Rh–Sr/Al2O3 Catalyst for N2O Decomposition in the Presence of O2

The improving effect of Sr in the catalytic activity of Rh for N₂O decomposition has been studied under 1,000 ppm N₂O/He and 1,000 ppm N₂O/5% O₂/He (GHSV = 10,000 h^?1). Different techniques have been used for catalysts characterization: TEM, SEM-EDX, XRD, N₂ adsorption at ?196 °C and in situ XPS. Sr favours the Rh dispersion and reduction under reaction conditions, and allows the low temperature removal of N₂O in the presence of O₂ (100% decomposition at 350 °C).     

The Chemical Background of Advanced Oxidation Processes

In advanced oxidation processes, the hydroxyl radical is the main initiator of the degradation of pollutants. For aromatic molecules, the rate coefficients are between 2×10⁹ and 1×10¹⁰ mol⁻¹ dm³ s⁻¹ and show some variation according to the electron-withdrawing or donating nature of the substituents. The one-electron oxidant ^.OH induces 2–4 electron oxidations of many aromatic pollutants. These high rates are explained by ^.OH addition to an unsaturated bond, scavenging of the organic radical by dissolved O₂, and subsequent reactions. In amino-substituted molecules and in azo dyes the efficiency is lower, because O₂ cannot compete efficiently with the unimolecular transformation of carbon-centered radicals. Generally, the toxicity first increases and then decreases with treatment time. The increase is attributed to the high toxicity of some degradation products and to H₂O₂ formation. In surface waters, traces of transition metal ions degrade some of the H₂O₂ in Fenton-like processes.     

Measuring technique and mathematical analysis of conical worms

Attrition and resharpening of tools, limited accuracy of machine setting, etc. can cause deformation and shape errors of the surfaces. A measuring method has been carried out in the recent years that is the measuring of helical surface without rotary table for conical worms. The use of this method makes it possible to explore the errors arising during production (e.g. thread pitch in axial plane, error of profile shape in axis or any illustrious planes, etc.) and to determine the values of these errors. We have worked out a mathematical model of the generatrix spiroid worm, which is used during the evaluation of the measuring results.     

Distinct composite structure and properties of Eu(phen)2Cl3(H2O)2 in poly(methyl methacrylate) and polyvinylpyrrolidone

The luminescent europium complex Eu(phen)₂ Cl₃(H₂O)₂ (phen refers to 1,10‐phenanthroline) was doped in poly(methyl methacrylate) (PMMA) and polyvinylpyrrolidone (PVP), respectively. The formed composite systems with different molar ratios of C?O groups in polymers and Eu ions were characterized by X‐ray diffractometry (XRD), FTIR, and photoluminescent (PL) spectroscopy and lifetime measurement. The XRD diffractograms show that the composites of PMMA/Eu(phen)₂Cl₃(H₂O)₂ and PVP/Eu (phen)₂Cl₃(H₂O)₂ have crystalline and amorphous structures, respectively, arising from different interactions between the polymers and the complex, as revealed by FTIR spectra. This leads to distinct luminescent characteristics arising from the ⁵D₀→⁷F_J transitions of Eu(III) ion (J = 0–4). For the composite systems of PMMA/complex, the characteristics of the emission lines change with decreasing molar ratios of C?O/Eu and approach that of the pure complex; whereas the composite systems of PVP/complex have similar spectral features, regardless of the molar ratios, differing from that of the pure complex. The polymer matrices have a substantial influence on the structure and properties of the composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3524–3530, 2004     

Enhancement of dielectric and energy density properties in the PVDF‐based copolymer/terpolymer blends

We investigated the high dielectric constant and energy storage density for the blends of P(VDF‐TrFE) copolymer and P(VDF‐TrFE‐CFE) terpolymer. The degradation of coercive field (E_c) and remnant polarization (P_r) of the copolymer under an electric field of 125 MV/m was observed and the copolymer changed into a typical relaxor ferroelectric with doping of terpolymer. The dielectric constant of P(VDF‐TrFE) was found to be ～11, but was enhanced to ～55 by blending with P(VDF‐TrFE‐CFE) at 60 wt%. Consequently, a higher energy density of about 4.2 J/cm³ was obtained in these blends in contrast to about 3.6 J/cm³ in the terpolymer at the very low applied electric field of 125 MV/m. These results demonstrate the promise of blend approaches for tailoring and enhancing the dielectric properties of ferroelectric polymers. POLYM. ENG. SCI., 55:1396–1402, 2015. © 2015 Society of Plastics Engineers     

Plasticity of bcc micropillars controlled by competition between dislocation multiplication and depletion

Recent micropillar experiments have shown strong size effects at small pillar diameters. This “smaller is stronger” phenomenon is widely believed to involve dislocation motion, which can be studied using dislocation dynamics (DD) simulations. In the present paper, we use a three-dimensional DD model to study the collective dislocation behavior in body-centered cubic micropillars under compression. Following the molecular dynamics (MD) simulations of Weinberger and Cai, we consider a surface-controlled cross-slip process, involving image forces and non-planar core structures, that leads to multiplication without the presence of artificial dislocation sources or pinning points. The simulations exhibit size effects and effects of initial dislocation density and strain rate on strength, which appear to be in good agreement with recent experimental results and with a simple dislocation kinetics model described here. In addition, at the high strain rates considered, plasticity is governed mainly by the kinetics of dislocation motion, not their elastic interactions.     

Hydroxyapatite formation by solvothermal treatment of α-tricalcium phosphate with water-ethanol solution

We investigated hydroxyapatite (HAp) formation from alpha-tricalcium phosphate (α-TCP) under solvothermal conditions using water-ethanol solution. The rate of HAp formation decreased with increasing ethanol fraction in the solution. Needle-like HAp was formed with a small amount of beta-tricalcium phosphate after solvothermal treatment for 3 h in solutions with water/ethanol volume ratios of 5/15 and 10/10. In the solution with water/ethanol volume ratio of 5/15, needle-like HAp formed with a small amount of dicalcium phosphate anhydrous (DCPA) at 12 h, and the amount of DCPA increased with increasing treatment period. The aspect ratio of the HAp crystals that formed increased with increasing ethanol fraction in the solution. The fraction of ethanol in the solution during the solvothermal processing affects not only the rate of transformation of α-TCP into HAp, but also the morphology of the HAp that is formed.     

Application of Empirical Mode Decomposition (EMD) on DaTSCAN SPECT images to explore Parkinson Disease

Parkinsonism is the second most common neurodegenerative disorder. It includes several pathologies with similar symptoms, what makes the diagnosis really difficult. I-ioflupane allows to obtain in vivo images of the brain that can be used to assist the PS diagnosis and provides a way to improve its accuracy. In this paper a new method for brain SPECT image feature extraction is shown. This novel Computer Aided Diagnosis (CAD) system is based on the Empirical Mode Decomposition (EMD), which decomposes any non-linear and non-stationary time series into a small number of oscillatory Intrinsic Mode Functions (IMF) a monotonous Residuum. A 80-DaTSCAN image database from the “Virgen de las Nieves” Hospital in Granada (Spain) was used to evaluate this method, yielding up to 95% accuracy, which greatly improves the baseline Voxel-As-Feature (VAF) approach.