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See detailA multi-epoch XMM-Newton campaign on the core of the massive Cygnus OB2 association
Rauw, Grégor ULg

in Astronomy and Astrophysics (2011), 536

Context. Cyg OB2 is one of the most massive associations of O-type stars in our Galaxy. Despite the large interstellar reddening towards Cyg OB2, many studies, spanning a wide range of wavelengths, have ... [more ▼]

Context. Cyg OB2 is one of the most massive associations of O-type stars in our Galaxy. Despite the large interstellar reddening towards Cyg OB2, many studies, spanning a wide range of wavelengths, have been conducted to more clearly understand this association. X-ray observations provide a powerful tool to overcome the effect of interstellar absorption and study the most energetic processes associated with the stars in Cyg OB2. <BR /> Aims: We analyse XMM-Newton data to investigate the X-ray and UV properties of massive O-type stars as well as low-mass pre-main sequence stars in Cyg OB2. <BR /> Methods: We obtained six XMM-Newton observations of the core of Cyg OB2. In our analysis, we pay particular attention to the variability of the X-ray bright OB stars, especially the luminous blue variable candidate Cyg OB2 #12. <BR /> Results: We find that X-ray variability is quite common among the stars in Cyg OB2. Whilst short-term variations are restricted mostly to low-mass pre-main sequence stars, one third of the OB stars display long-term variations. The X-ray flux of Cyg OB2 #12 varies by 37%, over timescales from days to years, whilst its mean log L[SUB]X[/SUB]/L[SUB]bol[/SUB] amounts to - 6.10. <BR /> Conclusions: These properties suggest that Cyg OB2 #12 is either an interacting-wind system or displays a magnetically confined wind. Two other X-ray bright O-type stars (MT91 516 and CPR2002 A11) display variations that suggest they are interacting wind binary systems. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).Full Table 2 and Table 4 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/536/A31">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/536/A31</A> [less ▲]

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See detailVLT adaptive optics search for luminous substructures in the lens galaxy towards SDSS J0924+0219
Faure, C.; Sluse, Dominique ULg; Cantale, N. et al

in Astronomy and Astrophysics (2011), 536

The anomalous flux ratios between quasar images are suspected of being caused by substructures in lens galaxies. We present new deep and high-resolution H and Ks imaging of the strongly lensed quasar SDSS ... [more ▼]

The anomalous flux ratios between quasar images are suspected of being caused by substructures in lens galaxies. We present new deep and high-resolution H and Ks imaging of the strongly lensed quasar SDSS J0924+0219 obtained using the ESO VLT with adaptive optics and the laser guide star system. SDSS J0924+0219 is particularly interesting because the observed flux ratio between the quasar images vastly disagree with the predictions from smooth mass models. With our adaptive optics observations we find a luminous object, Object L, located ~0.3'' to the north of the lens galaxy, but we show that it cannot be responsible for the anomalous flux ratios. Object L as well as a luminous extension of the lens galaxy to the south are seen in the archival HST/ACS image in the F814W filter. This suggests that Object L is part of a bar in the lens galaxy, as also supported by the presence of a significant disk component in the light profile of the lens galaxy. Finally, we find no evidence of any other luminous substructure that may explain the quasar images flux ratios. However, owing to the persistence of the flux ratio anomaly over time (~7 years), a combination of microlensing and millilensing is the favorite explanation for the observations. Based on observations obtained with the ESO VLT at Paranal observatory (Prog ID 084.A-0762(A); PI: Meylan). Also based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with the CASTLES (Cfa-Arizona Space Telescope LEns Survey) survey (ID: 9744, PI: C. S. Kochanek). [less ▲]

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See detailLa production de biohydrogène à partir de substrats carbohydratés : état de l'art
Hiligsmann, Serge ULg; Beckers, Laurent ULg; Masset, Julien ULg et al

in Récents progrès en génie des procédés (2011, December 01)

Hydrogen is being considered as an ideal and clean energy carrier. The recent advances to produce biohydrogen from renewable sources such as biomass and particularly by fermentation of carbohydrate-rich ... [more ▼]

Hydrogen is being considered as an ideal and clean energy carrier. The recent advances to produce biohydrogen from renewable sources such as biomass and particularly by fermentation of carbohydrate-rich substrates from agriculture and agro-industries appear promising. Such a process enables both organic waste treatment and renewable energy production to be coupled. The paper presents the state of the art about the different hydrogen-producing microorganisms and the parameters that have been investigated in order to improve the hydrogen production yields and rates. [less ▲]

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See detailUsing seismic targets as benchmarks for spectroscopic analyses of cool stars
Morel, Thierry ULg; Miglio, Andrea ULg; Valentini, Marica ULg

in Journal of Physics: Conference Series (2011), 328

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An ... [more ▼]

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An extensive comparison for about 40 well-studied pulsating stars with gravities derived by traditional means (ionization balance, pressure-sensitive spectral features or location with respect to evolutionary tracks) supports the validity of this technique and reveals an overall remarkable agreement with mean differences not exceeding 0.05 dex (although with a dispersion of up to ~0.2 dex). It is argued that interpolation in theoretical isochrones may be the most precise way of estimating the gravity by traditional means in nearby dwarfs. The use of seismic targets as benchmarks in the context of forthcoming large-scale surveys (such as the follow up of the Gaia mission) is briefly discussed. [less ▲]

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See detailRole of western lowland gorilla (Gorilla gorilla gorilla) to dispersal and regeneration of commercial trees in South-East Cameroon
Petre, Charles-Albert ULg; Tagg, Nikki; Beudels-Jamar, Roseline et al

Poster (2011, December 01)

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See detailCOSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses. IX. Time delays, lens dynamics and baryonic fraction in HE 0435-1223
Courbin, F.; Chantry, Virginie ULg; Revaz, Y. et al

in Astronomy and Astrophysics (2011), 536

We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010 ... [more ▼]

We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B. We measured ΔtBC = 7.8 ± 0.8 days, ΔtBD = -6.5 ± 0.7 days and ΔtCD = -14.3 ± 0.8 days. We spacially deconvolved HST NICMOS2 F160W images to derive accurate astrometry of the quasar images and to infer the light profile of the lensing galaxy. We combined these images with a stellar population fitting of a deep VLT spectrum of the lensing galaxy to estimate the baryonic fraction, fb, in the Einstein radius. We measured fb = 0.65-0.10+0.13 if the lensing galaxy has a Salpeter IMF and fb = 0.45-0.07+0.04 if it has a Kroupa IMF. The spectrum also allowed us to estimate the velocity dispersion of the lensing galaxy, σap = 222 ± 34 km s-1. We used fb and σap to constrain an analytical model of the lensing galaxy composed of an Hernquist plus generalized NFW profile. We solved the Jeans equations numerically for the model and explored the parameter space under the additional requirement that the model must predict the correct astrometry for the quasar images. Given the current error bars on fb and σap, we did not constrain H0 yet with high accuracy, i.e., we found a broad range of models with χ2 < 1. However, narrowing this range is possible, provided a better velocity dispersion measurement becomes available. In addition, increasing the depth of the current HST imaging data of HE 0435-1223 will allow us to combine ourconstraints with lens reconstruction techniques that make use of the full Einstein ring that is visible in this object. Based on observations made with the 1.2 m Euler Swiss Telescope, the 1.5 m telescope of Maidanak Observatory in Uzbekistan, and with the 1.2 m Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The NASA/ESA Hubble Space Telescope data was obtained from the data archive at the Space Telescope Science Institute, which is operated by AURA, the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26555.Light curves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/536/A53 [less ▲]

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See detailHerschel discovery of a new class of cold, faint debris discs
Eiroa, C.; Marshall, J. P.; Mora, A. et al

in Astronomy and Astrophysics (2011), 536

We present Herschel PACS 100 and 160 μm observations of the solar-type stars α Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel open time key programme (OTKP) DUNES ... [more ▼]

We present Herschel PACS 100 and 160 μm observations of the solar-type stars α Men, HD 88230 and HD 210277, which form part of the FGK stars sample of the Herschel open time key programme (OTKP) DUNES (DUst around NEarby Stars). Our observations show small infrared excesses at 160 μm for all three stars. HD 210277 also shows a small excess at 100 μm, while the 100 μm fluxes of α Men and HD 88230 agree with the stellar photospheric predictions. We attribute these infrared excesses to a new class of cold, faint debris discs. Both α Men and HD 88230 are spatially resolved in the PACS 160 μm images, while HD 210277 is point-like at that wavelength. The projected linear sizes of the extended emission lie in the range from ~115 to ≤ 250 AU. The estimated black body temperatures from the 100 and 160 μm fluxes are ≲22 K, and the fractional luminosity of the cold dust is L[SUB]dust[/SUB]/L[SUB] ⋆ [/SUB] ~ 10[SUP]-6[/SUP], close to the luminosity of the solar-system's Kuiper belt. These debris discs are the coldest and faintest discs discovered so far around mature stars, so they cannot be explained easily invoking "classical" debris disc models. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. [less ▲]

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See detailGeoelectrical monitoring on a contaminated site during biostimulation
Caterina, David ULg; Nguyen, Frédéric ULg

Poster (2011, December 01)

In Belgium, as in many other countries, relatively anarchic economical and industrial development of the past century has resulted in a significant number of contaminated sites. When one of these sites ... [more ▼]

In Belgium, as in many other countries, relatively anarchic economical and industrial development of the past century has resulted in a significant number of contaminated sites. When one of these sites poses a risk to human or ecosystem, measures need to be taken to clean it up. Among these measures, methods using in situ bioremediation are beginning to become more important because of their ease of implementation and their relatively low cost. However, it is often difficult to ensure their effectiveness except by carrying out extensive drilling and sampling, which can be long and expensive while offering only punctual information. Thus it becomes necessary to use other techniques to overcome these shortcomings. Recently, an increasing interest is being born to use geophysical methods as tools for remediation monitoring. As part of our work, we conducted several electrical resistivity tomography campaigns on a site contaminated by LNAPLs (gasoline) on which a biostimulation remediation device was set up. The aim of our investigations was to study the electrical response of the contaminated area during the remediation phase and whether electrical resistivity tomography allowed to monitor its effectiveness. After a year of monitoring, the time lapse images obtained show a significant decrease of the electrical resistivity (up to -50%) at the location of the main contaminant plume. This particular response during the biostimulation, in agreement with the models presented by several authors in the literature, tends to suggest that it is possible to use electrical resistivity tomography as a tool for qualitative control during the remediation. These findings may also lead in the future to the development of models to estimate more quantitatively the level of (de)contamination of a site. [less ▲]

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See detailCoRoT's view on variable B8/9 stars: spots versus pulsations. Evidence for differential rotation in HD 174648
Degroote, P.; Acke, B.; Samadi, R. et al

in Astronomy and Astrophysics (2011), 536

Context. There exist few variability studies of stars in the region in the Hertzsprung-Russell diagram between the A and B-star pulsational instability strips. With the aid of the high precision ... [more ▼]

Context. There exist few variability studies of stars in the region in the Hertzsprung-Russell diagram between the A and B-star pulsational instability strips. With the aid of the high precision continuous measurements of the CoRoT space satellite, low amplitudes are more easily detected, making a study of this neglected region worthwhile. <BR /> Aims: We collected a small sample of B stars observed by CoRoT to determine the origin of the different types of variability observed. <BR /> Methods: We combine literature photometry and spectroscopy to measure the fundamental parameters of the stars in the sample, and compare asteroseismic modelling of the light curves with (differentially rotating) spotted star models. <BR /> Results: We found strong evidence for the existence of spots and differential rotation in HD 174648, and formulated hypotheses for their origin. We show that the distinction between pulsations and rotational modulation is difficult to make solely based on the light curve, especially in slowly rotating stars. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.Based on observations made with the ESO telescopes at La Silla Observatory under the ESO Large Programme LP182.D-0356.Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Appendix A is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailLa pensée "cycle de vie" au cœur des démarches d'éco-conception des procédés
Léonard, Angélique ULg

Conference (2011, December 01)

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See detailSprache und Dialekt in der Euregio Maas-Rhein
Vromans, Joseph ULg

Scientific conference (2011, December 01)

The Meuse-Rhine Euregion (the Region of Aachen, the German-speaking Community of Belgium, the Belgian Province of Liège, the Belgian Province of Limburg and the southern part of the Dutch Province of ... [more ▼]

The Meuse-Rhine Euregion (the Region of Aachen, the German-speaking Community of Belgium, the Belgian Province of Liège, the Belgian Province of Limburg and the southern part of the Dutch Province of Limburg) is an interesting area from a linguistic point of view: the official languages of the three countries in in the Euregion are Dutch (in Belgium and the Netherlands), French (in Belgium) and German (in Belgium and Germany); regional languages / dialects are Limburgish (which is recognised as a regional language in Dutch Limburg), Ripuarian and Walloon. [less ▲]

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See detailGuide destiné à la formation d’animateurs pour les « animations pédagogiques »
Schiffers, Bruno ULg; Gilson, Julien; Prunier, Emmanuelle et al

Book published by édité par le COLEACP (2011)

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See detailL'identité wallonne aujourd'hui
Jacquemain, Marc ULg

in Germain, P.; Robaye, R. (Eds.) L'Etat de la Wallonie. Portrait d'un pays et de ses habitants (2011)

L'article fait le point sur le sentiment d'appartenance à la Wallonie et comment il a évolué au sein de la population au sein des quinze dernières années. Il remet en évidence la complémentarité naturelle ... [more ▼]

L'article fait le point sur le sentiment d'appartenance à la Wallonie et comment il a évolué au sein de la population au sein des quinze dernières années. Il remet en évidence la complémentarité naturelle entre le sentiment belge et le sentiment wallon. Il montre que le sentiment d'appartenance est évolutif, qu'il dépend non seulement de l'actualité mais des stratégies d'acteurs politique, économiques ou médiatiques. Il fait aussi l'hypothèse que l'identité wallonne, en terme de contenus, se définit davantage par un modèle socio-économique partagé que par des symboles et qu'elle ne présente donc pas de caractère d'identité nationale. [less ▲]

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See detailComparison of bovine and human O26 EHEC strains by the Whole Genome PCR Scanning
Bardiau, Marjorie ULg; Ogura, Y.; Mainil, Jacques ULg et al

Conference (2011, December)

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See detailControl of plankton dynamics and fish recruitment by climate variation : example of Corsica, a Mediterranean island
Goffart, Anne ULg; Hecq, Jean-Henri ULg

Conference (2011, December)

In coastal areas of temperate and tropical small islands, most exploited fish species have undergone large reductions in stock size over the last decades. This impact is believed to be due, in large ... [more ▼]

In coastal areas of temperate and tropical small islands, most exploited fish species have undergone large reductions in stock size over the last decades. This impact is believed to be due, in large measure, to overfishing. However, in some cases, the poor recruitment of young fish or crustaceans of commercial interest is related to climate change. Here we present results acquired from three decades in Corsica, a small Mediterranean island where water quality is unbiased by terrestrial inputs and local activities. We show how plankton dynamics and fish recruitment are controlled by climate variation. Long-term changes of surface plankton dynamics are studied from 1979 at a permanent station in the oligotrophic Bay of Calvi (Corsica, Mediterranean Sea). As a distinctive feature of the area, the plankton bloom is characterized by a very large interannual variability reaching one order of magnitude from one year to another. Studies conducted to understand mechanisms controlling plankton variability emphasize a close relationship between climate variation (mainly winter wind stress intensity), water temperature and phytoplankton biomass. Shifts in phytoplankton community structure contribute to control the dynamics of zooplankton that rely on phytoplankton as food and influence the temporal succession of zooplankton assemblages. Changes in the timing, the biomass and the composition of the zooplankton communities result in a mismatch with the presence of the main food source of the small fish and alter recruitment success. The Corsican example could help to be aware of the potential consequences that changes in plankton dynamics controlled by climate variation will pose to coastal fishermen of small islands. [less ▲]

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See detailFormation initiale des enseignants à l'éveil scientifique: comment en faire une occasion d'apprentissage pour tous?
Beckers, Jacqueline ULg; Simons, Germain; Crahay, Marcel ULg et al

in Beckers, Jacqueline; Crahay, Marcel (Eds.) Approche par compétences et réduction des inégalités d'apprentissage entre élèves : de l'analyse des situations scolaires à la formation de enseignants (2011)

L'approche par compétences en sciences prônée par le décret nécessite de travailler la démarche scientifique en classe de façon complète : poser une question, formuler une hypothèse, chercher des ... [more ▼]

L'approche par compétences en sciences prônée par le décret nécessite de travailler la démarche scientifique en classe de façon complète : poser une question, formuler une hypothèse, chercher des résultats, expérimentaux ou non, exploiter ces résultats et conclure provisoirement. Cette façon de travailler est complexe et la façon dont l'enseignant va mettre en oeuvre les choses peut engendrer ou non des inégalités d'un élève à l'autre. Cet article est le récit d'une formation initiale d'enseignants du primaire. [less ▲]

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See detailNightglow investigation in the Visible Range with the VIRTIS/Venus-Express instrument
Migliorini, A.; Slanger, T.; Saran, D. et al

Poster (2011, December)

In this study we report the investigation of the nightglow molecular oxygen emissions of Venus in the visible spectral range, observed by the VIRTIS instrument (Visible and InfraRed Spectral Imaging ... [more ▼]

In this study we report the investigation of the nightglow molecular oxygen emissions of Venus in the visible spectral range, observed by the VIRTIS instrument (Visible and InfraRed Spectral Imaging Spectrometer) on board the Venus Express spacecraft. The Herzberg II system was detected in the range 0.4-0.7 µm. The observed bands peak at 95-96 km altitude, with a limb mode intensity of 15-20 kR for the strongest band, similar to that seen in previous observations. Simultaneous observations in the visible and IR [O2 (a-X) 1.27 µm band] were obtained in March 2007, and the two systems are similar in peak altitude. In addition, three bands of the O2 Chamberlain system, at 0.558, 0.604, and 0.657 µm were detected. They are well detached from the Herzberg II bands, and more distinct than reported in previous observations (Garcia Munoz et al., 2009). A simulated spectrum is obtained using the DIATOM code, allowing accurate reproduction of the observed VIRTIS mean spectrum. [less ▲]

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See detailChronique bibliographique - Supplément 2000-2004
Veymiers, Richard ULg; Bricault, Laurent; Budischovsky, Marie-Christine et al

in Veymiers, Richard; Bricault, Laurent (Eds.) Bibliotheca Isiaca II (2011)

Chronique bibliographique qui, sur le modèle de "l’Inventaire Bibliographique des Isiaca" (IBIS), publié dans les "ÉPRO" entre 1972 et 1991, recense, avec un commentaire critique, les publications ... [more ▼]

Chronique bibliographique qui, sur le modèle de "l’Inventaire Bibliographique des Isiaca" (IBIS), publié dans les "ÉPRO" entre 1972 et 1991, recense, avec un commentaire critique, les publications touchant aux cultes isiaques entre 2000 et 2004. [less ▲]

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See detailLa performance de l’Etat-providence européen. Quel enseignement pour la Belgique?
Lefebvre, Mathieu ULg; Perelman, Sergio ULg; Pestieau, Pierre ULg

in Regards Economiques (2011), 93

Dans ce numéro de Regards économiques, nous présentons une mesure multidimensionnelle de la performance des Etats- providence de l’Union européenne. Cette mesure permet de comparer la performance des pays ... [more ▼]

Dans ce numéro de Regards économiques, nous présentons une mesure multidimensionnelle de la performance des Etats- providence de l’Union européenne. Cette mesure permet de comparer la performance des pays de l’Europe des 15 avec celle des 12 nouveaux membres; elle donne aussi la possibilité de tester l’hypothèse d’un éventuel dumping social; enfin elle peut être utilisée pour mieux appréhender la performance de la protection sociale de la Belgique et de ses composantes régionales. [less ▲]

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See detailLarge-Scale Fire Test of Unprotected Cellular Beam Acting in Membrane Action
Vassart, Olivier; Bailey, C. G.; Hawes, M. et al

in Journal of Structural Fire Engineering (2011), 2(4), 259-268

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in ... [more ▼]

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in the central part of the floor are made of cellular beams. The natural fire was created by a wood crib fire load of 700 MJ/m2 and the 9 × 15 m floor survived the fire that peaked at 1000°C and lasted for 90 minutes. Blind predictions of the air temperature development by the software OZone and of the structural behaviour by the software SAFIR which proved quite satisfactory are also described. [less ▲]

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