References of "Strivay, David"
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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 detailLight Induced Super-Hydrophilicity in Niobium and Tantalum Oxides Thin Films
Henry, Théo ULg; Bonsague, Fabio; Dubreuil, Olivier ULg et al

Poster (2017, July)

Since its discovery at the end of the nineties by Wang et al.,[1] the interest for light-induced superhydrophilicity is ever growing. The application fields for materials displaying such a property are ... [more ▼]

Since its discovery at the end of the nineties by Wang et al.,[1] the interest for light-induced superhydrophilicity is ever growing. The application fields for materials displaying such a property are wide and numerous:[2] self-cleaning surfaces, anti-fogging, anti-bacterial, water and air purification, microfluidics…Nowadays, a research emphasis is on relatively low energy bandgap semiconductors, targeting a higher efficiency under solar irradiation or more precisely in the near UV and low-end of the visible spectral range. Here, however, we report UV-induced superhydrophilicity in metal oxides thin films showing a relatively high transparency in the UV. Reactive ion beam sputtering (IBS) was used to deposit niobium, tantalum and titanium oxides thin films with thickness ranging from 10 nm to 120 nm on fused silica substrates at room temperature. Contact angle measurements were performed for progressively increasing UV doses and also as function of elapsed time after the termination of the exposure in order to investigate the UV-induced hydrophilicity and recovery behavior of tantalum and niobium oxide thin films in comparison to that of titanium oxide deposited in analogous conditions. [less ▲]

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See detailGeant4 code for gamma spectrometry measurement: a toolkit for Nuclear, Medical, Astronomical and High Energy Physics
Guembou Shouop, Cébastien Joel ULg; Ndontchueng Moyo, Maurice; Nguelem Mekongtso, Eric J. et al

Scientific conference (2017, June)

In the Monte Carlo method, quantities of interest for the application are calculated through statistical sampling of interaction processes. Gamma spectroscopy is a widely used technique, well-illustrated ... [more ▼]

In the Monte Carlo method, quantities of interest for the application are calculated through statistical sampling of interaction processes. Gamma spectroscopy is a widely used technique, well-illustrated by the following list of examples: Environmental Radioactivity Monitoring, nuclear industry, geochemical investigation, and astrophysics. Most radioactive sources produce gamma rays, which are of various energies and intensities. Geant4 (for GEometry ANd Tracking) is a platform for the simulation of the passage of particles through matter, using Monte Carlo methods. The GEANT4 toolkit allows the simulation of the following physical processes: the photo-electrical effect, the Compton Effect, the electron-positron pairs generation and the Rayleigh diffusion. Our study shows the combination of gamma spectrometry, development of related Monte Carlo equation and the presentation of the Geant4 toolkit for gamma spectrometry simulation (simulation of the interaction of gamma photon through matter). It is clearly found, at the end of this study, that Monte-Carlo simulation is a useful, inexpensive alternative that also provides greater flexibility and gained time when determining the detector response and efficiency during an environmental monitoring. [less ▲]

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See detailNon-Invasive Analysis of Mural Painting from a Late-Republican House (1st century B.C.) in Ostia
Strivay, David ULg; Herens, Elodie ULg; Morard, Thomas ULg et al

Conference (2017, May)

This paper is a comprehensive analytical study of the murals belonging to an ancient Roman house through the characterization of materials. The project focuses on the wall paintings of the Domus dei ... [more ▼]

This paper is a comprehensive analytical study of the murals belonging to an ancient Roman house through the characterization of materials. The project focuses on the wall paintings of the Domus dei bucranes, a house of the end of the Republican era discovered on the site of the Schola of Trajan in Ostia. This Domus has undergone several phases of development in the 1st century BC before being destroyed around 20 BC. A new house was immediately rebuilt after a major change from the ground, which allowed exceptional preservation of the decoration system. The results complement our knowledge of Roman painting techniques during the 1st century BC and also provide a comprehensive multidisciplinary approach to the problem of conservation of wall paintings. These two related objectives have been studied using non-destructive testing methods (MA-XRF, FTIR and Raman spectroscopy). The analyzes have been performed in situ using our mobile systems. The different set-ups had to be modified in order to be able to work on horizontal surfaces, specially our XRF scanner. The study of the pictorial layers address various issues in the field of archaeology: what technique has been implemented? Does the same technique was used in both phases of the development of Domus? Do they correspond to the techniques described by ancient writers? These responses are compared to those observed in other sets of murals dating from the 1st century BC. [less ▲]

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See detailNon-invasive analysis of mural paintings from a late-Republican house in Ostia
Strivay, David ULg; Morard, Thomas ULg; Herens, Elodie ULg et al

Conference (2017, April 21)

This paper is a comprehensive analytical study of the murals belonging to an ancient Roman house through the characterization of materials. The project focuses on the wall paintings of the Domus dei ... [more ▼]

This paper is a comprehensive analytical study of the murals belonging to an ancient Roman house through the characterization of materials. The project focuses on the wall paintings of the Domus dei Bucrani - a house of the end of the Republican era discovered on the site of the Schola del Traiano in Ostia. This domus has undergone several phases of development in the 1st century BC before being destroyed around 20 BC. A new house was immediately rebuilt after a major change from the ground, which allowed exceptional preservation of the decoration system. The results complement our knowledge of Roman painting techniques during the 1st century BC and also provide a comprehensive multidisciplinary approach to the problem of conservation of wall paintings. These two related objectives have been studied using non-destructive testing methods (MA-XRF, FTIR and Raman spectroscopy). The analyses have been performed in situ using our mobile systems. The different set-ups had to be modified in order to be able to work on horizontal surfaces, specially our XRF scanner. The study of the pictorial layers address various issues in the field of archaeology: what technique has been implemented? Does the same technique was used in both phases of the development of the domus? Do they correspond to the techniques described by ancient writers? These responses are compared to those observed in other sets of murals dating from the 1st century BC. [less ▲]

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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 (2017), 5(14),

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 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 detailOptimal measurement counting time and statistics in gamma spectrometry analysis: The time balance
Guembou Shouop, Cébastien Joel ULg; Penabei, Samafou; Ndontchueng Moyo, Maurice et al

Scientific conference (2017, January 04)

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours ... [more ▼]

The optimal measurement counting time for gamma-ray spectrometry analysis using HPGe detectors was determined in our laboratory by comparing twelve hours measurement counting time at day and twelve hours measurement counting time at night. The day spectrum does not fully cover the night spectrum for the same sample. It is observed that the perturbation come to the sun-light. After several investigations became clearer: to remove all effects of radiation from outside (earth, the 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 measured 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 on 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 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 detailEtude gemmologique de la croix-reliquaire à double traverse du Trésor de la Cathédrale de Liège
Demaude, Merry ULg; Bruni, Yannick ULg; Hatert, Frédéric ULg et al

in Bulletin trimestriel du Trésor de Liège (2017), 50

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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)

Detailed reference viewed: 27 (8 ULg)
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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)

Detailed reference viewed: 19 (2 ULg)