Abstract: We review methods and recent studies in which macroscopic to (sub)microscopic X-ray beams were used for nondestructive analysis and characterization of pigments, paint microsamples, and/or entire paintings. We discuss the use of portable laboratory- and synchrotron-based instrumentation and describe several variants of X-ray fluorescence (XRF) analysis used for elemental analysis and imaging and combined with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Macroscopic and microscopic (μ-)XRF variants of this method are suitable for visualizing the elemental distribution of key elements in paint multilayers. Technical innovations such as multielement, large-area XRF detectors have enabled such developments. The use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that take place during natural pigment alteration processes. However, synchrotron-based combinations of μ-XRF, μ-XAS, and μ-XRD are suitable for such studies.

Abstract: Iron mineral containing sensory dendrites in the inner lining of the upper beak of homing pigeons [1] and various bird species [2] are the first candidate structures for an avian magnetic field receptor. A new concept of magnetoreception [3, 4] is based on detailed ultra-structural optical and electron microscopy analyses in combination with synchrotron radiation microscopic X-ray fluorescence analysis (micro-XRF) and microscopic X-ray absorption near edge structures (micro-XANES). Several behavioral experiments [5, 6] and first mathematical simulations [6] affirm our avian magnetoreceptor model. The iron minerals inside the dendrites are housed in three different subcellular compartments (bullets, platelets, vesicles), which could be clearly resolved and identified by electron microscopy on ultrathin sections [1, 3]. Micro-XRF and micro-XANES data obtained at HASYLAB beamline L added information about the elemental distribution and Fe speciation [3], but are averaged over the complete dendrite due to limited spatial resolution. Here we present recently performed micro-XRF maps with sub-micrometer resolution (ESRF ID21), which reveal for the first time subcellular structural information from almost bulk-like dendrite sample material. Due to the thickness of 30 μm the microarchitecture of the dendrites can be considered as undisturbed and artefacts introduced by sectioning might be widely reduced.

Abstract: We present a combined study of experimental and computational work for a dielectric barrier discharge (DBD) used for CH4 conversion into H2. More specifically, we investigated the influence of N2 as an impurity (150,000 ppm) and as additive gas (199%) on the CH4 conversion and H2 yield. For this purpose, a zero-dimensional chemical kinetics model is applied to study the plasma chemistry. The calculated conversions and yields for various gas mixing ratios are compared to the obtained experimental values, and good agreement is achieved. The study reveals the significance of the View the MathML source and View the MathML source metastable states for the CH4 conversion into H2, based on a kinetic analysis of the reaction chemistry.

Abstract: Polyhedral magnetic iron oxide nanocrystals with multiple facets have been embedded in biocompatible and biodegradable polymeric matrices in order to study their structural, magnetic features and alternating-current (AC) magnetic heating efficiency. The encapsulation of iron oxide nanoparticles into a polymer matrix was confirmed by transmission electron microscopy and further corroborated by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). HAADF-STEM tomography proved that the iron oxide nanocrystals consist of well-defined polyhedral structures with multiple facets. The magnetic features were found to be in good agreement with the structural and morphological features and are maintained even after encapsulation. Furthermore, the magnetic nanoparticles inside these matrices may be considered as good candidates for biomedical applications in hyperthermia treatments because of their high heating capacity exhibited under an alternating magnetic field. The anticancer Taxol drug was encapsulated in these nanoparticles and its physical state and release rate at 37 and 42 °C was studied.

Abstract: The intensity levels in a three-dimensional (3D) reconstruction, obtained by electron tomography, can be influenced by several experimental imperfections. Such artifacts will hamper a quantitative interpretation of the results. In this paper, we will correct for artificial intensity variations by determining the 3D point spread function (PSF) of a tomographic reconstruction based on high angle annular dark field scanning transmission electron microscopy. The large tails of the PSF cause an underestimation of the intensity of smaller particles, which in turn hampers an accurate radius estimate. Here, the error introduced by the PSF is quantified and corrected a posteriori.

Abstract: The six platinum group elements (Ru, Rh, Pd, Os, Ir and Pt) can be determined in geological samples down to the μg kg−1 level, by using nickel sulphide fire assay and neutron activation of the residue ramaining after dissolution of the nickel sulphide button in concentrated hydrochloric acid. Losses for the platinum group elements during this dissolution step are usually insignificant, except when the elements are present at ultra-trace levels. The can be recovered from the filtrate by coprecipitation with tellerium. The latter approach also permits determination of silver, which is significantly lost in the hydrochloric acid treatment (recovery <98% instead of typically ≈ 10%). The coprecipitation with tellurium considerably improves the results for gold (recovery ≈ 95% instead of typically 75%).

Abstract: Stimulus-responsive shape-memory materials have attracted tremendous research interests recently, with much effort focused on improving their mechanical actuation. Driven by the needs of nanoelectromechanical devices, materials with large mechanical strain, particularly at nanoscale level, are therefore desired. Here we report on the discovery of a large shape-memory effect in bismuth ferrite at the nanoscale. A maximum strain of up to ~14% and a large volumetric work density of ~600±90 J cm−3 can be achieved in association with a martensitic-like phase transformation. With a single step, control of the phase transformation by thermal activation or electric field has been reversibly achieved without the assistance of external recovery stress. Although aspects such as hysteresis, microcracking and so on have to be taken into consideration for real devices, the large shape-memory effect in this oxide surpasses most alloys and, therefore, demonstrates itself as an extraordinary material for potential use in state-of-art nanosystems.

Abstract: Trace elements found in aerosols were monitored in Jerusalem during the 1979 winter season utilizing an X-ray fluoresence technique. Most of the particulate mass was associated with the natural soil elements, such as Ca, Fe, K and Ti. Only a small fraction of the mass was comprised of elements clearly emitted from human sources, e.g. Pb, Br, V, Ni and Zn. An excellent correspondence was found between the enrichment factors observed in this study and those postulated for other parts of the world. However, the concentration of Ca and Sr in the Jerusalem suspended dust is substantially higher when compared with world averages of urban aerosols.

Abstract: Five geothermal waters from the Mons area (southern Belgium) have been studied: one natural hot spring at Stambruges, one stagnant warm water from the inclined tunnels at Baudour, and three thermal waters from the drillholes at St. Ghislain, Ghlin and Douvrain, originating from the carbonate/anhydrite-bearing Visean strata, at depths of ca. 2600, 1550 and 1300 m, respectively. Multielement chemical analysis of the filtered water and its suspended matter > 0.4 μm) was carried out by instrumental neutron activation. Temperature in depth, calculated using the silica (chalcedony) chemical geothermometer, ranged from 75 to 88°C, in good agreement with experimentally determined values. Na/K and Na/K/Ca geothermometers yieilded erratic results, as expected from the geological environment in the aquifer. From the analytical data it can be calculated that the thermal waters of St. Ghislain, Ghlin and Douvrain are not only saturated with respect to chalcedony, but also to anhydrite, calcite, fluorite, barite, strontianite, and possibly zinc silicate, iron (III) hydroxide or siderite, albite, microcline, gibbsite and kaolinite. They are oversaturated with respect to muscovite. Data are also presented for the other thermal waters, and a cold spring water (Claire Fontaine, Stambruges). The similar trace-element composition of the thermal waters can be explained by percolation of the water in the same distant recharge zone, from where it descends, becomes heated at depth and rises along collapse breccia, and locally (Baudour, Stambruges) along fissures. The uptake of higher amounts of Ca, Mg, Sr and sulfate in St. Ghislain and Ghlin, as compared to Douvrain and Baudour is correlated with the boundary between the non-dissolved and dissolved evaporitic zones. This boundary is situated between St. Ghislain and Douvrain, and is roughly parallel with the direction of the groundwater flow (WNW).

Abstract: River sediments from all of the major drainage basins (except the Indus) in the Indian sub-continent were collected and analysed by thin-film X-ray fluorescence technique (XRF) to determine their chemical composition. On the basis of analysis of more than 120 samples, average chemical compositions of river-borne sediments from the Indian sub-continent have been calculated. Also, average concentration values for sediments from each of the river basins, and the sub-continent average and the inter-basin differences are discussed in relation to weathering processes in the drainage basins. Comparisons have been made with the chemistry of sediments from the Bay of Bengal (which receives the bulk of sediments delivered by Indian rivers). Our observations are discussed in the light of average chemical composition of world-river sediments and the world surface rock exposed for continental weathering.

Abstract: Composition of bed, core and suspended sediments collected from Krishna River sediments were studied and the observations are discussed in the light of other Indian rivers, world's average river suspended particles, surficial rock and soils. The contents of V, Cr, Co, Ni, Cu and Zn in the suspended particles are higher in the Krishna River than in the world's average, indicating pollution inputs. Suspended sediments are enriched (5 to 10 times) in all the elements considered relative to bed sediments. Downstream profile and metal/Al ratios of the elements indicate that the mobility of elements within the basin is controlled by basin geology, size and mineralogical characteristics. Good correlations observed for a number of elements point out to their common sink in the clay fraction of the sediments. There is no systematic variation with depth for the major elements and most of the elements are considerably higher compared to estuarine or Bay of Bengal sediments.

Abstract: Samples of water and sediments were collected over a three year period from the entire region of Cauvery river basin excluding the estuary. On the basis of our observations, we have calculated the average composition of the Cauvery river at several locations from the catchment to the river mouth, the downstream profile of sediment load, annual erosion rates, solute and sediment fluxes and have predicted on long term changes. The sediment chemistry was determined by x-ray fluorescence (xrf) technique, and calculated mean compositions of the Cauvery and its tributary bed and the suspended sediment were compared to those of world average river sediments. Downstream profiles of some of the elements appear to be controlled by size and mineralogical characteristics besides local factors specific to the location of the samples. Interelemental relationships indicated good correlation among the transition elements indicating their co-genetic behaviour within the drainage basin.