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941.
942.
943.
汽车空调系统中使用较多的制冷剂是R134a,但其GWP(全球变暖潜能值)高达1300,R1234yf作为一种新型制冷剂,其GWP仅为4,且具有与R134a相似的热力学性质。基于动磁式无油直线压缩机对R1234yf和R134a两种制冷剂的性能进行了试验分析,结果表明,当换热器温度分别为-3℃(蒸发器)、40℃(冷凝器)时,R1234yf和R134a的冷却能力分别为92 W和117 W;在冷凝器温度为50℃时,R1234yf的冷却性能与R134a几乎相同。验证了R1234yf替代R134a的可行性。 相似文献
944.
The linkage structures between monomers make great influence on the properties of polymers.The synthesis of some special linkage structures can be challenging,which is often overcome by employing special reaction conditions.Here,we build dihydropentalene linkage in poly-naphthalocyanine on Ag(110)surface.Scanning tunneling microscopy(STM)and non-contact atomic force microscopy(nc-AFM)measurements confirm the dihydropentalene linkage structure and a possible formation path with reconstruction steps is proposed.The controlled experiment on Ag(100)surface shows no dihydropentalene structures formed,which indicates the grooved substrate is necessary for the reconstruction.This work provides insights into the surface restricted reactions that can yield special structures in organic polymers. 相似文献
945.
In the article, by employing multiple-scale, perturbation method, a new model is derived to describe the algebraic Rossby solitary waves generated by periodic external source in stratified fluid. The local conservation laws and analytic solutions of the model are obtained, and the breakup properties are discussed. By numeric simulation, some problems on the generation and evolution of the algebraic solitary waves under the influence of periodic external source are theoretically investigated. The results show that besides the solitary waves, an additional harmonic wave appears in the region of the external source forcing. Furthermore, the periodic variation of the external source forcing can prevent solitary waves from breaking. Meanwhile, the detuning parameter has an important effect on the breakup of the algebraic Rossby solitary waves. 相似文献
946.
A synthetic strategy featuring efficient ruthenium-catalyzed asymmetric hydrogenation of racemic α-aryloxy cyclic ketone via dynamic kinetic resolution and palladium-catalyzed intramolecular reductive Heck cyclization has been developed for the asymmetric total synthesis of (-)-galanthamine (20.1%, 12 steps) and (-)-lycoramine (40.2%, 10 steps). 相似文献
947.
Yin Z Zhou W Gao Y Ma D Kiely CJ Bao X 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):4887-4893
Monodisperse bimetallic Pd-Cu nanoparticles with controllable size and composition were synthesized by a one-step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd and Cu precursors afforded nanoparticles with different compositions, such as Pd(85)-Cu(15), Pd(56)-Cu(44), and Pd(39)-Cu(61). The nanoparticles were separated from the solution mixture by extraction with non-polar solvents, such as n-hexane. Monodisperse bimetallic Pd-Cu nanoparticles with narrow size-distribution were obtained without the need for a size-selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as-prepared nanoparticles were loaded onto a Vulcan XC-72 carbon support. Supported bimetallic Pd-Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd-Cu catalyst that contained 15?% Cu, the activity was even comparable to the state-of-the-art commercially available Pt/C catalysts. A STEM-HAADF study indicated that the formation of random solid-solution alloy structures in the bimetallic Pd(85)-Cu(15)/C catalysts played a key role in improving the electrochemical activity. 相似文献
948.
Li J Jiang G Yang B Dong X Feng L Lin S Chen F Ashraf M Jiang Y 《Analytical and bioanalytical chemistry》2012,402(3):1347-1354
Fusarium proliferatum was isolated as a major pathogen causing the Fusarium disease in harvested banana fruit. One of its major compounds, fusaric acid, was identified by high-performance liquid chromatography–electrospray
ionization mass spectrometry (HPLC–ESI–MS). Because the light intensity of the luminescent bacterium Vibrio qinghaiensis sp. Nov. Q67 can be inhibited by fusaric acid, the fusaric acid content of F. proliferatum was assessed and compared by both the HPLC and luminescent bacterium methods. Although both methods afforded almost similar
values of fusaric acid, the latter indicated slightly lower content than the former. Czapek medium was more suitable for the
growth of F. proliferatum and fusaric acid production than modified Richard medium, with an optimum pH of approximately 7.0. However, no significant
(P < 0.05) correlation was obtained between the fusaric acid production and growth of mycelia of F. proliferatum. The study suggests that the bioevaluation by use of the luminescent bacterium was effective in monitoring fusaric acid production
by F. proliferatum without expensive equipment. 相似文献
949.
Detect early stage lung cancer by a LAMP microfluidic chip system with a real-time fluorescent filter processor 总被引:1,自引:0,他引:1
TongZhou Wang Ye Zhang GuoLiang Huang Can Wang Lan Xie Li Ma ZhiYong Li XianBo Luo Hao Tian Qiang Li Xin Li ZhouYan Lv XiaoFan Bao 《中国科学:化学(英文版)》2012,55(4):508-514
This work presents a promising clinical molecular diagnostics for early stage lung cancer. This novel diagnostic method utilized the loop-mediated isothermal amplification (LAMP), microfluidic chips and a confocal optical detector with a non-linear fluorescent filter processor. An isothermal amplification based microfluidic chip for the early diagnostics of lung cancer was developed and a confocal optical detector was improved by a novel real-time fluorescent filter to sensitively monitor the DNA amplification procedure with high signal to noise ratio and fluorescence collecting ability. Experiment showed that a rapid diagnostic of lung cancer by detecting the existence of the CEA mRNA could be performed in only 5 μL of reaction assay in less than 45 min. While the traditional in-tube RT-PCR set consumed more than 25 μL of the assay and took more than 90 min. 相似文献
950.
Najat Aburas Aleksandar Loli? Nikola Stevanovi? Tatjana Tripkovi? Sne?ana Nikoli?-Mandi? Rada Bao?i? 《Journal of the Iranian Chemical Society》2012,9(6):859-864
This study describes the effects of the substituents on electrochemical behavior and antioxidant activity of the six tetradentate Schiff bases, containing ethane-1,2-diamine or propane-1,2-diamine as the amine part and pentane-2,4-dione and/or 1-phenylbutane-1,3-dione as ??-diketone, and corresponding copper(II) complexes. Cyclic voltammograms of these compounds were recorded in dimethylsulfoxide and 0.1?M sodium perchlorate as supporting electrolyte with glassy carbon as working electrode at different scan rates. The voltammograms of Schiff bases alone showed only one irreversible peak. Voltammograms recorded for complexes showed the presence of quasi-reversible processes taking place at the metal center and reversible process at the ligand part. Both steric and inductive effects of substituents and structure of imine bridge of Schiff base ligands as well as complexes were discussed. These effects appear relevant for the antioxidant activity. Antioxidant activity of the investigated compounds expressed as Trolox equivalent antioxidant capacity is also discussed. The electrochemical behavior showed a high correlation with the antioxidant activity for investigated compounds. 相似文献