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81.
超共轭效应是基础有机化学教学中的一个重要知识点,是基团诱导效应和共轭效应的补充和发展。本文通过基础有机化学教学中的常见实例,分析和阐述了多种超共轭效应对有机化合物及中间体结构稳定性和相对反应性的贡献。 相似文献
82.
粉煤灰在环境材料中利用的研究进展 总被引:1,自引:0,他引:1
能源转化的燃煤过程产生大量粉煤灰,其资源化利用不但减少环境污染而且提高经济效益,已成为人们研究的热点。本文综述了粉煤灰作为吸附剂在去除烟气NOx、SOx、汞、有机芳烃和污水中重金属离子、磷和氟离子以及有机化合物中的应用。粉煤灰中未燃尽的炭在吸附过程中起重要作用。粉煤灰合成沸石控制污染物是粉煤灰在环境材料方面利用的发展方向。基于"以废治污"科学理念,提出了利用粉煤灰制备DeNOx添加剂降低流化催化裂化(FCC)再生过程NOx排放新工艺,开辟粉煤灰资源化利用新途径,同时为FCC再生过程NOx污染物控制技术提供理论支持。 相似文献
83.
For a general evolution equation with a Silnikov homoclinic orbit, Smale horseshoes are constructed with the tools of [1] and in the same way as in [1]. The linear part of the evolution equation has a finite number of unstable modes. For evolution equations with infinitely many linearly unstable modes, the problem is still open. 相似文献
84.
Allenephosphoramides were prepared from propargyl alcohols and diethyl arylphosphoramides using Yb(OTf)(3) as catalyst. In the presence of iodine, 4,9-dihydro-2H-benzo[f]isoindole derivatives could be efficiently constructed from the same two starting materials in a single step. 相似文献
85.
Polysubstituted pyrroles are regiospecifically synthesized via the copper-catalyzed three-component reaction of α-diazoketones, nitroalkenes, and amines under aerobic conditions. The cascade process involves an N-H insertion of carbene, a copper-catalyzed oxidative dehydrogenation of amine, and a [3 + 2] cycloaddition of azomethine ylide. 相似文献
86.
Shuo Li Xiantao Wei Kaimo Deng Xiuna Tian Yanguang Qin Yonghu Chen Min Yin 《Current Applied Physics》2013,13(7):1288-1291
The white light-emitting diode has recently attracted great attention as a promising candidate for next generation lighting. The solid solution of Sr1.80Eu0.10Li0.10MgMoxW1?xO6 was synthesized via high-temperature solid-state reaction and this solid solution is treated as a promising red emitting phosphor for white light-emitting diodes. In our cases, the X-ray diffraction, excitation spectra, emission spectra and decay curves of these solid solutions were measured as a function of the Mo/W ratio to characterize the structural and luminescent properties. The excitation bands of the series of phosphors are consistent well with the region of near ultraviolet light, and the phosphors present better color purity than the commercial phosphor Y2O2S:Eu3+ in current use. Taking these properties into consideration, this kind of material may find a great potential application as a red phosphor for near-ultraviolet excited white light-emitting diodes. 相似文献
87.
An efficient and highly regioselective synthesis of 2-amino-3-arylindoles via the BF3-promoted reaction of 3-diazoindolin-2-imines with aryl aldehydes is described. This reaction could be carried out under mild reaction conditions with a broad scope of substrates. Moreover, the operation is of practical usage and could be scaled up. 相似文献
88.
89.
Haiyong Chen Hongliang Lu Yanguang Nie Jiahua Zhang Mingzhe Zhang Quanqin Dai Shiyong Gao Shihai Kan Dongmei Li Guangtian Zou 《Physics letters. A》2007
We have fabricated sharp-tipped Te nanowires on a NaNO2 nanoparticles substrate by vapor deposition method. These nanowires are parallel or perpendicular to c-axis of hexagonal Te depending on the source temperature. We think the sharp-tip can efficiently reduce the energy of adsorbed atoms, leading to favorable growth along its direction. 相似文献
90.
Water-soluble non-structural carbohydrates (NSC) in the needles of Norway spruce Picea abies [L.] Karst have been studied by using a combination of several separation techniques, having various detectors, with mass spectrometry. The intent was to find a suitable methodology that enables the characterization and determination of NSC, covering a wide range of molar masses, and being suitable to assess how NCS are influenced by both external conditions, e.g. different carbon dioxide (CO(2)) concentrations, light intensity, and by internal conditions such as the needle age. The techniques were liquid-liquid extraction, high performance liquid chromatography (HPLC), size exclusion chromatography (SEC), asymmetrical flow field-flow fractionation (AsFlFFF), electrospray ionization mass spectrometry (ESI-MS), and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). NSC were extracted by a methanol/chloroform/water mixture into the water-rich phase. Application of AsFlFFF and SEC, using refractive index (RI) and multi-angle light scattering (MALS) detectors to the water-rich extracts resulted in three or four main fractions covering molar masses from 10(3) to 10(6)g/mol. Individual fractions collected from SEC were directly subjected to both MALDI and ESI-MS analysis in order to identify NSC. MALDI mass spectra confirmed the presence of hexose oligomers in individual fractions while ESI-MS was used for evaluation of low mass NSC. HPLC-RI was used for quantification of NSC and predominant carbohydrates were found to be fructose, glucose, and sucrose. The changes in their content during seasonal course were studied in detail. HPLC coupled to ESI-MS enabled the identification of low concentration NSC like raffinose that occurred in the needles of autumn samplings. An influence of the increased CO(2) concentration on sucrose and glucose accumulation was observed and it was found that the light intensity as well as the needle age has significant influence on the sucrose content. 相似文献