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See detailAbstract Numeration Systems : Recognizability, Decidability, Multidimensional S-Automatic Words, and Real Numbers
Charlier, Emilie ULg

Doctoral thesis (2009)

In this dissertation we study and we solve several questions regarding abstract numeration systems. Each particular problem is the focus of a chapter. The first problem concerns the study of the ... [more ▼]

In this dissertation we study and we solve several questions regarding abstract numeration systems. Each particular problem is the focus of a chapter. The first problem concerns the study of the preservation of recognizability under multiplication by a constant in abstract numeration systems built on polynomial regular languages. The second is a decidability problem, which has been already studied notably by J. Honkala and A. Muchnik and which is studied here for two new cases: the linear positional numeration systems and the abstract numeration systems. Next, we focus on the extension to the multidimensional setting of a result of A. Maes and M. Rigo regarding S-automatic infinite words. Finally, we propose a formalism to represent real numbers in the general framework of abstract numeration systems built on languages that are not necessarily regular. We end by a list of open questions in the continuation of the present work. [less ▲]

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See detailL'influence de la fréquence d'occurrence sur l'abstraction des schémas de construction linguistiques chez les enfants dysphasiques
Leroy, Sandrine ULg; Moulin, Mélissa; Parisse, Christophe et al

Poster (2009, December 04)

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See detailMiscellanea palaeontologica
Gerrienne, Philippe ULg; Petus, Elodie ULg; Steemans, Philippe ULg

Book published by Paléogéobio. Paléobot. Paléopalyno. (2009)

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See detailRépétition de non-mots et rappel sériel immédiat : Des mesures équivalentes de la mémoire à court terme verbale?
Leclercq, Anne-Lise ULg; Majerus, Steve ULg

Poster (2009, December 04)

En psychologie expérimentale et en neuropsychologie, les mesures classiques pour évaluer la mémoire à court terme verbale (MCTV) sont des tâches de rappel sériel immédiat (empan de chiffres ou de mots ... [more ▼]

En psychologie expérimentale et en neuropsychologie, les mesures classiques pour évaluer la mémoire à court terme verbale (MCTV) sont des tâches de rappel sériel immédiat (empan de chiffres ou de mots). Il a été démontré que cette même MCTV prédit les capacités de développement lexical, mais sur base d’une estimation de la MCTV à partir de tâches de répétition de non-mots. Même si ces deux procédures (répétition de non-mots, rappel sériel immédiat) sont censées mesurer la MCTV de façon équivalente, la répétition de non-mots recrute davantage de processus linguistiques tels que la segmentation phonologique et la coarticulation (Gathercole, 2006; Majerus, Van der Linden, Mulder, Meulemans, & Peters, 2004). Le but de cette étude est de déterminer dans quelle mesure ces deux types d’estimation de la MCTV sont des prédicteurs équivalents du développement lexical. Des tâches de rappel de syllabes présentées soit de manière sérielle (chaque syllabe étant séparée par une pause), soit de manière agglutinée (= répétition de non-mots) ont été administrées à des enfants de 4, 5, 6 et 8 ans (N=30 dans chaque groupe). Le niveau de vocabulaire a été évalué par le test EVIP (Dunn, Thériault-Whalen, & Dunn, 1993). Une analyse de variance sur les performances aux tâches de MCTV a montré un effet de l’âge (F(3,116)=26.87, p<.001) et un effet du type de tâche, avec de meilleures performances pour les syllabes présentées de façon agglutinée (F(1,116)=390.85, p<.001). Une analyse de régression sur le niveau de vocabulaire a indiqué qu’à la fois la répétition de non-mots et le rappel de séries de syllabes sont des prédicteurs significatifs, après contrôle de l’âge et du niveau intellectuel non-verbal. En outre, la répétition de non-mots reste un prédicteur significatif du niveau de vocabulaire après contrôle du rappel sériel de syllabes (Δ R²=.016). La relation inverse n’est pas significative. Cette étude montre que la répétition de non-mots et le rappel sériel immédiat ne reflètent pas des mesures identiques de la MCTV, et que la prédiction la plus robuste du niveau de vocabulaire est observée pour les tâches de MCTV recrutant un maximum de processus linguistiques. [less ▲]

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See detailRétention de l’ordre sériel en mémoire verbale à court-terme chez des adultes dyslexiques
Martinez Perez, Trecy ULg; Poncelet, Martine ULg; Majerus, Steve ULg

Poster (2009, December 04)

Les difficultés en mémoire verbale à court terme (MCTV) chez les dyslexiques sont interprétées comme le reflet de représentations phonologiques déficitaires (voir Snowling, 2000). Cependant, leurs ... [more ▼]

Les difficultés en mémoire verbale à court terme (MCTV) chez les dyslexiques sont interprétées comme le reflet de représentations phonologiques déficitaires (voir Snowling, 2000). Cependant, leurs capacités en MCTV sont généralement évaluées au moyen de tâches classiques (tâches d'empan) qui ne permettent pas de dissocier le stockage de l'information relative à l'identité des items (information « item ») du stockage de l'information concernant l'ordre de présentation de ces items (information « ordre sériel ») (Majerus et al., 2006). Or, ces deux aspects de la MCTV pourraient être différentiellement liés à l'apprentissage du langage écrit et être tous deux déficitaires dans la dyslexie. L’objectif de cette étude est de déterminer si les dyslexiques présentent des difficultés en MCTV non seulement pour l'information « item » mais également pour l'ordre sériel.  [less ▲]

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See detailLes TFE en didactique des langues et littératures modernes à l'ULg. Vers une "communauté de chercheurs"
Simons, Germain ULg

Diverse speeche and writing (2009)

Depuis 2007, le service de didactique des langues et littératures modernes de l'ULg organise des séances de "mémorants" dans le domaine de la didactique des langues étrangères. Cette communication décrit ... [more ▼]

Depuis 2007, le service de didactique des langues et littératures modernes de l'ULg organise des séances de "mémorants" dans le domaine de la didactique des langues étrangères. Cette communication décrit le dispositif mis en place et propose quelques éléments d'évaluation. [less ▲]

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See detailPRIX WALLON DE LA QUALITE 2009 : « La Qualité : ombre et lumière »
LEROY, Dominique; DELGAUDINE, Marie ULg

Article for general public (2009)

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See detailRecurrent energization of plasma in the midnight-to-dawn quadrant of Saturn's magnetosphere, and its relationship to auroral UV and radio emissions
Mitchell, D. G.; Krimigis, S. M.; Paranicas, C. et al

in Planetary and Space Science (2009), 57

We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although ... [more ▼]

We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although enhancements in energetic neutral atom (ENA) emission may in general occur at any local time and at any time in a Saturn rotation, those enhancements that exhibit a recurrence at a period very close to Saturn's rotation period usually recur in the same magnetospheric location. We suggest that these events result from current sheet acceleration in the 15-20 Rs range, probably associated with reconnection and plasmoid formation in Saturn's magnetotail. Simultaneous auroral observations by the Hubble Space Telescope (HST) and the Cassini Ultraviolet Imaging Spectrometer (UVIS) suggest a close correlation between these dynamical magnetospheric events and dawn-side transient auroral brightenings. Likewise, many of the recurrent ENA enhancements coincide closely with bursts of Saturn kilometric radiation, again pointing to possible linkage with high latitude auroral processes. We argue that the rotating azimuthal asymmetry of the ring current pressure revealed in the ENA images creates an associated rotating field aligned current system linking to the ionosphere and driving the correlated auroral processes. [less ▲]

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See detailVirtual model of the city of Liège in the eighteen century - "Virtual Leodium"
Billen, Roland ULg; Blain, Pascal ULg; Donneau, Olivier ULg et al

in Verly, Jacques (Ed.) Proceedings of 3D Stereo MEDIA 2009, International 3D Stereo Film and Technology Festival (3D Stereo MEDIA), Liège, Belgium, 1-3 Dec. 2009. (2009, December 01)

Virtual Leodium is a project aiming to scan and digitize a master piece of the collection of the University of Liège, the historical model of the city of Liège around 1730 realised by Gustave Ruhl. The ... [more ▼]

Virtual Leodium is a project aiming to scan and digitize a master piece of the collection of the University of Liège, the historical model of the city of Liège around 1730 realised by Gustave Ruhl. The two main originalities of the approach are to use a projected-fringes scanning technique and to generate a geo-database as a support for archaeological information. This interdisciplinary project gathers physicists, geomaticians, librarians, and archaeologists. [less ▲]

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See detailHD 174884: a strongly eccentric, short-period early-type binary system discovered by CoRoT
Maceroni, C.; Montalban Iglesias, Josefa ULg; Michel, E. et al

in Astronomy and Astrophysics (2009), 508

Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic ... [more ▼]

Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic binary in an eccentric orbit (eË 0.3), unusual for its short 3.65705° orbital period. The high eccentricity, coupled with the orientation of the binary orbit in space, explains the very unusual observed light curve with strongly unequal primary and secondary eclipses having the depth ratio of 1-to-100 in the CoRoT â seismoâ passband. Without the high accuracy of the CoRoT photometry, the secondary eclipse, 1.5 mmag deep, would have gone unnoticed. A spectroscopic follow-up program provided 45 high dispersion spectra. The analysis of the CoRoT light curve was performed with an adapted version of PHOEBE that supports CoRoT passbands. The final solution was obtained by a simultaneous fitting of the light and the radial velocity curves. Individual star spectra were obtained by spectrum disentangling. The uncertainties of the fit were achieved by bootstrap resampling and the solution uniqueness was tested by heuristic scanning. The results provide a consistent picture of the system composed of two late B stars. The Fourier analysis of the light curve fit residuals yields two components, with orbital frequency multiples and an amplitude of ~0.1 mmag, which are tentatively interpreted as tidally induced pulsations. An extensive comparison with theoretical models is carried out by means of the Levenberg-Marquardt minimization technique, and the discrepancy between the models and the derived parameters is discussed. The best fitting models yield a young system age of 125 million years which is consistent with the eccentric orbit and synchronous component rotation at periastron. Based on photometry collected by the CoRoT space mission and spectroscopy obtained with the CORALIE spectrograph attached to the 1.2 m Euler telescope at ESO, La Silla, Chile. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programs, Austria, Belgium, Brazil, Germany and Spain. Postdoctoral fellow of the Fund for Scientific Research of Flanders (FWO). [less ▲]

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See detailThe use of an adapted model allows contributing to the “Reduction” of mice used in experimental protocols: the case of the apoE–deficient (apo E-/-) mice in a model of atherosclerosis control
Cherdon, Céline ULg; Rolin, Stéphanie; de Leval, Laurence ULg et al

Poster (2009, December 01)

Atherosclerosis is a chronic vascular disease whose development is influenced by several mediators 1. Among them, the prostanoids large family lipids generated from the metabolism of arachidonic acid by ... [more ▼]

Atherosclerosis is a chronic vascular disease whose development is influenced by several mediators 1. Among them, the prostanoids large family lipids generated from the metabolism of arachidonic acid by the action of COX includes various types of PGs and thromboxane. Thromboxane A2 and PGI2 are present in abnormally elevated concentration in atherosclerosis 2-3. To exert its effects TXA2 and its precursor PGH2 act at a specific receptor termed TP receptor 4. As a result, TXA2 synthase inhibitors and TP antagonists have been developed to reduce and to prevent TXA2 production and actions, respectively. The present study was undertaken in order to investigate whether BM-573, an original sulfonylurea derivate synthesized in our lab 5, and aspirin would be effective in preventing the progression of atherosclerosis in an apo E deficient mouse model. [less ▲]

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See detailCollective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars
Aerts, C.; Puls, J.; Godart, Mélanie ULg et al

in Astronomy and Astrophysics (2009), 508

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains ... [more ▼]

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained.<BR /> Methods: We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude nonradial gravity-mode pulsations which are predicted to be excited for evolved massive stars.<BR /> Results: In general, line profiles based on macrotubulent broadening can mimic those subject to pulsational broadening. In several cases, though, good fits require macroturbulent velocities that pass the speed of sound for realistic pulsation amplitudes. Moreover, we find that the rotation velocity can be seriously underestimated by using a simple parameter description for macroturbulence rather than an appropriate pulsational model description to fit the line profiles.<BR /> Conclusions: We conclude that macroturbulence is a likely signature of the collective effect of pulsations. We provide line diagnostics and their typical values to decide whether or not pulsational broadening is present in observed line profiles, as well as a procedure to avoid an inaccurate estimation of the rotation velocity. [less ▲]

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See detailImpact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars
Hu, Haili; Nelemans, G.; Aerts, C. et al

in Astronomy and Astrophysics (2009), 508

Context: Realistic stellar models are essential to the forward modelling approach in asteroseismology. For practicality however, certain model assumptions are also required. For example, in the case of ... [more ▼]

Context: Realistic stellar models are essential to the forward modelling approach in asteroseismology. For practicality however, certain model assumptions are also required. For example, in the case of subdwarf B stars, one usually starts with zero-age horizontal branch structures without following the progenitor evolution. <BR /> Aims: We analyse the effects of common assumptions in subdwarf B models on the g-mode pulsational properties. We investigate if and how the pulsation periods are affected by the H-profile in the core-envelope transition zone. Furthermore, the effects of C-production and convective mixing during the core helium flash are evaluated. Finally, we reanalyse the effects of stellar opacities on the mode excitation in subdwarf B stars.<BR /> Methods: We computed detailed stellar evolutionary models of subdwarf B stars, and their non-adiabatic pulsational properties. Atomic diffusion of H and He is included consistently during the evolution calculations. The number fractions of Fe and Ni are gradually increased by up to a factor of 10 around log T = 5.3. This is necessary for mode excitation and to approximate the resulting effects of radiative levitation. We performed a pulsational stability analysis on a grid of subdwarf B models constructed with OPAL and OP opacities.<BR /> Results: We find that helium settling causes a shift in the theoretical blue edge of the g-mode instability domain to higher effective temperatures. This results in a closer match to the observed instability strip of long-period sdB pulsators, particularly for l â ¤ 3 modes. We show further that the g-mode spectrum is extremely sensitive to the H-profile in the core-envelope transition zone. If atomic diffusion is efficient, details of the initial shape of the profile become less important in the course of evolution. Diffusion broadens the chemical gradients, and results in less effective mode trapping and different pulsation periods. Furthermore, we report on the possible consequences of the He-flash for the g-modes. The outer edge of a flash-induced convective region introduces an additional chemical transition in the stellar models, and the corresponding spike in the Brünt-Väisälä frequency produces a complicated mode trapping signature in the period spacings. <BR /> [less ▲]

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See detailDetection of exozodiacal dust: a step toward Earth-like planet characterization with infrared interferometry
Defrere, Denis ULg

Doctoral thesis (2009)

The existence of other habitable worlds and the possible development of life elsewhere in the Universe have been among mankind's fundamental questions for thousands of years. These interrogations about ... [more ▼]

The existence of other habitable worlds and the possible development of life elsewhere in the Universe have been among mankind's fundamental questions for thousands of years. These interrogations about our origins and place in the Universe are today at the dawn of being answered in scientific terms. The key year was 1995 with the discovery of the first extrasolar planet orbiting around a solar-type star. About 400 extrasolar planets are known today and the possibility to identify habitable worlds and even life among them largely contributes to the growing interest about their nature and properties. However, characterizing planetary systems is a very difficult task due to both the huge contrast and the small angular separation between the host stars and their environment. New techniques have emerged during the past decades with the purpose of tackling these fantastic observational challenges. In that context, infrared interferometry is a very promising technique, since it provides the required angular resolution to separate the emission of the star from that of its environment. This dissertation is devoted to the characterization of extrasolar planetary systems using the high angular resolution and dynamic range capabilities of infrared interferometric techniques. The first part of the present work is devoted to the detection with current interferometric facilities of warm dust within the first few astronomical units of massive debris discs around nearby stars. In order to extend the imaging of planetary systems to fainter discs and to extrasolar planets, we investigate in a second step the performance of future space-based nulling interferometers and make a comparison with ground-based projects. Finally, the third part of this work is dedicated to the impact of exozodiacal discs on the performance of future life-searching space missions, the goal being to characterize extrasolar planets with sizes down to that of the Earth. [less ▲]

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See detailInfluence of Adhesive Rough Surface Contact on Micro-Switches
Wu, Ling ULg; Rochus, Véronique ULg; Noels, Ludovic ULg et al

in Journal of Applied Physics (2009), 106(11), 113502

Stiction is a major failure mode in micro electro-mechanical systems (MEMS). Undesirable stiction, which results from contact between surfaces, threatens the reliability of MEMS severely as it breaks the ... [more ▼]

Stiction is a major failure mode in micro electro-mechanical systems (MEMS). Undesirable stiction, which results from contact between surfaces, threatens the reliability of MEMS severely as it breaks the actuation function of MEMS switches for example. Although it may be possible to avoid stiction by increasing restoring forces using high spring constants, it follows that the actuation voltage has also to be increased significantly, which reduces the efficiency. In our research, an electrostatic-structural analysis is performed to estimate the proper design range of the equivalent spring constant which is the main factor of restoring force in MEMS switches. The upper limit of equivalent spring constant is evaluated based on the initial gap width, the dielectric thickness, and the expected actuation voltage. The lower limit is assessed on the value of adhesive forces between the two contacting rough surfaces. The MEMS devices studied here are assumed to work in a dry environment. In these operating conditions only the Van der Waals forces have to be considered for adhesion. A statistical model is used to simulate the rough surface, and the Maugis’s model is combined with Kim’s expansion to calculate adhesive forces. In the resulting model, the critical value of the spring stiffness depends on the material and surface properties, such as the elastic modulus, surface energy and surface roughness. The aim of this research is to propose simple rules for design purposes. [less ▲]

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See detailPhysical Properties of the 0.94-Day Period Transiting Planetary System WASP-18
Southworth, John; Hinse, T. C.; Dominik, M. et al

in Astrophysical Journal (2009), 707

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we ... [more ▼]

We present high-precision photometry of five consecutive transits of WASP-18, an extrasolar planetary system with one of the shortest orbital periods known. Through the use of telescope defocusing we achieve a photometric precision of 0.47-0.83 mmag per observation over complete transit events. The data are analyzed using the JKTEBOP code and three different sets of stellar evolutionary models. We find the mass and radius of the planet to be M [SUB]b[/SUB] = 10.43 ± 0.30 ± 0.24 M [SUB]Jup[/SUB] and R [SUB]b[/SUB] = 1.165 ± 0.055 ± 0.014 R [SUB]Jup[/SUB] (statistical and systematic errors), respectively. The systematic errors in the orbital separation and the stellar and planetary masses, arising from the use of theoretical predictions, are of a similar size to the statistical errors and set a limit on our understanding of the WASP-18 system. We point out that seven of the nine known massive transiting planets (M [SUB]b[/SUB] > 3 M [SUB]Jup[/SUB]) have eccentric orbits, whereas significant orbital eccentricity has been detected for only four of the 46 less-massive planets. This may indicate that there are two different populations of transiting planets, but could also be explained by observational biases. Further radial velocity observations of low-mass planets will make it possible to choose between these two scenarios. Based on data collected by MiNDSTEp with the Danish 1.54  m telescope at the ESO La Silla Observatory. [less ▲]

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See detailComparative Aspects Nationality Law - Selected Questions
Wautelet, Patrick ULg

Learning material (2009)

These slides were used as support for a course taught in English which provides an overview of the major questions arising in the field of nationality law. The course focuses on acquisition and loss of ... [more ▼]

These slides were used as support for a course taught in English which provides an overview of the major questions arising in the field of nationality law. The course focuses on acquisition and loss of nationality and touches upon other issues such as multiple nationalities and the influence of the European construction on nationality law. All these questions are studied using comparative materials as basis. [less ▲]

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