Raman spectroscopic investigations of epitaxial BiFeO3 thin films on rare earth scandate substrates

BiFeO₃ epitaxial thin films fabricated by pulsed laser deposition on different scandate substrates were investigated by means of Raman spectroscopy. We observed periodic changes in Raman position, full width at half maximum and intensity for some phonon modes as a function of the azimuthal angle ϕ. Further analysis revealed the possibility to assign the so far controversial discussed Raman modes at low wavenumbers (<250 cm⁻¹) through rotational Raman measurements at different azimuthal angles, which show high sensitivity to the aforementioned parameters. Furthermore, the ferroelectric/ferroelastic domain structure shown by piezo‐response force microscopy investigations of the samples was confirmed. Our results are supported by symmetry‐based calculations including the analysis of Raman scattering geometry as well as the dielectric function of BiFeO₃ in the infrared range. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and structure of tridentate bis(phosphinic amide)-phosphine oxide complexes of yttrium nitrate. Applications of 31P,89Y NMR methods in structural elucidation in solution

The synthesis and characterisation of a tridentate ligand containing two diphenylphosphinic amide side-arms connected through the ortho position to a phenylphosphine oxide moiety and the 1:1 and 2:1 complexes formed with yttrium nitrate are reported for the first time. The free ligand (R(P1)*,S(P3)*)-11 is obtained diastereoselectively by reaction of ortho-lithiated N,N-diisopropyl-P,P-diphenylphosphinic amide with phenylphosphonic dichloride. Complexes [Y((R(P1)*,S(P3)*)-11)(NO(3))(3)] and [Y((R(P1)*,S(P3)*)-11)(2)(NO(3))](NO(3))(2) were isolated by mixing ligand 11 with Y(NO(3))(3)·6H(2)O in acetonitrile at room temperature in a ligand to metal molar ratio of 1:1 and 2:1, respectively. The 1:1 derivative is the product of thermodynamic control when a molar ratio of ligand to yttrium salt of 1:1 is used. The new compounds have been characterised both as the solid (X-ray diffraction) and in solution (multinuclear magnetic resonance). In both yttrium complexes the ligand acts as a tridentate chelate. The arrangement of the two ligands in the 2:1 complex affords a pseudo-meso structure. Tridentate chelation of yttrium(III) in both complexes is retained in solution as evidenced by (89)Y NMR data obtained via(31)P,(89)Y-HMQC, and (89)Y,(31)P-DEPT experiments. The investigation of the solution behaviour of the Y(III) complexes through PGSE NMR diffusion measurements showed that average structures in agreement with the 1:1 and 1:2 stoichiometries are retained in acetonitrile.     

Scalarization and decomposition of vector variational inequalities governed by bifunctions

In this article we study the structure of solution sets within a special class of generalized Stampacchia-type vector variational inequalities, defined by means of a bifunction which takes values in a partially ordered Euclidean space. It is shown that, similar to multicriteria optimization problems, under appropriate convexity assumptions, the (weak) solutions of these vector variational inequalities can be recovered by solving a family of weighted scalar variational inequalities. Consequently, it is deduced that the set of weak solutions can be decomposed into the union of the sets of strong solutions of all variational inequalities obtained from the original one by selecting certain components of the bifunction which governs it.     

Multilayered catalysts for fatty acid ester hydrotreatment into fuel range hydrocarbons

This study aims to investigate Ni–Mo/γAl₂O₃ and Ni–La/Zn-ZSM-5–γAl₂O₃ catalysts, which convert methyl esters into various compounds with a similar composition to those found in diesel fuels. The catalysts were synthesized by impregnation using two different routes and characterized by atomic absorption spectrometry, Brunauer–Emmett–Teller, and scanning electron microscopy. The acid strength distribution indicates a relatively high concentration of weak acid centers for both materials. The disposal of the catalysts into the reactor system is an important factor for driving the process toward the desired reaction products. The hydrodeoxygenation becomes important and paraffins are formed as intermediaries when Ni–Mo/γAl₂O₃ is first disposed into the reactor, whereas hydrocracking is poor and the dehydrocyclization does not occur in the case of Ni–La/Zn-ZSM-5–γAl₂O₃ as first layer. Triple-layered catalytic systems enhance the production of n-paraffins with high carbon number, mainly C17 and C18, which are important as diesel component. The effect of temperature was also studied and it was found that aromatics are mainly formed over double-layered catalytic systems by varying the temperature. In the case of triple-layered catalysts, the change in the product composition from saturated hydrocarbons with 12–18 carbon atoms to aromatics was observed by increasing the temperature from 420 to 445 °C. An interesting finding by the addition of n-octane in the feed was observed and the considerable increase in C8 aromatics involved the dehydrocyclization that occurred faster than hydrocracking.     

Optical and electrochemical-mediated detection of ascorbic acid using manganese porphyrin and its gold hybrids

The developments concerning new hybrids based on porphyrin derivatives and colloids destined for the detection of ascorbic acid (AA) in the relevant range for medical investigations are presented. Mn(III) tetratolylporphyrin chloride (MnTTPCl), spherical gold colloid (n-Au), and their hybrid (MnTTPCl/n-Au) were chosen to be comparatively investigated by ultraviolet–visible spectroscopy in the presence of AA. The hybrid material (MnTTPCl/n-Au) has the best capacity to detect concentrations of AA in the range of 2.6 × 10^?6–4.38 × 10^?5 M. Modified glassy carbon (GC) electrodes were obtained by thin film deposition of MnTTPCl, n-Au alone, and in successive mixed thin films, comparing their response during the electrochemical oxidation of AA. The electrocatalytic effect of the MnTTPCl on the AA oxidation is justified both by the increase in the peak current density and by the shift toward more negative potentials (0.024 V). The GC/MnTTPCl electrode has the best electrocatalytic effect for the AA oxidation and is promising for sensor applications.     

The Balassa–Samuelson effect in Romania – The role of regulated prices

Due to the Balassa–Samuelson effect, the candidate countries to the European Monetary Union face a possible conflict between the effects of tradable productivity increase on inflation and on the appreciation of the real exchange rate on one hand, and the Maastricht criteria regarding inflation and exchange rate stability on the other hand. A restrictive monetary policy could succeed in reaching inflation criteria, but only with the cost of slowing down real convergence. This paper deals with the Balassa–Samuelson effect in Romania. The main conclusion of the paper is that in the period 1998–2006 the average annual rate of inflation generated by the Balassa–Samuelson effect in Romania was on average 0.6% in the case of the classical model. Due to the existence of government-regulated prices (mostly non-tradable goods) accounting for as much as 21% of the CPI basket in Romania – the price of non-tradables has increased by less than in the case those prices were market prices. If we include these regulated prices in non-tradable, which is named by us extended model, the impact of Balassa–Samuelson on inflation could have been on average 2.46%. Therefore, the Balassa–Samuelson effect is expected to result into higher inflation with future price liberalization for non-tradables.     

Scalar characterizations of weakly cone-convex and weakly cone-quasiconvex functions

The principal aim of this paper is to show that weakly cone-convex vector-valued functions, as well as weakly cone-quasiconvex vector-valued functions, can be characterized in terms of usual weakly convexity and weakly quasiconvexity of certain real-valued functions, defined by means of the extreme directions of the polar cone or by Gerstewitz’s scalarization functions.     

Controlled manufacturing of nanoparticles by the laser pyrolysis: Application to cementite iron carbide

The laser pyrolysis is an attractive technique for the synthesis of different nanostructures from gas-phase precursors. The characteristics of this synthesized method are here exemplified by the production of almost pure cementite Fe₃C nanomaterials, obtained by the pyrolysis of methyl methacrylate and iron pentacarbonyl (vapors). Those nanopowders exhibited core (Fe₃C)-shell (MMA polymer-based) morphologies and mean particle diameters of about 8-9 nm. Preliminary magnetic measurements indicate rather high values for the saturation magnetization. By irradiating the same reactive mixture with a lower intensity radiation, the chemical content of nanopowders shifts towards mixtures of iron and maghemite/magnetite iron oxides.     

ВЛИЯНИЕ ПОЛОГО КАТОД А НА РАССЛОЕНИЕ ТЛЕЮЩЕГО РАЗРЯДА

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The influence op a hollow cathode upon the striation of a glow discharge