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See detailEgyptian Gods in Graeco-Roman Context. I. Rediscovering the Temple of Isis at Pompeii
Veymiers, Richard ULg

Scientific conference (2014, November 24)

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See detailClustering and segregation in driven granular fluids
Opsomer, Eric ULg; Vandewalle, Nicolas ULg; Noirhomme, Martial ULg et al

in European Physical Journal E -- Soft Matter (2014)

In microgravity, the successive inelastic collisions in a granular gas can lead to a dynamical clustering of the particles. This transition depends on the filling fraction of the system, the restitution ... [more ▼]

In microgravity, the successive inelastic collisions in a granular gas can lead to a dynamical clustering of the particles. This transition depends on the filling fraction of the system, the restitution of the used materials and on the size of the particles. We report simulations of driven bi-disperse gas made of small and large spheres. The size as well as the mass difference imply a strong modification in the kinematic chain of collisions and therefore alter significantly the formation of a cluster. Moreover, the different dynamical behaviors can also lead to a demixing of the system, adding a few small particles in a gas of large ones can lead to a partial clustering of the taller type. We realized a detailed phase diagram recovering the encountered regimes and developed a theoretical model predicting the possibility of dynamical clustering in binary systems. [less ▲]

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See detailInteractions between particles in a magnetocapillary self-assembly
Lagubeau, Guillaume ULg; Darras, Alexis; Grosjean, Galien ULg et al

Conference (2014, November 24)

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See detailRemote control of self-assembled microswimmers
Vandewalle, Nicolas ULg; Grosjean, Galien ULg; Darras, alexis et al

Conference (2014, November 24)

Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the ... [more ▼]

Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Herein, we show that a magnetocapillary-driven self-assembly, composed of three soft-ferromagnetic beads, is able to swim along a liquid-air interface when driven by an external magnetic field. Moreover, the system can be fully controled, opening ways to explore low Reynolds number swimming and to create micromanipulators in various applications. [less ▲]

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See detailLe continent des couleurs
Dumortier, Tanguy; Vermeulen, Cédric ULg; Linchant, Julie ULg

Diverse speeche and writing (2014)

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See detailA capillary Archimedes’ screw
Darbois-Texier, Baptiste ULg; Dorbolo, Stéphane ULg

Conference (2014, November 23)

As used by Egyptians for irrigation and reported by Archimedes, a screw turning inside a hollow pipe can pull out a fluid againt gravity. At a centimetric scale, an analagous system can be found with a ... [more ▼]

As used by Egyptians for irrigation and reported by Archimedes, a screw turning inside a hollow pipe can pull out a fluid againt gravity. At a centimetric scale, an analagous system can be found with a drop pending on a rotating spiral which is tilted toward the horizontal. The ascent of the drop to the top of the spiral is considered and a theoretical model based on geometrical considerations is proposed. The climb of the drop is limited by the fluid deposition on the screw at high capillary number and by a centrifugation phenomenon. We find out the range of fluid proprities and spiral characteristics for which an ascending motion of the drop is possible. Finally we discuss the efficiency of such system to extract a fluid from a bath at a centrimetric scale. [less ▲]

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See detailFoucault et Deleuze et Sami-Ali : postmodernité et psychothérapie.
Englebert, Jérôme ULg

Conference (2014, November 22)

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See detailL'ECMO, Témoignage de deux infirmiers
KOCH, Jean-Noël ULg; BODSON, Sébastien ULg

Conference (2014, November 22)

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See detailLes attitudes des jeunes hétérosexuels envers les couples homosexuels et les familles homoparentales: premiers résultats d'une étude crossnationale (Belgique, France et Italie)
D'Amore, Salvatore ULg; Green, Robert-Jay; Gross, Martine et al

Scientific conference (2014, November 22)

Cette étude exploratoire vise à examiner les variables corrélées aux attitudes positives et négatives à l'égard du mariage (SSM) et des parents de même sexe (SSP) dans trois pays (France, Belgique, Italie ... [more ▼]

Cette étude exploratoire vise à examiner les variables corrélées aux attitudes positives et négatives à l'égard du mariage (SSM) et des parents de même sexe (SSP) dans trois pays (France, Belgique, Italie) où les personnes LGBT possèdent au moment de l’étude (2012-2013) différents niveaux de reconnaissance de leurs droits civils et parentales. Les attitudes ont été évaluées à travers de questionnaires en ligne chez une cohorte de 11180 participants s’auto-déclarant hétérosexuels résidants en Belgique, France et en Italie : 53% de femmes, 47% des hommes âgés de 18 à 25. Nous avons supposé que les attitudes positives envers les SSM et SSP seraient associées au sexe féminin, à une faible religiosité, à une idéologie politique libérale et à des autres variables comme le contact avec les personnes LGBT. Les résultats confirment que certaines variables sociodémographiques ainsi que le contact et la satisfaction relationnelle avec les personnes LGBT s’associent aux attitudes positives ou négatives. En particulier une plus grande satisfaction dans les relations avec les personnes LGBT s’associe à des attitudes plus positives envers les personnes LGBT en général, le mariage homosexuel et l’homoparentalité. La qualité de la relation semble être plus importante que la quantité dans la prédiction des attitudes positives. Limitations: Les étudiants qui ont participé à l’étude ne sont pas représentatifs de la population générale dans les trois pays. Ils n’ont pas été choisis au hasard parmi toutes les universités de chaque pays, de telle sorte les résultats ne sont pas généralisables à tous les étudiants. [less ▲]

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See detailSuicide et tentative de suicide chez les les adolescents
Malchair, Alain ULg

Scientific conference (2014, November 22)

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See detailPhysical and bacterial controls on inorganic nutrients and dissolved organic carbon during a sea ice growth and decay experiment
Zhou, Jiayun ULg; Delille, Bruno ULg; Kaartokallio, Hermanni et al

in Marine Chemistry (2014), 166

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day ... [more ▼]

We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day experiment that included periods of both ice growth and decay. The experiment was performed using two series of mesocosms: the first consisted of seawater and the second consisted of seawater enriched with humic-rich river water. We grew ice by freezing the water at an air temperature of -14 °C for 14 days after which ice decay was induced by increasing the air temperature to -1 °C. Using the ice temperatures and bulk ice salinities, we derived the brine volume fractions, brine salinities and Rayleigh numbers. The temporal evolution of these physical parameters indicate that there was a succession of 3 stages in the brine dynamics: forced-convection, followed by bottom convection during ice growth, and then brine stratification during ice decay. The major findings are: (1) the incorporation of dissolved compounds (nitrate, nitrite, ammonium, phosphate, silicate, and DOC) into the sea ice was not conservative (relative to salinity) during ice growth. Brine convection clearly influenced the incorporation of the dissolved compounds, since the non-conservative behavior of the dissolved compounds was particularly pronounced in the absence of brine convection. (2) Bacterial activity further regulated nutrient availability in the ice: ammonium and nitrite accumulated as a result of remineralization processes, although bacterial production was too low to induce major changes in DOC concentrations. (3) Different forms of DOC have different properties and hence incorporation efficiencies. In particular, the terrestrially-derived DOC from the river water was less efficiently incorporated into sea ice than the DOC in the seawater. Therefore the main factors regulating the distribution of the dissolved compounds within sea ice are clearly a complex interaction of brine dynamics, biological activity and in the case of dissolved organic matter, the physico-chemical properties of the dissolved constituents themselves. [less ▲]

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See detailPerceptual Experiences and their Parts
Dewalque, Arnaud ULg

Scientific conference (2014, November 22)

What is the phenomenal structure of our perceptual experiences? In this talk, I suggest that perceptual experiences – like consciousness in general – have a mereological structure, that is, a structure in ... [more ▼]

What is the phenomenal structure of our perceptual experiences? In this talk, I suggest that perceptual experiences – like consciousness in general – have a mereological structure, that is, a structure in which the most basic relation is that of parthood. I do not provide any definitive argument for this view. I just want to suggest (i) that the mereological approach is untouched by the usual objections coming from the proponents of the Unified Field Theory (James, Searle, Tye), (ii) that the Unified Field Theory faces some important difficulties of its own. [less ▲]

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See detailVers un transport aérien plus écologique et plus économique
Lurkin, Virginie ULg

Conference given outside the academic context (2014)

de l’avion en vol. Mieux, on peut montrer que la position du centre de gravité (qui dépend du chargement de l’avion) affecte la consommation de carburant. Ce résultat revêt une importance majeure dans un ... [more ▼]

de l’avion en vol. Mieux, on peut montrer que la position du centre de gravité (qui dépend du chargement de l’avion) affecte la consommation de carburant. Ce résultat revêt une importance majeure dans un contexte d’augmentation des prix du pétrole et où il s’agit de réduire les émissions polluantes. Pour un transport aérien plus économique, il s’agit aussi, en cas de livraisons à différents endroits, de réduire au maximum les temps de chargements et de déchargements afin de limiter les coûts liés aux paiements des salariés et à l’utilisation de chaque aéroport intermédiaire. Au cours de mon exposé, je présente un modèle mathématique qui vise à trouver le chargement qui minimise la consommation de carburant et les temps de chargements et déchargements. Je partage avec nous les résultats de mes recherches dont les applications garantissent un impact écologique et économique positif. [less ▲]

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See detailLong-term evolution and seasonal modulation of methanol above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, T; Muller, J-F et al

in Atmospheric Measurement Techniques (2014), 7

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5° N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995–2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June–July, minimum columns in winter and a peak-to-peak amplitude of 130%. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

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See detailOn the finiteness and uniqueness of the weighted likelihood estimator of ability in polytomous IRT models
Magis, David ULg; Verhelst, Norman

Conference (2014, November 21)

In item response theory (IRT), the weighted likelihood (WL) estimator has become a central method to estimate ability levels of respondents. Primarily introduced with dichotomous IRT models (Warm, 1989 ... [more ▼]

In item response theory (IRT), the weighted likelihood (WL) estimator has become a central method to estimate ability levels of respondents. Primarily introduced with dichotomous IRT models (Warm, 1989), it was later extended to polytomous IRT models (Samejima, 1998). However, very few information is available about the behavior of the WL estimator, and especially about the uniqueness of the ability estimates as well as their finiteness. The purpose of this talk is to establish that with polytomous item response models, the WL estimator of ability always returns finite values. This result is valid for the class of difference models and divide-by-total models, independently of the number of items and the response patterns. However, such estimates may not necessarily be unique, as the WL solving equation may provide several optimal values. Some examples are considered to illustrate both findings. [less ▲]

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See detailImpact environnemental des stations de méthanisation agricoles
Adam, Gilles ULg

Conference given outside the academic context (2014)

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See detailHow does gender socialisation influence teenagers' behaviors ? : Contribution of ISRD-2 and ISRD-3 to this question
Gavray, Claire ULg

Conference (2014, November 21)

In both gender groups, young people entering the spiral of violence negatively often react against personal insecurity, against a hostile and little promising environment. But those environments still ... [more ▼]

In both gender groups, young people entering the spiral of violence negatively often react against personal insecurity, against a hostile and little promising environment. But those environments still differ between girls and boys according to the sphere which remains the most valorized, 'suitable' for them (public and competitive sphere for the boys, family and emotional sphere for the girls). ISRD data allow to show links between, on one side, the production of not authorized and violent behaviors and, on the other side, gendered concrete life, gendered attitudes and values. The theory of the societal vulnerability (Walgrave, Vettenburg) and the theory of recognition (Honneth) are confirmed. [less ▲]

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See detailSpécificités syntaxiques des types de discours dans les Quatre Livres des Rois (12e s.)
Mazziotta, Nicolas ULg; Glikman, Julie

Conference (2014, November 21)

Detailed reference viewed: 9 (0 ULg)