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181.
《Journal of separation science》2018,41(10):2178-2187
An ion mobility quadrupole time‐of‐flight mass spectrometry‐based pesticide suspect screening methodology was developed and validated covering 20 plant‐derived food matrices deriving from six commodity groups of different complexity according to the actual European Commission document SANTE/11813/2017 applying a QuEChERS sample preparation protocol. The method combines ultra‐performance liquid chromatography, traveling wave ion mobility, and quadrupole time‐of‐flight mass spectrometry. Besides the determination of the physicochemical property collision cross‐section and the establishment of a corresponding scientific suspect screening database comprising 280 pesticides for several pesticides, different protomers, sodium adducts, as well as dimers were identified in ion mobility spectrometry traces. Additionally, collision cross‐section values were included in the validation requirements regarding chromatography and mass spectrometry for the detection of pesticides. A collision cross‐section value window was analyzed within a tolerable error of ±2%. For this cross‐matrix validation, screening detection limits were determined at concentration levels of 0.100 mg/kg (84% of the original pesticide scope), 0.010 mg/kg (56%), and 0.001 mg/kg (21%). By application of ion mobility spectrometry, the compound identification was improved due to independence of commodity of concern and concentration levels of analyte molecules, as false assignments are reduced by application of a collision cross‐section range. 相似文献
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184.
本文采用具有较大双光子吸收截面的有机分子2,5,2′,5′-(4′-N,N-二苯胺苯乙烯基)联苯(DPA-TSB)(双光子吸收截面δ: 3288 GM, 1 GM=1×10-50 cm4·s·photon-1·molecule-1), 通过再沉淀法制备水相分散的纳米粒子. 研究表明, 这种有机双光子纳米粒子可以有效地富集在细胞质中, 对细胞染色显示出良好的荧光成像能力. 相似文献
185.
在蓝宝石衬底上生长了以AlN/GaN超晶格准AlGaN合金作为势垒的HEMT结构材料,并与传统AlGaN合金势垒样品进行了对比.在高Al组分(≥40%)情况下,超晶格势垒样品的表面形貌明显改进,电学性能特别是2DEG面电子浓度也有所改进.对超晶格势垒生长参数进行了初步优化,使得HEMT结构薄层电阻进一步降低,最后获得了251 Ω/□的薄层电阻.
关键词:
AlGaN/GaN 结构
AlN/GaN超晶格
二维电子气
高电子迁移率晶体管 相似文献
186.
Theoretical equations were proposed to adequately simulate the electrical conductivity behavior of aqueous solutions of both
charged and uncharged polymers. The theory, based on the mixture equation of Boned and Peyrelasse, was experimentally verified
on poly(acrylic acid) (PAA) in water and poly(ethylene oxide) (PEO) in aqueous electrolyte solutions. The data analysis suggested
that both the polymer coils may be depicted as oblate ellipsoids. Subsequently, the semiaxes values of the polymer coils were
determined, and they were in good agreement with the results reported in the literature.
Received: 25 June 1996 Accepted: 2 October 1996 相似文献
187.
质子交换膜燃料电池零下冷启动研究 总被引:2,自引:0,他引:2
在零下启动过程中,质子交换膜燃料电池阴极中氧气还原反应生成的水会在催化剂层内部结冰,因而阻碍氧气传输,覆盖催化剂层反应活性位点,降低电化学活性面积,影响燃料电池发电性能,甚至会导致零下启动失败;同时,结冰/融化循环还会破坏膜电极结构,影响燃料电池寿命。因此,质子交换膜燃料电池零下启动技术的研究对促进燃料电池汽车的推广应用有重要意义。本文针对质子交换膜燃料电池的零下启动过程,从实验研究、机理解释、模型分析及策略开发等角度对文献内容进行了梳理,并对涉及质子交换膜燃料电池零下启动过程的专利技术进行了总结。 相似文献
188.
The drainage of thin liquid films between colliding bubbles is strongly influenced by the boundary conditions at the air–liquid interface. Theoretically, the interface should not resist any tangential stress (fully mobile) in a clean water system, resulting in very fast film drainage and coalescence between bubbles within milliseconds. In reality, under most experimental and industrial conditions, the presence of impurities or surfactants can immobilize the interface and significantly hinder bubble coalescence by several orders of magnitude. In this opinion, we introduce the recent progress on understanding the boundary conditions at the air–water interface, and how they may affect the outcome of bubble collisions. The transition from mobile to immobile boundary conditions in the presence of contaminations is discussed. Despite the considerable recent progress, there are still experimental and theoretical challenges remaining on this topic, for example, finding the mechanism for hindered bubble coalescence by high salt concentrations. 相似文献
189.
A series of transition metal (Ni, Cu, Pd) complexes derived from macrocyclic tetrabenzo[b,f,j,n] [1,5,9,13]tetraazacyclohexadecine (TAAB) was synthesized and their mesomorphic properties studied by differential scanning calorimetry, polarized optical microscopy and X-ray powder diffraction (XRD). These compounds have eight alkoxy side chains attached around the central molecular core and form disc-like molecules. All the derivatives exhibited columnar mesophases over a wide range of temperature. The mesomorphic behaviour was found to be dependent on the incorporated metal and the carbon length of the alkoxy side chains. The clearing temperatures decreased in the order M = Ni > Pd > Cu; this decrease was probably due to the size of the metal ions. Some derivatives with shorter side chains (n = 10, 12) were room temperature liquid crystals. All compounds were found to exhibit hexagonal columnar (Colh) phases which were confirmed by powder XRD. 相似文献
190.
结肠癌病人几种细胞的Raman光谱 总被引:6,自引:2,他引:6
文章给出了结肠癌病人的几种细胞的拉曼光谱。从实验谱线中得到,均有构像不灵敏的苯丙氨酸的单取代苯环的伸缩振动谱线1002cm~(-1),谱线强而半高宽较小,且不易改变,可作为生物细胞拉曼谱线的内标。白细胞拉曼谱线弱而少,红细胞拉曼谱线强而丰富,且有一个吡咯环的C—N呼吸振动谱带,窄而强的1919cm~(-1)的特征峰,宽而强的谱线1577,1560,1548cm~(-1),这是其他细胞不具有的。腺癌细胞的拉曼谱线相对较弱,许多谱线消失,生长在不同部位癌变细胞的荧光强度分布不同。通过这些特征拉曼谱线的不同,为癌症的诊断和治疗提供了有力的实验依据。 相似文献