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See detailThe Cyanobacterial Biota of Polar Regions: a Molecular Approach
Stelmach Pessi, Igor ULiege

Doctoral thesis (2017)

Cyanobacteria are major components of Polar ecosystems. They comprise a considerable amount of the total biomass, are the main primary producers, and play important roles in the initial development of ... [more ▼]

Cyanobacteria are major components of Polar ecosystems. They comprise a considerable amount of the total biomass, are the main primary producers, and play important roles in the initial development of terrestrial and aquatic habitats. Although the cyanobacterial diversity in the Polar Regions has been well studied, research has been mostly limited to traditional methods such as microscopy, culturing, and Sanger-based molecular ecology approaches. High-troughput sequencing (HTS) has revolutionized our knowledge of microbial diversity and distribution, but a thorough investigation of polar cyanobacterial communities using HTS has not yet been performed. As a result, knowledge of the distributional patterns of polar cyanobacterial communities and the mechanisms underlying their structure is fragmentary. In this thesis, we applied the HTS approach to investigate the diversity and distributional patterns of cyanobacteria in a range of polar habitats. The main goals were: 1. To evaluate the use of HTS as a tool for assessing the cyanobacterial diversity in polar environments, including an assessment of different bioinformatics pipelines and the improvement represented by HTS in comparison to traditional methods; 2. To assess the spatial patterns of cyanobacterial communities across polar environments and the environmental factors shaping cyanobacterial community composition; 3. Tho study the successional dynamics of cyanobacterial communities following the colonization of recently deglaciated habitats. Due to its higher analytical depth, HTS was proven a valuable tool for the study of the cyanobacterial biota of Polar Regions. Nevertheless, the analysis of artificial communities highlighted the importance of strict bioinformatics control of HTS reads, as PCR and sequencing errors might bias the observed structure of the communities. Given the strict bioinformatics workflow applied, our results suggest a previously undetected polar cyanobacterial rare biosphere. On one side, the HTS approach revealed that microbial mat and biological soil crust (BSCs) across different Antarctic and Svalbard (High Arctic) regions are somewhat homogeneous, being dominated by filamentous cyanobacteria from the orders Pseudanabaenales and Oscillatoriales. At the phylotype level (97.5% similarity threshold), on the other hand, cyanobacterial communities were highly variable along environmental gradients within and between habitats. A study of benthic mat communities in Antarctic lakes revealed cyanobacterial communities highly structured by lake conductivity, and comparable compositions in lakes from distant Antarctic regions. In a study of BSC communities in four nunataks and mountain ridges in the Sør Rondane Mountains (Dronning Maud Land), highly dissimilar communities were observed between locations. Finally, two studies of BSC communities in Petunia Bay (Svalbard) revealed a marked, linear cyanobacterial community turnover along gradients of soil development. Altogether, the results obtained in the present thesis show that HTS is a powerful yet underused tool for the study of cyanobacterial diversity, not only in Polar Regions, but also on a global scale. This can be attributed to the very high sequencing depth achieved by HTS, which provides more robust assessments of community turnover and with a stronger statistical support than Sanger- based molecular ecology approaches. [less ▲]

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See detailValence des verbes et interdépendances entre lexique et syntaxe en kirundi
Tuyubahe, Pascal ULiege

Doctoral thesis (2017)

Ce travail de recherche a pour objet de décrire des phénomènes lexicaux et syntaxiques du kirundi peu examinés précédemment. Il est subdivisé en deux principales parties : la première partie est consacrée ... [more ▼]

Ce travail de recherche a pour objet de décrire des phénomènes lexicaux et syntaxiques du kirundi peu examinés précédemment. Il est subdivisé en deux principales parties : la première partie est consacrée à l’élaboration d’un lexique valenciel des verbes avec un ou plusieurs compléments, en prenant comme points de départ la liste de lexèmes de de Samie (2008) ainsi que le dictionnaire rundi-français de Rodegem (1970). Il s’avère que beaucoup de verbes peuvent apparaître dans différents schémas de construction, ce qui implique plusieurs unités lexicales pour ces verbes dans le lexique valenciel. La deuxième partie, composée de sept chapitres, consiste en la recherche de généralisations pouvant être faites à partir de ce lexique ; ces généralisations reposant sur une large base empirique, elles sont assez fréquemment accompagnées d’exceptions. Le chapitre 1 concerne le comportement syntaxique des groupes nominaux et groupes prépositionnels dans la valence des verbes et leur caractérisation par des tests; il y est question des objets directs, des objets prépositionnels, des circonstants et des attributs. Un chapitre est consacré au passif impersonnel (chapitre 2) car cette construction fournit une justification purement empirique à la catégorie « objet prépositionnel » en kirundi, permettant de distinguer les objets prépositionnels (locatif ou non) des autres compléments (y compris les circonstants valenciels de lieu). Le chapitre 3 montre l’importance quantitative des objets directs par rapport aux autres objets du lexique valenciel des verbes en kirundi et montre comment cette importance est encore accrue par l’existence en kirundi d’objets directs non valenciels, en particulier les objets introduits par l’intermédiaire d’un suffixe verbal (suffixe applicatif -ir- ou suffixe causatif -i- ou -iish-) et les possesseurs inaliénables introduits sans intermédiaire. Après avoir fait une présentation générale des temps et aspects et de la concordance des temps en kirundi (chapitre 4), les chapitres 5, 6 et 7 montrent comment cela se manifeste dans les propositions subordonnées valencielles et les propositions avec auxiliaire, en distinguant celles qui ont un verbe conjugué et celles qui ont un infinitif. Les conclusions générales sont suivies des propositions prospectives permettant d’effectuer des recherches approfondies en vue de compléter le lexique valenciel, d’une part et, d’autre part, de déterminer les conditions d’emploi des suffixes causatifs -i- et -iish-. [less ▲]

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See detailFunctional diversity and mowing regime of flower strips as tools to support pollinators and to suppress weeds
Uyttenbroeck, Roel ULiege

Doctoral thesis (2017)

Intensification of agriculture during past decades is one of the causes of biodiversity declines. Ecological intensification has been proposed as a more sustainable alternative of intensive agriculture ... [more ▼]

Intensification of agriculture during past decades is one of the causes of biodiversity declines. Ecological intensification has been proposed as a more sustainable alternative of intensive agriculture that should be able to fulfill worldwide demands of food, by optimizing ecosystem functions and services and reducing environmental impacts. One way to restore ecosystem functions and services in arable fields is creating flower strips in field margins. These flower strips enable wild plant communities to thrive and provide food and shelter to associated fauna. It is often suggested that increasing plant functional diversity could be a tool to optimize ecosystem functioning and ecosystem service delivery, and it could thus be a goal for the creation and management of flower strips. An example of ecosystem functioning studied in this manuscript, is the mutualistic interaction between plants and pollinators. To convince European farmers to implement flower strips, they are included in the subsidized Agri-Environment Schemes. However, there exists no clear appraisal of the pros and cons of flower strips for farmers. By systematically reviewing the literature for pros and cons, we found that most studies concerned agronomical and ecological processes related to flower strips, but few or no studies were dedicated to the social and economic aspects. Furthermore, pollination appears to be an important pro, and weed infestation a possible con, depending on flower strip creation and management. We focused on these two examples in the further study. We investigated (1) whether the increase of plant functional diversity can be used as tool to optimize flower strips for pollinators, (2) whether forb competition and adapting timing and frequency of mowing can be used as tools to limit weeds in flower strips, and (3) whether flower strips perform equally in supporting pollinators as the natural habitat for which they are thought to be a surrogate. To use functional diversity as a tool to optimize flower strips for pollinators, we first tested whether it is possible to create a flower strip with a desired functional diversity level. We sew experimental flower strips with increasing functional diversity, based on visual, morphological and phenological flower traits and surveyed the vegetation composition the first year after sowing. The sown gradient of functional diversity was present, but with lower absolute values due to unequal cover of sown species and due to the presence of spontaneous species. To test the effect on pollinator support, we monitored the plant-pollinator networks in the experimental strips during two years. In contrast to our expectations, pollinator species richness and evenness were not influenced by functional diversity, and increasing functional diversity even resulted in lower flower visitation rates. To investigate the effect of forb competition and timing and frequency of mowing on weed infestation, we created experimental flower strips either with grass and forb species in the seed mixture, either with only grass species. Three different mowing regimes were applied: summer mowing, autumn mowing and mowing both in summer and autumn. The cover of important weed, Cirsium arvense, was limited by adding forbs to the seed mixture and by mowing in summer or in summer and autumn. At last, by surveying plant-pollinator networks in perennial flower strips and natural hay meadows in the same landscape context, we observed that both the plant and the pollinator communities differed between the flower strips and the meadows. Perennial flower strips can thus be considered as a complementary habitat in the landscape and not a hay meadow surrogate. This study suggests that it is possible to manipulate the vegetation as well as infestation by certain weeds in flower strips by adapting the seed mixture and the mowing regime. However, to promote pollinators in flower strips, increasing plant functional diversity appears not to be the key, and the abundance of certain attractive plant species can be more important. Moreover our results suggest that pollinators perceived a lower redundancy of functional plant trait values when functional diversity was higher, as they had more separate feeding niches (less visited flower species in common). Our results also suggest that there could be a trade-off between the increase of functional trait diversity and the floral resource abundance per niche or functional trait combination. With the results of the tested flower strip creation and management methods and their effect on pollinator support and weed infestation, farmers and administrations can try to create and manage flower strips with the desired balance between pros and cons, and researchers can try to refine these methods and test the effects on other pros and cons. [less ▲]

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See detailSpatial hybridization and its implications on housing in Brussels and Amsterdam
Uyttebrouck, Constance ULiege; Teller, Jacques ULiege

Conference (2017, September 04)

This paper aims to address the effects of labour market mutations on housing through an analysis of “spatial hybridization”, focusing on the qualitative comparison of Brussels and Amsterdam. The objective ... [more ▼]

This paper aims to address the effects of labour market mutations on housing through an analysis of “spatial hybridization”, focusing on the qualitative comparison of Brussels and Amsterdam. The objective is to provide first elements of context, methodology and results of a wider on-going research. In the first section, we highlight underlying trends, in particular the emergence of NWoW in a context of new economy, and current issues on the housing market (flexibilisation, commodification, gentrification). Then, we discuss the relevance of applying path dependence in our research, before presenting our two case-study cities from a historical perspective and pointing out innovative practices and the current public discourse. Finally, we discuss differences and similarities through four elements of comparison: functional mix at the block level, service-oriented housing, economic and housing paths. The discussion is based on our literature review, early policy analysis and interviews with key-stakeholders. [less ▲]

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See detailLCM of construction waste towards circular economy of buildings: VALDEM project
Roy, Aubin; Groslambert, Sylvie ULiege; Pasquet, Vanessa et al

Poster (2017, September 04)

From resource prospective, building and construction sector is responsible for more than third of global resource consumption, including 12% of the fresh water use and its generation of solid waste is ... [more ▼]

From resource prospective, building and construction sector is responsible for more than third of global resource consumption, including 12% of the fresh water use and its generation of solid waste is estimated to be 40% of the total waste volume. At European level, construction and demolition waste is the largest waste stream representing one third of all waste produced in EU. Therefore the resource efficiency and management is crucial in building construction. A very significant part of the Construction and Demolition Waste (CDW) is not recycled today. Also a very limited part is used as a recycled content in the construction and building products and materials. This lack is mainly due to heterogeneity and dispersion of waste flows decreasing efficiency and economic viability of recycling. To address this issue, VALDEM project (funded by Interreg FWVL European Fund) aims to overcome barriers to increase up-cycling applications. The project focuses its activities in North of France, Flanders and Walloon regions (Belgium), and stands out from usual approaches by its cross-border view of circular economy. VALDEM aims, on one hand, to optimize buildings end of life management by developing new deconstruction, sorting and recycling processes to produce uniform and accessible material flows. On the other hand, the project aims at increasing recycling and generating high quality secondary materials (concrete and other flows) to be used in future buildings within an up-cycling prospective. And finally it aims at validating the solutions from technical, scientific, economic and environmental point of view. The Environmental assessment, based on LCA, consists of identifying hotspots and key aspects to prioritize the efforts of different economic actors. As a first step, an LCA meta-analysis is conducted to provide an environmental picture for different potential activities within the scope of the project. As a next step, a comparative LCA is conducted to assess the environmental benefits and impacts of different solutions proposed in the framework of the project in a decision making context, and to limit the impact transfer and to generate the maximum value for all the stakeholders. Finally, results will be transferred to main actors (recycling operators, buildings contractors, product manufacturers …) in the three regions in order to consolidate future key aspects to eco-design a building in light of circular economy. [less ▲]

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See detailElectrochemical Mechanism of TiMnSn4 as Anode Material for Li-ion Batteries
Lippens, Pierre-Emmanuel; Jumas, Jean-claude; Olivier-Fourcade, Josette et al

Conference (2017, September 04)

Li-ion batteries are widely used in portable electronic devices, electric vehicles or energy storage systems for intermittent energy sources, due to their high energy density, light weight and long cycle ... [more ▼]

Li-ion batteries are widely used in portable electronic devices, electric vehicles or energy storage systems for intermittent energy sources, due to their high energy density, light weight and long cycle life. However, the performances must be continuously improved, which requires the development of new electrode materials. Carbon is commercially used for the anode but its specific capacity is limited to 372 mAh g-1 due to the electrochemical insertion mechanism involving only 1 Li per 6 C. In order to increase the specific capacity, Sn was considered as electrochemically active element although it is about ten times heavier than C. This is due to the alloying/dealloying mechanism with up to 4.4 Li per Sn, providing a theoretical capacity of 992 mAh g-1. However, the Sn ↔ Li4.4Sn reversible transformations are associated with large volume variations responsible for capacity fading.Tin intermetallic compounds of the form MSnx, where M is a transition metal, were proposed to overcome this problem. The first lithiation transforms the pristine material into Li7Sn2/M nanocomposites where the M nanoparticles are expected to buffer the volume variations [1]. However, the delithiation process is more complex involving a possible back reaction of M with Sn, which could play a crucial role in the cycling stability. Such reaction was observed for Ni3Sn4 [2] and MnSn2 [3] but not for FeSn2 [4]. In addition, TiSnx intermetallics show very poor electrochemical activity [5]. The present work concerns the tin based ternary phase TiMnSn4 as new anode material for Li-ion batteries. This compound is of particular interest because it contains two different transition metals that are expected to react differently with Sn during delithiation, if we consider the previous results obtained for MnSnx and TiSnx. TiMnSn4 was obtained by mechanosynthesis to optimize the microstructure and characterized by different experimental tools and DFT (density functional theory) calculations. We propose an analysis of the reaction mechanism based on operando X-ray diffraction and 119Sn Mössbauer spectroscopy combined with a DFT interpretation of the electrochemical potential curve. References 1) M. Chamas, M.T. Sougrati, C. Reibel, P.E. Lippens, Chem. Mater. 25, 2410 (2013). 2) K.K.D. Ehinon, S. Naille, R. Dedryvère, P.E. Lippens, J.C. Jumas, D. Gonbeau, Chem. Mater. 20, 5388 (2008). 3) A. Mahmoud, M. Chamas, J.C. Jumas, B. Philippe, R. Dedryvère, D. Gonbeau, I. Saadoune, P.E. Lippens, J. Power Sources 244, 246 (2013). 4) M. Chamas, P.E. Lippens, J.C. Jumas, K. Boukerma, R. Dedryvère, D. Gonbeau, J. Hassoun, S. Panero, B. Scrosati, J. Power Sources 196, 7011 (2011). 5) A. Ladam, L. Aldon, P.E. Lippens, J. Olivier-Fourcade, J.C. Jumas, C. Cenac-Morthe, Hyperfine Interact. 237, 51 (2016). [less ▲]

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See detailSurface solar radiation modelling over 1900-2014: comparison between the regional climate model MAR and reanalyses
Wyard, Coraline ULiege; Doutreloup, Sébastien ULiege; Belleflamme, Alexandre ULiege et al

Poster (2017, September 04)

Many studies show that the surface solar radiation has underwent large variations over the second half of the 20th century as a result of variations in cloud cover and aerosol loading in the atmosphere ... [more ▼]

Many studies show that the surface solar radiation has underwent large variations over the second half of the 20th century as a result of variations in cloud cover and aerosol loading in the atmosphere. However, it is difficult to build strong conclusions before the 1950s because of the observations scarcity. The evolution of the surface solar radiation has been reconstructed over 1900-2014 using the regional model MAR (« Modèle Atmosphérique Régional ») which has recently been chosen to be part of the EURO-CORDEX project, thanks to the CORDEX.be project. Simulations were performed at a horizontal resolution of 5 km over a domain of 600 x 550 km² covering Belgium. Boundary conditions were provided by four reanalysis products: ERA-interim (1979-2014) completed by the ERA40 (1958-1978), NCEP/NCAR-v1 (1948-2014), ERA-20C (1900-2010) and 20CRV2C (1900-2010). Surface solar radiation measurements from the Global Energy Balance Archive and cloud cover observations from Belgocontrol covering 1966-2007 were used for the evaluation of the MAR model and the forcing reanalyses. Results show that MAR produces much better results than the reanalyses. The driving reanalyses can generate divergent trends while they assimilate observations and are supposed to represent the same climate. [less ▲]

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See detailRadiological monitoring and statistical approach of primordial and anthropogenic radionuclides in surface soil of Mami-water site in the Western Cameroon
Nguelem, Eric J.; Ndontchueng, Maurice; Motapon, Ousmanou et al

in Environmental Earth Sciences (2017), 76

The study referred to measure activity concentrations of some primordial radionuclides and anthropogenic of 137Cs in soil samples of Mami-water in the Menoua subdivision, Dschang employing gamma-ray ... [more ▼]

The study referred to measure activity concentrations of some primordial radionuclides and anthropogenic of 137Cs in soil samples of Mami-water in the Menoua subdivision, Dschang employing gamma-ray spectrometry-based characterized Broad Energy Germanium (BE6350) detector and a comparison of radiological and safety impact parameters on human due to primordial radioactivity in soil with some internationally approved values. In addition, statistical analysis of primordial radionuclides of 226Ra, 232Th and 40K was performed to evaluate the distribution and the interrelation of radionuclides. Samples were randomly collected from a depth of about 0 to 5 cm from the top surface layer. Each of the sampling points was considered as being overlaid with a grid and subdivided into cells. The observed radioactivity level of 226Ra, 232Th and 40K in the investigated soil samples was compared with some published data available in some countries including Cameroon and observed varying within some reported data of radioactivity in soil from bauxite ore deposit. 235U and 137Cs were found in very few samples with a very low average of activity concentrations. In the majority of the samples, the observed radiological safety parameters seem to be greater than the internationally approved values. Consequently, using bricks made of soil as building materials might lead to an increase in radiation risk for the population. Multivariate statistical analysis of activity concentrations of primordial radionuclides performed showed an asymmetrical distribution with more peaked than Gaussian distribution and relatively flatter distribution of radionuclides in soil. In addition, a good positive interrelation between 226Ra and 232Th was observed and a weak negative one observed between 40K and 226Ra–232Th. [less ▲]

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See detailIntrasite spatial analysis based in a Geographic Information System and apply to extensive Middle Palaeolithic open-air sites in northern France. The example of Caours (Somme, France).
Moreau, Gwénaëlle ULiege; Locht, Jean-Luc; Auguste, Patrick

Conference (2017, September 02)

During middle Palaeolithic, northern France was occupied only by Neanderthals groups. However, the succession of glacial and interglacial periods explain a complex and discontinuous settlement, which ... [more ▼]

During middle Palaeolithic, northern France was occupied only by Neanderthals groups. However, the succession of glacial and interglacial periods explain a complex and discontinuous settlement, which involved complication in the study of the population dynamics at regional scale. Thereby, some aspects of Neanderthals behaviour are still obscure: in many cases, the sites function have to be precise. The intrasite spatial analysis will help us to answer those questions through the description of human activity areas and their interactions. However, for Middle Palaeolithic sites, we can’t see systematically on the field the spatial organisation directly, we sometimes need modelization. Therefore, we started to build a spatial analysis protocol based on a Geographic Information System and rely on sites of Caours and Beauvais (France). They are two open air sites that are exceptionally well preserved and displaying a large amount of faunal and lithic rests. Our protocol’s aim is showing the existence of a spatial organisation in form of artefacts concentration area. We first hypothesize with mesh analysis – or density, widely used in archaeology. Nevertheless, this method is limited by subjective choices like that of the mesh analysis. For that reason, we decided to use another methodology based on artefacts density but also on the distance between each other: The Kernel Density Estimation. Then, we will specified the function of this areas in a life space and their interactions through the spatial distribution of different lithic artefacts and faunal remains. [less ▲]

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See detailDiscrete and broadband electron acceleration in Jupiter's powerful aurora
Mauk, B. H.; Haggerty, D. K.; Paranicas, C. et al

in Nature (2017), 549

The most intense auroral emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons by ... [more ▼]

The most intense auroral emissions from Earth's polar regions, called discrete for their sharply defined spatial configurations, are generated by a process involving coherent acceleration of electrons by slowly evolving, powerful electric fields directed along the magnetic field lines that connect Earth's space environment to its polar regions. In contrast, Earth's less intense auroras are generally caused by wave scattering of magnetically trapped populations of hot electrons (in the case of diffuse aurora) or by the turbulent or stochastic downward acceleration of electrons along magnetic field lines by waves during transitory periods (in the case of broadband or Alfvénic aurora). Jupiter's relatively steady main aurora has a power density that is so much larger than Earth's that it has been taken for granted that it must be generated primarily by the discrete auroral process. However, preliminary in situ measurements of Jupiter's auroral regions yielded no evidence of such a process. Here we report observations of distinct, high-energy, downward, discrete electron acceleration in Jupiter's auroral polar regions. We also infer upward magnetic-field-aligned electric potentials of up to 400 kiloelectronvolts, an order of magnitude larger than the largest potentials observed at Earth. Despite the magnitude of these upward electric potentials and the expectations from observations at Earth, the downward energy flux from discrete acceleration is less at Jupiter than that caused by broadband or stochastic processes, with broadband and stochastic characteristics that are substantially different from those at Earth. [less ▲]

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See detailAnalyse de l’effet de la température et du préférendum thermique sur les mécanismes du déterminisme sexuel et de la différenciation gonadique chez le poisson-chat Africain, Clarias gariepinus
Santi, Saïdou ULiege

Doctoral thesis (2017)

Les poissons constituent le groupe de vertébré le plus diversifié présentant des systèmes de déterminisme et de différenciation sexuels aussi divers que variés. Ces systèmes sont caractérisés par une ... [more ▼]

Les poissons constituent le groupe de vertébré le plus diversifié présentant des systèmes de déterminisme et de différenciation sexuels aussi divers que variés. Ces systèmes sont caractérisés par une grande labilité et sont influencés par des facteurs génétiques, physiologiques et environnementaux, ces derniers pouvant influencer à la fois, le déterminisme du sexe et la différenciation des gonades. Le poisson chat africain Clarias gariepinus, une espèce présentant un déterminisme sexuel à homogamétie femelle (XX/XY), n’a fait l’objet que de peu d’études sur le rôle des facteurs environnementaux sur la détermination et différenciation sexuelle. Nous avons choisi d’étudier le rôle de la température dans ces mécanismes par trois approches complémentaires. Une approche histologique nous a permis de mettre en évidence qu’une haute température (36°C) influence la différenciation gonadique très précocement, de 6 à 8 jours post-l’éclosion (jpe), en entrainant fréquemment une déviation significative du sexe-ratio vers les mâles. La précocité de la thermosensibilité, avant le premier signe de différenciation histologique des gonades, suggère que la haute température pourrait agir sur d’autres cibles que les gonades elles-mêmes, telles que les cellules germinales primordiales, ou le cerveau, pour induire une masculinisation de la progéniture. Nous avons de plus mis en évidence que la distribution du sexe-ratio dans les différentes populations était très variable, suggérant le rôle de déterminants génétiques mineurs dans le processus de déterminisme du sexe chez le poisson-chat africain. Globalement, nous ces résultats sont caractéristiques de la présence d’une inversion du sexe température-induite (TISR) ainsi que des traits d’un déterminisme génétique polyfactoriel du sexe chez le poisson-chat africain. Une approche physiologique et génétique nous a permis de mettre en évidence que globalement, la haute température n’influence ni les profils des concentrations des trois principaux stéroïdes sexuels (17β-œstradiol, 11-cétotestostérone et testostérone), ni les expressions des gènes cyp19a1b et dmrt1 généralement impliqués dans ces mécanismes. Toutefois, les progénitures très thermosensibles présentent des expressions plus faibles du gène cyp19a1b six jours après l’exposition à la haute température. De même, les plus fortes expressions du gène de dmrt1 ont été observées chez les individus contrôles. Ces résultats renforcent notre hypothèse de sexualisation précoce du cerveau dans le processus de masculinisation température-induite. Des études supplémentaires sur l’action de la haute température sur la prolifération de cellules germinales primordiales, ainsi que d’autres processus comme l’activité ou la méthylation des gènes de la différenciation sexuelle doivent être envisagées. Une approche comportementale nous a finalement permis de mettre en évidence que les juvéniles indifférenciés présentent un comportement migratoire vers les hautes températures lorsqu’ils sont placés dans un continuum thermique (28,0 – 32,0 – 36,0°C), associés à une masculinisation de 50,0 à 82,5%, soulevant la question suivante : le déplacement à hautes températures confère-t-il des avantages particuliers aux individus ou à la population en milieu naturel ? Cette thermosensibilité contribuerait à augmenter la proportion de femelles dans la population, lorsque les pseudomales (XX) vont se reproduire avec des femelles XX. L’augmentation de la capacité reproductive de la population, résultante, pourrait permettre un accroissement de l’effectifs des larves et juvéniles, pour rétablir l’équilibre du sexe-ratio lors du retour à des conditions environnementales normales. Globalement nous pouvons conclure que Clarias gariepinus présente un TISR avec une implication des déterminants génétiques mineurs dans la différenciation du sexe. La thermolabilité pourrait conférer un avantage adaptatif à l’espèce, mais l’adaptabilité d’un tel processus d’établissement du sexe reste une question très ouverte. [less ▲]

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See detailApplication of a two-step approach for mapping ice thickness to various glacier types on Svalbard
Fürst, J.; Gillet-Chaulet, F.; Benham, T. et al

in Cryosphere (The) (2017)

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we ... [more ▼]

The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we present a two-step reconstruction approach for ice thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine- and land-terminating glaciers as well as a 2400 km2 ice cap on Svalbard. The input requirements are kept to a minimum for the first step. In this step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. These error estimates point out that the thickness field is least constrained near ice divides or in other stagnant areas. Withholding a share of the thickness measurements, error estimates tend to overestimate mismatch values in a median sense. We also have to accept an aggregate uncertainty of at least 25 % in the reconstructed thickness field for glaciers with very sparse or no observations. For Vestfonna ice cap (VIC), a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13 % area fraction of the ice cap is in fact grounded below sea level. The former 5 % estimate from a direct measurement interpolation exceeds an aggregate maximum range of 6–23 % as inferred from the error estimates here. [less ▲]

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See detailL'abandon de sanctuaires et le transfert de cultes en Grèce antique
Palamidis, Alaya ULiege

Doctoral thesis (2017)

Dans la Grèce antique, les sanctuaires anciens comme les sanctuaires nouvellement fondés étaient censés continuer à être fréquentés indéfiniment. Cependant, ce n’était pas le cas de tous les lieux de ... [more ▼]

Dans la Grèce antique, les sanctuaires anciens comme les sanctuaires nouvellement fondés étaient censés continuer à être fréquentés indéfiniment. Cependant, ce n’était pas le cas de tous les lieux de culte: certains pouvaient être abandonnés, de même que les divinités qui y étaient honorées, tandis que d’autres divinités continuaient à être honorées à un emplacement différent. Ce travail vise en premier lieu à analyser les sources littéraires, épigraphiques et surtout archéologiques qui nous renseignent sur des tels abandons de sanctuaires et transferts de cultes. L’étude de deux types de déplacements de population, les synécismes et les métécismes, au cours desquels de tels abandons et transferts sont documentés, permet par la suite de réfléchir notamment aux raisons qui expliquent l’abandon de certains sanctuaires plutôt que d’autres. L’analyse des sources disponibles suggère que ni les abandons de sanctuaires, ni les transferts de culte n’étaient considérés comme la transgression d’une norme tacite ou orale et que ces phénomènes sont beaucoup plus courants que ce qui est généralement supposé. [less ▲]

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See detailA bottom-up approach to the analysis of deliberate metaphors in Belgian political discourse
Heyvaert, Pauline ULiege

Conference (2017, September 01)

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See detailPouvoir et action publique
Grandjean, Geoffrey ULiege

Learning material (2017)

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See detailFirst-principles study of tungsten trioxide: Structural properties and polaron formation
Hamdi, Hanen ULiege

Doctoral thesis (2017)

Using first-principles calculations, we analyze the structural properties of tungsten trioxide WO3. Our calculations rely on density functional theory and the use of the B1-WC hybrid functional, which ... [more ▼]

Using first-principles calculations, we analyze the structural properties of tungsten trioxide WO3. Our calculations rely on density functional theory and the use of the B1-WC hybrid functional, which provides very good agreement with experimental data. We show that the hypothetical high-symmetry cubic reference structure combines several ferroelectric and antiferrodistortive (antipolar cation motions, rotations and tilts of oxygen octahedra) structural instabilities. Although the ferroelectric instability is the largest, the instability related to antipolar W motions combines with those associated to oxygen rotations and tilts to produce the biggest energy reduction, yielding a P2_1/c ground state. This non-polar P2_1/c phase is only different from the experimentally reported Pc ground state by the absence of a very tiny additional ferroelectric distortion. The calculations performed on a stoichiometric compound so suggest that the low temperature phase of WO3 is not intrinsically ferroelectric and that the {experimentally observed} ferroelectric character might arise from extrinsic defects such as oxygen vacancies. Independently, we also identify never observed R3m and R3c ferroelectric metastable phases with large polarizations and low energies close to the P21/c ground state, which makes WO3 a potential antiferroelectric material. The relative stability of various phases is discussed in terms of the anharmonic couplings between different structural distortions, highlighting a very complex interplay. On the second hand, the addition of a single electron to the largest supercell of the monoclinic P21/c ground state of WO3 causes the development of a medium polaron inside of this material. We then study and characterize a medium polaron formation in WO3 from first-principles calculation. We show how the medium polaron in the supercell of WO3 can change its structural, electronic and dynamical properties. [less ▲]

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