Determination of amino acids in tea leaves and beverages using capillary electrophoresis with light-emitting diode-induced fluorescence detection

The combination of capillary electrophoresis (CE) and light-emitting diode-induced fluorescence (LED-IF) detection has been demonstrated in the analysis of major amino acids in tea leaves and beverages. The separation efficiency of amino acids, which were derivatized with naphthalene-2,3-dicarboxaldehyde (NDA), depended on the capillary length and PEO concentration. We suggested that the interactions between the NDA derivatives and poly(ethylene oxide) (PEO) molecules are based on hydrogen bonding, hydrophobic patches, and Van der Waals forces. The magnitude of EOF and the interactions between them can be further controlled by the capillary length. The separation of 17 NDA-amino acids derivatives was completed within 16 min using 0.5% PEO and 60 cm capillary length. The relative standard deviations (R.S.D.) of their migration times (n = 5) were less than 2.7%. Additionally, the limits of detection at signal-to-noise ratio 3 for the tested amino acids ranged from 3.6 to 28.3 nM. Quantitative determination of amino acids in tea leaves and beverages was accomplished by our proposed method. This study showed that amino acid present in highest concentration in tea leaves and beverages is γ-aminobutyric acid and theanine, respectively. The experimental results suggest that our proposed methods have great potential in the investigation of the biofunction of different tea samples.     

Development of a stabilized low temperature infrared absorption cell for use in low temperature and collisional cooling experiments

We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80K or with liquid helium from 80K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases. We also recorded spectra at very low pressure to accurately model the diode laser emission. Spectra of the R(2) line in the fundamental band of 13CO cooled by collisions with helium buffer gas at 10.5K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (gamma(0) = 0.3 cm(-1) atm(-1)) has been derived from the simultaneous analysis of four spectra at different pressures.     

电缆充气设备、施工和维护的标准要求

介绍了电缆充气的必要性,电缆充气设备的选型,电缆施工和维护的具体要求和标准,这将有助于提高电缆电气特性和传输质量,延长电缆使用寿命,及时发现与减少电缆故障,确保通信质量.     

水泵远程控制系统设计与实现

本文为助力构建资源节约型社会，研究现今我国水泵监管以及维护情况，制定全新的水泵远程控制体系，给未来水泵的保护和管理提供参考。     

Use of Extraction Disks for Trace Enrichment of Various Pesticides from River and Sea Water Samples

Abstract

C-18 Empore extraction disks were used for the isolation and trace enrichment of different groups of pesticides from river water and artificial sea water at concentration levels of 0.2, 5 and 20 μg/l [chlorotriazines, (atrazine and simazine), their dealkylated metabolites, (deethyl- and deisopropylatrazine), organophosphorus (parathion-ethyl), phenylurea (linuron), anilide (propanil), carbamate (aldicarb and carbofuran) and carbamate transformation products (aldicarb sulfoxide, aldicarb sulfone and 3-hydroxy-7-phenol carbofuran]. The extraction disks allowed high flow rates thus 51 samples could be processed within 2h. 30 min.

For most of the pesticides the recoveries, as determined by liquid chromatography with diode array detection (LC-DAD), varied from 74 up to 125% with coefficients of variations (CV) of 5-10%, whereas for the carbamate transformation products the recoveries were in the range of 30-35% having a CV of 17-21%. At spiking level of 0.2 μg/l the dealkylated triazine metabolites and the carbamate transformation products were not detected at all.     

Organic wrinkles embedded in high-index medium as planar internal scattering structures for organic light-emitting diodes

Organic wrinkle structures are investigated as an internal scattering layer for the fabrication of highly efficient organic light-emitting diodes (OLEDs). The solution-processed wrinkle structures are planarized with a high-index layer, resulting in a reduced surface roughness and optical haze simultaneously. The OLED device including the wrinkle structures achieved external quantum efficiency (EQE) of 24.2%, corresponding to a 1.24 time enhancement with respect to that of a control device having no internal scattering layer. By attaching a micro lens array (MLA) or a half ball lens (HBL) on the external surface of the substrate, the proposed device exhibits an EQE of 30.5% (1.56 time enhancement) and 41.8% (2.14 time enhancement), respectively. Randomness of the distributed wrinkle structures is shown to provide additional benefits of reduced angular spectral distortion and Lambertian-like emission properties. Trans-scale optical simulation combining wave-optics and the geometrical effect are used for the quantitative analysis of the emission characteristics of the device.     

Transition metal oxides on organic semiconductors

Transition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices.     

浮游植物分布对强台风尼格的响应

研究调查了Ekman流对浮游植物生态动力过程的驱动机制。采用新的光学遥感算法提取浮游植物光学有效信息。该算法结合了近红外波段的浮游植物荧光信号以及可见光部分的弹性散射的辐射传输模型,通过两次迭代优化算法,提取浮游植物光学信号。采用辐射传输软件Hydrolight对海水水下光场进行了数值模拟,并结合新算法对模拟数据进行了对比分析。结果表明,新算法较好地表征了浮游植物叶绿素光学参数。利用MERIS光学遥感数据并结合了动力学参数,利用该算法分析了强台风尼格对我国海域浮游植物分布的影响。研究结果表明,Ekman流是我国海域浮游植物分布异常的原因之一。