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排序方式: 共有243条查询结果,搜索用时 16 毫秒
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Liu M. Lao J. Wang H. Xu Z. Li J. Wen L. Yin Z. Luo C. Peng H. 《Russian Journal of Electrochemistry》2021,57(1):41-50
Russian Journal of Electrochemistry - A electrochemical sensor based on graphene and gold nanoparticles modified glassy carbon electrode (GCE) was developed for the determination of tyrosine (Tyr).... 相似文献
3.
Y. Y. Shu J. E. Dowdall C. Chiu R. C. Lao 《International journal of environmental analytical chemistry》2013,93(2-4):185-194
Abstract Polychlorinated biphenyls (PCBs) are toxic, perssstent, global environmental contaminants which were formulated as complex mixtures of congeners. Many methods have been developed in the past to analyze PCB in transformer oil samples for regulatory purposes. The most important consideration in the cleanup procedure is the ability to remove the oil from the sample matrix, since trace amount of oil will interfere with the subsequent GC-MS analysis. Electron capture detection (ECD) has been the most common method for gas chromatographic analysis of PCBs because of its high sensitivity toward halogenated compounds. ECD can also respond to some non-PCB compound resulting in biased concentrations of PCB. In this work, a two-stage cleanup method, using DMSO liquid/liquid extraction and HPLC column chromatography. has been applied to two types of transformer oil. Five internal standards have been selected to show their performance in the presence of different oil matrices. The comparison of the PCB quantification at different conditions for GC-MS and GC-ECD will be demonstrated. 相似文献
4.
The reaction of halogenated 9H-carbazoles or carbazole with bromoesters in DMF under microwave irradiation readily affords a series of 9H-carbazoles-9-hydroxylic acids. 相似文献
5.
Determination of six polyynes in Oplopanax horridus and Oplopanax elatus using polyethylene glycol modified reversed migration microemulsion electrokinetic chromatography 下载免费PDF全文
Zhong‐mei Yang Jing Zhao Ka‐meng Lao Xiao‐jia Chen Fong Leong Chong‐Zhi Wang Chun‐Su Yuan Shao‐ping Li 《Electrophoresis》2014,35(20):2959-2964
A PEG‐modified reversed migration MEEKC method was developed for simultaneous determination of six polyynes, including oplopandiol, falcarindiol, oplopandiol acetate, (11S, 16S, 9Z)‐9,17‐octadecadiene‐12,14‐diyne‐1,11,16‐triol,1‐acetate, oplopantriol B, and oplopantriol A, in Oplopanax horridus and Oplopanax elatus. The running buffer containing 0.8% v/v ethyl acetate, 3.8% w/v SDS, 6.6% v/v n‐butanol in 20 mM phosphate buffer (pH 2.5), followed by mixing with propan‐2‐ol at 30% v/v and PEG‐1000 at 15% w/v, was applied in the analysis. The proposed method was successfully applied to determine the six polyynes in five samples of Oplopanax horridus and one of O. elatus. The result showed that the types and amounts of polyynes present were obviously different when comparing the two herbs. Besides, the developed PEG‐modified reversed MEEKC method might be suitable for the analysis of hydrophobic analytes in herbal medicines. 相似文献
6.
A high-speed counter-current chromatography (HSCCC) technique in a preparative scale has been applied to separate and purify cordycepin from the extract of Cordyceps militaris(L.) Link by a one-step separation. A high efficiency of HSCCC separation was achieved on a two-phase solvent system of n-hexane-n-butanol-methanol-water (23:80:30:155, v/v/v/v) by eluting the lower mobile phase at a flow rate of 2 ml/min under a revolution speed of 850 rpm. HSCCC separation of 216.2 mg crude sample (contained cordycepin at 44.7% purity after 732 cation-exchange resin clean-up) yielded 64.8 mg cordycepin with purity of 98.9% and 91.7% recovery. Identification of the target compound was performed by UV, IR, MS, (1)H NMR and (13)C NMR. 相似文献
7.
Non-collinear continuous frequency doubling with relatively high conversion efficiency is demonstrated in periodically-poled
lithium niobate. It is shown that about 80% of the total second harmonic energy can be collected to one output channel by
tuning incident angle. The fractional phase-matching condition is introduced to interpret the phenomenon. These results make
it possible for direct power applications of continuous frequency doubling over the broad spectral range from the visible
to the infrared without temperature or angle tuning. 相似文献
8.
Mengmeng Lao Kun Rui Guoqiang Zhao Peixin Cui Xusheng Zheng Shi Xue Dou Wenping Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5486-5491
Heterostructured nanomaterials, generally have physicochemical properties that differ from those of the individual components, and thus have potential in a wide range of applications. New platinum (Pt)/nickel bicarbonate (Ni(HCO3)2) heterostructures are designed for an efficient alkaline hydrogen evolution reaction (HER). Notably, the specific and mass activity of Pt in Pt/Ni(HCO3)2 are substantially improved compared to the bare Pt nanoparticles (NPs). The Ni(HCO3)2 provides abundant water adsorption/dissociation sites and modulate the electronic structure of Pt, which determine the elementary reaction kinetics of alkaline HER. The Ni(HCO3)2 nanoplates offer a platform for the uniform dispersion of Pt NPs, ensuring the maximum exposure of active sites. The results demonstrate that, Ni(HCO3)2 is an effective catalyst promoter for alkaline HER. 相似文献
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10.
评价网络中节点的信息传播影响力对于理解网络结构与网络功能具有重要意义.目前,许多基于最短路径的指标,如接近中心性、介数中心性以及半局部(SP)指标等相继用于评价节点传播影响力.最短路径表示节点间信息传播途径始终选择最优方式,然而实际上网络间的信息传播过程更类似于随机游走,信息的传播途径可以是节点间的任一可达路径,在集聚系数高的网络中,节点的局部高聚簇性有利于信息的有效扩散,若只考虑信息按最优传播方式即最短路径传播,则会低估节点信息传播的能力,从而降低节点影响力的排序精度.综合考虑节点与三步内邻居间的有效可达路径以及信息传播率,提出了一种SP指标的改进算法,即ASP算法.在多个经典的实际网络和人工网络上利用SIR模型对传播过程进行仿真,结果表明ASP指标与度指标、核数指标、接近中心性指标、介数中心性指标以及SP指标相比,可以更精确地对节点传播影响力进行排序. 相似文献