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151.
Dan Mu Jiong Sun Dept. of Math. Inner Mongolia University Hohhot 《Annals of Differential Equations》2010,(1):45-52
The problem of J-selfadjointness of the product of two nth-order J-symmetric operators on [a,b] is studied. We give a condition to ensure that the product operator is a J-selfadjoint extension. 相似文献
152.
Bi-f-harmonic maps are the critical points of bi-f-energy functional. This class of maps tends to integrate bi-harmonic maps and f-harmonic maps. In this paper, we show that bi-f-harmonic maps are not only an extension of f-harmonic maps but also an extension of bi-harmonic maps, and that there should exist many examples of proper bi-f-harmonic maps.In order to find some concrete examples of proper bi-f-harmonic maps, we study the basic properties of bi-f-harmonic maps from two directions which are conformal maps between the same dimensional manifolds and some special maps from or into a warped product manifold. 相似文献
153.
154.
155.
A. M. Al‐Sabagh Sabrnal H. El‐Hamouly Ayman M. Atta M. R. Noor El‐Din Moataz M. Gabr 《Journal of Dispersion Science and Technology》2013,34(5):661-670
In this respect mono‐, di‐, and tri‐ sorbitol oleate esters [SMO, SDO, and STO] were prepared and then ethoxylated using ethylene oxide to obtain six sorbitol esters at different ethylene oxide content (e.o=5, 12, 15, 20, 35, and 45). They were tested as oil spill dispersants individually and in blends. From the obtained data, it was found that the blends are more effective than the corresponding individual surfactants. The maximum dispersion capability for the prepared surfactants was obtained at HLB range from 9 to 11 for the both individual surfactants and blends. The increase of total carbon number in the surfactant alkyl group leads to increase dispersion capability of the dispersant. The wide range of ethylene oxide content was used, but the maximum dispersion efficiency was obtained at ethylene oxide=20 in E(20)STO. Meanwhile, the dispersion capability increases when the interfacial tension decreases. 相似文献
156.
Prof. Dr. Lutz F. Tietze Dr. Ling Ma Johannes R. Reiner Stefan Jackenkroll Sven Heidemann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8610-8614
Blennolide A can be synthesized through an enantioselective domino‐Wacker/carbonylation/methoxylation reaction of 7 a with 96 % ee and an enantioselective Wacker oxidation of 7 b with 89 % ee. Further transformations led to the α,β‐unsaturated ester (E)‐ 17 , which was subjected to a highly selective Michael addition, introducing a methyl group to give 18 a . After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (?)‐blennolide A (ent‐ 1 ) in a few steps. 相似文献
157.
Aetheramides A and B are very potent anti-HIV agents. An enantioselective synthesis of a MEM-protected aetheramide A derivative is described. The synthesis was accomplished in a convergent and stereoselective manner. The key reactions involved asymmetric dihydroxylation, asymmetric allylation, asymmetric syn-aldol reactions, and asymmetric hydrogenation. 相似文献
158.
A ring fragmentation and intramolecular azomethine ylide 1,3-dipolar cycloaddition sequence of reactions was successfully used in the preparation of a known (±)-cycloclavine precursor in good overall yield. Results of efforts to incorporate the tetrasubstituted cyclopropane ring present in cycloclavine are also discussed. 相似文献
159.
《Tetrahedron letters》2014,55(52):7147-7155
Desymmetrization synthesis strategy has simplified and improved the efficiency of synthesis, which attracted great attention in the past few decades. Since the strategy has been developed rapidly and got a wide range of applications in natural product total synthesis, the rules are urgent to be summarized. In this Letter, the recent developments of desymmetrization protocol in natural product total synthesis were summarized. 相似文献
160.
以正硅酸四甲酯(TMOS)为硅源,P123(EO20PO70EO20)为表面活性剂,在p H=6的磷酸缓冲体系中制备了囊泡状二氧化硅材料.利用乙醇萃取脱除模板剂P123,电镜观测结果表明所得二氧化硅具有大孔囊泡结构,N2吸附结果表明其具有高比表面积和大孔容.通过Boehm滴定法确定了硅羟基数量与吸水率呈正相关.用囊泡状二氧化硅材料与商业化活性炭(AC)和硅胶(SG)对水蒸气、正己烷和油气进行静态吸附.在自建的动态正己烷吸附装置上用对囊泡状二氧化硅材料和商业化AC和SG对正己烷进行动态吸附.吸附结果表明,囊泡状二氧化硅材料的静/动态吸附容量和稳定性都远高于商业化活性炭和硅胶. 相似文献