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171.
172.
Jiahuan Yuan Li Li Zhichen Cai Nan Wu Cuihua Chen Shengxin Yin Shengjin Liu Wenxin Wang Yuqi Mei Lifang Wei Xunhong Liu Lisi Zou Haijie Chen 《Molecules (Basel, Switzerland)》2021,26(21)
Taxilli Herba (TH) is a well-known traditional Chinese medicine (TCM) with a wide range of clinical application. However, there is a lack of comprehensive research on its chemical composition in recent years. At the same time, Taxillus chinensis (DC) Danser is a semi parasitic plant with abundant hosts, and its chemical constituents varies due to hosts. In this study, the characterization of chemical constituents in TH was analyzed by ultra-fast liquid chromatography coupled with triple quadrupole-time of flight tandem mass spectrometry (UFLC-Triple TOF-MS/MS). Moreover, partial least squares discriminant analysis (PLS-DA) was applied to reveal the differential constituents in TH from different hosts based on the qualitative information of the chemical constituents. Results showed that 73 constituents in TH were identified or tentatively presumed, including flavonoids, phenolic acids and glycosides, and others; meanwhile, the fragmentation pathways of different types of compounds were preliminarily deduced by the fragmentation behavior of the major constituents. In addition, 23 differential characteristic constituents were screened based on variable importance in projection (VIP) and p-value. Among them, quercetin 3-O-β-D-glucuronide, quercitrin and hyperoside were common differential constituents. Our research will contribute to comprehensive evaluation and intrinsic quality control of TH, and provide a scientific basis for the variety identification of medicinal materials from different hosts. 相似文献
173.
在气相色谱分析中,通常采用相对保留值和Kovats保留指数作为化学物质的定性参数。相对保留值在使用中受到参考标准不一致的限制而难于推广,况且柱温对相对保留值的影响很大,其重现性还受到待鉴定物与参考标准保留值差距大小的影响。只有在待鉴定物与参考标准的保留值差距不大时,相对保留值才可靠。 相似文献
174.
新型光催化剂的研制是光驱动下CO2转化为高附加值化学品或燃料的核心问题,对实现“碳达峰·碳中和”目标具有重要意义。本文通过乙二胺四乙酸(EDTA)辅助水热法合成一系列新型Bi-Y-O光催化剂体系,发现样品的晶体结构随EDTA的添加量不同而发生变化。添加0.4 g EDTA或未添加EDTA时均可得到BiYO3晶体,而添加0.8 g和1.2 g EDTA时分别制得Bi1.46Y0.54O3和Bi3YO6晶体。光催化CO2还原性能测试结果表明,添加0.4 g EDTA制备的BiYO3具有最佳光催化CO2还原活性,其CO产率为18.29 μmol·g-1·h-1,且3次循环使用后CO产率仍达17.32 μmol·g-1·h-1,明显高于其他样品。结合表征结果分析可知:EDTA的引入不仅可调控BiYO3的结构形貌,而且拓宽其光响应范围、提高光生电子-空穴的分离效率,从而增强光催化还原CO2性能,为新型高效B-Y-O光催化体系的研究提供基础科学数据。 相似文献
175.
176.
Liu Qi Lai Lifang Huang Hexiang Sun Jianhua Shang Tongming Zhou Quanfa Xu Zheng 《中国化学》2010,28(4):537-542
For developing new excellent electrocatalysts toward methanol and oxygen, branched Au nanocrystals have been prepared in high yield by the reaction of HAuCl4 and sodium diphenylamine‐4‐sulfonate in the presence of PEG (polyethylene glycol) at room temperature. When the amount of PEG was in the range of 1–3 mL, branched Au nanocrystals were all obtained, and the amounts of sodium diphenylamine‐4‐sulfonate and HAuCl4 had no obvious effect on the morphology of gold nanocrystals. PEG molecules play an important role in the formation of branched gold nanocrystals. The nanocrystals were characterized by transmission electron microscopy (TEM), selected area electron diffraction, high‐resolution transmission electron microscopy (HRTEM) and UV‐Vis absorption spectrum. HRTEM research suggests that the tips of gold nanocrystals grow selectively in the [111] directions. The UV‐Vis absorption spectrum displays two‐separated surface plasmon resonance peaks. 相似文献
177.
Fujun Zhang Zheng Xu Xiaojun Liu Suling Zhao Lifang Lu Yongsheng Wang Xurong Xu 《Superlattices and Microstructures》2009,45(6):612-617
Pentacene (C22H14) thin films with different thicknesses were fabricated to study the dynamic growth process and morphology of pentacene on different substrates. A discontinuous monomolecular layer was observed when a pentacene thin film is about 0.5 nm thick on native oxide silicon wafer. The terraced islands and dendritic structure gradually formed with increasing pentacene thin film thickness. The height of each layer is about 1.4 nm which corresponds well with the length of the long axis of the pentacene molecule at 1.45 nm. Experimental results show that the pentacene molecule is perpendicular to the silicon wafer surface with a slight tilted angle. However, the pentacene molecular orientation on a polymer pre-covered indium tin oxide coated substrate could not give any indication on the scale of nanometers. The surface roughness of substrates strongly influences pentacene molecular diffusion and the morphology of pentacene thin films. 相似文献
178.
根据矩阵分解性质及原子间的乘积关系,首先探究了单位上三角非负矩阵的原子因式分解性质,然后给出了任意单位上三角非负矩阵A的最小原子因式分解长度l(A)的计算公式,并得到了A具有最小的原子因式分解长度的其中一种分解,从而完善了相关文献中的结果. 相似文献
179.
Lang X Qiu T Yin Y Kong F Si L Hao Q Chu PK 《Langmuir : the ACS journal of surfaces and colloids》2012,28(23):8799-8803
Highly ordered silver nanovoid arrays are fabricated on porous anodic alumina membranes to produce robust and cost-efficient surface-enhanced Raman scattering (SERS) substrates. Plasmonic tunability can be accomplished by adjusting the topography with different anode voltages. Evenly distributed plasmonic fields, high average enhancement factor, and excellent ambient stability due to the natural protective layer are some of the unique advantages, and the silver nanovoid arrays are applicable to sensing devices. 相似文献
180.
We consider generalizations of Denjoy-Wolff theorem on strongly pseudo-convex domains. Beardon [3] gave a general Denjoy-Wolff theorem in hyperbolic domain in the complex plane. Our main results are generalizations of Beardon’s result in a higher dimensional setting. 相似文献