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See detailStudy of the ecology, population structure and dynamic of the macroalgae Codium elisabethae in Faial (Azores) with underwater visible imagery.
Sirjacobs, Damien ULg

Doctoral thesis (2011)

Codium elisabethae O.C. Schmidt is a dark green globose macroalgae isolating an internal sea water volume in a lumen. Codium elisabethae is endemic to the Macaronesian region and is very similar to Codium ... [more ▼]

Codium elisabethae O.C. Schmidt is a dark green globose macroalgae isolating an internal sea water volume in a lumen. Codium elisabethae is endemic to the Macaronesian region and is very similar to Codium bursa C. Agardh whose distribution range spans the West-European, North-Western African and Mediterranean coasts and which was proposed as a potential indicator of coastal environmental changes based on the study of its ecology, revealing its long lifespan. Until recently, relatively little was known on Codium elisabethae as compared to the more widespread Codium bursa. To fill this gap, the present research aimed at producing an accurate description of the ecology and population dynamics of Codium elisabethae occupying the rocky shores of the Monte da Guia Special Area of Conservation (SAC)/Natura 2000 network (Faial, Azores). To achieve this, two reference sites were selected for long term monitoring: a sheltered no-go reserve exhibiting a dense Codium elisabethae population (Caldeirinhas), and a location experiencing more exposed conditions holding a sparser population (Ponta Furada). First, environmental conditions experimented by benthic organisms were extensively quantified and interpretated in regard to topographical particularities of each site. The study of reproduction dynamics showed a persistent summer fertility and an important vegetative reproduction. Important nutrient concentration ratio was found between the Codium elisabethae lumen water and surrounding sea water (mean ratios: nitrates: 5.7; ammonium: 3.4; phosphates: 3.1). In situ counting’s and size measurements revealed much higher densities of young recruits in the site of the Caldeirinhas (order of 20 ind/m²) than in the one of Ponta Furada (order of 1/m), for both summer and winter. Secondly, underwater visible imagery was exploited as an efficient and non-invasive alternative to classical in situ population estimation. Between August 2003 and November 2005, fifteen seabed photo coverages were collected by scuba-divers. Subsequent image processing consisted in mosaicing, interactive identification, and automatic change detection methods. This allowed quantifying the seasonal fluctuations of population structures (density, percentage cover and biomass) and of population dynamics (growth, recruitment, mortality and primary production). Chi-square tests of image-derived estimates and in situ measurements confirmed the validity of a centimeter precision for the estimation of population structure of individuals above 4 cm diameter. Important variability of population structure and density was observed within the sites at small spatial scales. Significant differences of population structure and dynamics parameters are demonstrated between two close-by but contrasting coastal habitats. Population density showed a sharp reduction in autumn 2003 and did not recover fully in spring and summer 2004. During the following year, population of the protected site maintained density and biomass, while at the exposed site population density dropped. In contrast with conclusions from earlier studies on the Azorian Codium elisabethae and on the Mediterranean Codium bursa, the present study revealed higher biomass (34 - 730 g dry wt.m-²), growth rates (up to 2.5 cm/month in summer) and primary production (0.53 – 11.5 g dry wt.m-².day-1), and demonstrated the seasonal fluctuations of these parameters for the studied Azorian Codium elisabethae population. The lifespan of Codium elisabethae was estimated to reach at least 7 years in the SAC of Monte da Guia based on an integration of average seasonal growth rates measured by imagery on extended population samples. This study demonstrates the high potential of registered underwater photomosaics time-series for long term surveys of macroalgae populations. This work provides also a strong framework to further developments and applicability to other species, which should be helpful to strengthen our current understanding of benthic ecosystem processes. [less ▲]

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See detailIo's interaction with Jupiter's magnetosphere
Dols, Vincent ULg

Doctoral thesis (2011)

Io, the innermost Galilean moon of Jupiter, is the most volcanic body of the solar system. This volcanism is responsible for a tenuous atmosphere composed mainly of S, O and SO2. This atmosphere is ... [more ▼]

Io, the innermost Galilean moon of Jupiter, is the most volcanic body of the solar system. This volcanism is responsible for a tenuous atmosphere composed mainly of S, O and SO2. This atmosphere is constantly bombarded by the plasma that co-rotates with the magnetic field of Jupiter, producing new ions and perturbing locally the magnetic field. This local perturbation is responsible for auroral emissions in the atmosphere of Jupiter, at the foot of Io’s flux tube. The spacecraft Galileo made five flybys of Io between 1995 and 2001 at very low altitude (~100’s km) and made plasma and magnetic field measurements that reveal the complexity of Io’s interaction with Jupiter. Past studies have tackled the modeling of this interaction using different complementary approaches, each shedding a new light on the issue but each involving some simplifications. The MHD models (Linker et al., 1998) are based on an a priori parameterization of the ionization in the atmosphere, generally assuming spherical symmetry and a single atmospheric and plasma species (representative of O and S). They ignore the important effect of the cooling of electrons as well as the multi-species composition of both the plasma and the atmosphere. The two-fluid approach (Saur et al., 1999) computes precisely the ionization and collisions in the atmosphere of Io but make the assumption of a constant magnetic field, limiting the self-consistency of the model and potentially introducing large quantitative errors. We combine a multi-species chemistry model of the interaction that includes atomic and molecular species with a self-consistent Hall-MHD calculation of the flow and magnetic perturbation to model as self-consistently as possible the plasma variables along the different flybys of Io by the Galileo probe. [less ▲]

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See detailMODELISATION DE L’ACTIVITE DES BACTERIES DU SOUFRE EN LAGUNAGE
Harerimana, Casimir ULg

Doctoral thesis (2011)

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See detailSignal transduction in photodynamic therapy-mediated cell death
Coupienne, Isabelle ULg

Doctoral thesis (2011)

Les glioblastomes sont des tumeurs du cerveau comptant parmi les plus fréquentes et les plus agressives. En effet, l’espérance de vie médiane des patients est d’environ quinze mois après diagnostic ... [more ▼]

Les glioblastomes sont des tumeurs du cerveau comptant parmi les plus fréquentes et les plus agressives. En effet, l’espérance de vie médiane des patients est d’environ quinze mois après diagnostic. Malgré d’intenses recherches et l’utilisation de traitements combinant la chirurgie, la radiothérapie et la chimiothérapie, le pronostic des patients n’a guère évolué depuis une vingtaine d’années. Ces tumeurs sont caractérisées par la présence de diverses altérations génétiques et, généralement, par une activation constitutive du facteur de transcription NF-κB. Étant un régulateur majeur de l’apoptose et de la survie cellulaire, ce facteur pourrait jour un rôle central dans la résistance des glioblastomes aux diverses thérapies. Au cours de ce travail, nous avons étudié les effets de l’inhibition du NF-κB sur la mort cellulaire des glioblastomes induite en réponse à un traitement par PDT, dont l’efficacité repose sur la production d’espèces réactives de l’oxygène suite à la présence simultanée d’un photosensibilisateur, de lumière et d’oxygène. Ainsi, nos résultats montrent que les cellules dans lesquelles le NF-κB est inhibé présentent une sensibilité accrue au traitement par rapport aux cellules non-inhibées. De plus, cette augmentation de mort cellulaire est majoritairement due à de la nécrose. Le traitement par PDT conduit également à l’apparition d’autophagie cytoprotectrice dont l’inhibition améliore l’efficacité du traitement. Nous nous sommes ensuite focalisés sur la mort par nécrose et avons démontré l’implication de la kinase RIP3 dans la mort nécrotique induite par PDT. Il est apparu que l’oxygène singulet produit au cours du traitement était à l’origine de la nécrose RIP3-dépendante. Cependant, les intermédiaires transductionnels et la manière dont le NF-κB exerce ses effets anti-nécrotiques demeurent encore inconnus. Enfin, afin de mieux comprendre le rôle joué par RIP3 dans la mort induite par PDT, nous avons utilisé la lignée d’ostéosarcome U2OS, déficiente en cette protéine, et au sein de laquelle nous en avons restauré l’expression. De manière surprenante, les cellules sauvages se sont révélées plus sensibles au traitement que les U2OS exprimant RIP3. De plus, la lignée RIP3-U2OS montre un taux d’apoptose supérieur à celui de son homologue sauvage. Cette divergence peut en partie s’expliquer par une induction d’autophagie plus importante au sein des RIP3-U2OS. Celle-ci, pouvant être un mécanisme pro-survie, peut leur conférer une protection contre la mort cellulaire en facilitant l’élimination des organelles endommagés. Enfin, nous avons déterminé que les cellules sauvages présentent un taux de nécrose plus important que les cellules RIP3-U2OS en réponse au traitement. Nos résultats ont dont permis de prouver (i) que l’inhibition du NF-κB améliorait la sensibilité des glioblastomes à la mort cellulaire induite par un traitement par 5-ALA-PDT, (ii) que celle-ci était, dans ce cas, majoritairement de la nécrose RIP3-dépendante et (iii) de mettre au jour un rôle pour RIP3 dans la régulation de l’apoptose et de l’autophagie induites par PDT. [less ▲]

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See detailLa résilience des banques libanaises : analyse de certains aspects de la gestion des risques dans le cadre de l'accord de Bâle
El Khoury, Ghada ULg

Doctoral thesis (2011)

Located in an environment of high uncertainty, supervisors in Lebanon have decided to comply with regulations issued by the Basel Accords and to monitor the new Basel Committee prudential framework. This ... [more ▼]

Located in an environment of high uncertainty, supervisors in Lebanon have decided to comply with regulations issued by the Basel Accords and to monitor the new Basel Committee prudential framework. This thesis focuses on the Lebanese banking sector and on Basel II specific aspects in the Lebanese context. Four research areas are covered : 1. Evaluation of the capitalization level of Lebanese banks as required by Basel II prudential standards. 2. Lebanese sovereign risk analysis and its impact on the sustainability of banks through the measurement of probability of default of the Lebanese state on its Eurobonds denominated in U.S. dollars. 3. Examining the question of bank balance sheet procyclicality generated by the accounting and prudential framework, and by contextual factors specific to the resilience of the Lebanese banking sector. 4. Evaluation of the adaptation level of the Lebanese banking sector to new risk management approaches by estimating the probability that banks will well manage their risks. From a comparative analysis of the regulatory and economic capital, we found that 14 banks have a high economic capital relative to regulatory capital under Basel II in 2005. We also observed that the risks faced by Lebanese banks are primarily related to credit risk and sovereign risk in particular. Applying the valuation model of default risk, developed by Merrick (2001), and based on a review of scientific literature, we proposed a synthetic measure of credit risk of the Lebanese US dollar denominated Eurobonds. The results show that changes in the probability of default and recovery rates are explained by the trust vis-à-vis the market and state. Based on a review of the scientific literature, we have developed theories of economic fluctuations and financial instability. The analyses of procyclicality in the Lebanese context have shown that the factors leading to a balance sheet procyclicality in the Lebanese banking sector are atypical. We have also shown the resilience of the Lebanese banking sector to recent shocks and crises. Through a survey conducted between November 2009 and February 2010, we assessed the level of adaptation of the Lebanese banking sector to new risk management approaches. The results show that some banks have become more aware of the importance of developing proper risk management practices. Therefore, other banks remain in a precarious stage. [less ▲]

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See detailExtension of the Liège Intranuclear Cascade Model to the 2-15 GeV Incident Energy Range
Pedoux, Sophie ULg

Doctoral thesis (2011)

The Liège Intra-Nuclear Cascade model (INCL4) has been shown to be quite successful for the description of spallation reactions. However its validity domain is limited to an upper incident energy of ~2 ... [more ▼]

The Liège Intra-Nuclear Cascade model (INCL4) has been shown to be quite successful for the description of spallation reactions. However its validity domain is limited to an upper incident energy of ~2 GeV, because inelastic elementary processes are restricted to the excitation and de-excitation of the Delta resonance. In this thesis, the INCL4 model is extended to higher incident energy. This is realised by including other inelastic elementary collisions, direct multipion production in elementary nucleon-nucleon and pion-nucleon collisions. This is somehow opposite to the usual extension to high energy of such models, as it is usually realised by including excitation of heavier baryonic resonances. Experimental data and isospin symmetry have been exploited in the implementation of multipion channels, but we could not avoid to introduce specific models for the energy-momentum and charge repartition on the final pions. The predictions of the modified model for production of protons, neutrons and charged pions by proton and pion beams off nuclei are compared with experimental data. A short study on nuclear fragmentation is also presented. [less ▲]

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See detailBouncing droplets, the role of deformations
Terwagne, Denis ULg

Doctoral thesis (2011)

Nowadays, innovative applications such as "lab-on-a-chip", micro-reactors or biological chips are developed for industry, biology or medicine. Capillary issues are encountered which are not yet fully ... [more ▼]

Nowadays, innovative applications such as "lab-on-a-chip", micro-reactors or biological chips are developed for industry, biology or medicine. Capillary issues are encountered which are not yet fully understood. It is therefore essential to open up ways to manipulate tiny amounts of liquid in order to mix them, encapsulate them or to create emulsions. The bouncing droplets on an oscillating liquid interface allow their manipulation. Indeed, under certain conditions, droplets can bounce indefinitely on a bath surface as long as the squeezed air film which separates the drop from the bath is renewed at each bounce. We chose to study deformable droplets on a non-deformable bath. The droplets are deformable because they are large or made of a low viscous oil, the liquid of the bath being highly viscous silicone oil. We investigated how the deforma- tions, the stability and the trajectories of the droplets depends on the forcing parameters such as the frequency and the amplitude of the oscillation. We also studied the possibility of mixing and emulsifying droplets on the bath. Finally, we showed the effect of the deformation of the bath on these bouncing droplets and studied the trajectories of walking droplets [1] which are used as a model for quantum-like particles [2-5]. In this manuscript, we reported an exploration of the droplets behavior as a function of the ability of the bath and/or the droplet to deform. Depending on the forcing frequency, specific deformation modes are excited on the bouncing droplets. We used these modes to rationalize their bouncing stability and to create double emulsions in a compound droplet. Then, we determined numerically the complex bifurcation diagrams of the trajectories of a bouncing droplet thanks to a model based on a spring. On a low viscous bath, we evidenced the importance of its deformation. We showed that a walker exists as soon as the droplet experiences, once every two oscillation periods, a jump high enough to trigger a Faraday wave. As a consequence, we have to take the bouncing droplets into account when looking for an alternative way to manipulate them or as a model of quantum-like particles. The bouncing droplets still exhibit lots of intriguing behaviors which have yet to be explained. They can therefore remain the focus of future works. [less ▲]

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See detailApplication de la spectroscopie Raman à l’analyse de colorants sur fibres de coton dans le contexte de la criminalistique
Lepot, Laurent ULg

Doctoral thesis (2011)

Forensic examination of textile fibres is based on fibre morphology and on fibre material and dyes characterization. Cotton is the most frequently used fibre in textiles but also the most encountered in ... [more ▼]

Forensic examination of textile fibres is based on fibre morphology and on fibre material and dyes characterization. Cotton is the most frequently used fibre in textiles but also the most encountered in casework. While man-made fibres show various morphologies and materials, cotton is a natural cellulosic fibre with constant morphology. Cotton fibres examination can consequently be summarized in the characterization of fibre dyes. However forensic needs require non-destructive, fast and sensitive techniques. For fibres microspectrophotometry (MSP) is the commonly used technique and the obtained UV-Vis absorption spectrum reflects dyes used to colour the fibre. Any other technique suitable for dye characterization is thus helpful to reinforce MSP results on cotton fibres. Raman spectroscopy is a fast non-destructive technique, easy to integrate into the fibre analytical sequence without any additional sample preparation. Moreover it provides specific molecular information and seems convenient for the study of coloured molecules. This work allowed to demonstrate the potential of the technique in dyed cotton fibres examination through the characterization of pure dyes but also the ability to detect different components in dye mixtures. In order to help dye identification spectral databases were built using Raman spectra collected in the present work. Unfortunately such a database will never be exhaustive and the identification of an unknown dye would be compromised. An interesting option is to identify the general chemical class of the unknown dye, especially to evaluate its rarity. The recognition of some dye chemical classes has been made by the mean of characteristic peaks but this method remains somewhat subjective. This subjectivity can be bypassed using chemometric techniques; they are able to predict chemical class membership on the basis of Raman specific information. Some experiments have been performed on Raman spectra using PCA models and the SIMCA classification tool. [less ▲]

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See detailStudy of the Cape Ghir upwelling filament using variational data analysis and regional numerical model
Troupin, Charles ULg

Doctoral thesis (2011)

Aim: Upwelling filaments are shallow, elongated structures of cool waters often visible in the regions of coastal upwelling. The present thesis aims to improve our knowledge on the mechanisms responsible ... [more ▼]

Aim: Upwelling filaments are shallow, elongated structures of cool waters often visible in the regions of coastal upwelling. The present thesis aims to improve our knowledge on the mechanisms responsible for the generation of filaments. Location: the study is centered on the Canary Current Upwelling system, located off northwest Africa, in particular around Cape Ghir (30°38'N, 9°53'W), where these filaments are frequently observed. Methods: - We compiled historical in situ data to build a high-resolution climatology of temperature and salinity in the region of interest using the Data Interpolating Variational Analysis (\diva) method. - We ran the experiments with the numerical model ROMS to investigate the processes responsible for the filament generation. - We collected in situ measurements during a cruise in August-September 2009, in the frame of the CAIBEX project, in the filament area and analyzed them to get a detailed description of the Cape Ghir filament, its variability and its biogeochemical characteristics. - We computed anomalies of several variables with respect to a long-term mean to examine the time-evolution of the Canary Current Upwelling system. Results: The climatology showed improvements with respect to existing products, especially in the coastal area, and was a valuable asset to provide initial and boundary conditions for the numerical model. The results of the simulations underlined the role of the wind in the filament generation and confirmed our assumption of a mechanism based on the potential vorticity balance. Preliminary analysis of the cruise data allowed us to characterize the filament physical and biological properties, in particular we observed the signal of a subsurface (at a depth of 300~m) anticyclonic eddy on the northern flank of the filament, also present in the numerical model outputs. Anomalies for the year 2010 revealed a widespread warming over the tropical and subtropical Atlantic Ocean and a diminution of the upwelling activity. We attributed these anomalies to a weakening of the winds, itself related to a strongly negative North Atlantic Oscillation (NAO) index. [less ▲]

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See detailImpacts des changements climatiques passés et présents sur la génétique et la démographie du Cincle plongeur (Cinclus cinclus)
Hourlay, Frederic ULg

Doctoral thesis (2011)

Climate change is emerging as the greatest threat to natural communities in many, if not most, of the world’s ecosystems in coming decades. Numerous studies have revealed present and probable future ... [more ▼]

Climate change is emerging as the greatest threat to natural communities in many, if not most, of the world’s ecosystems in coming decades. Numerous studies have revealed present and probable future consequences that climate change will have on many animal and vegetal species. According to these studies, birds could be affected, mostly negatively, in various ways : distribution, abundance, phenology, ethology ... The purpose of this work is to determine how the White-throated Dipper (Cinclus cinclus), a Palearctic, temperate, passerine bird that is exclusively associated with flowing water, reacted to the climate changes that occurred during the Pleistocene, and how climate change currently affects this species : - For this purpose, we conducted a phylogeographic study : we analysed three fragments of mtDNA (i.e. fragments coding for cytochrome b, ND2 and domains II and III of the controle region) from 106 tissue samples originating from 24 dipper populations, mostly located in the Western Palearctic. - The second part of this work consisted in analysing ringing recoveries and nest-boxes frequentation from a dippers population settled on the river Syre and its tributaries (Luxemburg) and followed from 1979 to 2001. Populations census were also conducted on different water courses in Luxemburg, in order to determine dipper habitat preferences. 1. Phylogeography of the dipper in the Western Palearctic region In spite of a low genetic variability, the results of our phylogeographic study reveal a complex phylogeographic structure for this species with at least five distinct lineages for the Western Palearctic region. As for many species of the Western Palearctic fauna and flora, this genetic structure is probably linked to the isolation of populations in different southern refuges during glacial periods. Furthermore, the isolation of populations in Scandinavia and/or Eastern regions, but also in Morocco and probably in Corsica, was accentuated by ecological and biogeographic barriers during Quaternary interglacial periods. During glacial periods, Italy, Sicily and the Balkano-Carpathian region acted as major refuge zones for the dipper. At the end of the last ice age, Western Europe was repopulated by dippers from a refuge located in Italy and, probably, South-East France, while Eastern Europe was recolonised by Balkano-Carpathian birds. A large contact zone between these two lineages was evidenced and extends from Luxembourg to Hungary. Finally, our results indicate the need to clarify the taxonomic status of the dipper, especially concerning the European subspecies whose validity appears uncertain. 2. Dipper demography – Influence of climate change and other anthropic pertubations Results obtained from the analysis of demographic and morphologic variables of the Luxemburger population are in agreement with results obtained from other European populations. Differences observed between these populations are mostly due to climate and habitat quality differences. However, other factors could also partly explain these differences. As for other places in Europe, nest boxes installation dramatically increased dippers population size on the river Syre. Our results also suggest that the installation of nest boxes could influence some demographic and morphologic variables, probably as a result of population increase. But, above all, our results show how temperatures and precipitations affect these variables, and particularly laying dates. Climatic changes that occurred during the last decades provoked earlier laying dates. Whereas clutch size and nest size remained unchanged, the Luxemburger population size decreased during the same period, as observed for other European populations. The main cause to this decrease should be an increase of environmental instability inducing notably a decrease of food ressources for dippers. As a result, we observed a significant decrease of females body weight during this period. Climate change will also probably have a serious impact on dipper genetic diversity, leading to the disappearance of the most southern populations and eventually of certain genetic clades. The results obtained concerning the taxonomic status of the dipper and its demography could be useful in the framework of a conservation program, if necessary. In this perspective, the development of habitat suitability prediction tools, as the one we developed, could also be very helpful. [less ▲]

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See detailUnveiling the internal structure and evolution of massive stars through their pulsation modes
Godart, Mélanie ULg

Doctoral thesis (2011)

Stars in the night sky are not as quiet as they seem. A human being wandering on Earth few billions years ago would have seen a different night sky, with different stars forming different constellations ... [more ▼]

Stars in the night sky are not as quiet as they seem. A human being wandering on Earth few billions years ago would have seen a different night sky, with different stars forming different constellations. Moving forward in time, he would have been the witness of stellar evolution as some stars would have suddenly shined while others disappeared forever. Hard to realize at a time scale of human life, stars are born, evolve, and die in a limited lifetime which can last only a few million years for the most massive to trillion years for the less massive. Fortunately, it is not necessary to wait that long to study the formation and evolution of stars. Stellar evolution can be studied on shorter time scales, on thousands of stars, at various evolutionary stages. This is of great importance as stars shape the Universe and produce the chemical elements at the origin of life. Probing the internal structure of stars is however very challenging due to the opacity barrier of their superficial layers. One way to get around this issue is to study and interpret stellar pulsations. As seismologists extract information about Earth interior trough the study of earthquakes, asteroseismologists can study the internal structure of stars by studying their oscillations. In this thesis, this technique is used to study the internal structure and evolution of massive stars which are at least eight times more massive than our Sun and which have a spectral type between O and B. The first part of this work is devoted to the determination of the $\kappa$-mechanism instability domains for massive stars. In order to extend the computations to the post-main sequence phase of evolution, we develop a numerical technique in which the non-adiabatic computations for the stellar core are made, independently than for the envelope, within the quasi-adiabatic and the asymptotic treatment. In a second step, we investigate the pulsations modes in O main sequence stars and in B post-main sequence stars. The presence of g-modes in post-main sequence stars is closely related to the internal structure of the star and we study the effects of several physical factors on the occurrence of these modes. Finally, the last part of this work is dedicated to the characterization of strange mode pulsations. In particular, we focus on strange modes having an adiabatic counterpart, which are trapped into a superficial cavity. The effect of the model atmosphere on the excitation is investigated in addition to the characterization of their eigenfunctions. [less ▲]

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See detailCaractérisation des effets de température dans la zone endommagée autour de tunnels de stockage de déchets nucléaires dans des roches argileuses
Dizier, Arnaud ULg

Doctoral thesis (2011)

La solution du stockage des déchets nucléaires de haute activité et de longue durée de vie dans les couches argileuses profondes comporte de nombreuses incertitudes. Pour combler celles-ci de nombreux ... [more ▼]

La solution du stockage des déchets nucléaires de haute activité et de longue durée de vie dans les couches argileuses profondes comporte de nombreuses incertitudes. Pour combler celles-ci de nombreux projets européens sont réalisés de façon à les minimiser. Le projet TIMODAZ (Thermal Impact On the Damaged Zone Around a Radioactive Waste Disposal in Clay Host Rocks) étudie l'influence de la température sur la zone endommagée. Cette zone correspond à une zone soumise à la redistribution des contraintes lors de l'excavation constituant un lieu de développement de micro et macro fractures. Cet endommagement mécanique est complété par un endommagement thermique lors de la pose des canisters qui vont émettre de la chaleur durant des milliers d'années et donc provoquer une augmentation de la température du massif argileux. Cette élévation de température de l'argile peut faire apparaitre des déformations plastiques thermiques de contraction. Cette nouvelle plasticité peut contribuer au développement de la zone endommagée. L'objectif de ce travail est donc de caractériser la zone endommagée autour des tunnels souterrains, construits dans l'Argile de Boom, soumis à des élévations de température induites par les déchets nucléaires. Durant ce travail, une loi de comportement thermo-mécanique est implémentée. Celle-ci se base sur un "modèle à chapeau" étendu à la thermo-plasticité. Ce modèle comprend la combinaison d'un modèle à frottement interne, d'un critère Cam-Clay et d'un critère de rupture à la traction. Ce modèle est étendu à la température et en particulier à la thermo-plasticité en considérant les travaux de Sultan. Les paramètres thermo-hydro-mécaniques de l'Argile de Boom sont identifiés et servent à la modélisation d'expériences de laboratoire et in situ. Ces expériences consistent en outres en un cylindre creux, en l'expérience de chauffage ATLASIII et en l'expérience à grande échelle PRACLAY. Ces trois expériences ont pour objectif d'étudier l'Argile de Boom d'une petite échelle à une plus grande représentative du massif argileux. L'étude du comportement dans la zone élastique et plastique est également prise en compte via ces différentes expériences. Les résultats, avec différentes lois de comportement, montrent que l'influence de la thermo-plasticité est faible mais non négligeable vis-à-vis des déformations déviatoriques engendrées par l'excavation. [less ▲]

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See detailInSAR Applied to the Study of Active Volcanic and Seismic Areas in Africa
Wauthier, Christelle ULg

Doctoral thesis (2011)

Two active volcanic areas situated in immature portions of the East African Rift System (EARS): the Lake Kivu (Dem. Rep. of Congo) and Lake Natron (Tanzania) regions, which are located in the western and ... [more ▼]

Two active volcanic areas situated in immature portions of the East African Rift System (EARS): the Lake Kivu (Dem. Rep. of Congo) and Lake Natron (Tanzania) regions, which are located in the western and eastern branch, respectively, are still poorly known. Both areas indeed lack of ground-based networks, due to security problems or difficult field accessibility. The Lake Kivu area includes two volcanoes erupting frequently: the Nyamulagira and Nyiragongo volcanoes. The SAR database covering these volcanoes in- cludes data from JERS, ERS-1&2, ENVISAT, ALOS, RADARSAT-1&2 satellites back from year 1996. SAR Interferometry (InSAR) is thus applied to study the ground de- formations. MT-InSAR approaches, such as the ”‘StaMPS”’ method, are used to give us new complementary information to better constrain the previous established eruption models, or gain new insights on eruptions missed by the conventional InSAR, as well as on magmatic and tectonic activity. When enough constrains are available, the ground displacements are modeled using a 3D-Mixed Boundary Elements Method combined with a neighborhood algorithm. Hence, the 1996, 2002, 2004 and 2010 eruptions of Nyamu- lagira are modeled. The modeling results, coupled with the StaMPS MT-InSAR results, bring new insights concerning the magma plumbing system of this poorly known volcano and its eruptive mechanisms. The collapse of the eastern flank of Nyamulagira, along the NNW-trend fractures network linking Nyamulagira and Nyiragongo volcanoes, can also be identified. InSAR also captures the ground displacements associated with the January 2002 Nyiragongo eruption. The modeling of this major event evidences a deep magma intrusion beneath the Lake Kivu. Such intrusions should be taken into account for hazard assessment. The magma could indeed finds its way to the Lake Kivu floor, as evidenced by the presence of several old phreato-magmatic cones, and causes a lake overturn. The low dikes overpressures found in the North Kivu and Lake Natron areas indicate that, although the rift is considered as immature, the rift extension is driven by the supply of magma from depth, rather than by the tectonics. A new criterion to identify the rifting stage is found to be the stress state. In the southern part of the rift, tectonic activity dominates, indicating that the tectonics is probably driving the rift opening there. [less ▲]

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See detailDynamique des transactions foncières et vulnérabilité rurale au Niger : cas des communes rurales de Tchadoua et Yaouri
Lawali Mani, Sitou ULg

Doctoral thesis (2011)

Summary In Niger, agriculture is the principal activity of the rural populations. Unfortunately the access to the land becomes very difficult to the farmers in the center-south of the country. This area ... [more ▼]

Summary In Niger, agriculture is the principal activity of the rural populations. Unfortunately the access to the land becomes very difficult to the farmers in the center-south of the country. This area is confronted to the space saturation and the emergence of the land transactions whose causes, process and impacts on the agricultural households are little known. The study undertaken in the rural municipality of Tchadoua and Yaouri aimed at analyzing the dynamics of the land transactions in bond with the rural vulnerability in terms of the stakes of access and management of the grounds, but also their securisation. The problems were studied with a multidisciplinary approach. The analyses (quantitative and qualitative) were carried out on the basis of the data collected in the village areas of Maijanguero and Gomba through cards of investigations and semi-structured interviews with a sample of 30% of the households. We also used participatory observations of agricultural practices and consultation of different sources of documentation. Administration and others authorities have been also interviewed aswel as members of the land commissions and the intermediaries of the transactions. The results obtained show that the problem of access and management of the land in these agricultural areas is an important concern for rural producers. The land blocking due to the strong demographic pressure and the increase of economic stakes (crop rent) influence the excessive parceling out of the grounds and the individualization of the farms. This individualization supports consequently, the emergence of the commercial land speculations for the profit of the economic operators installed from now in logic of monopolization of grounds. The purchase, the pledge and the lease constitute the principal access modes to the ground instead of old forms of solidarity (gift, loan). Also, the new agrarian initiatives of assistance appear and take part in the improvement of the socio-economic conditions of the rural households. The results also made it possible to highlight a diversity of trajectories of the exploitations. The land ‘’monetarisation’’ influenced strongly the land management and reinforced the exclusion of the vulnerable groups. The strong changes of technical transformation and farming system are observed. It as revealed as the land accumulation or ‘’décapitalisation’’ depends of the type of farm, its strategy and its revenue. Indeed, three tendencies become apparent from the trajectories: great manufacturing units with dominant commercial accumulate land, use the hired labor work and araw cash crop (souchet); a strong land ‘’decapitalisation’’ at the extremely vulnerable and without viable strategy of adaptation in the long term. Lastly, the small farm witch made a diversification and a strong intensification, and there resist to the multiple attempts of land spoliation. These last constitute a model of stable and durable farm whose strategy is based primarily on the agricultural intensification through effective and less expensive agroforestry practices to increase their production and their land capital. The informel and discrete character of land transactions and the networks of intermediation by which are negotiated the land sales accentuate the land insecurity and contribute to increase the land prices. The analysis of the securisation practices of the land rights proves that legal formalization though timid, reduced considerably the frequency of the rural conflicts and offers agricultural opportunities of investments. However, the land commissions encounter difficulties which, slow down the generalization of the legal formalization of transactions. All things considered, the land problem remains a central stake of development thus, the securisation of the land rights of the rural poor must be a priority of the priorities to reach a durable food safety. It is thus urgent to make the land commissions more operational in their giving the means of operation in order to ensure a broad diffusion of the procedures of formalization for more impact and also encouraging the producers through small subsidies to practice the carrying agri-environmental measurements. [less ▲]

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See detailLe Caire : carrefour des ambassades. Étude historique et diplomatique de la correspondance échangée entre les sultans mamlouks circassiens et les souverains timourides et turcomans (Qara Qoyunlu-Qaramanides) au XVes. d’après le BnF ms.ar. 4440.
Dekkiche, Malika ULg

Doctoral thesis (2011)

Pendant près de 250 ans, les sultans Mamlouks d’Égypte (1250) et de Syrie (1260) furent les représentants suprêmes de l’Islam aussi bien aux yeux des Musulmans que des Chrétiens d’Occident. Leur capitale ... [more ▼]

Pendant près de 250 ans, les sultans Mamlouks d’Égypte (1250) et de Syrie (1260) furent les représentants suprêmes de l’Islam aussi bien aux yeux des Musulmans que des Chrétiens d’Occident. Leur capitale, Le Caire, s’érigea en véritable carrefour des ambassades venues des quatre coins du monde connu alors. Cependant, presque rien des archives de cette dynastie ne nous est parvenu sous sa forme originale. Heureusement, les secrétaires de chancellerie de cette époque nous ont laissé un nombre non négligeable d’ouvrages, manuels de chancellerie et Formulaires, dans lesquelles ils nous révèlent les pratiques de chancellerie en cours alors et nous présentent de nombreuses copies de lettres qui furent échangées entre les sultans mamlouks et d’autres dynasties, musulmanes, chrétiennes ou autres. La présente thèse de doctorat se fonde sur l’un de ces formulaires, conservé sous sa forme manuscrite à la Bibliothèque Nationale de France, Paris, sous la cote ms. ar. 4440. Nous avons extrait de ce manuscrit un corpus de 19 lettres échangées entre les sultans mamlouks et trois autres dynasties musulmanes du XVes. régnant sur un territoire allant de l’Anatolie à l’Iran en passant par l’Iraq: les Timourides, les Qara Qoyunlu et les Qaramanides. Après l’édition critique de ce corpus, nous nous sommes concentrée sur l’étude historique et diplomatique de celui-ci. La première partie de la thèse concerne l’étude historique du corpus et de ce que nous avons appelé « la réalité de l’ambassade ». Le protocole de réception des ambassades au Caire par les sultans mamlouks, est assez bien renseigné à travers les chroniques des historiens de l’époque. Il est important de bien connaître ces règles afin de mesurer l’importance que le souverain accordait à son correspondant. Après énonciation de ces règles protocolaires, nous proposons, pour chaque dynastie en question, un aperçu de l’état des relations qui étaient établies entre elles et les sultans mamlouks, avant de nous atteler à l’étude historique du corpus proprement dite. Pour ce faire, nous avons dépouillé années après années les chroniques mamloukes et tenté de remettre chacune des lettres du corpus dans le contexte de l’ambassade qui lui était propre. Enfin, nous nous sommes concentrée sur le contenu des messages de ces lettres et avons analysé les raisons qui étaient à l’origine de l’envoi de l’ambassade. Nous nous sommes rendue compte de l’importance que ces lettres possèdent en tant que sources historiques de la période couverte, car elles nous révèlent un grand nombre de détails omis par les historiens contemporains des faits, ce qui nous permet de réévaluer avec plus de précision le rôle que la dynastie mamlouke jouait encore à cette époque notamment en tant que représentant suprême de la communauté musulmane et ce malgré les affronts subis par les différents pouvoirs montants, comme les Timourides. Nous avons grâce à l’analyse du protocole de cérémonie et du contenu des messages deux grilles de lecture nous permettant d’évaluer l’état des relations établies entre les Mamlouks et les trois autres dynasties, mais pour que l’étude soit complète, il est une troisième grille qui doit être prise en compte. Elle nous est fournie par la diplomatique et elle fait l’objet de la seconde partie de notre thèse. Dans cette partie, nous nous sommes concentrée, outre sur notre corpus, sur l’étude des manuels de chancellerie de l’époque mamlouke et nous avons tenté, grâce à eux, de reconstituer les règles de chancellerie propres à la rédaction de la correspondance entre les sultans mamlouks et les souverains musulmans afin de mesurer de façon certaine les liens qui sous-tendaient les relations établies entre les différents correspondants. Une telle étude vient à point lorsque l’on sait le retard que la discipline diplomatique a pris dans le cadre des études arabo-musulmanes. Enfin, la mise en parallèle de cette partie avec la première nous permet de dresser un tableau assez complet de la perception que les Mamlouks avaient des autres dynasties avec lesquelles ils étaient en contact. [less ▲]

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See detailElaboration d’un modèle d’écobilan de l’exploitation agricole irriguée. Cas du périmètre du Tadla – Maroc
Krim, Lhassan ULg

Doctoral thesis (2011)

In Morocco, the agro environmental problem is mainly translated by a degradation of the waters quality and a soils salinization under irrigation. In the, studied zone of the present work, the lands ... [more ▼]

In Morocco, the agro environmental problem is mainly translated by a degradation of the waters quality and a soils salinization under irrigation. In the, studied zone of the present work, the lands irrigation started since several decades by using waters of sometimes very degraded mineral quality, on one hand, and the agricultural intensification essentially marked by the application of excessive nitrogenous fertilizers doses, on the other hand, engendered a strong nitric pollution of groundwater table and a spectacular salinization of soils and waters. In order to contribute to the environmental assessment of the irrigated agriculture in Morocco, an Ecobalance model baptized "EcoTadla" (TEB) was elaborated and validated in the Tadla perimeter through the adaptation of the "EcoFerme" model (MEF) developed by the Fluid Mechanics and Environment Unity of the Gembloux Agro-Bio Tech – University of Liege (Belgium). The general objective is to establish an Ecobalance model allowing to quantify and to analyse the materials fluxes exchanged between the farm and its environment and consequently to improve and\or to correct the agricultural practices aiming at a better agro environment preservation within an eco-advice initiative framework. The analysis of the inadequacies of MEF to make an operational model in the studied context allowed to bring the adaptations to be brought as regards the definition of the basic hypotheses to hold in the new model construction, the quantification of the parameters to be used as inputs of the model and the modifications to be introduced into the modelling of the fluxes equations. The TEB model subdivides the farm into three compartments the “Cultivated soil”, the “Cultures” and the “Animals”. The farm (studied system) exchanges materials fluxes with its environment subdivided, in his turn, into four compartments: The “Network waters”, the “Under ground” the "Atmosphere" and the "Third parties". The Ecobalance calculation period is of twelve months equivalent to an agricultural campaign and elements, taken into account at present, in the fluxes calculation are: the nitrogen (N), the phosphor (P), the potassium (K), the calcium (Ca), the magnesium (Mg), the chlorine (Cl), the sodium (Na) and the water (H20). Considering the specificities of the agro environmental problem in the studied context, the TEB global model was conceived as a general program which calculates the Ecobalance for the various taken elements and which offers the possibility to the user to focus the study on three sub models: The "Water" model (WEB), the "Nitrogen" model (NEB) and the "Salts" model (SEB). These three models allow to quantify and to analyse the materials fluxes respectively for "Water", "Nitrogen" and "Salts" on the farm or perimeter scale during the period calculation. The TEB model was tested, verified and validated on an optimised network of representative farms. In order to characterize better the studied domain and clarify more the main parameters and the inputs required by the model, this network was the object of a farming follow-up in the form of inquiries, local measures and analyses in the laboratory of samples of water and soil during three agricultural campaigns (2002-2003, 2003-2004 and 2004-2005). WEB sub model quantify a total of 15 fluxes between these compartments which are two types: "major fluxes" and "minor fluxes". The lysimétrique follow-up led in two contrasted farms allowed to conclude that this model is reliable with an error risk varying from 17 to 26 %. The irrigation water use efficiency remains globally weak with an average of 40 % exceeding 50 % only in 25 % of the farmers of the follow-up network while the irrigation valuation water rate in the production is 56 % on average. Therefore, it’s necessary to award more eco-advice efforts to improve the efficiency and rationalize the irrigation water use. The analysis of the model sensibility demonstrated that the varying fact of this rate of 5 % and 10 % leads a variation respectively of 17 % and 36 % on the final result represented mainly by the infiltration rate which is the vector of the nitrogenous pollution and the salts washing. Ultimately, the Web model is a tool that can be used by the manager to improve eco advice on recovery and rational use of water in agricultural irrigation. Similarly, the quantification of the indicators presented would help the manager make the right choice of crops for better utilization of irrigation water The NEB sub model allows quantifying 17 fluxes between the farm and its environment. The nitrogen potential lixiviation flux, main indicator of the pollution risk the groundwater, is on average 77,8 kg N ha-1 on the follow-up network scale with a maximum of 105 kg N ha-1 and a minimum of 35 kg N ha-1. The lysimetric follow-up curried out shows that 14 % and 13 % of the residual mineral nitrogen was respectively washed during the 2003-2004 campaign and the 2004 2005campaign. So it’s necessary to make more eco advice efforts in terms of nitrate fertilizers use. The analysis of sensibility of the model showed that the rate mineralization variation of 5 % and 10 % engendered a variation of the “nitrogen potential lixiviation” flux respectively of 10 and 19 %. The NEB sub model is very useful for the manager can learn about the potentially leachable inorganic nitrogen and the nitrogen fertilizer made unnecessarily by comparing the doses recommended. The SEB model quantifies 8 main fluxes mostly salts conveyed by irrigation waters of and washing salts. On 15 farms of the Ecobalance follow-up network, this “potentially washable salts” flux is about 4210 kg ha-1 on average with a variation coefficient of 52 %. The lysimetric follow-up realized showed that 18 % and 12 % of salts were respectively washed during the 2003-2004 campaign and the 2004-2005 campaign. Consequently, it’s required to think about rehabilitation measures within an interdisciplinary framework aiming at the durability preservation of the production systems. The analysis of sensibility of the model showed that the electric conductivity rate variation of 5 % and 10 % engendered a variation of the «washing salts" flux respectively of 8 % and 16 %. The analysis of SEB model results in relation with the NEB model in 10 farms studied showed that, given the quality of water and soil, the reasoning of the nitrogen should be reflected according to the timetable and efficiency of irrigation-dependent process of leaching of salts, but also according to the vegetative stage of the plant for better utilization of soil mineral nitrogen. Ultimately, a policy of eco efficient and appropriate advice to the problem of environmental study area inevitably involves consideration of three elements "water", "nitrogen" and "salts ". The TEB program could be one of the fundamental tools of policy All these results impose to think to technical support strategies to set up follow-up devices of the ground, to strengthen the capacities of taking targeted measures to validate and verify the developed models and cheer the work in interdisciplinary by developing the collaboration such as integrated projects aiming at the sustainability of the agricultural production systems. By more clarifying the parameters used as inputs, these models would become more successful and more reliable [less ▲]

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See detailSelection, efficacy, ecological characterization and formulation of fungal control agents against water hyacinth [Eichhornia crassipes (Martius) Solms] in Mali
Dagno, Karim ULg

Doctoral thesis (2011)

Rice and irrigated orchards are considered as the most important food and economical sources in Mali, which watered from Niger River. However, stable productions of rice and orchards products have been ... [more ▼]

Rice and irrigated orchards are considered as the most important food and economical sources in Mali, which watered from Niger River. However, stable productions of rice and orchards products have been limited by many disease, insects, and weeds. Recently, water hyacinth infestation in river of Niger has increased drastically and as affected by the decrease of water flow due to clogging dams and irrigation work. Biological control of weeds is an alternative approach to chemical herbicide use, focusing on the use of native fungal to control or reduce the population of water hyacinth. From 2006 to 2007, 1000 samples consisting of infected parts of water hyacinth were collected from the River Niger (District of Bamako, Segou and Niono with GPS coordinates “12° 40’ N, 7° 59’ W” ; “13° 26’ N, 6° 15’ W” and “14° 15’ N, 5° 59’ W” respectively) in Mali. Fungal belonging to seven genera (116 isolates in all) were recovered from surface-sterilized water hyacinth parts with pronounced blight symptoms. On the basis of in vivo pathogenicity tests in which the diseased leaf area percentage was estimated visually and disease severity was estimated (by calculating a disease severity index), three isolates emerged as causing severe disease: Fusarium sp. isolate Mln799 (DS = 70%), Cadophora sp. isolate Mln715 (70%), and Alternaria sp. isolate Mlb684 (71%), identified respectively as Gibberella sacchari (Anamorph. Fusarium sacchari), Cadophora malorum, and Alternaria sp. This is the first report to highlight C. malorum as a candidate biocontrol agent for water hyacinth. Influence of ecological parameter, water activity (0.880 - 0.960aw modified par glycerol) and temperature (15-35°C) on viable conidia and mycelial growth rate of Alternaria sp. (isolate Mlb684), F. sacchari (isolate Mln799) and C. malorum (isolate Mln715) were evaluated. Germination and mycelial growth dropped as aw of the medium decreased. Results showed a significant effect of aw, temperature and their interaction on mycelial growth (P < 0.0001). Growth models for F. sacchari (isolate Mln799), C. malorum (isolate Mln715) and Alternaria sp. (isolate Mlb684) differed slightly, with R2 values of 93.40, 85.89 and 77.31% respectively. Mycelial growth models, no different between predicted and experimental values was observed. Results confirm the previous finding that aw has greater influence on growth of F. sacchari (isolate Mln799), C. malorum (isolate Mln715) and Alternaria sp. (isolate Mlb684) than temperature. Analyse of 5 target regions of isolate Mlb684 genome (18 and 28S ribosomal RNA genes, Elongation factor-1 alpha gene, calmodulin gene and actin gene) allowed identifying this isolate as new specie in Alternaria genus. The strain has been deposited under accession number MUCL 53159 in the Industrial Fungal & Yeast Collection (BCCMTM/MUCL, Belgium) and DNA sequences have been deposited in GenBank. We have named it “Alternaria jacinthicola Dagno & M.H. Jijakli”. It was the first sequenced of calmodulin gene reported in Alternaria genus. Water hyacinth, paddy and wheat substrates for mass production of these biocontrol agents were evaluated. Greater sporulation of C. malorum (isolate Mln715) was observed on water hyacinth substrate (4.08 x 107 spores ml-1) following by wheat (1.06 x 107 spores ml-1). Biocontrol efficacy of fungal isolates found to be enhanced with unrefined Carapa procera (L) oil and refined palm oil supplemented with soybean lecithin in greenhouse. Applying C. malorum (isolate Mln715) and A. jacinthicola (MUCL 53159 strain) in vegetable oil emulsion [Carapa procera (L) and palm oils] caused 87.02 to 93.13% of damage severity on water hyacinth 6 weeks after treatment. Field trials showed lower efficacy control than greenhouse tests. In host specificity tests, neither C. malorum isolate Mln715 nor Alternaria sp. isolate Mlb684 showed any pathogenicity towards any member of a panel of 17 crop plants of economic importance in Mali. [less ▲]

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See detailGeometric optimization algorithms for linear regression on fixed-rank matrices
Meyer, Gilles ULg

Doctoral thesis (2011)

Nowadays, large and rapidly evolving data sets are commonly encountered in many modern applications. Efficiently mining and exploiting these data sets generally results in the extraction of valuable ... [more ▼]

Nowadays, large and rapidly evolving data sets are commonly encountered in many modern applications. Efficiently mining and exploiting these data sets generally results in the extraction of valuable information and therefore appears as an important challenge in various domains including network security, computer vision, internet search engines, bioinformatics, marketing systems, online advertisement, social networks, just to name a few. The rapid development of these modern computer science applications sustains an ever-increasing demand for efficient machine learning algorithms that can cope with large-scale problems, characterized by a large number of samples and a large number of variables. The research reported in the present thesis is devoted to the design of efficient machine learning algorithms for large-scale problems. Specifically, we adopt a geometric optimization viewpoint to address the problem of linear regression in nonlinear and high-dimensional matrix search spaces. Our purpose is to efficiently exploit the geometric structure of the search space in the design of scalable linear regression algorithms. Our search space of main interest will be the set of low-rank matrices. Learning a low-rank matrix is a typical approach to cope with high-dimensional problems. The low-rank constraint is expected to force the learning algorithm to capture a limited number of dominant factors that mostly influence the sought solution. We consider both the learning of a fixed-rank symmetric positive semidefinite matrix and of a fixed-rank non-symmetric matrix. A first contribution of the thesis is to show that many modern machine learning problems can be formulated as linear regression problems on the set of fixed-rank matrices. For example, the learning of a low-rank distance, low-rank matrix completion and the learning on data pairs are cast into the considered linear regression framework. For these problems, the low-rank constraint is either part of the original problem formulation or is a sound approximation that significantly reduces the original problem size and complexity, resulting in a dramatic decrease in the computational complexity of algorithms. Our main contribution is the development of novel efficient algorithms for learning a linear regression model parameterized by a fixed-rank matrix. The resulting algorithms preserve the underlying geometric structure of the problem, scale to high-dimensional problems, enjoy local convergence properties and confer a geometric basis to recent contributions on learning fixed-rank matrices. We thereby show that the considered geometric optimization framework offers a solid and versatile framework for the design of rank-constrained machine learning algorithms. The efficiency of the proposed algorithms is illustrated on several machine learning applications. Numerical experiments suggest that the proposed algorithms compete favorably with the state-of-the-art in terms of achieved performance and required computational time. [less ▲]

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See detailMultidisciplinary study of trophic diversity and functional role of amphipod crustaceans associated to Posidonia oceanica meadows
Michel, Loïc ULg

Doctoral thesis (2011)

Posidonia oceanica is the most abundant seagrass of the Mediterranean Sea. It can cover extensive areas with monospecific formations, called meadows. These meadows, whose extent is estimated to about 40 ... [more ▼]

Posidonia oceanica is the most abundant seagrass of the Mediterranean Sea. It can cover extensive areas with monospecific formations, called meadows. These meadows, whose extent is estimated to about 40,000 km2, are critical features of the Mediterranean coastal zones. Moreover, they shelter important biomass and biodiversity of vagile invertebrates. Among these invertebrates, amphipod crustaceans are, alongside gastropod mollusks and polychaete annelids, one of the dominant groups. Amphipods are key-features of other temperate seagrass systems. As they are generally primary consumers, they are important in the transfers of organic matter from producers to higher rank consumers. In addition, their grazing activity on the epiphytes that grow on the seagrasses influence the dynamics of the epiphytic cover, and therefore the functioning of the whole meadow as an ecosystem. However, the situation in Mediterranean Posidonia oceanica meadows is still unclear. In particular, several lacks of information limit the comprehension of actual trophic ecology of amphipods, and of the impact of their feeding activity on the meadow functioning. In this context, the main goal of this work was to enhance the knowledge of the trophic diversity and the functional role of amphipods associated to Posidonia oceanica meadows. To achieve this, we structured our research in three main tasks. For each of these tasks, we chose Calvi Bay (NW Corsica, France) as study site, and all sampling and experimentation was undertaken from the STARESO research station (University of Liège). The first task (chapter 3) was the study of the precise composition of the amphipod community structure at our study site, and its temporal variation at day/night and seasonal scale. Our results show that the fauna of Posidonia oceanica meadows of Calvi Bay is abundant and diverse. The density and the structure of the community were different in each season (November, March and June), probably in relation with meadow parameters such as foliar surface, epiphytic biomass and abundance of litter in the meadow. Moreover, day/night variations were very important. Most amphipods performed vertical migrations that could be a mechanism to avoid predation and/or competition for food and habitat. The comparison of three sampling techniques (hand-towed net, litter collection and light traps) yielded deeply different results, suggesting that each of them only collects a subset of a complex assemblage. Combination of several sampling methods is therefore advised to have a holistic and accurate view of the community. These faunistic data also allowed highlighting the most abundant and/or representative species of the studied community. These include Apherusa chiereghinii, Aora spinicornis, Dexamine spiniventris, Amphithoe helleri, Caprella acanthifera, Gammarella fucicola and Gammarus aequicauda. These species were therefore chosen as target species for the second task. The second task (chapter 4) was the assessment of the extent of interspecific trophic diversity among the studied community. This phenomenon could indeed be important to limit food competition. We tried to perform a full reconstruction of the diet of the dominant species of the community and to evaluate the contribution of each of the potential food items offered by the meadow (animal and vegetal epiphytes from the leaves, rhizomes and litter fragments, SPOM, BPOM, living and dead P. oceanica material). To have an accurate view of the dietary habits of the dominant species, we used a triple strategy based on the joint use of traditional methods (gut content examination) and trophic markers (stable isotopes of C & N, fatty acids). The combination of these three methods proved to be successful, as each method had specific strengths and weaknesses. Overall, results indicate that all dominant species relied on macroalgal epiphytes for a large part of their diet. Our insights were unfortunately limited by the poor discrimination between potential food items, due to high inter-source similarity. Considerable interspecific differences could nonetheless be highlighted, notably concerning preferences of epiphytes from leaves or litter fragments vs. epiphytes from rhizomes. In addition, most species had a mixed diet, and relied on several food items. None of the examined species seemed to graze on their seagrass host, but Gammarus aequicauda partly relied on seagrass leaf detritus. Contribution of microepiphytes (e.g. diatoms) to the diet of amphipods was apparently anecdotical. Our data also suggested the existence of a certain extent of intraspecific trophic diversity that should be taken into account for future work. In the third and final task (chapter 5), we aimed to put the data obtained in the first two parts of this study in the wider context of the functioning of the Posidonia oceanica meadow as an ecosystem. We used in vitro and in situ microcosms experiments to characterize the interaction between epiphytes and amphipods from a triple point of view (resource depletion, resource assimilation by the consumer and secondary production), and to understand how amphipod grazing could influence the dynamics of the epiphytic cover of the leaves of P. oceanica. Amphipod grazing had no effect on the total epiphytic biomass, or on the encrusting epiphytes’ biomass. However, all three taxa (A. chiereghinii, D. spiniventris and Gammarus spp.) consumed significant amounts (45 to 90 % of total biomass) of erected epiphytes, both vegetal and animal. This selective top-down control might influence the structure and biomass-specific productivity rates of the epiphytic cover. In addition, amphipod grazing caused an increase in N availability and residence time. Through epiphyte removal and N enrichment, amphipods could boost seagrass production. Overall, amphipods of Posidonia oceanica meadows could be seen as ecosystem engineers. Assimilation of the consumed epiphytes was clear for all taxa. However, the utilization of this biomass for secondary production was hard to measure, due to low survival rates of animals. In fine, by combining in situ sampling and microcosm experimentation, and trough the joint use of traditional and innovative techniques, we showed that feeding activity of amphipods influence their biotope through several effects, and that they could be pivotal items of Posidonia oceanica meadows. In doing so, we improved, to some extent, the understanding of these critically important, yet endangered ecosystems. [less ▲]

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See detailContribution to the study on sound production in clownfishes (Perciformes, Pomacentridae): a multidisciplinary approach
Colleye, Orphal ULg

Doctoral thesis (2011)

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live ... [more ▼]

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Several studies have reported that vocalizations are associated with agonistic interactions but precise data are lacking and further investigations are needed. The nature of the sound-producing mechanisms also remained unresolved, only resting on few assumptions. Thereby, the main aim of the present thesis is (1) to determine the fundamental components of the acoustic communication in clownfishes, and (2) to explain the mechanisms of sound production. In order to achieve these objectives, the research has been divided into three different axes. Firstly, the study of the acoustic behaviors shows that no acoustic signal is associated with reproductive activities in clownfishes. Sound recordings during agonistic interactions indicate that these fishes produce two types of sounds. Aggressive sounds are produced during chases and threat displays while submissive (or head shaking) sounds are emitted in reaction to aggressive acts by dominant. Both types of sounds show size-related intraspecific differences in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger individuals, and inversely. Consequently, these sonic features might be useful cues for individual recognition and maintenance of cohesion within the group. Secondly, the study of the sound-producing mechanism highlights that aggressive sounds are initiated by buccal jaw teeth snapping caused by rapid mouth closure attributed to a sonic ligament. It appears that the swimbladder does not function as a resonator that amplifies and changes the quality of sounds. This structure is a highly damped sound source prevented from prolonged resonant vibrations. On the other hand, the rib cage might be the major acoustic radiator and its resonant properties might explain the size-related variations observed in pulse duration and dominant frequency. Thirdly, the comparison of aggressive sounds among fourteen clownfish species indicates that the same relationship between fish size and both dominant frequency and pulse duration is spread over the entire group (i.e. tribe Amphiprionini). These results highlight all species use a highly conservative mechanism of vocalization. Pulse period appears to be the most variable acoustic feature and could be involved in species-specific recognition, as well as pulse duration and dominant frequency in a lesser extent through their relationship with body size. Although sound production appears to be restricted to some agonistic behaviors, these sounds seem to constitute an integral part of the peculiar way of life of clownfishes. The aggressive and submissive sounds would also result from two different mechanisms.   [less ▲]

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See detailLa place de l'identité dans la politique étrangère. Le cas de la Turquie dans la période de pos-11 septembre 2001
Arslan, Nevzat ULg

Doctoral thesis (2011)

Il est question, dans ce travail, de découvrir les variables qui jouent un rôle dans l'orientation et dans la détermination de la politique étrangère turque. Il s'agit donc de s'intéresser aux variables ... [more ▼]

Il est question, dans ce travail, de découvrir les variables qui jouent un rôle dans l'orientation et dans la détermination de la politique étrangère turque. Il s'agit donc de s'intéresser aux variables causales découlant de la politique intérieure de la Turquie. Ainsi est évaluée l'importance des variables individuelles, institutionnelles, gouvernementales et systémiques dans la détermination des idées et des intérêts défendus par les différents acteurs internes. Adoptant une approche constructiviste des relations internationales, cette étude consiste, d'une part, en une description de l'identité nationale de l'État turc et de l'autre en une explication de la redéfinition de cette identité par une nouvelle idéologie, défendue par une nouvelle classe dirigeante. Nous nous sommes penchés sur les valeurs et les identités nationales qui ont contribué à façonner les conceptions et les priorités de la politique étrangère turque. Ainsi, l'approche théorique choisie doit tenir compte de ces divers facteurs, qui exercent une influence sur la formulation des intérêts nationaux. [less ▲]

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See detailDa Alessandro ai Theoi Adelphoi. Fondazione e legittimazione della dinastia tolemaica, tra IV e III secolo a.C.
Caneva, Stefano ULg

Doctoral thesis (2011)

The research focuses on the first century of the Macedonian rule over Egypt in order to study how the Ptolemies had their power legitimated in Africa and in the broader Mediterranean context. Literary ... [more ▼]

The research focuses on the first century of the Macedonian rule over Egypt in order to study how the Ptolemies had their power legitimated in Africa and in the broader Mediterranean context. Literary sources (both prose and verse, in Greek and Egyptian language), inscriptions, papyri, and iconography are used to set an interdisciplinary approach to the topic. Major attention is paid to the social contexts where ideological motifs originate and spread; to the link between media, genres and consensus making; to the genealogy and development of specific legitimating themes and their later incorporation in learned traditions or local identities. Section I: From Alexander to the Ptolemies. Chapter I: Alexander in Egypt: focus is on the role of Siwah in the perspective of the Greek, Macedonian, and Egyptian legitimation of Alexander's power in Egypt; particular attention is paid to how legitimating traditions are used and reshaped to the purposes of broadening the limits of Macedonian kingship, depicting Alexander as a Greek hero, interpreting Egyptian kingship for Greeks and Macedonians and naturalizing Alexander as a Pharaoh. Chapter II: In the name of Alexander: how Ptolemy adapted to the hierarchy of proximity to the king to legitimate his power in Egypt and finally to establish a new dinasty; main topics are the use of Alexander's body in the historical context of the succession and in the local tradition of Alexandria; the historical events of the last decades of IV century are considered from the perspective of the development of legitimating themes, such as the political allegiance to Alexander, the right of conquest, the use of marriage diplomacy. Section II: The Political Use of Religious Festivals under Ptolemy II. Chapter III: Sources and Historical Problems concerning the Ptolemaia: sources on the Ptolemaia, Pentaeteris and Callixeinus' report in Athen. V are discussed to study dynastic festivals during Ptolemy II’s reing. Chapter IV: Anatomy of a Festival: The Grand Procession of Ptolemy II: focus is on the making of an historical and mythic legitimating past through the scenes in the procession. Section III: Patterns of Female Power: The Case of Arsinoe II Chapter V: Shaping Female Power: Arsinoe II as a Queen: Arsinoe II's career and political legacy are discussed to offer a gender-related evaluation of her role as a queen in both Greco-Macedonian and Egyptian traditions. Chapter VI: Female Ruler Cults. Arsinoe in Early Hellenistic Context: the analysis combines court poetry, iconography and documentary texts to study the cults for Arsinoe both as a member of the Theoi Adelphoi and as an individual goddess, the Philadelphos. Arsinoe's case is then discussed in the broader perspective of female ruler cults in early Hellenism. [less ▲]

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See detailCaracterización del producto cerámico en las comunidades neolíticas de mediados del V milenio Cal BC: El valle del Éufrates y el valle del Khabur en el Halaf final (Siria).
Gomez Bach, Ana Maria ULg

Doctoral thesis (2011)

The characterization of pottery production in the mid-sixt millennium cal BC in Neolithic communities: the Euphrates valley and Khabur basin in Late Halaf. SUMMARY The characterization of pottery ... [more ▼]

The characterization of pottery production in the mid-sixt millennium cal BC in Neolithic communities: the Euphrates valley and Khabur basin in Late Halaf. SUMMARY The characterization of pottery production in the mid-sixth millennium cal BC contexts in the Middle East arises from the need to understand how consolidated agricultural and pastoral communities of the Fertile Crescent were structured and organized. This chrono cultural period is embodied in an archaeological record of great interest in order to identify the different economic, social and symbolic responses at the final moment of the so-called Halaf culture. The opportunity to study the pottery assemblages from two sites and two regions, such as the Euphrates valley and the valley of Khabur, with new material from Tell Halula (16,668 sherds) and Chagar Bazar (21,194 sherds), allowed us to study and apply the same methodology to both sets from the very beginning of fieldwork. The analysis of 37,882 fragments from a comprehensive perspective and by using archaeometric techniques (chemical, petrographic and PIXE analysis) as well as morphometric and basic techno functional characterization analysis set new guidelines on the archaeological potential of these sets. Drawn up from Archaeology and Materials Science, this contribution has its methodological framework focused on rebuilding the chaîne operatoire. This reconstruction has allowed us to study and isolate two assemblages and to outline the existence of different socio economic practices, some of which had clear regional links and a strong substrate, but above all with basic subsistence practices which can be addressed from the ceramic product itself. Likewise, the specific chronological framework provided by new radiocarbon dates of both sites, which are between 5600-5300 cal BC, enables not only to characterise these productions but also to arise new questions to understand the interaction mechanisms between communities; mechanisms that cover from basic subsistence practices, i.e. the handling and processing of food and products, to mechanisms which regulate and structure the group. [less ▲]

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See detailDifférenciations sociospatiales et gouvernance municipale dans les banlieues de Beyrouth : à travers l'exemple de Sahel AlMatn AlJanoubi et des municipalités de Chiyah, Ghobeiri et Furn AlChebbak
Farah, Jihad ULg

Doctoral thesis (2011)

La thèse s’inscrit dans le débat sur une des “grandes questions urbaines contemporaines”: comment dans la multiplication des projets individuels et collectifs de plus en plus fragmentés se construit la ... [more ▼]

La thèse s’inscrit dans le débat sur une des “grandes questions urbaines contemporaines”: comment dans la multiplication des projets individuels et collectifs de plus en plus fragmentés se construit la ville d’aujourd’hui? Dans un contexte d’étalement urbain continu et de crise des “grands récits” de la modernité, l’individu comme le groupe connaît de plus en plus de difficultés à trouver sa place, son “lieu”, en ville. La recherche de l’entre-soi et l’altérité devient de plus en plus importante dans cette quête. La thèse revient sur les différents concepts traitant des différenciations sociospatiales en ville (ségrégation, marginalisation, relégation, fragmentation). Elle remarque que ces concepts favorisent une lecture systémique de la réalité urbaine où les éléments factoriels économiques, culturels et politiques ont un rôle central dans l’explication. Tout en se mettant dans la continuité de ces travaux, la thèse privilégie une lecture se basant sur trois entrées: - La crise de citoyenneté urbaine (crise de définitions de la ville, de ses limites, de ses citoyens, de leurs droits et surtout de sa gouvernance) comme principale grille explicative - Le local. Ce dernier étant d’une part l’échelle où ces différenciations sociospatiales sont les plus manifestes, et d’autre part car c’est à cette échelle que les phénomènes systémiques doivent se “redéfinir” en s’inscrivant dans le contexte. - Les périphéries et les banlieues où la cirse de citoyenneté est plus nette et où les acteurs locaux – dans un milieu à la recherche de sens, et en continuelle redéfinition – cherchent à avoir plus d’emprise sur leur milieu direct. Dans ce contexte la thèse avance que les spécificités du local, notamment la gouvernance locale et la spécialisation économique ont un poids déterminant dans la définition des dynamiques territoriales et par suite des différenciations sociospatiales. Cette hypothèse est déclinée en deux hypothèses opérationnelles: 1. - L’une s’inscrivant dans une perspective historique: Si incontestablement des dynamiques induites de la globalisation affectent les différenciations sociospatiales dans l’espace beyrouthin, nous pensons que l’héritage d’un temps long dans ses dimensions politiques et économiques pèse encore fortement sur ces différenciations dans les banlieues de Beyrouth. 2. L’autre dans une perspective politique: La stabilisation du régime municipal est aujourd’hui la rationalité qui domine l’action municipale. Elle est déterminante de la gouvernance locale dans chaque commune et par suite consubstantielle de l’évolution des différenciations sociospatiales dans ces banlieues. Les banlieues de Beyrouth, considérées comme cas révélateur, sont retenues pour comme terrain d’étude Deux méthodes d’analyse complémentaires sont mobilisées. L’une dite diachronique essaie de repérer les constantes et les variables dans l’histoire d’un district de ces banlieues comprenant les actuelles banlieues sud et sud-est, en insistant sur les rôles particuliers de la gouvernance et de l’économie. L’autre dite synchronique tente de souligner des liens entre des typologies de gouvernance urbaine différentes et leurs impacts en termes de différenciations sociospatiales en mobilisant le concept de régimes urbains. Les principales conclusions sont: - Des arrière-pays consolidés, avant l’étalement des villes centres, ayant leurs propres dynamiques: leur urbanisation, leurs économies et leurs gouvernances locale, leurs trajectoires propres connaissent très tôt la fragmentation urbaine (conclusion en porte-à-faux par rapport au corpus de la fragmentation soulignant le rôle fondateur de la globalisation) - L’architecture du régime urbain local et sa recherche de stabilité interne affectent fortement l’articulation de l’échelle d’action locale aux échelles d’action supérieures. Comme elles affectent certaines formes de dynamiques territoriales locales (notamment celles inscrites dans le registre de construction identitaire des territoires). Toutefois elles semblent avoir moins d’impact sur les aspects centralités et flux des dynamiques territoriales. - La fragmentation politique du territoire peut s’avérer une ressource importante pour les acteurs locaux pour négocier et s’approprier une place, un “lieu” dans les agglomérations urbaines d’aujourd’hui. D’autre part, devant la pression continue que connaissent les territoires urbains des périphéries pour se redéfinir et s’articuler à de nouvelles entités sociospatiales en formation, on peut observer dans certains cas de la véritable innovation en termes de politiques urbaines. Ces municipalités peuvent représenter, comme dans le cas de certaines dans les banlieues de Beyrouth, des laboratoires qui font émerger des nouveaux outils urbains qui pourront servir pour penser et gérer la ville à d’autres échelles. [less ▲]

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See detailDes loups dans la Cité. Eléments d'écologie pragmatiste
Doré, Antoine ULg

Doctoral thesis (2011)

Les politiques contemporaines sont marquées par des bouleversements écologiques qui interrogent la place à accorder à une liste toujours plus longue et hétérogène de prétendants à la vie publique. Cette ... [more ▼]

Les politiques contemporaines sont marquées par des bouleversements écologiques qui interrogent la place à accorder à une liste toujours plus longue et hétérogène de prétendants à la vie publique. Cette thèse propose un examen empirique d’une telle dynamique à partir du cas de la mise en politique des loups en France. En traçant les multiples manières dont les loups interpellent ceux et ce qui les entourent, en décrivant les agencements hybrides d’humains et de non-humains qu’ils forment et transforment sur leur passage et en prêtant attention aux différentes manières dont les acteurs affectés prennent en charge les situations générées par ces animaux, il s’agit d’identifier et de suivre, pas à pas, des portions importantes de quelques-unes des trajectoires qui composent la carrière politique des loups. Cette recherche montre alors comment des scientifiques, des juristes, des publics, des représentants de l’État, des journalistes, etc., mais aussi les loups eux-mêmes, composent ces trajectoires spécifiques marquées par des pratiques, des temporalités, des spatialités, des matérialités particulières. L’analyse révèle comment la présence publique des loups est instaurée par la science, le droit, l’État, etc. Elle rend compte également réciproquement de la manière dont la science, le droit, l’État, etc., s’inventent et se transforment à travers les loups. Cette thèse propose finalement un compte rendu synthétique et réaliste des modalités de construction d’une politique des loups et vise à éclairer deux questions plus générales : dans quel sens peut-on parler des implications politiques de la nature et en quoi cela nous invite-t-il à changer nos habitudes de description et d’aménagement de la vie ensemble ? [less ▲]

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See detailAlternative strategies for aphid biological control: special regard on honeydew and bacteria from aphids
Leroy, Pascal ULg

Doctoral thesis (2011)

Aphids constitute a scourge in agriculture and are a major problem for crops worldwide. By feeding on the phloem sap but also by injecting saliva and viruses in plant tissues, they cause a weakening and ... [more ▼]

Aphids constitute a scourge in agriculture and are a major problem for crops worldwide. By feeding on the phloem sap but also by injecting saliva and viruses in plant tissues, they cause a weakening and impair the growth of the host-plant. Moreover, honeydew, the aphid excretory product, reduces transpiration and photosynthesis. But honeydew also attracts many predators and parasitoids of aphids, playing a key role in tritrophic interactions between plants, pests and beneficial insects. In this context, the main objective of this thesis was to promote the use of the hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae) as an efficient biological control agent in aphid management strategies. Two different approaches have been developed here with success: (1) the introduction of this auxiliary in the fields or under greenhouses, using a biological control device developed in this work and (2) the attraction, the retention and the oviposition stimulation of the populations naturally present or manually introduced in the fields. To achieve these objectives, special attentions were focused on the aphid honeydew that is abundant on aphid infested plants, with special attention to the bacteria present in this aphid secretion. First, our studies allowed determining that honeydew acts as a volatile and a contact kairomone both for the E. balteatus larvae and adults but also on the Asian coccinellid Harmonia axyridis (Pallas) helping these aphidophagous predators to locate prey. In a second time, using semiochemicals from plants [(Z)-3-hexenol, R-(+)-limonene] and aphids [E-(β)-farnesene] but also crude and artificial honeydew, the hoverfly oviposition was artificially induced (without plants or aphids) on an inert surface. The so obtained eggs were then introduced in field crops to regulate aphid populations (biological control device). Then, the volatile compounds associated with honeydew were identified and tested as potential attractants and ovipositional stimulants: an artificial honeydew as well as an attractive formulation were composed and successfully tested in field crops since they both increased the presence of auxiliaries in targeted areas. Finally, the interaction between the host plant and aphids was envisaged to determine whether aphids are able to modify the host plant amino acid content in order to ingest sufficient nitrogen for growth: this study highlighted that the proportions of glutamine and asparagine significantly increase in the phloem sap when plants are infested. [less ▲]

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See detailImprimeurs et société dans les Pays-Bas méridionaux et en principauté de Liège (1473-ca 1520)
Adam, Renaud ULg

Doctoral thesis (2011)

La thématique placée au centre de cette dissertation doctorale pourrait se résumer à cette question : comment les premiers imprimeurs se sont intégrés au tissu socio-économique des Pays-Bas méridionaux et ... [more ▼]

La thématique placée au centre de cette dissertation doctorale pourrait se résumer à cette question : comment les premiers imprimeurs se sont intégrés au tissu socio-économique des Pays-Bas méridionaux et de la principauté de Liège aux tournants des XVe et XVIe siècles ? Cette étude a été structurée autour de trois axes. La vétusté des synthèses sur le sujet et l’évolution constante de la recherche ont rapidement imposé la nécessité de réécrire en premier lieu un historique détaillé, ville par ville, de l’introduction de l’art typographique et de son évolution jusqu’en 1520. Les regards se sont ensuite portés sur le métier d’imprimeur avec des questionnements centrés sur le statut juridique et l’organisation de cette profession, sur le fonctionnement interne d’une imprimerie ainsi que sur la commercialisation des livres et le profil de la clientèle. Les résultats de la dernière partie sont le fruit d’une investigation dans la composition de la communauté typographique et d’une tentative de décorticage des trames réticulaires nouées avec les autres acteurs de la société urbaine. [less ▲]

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See detailEvidence for a role of microRNA-21 and microRNA-125b in negatively regulating angiogenic processes
Malvaux, Ludovic ULg

Doctoral thesis (2011)

Recently discovered, miRNAs have quickly become strong regulators of biological processes. These small non-coding RNAs of about 22 nucleotides partially base pair to the 3’UTR of the targeted mRNAs and ... [more ▼]

Recently discovered, miRNAs have quickly become strong regulators of biological processes. These small non-coding RNAs of about 22 nucleotides partially base pair to the 3’UTR of the targeted mRNAs and repress them. Due to their wide range effects, microRNAs were extensively studied in various diseases and were rapidly demonstrated to be deregulated in pathologies such as cancer. More recently, they have been shown to be implicated in vascular network formation (angiogenesis) and were proposed to be used in anti-angiogenic therapies. Nowadays about twenty angiomiRs have been discovered including the endothelial specific miR-126. As observed in several miRNA profiling of endothelial cells and confirmed in our laboratory in HUVECs (human umbilical veins endothelial cells), miR-21 and miR- 125b are highly expressed in this cell type suggesting that these miRNAs could play a role in vascular network formation. We then studied the implication of miR-21 and miR-125b in in vitro as well as in vivo angiogenesis. One of the most studied miRNA in cancer progression is miR-21 as it was shown to modify proliferating properties of numerous tumor cells. Our experiments revealed that miR-21 overexpression and inhibition have no direct effect on endothelial cells proliferation rate. However, miR-21 overexpression leads to the inhibition of HUVECs migration and tube formation as demonstrated in in vitro angiogenic assays. Moreover, opposite effects were observed upon miR-21 inhibition. We also confirmed that RhoB, a small Rho-GTPase implicated in stress fibers formation, is involved in these phenomena as RhoB inhibition using siRNA mimics miR-21 overexpression in endothelial cells. Moreover, miR-21 modulation affects RhoB mRNA and protein expressions. We further demonstrated a direct interaction between miR-21 and the RhoB 3’UTR confirming that miR-21 modulates angiogenesis partially through its effect on RhoB expression. A similar approach was used to study the implication of miR-125b in vascular network formation. In vivo, miR-125b expression was modulated in the zebrafish revealing that miR-125b expression needs to be controlled for proper intersomitic blood vessels establishment. In vitro, miR-125b overexpression decreases HUVECs migration and tube formation whereas miR-125b inhibition increases these functions. A transcriptomic analysis suggests that numerous adhesion molecules such as VE-cadherin or MCAM are involved in these processes. Furthermore, other proteins known to regulate angiogenesis such as the transcription factor ETS1 and the VEGFA receptor, VEGFR2 were also shown to be regulated by miR-125b. This observation confirms that miR-125b modulates angiogenic properties of endothelial cells. Finally, we investigated the impact of miR-21 and miR-125b overexpression in an in vivo pathological model of angiogenesis. In a mouse model of choroïdal neovascularization we demonstrated that miR-21 or miR-125b overexpression in the eyes of these mice decreases blood vessel establishment suggesting that these microRNAs could be used as therapeutic antiangiogenic agents. Taken together, the results presented in this thesis show that miR-21 and miR-125b regulate angiogenesis in vitro and in vivo. [less ▲]

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See detailIntermédiaires et dynamique des réseaux fluides. Du mode d'existence de la norme ISO 14001 en Région wallonne
Semal, Nathalie ULg

Doctoral thesis (2011)

How does a standard "make a living"? How does a written list of requirements acquire some reality? How can a particular agreement take effect in numerous worldwide distant sites?

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See detailRole de l'ADN endogène et d'Interferon Response Factor-3 dans l'induction des réponses immunitaires médiées par les lymphocytes T auxiliaires de type 2.
Marichal, Thomas ULg

Doctoral thesis (2011)

Adaptative type 2 helper T cell (Th2) responses represent an important component of adaptative immunity and are implicated in various (patho)physiological processes such as allergic diseases, host defense ... [more ▼]

Adaptative type 2 helper T cell (Th2) responses represent an important component of adaptative immunity and are implicated in various (patho)physiological processes such as allergic diseases, host defense against helminths and artificially adjuvanted vaccination. Induction of adaptative T responses occurs with the help of innate immune cells, especially dendritic cells (DCs). These DCs make the link between innate and adaptative immunity by taking up antigens in peripheral tissues, migrating to lymphoïd organs and presenting antigens to T lymphocytes. Direct or indirect activation of these cells depends on the interaction between exogenous or endogenous danger signals and conserved innate immune receptors, mainly represented by Pattern Recognition Receptors (PRRs). Despite the importance of Th2 responses, the innate immune mechanisms leading to their activation remain partially unknown. For this reason, we have been interested in immune mechanisms underlying the induction of Th2 responses in two major Th2-dependent immunological processes : airway allergy and vaccination with aluminium hydroxides (alum). Airway allergy, of which the most severe manifestation is allergic ashma, is a constantly increasing disease in developped countries. It appears clearly that the stimulation of PRRs by allergens or immunostimulatory molecules plays a key role in the pathophysiology of airway allergy. In addition, PRRs transduce the signal though a limited number of signaling pathways and the role of Interferon Response Factor (IRF)-3 and IRF-7, two important transcription factors downstream of various PRRs, in the pathogenesis of allergic asthma, remains unknown. Therefore, we have investigated their potentiel implication in this disease. We have discovered that IRF-3, but not IRF-7, plays an essential role in allergic airway sensitization against house dust mite antigens, the main allergen source in humans. We have further demonstrated that IRF-3 was intrinsically required in lung DCs for their proallergic function. The IRF-3-dependent effects were independent of type I interferons, the main target genes of IRF-3. Alum is the most widely used artificial adjuvant in human and animal vaccination. Yet, little is known about its mechanism of action, in particular regarding the nature of signals and signaling pathways promoting Th2 responses. We have postulated that alum, like any other efficient adjuvant, must be expected to stimulate innate immunity. On one hand, alum does not contain any molecular pattern that is recognized by PRRs and, on the other hand, alum is known to be cytotoxic. Therefore, we hypothetised that alum-induced endogenous danger signals could play a role in its adjuvant activity. Here, we report that alum induces cell death and subsequent DNA release. This DNA acts as a endogenous immunostimulatory signal relaying alum adjuvant activity on adaptative responses. Furthermore, we propose that host DNA differentially regulates IgG1 and IgE production following alum immunization. Indeed, an IRF-3-dependent DNA signaling pathway plays a role in the activation of inflammatory DCs, the subsequent induction of Th2 response and IgE isotype switching, whereas DNA also induces IgG1 production through IRF-3- independent mechanisms. The finding that host cell endogenous DNA is a damageassociated molecular pattern relaying alum adjuvant activity may thus help in the comprehension of the mechanisms of action of current vaccines and in the design of novel adjuvants. In conclusion, this work has identified a previously unappreciated role for IRF-3, a transcription factor downstream of various PRRs primarily implicated in antiviral responses, in two Th2-dependent immunological processes: allergic asthma and alum-based vaccination. In these models, we have shown that IRF-3 was intrinsically required in professional antigen presenting cells, namely DCs, in order to activate them, a precondition for the priming of adaptative Th2 responses. In addition, we also discovered that host DNA released upon alum treatment acts as an endogenous danger signal mediating the adjuvant activity of alum. [less ▲]

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See detailSemi-solid constitutive modeling for the numerical simulation of thixoforming processes.
Koeune, Roxane ULg

Doctoral thesis (2011)

Semi-solid thixoforming processes rely on a material microstructure made of globular solid grains more or less connected to each other, thus developing a solid skeleton deforming into a liquid phase ... [more ▼]

Semi-solid thixoforming processes rely on a material microstructure made of globular solid grains more or less connected to each other, thus developing a solid skeleton deforming into a liquid phase. During processing, the material structure changes with the processing history due to the agglomeration of the particles and the breaking of the grains bonds. This particular evolutive microstructure makes semi-solid materials behave as solids at rest and as liquids during shearing, which causes a decrease of the viscosity and of the resistance to deformation while shearing. Thixoforming of aluminum and magnesium alloys is state of the art and a growing number of serial production lines are in operation all over the world. But there are only few applications of semi-solid processing of higher melting point alloys such as steel. This can partly be attributed to the high forming temperature combined with the intense high temperature corrosion that requires new technical solutions. However the semi-solid forming of steels reveals high potential to reduce material as well as energy consumption compared to conventional process technologies, such as casting and forging. Simulation techniques exhibit a great potential to acquire a good understanding of the semi-solid material process. Therefore, this work deals with the development of an appropriate constitutive model for semi-solid thixoforming of steel. The constitutive law should be able to simulate the complex rheology of semi-solid materials, under both steady-state and transient conditions. For example, the peak of viscosity at start of a fast loading should be reproduced. The use of a finite yield stress is appropriate because a vertical billet does not collapse under its own weight unless the liquid fraction is too high. Furthermore, this choice along with a non-rigid solid formalism allows predicting the residual stresses after cooling down to room temperature. Several one-phase material modeling have been proposed and are compared. Thermo-mechanical modeling using a thermo-elasto-viscoplastic constitutive law has been developed. The basic idea is to extend the classical isotropic hardening and viscosity laws to the non solid state by considering two non-dimensional internal parameters. The first internal parameter is the liquid fraction and depends on the temperature only. The second one is a structural parameter that characterizes the degree of structural build up in the microstructure. Those internal parameters can depend on each other. The internal parameters act on the the viscosity law and on the yield surface evolution law. Different formulations of viscosity and hardening laws have been proposed and are compared to each other. In all cases, the semi-solid state is treated as a particular case, and the constitutive modeling remains valid over the whole range of temperature, starting from room temperature to above the liquidus. These models are tested and illustrated by mean of several representative numerical applications. [less ▲]

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See detail"Intentionnalité et inconscient. Réflexions sur le fonctionnement de la vie psychique à partir du premier Husserl et de Freud"
Gyemant, Maria ULg

Doctoral thesis (2011)

This work tries the limits of Husserl’s concept of intentionality as it is conceived in the Logical Investigations. Once these limits exposed, we claim that Husserl’s theory of intentionality be completed ... [more ▼]

This work tries the limits of Husserl’s concept of intentionality as it is conceived in the Logical Investigations. Once these limits exposed, we claim that Husserl’s theory of intentionality be completed with a theory of the unconscious of Freudian inspiration. Thus, on the conceptual basis of Husserl and Freud’s work we elaborate an exhaustive map of the human mind, that shows not only the consciousness, but also the other mental phenomena. Our first section shows that Husserl’s concept of intentionality is established in opposition to Brentano’s intentionality. We also analyse the problem it is meant to solve, namely how exactly the mind connects with its objects. We show that this way of understanding intentionality cannot explain the dynamical aspect of intentional acts. Our second section is thus dedicated to this issue. A group of texts written by Husserl around 1913-1914 on the concept of tendency show clearly that Husserl never stopped in fact questioning the dynamical character of intentionality although he couldn’t explain it without thinking it as a form of intentionality. This solution leads nevertheless to an infinite regress. We have chosen thus in our third section to try a new approach of the dynamical aspect by using Freud’s approach to the Unconscious. The Freudian Unconscious has thus been articulated to Husserl’s theory of intentionality and at the same time the dynamical aspect of the latter has found an appropriate conceptual expression. [less ▲]

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See detailOn the sets of real vectors recognized by finite automata in multiple bases
Brusten, Julien ULg

Doctoral thesis (2011)

This thesis studies the properties of finite automata recognizing sets of real vectors encoded in positional notation using an integer base. We consider both general infinite-word automata, and the ... [more ▼]

This thesis studies the properties of finite automata recognizing sets of real vectors encoded in positional notation using an integer base. We consider both general infinite-word automata, and the restricted class of weak deterministic automata, used, in particular, as symbolic data structures for representing the sets of vectors definable in the first order additive theory of real and integer numbers. In previous work, it has been established that all sets definable in the additive theory of reals and integers can be handled by weak deterministic automata regardless of the chosen numeration base. In this thesis, we address the reciprocal property, proving that the sets of vectors that are simultaneously recognizable in all bases, by either weak deterministic or Muller automata, are those definable in the additive theory of reals and integers. Precisely, for weak deterministic automata, we establish that the sets of real vectors simultaneously recognizable in two multiplicatively independent bases are necessarily definable in the additive theory of reals and integers. For general automata, we show that the multiplicative independence is not sufficient, and we prove that, in this context, the sets of real vectors that are recognizable in two bases that do not share the same set of prime factors are exactly those definable in the additive theory of reals and integers. Those results lead to a precise characterization of the sets of real vectors that are recognizable in multiple bases, and provide a theoretical justification to the use of weak automata as symbolic representations of sets. As additional contribution, we also obtain valuable insight into the internal structure of automata recognizing sets of vectors definable in the additive theory of reals and integers. [less ▲]

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See detailNutrient fluxes and soil microbial processes
Bazgir, Masoud ULg

Doctoral thesis (2011)

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials ... [more ▼]

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials has been a common European afforestation strategy. However, the characteristics of Norway spruce such as susceptibility to windfall, forest dieback, drought, as well as soil acidification have caused negative ecological impacts in many sites. Conversion of conifers into deciduous or mixed stands has been suggested by some foresters, in order to improve the stability, ecology and biodiversity of forest ecosystems. Such changes in forest management require specific information on the impact of tree species on nutrient cycling, soil properties and microbial activities. In this study, six broadleaved species were growing at the same site with similar condition in terms of soil type, land use history and climate. Thus, the potential effects on biogeochemical cycling could be attributed to tree species. In this thesis, I focused on the effect of broadleaved species (conversion scenario) contrasting in terms of ecological characteristics (pioneer species versus main forestry species) and physiological characteristics (N2-fixing tree species (alder) versus non N2-fixing species) and Norway spruce (no conversion scenario) on (a) soil chemical properties (b) soil microbial activities and microbial biomass (c) nutrient input fluxes from throughfall and litterfall (d) foliar nutrient status. This investigation was carried out in south-eastern Belgium at a site converted in 1998 to a mixed deciduous stand, after two spruce generations. Plantations of common alder (Alnus glutinosa (L.) GAERTN.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula ROTH.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.) were located in 4 fenced plots within a 81 ha catchment. Soil chemical properties (soil organic matter, pH, cation exchange capacity, base saturation, exchangeable cations), soil microbial activities (net N mineralization, potential nitrification, basal respiration) and microbial biomass (microbial biomass C and N) were measured under broadleaves and spruce. Soil chemistry of this highly acid soil was improved, 11 years after conversion, through an increase in base saturation and the exchangeable Mg2+ pool under rowan, as well as an increase in the exchangeable Ca2+ pool under alder, oak and rowan. Exchangeable acidity due to H+ in the forest floor also decreased under broadleaves. Nitrification was increased under the N2 fixing alder and decreased under young spruce. The C:N ratio of cold water-extractable soil organic matter fractions revealed to be a good indicator of potential nitrification rates within this site and across species, with a threshold of a C:N ratio of 10 above which soils did not nitrify. Throughfall and litterfall under the tree species were investigated by installing 63 throughfall collectors and 63 litter traps within 3 fenced plots (broadleaves) and across the catchment (young spruce). We measured the quantity of litterfall (foliar, twigs, reproductive parts and total), the quality of foliar litterfall (macro and micro-elements and C/N ratio) and calculated the potential nutrient return to the forest floor though foliar litterfall. For throughfall, we analyzed macro and micro-element concentrations and throughfall fluxes. Foliar nutrient status was determined by chemical analyses of fresh leaves and spruce needles of 3 age classes. The throughfall deposition of Ca2+, Mg2 and K+ was significantly higher under rowan and birch. NO3--N throughfall fluxes were significantly higher under young spruce compared to broadleaves. We observed the lowest total litterfall quantity produced by oak, while the highest litterfall quantity observed under rowan. Foliar litterfall of rowan showed significantly higher potential nutrient fluxes of Ca, Mg and K compared to other species, which corresponds to fresh foliage concentrations. The foliar litterfall was a main source of Ca, while for K throughfall was the main source of nutrient return to the forest floor in the study area. In spruce needles, Ca and Mg concentrations were at deficiency level and K concentrations at critical level, according to threshold values. Our results demonstrated that the plantation of pioneer species, especially rowan, may enhance the base cations in the forest floor on nutrient poor, acid soils through higher input in litterfall and throughfall. [less ▲]

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See detailTheoretical and Experimental Analysis of Liquid Flooded Compression in Scroll Compressors
Bell, Ian ULg

Doctoral thesis (2011)

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat ... [more ▼]

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat pump systems, simple cycle modeling predicts that for systems that operate at very large temperature lifts, the increase in system coefficient of performance can be greater than 50%. In order to better understand the liquid-flooded working process, a detailed scroll compressor model has been developed which comprises a geometric model and an overall compressor model. The geometric model includes numerically validated analytic solutions for all geometric parameters, including force terms, for constant wall thickness scroll wraps that can have multiple pairs of compression chambers. The overall model includes a frictionally-corrected isentropic nozzle leakage model, adaptive Runge-Kutta solver for the system of differential equations, and numerically efficient thermodynamic and transport property routines. The compressor model has been validated against testing conducted on the Liquid-Flooded Ericsson Cycle for oil mass fractions as high as 92% oil by mass with error in predictions of shaft power and mass flow less than 3%. Optimization of the compressor performance with flooding for several applications is carried out, and with optimization, overall isentropic efficiencies over 75% are predicted for configurations with large amounts of oil flooding. Further testing on a refrigerant R410A vapor injected compressor with oil injection has shown that the performance with oil injection improves monotonically with the oil injection rate as long as the oil is cooled prior to injection. [less ▲]

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See detailEpigenetic Therapy of Lung Cancers: Anti-tumoral effect of valproate on small cell lung cancer
Hubaux, Roland ULg

Doctoral thesis (2011)

Lung cancer is the leading cause of cancer-related death worldwide. Among lung carcinomas, the outcome of small cell lung carcinoma (SCLC) patients is the poorest of any histological subtype with five ... [more ▼]

Lung cancer is the leading cause of cancer-related death worldwide. Among lung carcinomas, the outcome of small cell lung carcinoma (SCLC) patients is the poorest of any histological subtype with five-year survival rate of less than 20 and 5 % for limited and extensive stage respectively. Based on increasing evidence that inhibitors of histones deacetylases (HDAC) have anticancer properties, the goal of this study was to evaluate the ability of valproate (VPA) to improve efficacy of chemotherapeutic regimen in SCLC. We show that VPA directly induces apoptosis of SCLC cell lines at concentrations relevant for clinical uses. Furthermore, VPA synergizes with two chemotherapeutic regimen used in first (cisplatin + etoposide) and second line (cyclophosphamid + vindesine + doxorubicin) treatments. Both mitochondrial and death receptor pathways are involved in VPA-induced apoptosis. Although VPA promotes production of reactive oxygen species, free radical scavenger N-acetylcystein is not sufficient to inhibit apoptosis. As expected, VPA triggers hyperacetylation of histone H3 and increases expression of p21. VPA reduces levels of BclxL, induces cleavage of Bid, translocation of Bax to mitochondria, release of cytochrome c into cytosol and phosphorylation of Erk and H2AX. Transcriptomic analyses by microarrays and quantitative RT-PCR have underscored a series of genes candidates potentially implicated into sensitivity of SCLC to VPA. Among these, the Fzd7 receptor of the WNT pathway is essential for VPA proapoptotic activity. Efficiency of VPA combined to first and second line chemotherapeutic agents is supported by preclinical models of SCLC cells engrafted into SCID mice. The second line combination is presently tested in a clinical trial with patients presenting with refractory or relapsing small cell lung cancer (protocol 01081 at http://www.elcwp.org). [less ▲]

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See detailOptimally Locating Facilities with Variable Characteristics
Kucukaydin, Hande ULg

Doctoral thesis (2011)

Facility location problems aim at optimally locating facilities like plants, warehouses, convenience stores, shopping malls etc. They can have different objectives such as maximizing the profit gained ... [more ▼]

Facility location problems aim at optimally locating facilities like plants, warehouses, convenience stores, shopping malls etc. They can have different objectives such as maximizing the profit gained from the customers or minimizing the costs of locating facilities and serving the customers. In this thesis, we mainly focus on competitive facility location problems which constitute a special family. In a competitive facility location problem, a firm or franchise is concerned with installing new facilities to serve customers in a market where existing facilities with known locations and attractiveness levels compete for increasing their market share and profit. We can classify these problems into two groups: those with non-reactive competition and those with reactive competition. Three different types of competitive facility location models are proposed in order to determine the locations and attractiveness levels of the new facilities to maximize the profit in this thesis. The first one belongs to the former class, where the last two models fall into the latter one. We formulate the first one as a mixed-integer nonlinear programming problem and propose three methods for its solution: a Lagrangean heuristic, a branch-and-bound method with Lagrangean relaxation, and a branch-and-bound method with nonlinear programming relaxation. The computational results obtained on a set of problem instances show that the branch-and-bound method using nonlinear programming relaxation is the most efficient and accurate solution method in order to solve the proposed problem. We consider next an extension of this model by relaxing the assumption that the competitor in the market does not react to the opening of new facilities. In other words, the competitor can react by adjusting the attractiveness levels of its existing facilities with the objective of maximizing its own profit. To this end, a bilevel mixed-integer nonlinear programming model is formulated. We transform this bilevel model into an equivalent one-level mixed-integer nonlinear program and solve it by a global optimization method. For this problem, we also consider a scenario in which the new entrant firm ignores the reaction of the competitor. The experimental results indicate that anticipating the competitor's reaction by including this into his optimization problem increases the profit of the new entrant firm, whereas the competitor's profit is decreased. The last competitive facility location model relaxes the limitation about the competitor's reaction: now the competitor can also open new facilities, close existing ones and/or adjust their attractiveness. This also formulates a bilevel mixed-integer nonlinear programming problem which we try to solve by combining tabu search with global optimization algorithms. We develop three different tabu search methods and the computational results on a set of problem instances for comparing the performance of the solution methods show that the third tabu search method is the most accurate one, while the second tabu search method is the most efficient solution procedure. Finally, we consider a different facility location problem which takes the customer preferences into account. The facilities are not necessarily identical and customers visit different types of facilities according to some given probability distribution and the maximum distance which they are willing to travel. We formulate a binary linear programming problem and solve it by three procedures that include a Lagrangean heuristic whose solution is improved further using a local search method. Based on the experimental results carried out on a set of problem instances the third solution method is the most efficient one. However, a statistical analysis on the quality of the solutions states that there is no significant difference between the three solution procedures. [less ▲]

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See detailDéfinition du régulon DasR chez Streptomyces coelicolor, un réservoir pour la découverte de nouveaux gènes essentiels à l'induction de la différenciation morphologique et la production de métabolites secondaires
Colson, Séverine ULg

Doctoral thesis (2011)

Ce travail vise à comprendre les mécanismes d’induction du développement chez les Streptomyces. Chez ce genre bactérien, le facteur de transcription DasR a été identifié comme le premier régulateur global ... [more ▼]

Ce travail vise à comprendre les mécanismes d’induction du développement chez les Streptomyces. Chez ce genre bactérien, le facteur de transcription DasR a été identifié comme le premier régulateur global à la charnière entre le métabolisme primaire et le métabolisme secondaire, capable de percevoir l'état nutritionnel de l'environnement et d'adapter en conséquence la réponse des différents processus associés au développement (Rigali et al., 2006 et Rigali et al., 2008). La première ambition de cette thèse de doctorat a été d'évaluer l'ampleur du régulon DasR chez S. coelicolor afin d'obtenir une liste - exhaustive et appuyée par des critère de fiabilité - des gènes ciblés par ce régulateur global. L'hypothèse à la base de ce travail de prédiction était qu'au sein du régulon DasR se trouvaient peut-être des gènes de fonction encore inconnue mais essentiels au développement. Comprendre le rôle de ces protéines pouvait déboucher sur l'élucidation de nouvelles voies d'induction du développement et donc peut-être de nouvelles voies à exploiter pour induire le réveil des gènes cryptiques. La première démarche visant à répondre à ce premier objectif nous a amené à constater les lacunes des programmes web de prédiction des régulons existant, notamment le manque de flexibilité au niveau des critères de recherche et au niveau de l'exploitation des résultats obtenus, ainsi que l'absence de moyen permettant d'estimer la fiabilité de la prédiction. C'est pourquoi, dans un premier temps, nous nous sommes lancés le défi de créer un nouvel outil de prédiction des régulons procaryotiques qui répondrait davantage aux attentes des biologistes. Ce programme, nommé PREDetector (Prokaryotic Regulatory Elements Detector), a été réalisé en collaboration avec le Professeur Louis Wehenkel (Department of Electrical Engineering and Computer Science, Université de Liège) (Hiard et al., 2007). Les caractéristiques et les possibilités offertes par PREDetector sont expliquées et illustrées dans le premier chapitre des résultats. Le second chapitre des résultats - ainsi que l'annexe de cette thèse - sont quant à eux dédiés à l'exploitation de ce programme et la caractérisation de l'ensemble des cibles de DasR prédites chez S. coelicolor. Ensuite, et toujours motivé par un souci de présenter un travail fiable pour d'ultérieures investigations, une comparaison des régulons DasR prédits chez différents streptomycètes et autres actinomycètes (prédictions et démarches détaillées dans l'annexe de thèse), vient appuyer notre définition du noyau dur du régulon DasR - conservon DasR - déduit pour l'organisme modèle S. coelicolor. Enfin, nous passons à l'étape d'utilisation de ces données bioinformatiques avec l'étude de gènes/protéines dont l'expression est dépendante de DasR dans le but de peut-être établir de nouvelles connexions entre le métabolisme primaire et le développement chez la souche modèle S. coelicolor. De manière intéressante, le régulon DasR de S. coelicolor comprend plusieurs gènes codant pour des systèmes de transport ABC de sucre. A l'instar du PTSGlcNAc, ces transporteurs situés à l'interface cellule/environnement peuvent aussi être les senseurs de molécules cruciales pour l'induction du développement. Après le PTSGlcNAc, nous nous sommes donc concentrés sur l'étude du premier transporteur ABC de sucre régulé par DasR - en termes de fiabilité des prédictions et de conservation inter-espèces/-genres -, c'est-à-dire, le système DasABC. Dans le troisième chapitre des résultats nous démontrerons ainsi que DasA est une protéine impliquée dans le processus de différenciation morphologique de S. coelicolor (Colson et al., 2008). [less ▲]

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See detailVERS UNE EXPERTISE HYBRIDE AU SERVICE DU DROIT: LE CAS DES ALIMENTS FONCTIONNELS ET DU DOMMAGE ECOLOGIQUE
Kouembeu Tagne, Jean Jacques ULg

Doctoral thesis (2011)

L’apparition récurrente de phénomènes nouveaux et incertains dans le domaine de l’environnement bouscule de façon permanente les cadres de références législatives et interpelle quant à la place, le rôle ... [more ▼]

L’apparition récurrente de phénomènes nouveaux et incertains dans le domaine de l’environnement bouscule de façon permanente les cadres de références législatives et interpelle quant à la place, le rôle et à l’apport des prétendants à l’expertise. Au sens de la Cour de cassation belge, (Cass 15.02.2006, numéro RC 062F2_7, numéro de rôle P051583F) l’expert judiciaire est un auxiliaire de justice. Il n’est ni mandataire, ni préposé des parties. Il assiste le juge, sans empiéter sur la fonction de juger qui est confiée à ce dernier. L’expert est alors appelé à traduire des preuves scientifiques en preuves factuelles destinées à des profanes de sa discipline que sont les juges. Dans ce cas de figure, l’expertise participe de la bonne organisation judiciaire, assure une base de connaissance solide à l’élaboration des décisions judiciaires et se présente comme un partenaire qui pénètre dans le cœur du droit. L’expertise est considérée de la même manière quand dans les processus législatifs elle s’adresse à des parlementaires ou quand elle est convoquée par des politiques voire par le public. Considérée sous cet angle, l’expertise se présente comme un savoir limité aux faits, et non une connaissance discutable, en train de se construire. Cette thèse examine comment, dans des domaines complexes caractérisés par l’incertitude, le savoir objectif n’existe que comme construction. L’expertise n’est plus spécifique à une branche, elle est hétérogène, elle est hybride. Plus fondamentalement, cette expertise est appelée à articuler et à intégrer plusieurs objectivités à la fois, qu’elles soient scientifiques, socio-économiques, sanitaires ou politiques. Cette thèse montre à partir des cas de la réglementation sur les aliments fonctionnels d’une part et celui du dommage écologique d’autre part, comment les cadres juridiques sont investis par des scientifiques, des publics, des juristes, des associations, des politiques, des industriels, etc., et comment ceux-ci contribuent en retour à la modification de ces cadres. Si le droit se singularise par son devoir de qualification, c’est-à-dire, celui qui lui permet d’établir une distance avec les autres disciplines, avec le monde extérieur, la complexité des phénomènes environnementaux invite aujourd’hui à aller au-delà des cloisonnements du raisonnement juridique. En ce sens, cette thèse vise à éclairer la question essentielle suivante : comment le droit peut-il intégrer plusieurs objectivités dans un processus d’élaboration de la norme environnementale ? [less ▲]

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See detailContribution to the study of semiochemical slow-release formulations as biological control devices
Heuskin, Stéphanie ULg

Doctoral thesis (2011)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis, two sesquiterpenoids, E-β-farnesene and E-β-caryophyllene, were formulated for their related properties as aphid enemy attractants. E-β-farnesene, the alarm pheromone of many aphid species, was also identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)). E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas, another aphid predator. The two products were purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) for E-β-farnesene and E-β-caryophyllene, respectively. Natural and biodegradable slow-release formulations were then investigated in order to deliver these molecules on crop fields for a long period of time as biological control devices. Due to their sensitivity to oxidation, both sesquiterpenes needed to be protected from oxygen degradation. For this purpose, alginate – hydrophilic matrix with low oxygen permeability – was used as polymer for the formulations: the main objective was to deliver semiochemical substances in the air in a controlled way. Consequently, a careful selection of alginates was realised. Formulated beads showed different structural and encapsulation properties depending on various formulation factors. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step of alginate bead characterisation consisted in studying release rate of semiochemicals in laboratory-controlled conditions by optimised trapping and validated Fast-GC procedures. Finally, the efficiency of formulations as aphid predator (Syrphidae) and parasitoids (A. ervi) attractants was demonstrated by field trapping and olfactometry experiments. [less ▲]

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See detailLa qualité de vie dans la maladie d'Alzheimer et les syndromes apparentés
Missotten, Pierre ULg

Doctoral thesis (2011)

La question de la qualité de vie dans la démence, envisagée par rapport au patient, constitue l’objet d’étude de ce travail de thèse. Plus précisément, la première partie théorique du présent travail fait ... [more ▼]

La question de la qualité de vie dans la démence, envisagée par rapport au patient, constitue l’objet d’étude de ce travail de thèse. Plus précisément, la première partie théorique du présent travail fait le point sur les connaissances actuelles dans la littérature sur la qualité de vie. Cette dernière est appréhendée sous la double perspective conceptuelle et méthodologique. L’état des lieux dans la démence constitue, pour chacune des différentes caractéristiques conceptuelles et méthodologiques envisagées, le dernier élément qui est aussi le plus détaillé. Il est précédé d’un point centré sur la littérature gérontologique qui, lui-même, est devancé par une petite recherche focalisée sur la littérature « générale » (essentiellement issue de la littérature centrée sur des populations adultes). En ce sens, le développement de chaque caractéristique, tant conceptuelle que méthodologique, se fait donc en trois temps : général, gérontologie et démence. Ces trois phases témoignent d’une présentation allant dans le sens du général au spécifique et du moins développé au plus développé. Pour clôturer la première partie théorique, un recensement des outils de qualité de vie (instruments et méthodes d’observation directe) est présenté. En accord avec ce qui vient d’être énoncé pour les caractéristiques conceptuelles et méthodologiques, ce développement des outils est surtout détaillé pour la démence. Ensuite, les objectifs du travail de thèse sont développés pour commencer la partie expérimentale. Ils sont suivis par la présentation des quatre articles scientifiques. Ceux-ci sont centrés sur l’étude transversale et longitudinale (follow-up de 2 ans) de la qualité de vie et des principaux paramètres sociodémographiques (âge, sexe, lieu de résidence) et cliniques (fonctionnement cognitif, dépendance, troubles psychologiques et comportementaux, stade évolutif) de patients déments situés à tous les stades de l’évolution démentielle. De manière générale, les résultats démontrent que les patients déments sont capables de maintenir un niveau de qualité de vie acceptable. Cette constatation a notamment été établie sur base de la comparaison de la qualité de vie de ces patients avec celle de patients présentant des troubles cognitifs légers ainsi que des personnes âgées « contrôles ». Le niveau de qualité de vie des sujets déments est influencé par les variables cliniques dont l’impact a tendance à augmenter avec le temps. Toutefois, une part importante de la variance reste non expliquée, ce qui démontre l’influence d’autres variables. Enfin, le profil de qualité de vie en fonction du lieu de résidence et du fonctionnement cognitif montre des périodes de stabilisation et de détérioration. Cette observation permet 1) d’affiner la question du lien entre qualité de vie et paramètres cliniques ; 2) de démontrer l’absence de diminution strictement linéaire de la qualité de vie en fonction de l’état cognitif ; 3) de questionner le postulat d’une qualité de vie nécessairement meilleure au domicile par rapport à l’institution. Suite à la présentation de ces articles, le présent travail se centre sur une discussion générale. Celle-ci débute par une synthèse intégrée des résultats dégagés au sein des quatre articles. Elle se poursuit par le dégagement des principaux points conceptuels et méthodologiques avant de se terminer par une réflexion clinique et scientifique basée sur les résultats des articles et les principaux points théoriques abordés. Aussi, la présence d’un niveau de qualité de vie non catastrophique pour les patients déments est mis en parallèle avec les notions de buts et de priorités retrouvées dans la prise en charge actuelle des patients déments mais également avec les concepts de personnalité et de citoyenneté ainsi qu’avec les théories du vieillissement réussi et les stratégies d’adaptation. Enfin, ce travail se clôture par une conclusion générale. [less ▲]

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See detailFluorine in the atmosphere: Inorganic fluorine budget and long-term trends based on FTIR measurements at Jungfraujoch
Duchatelet, Pierre ULg

Doctoral thesis (2011)

High resolution solar spectra are routinely recorded since more than two decades by the University of Liège at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m ... [more ▼]

High resolution solar spectra are routinely recorded since more than two decades by the University of Liège at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with Fourier Transform Infrared (FTIR) spectrometers. Over the last years, major improvements have been implemented in the algorithms used to retrieve the abundances of atmospheric constituents accessible to the FTIR technique. Now, in addition to total column, information on the vertical distribution of the target gas is often available, allowing producing partial column data sets. We take advantage of these improvements to generate and characterize long-term total and partial columns time series of some important inorganic fluorinated trace gases deduced from FTIR measurements performed at Jungfraujoch. First, our investigations on hydrogen fluoride (HF) indicate that the adoption of a Galatry line shape model for this species significantly improves the fitting quality of the retrievals. The sensitivity of our FTIR measurements to HF inversions in three distinct regions that range from the low to the high stratosphere is confirmed thanks to products derived from two satellites and from two numerical models. We further demonstrate that the HF seasonal variations that occur in the low stratosphere are mainly responsible for the seasonal cycle observed in our HF total column time series. We have also developed an original multi-spectrum multi-window retrieval strategy allowing to derive, for the first time, some information on the vertical distribution of carbonyl fluoride (COF2) from ground-based FTIR measurements. After comparison with model data, our COF2 and HF FTIR datasets are combined to assess the atmospheric inorganic fluorine burden Fy. A trend analysis of our HF, COF2 and Fy time series is then performed for four different time periods spanning the 1985-2010 time interval. While we observe a recent stabilization for HF, corresponding COF2 data show a significant rise, after a period of significant reduction in its accumulation rate. This is probably ascribable to the combination of the decrease of its main source gas CFC-12 with the increase of the substitute product HCFC-22. However, this increase in the COF2 rate of change does not significantly impact the Fy trend, which is essentially driven by the change in HF. In addition, we show that the partitioning between the two major fluorine reservoirs HF and COF2 has not changed since the beginning of this century. Together, they account for around 95% of total inorganic fluorine in the atmosphere. Finally, we study the long-term evolution of carbon tetrafluoride (CF4), for the first time from ground-based FTIR measurements. The trend analysis of our time series indicates a slowing, initiated during the nineties, in the CF4 growth rate despite the fact that the absolute loading of this compound is still increasing. Our linear accumulation rates are consistent with those deduced from space or surface measurements. [less ▲]

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See detailEtude de l’évolution de l’état de surface de matériaux optiques sous bombardement ionique à faible énergie
Gailly, Patrick ULg

Doctoral thesis (2011)

In this work the roughness and topography evolution of optical materials sputtered with low energy ion beam (≤1 keV) has been investigated. These materials (bulk or thin layer) are used in the ... [more ▼]

In this work the roughness and topography evolution of optical materials sputtered with low energy ion beam (≤1 keV) has been investigated. These materials (bulk or thin layer) are used in the manufacturing of mirrors for scientific (ground or space) instruments or for other optical applications. In the first part of the work, the roughness evolution of optical surfaces under sputtering has been investigated in the frame of the industrial process known as Ion Beam Figuring. This technique consists in removing shape errors on optical surfaces with a low energy ion beam (≤1 keV). One disadvantage of this process is a potential increase of roughness for surfaces under treatment. The roughness evolution of some materials relevant to the optical industry has been accurately characterized as function of etching depth down to 5 µm. These sputtering experiments have been carried out at normal incidence, mainly with argon ions (but also in a lesser extent with krypton and xenon ions), ion current density of ~1 mA/cm2 and ion beam energy ranging from 200 eV to 1000 eV. The roughness evolution under sputtering is low for materials with amorphous (glass, electroless nickel), monocrystalline (silicon) or even polycrystalline structure (CVD silicon carbide, PVD gold or nickel film), whereas it is considerably more important for some other metallic materials such as electroplated nickel and aluminium. This work has shown small differences in the roughness evolution of CVD silicon carbide as function of the ion beam energy. The roughness increase is faster at low ion energy (<500 eV) than at higher ion energy (650-1000 eV). The grain structure of this material is less revealed at higher energy, which is supposed to be due to a larger amorphization of the sputtered layer in this case. The influence of the ion mass on CVD silicon carbide and gold films on nickel substrates has been also illustrated. Our measurements have been also compared to scaling laws. Various growth and roughness exponents have been found, sometimes rather different from those foreseen by the KPZ equation. In the second part, we focus on periodically modulated structures (ripples) which developed on many solids when sputtered by an off-normal ion bombardment. In this work, we first observed these ripples on gold films deposited on electroplated nickel (materials used as reflective surfaces for X-ray space telescope) sputtered at grazing incidence. We studied the influence of sputtering parameters (ion beam incidence angle, energy and flux) on the characteristics of ripples induced on gold and silver thin film (~0.2 µm). Ion-induced ripples have also been observed on CdS, an interesting semiconductor crystal for optical applications. The ripples orientation and dimensions (spatial wavelengths from 0.13 µm to 0.29 µm) have been confronted to the Bradley-Harper (B-H) linear model. We used the SRIM software to evaluate the deposited energy and the surface tension coefficient distributions. Our results can be in great part explained by the current theories (Bradley-Harper, Makeev) on morphology of ion-sputtered surfaces. These results can be summarized hereunder: • Clear development of ripples for angle of incidence equal or higher than 60° on gold film and 70° on silver film. • In this work the ripples wave vector is always perpendicular to the ion beam direction for all angles, whereas the change in ripple orientation beyond a critical angle is usually reported in literature. This is a due to the different shape of the energy distribution function for our sputtering conditions. • Different regimes for roughness and topography evolution (grains, ripples) have been observed in function of the angle of incidence. 3 different areas can be distinguished, as predicted by Makeev non-linear model. • The diminution of ripple wavelength with ion energy shows that thermal diffusion is the main relaxation mechanism. [less ▲]

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See detail'D’abord sa manière étoit gottique'. L'œuvre peint de Bernard van Orley jusqu'au début des années 1520
Galand, Alexandre ULg

Doctoral thesis (2011)

Les années 1510 et 1520 apparaissent comme un moment crucial pour l’introduction de la Renaissance dans les anciens Pays-Bas. Or, cette période coïncide avec la première période d’activité de Bernard van ... [more ▼]

Les années 1510 et 1520 apparaissent comme un moment crucial pour l’introduction de la Renaissance dans les anciens Pays-Bas. Or, cette période coïncide avec la première période d’activité de Bernard van Orley, un témoin majeur de cette époque de transition. Jusqu’à présent, la recherche a surtout envisagé l’artiste par le prisme de ses magnifiques tapisseries. De la fin de la première décennie du 16e siècle à 1521 où il signe le monumental Polyptyque de Job et de Lazare (Bruxelles, MRBAB/KMSKB, Inv. 1822), l’artiste a pourtant élaboré un œuvre peint de plus en plus perméable aux formes en provenance de la péninsule italienne. Ce changement de perspective a-t-il entraîné des différences importantes en termes de pratiques d’atelier ? Comment peuvent être caractérisées de manière précise les œuvres constituant le noyau dur d’un catalogue aux frontières mouvantes ? En quoi les documents d’archives peuvent-ils donner un nouvel éclairage sur l’activité de l’artiste ? Ces questions sont au centre d’un travail qui se donne pour ambition de renouveler la vision de la peinture de Bernard van Orley, domaine jusqu’à aujourd’hui négligé. [less ▲]

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See detailEtude expérimentale de la cristallochimie et de la stabilité des phosphates à structure fillowite
Rondeux, Mélanie ULg

Doctoral thesis (2011)

Les minéraux du groupe de la fillowite sont des phosphates sodiques de manganèse, de fer, de magnésium et de calcium. On rencontre ces phosphates essentiellement dans les pegmatites granitiques, en ... [more ▼]

Les minéraux du groupe de la fillowite sont des phosphates sodiques de manganèse, de fer, de magnésium et de calcium. On rencontre ces phosphates essentiellement dans les pegmatites granitiques, en contextes métamorphiques, mais aussi dans certaines météorites. A l’heure actuelle, on compte cinq minéraux appartenant à ce groupe ; la fillowite sensu stricto [Na2CaMn7(PO4)6], la chladniite [Na2CaMg7(PO4)6], la galileiite [Na2Fe2+8(PO4)6], la johnsomervilleite [Na2CaFe2+7(PO4)6] et la stornesite-(Y) [(Y,Ca)□2Na6(Ca,Na)8(Mg,Fe)43(PO4)36]. Ces minéraux cristallisent dans le système rhomboédrique (groupe spatial R ) et présentent une maille cristalline de très grande taille (a = 15,28 Å, c = 43,51 Å, Z = 18) contenant 756 atomes dont 45 sont non équivalents. Le premier but de ce travail a été d’obtenir de nouvelles données sur la cristallochimie des minéraux du groupe de la fillowite, et de déterminer les limites d’incorporation de différents cations dans cette structure. La synthèse par voie sèche a été utilisée, à diverses températures (entre 650 et 970°C), lors des essais d’insertion des cations monovalents (Li+, Ag+ et K+), des cations bivalents (Mg2+, Fe2+, Zn2+, Ni2+, Ca2+ et Cd2+) et des cations trivalents (Fe3+, Al3+, Y3+, Cr3+ et Sc3+). Les cations monovalents sont toujours présents dans les minéraux du groupe de la fillowite. Nos résultats confirment cette observation et indiquent que, à l’exception de Ag+ qui peut totalement se substituer à Na+, les autres cations monovalents (Li+ et K+) ne rentrent que très difficilement dans la structure fillowite. Concernant les cations bivalents, les résultats de nos recherches montrent que c’est le manganèse qui s’incorpore le plus facilement dans la structure fillowite. En effet, la synthèse des phosphates de compositions Na2Mn8(PO4)6 ou encore Na2CaMn7(PO4)6, isotypes à la fillowite, est très commode. De plus, les analyses chimiques à la microsonde électronique des fillowites, obtenues par voie hydrothermale dans les systèmes Na-Mn-Fe2+-Mg-(PO4) et Na-Ca-Mn-Fe2+-Mg-(PO4), se localisent essentiellement dans la partie riche en Mn des diagrammes Mn-Fe-Mg. Nous avons également prouvé expérimentalement que d’autres cations bivalents comme le magnésium, le calcium et le cadmium peuvent également s’y introduire assez aisément, à l’opposé du zinc et du nickel qui forment préférentiellement des phases orthorhombiques ou de l’alluaudite. Finalement nos données montrent que le fer ferreux se substitue au manganèse, jusqu’à la composition Na2,244(Fe2+3,791Mn3,172Fe3+0,610)(PO4)6 obtenue à 600°C / 1 kbar. La structure fillowite ne semble pas affectionner les cations trivalents. Nos données corroborent cette observation car il est plus aisé d’insérer des cations bivalents que des cations trivalents, à l’exception de Sc. En effet, le scandium, dont le rayon ionique est le plus proche de celui de Mg2+, s’incorpore bien dans la structure fillowite. L’insertion de Al3+ dans cette structure se révèle également assez facile, comme en témoigne la détection de composés à structure fillowite obtenus sans impuretés dans les échantillons de compositions de départ : Na2(Mn7,4Al0,4)(PO4)6 et Na2Ca(Mn6,25Al0,5)(PO4)6. Enfin, ce sont Fe3+, Cr3+ et Y3+ qui entrent le plus difficilement dans cette structure. La substitution de Mn2+ par Fe3+ ou Cr3+ dans les systèmes étudiés en voie sèche induit immédiatement l’apparition de composés à structure alluaudite en association avec les phosphates à structure fillowite. Des analyses chimiques à la microsonde électronique indiquent toutefois que Fe3+ s’incorpore en faible teneur dans la structure fillowite. Le second objectif de ce travail a été d’appliquer les techniques de synthèse hydrothermale afin de mieux cerner la stabilité des minéraux du groupe de la fillowite. Dans ce but, les systèmes Na-Mn-Fe2+-Mg-(PO4) et Na-Ca-Mn-Fe2+-Mg-(PO4) ont été investigués, à des températures comprises entre 400 et 700°C (1 kbar). Des phosphates à structure fillowite sont formés, sans impureté, à toutes les températures étudiées, à partir des mélanges initiaux dépourvus de fer. L’incorporation du fer implique immédiatement l’apparition d’alluaudite et de sarcopside, alors que la marićite cristallise comme phase supplémentaire pour les compositions très riches en fer. Le contenu de ce dernier dans les composés à structure fillowite augmente entre 400 et 600°C, puis diminue légèrement entre 600 et 700°C (1 kbar). La composition de ces phosphates, obtenus à 600°C / 1 kbar, est très proche de celles des johnsomervilleites naturelles de Loch Quoich (Ecosse) et de Kiluli (Rwanda) indiquant que ceux-ci auraient pu se former dans des conditions similaires. Pour le mélange initial Na2Fe2+8(PO4)6, les phosphates à structure fillowite sont absents à 1 kbar, alors qu’ils apparaissent timidement lors des synthèses réalisées à 3 kbar. Ces résultats démontrent le rôle essentiel joué par la pression sur l’incorporation du fer dans la structure fillowite. [less ▲]

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See detailParameter identification for biological models
Fey, Dirk ULg

Doctoral thesis (2011)

This thesis concerns the identification of dynamic models in systems biology. and is structured into two parts. Both parts concern building dynamic models from observed data, but are quite different in ... [more ▼]

This thesis concerns the identification of dynamic models in systems biology. and is structured into two parts. Both parts concern building dynamic models from observed data, but are quite different in perspective, rationale and mathematics. The first part considers the development of novel identification techniques that are particularly tailored to (molecular) biology and considers two approaches. The first approach reformulates the parameter estimation problem as a feasibility problem. This reformulation allows the invalidation of models by analysing entire parameter regions. The second approach utilises nonlinear observers and a transformation of the model equations into parameter free coordinates. The parameter free coordinates allow the design of a globally convergent observer, which in turn estimates the parameter values, and further, allows to identify modelling errors or unknown inputs/influences. Both approaches are bottom up approaches that require a mechanistic understanding of the underlying processes (in terms of a biochemical reaction network) leading to complex nonlinear models. The second part is an example of what can be done with classical, well developed tools from systems identification when applied to hitherto unattended problems.In particular, part two of my thesis develops a modelling framework for rat movements in an experimental setup that it widely used to study learning and memory.The approach is a top down approach that is data driven resulting in simple linear models. [less ▲]

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See detailDes guerres en Italie avant les Guerres d'Italie. Les entreprises militaires françaises dans la Péninsule à l'époque du Grand Schisme d'Occident
Masson, Christophe ULg

Doctoral thesis (2011)

Si la guerre de Cent Ans stricto sensu, est depuis des années l'objet de recherches de tout premier plan, la question des expéditions françaises en Italie à l'époque du Grand Schisme d'Occident était ... [more ▼]

Si la guerre de Cent Ans stricto sensu, est depuis des années l'objet de recherches de tout premier plan, la question des expéditions françaises en Italie à l'époque du Grand Schisme d'Occident était restée vierge de toute étude de synthèse, à tout le moins sur le plan qui semble pourtant le plus évident, celui de la guerre, et ce alors même que les implications politiques de ces mêmes guerres italiennes sont étudiées depuis aujourd'hui plus d'un siècle. Au croisement des sources – sources narratives et documents d'archives se sont révélés être le socle sur lequel s'est progressivement construite notre synthèse puisqu'au caractère lacunaire des premières en terme de fiabilité ou de chronologie a fait pièce la précision des secondes qui trouvaient pour leur part dans la confrontation avec les chroniques les éléments de nature à enrayer l'aridité des relevés financiers – fait écho celui des approches, que nous avons souhaitées multiples, de notre sujet d'études. Pour appréhender le fait militaire, nous avons privilégié une vision globalisante, eu égard au fait que, à nos yeux, l'armée représentait un tout qui se doit d'être étudié de la sorte. Les divers éléments qui la composent étant interdépendants, on ne peut connaître l'un sans envisager l'autre. Il ressort de cette approche plurielle plusieurs observations. Alors que l'Europe se cliche au gré des intérêts politiques et spirituels en obédiences rivales, l'on aurait pu s'attendre à ce que des princes français, traditionnellement favorables à la papauté d'Avignon, deviennent les champions des prélats des bords du Rhône. Or, il n'en fut rien. Ce qui intéressa au premier chef les ducs d'Anjou fut non de déposer celui qu'il tenait pour un usurpateur et d'établir le successeur de saint Pierre pour lequel ils avaient opté sur le trône de Rome mais de profiter des ressources financières de la papauté, considérées alors, avec le trésor du roi de France, comme les plus massives de l'Occident. De la même façon, les ressources du duc d'Orléans et celles du roi de France furent, en toute logique, très largement sollicitées par les lieutenants de ceux-ci. Mais, à cette occasion encore, on constate une indépendance certaine des bénéficiaires vis-à-vis de leurs bailleurs de fonds. La mission qui leur est confiée offre un cadre relativement lâche à leurs actions, cadre qui, joint à l'éloignement géographique, facilite l'exercice d'un pouvoir des capitaines ouvertement personnel. Les actions menées en Italie se trouvent tout à fait différer des usages en cours lors de la guerre qui opposait la France à l'Angleterre. Depuis Charles V, en effet, les armées françaises s'étaient vues ordonner l'abandon de la charge de cavalerie au profit d'options tactiques mieux à même de contrer une infanterie adverse qui s'était signalée lors des sanglantes batailles de Crécy et de Poitiers. En Italie, au contraire, si les compagnies fleurdelysées ressemblaient par la taille à leurs homologues cisalpines, leur aspect les en faisait parfaitement différer. La prééminence est à nouveau le fait d'hommes d'armes montés. Le basculement est donc complet et rapide de la part de guerriers qui s'adaptent d'autant plus rapidement à leur nouvel ennemi que celui-ci se révèle être un fervent adepte du choc frontal, du moins lorsqu'il accepte le combat. C'est d'ailleurs un trait marquant des opérations françaises que de n'avoir que rarement produit de grandes batailles. Au vrai, les Italiens s'efforçaient le plus souvent d'éviter tout affrontement d'importance afin de tirer profit de leur établissement dans le royaume de Naples ou dans la République de Gênes. Partant, les Français organiseront leurs campagnes autour d'un objectif prioritaire, la soumission de la capitale adverse et auront donc recours à des moyens moins typiquement « chevaleresques » pour assurer le triomphe de leur cause. Si Louis Ier d'Anjou n'a visiblement pu compter que sur une faible artillerie, ceux qui, à sa suite, prirent le chemin de l'Italie ne semblent pas avoir négligé cette composante de plus en plus importante de l'art de la guerre. D'autres moyens pour emporter des places fortes furent mis en œuvre, qui tous s'éloignaient un peu plus de la morale traditionnellement défendue par cette classe sociale particulière qu'était la chevalerie. Or, ces pratiques étaient loin d'être étrangères aux capitaines royaux et ducaux. L'idée de l'honorable et pur chevalier parangon de vertu confronté à des réalités italiennes qu'il ne peut comprendre car trop ignobles ne résiste pas à l'examen attentif des faits. Les armées médiévales – de terre ou de mer – tiraient évidemment leur puissance de leur importance numérique. Par suite, ce sont les chefs de guerre à la tête des plus nombreuses compagnies qui reçurent le commandement de l'ensemble des troupes. Le recrutement en cascade – les fidèles d'un seigneur conduisant à leurs côtés certains de leurs fidèles et ainsi de suite – explique que, contrairement, une fois encore, à ce que l'on aurait pu croire, le service d'Italie ne s'est pas révélé un accélérateur de carrière chez les gens d'armes. Leur présence dépendait plus de liens personnels les unissant à un chef de guerre que de relations de service ou de vassalité les attachant au souverain commanditaire de l'entreprise. Nulle surprise donc à ce que ce dernier ne juge pas nécessaire de les récompenser à la fin de leur mission. Au contraire, ce sont les techniciens, gens de finances et de lettres, qui bénéficièrent de promotions à leur retour d'Italie. La guerre dans la Péninsule n'était qu'une étape de plus dans la carrière d'un homme d'armes alors qu'elle prouvait les capacités des « petites mains » de l'armée à affronter des situations auxquelles l'on ne pouvait se préparer. Si la délégation de pouvoir est importante, il n'en reste pas moins que l'on assiste tout au long de ces campagnes à la négation de la personnalité du capitaine dans le domaine pourtant si important des symboles politiques. L'armée demeure ainsi un instrument de pouvoir aux mains du souverain. Au-delà de l'aspect spécifiquement politico-militaire, elle exprime l'excellence de ce dernier, qu'il s'agisse des ducs d'Anjou et d'Orléans ou du roi de France, lequel prouve par le succès des armes et la qualité – sociale aussi bien qu'esthétique – de son armée la valeur et la justesse de ses prétentions. Au vrai, si c'est la noblesse qui, logiquement, compose les armées françaises et occupe les principales charges de gouvernement, elle est subjuguée par l'État qu'elle sert. Elle en retire un prestige certain mais renonce aussi, simultanément, à son indépendance. Ici encore, l'état moderne en construction se bâtit sur et grâce à une aristocratie relais des intérêts ducaux ou royaux. De la même façon, la présence de Français au sein de ces administrations locales trahit l'importance prise par les liens sociaux dans l'exercice du pouvoir et sa délégation. Ce sont leur proximité et leur amitié qui font des lieutenants du capitaine les officiers du roi. La fidélité personnelle intervient donc comme ciment d'un pouvoir étatique. La noblesse, bien qu'elle soit en Italie moins soumise au pouvoir royal en Italie qu'en France, constitue le véritable cœur de l'armée, tout comme cette dernière est le noyau de l'état princier que l'on développe outremonts grâce au cadre fourni par le modèle royal. [less ▲]

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See detailInnovative strategies for the control of apple scab (Venturia inaequalis [Cke.] Wint.) in organic apple production
Jamar, Laurent ULg

Doctoral thesis (2011)

The aim of this thesis, conducted over six growing seasons (2003-2008), is to define new measures for reducing the use of fungicides and in particular, copper fungicides, for the control of apple scab (V ... [more ▼]

The aim of this thesis, conducted over six growing seasons (2003-2008), is to define new measures for reducing the use of fungicides and in particular, copper fungicides, for the control of apple scab (V. inaequalis) in organic apple production. Special emphasis is put on primary scab infection control during spring season. An original approach is proposed for defining a specific spray timing involving spraying during the infection processes, especially before fungal penetration, determined by the RIMpro software warning system. This ‘during-infection’ spray strategy allows reducing from 30 to 50% the amount of fungicide usually used for effective apple scab control, on high scab-susceptible cultivars. The field study shows that six alternative products (e.g., potassium bicarbonate and lime sulphur), among 60 products tested, have the potential to reduce copper use. However, copper use, even with low doses, seems to be still necessary in presence of scab-susceptible cultivars. The results obtained in these experiments could not be attributed to the specific technical performances of the tunnel sprayer used, which however, offer valuable environmental benefits. On the basis of the present study, the organic management system seems a good farming approach for maintaining soil quality with regard to biological indicators. This work shows and draws attention to the fact that (i) planting cultivars with polygenic scab-resistance traits, (ii) increasing emphasis on sanitation practices aimed at reducing initial inoculum in autumn, and (iii) applying an accurate spray strategy in spring, as defined in the present study, are the three most promising approaches for substantial further reductions in protection products fully compliant with international organic crop production standards. [less ▲]

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See detailOptimisation contrainte et non-contrainte par régions de confiance avec approximations locales quadratiques
Walmag, Jérôme ULg

Doctoral thesis (2011)

This work deals with optimisation problems in which the numerical cost associated with the evaluation of the target function and/or of the constraints is large; the number of calls to these functions by ... [more ▼]

This work deals with optimisation problems in which the numerical cost associated with the evaluation of the target function and/or of the constraints is large; the number of calls to these functions by the optimisation algorithm should therefore be kept as small as possible. The first part of the work is about globalisation by trust regions where the objective function and the constraints are replaced by a local approximation, easier to use, in a certain region of confidence. Different types of local approximations are introduced but the main part of the work deals with quadratic approximations. The theoretical aspects of the global convergence of trust regions methods are also presented. One of the applications considered in this work is the parametrical identification of a dynamical model with respect to experimental measurements. This identification can be expressed in the form of an unconstrained optimisation problem. For the practical implementation of the identification algorithm, the derivative of the objective function is required, which asks for the derivation of the underlying model. An algorithm, named Trust, has been implemented: it is a trust region method of quasi-Newton type which uses quadratic local approximations. The choice of the differentiation method is analysed in details in relation with its influence on the rate of convergence. A brand new update strategy of the trust region radius is also introduced. The trust region radius is a parameter that measures the size of the trust region around the current iterate. The new approach relies on the identification and appropriate handling of so-called “too successful iterations” that lead to a much more important reduction of the function objective than predicted by the local approximation. This approach goes with a significant improvement of the performances of the algorithm. Constrained optimisation is then considered using sequential quadratic methods. A fully effective algorithm for the resolution of quadratic convex sub-problems with quadratic constraints is introduced. This original method, named UVQCQP, makes use of an exact non-differentiable penalty function to addresses the constrained optimisation problem. The algorithm relies on a decomposition of the variable space into three orthogonal subspaces: a first subspace taking into account bound constraints, a second one in which the objective function is continuously derivable and a third one with slope discontinuities. The performances of this algorithm are further improved by the implementation of a fast mode taking into account the second order corrections. Eventually, the UVQCQP algorithm is applied within the framework of sequential algorithms of quadratic programming with quadratic constraints: its advantages are demonstrated through some examples. The numerical tests carried out reveal very encouraging prospects. [less ▲]

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See detailLa représentation documentaire des années de plomb allemandes (1970-1979): de la contrinformation au mélancolique
Hamers, Jérémy ULg

Doctoral thesis (2011)

Comment représenter un ensemble d’évènements affectés par leur inaccessibilité, la polarisation extrême du contexte qu’ils contribuent à mettre en place, et une censure à la fois morale et financière ... [more ▼]

Comment représenter un ensemble d’évènements affectés par leur inaccessibilité, la polarisation extrême du contexte qu’ils contribuent à mettre en place, et une censure à la fois morale et financière ? Telle était la question de départ de notre recherche doctorale, à laquelle nous avons soumis un corpus de films documentaires allemands traitant des événements de la crise terroriste des années septante, et réalisés entre 1970 et 1979. Un rappel chronologique de quelques évènements saillants des années de plomb allemandes nous a permis d’examiner d’abord les multiples liens et interactions entre terrorisme allemand et représentation. L’analyse de l’usage des médias par les terroristes et l’examen de quelques représentations produites par les médias, ont révélé un double lien symbiotique entre acte terroriste et discours médiatique : intrication de l’événement et de sa représentation en vertu de laquelle certaines images s’érigent d’abord en emblèmes des évènements avant de s’y substituer totalement ; chassé-croisé de représentations terroristes, étatiques et médiatiques, qui révèle que les productions audiovisuelles des terroristes et les représentations produites par l’Etat appartiennent en réalité à un seul et même grand réseau de représentations, sémantiquement violentes, dont les principaux moteurs sont la citation et le détournement ainsi que le remplissage de décors vides dans lesquels se sont déroulés des événements révolus. Cet état de fait compromet a priori toute approche documentaire indépendante des événements. La suite de notre étude a dès lors été consacrée à la recherche d’une forme documentaire qui serait en mesure d’échapper à ce grand réseau de représentations. Cette recherche a d’abord abouti à l’analyse de six documentaires – totalement ignorés par la littérature scientifique pour la plupart – issus d’écoles de cinéma et de groupes de vidéastes militants. Ces films ont été réunis au nom de leur capacité structurelle à échapper à la censure financière et morale de l’époque. L’analyse de ces œuvres nous a permis d’identifier quelques modes de représentation qui tous peuvent contribuer à l’élaboration d’un regard sur le réel, affranchi partiellement de l’irreprésentabilité de la crise terroriste et du réseau de représentations qu’elle contribue à mettre à place. Mais il est également apparu que ces œuvres reproduisent des logiques narratives et informationnelles héritées des médias, qui compromettent in fine l’existence d’un regard non polarisé sur les événements. La suite de notre étude s’est alors focalisée sur le film collectif L’Allemagne en automne. L’analyse de différentes formes de signatures auctoriales a révélé d’abord que si le film est à considérer comme une œuvre signée en groupe, sa signature « désindividualisante » entre aussi en concurrence directe avec un ensemble de marqueurs d’énonciation individuelle. En résulte l’oscillation d’un auteur, reconnaissable et anonyme, proposant de la sorte un nouveau lieu du discours. Enfin, nous nous sommes penchés sur les mises en scène des séquences du film. Notre analyse a mis en évidence que les évènements précis de l’automne '77 agissent seulement comme des rappels visuels d’un contexte particulier. Ce contexte anxiogène nous a amené à conclure provisoirement à l’échec de l’auteur : incapable de se libérer du camp qui lui est attribué a priori, il reproduit les comportements et regards de ses « adversaires » (point de vue du « policier embusqué, etc.). Conscient de cette paralysie, l’auteur est pourtant aussi le premier créateur de ces manifestations d’échec. En ce sens, il ne subit pas la crise dans laquelle le précipite l’Automne Allemand, mais il la (re)met en scène. Le produit de cette lucidité, de cette conscience est le mélancolique : une représentation ou un discours produits par un sujet conscient mettant en abyme le retournement contre soi, la perte de soi qui lui paraît inéluctable dans le contexte des années de plomb. [less ▲]

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See detailProphétisme, hétérodoxie et dissidence. L’imaginaire kimbanguiste en mouvement
Melice, Anne ULg

Doctoral thesis (2011)

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See detailMolecular characterization of the host-pathogen relationships involved during an infection of GF-305 peach trees by the Peach latent mosaic viroid (PLMVd)
Parisi, Olivier ULg

Doctoral thesis (2011)

The Peach latent mosaic viroid (PLMVd) infects peach trees in all production areas. This pathogen is responsible of direct and indirect crop losses. However only a few data are available as regards on one ... [more ▼]

The Peach latent mosaic viroid (PLMVd) infects peach trees in all production areas. This pathogen is responsible of direct and indirect crop losses. However only a few data are available as regards on one hand the determinant of pathogenicity of this viroid and on the other hand the resistance mechanisms of plants against this pathogen. The original approach of this work was to give the foundation of this double characterization. Firstly, the role of the P8 pseudoknot, present in every sequenced PLMVd, was studied by directed mutagenesis. Secondly, the molecular response of different peach trees infected by different variants was evaluated by the use of the cDNA-AFLP. The main objective of this thesis was to identify a metabolic pathway implicated in the plant defence against the PLMVd. In the term of this work, it seemed that the P8 pseudoknot was implicated either in the stability or in the replication of the viroid into the infected cells. Indeed, the inoculated variant (with a destabilized pseudoknot) has shown a reduced replication during the cultural season. In spite of the presence of the mutated variant in the plants, no symptom was observed on the peach tree leaves. However, we cannot conclude if this absence of symptom is due to the low viroid quantity either to an implication of the pseudo-knot in the pathogenicity of the PLMVd. The characterization of the gene expression in the infected peach trees has allowed to highlight that the PLMVd represses genes implicated in the photosynthesis and more specifically genes involved in the protection of the two photosystems. This particular gene expression in the infected leaves was linked to the chlorosis and mosaic induced by the PLMVd. However, we cannot conclude with certitude if these symptoms are a cause or a consequence of this particular genes expression. The cDNA-AFLP has also allowed to identify the repression of genes coding for heat shock proteins (HSPs) in symptomatic leaves. These proteins generally have a role in the protein folding, assembly, translocation, stabilization and degradation. The regulation of their expression may have a great influence in the infected plants and, maybe, play a role in the symptoms expression. The gene coding for the novel cap-binding protein (nCBP) was also identified has repressed in the symptomatic leaves. The biological role of these proteins is unclear but it seems that these proteins act in the regulation of the mRNA translation. The repression of nCBP may thus have an important impact and to destabilize various biological pathways. Finally, two genes implicated in the plant defence were identified. One coding for a polygalacturonase inhibitor (over-expressed in symptomatic leaves) and the other one coding for a thiamine intermediate (involved in the SAR and over-expressed in the non-symptomatic leaves). The role of these proteins in the plant defence against the PLMVd is however unclear. To our knowledge, this is the first work where the host-pathogen relationship established during a PLMVd infection are studied. This is also the first time were the gene expression is linked to the viroid-induced symptoms. [less ▲]

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See detailApproaches for assessing the presence and impact of thyroid hormone disrupting chemicals in sea bass (Dicentrarchus labrax) from European coasts
Schnitzler, Joseph ULg

Doctoral thesis (2011)

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro ... [more ▼]

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, Cu, Se, Pb, Zn and Hg) were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in coastal regions near several important European river mouths (Gironde, Charente, Loire, Seine and Scheldt). We applied a multi-level approach of thyroid function assessment. Thyroxine (T4) and triiodothyronine (T3) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that lead to an increased conversion of T4 to T3 and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. The higher chlorinated PCBs seemed to be the most implicated in this perturbation. To gain a more integrated insight, we examined the effect of subchronic exposure to a mixture of Aroclor standards on thyroid hormone physiology and metabolism in juvenile sea bass. After 120 days of exposure, histomorphometry of thyroid tissue, muscular thyroid hormone concentration and activity of enzymes involved in metabolism of thyroid hormones were assessed. The results show that the effects of PCB exposures on the thyroid system are dose-dependent. Exposure to environmentally relevant doses of PCB (0.3 to 1.0 μg Σ7PCBs per g food pellets) increases thyroid hormone synthesis and stimulates hepatic T4 outer ring deiodinase and T4 sulfation. Thyroid hormone tissue levels were preserved thanks to the PCB induced changes in T4 dynamics. At 10 times higher concentrations (10 μg Σ7PCBs per g food pellets) an important depression of T3 and T4 levels could be observed which are apparently caused by degenerative histological changes in the thyroid tissue. We propose accurate interpretations, by reviewing the different stages of teleost thyroid function and regulation. [less ▲]

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See detailUn médiateur invisible. Analyse et mise en perspective du régime de régulation des ondes électromagnétiques
Joris, Geoffrey ULg

Doctoral thesis (2011)

La présente thèse de doctorat propose une analyse du régime de régulation des risques liés à la téléphonie mobile et ce à différents niveaux de pouvoir (International, européen, belge - échelons fédéral ... [more ▼]

La présente thèse de doctorat propose une analyse du régime de régulation des risques liés à la téléphonie mobile et ce à différents niveaux de pouvoir (International, européen, belge - échelons fédéral, régional et local). L'idée est de démontrer la dynamique d'ouverture et de fermeture tout au long de la "séquence" de la politique publique construisant progressivement un régime de régulation du risque "électromagnétique" [less ▲]

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See detailOptimisation et caractérisation d’un extrait de cassis riche en antioxydants utilisable comme complément alimentaire
Tabart, Jessica ULg

Doctoral thesis (2011)

Blackcurrant (Ribes nigrum, family Saxifragaceae) produces fruits with a high antioxidant content. This shrub is much known for its strongly aromatic fruits. It is largely used in the industrial ... [more ▼]

Blackcurrant (Ribes nigrum, family Saxifragaceae) produces fruits with a high antioxidant content. This shrub is much known for its strongly aromatic fruits. It is largely used in the industrial production of syrups and of concentrates, it contains very high quantities of phenolic compounds, particularly anthocyanins. Blackcurrant buds and leaves are also used as a food complement for their tonic and diuretic properties, as well as for the treatment of rheumatic affections. With this plant, we tried to develop, on a laboratory scale, a flavonoid-rich extract, stable in time and to show several biological activities. Initially, different plant materials were compared (fruits, leaves, buds, from different cultivars harvested at different times) and the method of extraction were optimized. Lyophilised-leaf extracts obtained with the acetone-water-acetic acid mixture (70: 28: 2) show an excellent yield in antioxidant compounds. These freeze-dried extracts have also the advantage of being stable for several months. We characterized these extracts for their content in various classes of antioxidant molecules. The leaves and the buds yielded extracts containing mainly flavonols, flavanols and total phenolic compounds, as compared to berries. On the other hand, these fruits showed higher contents of ascorbic acid and anthocyanins. In a third part, we analyzed certain health-properties (antioxidant capacity, anti-inflammatory capacity and the properties in vasorelaxation process) of the blackcurrant extracts by using in vitro methods as well as cellular and isolated organ models. Our study highlighted the intracellular and the extracellular properties of the blackcurrant extract as radical scavenger. We also showed an inhibition of the myeloperoxydase activity in the activated neutrophils, and an activation of the vasorelaxation process of the blood-vessels (production of NO, modulation of the expression of ARNm eNOS in the endothelial cells and relaxing effect in isolated organ), and this, without presenting any toxic effects. In conclusion, the black currant leaf extract obtained through extraction in acetone-water- acetic acid mixture has many interesting properties for health-protection. This extract, rich in phenolic compounds and having a high antioxidant activity, can also modulate the activity of several enzymes involved in inflammation or in vascular motricity. [less ▲]

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See detailContributions to Batch Mode Reinforcement Learning
Fonteneau, Raphaël ULg

Doctoral thesis (2011)

This dissertation presents various research contributions published during these four years of PhD in the field of batch mode reinforcement learning, which studies optimal control problems for which the ... [more ▼]

This dissertation presents various research contributions published during these four years of PhD in the field of batch mode reinforcement learning, which studies optimal control problems for which the only information available on the system dynamics and the reward function is gathered in a set of trajectories. We first focus on deterministic problems in continuous spaces. In such a context, and under some assumptions related to the smoothness of the environment, we propose a new approach for inferring bounds on the performance of control policies. We also derive from these bounds a new inference algorithm for generalizing the information contained in the batch collection of trajectories in a cautious manner. This inference algorithm as itself lead us to propose a min max generalization framework. When working on batch mode reinforcement learning problems, one has also often to consider the problem of generating informative trajectories. This dissertation proposes two different approaches for addressing this problem. The first approach uses the bounds mentioned above to generate data tightening these bounds. The second approach proposes to generate data that are predicted to generate a change in the inferred optimal control policy. While the above mentioned contributions consider a deterministic framework, we also report on two research contributions which consider a stochastic setting. The first one addresses the problem of evaluating the expected return of control policies in the presence of disturbances. The second one proposes a technique for selecting relevant variables in a batch mode reinforcement learning context, in order to compute simplified control policies that are based on smaller sets of state variables. [less ▲]

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See detailRhizosphere-driven lipopeptide production by different strains of Bacillus spp. as mechanism involved in biological control of plant pathogens
Nihorimbere, Venant ULg

Doctoral thesis (2011)

Some plant-beneficial bacteria with biopesticide potential produce antimicrobial compounds that are tightly involved in multitrophic interactions occurring in the phytosphere among which antagonism toward ... [more ▼]

Some plant-beneficial bacteria with biopesticide potential produce antimicrobial compounds that are tightly involved in multitrophic interactions occurring in the phytosphere among which antagonism toward a diverse range of phytopathogens. However, there is a crucial need for an accurate assessment of antibiotic production rate in this environment colonized by these bacteria. In this context, we conducted the present thesis work with the scope to better understand how two different Bacillus genus strains produce lipopeptides in the rhizosphere of plants. In the first part, one of the strains (B. amyloliquefaciens S499) was selected out of other isolates for its technological traits and in vitro inhibition growth activity of plant pathogenic fungi. We further demonstrated its biocontrol potential in tomato open-field experiments where plantings have been devastated by a local fungus preliminary identified as Fusarium semitectum. In a second part, we combined two mass spectrometry-based approaches (electrospray ionization and imaging) to analyze the pattern of surfactin, iturin and fengycin lipopeptide families produced in planta by strain S499. Our results show that rhizosphere conditions are conducive for surfactin synthesis but not for other types of lipopeptides and that the lipopeptide pattern can be markedly influenced by nutritional factors, biofilm formation and oxygen availability. In a last part, surfactin gene expression (srfA) level was evaluated in situ on tomato root using the reporter gene (LacZ) inserted in B. subtilis strain BGS3. Results showed effective expression of srfA and production of surfactin in biologically important level quantities upon establishment of bacterial population on roots. Our results also demonstrate that BGS3 developing in colonies, efficiently utilizes the main substrates from plant exudates to produce surfactins. The production may also be favored in bacteria growing slowly in the rhizosphere. Globally, this work contributes to better appreciate the impact of some environmental factors on the in situ biosynthesis of lipopeptides by strains of Bacillus which is probably an essential step for improving the level and reliability of their efficacy as biological agents for the control of plant diseases. [less ▲]

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See detailConscience de soi dans le vieillissement normal et pathologique
Feyers, Dorothée ULg

Doctoral thesis (2011)

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See detailContribution to pomegranate seeds conservation (Punica granatum L.) by osmotic dehydration
Bchir, Brahim ULg

Doctoral thesis (2011)

The aim of this work was to create a complete conservation process of pomegranate seeds (Punica granatum L.). This process is essentially based on osmotic dehydration (OD), which was associated to ... [more ▼]

The aim of this work was to create a complete conservation process of pomegranate seeds (Punica granatum L.). This process is essentially based on osmotic dehydration (OD), which was associated to freezing and air-drying process. Several parameters were studied to optimize the process such as osmotic solution (sucrose, glucose, and sucrose/glucose and date juice with sucrose added), temperature (30, 40, and 50°C) and state of the fruit (fresh and frozen). All these conditions were linked to seed proprieties (texture, structure, and colour). The study of osmotic dehydration parameters (water loss (WL), solids gain (SG) and weight reduction (WR)) showed that most significant changes of mass transfer took place during the first 20 min of dewatering using frozen seeds, independently of temperature and sugar type. During this period, seeds water loss was estimated at 46% in sucrose, 41% in sucrose/glucose mix, 39% in date juice, and 37% in glucose. Mass transfer was slower starting from fresh fruit but led to a higher rate of WL at the end of the process. This fact can be explained by scanning electron microscopy, which showed damage of seed cell structure after freezing. This has practical consequences in terms of the modification of seeds texture. The same process also revealed a modification of seed texture and cell structure after osmotic dehydration. Using a sucrose solution and a temperature of 50°C favoured the best mass transfer. The determination of different water fractions of seed by differential scanning calorimetry (DSC) showed that the % of frozen water decreased 3.5 times contrary the % of unfreezable water that increased 2.5 times. This favours a better seeds conservation. During osmotic dehydration, there was a non negligible leaching of natural solutes from seeds into the solution, which might have an important impact on the sensorial and nutritional value of seeds. Using only osmotic dehydration could not maintain the stability of seeds during conservation. In fact, after the osmotic process, water activity of seeds was found to be higher than 0.9, allowing to the development of microorganisms and some undesirable reactions. As a consequence, a drying of the pomegranate seeds (during four hours) was investigated at three different temperatures (40, 50, and 60 °C) with air flow rate of 2 ms-1. Prior to the drying process, seeds were osmodehydrated in a sucrose solution (55°Brix) during 20 min at 50°C. The drying kinetics and the effects of OD and air-drying temperature on antioxidant capacity, total phenolic, colour, and texture were determined. This work is a contribution to the study of physico-chemical properties of pomegranate seeds (Punica granatum L.) during freezing, osmotic dehydration and drying. After the global process, the pomegranate seed characteristics lead to new industrial developments. [less ▲]

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See detailInfluence of Biomaterials in Alveolar Bone Regeneration and Preservation
LAMBERT, France ULg

Doctoral thesis (2011)

Dental implants are nowadays a reliable solution to replace missing teeth and have been widely documented. However, they require a minimal bone quantity (in height and thickness). But alveolar bone ... [more ▼]

Dental implants are nowadays a reliable solution to replace missing teeth and have been widely documented. However, they require a minimal bone quantity (in height and thickness). But alveolar bone defects are very frequent, for instance due to periodontitis, traumatism or acute dental infection. Moreover, a simple tooth extraction leads to significant bone resorption. Therefore, alveolar bone regeneration is often necessary in order to place implants and to restore the patient's dentition with implant-supported prosthesis. Even though alveolar bone reconstructions have been considered as traumatic, especially due to the need of a second surgical site for bone harvesting, techniques have evolved with the introduction of biomaterials. However, it is difficult to compare the influences of such biomaterials on osteogenesis and to elaborate on the advantages of one product over another. The overall objective of this thesis is to contribute to the understanding of the biological concept of alveolar bone regeneration, in particular sinus lift and socket preservation procedures. The influence of biomaterials on bone regeneration has been emphasized through preclinical and clinical studies. The number of commercially available biomaterials for bone regeneration is growing every day and some materials are not supported by strong scientific data in the literature. The first part of this thesis (Chapter 1) is dedicated to the characterization of several biomaterials often used in dentistry. The impact of their various characteristics on osteogenesis has been reviewed, from chemical aspect to micro- and macromorphology. Furthermore, a data sheet integrating the physico-chemical and morphological properties of each studied biomaterial has been developed as a tool for clinicians. Sinus floor elevation has often been considered as a bone graft. In 1996, a consensus conference on “sinus lift” took place and the procedure was qualified as “sinus bone-graft”. But new scientific evidence has shown that this qualification is not justified. Chapter 2 aims at understanding the physiology and the biological model of sub-sinusal bone augmentation by using either a simple blood clot, autogenous bone chips or biomaterials (BHA) as space fillers under the lifted sinusal membrane. If bone formation did occur with the 3 types of space fillers, the augmented volumes significantly dropped with the blood clot or the autogenous bone chips but remained stable with BHA. Therefore, a slowly resorbable biomaterial such as BHA might be suitable in sub-sinusal bone augmentation to prevent the re-expansion process. Understanding the biological concept of sinus lift procedures, several authors demonstrated the clinical efficacy of biomaterials when used alone in this specific model. Nevertheless, biomaterials known to be resorbable led to a lamellar bone architecture that might not be able to maintain the volume of the regenerated tissue over time. Moreover, many types of biomaterials are available and scientific evidence of short and long-term performance of newly introduced biomaterials is still poor. Chapter 3 aims at comparing the performances, in terms of bone formation, resorption rate and 3-D stability, of four calcium phosphate-based biomaterials often used for sub-sinusal bone augmentation, in a rabbit model. Particulated space-filling biomaterials seemed to be more efficient to promote osteogenesis compared to paste-like biomaterials. Highly resorbable biomaterials appeared to withstand intrasinusal pressure after a period of six months in rabbits. Non- or slowly resorbable biomaterials are of great interest in the dental field because the long-term stability of 3-D bone augmentation is a key factor for dental implant and aesthetic outcomes. Therefore, the mechanical and non-resorbable properties of titanium, known to be highly compatible in vivo and highly resistant to body fluid corrosion, are potential advantages for bone augmentation prior to dental implantation. Nevertheless, the use of titanium particles as space fillers in bone regeneration was weakly reported in the literature from a histological point of view. Thus, Chapter 4 compares the behavior and the effect of porous titanium particles versus the well-documented BHA. Even though both biomaterials allowed osteogenesis and adequate 3-D stability, the bone architecture, and more specifically the amount of bone-to-material contact (BMC), was significantly different. Inclusion of the particles in a carrier or in binding agents such as a collagen gel or fibers might be of interest in order to ease surgical handling. However, the possible influence of those collagen carriers on bone tissue responses remains poorly investigated. The objective of Chapter 5 was to investigate the effect of collagen at different stages of the osteogenesis process, still in the same rabbit model. The findings clearly showed the presence of inflammatory cells at an early stage of bone regeneration when collagenated xenogenic biomaterials were used compared to collagen-free xenogenic granules. Nevertheless, despite the transient inflammation, the final quantity of newly formed bone was similar in the various groups. The last two chapters of this thesis take some of the preclinical findings of the previous chapters to the clinical field. The objective of Chapter 6 was to assess the clinical outcome of a minimalized sub-sinusal bone augmentation procedure using only biomaterials, simultaneously with the placement of 102 non-submerged implants in 40 patients. Implant and prosthodontic survival rates as well as complications were evaluated after a follow-up period of 2 to 6 years. This clinical trial emphasized that, if the amount of remaining bone height is sufficient to ensure implant primary stability, their placement can be performed simultaneously with sinus lifting, even in a non-submerged fashion. This procedure reduces the number of surgeries and the time before prosthetic rehabilitation. The objective of Chapter 7 was to to develop a new method to objectively evaluate in humans the 3-D volume variation of alveolar socket preservation over time by means of computed tomography and 3-D image analysis. Short summary: Before placing dental implants, alveolar bone regeneration is often required due to bone defects caused by periodontitis, traumatism or even a simple tooth extraction. Bone augmentation surgical procedures have very much evolved thanks to a better understanding of biological processes and to the introduction of biomaterials. The overall objective of this thesis is to bring a contribution to the understanding of the biological concept of alveolar bone regeneration, and in particular sinus lift and socket preservation procedures. The influence of biomaterials on bone regeneration has been emphasized through preclinical and clinical studies. [less ▲]

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See detailDesign and Implementation of a Distributed Lattice Boltzmann-based Fluid Flow Simulation Tool
Dethier, Gérard ULg

Doctoral thesis (2011)

Lattice Boltzmann-based (LB) simulations are well suited to the simulation of fluid flows in complex structures encountered in chemical engineering like porous media or structured packing used in ... [more ▼]

Lattice Boltzmann-based (LB) simulations are well suited to the simulation of fluid flows in complex structures encountered in chemical engineering like porous media or structured packing used in distillation and reactive distillation columns. These simulations require large amounts of memory (around 10 gigabytes) and would require very long execution times (around 2 years) if executed on a single powerful desktop computer. The execution of LB simulations in a distributed way (for example, using cluster computing) can decrease the execution time and reduces the memory requirements for each computer. Dynamic Heterogeneous Clusters (DHC) is a class of clusters involving computers inter-connected by a local area network; these computers are potentially unreliable and do not share the same architecture, operating system, computational power, etc. However, DHCs are easy to setup and extend, and are made of affordable computers. The design and development of a software system which organizes large scale DHCs in an efficient, scalable and robust way for implementing very large scale LB simulations is challenging. In order to avoid that some computers are overloaded and slow down the overall execution, the heterogeneity of computational power should be taken into account. In addition, the failure of one or several computers during the execution of a simulation should not prevent its completion. In the context of this thesis, a simulation tool called LaBoGrid was designed. It uses existing static load balancing tools and implements an original dynamic load balancing method in order to distribute the simulation in a way that minimizes its execution time. In addition, a distributed and scalable fault-tolerance mechanism based on the regular saving of simulation’s state is proposed. Finally, LaBoGrid is based on a distributed master-slave model that is robust and potentially scalable. [less ▲]

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See detailMolecular characterization of embryogenesis in Phaseolus
Abid, Ghassen ULg

Doctoral thesis (2011)

Chez les végétaux supérieurs, l’embryogenèse est une phase clé du développement au cours de laquelle l’embryon établit les principales structures de la future plante. La compréhension des processus ... [more ▼]

Chez les végétaux supérieurs, l’embryogenèse est une phase clé du développement au cours de laquelle l’embryon établit les principales structures de la future plante. La compréhension des processus moléculaires et physiologiques menant à la formation de la graine est donc d’un intérêt agronomique majeur. Chez Phaseolus la caractérisation moléculaire de l’embryogenèse permet de mieux comprendre les mécanismes du développement embryonnaire et de son dysfonctionnement observé chez les hybrides interspécifiques. Cette thèse s’inscrit dans ce cadre et vise à identifier et caractériser des gènes clés impliqués dans le développement de l'embryon chez Phaseolus. Des hybridations interspécifiques ont été réalisées entre l’espèce P.vulgaris L. (cultivar NI637) utilisée comme parent mâle et l’espèce P. coccineus L. (cultivar NI16) utilisée comme parent femelle. Des analyses ont aussi été effectuées sur un mutant obtenu par mutagenèse chimique à l'EMS (Ethyl Méthyl Sulfonate) de graines de la variété BAT93 de P.vulgaris. Une étude histologique comparative a permis de suivre la dynamique de l’embryogenèse du haricot commun à partir d’embryons prélevés 3 à 12 jours après la pollinisation et provenant de plantes normales et déficients dans la production de graines. Les embryons de P. vulgaris se développent plus rapidement par rapport à ceux issus du mutant EMS. Ces derniers présentent des anomalies au niveau de l’embryon et du suspenseur. La caractérisation fonctionnelle de deux gènes candidats MIPS (myo-inositol phosphate synthase) et Sus (sucrose synthase) a été réalisée par RT-PCR quantitative et hybridation in situ suite à une étude spatio-temporelle d’expression de ces deux gènes candidats au cours de développement embryonnaire chez Phaseolus. L’analyse du profil d’expression de ces deux gènes montre qu’ils sont exprimés différemment au niveau des tissus de l’embryon et du suspenseur. L’analyse in silico nous a permis de sélectionner 22 gènes candidats dont nous avons vérifié l'expression au cours de développement de la graine chez Phaseolus. Des variations au niveau de la méthylation de l’ADN ont été déterminées chez les hybrides interspécifiques comparativement à leurs parents. La technique de l’HSS a permis d’isoler des fragments d’ADNs complémentaires différemment exprimés au cours de développement de la graine chez Phaseolus. L’analyse des séquences de ces ADNs complémentaires montre qu’ils codent pour plusieurs protéines intervenant dans le développement cellulaire et embryonnaire, en particulier le "storage protein activator" (SPA), le "pentatricopeptide repeat-containing protein" (PPR) et l’acetyl-CoA carboxylase (ACCase). La caractérisation de ces différents gènes exprimés au cours du développement de la graine, fournit de nouveaux outils susceptibles de mettre en évidence des mécanismes de dysfonctionnement embryonnaire chez le genre Phaseolus. [less ▲]

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See detailOptimal experimental designs for funtional magnetic resonance imaging
Maus, Bärbel ULg

Doctoral thesis (2011)

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See detailLattice dynamics in thermoelectric Zintl phases
Möchel, Anne ULg

Doctoral thesis (2011)

A brief introduction to the thermoelectric effects, the studied materials, and the experimen- tal methods is given in the first chapter. The introduction is not intended to be exhaustive, but only to ... [more ▼]

A brief introduction to the thermoelectric effects, the studied materials, and the experimen- tal methods is given in the first chapter. The introduction is not intended to be exhaustive, but only to summarize important basic information for the reader. The introduction is followed by four chapters dedicated to detailed experimental studies of the lattice dynamics in selected thermoelectric Zintl phases. First, the lattice dynamics in the unfilled and filled skutterudites FeSb3 , CoSb3 , and YbFe4 Sb12 were studied by nuclear inelastic scattering, inelastic neutron scattering, and several macroscopic methods. These studies reveal that FeSb3 exhibits softer Sb bonds than CoSb3 , that the density of phonon states is shifted towards lower energies and the velocity of sound is lower in FeSb3 as compared to CoSb3 . It appears thus that the soft [Fe4 Sb12 ] framework dynamics might play an important role in the thermoelectric properties of filled skutterudites. The observed anomalous temperature dependence of the elastic constants and the rearrangement of the spectral weight of the Yb phonon states in YbFe4 Sb12 can be explained by a change of the Yb valence state with the temperature. Second, the lattice dynamics in the Sr8 Ga16 Ge30 clathrate was investigated by inelastic neutron scattering measurements on a single crystal. We found that several mechanisms contribute to the low thermal conductivity in this system and that the reduction of the heat capacity contribution to the thermal conductivity plays a significant role to the low thermal conductivity, besides the reduction in the phonon lifetime and the phonon group velocity that is related to the guest atom. Third, the lattice dynamics of the Zintl phase Yb14 MnSb11 was studied by inelastic neu- tron scattering and nuclear inelastic scattering measurements. All phonon modes of these complex crystal systems are in a narrow energy range below ∼25 meV and the Debye tem- perature, the velocity of sound and the mean force constants are small compared to those of other thermoelectric materials such as Zn4 Sb3 . By comparing the lattice dynamics in Yb14 MnSb11 and Zn4 Sb3 different mechanisms which lead to the low thermal conductivity in Zintl phases have been identified. Between 300 and 1200 K no softening of the velocity of sound in Yb14 MnSb11 was observed by temperature dependent inelastic neutron scattering measurements, which is in line with its large melting temperature. [less ▲]

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See detailDéveloppement d’un modèle hydrologique sol et zone vadose afin d’évaluer l’impact des pollutions diffuses et des mesures d’atténuation sur la qualité des eaux en Région wallonne
Sohier, Catherine ULg

Doctoral thesis (2011)

Implementation of new European directives in the environmental field and, specially, in the water field, generate a request from policy-makers for news tools able to evaluate impact of measures token in ... [more ▼]

Implementation of new European directives in the environmental field and, specially, in the water field, generate a request from policy-makers for news tools able to evaluate impact of measures token in order to reduce pressures on ecosystems. In this context, the objective of this PhD thesis is to develop a “soil and vadose” hydrological model in order to evaluate impact of diffuses pollutions and mitigation measures on water quality in the Walloon region. The “soil and vadose zone” model of the Walloon region (EPICgrid model) has been developed at catchment scale with an original modular concept on the basis of the field scale “water-soil-plant” EPIC model (Williams et al., 1984). After that the model was validated at field scale and at catchment scale, the EPICgrid model was used to simulate the hydrological behaviour of the Walloon region catchments and to produce environmental indicators for surface water and groundwater bodies of the Walloon region. The simulated fluxes are related to unsaturated or temporarily saturated soils. The simulations are focused, on the one hand, on hydrological balance terms (direct runoff, subsurface fluxes, groundwater recharge, soil moisture variability, actual evapotranspiration) and, on the other hand, on associated fluxes of nitrogen, phosphorus, organic matters and sediments, from agricultural origin. The EPICgrid model was then used to evaluate water quality impact of mitigation measures token in order to reduce agricultural diffuse pollution effect on the quality on surface water and groundwater bodies in the Walloon region. [less ▲]

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See detailEtude de l'activité antifongique des bactéries lactiques isolées de produits alimentaires fermentés et caractérisation de leurs métabolites inhibiteurs
Ndagano, Dora ULg

Doctoral thesis (2011)

Summary: The aim of this present research was to study the antifungal properties of lactic acid bacteria (LAB) isolated from fermented Mill flour and fermented cassava in order to use them for ... [more ▼]

Summary: The aim of this present research was to study the antifungal properties of lactic acid bacteria (LAB) isolated from fermented Mill flour and fermented cassava in order to use them for biopreservation. Antifungal activity of these LAB were assessed in MRS solid medium against food spoilage moulds as Aspergillus niger MUCL 28699, Aspergillus niger CWBIF194, Aspergillus tubingensis MP1 and Penicillium crustosum MY1. Three strains, Lactobacillus plantarum VE56, Weissella cibaria FMF4B16 and Weissella paramesenteroides LC11 were selected among 116 for their strongest inhibitory activity and their broad inhibitory spectrum against food moulds. The 4-fold concentrated supernatant of L. plantarum VE56 and W. paramesenteroides LC11 had the strongest inhibitory activity to compare to W. cibaria FMF4B16. The antifungal activity of the cell-free supernatant was pH dependent and insensitive to proteolytic enzymes action suggesting that the inhibitory activity was due to other compounds than proteins. The identification of antifungal compounds by chromatographic studies highlighted the production of phenyllactic acid by the three strains. In addition, 2-hydroxy-3-methylpentanoic acid and 2-hydroxy-4-methylpentanoic acid were produced by L. plantarum VE56 and W. paramesenteroides LC11. However, the concentration assessed in the supernatant was lower than the minimal inhibitory concentration showing a synergic action of all these produced compounds. The effect of the antifungal supernatant of L. plantarum VE56 and W. paramesenteroides LC11 on Aspergillus flavus NRRL 3357 resulted to an inhibition of conidial development and aflatoxin B1 production which was reflected in decreased gene expression of brlA (conidiophore specific transcription factor) and laeA (global regulator of secondary metabolism). These two bacteria also delayed Penicillium expansum MUCL 14498 conidial development in bread. [less ▲]

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See detailSonia Hajjar Domaine : Human resource management Titre : Status of Female Auditors in Lebanon: Careers and Family Concerns
Hajjar, Sonia ULg

Doctoral thesis (2011)

This research discusses the status of female auditors in Lebanon with a special emphasis on individual career and family concerns. It attempts at investigating the status of female auditors, and at ... [more ▼]

This research discusses the status of female auditors in Lebanon with a special emphasis on individual career and family concerns. It attempts at investigating the status of female auditors, and at pointing out the major hindrances that they face when trying to achieve a balance between career and family life; thus, issues such as organizational, individual, and social factors are discussed. The focus is to discuss the status of female Lebanese auditors through analysis and conclusions drawn from practical experience and to present a model of the issues in relation to certain variables and factors. Questionnaires and interviews were used to collect the data. Results show that the above-mentioned factors, cross-referenced with the glass ceiling, work life balance, and turnover, are combined. Research revealed that many factors mold the status of female auditors in Lebanon. The limitations of the study stem from the fact that no such studies have been conducted in Lebanon and, thus, the literature review was mainly constructed on published research done in the West. Results reveal that the individual Lebanese female auditor is faced with a glass ceiling only because she chose her family over her career, and when she chose to leave the profession (turnover) it was because of her family duties, the long working hours, stress, and work life balance that forced her to make a choice between herself as a career women, or as a mother and wife. The study is aimed at establishing possible relationship between academia, audit profession, and the business market. [less ▲]

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See detailLes cultes de l'île de Cos après le synécisme de 366 avant notre ère. Contribution à l'étude du fonctionnement du polythéisme grec
Paul, Stéphanie ULg

Doctoral thesis (2011)

L’étude des cultes de l’île de Cos vise à discerner les modalités selon lesquelles une cité grecque organise ses relations avec le monde supra-humain. L’exposé est articulé en deux volets complémentaires ... [more ▼]

L’étude des cultes de l’île de Cos vise à discerner les modalités selon lesquelles une cité grecque organise ses relations avec le monde supra-humain. L’exposé est articulé en deux volets complémentaires. La première partie propose une analyse systématique des différents cultes attestés dans l’île, fondée sur l’exploitation de toutes les sources à disposition, épigraphiques principalement, mais également littéraires et archéologiques. Les cultes sont ordonnés selon une répartition géographique, ceux de la cité, puis des dèmes. Le sanctuaire de l’Asclépieion, situé à quelques kilomètres à l’extérieur de la ville de Cos et jouissant d’une cohérence propre, fait l’objet d’un chapitre à part. Cette analyse exhaustive, incluant les nouvelles inscriptions publiées en nombre ces dernières années et encore peu étudiées, permet de pallier une lacune dans la bibliographie actuelle. La seconde partie du travail se conçoit comme une synthèse de cette analyse des cultes et propose une réflexion sur le fonctionnement du polythéisme tel que la cité de Cos permet de le saisir. Le premier chapitre, consacré aux « configurations du panthéon », s’attache à définir, dans la mesure du possible, le profil des divinités qui constituent ce dernier, ainsi que les relations qui se nouent entre elles. L’intérêt d’une telle approche régionale est de pouvoir ancrer ces cultes dans le contexte historique auquel ils appartiennent, et cela se justifie d’autant plus que les panthéons locaux « cristallisaient » les préoccupations des communautés qui les construisaient. Ainsi, on observe qu’un événement particulier de l’histoire de l’île a eu une influence remarquable sur l’organisation des cultes. Il s’agit du synécisme de 366 avant notre ère, qui a vu l’unification des différentes communautés en une seule cité, dont le centre urbain a été fondé sur la pointe nord de l’île. Cette influence résulte notamment en une orientation spécifique conférée à une série de cultes, qui mettent une emphase particulière sur la communauté et sur l’unité de la cité, tels que ceux de Zeus Polieus ou d’Aphrodite Pandamos. En outre, et en dépit de l’ancrage local de cette étude, le recours fréquent à la comparaison avec les panthéons d’autres cités grecques permet d’inscrire largement l’interprétation de celui de Cos sur un plan panhellénique. À côté de cette réflexion sur le panthéon de Cos, un second chapitre se propose d’affiner l’interprétation de certaines procédures sacrificielles, décrites dans les inscriptions et évoquées dans la première partie, et de les mettre en perspective par rapport au reste de la documentation de Cos. Une telle étude contextuelle du sacrifice a l’avantage d’apporter un éclairage complémentaire aux études thématiques plus générales, qui ne permettent guère de remettre les pratiques en contexte. L’acte sacrificiel étant au cœur du système religieux des Grecs et de leur communication avec le monde supra-humain, son étude ne peut être dissociée de celle de la représentation du divin. Ainsi, la manière dont ces actes sacrificiels sont posés est porteuse de sens quant au profil du destinataire ou encore au message précis qui lui était adressé. En conclusion, par les diverses configurations qu’elle met en évidence, qu’elles relèvent de spécificités locales ou de représentations plus largement partagées, l’étude des cultes de Cos permet d’apporter une contribution à notre compréhension du système religieux des Grecs et de son imbrication dans la vie des communautés. [less ▲]

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See detailPhysical modelling of overbank flows with a groyne set on the floodplain
Peltier, Yann ULg

Doctoral thesis (2011)

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See detailA 3D model of ocean biogeochemical cycles and climate sensitivity studies
Mouchet, Anne ULg

Doctoral thesis (2011)

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See detailPhenomenology of supersymmetric neutrino mass models
Vicente, Avelino ULg

Doctoral thesis (2011)

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See detailSupervised Learning for Sequential and Uncertain Decision Making Problems - Application to Short-Term Electric Power Generation Scheduling
Cornélusse, Bertrand ULg

Doctoral thesis (2010)

Our work is driven by a class of practical problems of sequential decision making in the context of electric power generation under uncertainties. These problems are usually treated as receding horizon ... [more ▼]

Our work is driven by a class of practical problems of sequential decision making in the context of electric power generation under uncertainties. These problems are usually treated as receding horizon deterministic optimization problems, and/or as scenario-based stochastic programs. Stochastic programming allows to compute a first stage decision that is hedged against the possible futures and -- if a possibility of recourse exists -- this decision can then be particularized to possible future scenarios thanks to the information gathered until the recourse opportunity. Although many decomposition techniques exist, stochastic programming is currently not tractable in the context of day-ahead electric power generation and furthermore does not provide an explicit recourse strategy. The latter observation also makes this approach cumbersome when one wants to evaluate its value on independent scenarios. We propose a supervised learning methodology to learn an explicit recourse strategy for a given generation schedule, from optimal adjustments of the system under simulated perturbed conditions. This methodology may thus be complementary to a stochastic programming based approach. With respect to a receding horizon optimization, it has the advantages of transferring the heavy computation offline, while providing the ability to quickly infer decisions during online exploitation of the generation system. Furthermore the learned strategy can be validated offline on an independent set of scenarios. On a realistic instance of the intra-day electricity generation rescheduling problem, we explain how to generate disturbance scenarios, how to compute adjusted schedules, how to formulate the supervised learning problem to obtain a recourse strategy, how to restore feasibility of the predicted adjustments and how to evaluate the recourse strategy on independent scenarios. We analyze different settings, namely either to predict the detailed adjustment of all the generation units, or to predict more qualitative variables that allow to speed up the adjustment computation procedure by facilitating the ``classical'' optimization problem. Our approach is intrinsically scalable to large-scale generation management problems, and may in principle handle all kinds of uncertainties and practical constraints. Our results show the feasibility of the approach and are also promising in terms of economic efficiency of the resulting strategies. The solutions of the optimization problem of generation (re)scheduling must satisfy many constraints. However, a classical learning algorithm that is (by nature) unaware of the constraints the data is subject to may indeed successfully capture the sensitivity of the solution to the model parameters. This has nevertheless raised our attention on one particular aspect of the relation between machine learning algorithms and optimization algorithms. When we apply a supervised learning algorithm to search in a hypothesis space based on data that satisfies a known set of constraints, can we guarantee that the hypothesis that we select will make predictions that satisfy the constraints? Can we at least benefit from our knowledge of the constraints to eliminate some hypotheses while learning and thus hope that the selected hypothesis has a better generalization error? In the second part of this thesis, where we try to answer these questions, we propose a generic extension of tree-based ensemble methods that allows incorporating incomplete data but also prior knowledge about the problem. The framework is based on a convex optimization problem allowing to regularize a tree-based ensemble model by adjusting either (or both) the labels attached to the leaves of an ensemble of regression trees or the outputs of the observations of the training sample. It allows to incorporate weak additional information in the form of partial information about output labels (like in censored data or semi-supervised learning) or -- more generally -- to cope with observations of varying degree of precision, or strong priors in the form of structural knowledge about the sought model. In addition to enhancing the precision by exploiting information that cannot be used by classical supervised learning algorithms, the proposed approach may be used to produce models which naturally comply with feasibility constraints that must be satisfied in many practical decision making problems, especially in contexts where the output space is of high-dimension and/or structured by invariances, symmetries and other kinds of constraints. [less ▲]

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See detailMachine Learning Solution Methods for Multistage Stochastic Programming
Defourny, Boris ULg

Doctoral thesis (2010)

This thesis investigates the following question: Can supervised learning techniques be successfully used for finding better solutions to multistage stochastic programs? A similar question had already been ... [more ▼]

This thesis investigates the following question: Can supervised learning techniques be successfully used for finding better solutions to multistage stochastic programs? A similar question had already been posed in the context of reinforcement learning, and had led to algorithmic and conceptual advances in the field of approximate value function methods over the years. This thesis identifies several ways to exploit the combination "multistage stochastic programming/supervised learning" for sequential decision making under uncertainty. Multistage stochastic programming is essentially the extension of stochastic programming to several recourse stages. After an introduction to multistage stochastic programming and a summary of existing approximation approaches based on scenario trees, this thesis mainly focusses on the use of supervised learning for building decision policies from scenario-tree approximations. Two ways of exploiting learned policies in the context of the practical issues posed by the multistage stochastic programming framework are explored: the fast evaluation of performance guarantees for a given approximation, and the selection of good scenario trees. The computational efficiency of the approach allows novel investigations relative to the construction of scenario trees, from which novel insights, solution approaches and algorithms are derived. For instance, we generate and select scenario trees with random branching structures for problems over large planning horizons. Our experiments on the empirical performances of learned policies, compared to golden-standard policies, suggest that the combination of stochastic programming and machine learning techniques could also constitute a method per se for sequential decision making under uncertainty, inasmuch as learned policies are simple to use, and come with performance guarantees that can actually be quite good. Finally, limitations of approaches that build an explicit model to represent an optimal solution mapping are studied in a simple parametric programming setting, and various insights regarding this issue are obtained. [less ▲]

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See detailModelling Transient Air-water Flows in Civil and Environmental Engineering
Kerger, François ULg

Doctoral thesis (2010)

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See detailSynthèse et caractérisation de nanomatériaux fonctionnels siliciques structurés à l’aide de micelles complexes de copolymères séquencés doublement hydrophiles
Warnant, Jérôme ULg

Doctoral thesis (2010)

This study focused on the design and development of new structuring agents of silica constituted of induced and reversible assemblies of original copolymers, the double hydrophilic block copolymers (DHBC ... [more ▼]

This study focused on the design and development of new structuring agents of silica constituted of induced and reversible assemblies of original copolymers, the double hydrophilic block copolymers (DHBC). The first system studied consists of a neutral-anionic DHBC PAPEO-b-PAA ou poly(acrylate methoxy poly (ethylene oxide))-b-poly (acrylic acid). The PAA block is a weak polyacid with a degree of ionization depending on the pH. In aqueous solution and in a right pH range, the association of this copolymer with a weak polybase, an oppositely charged polyamine, such as an oligochitosan, leads to the formation of polyion complex micelles (PIC) with a core/corona structure. These micelles can direct the structure of highly organized inorganic materials with different types of mesostructures. In a second step, by adjusting the conditions of pH, ionic strength, it is possible to "control" the extraction of organic species to get functional porous materials able to trap species of charge opposite to the functionality. Organized materials are obtained because of a favourable balance of the interactions between organic and inorganic species. If a polyamine/silica interaction occurs at the expense of the interaction polyamine/DHBC, the mesostructuring process by the micelles is limited. A neutral-cationic DHBC PEO-b-PDMAEMA poly(ethylene oxide)-b-poly(2-(dimethylamine)ethyl) associated with an anionic PVS poly(vinyl sulfonic acid) polymer can play a dual role in the synthesis of silica materials: firstly managing the growth of silica particles by interacting with the silicates and secondly acting as a structuring agent in association with PVS, confering a mesostructuration to the material. Finally, a very promising approach allowed to encapsulate water-soluble and charged drugs in a material by using as silica complexing agent a complex between the drug and a DHBC. [less ▲]

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See detailLES PRODUCTIONS LITHIQUES DU PALÉOLITHIQUE MOYEN DE BELGIQUE : VARIABILITÉ DES SYSTÈMES D’ACQUISITION ET DES TECHNOLOGIES EN RÉPONSE À UNE MOSAÏQUE D’ENVIRONNEMENTS CONTRASTÉS
Di Modica, Kévin ULg

Doctoral thesis (2010)

LITHIC PRODUCTION FROM THE MIDDLE PALAEOLITHIC OF BELGIUM VARIABILITY OF RAW MATERIAL PROCUREMENT SYSTEMS AND TECHNOLOGIES AS A RESPONSE TO A MOSAIC OF CONTRASTING ENVIRONMENTS Belgium is noted for its ... [more ▼]

LITHIC PRODUCTION FROM THE MIDDLE PALAEOLITHIC OF BELGIUM VARIABILITY OF RAW MATERIAL PROCUREMENT SYSTEMS AND TECHNOLOGIES AS A RESPONSE TO A MOSAIC OF CONTRASTING ENVIRONMENTS Belgium is noted for its many ancient prehistoric sites which are spread over a limited geographic area. Despite its limited size, this area shows important regional contrasts in terms of topographic relief and availability of mineral resources. These factors in conjunction with important regional differences related to the types of sites represented (cave/open air) as well as the proximity and morphology of the available flint make this area favorable for the study of man's relationship with his environment. The connection between the Neanderthal populations and the types of environments encountered constitutes the focus of this study which is divided into four closely associated parts. The first part is devoted to environmental variation starting with the interface between the flint-rich plains of Middle Belgium and the deep valleys of Upper Belgium. Only a few kilometers separate these two contrasting environments. Chronological variations follow because quaternary sedimentation had as much impact on the accessibility of lithic resources as on site preservation. The history of the research from 1829 to the present is also addressed. The motives and constraints of the researchers are responsible for both the abundance of documentary evidence and for the extremely variable quality of these documents. The second part concerns the previously mentioned documentation. Artifacts attributable to the Middle Paleolithic have been recovered from 437 sites : 46 sites (16 major ones) are found in karstic contexts and 391 sites (31 major ones) are open air sites. The distribution of these sites is a direct result of taphonomic processes, circumstances of discovery, and choices made by the Neanderthals themselves. In particular, two environments were favored : the plains which have abundant flint resources and the caves of the Mosan Basin. Prehistoric Man's choice of sites appears to be linked to topographical position : plateaus or cliff tops overhanging small valleys were preferred. Chronological distribution is also examined. It notably shows an abundant documentation from the Beginning of the Weichselian Pleniglacial and an absence of occupation during the Lower Weichselien Pleniglacial It also shows a concentration of archaeological evidences related to the Middle Weichselian Pleniglacial which is very exceptional for Northwest Europe. Based on research to date, Scladina Cave (38.000 B.P.) gives the most recent date for Middle Palaeolithic industries and Betche-aux-Rochtes at Spy (36.000 B.P.) provides the date for the last Neanderthals. The third part consists of a detailed study of ten lithic industries and their environmental context. Several general tendencies were detected in the way Palaeolithic populations adapted their systems of acquisition and exploitation of rocks. Clear variations in the systems of acquisition and exploitation along a northwest/southeast gradient were noted. In Lower Belgium, the use of local flint pebbles was coupled with the importation of nuclei and flakes from Middle Belgium. In Middle Belgium, the available local flint was used almost exclusively. Recourse to other local rocks or to imports was very exceptional. In Upper Belgium, the importation of flint from Middle Belgium in combination with other locally available materials constituted the rule. These variations in the systems of raw material procurement generated diversity in terms of nature, morphology, conditioning, and availability of the nodules chosen by the knappers. These diverse parameters impacted the technical choices of the Neanderthals during the reduction or debitage stage. Other important regional differences were also observed. The sites of Upper Belgium exhibited economic options which manifested in the reduction of blocks (Trou du Diable at Hastière) and in extreme adaptations or manipulation of concepts of reduction such as those recognized in several refittings from Scladina Cave. The sites of Middle Belgium exhibited an extravagant use of the primary material and a strict expression of different concepts : mainly Levallois, also Discoid, and volumetric blade production (gisement paléolithique d'otrange, Obourg Canal). The fourth part is devoted to a discussion of the results and a preliminary comparison to the rest of Europe. The connection of the diversity in lithic productions and the geographic position of the sites is particularly important. Lithic industries from the two occupation layers of Scladina (layers 5 and 1A) present more analogies between themselves than other plenicomtemporaneous sites in different environments (lays 1A of Scladina and WFL of Veldwezelt-Hezerwater). Other factors of variability superimpose themselves in this diverse region : function of the sites, cultural traditions and techniques, palaeoenvironmental variations, chronology. Comparisons with the results obtained from regions bordering Belgium as well as those obtained from greater distances showed some behavioural similarities in southern Europe in environments which evoke aspects of the karst valleys of the Mosan Basin. Translation : Cheryl Roy, Department of Anthropology, Faculty of Social Sciences, Vancouver Island University [less ▲]

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