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91.
Judicious choice of cation allows the selective cyclization of substituted gamma-hydroxynitriles to trans- or cis-decalins and trans- or cis-bicyclo[5.4.0]undecanes. The stereoselectivities are consistent with deprotonations generating two distinctly different metalated nitriles: an internally coordinated nitrile anion with BuLi, and a C-magnesiated nitrile with i-PrMgCl. Employing cations to control the geometry of metalated nitriles permits stereodivergent cyclizations with complete control over the stereochemistry of the quaternary, nitrile-bearing carbon. 相似文献
92.
本文利用半等价算子εi和相等化算子δi研究了复杂系统的聚类问题;阐述了分析运筹复杂系统的δ(1,3)解耦原理、对偶转化原理和大系统分解原理;详细讨论了复杂系统的连通性与解耦性并提供了有关定理.最后,利用泛系聚类方法讨论了复杂系统的层次分析. 相似文献
93.
昝廷全 《应用数学和力学(英文版)》1989,10(2):167-173
This paper is a further study of reference [1]. In this paper, we mainly discuss the complicated dynamical behaviors resulting from a simple one-dimensional model of nonlinear ecosystems: fixed point motion, periodic motion and chaotic motion etc., and briefly discuss the universality of the complicated dynamical behaviors, which can be described by the first and the second M. Feigenbaun. constants. At last, we discuss the one-side lowering phenomenon due to near unstabilization when the nonlinear ecosystem approaches bifurcation points from unbifurcation side. It is of important theoretical and practical meanings both in the development and utilization of ecological resources and in the design and management of artifitial ecosystems.Supported by the Youth Science Fundation of Chinese Academia Sinica and Youth Fundation of Lanzhou Unviersity. 相似文献
94.
葡聚糖及其衍生物对大麦细胞电融合的影响①王伟江志裕*(复旦大学化学系上海200433)细胞融合是指用人工方法使两个细胞融合成一个细胞的过程[1,2].体细胞融合可在不同种,不同属,甚至更远的生物间进行,所得到的细胞可具有新的特性.对于植物细胞,有望通... 相似文献
95.
96.
In this paper, we propose a competition-share 3-category principle, on which we unite the problems of natural resources, energy,
population and environment and so on into a mutual scheme, and provide a united model for the comprehensive research on these
problems. This makes the idea of operation analysis of natural resources clearer and the relationships between each of their
parts more obvious. On the basis of the above discussion, we propose mathematical models for the operation analysis of multi-networks
and the solution of the above global comprehensive problems. We discuss, especially, Shengke (growth and restraint) relationships
between two networks of natural resources and share-competitors and their analysis models, providing mathematical tools for
solving the problems of the resource-population and the resource-economy, etc.
Supported by Science Fund of Lanzhou University. 相似文献
97.
镍在碱溶液中阳极膜的形成和性质与化学电源和金属腐蚀等有关.在这方面已有较深入的研究报导.其研究方法也是多种多样,除一般的电化学方法[1,2]外,还有许多现场谱学方法,如:紫外_可见光谱[3],红外光谱[4],光热光谱[5],拉曼光谱[6],椭圆法[7... 相似文献
98.
Muhammad Sajjad Jing Zhang Shiwen Zhang Jieqing Zhou Zhiyu Mao Zhongwei Chen 《Chemical record (New York, N.Y.)》2024,24(3):e202300315
Owing to the mature technology, natural abundance of raw materials, high recycling efficiency, cost-effectiveness, and high safety of lead-acid batteries (LABs) have received much more attention from large to medium energy storage systems for many years. Lead carbon batteries (LCBs) offer exceptional performance at the high-rate partial state of charge (HRPSoC) and higher charge acceptance than LAB, making them promising for hybrid electric vehicles and stationary energy storage applications. Despite that, adding carbon to the negative active electrode considerably enhances the electrochemical performance. However, carbon brings some adverse effects, such as the severe hydrogen evolution reaction (HER) in the NAM due to the low overpotential of carbon material, promoting severe water loss in LCBs. From a practical application point of view, the irreversible sulfation of the negative active material (NAM) and extreme shedding and softening of the positive active material (PAM) are the main obstacles for next-generation LCBs. Recently, a lead-carbon composite additive delayed the parasitic hydrogen evolution and eliminated the sulfation problem, ensuring a long life of LCBs for practical aspects. This comprehensive review outlines a brief developmental historical background of LAB, its shifting towards LCB, the failure mode of LAB, and possible potential solutions to tackle the failure problems. The detailed LCB′s development towards long life was discussed in light of the reported literature to guide the researcher to date progress. More emphasis was directed toward the new applications of LCBs for stationary energy storage applications. Finally, state-of-the-art progress and further research gaps were pointed out for future work in this exciting era. 相似文献
99.
100.