New insights into BaTi1-xSnxO3 (0 LT = x LT = 0.20) phase diagram from neutron diffraction data

Neutron powder diffraction (NPD) was employed to further investigate the BaTi1-xSnxO3 (BTS) system previously studied by X-ray diffraction. The room-temperature phase compositions and crystal structures of BTS samples with x = 0, 0.025, 0.05, 0.07, 0.10, 0.12, 0.15 and 0.20 were refined by the Rietveld method using NPD data. It is well known that barium titanate powder (x = 0) crystallizes in the tetragonal P4mm space group. The crystal structures of the samples with 0.025 LT = x LT = 0.07 were refined as mixtures of P4mm and Amm2 phases; those with x = 0.1 and 0.12 show the coexistence of rhombohedral R3m and cubic phases, while the samples with x = 0.15 and 0.20 crystallize in a single cubic Pm (3) over barm phase. Temperature-dependent NPD was used to characterize the BaTi0.95Sn0.05O3 sample at 273, 333 and 373 K, and it was found to form single-phase Amm2, P4mm and Pm (3) over barm structures at these respective temperatures. The NPD results are in agreement with data obtained by differential scanning calorimetry and dielectric permittivity measurements, which show a para-electric-ferroelectric transition (associated with structural transition) from Pm (3) over barm to P4mm at about 353 K followed by a P4mm to Amm2 phase transition at about 303 K

Field experience with Direct Radon and Thoron Progeny Sensors (DRPS/ DTPS) results being distributed in the Balkan Region

Purpose: This paper reports the results of the international collaboration on direct measurements of radon (Rn) and thoron (Tn) progeny in in- door environments (dwellings and schools) in some parts of the whole of Balkan region (Serbia with Kosovo, Republic of Srpska, Slovenia and Macedonia). Argumentations: Direct and time integrated measurements of Rn and Tn progeny were carried out using direct Radon and Thoron Progeny Sensors (DTPS and DRPS), which are basically deposition based progeny sensors, in which the deposited progeny activity is detected by SSNTDs. These are passive detectors meant for long term time integrated measurements. The progeny or the decay products of Rn and Tn are the major dose givers. While assessing the inhalation doses to the public, pas- sive long term measurements are essential. Large scale Rn and Tn decay product monitoring was carried out in dwellings (appr.300) during a period 2011-2013, in each house for minimum 6 months up to one year (Serbia with Kosovo, Republic of Srpska, Slovenia) and/or 68 schools (Republic of Srpska, Macedonia). In Kosovo 40 houses were monitored for 2 two different seasons, one during December – May 2011 and the other May – December 2012. In Slovenia 100 houses were monitored for progeny concentration during 2011-2012. The results are further discussed. Conclusion: The overall analysis of around 400 detectors deployed showed t • Both EETC and EERC obtained using DTPS and DRPS respectively showed a log normal distribution pattern. • The overall GM of EETC was obtained as 0.69 Bq/m3 with a GSD of 2.0; • The GM of EERC was obtained as 11.02 Bq/m3 with a GSD of 2.6; • In Kosovo during the winter December to May 2011, the EERC and EETC were twice that during May to December 2012. • A remarkable finding is the positive correlation between EERC and EETC, while there is none for the parents Rn and Tn. . The average EERC and EETC were measured as 11.31 ± 3.2 and 0.34 ± 0.22 Bq/m3 respectively. Decay product monitoring was carried out in 43 schools of Macedonia. The geometric mean values (and geometric standard deviation) of EERC and EETC were 27 Bq/m3(1.4) and 0.75 Bq/m3(1.4) respectively. The results are further discussed

Poly (epsilon-caprolactone) microspheres for prolonged release of selenium nanoparticles

Poly (e-caprolactone) (PCL) microspheres as a carrier for sustained release of antibacterial agent, selenium nanoparticles (SeNPs), were developed. The obtained PCL/SeNPs microspheres were in the range 1-4 mu m with the encapsulation efficiency of about 90%. The degradation process and release behavior of SeNPs from PCL microspheres were investigated in five different degradation media: phosphate buffer solution (PBS), a solution of lipase isolated from the porcine pancreas in PBS, 0.1 M hydrochloric acid (HCl), Pseudomonas aeruginosa PAO1 cell-free extract in PBS and implant fluid (exudate) from the subcutaneously implanted sterile polyvinyl sponges which induce a foreign-body inflammatory reaction. The samples were thoroughly characterized by SEM, TEM, FTIR, XRD, PSA, DSC, confocal microscopy, and ICP-OES techniques. Under physiological conditions at neutral pH, a very slow release of SeNPs occurred (3 and 8% in the case of PBS or PBS + lipase, respectively and after 660 days), while in the acidic environment their presence was not detected. On the other hand, the release in the medium with bacterial extract was much more pronounced, even after 24 h (13%). After 7 days, the concentration of SeNPs reached a maximum of around 30%. Also, 37% of SeNPs have been released after 11 days of incubation of PCL/SeNPs in the implant exudate. These results suggest that the release of SeNPs from PCL was triggered by Pseudomonas aeruginosa PAO1 bacterium as well as by foreign body inflammatory reaction to implant. Furthermore, PCL/SeNPs microspheres were investigated in terms of their biocompatibility. For this purpose, cytotoxicity, the formation of reactive oxygen species (ROS), and genotoxicity were evaluated on HepG2 cell line. The interaction of PCL/SeNPs with phagocytic cell line (Raw 264.7 macrophages) was monitored as well. It was found that the microspheres in investigated concentration range had no acute cytotoxic effects. Finally, SeNPs, as well as PCL/SeNPs, showed a considerable antibacterial activity against Gram-positive bacteria: Staphylococcus aureus (ATCC 25923) and Staphylococcus epidermidis (ATCC 1228). These results suggest that PCL/SeNPs-based system could be an attractive platform for a prolonged prevention of infections accompanying implants

Effect of PEO molecular weight on sunlight induced photocatalytic activity of ZnO/PEO composites

ZnO spheroidal nanoparticles, synthesized by microwave processing, were used for preparation of composites with polyethylene oxide (PEO). The phase purity and crystal structure of the composites were investigated by X-ray diffraction (XRD) and Raman spectroscopy. The composites particles morphology and size distributions were studied by FE-SEM and laser diffraction particle size analyzer, respectively. The optical properties were studied using UV Vis diffuse reflectance and photoluminescence spectroscopy. It is found that in the wavelength range 550-800 nm, ZnO and ZnO/PEO composites absorb about 50% of the incident light intensity. Also red-shift of band gap energy (0.12-0.15 eV) compared to bulk ZnO was determined. The effect of PEO molecular weights, 200,000, 600,000 and 900,000 g/mol, on photocatalytic activity of ZnO/PEO composites were examined via de-colorization of methylene blue (MB) under direct sunlight irradiation. A large efficiency of MB de-colorization was found after 6 h of irradiation. The enhanced photocatalytic activity of ZnO/PEO composites is attributed to the: (1) lattice defects introduced in ZnO crystal structure by rapid microwave processing, and (2) presence of PEO as a source of oxygen interstitials. In order to confirm and further clarify the experimental results ab initio calculations based on density functional theory (DFT) were performed. (C) 2016 Elsevier Ltd. All rights reserved

Transesterification of used cooking sunflower oil catalyzed by hazelnut shell ash

Hazelnut shell ash was investigated as a new base catalyst for the transesterification of used cooking sunflower oil to biodiesel. To understand its catalytic properties, the prepared ash was characterized by EDX, XRD, TGA/DTA, Hg porosimetry, N-2 physisorption, FE-SEM, and basic strength measurements. The effects of the catalyst loading in the range of 1-5% of the oil weight and the methanol-to-oil molar ratio of 6:1-18:1 on the kinetics of the fatty acid methyl esters synthesis were established. Moreover, the leaching and reusability of the catalyst were assessed. The obtained results revealed that hazelnut shell ash was mostly composed of K, Ca, and Mg. The highest ester content (98%) was achieved at the catalyst loading of 5%, the methanol-to-oil molar ratio of 12:1, and the reaction time of 10 min. The contribution of homogeneous catalysis because of the catalyst leaching was confirmed but did not determine the overall reaction rate. The catalyst can be reused after the recalcination at 800 degrees C for 2 h achieving the high methyl esters content (>96%) in 30 min after three subsequent runs. The overall reaction followed the pseudo-first-order kinetics with respect to triacylglycerols. A linear relationship between the apparent reaction rate constant and the catalyst loading and the methanol-to-oil molar ratio was determined. The determined value of the reaction rate constant was 0.0576 dm(6)/(min.mol(2))

Effective doses estimated from the results of direct radon and thoron progeny sensors (DRPS/DTPS), exposed in some regions of Balkans

The main contribution to the population exposure is due to radon and thoron progenies and not radon and thoron itself. Nevertheless, due to the simplicity and cost effectiveness of radon/thoron measurements compared to the measurements of their progenies, effective doses are usually estimated from the measured Rn/Tn concentrations with the assumed value of equilibrium factor. In this paper, an overview of direct measurements of radon and thoron progenies is some parts of Balkans performed within the framework of large international collaboration is given. In this joint venture, long-term measurements were carried out in dwellings and schools using direct radon progeny sensors/direct thoron progeny sensors (DRPSs/DTPSs). Large scale Rn/Tn progeny survey was performed using 321 DRPSs/DTPSs detectors in the period from 2011 till 2013 encompassing some parts of Serbia: 125 dwellings in the region of Soko Banja (Southern Serbia), 48 dwellings in Kosovo, 44 schools in FYR of Macedonia and 37 dwelling and 25 schools in Republic of Srpska. The detectors were deployed from 3 months up to one year, since long term measurements are essential for assessing inhalation doses to the public. In case where possible seasonal variations were discussed as well. Effective doses were estimated from measured equilibrium equivalent radon and thoron concentrations (EERC and EETC) considering different occupancy factors for inhabitants and pupils

Effective doses estimated from the results of Direct radon and thoron progeny sensors (Drps/Dtps), exposed in selected regions of Balkans

The main contribution to population exposure is due to radon and thoron progenies and not radon itself. The aim of this study was therefore to estimate annual effective dose using the results of Direct Radon and Thoron Progeny Sensors were exposed in 69 selected schools and 319 dwellings in several regions of Balkans: in Serbia: regions of Sokobanja and Kosovo and Metohija, Republic of Macedonia, Republic of Srpska and Slovenia. Obtained average total effective doses are in the range from 0.22 mSv a−1 (schools in Republic of Srpska) to 2.5 mSv a−1 (dwellings in Kosovo) and are below the reference level of 10 mSv a−1 recommended by International Commission on Radiological Protection