A rapid and sensitive LC-MS/MS method for determination of coenzyme Q10 in tobacco (Nicotiana tabacum L.) leaves

A rapid and sensitive liquid chromatography-tandem mass spectrometry method with multiple reaction monitoring has been proposed for the analysis of coenzyme Q10 in (CoQ10) tobacco leaves. The method used electrospray ionization with detection in positive ion mode. Sample pretreatment involved ultrasonic extraction of fresh tobacco leaves with anhydrous ethanol for 15 min and followed by extraction of the supernatant with hexane. The separation of CoQ10 was performed on a Symmetry Shield RP18 column with a mixture of acetonitrile and isopropanol (8:7, v/v) containing 0.5% formic acid as mobile phase. Quantification of CoQ10 was performed by the standard addition method. The limit of detection and limit of quantitation of CoQ10 were, respectively, 1.2 ng/mL (S/N = 3) and 4.0 ng/mL (S/N = 10). The relative standard deviations of peak area were 0.91% and 1.21% for intra-day and inter-day, respectively. The recoveries of CoQ10 ranged from 98.2 to 99.3% and the corresponding RSDs were less than 2.4%. Analysis took 5 min, making the method suitable for rapid determination of CoQ10 in tobacco leaves. The proposed method has been successfully applied to the analysis of CoQ10 in the leaves from eight varieties of tobacco.     

New approach to the total synthesis of (-)-zeylenone from shikimic acid

The natural antitumor product (-)-zeylenone was prepared for the first time in a stereoselective synthesis from shikimic acid.     

忆阻电路的基本性质及其应用

对有边界的忆阻元件与电容、 电感的串、 并联电路分别进行了研究, 分析了电路所具有的特性和频率及元件的电容、 电感对电路的影响, 通过仿真验证了理论结果.根据有边界的忆阻元件及其构成电路的性质研究, 对其潜在的应用进行了预测.     

形状与位置对断点划痕场分布的影响研究

用3维时域有限差分方法分别研究了在355 nm入射激光作用下, 熔石英后表面具有不同形状 和位置的断点划痕对场分布的影响.研究表明,对于椭圆状的坑点, 当共线的轴长逐渐 增大时, 电场幅值与强点数目先增大后减小, 获得最大光强增强因子的两轴 比是1.1-1.2, 此时坑点呈近圆形. 当平行的轴长逐步增大时,电场幅值先逐渐增大, 当两轴比为0.53时趋于平缓, 而强点总数则呈"J"形曲线不断增长. 当坑点尺寸相同 但排放位置不同时, 相邻坑点的相对面积愈大, 调制愈强.     

氘化及氦离子注入对钪膜的表面形貌和相结构的影响

采用XRD, SEM, AFM等详细研究了氘化及氦离子注入对钪膜的表面形貌和相结构的影响. 结果表明,在单晶硅及抛光Mo基片上制备的钪膜均具有(002)晶面择优取向;钪膜氘化后表面会出现大量孔洞, 氘化后氘化钪(ScD₂)晶粒长大,但内部会残留少量未完全氘化反应的晶粒尺寸较小的 ScD_0.33/Sc晶粒;氦离子注入对钪及氘化钪的表面形貌没有明显影响, 离子注入的氦将在钪及氘化钪晶格中聚集成泡,导致氦离子注入层中的钪及氘化钪衍射峰向低角度偏移, 并且氦泡的聚集具有择优取向性.     

Multi-pulse chaotic dynamics in non-planar motion of parametrically excited viscoelastic moving belt

This paper investigates the multi-pulse global bifurcations and chaotic dynamics for the nonlinear, non-planar oscillations of the parametrically excited viscoelastic moving belt using an extended Melnikov method in the resonant case. Using the Kelvin-type viscoelastic constitutive law and Hamilton's principle, the equations of motion are derived for the viscoelastic moving belt with the external damping and parametric excitation. Applying the method of multiple scales and Galerkin's approach to the partial differential governing equation, the four-dimensional averaged equation is obtained for the case of 1:1 internal resonance and primary parametric resonance. From the averaged equations obtained, the theory of normal form is used to derive the explicit expressions of normal form with a double zero and a pair of pure imaginary eigenvalues. Based on the explicit expressions of normal form, the extended Melnikov method is used for the first time to investigate the Shilnikov-type multi-pulse homoclinic bifurcations and chaotic dynamics. The paper demonstrates how to employ the extended Melnikov method to analyze the Shilnikov-type multi-pulse homoclinic bifurcations and chaotic dynamics of high-dimensional nonlinear systems in engineering applications. Numerical simulations show that for the nonlinear non-planar oscillations of the viscoelastic moving belt, the Shilnikov-type multi-pulse chaotic motions can occur. Overall, both theoretical and numerical studies suggest that the chaos for the Smale horseshoe sense in motion exists.     

Synthesis of Diverse Aryliodine(Ⅲ) Reagents by Anodic Oxidation

An anodic oxidation enabled synthesis of hypervalent iodine(Ⅲ) reagents from aryl iodides is demonstrated.Under mild electrochemical conditions,a range of aryli...     

飞秒多脉冲激光烧蚀金属过程中的能量剩余现象

提出了描述整个飞秒多脉冲激光烧蚀过程的物理模型,模型考虑了多脉冲烧蚀的新的特点,考虑靶材吸收率随温度的变化和蒸发效应,建立了激光烧蚀不同阶段的热传导方程,给出了相应的定解条件。以金靶材为例,利用有限差分法,求解了热传导动力学方程,分别给出单脉冲和多脉冲作用下相应的靶材电子和离子亚系统的温度演化图像,及多脉冲激光作用下能量剩余系数和脉冲个数的变化规律,发现理论曲线与相应的实验数据吻合较好。研究结果充分证明多脉冲激光烧蚀过程中剩余能量的存在。     

饱含液体的单胞结构对射流的干扰特性分析

基于虚拟原点理论、冲击波反射理论和射流干扰理论,考虑液体的喷散特性和径向汇聚特性,改进并完善了射流侵彻饱含液体的单胞结构的理论模型,得到了精确的射流受干扰速度区间的表达式、液体喷散速度的表达式和液体喷散流量的表达式。通过对比理论和试验得到的射流受干扰的速度区间,证明了本文理论模型的可靠性。研究结果表明：液体的喷散和径向汇聚都会影响射流的稳定性,使射流出现颈缩和提前断裂,降低射流的剩余头部速度从而降低射流的剩余侵彻能力。