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See detailEngineering and manufacturing for biotechnology
Hofman, M.; Thonart, Philippe ULg

Book published by Kluwer academic publishers (2001)

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See detailAssociation between lipoprotein (A) and cardiac troponins in PTCA patients
Lutteri, Laurence ULg; Legrand, Victor ULg; Gielen, Jacques et al

in Clinical Chemistry & Laboratory Medicine (2001), 39(suppl), 278

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See detailRelationship between lipoprotein (a) and cardiac troponins in PTCA patients
Lutteri, Laurence ULg; Legrand, Victor ULg; Gielen, Jacques et al

in Acta Clinica Belgica (2001), 56

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See detailQuelques réflexions à propos de l'incidence des fixations, remises ou redistributions de la cause sur la qualification d'un jugement ou d'un arrêt
Boularbah, Hakim ULg

in Revue de Droit Judiciaire et de la Preuve = Tijdschrift voor Procesrecht en Bewijsrecht (2001)

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See detailConsidérations sur le taux du ressort lorsque les bases de détermination de la valeur du litige font défaut
Boularbah, Hakim ULg

in Revue de Droit Judiciaire et de la Preuve = Tijdschrift voor Procesrecht en Bewijsrecht (2001)

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See detailCompetition between deep impurity and dopant behavior of Mg in GaN Schottky diodes
Schmeits, Marcel; Nguyen, Ngoc Duy ULg; Germain, Marianne

in Journal of Applied Physics (2001), 89

The effect of the deep acceptor Mg on the electrical characteristics of p-doped GaN Schottky diodes is analyzed. The theoretical study is based on the numerical resolution of the basic semiconductor ... [more ▼]

The effect of the deep acceptor Mg on the electrical characteristics of p-doped GaN Schottky diodes is analyzed. The theoretical study is based on the numerical resolution of the basic semiconductor equations, including the continuity equation for the Mg-related acceptor level. It gives the steady-state and small-signal analysis of p-doped GaN:Mg Schottky diodes, yielding as final result the frequency dependent capacitance and conductance of the structure. It is shown that the low-frequency characteristics are determined by the carrier exchange between the Mg related impurity level and the valence band, whereas above the impurity transition frequency, the hole modulation of the depletion layer edge governs the electrical response. Detailed results are shown on the effect of temperature, applied steady-state voltage and series resistance. The study of two back-to-back connected GaN Schottky diodes reveals the appearance of typical features in the electrical characteristics, depending on the respective Schottky barrier height of the two junctions. [less ▲]

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See detailSexual compatibility between two heterochronic morphs in the Alpine newt, Triturus alpestris
Denoël, Mathieu ULg; Poncin, Pascal ULg; Ruwet, Jean-Claude

in Animal Behaviour (2001), 62(3), 559-566

Paedomorphosis, in which individuals retain ancestral characteristics in the adult stage, is widespread in newts and salamanders and is suspected to play an important role in evolution. In some species ... [more ▼]

Paedomorphosis, in which individuals retain ancestral characteristics in the adult stage, is widespread in newts and salamanders and is suspected to play an important role in evolution. In some species, paedomorphosis is facultative with some individuals forgoing metamorphosis. Optimality models have been proposed to explain the maintenance of this polymorphism, but require the integration of reproductive patterns into the models. We investigated the frequencies of inbreeding and outbreeding in two syntopic heterochronic morphs of the Alpine newt. The two morphs are sexually compatible: encounters between and within morphs were equally successful in terms of spermatophore transfer. Behavioural observations were in agreement with the sexual compatibility observed. Nevertheless, paedomorphic males displayed to females less frequently than metamorphic males. The two morphs differ largely on the basis of sexual secondary characteristics, but the majority of these traits did not affect mating success. Because of the large flow of genes between the two heterochronic morphs and because of the absence of spatial and temporal isolation, these results do not support sympatric speciation models, but are in favour of the maintenance of polymorphism in natural populations. (C) 2001 The Association for the Study of Animal Behaviour. [less ▲]

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See detailA STUDY OF VACUUM FREEZE-DRYING OF FROZEN WET PAPERS
Carapelle, Alain ULg; Henrist, Marc; Rabecki, Frédéric ULg

in Drying Technology (2001), 19(6), 1113-1124

Vacuum freeze-drying of frozen wet papers was investigated experimentally. A freeze-drying facility was built to study the process by monitoring the various physical parameters (pressure, sample ... [more ▼]

Vacuum freeze-drying of frozen wet papers was investigated experimentally. A freeze-drying facility was built to study the process by monitoring the various physical parameters (pressure, sample temperature, heater temperature, water content of the sample and cold panel temperature). A simple phenomenological model was developed to explain experimental results. The values of the physical parameters were optimized to make the process cost effective. [less ▲]

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See detailAdvances in Palaeozoic Palynology. PPMB Special Issue in Honour of Dr.Stanislas Loboziak. Abstract volume.
Steemans, Philippe ULg; Servais, T.; Streel, Maurice ULg

Book published by Paleopalyno. Paléobot. Micropal. (2001)

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See detailRésumé C.E. n°89.185, du 31 juillet 2000, Van Den Borre
Delnoy, Michel ULg

in Aménagement - Environnement (2001), 1

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See detailDynamique de modification de l'habitat physique de reproduction des pondeurs lithophiles sous gravier. Cas de deux frayères à ombre dans l'Aisne
Parkinson, Denis; Petit, François ULg; Houbrechts, Geoffrey ULg et al

in Bulletin de la Société Géographique de Liège (2001), 40

D’octobre 1998 à mars 1999, nous avons étudié dans l’Aisne, petit affluent ardennais de l’Ourthe, la dynamique de modification de deux bancs de gravier utilisés comme frayère par l’ombre commun en mars ... [more ▼]

D’octobre 1998 à mars 1999, nous avons étudié dans l’Aisne, petit affluent ardennais de l’Ourthe, la dynamique de modification de deux bancs de gravier utilisés comme frayère par l’ombre commun en mars-avril 1998. L’étude a été réalisée dans deux stations du cours inférieur de l’Aisne où se sont succédé quatre crues morphogènes. Dans chaque station, nous avons déterminé à intervalle d’environ 1 mois, la profondeur d’érosion et la hauteur de dépôt des sédiments (méthode de la barre d’érosion à chaînes), la granulométrie des matériaux des couches de surface et de subsurface, le dépôt des sédiments fins (placement de pièges à sédiments) et la perméabilité du substrat (méthode du standpipe). En complément, nous avons entrepris dans une station de l’Aisne moyenne, une caractérisation de divers éléments de la dynamique fluviale : identification des débits mobilisateurs (par marquage colorimétrique des sédiments en place), estimation de la vitesse de déplacement de la charge de fond (par étude de la dispersion longitudinale de scories, résidu d’anciennes industries métallurgiques) et estimation des quantités de sédiments charriés par la rivière (à partir des données de dragage). [less ▲]

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See detailQualité organoleptique de la viande de porc
Sindic, Marianne ULg; Faes, Th.; Wavreille, J. et al

in L'avenir de la production porcine en wallonie (2001)

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See detailChanges in lipoxygenase and hydroperoxide decomposition activity in tissues cultures of soybean
Fauconnier, Marie-Laure ULg; Mouttalib, A.; Billo, D. et al

in Journal of Plant Physiology (2001), 158(7), 953-955

Glycine max L. tissue cultures were initiated on different media supplemented with appropriate plant growth regulators that specifically induce the formation of callus, root, or shoot primordia ... [more ▼]

Glycine max L. tissue cultures were initiated on different media supplemented with appropriate plant growth regulators that specifically induce the formation of callus, root, or shoot primordia. Exogenously applied hormones resulted in important changes in both Lox and HPO decomposition activity. Lox activity was higher in extracts from tissues cultured in medium supplemented with NAA or 2,4-D, while a lowest activity was recorded in extracts from cultures treated with BA. 13-HPOD was cleaved by all tested extracts, while 13-HPOT and 9-HPOD were cleaved exclusively by extracts from tissues cultured in the presence of BA. [less ▲]

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See detailAvantages sélectifs d'un phénotype hétérochronique. Eco-éthologie des populations pédomorphiques du Triton alpestre, Triturus alpestris (Amphibia, Caudata)
Denoël, Mathieu ULg

Doctoral thesis (2001)

Facultative paedomorphosis is a polyphenism that has important evolutionary implications in promoting morphological differentiation and habitat use variation, and has occurred in several urodele species ... [more ▼]

Facultative paedomorphosis is a polyphenism that has important evolutionary implications in promoting morphological differentiation and habitat use variation, and has occurred in several urodele species throughout the world. Several hypotheses based on life-history theory have been proposed to explain the wide range of habitats where facultative paedomorphosis occurs, suggesting multiple causes. In populations experiencing facultative paedomorphosis, some individuals metamorphose and mature (metamorphs), while others attain sexual maturity while still retaining traits of larval somatic morphology (paedomorphs). The paedomorphic process by which the development of somatic and reproductive organs is shifted between related individuals is assumed to significantly contribute to macro-evolutionary processes. Indeed, it implies large phenotypic variations in the absence of deep genetic changes. A way to explain the importance of these developmental heterochronies is to show their adaptive value in the micro-evolutive stage. The aim of this thesis is to determine the advantages gained by an individual that adopts a paedomorphic developmental pathway rather than a metamorphic one. To do this, we studied five factors: habitat use; resource partitioning; age and size structures; sexual compatibility; and the effect of environmental factors. The ecological and ethological characteristics of several mixed populations (composed of both paedomorphic and metamorphic individuals) of the Alpine newt Triturus alpestris (Amphibia, Salamandridae) were investigated from 1997 to 2000. These populations were located in France, Italy and Greece. The habitats occupied by dimorphic populations of the Alpine newt are highly variable. We have found the two morphs in syntopy in deep permanent lakes, and in small shallow and temporary ponds. Aquatic habitats were surrounded by various terrestrial habitats. As a result, it was not possible to correlate any particular environment type with the maintenance of the polymorphism in natural populations. The only common trait of the paedomorphic populations was that they were located at the southern margin of the range of the species (Italy, the Balkan peninsula, and southeastern France). Such a restriction of the distributional range of paedomorphosis suggests that this trait is maintained by genes which are shared only by these populations. Such a restriction may be due to Holocene colonizations from Pleistocene refugia, in which case paedomorphosis may have appeared in these refugia during the last glaciations. Nevertheless, as long as the phylogeny of the group remains uncertain, we cannot reject the possibility of an earlier origin of paedomorphosis. The two morphs primarily differed in space use and feeding habits. These differences were particularly marked in deep alpine aquatic habitats, where the paedomorphs occupy deep waters devoid of competitors, such as fish. In such waters, the paedomorphs were more abundant on the bottom and in the water column, whereas the metamorphs mainly occupied the water surface and shore. The paedomorphs primarily ingested plankton, while the metamorphs mainly foraged on terrestrial prey that had fallen on the water surface. Although these feeding habits depend on newt habitats - plankton being more abundant in the water column, and terrestrial prey at the water surface - the trophic spectrum in each habitat still differed. While the energetic values of the prey eaten by the two morphs strongly differed, by ingesting a large number of planktonic organisms, the paedomorphs attained similar or even larger caloric intake rates than metamorphs. The paedomorphs' superior body condition suggests that they may have higher long-term success than the metamorphs. Differences in body condition may also reflect the terrestrial life habit of the metamorphs, since metamorphosed individuals are able to avoid competition with reproductive adults and larvae by leaving the water. In the paedomorphic populations, several size-structured cohorts of larvae coexist, and competition among these cohorts is lowered by size-selective predation, since small larvae catch smaller prey than larger larvae and paedomorphs. Although this difference in diet was in part due to gape-size limitation, the gilled individuals also size-selected prey among a range of catchable items. Resource partitioning then favoured the coexistence of the two adult morphs, and their gilled descendants, which coexist with them. The two morphs also differed in feeding performance. Whereas the paedomorphs were better predators than metamorphs on water fleas, metamorphs were more adept at capturing large terrestrial invertebrates (flies). These differences in feeding performances were caused by the morphological particularities of the two morphs. Paedomorphs had a fish-like feeding structure with a unidirectional water flow passing through the oral cavity, and then being expelled through gill slits on the posterior side of the head. In contrast, metamorphs had a smaller oral cavity and a bidirectional water flow due to closed gill slits. Although the metamorphic structure produces less suction, it allows for catching bigger prey because of a larger gape-size (biting rather than sucking). Our measures of feeding performances confirmed the data from natural populations, with each of the morphs preferentially eating their predicted prey. The particular use of micro-habitats by the two morphs is also in agreement with optimality models predicting predation in the more profitable patches. In the Alpine newt, paedomorphosis can be produced by two main processes: neoteny and progenesis. In some populations, the two morphs reached sexual maturity at the same age (neoteny); in other populations, sexual maturity was reached earlier by paedomorphs (progenesis). Progenesis was observed in unstable water habitats. Pond drying suppressed the possibility of late maturation, which is characteristic of a neotenic developmental pathway. On the other hand, the precocious sexual maturation of paedomorphs favoured the fast colonization of new habitats, owing to a high intrinsic rate of natural increase. Neoteny was typical of permanent waters with harsh constraints on growth. By forgoing metamorphosis, larvae also avoid the cost of changing of structure (decrease in body weight in our experiments). Progenetic paedomorphosis appears then as a major trait that can be selected due to the advantages of earlier maturation. The two morphs are sexually compatible; thus, metamorphs can "exchange" genes with paedomorphs at each generation. While the two morphs markedly differ in their secondary sexual characteristics, females did not show any preference related to these characteristics. The absence of sexual isolation between the morphs shows that they are not involved in a sympatric speciation process. The maintenance of the polymorphism is more advantageous than the formation of two isolated species. Paedomorphosis occurs in aquatic habitats where total drying can occur, and where the maintenance of facultative paedomorphosis is maintained by metamorphs that have paedomorphic genes but do not (permanently) express them. In such habitats, the sexual isolation of the two morphs would lead to the extinction of paedomorphosis in the event of pond drying or similar catastrophe. Because the environment can modify the ontogenetic pathway, paedomorphosis in the Alpine newt can be considered a polyphenism. Indeed, restricting the amount of water or food available induces paedomorphs to metamorphose. The marking of individual paedomorphs in a natural population proved that metamorphosis also occurs in the field. However, salamander density and progressive drying of aquaria did not have any apparent effect on paedomorph metamorphosis. When the possibility of a short migration across dry land was given, paedomorphs moved towards an available water basin and maintained their larval somatic characters during the migrations. By being able to migrate on land towards permanent water, paedomorphs are able to retain a feeding morphology that favors them in microhabitats where plankton is abundant. Facultative paedomorphosis in the Alpine newt allows populations to cope with environmental variability, and is adaptive in allowing precocious maturation or a larger use of resources in spatially heterogeneous environments. Thus, it is not surprising that paedomorphosis can evolve in such dissimilar environments as lowland temporary ponds and highland deep lakes. In such places, paedomorphosis appears to be the best solution as long as fish predation is relaxed. The introduction of fish throughout Europe is thus a serious problem, and has resulted in the extinction of several large paedomorphic populations. If this trend is not stopped rapidly, paedomorphosis in the Alpine newt - and in other species - will belong to the past. [less ▲]

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See detailL'activité physique de jeunes adolescents en Communauté française de Belgique
Piéron, Maurice; Cloes, Marc ULg

in Revue de l'Education Physique (2001), 41(1), 42-48

La santé figure dans la plupart des préoccupations des théoriciens et des praticiens de l'éducation physique. Les effets de santé associés à la pratique régulière d'activités physiques suscitent un ... [more ▼]

La santé figure dans la plupart des préoccupations des théoriciens et des praticiens de l'éducation physique. Les effets de santé associés à la pratique régulière d'activités physiques suscitent un intérêt fondamental chez de nombreux chercheurs. En effet, à deux reprises, un groupe de consensus s'est réuni pour établir un bilan des certitudes et des doutes en matière de relations entre l'activité physique et la santé. ... [less ▲]

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See detailSexual compatibility between two heterochronic morphs in the Alpine newt
Denoël, Mathieu ULg; Poncin, Pascal ULg

Poster (2001)

Numerous populations of newts and salamanders are dimorphic: while some larvae become mature and thus paedomorphic, others metamorphose and become adult later. The two morphs largely differ in morphology ... [more ▼]

Numerous populations of newts and salamanders are dimorphic: while some larvae become mature and thus paedomorphic, others metamorphose and become adult later. The two morphs largely differ in morphology. According to sexual selection theories, we could expect some female choice towards the alternative morphs. Although paedomorphosis can be adaptive in allowing resource partitioning and an earlier age at maturity, it is worth to determine the strength of sexual isolation between morphs. Indeed, whereas sexual compatibility may promote maintenance of polymorphism by mixing genes, sexual isolation could be the first step to sympatric speciation. We staged more than 200 encounters involving the four possible crosses within and between the heterochronic morphs of the Alpine newt, Triturus alpestris (Amphibia, Caudata). We took into account both quantitative and qualitative aspects of behaviours, with particular emphasis on the success of sperm transfer. We also determined secondary sexual characters. The success of heterotypic and homotypic encounters was similar, involving then sexual compatibility between the two heterochronic morphs. Paedomorphs and metamorphs displayed identical behavioural patterns at similar frequencies. Females did not appear to be selective against males on the basis of their epigamic characters. Our results do not support hypotheses predicting sympatric speciation from polymorphic species. On the other hand, they are in favour of the models predicting maintenance of polymorphism [less ▲]

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