References of "Strivay, David"
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See detailDiscovery of a woman portrait behind La Violoniste by Kees Van Dongen through hyperspectral imaging
Herens, Elodie ULg; Defeyt, Catherine ULg; Walter, Philippe et al

in Heritage Science (in press)

Despite the fact that Kees Van Dongen was one of the most famous painter of the 20th century, only little information about his palette and his technique is available. To contribute to the ... [more ▼]

Despite the fact that Kees Van Dongen was one of the most famous painter of the 20th century, only little information about his palette and his technique is available. To contribute to the characterization of Van Dongen's painting materials, La Violoniste, painted by the artist around 1923, has been analyzed by using three complementary techniques: macro X-ray fluorescence (MA-XRF), Raman spectroscopy and hyperspectral imaging. The elemental repartition given by MA-XRF and the results obtained thanks to Raman spectroscopy help us to complete the identification of pigments contained in La Violoniste (lead white, iron oxides, cadmium yellow, vermilion, Prussian blue, titanium white, ultramarine, a chromium pigment and carbon black) while the results obtained via hyperspectral imaging reveal a hidden woman portrait. Besides the fact that Kees Van Dongen was particularly renowned for his female portraits, this hidden composition presents obvious stylistic similarities with the well-known portraits produced by the artist during his Parisian stay (starting from 1899). Thanks to Raman spectroscopy, visual examination and MA-XRF, we show that the original background contains ultramarine, the hidden portrait's clothes are probably made of the same colour as the present violinist's dress and her carnation contains zinc, contrary to the violinist's flesh which is mainly made of lead white. [less ▲]

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See detailNew insights on the Picasso’s Blue Period painting La famille Soler through non-invasive imaging and analytical techniques
Defeyt, Catherine ULg; Walter, Philippe; Rousselière, Hélène et al

in Studies in Conservation (in press)

The material study of La Famille Soler through non-invasive imaging, molecular, structural and elemental techniques, permitted a relevant re-examination of this singular blue period painting, which is ... [more ▼]

The material study of La Famille Soler through non-invasive imaging, molecular, structural and elemental techniques, permitted a relevant re-examination of this singular blue period painting, which is considered as the earliest Picasso’s version of Le déjeuner sur l’herbe by E. Manet. On the one hand, it was concluded that the underlying landscape painted by Vidal in 1903 referred to Manet’s masterpiece. On the other hand, it was assumed that the cubist sketch undertaken by Picasso in 1912, prior to the current blue background, consists of an uncompleted transformation of Vidal’s landscape into synthetic cubism. Additionally, the main pigments associated to the underlying compositions were successfully identified. [less ▲]

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See detailAssessment of natural radioactivity and associated radiation hazards in sand building material used in Douala Littoral Region of Cameroon, using gamma spectrometry
Guembou Shouop, Cébastien Joel ULg; Ndontchueng Moyo, Maurice; Chene, Grégoire ULg et al

in Environmental Earth Sciences (2017), 76(164),

Twenty-four sand samples were collected from different sand quarries from Douala Littoral Region (Wouri, Dibamba, Mungo and Docteur Anse rivers and Atlantic Sea) along the Guinea Golf. These samples were ... [more ▼]

Twenty-four sand samples were collected from different sand quarries from Douala Littoral Region (Wouri, Dibamba, Mungo and Docteur Anse rivers and Atlantic Sea) along the Guinea Golf. These samples were investigated using gamma-ray spectrometry system. Highest values of 226Ra, 232Th and 40K measured specific activities expressed in Bq Kg−1 units were, respectively, 146.7 (in Youpoue–Bamenda 2) 102.9 (in Village 1) and 928 (in Northern Akwa 6) while the lowest values were found to be, respectively, 11.8 (in Northern Akwa 6), 8.0 (in Bonaberi–Bonamikano 4) and 54.0 (Youpoue 3). The potential radiological hazards parameters were assessed by calculating successively radium equivalent activity (Raeq), outdoor absorbed gamma dose rate (Dout), annual effective dose rate, internal hazard (Hin) and external hazard (Hex) indices and alpha and gamma index from using those sand in the construction of dwellings and large buildings. Results obtained show that annual dose absorbed by inhabitants due to sand construction use in Douala is below 1.0 mSv year−1. Therefore, most of the types of sands studied and incorporated in constructions appear to be safe as building material. The outputs from this research will be useful to assess the radiation hazards of sand building material in humans and to initiate a sand database together with a radiological map of the area at stake. [less ▲]

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See detailPrecision measurement of radioactivity in Gamma-rays spectrometry using two HPGe detectors (BEGe-6530 and GC0818-7600SL models) comparison techniques: Application to the soil measurement.
Guembou Shouop, Cébastien Joel ULg; Samafou Penabei; NDONTCHUENG MOYO, Maurice et al

in MethodsX (2017), 4(42-54), 2017

To obtain high quality of results in gamma spectrometry, it is necessary to select the best HPGe detector for particular measurements, to calibrate energy and efficiency of gamma detector as accurate as ... [more ▼]

To obtain high quality of results in gamma spectrometry, it is necessary to select the best HPGe detector for particular measurements, to calibrate energy and efficiency of gamma detector as accurate as possible. To achieve this aim, the convenient detector model and gamma source can be very useful. The purpose of this study was to evaluate the soil specific activity using two HPGe model (BEGe-6530 and GC0818-7600SL) by comparing the results of the two detectors and the technics used according to the detector type. The relative uncertainty activity concentration was calculated for 226Ra, 232Th and 40K. For broad energy germanium detector, BEGe-6530, the relative uncertainty concentration ranged from 2.85 to 3.09% with a mean of 2.99% for 226Ra, from 2.29 to 2.49% with a means of 2.36% for 232Th and from 3.47 to 22.37% with a mean of 12.52% for 40K. For GC0818-7600SL detector, it was ranged from 10.45 to 25.55% with a mean of 17.10% for 226Ra, from 2.54 to 3.56% with a means of 3.10% for 232Th and from 3.42 to 7.65% with a mean of 5.58% for 40K. The average report between GC0818-7600SL model and BEGe-6530 model was calculated and showed the mean value of 3.36. The main study was based on the following points: • Determination of The relative uncertainty activity concentration of 226Ra, 232Th and 40K • Determination of the relative uncertainty related to the radium equivalent activity to compare the performance of the two detection systems • Proved that the activity concentration determination in gamma spectrometry depended on the energy range emitted by a radionuclide. This study showed that the standard deviation measurement was less important to the result realized with BEGe-6530 HPGe model. Our findings were demonstrated that the results of the Broad Energy Germanium detector were more reliable. [less ▲]

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See detailMultianalytical Study of “Le Sorcier d’hiva Oa” by Gauguin
Defeyt, Catherine ULg; Remon, Regine; Strivay, David ULg

Poster (2016, December)

Although there is abundant literature on the worldwide famous French painter, Paul Gauguin, very little is known concerning his painting techniques and materials. The present research aims to throw a new ... [more ▼]

Although there is abundant literature on the worldwide famous French painter, Paul Gauguin, very little is known concerning his painting techniques and materials. The present research aims to throw a new light on Gauguin’s œuvre through the in depth study of Le Sorcier d’ Hiva Oa, painted by Gauguin during his stay in French Polynesia in 1902, by means of non-invasive imaging and analytical techniques. While the infrared reflectography examination of the painting revealed how the artist achieved his final composition, the results obtained by Raman spectroscopy and X ray fluorescence spectroscopy in punctual and mapping modes allowed identifying the different pigments he combined to obtain the bright color shades characterizing this artwork. [less ▲]

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See detailANALYSES OF EARLY MEDIEVAL STAINED WINDOW GLASS FROM THE MONASTERY OF BAUME-LES- MESSIEURS (JURA, FRANCE)
Van Wersch, Line ULg; Loisel, C.; Mathis, François ULg et al

in Archaeometry (2016), 58(6), 930-946

The collection of early medieval window glass found in the abbey of Baume-les-Messieurs (Jura, France) is exceptional because it dates to the end of the eighth century, and due to the number of fragments ... [more ▼]

The collection of early medieval window glass found in the abbey of Baume-les-Messieurs (Jura, France) is exceptional because it dates to the end of the eighth century, and due to the number of fragments as well as their state of conservation. Different colours and forms have been identified. These pieces are a rare opportunity to address the glass craft, its recipes and techniques for a phase of its history that has remained little known. Analyses in PIXE–PIGE prove that, in addition to fragments from two soda glass items, the pieces are made from wood-ash glass. Most of them probably came from the same production and the raw material is present in the region. At this early stage of wood-ash glass production, the glassmakers had mastered the glass as well as the colour processes. [less ▲]

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See detailGamma-Ray Spectrometry: Experimental Measurement and Monte Carlo Simulation using GEANT4 toolkit
Guembou Shouop, Cébastien Joel ULg; Ndontchueng Moyo, Maurice; Chene, Grégoire ULg et al

Poster (2016, July 13)

Nowadays the precision in the measurement has become a challenge for physicists. That is why in recent decades, the interest is very granted to simulation. Since 1940, the method Monte Carlo is more ... [more ▼]

Nowadays the precision in the measurement has become a challenge for physicists. That is why in recent decades, the interest is very granted to simulation. Since 1940, the method Monte Carlo is more useful for validation and even for prediction of the results of the experiment. The aim of this study is to validate experimental models. Our laboratories are equipped with HPGe gamma spectrometers for measuring the natural radioactivity, it becomes interesting to compare and even to improve the performance of our system. Geant4 is used for the construction of the geometry of detection, the physics processes and the primary particles. First and prliminary result was prsented in this paper. [less ▲]

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See detailCounting time measurement and statistics in gamma spectrometry: the balance
Guembou Shouop, Cébastien Joel ULg; Ndontchueng Moyo, Maurice; Chene, Grégoire ULg et al

Poster (2016, July 11)

Nuclear counting statistics at high count rate are assessed on a γ-ray spectrometer set-up. Our typical gamma spectrometry system consists of a High Purity Germanium (HPGe) detector, liquid nitrogen ... [more ▼]

Nuclear counting statistics at high count rate are assessed on a γ-ray spectrometer set-up. Our typical gamma spectrometry system consists of a High Purity Germanium (HPGe) detector, liquid nitrogen cooling system, preamplifier, detector bias supply, linear amplifier, analog-to-digital converter (ADC), multichannel storage of the spectrum, and data readout devices. Although the system is powerful enough for background measurements, it is important, nowadays, to have a great statistical in short time measurement: which is a challenge for scientists. The purpose of this study was to determine the average time for gamma spectrometry measurement. To detect Uranium, Thorium and their respective daughters and Potassium series with a relative related error less than 1%, it was found that it is necessary to count during a minimum of 24 Hours (86,400 s). This result is in accordance to the literature with planar geometry detector. These results conduct us to make the following three guidelines for selecting the detector best suited for an application: 1. The more detector material available (germanium semi-conductor), the higher the full-energy peak efficiency. 2. The smaller the distance between the detector and the source material, the higher the full- energy peak efficiency. 3. While better resolution gives a better MDA, the resolution contributes only as the square root to the MDA value, whereas the MDA is proportional to the full-energy peak efficiency. This idea came to us by comparing the spectra of measuring radioactivity lasts for 12 hours in the day that does not fully covered the night spectra for the same sample. The conclusion after several investigations became clearer: to remove all effects of radiation from outside (earth, sun and universe) our system, it is necessary to measure the background for 24, 48 or 72 hours. In the same way, the samples have to be measures for 24, 48 or 72 hours to be safe to be purified the measurement (equality of day and night measurement). It is also possible to not use the background of the winter in summer. Depend to the energy of radionuclide we seek, it is clear that the most important steps of a gamma spectrometry measurement are the preparation of the sample and the calibration of the detector. [less ▲]

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See detailMultiscale study of the Carolingian mosaic of Germigny-des-Prés (Loiret, Fr
Van Wersch, Line ULg; Kronz, L.; Simon, K. et al

Conference (2016, July 08)

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See detailInsight on Van Dongen’s La Violoniste by hyperspectral imaging and MA-XRF
Herens, Elodie ULg; Strivay, David ULg; Walter, Philippe et al

Conference (2016, July 06)

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See detailPIXE-PIGE analysis of Early Medieval Glass Artefacts at IPNAS cyclotron external beam line
Chene, Grégoire ULg; Van Wersch, Line ULg; Biron, Isabelle et al

Poster (2016, July 05)

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See detailGeochemistry and mineralogy approaches to characterize brick and its lake sediments sources: Antioch Roman City (Southern Turkey)
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Benjelloun, Yacine et al

Poster (2016, July)

The Roman aqueduct of Antioch-on-the-Orontes (Southern Turkey) is situated close to the Antioch city. This last is located near the Amik Lake (Lake of Antioch) and close to the junction between the active ... [more ▼]

The Roman aqueduct of Antioch-on-the-Orontes (Southern Turkey) is situated close to the Antioch city. This last is located near the Amik Lake (Lake of Antioch) and close to the junction between the active Dead Sea fault and the East Anatolian fault. During the Roman period, the Amik Plain was more densely occupied than at any time in its history [1]. The study focuses on the bricks and the lake sediments characterization in order to determine the source area as well as the technical production used at this period. For this purpose, several bricks were sampled on different parts of the city's aqueducts. Furthermore, a core of about 6 m of sediments was also collected from the dried Amik Lake. The bricks were characterized through a mineralogical (XRD) and chemical (PIXE-PIGE) approaches. Unfired clay fraction remained as inclusion in the brick was separated and then analysed using XRD. Geochemical composition and clay mineralogy were performed on the raw sediments from the Amik Lake in order to compare the source area. Technological test will be performed on the raw clay sediments from the Amik Lake in the purpose to understand the production techniques used at this time. The age of the brick production was previously dated to the Roman Period [2]. The synthesis of all the data attested the Amik Lake sediment as the raw material for the bricks of the aqueduct. Clay mineral composition from the Roman period deposited in the lake is smectite, illite, kaolinite and small amount of mixed-layer clays. The similar clays composition is found in the remained clays on the brick used for the aqueduct construction. Fast and heterogeneous firing practice characterized the manufacturing of these materials due to the rapid need for the materials during the post-seismic repairs after earthquakes that are mentioned in historical written works. [1] J. Casana, Geomorphology, 101, 429-442 (2008) [2] Y. Benjelloun, J. de Sigoyer, J. Carlut, A. Hubert-Ferrari, H. Dessales, H. Pamir, V. Karabacak, Comptes Rendus Geoscience, 347, 170-180 (2015) [less ▲]

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See detailNatural radioactivity and elemental composition of sands in the Douala region, Littoral of Cameroon Using Portable XRF and HPGe detector
Guembou Shouop, Cébastien Joel ULg; Ndontchueng Moyo, Maurice; Chene, Grégoire ULg et al

Poster (2016, June 21)

Twenty four sand samples from seven sand quarries alone the Gulf of Guinea, Douala Littoral region of Cameroon, were analyzed using high purity germanium detector and a portable X-ray fluorescence (PXRF ... [more ▼]

Twenty four sand samples from seven sand quarries alone the Gulf of Guinea, Douala Littoral region of Cameroon, were analyzed using high purity germanium detector and a portable X-ray fluorescence (PXRF) spectrometer. A comprehensive study was conducted to determine the natural radioactivity concentrations and the geological provenience of sand samples from seven different quarries sites of the Douala, a popular city, and its surroundings. The radioactivity investigation was performed by using high resolution gamma-ray spectrometry. From the measured gamma-spectra, the average activity concentrations were determined for 226Ra, 232Th, 40K and 235U for a depth of 5–25 cm. Results of this study were compared to values from other locations around the world. X-ray fluorescence spectrometry (XRF) measurements were performed for the quantitative elemental analysis of the sands, revealing the major, minor and trace elements present in the investigated samples. Reference marine and geological sample are used to check precision and accuracy of the equipment for major and minor components. From XRF experimental results it was possible to estimate the geological provenience of the analyzed sands. These data record the radioactivity background levels in sands and could be used as reference information in Cameroon. The comparison of major (Si, Al), minor (K, Ca,Fe), and trace (Ti, Mn, Zr, Rb, Sr) element ratios was made. The results indicate that the levels of Si and Al can be very helpful in subgroup definition and provide useful clues to the raw materials used for glassmaking in Cameroon. [less ▲]

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See detailDevelopment of a translation stage for in situ non-invasive analysis and high resolution imaging
Strivay, David ULg; Clar, Mathieu ULg; Rakkaa, Saïd ULg et al

Poster (2016, March)

Non-invasive imaging techniques and analytical instrumentation for cultural heritage object studies have undergone a tremendous development over the last years. Many new miniature and/or handheld systems ... [more ▼]

Non-invasive imaging techniques and analytical instrumentation for cultural heritage object studies have undergone a tremendous development over the last years. Many new miniature and/or handheld systems have been developed and optimized. Nonetheless, these instruments are usually used with a tripod or a manual position system. This is very time consuming when performing point analysis or 2D scanning of a surface. The Centre Européen d’Archéométrie (CEA) has build a translation system made of pluggable rails of 1 m long with a maximum length and height of 3 m. Three motors embedded in the system allow the platform to be moved along these axis, toward and backward from the sample. The rails hold a displacement system, providing a continuous movement. Any position can be reached with a reproducibility of 0.1 mm. The displacements are controlled by an Ethernet connection through a laptop computer running a multiplatform homemade software written in JAVA. This software allows a complete control over the positioning using a simple, unique, and concise interface. Automatic scanning can be performed over a large surface of 3 meters on 3 meters. The Ethernet wires provide also the power for the different motors and, if necessary the detection head. The platform has been originally designed for a XRF detection head (with its full power alimentation) but now can accommodate many different systems like IR reflectography, digital camera, hyperspectral camera, Raman probes, etc. The positioning system can be modified to combine the acquisition software of the imaging or analytical techniques and the positioning software. [less ▲]

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See detailDevelopment of a translation stage for in situ noninvasive analysis and high-resolution imaging
Strivay, David ULg; Clar, Mathieu ULg; Rakkaa, Saïd ULg et al

in Applied Physics A : Materials Science & Processing (2016), 122

Non-invasive imaging techniques and analytical instrumentation for cultural heritage object studies have undergone a tremendous development over the last years. Many new miniature and/or handheld systems ... [more ▼]

Non-invasive imaging techniques and analytical instrumentation for cultural heritage object studies have undergone a tremendous development over the last years. Many new miniature and/or handheld systems have been developed and optimized. Nonetheless, these instruments are usually used with a tripod or a manual position system. This is very time consuming when performing point analysis or 2D scanning of a surface. The Centre Européen d’Archéométrie has built a translation system made of pluggable rails of 1 m long with a maximum length and height of 3 m. Three motors embedded in the system allow the platform to be moved along these axis, toward and backward from the sample. The rails hold a displacement system, providing a continuous movement. Any position can be reached with a reproducibility of 0.1 mm. The displacements are controlled by an Ethernet connection through a laptop computer running a multiplatform custom-made software written in JAVA. This software allows a complete control over the positioning using a simple, unique, and concise interface. Automatic scanning can be performed over a large surface of 3 m on 3 m. The Ethernet wires provide also the power for the different motors and, if necessary, the detection head. The platform has been originally designed for a XRF detection head (with its full power alimentation) but now can accommodate many different systems like IR reflectography, digital camera, hyperspectral camera, and Raman probes. The positioning system can be modified to combine the acquisition software of the imaging or analytical techniques and the positioning software. [less ▲]

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See detailDevelopment of a Reference Database for Particle-Induced Gamma-ray Emission spectroscopy
Dimitriou, P.; Becker, H.-W.; Bogdanović-Radović, I. et al

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2016), 371

Particle-Induced Gamma-ray Emission (PIGE) is a powerful analytical technique that exploits the interactions of rapid charged particles with nuclei located near a sample surface to determine the ... [more ▼]

Particle-Induced Gamma-ray Emission (PIGE) is a powerful analytical technique that exploits the interactions of rapid charged particles with nuclei located near a sample surface to determine the composition and structure of the surface regions of solids by measurement of characteristic prompt γ rays. The potential for depth profiling of this technique has long been recognized, however, the implementation has been limited owing to insufficient knowledge of the physical data and lack of suitable user-friendly computer codes for the applications. Although a considerable body of published data exists in the nuclear physics literature for nuclear reaction cross sections with γ rays in the exit channel, there is no up-to-date, comprehensive compilation specifically dedicated to IBA applications. A number of PIGE cross-section data had already been uploaded to the Ion Beam Analysis Nuclear Data Library (IBANDL) (http://www-nds.iaea.org/ibandl) by members of the IBA community by 2011, however a preliminary survey of this body of unevaluated experimental data has revealed numerous discrepancies beyond the uncertainty limits reported by the authors. Using the resources and coordination provided by the IAEA, a concerted effort to improve the situation was made within the Coordinated Research Project on the Development of a Reference Database for PIGE spectroscopy, from 2011 to 2015. The aim of the CRP was to create a data library for Ion Beam Analysis that contains reliable and usable data on charged particle γ-ray emission cross sections that would be made freely available to the user community. As the CRP has reached its completion, we shall present its main achievements, including the results of nuclear cross-section evaluations and the development of a computer code that will become available to the public allowing for the implementation of a standardless PIGE technique. © 2015 Elsevier B.V. All rights reserved. [less ▲]

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