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See detailLA STEAM EXPLOSION : PRINCIPE ET ACTION SUR LES MATERIAUX LIGNOCELLULOSIQUES
Jacquet, Nicolas ULg; Blecker, Christophe ULg; Paquot, Michel ULg

Poster (2009, December 16)

La steam explosion est un procédé thermomécanochimique qui va permettre la déstructuration de la matière lignocellulosique par l’action combinée de la chaleur issue de la vapeur, des hydrolyses induites ... [more ▼]

La steam explosion est un procédé thermomécanochimique qui va permettre la déstructuration de la matière lignocellulosique par l’action combinée de la chaleur issue de la vapeur, des hydrolyses induites par la formation d’acides organiques et du cisaillement résultant de la chute brutale de pression. Le procédé est composé de deux phases distinctes. D’une part, le vapocraquage qui consiste à faire pénétrer par diffusion, puis à condenser, la vapeur sous haute pression à l’intérieur de la structure du matériau. L’eau condensée à température élevée va initier l’hydrolyse des groupements acétyles contenus dans les xylanes et induire la formation d’acides organiques. Selon la sévérité des conditions (pression, température), les acides vont catalyser l’hydrolyse des fractions hémicellulosiques, induire des modifications dans la structure des lignines et modifier le degré de cristallinité de la fraction cellulosique. D’autre part, la décompression explosive. Cette phase est provoquée par une chute brutale de pression qui va entraîner la revaporisation d’une partie de l’eau condensée. L’expension brutale de la vapeur va induire des forces de cisaillement qui vont modifier les propriétés physiques (granulométrie, surface spécifique, rétention d’eau…) du matériau. [less ▲]

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See detailSommet de Copenhague: Que veut l’Afrique ?
Ozer, Pierre ULg

Article for general public (2009)

Les pays pauvres sont moins armés pour faire face aux changements climatiques. Ils revendiquent une “justice climatique” avec des mécanismes de compensation. Est-ce juste ? Est-ce trop ? Ils se heurtent ... [more ▼]

Les pays pauvres sont moins armés pour faire face aux changements climatiques. Ils revendiquent une “justice climatique” avec des mécanismes de compensation. Est-ce juste ? Est-ce trop ? Ils se heurtent au mode de vie non négociable des nantis. [less ▲]

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See detailUne très brève histoire des musiques populaires afro-américaines
Pirenne, Christophe ULg

Scientific conference (2009, December 15)

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See detailVariation in external morphology of resident bottlenose dolphins in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg; Cammareri, Alejandro

in Journal of Marine Animals and Their Ecology (2009), 2(2), 3-6

A photo-identification study carried out in Bahía San Antonio (Patagonia Argentina) showed a variation in external morphology among year-round resident bottlenose dolphins. Out of 63 individually ... [more ▼]

A photo-identification study carried out in Bahía San Antonio (Patagonia Argentina) showed a variation in external morphology among year-round resident bottlenose dolphins. Out of 63 individually identified bottlenose dolphins, 15 were considered year-round residents of which three show variations in external morphology: they have a more falcate dorsal fin, darker coloration and shorter beak, physical characteristics described for the regional form of bottlenose dolphins present in the more southern province Chubut. The three morphologic distinct individuals, with one associated calf, could be re-identified in the study area up to 10 times over all the different seasons and up to now, no other bottlenose dolphins with similar characteristics could be observed in the area. On all occasions, they were re-identified in close occasions with each other and on 8 occasions in close association with other identified individuals. So far it was believed that the two regional forms of bottlenose dolphins present in Argentina were isolated. This communication is meant to document the residency and interaction of both regional forms in the same area. [less ▲]

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See detailANNUAL SCIENTIFIC REPORT PHASE II "Impact of Phenology and Environmental Conditions on BVOC Emissions from Forest Ecosystems" "IMPECVOC"
Dewulf, Jo; Joó, Eva; Steppe, Kathy et al

Report (2009)

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See detailThe diversity of clostridial hydrogenases revealed by genome sequencing projects
Calusinska, Magdalena ULg; Wilmotte, Annick ULg; Joris, Bernard ULg

Poster (2009, December 15)

Molecular hydrogen is a key intermediate in metabolomic interactions of a wide range of microorganisms. Hydrogen is also regarded as a key component in future energy systems as it is a sustainable, clean ... [more ▼]

Molecular hydrogen is a key intermediate in metabolomic interactions of a wide range of microorganisms. Hydrogen is also regarded as a key component in future energy systems as it is a sustainable, clean, and transportable energy carrier. Some microorganisms can produce hydrogen during a reversible reduction of protons to dihydrogen, a reaction which is catalyzed by the enzyme hydrogenases. On the basis of their bimetallocenter composition, hydrogenases are divided into three main groups, phylogenetically not related: [NiFe] hydrogenases, [Fe] only hydrogenases and FeS cluster free hydrogenases. The latter were described in methanogenic Archaea only. [NiFe] hydrogenases, composed of at least two subunits are well characterized and widely distributed between Archaea and Bacteria. However, only a few representatives of Clostridium sp. possess this type of enzyme. On the other hand, much less is known about the [Fe] only hydrogenases, that are usually monomeric enzymes and restricted to Bacteria and a few eukaryotic species. Genome sequencing projects gave a completely new insight into the diversity of forms of putative [Fe] only hydrogenases within the genus Clostridium. With the use of bioinformatic tools, we have described the unusual modularity of forms of these enzymes, from monomeric to tetrameric with a different number of accessory domains reacting with diverse redox partners. This fact seems to support the central role of hydrogenases in cell metabolism and quick adaptation of the host to changing environmental conditions. Moreover, the presence of multiple putative operons encoding for multisubunit [FeFe] hydrogenases is highlighting the fact that hydrogen metabolism is very complex in the Clostridium genus. [less ▲]

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See detailLes norovirus: nouveaux agents entéropathogènes.
HUYNEN, Pascale ULg; Mathijs, Elisabeth

Conference (2009, December 15)

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See detailLe Calvin's Case (1608), les deux corps du roi et la souveraineté divisée
Braillon, Charlotte ULg

Scientific conference (2009, December 15)

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See detailSuperhydrophobic surfaces by electrospinning of polymer mixtures
Grignard, Bruno ULg; Vaillant, Alexandre; De Coninck, Joel et al

Poster (2009, December 14)

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See detailAFM-based mechanical testing of electrospun PCL fibers
Croisier, Florence ULg; Duwez, Anne-Sophie ULg; Jérôme, Christine ULg et al

Poster (2009, December 14)

Poly(ε-caprolactone)(PCL forms a part of the aliphatic polyesters; the biodegradable and biocompatible character of these polymers makes them outstanding candidates for short-to medium-term biomedical ... [more ▼]

Poly(ε-caprolactone)(PCL forms a part of the aliphatic polyesters; the biodegradable and biocompatible character of these polymers makes them outstanding candidates for short-to medium-term biomedical applications, especially in the form of nanometric fibers,as their assembly mimics the extracellular matrix structure. However, a prerequisite to their application as nanofibrous biomaterial scaffolds is the investigation of their mechanical strength. In the present study, PCL fibers produced by electrospinning were individually tested using an AFM-based nano-scale three-point bending technique. [less ▲]

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See detailAdherent functional coatings from readily available acrylates
Cecius, Michaël ULg; Jérôme, Christine ULg

Poster (2009, December 14)

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See detailSynthesis of novel amphiphilic mikto-arm star-shaped copolymers
Riva, Raphaël ULg; Lazarri, Wenda; Billiet, Leen et al

Poster (2009, December 14)

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See detailCobalt-mediated radical polymerization (CMRP) and coupling reaction (CMRC): mechanistic advances ans synthetic opportunities
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

Poster (2009, December 14)

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See detailCharacterization of spatio-temporal organization of slow waves during human NREM sleep
Schrouff, Jessica ULg; Leclercq, Yves ULg; Foret, Ariane et al

Poster (2009, December 14)

Sleep is a behavior commonly observed in a large number of animal species. However, neuroscientists still poorly understand the meaning of this loss of consciousness absolutely needed for life. In the ... [more ▼]

Sleep is a behavior commonly observed in a large number of animal species. However, neuroscientists still poorly understand the meaning of this loss of consciousness absolutely needed for life. In the present work, we established different methods to characterize the Slow Wave Sleep most recognizable patterns: the Slow Waves (SWs). Since the anatomical structure of white matter tracts that connect various brain regions is not random and thus must constraint the propagation of waves (Hagmann et al., 2008), our basic hypothesis was that large white matter bundles would bias the propagation of SW along specific patterns, which could be identified in homogeneous clusters of waves. To investigate our hypothesis, SWs were detected automatically on the three first periods of SWS using an algorithm based on Massimini et al., 2004. They were then clustered using a two steps procedure involving a hierarchical clustering based on delay maps and a k-means clustering based on the SWs potential in a given time interval around the maximum power of the SW negative peak. To compute the relevance of the final clusters, a mathematical criterion was implemented as well as a visual check. Results of the multisubjects study showed that only bad quality and small clusters could be obtained, suggesting that there is no particular organization of SWs across the night and inforcing the hypothesis that SWs are local phenomena, each one decreasing the homeostatic pressure in only one specific area. [less ▲]

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See detailMicrobial diversity and activity in temperate forest and grassland ecosystems
Malchair, Sandrine ULg

Doctoral thesis (2009)

Ecosystems currently face widespread biodiversity losses and other environmental disturbances, such as climate warming, related to increased anthropogenic activities. Within this context, scientists ... [more ▼]

Ecosystems currently face widespread biodiversity losses and other environmental disturbances, such as climate warming, related to increased anthropogenic activities. Within this context, scientists consider the effects of such changes on the biodiversity, and hence on the activity, of soil microorganisms. Indeed, soil microorganisms mediate a wide range of soil processes. Currently, knowledge on soil microbial diversity is still limited, partially due to technical limitations. The advent of molecular-based analyses now allows studying the soil microbial diversity. These advances in the study of soil microbial communities have lead to a growing evidence of the critical role played by the microbial community in ecosystem functioning. This relationship is supposed to be relevant for narrow processes, regulated by a restricted group of microorganisms, such as the nitrification process. This PhD thesis aimed at studying ammonia oxidizing bacteria (AOB) community structure and richness as an integrated part of soil functioning. This research aimed at investigating the effect of aboveground plant diversity on ammonia oxidizing bacteria diversity and function in forest and grassland soils with focus on the influence of (a) functional group identity of grassland plants (legumes, grasses, forbs), (b) grassland plant species richness and (c) tree species, on AOB diversity and function. Another objective of this research was to study the effect of a 3°C increase in air temperature on AOB diversity and function. The link between AOB diversity and function (potential nitrification) is also investigated. For grassland ecosystems, a microcosm experiment was realized. An experimental platform containing 288 assembled grassland communities was established in Wilrijk (Belgium). Grassland species were grown in 12 sunlit, climate controlled chambers. Each chamber contained 24 communities of variable species richness (S) (9 S=1, 9 S=3 and 6 S=9).The grassland species belonged to three functional groups: three species of each grasses (Dactylis glomerata L., Festuca arundinacea SCHREB., Lolium perenne L.), forbs (non-N-fixing dicots; Bellis perennis L., Rumex acetosa L., Plantagolanceolata L.), and legumes (N-fixing dicots; Trifolium repens L., Medicago sativa L., Lotus corniculatus L.). Half of these chambers were exposed to ambient temperature and the other half were exposed to (ambient +3°C) temperature. One ambient and one (ambient+3°C) chambers were destructively harvested 4, 16 and 28 months after the start of the experiment. The influence of plant functional group identity on the nitrification process and on AOB community structure and richness (AOB diversity) was assessed in soils collected from the first two destructive amplings (chapter 2). The effect of plant species richness on AOB diversity and function was considered for soils sampled after 16 and 28 months (chapter 3). AOB function was determined by potential nitrification. AOB community structure and richness were assessed by polymerase chain reaction followed by denaturing gradient gel electrophoresis (DGGE) and sequencing of excised DGGE bands. I found that functional group identity can affect AOB community structure. In particular, the presence of legumes, both in monoculture or in mixture with forbs and grasses, lead to AOB community composition changes towards AOB clusters tolerating higher ammonium concentrations. This change in AOB community structure was only linked to increased potential nitrification under monocultures of legumes, when ammonium was supposed to be not limiting. This study revealed that physiological attributes of AOB and resource availability may be important factors in controlling the nitrification process. This research showed that the impact of plant species richness on the nitrification process could be mediated by the interactions between plants and AOB, through competition for substrate. A 3°C increase in air temperature did not affect AOB community structure, richness or function. In forest ecosystems, we studied the effect of tree species in forest sites located in Belgian and in the Grand-Duchy of Luxembourg covered each by several deciduous or coniferous tree species (Fagus sylvatica L., Quercus petraea (Mattuschka) Lieblein, Picea abies (L.) Karst, Pseudotsuga menziesii (Mirbel) Franco). We investigated the influence of these tree species on microbial processes (chapter 5) related to C and N cycling, particularly with emphasize on the nitrification process and on the diversity of AOB (chapter 6). The results showed that the effect of tree species on net N mineralization was likely to be mediated through their effect on soil microbial biomass, reflecting their influence on organic matter content and carbon availability. Influence of tree species on nitrification (potential and relative) might be related to the presence of ground vegetation through its influence on soil ammonium and labile C availability. AOB community structure was more site-specific than tree specific. However, within sites, AOB community structure under broadleaved trees differed from the one under coniferous trees. The effect on tree species on AOB was likely to be driven by the influence of tree species on net N mineralization, which regulates the substrate availability for AOB. The results also demonstrated that the relationship between AOB diversity and function might be related both to AOB abundance and AOB community structure and richness. This thesis showed no clear relationship between AOB community structure or richness and AOB function. However, we revealed that aboveground grassland plant richness, grassland plant functional groups and tree species influence AOB community structure and richness. [less ▲]

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