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991.
992.
A series of M-substituted hexaaluminates LaMAl11O19-δ (M=Fe, Co, Ni, Mn, and Cu)were prepared and characterized by XRD, XPS, TPR and TGA techniques, respectively. They exhibited different reducibility and catalytic activity for partial oxidation of methane (POM) to synthesis gas. Among the LaMAl11O19-δ samples, LaNiAl11O19-δ showed the best catalytic activity for the topic reaction and selectivity for synthesis gas at 780 ℃ for 2 h. The conversion of CH4 was over 99.2%, and the product selectivity for both CO and H2 was above 90.3%. 相似文献
993.
雷公藤的药效及毒性与微量元素的研究 总被引:4,自引:0,他引:4
雷公藤是一种药效大、毒性也大的中药。研究了雷公藤的28种无机元素,发现其有益元素铁、锰、锌、硒含量较高.其有害元素铅、砷、镉含量也较高,与其药效和毒性一一相对应。雷公藤对风湿性关节炎、肾病、肝脏病、皮肤病的疗效.与铁、锰、锌、硒在人体中生物学机理一致。雷公藤对消比道、心血管、肝脏、泌尿系统、造血系统的毒害作用,与铅、砷、镉在人体中的生物学效应一致。所以在使用雷公藤时,应考虑到微量元素作用.可提高雷公藤的疗效,降低其毒性。 相似文献
994.
995.
The molecular species of phosphatidylcholine from freshwater sources (Macrobranchium nipponense and Macrobranchium rosenbergii) and marine sources (Euphausia superba and Penaeus chinesis) were characterized by high-resolution mass spectrometry. The tandem secondary mass spectrometry (MS/MS) fragmentation allowed for the identification of fatty acyl residues of phosphatidylcholine molecular species. (16:0–18:1)Phosphatidylcholine was the main phosphatidylcholine molecular species determined in all shrimp samples, especially in E. superba. Macrobranchium rosenbergii phosphatidylcholine was particularly rich in (16:0–20:5)phosphatidylcholine and (16:0–22:6)phosphatidylcholine. The proportion of the two molecular species was next to the phosphatidylcholine of E. superba. Therefore, M. rosenbergii appears to be a potential freshwater source for the supplementation of polyunsaturated fatty acids, particularly eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). This approach may be used as an efficient method for the identification of natural phosphatidylcholine sources from the broad range of plant, animal, and marine origins. 相似文献
996.
Chao Tian Yuanli Liang Haixia Lin Jie Song Qi Li Rui Li 《Journal of Dispersion Science and Technology》2019,40(6):892-900
A rosin-based ester tertiary amine salt (RETAS) cationic surfactant was obtained using natural rosin as raw material. GC-MS of RETAS was detailed analyzed. The pH-responsive mechanism of rosin-based ester tertiary amine (RETA) and RETAS was confirmed by applying theoretical calculations about electrostatic potential maps of RETA and RETAS cation using Gaussian software. Mixed system surfactants were obtained by blending RETAS cationic surfactant with sodium dodecyl benzene sulfonate (SDBS) anionic surfactant. The binary mixed surfactant systems of RETAS and SDBS had obvious synergistic effect. The γcmc and CMC were 39.40?mN/m and 0.56?mmol/L at the optimum molar fraction of RETAS (α)?=?0.6, respectively. The stability time of emulsion with the optimum mixed system as emulsifier increased to 309?s at α?=?0.6. The emulsifying capacity of RETAS was much better than that of RETA. RETAS had pH-responsive targeted release and the optimum mixed system showed a relatively sustained drug release by using doxorubicin (DOX) as a model drug. These results indicate that RETAS surfactant and mixed system surfactant are both promising for applications in drug delivery and emulsification. 相似文献
997.
Qing Zhang Liangbiao Fan Qiaomei Lu Xiaozhang Yu Meina Liang Jinfang Nie Ningjie Li Lan Zhang 《Journal of separation science》2019,42(16):2687-2695
As signal molecules, auxins play an important role in mediating plant growth. Due to serious interfering substances in plants, it is difficult to accurately detect auxins with traditional solid‐phase extraction methods. To improve the selectivity of sample pretreatment, a novel molecularly imprinted polymer ‐coated solid‐phase microextraction fiber, which could be coupled directly to high‐performance liquid chromatography, was prepared with indole acetic acid as template molecule for the selective extraction of auxins. The factors influencing the polymer formation, such as polymerization solvent, cross‐linker, and polymerization time, were investigated in detail to enhance the performance of indole acetic acid‐molecularly imprinted polymer coating. The morphological and chemical stability of this molecularly imprinted polymer‐coated fiber was characterized by scanning electron microscopy, infrared spectrometry, and thermal analysis. The extraction capacity of the molecularly imprinted polymer‐coated solid‐phase microextraction fiber was evaluated for the selective extraction of indole acetic acid and indole‐3‐pyruvic acid followed by high‐performance liquid chromatography analysis. The linear range for indole acetic acid and indole‐3‐pyruvic acid was 1–100 µg/L and their detection limit was 0.5 µg/L. The method was applied to the simultaneous determination of two auxins in two kinds of tobacco (Nicotiana tabacum L and Nicotiana rustica L) samples, with recoveries range from 82.1 to 120.6%. 相似文献
998.
以SPSS、Origin为主要数据分析工具,对某大学化工学院本科生期末考试成绩进行分析。对降序排列的平均学分绩点一元拟合曲线的残差进行了拟合,对其拟合函数进行求导,发现可以将样本按照20%、50%、30%的比例分为3个集团。通过层次聚类也得到类似的结果。不同集团的学生的学分获得率的组成、标准偏差分布明显不同。重要的专业基础课程在学生学习集团的形成中起到了重要的作用,基于统计结果,建议针对不同集团学生的学习特点应采取相应的差异化教学策略。 相似文献
999.
Xiao-Jing Lv Li-Bin Xu Liang Qian Yuan-Yuan Yang Zhi-Yi Xu Jin Li Cheng Zhang 《高分子科学》2021,39(5):537-544
An imidazolium-based ionic liquid(IL) modified triphenylamine derivative,namely 1-(4-((4-(diphenylamino)benzoyl) oxy)butyl)-3-methyl imidazole tetrafluoroborate(TPAC_6 IL-BF_4),was designed and synthesized,and further applied with 3,4-ethylene dioxythiophene(EDOT)to prepare conjugated copolymer P(EDOT:TPAC_6 IL-BF_4) via electrochemical polymerization.The cyclic voltammetry curves show that the copolymer P(EDOT:TPAC_6 IL-BF_4) possesses two pairs of redox peaks,which should be ascribed to the redox behaviors of EDOT and triphenylamine.The ultraviolet-visible(UV-Vis) absorption spectrum of P(EDOT:TPAC_6 IL-BF_4) exhibits one maximum absorption peak at 580 nm and a small shoulder characteristic peak at 385 nm under neutral state which are assigned to π-π~* conjugated structure of EDOT and triphenylamine.After being applied at the positive voltage,the copolymer color changes from dark blue to light blue,which is close to the color of poly(3,4-ethylenedioxythiophene)(PEDOT).Surprisingly,the copolymer P(EDOT:TPAC_6 IL-BF_4) shows shorter switching time of 0.37 s,0.30 s at 580 nm and 0.38 s,0.45 s at 1100 nm compared with PEDOT.It is more intriguing that the copolymer P(EDOT:TPAC_6 IL-BF_4) exhibits electrochromism even in free supporting electrolyte.The results confirm that the existence of imidazolium-based ionic liquid has an improvement on the ion diffusion properties and the switching time of conjugated polymer,which may provide a potential direction for the preparation of high-performance electrochromic materials. 相似文献
1000.
研究了金属有机骨架化合物NH2-Ga-MIL-53对多种N-苯基亚胺底物的Strecker反应的催化性能,研究结果表明:(1)NH2-Ga-MIL-53具有高度催化活性和良好的底物普适性;(2)亚胺底物上取代基的电子效应是影响催化反应速率的关键因素,在亚胺底物上引入给电子取代基团(如甲氧基和苯基)可以加快反应速率,引入吸电子取代基团(如三氟甲基和硝基)可降低反应速率;(3)亚胺底物上取代基的位置对于催化反应速率同样具有重要影响,在亚胺底物的邻位引入甲氧基取代基团时,反应速率加快得最明显;(4)作为非均相催化剂,NH2-Ga-MIL-53可循环使用9次而不失活且保持骨架结构不变;(5)NH2-Ga-MIL-53和Ga-MIL-53催化性能的对比结果表明,NH2-Ga-MIL-53结构中的氨基可以作为路易斯碱活性中心协同路易斯酸催化中心(Ga3+)有效促进strecker反应的进行。此外,由NH2-Ga-MIL-53、六水合硝酸镓和2-氨基对苯二甲酸对Strecker反应的催化效果的对比可知,NH2-Ga-MIL-53的孔结构是提高反应产物专一性的重要因素。 相似文献