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61.
拓扑近藤绝缘体是一种本征的强关联拓扑电子体系,其体能隙来源于近藤关联效应。自2010年拓扑近藤绝缘体的理论概念被提出后,六硼化钐(SmB6) 作为第一种被预测为拓扑近藤绝缘体的材料在这十多年中被多种实验手段反复研究验证,被广泛接受认为是第一种拓扑近藤绝缘体。在这篇综述中,我们回顾了关于SmB6 的一些重要实验结果,比如电输运测量,角分辨光电子能谱(ARPES), 表面形貌分析(STM) 等,并论述了如何通过这些关键的实验证据证实SmB6 的拓扑近藤绝缘物相。同时,我们也展示了SmB6 这一关联电子体系的其他奇异物性,包括中间价态在表面和体内的分离现象,以及量子振荡发现的体振荡信号等等。这些性质表明我们对SmB6 这一材料的理解仍然不充分,其中还有更为丰富的物理值得挖掘。 相似文献
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Weiping Gan Xiaosong Cao Yi Shi Lei Zou Haifeng Gao 《Journal of polymer science. Part A, Polymer chemistry》2018,56(19):2238-2244
Copper-catalyzed azide-alkyne cycloaddition polymerization (CuAACP) of AB2 monomers demonstrated a chain-growth mechanism without any external ligand because of the complexation of in situ formed triazole groups with Cu catalysts. In this study, we explored the use of various ligands that affected the polymerization kinetics to tune the polymers’ molecular weights and the degree of branching (DB). Eight ligands were studied, including polyethylene glycol monomethyl ether (PEG350, Mn = 350), tris(benzyltriazolylmethyl)amine (TBTA), 2,6-bis(1-undecyl-1H-benzo[d]imidazol-2-yl)pyridine (Py(DBim)2), 2,2′-bipyridyl (bpy), 4,4′-di-n-nonyl-2,2′-bipyridine (dNbpy), N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), N,N,N′,N″,N″-penta(n-butyl)diethylenetriamine (PBuDETA), and N,N,N′,N″,N″-pentabenzyldiethylenetriamine (PBnDETA). All ligands except PEG350 exhibited stronger coordination with Cu(I) than the polytriazole polymer, which freed the Cu catalyst from polymers and resulted in dominant step-growth polymerization with simultaneous chain-growth feature. Meanwhile, the use of PEG350 ligand retained the confined Cu in the polymer, demonstrating a chain-growth mechanism, but lower polymer molecular weights as compared with the no-external-ligand polymerization. Results indicated that aliphatic substituent groups on ligands had little effect on the molecular weights and DB of the polymers, but rigid aromatic substituent groups decreased both values. By varying the ligand species and amounts, hyperbranched polymers with DB value ranging from 0.53 ([TBTA]0/[Cu]0 = 5) to 0.98 ([PMDETA]0/[Cu]0 = 2) have been achieved. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2238–2244 相似文献
64.
Determination of hydroxysafflor yellow A in biological fluids of patients with traumatic brain injury by UPLC‐ESI‐MS/MS after injection of Xuebijing 下载免费PDF全文
Yong Guo Yang Wang Xi. Huang Huiying Lv Rong Fan Wei Huang Pingping Gan Wei Liu Kuipo Yan Zian Xia Jinfang Liu 《Biomedical chromatography : BMC》2014,28(8):1090-1095
A simple, novel, specific, rapid and reproducible ultra‐performance liquid chromatography electrospray ionization tandem mass spectrometry method has been developed and validated for the determination of hydroxysafflor yellow A (HSYA) in biological fluids (plasma, urine and cerebrospinal fluid) of patients with traumatic brain injury after intravenous injection of Xuebijing (XBJ). Liquid–liquid extraction was performed, and separation was carried out on an Acquity UPLC? BEH C18 column, with gradient elution using a mobile phase composed of methanol and 0.1% formic acid at a flow rate of 0.3 mL/min. A triple quadrupole tandem mass spectrometer with electrospray ionization was used for the detection of HSYA. The mass transition followed was m/z 611.0 → 491. The retention time was less than 3.0 min. The calibration curve was linear in the concentration range from 2 to 6125 ng/mL for cerebrospinal fluid, plasma and urine. The intra‐ and inter‐day precisions were <10%, and the relative standard deviation of recovery was <15% for HSYA in biological matrices. The method was successfully applied for the first time to quantify HSYA in the biological fluids (especially in cerebrospinal fluid) of patients with traumatic brain injury following intravenous administration of XBJ. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
65.
Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries.Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS).The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly (vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent.The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g-1and 65.4% at the 50th cycle with a current density of 335 mA·g-1.Compared with PVDF sulfur cathode,the alginate sulfur cathode showed a remarkably better cycle performance.These results show that the alginate binder has promising potential for lithium-sulfur battery applications. 相似文献
66.
Pei Gan Myles W. Smith Nathaniel R. Braffman Scott A. Snyder 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(11):3689-3694
Although the Diels–Alder reaction has long been utilized for the preparation of numerous heterocycles, opportunities to extend its power remain. Herein, we detail a simple, modular, and robust approach that combines various amines regioselectively with 4,6‐dichloropyrone to create substrates which, under appropriate conditions, can directly deliver varied indolines and hydroindolines through [4+2] cycloadditions with substitution patterns difficult to access otherwise. As an initial demonstration of the power of the strategy, several different natural products have been obtained either formally or by direct total synthesis, with efforts toward one of these—the complex amaryllidaceae alkaloid gracilamine—affording the shortest route to date in terms of linear step count. 相似文献
67.
Gan Ning Bukur Dragomir Mannan M. Sam 《Journal of Thermal Analysis and Calorimetry》2018,134(2):1169-1182
Journal of Thermal Analysis and Calorimetry - Accurate data of flammability limits for flammable gases and vapors are needed to prevent fires and explosions. The flammability limit, which is the... 相似文献
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Triterpenoids from the Roots and Stems of Rubus alceaefolius 总被引:1,自引:0,他引:1
70.