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951.
The effect of the pristine sodium montmorillonite (Na+-MMT) on the styrene emulsion polymerizations with different concentrations of SDS ([SDS]) was investigated. At constant [SDS], the polymerization rate is faster for the run with 1 wt.% Na+-MMT compared to the counterpart without Na+-MMT. Micelle nucleation predominates in the polymerizations with [SDS] ≧ 13 mM. On the other hand, the contribution of the polymerization associated with the Na+-MMT platelets increases significantly when [SDS] decreases from 13 to 9 mM. At [SDS] (e.g., 2 mM) < CMC, homogeneous nucleation controls the particle formation process and polymerization kinetics. Moreover, the contribution of the Na+-MMT platelets that act as extra reaction loci to the polymerization kinetics is even comparable to the run in the absence of Na+-MMT. The resultant polymer particle size, polymer molecular weight and zeta potential were characterized and a preliminary model was developed to qualitatively study the differences between the polymerizations in the presence and absence of 1 wt.% Na+-MMT. 相似文献
952.
“消障灵”治疗早期老年性白内障疗效研究 总被引:1,自引:0,他引:1
对102例老年性白内障病人服药前后检测血中微量元素及红细胞酶活性.用高锌微量元素的中药内服,观察6个月~2年,结果视力增进70.5%;血锌提高1.6μg/mL(P值<0.001),血红细胞过氧化酶提高4.87IU/gHb(P值<0.001),血红细胞谷胱甘肽还原酶提高4.37IU/gHb(P值<0.001).说明锌对治疗早期老年性白内障有一定临床意义. 相似文献
953.
Huang HS Chiu HF Hwang JM Jen YM Tao CW Lee KY Lai YL 《Chemical & pharmaceutical bulletin》2001,49(10):1346-1348
The synthesis and cytotoxic evaluation of 9-acyloxy 1,8-dichloroanthracene derivatives are described. The system selectively reduces the carbonyl group flanked by the peri substituents of the anthracenediones to give the corresponding 1,8-dichloro-9(10H)-anthracenone. Simple acylation of anthracenone occurred with appropriate acyl chlorides in CH2Cl2 with a catalytic amount of pyridine to give the 9-acyloxy-1,8-dichloroanthracene derivatives. Considerable interest has developed in the mechanism of how anthracenones achieve this desirable selectivity. These compounds were evaluated in vitro for their ability to inhibit the growth of human oral epidermoid carcinoma cells (KB cell line), human cervical carcinoma cells of ME 180 (GBM 8401) and Chinese hamster ovary (CHO) cells, respectively, as compared to mitoxantrone. The in vitro cytotoxicity evaluation of 9-acyloxy 1,8-dichloroanthracenes against these above cell lines revealed for most of the compounds a cytotoxic potency lower than that of mitoxantrone. The most active compounds were thus selected for further in vitro biological evaluation and structural modification. 相似文献
954.
ShuFengZHANG QingLiQIAN PingLaiPAN YiCHEN GuoQingYUAN 《中国化学快报》2005,16(1):100-102
ANd promoted-Rh catalysts supported on polymer-derived carbon beads for vapor-phas emethanol carbonylation was developed. Rh-Nd bimetallic catalysts obviously have higher activity than that of supported Rh catalyst under similar reaction condition. The difference between the activity of above two catalyst systems is clearly caused by the intrinsic properties generated by the introduction of Nd. 相似文献
955.
Kun-Chun Hsieh Chun-Liang Lai Hon Man Lee Shie-Ming Peng 《Journal of organometallic chemistry》2004,689(21):3362-3369
A bis(diethylamido)hafnium compound [C4H3N(CH2NMe2)-2]2Hf(NEt2)2 (1) has been prepared in 79% yield by reacting Hf(NEt2)4 with 2 equiv. of [C4H3NH(CH2NMe2)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt2 bonds to generate [C4H3N(CH2NMe2)-2]2Hf[PhNC(NEt2)O]2 (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C4H3N(CH2NMe2)-2]Hf[PhNC(NEt2)O]3 (3). For comparison, reacting Hf(NEt2)4 with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt2)O]4 (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt2 bonds, which are all partially doubly bonded. 相似文献
956.
Lai‐Cai Li Jing Wang Xin Wang An‐Min Tian Ning‐Bew Wong 《International journal of quantum chemistry》2002,87(5):288-292
Ab initio calculations of the potential energy surface for the F + O3 and Cl + O3 reactions have been performed using the G3 and G3MP2 methods, which optimize the geometry configuration of reactants, products, intermediates, and transition states. The results show that fluorine atoms react with ozone as violently as chlorine atoms. At the same time, we have studied the reaction mechanisms of F atoms and Cl atoms with methane. It is found that fluorine atoms prefer to react with methane and chlorine atoms with ozone when there is competition between ozone and methane. Therefore, we can reasonably explain why chlorine atoms play the main role of reactants depleting ozone, while the more active fluorine atoms deplete less ozone. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/qua.10119 相似文献
957.
A synthetic sequence involving dithiametacyclophane --> metacyclophanediene --> dihydropyrene was employed to prepare trans-10b-methyl-10c-(2-naphthyl)- and trans-10b-methyl-10c-(1-naphthyl)-10b,10c-dihydropyrene 5 and 6, respectively. Both exhibit a strong diamagnetic ring current despite the introduction of an internal bulky substituent within the pi-electron cloud. Their electronic spectra suggest interaction between the two near-perpendicular naphthyl and dihydropyrenyl pi systems, resulting in red shift and band broadening. All naphthyl protons are well resolved in their 1H NMR spectra due to a strong shielding effect of the dihydropyrene ring. The most shielded protons in 5 and 6 are H1' and H2' at delta 2.47 and 1.42, respectively, being 5.25 and 5.95 ppm shifted from those of reference protons. There is evidence for free rotation on the NMR time scale of the 2-naphthyl ring in 5 with a preference for a particular conformer, whereas the 1-naphthyl ring in 6 is conformationally rigid with its H2' projecting deeply into the pi-cloud, thus accounting for the most shielded aromatic proton (H2' in 6) reported to date. 相似文献
958.
Yu-Chin Lai Richard Ozark Edmond T. Quinn 《Journal of polymer science. Part A, Polymer chemistry》1995,33(11):1773-1782
α,ω-Bis(4-hydroxybutyl) polydimethylsiloxane (molecular weight 1500 to 4500) can be pre-pared with well-controlled molecular weight through the reaction of 1,3-bis(4-hydroxybu-tyl)tetramethyl disiloxane and dimethoxydimethyl silane or diethoxydimethyl silane in the presence of a stoichiometric amount of water and hydrochloric acid. The molecular weight of these hydroxybutyl-terminated polysiloxanes can be determined fairly consistently by a titration method. These polysiloxanes are stable toward cyclization. © 1995 John Wiley & Sons, Inc. 相似文献
959.
Development of Photoactivated Fluorescent N‐Hydroxyoxindoles and Their Application for Cell‐Selective Imaging
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Dr. Jinping Lai An Yu Letao Yang Yixiao Zhang Dr. Birju P. Shah Prof. Dr. Ki Bum Lee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(18):6361-6367
Photoactivatable fluorophores are essential tools for studying the dynamic molecular interactions within important biological systems with high spatiotemporal resolution. However, currently developed photoactivatable fluorophores based on conventional dyes have several limitations including reduced photoactivation efficiency, cytotoxicity, large molecular size, and complicated organic synthesis. To overcome these challenges, we herein report a class of photoactivatable fluorescent N‐hydroxyoxindoles formed through the intramolecular photocyclization of substituted o‐nitrophenyl ethanol (ONPE). These oxindole fluorophores afford excellent photoactivation efficiency with ultra‐high fluorescence enhancement (up to 800‐fold) and are small in size. Furthermore, the oxindole derivatives show exceptional biocompatibility by generating water as the only photolytic side product. Moreover, structure–activity relationship analysis clearly revealed the strong correlation between the fluorescent properties and the substituent groups, which can serve as a guideline for the further development of ONPE‐based fluorescent probes with desired photophysical and biological properties. As a proof‐of‐concept, we demonstrated the capability of a new substituted ONPE that has an uncaging wavelength of 365–405 nm and an excitation/emission at 515 and 620 nm, for the selective imaging of a cancer cell line (Hela cells) and a human neural stem cell line (hNSCs). 相似文献
960.
Sulfur Encapsulated in a TiO2‐Anchored Hollow Carbon Nanofiber Hybrid Nanostructure for Lithium–Sulfur Batteries
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Prof. Zhian Zhang Qiang Li Shaofeng Jiang Dr. Kai Zhang Prof. Yanqing Lai Prof. Jie Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1343-1349
A hollow carbon nanofiber hybrid nanostructure anchored with titanium dioxide (HCNF@TiO2) was prepared as a matrix for effective trapping of sulfur and polysulfides as a cathode material for Li–S batteries. The synthesized composites were characterized and examined by X‐ray diffraction, nitrogen adsorption–desorption measurements, field‐emission scanning electron microscopy, scanning transmission electron microscopy, and electrochemical methods such as galvanostatic charge/discharge, rate performance, and electrochemical impedance spectroscopy tests. The obtained HCNF@TiO2–S composite showed a clear core–shell structure with TiO2 nanoparticles coating the surface of the HCNF and sulfur homogeneously distributed in the coating layer. The HCNF@TiO2–S composite exhibited much better electrochemical performance than the HCNF–S composite, which delivered an initial discharge capacity of 1040 mA h g?1 and maintained 650 mAh g?1 after 200 cycles at a 0.5 C rate. The improvements of electrochemical performances might be attributed to the unique hybrid nanostructure of HCNF@TiO2 and good dispersion of sulfur in the HCNF@TiO2–S composite. 相似文献