Electrochemical Synthesis and Physicochemical Properties of Nanostructured Al2O3–ZrO2–MgO Oxide Systems

Protection of Metals and Physical Chemistry of Surfaces - Based on the use of electrogenerated reactants, a method for producing Al2O3–ZrO2–MgO oxide systems has been proposed. Their...     

The effect of different pollutants exposure on the pigment content of pigmented macrophage aggregates in the spleen of Vardar chub (Squalius vardarensis Karaman, 1928)

Pigmented macrophage aggregates (MAs) are known to change under influence of various factors, such as aging, season, starvation, and/or pollution. In this study, changes in the pigment content of the MAs in the spleen of Vardar chub (Squalius vardarensis, Karaman) (n = 129) collected in spring and autumn, from three rivers with different pollution impact was examined: Zletovska River (metals), Kriva River (metals and municipal wastewater), and Bregalnica River (municipal wastewater). Collected data revealed increased relative volume and number of MAs containing hemosiderin under the influence of metals, significant in autumn (p < .05). In chub exposed to metals combined with municipal wastewater, significant increase of lipochrome accumulation in MAs in autumn, melanin in MAs in fish captured in the spring season, and number of splenic MAs containing combination of melanin and lipochrome was noted. Volumes and number of MAs containing combination of hemosiderin and lipochrome increased in spleen of fish captured in autumn from both Zletovska River and Kriva River, most likely due to the contribution of hemosiderin and lipochrome, respectively. Values measured for the various pigments in splenic MAs in fish captured from Bregalnica River, were overall closer to the values measured for fish captured from Kriva River. Notably, melanin and lipochrome are more likely to be found in fish from waters influenced by municipal wastewater (organic pollution) and hemosiderin in fish spleen from water influenced by mining activity (heavy metals pollution).     

Disseminated tuberculosis: A neglected entity in immunocompromised hemodialysis patients

End‐stage renal disease is considered a factor predisposing to increased risk of tuberculosis with frequent extrapulmonary localization. Although extrapulmonary tuberculosis has been observed for decades, disseminated tuberculosis, a major cause of morbidity and mortality in immunocompromised hosts, remains rather neglected. We report an unusual case of an immunocompromised patient with a late diagnosis and delayed treatment of genitourinary tuberculosis that subsequently led to the diagnosis of vertebral and miliary tuberculosis (disseminating tuberculosis). Therefore, increased awareness is warranted from physicians dealing with hemodialysis patients in order to avoid delays in diagnosis and treatment initiation.     

The effect of synthesis conditions on the physicochemical properties of magnesium aluminate materials

Magnesium aluminate-based materials were prepared by applying different methods: (i) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and (ii) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure.     

Synthesis of Precursors of Complex Oxide Systems Using Electrogenerated Reagents

Glass Physics and Chemistry - The scientific foundations for the synthesis of precursors of nanostructured oxide systems Al2O3–ZrO2–MxOy (M = Mg, Y) are developed. The processes...     

Assessment of chromium biostabilization in contaminated soils using standard leaching and sequential extraction techniques

The iron reducing microorganism Desulfuromonas palmitatis was evaluated as potential biostabilization agent for the remediation of chromate contaminated soils. D. palmitatis were used for the treatment of soil samples artificially contaminated with Cr(VI) at two levels, i.e. 200 and 500 mg kg^− 1. The efficiency of the treatment was evaluated by applying several standard extraction techniques on the soil samples before and after treatment, such as the EN12457 standard leaching test, the US EPA 3060A alkaline digestion method and the BCR sequential extraction procedure. The water soluble chromium as evaluated with the EN leaching test, was found to decrease after the biostabilization treatment from 13 to less than 0.5 mg kg^− 1 and from 120 to 5.6 mg kg^− 1 for the soil samples contaminated with 200 and 500 mg Cr(VI) per kg soil respectively. The BCR sequential extraction scheme, although not providing accurate estimates about the initial chromium speciation in contaminated soils, proved to be a useful tool for monitoring the relative changes in element partitioning, as a consequence of the stabilization treatment. After bioreduction, the percentage of chromium retained in the two least soluble BCR fractions, i.e. the “oxidizable” and “residual” fractions, increased from 54 and 73% to more than 96% in both soils.     

Biosorption of nickel ions from aqueous solutions by natural and modified peanut husks: equilibrium and kinetics

The toxicity and non‐biodegradation of heavy metals, as well as their tendency to accumulate in the soils, water resources and the living organisms, makes them the significant environmental pollutants. Therefore, the reduction and elimination of heavy metal ions from aqueous systems is very important from the ecological, nutritional and environmental reasons. The aim of this study is to investigate whether the natural peanut husks, an agricultural waste, and their chemically modified form are capable to remove Ni(II) ions from aqueous solutions using batch method and to compare their efficiency. The effects of the mass of the natural peanut husks and the initial pH of the solution were studied to find the optimal conditions for maximal removal of Ni(II) ions. MATLAB/Curve Fitting Toolbox was implemented to determine the adequate adsorption isotherm as well as to optimise the equilibrium state of the investigated systems.     

Photoluminescence decay rate of silicon nanoparticles modified with gold nanoislands

We investigated plasmon-assisted enhancement of emission from silicon nanoparticles (ncs-Si) embedded into porous SiO _x matrix in the 500- to 820-nm wavelength range. In the presence in the near-surface region of gold nanoisland film, ncs-Si exhibited up to twofold luminescence enhancement at emission frequencies that correspond to the plasmon resonance frequency of Au nanoparticles. Enhancement of the photoluminescence (PL) intensity was attributed to coupling with the localized surface plasmons (LSPs) excited in Au nanoparticles and to increase in the radiative decay rate of ncs-Si. It has been shown that spontaneous emission decay rate of ncs-Si modified by thin Au film over the wide emission spectral range was accelerated. The emission decay rate distribution was determined by fitting the experimental decay curves to the stretched exponential model. The observed increase of the PL decay rate distribution width for the Au-coated nc-Si-SiO _x sample in comparison with the uncoated one was explained by fluctuations in the surface-plasmon excitation rate.

PACS

78. 67. Bf; 78.55.-m     

Thermal conductivity of highly porous Si in the temperature range 4.2 to 20?K

We report on experimental results of the thermal conductivity k of highly porous Si in the temperature range 4.2 to 20 K, obtained using the direct current (dc) method combined with thermal finite element simulations. The reported results are the first in the literature for this temperature range. It was found that porous Si thermal conductivity at these temperatures shows a plateau-like temperature dependence similar to that obtained in glasses, with a constant k value as low as 0.04 W/m.K. This behavior is attributed to the presence of a majority of non-propagating vibrational modes, resulting from the nanoscale fractal structure of the material. By examining the fractal geometry of porous Si and its fractal dimensionality, which was smaller than two for the specific porous Si material used, we propose that a band of fractons (the localized vibrational excitations of a fractal lattice) is responsible for the observed plateau. The above results complement previous results by the authors in the temperature range 20 to 350 K. In this temperature range, a monotonic increase of k with temperature is observed, fitted with simplified classical models. The extremely low thermal conductivity of porous Si, especially at cryogenic temperatures, makes this material an excellent substrate for Si-integrated microcooling devices (micro-coldplate).

PACS

61.43.-j; 63.22.-m; 65.8.-g