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Author Rojas, C.M.; Figueroa, L.; Janssens, K.H.; Van Espen, P.E.; Adams, F.C.; Van Grieken, R.E.
Title The elemental composition of airborne particulate matter in the Atacama desert, Chile Type A1 Journal article
Year 1990 Publication The science of the total environment Abbreviated Journal
Volume 91 Issue Pages 251-267
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos A1990CM36100019 Publication Date 2003-09-12
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0048-9697 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:116652 Serial 5602
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Author van der Snickt, G.; Dubois, H.; Sanyova, J.; Legrand, S.; Coudray, A.; Glaude, C.; Postec, M.; van Espen, P.; Janssens, K.
Title Large-area elemental imaging reveals Van Eyck's original paint layers on the Ghent altarpiece (1432), rescoping its conservation treatment Type A1 Journal article
Year 2017 Publication Angewandte Chemie: international edition in English Abbreviated Journal Angew Chem Int Edit
Volume 56 Issue 17 Pages 4797-4801
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000398576000019 Publication Date 2017-03-23
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1433-7851; 0570-0833 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 11.994 Times cited 11 Open Access
Notes ; This research was supported by the Baillet Latour fund, the Belgian Science Policy Office (Projects MO/39/011) and the Gieskes-Strijbis fund. The authors are also indebted to the BOF-GOA SOLAR Paint project of the University of Antwerp Research Council. The church wardens of the cathedral of St. Bavo and their chairman L. Collin are acknowledged for this agreeable collaboration. We also wish to thank conservators L. Depuydt, B. De Volder, F. Rosier, N. Laquiere and G. Steyaert as well as the members of the international committee. We are indebted to Prof. Em. A. Van Grevenstein-Kruse. ; Approved Most recent IF: 11.994
Call Number UA @ admin @ c:irua:142376 Serial 5688
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Author Cabal, A.; Legrand, S.; Van den Bril, B.; Tote, K.; Janssens, K.; van Espen, P.
Title Study of the uniformity of aerosol filters by scanning MA-XRF Type A1 Journal article
Year 2017 Publication X-ray spectrometry T2 – 17th European Conference on X-Ray Spectrometry (EXRS), JUN 19-24, 2016, Univ Gothenburg, Univ Gothenburg, Gothenburg, SWEDEN Abbreviated Journal X-Ray Spectrom
Volume 46 Issue 5 Pages 461-466
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000409246400026 Publication Date 2017-03-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0049-8246 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 1.298 Times cited 4 Open Access
Notes ; ; Approved Most recent IF: 1.298
Call Number UA @ admin @ c:irua:145644 Serial 5852
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Author Serneels, S.; Faber, K.; Verdonck, T.; van Espen, P.J.
Title Case specific prediction intervals for tri-PLS1 : the full local linearisation Type A1 Journal article
Year 2011 Publication Chemometrics and intelligent laboratory systems Abbreviated Journal
Volume 108 Issue 2 Pages 93-99
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract A new method to estimate case specific prediction uncertainty for univariate trilinear partial least squares (tri-PLS1) regression is introduced. This method is, from a theoretical point of view, the most exact finite sample approximation to true prediction uncertainty that has been reported up till now. Using the new method, different error sources can be propagated, which is an advantage that cannot be offered by data driven approaches such as the bootstrap. In a concise example, it is illustrated how the method can be applied. In the Appendix, efficient algorithms are presented to compute the estimates required.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000295310000002 Publication Date 2011-05-12
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0169-7439; 1873-3239 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:92788 Serial 7580
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Author Abreu, Y.; Cruz, C.M.; Pinera, I.; Leyva, A.; Cabal, A.E.; van Espen, P.
Title DFT study of the hyperfine parameters and magnetic properties of ZnO doped with 57Fe Type A1 Journal article
Year 2014 Publication Solid state communications Abbreviated Journal
Volume 185 Issue Pages 25-29
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000333751400007 Publication Date 2014-01-23
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:116839 Serial 7806
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Author Abreu, Y.; Cruz, C.M.; van Espen, P.; Pérez, C.; Piñera, I.; Leyva, A.; Cabal, A.E.
Title Electric field gradient calculations in ZnO samples implanted with 111In(111Cd) Type A1 Journal article
Year 2012 Publication Solid state communications Abbreviated Journal
Volume 152 Issue 5 Pages 399-402
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract A first-principles study of the electric field gradient (EFG) calculated for ideal and In-111(Cd-111) implanted ZnO samples is reported in the present work. The study was made for ZnO ideal hexagonal structures and supercells were introduced in order to consider the possible implantation environments. The calculation was done using the “WIEN2k” code within the density functional theory, the exchange and correlation effects were determined by the GGA approximation. Three possible In-111(Cd-111) implantation configurations were studied, one substitutional incorporation at cation site and two interstitials. The obtained EFG values for the ideal structure and the substitutional site are in good agreement with the experimental reports measured by perturbed angular correlation (PAC) and high precision nuclear magnetic resonance (NMR). Thus, the ascription of substitutional incorporation of In-111(Cd-111) probe atom at the ZnO cation site after annealing was confirmed. (C) 2011 Elsevier Ltd. All rights reserved.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000301329200016 Publication Date 2011-12-09
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0038-1098 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:97821 Serial 7857
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Author Schalm, O.; Cabal, A.; van Espen, P.; Laquière, N.; Storme, P.
Title Improved radiographic methods for the investigation of paintings using laboratory and synchrotron X-ray sources Type A1 Journal article
Year 2011 Publication Journal of analytical atomic spectrometry Abbreviated Journal
Volume 26 Issue 5 Pages 1068-1077
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract It is generally known that radiographic inspection of 1517th 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.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000289731900023 Publication Date 2011-04-11
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0267-9477 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:89928 Serial 8070
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Author Alejo, ellys; Morales, M.C.; Nuñez, V.; Bencs, L.; Van Grieken, R.; van Espen, P.
Title Monitoring of tropospheric ozone in the ambient air with passive samplers Type A1 Journal article
Year 2011 Publication Microchemical journal Abbreviated Journal
Volume 99 Issue 2 Pages 383-387
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract Two sampling campaigns in suburban places in the north zone of Santa Clara city, Cuba, have been carried out on a weekly base with the use of Radiello passive diffusion tubes in order to monitor the tropospheric ozone (O3) levels in 2010. The first campaign was scheduled from February to April (cold season) and the second one in August and October (warm season), both of them at two sampling sites, i.e., Farm and School of Art Instructors. After aqueous extraction, the samples were analyzed by UVVIS spectrophotometry. A seasonal trend was observed with the maximum O3 concentrations in the cold season and the minimum levels in the warm season. Samples collected during the cold season showed the highest O3 levels. Higher levels were reached at the Farm site with average values of about 58 ± 12 μg/m3, which exceeded the limit of the Cuban Standard 99:1999. In the warm season, the O3 concentrations were similar for both sites, but lower than those observed in the cold season. The overall, seasonal average value was found to be 24 μg/m3. Despite the higher weekly average temperatures in August, the O3 concentrations during this month showed the lowest values of the whole sampling period, which finding is in agreement with that reported by the Meteorological Institute of Cuba. Mathematical models, based on the Cochrane-Orcutt algorithm, were fitted to the acquired data set to explain the change in the tropospheric ozone concentrations under various meteorological conditions during the two campaigns. The correlation coefficients for both the cold and the warm seasons demonstrated a strong correlation, i.e., 0.779 and 0.951, respectively. The high correlation of wind speed in the model from the first sampling campaign explains the sharp decrease in O3 concentrations at the SAI sampling site from the sixth week of sampling.
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Publisher Place of Publication Editor
Language Wos 000295770700034 Publication Date 2011-06-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0026-265x; 0026-265x ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:93294 Serial 8277
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Author Roet, D.; van Espen, P.
Title Monte Carlo simulation of X-ray spectra from low energy electrons using optical data Type A1 Journal article
Year 2010 Publication Nuclear instruments and methods in physics research: B: beam interactions with materials and atoms Abbreviated Journal
Volume 268 Issue 17/18 Pages 2794-2800
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract An approach using optical data to simulate both the bremsstrahlung continuum and characteristic K and L X-ray lines generated by low energy electrons (cfr. electron microscopy) in solids is discussed in this paper. The necessary analytical expressions together with the data to calculate the relevant cross sections for elastic and inelastic interactions at these energies along with variance reduction techniques are given. The results of the Monte Carlo simulation are compared to experimental data measured with a JEOL 6300 electron microscope.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000281498900039 Publication Date 2010-07-15
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0168-583x ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:84261 Serial 8281
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Author Cabal Rodríguez, A.E.; Leyva Pernia, D.; Schalm, O.; van Espen, P.J.M.
Title Possibilities of energy-resolved X-ray radiography for the investigation of paintings Type A1 Journal article
Year 2012 Publication Analytical and bioanalytical chemistry Abbreviated Journal
Volume 402 Issue 4 Pages 1471-1480
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract X-ray radiographic images of paintings often show little or no contrast. In order to increase the contrast in radiographic images we measured the X-ray spectrum of a low power X-ray tube, after passing through the painting, with a high energy-resolution SDD detector. To obtain images, the detector is collimated with a 400 mu m diameter pinhole and the painting was moved through the beam in the x and y-direction using a dwell time of a few seconds per pixel. The data obtained consists of a data cube of, typically, 200 x 200 pixels and a 512-channel X-ray spectrum for each pixel, spanning the energy range from 0 to 40 keV. Having the absorbance spectrum available for each pixel, we are able, a posteriori, to produce images by edge subtraction for any given element. In this way high contrast, element-specific, images can be obtained. Because of the high energy-resolution a much simpler edge subtraction algorithm can be applied. We also used principal-component imaging to obtain, in a more automated way, images with high contrast. Some of these images can easily be attributed to specific elements. It turns out that preprocessing of the spectral data is crucial for the success of the multivariate image processing.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000299842000008 Publication Date 2011-07-14
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1618-2642; 1618-2650 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:96200 Serial 8394
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Author Alejo, D.; Morales, M.C.; de la Torre, J.B.; Grau, R.; Bencs, L.; Van Grieken, R.; van Espen, P.; Sosa, D.; Nuñez, V.
Title Seasonal trends of atmospheric nitrogen dioxide and sulfur dioxide over North Santa Clara, Cuba Type A1 Journal article
Year 2013 Publication Environmental monitoring and assessment Abbreviated Journal
Volume 185 Issue 7 Pages 6023-6033
Keywords (down) A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Abstract Atmospheric nitrogen dioxide (NO2) and sulfur dioxide (SO2) levels were monitored simultaneously by means of Radiello passive samplers at six sites of Santa Clara city, Cuba, in the cold and the warm seasons in 2010. The dissolved ionic forms of NO2 and SO2 as nitrate and sulfite plus sulfate, respectively, were determined by means of ion chromatography. Analysis of NO2 as nitrite was also performed by UVVis spectrophotometry. For NO2, significant t tests show good agreement between the results of IC and UVVis methods. The NO2 and SO2 concentrations peaked in the cold season, while their minimum levels were experienced in the warm season. The pollutant levels do not exceed the maximum allowable limit of the Cuban Standard 39:1999, i.e., 40 μg/m3 and 50 μg/m3 for NO2 and SO2, respectively. The lowest pollutant concentrations obtained in the warm season can be attributed to an increase in their removal via precipitation (scavenging) while to the decreased traffic density and industrial emission during the summer holidays (e.g., July and August).
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000319753600053 Publication Date 2012-12-03
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1420-2026; 1573-2967 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor Times cited Open Access
Notes Approved no
Call Number UA @ admin @ c:irua:107293 Serial 8501
Permanent link to this record