Diffusion of Mn interstitials in (Ga,Mn)As epitaxial layers

Magnetic properties of thin (Ga,Mn)As layers improve during annealing by out-diffusion of interstitial Mn ions to a free surface. Out-diffused Mn atoms participate in the growth of a Mn-rich surface layer and a saturation of this layer causes an inhibition of the out-diffusion. We combine high-resolution x-ray diffraction with x-ray absorption spectroscopy and a numerical solution of the diffusion problem for the study of the out-diffusion of Mn interstitials during a sequence of annealing steps. Our data demonstrate that the out-diffusion of the interstitials is substantially affected by the internal electric field caused by an inhomogeneous distribution of charges in the (Ga,Mn)As layer.Comment: 11 pages, 5 figure

On the utilization of modified red mud in dimethyl disulfide and methyl mercaptan emission abatement

In this paper, a novel application of industrial waste, namely red mud (RM), in the abatement of two malodorous and harmful sulfur compounds, dimethyl disulfide (DMDS) and methyl mercaptan (MM), is presented. The effects of calcination and activations with hydrochloric acid or a mixture of hydrochloric and orthophosphoric acid on the properties and performance of RM are compared using laboratory-scale experiments. The RM-based materials were characterized by XRF, XRD, FE-SEM, N2 -physisorption, TGA/DTA, and FTIR analyses. RM exhibits very promising catalytic properties in the abatement of both DMDS and MM. The hydrochloric acid-activated RM was the most active in both cases, which was explained by its rather high specific surface area (144 m2 g −1 ), higher contents of Fe2O3 and TiO2, as well as lower content of phosphorus. For both DMDS and MM, the main oxidation products were sulfur dioxide, carbon monoxide, and carbon dioxide. DMDS was observed as a reaction intermediate in MM oxidation. While the final conversions of DMDS and MM were high, the oxidation was not complete, indicated by the formation of carbon monoxide. Nevertheless, the modified RM appears as a very interesting alternative to the existing DMDS and MM abatement catalysts.Web of Science121art. no.

DECENTRALISATION AND QUALITY OF GOVERNANCE: SELECTED ISSUES FROM THE CZECH AND SLOVAK REPUBLIC

Public administration reforms in the Czech Republic and in Slovakia started almost immediately after the "Velvet Revolution" in 1989. More than two decades of concrete experience with decentralisation in the specific environment of two selected transitional countries, now provides enough material for an attempt to assess the main pros, cons and risks of decentralisation as a public administration reform tool in these conditions. The goal of the paper is to discuss some important issues connected with processes of creation of modern governance in transitional countries, focusing mainly on decentralisation, its general problems and its specific limits in the environment of accession countries in Central Europe. Both Slovakia and the Czech Republic use decentralisation as the dominant tool to change their current public administrations. decentralisation might well be a good thing to achieve better governance in accession countries in Central Europe, but only under certain circumstances. Decentralisation alone does not bring positive results, automatically and immediately

Effect of nanoparticle size in Pt/SiO2 catalyzed nitrate reduction in liquid phase

Effect of platinum nanoparticle size on catalytic reduction of nitrate in liquid phase was examined under ambient conditions by using hydrogen as a reducing agent. For the size effect study, Pt nanoparticles with sizes of 2, 4 and 8 nm were loaded silica support. TEM images of Pt nanoparticles showed that homogeneous morphologies as well as narrow size distributions were achieved during the preparation. All three catalysts showed high activity and were able to reduce nitrate below the recommended limit of 50 mg/L in drinking water. The highest catalytic activity was seen with 8 nm platinum; however, the product selectivity for N-2 was highest with 4 nm platinum. In addition, the possibility of PVP capping agent acting as a promoter in the reaction is highlighted.Web of Science111art. no. 19

On the Utilization of Modified Red Mud in Dimethyl Disulfide and Methyl Mercaptan Emission Abatement

In this paper, a novel application of industrial waste, namely red mud (RM), in the abatement of two malodorous and harmful sulfur compounds, dimethyl disulfide (DMDS) and methyl mercaptan (MM), is presented. The effects of calcination and activations with hydrochloric acid or a mixture of hydrochloric and orthophosphoric acid on the properties and performance of RM are compared using laboratory-scale experiments. The RM-based materials were characterized by XRF, XRD, FE-SEM, N2-physisorption, TGA/DTA, and FTIR analyses. RM exhibits very promising catalytic properties in the abatement of both DMDS and MM. The hydrochloric acid-activated RM was the most active in both cases, which was explained by its rather high specific surface area (144 m2 g−1), higher contents of Fe2O3 and TiO2, as well as lower content of phosphorus. For both DMDS and MM, the main oxidation products were sulfur dioxide, carbon monoxide, and carbon dioxide. DMDS was observed as a reaction intermediate in MM oxidation. While the final conversions of DMDS and MM were high, the oxidation was not complete, indicated by the formation of carbon monoxide. Nevertheless, the modified RM appears as a very interesting alternative to the existing DMDS and MM abatement catalysts

Effect of nanoparticle size in Pt/SiO₂ catalyzed nitrate reduction in liquid phase

Abstract Effect of platinum nanoparticle size on catalytic reduction of nitrate in liquid phase was examined under ambient conditions by using hydrogen as a reducing agent. For the size effect study, Pt nanoparticles with sizes of 2, 4 and 8 nm were loaded silica support. TEM images of Pt nanoparticles showed that homogeneous morphologies as well as narrow size distributions were achieved during the preparation. All three catalysts showed high activity and were able to reduce nitrate below the recommended limit of 50 mg/L in drinking water. The highest catalytic activity was seen with 8 nm platinum; however, the product selectivity for N₂ was highest with 4 nm platinum. In addition, the possibility of PVP capping agent acting as a promoter in the reaction is highlighted

Leaching of metals from red mud and toxicity in human cells in vitro

Toxicity of red mud, a waste from alumina production, was studied using human breast cancer MCF-7 cells. Culture medium was prepared by mixing water for 3 days with the red mud and removing solid particles afterwards (red mud water). Culture for 48 h of the cells in this medium in neutral pH decreased the cell viability, as analyzed by the MTT-test, and increased the formation of reactive oxygen species. Thus, neutralization does not eliminate the toxicity of red mud. In preliminary experiments, a combined effect of five metals (Cr, Li, V, Al, As) increased the formation of ROS (reactive oxygen species) statistically significantly. Each element separately did not have a similar effect. In environmental applications, red mud is likely to be used after activation. In this work, the red mud was activated using hydrochloric acid to study the physical and chemical properties before and after the treatment. Activation increased the specific surface area of red mud from 16 m2 g−1 to 148 m2 g−1, which is beneficial in many environmental applications such as in the adsorptive removal of pollutants. After activation, leaching of some elements from the red mud decreased (e.g. Al from 38.0 to 0.56 mg L−1, As from 21.0 to 2.1 μg L−1, V from 172.0 to 29.8 μg L−1) while some increased (e.g. Li from 0.04 to 2.81 mg L−1, Cr from 0.35 to 3.23 mg L−1).Web of Science332art. no. 13880

Leaching of metals from red mud and toxicity in human cells in vitro

Abstract Toxicity of red mud, a waste from alumina production, was studied using human breast cancer MCF-7 cells. Culture medium was prepared by mixing water for 3 days with the red mud and removing solid particles afterwards (red mud water). Culture for 48 h of the cells in this medium in neutral pH decreased the cell viability, as analyzed by the MTT-test, and increased the formation of reactive oxygen species. Thus, neutralization does not eliminate the toxicity of red mud. In preliminary experiments, a combined effect of five metals (Cr, Li, V, Al, As) increased the formation of ROS (reactive oxygen species) statistically significantly. Each element separately did not have a similar effect. In environmental applications, red mud is likely to be used after activation. In this work, the red mud was activated using hydrochloric acid to study the physical and chemical properties before and after the treatment. Activation increased the specific surface area of red mud from 16 m2 g−1 to 148 m2 g−1, which is beneficial in many environmental applications such as in the adsorptive removal of pollutants. After activation, leaching of some elements from the red mud decreased (e.g. Al from 38.0 to 0.56 mg L−1, As from 21.0 to 2.1 μg L−1, V from 172.0 to 29.8 μg L−1) while some increased (e.g. Li from 0.04 to 2.81 mg L−1, Cr from 0.35 to 3.23 mg L−1