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Abstract: Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the total amount of trace elements in retina from adult male Sprague-Dawley rats (n = 6). Concentration of trace elements within individual retinal areas in frozen sections of the fellow eye was established with the use of two methodologies: (1) particle-induced X-ray emission (PIXE) in combination with 3D depth profiling with Rutherford backscattering spectrometry (RBS) and (2) synchrotron X-ray fluorescence (SXRF) microscopy. The most abundant metal in the retina was zinc, followed by iron and copper. Nickel, manganese, chromium, cobalt, selenium and cadmium were present in very small amounts. The PIXE and SXRF analysis yielded a non-homogenous pattern distribution of metals in the retina. Relatively high levels of zinc were found in the inner part of the photoreceptor inner segments (RIS)/outer limiting membrane (OLM), inner nuclear layer and plexiform layers. Iron was found to accumulate in the retinal pigment epithelium/choroid layer and RIS/OLM. Copper in turn, was localised primarily in the RIS/OLM and plexiform layers. The trace elements iron, copper, and zinc exist in different amounts and locations in the rat retina.

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Abstract: Soil collected from beneath a chromite ore processing residue (COPR) disposal site contained a diverse population of anaerobic alkaliphiles, despite receiving a continuous influx of a Cr(VI) contaminated, hyperalkaline leachate (pH 12.2). Chromium was found to have accumulated in this soil as a result of an abiotic reaction of Cr(VI) with Fe(II) present in the soil. This sediment associated Fe(II) was, therefore, acting as a natural reactive zone beneath the COPR and thereby preventing the spread of Cr(VI). In anaerobic microcosm experiments soil microorganisms were able to reduce NO3- at pH 11.2 coupled to the oxidation of electron donors derived from the original soil organic matter, but progressive anoxia did not develop to the point of Fe reduction over a period of 9 months. It is not clear, therefore, if Fe(II) can be actively replenished by microbial processes occurring within the soil at in situ conditions. Sodium bicarbonate was added to this soil to investigate whether bioreduction of Fe in hyperalkaline Cr contaminated soils could be enhanced by reducing the pH to a value optimal for many alkaliphilic bacteria. The addition of NaHCO3 produced a well buffered system with a pH of ∼9.3 and Fe reducing conditions developed within 1 month once complete denitrification had occurred. Fe(III) reduction was associated with an increase in the proportion of genetic clone libraries that were from the phylum Firmicutes, suggesting that these species are responsible for the Fe(III) reduction observed. Amendment of the pH using bicarbonate may provide a suitable strategy for stimulating the bioreduction of Fe(III) in COPR leachate contaminated soils or other environments where microbial reduction is inhibited by elevated pH.

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Abstract: We present recent experimental results on the structural, electrical, magnetic, and magneto-optical properties of Mn-implanted Si and Co-doped TiO2?? magnetic oxides. Si wafers, both n- and p-type, with high and low resistivity, were used as the starting materials for implantation with Mn ions at the fluencies up to 5 × 1016 cm?2. The saturation magnetization was found to show the lack of any regular dependence on the Si conductivity type, type of impurity and the short post-implantation annealing. According to XMCD Mn impurity in Si does not bear any appreciable magnetic moment at room temperature. The obtained results indicate that above room temperature ferromagnetism in Mn-implanted Si originates not from Mn impurity but rather from structural defects in Si. The TiO2?? :Co thin films were deposited on LaAIO3 (001) substrates by magnetron sputtering in the argon–oxygen atmosphere at oxygen partial pressure of 2·10?6–2·10?4 Torr. The obtained transverse Kerr effect spectra at the visible and XMCD spectra indicate on intrinsic room temperature ferromagnetism in TiO2?? :Co thin films at low (< 1%) volume fraction of Co.

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Abstract: We have demonstrated the successful production of titanium phosphate glass microspheres in the size range of ?10–200 ?m using an inexpensive, efficient, easily scalable process and assessed their use in bone tissue engineering applications. Glasses of the following compositions were prepared by melt-quench techniques: 0.5P2O5–0.4CaO–(0.1 ? x)Na2O–xTiO2, where x = 0.03, 0.05 and 0.07 mol fraction (denoted as Ti3, Ti5 and Ti7 respectively). Several characterization studies such as differential thermal analysis, degradation (performed using a novel time lapse imaging technique) and pH and ion release measurements revealed significant densification of the glass structure with increased incorporation of TiO2 in the glass from 3 to 5 mol.%, although further TiO2 incorporation up to 7 mol.% did not affect the glass structure to the same extent. Cell culture studies performed using MG63 cells over a 7-day period clearly showed the ability of the microspheres to provide a stable surface for cell attachment, growth and proliferation. Taken together, the results confirm that 5 mol.% TiO2 glass microspheres, on account of their relative ease of preparation and favourable biocompatibility, are worthy candidates for use as substrate materials in bone tissue engineering applications.

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Abstract: The variation in geographical distribution of selenium (Se) in environmental settings and the food chain can cause serious human health deficiencies, or poisoning and fatal death. Although Se toxicity is usually inferred as caused by local geology or human activities, the current food trade practices raise Se concerns to a global level, as the Se contained in agricultural products is often unknown. In most natural settings, the prime -. source of Se are shale rocks. Yet, Se weathering pathways and release mechanisms are poorly understood because the locus and the distribution of Se in shales are unknown. Therefore, this thesis assessed the geochemical environment surrounding Se in shales and identified the main inorganic and organic host phases and elucidated the Se speciation and the way this may affect the Se mobilization pathways. This was done by combining simple and complex geochemical, mineralogical and spectroscopic techniques -that were statistically validated to analyse shale samples from the UK, Colombia and China that were representative for typical (1 - 10 ug/g) and extreme (>1 %) Se concentrations. The first important result was the identification of pyrite and organic matter as the two main Se host phases. Additionally, the data showed that in typical shales (e.g. with <6% organic C and 1-2% reduced inorganic S) Se was preferentially associated to pyrite, while in low pyrite shales the association between Se and organic matter was favoured. Interestingly, the data also revealed that depending on the formation pathways pyrite morphology also differentially bound Se with euhedrals concentrating more Se than framboids. Finally, the spectroscopic data showed that Se was not substituting S in pyrite, instead Se was present as an independent FeSex species in close association with both euhedral and framboidal pyrite. Conversely, in the organic matrix, nanosized elemental Se and organo-Se species (Se=C, Se-Se and Se-C bonds) were the main Se carriers.