Synergistic Effect of Polyoxometalate and Single Walled Carbon Nanotubes on Peroxidase‐like Mimics and Highly Sensitive Electrochemical Detection of Hydrogen Peroxide

A novel Keggin‐type metatungstate hybrid POMs ((APy)₆[H₂W₁₂O₄₀])/carboxylic acid functionalized single‐walled carbon nanotube based amperometric sensing platform was successfully constructed for the sensitive detection of hydrogen peroxide. A simple and reliable procedure was implemented for the synthesis of new composite materials obtained by the covalent grafting of (APy)₆[H₂W₁₂O₄₀] onto the surface of (SWCNT‐COOH). The synergistic effect of single walled carbon nanotubes on the electrochemical behavior of (APy)₆[H₂W₁₂O₄₀] was evidenced through the increase of the oxidation and reduction peaks of the polyoxometalate. The sensitivity of hydrogen peroxide detection was increased by a factor of 38.5 in presence of SWCNTs, showing their high influence on peroxidase‐like mimics of (APy)₆[H₂W₁₂O₄₀]. The detection limit, the response time, the repeatability and the shelf lifetime were respectively 0.4 μM, 10 s, <4%, 60 days.     

Frequency doubling of CO2 laser radiation at 10.6 microm in the highly nonlinear chalcopyrite LiGaTe2

Type-I phase matching for second-harmonic generation at 10.6 microm in LiGaTe(2) is demonstrated by using a tunable single-frequency continuous-wave CO(2) laser, and the nonlinear coefficient of LiGaTe(2) is determined from comparison with AgGaSe(2). The effective nonlinearity of LiGaTe(2) for this process amounts to 34.5 pm/V.     

Distortions of polymer melt extrudates and their elimination using slippery surfaces

An overview is given of extrudate distortions, flow fields and flow curves observed for flexible polymer melts, when they are extruded using axisymmetric or two-dimensional dies.Die walls with high surface energy and low-energy slippery surfaces are considered, as well as the influence of wall roughness.     

A comparative study on the nanocrystalline ZnO thin films prepared by ultrasonic spray and sol⿿gel method

Nanocrystalline ZnO thin films are deposited through two different chemical methods: (i) the films prepared by ultrasonic spray with 0.1 M and (ii) dip-coating from zinc acetate complex solutions with 0.5 M, the films obtained at different temperatures. The XRD analyses indicated that ZnO films have nanocrystalline hexagonal structure with (0 0 2) preferential orientation and the maximum crystallite size value of 103 nm measured from the films prepared by dip-coating. UV?vis measurement indicated that all films are transparency in the visible region. The optical band gap increased with decreasing of the Urbach tail energy indicating that the increase in the transition tail width and decrease of the defects, respectively.     

Distribution of nonliner relaxation (DNLR) approach of the annealing effects in semicristalline polymers: structure–property relation for high-density polyethylene (HDPE)

This work is devoted to the numerical and experimental study of annealing effects on microstructure and mechanical properties of the high-density polyethylene (HDPE). Uniaxiale tension tests are conducted at 25 °C in order to characterize the mechanical behavior of HDPE. The influence of the annealing treatment on the material microstructure is examined by the Fourier transform infrared spectroscopy, and microstructures are characterized using differential scanning calorimetry. The distribution of nonlinear relaxation approach is adopted to describe the mechanical response of virgin and annealed HDPE. Annealing effects are incorporated into the constitutive model by introducing the microstructure (crystallinity degree) evolution on the macroscopic response of the material. The numerical predictions of the model are in good agreement with experimental results for the different states of the material.     

Structural, optical and electrical properties of ZnO:Al thin films for optoelectronic applications

Undoped and aluminum-doped ZnO thin films are prepared by the sol–gel spin-coating process. Zinc acetate dihydrate, ethanol and mono-ethanolamine are used as precursor, solvent and stabilizer, respectively. The atomic percentage of dopant in solution were [Al/Zn] = 1 %, 2 % and 3 %. The effect of Al doping on the optical and electrical properties of ZnO films was investigated by X-ray diffraction (XRD), Four-Point probe technique and UV–visible spectrophotometery. The results from the X-ray diffraction show that the pure ZnO thin films had a polycrystalline structure of the hexagonal Wurtzite Type. A minimum resistivity of $3.3 \times 10^{-3} \Omega \cdot \mathrm{cm}$ was obtained for the film doped with 2 mol % Al. Optical transmissions reveal a good transmittance within the visible wavelength spectrum region for all of the films. The value of the band gap is enhanced from 3.21 eV (undoped ZnO) to 3.273 eV (Al/Zn = 3 %), the increase in the band gap can be explained by the Burstein–Moss effect.     

Global optimization for parameter estimation of differential-algebraic systems

The estimation of parameters in semi-empirical models is essential in numerous areas of engineering and applied science. In many cases, these models are described by a set of ordinary-differential equations or by a set of differential-algebraic equations. Due to the presence of non-convexities of functions participating in these equations, current gradient-based optimization methods can guarantee only locally optimal solutions. This deficiency can have a marked impact on the operation of chemical processes from the economical, environmental and safety points of view and it thus motivates the development of global optimization algorithms. This paper presents a global optimization method which guarantees ɛ-convergence to the global solution. The approach consists in the transformation of the dynamic optimization problem into a nonlinear programming problem (NLP) using the method of orthogonal collocation on finite elements. Rigorous convex underestimators of the nonconvex NLP problem are employed within the spatial branch-and-bound method and solved to global optimality. The proposed method was applied to two example problems dealing with parameter estimation from time series data.     

Reactions de l'acide perchlorique avec le phenylacetylene en solvant acide acetique anhydre

Perchloric acid in acetic acid reacts with phenylacetylene to give acetophenone, α-chloroacetophenone, α,α'-dichloroacetophenone, α-acetoxy α'chloroacetophenone, dichloro-styrène and chlorophenylacetylene. Kinetics of these reactions have been established.