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See detailBildwissenschaft - Image et langage (introduction au colloque)
Hagelstein, Maud ULg

Conference (2016, May 12)

En guise d’introduction très rapide, je voudrais rappeler dans ses grandes lignes le projet auquel est liée l’organisation de ces journées de recherche. Le projet tente d’établir une archéologie de la ... [more ▼]

En guise d’introduction très rapide, je voudrais rappeler dans ses grandes lignes le projet auquel est liée l’organisation de ces journées de recherche. Le projet tente d’établir une archéologie de la théorie de l’image contemporaine, en particulier (en priorité) dans son versant germanophone, celui de la « science de l’image » (Bildwissenschaft) – discipline qui est, pour des raisons diverses (obstacle de la langue, nouveauté des problèmes, hermétisme des débats, etc.), encore peu connue chez nous. Or, me semble-t-il, l’explosion récente de la théorie de l’image (depuis les années 1990), théorie de l’image qui s’est décentrée par rapport à son milieu naturel et déployée sur de multiples territoires disciplinaires, appelle une nouvelle cartographie des études visuelles, qui reste à établir, ainsi qu’une redéfinition philosophique de l’image (ou des images) et de l’expérience qui en découle (les phénomènes visuels et iconiques étant à ce point diversifiés aujourd’hui que de nombreuses définitions sont en circulation sans que l’on perçoive toujours leur cohérence). Comme l’écrivait récemment Klaus Sachs-Hombach : « Une science générale de l’image n’a pas encore réussi à s’établir » (I, §1). L’idée de ce projet sur la Bildwissenschaft consiste donc à envisager du point de vue de la méthode les différentes approches récentes de l’image pour tenter d’identifier ce qu’elles ont en commun (c’est loin d’être évident). L’option qui me semblait pouvoir être investie dans un premier temps consiste à rapporter ces développements récents à la discipline d’interprétation des images née en Allemagne au début du XXe siècle, quelques décennies auparavant, (avec A. Warburg et surtout E. Panofsky), à savoir : l’iconologie. En effet, à mes yeux, du point de vue de son ancrage philosophique, la théorie de l’image actuelle puise ses principales ressources conceptuelles dans l’iconologie (et les problèmes théoriques qui lui sont associés). En quoi consiste ce modèle ? Pour le dire trop vite, la méthode iconologique vise principalement l’interprétation du contenu symbolique des images. Elle repose entièrement – ou en tout cas majoritairement – sur une compréhension symbolique des artefacts visuels : face à une œuvre picturale, par ex., on part bien entendu de ce qui est donné à la perception (les éléments sensibles et matériels présentés par l’œuvre), pour dégager petit à petit la signification profonde et intrinsèque de l’œuvre. Dans cette optique, l’image a donc pour vocation de délivrer un message, au même titre que le langage, mais avec des moyens différents. Or, si on tente de rapporter la Bildwissenschaft – telle qu’elle se déploie considérablement depuis quelques années – à l’iconologie, on doit admettre que ce modèle (le modèle iconologique) joue surtout négativement. Depuis la fin des années 1980, la méthode iconologique a commencé à générer chez les théoriciens de l’art et du visuel (en général), toutes sortes de réactions d’insatisfaction – voire même de franche hostilité. Et pour la plupart de ces auteurs, l’iconologie va servir de repoussoir autant que de modèle. Pour quelle raison ? Les critiques généralement adressées par les théoriciens contemporains à la méthode iconologique s’articulent le plus souvent autour du problème de la prédominance du paradigme langagier pour l’analyse des images. Or, à force de considérer trop strictement l’image sur le mode du signe qu’il faut lire et décrypter, on risque de l’assimiler purement et simplement à d’autres types de signes, notamment langagiers, et de diluer sa spécificité dans une théorie symbolique trop large. Globalement, il me semble que les différentes réactions s’accordent (ou en tout cas pourraient s’accorder) sur le fait que l’iconologie – telle qu’elle se présente dans sa version traditionnelle – doit être complétée : l’approche symbolique des œuvres doit par ex. pouvoir s’appuyer sur une attention soutenue à leurs modes de présentation (dans ce cas, les outils du « formalisme esthétique » peuvent alors être convoqués) ou à leur matérialité (les outils « phénoménologiques » peuvent idéalement venir au secours de l’analyse). En résumé, depuis la fin des années 1980, l’héritage iconologique est mis en question par des chercheurs qui – en réalité – veulent donner au concept d’iconologie un sens plus actuel et consacrent leurs efforts à l’étude de la logique des images (logique iconique), en tant qu’elle n’est pas contaminée par le modèle langagier. Autrement dit, les protagonistes de la Bildwissenschaft concernés par ces problématiques font le pari suivant : on peut étudier la logique du visuel en dehors de toute référence au langage et à sa syntaxe propre. Ils pensent pouvoir montrer en quoi une proposition visuelle diffère radicalement d’une proposition langagière. En rapportant la Bildwissenschaft à l’iconologie, on rencontre donc très vite la thématique centrale de l’iconic turn (tournant iconique), qui consiste à défendre l’idée d’une spécificité absolue de l’image à l’égard du langage. On l’a dit : Les défenseurs du tournant iconique pensent renverser la domination du paradigme langagier pour l’interprétation des images. Plutôt que de se concentrer exclusivement sur l’étude des contenus symboliques, il importe à leurs yeux de se concentrer sur ce qui fait la spécificité intrinsèque de l’image et de montrer comment sa matérialité affecte et contamine directement la production du sens. Contre la sémiotisation excessive des formes d’expression visuelle, il faudrait donc affirmer une fonction intransitive des images, c’est-à-dire redonner à l’image une épaisseur propre, qui ne renvoie qu’à elle-même. De nombreux auteurs s’inscrivent dans cette perspective (c’est le cas notamment de G. Boehm, qui veut sortir du paradigme langagier pour l’interprétation des images, ou de L. Wiesing, qui tente une définition asémantique de l’image). Les débats autour de l’iconic turn sont très particuliers et finalement difficiles à traiter. D’abord parce que l’iconic turn fait suite au linguistic turn (tournant déclaré dans la célèbre anthologie de Rorty - 1967), et appelle à sa suite d’autres tournants (on parle volontiers aujourd’hui d’un tournant anthropologique des études visuelles, comme on parle d’ailleurs aussi d’un tournant visuel de l’anthropologie, etc.). Or, ces changements radicaux de direction, ces changements de paradigme, finissent à mon avis par nous faire perdre nos repères (il y a trop de turn, pour le dire platement) et on a le sentiment de tourner en rond. Ensuite, autre difficulté : les débats liés à l’iconic turn sont souvent animés par la volonté de défendre – jusqu’à l’absurde – la valeur primordiale et la préséance absolue de l’image sur le langage. Si on s’enlise dans les positions parfois stéréotypées de ce débat, on pourra difficilement sortir du scepticisme langagier le plus stérile (l’idée que le langage manque inévitablement le caractère sensible de l’image). Pourtant, je ne voudrais pas non plus rendre trop caricatural ce débat qui m’intéresse tellement. D’un côté, j’ai l’impression qu’on y revient toujours, de l’autre, qu’on en est déjà sorti. On y revient toujours parce que ce problème continue à être essentiel pour toute une série d’auteurs qui cherchent obstinément à vouloir distinguer l’image des autres formes d’expression, à vouloir construire de nouvelles iconologies. Et l’effort qui consiste à essayer d’identifier les spécificités logiques du visuel doit sans cesse se renouveler ; les théories de la spécificité sont très fragiles parce que les contre-exemples et contre-arguments viennent très vite à l’esprit dès qu’il s’agit de séparer les pouvoirs de l’image et du langage. Dès que quelqu’un dit : « l’image fait ceci que le langage ne fait pas », on trouve quelqu’un d’autre pour répondre : « comment ? Mais si, le langage fait ça aussi ». Néanmoins, si on dégage peu de certitudes, de points fixes, ces débats sont loin d’être stériles (pour le dire vite : on a l’impression tout de même d’augmenter notre connaissance des images en traversant ces discussions). On y revient donc toujours mais en même temps on en est déjà sorti (et presque toujours déjà sorti) : aujourd’hui, on rencontre de multiples propositions, qui émanent soit du champ de la Bildwissenschaft lui-même, soit de l’extérieur (et parfois même très en amont de ces débats), et qui présentent des modèles plus complexes et nuancés qui n’opposent pas frontalement image et langage. Mais qui font l’effort de penser leur complémentarité. Et en réalité, ces efforts nous donnent à penser que la séparation des pouvoirs de l’image et du langage est peut-être très artificielle – ou en tout cas fragile – dans certains cas, mais qu’elle continue à être utile. [less ▲]

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See detailSolid-supported synthesis of peptidoglycan fragments and their biological evaluation
Simon, Justine ULg

Doctoral thesis (2016)

In this work, a new methodology for the synthesis of peptidoglycan fragments containing (2S,6R)-A2pm is proposed. Thanks to a solid phase platform, cross metathesis was achieved between two easily ... [more ▼]

In this work, a new methodology for the synthesis of peptidoglycan fragments containing (2S,6R)-A2pm is proposed. Thanks to a solid phase platform, cross metathesis was achieved between two easily manufactured chiral synthons, allylglycine anchored to a resin and vinylglycine derivatives. Due to the need of fragments for the study of the peptidoglycan recycling, this modular efficient platform could be useful to synthesize diverse derivatives of other peptides and muropeptides containing (2S,6R)-A2pm. In the framework of this project, (S)-Ala-γ-(R)-Glu-(2S,6R)-A2pm-(R)-Ala and γ-(R)-Glu-(2S,6R)-A2pm were synthesized. Their interactions with the R39 peptidase were studied by X-ray diffraction. According to the crystallographic results, (S)-Ala-γ-(R)-Glu-(2S,6R)-A2pm-(R)-Ala 1 is a reversible covalent binding inhibitor of R39. These data are supported by an enzymatic study using the thioesterase activity of the R39 peptidase on (R)-S2d. Because of the specific affinity for the R enantiomer of thioesters, the enantioselective synthesis of (R)-S2d is described that makes use of the coupling agent T3P. A chromatographic method is proposed to evaluate the degree of thioester racemization. The kinetics of the interaction between the thioester and different PBPs were studied and a protocol for microtiter plate-based assays is developed allowing the screening of compound libraries for inhibitors of PBPs. In the future, the synthesized peptidoglycan fragments will be used as reference compounds in the framework of the NetRBI project. [less ▲]

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See detailCharacterization, dynamics and trophic ecology of macrofauna associated to seagrass macrophytodetritus accumulations (Calvi Bay, Mediterranean Sea)
Remy, François ULg

Doctoral thesis (2016)

Posidonia oceanica meadows are a major coastal Mediterranean ecosystem. Although highly productive this Mediterranean marine flower plant is not much consumed by herbivore organisms. During autumnal ... [more ▼]

Posidonia oceanica meadows are a major coastal Mediterranean ecosystem. Although highly productive this Mediterranean marine flower plant is not much consumed by herbivore organisms. During autumnal senescence, most (up to 90%) of the foliar primary production of P. oceanica ends in the “detrital compartment”. These dead leaves, also called “macrophytodetritus”, begin to degrade immediately inside the meadow, but a large amount will be rapidly exported to adjacent unvegetated accumulation zones, such as bare sand patches. Associated to drift macroalgae, living detached P. oceanica shoots, micro-organisms and fine sediment, these macrophytoderitus form what we call “exported P. oceanica litter”. This exported litter is a highly dynamic habitat for a whole community of invertebrates: meiofauna (38µm < size < 500µm) and macrofauna (size ≥ 500µm) on which we focused on. This dynamic nature of exported litter could play a major structuring role in terms of abundance, diversity and trophic ecology of this vagile macrofauna community at a seasonal, annual or spatial scale, but also during stochastic, brief and very strong perturbations: resource pulses. In this context, this PhD Thesis had 7 main objectives: i. Characterize for the first time exhaustively the macrofauna community. ii. Evaluate the spatiotemporal changes occurring at two different time scales in the detritus themselves and in the macrofauna community. iii. Relating these variations with measured environmental parameters. iv. Experimentally demonstrate the stratification occurring in a stable P. oceanica litter accumulation and the impact of this stratification on environmental conditions and on the macrofauna. v. Experimentally demonstrate the impact of resource pulses on the exported P. oceanica litter macrofauna community. vi. Unravel for the first time the global P. oceanica litter macrofauna food web using gut contents examinations and stable isotopes (C and N). vii. Evaluate the spatiotemporal changes of diet preferences of this community and determine if the observed changes are really synonym of true diet changes. This PhD Thesis demonstrated that exported P. oceanica litter was mainly composed of dead P. oceanica leaves (70-80%). It followed the natural annual cycle of P. oceanica and presented a maximum abundance in autumn just after leaves senescence. Measured environmental parameters also showed important variations linked to different factors such as force and direction of the wind, litter abundance and probably temperature. The continuous presence of the vagile macrofauna community throughout the year was demonstrated as well. This community was composed of 115 species and largely dominated by arthropods (77%), followed by annelids (12%) and mollusks (7%), while other taxa were much more anecdotal. Even if diversity is quite important, only a few species dominate largely the community. Indeed, 19 species represent more than 90% of the total abundance. One species to keep in mind: Gammarella fucicola, the most typical dominant and abundant amphipod species, representing 40-50% of the total abundance. In addition to this general pattern, litter vagile macrofauna presented important seasonal and annual variations. In the case of several species, these variations could be linked to some measured environmental parameters, but we had to recognize that most species did not seem to be influenced by environmental parameters measured during this PhD. However, oxygen concentration was the most important environmental parameter, potentially influencing 7 of the 19 most dominant and abundant species. The experimentally demonstrated physico-chemical stratification occurring inside litter accumulations was strongly related to this oxygen parameter. Indeed we demonstrated that several species were distributed in the different layers of a litter accumulation according to oxygen concentration and to a lesser extent, to nutrients concentration (mostly NH4). Besides, smaller time scale sampling allowed the identification of several stormy events corresponding to the definition of resource pulses. These pulses were demonstrated to play a potentially important role on the structure of the macrofauna community, favoring importantly the detritivore species and hypoxia tolerant species. It was also demonstrated that resource pulses could induce diet switching increasing the consumption of dead P. oceanica leaves just after the events, potentially increasing the litter decomposition by the macrofauna. The trophic web described in this PhD Thesis was composed of several trophic levels, from the primary herbivore/detritivore consumer, to second order carnivore predators. Different dietary preferences were highlighted, but major information was that dead P. oceanica leaves were ingested by a majority (85%) of the sampled species. Moreover, stable isotope analysis confirmed that P. oceanica litter was assimilated by most primary consumers and this “detrital signal” could be identified to the upper trophic levels, which is an argument in favor of the importance of macrofauna as major dead P. oceanica leaves decomposers. This also highlighted their potential role in terms of organic matter transfer from the P. oceanica meadow itself to the Mediterranean coastal food webs. Seasonal variations were observed in terms of trophic niches, and SIAR mixing model confirmed that this variability was sometimes caused by real diet modifications, potentially linked to the variable availability of food sources. This PhD Thesis, combining standardized sampling at two different time scales, trophic web analysis (gut contents and stable isotopes) and original experimentation allowed us to describe a diverse and abundant macrofauna community associated to P. oceanica exported litter, its temporal variations, potential responses to resource pulses as well as the link existing between some species and measured environmental parameters. This PhD also described the food web of this community and demonstrated the importance of dead P. oceanica leaves as food source for many invertebrates composing this community. These invertebrates thus seemed to play an important role in both litter decomposition and organic matter flux from the P. oceanica meadow to the Mediterranean coastal food webs. [less ▲]

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See detailMolecular detection of single nucleotide polymorphisms on whole blood without DNA extraction
Detemmerman, L.; BOEMER, François ULg; SEGERS, Karin ULg et al

Poster (2016, May 12)

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See detailEnhancing Spatio-Temporal Identity: States of Existence and Presence
Hallot, Pierre ULg; Billen, Roland ULg

in International Journal of Geo-Information (2016), 5(62),

This work presents a new approach that aims to characterize the spatio-temporal relationships that exist between geographical objects that are absent or non-existent at the moment of analysis. First, we ... [more ▼]

This work presents a new approach that aims to characterize the spatio-temporal relationships that exist between geographical objects that are absent or non-existent at the moment of analysis. First, we would like to propose a formal analysis of the spatio-temporal states of presence and existence of a geographical object. We will then use a combination of these states in order to define a set of life and motion configurations. The model developed then serves as a formal basis for the realization of a series of spatio-temporal queries based on an analysis of patterns in the succession of spatio-temporal states. The entire approach is then demonstrated by using the example of the organization of a scientific conference by defining the spatio-temporal relationships between the conference participants. The research methodology is finally compared with a real dataset taken from a geolocalized social network to show the efficiency of this type of management. [less ▲]

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See detailLes partenariats et la confiance sur chantiers participatifs
Remy, Céline ULg

Conference given outside the academic context (2016)

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See detailWhat Are the Impacts of Deforestation on the Harvest of Non-Timber Forest Products in Central Africa?
Gillet, Pauline ULg; Vermeulen, Cédric ULg; Doucet, Jean-Louis ULg et al

in Forests (2016), 7(5),

The objective of the study is to evaluate the impact of forest transition on non-timber forest product (NTFP) harvesting in Central Africa. We analyze the evolution of several parameters, including ... [more ▼]

The objective of the study is to evaluate the impact of forest transition on non-timber forest product (NTFP) harvesting in Central Africa. We analyze the evolution of several parameters, including distance from NTFP harvest site to road, proportion of dietary intake and villagers’ incomes. The research is based on field surveys, participatory mapping and the geolocation of activities in three study sites representing different stages along the Mather’s forest transition curve: (i) intact forest; (ii) partially degraded forest; and (iii) small areas of degraded forest with plantations of useful trees. The results show that the maximum distance from harvest site to road is higher in Site 2 compared to Site 1 as a consequence of a lower availability of NTFPs; and that this distance is significantly lower in Site 3 due to a drastically smaller village territory. The diversity of bushmeat decreases as game evolves from large to small species, commensurate with the progression of forest transition. As a consequence, there is also a reduction in the proportion of these products represented both in household dietary intake and cash income. This analysis establishes a strong link between the Mather’s forest transition curve and a decline in the importance of NTFPs in village production and livelihoods. [less ▲]

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See detailThe determinants of tropical forest deciduousness: disentangling the effects of rainfall and geology in central Africa
Ouedraogo, Dakis-Yaoba ULg; Fayolle, Adeline ULg; Gourlet-Fleury, Sylvie et al

in Journal of Ecology (2016)

1. Understanding the environmental determinants of forests deciduousness i.e. proportion of deciduous trees in a forest stand, is of great importance when predicting the impact of ongoing global climate ... [more ▼]

1. Understanding the environmental determinants of forests deciduousness i.e. proportion of deciduous trees in a forest stand, is of great importance when predicting the impact of ongoing global climate change on forests. In this study, we examine (i) how forest deciduousness varies in relation to rainfall and geology, and (ii) whether the influence of geology on deciduousness could be related to differences in soil fertility and water content between geological substrates. 2. The study was conducted in mixed moist semi-deciduous forests in the northern part of the Congo basin. We modelled the response of forest deciduousness to the severity of the dry season across four contrasting geological substrates (sandstone, alluvium, metamorphic and basic rocks). For this, we combined information on forest composition at genus level based on commercial forest inventories (62 624 0.5 ha plots scattered over 6 million of ha), leaf habit, and rainfall and geological maps. We further examined whether substrates differ in soil fertility and water-holding capacity using soil data from 37 pits in an area that was, at the time, relatively unexplored. 3. Forest deciduousness increased with the severity of the dry season, and this increase strongly varied with the geological substrate. Geology was found to be three times more important than the rainfall regime in explaining the total variation in deciduousness. The four substrates differed in soil properties, with higher fertility and water-holding capacity on metamorphic and basic rocks than on sandstone and alluvium. The increase in forest deciduousness was stronger on the substrates that formed resource-rich clay soils (metamorphic and basic rocks) than on substrates that formed resource-poor sandy soils (sandstone and alluvium). 4. Synthesis. We found evidence that tropical forest deciduousness is the result of both the competitive advantage of deciduous species in climates with high rainfall seasonality, and the persistence of evergreen species on resource-poor soils. Our findings offer a clear illustration of wellknown theoretical leaf carbon economy models, explaining the patterns in the dominance of evergreen versus deciduous species. And, this large-scale assessment of the interaction between climate and geology in determining forest deciduousness may help to improve future predictions of vegetation distribution under climate change scenarios. In central Africa, forest is likely to respond differently to variation in rainfall and/or evapotranspiration depending on the geological substrate. [less ▲]

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See detailBiotechnologies algales: état actuel et perspectives de valorisation de la biomasse
Franck, Fabrice ULg

Scientific conference (2016, May 12)

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See detailCombined Centralized and Local Voltage correction in Active Distribution Network
Soleimani Bidgoli, Hamid ULg

in Combined Centralized and Local Voltage correction in Active Distribution Network (2016, May 12)

This paper presents a two-level real-time voltage control scheme to address the voltage violations in distribution grids hosting a significant number of Dispersed Generation Units (DGUs). The proposed ... [more ▼]

This paper presents a two-level real-time voltage control scheme to address the voltage violations in distribution grids hosting a significant number of Dispersed Generation Units (DGUs). The proposed scheme consists of a centralized and a local reactive power control. The local control provides fast response after a disturbance, reducing its impact and enhancing voltage quality. The centralized control relies on Model Predictive Control (MPC). It uses measurements collected throughout the network to bring the voltages inside desired limits. To do so, it adjusts in a coordinated way the reactive power set-points of the DGUs taking into account the local controls. The control method effectiveness has been evaluated on a 75-bus 11-kV test system hosting 22 DGUs. [less ▲]

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See detailLa cristallurie
GADISSEUR, Romy ULg

Conference (2016, May 12)

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See detailMédecine et philosophie dans l'Anonyme de Londres
Ricciardetto, Antonio ULg

Scientific conference (2016, May 12)

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See detailLa légistation REACH: une opportunité d’innovation pour l’économie biobasée
Schmetz, Quentin ULg; Istasse, Thibaut ULg; Jacquet, Nicolas ULg et al

Scientific conference (2016, May 12)

Cet exposé fait le point sur les tendances en cours dans ce secteur au travers de divers cas concrets tels que la substitution de retardateur de flamme, plastifiant et surfactant par des alternatives ... [more ▼]

Cet exposé fait le point sur les tendances en cours dans ce secteur au travers de divers cas concrets tels que la substitution de retardateur de flamme, plastifiant et surfactant par des alternatives issues du végétale. Il aborde également les différents programmes de recherche réalisés au laboratoire de Chimie Biologique Industrielle de Gembloux Agro-Bio Tech qui ont permis le développement de nouvelles substances biobasées en accord avec une chimie plus durable et répondant aux exigences de REACH. [less ▲]

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See detailCentralized Model Predictive Control of Multi-Terminal Direct Current Grids
Papangelis, Lampros ULg

in Proc. of the 8th IEEE Benelux Young Researchers Symposium 2016 (2016, May 12)

This work describes a centralized control for Multi-Terminal Direct Current (MTDC) grids. It is based on Model Predictive Control (MPC) whose aim is to satisfy a desired schedule, while avoiding or ... [more ▼]

This work describes a centralized control for Multi-Terminal Direct Current (MTDC) grids. It is based on Model Predictive Control (MPC) whose aim is to satisfy a desired schedule, while avoiding or correcting any system limit violation. The central controller collects voltage and power measurements from the converters of the system in regular intervals and sends back converter power setpoints. The latter are calculated by solving a quadratic programming problem subject to linear constraints and using a simplified model for the DC system. In addition, the overall MTDC grid control structure including the local and the centralized controllers is described. [less ▲]

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See detailModelling nitrogen incorporation by primary producers of a Mediterranean coastal area
Elkalay, Khalid; Frangoulis, Constantin; Richir, Jonathan ULg et al

Conference (2016, May 11)

The aim of this study was to simulate the uptake flow of nitrogen (gN m-2) of P. oceanica meadow for 4 primary producers of the bay of Calvi (Corsica, France) (phytoplankton, macro-algae, the Posidonia ... [more ▼]

The aim of this study was to simulate the uptake flow of nitrogen (gN m-2) of P. oceanica meadow for 4 primary producers of the bay of Calvi (Corsica, France) (phytoplankton, macro-algae, the Posidonia oceanica leaves and their epiphytes). The model developed for this purpose simulates the evolution of nitrogen incorporation. The effect of the light intensity, and the water column temperature and concentration in internal and external nitrogen on nitrogen incorporation by the 4 primary producers is modeled. Thus, the incorporation rate of both NO3-and NH4+by phytoplankton was more important than for benthic producers. Macro-algae incorporations had intermediate incorporation rates between the ones of, the phytoplankton and P. oceanic leaves and their epiphytes. The incorporation of NH4+ by the phytoplankton is higher than the incorporation of NO3-. The model appears well adapted to establish the main environmental factors that determine the incorporation of inorganic nitrogen by the various primary producers. It is also able to represent the relative importance of nitrogen incorporation by the various producers. [less ▲]

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See detailAudition à la Chambre des représentants sur les aspects constitutionnels du droit de grève
Behrendt, Christian ULg

Report (2016)

Audition publique en Commission des affaires sociales de la Chambre des Représentants, Bruxelles, 11 mai 2016

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See detailImpact de l’ancrage sur les herbiers de posidonie
Abadie, Arnaud ULg

Scientific conference (2016, May 11)

La posidonie (Posidonia oceanica), forme en Corse des herbiers colonisant les substrats depuis la surface jusqu’à 40 m de profondeur. Ces herbiers jouent un rôle écologique essentiel en oxygénant le ... [more ▼]

La posidonie (Posidonia oceanica), forme en Corse des herbiers colonisant les substrats depuis la surface jusqu’à 40 m de profondeur. Ces herbiers jouent un rôle écologique essentiel en oxygénant le milieu grâce à la photosynthèse et en séquestrant du CO2 au sein de leur complexe racinaire dans le sédiment (ou "matte"). Ces activités métaboliques entraînent une importante modification des conditions biogéochimiques du substrat qui favorisent le maintien de la plante. Les herbiers de posidonie se développant dans les zones côtières, ils sont impactés par les activités anthropiques (urbanisation, pollution, fermes aquacoles, ancrage) qui peuvent entraîner d’importantes destructions et des régressions de leur zone de recouvrement. L’ancrage intensif dans les herbiers à faible profondeur y génère des trouées, ou "intermattes". Les destructions engendrées par les navires de petite taille (< 10 m) peuvent, dans certaines conditions, être recolonisées par la posidonie. Cependant certaines zones sont soumises à l’ancrage intensif de navires de plaisance de grande taille (> 20m), qui est susceptible de générer des intermattes d’une étendue plus importante. Ce phénomène d’expansion ne peut s’expliquer par la seule destruction mécanique. L’arrachage de la strate foliaire de la posidonie par les ancres semble entraîner de profondes modifications physiques et chimiques dans le sédiment. Un milieu anoxique défavorable à son développement paraît se créer. Des composés toxiques pour la plante, tel que le sulfure d’hydrogène (H2S), pourraient alors s’introduire dans ses tissues entraînant une limitation de son développement, voire sa disparition menant ainsi à une amplification des dégâts mécaniques de l’ancrage. [less ▲]

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See detailAccurate measurement of radius evolution as a function of direction in 3D images
Plougonven, Erwan ULg; Hubert, Julien ULg; Collin, Frédéric ULg et al

Poster (2016, May 11)

Very often the reason for using of X-Ray tomography in a research project is to measure the evolution of some geometrical characteristic. The sought characteristic may be explained in simple words like ... [more ▼]

Very often the reason for using of X-Ray tomography in a research project is to measure the evolution of some geometrical characteristic. The sought characteristic may be explained in simple words like size, shape, or distance, but in practice measures based on these notions can have a complex implementation. We present a simple problem, measuring the evolution of radius in a cylindrical sample (a common shape for sample preparation for tomography) and how this value differs according the direction in which we look, when such evolution is known to be anisotropic. The solution is not unique, but we show that a naïve manual approach are not accurate enough, and how even a simple geometric notion such as radius needs a thorough definition in relation to its applicability to 3D image analysis. We extend the argument to how a good understanding of the notions and algorithms used in the quantification of geometrical characteristics can directly affect the pertinence and representativity of the results. [less ▲]

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See detailOzone concentration and CO2 flux monitoring in a belgian forest
Hurdebise, Quentin ULg; Bergmans, Benjamin; Aubinet, Marc ULg

Poster (2016, May 11)

Temperate forests, as other ecosystems and oceans, mitigate the accumulation in the atmosphere of CO2, the main responsible for the current climate change. It is, therefore, a necessity to understand how ... [more ▼]

Temperate forests, as other ecosystems and oceans, mitigate the accumulation in the atmosphere of CO2, the main responsible for the current climate change. It is, therefore, a necessity to understand how these forests react and will react in a changing environment. That requires long-term monitoring of the environment. Tropospheric ozone is one parameter to monitor as it affects the forest by inducing oxidative stress once inside the leaves. Using 16 years of continuous data from an air quality monitoring station managed by the ISSeP (Institut Scientifique de Service Public) located in a mixed forest in east Belgium, we identified ozone concentration extreme events and we investigated their occurrence frequency as well as their relation with climatic variables and air components. As variables are subjected to daily, yearly and inter-annual dynamics, anomalies were used to detect extreme events. To obtain anomalies, we removed the previously mentioned dynamics from half-hourly raw data. Daily and yearly dynamics were removed first and explained 40% of the variability observed in half-hourly ozone concentrations. Then, the inter-annual dynamic was obtained by computing the yearly mean of the residuals, it accounted for 2% of the variability observed. A significant (p<0.01) decreasing trend was observed for these residuals. Determining if that trend is site specific or regionally observed can be done by applying the same analysis to the other sites from the network managed by the ISSeP. No significant trend in the yearly frequency and intensity of extreme events was observed. We used a stepwise regression to identify the variables that explain these extreme events. Significant relations were found between ozone concentration and climatic variables (vapor pressure deficit, temperature, radiation and wind direction) as well as other air components concentration (NO2, NO, NOX, CO). The next step will be to estimate the forest capacity to uptake ozone in order to predict ozone-induced damage and compared it to the CO2 uptake and H2O emissions measured in an ICOS site, the Vielsalm Terrestrial Observatory, located in the same forest at less than 300 meters from the air quality monitoring station. [less ▲]

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