广东省南澳岛水产品中硼元素本底值测定研究

水产品中硼元素本底值背景资料对于判断水产品中是否添加硼砂或硼酸至关重要。采用ICP–MS法测定了广东省南澳岛海水养殖的315份不同水产品中的硼含量,为水产品质量安全检测提供本底值判断依据。结果显示,硼含量(mg/kg)由高到低依次为龙须菜干制品(152.324)、干海带(78.628)、龙须菜盐渍样(31.146)、龙须菜鲜样(24.168)、海洋杂草(18.983)、昆布(16.541)、新鲜海带(6.164)、贝类(5.351)、紫菜(4.541)、养殖区海水(4.311)、牡蛎(3.820)、虾类(3.662)、非养殖区海水(3.532)、螃蟹(3.038)、鲍鱼(2.119)、鱼类(2.056)。海洋藻类利用同化作用富集硼元素,而动物性水产品可利用异化作用将硼元素排出体外。     

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.     

An alternative CuCl–piperidine‐catalyzed oxidative homocoupling of terminal alkynes affording 1,3‐diynes in air

CuCl with the use of a catalytic amount of piperidine as additive shows high catalytic activity for the oxidative homocoupling reactions of terminal alkynes in toluene at 60 °C in air to afford 1,3‐diynes in high yields. Copyright © 2009 John Wiley & Sons, Ltd.     

高斯光束通过单丝的Fraunhofer衍射

本文给出了高斯光束通过单丝和单缝的 Fraunhofer 衍射公式,从理论上论证了衍射斑主极大的三分裂现象,并进行了较严格的计算。计算结果与实验基本一致。     

二维体系的超导转变温度

如何解释氧化物超导体的高 T_c,是目前高温超导研究的主要任务之一。由于所发现的氧化物超导体具有二维的结构特征,态密度的 Van Hove 奇异性的作用又重新引起注意。本文较为严格地求解了决定 T_c 的积分方程,结果表明态密度的 Van Hove奇异性虽然可以提高 T_c,但并不如人们所估计的那么显著。     

Syntheses,Phase Behavior,Supramolecular Chirality,and Field‐Effect Carrier Mobility of Asymmetrically End‐Capped Mesogenic Oligothiophenes

Supramolecular chirality and liquid crystalline OFET : Achiral end‐capped oligothiophenes can be tuned to exhibit supramolecular chirality with unique striped textures showing distinct circular dichroism signals as well as a highly ordered SmE phase that leads to high hole carrier mobility.

     

Ligand-free Heck reaction: Pd(OAc)2 as an active catalyst revisited

Palladium acetate was shown to be an extremely active catalyst for the Heck reaction of aryl bromides. Both the base and the solvent were found to have a fundamental influence on the efficiency of the reaction, with K(3)PO(4) and N,N-dimethylacetamide being the optimal base and solvent, respectively.     

La_(2-x)Sr_xCuO_4准二维体系的反常同位素效应

本文针对La_(2-x)Sr_xCuO_4的Cu-O面准二维体系给出了一个简单的物理掺杂模型。利用BCS理论弱耦合框架下的Van Hove奇点模型进行了掺杂量x与同位素效应指数α之间关系的计算,发现能与实验基本一致。     

Objective evaluation of pronunciation of standard Chinese final based on formant pattern

A method used for objective evaluation of pronunciation of finals in standard Chinese is presented. The formant pattern of final is selected as the mam feature and an improved evaluation algorithm based on Support Vector Machine is proposed. In this algorithm, two-level classification strategy is employed. A full-classification model and a sub-classification model are trained for each final. The pronunciation quality is evaluated based on the classification results of this two-level strategy with scoring model of each final. The new evaluation method is compared with traditional methods such as Hidden Markov Model (HMM) posterior probability scoring method and feature of Mel-Frequency Cepstrum Coefficients (MFCC), and the results show that the performance is effectively improved by the proposed method. The correlation of scores between human testers and machine has achieved 82%.