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151.
Zhao Yang WANG Jia Ling CUI Bao Shan DU* Qing Hua CHEN Department of Chemistry Beijing Normal University Beijing Present address: Dept. of Chem. South China Nor. Univ Guangzhou Present address: School of Pharm. Beijing Univ 《中国化学快报》2001,(4)
Recently, much effort has been made in the development of generally applicable organic synthesis of 5-alkyloxy-2(5H)-furanones due to their essential structure entities in the synthesis of some biologically active natural products and their application as useful intermediates in organic synthesis1. Their reactions such as Michael addition, Diels-Alder reaction and photocatalyzed conjugate addition have been studied extensively2-4.However, Michael addition reaction of Grignard reagents to 5-m… 相似文献
152.
《Communications in Nonlinear Science & Numerical Simulation》2008,13(7):1384-1396
The series of lightning measured during 2002 and 2003 in two areas of Italy, Lombardia (northern Italy) and Campania (southern Italy), has been deeply investigated to detect and quantify time-clustering structures by using several methods. Our results suggest the existence of time-clustering in the sequence of lightning time-occurrences, characterized by the presence of two scaling regions, respectively related with clustering effect inside a single thunderstorm and among successive thunderstorms. 相似文献
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We study thermal rectification of a two-quantum-dots system with Dzyaloshinskii–Moriya (DM) interaction and coupling to two bosonic reservoirs. Compared with other proposals (Zhang et al., 2009 [9]), our model can offer larger rectification efficiency through different modulations in small size systems (N=2). 相似文献
158.
Ricardo Elgul Samad Lilia Coronato Courrol Ademar Benévolo Lugão Anderson Zanardi de Freitas Nilson Dias Vieira 《Radiation Physics and Chemistry》2010,79(3):355-357
We report here the creation of color centers in commercial, transparent PMMA samples by ultrashort pulses from a Ti:Sapphire laser emitting at 800 nm, with spatial control. Although the 800 nm photon energy is not sufficient to ionize the polymer, the centers are created following a multiphotonic absorption that causes the ionization. We propose that the free electrons quivering motion on the pulse electric field displaces atoms from its equilibrium positions, creating free radicals and double bonds that coalesce into color centers. The absorption and emission spectra of the centers were measured, but a dose-like curve could not be built due to the presence of damages created along with the centers that scatter the excitation and emission lights due to the commercial sample's poor optical quality. 相似文献
159.
In this paper, the authors consider the Gevrey class regularity of a semigroup associated with a nonlinear Korteweg-de Vries(Kd V for short) equation. By estimating the resolvent of the corresponding linear operator, the authors conclude that the semigroup generated by the linear operator is not analytic but of Gevrey class δ∈( 3/2, ∞) for t 0. 相似文献
160.
通过分析竞争反应的过渡态在构象上能量的高低,探讨构象效应(立体电子效应和位阻效应)对一些有机反应的立体性的影响;而立体电子效应和位阻效应与反应机制,反应物的结构-构象和反应条件等都有关系,最终能影响反应产物的立体结构。阐明其中的缘由可有助于正确预测产物的结构及选择可行的合成线路。 相似文献