ,从而说明当 m[0 ,a]上两个函数变化不大时 ,不会使相应的模糊积分变换与模糊 Choquet积分产生较大的变化 . 相似文献