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See detailContribution au classement des fruits par analyse d'images numériques. Application au tri en ligne des pommes Golden delicious et Jonagold.
Leemans, Vincent ULg

Doctoral thesis (2000)

This work aims to set up an automatic quality fruit grading method based on external characteristics. Special attention is drawn to various defects such as wounds, bruises, physiological diseases, fungi ... [more ▼]

This work aims to set up an automatic quality fruit grading method based on external characteristics. Special attention is drawn to various defects such as wounds, bruises, physiological diseases, fungi attack, etc. Two 3-CCD cameras mounted on a test rig were used for the image acquisition. Golden delicious apples are characterised by their uniform colour. This later was modelled by a multivariate Gaussian distribution and the defect detection was carried out by computing the Mahalanobis distance separating a pixel's colour and the mean colour of the fruit. For Jonagold apples, having a multimodal colour frequency distribution, the defect location was based on a non-parametric model of the fruit colour and on Bayes' theorem. In both cases, the development of an algorithm, taking into account local information, enhanced the segmentation precision. The calyx and stem ends, which appear as defects on the image, were detected by a pattern correlation technique. The segmented areas (poles, defects and over-segmentation zones) were characterised with shape, colour and texture descriptors. The fruit grading into four classes (Extra, A, B and cull) according to European standards is obtained by using a cluster analysis on the segmented regions. The results obtained are favourable and make it possible to envisage the transfer of developed algorithms onto a commercial sorting machine. [less ▲]

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See detailL'homme descend du songe: Approches anthropologiques de l'enfant sauvage
Strivay, Lucienne ULg

Doctoral thesis (2000)

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See detailContribution à l'étude de la gliogenèse - Perspectives physiopathologiques et thérapeutiques
Rogister, Bernard ULg

Thèse d’agrégation de l’enseignement supérieur (2000)

In this work, we demonstrated that neonatal cortical progenitors characterized by an expression of a polysialilated form on NCAM (Neural Cell Adhesion Molecule) are able to differentiate into astrocytes ... [more ▼]

In this work, we demonstrated that neonatal cortical progenitors characterized by an expression of a polysialilated form on NCAM (Neural Cell Adhesion Molecule) are able to differentiate into astrocytes or oligodendrocytes. Moreover, those precursors are able of a phenotypic plasticity as they differnetiate into Schwann Cells when grafted into adult demyelinated lesions. [less ▲]

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See detailGénéalogie de la figure : Médiation esthétique et destination
Servais, Christine ULg

Doctoral thesis (2000)

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See detailAnomalies fonctionnelles des lymphocytes T dans un modèle murin d'infection rétrovirale
Moutschen, Michel ULg

Thèse d’agrégation de l’enseignement supérieur (2000)

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See detailPour une analyse politique des situations migratoires et post-migratoires en Belgique et dans l’Union européenne.
Martiniello, Marco ULg

Thèse d’agrégation de l’enseignement supérieur (2000)

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See detailEntre ville et village. Identité et échange chez les Lamba du Katanga
Rubbers, Benjamin ULg

Master's dissertation (2000)

Ce mémoire se penche sur les relations entre les habitants de la ville de Lubumbashi et ceux du village de Lwansobe pour appréhender la définition des modes de vie citadin et villageois ainsi que la ... [more ▼]

Ce mémoire se penche sur les relations entre les habitants de la ville de Lubumbashi et ceux du village de Lwansobe pour appréhender la définition des modes de vie citadin et villageois ainsi que la mobilité des individus, les échanges commerciaux et la négociation des rapports de parenté entre ces deux espaces. [less ▲]

Detailed reference viewed: 142 (8 ULg)
See detailLes traumatismes de la moelle épinière. Aspects cliniques et expérimentaux.
Martin, Didier ULg

Thèse d’agrégation de l’enseignement supérieur (2000)

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See detailLe Rock progressif anglais: 1966 - 1977
Pirenne, Christophe ULg

Doctoral thesis (2000)

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See detailLes sanctuaires médicaux en Asie Mineure
Nissen, Cécile ULg

Master's dissertation (2000)

Detailed reference viewed: 34 (4 ULg)
See detailComparative imaging of the podotrochlear apparatus in the horse
Schneider, Nicole ULg

Master of advanced studies dissertation (2000)

Detailed reference viewed: 13 (3 ULg)
See detailMaxillary reconstruction by parietal bone grafts before implant placement: a histomorphometrical study
MAINJOT, Amélie ULg

Master of advanced studies dissertation (2000)

Detailed reference viewed: 2 (0 ULg)
See detailSystèmes linéaires et nombres de Carmichael en cryptographie
Lecharlier, Loïc ULg

Master's dissertation (2000)

Detailed reference viewed: 39 (12 ULg)
See detailLe néo-japonisme. La contribution de la calligraphie japonaise à la peinture abstraite d’après-guerre
Bawin, Julie ULg

Master of advanced studies dissertation (2000)

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See detailMots générés par tag systèmes
Nicolay, Samuel ULg

Master's dissertation (2000)

Detailed reference viewed: 13 (0 ULg)
See detailProduction et purification d'une ribonuclease A recombinante chez Escherichia coli
Charlier, Thierry ULg

Master of advanced studies dissertation (2000)

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See detailLinguistics : An Introduction : traduction d'extraits
Renaville, François ULg

Master of advanced studies dissertation (2000)

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See detailEtude de la pollution atmosphérique des porcheries
Degre, Aurore ULg

Master of advanced studies dissertation (2000)

Detailed reference viewed: 19 (2 ULg)
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See detailModeling of the auroral thermal structure and morphology of Jupiter
Grodent, Denis ULg

Doctoral thesis (2000)

The general introduction of this work presents the main characteristics of the planet Jupiter and a detailed description of its magnetosphere. The latter reminds the basic motion of a charged particle in ... [more ▼]

The general introduction of this work presents the main characteristics of the planet Jupiter and a detailed description of its magnetosphere. The latter reminds the basic motion of a charged particle in a magnetic field. It describes the interplanetary magnetic field and its reconnection with the planetary magnetosphere. The notions of corotating field and magnetospheric convection are used to differentiate the Earth and Jovian magnetospheres. Among these differences the interaction with the satellite Io is stressed out as Io provides most of the magnetospheric plasma material. These notions allow to discuss the potential origin of the particles responsible for the Earth aurorae and, by extension, the Jovian aurorae. It is postulated that the auroral particles are related to the presence of field-aligned currents and fields. The main characteristics of the Hubble Space Telescope and of the WFPC2 and GHRS instruments, which were used for this work, are briefly described at the end of the introduction. The first part describes a model simulating Earth views of UV auroral arcs and diffuse emissions in the Jovian north polar region. Simple geometric cases are described to illustrate the dependence of the altitude, atmospheric scale height and central meridian longitude of an idealized auroral morphology seen from Earth orbit. As an application of the simulation model, four images obtained with the WFPC2 camera on board the Hubble Space Telescope are used to determine the characteristics of their auroral (discrete and diffuse) structures. A composite average auroral distribution is built by mapping 10 WFPC2 images from the same dataset. It illustrates the dichotomy frequently observed between a narrow single structure confined to the morning sector, and the multiple arc and broad diffuse emission in the afternoon sector. Location of these structures are given and constrained in a reference frame linked to the GSFC-O6 magnetic field model. This model is then applied to assess the role of the viewing geometry on the auroral far UV color ratio. This value gives the ratio between the intensity measured in an unabsorbed spectral band and the intensity in a methane-absorbed band. The simulated color ratios, obtained from a geometry deduced from images taken with HST, are compared to the color ratio measurements obtained with the IUE spectrograph. We attempt to reproduce the IUE observations by imposing an intrinsic longitudinal dependence of the column of methane above the level of the auroral emission. The second part is devoted to the energy degradation model of the auroral electrons in the jovian atmosphere. It then describes the coupling of this model with a thermal conduction model. The theoretical section includes an introduction on the jovian atmosphere and its confinement in regions characterized by different dynamical and thermal regimes. The notion of hydrostatic equilibrium is reminded and used to establish a pressure-altitude relationship. We describe the electron transport model of Banks and Nagy and the numerical resolution method that we applied to it. The set of cross sections used to quantify the energy loss processes is described along with the numerical treatment of the energy "reapportionment" of the auroral electrons. The vertical thermal profile is calculated from the heat conduction equation. Among the different heat sources we consider H2 dissociation, thermal electron heating, and chemical heating. Other sources, such as the breaking gravity waves, are indirectly accounted for. The heat sinks account for the IR radiative cooling from H3+, CH4 and C2H2. A correction regarding the departure from local thermodynamic equilibrium is applied for these species. In order to calculate the response of the atmospheric structure to the auroral precipitation, the model iteratively solves the diffusion equation for the major constituents. The vertical profiles of the eddy and molecular diffusion coefficients and their connection are addressed. The adopted method for the approximation of the H3+ density in the ionosphere as a function of the auroral activity is presented. The thermostatic role of H3+ in the thermosphere is then discussed. The heat conduction equation, the diffusion equation and the electron transport equations are tightly coupled. The resolution of this set of equations therefore requires an iterative approch for which we describe a strategy meant to limit the convergence speed. The energy degradation model is then applied with different energy distributions to assess the importance of the energy spectrum of the incident electrons for the thermal balance of Jupiter's auroral thermosphere. The values of observable quantities such as the altitude of the H2 emission peak, the IR and UV emissions, the FUV color ratio and temperatures associated with various optical signatures are used to constrain the parameters of these energy distributions. A series of sensitivity tests are carried out to analyse the role of critical parameters such as the value of the eddy diffusion coefficient at the homopause. The third part describes the H2 UV high-resolution spectral generator and the global coupling of the different models. We begin with an overview of H2 far-UV spectroscopy notions that are used in the spectral generator, especially regarding the Lyman and Werner band systems. For the Werner bands, the cascade effect from the E,F state is considered. The coupling of the energy degradation model with the spectral generator is described. In a first stage an unconverged thermal profile is adopted. Three examples are used to illustrate the effect of the electron energy distribution on the spectra. The temperature effect is also highlighted. The H2 temperature is determined from two GHRS spectra. It gives a best fit temperature of 600 K, in disagreement with the temperature predicted by the energy degradation model. The latter predicts an average temperature, weighted by the H2 UV emission profile, of the order of 200 K. It is shown that the use of converged thermal profiles, obtained with the heat conduction equation, does not remove the contradiction. The coupling of the three models (energy degradation, spectral generator, and morphology) is performed in the last section. This coupling reveals a wavelength and a viewing geometry effect on the temperature deduced from the observed spectra. It is shown how these effects impinge on the thermal, density and emission vertical profiles to produce an effective H2 temperature of 600 K in agreement with the temperature deduced from the observed spectra. We finally discuss a possible application of the coupled models that would allow a spectroscopic probing of the jovian thermal profile. [less ▲]

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See detailDetermination automatique de la taille du pas de temps pour les schémas implicites en dynamique non-linéaire
Noels, Ludovic ULg

Master's dissertation (2000)

Ce travail propose une gestion du choix de la durée du pas de temps. Pour ce faire nous choisissons d’utiliser un indicateur de l’erreur d’intégration numérique. La gestion développée s’adapte aux ... [more ▼]

Ce travail propose une gestion du choix de la durée du pas de temps. Pour ce faire nous choisissons d’utiliser un indicateur de l’erreur d’intégration numérique. La gestion développée s’adapte aux différents schémas d’intégration implicites étudiés. Elle garantit une précision sur les résultats obtenus tout en assurant un coût de calcul réduit. Cette stratégie est d’abord validée sur des cas généraux de grandes déformations afin de mettre en évidence son large domaine d’application. Ensuite, elle est validée sur des cas industriels. Pour l’étude de ces cas industriels, la nouvelle gestion du pas de temps est associée à un nouveau critère de convergence ainsi qu’à un nouveau schéma de décision de remise à jour de la matrice d’itération. L’intérêt principal de l’étude de cas industriels est leur nombre important de degrés de liberté ainsi que la variation des phénomènes physiques qui apparaissent au cours du temps. Les intérêts pratiques (gain de temps de calcul, garantie de précision et diminution du nombre de paramètres utilisateur) des nouveaux schémas sont alors clairement mis en évidence. Nous sommes ainsi parvenus à réduire fortement les temps de calcul de ces cas. [less ▲]

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See detailPhénomènes karstiques en roches silicatées non carbonatées. Cas des grès, des micaschistes, des gneiss et des granites en Afrique sahélienne et équatoriale
Willems, Luc ULg

Doctoral thesis (2000)

Cette recherche comprend six parties : 1. Un inventaire des karsts ou des phénomènes assimilés aux karsts en roches non carbonatées silicatées - grès, quartzites, granites, gneiss et schistes. Cet ... [more ▼]

Cette recherche comprend six parties : 1. Un inventaire des karsts ou des phénomènes assimilés aux karsts en roches non carbonatées silicatées - grès, quartzites, granites, gneiss et schistes. Cet inventaire s’appuie sur plusieurs centaines de références bibliographiques. Pour chacune des lithologies, une synthèse des différents processus génétiques proposés par les différents auteurs est réalisée. 2. Un état de la connaissance sur la solubilité de la silice, de l’aluminium et du fer. Cette partie intègre notamment les avancées bio géochimiques réalisées depuis les années 80. Cette partie de la thèse reprend différentes études montrant : • que la silice, l’aluminium et le fer peuvent se retrouver dans des domaines de solubilité identiques notamment en présence d’acides organiques ou inorganiques ; • que ces acides augmentent de façon considérable la solubilité des éléments ; • que ces acides peuvent être générés par des bactéries en milieu anaérobie ; • que ces bactéries peuvent se trouver en grand nombre à grande profondeur dans les roches et dans des milieux anaérobies (les complexes organométalliques solubles peuvent donc voyager sur de grandes distances et non être rapidement détruits comme c’est le cas en surface). L’hypothèse d’une dissolution généralisée de roches silicatées non carbonatées peut donc être envisagée au regard des modèles classiquement proposés pour expliquer la karstification des massifs. 3 & 4. Une étude de différentes formes de surface ou souterraines trouvées dans les formations gréseuses et les métagabbros du Niger occidental ainsi que dans les granites, les gneiss et les micaschistes du Cameroun méridional. Une analyse morphologique détaillée des grottes et autres conduits liée aux données hydrogéologiques, tectoniques et pétrographiques des différents sites est à la base des interprétations génétiques. 5. Une étude de concrétions et enduits siliceux trouvés dans des cavités du Niger et du Cameroun. L’analyse par microscope électronique à balayage, par diffractogramme des rayons X et par mapping compositionnel élémentaire, a été menée afin de préciser les conditions physico-chimiques dans lesquelles certaines cavités ont été générées. Ainsi, pour une des cavités ouvertes dans les granites, les analyses ont montré le rôle probable des bactéries dans la mise en place des karsts. 8. Une synthèse sur la problématique des karsts en roches non carbonatées et sur les conditions de leur développement. Les conclusions principales de la thèse sont : • l’importance de l’érosion chimique dans la genèse des différentes formes souterraines étudiées avec des phénomènes d’érosion mécanique tardifs (tout comme ce qui se passe dans les calcaires) ; • la mise en place d’une karstification initiale à grande profondeur, indépendamment des conditions de surface, peut être en relation avec la faune bactérienne découverte ces dernières décennies à grande profondeur. Si, à l’heure actuelle, de nombreux chercheurs envisagent la karstification à partir d’une altération progressant de la surface vers la profondeur, cette vision des choses peut être en partie erronée. La vitesse d’altération des processus de surface dans des lithologies carbonatées doit entraîner une modification également rapide des formes issues de la profondeur (élargissement des entrées supérieures,...) et masquer l’histoire ancienne de ces morphologies. • la nécessité d’envisager certaines lithologies et leur potentialité en eau sous l’angle de massifs karstifiés. Les nombreux karsts trouvés au Niger occidental et oriental influencent incontestablement l’évolution géomorphologique des paysages tant dans le développement des réseaux hydrographiques que dans la dissection des plateaux. Les lithologies gréseuses sont fort abondantes dans tout le Sahel et ont une structuration similaire à celle de la région de Niamey. On peut donc envisager qu’une grande partie du Sahel est karstifiée. [less ▲]

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See detailEvolution régressive récente de la végétation des tourbières hautes à sphaignes en Haute Ardenne (Hautes-Fagnes, Belgique)
Hindryckx, Marie-Noëlle ULg

Doctoral thesis (1999)

In temperate Europe, intact raised bogs from Northern Germany to the French Massif Central are part of rare postglacial ecosystems that one can consider as natural or very close to the natural state ... [more ▼]

In temperate Europe, intact raised bogs from Northern Germany to the French Massif Central are part of rare postglacial ecosystems that one can consider as natural or very close to the natural state. Unfortunately, many of them have been degraded or highly disturbed by intense human activities. Some of them, however, kept a subintact central part. This is the case for the three big raised bogs situated in the Hautes-Fagnes plateau in Belgium: the fagne Wallonne, the fagne de Clefaye and the Misten raised bogs. Their vegetation belongs to the Vaccinio oxycocci-Sphagnetea magellanici Br.-Bl. & Tx. 43 and Eriophoro vaginati-Sphagnetalia papillosi Tx. 70. But the legal conservation measures are not sufficient to guarantee their protection : in the course of the last 30 years, 10 to 25% of the area covered with intact raised bogs of the Hautes-Fagnes plateau have been degraded, mainly invaded by Molinia caerulea. Although it is important to bring forward such alarming observations, it is more essential to understand exactly the origin of the factors causing the degradation, if suitable measures to thwart the factors that condition them, and try to attenuate if not suppress their harmful effects, and thereby restore the conditions that will enable the natural vegetation from these environments to recover the lost areas. Here are the main objectives of this work: • To highlight the current and recent ecological and phytodynamic consequences of the degradation of the raised bogs; • To identify and date the causes of the degradation that struck the intact parts of the raised bogs present on the Hautes-Fagnes plateau; • To examine the practical management measures in the short-, medium-, and long-term taken in Belgium and abroad in order to restore the natural evolution of the peatlands. Studies of the vegetation The vegetation maps, on a scale of 1/250, indicate that, despite some differences, the degradation phenomenon seems to begin in the same way in the three bogs. We can notice: • an invasion by Molinia caerulea of the intact peat areas (in sometimes very high tussocks) but also its presence, in a more diffuse form, within the -narrowzones of transition and even among typical bog species; • a soil draining, resulting in the proliferation of Ericaceae, especially around relatively intact zones; • the existence of Deschampsia flexuosa, which seems to be linked to rather steep slopes at the edge of zones exclusively colonised by Molinia caerulea,; • the poor representation, both in terms of quality as quantity, of bryophytes; fewer than 10 species of peatmosses occur in these peatlands, where they are often little or ill-developed; • the occupation of peat bogs by relatively exclusive species (Empetrum nigrum, Molinia caerulea and other very thick Ericaceae bushes) which prevent other peat forming communities from developing. The analysis of the vegetation releves taken along three transects shows that the Misten bog appears as the most intact one (or the best preserved one) based on the cover, distribution and vitality of peatmosses, although as indicated by the vegetation map, Molinia caerulea surrounds this raised bog. The fagne de Clefaye peat bog seems much drier and the percentage of peatmosses cover is lower compared to the Misten bog. Some Empetrum nigrum clumps no longer contain any mosses. On the other hand, this bog holds more Sphagnum species than either of the other two bogs investigated. The raised bog of the fagne Wallonne is the most degraded one (at least the north-west part of it). The complexity of the problem composed already the focus of several studies as part of a graduate work. In order to have some idea of the evolution of the vegetation, all the releves which have been carried out along the transects of the three bogs have been the subject of an observation follow-up. Even if six or seven years between the vegetation releves is too short a time to show some significant evolution in a peat bog, the results nonetheless enable to bring to the fore some trends in the evolution of the vegetation present in the main bogs of the haut-plateau, Along the itemised transect, the vegetation of the peat bog seems to be stable and optimal for a peat forming activity typical of an ombrotrophic raised bog, to develop. The northern part of the fagne Wallonne bog shows much more worrying signs of evolution (heaths developing quickly) or signs of degradation of its vegetation (reduction of the number of peatmosses, increasing density of Molinia caerulea, and invasion by Betula alba subsp. glutinosa). The vegetation of the fagne de Cléfaye bog clearly evolves towards a drier phase (high intensification of heaths development) without leading to the rarefaction of peatmosses. We wanted to put these evolutional studies in a broader context and take advantage of previous studies carried out on the haut-plateau in similar conditions. Despite the interpretation difficulties that were met, the different studies allow to assert that there has been a quick change in the vegetation of the raised bogs in the last forty years. Are we in the presence of a Natural evolution or a degradation process? The ground cover in the northern part of the fagne Wallonne bog shows obvious signs of degradation. The southern part of it as well as the fagne de Cléfaye bog show instead an evolution of the vegetation towards a stage heavily composed of heaths, with, however, a strong reduction of peatmosses. The Misten bog seems to experience the slowest evolution: is this a former evolution stage of the vegetation or is the balance achieved? Hydrological studies In natural conditions, the fluctuations of the water table of an ombrotrophic bog on a one-year scale remain modest: about 10 centimetres from one season to the other. It is thus interesting to check if the variations of the water table level are of the same nature in different spots of the three studied bogs or if the alteration phenomena, that are visible at the vegetation level and are present on the three bogs also appear in the behaviour of water tables at the surface of these bogs. Based on the follow-up of the 148 dip wells scattered on the three peat bogs, it appears that the Misten bog water table level is the most stable one. This means that the peat forming species, present on the fagne de Clefaye and especially in the studied part of the fagne Wallonne, are constantly subjected to fluctuations (which are sometimes significant) of the water table level. Now, if the peatmosses usually spread according to a humidity gradient, some of them tolerating a greater distance of the water table level than others, it does not mean however that a same species can survive such variations. The dip wells maps and the 3-dimensional representations of the water table enable to better understand the spreading of the vegetation at the surface of the bog. But these measures also reveal the presence of pedological phenomena, natural or not, such as drainage ditches, outlet, exploitation scar, fissures in the peat mass and others, that very much influence the variation of the water table level and thereby the surface vegetation in the short-, medium-, and long-term Paleo-ecological studies In order to better understand the evolution of raised bogs and especially try to find signs of their degradation, it is essential to investigate the peat lying right under the present vegetation. All the steps that have been set about within this context tried to answer the following questions: Is there a link between the vegetation present at the surface and the recent peat composition lying right under? Is there a link between the recently formed peat composition and the water table level observed on the peat bog? Are the microfossils, that are contained in the peat, affected by variations of the water table? Can we draw differences in the composition of the peat according to how far the boring has been carried out from the current active central zone of the peat bog? It clearly appears that the composition of the peat varies according to the type of present vegetation under which the sample was taken and the range of fluctuations of the water table level recorded on this spot. On the Misten peat bog, the palynological study of peat borings 10 m away from one another allowed to show that peat layers representing the same paleobotanical event(s) do not have the same thickness in each boring and can even be absent. In the same way, at a constant rate of pollen, the accumulation speed of the peat is higher in the bog centre compared to its margins. If one considers a same paleo-botanical event, and thus a same period of time, one can see that the pollen concentration is inversely proportional to the thickness of the peat. Two distinct parts are visible on the borings of the Misten peat bog surface: the upper part, the most recent one, characterised by the influence of the topographic position of the boring on the peat forming speed; the lower part, the oldest one, in which the influence is less pronounced. Thanks to different dating techniques (l4C, pollen concentrations and reference borings), this boundary between the two parts can approximately be dated back to the middle of the 14th century. This phenomenon should be related to an anthropogenic phenomenon rather than to a climatic one, given the short distance separating the borings. It would rather be the result of the manual exploitation of the peat than the harmful effects of the Eupen ditch which was dug much later (1774). A lot of microfossils, identifiable or not, present in the borings (rhizopodes, conidia ...) can doubtless be used as degradation indicators. Of course, these studies need to be deepened and systematised before going any further. What emerges especially from these studies is that when one undertakes regeneration attempts on a peat bog, one should not only take the present vegetation and hydrological parameters into account, but also the peat structure and composition, in at least the upper part of the deposits. Research and management Although acting on the current evolution of the Belgian bogs appears essential in order to prevent them from disappearing, it is clear that restoration measures that were appropriate elsewhere, cannot be applied to other areas without some thorough knowledge of the ecological parameters that govern them. The obvious result of this work is that the scientific follow-up of the management measures that have been taken is not only imperative, but that prior study measures of the sites and their characteristics are indispensable. This type of study is heavy because it requires an important investment from the researcher and often causes a lot of damage to the studied flora and fauna. However, these studies are necessary to understand the peatland systems and should even be complemented by further studies (lysimetric, structural or chemical...) . The standardisation of the data gathering system, the improvement of the information techniques and the management of the results organised in a way that allows all the researchers to consult them should contribute towards some lightening of the work. The computer science and the miniaturised electronic technology could improve the efficiency of the measures implemented, thereby benefiting the researcher and the reserve. Given the implied advanced technologies, these modern studies and data gathering processes would be expensive but it is cheap in comparison to the costs of the heavy works that are to be undertaken in the hope of preserving the raised bogs. Moreover, such a preparation of management measures can only improve their efficiency. If, despite all the efforts, the preservation of the jewels of the state nature reserve of the Haute-Fagnes is jeopardised, these studies will at least allow to go further in the understanding of the raised bogs systems. [less ▲]

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See detailLes sensibilités territoriales
Schmitz, Serge ULg

Doctoral thesis (1999)

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See detailLa presse quotidienne belge francophone face au conflit social des Forges de Clabecq. Du pluralisme précaire à l’uniformité idéologique
Geuens, Geoffrey ULg

Master's dissertation (1999)

The journalistic coverage of the social struggle of the Forges de Clabecq was characterized by the growing development of stereotypes which were supposed to describe the very singular personality of the ... [more ▼]

The journalistic coverage of the social struggle of the Forges de Clabecq was characterized by the growing development of stereotypes which were supposed to describe the very singular personality of the trade unionist leader. Populist, extremist, dictator, gangster or even guru, the journalistic figures of the proletarian leader followed one another throughout the conflict. This growing criminalization of the social movement is explained by the intensity of the political stakes of this affair but also by the deep ignorance of the working-class in the case of journalists who belong to the middle class. [less ▲]

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See detailMultitude et pouvoir : approche des pensées politiques de Spinoza et Hobbes
Herla, Anne ULg

Master's dissertation (1999)

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See detailLe japonisme en Belgique : l'influence de l'ukiyo-e sur l'affiche art nouveau
Bawin, Julie ULg

Master's dissertation (1999)

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See detailINFERNET : A neurocomputational model of binding and inference
Sougné, Jacques ULg

Doctoral thesis (1999)

We know that color and form are processed in distinct areas of the human brain. This information must somehow be brought together. How the brain might achieve these colorform associations, as well as all ... [more ▼]

We know that color and form are processed in distinct areas of the human brain. This information must somehow be brought together. How the brain might achieve these colorform associations, as well as all other associations of this type, is one of the central themes of this dissertation. When looking at a field of poppies on a sunny day, how can we correctly associate the color red with the poppies, green with the grass, and blue with the sky, while avoiding associating the color red with the grass and the color blue with poppies? How can we associate the perception of red poppies with the name “red poppy,” and with its superordinate category “flower?” A red poppy is composed of several features, like its shape, color, texture, etc. How might a cognitive system bind these features to build a coherent whole? If we see Louise picking a red poppy, how can we correctly associate Louise with the picker and the red poppy with the picked object, without making the opposite and incorrect association? These associations may seem easy to us, but how does the brain achieve them? How a cognitive system binds a set of features together, associates a filler with a role, a value with a variable, an attribute with a concept, ... is what we mean by “the binding problem.” This thesis focuses on the neurobiological processes that enable connectionist cognitive systems to display binding abilities, on the constraints that affect the binding process, and on the cognitive consequences of these constraints. To study these processes, we developed a computer model of them. This method forces a detailed and unequivocal description of processes used by the simulation. This method is also a powerful means of generating new hypotheses. In this study we attempt to link psychological processes with the neuronal constraints that act on brain functioning. The brain is composed of approximately 10 billion highly interconnected neurons. To achieve binding it is necessary for neurons to communicate with each other because it has been shown that different aspects of a perceived object are not processed in the same cortical areas. Therefore, there must be a means for binding neurons responding to each of these different aspects. The neurons responding to the color red, to the object’s shape, and to its name must be linked to produce a coherent whole representing the red poppy. Neurons are connected by synapses. The functioning of these connections is constrained by the architecture of the brain and by the process of signal transmission. A particular neuron is connected to a relatively small set of other neurons. Therefore, communication between any two neurons generally requires a chain of transmission through intermediate neurons. A pre-synaptic neuron has an effect on another neuron (called the post-synaptic neuron) only if the pre-synaptic neuron emits an action potential (i.e., if it fires). As a consequence, this brief polarization, which last a few milliseconds, results in a modification of other neurons' firing potential. Transmission efficiency depends on the strength of the connecting synapses and the state of the post-synaptic neuron. When a neuron emits an action potential, it is completely insensitive to incoming signals for a short period, then its sensitivity slowly increases. A single pre-synaptic cortical neuron cannot alone provoke the post-synaptic neuron firing. This post-synaptic neuron must receive convergent and more or less synchronized signals from many synapses in order to fire. These neurobiological properties of neurons and neuronal firing constrain the way in which the brain can achieve binding. Among the various hypotheses of how this could be done, we chose synchronization of action potentials for our model. In the red poppy example, neurons responding to the color red will fire in synchrony with those responding to the shape of the flower and to the name “red poppy.” This particular synchronized cluster corresponding to “red poppy” must be temporally distinguished from the cluster responding to “green grass.” Numerous neurobiological studies seem to confirm this action-potential synchrony hypothesis. They show that synchronization involves a particular timing precision and occurs at a particular oscillation frequency. This oscillation requires participating neurons to fire repeatedly and rhythmically for a particular period of time. These properties of firing timing and duration have been implemented in a computer simulation called INFERNET. This artificial neural network uses integrate-and-fire nodes (artificial neuronlike elements). These nodes fire at a precise moment and transmit their activation, with a particular strength and delay, to nodes connected to them. When the potential of the node reaches a particular threshold, it emits a spike. Thereafter, the potential is reset to a resting value. As with real neurons, this node will then be completely insensitive to incoming signals for a short period, after which its sensitivity will slowly increase. INFERNET solves the binding problem by means of oscillation synchrony. Symbols are represented by clusters of nodes firing in synchrony. Fillers are also bound to their roles by synchrony. This synchronous activity defines a window of synchrony i.e., an interval during which the required nodes fire. This time interval takes neurally plausible values. Object discrimination is achieved by a succession of windows of synchrony. Bindings are maintained in memory by the use of particular oscillations. The rhythmic activity and the synchrony precision constrain the number of distinct entities that the system is able to maintain in memory. This represents the short term memory span of INFERNET. We show that this span is comparable with human short term memory span. The limited number of windows of synchrony also constrains predicate representations. This prediction is tested on human participants. If there are too many windows of synchrony, these will interfere with each other. In addition, binding strength decreases with time. These two properties explain why the short-term memory of INFERNET displays primacy and recency effects similar to those observed in humans. Bindings in INFERNET are also constrained by the number of intermediate steps required for particular role nodes to enter into synchrony with the filler nodes. This constraint is shown to provided a plausible explanation of various differences human reasoning. The last INFERNET constraint concerns multiple instantiation. This problem arises in connectionist networks as soon as a symbol has to be simultaneously used twice in different ways. Since INFERNET’s short term memory is the transient activation of parts of long term memory, it cannot make multiple copies of a symbol, in the same way, for example, that a symbolic system does. The INFERNET solution to the multiple instantiation problem involves superposition of different node oscillations. This process is constrained by the refractory period of the nodes. A number of simulations with INFERNET and experiments on humans show that this solution is psychologically plausible. Multiple instantiation is also shown to be a plausible explanation of certain similarity effects in short term memory. INFERNET is also shown to be capable of symbolic processing with using neurologically and psychologically plausible mechanisms that have the advantages of generalization and noise tolerance found in connectionist networks. Finally, under certain circumstances, noise is shown to enhance INFERNET’s processing capabilities. [less ▲]

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See detailNeurotransmission et oligodendrogliogenèse
Belachew, Shibeshih ULg

Doctoral thesis (1999)

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See detailDas Drei-Körper-Coulombproblem unter periodischem Antrieb
Schlagheck, Peter ULg

Doctoral thesis (1999)

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See detailInvestigation of Nonlinear Aeroelasticity
Dimitriadis, Grigorios ULg

Doctoral thesis (1999)

The investigation of nonlinear aeroelastic phenomena is becoming increasingly important to the aerospace community. The existence of structural and aerodynamic nonlinearities in aircraft has always been ... [more ▼]

The investigation of nonlinear aeroelastic phenomena is becoming increasingly important to the aerospace community. The existence of structural and aerodynamic nonlinearities in aircraft has always been acknowledged but, it is only mainly with the advent of modern digital computers that their investigation has become possible. Additionally, aircraft control systems are becoming increasingly nonlinear with the introduction of Active Control Technology. The effects of these nonlinearities on the dynamic response of aircraft have created the need for further research into the modelling, identification and prediction nonlinear aeroelastic systems. This thesis deals with four aspects of nonlinear aeroelasticity. Firstly, the effect of the common industrial approach to nonlinearity, i.e. that of linearisation, is investigated. Six flutter prediction methods for linear aircraft are tested and compared on linear and nonlinear mathematical models of aeroelastic systems. The performances of the methods on linear systems are evaluated and compared. Subsequently, their predictions predictions when applied to nonlinear systems are assessed. Secondly, the dynamic response of nonlinear aircraft is investigated by means of the Harmonic Balance method and the direct integration of the nonlinear mathematical model. Emphasis is given to the explanation of the appearance of Limit Cycle Oscillations as Hopf bifurcations and on the control and suppression of these oscillations by means of a feedback control system. The chaotic vibration of nonlinear aeroelastic systems is also investigated by means of Poincare diagrams and Lyapunoff exponents. Thirdly, the identification of nonlinear aeroelastic systems is considered. Identification of aeroelastic systems is important since, especially in the case of structural nonlinearities, it is often not known whether an aircraft is linear or not and what nonlinearities it may contain until it is tested, either on the ground (Ground Vibration Testing) or in the air (Flight Flutter Testing). An existing nonlinear system identification method is compared to an approach developed during the course of the present project. The two techniques are applied to a nonlinear mathematical aeroelastic system and to a set of nonlinear input-output data obtained from an experimental system. Both methods were found to be able to deal with both systems with varying degrees of success. Finally, the gust response of nonlinear aircraft is investigated with particular emphasis on the calculation of gust design loads. Turbulent gust clearance is a very important part of any airworthiness testing procedure. Until recently, the linear assumption was considered adequate by the requirements however, there is a current shift towards setting new requirements that take into account nonlinear phenomena. Eight gust load prediction methods for nonlinear aircraft(both stochastic and deterministic) are applied to a simple and a more complex nonlinear mathematical aircraft model. The performance of the methods is assessed with respect to both accuracy and computational efficiency. [less ▲]

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See detailLes adénomes somatotropes: etude clinique, biologique et neuroradiologique portant sur 85 cas d'acromégalie suivis à l'Hôpital de la Timone.
VALDES SOCIN, Hernan Gonzalo ULg

Master of advanced studies dissertation (1999)

Introduction Selective acromegaly for acromegaly may have a wide range of remission rates, ranging from 40 to 80% in published series. These heterogeneous results rely not only on the surgeon experience ... [more ▼]

Introduction Selective acromegaly for acromegaly may have a wide range of remission rates, ranging from 40 to 80% in published series. These heterogeneous results rely not only on the surgeon experience, but also depend on the use of different biochemical remission criteria. Aim of the work The first part of this study is to evaluate clinical, biochemical and radiological data in a consecutive series of 85 patients diagnosed with acromegaly and followed-up by the endocrine team of Prof Jaquet in La Timone University Hospital (Marseille, FRANCE). The aim of the second part of this study is to settle a predictive model of surgical remission , after univariate and multivariate analysis of this clinical, biochemical, radiological and pathological data. Methods Biological criteria of acromegaly surgical remission included: normal IGF1 values according to age and sex, mean GH values <2µg/L and GH<1µg/L after 75g OGTT. In mixed somatotroph adenomas, remission criteria also included prolactin and alpha subunit hypersecretion normalization at last follow up. Results The first part of the study included 85 acromegalics (39 males, 46 females). Mean age at diagnosis was 43,5 years (range 13-68) and mean delay of acromegaly diagnosis was 6,2± 4,7 years.Mean follow up was 29 ±32 months. Among the 85 patients: 52/85 had headaches, 33/80 had a visual impairment (scotomas= 22, quadrantopsias= 2, hemianopsias= 9). Mean hormonal values at diagnosis were: GH=66,5µg/L (range 1-1730), IGF1=769 (range 300-1900 µg/L), PRL=27,3 µg/L (range 9-130, n=67), alpha subunit=4,4 UI/L (range 0,2-60). Pituitary MRI identified 3/19 microadenomas (frontal diameter<10 mm) invading cavernous sinus and 49/66 macroadenomas (frontal diameter equal or > 10 mm) with invading features. Frontal diameter had a good correlation with cavernous sinus invasion (r=0,48 , p<0,01) and sphenoidal sinus extension (r=0,46,p<0,01). GH hypersecretion had a good positive correlation with tumoral diameter (r=0,46 , p<0,01). In the second part of the study, there were 72 acromegalic patients that underwent transphenoidal surgery by the same neurosurgeon (Prof F. Grisoli), with a mean post surgical follow up of 26 months. Using astringent biochemical remission criteria, there were 27 patients (38%) in remission and 45 patients not cured. In univariate analysis none of the following criteria was predictive of remission: age, sex, headaches, visual disturbances, adenoma immunostaining. Pathological data included: 29 GH adenomas, 18 mixed GH/alpha SU, 12 mixed GH/prolactin, 11 GH/prolacti/alpha SU and two mixed GH (with TSH and/or LH staining). In univariate and multivariate analysis MRI radiological signs of invasion (carotideal extension) and mean tumoral diameter>22 mm independently predicted surgical failure (p<0,0001 and p=0,00054 respectively). Conclusions In this series GH nadir <1 µg/L is highly specific (89%) as an early surgical remission criteria (day 8) , whereas normalization of IGF1 is not predictive. Using astringent biochemical remission criteria, only 38 % of patients were in remission. Our multivariate predictive model identified MRI radiological cavernous sinus invasion and tumor diameter as main failure presurgical predictive factors.In GH tumors which diameter was >30 mm, surgical failure was 100%. Clinicians should integrate these parameters when evaluating surgical treatment in acromegaly. [less ▲]

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See detailConception d’un catalogue des stations dans le cadre de la gestion intégrée des forêts hygrophiles : application à l’aulne glutineux (Alnus glutinosa (L.) Gaertn.) en Région wallonne
Claessens, Hugues ULg

Doctoral thesis (1999)

The present study aims at conception of a site classification wich contains most of the usefull information for forest integrated management. It has been applied to humid forests of Wallonia, specially ... [more ▼]

The present study aims at conception of a site classification wich contains most of the usefull information for forest integrated management. It has been applied to humid forests of Wallonia, specially related to black alder, indigenous tree of those sites, but slightly known and under-valorized. After the presentation of some ecological and silvicultural aspects of black alder related in the litterature, we proceed to review site classification, productivity estimation and site productivity evaluation methods. Then, we relate the ecological caracterization of the 166 alder sites of the sampling, with humid sites specific variables, espacially in relation to the phreatic water. Those descriptions allow us to establish a site-classification of the humid forest sites with alder. In the same time, we proceed to the elaboration of site index curves, to the stands productivity estimation and to the analyse of the dominant girth evolution from dendrometric data collected on 106 of the alder sites. Those analysis allow us to evaluate the black alder sylvicultural potentialities. Using the results of the 2 studies, we analyse the site productivity in order to evaluate sylvicultural potentialities of each site type of the classification, and to contribue to the knowledge of alder autecology in Wallonia. In the last chapter, we develop a practical application for the humid forests of the Arden : the « site types catalogue » wich presents ecological fonctions, and sylvicultural potentialities for each site type. This constitue a modern tool of integrated management tacking account of all fonctions and services produced by the forest. [less ▲]

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See detailSur la nature de la variabilite spectrale et photometrique periodique d'etoiles Wolf-Rayet apparemment isolees
Morel, Thierry ULg

Doctoral thesis (1999)

Il est depuis longtemps suspecté que les étoiles Wolf-Rayet apparemment isolées présentant des variations périodiques dans le profil de leurs raies spectrales, en photométrie ou en polarimétrie ... [more ▼]

Il est depuis longtemps suspecté que les étoiles Wolf-Rayet apparemment isolées présentant des variations périodiques dans le profil de leurs raies spectrales, en photométrie ou en polarimétrie sont associées à un compagnon dégénéré (étoile à neutron ou trou noir), et constituent ainsi une phase évolutive dont l'existence, bien que prédite par les modèles évolutifs des systèmes binaires massifs rapprochés, n'a pas encore été catégoriquement confirmée observationnellement. Cependant, de récentes études ayant trait à la variabilité spectrale des étoiles OB laissent émettre quelques doutes quant à la pertinence de ce modèle, en démontrant que des vents largement asphériques peuvent se développer dans les étoiles de type précoce. Le scénario alternatif serait donc de considérer que la variabilité périodique observée n'est pas due à la présence d'un compagnon dégénéré affectant la structure à grande échelle du vent de l'étoile Wolf-Rayet, mais est au contraire induite par la modulation par rotation d'un vent nettement anisotropique. Cet ouvrage présente les résultats d'un vaste programme d'observations spectroscopiques et photométriques (généralement simultanées) se proposant de lever l'ambiguïté sur la nature précise des étoiles Wolf-Rayet apparemment isolées dont la périodicité des variations est. soit depuis longtemps établie (WR 6), soit suspectée (WR 1, WR 134, WR 136). Notre étude a permis de confirmer l'existence d'une périodicité de 2.3 jours pour l'étoile WR 134. En outre, nous présentons des arguments mettant en doute l'éventuelle association de WR 6 et WR 134 avec un compagnon dégénéré. Alternativement, nous proposons que la variabilité périodique observée serait plutôt induite, à l'instar de nombreuses étoiles OB, par la rotation de structures azimutalement étendues dans le vent. Ce modèle est plus à même d'appréhender certains aspects de la variabilité, notamment la nature globalement différente du patron de variabilité selon l'époque d'observation, le caractère périodique des variations présentées par les raies spectrales formées à proximité du coeur stellaire, ou encore la causalité des variations affectant les parties internes et externesdu vent. Cette assertion est également supportée par la déficience de rayons-X observée dans le contexte d'une accrétion du vent stellaire par un objet dégénéré. La similitude des variations spectrales de l'étoile WR 1 avec celles des étoiles précitées laisse présumer qu'une variabilité de nature cyclique pourrait éventuellement être révélée dans un proche avenir. Dans ce cas de figure, nos données semblent imposer une limite inférieure de 5 jours pour une quelconque périodicité. Le cas échéant, ces structures à grande échelle dans le vent des étoiles WR 6 et WR 134 doivent probablement leur formation à une activité photosphérique dont la nature précise reste à déterminer. L'existence de pulsations radiales ou non radiales du noyau, ou de structures magnétiques (``photosphériques'' ou plus vraisemblablement d'origine fossile) pourrait néanmoins être à l'origine de ce phénomène. [less ▲]

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See detailDNA repair mechanisms: implication in cancer
Habraken, Yvette ULg

Thèse d’agrégation de l’enseignement supérieur (1999)

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See detailDetermination of critical current in bulk high temperature superconductors by magnetic flux profile measuring methods
Vanderbemden, Philippe ULg

Doctoral thesis (1999)

In this thesis, the emphasis is placed on determining the critical current density in bulk high-temperature superconductors by magnetic flux profile measuring methods. The thesis involves three different ... [more ▼]

In this thesis, the emphasis is placed on determining the critical current density in bulk high-temperature superconductors by magnetic flux profile measuring methods. The thesis involves three different aspects : a brief theoretical investigation of the flux profile methods, the practical realization of an experimental set-up intended for measuring such profiles and a discussion of flux profile measurements in several bulk high-temperature superconductors. [less ▲]

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See detailAnalyse des performances instrumentales du télescope spatial EIT
Defise, Jean-Marc ULg

Doctoral thesis (1999)

Not Available

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See detailBases neurobiologiques des comportements d’alcoolisation: implication des acides aminés neuro-excitateurs et neuro-inhibiteurs
Quertemont, Etienne ULg

Doctoral thesis (1999)

Les théories traditionnelles qui essaient d’expliquer le phénomène d’addiction rencontrent généralement de grandes difficultés à rendre compte de deux particularités importantes de cet état de ... [more ▼]

Les théories traditionnelles qui essaient d’expliquer le phénomène d’addiction rencontrent généralement de grandes difficultés à rendre compte de deux particularités importantes de cet état de pharmacodépendance: le caractère compulsif de la consommation de drogue et la très grande fréquence des rechutes parfois très longtemps après le sevrage. Les théories de l’apprentissage par conditionnement apportent une solution originale à ces questions non résolues. En effet, de nombreuses expériences animales ont démontré que des stimuli environnementaux associés de manière répétée à l’administration de ces drogues peuvent acquérir le statut de stimuli conditionnés capables d’induire à eux seuls certains effets physiologiques et comportementaux spécifiques. On a de plus suggéré que ces réponses conditionnées sont responsables du déclenchement des comportements compulsifs de recherche de drogue et participent dès lors aux rechutes dans sa consommation incontrôlée. Parmi les drogues addictives, l’alcool est probablement la substance la plus difficile à étudier. En effet, sa simplicité moléculaire lui permet paradoxalement d’affecter tous les systèmes de neurotransmission cérébrale. Il est donc difficile d’identifier clairement les bases neurochimiques des différents effets psychotropes de l’alcool. D’autre part, la littérature scientifique confirme également le rôle des apprentissages par conditionnement dans le maintien de la consommation d’alcool et dans l’alcoolodépendance. Bien que l’importance des réponses conditionnées à l’éthanol est maintenant reconnue, les bases neurochimiques de ces effets conditionnés sont encore méconnues. Le présent travail est donc destiné à faire le point sur les connaissances actuelles des bases neurochimiques et comportementales de la consommation d’alcool et de l’addiction alcoolique. Plus particulièrement les neurotransmetteurs acides aminés ont fait l’objet d’investigations expérimentales destinées à élucider leur rôle dans les effets conditionnés à l’éthanol. [less ▲]

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See detailComportement éléctrochimique du C60 et du C70 en milieu aqueux
Richel, Aurore ULg

Master's dissertation (1999)

The electrochemical behavior of C60 and C70 has been investigated either in organic media or in water, using notably platinium ultramicroelectrode as the working electrode. The differences between the ... [more ▼]

The electrochemical behavior of C60 and C70 has been investigated either in organic media or in water, using notably platinium ultramicroelectrode as the working electrode. The differences between the redox potentials of C60 relative to C70 indicate that it is easier to add electrons to C70 and its anions compared to the counterparts of C60. In the second part of the work, the solubilisation of C60 has been achieved using cyclodextrine or triton X-100. The determination of the amount of C60 per micelle was investigated using UV-Visible spectroscopy. [less ▲]

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See detailDynamique de l'adaptation au temps et modèle de l'horloge interne
Ferrara, André ULg

Doctoral thesis (1999)

Detailed reference viewed: 36 (8 ULg)
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See detailModifications fonctionelles et tissulaires induites par la préservation et la reperfusion des greffons pulmonaires
Detry, Olivier ULg

Doctoral thesis (1999)

The lungs are organs whose sensitivity to ischaemia and reperfusion is well known. In a rabbit model of lung ischaemia, we showed that the cold ischaemia longer than 6 hours is accompanied by a ... [more ▼]

The lungs are organs whose sensitivity to ischaemia and reperfusion is well known. In a rabbit model of lung ischaemia, we showed that the cold ischaemia longer than 6 hours is accompanied by a significant reduction in tissue contents in vitamins E and C, two important protectors against the lesions appearing at the time of ischaemia and the reperfusion (Pincemail 1999). Moreover, lungs are different from the other transplanted organs by the importance of a fragile structure, the alveole, zone of exchange between the alveolar air and the capillary blood. It was shown that among the alveolar cells, the type II pneumatocytes, secreting the surfactant, is of primary importance for the post-transplant function. It was shown that the quality of surfactant decreases after conservation and reperfusion of the lungs, and that, in vitro, the effectiveness of surfactant continuously decreases with the prolongation of the duration of ischaemia (Erasmus 1994). Moreover the administration of surfactant before the pulmonary reperfusion improves the postoperative function of the grafts in the rat (Erasmus 1996). It is known that, if all the pulmonary cells contain mitochondria, more than 50% of the mitochondria isolated from lungs come from type II pneumatocytes (Fisher, 1976). We chose to study the mitochondrial respiratory function of these important alveolar cells for the pulmonary function after ischaemia and reperfusion. In this work, we developed a porcine model of ischaemia (hypo- and/or normothermic) and of normothermic reperfusion. This reperfusion was accompanied by a postoperative non-function, objectified by aerodynamic and hemodynamic parameters, as by the appearance of pulmonary oedema. This non-function was observed after 24 hours a hypothermic ischaemia, which is incompatible with a normal function of the pulmonary grafts in clinical transplantation. The reperfusion with a solution of Krebs-Henseleit bicarbonate remove any immunological artefact and any influence of the circulating blood cells in the pulmonary lesions appearing at the time of the reperfusion. On the other hand, this solution is different from blood to a significant degree, by not containing protectors against the production of free radicals at reperfusion. It is thus possible that our model exacerbates this production of free radicals, more especially as the lung is a tissue particularly rich in polymorphonuclear cells. In this model, we could show that after 24 hours of cold ischaemia the mitochondria underwent a moderate deterioration of the oxidoreductases but without decrease in the effectiveness of oxidative phosphorylation, decrease that could be demonstrated after 48 hours of cold ischaemia. These lesions are comparable to the mitochondrial lesions that we had observed after cold ischaemia of rabbit kidney (Willet 1995). After reperfusion, the mitochondrial lesions are more severe, with a decrease in the effectiveness of oxidative phosphorylation. Concerning normothermic ischaemia, the first 30 minutes did not cause significant mitochondrial lesions. These results at least corroborate the literature data on the relative good pulmonary tolerance to normothermic ischaemia, explained in theory by the persistence of oxygen in the airways and thus of the persistence of aerobic metabolism in spite of the circulatory arrest. For the other organs, the circulatory arrest implies anoxia, that is not really the case of lung, as oxygen is present in airways. Pulmonary transplantation could thus profit from an increase in graft pool available by harvesting lung graft from non-heart beating donors. After 45 minutes of normothermic ischaemia, mitochondrial oxidative phosphorylation dysfunction appears, related to a significant deterioration in the ATP synthase function. These results confirm that the cellular metabolism is then disturbed by the appearance of cellular anoxia because of the progressive consumption of oxygen present in the alveoles, or of the substrates necessary to the cellular metabolism. The description and the discussion of the importance of these mitochondrial alterations in the genesis of lung graft dysfunction after transplantation must be integrated with the very broad framework of the disturbances appearing at the time of tissue ischaemia and reperfusion. From our study it comes out that hypothermia at 4°C protects effectively the pulmonary mitochondrial function since significant deteriorations do not appear before 24 hours of hypothermic ischaemia. To determine if mitochondrial deteriorations appearing after normothermic reperfusion are the cause or the consequence of the non-function of the lung appears difficult. On the other hand the lesions appearing after 45 minutes of normothermic ischaemia deserve in an unquestionable way a later study, with evaluation of the mitochondrial function after circulatory arrest in normothermy (30 and 45 minutes) and normothermic reperfusion, and with evaluation of the mitochondrial function after 30 and 45 minutes (or more) of circulatory arrest normothermic but continuation of pulmonary ventilation, or conservation of the lungs in inflation with air or pure oxygen. Our mitochondrial data should also be compared with a study of the pulmonary function by a model of transplantation with survival of the receiver pig. [less ▲]

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See detailLes conceptions de l’au-delà en Mésopotamie
Van der Stede, Véronique ULg

Master's dissertation (1999)

Detailed reference viewed: 27 (0 ULg)
See detailLe discours européen du Front national français
Jamin, Jérôme ULg

Master of advanced studies dissertation (1999)

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See detailParticipation et intérêt politiques de lycéens français, belges et québécois au début des années quatre-vingt-dix : Une analyse plurielle fondée sur la dynamique de construction des univers de référence
Fournier, Bernard ULg

Doctoral thesis (1998)

Although certain recent theoretical developments insist more on the plurality of social and individual realities, the answers to empirical questions such as Are the young involved? or Are they interested ... [more ▼]

Although certain recent theoretical developments insist more on the plurality of social and individual realities, the answers to empirical questions such as Are the young involved? or Are they interested in politics? still too often fit in a univocal logic of comprehension where concepts used are thought to be homogeneous, as if they were “subsumptions”. This is why it is coherent to explain phenomena from a linear point of view which supposes a precise vision of the processes of construction of individual worlds of reference. Jean Piaget’s perspective of socialization reminds us that the individual is not a passive being in the dynamics of appropriation of the world, but that he assimilates the social context, accommodates it to what he already understands and, thus, transforms it. Consequently, this opens the way to a form of conceptual relativism, with a plural logic of comprehension where each reality, each concept cannot be defined without being replaced in the context of the singular worlds of reference. Thus, the theoretical consideration of the plural possibilities must also emerge from our interpretations. This research challenge is raised in this thesis by studying a series of profiles of dimensions, where each dimension can be replaced in a context which materializes a certain organization of realities. The complexity thus introduced into the analysis is synthesized by multivariate statistical methods (analysis of multiple correspondences and hierarchical ascending classification) which respect the initial organization of profiles. On the basis of data from an original inquiry among French, Belgian and Québécois high-school students, series of “clusters” of similar individuals are presented to describe, in a plural way, their participation and their political interests at the beginning of the nineties. [less ▲]

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See detailDéveloppement d’un modèle intégré d’optimisation des structures navales et hydrauliques
Rigo, Philippe ULg

Thèse d’agrégation de l’enseignement supérieur (1998)

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See detailLe traitement des infections artérielles. Apport de l’allogreffe
LAVIGNE, Jean-Paul ULg

Doctoral thesis (1998)

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See detailLe martyre et le temps : Tieleman Jansz. van Braght, le martyrologe mennonite et l'histoire
Donneau, Olivier ULg

Master of advanced studies dissertation (1998)

In his martyrology (published in 1660), the conservative Dutch Mennonite Tieleman Jansz. van Braght propose an original interpretation of the Christian past. In order to put together a succession of ... [more ▼]

In his martyrology (published in 1660), the conservative Dutch Mennonite Tieleman Jansz. van Braght propose an original interpretation of the Christian past. In order to put together a succession of witnesses, he examines one by one the ancient or medieval spiritual ancestors who, at the time, were claimed by both Catholics and Protestants. Those who seems to have been submitting to the divine principles - such as the practice of adult baptism - are considered as orthodox ; furthermore, if the orthodox suffered for their faith, they were given the title of martyr. Among the chosen ones, we thus have, besides the Anabaptists themselves: the early Christians, the Donatists, the Waldenses and the Hussites. These believers become the members of a dissenting and persecuted Church, which had held its own since the days of the Apostles. This notion conflict with the idea of Reformatio et, a fortiori, with that of Restitutio which is generally ascribed to the Anabaptists of the sixteenth century. [less ▲]

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See detailÉtude d'une unité industrielle de séchage de boues de station d'épuration
Léonard, Angélique ULg

Master's dissertation (1998)

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See detailSymbolic Methods for Exploring Infinite State Spaces
Boigelot, Bernard ULg

Doctoral thesis (1998)

In this thesis, we introduce a general method for computing the set of reachable states of an infinite-state system. The basic idea, inspired by well-known state-space exploration methods for finite-state ... [more ▼]

In this thesis, we introduce a general method for computing the set of reachable states of an infinite-state system. The basic idea, inspired by well-known state-space exploration methods for finite-state systems, is to propagate reachability from the initial state of the system in order to determine exactly which are the reachable states. Of course, the problem being in general undecidable, our goal is not to obtain an algorithm which is guaranteed to produce results, but one that often produces results on practically relevant cases. Our approach is based on the concept of meta-transition, which is a mathematical object that can be associated to the model, and whose purpose is to make it possible to compute in a finite amount of time an infinite set of reachable states. Different methods for creating meta-transitions are studied. We also study the properties that can be verified by state-space exploration, in particular linear-time temporal properties. The state-space exploration technique that we introduce relies on a symbolic representation system for the sets of data values manipulated during exploration. This representation system has to satisfy a number of conditions. We give a generic way of obtaining a suitable representation system, which consists of encoding each data value as a string of symbols over some finite alphabet, and to represent a set of values by a finite-state automaton accepting the language of the encodings of the values in the set. Finally, we particularize the general representation technique to two important domains: unbounded FIFO buffers, and unbounded integer variables. For each of those domains, we give detailed algorithms for performing the required operations on represented sets of values. [less ▲]

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See detailLe reengineering : aspects sociaux
Cornet, Annie ULg

Doctoral thesis (1998)

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See detailDifferential operators acting on tensor densities
Mathonet, Pierre ULg

Doctoral thesis (1998)

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See detailContribution à l’analyse des paramètres influençant la création de l’interface entre un béton et un système de réparation. Appétence et adhérence : cause et effet d’une liaison
Courard, Luc ULg

Doctoral thesis (1998)

Consacrer son temps à étudier le matériau "béton", voilà qui peut paraître anachronique, voire désuet : en effet, un matériau vieux de plus d'un siècle (sinon de plusieurs siècles si on pense aux Romains ... [more ▼]

Consacrer son temps à étudier le matériau "béton", voilà qui peut paraître anachronique, voire désuet : en effet, un matériau vieux de plus d'un siècle (sinon de plusieurs siècles si on pense aux Romains), que les ingénieurs utilisent, calculent, mettent en œuvre, coulent, coffrent et ferraillent à longueur de journée, peut-il encore livrer des secrets que nous ne connaissons pas ? La réponse est à la fois oui et non. Non, parce qu'il est clair que nous pouvons donner sans hésiter la résistance en compression, en traction ou le retrait d'un béton de composition donnée. Oui, parce qu'il est beaucoup plus compliqué d'expliquer la cohésion, l'hydratation ou de chiffrer la perméabilité et la durabilité d'un béton. Ce dernier point est essentiel car il ne faut pas oublier que ce qui fait la force du béton, outre son prix, c'est qu'il est un matériau durable. Durable, mais non intemporel : d'autant que les agressions deviennent plus importantes et concentrées, qu'elles trouvent sans cesse de nouvelles formes et de nouveaux moyens de transport. Le béton n'est pas immuable et indestructible : il vit et par conséquent il faut le protéger, le soigner, le rénover comme toute "chose" vivante. La philosophie générale de la réparation des ouvrages d'art ainsi que les principaux produits sont définis et décrits dans un premier chapitre. Le deuxième chapitre tente d'appliquer les théories de l'adhésion au problèmes particuliers des liants hydrauliques et des supports poreux et rugueux. La notion de cohésion est évoquée dans le troisième chapitre, dans la mesure où elle constitue pour nous un processus tout à fait similaire à celui observé dans le cadre restreint de la réparation des bétons par des produits à base de liants hydrauliques. Nous avons réalisé dans le quatrième chapitre l'exercice qui consistait de la façon la plus exhaustive possible à dresser la liste et à classer par catégories l'ensemble des facteurs liés au support, à la couche d'apport et à l'environnement, et qui agissent sur la qualité du lien créé entre le support en béton et le système de réparation. L'étude de l'interaction du support en béton avec un produit de réparation nécessite bien entendu une connaissance approfondie des propriétés mécaniques, physiques et chimiques des matériaux en présence, ce qui a fait l'objet du cinquième chapitre. Le sixième chapitre a, quant à lui, été consacré à la mesure des propriétés d'adhérence et à la description au microscope des différentes interfaces observées. Trois paramètres réputés fondamentaux ont été étudiés, dans le but de quantifier leur effet sur l'adhésion et surtout d'analyser leur synergie éventuelle : la préparation de surface, qui définit la rugosité du support et est à la base du mécanisme d'interpénétration (septième chapitre); les propriétés thermodynamiques des phases liquides et solides en présence qui régissent la création et la stabilité de l'interface (huitième chapitre); les phénomènes de transfert à l'interface, en particulier par absorption capillaire et par diffusion, qui contribuent à la qualité et la durabilité des liaisons établies (neuvième chapitre). Pour terminer, les conclusions résument l'ensemble des résultats, avant de lancer quelques pistes pour des travaux de recherche à venir. L'observation est à la base de toute science : nous avons essayé d'adopter la démarche du naturaliste qui analyse, décrit, représente l'objet de son observation sans interférer, ou à tout le moins en tentant de le faire, sur les phénomènes observés. C'est une façon de travailler peu aisée pour un ingénieur qui, par sa formation, est plus orienté vers l'utilisation de lois ou de modèles et donc la prévision de comportements "a priori" plutôt que l'observation "a posteriori". Mais c'est aussi ce qui a fait le principal intérêt de ce travail. [less ▲]

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