Sensitive Molecularly Imprinted Fluorescence Determination of Pyrethroids using Green Zinc Oxide Quantum Dots

Pyrethroids are similar to the natural pyrethrins produced by the flowers of pyrethrums that are effective insecticides but with potential toxicity. Here, a novel core–shell fluorescence probe for pyrethroids was prepared by precipitation polymerization. ZnO quantum dots and cyhalothrin were used as the substrate and template, respectively. Due to the formation of reversible specific recognition sites during copolymerization in the presence of acrylamide and ethyl glycol dimethacrylate, ZnO-based molecularly imprinted polymers containing cyhalothrin recognition sites were obtained. Transmission electron microscopy, infrared spectroscopy, and fluorescence spectroscopy were used to characterize the resulting ZnO-based imprinted polymers. The polymer microspheres were used to sensitively and selectively determine cyhalothrin. In addition, a linear relationship between the concentration of cyhalothrin and the fluorescence intensity was obtained from 0 to 80 µmol L^?1 with a correlation coefficient of 0.9964 using the Stern–Volmer equation. The protocol was used for the determination of cyhalothrin in milk demonstrating the suitability of the methodology for practical sample analysis. The selective and sensitive fluorescence recognition, low production cost, and facile synthesis demonstrate attractive properties of ZnO-based molecularly imprinted polymers for specific molecule recognition.     

A Chemosorption Vacuum Pump for a Chemical Oxygen Iodine Laser with CO<Subscript>2</Subscript> Buffer Gases

We present the design and investigation of a novel chemosorption vacuum pump (CSVP) for discharging the exhaust gases of a chemical oxygen-iodine laser system diluted with carbon dioxide (CO₂-COIL). The CSVP comprises two fixed-bed reactors separately filled with CO₂/H₂O and O₂/I₂/Cl₂ adsorbents, which can efficiently chemically absorb the CO₂-COIL exhaust gases at room or higher temperature. We consider the effects of the adsorbents in different specifications and fixed beds of various constructions on the adsorption performance of the CSVP. We develop and study the sealed CO₂-COIL system with the CSVP. We achieve a stable operation with a cumulative duration time of 40 s for four runs and an average output power up to 2.0 kW at a Cl₂ flow rate of ～158 mmol/s and a CO₂ flow rate of 132 mmol/s. The experimental results indicate that the COIL system with the CSVP performs similarly to a conventional COIL with a vacuum tank. Taking into account that the CSVP is free of vibration and noise, avoids air pollution, is easily operated, and has a short preparation time, we believe that the chemosorption vacuum pump is an excellent alternative pump system for a transportable COIL system.     

三苯基膦氧基团在合成高性能有机电致发光材料中的应用

有机电致发光技术在通讯、信息、显示和照明等领域显现出巨大的商业应用前景, 十几年来一直是光电信息领域的研究热点之一。相对于无机电致发光材料,有机电致发光材料具有许多优点。近年来,三苯基膦氧基团在合成高性能有机电致发光材料方面的研究吸引了大批研究者的关注。由于磷原子自身性质,可以形成5个共价键,所以膦氧基团极易和其他基团连接形成以其为核的衍生物。由于氧原子具有很强的电负性,这就使膦氧结构高度极化并具有强的吸电子性。吸电子的膦氧基团连接苯环形成的三苯基膦氧单元也具有较强的吸电子性,其对所形成的化合物的能级结构也会产生明显影响。本文从材料合成的角度综述了三苯基膦氧基团在合成高性能有机电致发光材料中的应用方面所取得的最新研究进展,重点介绍了三苯基膦氧基团在合成高性能磷光二极管主体材料、电子传输材料和单分子电致发光材料等方面的应用。最后讨论了三苯基膦氧基团在上述领域应用过程中所存在的问题和功能拓展方向,并对下一步需要研究的热点问题作了展望。     

基于鼻韵尾分离的汉语声韵母识别模型

研究汉语自然口语识别中的建模单元选择问题。在HMM三状态模型中,声韵母单元与音素单元作为两种最流行的建模单元各有优劣。一方面从自然口语音变严重的问题出发,倾向采用粗粒度的声韵母单元以概括各种音变;另一方面从三状态结构可能无法有效描述复杂单元的问题出发,又倾向采用细粒度的音素单元。本文在实验语音学理论研究成果与声韵母时长分析实验结果的基础上,主张对扩展声韵母单元进行有选择的拆分,提出了基于鼻韵尾分离的声韵母拆分方法。实验结果表明本文的方法与扩展声韵母单元、音素单元相比,识别性能有了明显改善,其字错误率分别降低2.23%和9.45%。      

基于傅里叶变换轮廓术的动态液膜测量

动态液膜三维形貌的高速测量及重建,对于能源动力领域的工业过程优化十分重要。基于傅里叶变换轮廓术,对缓变表面和非缓变表面分别进行了模拟仿真,研究了物体表面形貌重建精度的影响因素,包括物体表面高度变化率、环境随机噪声以及条纹频率。并根据模拟结果对实验参数进行了优化,研发构建了高速三维结构光测量系统,对竖直壁面下降液膜表面形貌进行了动态测量。实验结果表明:随着液膜沿竖直壁面向下流动,液膜厚度呈现先增大后减小的趋势,高度方向的平均误差为0.1 mm,傅里叶变换轮廓术能够精确地应用于动态液膜高速测量。     

投资机会与VaR约束下的投资组合分析

在证券收益率服从正态分布的前提下 ,建立了投资机会与 Va R双重约束下的投资组合模型 ,讨论了最优解的存在唯一性 ,并得到了最优解的解析表达式 .     

(O)ffner展宽器曲面镜误差对输出脉冲对比度的影响

在(O)ffner展宽器的设计研究中,对曲面镜曲率半径的误差研究非常重要,它直接影响输出脉冲的质量.因此有必要分析(O)ffner展宽器中曲面镜曲率半径的误差对输出脉冲对比度的影响.参考(O)ffner展宽器的光线追迹模型,建立了(O)ffner展宽器中曲面镜曲率半径存在误差时的光线追迹模型;根据建立的模型.详细分析了曲面镜曲率半径的误差对输出脉冲质量的影响;发现在目前曲面镜曲率半径的加上误差在0.2%～0.5%的情况下,完全可以满足神光Ⅱ拍瓦激光装置中对展宽器的要求;同时发现如果曲面镜曲率半径存在误差时,应该尽量使两曲面镜之间的距离保持为凹面反射镜曲率半径的一半,而不是使两曲面镜保持同心.