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991.
992.
Chitosan derivatives have been studied widely, but poor solubility in water restricts their applications. In this study, four types of amine‐based chitosan derivatives were prepared and modified further with beta‐cyclodextrin. The sequential microextraction of catechins ((+)‐catechin and (?)‐epigallocatechin gallate) from green tea powder by an optimized solid‐phase extraction method using these four derivatives was investigated. The optimal conditions for the extraction of catechins were 60°C for a 40 min extraction period. The purity and amount of each catechin were determined by high‐performance liquid chromatography. The different amines strengthened the extraction capacity of chitosan. Among the four types of amines, ethylene diamine grafted chitosan beta‐cyclodextrin had the highest extraction capacity to catechins. Therefore, this material was used in the extraction assay, and the standard curves of (+)‐catechin and (?)‐epigallocatechin gallate were linear over the concentration range, 0.25–500 µg/mL, after assaying five data points in duplicate. Solid‐phase extraction with the amino‐based chitosan beta‐cyclodextrin system is a new application of chitosan, which has potential applications in the extraction of bioactive compounds from plant materials or the removal of different impurities from specific extracts. 相似文献
993.
Shuai Liu Haofu Dai Christian Heering Christoph Janiak Wenhan Lin Zhen Liu Peter Proksch 《Tetrahedron letters》2017,58(3):257-261
Two new lactones, pestalotiolactones A (1) and B (2), together with three known compounds (3–5) were isolated from the axenic culture of the endophytic fungus Pestalotiopsis sp., obtained from fruits of Drepanocarpus lunatus (Fabaceae). Co-culture of this fungus with Bacillus subtilis afforded two new sesquiterpenoids pestabacillins A (6) and B (7) as well as eight known compounds (8–15). Their structures were elucidated by extensive analysis of the NMR and MS data as well as by comparison with literature data. All isolated compounds were evaluated for their cytotoxic and antimicrobial activities but proved to be inactive. 相似文献
994.
Nonlinear Dynamics - This paper focuses on the finite-time synchronization problem for a kind of general complex networks with intrinsic time-varying delays and hybrid couplings (i.e., containing... 相似文献
995.
Yan Dai 《Journal of statistical physics》2017,166(6):1455-1463
It has been proved that the distribution of the point where the smart kinetic walk (SKW) exits a domain converges in distribution to harmonic measure on the hexagonal lattice. For other lattices, it is believed that this result still holds, and there is good numerical evidence to support this conjecture. Here we examine the effect of the symmetry and asymmetry of the transition probability on each step of the SKW on the square lattice and test if the exit distribution converges in distribution to harmonic measure as well. From our simulations, the limiting exit distribution of the SKW with a non-uniform but symmetric transition probability as the lattice spacing goes to zero is the harmonic measure. This result does not hold for asymmetric transition probability. We are also interested in the difference between the SKW with symmetric transition probability exit distribution and harmonic measure. Our simulations provide strong support for a explicit conjecture about this first order difference. The explicit formula for the conjecture will be given below. 相似文献
996.
997.
Chang Ling Chang Shuquan Han Wei Li Zheng Zhang Zheng Dai Yaodong Zhang Haiqian 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):289-299
Journal of Radioanalytical and Nuclear Chemistry - The present paper, for the first time, reports the application of Ba2TiSi2O8 (BTS) for management of trivalent actinides present in radioactive... 相似文献
998.
Chen Haijun Wang Youqun Zhao Wuwei Xiong Guoxuan Cao Xiaohong Dai Ying Le Zhanggao Zhang Zhibin Liu Yunhai 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(1):175-189
Journal of Radioanalytical and Nuclear Chemistry - The graphene oxide (GO) was functionalized with phosphate groups and applied as an effective adsorbent for the removal of uranium from aqueous... 相似文献
999.
1000.
Exact travelling-wave solutions of an integrable equation arising in hyperelastic rods 总被引:1,自引:0,他引:1
H.-H. Dai 《Wave Motion》1998,28(4):367-381
In this paper, we study an integrable nonlinear evolution equation which arises in the context of nonlinear dispersive waves in hyperelastic rods. To consider bounded travelling-wave solutions, we conduct a phase plane analysis. A new feature is that there is a vertical singular line in the phase plane. By considering equilibrium points and the relative position of the singular line, we find that there are in total three types of phase planes. The trajectories which represent bounded travelling-wave solutions are studied one by one. In total, we find there are 12 types of bounded travelling waves, both supersonic and subsonic. While in literature solutions for only two types of travelling waves are known, here we provide explicit solution expressions for all 12 types of travelling waves. Also, it is noted for the first time that peakons can have applications in a real physical problem. 相似文献