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61.
Nonlinear Dynamics - Active researches on the water waves have been done, and water waves are essentially complex waves controlled by gravity field and surface tension. Using the Hirota bilinear... 相似文献
62.
63.
Yun-Feng Zhang Zhi-Xiang Zhu Hui Sun Hui-Na Yao Xiao-Nan Chen Li Liu Shi-Lin Zhang Yun-Fang Zhao Peng-Fei Tu Jun Li 《Tetrahedron letters》2018,59(51):4514-4516
Stachyodin A (1), a rearrangement product of pterocarpan featuring a 6/5/5/6 tetracyclic ring system with an unusual spirotetrahydrofuran ring, and stachyodin B (2), a new dihydrochalcone, along with five known analogues (3–7) were isolated from the roots of Indigofera stachyodes. The structures of 1 and 2 were elucidated on the basis of their HRESIMS and NMR spectroscopic data, and their absolute configurations were determined by X-ray crystallographic analysis and electronic circular dichroism (ECD) data, respectively. Compounds 2–4 showed inhibition of nitric oxide production in lipopolysaccharide-activated BV-2 microglial cells. 相似文献
64.
近年来,氮杂环卡宾作为有机小分子催化剂在共催化领域取得了飞速发展,氮杂环卡宾通过与Lewis酸、Brønsted酸、Brønsted碱、氢键等不同催化模式相结合,可以有效提升惰性底物的活性和催化体系的立体控制能力,该策略已经成为复杂手性分子骨架合成的重要工具.相对而言,由于氮杂环卡宾与过渡金属的强配位能力,其与过渡金属共催化反应依旧是氮杂环卡宾在共催化领域中长期存在的挑战性工作.目前,氮杂环卡宾在与钯、铜和钌的共催化反应中取得了重要进展,通过配体和反应体系中碱性强弱的调控,可以有效实现氮杂环卡宾与过渡金属配位的可控调节,避免催化剂失活的同时提升反应体系催化活性.这一策略已经被成功用于一些活性分子骨架构建.本文将对该领域中的研究进展进行介绍. 相似文献
65.
Quan-Zheng Zhang Guo-Quan Shao Gang Chen Huan Shen Guo-Hui Lu Rang Ping Peng-Fei Xie Yang Jiang Jie Zhang 《Journal of chemical crystallography》2007,37(5):369-373
A new organic-inorganic hybrid γ-octamolybdate complex, (NH4)4[(C3H7NO)2Mo8O26]·2CH3CH2OH·2H2O was synthesized from the mixture of ethanol, DMF, 4-aminobenzoic acid, (NH4)6Mo7O24·4H2O, HCl and H2O. The structure was determined by X-ray crystallography. It crystallizes in monoclinic P21/n space group with the crystal cell parameters of a = 8.8825(4), b = 21.1608(10), c = 11.1343(6) ?, β = 104.7720(10)°, V = 2023.64(17) ?3 and Z = 2. The crystal X-ray analysis shows that two DMF molecules are bound to γ-octamolybdate anion. The molecular structure
is stabilized by the complex hydrogen bonding. 相似文献
66.
Dr. Jiancheng Luo Dr. Xiao Zhao Hao Ju Dr. Xiangjun Chen Dr. Sheng Zhao Dr. Zoriana Demchuk Dr. Bingrui Li Dr. Vera Bocharova Dr. Jan-Michael Y. Carrillo Dr. Jong K. Keum Prof. Sheng Xu Prof. Alexei P. Sokolov Dr. Jiayao Chen Prof. Peng-Fei Cao 《Angewandte Chemie (International ed. in English)》2023,62(47):e202310989
Despite intensive research on sustainable elastomers, achieving elastic vitrimers with significantly improved mechanical properties and recyclability remains a scientific challenge. Herein, inspired by the classical elasticity theory, we present a design principle for ultra-tough and highly recyclable elastic vitrimers with a defined network constructed by chemically crosslinking the pre-synthesized disulfide-containing polydimethylsiloxane (PDMS) chains with tetra-arm polyethylene glycol (PEG). The defined network is achieved by the reduced dangling short chains and the relatively uniform molecular weight of network strands. Such elastic vitrimers with the defined network, i.e., PDMS-disulfide-D, exhibit significantly improved mechanical performance than random analogous, previously reported PDMS vitrimers, and even commercial silicone-based thermosets. Moreover, unlike the vitrimers with random network that show obvious loss in mechanical properties after recycling, those with the defined network enable excellent thermal recyclability. The PDMS-disulfide-D also deliver comparable electrochemical signals if utilized as substrates for electromyography sensors after the recycling. The multiple relaxation processes are revealed via a unique physical approach. Multiple techniques are also applied to unravel the microscopic mechanism of the excellent mechanical performance and recyclability of such defined network. 相似文献
67.
采用溶胶-凝胶法和光还原沉积贵金属法结合制备出Ag改性的纳米ZnO薄膜。利用FESEM、XPS、ESR、UV-Vis分析了纳米Ag-ZnO薄膜的表面形貌、表面组成和光谱特征。FESEM分析表明银在纳米ZnO薄膜表面形成原子簇而没有形成均匀覆盖层。XPS分析表明负载在纳米ZnO薄膜表面的银以Ag0形式存在; 相对于纳米ZnO薄膜, 纳米Ag-ZnO薄膜中晶格氧的含量有所下降,而表面羟基氧和吸附氧的含量显著增加。纳米Ag-ZnO薄膜的ESR峰强比纳米ZnO薄膜大,表明纳米Ag-ZnO薄膜中束缚单电子的氧空位的浓度高于纳米ZnO薄膜。UV-Vis分析纳米Ag-ZnO薄膜的紫外可见吸收光谱可能是纳米银粒子与纳米ZnO薄膜共同作用的结果。以甲基橙为模拟污染物,考察了纳米Ag-ZnO薄膜的光催化活性以及银沉积量对催化剂活性的影响。光催化降解结果表明,银的沉积量为0.018 2 mg·cm-2的纳米Ag-ZnO薄膜的光催化活性最高,在紫外光照射3 h后甲基橙降解率约为78%,而纳米ZnO薄膜约为62%。 相似文献
68.
Yin-Di Zhu Jing-Yi Zhang Peng-Fei Li Hai-Feng Wu Nai-Liang Zhu Hai Jiang 《Natural product research》2016,30(9):1075-1080
Two new abietane diterpenoid glycosides, named clinopoditerpenes B (1) and C (2), were isolated from Clinopodium chinese. The structures of the new compounds were determined on the basis of extensive spectral analysis. Compound 1 exhibited cardioprotective effect against H2O2-induced apoptosis in H9c2 cells. 相似文献
69.
Wu JS Wang PF Zhang XH Wu SK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(2):281-286
A new complex Cu(II)/L, composed of 2,9-bis(4'-hydroxyphenyl)phenanthroline (L) and Cu(II), was synthesized as an efficient chloride-detection fluorescent chemosensor with high selectivity and sensitivity over other halide anions, F(-), Br(-), I(-). The recognition mechanism was discussed primarily. 相似文献
70.
Jin W Wang YF Ge RL Shi HM Jia CQ Tu PF 《Rapid communications in mass spectrometry : RCM》2007,21(14):2351-2360
A simple, rapid method was developed using on-line high-performance liquid chromatography (HPLC)-diode array detection (DAD)/electrospray ionization mass spectrometry (ESI-MS) to simultaneously analyze multiple bioactive constituents in the extract of Rheum tanguticum Maxim. ex Balf. (Dahuang), a traditional Chinese medicine (TCM). Many bioactive constituents gave prominent [M-H]- ions in the negative ion ESI mass spectra. Among them, 41 different constituents including 16 anthraquinone derivatives, 7 phenylbutanone glucopyranosides, 4 stilbenes and 14 tannins were unambiguously identified or tentatively characterized based on their retention times, UV spectra and mass spectra in comparison with the data from standards or references. Meanwhile, some principles of fragmentation behavior for different types of constituents were proposed, which could contribute to the elucidation of these constituents in Rheum tanguticum. 相似文献