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排序方式: 共有284条查询结果,搜索用时 31 毫秒
71.
Pin Gao Yanfang Zhang Guangsu Huang Mengmeng Chen Jing Zheng 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(2):142-147
The multi-hydroxymethyl structure of resol makes it suitable for connecting two or more polyacrylamide chains as a crosslinker in oil recovery applications, but control of the structure and composition of the resol, whether in practice or theory, is still a controversial problem. In the present research, a series of resol prepolymers synthesized with different amounts and types of catalysts, formaldehyde to phenol molar ratio, reaction temperature and charging steps were characterized by high-performance liquid chromatography. It is found that the compositions of the resols barely changed with almost all the varying conditions, but the contents of each component were greatly affected by the variation of reaction conditions. Finally, the best conditions for preparing resol crosslinker were obtained. 相似文献
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Three‐Dimensional Multilayer Assemblies of MoS2/Reduced Graphene Oxide for High‐Performance Lithium Ion Batteries 下载免费PDF全文
Geng Liu Yiyu Feng Yu Li Mengmeng Qin Haoran An Wenping Hu Wei Feng 《Particle & Particle Systems Characterization》2015,32(4):489-497
Three‐dimensional (3D) multilayer molybdenum disulfide (MoS2)/reduced graphene oxide (RGO) nanocomposites are prepared by a solution‐processed self‐assembly based on the interaction using different sizes of MoS2 and GO nanosheets followed by in situ chemical reduction. 3D multilayer assemblies with MoS2 wrapped by large RGO nanosheets and good interface are observed by transmission electron microscopy. The interaction of Na+ ions with oxygen‐containing groups of GO is also investigated. The measurement of lithium ion batteries (LIBs) shows that MoS2/RGO anode nanocomposite with a weight ratio of MoS2 to GO of 3:1 exhibits an excellent rate performance of 750 mAh g?1 at 3 A g?1 outperforming many previous studies and a high reversible capacity up to ≈1180 mAh g?1 after 80 cycles at 100 mA g?1. Good rate performance and high capacity of MoS2/RGO with 3D unique layered‐structures are attributed to the combined effects of continuous conductive networks of RGO, good interface facilitating charge transfer, and strong RGO sheets preventing the volume expansion. Results indicate that 3D multilayer MoS2/RGO prepared by a facile solution‐processed assembly can be developed to be an excellent nanoarchitecture for high‐performance LIBs. 相似文献
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Andrei V. Churakov Elmira Kh. Lermontova Kirill V. Zaitsev Mengmeng Huang Sergey S. Karlov Galina S. Zaitseva Judith A. K. Howard 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(11):o587-o592
Four distinct hydrogen‐bonding topologies were observed in the structures of six diethanolamine ligands. These compounds are (1R*,2R*)‐2‐[(2‐hydroxyethyl)(methyl)amino]‐1,2‐diphenylethanol, C17H21NO2, (I), 1‐[(2S)‐2‐(hydroxydiphenylmethyl)pyrrolidin‐1‐yl]‐2‐methylpropan‐2‐ol, C21H27NO2, (II), 2‐[(2‐hydroxyethyl)(methyl)amino]‐1,1‐diphenylethanol, C17H21NO2, (III), 1‐{(2‐hydroxy‐2‐methylpropyl)[(1S)‐1‐phenylethyl]amino}‐2‐methylpropan‐2‐ol, C16H27NO2, (IV), 1‐{[(2R)‐2‐hydroxy‐2‐phenylethyl][(1S)‐1‐phenylethyl]amino}‐2‐methylpropan‐2‐ol, C20H27NO2, (V), and (1R*,2S*)‐2‐[(2‐hydroxyethyl)(methyl)amino]‐1,2‐diphenylethanol, C17H21NO2, (VI). In each compound, all `active' hydroxy H atoms are engaged in hydrogen bonding, but the N atoms are not involved in intermolecular hydrogen bonding. In the structures of (I), (II) and (IV)–(VI), molecules are linked into chains by intermolecular O—H...O interactions. These chains are organized in such a way as to hide the hydrophilic groups inside, and so the outer surfaces of the chains are hydrophobic. The structure of (VI) contains two distinct non‐equivalent systems of intermolecular O—H...O hydrogen bonds formed by disordered hydroxy H atoms. 相似文献
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AbstractIn Dedekind-finite ring, we present the group inverse of sum of two group invertible elements under different conditions. Then, the core inverse of a sum of two core invertible elements is investigated. Furthermore, the core inverse of the difference of two core invertible elements is presented. These results generalized the corresponding results of complex matrices. 相似文献
78.
H. Mengmeng S. S. Karlov M. V. Zabalov K. V. Zaitsev D. A. Lemenovskii G. S. Zaitseva 《Russian Chemical Bulletin》2009,58(8):1576-1580
Geometries of 20 germylenes and 18 stannylenes based on dialkanolamines, diethylenetriamines, and related compounds were optimized
by the DFT method. It was found that the most of the germylenes and stannylenes studied are more stable as dimeric structures
of different types. The dimerization is possible due to either additional Ge-O(N) interactions or Ge-Ge bonding. The factors
leading to the stabilzation of one or another isomer are examined. 相似文献
79.
为了观察宫腔粘连患者行三维经阴道超声(3D-TVS)检查时宫腔容积及血流的变化,本文纳入2016年11月~2018年11月于我院收治的68例宫腔粘连患者为观察组,另选取同期来我院体检的健康女性68例为对照组,均于月经周期中晚期行3D-TVS检查,并以病理诊断结果为金标准,观察了3D-TVS诊断宫腔粘连的灵敏度及特异度。同时,对比了两组患者3D-TVS参数如子宫内膜容积(EV)、血流指数(FI)、血管血流指数(VFI)及内膜区血管指数(VI)的变化,并分析了宫腔粘连不同分级患者上述3D-TVS参数的变化情况。经病理确诊的68例患者中,3D-TVS诊断为宫腔粘连64例,其中Ⅰ型21例,Ⅱ型31例,Ⅲ型9例,Ⅳ型3例。3D-TVS诊断宫腔粘连的灵敏度为92.65%,特异度为98.53%,准确率为95.59%,阳性预测值为98.44%,阴性预测值为93.06%,Kappa值为0.91。观察组EV、FI、VFI、VI均显著低于对照组。Ⅰ型宫腔粘连者EV显著大于Ⅱ、Ⅲ、Ⅳ型者,Ⅱ型宫腔粘连者EV显著大于Ⅲ、Ⅳ型者,Ⅲ型宫腔粘连者EV显著大于Ⅳ型者;Ⅰ型宫腔粘连者的VFI、VI显著大于Ⅲ、Ⅳ型者。上述结果证实3D-TVS对宫腔粘连患者宫腔容积及血流变化具有重要的评估价值。 相似文献
80.
Dongsheng Xue Mengmeng Xu Chaoying Zheng Baochao Yang Min Hou Haibing He Shuanhu Gao 《中国化学》2019,37(2):135-139
A titanium‐promoted intramolecular photoenolization/Diels–Alder (PEDA) reaction was developed to construct the core skeleton of aromatic polycyclic terpenoids bearing an all‐carbon quaternary center on the benzylic position. Titanium(IV) isopropoxide [Ti(Oi‐Pr)4] plays a key role during the photo cycloaddition, which may help to accelerate the interaction between dienophile and the stereo‐hindered diene species as well as control the diastereoselectivity. This photolysis provides a new solution for the stereospecific formation core structures of aromatic abietane diterpenoids and sesquiterpenoids, which have multiple functional groups for the further transformations. As a synthetic application, it was successfully used in the synthesis of indolosesquiterpenoid mycoleptodiscin A. 相似文献