Abstract: Submicron colloidal Ag particles and nano-sized filaments forming a statistical percolation network during ''in situ'' development of double structure tabular microcrystals of AgRr(I) emulsions have been studied by electron energy-loss spectroscopy and zero-loss electron spectroscopic imaging (EELS/ZLESI). Image analysis has shown that random quasi-fractal clusters were formed in the colloid. ZLESI has been applied to characterise the morphology and defect structure of aggregated particles and filaments. Their energy-loss spectra revealed plasmon excitations and interband 4d electron transitions between 4-32 eV energy-loss. To study the cluster structure and its relation to the physical properties, fractal analysis including estimations of cluster fractal dimensions and of density autocorrelation functions has been performed. Mechanisms of fractal aggregation based on known models of diffusion limited aggregation, cluster-cluster aggregation and percolation are discussed.

Abstract: Air particulate samples were collected at Chapiquiña near Arica (Chile) with a six-stage cascade impactor for about 17-day periods during a 31 month interval. Sixteen elements were determined by energy dispersive X-ray fluorescence analysis, and the elemental concentrations were subjected to principal factor analysis. The variability with time of the coarse particles was described by two factors both related to soil dispersion, whereas the fine particle variations could be explained by a third factor related to marine influence. Enrichment factors were compared with those obtained in other remote continental areas, in particular those of air particulate matter sampled at Chacaltaya, Bolivia. Results point to a negligible anthropogenic influence.

Abstract: Size-fractionated aerosol samples, collected over the Atlantic Ocean, were analyzed for up to 20 elements by PIXE. Using a sailboat as sampling platform, duplicate samples were taken for two-day periods by means of battery operated 6-stage cascade impactors, positioned about 8 m above the sea surface. In the PIXE analysis of the fine particle stages (stages 3 to 5) a 5 times smaller beam size was used than for stages 1 and 2. This led to significant improvement in the detection limits for the former stages. The results from the duplicate impactor samples were normally in good agreement, indicating that the combined uncertainty of sampling and PIXE analysis was of the order of 20%. The precision of the PIXE analysis alone was investigated by rebombarding some samples six months after the first analysis. The trends with time of the fine particle sulfur and the coarse particle iron concentrations are discussed in some detail.

Abstract: Bridging the gap between complex signal data output and clear interpretation by non-expert end-users is a major challenge many scientists face when converting their scientific technology into a real-life application. Currently, pattern recognition algorithms are the most frequently encountered signal data interpretation algorithms to close this gap, not in the least because of their straight-forward implementation via convenient software packages. Paradoxically, just because their implementation is so straight-forward, it becomes cumbersome to integrate the expert's domain-specific knowledge. In this work, a novel signal data interpretation approach is presented that uses this domain-specific knowledge as its fundament, thereby fully exploiting the unique expertise of the scientist. The new approach applies data preprocessing in an innovative way that transcends its usual purpose and is easy to translate into a software application. Multiple case studies illustrate the straight-forward application of the novel approach. Ultimately, the approach is highly suited for integration in various (bio)analytical applications that require interpretation of signal data.

Abstract: Energy-dispersive X-ray fluorescence (XRF) is an attractive analytical method to determine the level of air pollution by heavy metals. The concentration of the filter in ng/cm(2) is obtained by direct comparison of the net characteristic line intensity of an element with that of a thin film standard. As the sampled area on the filter and the area of the standard are larger than the area analysed by the instrument, the distribution of the elements on the surface of both samples and standards have to be sufficiently uniform. If this is not the case, biased concentration estimates are obtained. Two scanning macro-XRF setups with a beam diameter of similar to 0.5 mm were used to investigate the distribution of elements in (1) commercially available (Micromatter) standards, (2) in-house quartz filter standards obtained with an aerosol generator and (3) particulatematter (PM10) collected on quartz filters by a Leckel SEQ 47/50 sampler. The uniformity of the Micromatter standards was better than 2%. At least some in-house standards showed a concave distribution with less material at the edges. The maximum bias introduced by this is less than 5%. Because of the limited sensitivity of scanning XRF compared with conventional XRF, the distribution of only a few common elements like Ca and Fe could be determined reliably in aerosol filters. The distribution of some heavy elements could only be measured in filters sampled in polluted regions. In general, the loading of particulate matter over the filters was uniform. Copyright (C) 2017 John Wiley & Sons, Ltd.

Abstract: The radiation damage, in terms of atom displacements, induced by gamma irradiation in LYSO and LuYAP crystals is presented. Sc-44, Na-22 and V-48 are used as gamma sources for this study. The energy of gammas from the electron positron annihilation processes (511 keV) is also included in the study. The atom displacements distributions inside each material are calculated following the Monte Carlo assisted Classical Method introduced by the authors. This procedure also allows to study the atom displacements in-depth distributions inside each crystal. The atom displacements damage in LYSO crystals is found to be higher than in LuYAP crystals, mainly provoked by the displacements of silicon and oxygen atoms. But the difference between atom displacements produced in LYSO and LuYAP decreases when more energetic sources are used. On the other hand, the correlation between the atom displacements and energy deposition in-depth distributions is excellent. The atom displacements to energy deposition ratio is found to increases with more energetic photon sources. LYSO crystals are then more liable to the atom displacements damage than LuYAP crystals. (C) 2015 Elsevier B.V. All rights reserved.

Abstract: The most unique and only known 16th century Antwerp majolica tile floor in Belgium is situated in a tower of the Rameyenhof castle (Gestel, Belgium). This exceptional work of art has recently been investigated in situ by using X-ray fluorescence (XRF) and Raman spectroscopy in order to study the material characteristics. This study reports on the result of the analyses based on the novel combination of non-destructive and portable instrumentation, including a handheld XRF spectrometer for obtaining elemental information and a mobile Raman spectrometer for retrieving structural and molecular information on the floor tiles in the Rameyenhof castle and on a second, similar medallion, which is stored in the Rubens House museum in Antwerp (Belgium). The investigated material, majolica, is a type of ceramic, which fascinated many people and potters throughout history by its beauty and colourful appearance. In this study the characteristic major/minor and trace element signature of 16th century Antwerp majolica is determined and the pigments used for the colourful paintings present on the floor are identified. Furthermore, based on the elemental fingerprint of the white glaze, and in particular on the presence of zinc in the tiles – an element that was not used for making 16th century majolica – valuable information about the originality of the chapel floor and the two central medallions is acquired. (C) 2014 Elsevier B.V. All rights reserved.