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See detailInteractions between calcium channels and SK channels in midbrain dopamine neurons and their impact on pacemaker regularity: Contrasting roles of N- and L-type channels.
de Vrind, V.; Scuvée-Moreau, Jacqueline ULg; Drion, Guillaume ULg et al

in European Journal of Pharmacology (2016)

Although small-conductance Ca2+-activated K+ (SK) channels and various types of voltage-gated Ca2+ (Cav) channels have been described in midbrain dopaminergic neurons, the nature of their interactions is ... [more ▼]

Although small-conductance Ca2+-activated K+ (SK) channels and various types of voltage-gated Ca2+ (Cav) channels have been described in midbrain dopaminergic neurons, the nature of their interactions is unclear. More particularly, the role of various Cav channel types in either promoting irregularity of firing (by generating an inward current during SK channel blockade) or promoting regularity of firing (by providing the source of Ca2+ for the activation of SK channels) has not been systematically explored. We addressed this question using intracellular and extracellular recordings from substantia nigra, pars compacta (SNc), dopaminergic neurons in rat midbrain slices. Neurons were pharmacologically isolated from their differences. When examining the ability of various Cav channel blockers to inhibit the SK-mediated afterhyperpolarization (AHP), we found that only the N-type Cav channel blocker ω-conotoxin-GVIA was able to reduce the apamin-sensitive AHP, but only partially (~40%). Specific blockers of L, P/Q, T or R channels had no effect on this AHP. Combining ω-conotoxin-GVIA and other specific blockers did not yield greater block and even the broad Cav blocker Cd2+ induced a submaximal (~75%) effect. Extracellular recordings examining firing regularity yielded congruent results: none of the specific blockers was able to increase firing irregularity to the extent that the specific SK blocker apamin did. The irregularity of firing observed with apamin could only be reversed by blocking L-type Ca2+ channels. Thus various sources of Ca2+ appear to be required for SK channel activation in SNc neurons (some of them still unidentified), ensuring robustness of pacemaking regularity. [less ▲]

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See detailWaveguides for walking droplets
Filoux, Boris ULg; Hubert, Maxime ULg; Schlagheck, Peter ULg et al

E-print/Working paper (2016)

When gently placing a droplet onto a vertically vibrated bath, a drop can bounce without coalescing. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes ... [more ▼]

When gently placing a droplet onto a vertically vibrated bath, a drop can bounce without coalescing. Upon increasing the forcing acceleration, the droplet is propelled by the wave it generates and becomes a walker with a well defined speed. We investigate the confinement of a walker in different rectangular cavities, used as waveguides for the Faraday waves emitted by successive droplet bounces. By studying the walker velocities, we discover that 1d confinement is optimal for narrow channels of width of D≃1.5λF. We also propose an analogy with waveguide models based on the observation of the Faraday instability within the channels. [less ▲]

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See detailNappe Vibration Mitigation Techniques for Free-overfall Structrures
Lodomez, Maurine ULg; Crookston, Brian M.; Tullis, Blake P. et al

in Full Proceedings: Hydraulic Structures and Water System Management (2016, June 27)

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This ... [more ▼]

Nappe vibration is a phenomenon that has been witnessed in the field for a variety of different free overflow hydraulic structures operating at low heads, such as fountains, crest gates, and weirs. This phenomenon is visually characterized by oscillations in the thin nappe cascading downstream of the control structure. These oscillations can produce a significant level of noise and acoustic pressure waves, which can increase the environmental and societal impacts of the hydraulic structure. As a result, a detailed investigation has been undertaken to identify practical and effective mitigation solutions for free-overfall structures where nappe vibration may be of concern. Research is being performed with a prototype-scale linear weir (weir length of 3.5 m and fall height of 3 m) located at the Engineering Hydraulics laboratory of the University of Liège, to assess the effectiveness of various crest modifications and any corresponding impacts to hydraulic efficiency (i.e., flow rate). The test matrix includes the optimization (position and spacing of elements) of three mitigation solutions which are projecting bolts, deflectors and step. In addition, a high-speed camera and audio equipment have been used to evaluate effectiveness of the configurations in reducing nappe vibration. Finally, this practical study has identified countermeasures suitable for retrofits and new construction, easy to construct, durable, hydraulically efficient, and with minimal potential for debris collection. [less ▲]

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See detailMobilité physique et chimique du 10Be, 137Cs et 210Pb (xs) dans les sols : rôle des caractéristiques pédologiques.
de Tombeur, Félix ULg

Master's dissertation (2016)

Les processus de transferts de matières verticaux dans les sols (bioturbation et lessivage) sont jusqu’à présent mal contraints bien qu’ils soient responsables de l’évolution temporelle des services ... [more ▼]

Les processus de transferts de matières verticaux dans les sols (bioturbation et lessivage) sont jusqu’à présent mal contraints bien qu’ils soient responsables de l’évolution temporelle des services écosystémiques rendus par les sols. Afin de mieux contraindre ces processus, une méthode de quantification cinétique basée sur les profils verticaux de 210Pb (xs), 10Be et 137Cs a été développée pour les Luvisols, dans lesquels les transferts solubles peuvent être négligés. Les limites d’applicabilité de ce type d’approche n’ont cependant pas été testées. Dans ce travail, nous avons analysé le 210Pb (xs), 10Be et 137Cs dans des sols présentant des gradients de carbone organique, de pH et de teneurs en < 2 μm (Podzol, Andosol, Ferralsol, Leptosol). Des sols acides et des teneurs en matières organiques importantes ont été considérés. La distribution verticale des isotopes étudiés a été interprétée en fonction de la teneur en matière organique, du pH et de la fraction < 2 μm. Nous démontrons que des pertes de 10Be et de 137Cs sous forme solubles sont présentes dans les Podzols, spécialement sous forêt, plus acide, pour le dernier. Des transferts solubles de 10Be ont également été identifiés dans l’Andosol mais considérés comme négligeables dans le Leptosol. Pour le 210Pb (xs), les transferts solubles sont également probables pour les sols au pH inférieurs à 5.5 (Andosol et Ferralsol) et une forte affinité pour la matière organique a été démontrée. Ainsi, en conditions acides et teneur en particules < 2 μm faible, les transferts solubles ne peuvent plus être négligés. [less ▲]

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See detailLa joie qui vient après l'attente. Retour sur la parution de J.-M. Mouillie et J.-P. Narboux, Sartre. L'Être et le néant. Nouvelles lectures, Paris, Les Belles Lettres, 2015, 212 p.
Recchia, Fabio ULg

in Année Sartrienne (L') (2016)

Cette publication consiste en une recension des "Nouvelles lectures" de "L'Être et le Néant", publiées à l'occasion de la sélection de ce texte à l'agrégation externe de philosophie 2015. Il s'agit de ... [more ▼]

Cette publication consiste en une recension des "Nouvelles lectures" de "L'Être et le Néant", publiées à l'occasion de la sélection de ce texte à l'agrégation externe de philosophie 2015. Il s'agit de faire retour sur cet événement que constitue la parution d'un tel recueil proposant, selon nous, une "relecture franche" de l'Essai de 1943 - un texte longtemps tenu pour le parent pauvre de la philosophie de Sartre, dans la mesure où cet ouvrage compte peu de monographies spécialisées à son sujet. Identifiant par ailleurs que ces "Nouvelles lectures" renvoient à nouvelle génération de chercheurs, cette recension souligne de quelle manière ce recueil apporte un commentaire lumineux de l'appareillage ontologique de l'Essai de 1943, témoigne en outre d'une attention particulièrement vive à l'égard des thématiques de l'individuation ainsi que de l'intersubjectivité chez Sartre, et articule enfin un dialogue entre les champs des "Études sartriennes" et celui de la philosophie de l'esprit contemporaine. [less ▲]

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See detailMarijan Molé à l'aube du nouveau comparatisme indo-iranien
Swennen, Philippe ULg

Conference (2016, June 24)

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See detailHealth Literacy: Eduquer pour mieux soigner
Bragard, Isabelle ULg

Scientific conference (2016, June 24)

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See detailThe implication of short-term memory in numerical magnitude processing: evidence from Turner syndrome
Attout, Lucie ULg; Noël, Marie-Pascale; Rousselle, Laurence ULg

Poster (2016, June 24)

Most studies on early magnitude representation focused on the visual modality with no possibility to disentangle the influence of visuo-spatial skills and short-term memory (STM) abilities on visual ... [more ▼]

Most studies on early magnitude representation focused on the visual modality with no possibility to disentangle the influence of visuo-spatial skills and short-term memory (STM) abilities on visual quantification processes. In order to specify the influence of visuo-spatial and STM processing on numerical abilities, a series of magnitudes comparison tasks differing on visuo-spatial processing requirement (no/high), on the nature of the magnitude to be processed (continuous/discrete/symbolic magnitude) and on WM demands (simultaneous/sequential presentation) were administred to twenty patients with Turner syndrome (TS), a genetic condition characterized by poor mathematical achievement, low spatial skills and reduced STM abilities. Our results showed a lower acuity than a control group matched on verbal IQ when participants with TS compared the numerical magnitudes of stimuli presented sequentially (low visuo-spatial processing and high STM load: Dot sequence and Sound sequence). No difference was observed in the numerical comparison of sets presented simultaneously or when comparing continuous and symbolic magnitude stimuli. Besides, the group difference in sequential tasks disappeared when controlling for STM abilities. These results highlight the importance of STM abilities to extract numerosity through a sequential presentation and underline the importance of considering the impact of format presentation on magnitude judgments. [less ▲]

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See detailEvolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field
Olaerts, Heleen; Roye, Chiara; Derde, Liesbeth et al

in Journal of Agricultural and Food Chemistry (2016), 64

To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed ... [more ▼]

To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α- and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α- and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin. [less ▲]

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See detailEmerging Hybridities under Networked Agribusiness in Argentina
Delvenne, Pierre ULg

Conference (2016, June 24)

Science and Technology Studies (STS) are paying greater attention to the interactions between new technologies and politico-economic orders. Dynamics of promises and expectations with regard to ... [more ▼]

Science and Technology Studies (STS) are paying greater attention to the interactions between new technologies and politico-economic orders. Dynamics of promises and expectations with regard to technological developments, and their uptake, play a major role in shaping political-economic policies, institutional practices and wider societal mutations. Informed by the theoretical perspective of co-production (Jasanoff 2004), this paper addresses the political economy of GM soy agriculture in Argentina as both epistemic and social orders. We engage ‘micro’ perspectives looking at situated social experiments with farmers and their interrelations with ‘macro’ phenomena such as capital-labour relations and forms of ‘neoliberalism’. We find that the emerging hybridities in present time’s Argentina are caught between the promissory futures of agroindustrial innovation and the historical, political and material conditions of agricultural production that give rise to these presents in the first place. Looking at three of such hybridities (the blurring of boundaries between modern/national, agriculture/industry and leasing/ownership), we highlight the ways in which elements of political-economic structures and human agency got bound up with technoscientific advances (Jasanoff 2015). Our contribution reveals the importance of the concept of ‘network’ to make sense of the dominant logic of agribusiness and it amounts to ‘rugged’ approach to networks with due attention to the complex topographies of circulating power and morality. [less ▲]

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See detailResponse to droughts and heat waves of the productivity of natural and agricultural ecosystems in Europe within ISI-MIP2 historical simulations
François, Louis ULg; Henrot, Alexandra-Jane ULg; Dury, Marie ULg et al

Conference (2016, June 23)

According to the projections of climate models, extreme events such as droughts and heat waves are expected to become more frequent and more severe in the future. Such events are known to severely impact ... [more ▼]

According to the projections of climate models, extreme events such as droughts and heat waves are expected to become more frequent and more severe in the future. Such events are known to severely impact the productivity of both natural and agricultural ecosystems, and hence to affect ecosystem services such as crop yield and ecosystem carbon sequestration potential. Dynamic vegetation models are conventional tools to evaluate the productivity and carbon sequestration of ecosystems and their response to climate change. However, how far are these models able to correctly represent the sensitivity of ecosystems to droughts and heat waves? How do the responses of natural and agricultural ecosystems compare to each other, in terms of drought-induced changes in productivity and carbon sequestration? In this contribution, we use ISI-MIP2 model historical simulations from the biome sector. Eight dynamic vegetation models have participated in the biome sector intercomparison of ISI-MIP2: CARAIB, DLEM, JULES, LPJ-GUESS, LPJml, ORCHIDEE, VEGAS and VISIT. We focus the analysis on well-marked droughts or heat waves that occured in Europe after 1970, such as the 1976, 2003 and 2010 events. For most recent studied events, the model results are compared to the response observed at several eddy covariance sites in Europe, and, at a lager scale, to the drops in crop productivities reported in national statistics or to the drought impacts retrieved from satellite data (Terra MODIS instrument). [less ▲]

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See detailReceding-Horizon Control of Distributed Generation to Correct Voltage or Thermal Violations and Track Desired Schedules
Soleimani Bidgoli, Hamid ULg; Glavic, Mevludin ULg; Van Cutsem, Thierry ULg

in Proceedings of the 19th PSCC (2016, June 23)

This paper presents a real-time, centralized control system acting on the active and reactive powers of distributed generators when the network experiences voltage and/or thermal limits violation. The ... [more ▼]

This paper presents a real-time, centralized control system acting on the active and reactive powers of distributed generators when the network experiences voltage and/or thermal limits violation. The control resorts on multi-step receding-horizon optimization. The objective is to minimize the deviations of Dispersed Generation Units (DGU) active and reactive powers from reference values. The reactive power corrections have priority over the active ones. Furthermore, the formulation is such that DGU powers are restored to their desired schedule as soon as operating conditions allow doing so. Three modes of operation of the proposed controller are presented, involving dispatchable units as well as DGUs operated to track maximum power output. The effectiveness of the proposed control is illustrated through detailed simulations of a 75-bus, 11-kV system hosting 22 DGUs. [less ▲]

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See detailPublic Education Expenditures, Growth and Income Inequality
Artige, Lionel ULg; Cavenaile, Laurent

Conference (2016, June 23)

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See detailInfluence du conditionnement et de la déshydratation mécanique sur le séchage des boues d'épuration
Pambou, Yvon-Bert ULg

Doctoral thesis (2016)

Wastewater treatment plants generate a byproduct which is found in the form of a colloidal suspension, known under the generic term of sludge. At present time, its valorization after a treatment step is a ... [more ▼]

Wastewater treatment plants generate a byproduct which is found in the form of a colloidal suspension, known under the generic term of sludge. At present time, its valorization after a treatment step is a topical environmental issue. This work focuses on the study of the impact of the conditioning step, i.e., the addition of chemicals such as coagulants and flocculants, on the mechanical dewatering and thermal drying steps. The coagulant used (polyaluminum chloride) is combined with a cationic polymer type (flocculant), ranging from linear to complex structures (branched and cross-linked), two of the four flocculants tested with the coagulant are linear structures only differing by their molecular weight. Specifically, the study highlights the role of polyaluminum chloride (PAX-14) as a co-activating agent of the water release during the flocculation stage, when it is combined with the polymer. To better understand the link between this flocculation stage and mechanical dewatering and drying performances, many conditioning ways have been studied and the flocculated sludge obtained was dewatered under a constant pressure using a normalized filtration-expression cell. The dewatered cake obtained after the filtration stage was then characterized in terms of dry solids content, textural properties, desorption isotherms, and finally submitted to a convective drying post-treatment, after the sample was extruded through a circular diameter of 14 mm and cut at a height of a same length, yielding cylindrical samples with a mass of around 2.5 g. Results show that, dual conditioning by applying PAX-14 as a coagulant is an excellent way to improve the cake dryness after the mechanical dewatering step. The interaction between the liquid suspension with polyaluminum chloride and the flocculant offers more attractive yields compared with the use of single conditioning to flocculate the bio-material. Moreover, the efficiency of the two linear flocculants including the use of PAX-14, were shown to produce rather similar performances, while for the same coagulant coupled with trendy or branched macromolecules produce significant differences in terms of increase in dry solids content of the dewatered cake, differences for which the polymer having the highest degree of cross-linking appears to be more beneficial to remove more water contained in the floc after filtration. Sorption isotherms, curves reflecting the hygroscopicity of the product were carried out on the dewatered samples using the DVS equipment (Dynamic Vapor Sorption). Firstly, these experiments confirmed that, curves obtained for wastewater sludge exhibit a sigmoidal shape characteristic of type II, and secondly, an impact of dual PAX-14/polymer conditioning on hydro-textural properties remains difficult to assess. Based on the statistical parameters, GAB equation appears the best formulation to model the sludge sorption isotherms of the Grosses-battes wastewater treatment plant. By studying the texture evolution of sludge for different levels of cake dryness, this work has compared the sludge mechanical properties from the four conditioning types. Globally, results show a more pronounced firmness of the dewatered cake when using the couple PAX-14/polymer in the flocculation stage compared to the single conditioning one. However, from the determined sludge texture parameters it seems difficult to argue that the contribution of both coagulant and cross-linked polymers is better than the association involving aluminum polymerized salt and linear flocculants. Finally, it can be noted that the effects of under or overdosing of chemical can lead to the destruction of material and then, a decrease of sludge cohesion drying rate can be observed. In order to access at the effect of the dual PAX-14/polymer conditioners on drying behavior of sludge samples, some characteristics associated with drying kinetics were compared. According to the statistical analysis, the most significant results were obtained by the association involving PAX-14 and the use of cross-linked flocculants, for which, the polymer which has the highest degree of cross-linking provides a better propensity to remove water contained into flocs after filtration. Linear polymers were shown to produce the same performance. During drying, the texture of the material evolves, including shrinkage and voids development. By X-ray microtomography, this phenomenon has been characterized. The curves of shrinkage volume exhibited a linear decrease with two straight line periods, which the transition seems to be correlated to the sludge water behavior. On the first period, the shrinkage volume can be correlated to the quantity of evaporated water. The texture of the solid material does not hamper the shrinkage process. However, during the second period, the structure of solid stiffens and then influences the shrinkage phenomenon: water is replaced by air and porosity is created. This period corresponds to a phase of decreasing deformation rate (ε) marking the gradual rigidifying of the matrix until no further deformation was observed, the solid was totally rigidified. After drying, the final volume reduction was found to be close to 70% of the initial sample volume for linear and cross-linked flocculants combined with PAX-14, while it was around 75% of the sample initial volume in the case of branched flocculant co-conditioning with the sample coagulant. According to this result, shrinkage depends on both the nature of the sludge and the polyelectrolyte types or dosage. An impact was also found of chemical conditioners on the evolution of porosity. For sludge flocculated by single conditioning, it appears that the porosity was centered on the solid material while for dual conditioning a porosity structured in slats, was identified. This difference in internal structure of the porosity explains the difference in drying kinetics, including the modification of the exchange surfaces available and the average distance of transfer, allowing acceleration or a slow-down of the water removal. [less ▲]

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See detailImpact of fire on resilience of tropical dry forests: miombo in Lubumbashi (Democratic Republic of Congo)
Hick, Aurélie ULg

Conference (2016, June 23)

Dry tropical forests are widespread in continental Africa where they account for 70-80% of forested area. Miombo is a dry forest characterized by the dominance of trees in the genera Brachystegia ... [more ▼]

Dry tropical forests are widespread in continental Africa where they account for 70-80% of forested area. Miombo is a dry forest characterized by the dominance of trees in the genera Brachystegia, Julbernardia and Isoberlinia. Dry-season fires are a characteristic feature of these forests. Fire is not a frequent natural disturbance but they originate from anthropic. The impact of fire on forest species depends on the intensity and timing in relation to plant phenology. Due to urban pressure, more than 85% of woodland forests were converted to savannahs given several degree of forest degradation in the landscape. After a disturbance, tropical forest ecosystem can return to a trajectory close to the original ecosystem. The time it takes for this ecosystem recover to its predisturbance ecological condition is termed resilience. Loss of resilience can trigger a shift to another ecological state with ecosystems that are different in species and/or that are different in their functional and structural aspects. The broad goal of our study was to examine impact of fire on resilience of miombo after human disturbances. Mosaic of the MODIS 500m burned area product from 2002 to 2012 were used to calculate return frequency of fires around Lubumbashi. Five degrees of miombo degradation have been established : no degraded forest/little disturbed (level 1), moderately degraded forest (level 2), degraded forest (level 3), severely degraded forest (level 4) et deforested (level 5). For each degree of degradation, 9 circular plots (18 m radius, 0.1ha) were established, excepted for level 4 where 8 plots were laid. Within each circular plot, all woody individuals >= 2 cm diameter at breast height (DBH) were tagged, measured (height and diameter) and identified. Tree seedlings < 2 cm DBH and of height > 20cm were also sampled and identified. Herbaceous biomass was measured. Floristic composition in level 4 corresponded to fire-tolerant species. In other degree of forest degradation, most abundant species in mature trees consisted to tolerant or semi-tolerant species. Floristic composition of regeneration in most degraded degree consisted to a mixte of miombo species and fire-tolerant species. Fire has an impact on resilience of miombo after human degradation. Level 4 corresponded to a typical floristic community of a chipya habitat, where all woody species are fire tolerant. Fire can lead degraded miombo toward an alternative stable degraded states. [less ▲]

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