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排序方式: 共有910条查询结果,搜索用时 31 毫秒
31.
Pei‐Hong Ni Qi‐Sheng Pan Liu‐Sheng Zha Chang‐Chun Wang Abdelhamid Elaïssari Shou‐Kuan Fu 《Journal of polymer science. Part A, Polymer chemistry》2002,40(4):624-631
A novel, near‐monodisperse, well‐defined ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(propylene oxide)‐b‐poly[2‐(dimethylamino)ethyl methacrylate], was synthesized via oxyanion‐initiated polymerization. The initiator was a telechelic‐type potassium alcoholate prepared from poly(propylene glycol) and KH in dry tetrahydrofuran. The copolymers produced were characterized by Fourier transform infrared, 1H NMR, and gel permeation chromatography (GPC). GPC and 1H NMR analyses showed that the products obtained were the desired copolymers, with narrow molecular weight distributions (ca. 1.09–1.11) very close to that of the original poly(propylene glycol). 1H NMR, surface tension measurements, and dynamic light scattering all indicated that the triblock copolymer led to interesting aqueous solution behaviors, including temperature‐induced micellization and very high surface activity. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 624–631, 2002; DOI 10.1002/pola.10144 相似文献
32.
Huang WL Cui SH Liang KM Gu SR Yuan ZF 《Journal of colloid and interface science》2002,246(1):129-134
Silica xerogels were prepared by thermal drying wet gels in an electric oven (70 degrees C) after certain duration of ambient drying, and the relevant effect is investigated on the mesopore structures and surface fractal dimensions of the resultant xerogels. The silica gels were derived from a hydrochloric acid-catalyzed TEOS (tetraethylorthaosilicate) system, and both magnetic stirring and ultrasonic vibration were adopted during sol preparation. The percentage mesoporosity and surface fractal dimensions are evaluated using image analysis methods, based on FE-SEM (field emission gun-scanning electron microscopy) images. The results show that the mesoporosity of the resultant xerogels decreases with the duration of ambient drying for samples prepared using magnetic stirring and low-intensity ultrasonic vibration, while samples subjected to high-intensity ultrasound show a somewhat reverse trend. Samples prepared with magnetic stirring have almost constant surface fractal dimensions (nearly 3), irrespective of the ambient drying before thermal drying. The surface fractal dimensions of samples prepared using ultrasound increase with the duration of ambient drying. 相似文献
33.
ZiYunLI XinSUN QiangXIAO ShouHeXIANG 《中国化学快报》2005,16(1):115-118
Catalytic properties of ZSM-5 zeolite samples pretreated with NaOH solution have been investigated. The samples are characterized by XRD, SEM, chemical analysis, and N2 adsorption.The results indicate that mesopores are created in ZSM-5 crystals under alkali treatment without change the microporous structure and acidic strength of the zeolite, but the crystallinity is greatly decreased under severe treatment. IR indicates that the concentration of silanol is greatly enriched by alkali treatment. The etherification activities of ZSM-5 zeolites are greatly increased byalkali-treatment. The noticeably improved catalytic activity of treated samples is ascribed to the formation of mesopores and greatly enriched silanol group. 相似文献
34.
A highly rigid diamine monomer derived from naturally occurring myo‐inositol and its use for polyamide synthesis
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Atsushi Sudo Shou Sugita 《Journal of polymer science. Part A, Polymer chemistry》2016,54(21):3436-3443
A rigid diamine was synthesized from myo‐inositol, a naturally occurring cyclic hexaol, and used as a monomer to synthesize polyamides. myo‐Inositol was treated with 1,1‐dimethoxycyclohexane to yield a bisketal bearing two hydroxyl groups, and from this bisketal, the target diamine was synthesized in three steps: (1) derivation of the diol into the corresponding bistriflate, (2) nucleophilic substitution of the bistriflate with sodium azide yielding a diazide, and (3) reduction of the diazide to the target diamine. The target diamine readily underwent polycondensation with dicarboxylic acid chloride in solution. The resulting polyamides, whose main chain inherited the rigid 5‐6‐5 system from the diamine monomers, have high glass transition temperatures. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3436–3443 相似文献
35.
Chang Shou Lin 《偏微分方程通讯》2013,38(14):1515-1538
We use elementary methods to prove a sufficient and necessary condition for a Sobolev interpolation inequalities with weight [ILLM0001] where [ILLM0001] are real numbers, and [ILLM0001] 相似文献
36.
37.
Jørgen Hoffmann-Jørgensen Yu Miao Xiao Chun Li Shou Fang Xu 《Journal of Theoretical Probability》2016,29(1):32-47
In this paper, we establish the analogue of Kolmogorov-type law of the logarithm for an array of independent random variables. The main methods are to develop the classic Bernstein’s and Kolmogorov’s inequality and replace the boundedness condition by conditions on the cumulant transform. 相似文献
38.
Ruliang Xie Ting Zhang Qianfei Zhao Tao Zhang Xiangdong Mei Huizhu Yuan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1095-1103
Abstract A series of novel symmetric S,S′-2,2′-(ethane-1,2-diylbis(azanediyl)) bis(2-oxoethane-2,1-diyl) O,O,O′,O′-tetraethyl diphosphorodithioate derivatives (12) was designed and synthesized based on the cluster effect and the multiple binding sites of acetylcholinesterase (AChE). The structures of all the newly synthesized title compounds were characterized by 1 H and 13 C NMR as well as elemental analyses. Their inhibitory activities against AChE were tested, and compound 12b exhibited the best activity (6.60-fold higher than ethion). The results suggested that the compound would bind to the catalytic center and the narrow gorge of the AChE simultaneously. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional table. 相似文献
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40.
αB‐crystalin, a small heat shock protein and a component of α‐crystalin, is a molecular chaperone playing an important role in preventing the formation of cataracts. It has been reported that His18 is an important site for Cu2+ to bind with to form a stable metal complex and thus to enhance this chaperone‐like activity of human αB‐crystalin. In this work, we used site‐directed mutagenesis to clone and express H18G rat lens αB‐crystalin in order to investigate the role of His18 in chaperoning activity. We found that 1 mM of Cu2+, or Zn2+, rather than Mg2+, significantly enhanced the chaperone‐like activity of wild type αB‐crystalin. Whereas, it is Zn2+ and Mg2+, not Cu2+, that significantly reduced this activity of H18G αB‐crystalin. In the absence of cation, H18G showed better activity compared to the wild type αB‐crystalin. ANS fluorescence measurement showed there was no linear relationship between chaperone‐like activity and surface hydrophobicity, indicating that surface hydrophobicity is not a prerequisite for chaperone‐like activity. An HPLC size‐exclusion chromatography study showed that in the presence of metal ions, wild type αB‐crystalin tended to aggregate via dissociation and re‐association into a high molecular aggregate with a molecular weight higher than 1400 kDa and then precipitated, suggesting that the presence of metal ions is a factor leading to the formation of cataracts. Both the near and far UV‐CD spectra suggested that the wild type αB‐crystalin reflected more β‐sheet structural characteristics; whereas the H18G reflected more random coil characteristics. The H18G induced structural alterations as to develop more random coil characteristics and more micro‐environmental changes around the tryptophan residues. This work suggested that His18 may not be a crucial binding site for Cu2+, but rather that it may be an important binding site for Zn2+ in terms of chaperone‐like activity and the process of metal induced self‐aggregation is prerequisite for chaperone‐like activity to occur. 相似文献