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931.
A new approach to isoprostanes and neuroprostanes featuring cis-dialkyl stereochemistry at the cyclopentane ring has been developed by employing an intramolecular cross-coupling reaction of an alkyl iodide and a tethered alkenylsiloxane for stereoselective installation of a functionalized omega-side chain. 相似文献
932.
Kun Lu Ju Huang Li Ren Chao Li Yejun Guan Bingwen Hu Hao Xu Jingang Jiang Yanhang Ma Peng Wu 《Angewandte Chemie (International ed. in English)》2020,59(15):6258-6262
Precisely controlled crystal growth endows zeolites with special textural and catalytic properties. A nanosheet mordenite zeolite with a thickness of ca. 11 nm, named as MOR‐NS, has been prepared using a well‐designed gemini‐type amphiphilic surfactant as bifunctional structure‐directing agent (SDA). Its benzyl diquarternary ammonium cations structurally directed the formation of MOR topology, whereas the long and hydrophobic hexadecyl tailing group prevented the extensive crystal growth along b axis. This kind of orientated crystallization took place through the inorganic–organic interaction between silica species and SDA molecules present in the whole process. The thin MOR nanosheets, with highly exposed (010) planes and 8‐membered ring (MR) windows, exhibited a much improved ethylene selectivity (42.1 %) for methanol‐to‐olefin (MTO) reactions when compared with conventional bulk MOR crystals (3.3 %). 相似文献
933.
Kun Meng Xia Dong Xiaohua Zhang Chenggui Zhang Charles C. Han 《Macromolecular rapid communications》2006,27(19):1677-1683
Summary: Shear‐induced crystallization in a blend of isotactic poly(propylene) and poly(ethylene‐co‐octene) (iPP/PEOc) has been investigated by means of in‐situ optical microscopy and a shear hot stage under various thermal and shear histories. Cylindrites are observed after shear in the phase‐separated iPP/PEOc blends for the first time. The nuclei (shish) come from the orientation of the entangled network chains, and the relationship between the shear rate and the network relaxation time of the oriented iPP chains is a very important factor that dominates the formation of the cylindrites after liquid‐liquid phase separation. The cylindrites can grow through phase‐separated domains with proper shear rate and shear time. In addition, the number of spherulites increases with shear rate, which is consistent with the notion of fluctuation‐induced nucleation/crystallization.
934.
采用分光光度法研究了电子给体苯巴比妥钠与π电子受体茜素红的荷移反应,建立了荷移分光光度法测定苯巴比妥钠的方法。在水溶液中,苯巴比妥钠与茜素红荷移络合物的最大吸收波长为530 nm,该络合物的组成为1∶1,表观摩尔吸光系数ε为4.43×103L.mol-1.cm-1,稳定常数为2.30×105。药物质量浓度在5~40 mg/L范围内符合比尔定律,相关系数为0.9996。当苯巴比妥钠浓度为20 mg/L时,10次测定结果的相对标准偏差为1.3%。测定了针剂中的苯巴比妥钠,加标回收率在98.9%~105%之间。 相似文献
935.
Easy deposition of Ag onto polystyrene beads for developing surface-enhanced-Raman-scattering-based molecular sensors 总被引:1,自引:0,他引:1
We describe a very simple electroless plating method that can be used to prepare Ag-coated polystyrene beads. Robust Ag nanostructures are reproducibly fabricated by soaking polystyrene beads in ethanolic solutions of AgNO(3) and butylamine. When the molar ratio of butylamine to AgNO(3) is far below 1.0, distinct nanosized Ag particles are formed on the polystyrene beads, but by increasing the amount of butylamine, network-like Ag nanostructures are formed that possess very broad UV/vis absorption characteristics extending from the near-UV to near-infrared regions. In conformity with the UV/vis absorption characteristics, the Ag-deposited polystyrene beads were highly efficient surface-enhanced Raman scattering (SERS) substrates, with an enhancement factor estimated using 4-aminobenzenethiol (4-ABT) as a model adsorbate to be larger than 1.1x10(6). On the basis of the nature of the SERS peaks of 4-ABT, those Ag-deposited polystyrene beads were confirmed, after attaching biotin groups over 4-ABT, to selectively recognize streptavidin molecules down to concentrations of 10(-11) g mL(-1) (i.e., approximately 0.2 pM). Since a number of different molecules can be used as SERS-marker molecules (such as 4-ABT), multiple bioassays are readily accomplished via SERS after attaching appropriate host or guest molecules onto them. 相似文献
936.
LI Zhi-Feng ZHU Yuan-Cheng YUAN Kun KANG Jing-Wan 《结构化学》2008,27(1):63-69
The structures of 2,7'-(ethylene)-bis-8-hydroxyquinoline and its derivatives were optimized at the ground states using ab initio HF and B3LYP methods. At the same time, the molecular structures of the first singlet excited state for 2,7'-(ethylene)-bis-8-hydroxyqulnoline and its derivatives were optimized by CIS/6-31G(d). The absorption and emission spectra based on the above structures were obtained by the time-dependent density functional theory (TD-DFT) by the B3LYP method with the 6-31G(d) basis set. The calculated results of luminescence originate from the electronic transition from the hydroxphenol ring of 8-hydroxyquinoline A to the pyridine ring of 8-hydroxyquinoline B. Their luminescence wave bands can be tuned by different substituents on the ligand of 8-hydroxyquinoline. 相似文献
937.
2,5-二取代-1,3,4-噻二唑衍生物的一锅法合成、结构表征及生物活性研究 总被引:4,自引:0,他引:4
采用超声波辐射与相转移催化联用技术, 一锅法合成出了8个新的2-(1-萘乙酰氨基)-5-芳氨甲基-1,3,4-噻二唑化合物, 这种合成方法具有反应条件温和、反应时间较短、产率较高等特点. 新化合物的结构利用IR, 1H NMR, 13C NMR, 1D NOE, MS和元素分析进行了表征. 人环氧酶-2 (COX-2)活性抑制实验结果表明, 目标化合物5f对COX-2具有很强的抑制活性, 抑制率高达95.59%; 化合物5g对COX-2也具有一定的抑制活性. 目标化合物无抗惊厥活性. 相似文献
938.
Hong SS Lee SA Han XH Lee MH Hwang JS Park JS Oh KW Han K Lee MK Lee H Kim W Lee D Hwang BY 《Chemical & pharmaceutical bulletin》2008,56(2):199-202
Two new melampolide-type sesquiterpene lactones, 8beta-epoxyangeloyloxy-9alpha-ethoxy-14-oxo-acanthospermolide (1) and 8beta-angeloyloxy-9alpha-ethoxy-14-oxo-acanthospermolide (2), were isolated from the leaves of yacon [Smallanthus sonchifolia (POEPP. et ENDL.) H. Robinson] along with eleven known melampolides, allo-schkuhriolide (3), enhydrin (4), polymatin A (5), fluctuanin (6), 8beta-angeloyloxy-9alpha-acetoxy-14-oxo-acanthospermolide (7), 8beta-angeloyloxy-14-oxo-acanthospermolide (8), 8beta-methacryloyloxymelampolid-14-oic acid methyl ester (9), uvedalin (10), polymatin B (11), 8beta-tigloyloxymelampolid-14-oic acid methyl ester (12), and sonchifolin (13). Their structures were established on the basis of spectroscopic evidence including 1D- and 2D-NMR experiments. All isolates were evaluated for inhibition of LPS-induced nitric oxide production in murine macrophage RAW 264.7 cells. 相似文献
939.
通过丙烯酰胺(AM),丙烯酸(AA),烯丙醇聚氧乙烯醚(APEG)和N,N-二烯丙基苄胺(NANB)制备共聚物P(AM/AA/APEG/NANB)。确定了最佳反应条件:m(AM)∶m(AA)=6.5∶3,APEG为5 wt%,NANB加量0.2 wt%,pH为7,反应温度40℃,引发剂0.4 wt%。通过IR和1H NMR确定了聚合物的分子结构,并对其进行性能测试。结果表明:2000 mg·L-1的AM/AA/APEG/NANB溶液具有较好的流变性能(120℃,粘度保留率:38.56%;1000 s-1,粘度保留率:17.93%)和抗盐性能(20 000 mg·L-1Na Cl,2000 mg·L-1Mg Cl2或Ca Cl2,粘度保留率分别为22.14%、18.34%和15.33%),且提高采收率可达16.12%。 相似文献
940.