Potentiometric sensors based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated calix[4]arene and calix[4]resorcarenes

Potentiometric ion sensors have been prepared by galvanostatic electrosynthesis of the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-sulfonated calix[4]arene (C[4]S) and p-methylsulfonated calix[4]resorcarenes (R_n[4]S) with alkyl substituents of different chain length (R₁=CH₃; R₂=C₂H₅; R₃=C₆H₁₃). The bowl-shape of these doping ions makes them suitable as ionic recognition sites, and their bulky character is expected to prevent them from leaching out of the conducting polymer membrane. For comparison, sensors based on PEDOT doped with poly(styrene sulfonate) (PSS) and poly(vinyl sulfonate) (PVS) were also constructed. The resulting GC/PEDOT electrodes were conditioned in 0.01 mol L^–1 AgNO₃ and their performance as Ag⁺ ion-selective electrodes (ISEs) studied. Results reveal that selectivity and lifetime of the electrodes is affected by the doping anion structure, although all electrodes show selectivity towards Ag⁺ ions. Interaction of Ag⁺ with sulfur atoms present in the conducting polymer backbone is considered to be the main reason for this behavior. A second set of electrodes was constructed and conditioned in 0.1 mol L^–1 KCl. These electrodes were tested in chloride solutions of quaternary ammonium cations, showing that C[4]S and R₂[4]S exhibit significant sensitivity towards pyridinium.Dedicated to Professor György Horányi on the occasion of his 70th birthday in recognition of his outstanding contributions to electrochemistry     

疏水载流子传输层上制备高效钙钛矿太阳电池的锚固策略

几种常用的导电聚合物(如PTAA(聚三芳基胺))具有优良的光电特性,因此适合用作钙钛矿太阳电池中的空穴传输材料来提升器件性能。然而,这些材料的疏水特性导致难以形成致密且高质量的钙钛矿薄膜。此外,即使通过一些方法实现载流子传输层与钙钛矿膜之间的接触,但界面处也会存在严重的载流子复合。同时,这样制备出的粗糙钙钛矿薄膜会导致后续沉积在钙钛矿薄膜上的电子传输层的非均匀覆盖。因此,在疏水载流子传输层上实现良好钙钛矿薄膜沉积以获得优良器件性能仍然具有很大挑战性。在本研究中,利用PbI₂进行锚固工程被证明是一种简便、绿色且有效的方法,可有效解决疏水载流子传输层浸润性问题。通过本方法,钙钛矿薄膜质量和器件性能得到了显著提高,并获得了效率高达19.53%的器件。同时,本方法也普遍适用于其他疏水的载流子传输层,进而制备优异的钙钛矿薄膜,这为高性能钙钛矿太阳电池的发展提供了一种可行策略。     

Fingerprinting the degradation product patterns of different polyester‐ether networks by electrospray ionization mass spectrometry

Fingerprinting of the degradation product patterns by electrospray ionization mass spectrometry (ESI‐MS) was evaluated as a tool to monitor the degree of degradation in polyester‐ether networks. Four different crosslinked caprolactone (CL) and/or 1,5‐dioxepan‐2‐one (DXO) networks were subjected to hydrolytic degradation in aqueous solution at 37 °C for up to 147 days. After predetermined time periods, the water‐soluble degradation products were analyzed by ESI‐MS and tandem ESI‐MS. In addition, changes in pH, mass loss, and copolymer composition were determined. In the case of more slowly hydrolyzed CL‐rich (co)polymers, CL and/or DXO oligomers terminated by hydroxyl and carboxyl end groups were predominantly formed as degradation products. However, on prolonged hydrolysis oligomers with attached crosslinking agent dominated the degradation product patterns of more easily hydrolyzed DXO‐rich (co)polymers. It was shown that in the recorded mass spectra the variation of intensities in the series of ions corresponding to DXO and CL/DXO oligomers with or without attached crosslinking agent could be utilized to monitor the extent of hydrolytic degradation in the polyester matrix and the disruption of the network structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4617–4629, 2008     

Grafting of hydroxymethylacrylamide and acrylic acid copolymer onto polyvinylidene fluoride membrane by supercritical carbon dioxide and its application in dye separation

We report a thermally induced graft copolymerization of acrylic acid and N‐hydroxymethylacrylamide onto polyvinylidene fluoride microporous membrane by using supercritical carbon dioxide as a solvent and carrier agent. The effects of monomer mole ratio, pressure, reaction temperature, time, and initiator concentration on the degree of grafting were investigated. The morphology of the grafted membrane was studied via scanning electron microscopy. Attenuated total reflectance infrared spectroscopy spectroscopy and X‐ray diffraction proved the existence of grafting monomers. The results of contact angle measurement and water filtration at different pH levels indicated pronounced pH‐sensitive behavior and increased hydrophilicity of the polyvinylidene fluoride grafted membrane. In particular, the grafted membrane was applied to the removal of methylene blue with a relative rejection of 98.1% compared with 30.5% of rejection observed from the pristine polyvinylidene fluoride membrane. Copyright © 2014 John Wiley & Sons, Ltd.     

Young children's recognition of quantitative relations in mathematically unspecified settings

Children have been found to be able to reason about quantitative relations, such as non-symbolic proportions, already by the age of 5 years. However, these studies utilize settings in which children were explicitly guided to notice the mathematical nature of the tasks. This study investigates children's spontaneous recognition of quantitative relations on mathematically unspecified settings. Participants were 86 Finnish-speaking children, ages 5–8. Two video-recorded tasks, in which participants were not guided to notice the mathematical aspects, were used. The tasks could be completed in a number of ways, including by matching quantitative relations, numerosity, or other aspects. Participants’ matching strategies were analyzed with regard to the most mathematically advanced level utilized. There were substantial differences in participants’ use of quantitative relations, numerosity and other aspects in their matching strategies. The results of this novel experimental setting show that investigating children's spontaneous recognition of quantitative relations provides novel insight into children's mathematical thinking and furthers the understanding of how children recognize and utilize mathematical aspects when not explicitly guided to do so.     

An anisotropic elastic–viscoplastic model for soft clays

Experimental evidences have shown deficiencies of the existing overstress and creep models for viscous behaviour of natural soft clay. The purpose of this paper is to develop a modelling method for viscous behaviour of soft clays without these deficiencies. A new anisotropic elastic–viscoplastic model is extended from overstress theory of Perzyna. A scaling function based on the experimental results of constant strain-rate oedometer tests is adopted, which allows viscoplastic strain-rate occurring whether the stress state is inside or outside of the yielding surface. The inherent and induced anisotropy is modelled using the formulations of yield surface with kinematic hardening and rotation (S-CLAY1). The parameter determination is straightforward and no additional experimental test is needed, compared to the Modified Cam Clay model. Parameters determined from two types of tests (i.e., the constant strain-rate oedometer test and the 24 h standard oedometer test) are examined. Experimental verifications are carried out using the constant strain-rate and creep tests on St. Herblain clay. All comparisons between predicted and measured results demonstrate that the proposed model can successfully reproduce the anisotropic and viscous behaviours of natural soft clays under different loading conditions.     

A Supramolecular Hydrogen‐Bonded Network as a Diffusion Barrier for Metal Adatoms

Confined in a molecular corral : A supramolecular network changes the mechanism by which underpotential deposition (UPD) of copper proceeds on a gold electrode modified by a self‐assembled monolayer (SAM). Lateral diffusion of Cu adatoms is suppressed between adjacent cells of a network/SAM hybrid structure. Instead, UPD occurs by direct deposition into the SAM filled pores of the network, where the Cu adatoms are confined.

     

求解非凸区域上凸函数比式和问题的全局优化方法

针对非凸区域上的凸函数比式和问题,给出一种求其全局最优解的确定性方法.该方法基于分支定界框架.首先通过引入变量,将原问题等价转化为d.c.规划问题,然后利用次梯度和凸包络构造松弛线性规划问题,从而将关键的估计下界问题转化为一系列线性规划问题,这些线性规划易于求解而且规模不变,更容易编程实现和应用到实际中;分支采用单纯形对分不但保证其穷举性,而且使得线性规划规模更小.理论分析和数值实验表明所提出的算法可行有效.     

Negative gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles at 0.02 Tesla

Gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles were evaluated in vitro and in rabbits at 0.02 Tesla. Test tubes containing 0.01–1.0 mg particles/ml were imaged in an oil or water bath in order to demonstrate the concentration-dependent signal void and image distortion in vitro at several pulse sequences. The lowest concentration of particles tested clearly decreased the signal intensity. Image distortion was observed when the concentration exceeded 0.07 mg/ml and was more pronounced on the T₂-weighted images. The in vitro T₂ relaxation time decreased from 122 ms to 56 ms with an increase in the particle concentration from 0.01 to 0.06 mg/ml. A loss of the GI-tract signal was observed in rabbits after the administration of 1 mg particles/kg, given as a 0.03 mg/ml suspension. At a dose of 20 mg/kg (0.6 mg/ml suspension) significant image distortion was observed.