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See detailLa difficile jointure des directives EU anti-BEPS et des traités fiscaux
Docclo, Caroline ULg

in Fiscologue International = Fiscoloog internationaal (2017)

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See detailHigh School Sport in Belgium (Wallonia)
Cloes, Marc ULg

Conference (2017, July 31)

In Belgium, since 1969, sport is a competence under the control of public authorities defined according to the linguistic regime. As in most Western European countries, sport has been compartmentalised by ... [more ▼]

In Belgium, since 1969, sport is a competence under the control of public authorities defined according to the linguistic regime. As in most Western European countries, sport has been compartmentalised by giving rise to three main types of practice: "professional", "traditional" and "alternative" sports (Diegel, 1995). Clubs linked to sports federations constitute the local setting up of the sports organization, which is largely a majority (Zintz, 2014). Other operators from the public domain and the private sphere coexist (Cloes, 2012). In the school environment, sport can be found in three contexts: within the compulsory curriculum (physical education), integrated to extracurricular activities (activities organized during recess or free periods), and peripheral activities (use of school sports facilities by organizers who are not belonging to the school actors). If inter-school competitions are organized by several school sports federations (depending to the educational network), they are far from reaching the interest and involvement reached by the competitions managed by the traditional sports federations. So there is hardly any systematic sports training in French-speaking Belgian schools. Some PE teachers propose voluntary training sessions but there are less and less connections between their actions and sport clubs. On the other hand, young sportsmen appointed by the Minister of Sports have a special status enabling them to benefit facilities to pursue their double career. They are sometimes gathered in special organizations - sport-studies or development centers - which have been the subject of several studies (Cloes et al., 2002, Lacrosse et al., 2014, Theunissen et al., 2016) but PE teachers are very few involved in these development opportunities. In many situations of partnership between the school and sports structures, their role is often limited to a simple accompanying action (sports days, projects "My club-My school." Cloes (2017) insisted however on the need to make them a priority in the coordination of the preparation of physically educated citizens. References Cloes, M. (2012). La Wallonie en mouvement : vers une culture sportive et de l’activité physique ? In, M. Germain et R. Robaye (Eds.), L'état de la Wallonie. Portrait d'un pays et de ses habitants – 2011. (pp. 70-80). Namur : Les éditions namuroises. Available on Internet : http://hdl.handle.net/2268/117294 Cloes, M. (2017). Preparing physically educated citizens in physical education. Expectations and practices. Retos, 31, 245-251. Available on Internet : http://recyt.fecyt.es/index.php/retos/article/view/53497/32304 Cloes, M., Schelings, V., Ledent, M, & Piéron, M. (2002). Sport-études : comparaison des caractéristiques motivationnelles et des relations sociales des élèves sportifs et de leurs condisciples. eJRIEPS (e Journal de la Recherche sur l'Intervention en Éducation Physique et Sport), 1, 57-72. Available on Internet: http://hdl.handle.net/2268/10187 Diegel, H. (1995). Sport in changing society – Sociological essays. Schorndorf: Verlag Karl Haufmann. Lacrosse, Z., Martin, V., & Cloes, M. (2014, July). Analyse qualitative du fonctionnement du centre de formation d’une fédération sportive. Paper presented at the 8ème biennale de l’ARIS ‘Temps, temporalités et intervention en EPS et en sport’, Genève, Suisse. Available on Internet: http://hdl.handle.net/2268/170020 Theunissen, C., Meys, G., & Cloes, M. (2016). Encadrement du staff autour du double projet des sportifs dans un centre de formation en handball. Revue de l’Éducation physique, 56, 1/2, 20. Disponible sur Internet: http://yessport.be/educationphysique/file/REVUE_1_ET_2_2016_-2eme_COLLOQUE_GUY_NAMUROIS.pdf ou http://orbi.ulg.ac.be/handle/2268/199016 Zintz, T. (2014). Module 3 - Le paysage sportif : du pratiquant aux fédérations. Thématique 1 - Cadre institutionnel et législatif. Cours généraux de la formation ‘Moniteur Sportif Initiateur’. Brussels, Belgium : Administration des sports, Fédération Wallonie-Bruxelles. Internet : http://www.sport.cfwb.be/index.php?id=7370 [less ▲]

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See detailDynamicized semantic maps of content words. Comparing long-term lexical changes in Ancient Egyptian and Greek
Georgakopoulos, Athanasios ULg; Polis, Stéphane ULg

Conference (2017, July 31)

This paper aims at demonstrating how information on the paths of semantic extensions undergone by content words may be incorporated into semantic maps. For this purpose, particular changes that affected ... [more ▼]

This paper aims at demonstrating how information on the paths of semantic extensions undergone by content words may be incorporated into semantic maps. For this purpose, particular changes that affected the meanings of words in the course of the Ancient Egyptian and of the Ancient Greek language history are investigated. [less ▲]

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See detailThermoelectric properties of heavily-doped Fe2YZ full-Heusler compounds
Lemal, Sébastien ULg; Ricci, Fabio ULg; Verstraete, Matthieu ULg et al

Poster (2017, July 31)

Fe2YZ full-Heusler compounds were recently predicted to exhibit very large thermoelectric power factors [Phys. Rev. Lett. 114, 136601 (2015)]. Combining first-principles density functional theory ... [more ▼]

Fe2YZ full-Heusler compounds were recently predicted to exhibit very large thermoelectric power factors [Phys. Rev. Lett. 114, 136601 (2015)]. Combining first-principles density functional theory calculations within a hybrid functional approach and Boltzmann semi-classical transport theory, we investigate the limits of the rigid band doping approximation, and the properties of heavily n-type doped full-Heusler Fe2YZ1-xAx compounds. Using a supercell approach and including explicit dopant impurities, we recover in some cases giant thermoelectric power factors, as previously predicted within the rigid band approximation. In others the effect on the electronic structure is very different from rigid shifts. Interestingly, we find that some systems present a magnetic instability consistent with the Stoner model, and evolve towards a ferromagnetic half-metallic ground state, with a strongly modified power factor. Our results show the promise of the heavily-doped phases of the studied Fe2YZ1-xAx compounds for Seebeck and spin-dependent Seebeck applications. [less ▲]

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See detailCation Distribution Dependent Magnetic Properties in CoCr 2-x Fe x O 4 (x= 0.1 to 0.5): EXAFS, Mӧssbauer and Magnetic Measurements
Kumar, Durgesh; Banerjee, Alok; Mahmoud, Abdelfattah ULg et al

in Dalton Transactions (2017), 46

In this report, we have examined the evolution of the structure and rich magnetic transitions such as a paramagnetic to ferrimagnetic phase transition at the Curie temperature (TC), spiral ordering ... [more ▼]

In this report, we have examined the evolution of the structure and rich magnetic transitions such as a paramagnetic to ferrimagnetic phase transition at the Curie temperature (TC), spiral ordering temperature (TS) and lock-in temperature (TL) observed in the CoCr2O4 spinel multiferroic after substituting Fe. The crystal structure, microstructure and cation distribution among the tetrahedral (A) and octahedral (B) sites in the spinel lattice are characterised by X-ray diffraction, transmission electron microscopy, Extended X-ray Absorption Fine Structure (EXAFS) and Mössbauer spectroscopy. Due to the same radial distances of the first coordination shell in both tetrahedral and octahedral environments observed in EXAFS spectra, the position of the second coordination shell specifies the preference of more Fe ions towards the A site at x = 0.1. At x = 0.5, more Fe ions favour the B site. The cation distribution quantitatively obtained from the Mössbauer spectral analysis shows that while 60% of Fe ions occupy the A site in x = 0.1, 40% occupy it in x = 0.5. Surprisingly at x = 0.3, Fe ions are distributed equally among the A and B sites. dc magnetization reveals an increase in TC from 102 K to 200 K and in TS from 26 to 40 K with an increase in Fe concentration, indicating an enhancement in A–B exchange interaction at the expense of B–B. No report has until now demonstrated such an enhancement in TS either in pure or in doped CoCr2O4. Furthermore, frequency-dependent ac susceptibility (χ) data fitted with different phenomenological models such as the Néel–Arrhenius, Vogel–Fulcher and power law confirm a spin-glass and/or cluster-glass behaviour in nanoparticles of CoCr2−xFexO4. [less ▲]

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See detailLe maraîchage périurbain à Libreville et Owendo (Gabon) : pratiques culturales et durabilité
Bayendi-Loudit, Sandrine ULg; Ndoutoume Ndong, Auguste; Francis, Frédéric ULg

in Cahiers Agricultures (2017)

In Gabon, peri-urban gardening is an opportunity to provide vegetables to the main cities, such as Libreville and Owendo. Following a survey conducted in three market gardening areas, an inventory was ... [more ▼]

In Gabon, peri-urban gardening is an opportunity to provide vegetables to the main cities, such as Libreville and Owendo. Following a survey conducted in three market gardening areas, an inventory was conducted on the socio-economic characteristics, the diversity of crops, and pesticide uses. The cropped areas range from 0.08 ha to 0.4 ha per farmer, according to the site. National operators represent 51%, while people from Burkina Faso manage 40% of vegetable production. The most cultivated species throughout the year are amaranth (Amaranthus hybridus L.), lettuce (Lactuca sativa L.), Guinea sorrel (Hibiscus sabdariffa L.) and black nightshade (Solanum nigrum L.). The most important pests are Aphididae and some beetles. The most commonly used plant protection products are insecticides, mainly conventional neurotoxic. Best crop monitoring, pest control including pesticide application reduction, and the possibility to offer microcredit systems to small producers would help increasing peri-urban healthy vegetable production and increase local food autonomy [less ▲]

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See detailEl impacto del fin del “giro al la izquierda” sobre las relaciones entre China y América Latina
Wintgens, Sophie ULg

Conference (2017, July 28)

La llegada de China en América Latina a finales de los años 2000 se ha presentado como una nueva opción en el contexto histórico de un “movimiento pendular” que siempre ha visto los países latino ... [more ▼]

La llegada de China en América Latina a finales de los años 2000 se ha presentado como una nueva opción en el contexto histórico de un “movimiento pendular” que siempre ha visto los países latino-americanos girar principalmente en torno a Europa y sus antiguas potencias coloniales o en torno a los Estados Unidos. En el marco de esa dinámica del “triángulo Atlántico” en la que se encuentra encerrada América Latina, China ha también beneficiado de un entorno regional propicio como consecuencia de factores tanto estructurales (las debilidades del regionalismo latinoamericano), como coyunturales (la escalada de la “nueva” izquierda sudamericana). El inicio de la década de 2010, sin embargo, parece marcar el final del “giro à la izquierda” y los límites del modelo de desarrollo extractivo adoptado por la mayoría de los gobiernos progresistas latino-americanos. Al mismo tiempo, las autoridades chinas han también iniciado un cambio de modelo de desarrollo económico con el undécimo Plan Quinquenal (2006-2010) para que sea más autocentrado y basado en la producción de productos de alta calidad. Basándose en estas observaciones, este ponencia interroga el impacto de este contexto sobre las relaciones entre China y América Latina. [less ▲]

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See detailSpray-drying as a tool to disperse conductive carbon inside Na2FePO4F particles by addition of carbon black or carbon nanotubes to the precursor solution
Mahmoud, Abdelfattah ULg; Caes, Sebastien; Brisbois, Magali et al

in Journal of Solid State Electrochemistry (2017)

In this work, Na2FePO4F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare ... [more ▼]

In this work, Na2FePO4F-carbon composite powders were prepared by spray-drying a solution of inorganic precursors with 10 and 20 wt% added carbon black (CB) or carbon nanotubes (CNTs). In order to compare the effect of CB and CNTwhen added to the precursor solutions, the structural, electrochemical, and morphological properties of the synthesized Na2FePO4F-xCB and Na2FePO4F-xCNT samples were systematically investigated. In both cases, X-ray diffraction shows that calcination at 600 °C in argon leads to the formation of Na2FePO4F as the major inorganic phase. 57Fe Mössbauer spectroscopy was used as complementary technique to probe the oxidation states, local environment, and identify the composition of the iron-containing phases. The electrochemical performance is markedly better in the case of Na2FePO4F-CNT (20 wt%), with specific capacities of about 100 mAh/g (Na2FePO4F-CNT) at C/4 rate vs. 50 mAh/g for Na2FePO4F-CB (20 wt%). SEM characterization of Na2FePO4F-CB particles revealed different particle morphologies for the Na2FePO4F-CNT and Na2FePO4F-CB powders. The carbon-poor surface observed for Na2FePO4FCB could be due to a slow diffusion of carbon in the droplets during drying. On the contrary, Na2FePO4F-CNT shows a better CNT dispersion inside and at the surface of the NFPF particles that improves the electrochemical performance. [less ▲]

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See detailSynthesis and complexation of superbulky imidazolium-2-dithiocarboxylate ligands
Beltran Alvarez, Tomás Francisco ULg; Zaragoza, Guillermo; Delaude, Lionel ULg

in Dalton Transactions (Cambridge, England : 2003) (2017), 46(28), 9036-9048

The superbulky N-heterocyclic carbenes (NHCs) 2,6-bis(diphenylmethyl)-4-methylimidazol-2-ylidene (IDip*Me) and its 4-methoxy analogue (IDip*OMe) reacted instantaneously with carbon disulfide to afford the ... [more ▼]

The superbulky N-heterocyclic carbenes (NHCs) 2,6-bis(diphenylmethyl)-4-methylimidazol-2-ylidene (IDip*Me) and its 4-methoxy analogue (IDip*OMe) reacted instantaneously with carbon disulfide to afford the corresponding imidazolium-2-dithiocarboxylate zwitterions in high yields. These new dithiolate ligands were fully characterized and their coordination chemistry toward common Re(i) and Ru(ii) metal sources was thoroughly investigated. Neutral [ReBr(CO)3(S2C[middle dot]NHC)] chelates featured three facially-arranged carbonyl groups on a distorted octahedron, whereas cationic [RuCl(p-cymene)(S2C[middle dot]NHC)]PF6 complexes displayed a piano-stool geometry. The molecular structures of the six new compounds revealed that the NHC[middle dot]CS2 inner salts were highly flexible. Indeed, the torsion angle between their anionic and cationic moieties varied between ca. 63[degree] in the free ligands and 3[degree] in the ruthenium complexes. Concomitantly, the S-C-S bite angle underwent a contraction from 131[degree] to 110-113[degree] upon chelation. Computation of the %VBur parameter showed that the dithiocarboxylate unit of the NHC[middle dot]CS2 betaines chiefly determined the steric requirements of the imidazolium moieties, irrespective of the metal center involved in the complexation. The replacement of the p-methyl substituents of IDip*Me with p-methoxy groups in IDip*OMe did not significantly affect the ligand bulkiness. The more electron-donating methoxy group led, however, to small changes in various IR wavenumbers used to probe the electron donor properties of the carbene moiety. [less ▲]

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See detailÉcrire de “Guiron” en Flandre à la fin du Moyen Âge
Veneziale, Marco ULg

Conference (2017, July 28)

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See detailOccupational social and mental stimulation and cognitive decline with advancing age
Grotz, Catherine ULg; Meillon, Céline; Amieva, Hélène et al

in Age and Ageing (2017)

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See detailThe Prediction-Focused Approach: An opportunity for hydrogeophysical data integration and interpretation in the critical zone
Hermans, Thomas ULg; Nguyen, Frédéric ULg; Klepikova, Maria et al

Poster (2017, July 27)

Two important challenges remain in hydrogeophysics: the inversion of geophysical data and their integration in quantitative subsurface models. Classical regularized inversion approaches suffer from ... [more ▼]

Two important challenges remain in hydrogeophysics: the inversion of geophysical data and their integration in quantitative subsurface models. Classical regularized inversion approaches suffer from spatially varying resolution and yield geologically unrealistic solutions, making their utilization for model calibration less consistent. Advanced techniques such as coupled inversion allow for a direct integration of geophysical data; but, they are difficult to apply in complex cases and remain computationally demanding to estimate uncertainty. We investigated a prediction-focused approach (PFA) to directly estimate subsurface physical properties relevant in the critical zone from geophysical data, circumventing the need for classic inversions. In PFA, we seek a direct relationship between the data and the subsurface variables we want to predict (the forecast). This relationship is obtained through a prior set of subsurface models for which both data and forecast are computed. A direct relationship can often be derived through dimension reduction techniques (Figure 1). For hydrogeophysical inversion, the considered forecast variable is the subsurface variable, such as the salinity or saturation for example. An ensemble of possible solutions is generated, allowing uncertainty quantification. For data integration, the forecast variable is the prediction we want to make with our subsurface models, such as the concentration of contaminant in a drinking water production well. Geophysical and hydrological data are combined to derive a direct relationship between data and forecast. We illustrate the methodology to predict the energy recovered in an ATES system considering the uncertainty related to spatial heterogeneity. With a global sensitivity analysis, we identify sensitive parameters for heat storage prediction and validate the use of a short term heat tracing experiment to generate informative data. We illustrate how PFA can be used to successfully derive the distribution of temperature in the aquifer from ERT during the heat tracing experiment. Then, we successfully integrate the geophysical data to predict heat storage in the aquifer using PFA. The result is a full quantification of the posterior distribution of the prediction conditioned to observed data in a relatively limited time budget. [less ▲]

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See detailDeep imaging search for planets forming in the TW Hya protoplanetary disk with the Keck/NIRC2 vortex coronagraph
Ruane, G.; Mawet, D.; Kastner, J. et al

in Astronomical Journal (The) (2017), 154

Distinct gap features in the nearest protoplanetary disk, TW Hya (distance of 59.5$\pm$0.9 pc), may be signposts of ongoing planet formation. We performed long-exposure thermal infrared coronagraphic ... [more ▼]

Distinct gap features in the nearest protoplanetary disk, TW Hya (distance of 59.5$\pm$0.9 pc), may be signposts of ongoing planet formation. We performed long-exposure thermal infrared coronagraphic imaging observations to search for accreting planets especially within dust gaps previously detected in scattered light and submm-wave thermal emission. Three nights of observations with the Keck/NIRC2 vortex coronagraph in $L^\prime$ (3.4-4.1$\mu$m) did not reveal any statistically significant point sources. We thereby set strict upper limits on the masses of non-accreting planets. In the four most prominent disk gaps at 24, 41, 47, and 88 au, we obtain upper mass limits of 1.6-2.3, 1.1-1.6, 1.1-1.5, and 1.0-1.2 Jupiter masses ($M_J$) assuming an age range of 7-10 Myr for TW Hya. These limits correspond to the contrast at 95\% completeness (true positive fraction of 0.95) with a 1\% chance of a false positive within $1^{\prime\prime}$ of the star. We also approximate an upper limit on the product of planet mass and planetary accretion rate of $M_p\dot{M}\lesssim10^{-8} M_J^2/yr$ implying that any putative $\sim0.1 M_J$ planet, which could be responsible for opening the 24 au gap, is presently accreting at rates insufficient to build up a Jupiter mass within TW Hya's pre-main sequence lifetime. [less ▲]

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See detailIs supercritical fluid chromatography hyphenated to massspectrometry suitable for the quality control of vitamin D3 oilyformulations?
Andri, Bertyl ULg; Dispas, Amandine ULg; Klinkenberg, Régis et al

in Journal of Chromatography. A (2017), 1515

Nowadays, many efforts are devoted to improve analytical methods regarding efficiency, analysis timeand greenness. In this context, Supercritical Fluid Chromatography (SFC) is often regarded as a ... [more ▼]

Nowadays, many efforts are devoted to improve analytical methods regarding efficiency, analysis timeand greenness. In this context, Supercritical Fluid Chromatography (SFC) is often regarded as a goodalternative over Normal Phase Liquid Chromatography (NPLC). Indeed, modern SFC separations arefast, efficient with suitable quantitative performances. Moreover, the hyphenation of SFC to mass spec-trometry (MS) provides additional gains in specificity and sensitivity. The present work aims at thedetermination of vitamin D3 by SFC-MS for routine Quality Control (QC) of medicines specifically. Basedon the chromatographic parameters previously defined in SFC-UV by Design of Experiments (DoE) andDesign Space methodology, the method was adapted to work under isopycnic conditions ensuring a base-line separation of the compounds. Afterwards, the response provided by the MS detector was optimizedby means of DoE methodology associated to desirability functions. Using these optimal MS parameters,quantitative performances of the SFC-MS method were challenged by means of total error approachmethod validation. The resulting accuracy profile demonstrated the full validity of the SFC-MS method. It was indeed possible to meet the specification established by the European Medicines Agency (EMA) (i.e. 95.0 − 105.0% of the API content) for a dosing range corresponding to at least 70.0-130.0% of theAPI content. These results highlight the possibility to use SFC-MS for the QC of medicine and obviouslysupport the switch to greener analytical methods. [less ▲]

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See detailMapping the dependency of crops on pollinators in Belgium
Jacquemin, Floriane ULg; Violle, Cyrille; Rasmont, Pierre et al

in One Ecosystem (2017)

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See detailBuilding flow and transport models with electrical resistivity tomography data
Gottschalk, Ian; Hermans, Thomas ULg; Knight, Rosemary et al

Poster (2017, July 26)

Aquifer recharge and recovery (ARR) is the process of enhancing natural groundwater resources and recovering water for later use by constructing engineered conveyances. Insufficient understanding of ... [more ▼]

Aquifer recharge and recovery (ARR) is the process of enhancing natural groundwater resources and recovering water for later use by constructing engineered conveyances. Insufficient understanding of lithological heterogeneity at ARR sites often hinders attempts to predict where and how quickly infiltrating water will flow in the subsurface, which can adversely affect the quality and quantity of available water in the ARR site. In this study, we explored the use of electrical resistivity tomography (ERT) to assist in characterizing lithological heterogeneity at an ARR site, so as to incorporate it into a flow and contaminant transport model. In this case, we had non-collocated well core log data and ERT data from a full-scale ARR basin. We compared three independent methods for producing conditional lithology-resistivity probability distributions: 1) a search template to relate the nearest logged well lithologies with ERT resistivity panels, given search criteria; 2) a maximum likelihood estimation (MLE) to match bimodal normal distributions to the histogram of each ERT line; and 3) variogram-based lithology indicator simulations constrained to well data. Each approach leverages Bayes’ Rule to estimate lithology probability given electrical resistivity. The simplest approach (method 1) yields an erroneous conditional probability function where sand dominates the conditional probability at nearly all resistivities, due in part to the strong presence of sand in the wells nearest the ERT lines. The approaches using MLE and lithology simulations (methods 2 and 3) produce similar, more realistic lithofacies probability functions. The range of resistivities where clay and sand overlap differs between methods 2 and 3: ranging between 100 and 200 ohm-m for method 2, and between 30 and 50 ohm-m for the method 3. These differences affect the posterior lithology distributions in multiple point geostatistical (MPS) simulations, and in turn, predictions of flow from models which integrate these results. To test the models, we can compare measured breakthrough times of recharged water at the site to groundwater flow simulation results using the lithofacies models created by each method. The methods described here can inform the integration of non-collocated geophysical data into a variety of applications. [less ▲]

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See detailEvaluating model simulations of 20th century sea-level rise. Part 1: Global mean sea-level change
Slangen, A.; Meyssignac, B.; Agosta, Cécile ULg et al

in Journal of Climate (2017)

Sea-level change is one of the major consequences of climate change and is projected to affect coastal communities around the world. Here, we compare Global Mean Sea-Level (GMSL) change estimated by 12 ... [more ▼]

Sea-level change is one of the major consequences of climate change and is projected to affect coastal communities around the world. Here, we compare Global Mean Sea-Level (GMSL) change estimated by 12 climate models from the 5th phase of the World Climate Research Programme’s Climate Model Intercomparison Project (CMIP5) to observational estimates for the period 1900-2015. We analyse observed and simulated individual contributions to GMSL change (thermal expansion, glacier mass change, ice sheet mass change, landwater storage change) and compare the summed simulated contributions to observed GMSL change over the period 1900-2007 using tide gauge reconstructions, and over the period 1993-2015 using satellite altimetry estimates. The model-simulated contributions allow us to explain 50 ± 30% (uncertainties 1.65σ unless indicated otherwise) of the mean observed change from 1901-1920 to 1988-2007. Based on attributable biases between observations and models, we propose to add a number of corrections, which result in an improved explanation of 75 ± 38% of the observed change. For the satellite era (1993-1997 to 2011-2015) we find an improved budget closure of 102 ± 33% (105 ± 35% when including the proposed bias corrections). Simulated decadal trends over the 20th century increase, both in the thermal expansion and the combined mass contributions (glaciers, ice sheets and landwater storage). The mass components explain the majority of sea-level rise over the 20th century, but the thermal expansion has increasingly contributed to sea-level rise, starting from 1910 onwards and in 2015 accounting for 46% of the total simulated sea-level change. [less ▲]

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See detailThe effect of initial water distribution and spatial resolution on the interpretation of ERT monitoring of water infiltration
Dumont, Gaël ULg; Pilawski, Tamara ULg; Robert, Tanguy et al

Poster (2017, July 25)

A better understanding of the water balance of a landfill is crucial for its management, as the waste water content is the main factor influencing the biodegradation process of organic waste. In order to ... [more ▼]

A better understanding of the water balance of a landfill is crucial for its management, as the waste water content is the main factor influencing the biodegradation process of organic waste. In order to investigate the ability of long electrical resistivity tomography (ERT) profiles to detect zones of high infiltration in a landfill cover layer, low resolution time lapse data were acquired during a rainfall event. Working at low resolution allows to cover large field areas but with the drawback of limiting quantitative interpretation. In this contribution, we use synthetic modeling to quantify the effect of the following issues commonly encountered when dealing with field scale ERT data: (i) the effect of low resolution on electrical resistivity changes interpretation, (ii) the effect of the original heterogeneous resistivity distribution on the observed relative resistivity changes, (iii) the need for temperature and pore fluid conductivity data in order to compute water content and absolute changes of water content, and (iv) the interpretation error commonly made while neglecting the dilution effect during fresh water infiltration. Firstly, due to the lack of spatial resolution, the regularized inversion process yields a smoothed distribution of resistivity changes that fail to detect small infiltration zones and yields an overestimation of the infiltration depth and an underestimation of the infiltrated volume in large infiltration areas. Secondly, the analysis of relative changes, as commonly used in literature, is not adequate when the background water content is highly heterogeneous. In such a case, relative changes reflect both the initial water content distribution and the observed changes. Thirdly, the computation of absolute water content changes better reflects the infiltration pattern, but requires spatially distributed temperature and pore fluid conductivity input data. Lastly, the dilution effect, if not considered, leads to an underestimation of the infiltrated volume. Taking into account these elements, we extracted the maximum amount of information from our field data without over-interpreting the results. This allowed the detection of larger infiltration areas possibly responsible for a large part of the annual water infiltration and landfill gas loss. [less ▲]

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