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71.
Bang-Bang Jiang Ming Pan Chen Wang Hua-Fei Li Ning Xie Hai-Yan Hu Fan Wu Xiao-Ling Yan Marvin H. Wu K. Vinodgopal Gui-Ping Dai 《Journal of Saudi Chemical Society》2019,23(2):162-170
Controlled growth of single-crystal high-quality ‘track-and-field ground’ shaped graphene domains and the morphological evolution from hexagonal to hexagram graphene domain even square and circular graphene domain has been achieved by low-pressure CVD on solid copper substrate, thereby demonstrating that the shape of the graphene grains can potentially be precisely tuned by optimizing growth parameters. The etching reaction of graphene has also been studied, and results show that a low flow rate of hydrogen (99.999%) is favorable to form hexagonal structure for the etching reaction of graphene due to the exist of oxygen or oxidizing impurities in hydrogen gas commonly used. Controlled growth and etching reaction of graphene determine the final shape of graphene domains and all these efforts contribute to the study of size and morphology and the growth mechanism of graphene domains. 相似文献
72.
Da-Liang Zhu Qi Wu Prof. Hai-Yan Li Prof. Dr. Hong-Xi Li Prof. Dr. Jian-Ping Lang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(16):3484-3488
Diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (HEH) has been utilized as a visible-light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE−, single electron transfer (SET) in donor–acceptor complex (DAC) from *HE− to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE. to sulfone by the DAC method. 相似文献
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74.
A single nanopore represents a versatile single-molecule probe that can be employed to reveal several important features of proteins, such as physical structure, backbone flexibility, mechanical stability, their folding state, binding affinity to other interacting ligands and enzymatic activity. In this review, we summarize the development and current research related to the field of protein detection by nanopore, as well as a few examples of the pioneer work on protein detection. We first discuss the principle of electrical detection with nanopores and how this technique provides information from current traces. Then the development from peptide detection with biological nanopore to protein detection through solid-state nanopore is described. Finally, we prospect the measurement of protein shape and construction using nanopore technology for the applications in life research area. 相似文献
75.
Walsucochins A and B with an unprecedented skeleton isolated from Walsura cochinchinensis 总被引:1,自引:0,他引:1
Walsucochins A (1) and B (2) with an unprecedented skeleton were isolated from Walsura cochinchinensis. Their structures including absolute configuration were elucidated by spectral methods. A biosynthetic pathway of 1 and 2 was postulated. Both 1 and 2 exhibited significant cell protecting activities against H2O2-induced PC12 cell damage. 相似文献
76.
Yan-Ni Chen Hong-Ke Du Hai-Yan Zhang 《Proceedings of the American Mathematical Society》2008,136(10):3483-3492
Let and be two idempotents on a Hilbert space. In 2005, J. Giol in [Segments of bounded linear idempotents on a Hilbert space, J. Funct. Anal. 229(2005) 405-423] had established that, if is invertible, then and are homotopic with In this paper, we have given a necessary and sufficient condition that where denotes the minimal number of segments required to connect not only from to , but also from to in the set of idempotents.
77.
降解前后异枝麒麟菜硫酸多糖对草酸钙晶体生长的调控作用 总被引:1,自引:0,他引:1
采用过氧化氢法降解产于印尼的海藻异枝麒麟菜硫酸多糖(ESPS). 降解前ESPS的平均分子量为1410000, 硫酸基(OSO2-3)含量为16.0%(w); 而降解后其分子量显著下降至4819, 硫酸基含量则略微下降至15.2%. 采用体外模拟方法研究了降解前后ESPS对草酸钙晶体生长的抑制作用. 扫描电子显微镜(SEM)和X射线衍射(XRD)结果表明, 降解后ESPS能使一水草酸钙(COM)晶体数量进一步减少, 晶粒尺寸进一步减小. 当降解ESPS浓度从0.006 g·L-1分别增加到0.010 和0.050 g·L-1时, COM晶体平均尺寸由11.5 μm×2.9 μm分别减小到9.2 μm×2.9μm 和6.0 μm×2.5 μm, 晶体数量由3357 mm-2分别减少到2298和1532 mm-2, COM 的(101)面衍射峰强度I(101)与(010)面对应的(020)衍射峰强度I(020)之比(I(101)/I(020))由5.54 分别增加到16.2 和20.0. 结果显示, 具有小分子量的降解ESPS对草酸钙晶体成核与生长的抑制效果明显优于大分子量的未降解ESPS. 相似文献
78.
79.
Xue-Li Zheng Cong-Ye Zheng Fan-Ding Zhou Hai-Yan Fu Mao-Lin Yuan Rui-Xiang Li Bin Xu Hua Chen 《中国化学快报》2016,27(5):678-680
Rhodium catalyzed hydroformylation of a-methylstyrene was investigated in the presence of monodentate phosphine ligands L1–L6. We found that the phosphine with good p-acceptability could efficiently improve the activity of the a-methylstyrene hydroformylation. The big steric hindrance of a-C in a-methylstyrene enhanced the regioselectivity towards the linear aldehyde, which resulted in3-phenylbutanal as the predominant product(99.0%). When tris(N-pyrrolyl)phosphine(L1) modified Rh(acac)(CO)_2was employed as the catalyst, the TOF could reach up to 5786 h~(-1)in the a-methylstyrene hydroformylation at relatively mild conditions(110 8C, 6 MPa). 相似文献
80.
D-A型共聚物作为有机聚合物太阳能电池的电子给体材料近年来引起广泛关注. 本文以苯并二噻吩(BDT)为电子给体单元, 苯并噻二唑(BT)为电子受体单元来模拟D-A共聚体; 并用噻吩环作为π桥, 构造出D-π-A(PBDT-DTBX, X = O, S, Se, Te)结构. 采用第一性原理的密度泛函理论, 系统地计算相应的电子结构和光吸收谱. 比较不同氧族元素和噻吩π-键桥对聚合物光吸收谱的影响. 研究结果表明: D-A共聚体中当X位元素以O, S, Se, Te 替换时, 其体系的最高占有分子轨道(HOMO)能级变化不大, 最低未占有分子轨道(LUMO)能级逐渐靠近费米能级, 带隙逐渐减小. 在可见光区有两个较强的吸收峰, 随着X位元素原子序数增大, 位于4.0 eV左右的光吸收峰位基本不变, 另一光吸收峰强度明显增大并发生红移. 与D-A结构相比, D-π-A结构的带隙均有所减小, 其中X为Te时带隙最小; 光吸收峰强度随着氧族元素原子序数的增大也明显增大并发生红移. 通过比较光吸收系数和相应态密度, 结果表明, 4.0 eV 左右的光吸收峰主要是BDT单元的贡献, 氧族元素的改变主要影响519.4-703.9 nm范围的光吸收. 相似文献