Living cationic polymerization of vinyl ethers in the presence of a strong base: Poisonous or helpful?

A quite small dose of a poisonous species was found to induce living cationic polymerization of isobutyl vinyl ether (IBVE) in toluene at 0 °C. In the presence of a small amount of N,N‐dimethylacetamide, living cationic polymerization of IBVE was achieved using SnCl₄, producing a low polydispersity polymer (weight–average molecular weight/number–average molecular weight (M_w/M_n) ≤ 1.1), whereas the polymerization was terminated at its higher concentration. In addition, amine derivatives (common terminators) as stronger bases allow living polymerization when a catalytic quantity was used. On the other hand, EtAlCl₂ produced polymers with comparatively broad MWDs (M_w/M_n ～ 2), although the polymerization was slightly retarded. The systems with a strong base required much less quantity of bases than weak base systems such as ethers or esters for living polymerization. The strong base system exhibited Lewis acid preference: living polymerization proceeded only with SnCl₄, TiCl₄, or ZnCl₂, whereas a range of Lewis acids are effective for achieving living polymerization in the conventional weak base system such as an ester and an ether. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6746–6753, 2008     

银微盘电极上碘离子的示差脉冲溶出伏安法

基于Ｉ能与Ａｇ生成难溶出化合物特性，在银微盘电极上研究了Ｉ的示差脉冲溶出伏安法（ＤＰＳＶ）。该法不需镀汞，不要搅拌，可在较稀稀的支持电解质溶液中实施。于０．０８ｍｏｌ／ＬＨＡｃ－ＮａＣ及０．０１ｍｏｌ／ＬＥＤＴＡ介质中，能检出１．００×１０＾－８ｍｏｌ／Ｌ的Ｉ，Ｉ的浓度为５．００×１０＾－６－－１．２０×１０＾－８ｍｏｌ／Ｌ范围与峰电流有良好的线性关系。该法用于自来水中Ｉ的测定，相对偏差为４．３％     

Effect of Plasticizer on the Performance of the Surfactant-Selective Electrode Based on a Poly(Vinyl Chloride) Membrane with no Added Ion-Exchanger

The effect of different plasticizers in the sensing membrane on the performance of a surfactant ISE based on a PVC membrane with no added ion-exchanger was investigated. o-nitrophenyl octyl ether (NPOE), o-nitrophenyl decyl ether (NPDE), o-nitrophenyl dodecyl ether (NPDOE) and o-nitrophenyl tetradecyl ether (NPTE) were used as plasticizers. Electrodes based on NPDE, NPDOE and NPTE produced better results than NPOE-plasticized PVC membrane electrodes in terms of low detection limits. Electrodes based on NPDE, NPDOE and NPTE displayed a Nernstian slope in the concentration range of 10^–6 to 10^–2M. NPOE-plasticized PVC membrane electrodes displayed a Nernstian slope in the concentration range of 10^–5 to 10^–2M. The three electrodes other than the NPOE-plasticized PVC membrane electrode showed a similar performance to that of the NPOE-plasticized PVC membrane electrode concerning low detection limits and slope sensitivity. The four electrodes examined in this study are excellently selective for the dodecyltrimethylammonium ion over inorganic anions, but interference from other cationic surfactants such as tetradecyltrimethylammonium ions is significant. With respect to slope sensitivity, selectivity, response time and pH effect, the four electrodes showed a similar performance.     

面板数据的单位根检验和协整检验——实证分析西部省市固定投资与工业增加值之间的关系

本文介绍了面板数据的单位根检验和协整检验,实证分析西部九省市固定投资和工业增加值的关系,Engle-G ranger检验拒绝部分省市具有均衡增长关系,面板协整检验接受西部地区具有均衡增长关系。     

增加光子纠缠相干态的统计性质

引入了增加光子纠缠相干态.研究了在纠缠相干态的某个模上加入光子对光场统计性质的影响.由于两个场模间的纠缠,在a模上加入光子不但可以使a模的平均光子数增加,也可以使b模的平均光子数发生变化(增加或减少).加入光子后,光场的亚泊松分布和压缩特征得到明显增强. 关键词： 纠缠 增加光子态 统计性质     

Birth of room‐temperature magnons and Raman line enhancement in ZnO nanostructures containing cobalt oxide

Cobalt (Co) addition and thermal annealing induced structural and vibrational properties of ZnO nanostructures were analysed. X‐ray diffraction pattern reveals that the nanostructures are in hexagonal wurtzite type and the formation of Co₃O₄. The Co ion induced morphology changes have been studied by high‐resolution scanning electron microscope images and energy dispersive spectroscopy measurements confirm the presence of Co ions. CoO‐related magnon excitation bands are emerged at room temperature for the Co‐added samples. There are no changes in the band positions of the Raman spectra of pure and Co‐added materials. Annealed sample exhibits the suppression of magnon bands and formation of Co₃O₄: ZnO composites. Raman line width and the electron phonon coupling constant are decreased with respect to the annealing temperature. The formation of Co₃O₄ : ZnO composite phases have further confirmed by infrared spectra. Copyright © 2013 John Wiley & Sons, Ltd.     

Aromatic amines from polyurethane adhesives in food packaging: The challenge of identification and pattern recognition using Quadrupole-Time of Flight-Mass Spectrometry

Toxic primary aromatic amines (PAAs) are reaction products from residual isocyanates in polyurethane adhesives. The maximum migration level of the total sum of PAAs is 10 ng g⁻¹ of food. This paper reports on a method for quantification of 18 PAAs by UHPLC–MS/MS that was optimised and applied to a series of industrial laminates prepared from polyurethane adhesives. Non-intentionally added substances (NIAS), impurities and other migrants were identified by Q-TOF/MS^E. A comparison of the quantitative values obtained by the colorimetric method using NEDA and by UHPLC–MS/MS confirmed that the first method can overestimate the quantification of PAAs. This could be attributed to the impurities and other NIAS present in the plastic laminate. Values of R² in the analytical characteristics of UHPLC–MS/MS were obtained, the best value being 0.9964 and the most unfavourable 0.7626. The detection limit (LOD) and the quantification limit (LOQ) were 2 pg g⁻¹ and 7 pg g⁻¹, respectively. The stability of the PAAs over time in the acidic simulant in contact with the plastic laminate is also reported.     

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为研究轻钢增层结构的动力特性,本文详细介绍了以有机玻璃为模型材料轻钢增层结构采用共振法试验的方法．将共振法测试到的模型动力特性,与理论计算作了对比,二者具有较好的一致性,并对试验结果进行了理论与计算分析．     

关于避免多个不可实施因子水平组合的正交表构造

在正交表的实际应用中，有时会发生某些因子的水平组合无法进行试验的情形，使得现有的正交表不适用。Ｃｈｅｎｇ和Ｌｉ讨论了这种情况下的正交表的构造问题，并给出了关于避免两个不可实施的因子水平组合的正交表的构造方法。     

The added mass coefficient of a dispersion of spherical gas bubbles in liquid

Models published in the two-phase flow literature for the added mass coefficient of a dilute bubbly dispersion are discussed and compared. It is shown that the differences between the models are mainly due to the different ways in which the added mass is defined. Also, approximate expressions for the added mass coefficient of non-dilute bubbly dispersions are given. Finally, the use of the models in an equation for the average motion of the bubbles is briefly discussed.