排序方式: 共有33条查询结果,搜索用时 15 毫秒
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Lei Liu Jing Li Mingan Wang Fengpei Du Zhaohai Qin Bin Fu 《Tetrahedron: Asymmetry》2011,22(5):335-557
A series of novel heteroarylidene malonate derived bis(thiazoline) ligands 1 and 2 were synthesized and applied to a Friedel-Crafts reaction between indole and alkylidene malonate. The Cu(OTf)2 complex of ligand 2b bearing a benzyl group afforded moderate to excellent enantioselectivity for the adducts (up to >99% ee). 相似文献
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Multidimensional stability of planar waves for delayed reaction-diffusion equation with nonlocal diffusion
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In this paper, we consider the multidimensional stability of planar waves for a class of nonlocal dispersal equation in $n$--dimensional space with time delay. We prove that all noncritical planar waves are exponentially stable in $L^{\infty}(\RR^n )$ in the form of $\ee^{-\mu_{\tau} t}$ for some constant $\mu_{\tau} =\mu(\tau)>0$( $\tau >0$ is the time delay) by using comparison principle and Fourier transform. It is also realized that, the effect of time delay essentially causes the decay rate of the solution slowly down. While, for the critical planar waves, we prove that they are asymptotically stable by establishing some estimates in weighted $L^1(\RR^n)$ space and $H^k(\RR^n) (k \geq [\frac{n+1}{2}])$ space. 相似文献
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Shaojin Chen Zhaohai Ge Qiang Jia Kun‐Peng Wang Li‐Hua Gan Zhi‐Qiang Hu 《化学:亚洲杂志》2019,14(9):1462-1466
A general and efficient synthetic methodology for the preparation of enantio‐ and diastereopure [6]‐, and [7]helicenes is developed. Commercially available chiral binaphthanols are utilized to generate the arylene‐vinylene precursors, which undergo helical folding via photocyclization to give enantio‐ and diastereopure [6]‐, and [7]helicenes. These optically pure helicenes could be easily obtained via silica gel column chromatography without the use of expensive HPLC or chiral resolution reagents. The configurations and structures of these helicenes are confirmed by CD spectra and X‐ray crystallographic analysis. This work provides a new method for preparation of enantiopure helicenes. 相似文献
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L Liu H Ma Y Xiao F Du Z Qin N Li B Fu 《Chemical communications (Cambridge, England)》2012,48(74):9281-9283
The simple and cheap chiral catalyst, heteroarylidene-tethered Ph-bis(oxazoline)-Cu(OTf)(2), can efficiently catalyze the asymmetric F-C alkylation of indoles and pyrrole with β,γ-unsaturated α-ketoesters. The 3-indolyl adducts were obtained in up to >99% ee. Moreover, the 2-pyrrolyl adducts were achieved in up to 92% ee for the first time. 相似文献
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To better describe and understand the time dynamics in functional data analysis, it is often desirable to recover the partial derivatives of the random surface. A novel approach is proposed based on marginal functional principal component analysis to derive the representation for partial derivatives. To obtain the Karhunen-Lo`eve expansion of the partial derivatives, an adaptive estimation is explored. Asymptotic results of the proposed estimates are established. Simulation studies show that the proposed methods perform well in finite samples. Application to the human mortality data reveals informative time dynamics in mortality rates. 相似文献
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Xianyou Wang Zhuoqun Xie Bin Fu Nan Li Mingan Wang Yongqiang Ma Fengpei Du Yanjun Xu Zhaohai Qin 《Journal of heterocyclic chemistry》2014,51(5):1430-1434
The synthesis of the key intermediate of rocaglamide, oxidative aglafolin, was studied, and its diastereoisomers were obtained. The amination of oxidative aglafolin was also investigated, affording amino derivatives. The preliminary bioassay results indicate that these new aglafolin derivatives showed certain degree of insecticidal and repellent activity against Plutella xylostella and Laphygma exigua. 相似文献
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对Goodgrant基金的投资策略进行研究。首先,根据投资要求,对候选学校进行初步筛选,基于筛选后的学校,选取与教育绩效有关且数据信息完整的变量对学校进行聚类,并利用聚类结果对缺失数据进行补全;然后,提出了评价学生教育表现的绩效指标、绩效指示变量及绩效贡献变量的定义与关系,通过对绩效指示变量进行主成分分析,确定出每个学校当前的绩效值,并以此对所有学校进行初步排名;最后,以获得奖学金的学生占当年入学学生总数的比例作为绩效贡献变量,给出每个学校投资回报率的计算公式,并以该公式为依据,从绩效排名前100的学校中选出待投资的10所学校及捐赠数额。 相似文献
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Baosan Han Baiyong Shen Zhaohai Wang Minmin Shi Hongwei Li Chenghong Peng Qinghe Zhao Changyou Gao 《先进技术聚合物》2008,19(1):36-46
Anti‐cancer drug daunorubicin (DNR) was encapsulated in preformed multilayer microcapsules and was applied in tumor treatment by in vitro cell culture and in vivo animal experiments. The microcapsules were fabricated by an alternate deposition of oppositely charged polysaccharides, i.e. chitosan and alginate onto carboxymethyl cellulose (CMC) doped CaCO3 colloidal particles in a sequential assembly procedure, followed by crosslinking of the capsule shells with glutaraldehyde (GA) and removal of the templates by disodium ethylenediaminetetraacetic acid (EDTA). The as‐prepared microcapsules showed strong ability to induce the positively charged DNR to deposit into the microcapsule interiors. Confocal microscopy and transmission electron microscopy observed homogeneous distribution of the drug within microcapsules. The loaded DNR could be released again, following a diffusion‐controlled model at the initial stage. In vitro experiments demonstrated that the encapsulated DNR can effectively induce the apoptosis of BEL‐7402 tumor cells, as evidenced by various microscopy techniques after acridine orange (AO), Hoechst 33342, and osmium tetraoxide staining. By seeding the BEL‐7402 hepatoma cells into BALB/c/nu mice, tumors were created for the animal experiments. The results showed that the encapsulated DNR had better efficacy than that of the free drug in terms of tumor inhibition in a 4 week in vivo culture period. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献