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See detailDynamics of ligands on gold surface to obtain Janus nanoclusters: A theoretical and experimental investigation
Lugo Preciado, Jesús Gustavo ULg

Doctoral thesis (2016)

We performed a joint computational – experimental investigation of the dynamics of ligand exchange on gold nanoclusters (GNC) surface with the aim to understand how to control the structural and optical ... [more ▼]

We performed a joint computational – experimental investigation of the dynamics of ligand exchange on gold nanoclusters (GNC) surface with the aim to understand how to control the structural and optical properties of GNC through the design of their ligand shell. Our computational studies were carried out in the framework of the Kohn – Sham implementation of density functional theory in quantum chemistry. We analyzed the main features of UV – Vis spectra computed at the TD – DFT / CAM – B3LYP level for the Au13, Au25, and Au28 metallic cores protected by thiolate, chloride, and phosphine ligands. Our results show that it is possible to tune the energy of the lowest absorption band of gold clusters by ligand shell engineering in order to control the charge redistribution between ligand shell and metallic core. In parallel we synthesized a set of Au25(ATP)x(TP)18 – x clusters with different ATP/TP ratios using an adapted Demessence protocol by combining 4ATP (4 – aminothiophenol) and TP (thiophenol) ligands. ESI – MS measurements evidence that for these mixed ligand shells the Au25 nuclearity is preserved. However, the addition of the DDT (1 – dodecanethiol) ligand in the mixture leads to nanoparticle formation. FT – IR spectroscopy confirms the absorption of two different ligands on the gold surface and SAXS shows that we have a good correlation between the distance between two clusters and the length of the ligand protecting them. Furthermore, we collaborated with the Institut Charles Gerhardt in the Université de Montpellier, France whose experimental results show that several n – heterocyclic carbenes (NHC) bearing different groups on the N atoms exhibit similar reactivity when protecting a gold nanosurface. The formation of the bis(NHC) AuI gold complexes is evidenced by 13C NMR. In order to complement and interpret the experimental results, we carried out a computational study of the adsorption of a single NHC on Au38 which acts as a model for the gold surface, as well as of the fully NHC ligated Au38 cluster. The joint experimental – theoretical study, in particular the comparison between computed and 13C NMR spectra allows proposing a possible mechanism explaining the formation of [NHC – Au – NHC]+ complexes and the erosion experienced by the nanoparticle. Finally, we carried out a comparison of the mode of binding and the structural and optical properties of the fully ligated PH3 and NHC GNC with metallic cores of different nuclearities. Our computations show that the Au – P bond is weaker than the Au – NHC one. Additionally, our study confirms that the ligand – to – metal charge transfer is an important parameter for understanding the electronic transitions and the UV – Vis spectra in these clusters. Our computations on the PH3 – Au38 set of complexes show that there is a site selectivity for the reactivity for the PH3 interacting on the Au38 surface which allows predicting where the PH3 is likely to be adsorbed. This selectivity is not observed in the case of the binding of a single NHC ligand on the surface of the Au38 cluster. [less ▲]

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See detailUn demi-siècle d''exploration de la planète Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2016)

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See detailEffects of equine chorionic gonadotropin (eCG) on the sexual behaviour and ovulatory characteristics of female african N'Dama cattle.
Okouyi, M.W. Marcel; Hanzen, Christian ULg

in Revue de Médecine Vétérinaire (2016), 167(7-8), 211-215

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days ... [more ▼]

This paper evaluated the effects of eCG on the characteristics of oestrus and ovulation after heifers and cows had been synchronised following vaginal administration of progesterone for seven days (Controlled Internal Drug Released) and a PGF2α injection two days after the end of treatment. The animals were randomly split into a non-treated control group (n=26) and four groups with increasing doses of eCG: 300 IU (n=25), 400 IU (n=24), 500 IU (n=23) and 600 IU (n=23), which were injected on the day of CIDR withdrawal. The animals were then followed (24 hours a day) for six days. Oestrus was confirmed on the basis of identifying 'standing oestrus', i.e., when the cow stood to be mounted. Seven to ten days after the CIDR® was withdrawn, the animals were slaughtered, and their ovaries were examined to identify and count the number of follicular and/or luteal structures. The onset of heat was 48.6 ± 5.3 hours after eCG injection, and the average length of oestrus was 9.9 ± 2 hours. The eCG dosage had no significant effect on these two parameters. In contrast, the observed rate of oestrus was significantly (p<0.05) higher in animals that had been treated (70.8 to 84.0%) in comparison with animals that had not been treated (50%). Similarly, the ovulation rate was significantly (p<0.05) higher in treated animals (88.0 to 100%) than in untreated animals (73.1%). The percentage of animals that presented multiple ovulations increased significantly (p <0.001) with the dosage of eCG administered (4.5% to 36.4%). [less ▲]

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See detailProfessionalization of Human Resource Management in Social Enterprises
Moreau, Charlotte ULg

Doctoral thesis (2016)

Social enterprises put the human being at the heart of their functioning. But managing human beings, and consequently managing human resources, remains poorly developed and studied in social enterprises ... [more ▼]

Social enterprises put the human being at the heart of their functioning. But managing human beings, and consequently managing human resources, remains poorly developed and studied in social enterprises. However, the social enterprise sector is currently undergoing important changes: increased complexity of legal and institutional frameworks; focus on impact evaluation; transformation of public funding schemes; increased competition, etc. Those evolutions question the functioning of social enterprises and strongly impact their human resource management (HRM) practices. A movement towards professionalization of social enterprises is observed. In this doctoral thesis, we focus on the topic of HRM professionalization in social enterprises. First, we clarified our understanding of the black box of professionalization. We developed a conceptual model composed of three dimensions, the HR tools, the HR function and the HR philosophy, which together allowed apprehending HRM professionalization. Then, the data collection was achieved through a methodology mixing quantitative and qualitative approaches. Indeed, a large quantitative survey was conducted by sending a questionnaire to the Belgian French-speaking social enterprises working with at least ten workers. In parallel, in-depth case studies were performed in four voluntary very different social enterprises, as the objective was to observe the diversity of the HR practices. The results of those mixed-methodologies offer a wealth of learning opportunities and allow for a better apprehension of HRM and its evolution in social enterprises. An important diversity in the HR practices is observed. A certain level of formalization has to be highlighted but the real stakes lay elsewhere. The deeper issues in terms of HRM professionalization occur around the HR function, i.e. the roles of the HR actors, but above all around the philosophy underlying the HR evolutions. Indeed, social enterprises seem constructed, even implicitly, around a critical choice that impacts the whole organization and its functioning. That critical choice can be conceived as the internal concretization of the organization’s larger mission and is thus specific to each social enterprise. The paths of HRM professionalization and its different dimensions are strongly influenced by these critical choices. In social enterprises, the critical choices act as a filter toward the potential external pressures. Furthermore, critical choices are the results of an evolving compromise between different logics. If new logics arise, the critical choice is challenged, leading to strong questionings of HR issues among others. Critical choices are subject to an important legitimization and power stakes between the actors. Finally, these different elements let us think that the classic perspectives on HRM (universalistic, contingency and configurational) are hardly appropriate here. Consequently, we offer a new approach, a “processual” perspective to study the paths of HRM professionalization by considering the contexts surrounding the social enterprise, their internal characteristics, the power stakes around those questions and the evolution of all these elements through time. The contributions of this work include the “processual” approach, the conceptual model or the analysis of a poorly studied phenomenon. [less ▲]

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See detailCaractérisation multiscalaire de contaminations en éléments traces dans les sols : distribution spatiale et verticale, évaluation du transfert sol-plante-vers de terre et gestion potentielle par amendements organiques
Liénard, Amandine ULg

Doctoral thesis (2016)

Human economic and technological development has a negative impact on the environment. The soil is not spared from this growing threat through its role in the environmental interface. Once degraded as a ... [more ▼]

Human economic and technological development has a negative impact on the environment. The soil is not spared from this growing threat through its role in the environmental interface. Once degraded as a result of contamination, it can no longer fulfill its ecosystem functions such as the protection of ecosystems, food production or preservation of the quality of surface water and groundwater. The studies presented in the thesis are on soil contaminated by atmospheric fallouts enriched by trace elements. This type of contamination increases the natural levels of contaminants in soils and particularly in surface horizons to exceed the maximum levels set by legislation. The first axe of research concerns the assessment of contamination at a landscape scale around a former zinc-lead ore-treatment plant. The spatial distribution of cadmium, lead and zinc in the topsoil (0-20 cm) was characterized using 247 samples taken in crop, grassland and forest on three major types of loam soils representative of the study area Sclaigneaux (Wallonia, Belgium). The distribution of contaminants is explained by the distance to the source of contamination, direction of dominant winds, land use and soil type. Subsequently, 22 soil profiles were sampled within the study area to estimate the vertical transfer of contaminants. Based on various indexes of contamination, no migration along the profiles has been demonstrated. Only some more clay horizons presented contaminant levels that increased relative to their upper horizons. The second approach studied the soil-plant transfer and soil-plant-worm transfer of contaminants. First, a field study of the quality of grains of barley (Hordeum vulgare L.) harvested in the study area Sclaigneaux was performed. It appears that the concentration of cadmium in the grain meets quality standards for placing the cereals on the market. However, 78% and 94% of zinc and cadmium, respectively, concentrations measured in grains exceed the expected levels of a non-impacted environment by human activity. Secondly, a study on microcosms was conducted with soils of agricultural parcels around Sclaigneaux on which two crops (faba bean, Vicia faba L. and corn, Zea mays L.) were grown and where earthworms (Eisenia fetida (Savigny)) were introduced. The life traits of E. fetida such as mortality and adult weight were not affected by the levels of contaminants unlike the presence of plants which limit their reproduction (weight and number of cocoons). Moreover, the presence of E. fetida in microcosms influenced the mobility and bioavailability of contaminants. The third approach deals with metal contaminations in vegetable gardens and their management using organic amendments. This method of stabilization aims to decrease the labile fraction of soil contaminants and further reduce their transfer to plants. To do so, two vegetables (spinach, Spinacia oleracea L. and lettuce, Lactuca sativa L.) were grown on contaminated garden soils enriched in various amendments sold in garden centers. The major finding of this study is that management by amendments does not allow a systematic decrease in the soluble fraction contaminants. This is mainly due to the direct intake of rapidly mobilized trace elements produced by the addition of some of the studied amendments. [less ▲]

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See detailModelling the mortality of Hylotrupes bajulus (L.) larvae exposed to anoxic treatment for disinfestation of wooden art objects
de Streel, Géraud; Henin, Jean-Marc; Bogaert, Patrick et al

Conference (2016, September 13)

Experiments were conducted to quantify the effect of several variables on the mortality of insects exposed to an anoxic treatment in order to generate a model linking mortality to these variables. This ... [more ▼]

Experiments were conducted to quantify the effect of several variables on the mortality of insects exposed to an anoxic treatment in order to generate a model linking mortality to these variables. This study aims to explore the possible interest of using such a model to determine the characteristics of treatment (especially duration) needed to guarantee insect mortality with a given level of probability. Trials were performed on Hylotrupes bajulus larvae, which is a widespread species known for its high tolerance to anoxic conditions. The studied variables are the initial mass of the larvae, the treatment temperature (21, 30 and 40 °C), the treatment duration (four durations for each temperature tested) and whether the larva is held in wood or in a petri dish (directly exposed to anoxic atmosphere) during the experiment. It was found that, while the last variable is not correlated with mortality, treatment duration and temperature are significantly and positively correlated with it. Larvae with higher body mass were also shown to have a better resistance to the treatment. Based on these results, a model including insect initial mass, treatment temperature and duration, together with the interaction between these two variables, was determined. This relatively simple model appeared to be a useful tool in overcoming the difficulty in defining the modalities for anoxic treatment in order to reach a given level of mortality. [less ▲]

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See detailSynthesis and characterizations of non-isocyanate polyurethane (NIPU) hydrogels
Gennen, Sandro ULg; Grignard, Bruno ULg; Thomassin, Jean-Michel ULg et al

Poster (2016, September 12)

Polyurethane (PU) is on of the most used polymers for the preparation of hydrogels due to its good biocompatibility, biodegradation and excellent mechanical properties. PU hydrogels are found in lot of ... [more ▼]

Polyurethane (PU) is on of the most used polymers for the preparation of hydrogels due to its good biocompatibility, biodegradation and excellent mechanical properties. PU hydrogels are found in lot of applications such as wound dressing, soft contact lenses, drug delivery and scaffolds for tissue engineering. Classicaly, PU is produced by a step-growth polymerization between diols and diisocyanates. However, in order to avoid the use of harmful isocyanates compounds and because of regulations which tend to ban the use of isocyanates, we developed hydrogels based on a non-isocyanate polyurethane (NIPU) chemistry by valorizing CO2-sourced cyclic carbonates and amines. Precisely, NIPU hydrogels were prepared by a solvent-free copolymerization between bifunctional hydrophilic polyethylene glycol cyclic carbonates and diamines in presence of a triamine as a crosslinker, followed by a water swelling of the obtained cross-linked gel. Parameters such as the cross-linking ratio and diamine’s nature were optimized. Different clay contents (cloiste 30B) as nanofiller were dispersed in the ideal cyclic carbonate/diamine/triamine formulation prior polymerization in order to reinforce the compression properties of NIPU hydrogels. Finaly, we were able to prepare NIPU hydrogels with water content up to 80 % and good compression properties using low clay content. [less ▲]

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See detailPolyphosphoester containing amphiphilic block copolymers as drug nanocarriers
Ergül, Zeynep ULg; Vanslambrouck, Stéphanie; Thiry, Justine ULg et al

Poster (2016, September 12)

The design of drug delivery systems often requires biodegradable and biocompatible materials that allow safe retention and controlled release of the drug. In this respect, supramolecularly self-assembled ... [more ▼]

The design of drug delivery systems often requires biodegradable and biocompatible materials that allow safe retention and controlled release of the drug. In this respect, supramolecularly self-assembled amphiphilic block copolymers into spherical micelles are appropriate carriers for poorly soluble drugs. In that framework, we have designed novel functional poly(ethylene oxide)-b-polyphosphoester amphiphilic block copolymers able to cross-linked under UV and degrade in response to a reduction of the pH from neutral conditions. Therefore, an unsaturated alkene side-chain was introduced on the cyclic phosphate monomer according to a one-step reaction followed by its organocatalyzed polymerization initiated by a poly(ethylene oxide) macroinitiator. After self-assembly into water, the micelles were cross-linked by UV irradiation. Then, these cross-linked micelles have been loaded by doxorubicin, i.e. a drug used in cancer therapy. We observed that the doxorubicin loading increased with the number of double bonds on the polyphosphate block of non-cross-linked micelles. This diblock amphiphilic copolymer bearing pendant unsaturations appears thus particularly promising candidate to build micellar drug delivery systems for intravenous injection. [less ▲]

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See detailJoint learning and pruning of decision forests
Begon, Jean-Michel ULg; Joly, Arnaud ULg; Geurts, Pierre ULg

Conference (2016, September 12)

Decision forests such as Random Forests and Extremely randomized trees are state-of-the-art supervised learning methods. Unfortunately, they tend to consume much memory space. In this work, we propose an ... [more ▼]

Decision forests such as Random Forests and Extremely randomized trees are state-of-the-art supervised learning methods. Unfortunately, they tend to consume much memory space. In this work, we propose an alternative algorithm to derive decision forests under heavy memory constraints. We show that under such constraints our method usually outperforms simpler baselines and can even sometimes beat the original forest. [less ▲]

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See detailOverhanging Constraints in Addivitive Manufacturing Using Two Different Tools
Bauduin, Simon ULg; Collet, Maxime ULg; Duysinx, Pierre ULg

Conference (2016, September 12)

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount ... [more ▼]

Topology optimization is widely used as a design tool for advanced application in mechanical, aerospace and automotive industries. This technique offers an optimal distribution of a predetermined amount of material in a given design space. In the last years, a lot of efforts has been invested into the development of high performance methods such as homogenization, SIMP or BESO. However as the state of the art in manufacturing experiences evolution, a coupling between topology optimization and additive manufacturing is needed. Additive manufacturing has numerous advantages that fits the characteristics of topology optimized designs. It can manufacture highly complex design without high cost increase and furthermore continuous density material of the SIMP method could be manufactured by lattice structures. With all the opportunities given by the additive manufacturing the urge to bind the last one to topology optimization is heavily required. Specific constraints related to manufacturing issues have to be taken into account such as the need of supports structures to ensure a good heat evacuation during the manufacturing process, as well as to hold up overhanging section. Some researches have been done to try to include this constraint in the optimization problem such as Leary and al or Andrew T. Gaynor. However this work focuses on 2 different methods (projection scheme and mechanical approach) to tackle the overhanging problem and compare them . [less ▲]

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See detailOrganocobalt complexes as source of radicals for the controlled polymerization of unconjugated monomers
Demarteau, Jérémy ULg; Cordella, Daniela ULg; Kermagoret, Anthony et al

Poster (2016, September 12)

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See detailETUDE FONCTIONNELLE DES FACTEURS D’ÉPISSAGE SR D’ARABIDOPSIS THALIANA
Stankovic, Nancy ULg

Doctoral thesis (2016)

Dans ce travail, nous avons montré que la protéine RSZ22, est une protéine hautement dynamique. Cette protéine fait partie de la sous-famille des protéines RSZ d’Arabidopsis et est l’homologue de la ... [more ▼]

Dans ce travail, nous avons montré que la protéine RSZ22, est une protéine hautement dynamique. Cette protéine fait partie de la sous-famille des protéines RSZ d’Arabidopsis et est l’homologue de la protéine SRSF7 humaine. Elle possède un domaine RRM, un domaine RS et entre les deux un domaine de liaison au RNA Zn-knuckle de type CCHC. L’utilisation des approches de FRAP (Fluorescence Recovery After Photobleaching) et de FLIP (Fluorescence Loss In Photobleaching) ont permis d’étudier la dynamique de cette protéine mais aussi sa capacité de navette entre le noyau et le cytoplasme comme son homologue humain SRSF7. Ces études ont été réalisées avec RSZ22 fusionnée à la GFP et surexprimée transitoirement dans des cellules foliaires mais aussi en transformation stable chez Arabidopsis (Rausin et al., 2010; Tillemans et al., 2006). Dans cette étude, nous avons montré que RSZ22, comme les protéines de la famille SR, est une protéine navette. Par analyses de FLIP-shuttling nous avons pu établir des cinétiques d'exportation et confirmer que les protéines SR végétales utilisent le récepteur CRM1/XPO1 comme voie d’exportation. Sa mobilité dépend du niveau de phosphorylation et de la concentration en ATP de la cellule. La complémentarité des techniques de surexpression en transformation transitoire et de l’expression stable ayant été démontrée (Rausin et al., 2010), nous nous y sommes référés pour notre étude de dynamique des protéines nucléaires. Nous avons également cherché à évaluer les rôles des domaines d’accrochage au RNA de RSZ22 dans sa localisation et sa dynamique. Par mutagenèse dirigée, nous avons modifié les acides aminés conservés connus pour jouer un rôle dans les interactions avec le RNA (Clery et al., 2008; Hargous et al., 2006; Lunde et al., 2007; Maris et al., 2005; Phelan et al., 2012). Nos résultats montrent que les domaines Zn-knuckle et RRM fonctionnels ne sont pas nécessaires à la localisation nucléaire de la protéine RSZ22, ni à sa localisation en speckles. La dynamique nucléocytoplasmique de la protéine RSZ22 n’est pas altérée par la mutation des motifs Zn-knuckle et RNP1. Cependant, les protéines mutées de RSZ22 répondent différemment aux traitements par la LMB. En effet, celles-ci ne sont plus « retenues » dans le noyau après un tel traitement et continuent d’être exportées vers le cytoplasme. Sachant que la LMB est un inhibiteur spécifique de la voie CRM1/XPO1, ce dernier récepteur est impliqué dans l’exportation des protéines SR en interaction avec le RNA (Williams et al., 2008). Dans la suite des recherches réalisées au sein du laboratoire, nous avons étudié la dynamique nucléo-cytoplasmique des protéines SR, en étudiant la sous-famille SRSF1-like. Chez Arabidopsis thaliana, cette famille se compose des protéines SR34, SR34a, SR34b et SR30 et possède deux domaines RRM et un domaine RS. Comme RSZ22, SR34 et SR34a font la navette entre le noyau et le cytoplasme. Nous formulons ainsi l’hypothèse que comme son homologue humain SRSF1, SR34 pourrait être impliquée dans l’exportation du mRNA vers le cytoplasme. Nous avons analysé les rôles des différents domaines de SR34 par mutagénèse dirigée. Nous avons montré que le domaine RS de la protéine SR34 est nécessaire pour la localisation nucléaire et la stabilité de la protéine. Les motifs de liaison au RNA sont impliqués dans l’exportation de SR34 par la voie CRM1/XPO1. Par la technique du double hybride en levure, une interaction entre SR34 et SR45 a pu être mise en évidence et confirmée par FLIM-FRET (Fluorescence-Lifetime Imaging Microscopy - Fluorescence Resonance Energy Transfert). L’analyse des interactions entre SR45 et les protéines SR34 mutantes montre l’importance des différents domaines de la protéine dans les interactions protéine-protéine. [less ▲]

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See detailChapter 16 - Solar thermal powered Organic Rankine Cycles
Orosz, Matthew; Dickes, Rémi ULg

in Macchi, Ennio; Astolfi, Marco (Eds.) Organic Rankine Cycle (ORC) Power Systems: Technologies and Applications (2016)

Reference chapter about solar-based organic Rankine cycle power systems published in the book "Organic Rankine Cycle (ORC) Power Systems: Technologies and Applications"

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See detailRandom subspace with trees for feature selection under memory constraints
Sutera, Antonio ULg; Châtel, Célia; Louppe, Gilles et al

Conference (2016, September 12)

Detailed reference viewed: 41 (7 ULg)