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961.
Gao Lidi Xing Zhanfen Zhang Shuai Lin Xiaotong Qin Shili Chu Hongtao Tang Yimin Zhao Xuan 《Chromatographia》2022,85(4):373-382
Chromatographia - Simultaneous enantioseparation and rapid determination method of atenolol (AN) and amlodipine besylate (AMB) was firstly established using diphenylmethane... 相似文献
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Wormlike micelles and low-molecular-weight hydrogels are composed of three-dimensional networks that endow them with viscoelasticity, but their viscoelastic properties are markedly different. The viscosity of wormlike micelles is attributed to a transient network, while that of gels is due to a stable network. Under certain conditions, wormlike micelles can undergo transition to gels with an increase in the density of the network. In our previous study, we found that the wormlike micelle formed by the ionic liquid-type surfactant 1-hexadecyl-3-octyl imidazolium bromide ([C16imC8]Br) without any additive has high viscoelasticity. The inclusion of a nonionic surfactant polyoxyethylene lauryl ether (Brij 30) is expected to enhance the viscoelasticity of [C16imC8]Br wormlike micelles via electrostatic shielding and strong hydrophobic interactions, which may be the driving factor for the wormlike micelle-to-gel structural transition. The morphology and viscoelasticity of [C16imC8]Br wormlike micelles with Brij 30 were studied as a function of concentration by rheological measurements and freeze-fracture transmission electron microscopy. The thermal stability and gel-sol transition temperature of the Brij 30/[C16imC8]Br gels were studied using rheology. The interaction between Brij 30 and [C16imC8]Br was studied by zeta potential measurements and nuclear magnetic resonance (NMR) spectroscopy. Upon the inclusion of Brij 30 into the [C16imC8]Br wormlike micelles, the viscoelasticity of the Brij 30/[C16imC8]Br samples first increased and then decreased with an increase in the Brij 30 concentration, at different initial concentrations of [C16imC8]Br. At a certain Brij 30 concentration, the Brij 30/[C16imC8]Br samples rheologically behaved as a gel. The maximum viscoelasticity of the [C16imC8]Br (4.06% (w))/Brij 30 gel was observed at a Brij 30/[C16imC8]Br molar ratio of 4.55. The viscoelasticity of the Brij 30/[C16imC8]Br gels was positively correlated with the activation energy of the gels. The gel-sol transition temperature of the Brij 30/[C16imC8]Br gels also increased first and then decreased with an increase in the Brij 30 concentration. The highest gel-sol transition temperature of the Brij 30/[C16imC8]Br (4.06% (w)) gel was observed at a Brij 30/[C16imC8]Br molar ratio of 2.93. The Brij 30 concentration had a notable impact on the viscoelasticity, thermal stability, and gel-sol transition temperature of the Brij 30/[C16imC8]Br gels. The zeta potential and 1H NMR measurements revealed that the neutral Brij 30 molecules are inserted into the palisade layer of the [C16imC8]Br wormlike micelles via hydrophobic interactions. This decreased the electrostatic repulsion between the [C16imC8]Br headgroups, which in turn induced the rapid growth of wormlike micelles and the formation of a stiffer network structure. Finally, the wormlike micelles underwent a structural transition to gels. The obtained results would aid in better understanding the relationship between wormlike micelles and gels, and may be of potential value for industrial and technological applications. 相似文献
966.
Taurine was employed as an additive to improve the thermal stability and electrochemical performance of positive electrolyte for a vanadium redox flow battery. The addition of taurine could significantly improve the thermal stability of positive electrolyte, and 2 M V(V) electrolyte with 4 mol% taurine could keep it stable at 40 °C for 120 h, which was 54 h longer than the pristine one. Electrochemical measurements showed that the electrolyte with taurine exhibited superior electrochemical activity and reaction kinetics with a larger diffusion coefficient, exchange current density and reaction rate constant compared with the pristine one. Moreover, the cell using taurine as additive achieved higher average energy efficiency (81.75%) than the pristine cell (79.15%). The Raman and XPS spectroscopy illustrated that taurine could combine with VO2+ to form a small molecule complex and the –NH2 in taurine could be adsorbed on the surface of the electrode to provide more active sites for the electrode reaction, which led to the improvement of mass transfer and the charge transfer process for the V(IV)/V(V) redox reaction. 相似文献
967.
Mingliang Wang Jilai Han Xiaojia Si Yimin Hu Jidong Zhu Xun Sun 《Tetrahedron letters》2018,59(17):1614-1618
An efficient approach to N, N′-unsymmetrically substituted ureas 9 has been developed through the ammonolysis process of N-Boc protected anilines 7 with amines prompted by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). Moreover, a convenient protocol for the synthesis of the symmetric N, N'-substituted ureas 12 by one-pot diammonolysis process of Boc2O with amines catalyzed by DABCO has also been achieved. With broad substrate scope and mild conditions, these two methods demonstrate practical preparation of both unsymmetrical and symmetrical ureas. 相似文献
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给出了一种靶压固定式PEV极化时序;提出了一种独特的采用电压比较器作定时器的PEV红外摄像机自动极化系统.该自动极化系统具有结构简单、参数选择容易、调试方便、工作稳定可靠、抗干扰性能强等优点. 相似文献
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研究了一种用于回转窑的红外成像系统;讨论了系统的基本组成原理、红外摄像机主要参数的选择和微计算机处理系统的有关接口电路.该系统能对回转窑表面的二维热图像进行实时摄取、显示、存储和分析.实践证明,该系统具有处理实时、操作简便、稳定可靠、功能齐全等优点. 相似文献
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应用一种高效,可靠的数据方法来模拟叶轮机叶栅内部的实际流动,获取大量真实的流动信息,据此,在工程上可以总结出各种实用的规律,这样,可以为现代叶型设计提供一种快速,可靠,实用的途径,数值试验表明:用文中提出的二阶精度隐式矢量单步差分格式求解叶栅的跨音流场,具有精度高,稳定性好,计算量少,收敛快等优点,在流场的计算中,较好地捕获了激波,与实验比较,结果令人满意。 相似文献