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See detailHydrodynamique et distribution de temps de séjour dans les lits bactériens
Crine, Michel ULg; Marchot, Pierre ULg; Schlitz, Marc et al

in Les réacteurs gaz-liquide et gaz-liquide-solide (1990)

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See detailHydrodynamique et morphologie d'une bactérie filamenteuse dans un fermenteur à cuve agitée
Groslambert, Sylvie ULg; Blacher, Silvia ULg; Crine, Michel ULg

in Tribune de l'Eau (La) (2003), 56(622), 58-64

Afin d'étudier l'influence de l'hydrodynamique sur une bactérie filamenteuse, Actinomadura R39, nous l'avons cultivée dans un fermenteur de laboratoire de 5 litres à cuve agitée en faisant varier les ... [more ▼]

Afin d'étudier l'influence de l'hydrodynamique sur une bactérie filamenteuse, Actinomadura R39, nous l'avons cultivée dans un fermenteur de laboratoire de 5 litres à cuve agitée en faisant varier les conditions d'agitation. Les variables sont la vitesse de rotation et le type de mobile utilisé: turbines Rushton ou Intermig. Les deux mobiles se distinguent par leur géométrie et par les schémas d'écoulement qu'ils induisent dans la cuve. L'influence de l'hydrodynamique sur Actinomadura R39 est quantifiée par l'évolution de sa morphologie. Cette dernière est estimée par analyse d'images sur des échantillons prélevés lors des cultures. Parallèlement, nous avons caractérisé l'hydrodynamique du fermenteur dans un milieu artificiel reproduisant la rhéologie des fermentations en mesurant la puissance dissipée et en effectuant des essais de traceurs. Ces derniers sont utilisés pour la modélisation du fermenteur par un modèle compartimenté et le calcul du temps de mélange. Nous avons pu ainsi mettre en relation les modifications de la morphologie et des grandeurs caractérisant les écoulements dans le fermenteur. L'existence de corrélations entre les paramètres du modèle et la morphologie a également permis une validation de la signification physique de ce modèle. [less ▲]

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See detailHydrodynamique souterraine et vulnérabilité à la pollution des ressources en eau en zone urbaine tropicale : cas du bassin versant de Mingoa (Yaoundé-Cameroun)
Kouam Kenmogne, Guy Romain; Ntep, François; Rosillon, Françis ULg et al

Conference (2010, March 29)

Une étude conjointe visant la compréhension des phénomènes d’hydrodynamique souterraine et de vulnérabilité des eaux à la pollution a été menée dans le bassin versant de Mingoa situé dans le périmètre ... [more ▼]

Une étude conjointe visant la compréhension des phénomènes d’hydrodynamique souterraine et de vulnérabilité des eaux à la pollution a été menée dans le bassin versant de Mingoa situé dans le périmètre urbain de Yaoundé. Il ressort de cette étude que le comportement hydrodynamique dans ce bassin est étroitement lié aux fluctuations pluviométriques. La carte hydrodynamique de l’aquifère supérieur du bassin versant de Mingoa révèle deux types d’écoulements convergents et divergents avec les grands axes de drainage d’orientation globale NE - SW ; SE - NW et N - S permettant de délimiter des sites favorables à l’implantation d’ouvrages de captage des eaux souterraines. Les sources potentielles de pollution répertoriées sont nombreuses et variées (latrines, tas d’ordures sauvages,...). Les résultats des analyses physico-chimiques ont permis de constater que hormis la température, le potentiel d’hydrogène (pH), CO2 libre et l’azote ammoniacal, les valeurs des autres paramètres sont bien centrées sur les normes de qualité des eaux destinées à la consommation humaine prescrite par l’Organisation Mondiale de la Santé (OMS). Cependant, les valeurs des teneurs en en Streptocoques Fécaux (de 48 UFC/100 ml à 5,80 x 105 UFC/100 ml) et en Coliformes Fécaux (de 300 UFC/100 ml à 1,07 x 106 UFC/100 ml) sont largement supérieures aux valeurs seuils requises par l’OMS et permettent de conclure que ces eaux sont polluées et vivement déconseillées à la consommation humaine. Sur la base des données ponctuelles issues des simulations et des différentes analyses des eaux et des sols, la dynamique de contamination des nappes d’eau superficielles et souterraines dans les zones cristallines fracturées et densément peuplées a été posée. Deux zones de protection ayant respectivement des rayons de 10 mètres et de 20 mètres peuvent être envisagées afin de permettre au sol de jouer pleinement son rôle épurateur. Des mesures adéquates (campagnes d’information, établissement des zones de protection, ...) doivent être engagées dans ce bassin versant et au-delà dans toute la ville de Yaoundé afin de faire face à la dégradation assez avancée des ressources en eau et ceci malgré des contraintes socio-économiques et foncières qui constituent des freins à cette dynamique. [less ▲]

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See detailHydroélectricité et poissons
Ovidio, Michaël ULg; Florence, Hauregard

Learning material (2009)

Chercheur au Laboratoire de Démographie des Poissons et d’Hydroécologie de l’Université de Liège, Michaël OVIDIO présentait le 30 avril dernier, dans le cadre des Jeudis de l’Aquapôle, un exposé sur l’ « ... [more ▼]

Chercheur au Laboratoire de Démographie des Poissons et d’Hydroécologie de l’Université de Liège, Michaël OVIDIO présentait le 30 avril dernier, dans le cadre des Jeudis de l’Aquapôle, un exposé sur l’ « Impact des barrages et des turbinages hydroélectriques sur la dynamique des populations de poissons et la qualité de leurs habitats » . Sans vouloir être source de conflits avec les producteurs d’hydroélectricité, cet exposé avait pour objectif d’informer le grand public sur cette problématique, car la notion d’énergie verte, largement utilisée pour caractériser l’hydroélectricité, ne doit pas s’arrêter au seul aspect des pollutions. [less ▲]

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See detailHydrogel nanocomposites: a potential UV/blue light filtering material for ophthalmic lenses
Bozukova, Dimitriya; Pagnoulle, Christophe; De Pauw-Gillet, Marie-Claire ULg et al

in Journal of Biomaterials Science. Polymer Edition (2011), 22

Poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (poly(HEMA-co-MMA)) and ZnS hydrogel nanocomposites were prepared and characterized. The chemical composition of the inorganic nanoparticles was ... [more ▼]

Poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (poly(HEMA-co-MMA)) and ZnS hydrogel nanocomposites were prepared and characterized. The chemical composition of the inorganic nanoparticles was confirmed by X-ray diffraction, and the homogeneity of their distribution within the hydrogel was assessed by transmission electron microscopy. The influence of the content of ZnS nanoparticles on the optical performances of the nanocomposites was investigated by UV-Vis spectroscopy. The ability of the hydrogel nanocomposites to filter the hazardous UV light and part of the blue light was reported, which makes them valuable candidates for ophthalmic lens application. In contrast to the optical properties, the thermo-mechanical properties of neat poly(HEMA-co-MMA) hydrogels were found to be largely independent of filling by ZnS nanoparticles ( 2 mg/ml co-monomer mixture). Finally, in vitro cell adhesion test with lens epithelial cells (LECs), extracted from porcine lens crystalline capsule, showed that ZnS had no deleterious effect on the biocompatibility of neat hydrogels, at least at low content. [less ▲]

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See detailHydrogen atom loss from the benzene cation. Why is the kinetic energy release so large?
Gridelet, E.; Lorquet, Andrée ULg; Locht, Robert ULg et al

in Journal of Physical Chemistry A (2006), 110(27), 8519-8527

The kinetic energy release distributions (KERDs) associated with the hydrogen loss from the benzene cation and the deuterium loss from the perdeuteriobenzene cation have been remeasured on the metastable ... [more ▼]

The kinetic energy release distributions (KERDs) associated with the hydrogen loss from the benzene cation and the deuterium loss from the perdeuteriobenzene cation have been remeasured on the metastable time scale and analyzed by the maximum entropy method. The experimental kinetic energy releases are larger than expected statistically, in contradistinction to what has been observed for the C-X fragmentations of the halogenobenzene cations. H(D) loss from C6H6+ (C6D6+) occurs via a conical intersection connecting the (2)A(2) and (2)A(1) electronic states. Two models are proposed to account for the experimental data: (i) a modified orbiting transition state theory (OTST) approach incorporating electronic nonadiabaticity; (ii) an electronically nonadiabatic version of the statistical adiabatic channel model ( SACM) of Quack and Troe. The latter approach is found to be preferable. It leads to the conclusion that the larger the energy stored in the transitional modes, which partly convert to the relative interfragment motion, the shorter the value of the reaction coordinate at which the adiabatic channels cross, and the larger the probability of undergoing the (2)A(2) -> (2)A(1) transition required for hydrogen loss. [less ▲]

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See detailA HYDROGEN BOND INFLUENCES THE 5-HT1A/D4 SELECTIVITY OF WAY-100635 ANALOGUES: AN IN SILICO APPROACH
Dilly, Sébastien ULg; Liégeois, Jean-François ULg

Poster (2013, June)

WAY-100635 is widely used in vitro and in vivo as an antagonist of 5-HT1A receptors. In terms of pharmacological tools and pharmacological investigations, the ideal reference molecule would be highly ... [more ▼]

WAY-100635 is widely used in vitro and in vivo as an antagonist of 5-HT1A receptors. In terms of pharmacological tools and pharmacological investigations, the ideal reference molecule would be highly selective for its target over other related and non-related targets. However WAY-100635 displays affinity for and activity at D4 dopamine receptors, and that "off-target" activity confounds its use in pharmacological studies, particularly when both receptors are present. In this context, we carried out various chemical modifications of the WAY-100635 structure in order to improve its 5-HT1A versus D4 selectivity. An important increase of selectivity was obtained when the basic side chain of WAY-100635 was replaced by a 4-phenylpiperazine or a 4-phenyl-1,2,3,6-tetrahydropyridine moiety. In contrast, the introduction of nitrogen atoms in the acyl group decreased the selectivity by reducing the affinity for 5-HT1A receptors, on the one hand, and enhancing the affinity for D4 receptors on the other hand. In order to explain the reduced 5-HT1A/D4 selectivity of aza-derivatives, the binding modes of the compounds were explored by docking analysis on homology models of the two receptors. It appears that the formation of an additional hydrogen bond within D4 receptors could be the key of the decreased selectivity. These results will be very helpful for developing molecules with an improved 5-HT1A/D4 selectivity. [less ▲]

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See detailThe Hydrogen Electrode in Ionic Liquids: Acidity Measurements and Titrations
Robert, Thierry ULg; Malherbe, Cédric ULg; Magna, lionel et al

Poster (2010, March)

The acidity level in ILs containing acid was first determined using the Hammett acidity function (H0)1-2 in our laboratory. It was demonstrated that this attainable acidity, extending from -3 to -8, is ... [more ▼]

The acidity level in ILs containing acid was first determined using the Hammett acidity function (H0)1-2 in our laboratory. It was demonstrated that this attainable acidity, extending from -3 to -8, is exclusively depending of the nature of anion and follow the order: PF6 > BF4 > NTf2 > OTf. Nevertheless, the Hammett acidity function is an apparent function in this media and must then be corrected for. Consequently, in a second step, we tried to evaluate directly the proton activity from the determination of a potentiometric acidity function (R0) based on the extrathermodynamic Strehlow assumption.3 Therefore, the equilibrium potential of the H+/H2 couple was measured with an hydrogen electrode versus the ferricinium/ferrocene couple for which the potential is considered as independent of the solvent. [less ▲]

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See detailHydrogen fluoride total and partial column time series above the Jungfraujoch from long-term FTIR measurements: Impact of the line-shape model, characterization of the error budget and seasonal cycle, and comparison with satellite and model data
Duchatelet, Pierre ULg; Demoulin, Philippe ULg; Hase, Frank et al

in Journal of Geophysical Research. Atmospheres (2010), 115

Time series of hydrogen fluoride (HF) total columns have been derived from ground-based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International ... [more ▼]

Time series of hydrogen fluoride (HF) total columns have been derived from ground-based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with two high resolution spectrometers (one home-made and one Bruker 120-HR). Solar spectra have been inverted with the PROFFIT 9.5 algorithm, using the optimal estimation method. An inter-comparison of HF total columns retrieved with PROFFIT and SFIT-2 – the other reference algorithm in the FTIR community - is performed for the first time. The effect of a Galatry line shape model on HF retrieved total columns and vertical profiles, on the residuals of the fits and on the error budget is also quantified. Information content analysis indicates that, in addition to HF total vertical abundance, three independent stratospheric HF partial columns can be derived from our Bruker spectra. A complete error budget has been established and indicates that the main source of systematic error is linked to HF spectroscopy and that the random error affecting our HF total columns does not exceed 2.5%. Ground-based middle and upper stratospheric HF amounts have been compared to satellite data collected by the HALOE or ACE-FTS instruments. Comparisons of our FTIR HF total and partial columns with runs performed by two 3D numerical models (SLIMCAT and KASIMA) are also included. Finally, FTIR and model HF total and partial columns time series have been analyzed to derive the main characteristics of their seasonal cycles. [less ▲]

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See detailHydrogen in the atmosphere of the evolved WN3 Wolf-Rayet star WR 3: defying an evolutionary paradigm?
Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A. et al

in Monthly Notices of the Royal Astronomical Society (2004), 353(1), 153-161

WR 3 is the brightest very early-type WN star in the sky. Based on several years of time-resolved spectroscopy and precision photometry on various time-scales, we deduce that WR 3 is most likely a single ... [more ▼]

WR 3 is the brightest very early-type WN star in the sky. Based on several years of time-resolved spectroscopy and precision photometry on various time-scales, we deduce that WR 3 is most likely a single, weak-lined star of type WN3ha (contrary to its current catalogue-type of WN3 + O4), with H lines occurring both in emission and absorption in its wind. This conclusion is confirmed and strengthened via detailed modelling of the spectrum of WR 3. Given the similarity of WR 3 with numerous H-rich WNE stars in the Large Magellanic Cloud and especially the Small Magellanic Cloud, and its location towards the metal-deficient exterior of the Galaxy, we conclude that rotationally induced meridional circulation probably led to the apparently unusual formation of this hot Galactic WN star with enhanced hydrogen. Although we cannot completely rule out the possibility of a binary with a low orbital inclination and/or long period, we regard this latter possibility as highly unlikely. [less ▲]

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See detailHydrogen Peroxide Hyperpolarizes Rat Ca1 Pyramidal Neurons by Inducing an Increase in Potassium Conductance
Seutin, Vincent ULg; Scuvée-Moreau, Jacqueline ULg; Massotte, Laurent ULg et al

in Brain Research (1995), 683(2), 275-8

It has been suggested that hydrogen peroxide is involved in cascades of pathological events affecting neural cells. The aim of this study was therefore to examine whether this molecule is able by itself ... [more ▼]

It has been suggested that hydrogen peroxide is involved in cascades of pathological events affecting neural cells. The aim of this study was therefore to examine whether this molecule is able by itself to modify membrane properties of pyramidal neurons in the CA1 region of the rat hippocampus. Intracellular recordings in the slice preparation showed that 3.3 mM hydrogen peroxide hyperpolarized all neurons tested (n = 41) by 11 +/- 3 mV. This effect persisted in the presence of tetrodotoxin. It developed slowly, was reversible and reproducible. In the presence of tetrodotoxin, the extrapolated reversal potential of this effect was -95 +/- 5 mV in 2.5 mM external potassium. This value was not significantly different from the one obtained with the GABAB agonist baclofen (10 microM) (-98 +/- 5 mV). It shifted when the concentration of external potassium was increased to 10.5 mM (from -96 +/- 5 to -62 +/- 4 mV), in close agreement with the Nernst equation potassium ions. The hyperpolarization was significantly reduced (by 65 +/- 22%) by the potassium channel blocker barium (100 microM). We suggest that hydrogen peroxide is able to induce an increase in potassium conductance in rat CA1 pyramidal neurons. The exact mechanism by which it produces this effect (direct action on channels or indirect effect) remains to be determined. [less ▲]

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See detailHydrogen peroxide increases transforming factor-β3 gene expression in human chondrocytes and reverses interleukin-1β inhibitory effect
Mathy-Hartert, Marianne ULg; Devel, P.; Hoormaert, S. et al

in Osteoporosis International (2002, November), 13(Suppl.3), 52

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See detailHydrogen peroxyde in breath condensate as marker of lower airway inflammation in an experimental model of feline asthma
Kirschvink, Nathalie; Malin, D.; Delvaux, Francois et al

Conference (2003)

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See detailHydrogen photo-evolution upon S deprivation stepwise: An illustration of microalgal photosynthetic and metabolic flexibility and a step stone for future biotechnological methods of renewable H2 production
Ghysels, Bart ULg; Franck, Fabrice ULg

in Photosynthesis Research (2010), 106

The metabolic flexibility of some photosynthetic microalgae enables them to survive periods of anaerobiosis in the light by developing a particular photofermentative metabolism. The latter entails ... [more ▼]

The metabolic flexibility of some photosynthetic microalgae enables them to survive periods of anaerobiosis in the light by developing a particular photofermentative metabolism. The latter entails compounds of the photosynthetic electron transfer chain and an oxygen-sensitive hydrogenase in order to reoxidise reducing equivalents and to generate ATP for maintaining basal metabolic function. This pathway results in the photo-evolution of hydrogen gas by the algae. A decade ago Melis and coworkers managed to reproduce such a condition in a laboratory context by depletion of sulfur in the algal culture media, making the photo-evolution by the algae sustainable for several days (Melis et al. 2000). This observation boosted research in algal H2 evolution. A feature, which due to its transient nature was long time considered as a curiosity of algal photosynthesis suddenly became a phenomenon with biotechnological potential. Although the Melis procedure has not been developed into a biotechnological process of renewable H2 generation so far, it has been a useful tool for studying microalgal metabolic and photosynthetic flexibility and a possible step stone for future H2 production procedures. Ten years later most of the critical steps and limitations of H2 production by this protocol have been studied from different angles particularly with the model organism C. reinhardtii, by introducing various changes in culture conditions and making use of mutants issued from different screens or by reverse genomic approaches. A synthesis of these observations with the most important conclusions driven from recent studies will be presented in this review. [less ▲]

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See detailHydrogen Storage and Carbon Dioxide Capture in an Iron-Based Sodalite-Type Metal-Organic Framework (Fe-BTT) Discovered via High-Throughput Methods
Sumida, Kenji; Horike, S; Kaye, S.S. et al

in Chemical Science (2010), 1

Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT.2HCl(BTT3-=1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe3[(Fe4Cl)3(BTT ... [more ▼]

Using high-throughput instrumentation to screen conditions, the reaction between FeCl2 and H3BTT.2HCl(BTT3-=1,3,5-benzenetristetrazolate) in a mixture of DMF and DMSO was found to afford Fe3[(Fe4Cl)3(BTT)8]2.22DMF.32DMSO.11H2O. THis compound adopts a porous three-dimensional framework structure consisting of squre [Fe4CL]2+ units linked via triangulat BTT3- bridging ligands to give an anionic 3.8-net. Mossbauer spectroscopy carried out on a DMF-solvated version of the material indicated the framework to contain high-spin Fe2+ with a distribution of local environments and confirmed the presence of extra-framework iron cations. Upon soaking the compound in methanol and heating at 135 C for 24 h under dynamic vacuum, most of the solvent is removed to yield Fe3[(Fe4Cl)3(BTT)8(MeOH)4]2(Fe-BTT), a microporous solid with a BET surface area of 2010 m2g-1 and open Fe2+ coordination sites. Hydrogen adsorption data collected at 77 K show a steep rise in the isotherm, associated with an initial isosteric heat of adsorption of 11.9 kJ/mol, leading to a total storage capacity of 1.1 wt% and 8.4 g/L at 100 bar and 298 K. Powder neutron diffraction experiments performed at 4 K under various D2 loadings enabled identification of ten different adsorption sites. with the strongest binding site residing just 2.17(5) Å from the framework Fe2+ cation. Inelastic neutron scattering spectra are consistent with the strong rotational hindering of the H2 molecules at low loadings, and further reveal the catalytic conversion of ortho-H2 to para-H2 by the paramagnetic iron centers. The exposed Fe2+ cation sites within Fe-BTT also lead to the selective adsorption of CO2 over N2, with isotherms collected at 298 K indicating uptake ratios of 30.7 and 10.8 by weight at 0.1 and 1.0 bar, respectively. [less ▲]

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See detailHydrogen-bonded block copolymer complexes as possible precursors for thin films with hairy nanopores
Lefèvre, Nathalie ULg; Fustin, Charles-André; Gohy, Jean-François

Conference (2008)

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