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通过控制制备过程中的洗涤次数,采用沉淀凝胶法制备了一系列不同钠离子含量的Co/SiO2催化材料,并采用X射线衍射、N2吸脱附、X射线能谱衍射、H2-程序升温还原、透射电镜和原子吸收光谱等多种表征手段系统研究了材料中残留钠离子对Co/SiO2材料的结构、分散性、氧化还原性和形貌的影响.结果表明,残留的钠离子使得样品比表面积下降,平均孔径增大,导致Co3O4的颗粒尺寸迅速增大.同时钠离子对Co3O4的还原具有抑制作用,使得样品的还原难度增大.结果导致Co/SiO2催化材料在乳酸酯加氢反应中的活性大大降低,同时造成丙酸乙酯副产物增加,对1,2-丙二醇(1,2-PDO)选择不利. 相似文献
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为了研究H7N9禽流感病毒的传播过程,考虑到有染病禽类输入和无染病禽类输入以及禽类的因病死亡率对模型的影响,得到禽类-人类动力学模型.针对两种不同的情况,得到了系统平衡点的存在性及基本再生数,并通过构造Lyapunov函数及利用Bendixson-Dulac定理给出了系统平衡点的稳定性条件.最后通过数值模拟验证了理论结果并给出了预防禽流感的有效措施. 相似文献
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Jingjing Xue 《中国物理 B》2022,31(4):48702-048702
A-form DNA is one of the biologically active double helical structure. The study of A-DNA structure has an extensive application for developing the field of DNA packaging in biotechnology. In aqueous solution, the A-DNA structure will have a free transformation, the A-DNA structure will be translated into B-form structure with the evolution of time, and eventually stabilized in the B-DNA structure. To explore the stability function of the bivalent metal ions on the A-DNA structure, a series of molecular dynamics simulations have been performed on the A-DNA of sequence (CCCGGCCGGG). The results show that bivalent metal ions (Mg2+, Zn2+, Ca2+) generate a great effect on the structural stability of A-DNA in the environment of high concentration. As the interaction between metal ions and electronegative DNA chains, the stability of A-DNA in solution is gradually improved with the increasing solution concentration of ions. In metal salt solution with high concentration, metal ions can be easily distributed in the solvation shells around the phosphate groups and further lead to the formation of shorter and more compact DNA structure. Also, under the condition of the same concentration and valency of the metal ions, the stability of A-DNA structure is different. The calculations indicate that the structure of A-DNA in CaCl2 solution is less stable than in MgCl2 and ZnCl2 solution. 相似文献
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以2-氯硒基-苯甲酰氯(1)为原料,在二氯甲烷溶液中与不同类型的胺(2a~2r)反应,合成了18个依布硒啉衍生物3a~3r(3i为新化合物),其结构经1H NMR, 13C NMR和HR-MS(ESI)表征。利用分子对接技术预测了化合物3a~3r与甲硫氨酸氨肽酶2(MetAP2)5D6E蛋白的亲和活性,并采用MTT法研究了化合物对食管癌细胞(EC109)的体外增殖抑制活性。结果表明:浓度为100 μg·mL-1时,2-(2-氯乙氧基-乙基)-1,2-苯并异硒唑-3(2H)-酮(3r)对EC109的增殖有良好的抑制活性,抑制率32%。 相似文献
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