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排序方式: 共有284条查询结果,搜索用时 31 毫秒
51.
Louis Pergaud Sandjo Victor Kuete Frederic Nana Gilbert Kirsch Thomas Efferth 《Helvetica chimica acta》2016,99(4):310-314
Eight heterocycles have been prepared in a one‐pot reaction manner based on the Hantzsch dihydropyridine synthesis. The synthesis afforded seven dihydropyridines (DHP) and one unexpected 1,3‐oxazin‐6‐one. Their structures were confirmed based on NMR spectroscopy and mass spectrometry. The obtained products have been evaluated for their cytotoxicity against eight cancer cell lines and one normal cell line. Two halogenated DHPs ( 7 and 8 ) displayed cytotoxicity toward all the nine tested cancer cell lines with IC50 values from 4.10 to 58.90 μm, while others showed selective activities. DHPs ( 7 and 8 ) bearing a Me group at C(2) and C(6) as well as a halogenated substituent at C(4′) were more antiproliferative than the others. 相似文献
52.
Haoyi Wu Yihua Hu Wei Zhang Fengwen Kang Nana Li Guifang Ju 《Journal of Sol-Gel Science and Technology》2012,62(2):227-233
In order to develop high efficiency red emitting phosphors, Ca0.76MoO4: Eu 0.24 3+ samples are investigated via sol–gel and solid state reaction. The XRD analysis reveals that both methods can synthesize phosphors with tetragonal CaMoO4 phase successfully. Smaller crystal size of samples prepared by sol–gel can be observed, and the grain size of these samples are around 100–200 nm, which is also smaller than the one prepared by solid state reaction. All phosphors present a red emission at 616 nm wavelength and one sol–gel synthesized sample exhibits the strongest emission intensity because of the higher quantum efficiency. It is attributed to the removal of lattice defects by sol–gel, in which way luminescent efficiency is enhanced. This can be reflected by the longer fluorescent lifetime of phosphors. 相似文献
53.
The fullerendiol C60(OH)2(OOt-Bu)4 1 reacts with various arylboronic acids ArB(OH)2 to form fullerene-containing boronic esters C60(O2BAr)(OOt-Bu)4 in up to 95% yield depending on the structure of aryl group. Bis(pinacolato)diboron (B(OCMe2)2)2 also reacts with 1 to form C60(O2BB(OCMe2)2)(OOt-Bu)4. The bisboronic ester C60(O)(O2BAr)2(OOt-Bu)2 was also obtained starting from a tetrahydroxyl fullerene derivative C60(O)(OH)4(OOt-Bu)2. The fullerenyl boronic esters are moderately stable in air. Single crystal X-ray structure of C60(O2BPh)(OOt-Bu)4 was obtained. 相似文献
54.
A series of isomerically pure alkynyl-substituted fullerenol derivatives such as C(60)(OH)(6)(O(CH(2))(3)CCH)(2) were synthesized through Lewis acid catalyzed epoxy ring opening and/or S(N)1 replacement reactions starting from the fullerene-mixed peroxide C(60)(O)(t-BuOO)(4). Copper-catalyzed azide-alkyne cycloaddition readily converted the terminal alkynyl groups into triazole groups. Intramolecular oxidative alkyne coupling afforded a fullerenyl crown ether derivative. 相似文献
55.
The second-order nonlinear optical (NLO) properties of the Cp*Co(C(2)H(5))(2)C(2)B(4)H(3)-expanded (metallo)porphyrins (Cp* = C(5)Me(5)) have been investigated by using ab inito RHF and density functional theory (DFT) methods. The investigation shows that the compound with expand porphyrin possesses remarkable large molecular hyperpolarizability β(tot) value, ~414.1 × 10(-30) esu (at LC-ωPBE level), and might be an excellent second-order NLO material. From the character of charge transfer (CT) transition, it indicates that the -Cp*Co(C(2)H(5))(2)C(2)B(4)H(3) acts as an electron donor in this kind of systems. As a result of the redox behavior on expanded (metallo)porphyrin, the redox switching character of the NLO responses for the systems 2a-4a has also been studied. The results show that the β(tot) values of reduced forms are larger than that of neutral ones. Furthermore, the time-dependent DFT calculation illustrates that reduced forms have a significant difference on the CT patterns versus neutral ones. The present investigation provides insight into the comparison with DFT results on estimating first hyperpolarizability and the NLO properties of the series of push-pull compounds. 相似文献
56.
易贡滑坡堰塞湖溃坝洪水分析 总被引:4,自引:0,他引:4
滑坡堰塞坝体主要由块石、碎石土等松散材料组成,随着上游水位的不断上升,极易失稳,一旦决口将对给下游人民的生命财产安全造成极大的威胁。因此,研究堰塞坝溃坝问题具有重要的学术意义和应用价值。2000 年 4 月 9 日,西藏林芝地区波密县易贡藏布河扎木弄沟发生大规模山体滑坡堵塞易贡藏布江,形成坝高60m,长约2500m,库容可达288×108m3,体积约28×108~30×108m3的滑坡堰塞湖, 2000年6月10日堰塞坝溃决。本文以易贡堰塞湖溃坝为例,从连续性方程及Navier Stokes方程出发,结合标准型湍流模型,并采用VOF方法进行自由面处理,基于流体计算软件Fluent模拟分析了溃坝洪水在下游弯曲河道的演进过程及不同位置的流速变化。数值模拟结果与实测资料记录基本一致,表明该模型能够模拟溃坝洪水在地形复杂弯曲河道中的演进过程。 相似文献
57.
强激光与一维多原子分子离子的相互作用及高次谐波的增强 总被引:1,自引:1,他引:0
研究强激光脉冲与一维多原子分子离子的相互作用,讨论双色激光场中高次谐波转化效率的提高,并应用经典三步模型说明高次谐波平台展宽的物理机制. 相似文献
58.
59.
To understand the influence of fear effect on population dynamics, especially for the populations with obvious stage structure characteristics, we propose and investigate a diffusive prey-predator model with stage structure in predators. First, we discuss the existence and stability of equilibrium of the model in the absence of diffusion. Then, we obtain the critical conditions for Hopf and Turing bifurcations. Some numerical simulations are also carried out to verify our theoretical results, which indicate that the fear can induce the prey population to show five pattern structures: cold-spot pattern, mixed pattern with cold spots and stripes, stripes pattern, hot-spot pattern, mixed pattern with hot spots and stripes. These findings imply that the fear effect induced by the mature predators plays an important role in the spatial distribution of species. 相似文献
60.
Gerhard Quinkert Uta-Maria Billhardt Harald Jakob Gerd Fischer Jürgen Glenneberg Peter Nagler Volker Autze Nana Heim Manfred Wacker Thomas Schwalbe Yvonne Kurth Jan W. Bats Gerd Dürner Gottfried Zimmermann Horst Kessler 《Helvetica chimica acta》1987,70(3):771-861
Photolactonization: A Novel Synthetic Entry to Macrolides o-Quinol acetates, hydroxyalkylated at C(6), are easily accessible from simple phenols by Wessely acetoxylation (preferentially catalyzed by BF3). On UV irradiation (in the presence of an appropriate tertiary amine), they are smoothly converted to macrocyclic lactones. Subtle conditions have been elaborated to lead to high overall yields, and the scope of the conversion of phenols to macrolides has been elucidated. 相似文献