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Four chromophores, of different dipole moment and polarizable anisotropy and which comprised conjugation bridges of both benzene and polyene with strong electron-donor and electron-acceptor groups, were characterized using 1H NMR, FT-IR, UV–vis, and electrochemical analyses. The electric dipole moment (μ), polarizability (α) and the first hyperpolarizability (β) values of the chromophores were examined using computational methods. The contribution of orientational birefringence to total birefringence was estimated from the calculated molecular parameters of the chromophores; these parameters are important factors for predicting photorefractive efficiency. 相似文献
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目的 对气相色谱内标法测定塑料制品中乙苯和苯乙烯含量进行不确定度评定,为塑料制品中乙苯、苯乙烯含量测定的准确性提供参考。方法 依据GB 31604.16—2016采用气相色谱内标法对塑料制品中乙苯和苯乙烯含量进行测定,根据相应的测量模型,分析不确定度主要影响因素的来源,并对各影响因素引入的相对标准不确定度进行评估。结果 测量塑料制品中乙苯、苯乙烯的扩展不确定度分别为(23.83±1.50)、(23.90±1.26)mg/kg(P=95%、k=2)。结论 结果表明,混标工作液配制、试样重复测量、气相色谱仪性能是影响乙苯和苯乙烯含量测量不确定度的主要因素,应选择精度高且量程合适的量具,加强气相色谱仪的期间核查,提高实验人员操作的熟练水平,进一步减小测量不确定度,使测量结果更为准确、可靠。 相似文献
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In the paper the authors refer to a new computational tool for the transient prediction of the car cabin environment and heat load during real operating conditions. The aim of the Virtual Testing Stand software is to support an early stage of the HVAC design process to predict demands for the heating and cooling for various operational conditions and types of car. This software was developed in Matlab as a standalone executable application including a parametric generator of car cabin geometry, a heat transfer model and a graphical user interface. The mathematical model is formed by the set of heat balance equations, which takes into account the heat accumulation, and the heat exchange between the car cabin, the outside environment, the HVAC system and the passengers. In this paper the main features of Matlab application are presented together with a selected sensitivity study of two significant parameters in a winter test case. 相似文献
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建立了分散固相萃取-超高效色谱-电喷雾串联质谱快速测定鸡肉中盐霉素残留的方法。样品经乙腈提取后,采用QuEChERS方法净化,氮吹转换溶剂后,采用Acquity BEH C18柱进行分离,0.3%甲酸水溶液-甲醇体系为流动相,梯度洗脱,电喷雾质谱正离子多反应监测模式测定,外标法定量。结果表明,在优化的条件下对样品进行分析检测,盐霉素的检出限为0.03μg·kg-1,添加水平为5.5~31.4μg·kg-1时,加标回收率为78.2-97.8%,RSD<2.0%(n=6),在0.630~25.2μg·L-1质量浓度范围内呈良好线性,相关系数R2>0.9989。该方法前处理步骤简单,具有较高灵敏度,可用于大批量样品的快速筛查检测。 相似文献
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基于插值法建立乳制品中酪蛋白的核磁共振磷谱定量检测方法。结果表明,该方法的检出限为0.38 g/L(信噪比(RSN)=3),定量限为1.25 g/L(RSN=10);在5.00~35.00 g/L质量浓度范围内线性良好,相关系数R2大于0.999;加标回收率在91.94%~105.10%范围区间;日内精密度在0.65%~1.40%范围区间;日间精密度在1.40%~1.80%范围区间。对市售不同乳制品中酪蛋白含量进行检测,该方法与GB 31638—2016《酪蛋白》测定结果误差在±5%以内,满足方法可行性对比分析验证要求。该方法相比常规方法样品前处理简单、定量准确性高,大大缩短了检测时间,且有更广泛的适用性,满足乳制品中酪蛋白快速定量检测的要求。 相似文献
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BackgroundLycium barbarum polysaccharides (LBPs) are considered to be the major bioactive components in L. barbarum. Due to the considerable health benefits of LBPs, and the significant research interest in LBPs, quality evaluation of LBPs and their related products is imperative for ensuring their efficacy and safety. The bioactivities of polysaccharides are closely associated with their physicochemical properties, which can be easily monitored via chemical techniques. Therefore, analysis of physicochemical properties is a more straightforward and viable approach for the quality control of polysaccharides.Scope and approachIn this review, special techniques for the structural characterization of LBPs are summarized and discussed. In addition, quality evaluation approaches of LBPs that have never been emphasized are highlighted herein. Furthermore, industrial applications of LBPs are reviewed and discussed.Key findings and conclusionsHigh-performance anion-exchange chromatography coupled with pulsed amperometric detection is one of the most effective techniques for analysis of both acidic and neutral LBPs. Size-exclusion chromatography coupled with multi-angle laser light scattering and refractive index detection is able to determine absolute molecular weights, chain conformations, and contents of LBPs. Fingerprinting analysis and saccharide mapping analysis are effective approaches for quality evaluation of LBPs. However, the lack of appropriate quality evaluation approaches indicates an unreliable regulation of LBPs and their related products. This reveals the deficiency in the quality control of commercial products. Thus, the development of reliable approaches for pharmacological activity-based quality control of LBPs and their related products must be extensively investigated. 相似文献
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