Piet Van Espen

A new electrostatic transfer line for improved transmission in Fourier transform laser microprobe mass spectrometry with external ion source

The efficient extraction and transfer of ions from an external ion source outside the magnet and their injection through the inhomogeneous fringing field becomes a key factor in the micro-analytical application of Fourier transform mass spectrometry (FTMS) instruments with an external ion source. This paper reports on a new ion transfer line with static electrical fields for a source at a distance of 131 cm from the cylindrical ion cyclotron resonance (ICR) “Infinity” cell in an unshielded 4.7 Tesla superconducting magnet. Basically, ions are accelerated to 2–3 kV, transported through a time-of-flight (TOF) system and decelerated at the entrance of the magnet. The size of the system, the magnetic stray field and the significant electrical field gradients require careful optimisation of the simulations with the SIMION software. According to our calculations, the new ion transfer line should allow transport and trapping of ions initially emitted with an angle of up to 35° with the normal, as opposed to 5° with the former commercial transfer line with improved cylindrical front optics. The design has been experimentally verified using focused laser desorption/ionisation of solids. The data on reference compounds have demonstrated that the sensitivity with the new transfer line increases by a factor of 10. A substantial gain of sensitivity is also expected for other ionisation methods producing ions with a more isotropic angular emission than focused laser irradiation. The new ion optics are fully compatible with the existing hardware so that conversion becomes a minor operation.

Improved radiographic methods for the investigation of paintings using laboratory and synchrotron X-ray sources

It is generally known that radiographic inspection of 15–17th century paintings can easily be done with a polychromatic X-ray source using a voltage between 20 kV and 40 kV in combination with classic X-ray films. Unfortunately, the spatial structure of numerous 19th and early 20th century paintings cannot be visualized with conventional radiography due to several reasons such as the use of lead white grounds or low absorbing pigments. Radiographic images are blurred or worse, they do not contain the picture of the painting. During the last decades, many technological innovations have been introduced in the field of radiography but their possibilities in cultural heritage have not been explored in full detail. In our investigation we used phosphor imaging plates, energy dispersive detectors and CCD-cameras in combination with synchrotron radiation and conventional X-ray tubes in order to improve the quality of radiographic images. Several promising techniques that could improve the quality of radiographs of paintings were identified.

Large-Area Elemental Imaging Reveals Van Eyck's Original Paint Layers on the Ghent Altarpiece (1432), Rescoping Its Conservation Treatment

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 μ-XRF) imaging was employed to reorient and optimize the conservation strategy of van Eycks 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 μ-XRF imaging was used on paint cross sections to record micro-scale elemental maps.

Concentration profiles of metal contaminants in fluvial sediments of a rural-urban drainage basin in Tanzania

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 (0.3–3.5 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.

Quantitative reconstruction of objects from spatially correlated image sequences

Abstract Multivariate image analysis (MIA) is classically used on image sequences, in order to exhibit inter-images correlation. The goal of this study is to demonstrate that it can also be used on correlated image sequences. Such dataset can be obtained when using multi-sensor technique such as secondary ion mass spectrometry (SIMS). It is then possible to compute analyte relative abundance from principal component loadings and reconstruct complex sample internal structure. The principles of the technique are presented and applied to multi-layer electronic component. It was possible to show that the sample was not correctly manufactured and that several unexpected layers have been added.

Non-linear mapping of microbeam proton-induced X-ray emission data for source identification of North Sea aerosols

Abstract A multivariate statistical evaluation technique, non-linear mapping, is proposed to extract information from a multielement microbeam proton-induced X-ray emission data set. Individual aerosol particles, collected in the North Sea troposphere, were classified according to their composition. Several groups of particles were identified and suggestions were made for their sources.

Classification of mineral particles by non-linear mapping of electron microprobe energy dispersive X-ray spectra

A simplified non-linear mapping procedure was applied to energy dispersive electron microprobe X-ray spectra of coal mine dust particles and to those of mineral standards. It is shown that this method allows supervised classification provided that mineral standards are chosen correctly.

Radiation damage evaluation on LYSO and LuYAP materials through dpa calculation assisted by Monte Carlo method

The aim of the present work is to study the radiation damage induced in LYSO and LuYAP crystals by the gamma radiation and the secondary electrons/positrons generated. The displacements per atom (dpa) distributions inside each material were calculated following the Monte Carlo assisted Classical Method (MCCM) introduced by the authors. As gamma sources were used Sc-44, Na-22 and V-48. Also the energy of gammas from the annihilation processes (511 keV) was included in the study. This procedure allowed studying the in-depth dpa distributions inside each crystal for all four sources. It was also possible to obtain the separate contribution from each atom to the total dpa. The LYSO crystals were found to receive more damage, mainly provoked by the displacements of silicon and oxygen atoms.

Binarization of Inhomogeneously Illuminated Images

Most grey level thresholding methods produce good results only when the illumination of the image is homogeneous. An automatic binarization technique suitable for images containing regions of different brightness is presented. It does not use images grey level histogram as a source of information. Rather, the method is based on the transformation of the raster image in such a way that the transformed image can be easy thresholded. A comparison with histogram based threshold selection technique is given.

Development of chemically cross-linked biopolymer based burn wound dressings with antimicrobial properties

Abstracts from the XLII Congress of the European Society for Artificial Organs, 2-5 September 2015, Leuven, Belgium.