Abstract: Magnetic state of Fe-57 implanted and doped ZnO samples have been reported and studied by Mossbauer spectroscopy at different temperatures. The Mossbauer spectra mainly showed four doublets and three sextets, but some ambiguous identification remains regarding the probe site location and influence of defects in the hyperfine and magnetic parameters. In the present work some possible implantation configurations are suggested and evaluated using Monte Carlo simulation and electronic structure calculations within the density functional theory. Various implantation environments were proposed and studied considering the presence of defects. The obtained Fe-57 hyperfine parameters show a good agreement with the reported experimental values for some of these configurations. The possibility of Fe pair formation, as well as a Zn site vacancy stabilization between he second and third neighborhood of the implantation site, is supported. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract: As swipe samples from enrichment activities typically contain uranium particles with a detectable amount of fluorine, the question was raised whether the analysis of fluorine in particles could complement the information on the uranium isotope ratios. For this, uranium oxyfluoride particles were prepared from the controlled hydrolysis of uranium hexafluoride (UF6). The relative amount of fluorine was characterized by scanning electron microscopy combined with energy-dispersive X-ray spectrometry (SEM-EDX), as well as ion-microprobe secondary ion mass spectrometry (IM-SIMS). Of particular interest was the assessment of the reduction of the amount of fluorine over time, and after exposure to UV-light and high temperatures. Micro-Raman spectrometry (MRS) was applied to look for differences in molecular structure between these various sample types. Both SEM-EDX and IM-SIMS showed a general reduction of the fluorine-to-uranium ratio after 12 years of storage. The exposure to UV-light and high temperatures was found to have accelerated the loss of fluorine. A distinct peak at 865 cm− 1 Raman shift was detected for the majority of particles analyzed by MRS. For the particles that were heat-treated, the Raman spectra were similar to the spectrum of U3O8. Although often large variations were observed between particles from the same sample, the three particle measurement techniques (IM-SIMS, SEM-EDX and MRS) showed some consistent trends. They therefore appear promising in terms of the ability to place bounds on particle age, as well as shedding light on the complex processes involved in UO2F2 particle ageing.

Abstract: Recent studies in which X-ray beams of (sub)micrometre to millimetre dimensions have been used for non-destructive analysis and characterization of pigments, minute paint samples and/or entire paintings from fifteenth to twentieth century artists are discussed. The overview presented encompasses the use of laboratory and synchrotron radiation-based instrumentation and deals with the use of several variants of X-ray fluorescence (XRF) as a method of elemental analysis and imaging as well as with the combined use with X-ray diffraction (XRD). Microscopic XRF (μ-XRF) is a variant of the XRF method able to visualize the elemental distribution of key elements, mostly metals, on the scale from 1 μm to 100 μm present inside multi-layered micro samples taken from paintings. In the context of the characterization of artists’ pigments subjected to natural degradation, in many cases the use of methods limited to elemental analysis or imaging does not suffice to elucidate the chemical transformations that have taken place. However, at synchrotron facilities, combinations of μ-XRF with related methods such as μ-XAS (microscopic X-ray absorption spectroscopy) and μ-XRD have proven themselves to be very suitable for such studies. Since microscopic investigation of a relatively limited number of minute paint samples may not yield representative information about the complete artefact they were taken from, several methods for macroscopic, non-invasive imaging have recently been developed. Combined macroscopic XRF/XRD scanning is able to provide a fairly complete overview of the inorganic pigments employed to create a work of art, to answer questions about ongoing degradation phenomena and about its authenticity. As such these newly developed non-invasive and highly specific imaging methods are of interest for many cultural heritage stakeholders.

Abstract: A combination of large-scale and micro-scale elemental imaging, yielding elemental distribution maps obtained by, respectively non-invasive macroscopic X-ray fluorescence (MA-XRF) and by secondary electron microscopy/energy dispersive X-ray analysis (SEM-EDX) and synchrotron radiation-based micro-XRF (SR m-XRF) imaging was employed to reorient and optimize the conservation strategy of van Eyck's renowned Ghent Altarpiece. By exploiting the penetrative properties of X-rays together with the elemental specificity offered by XRF, it was possible to visualize the original paint layers by van Eyck hidden below the overpainted surface and to simultaneously assess their condition. The distribution of the high-energy Pb-L and Hg-L emission lines revealed the exact location of hidden paint losses, while Fe-K maps demonstrated how and where these lacunae were filled-up using an iron-containing material. The chemical maps nourished the scholarly debate on the overpaint removal with objective, chemical arguments, leading to the decision to remove all skillfully applied overpaints, hitherto interpreted as work by van Eyck. MA-XRF was also employed for monitoring the removal of the overpaint during the treatment phase. To gather complementary information on the in-depth layer build-up, SEM-EDX and SR mu-XRF imaging was used on paint cross sections to record microscale elemental maps.

Abstract: This study investigated concentration profiles of trace, rare earth and platinum group metals in fluvial sediments from the Pangani river basin (43,650 km2), one of the largest river basins in Tanzania, to assess its environmental quality. Sediment samples were collected in two distinct seasons from 12 representative sites of diverse land-use practices and characterised by ICP-MS after optimised microwave digestion. Ecological risks were assessed by evaluation of pollution index and comparison with legislated sediment quality guidelines (SQG). The results revealed contamination by some trace metals (e.g. Pb, V, Cu, Cr, Ni, Cd, As, Co, Mn and Zn) in concentrations ranging from 0.7 to 2940 mg kg−1, and four rare earth elements (Y, Ce, Nd, Yb) in concentrations ranging from 0.9 (Yb) to 500 mg kg−1 dry weight (Ce), which significantly exceeded the estimated background values at some stations. Palladium was the only platinum group element that was detected in quantifiable concentrations (0.33.5 mg kg−1). Concentrations of some trace metals exceeded the SQGs at some localised areas. Principal component analysis and multivariate correlations indicated geochemical characteristics of the area as the major control of metal concentrations and spatial variability. Organic matter and clay contents also played a significant role in metal distributions. Assessment of land-use practices upstream of the sampling locations was used to trace potential anthropogenic sources of metal enrichments, where highest levels were found in areas close to urban centres and agricultural activities. The study provides baseline data for future monitoring programs, and highlights the need for more comprehensive analysis involving a wider spatio-temporal scale and ecotoxicological risk assessment.