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See detailVers une Politique de la Ville en Wallonie : recommandation pour la mise en oeuvre d'une politique transversale et intégrée de dynamisation des quartiers urbains
Mercenier, Chloé ULiege; Ruelle, Christine ULiege; Bastin, Florine et al

E-print/Working paper (2017)

La note de recherche propose les principaux résultats de la recherche CPDT 2015-2016 sur la Politique de la Ville en Wallonie. Elle concerne, plus précisément, les constats et recommandations pour le ... [more ▼]

La note de recherche propose les principaux résultats de la recherche CPDT 2015-2016 sur la Politique de la Ville en Wallonie. Elle concerne, plus précisément, les constats et recommandations pour le développement des quartiers urbains selon trois grandes catégories de difficultés : le cadre de vie dégradé, le contexte social défavorable et le contexte économique défavorable. [less ▲]

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See detailHow are youth philanthropy practices transforming the philanthropic field?
Dessy, Elodie ULiege; Xhauflair, Virginie ULiege

Conference (2017, July 05)

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See detailUn dispositif de formation initiale des enseignants en didactique des mathématiques au niveau du secondaire supérieur en Belgique francophone
Balhan, Kevin ULiege; Gérard, Isaline; Nguyen, Giang et al

Conference (2017, July 05)

L'article présenté lors du symposium fédère plusieurs recherches menées dans notre laboratoire de didactique des mathématiques : le « Ladimath », autour de la formation initiale des enseignants de ... [more ▼]

L'article présenté lors du symposium fédère plusieurs recherches menées dans notre laboratoire de didactique des mathématiques : le « Ladimath », autour de la formation initiale des enseignants de mathématique au niveau du lycée et, plus particulièrement, autour d’une question de recherche qui concerne une dimension particulière de la « réflexivité » : « les mathématiques comme problème professionnel ». Nous y décrivons le dispositif mis en place dans la formation initiale des enseignants en mathématique à l’Université de Liège, celui-ci étant alimenté de différentes manières selon l’épistémologie du savoir mathématique questionné lors de la formation. Dans cet article, nous l’illustrons sur trois thèmes différents : celui de l’analyse mathématique, de la géométrie, et des probabilités/statistiques. [less ▲]

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See detailConditions, apports et limites du e-tutorat dans un dispositif de formation hybride
Denis, Brigitte ULiege

in Rinaudo, Jean-Luc (Ed.) Symposium du REF - Téléprésence en éducation (2017, July 04)

Un des enjeux de la formation à distance en formation d’adultes est de mettre en place des dispositifs répondant aux besoins des apprenants, respectant des principes andragogiques et procurant un ... [more ▼]

Un des enjeux de la formation à distance en formation d’adultes est de mettre en place des dispositifs répondant aux besoins des apprenants, respectant des principes andragogiques et procurant un environnement de qualité pédagogique (activités, ressources...) et ergonomique. De plus, le tutorat est un facteur primordial dans la mise en œuvre de tels dispositifs. Procurant un sentiment de présence (Jacquinot, 2002), fournissant un soutien (socio-affectif, cognitif, organisationnel...) à l’apprenant, il influence sa persévérance et l’atteinte de ses objectifs. Cette étude traite de la médiation entre e-tuteurs et apprenants dans un dispositif de formation hybride (certificat d'université en gestion de dispositifs techno-pédagogiques innovants). La mise en place de ce dernier a impliqué d’une part un processus d’ingénierie pédagogique incluant une médiatisation des savoirs (ressources) et des activités à distance (consignes, outils de communication, de dépôt de travaux, etc.) et, d’autre part, un processus d’ingénierie tutorale (Rodet, 2010). Les e-tuteurs ont été formés (Denis, 2003) et se sont accordés sur leur profil d’interventions vis-à-vis des apprenants. En outre, des réunions de concertation ont été organisées à plusieurs reprises durant la formation afin de réguler, au besoin, les interventions tutorales. Le principe de ce dispositif est de s’ancrer dans le projet personnel du participant. Il prévoit au fil de la formation des interactions régulières entre un e-tuteur et son (ses) tutoré(s) sur base d’un carnet de route (Roadbook) hebdomadaire complété en ligne. Ces interactions ont généralement lieu par courriel ou via l’annotation de documents partagés. Par ailleurs, les tutorés reçoivent également de la part des formateurs des feedback écrits personnalisés au fur et à mesure de la rentrée de leurs travaux. Ces derniers, ainsi que leurs réflexions tout au long du processus de formation, sont compilés dans leur Roadbook. Les conditions, apports et limites du e-tutorat dans ce dispositif seront appréhendées à partir de l’analyse des Roadbooks des apprenants et d’interviews de l’un d’entre eux ainsi que des e-tuteurs. [less ▲]

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See detailUnsteady pressure distributions on a 4:1 rectangular cylinder: comparison of numerical and experimental results using decomposition methods.
Guissart, Amandine ULiege; Andrianne, Thomas ULiege; Dimitriadis, Grigorios ULiege et al

Conference (2017, July 04)

Detached flows around bluff bodies are ubiquitous in civil engineering applications. In this work, the flow around a static 4:1 rectangular cylinder at moderate Reynolds number and at different angles of ... [more ▼]

Detached flows around bluff bodies are ubiquitous in civil engineering applications. In this work, the flow around a static 4:1 rectangular cylinder at moderate Reynolds number and at different angles of incidence is studied using both Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD). Typically, the integration of EFD and CFD allows a better understanding of the flow of interest by leveraging the complementary of their respective outputs. However, the comparison of computational and experimental results is an important but difficult step of this integration, particularly in the case of local quantities related to unsteady flows. In this work, decomposition methods are used to compare unsteady loads and pressure distributions coming from EFD and CFD. In particular, Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are used to extract the dominant structures of the aerodynamic coefficients. The experimental data are obtained from dynamic pressure measurements in wind tunnel while numerical data come from two-dimensional unsteady Reynolds-Averaged Navier-Stokes (uRANS) simulations and tri-dimensional Delayed-Detached Eddy Simulations (DDES). This work shows that the decomposition methods represent a powerful tool enabling the analysis and the quantitative comparison of the main spatial and temporal characteristics of unsteady flows. Moreover, the accuracy of uRANS and DDES results is analyzed in light of the capacity of both CFD techniques to capture the reattachment occurring on the upper part of the rectangular cylinder. [less ▲]

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See detailEffect of Organic Solvents on Microalgae Growth, Metabolism and Industrial Bioproduct Extraction: A Review
Miazek, Krystian ULiege; Kratky, Lukas; Sulc, Radek et al

in International Journal of Molecular Sciences (2017)

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See detailFor your ka! How to give something as a present to the tomb owner?
Motte, Aurore ULiege

Conference (2017, July 04)

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See detailMaximal voluntary isometric contraction tests for normalizing surface EMG of scapular stabilizers muscles
Schwartz, Cédric ULiege; Tubez, François ULiege; Soulier, Maxime et al

Conference (2017, July 04)

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See detailUsing amino acid stable isotopes to estimate trophic position
Sturaro, Nicolas ULiege

Conference (2017, July 04)

Estimating the trophic positions of animals in food webs is useful in addressing many fundamental ecological and ecotoxicological questions. These estimates are generally based on gut content and stable ... [more ▼]

Estimating the trophic positions of animals in food webs is useful in addressing many fundamental ecological and ecotoxicological questions. These estimates are generally based on gut content and stable isotope analyses, which have become essential tools for ecotoxicologists. While these tools have proven their usefulness, they involve several pitfalls that can result in large errors in the estimation of animals’ trophic positions. Relatively recently, these tools were improved with the analysis of the compound-specific amino acid nitrogen stable isotopes. The approach is based on the fact that certain amino acids (e.g., glutamic acid) exhibit metabolic isotope fractionation and others (e.g., phenylalanine) are incorporated into the tissues of consumers in a conservative manner. Indeed, amino acids of the latter category exhibit only a small change in their nitrogen isotope composition, which is similar to that found in primary producers. Therefore, the trophic position of an animal species is estimated based on a comparison of the nitrogen isotope composition of these two groups of amino acids from a single organism. This lecture will try to show the potential of the compound-specific stable isotope analysis of amino acids to illustrate food-web structure and estimate trophic positions in wild animal populations. It will summarize recent advances from field and laboratory studies and present case studies taken from the aquatic environment. In addition, this lecture will discuss the benefits, current limitations and analytical challenges related to this approach, which continues to open new research routes in many fields of ecology, including ecotoxicology. [less ▲]

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See detailLes relations de pouvoir dans l’accompagnement des demandeurs d’emploi par les intermédiaires privés de l’emploi
Gérard, Julie ULiege

Conference (2017, July 04)

Cette contribution s’intéresse à la mise en oeuvre de l’accompagnement des demandeurs d’emploi, en tant que politique sociale visant la (ré)insertion socioprofessionnelle des personnes éloignées de ... [more ▼]

Cette contribution s’intéresse à la mise en oeuvre de l’accompagnement des demandeurs d’emploi, en tant que politique sociale visant la (ré)insertion socioprofessionnelle des personnes éloignées de l’emploi par une lutte contre le chômage de longue durée et l’exclusion sociale. Plus précisément, elle porte un intérêt singulier aux relations de pouvoir qui s’exercent, dans les échanges et les interactions, entre les intermédiaires privés du marché du travail et leurs usagers, dès la phase de sélection des projets d’accompagnement. Cette contribution s’attèle dès lors à rendre compte des formes de contrôle qu’exercent les intermédiaires privés dans la concrétisation de leur action d’insertion lorsqu’ils sont contraints de respecter les orientations européennes en matière de profilage. Elle repose, par conséquent, sur l’analyse des ressorts et des effets de pouvoir en considérant l’influence de pressions institutionnelles induites par le contexte de rationalisation et d’efficacité à l’intérieur duquel la prise en charge des demandeurs d’emploi est réalisée.Ce faisant, cette contribution s’attache à illustrer l’influence de l’action d’intermédiation exercée sur les transitions des demandeurs d’emploi par la présence de deux effets de trappe, étayés par l’activation de mécanismes de filtrage à différents moments de l’accompagnement. Par ce biais, elle vise à rendre compte de la logique structurelle qui oriente les transitions professionnelles des usagers vers une forme de « précariat social » sur le marché du travail. Elle s’appuie, pour ce faire, sur une recherche empirique de nature qualitative, menée entre septembre 2013 et juin 2015, en Belgique Francophone, auprès de six structures privées spécialisées dans l’accompagnement vers et dans l’emploi. [less ▲]

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See detailLes organismes d’insertion socioprofessionnelle mis à l’épreuve des dispositifs techniques de l’action publique
Gérard, Julie ULiege

Conference (2017, July 04)

Cette contribution porte un intérêt singulier aux enjeux relatifs à l’externalisation de l’accompagnement des demandeurs d’emploi, en tant que mesure d’activation, auprès d’organismes privés d’insertion ... [more ▼]

Cette contribution porte un intérêt singulier aux enjeux relatifs à l’externalisation de l’accompagnement des demandeurs d’emploi, en tant que mesure d’activation, auprès d’organismes privés d’insertion socioprofessionnelle en Belgique francophone. Plus précisément, elle s’intéresse à l’influence de dispositifs techniques dans la concrétisation de leur mission de réinsertion. Pour ce faire, elle porte une attention particulière à l’analyse des relations de pouvoir qui s’exercent, à distance, entre les services publics de l’emploi et les prestataires privés, par le biais de technologies afin de coordonner et de contrôler l’activité déléguée. Elle s’attache, dès lors, à rendre compte des différentes formes de pression institutionnelle qui émanent de ces technologies, à différentes phases de l’accompagnement, sous-tendant un mouvement de standardisation de l’action publique. Par ce biais, cette contribution démontre à quel point la standardisation et les indicateurs chiffrés deviennent de véritables outils de pouvoir destinés à évaluer tant la performance des opérateurs privés que l’efficacité de leur action. Par ce gouvernement par les instruments, les organismes privés sont à présent confrontés à un nouveau modèle de gouvernance qu’il convient de s’approprier et/ou de contourner. Partant de ces constats, notre raisonnement sera guidé autour de deux questions : quel est l’effet de ces dispositifs techniques dans le travail quotidien d’accompagnement des opérateurs privés ? Et de quelle marge de manoeuvre disposent-ils pour se les réapproprier et contourner les contraintes qui en résultent ? De la sorte, cette contribution s’inscrit dans une approche analytique qui s’attache à rendre compte des jeux de pouvoir en présence, en appréhendant l’accompagnement au concret, saisi dans ses actions de suivi et d’opérationnalisation. [less ▲]

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See detailInfluence of environmental factors on food intake among nursing home residents: a survey combined with a video approach
Buckinx, Fanny ULiege; Reginster, Jean-Yves ULiege; Morelle, Alison et al

in Clinical Interventions in Aging (2017), 12

Background: In addition to the well-known physiological factors, dietary behavior that affects health seems to be influenced by a wide variety of environmental factors. The aim of this study was to assess ... [more ▼]

Background: In addition to the well-known physiological factors, dietary behavior that affects health seems to be influenced by a wide variety of environmental factors. The aim of this study was to assess, by means of an original video approach, the influence of the environment on food intake in nursing homes. Methods: The perception of the environment during meals in nursing homes was evaluated by residents and by two groups of volunteers who either work in the field of geriatrics, or who do not work in the field of geriatrics. First, a random sample of residents answered a self-administered questionnaire related to different indicators (ie, noise, space, comfort, light, odors, perceived satisfaction of meals, taste of meals, presentation of meals, service and setting). Second, two separate panels, one including the people who work in the field of geriatrics (ie, experts) and one including the people who have no particular interest in geriatrics (ie, nonexperts), were asked to answer a questionnaire on their perception of the environment after having watched a video of the lunch in each nursing home. Then, the food intake of the residents was measured by a precise food-weighing method. Results: A total of 88 residents from nine different nursing homes, 18 experts and 45 nonexperts answered the questionnaires. This study highlighted that, on the one hand, after adjustment on confounding variables, the perception of the quantity of food served by the residents is the only single factor associated with food consumption (P=0.003). On the other hand, experts and nonexperts did not perceive any environmental factor that seems to be significantly associated with residents’ food intake. Conclusion: Our results highlighted that, in a nursing home setting, environmental factors have limited influence on the food intake of the residents, with the exception of their own perception of the quantity served. The relevance of this factor deserves further investigation. [less ▲]

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See detailComparative Proteomics Analysis Provides New Candidates for Zinc Homeostasis Regulation in Arabidopsis
Amini, Sahand ULiege; Arsova, Borjana ULiege; Scheepers, Maxime ULiege et al

Poster (2017, July 03)

Zinc (Zn) is an essential micronutrient for plants and around two billion people are depending on grains and legumes as their main Zn source. On the other hand, this transition metal is toxic for plants ... [more ▼]

Zinc (Zn) is an essential micronutrient for plants and around two billion people are depending on grains and legumes as their main Zn source. On the other hand, this transition metal is toxic for plants at high concentrations in soils. This calls for a better unravelling of Zn homeostasis regulation mechanisms, including sensing and signaling in plants. In order to fulfill this aim, we are testing for novel proteins involved in Zn homeostasis in the model plant Arabidopsis thaliana. First, quantitative proteomics was performed on root and shoot samples obtained upon Zn starvation and re-supply in different spatio-temporal conditions. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis was also performed for those treatments to measure the Zn concentration in tissues. It showed very rapid Zn uptake in root upon re-supply. Moreover, quantitative expression studies of known players of Zn homeostasis confirmed our large-scale proteomic results, although for a few genes lack of correlation between transcript and protein regulation was observed. Using clustering, statistical and gene ontology analyses, we selected candidate genes for further studies. Among more than 5000 detected proteins in roots by shotgun proteomics, 75 genes were selected for targeted analyses. In general, our results show that comparative proteomics study can be useful to reveal new players in the Zn regulatory network in plants, which can lead to new Zn biofortification and phytoremediation strategies. [less ▲]

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See detailBenchmarking the Environmental Impact of Green and Traditional Masonry Wall Constructions
Gauvreau-Lemelin, Corinne; Attia, Shady ULiege

in Brotas, Luisa; Roaf, Susan; Fergus, Nicol (Eds.) Passive low energy architecture design to thrive (2017, July 03)

In Belgium, the most common approach for nearly Zero Energy Buildings is to comply with the locally modified version of the German Passive House (PH) Standard that requires a very low conductivity of ... [more ▼]

In Belgium, the most common approach for nearly Zero Energy Buildings is to comply with the locally modified version of the German Passive House (PH) Standard that requires a very low conductivity of exterior walls. The conventional PH brick constructions are dominated by building materials with high environmental impact including concrete blocks, firebrick and petrochemical insulation materials that produce a great amount of greenhouse gases (GHG). Moreover, there are very few studies that assessed the holistic environmental impact of conventional wall compositions against ecological wall compositions. Therefore, this research compares a traditional Belgian representative wall against a hemp block wall, according to the PH standard. The environmental impact of each wall is quantified through a life cycle assessment. The final results indicate that the hemp wall reinforced with a wood skeleton has a much lower impact on the environment: up to 60% reduction on total primary energy, 72% on climate changes, 93% on eutrophication, 61 % on ozone layer depletion and 74% on acidification. Future work may refine the assessment process. The study provides novel and significant findings that can inform building owners, architects and contractors and encourage them to choose environmentally friendly masonry wall compositions. [less ▲]

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See detailCharacterizing Thiamine Status and Mechanisms of Thiamine Supplementation on Subacute Ruminal Acidosis Attenuation in Dairy Cows
Pan, Xiaohua ULiege

Doctoral thesis (2017)

Dairy cows are often fed high grain diets to maximize milk production in today’s intensive management farms. However, overfeeding high grain diets increases the risk of subacute ruminal acidosis (SARA ... [more ▼]

Dairy cows are often fed high grain diets to maximize milk production in today’s intensive management farms. However, overfeeding high grain diets increases the risk of subacute ruminal acidosis (SARA), which is characterized by prolonged decrease in rumen pH and high levels of lipopolysaccharide (LPS). SARA challenge has been confirmed to severely impair animal health, production performance and farm profitability, and more and more attentions have been paid to prevent the occurrence of SARA in dairy industry worldwide. Our teams’ previous research found that thiamine supplementation relieved SARA in dairy cows, but the modes of action of thiamine in SARA attenuation are still unclear. In this context, this thesis was conducted to increase our understanding of relationships between SARA induction and thiamine, and to explore the mechanisms of thiamine supplementation on SARA attenuation by determining its effects on rumen fermentation, microbiome composition and anti-inflammatory response. Firstly, the first experiment in Chapter III demonstrated that thiamine status in rumen and blood were altered by SARA induction and thiamine deficiency occurred during SARA challenge. Regression analysis proved the ruminal thiamine content was positively related to pH and the concentrations of acetate in the rumen, and negatively correlated to the lactate contents, indicating the altered rumen fermentation would affect thiamine status. Secondly, the mRNA expression of thiamine transporters in ruminal epithelium (Chapter IV) and ruminal bacteria compositions (Chapter V) in SARA and control cows were detected. We found that thiamine concentration was positively correlated with Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter and Fibrobacter, and the decrease in these genera implied SARA challenge altered ruminal thiamine status by inhibiting the growth of thiamine synthesis related bacteria. The positive correlation between ruminal and blood thiamine, and the down-regulation of thiamine transporters’ expression in rumen epithelium indicated the reduced ruminal thiamine synthesis and thiamine absorption by SARA challenge resulted in low blood thiamine content of SARA cows. Thirdly, the effects of thiamine on rumen fermentation (Chapter III), anti-inflammatory response (Chapter IV) and microbiome composition (Chapter V) were evaluated to reveal its mechanisms on SARA attenuation. We found that thiamine supplementation promoted acetate-producing bacteria including Ruminococcus 1, Pyramidobacter, Succinivibrio and Bacteroides, and decreased bacteria positively related to ruminal lactate (Succiniclasticum and Ruminococcaceae NK4A214). Consequently, rumen fermentation was improved by reducing the accumulation of lactate and increasing ruminal pH. In addition, thiamine supplementation alleviated inflammatory response in rumen epithelium by reducing the release of LPS and phosphorylation of NFκB protein, which is conducive to SARA attenuation. In summary, this thesis had increased our understanding of thiamine nutrition in dairy cows, and provided a new control strategy for subacute ruminal acidosis in dairy cows. However, further investigations are needed to deeply understand the relationship between thiamine and SARA induction, such as the isolation and validation of thiamine synthesis bacteria affected by SARA challenge, as well as to figure out metabolic pathways through which SARA induction affects thiamine synthesis in the rumen. Moreover, the impacts of overfeeding high grain diets on intestinal thiamine absorption are still unclear and need to be illuminated in dairy cows. [less ▲]

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See detailOmics insights into rumen ureolytic bacterial community and urea metabolism in dairy cows
Jin, Di ULiege

Doctoral thesis (2017)

Urea has been used in the diets of ruminants as a non-protein nitrogen source. Ureolytic bacteria are key organisms in the rumen producing urease enzymes to catalyze the breakdown of urea to ammonia (NH3 ... [more ▼]

Urea has been used in the diets of ruminants as a non-protein nitrogen source. Ureolytic bacteria are key organisms in the rumen producing urease enzymes to catalyze the breakdown of urea to ammonia (NH3), and the NH3 is used as nitrogen for microbial protein synthesis. In the rumen, hydrolysis of urea to NH3 occurs at a greater rate than NH3 can be utilized by rumen bacteria, and excess ammonia absorbed into blood may be harmful to the animals. Nowadays, little is known about the information of ureolytic microorganisms in the rumen, and the changes that occur in the rumen microbial and host metabolites induced by urea nitrogen have not been fully characterized. ‘Omics’ approaches, such as metagenomics and metabolomics have been applied to analyzing rumen microbial community and nutrients metabolism in dairy cows. The objective of this study is to investigate the rumen predominant ureolytic bacteria community and the mechanisms of urea utilization in ruminants using sequencing and metabolomics approaches. Firstly, an in vitro experiment trying to explore the ruminal ureolytic bacterial community was performed. Urea or acetohydroxamic acid were supplemented into the rumen simulation systems as the stimulator and inhibitor for ureolytic bacteria, respectively. The bacterial 16S rRNA genes were analyzed by Miseq sequencing and used to reveal the ureolytic bacteria by comparing different treatments. We found that urea supplementation significantly increased the proportion of ureC genes. The rumen ureolytic bacteria were abundant in the genera of Pseudomonas, Haemophilus, Neisseria, Streptococcus, Actinomyces, Bacillus and unclassified Succinivibrionaceae. Secondly, an in vivo experiment was taken to investigate differences in ureolytic bacterial composition between the rumen digesta and rumen wall based on ureC gene classification. Six dairy cows with rumen fistula were assigned to a two-period cross-over trial. One group was fed a total mixed ration without urea and the treatment group was fed rations plus 180 g urea per cow per day. Rumen bacterial samples from rumen content and rumen wall fractions were collected for ureC gene amplification and sequencing using Miseq. More than 55% of the ureC sequences did not affiliate with any known taxonomically assigned urease genes. The wall-adherent bacteria had a distinct ureolytic bacterial profile compared to the bacteria in the rumen content. The most abundant ureC genes were affiliated with Methylococcaceae, Clostridiaceae, Paenibacillaceae, Helicobacteraceae and Methylophilaceae families. Relative abundance of the operational taxonomic units (OTUs) affiliated with Methylophilus and Marinobacter genera were significantly higher in the bacteria on the rumen wall than that in the rumen content. Thirdly, based on the in vivo experiment, rumen fluid and blood samples were collected and analyzed using nuclear magnetic resonance spectroscopy and multivariate analysis of variance. Concentrations of valine, aspartate, glutamate, and uracil in the rumen, and urea and pyroglutamate in the plasma were increased after urea supplementation. Metabolic pathways include pantothenate and CoA biosynthesis, beta-alanine metabolism, valine, leucine, and isoleucine metabolism in the rumen, and urea and glutathione metabolism in the plasma were significantly increased by urea nitrogen. In conclusion, this study identified significant populations of ureolytic bacterial community that have not been recognized or studied previously in the rumen and provides a basis for obtaining regulatory targets to moderate urea hydrolysis in the rumen. The findings also provided novel information to aid understanding of the metabolic pathways affected by urea nitrogen in dairy cows, and could potentially help to guide efforts directed at improving the efficiency of urea utilization in the rumen. [less ▲]

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See detailHistoire évolutive du complexe Afzelia Smith (Leguminosae - Caesalpinioideae) dans les écosystèmes forestiers et savanicoles en Afrique tropicale
Donkpegan, Segbedji ULiege

Doctoral thesis (2017)

The genus Afzelia Smith (Fabaceae, Caesalpinioideae) is known to have seven African tree species two of which are found in the Zambezian region, one is distributed in the Sudanian region and the four ... [more ▼]

The genus Afzelia Smith (Fabaceae, Caesalpinioideae) is known to have seven African tree species two of which are found in the Zambezian region, one is distributed in the Sudanian region and the four other are endemic to the Guineo-Congolian region. These taxa, of high commercial value, are difficult to identify. They are therefore marketed under the same "doussié" name. These difficulties of distinction can prove detrimental to the sustainable management of populations. The aim of this doctoral thesis is to characterize the evolutionary history of the Afzelia genus. More specifically, this study aims to: (i) evaluate the level of morphological divergences within the Afzelia genus and describe the phylogenetic relationships in order to quantify the reproductive isolation between taxa by highlighting the role of past climate change and / or ecological gradients in the speciation of the genus; (ii) proceed to an analysis of the spatial genetic diversity and structure of Afzelia spp.; (iii) identify and describe ecological, biotic and abiotic factors that may influence population-level gene flows of an Afzelia species (A. bipindensis). A morpho-genetic analysis of Afzelia species was carried out and confirmed the strong botanical resemblance between the taxa. The savannah species are diploid and have half the size of the genome of forest species that are tetraploid. The phylogenies of genes (nuclear and chloroplastic) differ from one another and do not allow the separation of tetraploid taxa from one another. Such differences can be generated as a result of episodes of ancestral hybridization between species. These hybridizations would probably be old and would have occurred between lineages of the forest species and A quanzensis (a species of the Zambezian savannahs) lineages. Polyploidy would have occurred between 7 and 9.4 million years in the evolutionary history of the genus. In addition, Bayesian assignment and reproductive isolation analyzes suggested interspecific crosses, but only in forest species distributed sympatrically. At a more limited spatial scale, we observed two well differentiated genetic groups in sympatry in A. bipindensis. These show a morphological differentiation and a phenological shift of flowering which can contribute to their reproductive isolation. This study highlighted some important points: the discovery of a polyploid complex within the Afzelia genus, the confirmation of the delimitation of the diploid savannah species and the need to revise the delimitation of forest tetraploid species. [less ▲]

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