Results 1 - 10 of 4735
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[en] Highlights: • The energy landscapes of vacancy diffusion in ionic nano particles are revealed. • Topological features of the landscapes are visualized by a graph-based analysis. • The most probable paths of vacancy migration enhanced by the surface are identified. • Size-dependence of diffusion rate is characterized by mean first-passage time. Size dependence of vacancy migration energy in ionic nano particles is investigated by analysis of potential energy surfaces in potassium chloride clusters. Numerical methods are used to find almost all local minima and transition states for vacancy migration in clusters of different sizes, and reveal characteristic features of energy surface structure. It is shown that migration energy is significantly lower near a cluster surface than near a cluster core, and the mean first-passage time for migration of a vacancy decreases with cluster size. These results are consistent with observations of high diffusion rates in small clusters.
[en] Optically stimulated luminescence (OSL) of pure analytical potassium chloride (KCl) prepared in two different forms (crystals and pellets) was studied. The occurrence of regeneration effect (self-renewal of the OSL signal) in the material was examined. The experiments using the variable delay OSL (VD-OSL) method were carried out. Performed measurements allowed to determine time scale of the phenomenon, as well as quantitative changes of regeneration depending on thermal treatment before and after irradiation. Significant increase of the OSL regeneration was noticeable for pellets after the application of the annealing before irradiation, while for crystals a substantial decrease of regeneration was observed. Preheating applied after irradiation caused that self-renewal of OSL signal was drastically reduced or completely suppressed depending on the form of KCl samples. - Highlights: • Optically stimulated luminescence (OSL) of potassium chloride (KCl) was studied. • The measurements were performed using the variable delay OSL method (VD-OSL). • It was found that regeneration of OSL intensity in KCl could be as high as 2000%. • Annealing caused reduction of OSL renewal for crystals and its increase for pellets. • Preheating after irradiation removed or significantly reduced the OSL regeneration.
[en] Highlights: ► Ternary diffusion coefficients for the systems KCl/βCD/H2O and KCl/HP-βCD/H2O. ► Influence of the KCl on diffusion of some cyclodextrins in the aqueous media. ► Estimation of the association constants of the complexes KCl/βCD and KCl/HP-βCD. - Abstract: Ternary mutual diffusion coefficients measured by the Taylor dispersion method (D11, D22, D12 and D21) are reported for two aqueous systems, that is, potassium chloride and 2-hydroxypropyl-β-cyclodextrin (HP-βCD), and potassium chloride and β-cyclodextrin (βCD) at T = 298.15 K and T = 310.15 K, and at carrier concentrations from (0.000 to 0.010) mol·dm−3 for each solute. Based on these data, some conclusions about the influence of KCl on the diffusion of the cyclodextrins (HP-βCD and βCD) were made, and the association constants of the complexes formed between the two components for each system (KCl and βCD, and KCl and HP-βCD) were estimated.
[en] Within a revival of interest in the emission properties of Tl+-like impurity centers in alkali-halide crystals, the problem of a complete interpretation of high-energy and low-energy emissions in the A-band of KCl:Tl remains without a satisfactory explanation. Two previous works reported experimental results relative to spectral and decay-time measurements for low-energy (weak) emission at 475 nm, and for high-energy emission at 300 nm. In the latter case, however, a confirmation of the existence of an anomalous type of behavior in the slow decay time needed to be clarified. The results reported here demonstrate that this anomaly is not present in high-energy emission. On the basis of these more recent experimental results, an attempt is made to obtain a unifying model, one always based on the Jahn–Teller effect, which could serve in interpreting both high- and low-energy emissions.
[en] One year field experiment of spring barley (Hordeum vulgare L.) was carried out to evaluate the effect of biochar amendment on the pH of Orthic Luvisol at the research site located in western Slovakia (lat. 48°19´00´´; lon. 18°09´00´´). Biochar with higher pH (8.8) was applied to the slightly acidic soils with the initial pH at 5.6. The field experiment consisted of control, 10 and 20 tha-1 of biochar application to soils where all treatments were equally fertilized with 80 kg N ha-1. The soil pH (KCl) at depth 0-10 cm was measured once a month (March-October, 2014). Amendment of 10 tha-1 biochar increased pH (in all months) by 0.49-0.67 but the difference wasn’t significant (P < 0.05) compared to control plots. Higher application rate of biochar (20 tha-1) increased pH (in all months) by 0.62-1.09 with the significant difference in 5 of 8 measurements events compared to control.
[en] Cd(II)-DTPA-tartaric acid mixed system has been examined polaro-graphically. The reduction of the complex is reversible. The complex species [Cd(II)-DTPA]3-, [Cd(II)-TA] and [Cd(II)-DTPA-TA]5- have been observed in the system. The value of equilibrium constant for the mixed system was found to be log b11=4.05. (author)