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921.
芳基三氮烯4-位取代基对抗癌活性影响的构象分析 总被引:1,自引:0,他引:1
传统的药物设计和新药开发主要是依靠随机筛选,这种方法误差大,且需要费大量时间和经费,其结果也经常不能达到预期的设想。即使是一个国际性的大制药集团,每年平均要合成上万个化合物才能从中筛选出一个可以成为商品的新药。这种状况迫使我们去寻找一条新的打破常规的途径研究新药。近年来,随着计算机图形系统的广泛应用,对药物构效关系的研究得到了卓有成效的发展,取得了一些成功的例子。如抗菌抗癌琥珀酰-L脯氨酸就是计算化学与分子图形技术相结合的成果,目前已投放市场。 相似文献
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An efficient and simple oil bath method for rapid synthesis of graphene/BiOI as visible light active photocatalyst was described. The resultant graphene/BiOI composites were characterized by different techniques, including scanning electron microscopy, X-ray diffraction, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of the as-prepared graphene/BiOI composites for methyl orange degradation was also investigated under visible light irradiation. The results show that BiOI and graphene taken with a mass ratio of 100: 1 exhibited the highest photocatalytic efficiency, which is two times that of pure BiOI. Part of this effect results from higher specific surface area that provides an increased number of active sites. A relatively narrow band gap (2.08 eV) formed in the heterostructure can also contribute to this effect. A suggestion of the photocatalytic mechanism was also offered. 相似文献
924.
Wei Jiang Hongping Li Sheng Yin Xin Wang Wei Liu Hui Liu Wenshuai Zhu Huaming Li 《应用有机金属化学》2016,30(9):753-758
Two hexacyanoferrate‐based ionic liquids, [C4Py]3Fe(CN)6 and [C16Py]3Fe(CN)6, were synthesized and characterized using Fourier transform infrared and mass spectroscopies and CHN analysis. They were employed as Fenton‐like catalysts in extraction and catalytic oxidative desulfurization of model oil with dibenzothiophene (DBT), benzothiophene (BT), 4,6‐dimethyldibenzothiophene (4,6‐DMDBT), 4‐methyldibenzothiophene (4‐MDBT) and 3‐methylbenzothiophene (3‐MBT) as substrates. Various polar solvents, such as ionic liquids, water and organic solvents, were applied to choose a suitable extractant. The results showed the removal of DBT reached 97.1% with [C4Py]3Fe(CN)6 as a catalyst and 1‐n‐octyl‐3‐methylimidazolium hexafluorophosphate ([C8mim]PF6) as an extractant under optimal conditions. The activity of sulfur removal followed the order DBT > 3‐MBT > BT > 4‐MDBT >4,6‐DMDBT. The effect of water content on sulfur removal was investigated by adding various concentrations of H2O2. It was found that excess water had a positive effect on sulfur removal but the catalysts were less sensitive than [FeCl4?]‐based catalysts to water. The mechanism was studied using electron spin‐resonance spectroscopy and gas chromatography–mass spectrometry. O2?? may be the active oxygen species in the catalytic oxidative desulfurization process and the oxidation products of various sulfur compounds were the corresponding sulfoxides and sulfones. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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926.
Seed‐Mediated Synthesis of Gold Tetrahedra in High Purity and with Tunable,Well‐Controlled Sizes 下载免费PDF全文
Yiqun Zheng Wenying Liu Tian Lv Ming Luo Dr. Hefei Hu Dr. Ping Lu Dr. Sang‐Il Choi Chao Zhang Dr. Jing Tao Prof. Yimei Zhu Prof. Zhi‐Yuan Li Prof. Younan Xia 《化学:亚洲杂志》2014,9(9):2635-2640
We report a facile synthesis of Au tetrahedra in high purity and with tunable, well‐controlled sizes via seed‐mediated growth. The success of this synthesis relies on the use of single‐crystal, spherical Au nanocrystals as the seeds and manipulation of the reaction kinetics to induce an unsymmetrical growth pattern for the seeds. In particular, the dropwise addition of a precursor solution with a syringe pump, assisted by cetyltrimethylammonium chloride and bromide at appropriate concentrations, was found to be critical to the formation of Au tetrahedra in high purity. Their sizes could be readily tuned in the range of 30–60 nm by simply varying the amount of precursor added to the reaction solution. The current strategy not only enables the synthesis of Au tetrahedra with tunable and controlled sizes but also provides a facile and versatile approach to reducing the symmetry of nanocrystals made of a face‐centered cubic lattice. 相似文献
927.
In this paper we propose a new method for the study and visualization of dynamic processes in magnetic nanostructures, and for the accurate calculation of rates for such processes. The method is illustrated for the case of switching of a grain of an exchange-coupled recording medium, which switches through domain wall nucleation and motion, but is generalizable to other rate processes such as vortex formation and annihilation. The method involves calculating the most probable (lowest energy) switching path and projecting the motion onto that path. The motion is conveniently visualized in a two-dimensional (2D) projection parameterized by the dipole and quadrupole moment of the grain. The motion along that path can then be described by a Langevin equation, and its rate can be computed by the classic method of Kramers [4]. The rate can be evaluated numerically, or in an analytic approximation—interestingly, the analytic result for domain-wall switching is very similar to that obtained by Brown in 1963 for coherent switching, except for a factor proportional to the domain-wall volume. Thus in addition to its lower coercivity, an exchange-coupled medium has the additional advantage (over a uniform medium) of greater thermal stability, for a fixed energy barrier. 相似文献
928.
Sanguo Zhu 《Monatshefte für Mathematik》2012,259(1):291-305
We study the quantization with respect to the geometric mean error for probability measures μ on for which there exist some constants C, η > 0 such that for all ε > 0 and all . For such measures μ, we prove that the upper quantization dimension of μ is bounded from above by its upper packing dimension and the lower one is bounded from below by its lower Hausdorff dimension. This enables us to calculate the quantization dimension for a large class of probability measures which have nice local behavior, including the self-affine measures on general Sierpiński carpets and self-conformal measures. Moreover, based on our previous work, we prove that the upper and lower quantization coefficient for a self-conformal measure are both positive and finite. 相似文献
929.
930.