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See detailMinimum gradient support and geostatistics regularization approaches for inverting time-lapse data
Nguyen, Frédéric ULg; Hermans, Thomas ULg; Robert, Tanguy ULg

Conference (2013, December 05)

Inversion of time-lapse resistivity data allows obtaining ‘snapshots’ of changes occurring in monitored systems for applications such as aquifer storage, site remediation or tracer tests. Based on these ... [more ▼]

Inversion of time-lapse resistivity data allows obtaining ‘snapshots’ of changes occurring in monitored systems for applications such as aquifer storage, site remediation or tracer tests. Based on these snapshots, one can infer qualitative information on the location and morphology of changes occurring in the subsurface but also quantitative estimates on the degree of changes in certain property such as temperature or total dissolved solid content. Analysis of these changes can provide direct insight into flow and transport processes and controlling parameters. However, the reliability of the analysis is dependent on survey geometry, measurement schemes, data error, or regularization. Except regularization, survey design parameters may be optimized prior to the monitoring survey. Regularization, on the other hand, may be chosen depending on available information collected during the monitoring. Common approaches consider smoothing model changes both in space and/or time. We here propose to use two alternative regularization approaches which may be better suited to invert time-lapse data. The first approach is the minimum gradient support (MGS) regularization, which focus the changes in tomograms snapshots. MGS will limit the occurrences of changes in electrical resistivity but will also restrict the variations of these changes inside the different zones. The second approach is based on geostatistics and requires first to derive variogram parameters for the model changes. In this contribution, we demonstrate the benefits and limitations of these regularization approaches to time-lapse data on numerical benchmarks and three case studies. [less ▲]

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See detailSoil infrastructure evolution and its effect on water transfer processes under contrasted tillage systems
Parvin, Nargish; Degré, Aurore ULg; Garré, Sarah ULg et al

Poster (2013, December 05)

The heterogeneity of soil structure and porosity are highly influenced by external factors like tillage systems and other land management approaches. The aim of this project is to investigate the effect ... [more ▼]

The heterogeneity of soil structure and porosity are highly influenced by external factors like tillage systems and other land management approaches. The aim of this project is to investigate the effect of soil tillage along with residue management on the changing pattern of soil structure. This investigation will help to emphasize the different water flow dynamics especially the preferential flow processes through the soil that are influenced by the changes in structural distribution in the soil profile. Mostly the preferential flow of water is addressed by the apparent velocity through the soil but this study will focus on soil structure along with soil moisture dynamics at aggregate scale or more specifically at pedon scale. The experimentation has been started from June 2013 in the research field known as Solcouvert (objects: strip-till versus winter ploughing) and Solresidus (objects: no-till with organic matter restitution versus no-till without organic matter restitution). Soil profile description has been carried out in the four objects of land management. Soil sampling has been done in different depths of soil according to the soil profile description. Soil samples will be used for the measurement of water retention capacity, hydraulic conductivity and x-ray microtomography. In addition there will be soil moisture sensors (Decagon 10HS, 5TM and ML3 Thetaprobe) in the field under four different trials. The soils from the different trials and also from different depths (0-15, 25-30 and 50-60 cm) were calibrated with the sensors. The calibration results were significantly (p<0.05) different between Solcouvert and Solresidus and there was also significant (p<0.05) difference among depths of same field especially between 0-15 and 50-60 cm. Soil bulk density and textural differences are the main reason for the differences of moisture content of different sites and depths measured by the moisture probes. In addition, the results were inconsistent along with overestimation of moisture content if the manufacturer based equation is used for the calibration. We conclude that, site and depth wise calibration of low cost sensors is very essential for the interpretation of results. In our study, to capture the total soil moisture networks, the moisture sensors will be in the field during the crop season. All the experiments will be repeated twice a year. For the specific spatio-temporal comparison, the monitoring results from electrical resistance tomography will be available from the collaborated project of the same faculty. [less ▲]

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See detailBrûlure et infection
ROUSSEAU, Anne-Françoise ULg

Scientific conference (2013, December 05)

Detailed reference viewed: 17 (1 ULg)
See detailSources, transport et transformation du carbone, de l’azote et du phosphore dans le fleuve Niger : résultats après 2 années d’observations à Niamey
Alhou, Bassirou; Darchambeau, François ULg; Bouillon, Steven et al

Conference (2013, December 05)

Le fleuve Niger est le troisième plus important fleuve d'Afrique et draine une superficie d'environ 2 120 000 km². Il englobe six régions hydrographiques caractéristiques des écosystèmes de l’Afrique ... [more ▼]

Le fleuve Niger est le troisième plus important fleuve d'Afrique et draine une superficie d'environ 2 120 000 km². Il englobe six régions hydrographiques caractéristiques des écosystèmes de l’Afrique occidentale. Nonobstant l’importance de ce fleuve à l’échelle régionale et continentale, peu de données ont été récemment collectées sur la biogéochimie du fleuve et en particulier sur son rôle dans le transport et la transformation de la matière, dont le carbone, l’azote et le phosphore. La présente communication traite des résultats d’un suivi sur deux années, d’avril 2011 à mars 2013 dans le Niger moyen, en amont de la ville de Niamey (Niger) [2.01° E, 13.57° N], selon une fréquence d’observation bihebdomadaire. Les variables mesurées sont la température, la conductivité, l’oxygène dissous, le pH, la matière en suspension (MES), l’alcalinité totale (TA), les différentes formes du carbone (C), de l’azote (N) et du phosphore (P) inorganiques dissous, le C, l’N et le P organiques particulaires, ainsi que la composition isotopique de ces éléments. Une attention particulière est portée aux concentrations des gaz à effet de serre (GES) que sont le dioxyde de carbone (CO2), le méthane (CH4) et l’hémioxide d’azote (N2O). Les débits journaliers du fleuve proviennent de la station de mesure hydrologique de l’autorité du Bassin du Niger (ABN) à Niamey. Les flux annuels ont été calculés par la méthode de Beale pour les régimes stratifiés (Gumleaf v0.1) à partir des débits quotidiens et des concentrations observées. La situation hydrologique a été fort contrastée entre les 2 années d’étude puisque le débit moyen sur la première année était de seulement 674 m3 s-1, soit un des débits les plus faibles enregistrés sur le fleuve à Niamey depuis 1940, et de 1096 m3 s-1, soit une valeur médiane, lors de la deuxième année. Nos résultats montrent que la MES, le carbone organique particulaire, le carbone organique dissous et le carbone inorganique dissous sont principalement transportés lors de la crue locale, engendrée par les précipitations de la mousson en juillet-août. La seconde crue, ou crue guinéenne, qui a lieu de novembre à janvier, est caractérisée par une chute des températures et des eaux claires. Les flux annuels des différentes espèces transportées étaient en relation directe avec les différences de régime hydrologique. [less ▲]

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See detailElectroencephalogram approximate entropy influenced by both age and sleep
Lee, Gerick; Fattinger, Sara; Mouthon, Anne-Laure et al

in Frontiers in Neuroinformatics (2013), 7(33),

The use of information-based measures to assess changes in conscious state is an increasingly popular topic. Though recent results have seemed to justify the merits of such methods, little has been done ... [more ▼]

The use of information-based measures to assess changes in conscious state is an increasingly popular topic. Though recent results have seemed to justify the merits of such methods, little has been done to investigate the applicability of such measures to children. For our work, we used the approximate entropy (ApEn), a measure previously shown to correlate with changes in conscious state when applied to the electroencephalogram (EEG), and sought to confirm whether previously reported trends in adult ApEn values across wake and sleep were present in children. Besides validating the prior findings that ApEn decreases from wake to sleep (including wake, rapid eye movement (REM) sleep, and non-REM sleep) in adults, we found that previously reported ApEn decreases across vigilance states in adults were also present in children (ApEn trends for both age groups: wake > REM sleep > non-REM sleep). When comparing ApEn values between age groups, adults had significantly larger ApEn values than children during wakefulness. After the application of an 8 Hz high-pass filter to the EEG signal, ApEn values were recalculated. The number of electrodes with significant vigilance state effects dropped from all 109 electrodes with the original 1 Hz filter to 1 electrode with the 8 Hz filter. The number of electrodes with significant age effects dropped from 10 to 4. Our results support the notion that ApEn can reliably distinguish between vigilance states, with low-frequency sleep-related oscillations implicated as the driver of changes between vigilance states. We suggest that the observed differences between adult and child ApEn values during wake may reflect differences in connectivity between age groups, a factor which may be important in the use of EEG to measure consciousness. [less ▲]

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See detailTandem MS of -new- antibiotics from Bacillus guided by MALDI Mass Spectrometry Imaging
Debois, Delphine ULg; Jourdan, Emmanuel; Cawoy, Hélène ULg et al

Conference (2013, December 05)

Generally, an antibiotic is thought to have a role in antagonism simply because the producing strain is known to exhibit a potential for pathogen growth inhibition. Some genetic approaches such as PCR ... [more ▼]

Generally, an antibiotic is thought to have a role in antagonism simply because the producing strain is known to exhibit a potential for pathogen growth inhibition. Some genetic approaches such as PCR using specific primers or genome mining using known sequence data of close relatives are also used. Nevertheless, none of these methods allows stating for a link between a specific compound and the observed antagonism. Yet MALDI Mass Spectrometry Imaging (MSI) is a powerful tool to decipher the chemical messengers exchanged by two protagonists [1,2,3;]. Tandem mass spectrometry (MS/MS) may be also used, either on extracts [2,3] or directly on the microbial colonies [4]. The presentation will thus be focused on two examples of application of MALDI MSI combined to in situ tandem mass spectrometry. The first presented case will be the antagonism between soilborne strain Paenibacillus polymyxa Pp56 and the fungal phytopathogen Fusarium oxysporum. Using MALDI MSI, we were able to precisely localize each detected antibiotic, allowing discriminating which LI-F lipopeptides (fusaricidin) were really active against the pathogen progression. Besides, the use of in situ MS/MS allowed us to sequence the peptide moiety of several LI-F lipopeptides, showing that some of them are actually a mixture of several forms. The second example concerns the metabolites that are released by Bacillus amyloliquefaciens S499 cells following their inoculation on 7 days old tomato roots. We developed specific bioassays for time-course monitoring by MALDI MSI. First analyses revealed an efficient secretion of surfactin by Bacillus cells after 3 days when colonization as biofilm-structured populations is well established. Even if the composition of antibiotic mixture does not greatly evolve over time, after long incubation periods (32 or 35 days post inoculation), new series of compounds are detected in the tomato root -surrounding medium. Structural analysis based on exact mass measurements and MS/MS experiments, performed directly on the semi-solid agar medium, allowed us to identify these compounds as new variants of surfactins. [1] Barger, S., et al., Anton Leeuw Int J G, 2012, 102, 435-445. [2] Hoefler, B. C., et al,. Natl Acad Sci USA, 2012, 109, 13082-13087. [3] Moree, W. J., et al., Natl Acad Sci USA, 2012, 109, 13811-13816. [4] Debois, D., et al., J Am Soc Mass Spectrom. 2013, 24, 1202-1213 [less ▲]

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See detailOn the Verification of Programs on Relaxed Memory Models
Linden, Alexander ULg

Doctoral thesis (2013)

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and ... [more ▼]

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and where model-checking consists in verifying a given property when exploring the state space of a program. However, modern multi-core processor architectures implement relaxed memory models, such as "Total Store Order" (TSO), "Partial Store Order" (PSO), or an extension with locks such as "x86-TSO", which allow stores to be delayed in various ways and thus introduce many more possible executions, and hence errors, than those present in SC. Of course, one can force a program executed in the context of a relaxed memory system to behave exactly as in SC by adding synchronization operations after every memory access. But this totally defeats the performance advantage that is precisely the motivation for implementing relaxed memory models instead of SC. Thus, when moving a program to an architecture implementing a relaxed memory model (which includes most current multi-core processors), it is essential to have tools to help the programmer check if correctness (e.g. a safety property) is preserved and, if not, to minimally introduce the necessary synchronization operations. The proposed verification approach uses an operational store-buffer-based semantics of the chosen relaxed memory models and proceeds by using finite automata for symbolically representing the possible contents of the buffers. Store, load, commit and other synchronization operations then correspond to operations on these finite automata. The advantage of this approach is that it operates on (potentially infinite) sets of buffer contents, rather than on individual buffer configurations, and that it is compatible with partial-order reduction techniques. This provides a way to tame the explosion of the number of possible buffer configurations, while preserving the full generality of the analysis. It is thus possible to even check designs that may contain cycles. This verification approach then serves as a basis to a memory fence insertion algorithm that finds how to preserve the correctness of a program when it is moved from SC to TSO or PSO. Its starting point is a program that is correct for the sequential consistency memory model (with respect to a given safety property), but that might be incorrect under TSO or PSO. This program is then analyzed for the chosen relaxed memory model and when errors are found (a violated safety property), memory fences are inserted in order to avoid these errors. The approach proceeds iteratively and heuristically, inserting memory fences until correctness is obtained, which is guaranteed to happen. [less ▲]

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See detailCapture of 3D sound with a spherical microphone array
Feron, Hermine; Embrechts, Jean-Jacques ULg

Conference (2013, December 05)

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See detailPartager nos histoires et nos savoirs, gage de qualité dans les lieux d'accueil ?
Pirard, Florence ULg

Conference given outside the academic context (2013)

Cette conférence porte sur la notion d'accompagnement de professionnel-le-s de l'enfance à partir d'une expérience de démarche narrative collective expérimentée dans les villes de Genève et de Lausanne où ... [more ▼]

Cette conférence porte sur la notion d'accompagnement de professionnel-le-s de l'enfance à partir d'une expérience de démarche narrative collective expérimentée dans les villes de Genève et de Lausanne où les questions de diversités sont actuellement au cœur des préoccupations professionnelles. Elle fait suite à une autre communication présentée un an plus tôt à Genève ("Diversités: une petite enfance engagée!", 2-3 novembre 2012) [less ▲]

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See detailFriction Stir Processing of Magnesium Matrix Composites Reinforced with Carbon Fibres or Carbon Nanotubes - A Comparative Study
Mertens, Anne ULg; Simar, Aude; Garray, Didier et al

Conference (2013, December 05)

The poor wettability of carbon substrates by liquid Mg and, in the case of carbon nanotubes (CNTs), their strong tendency to agglomerate, are major obstacles to the large-scale production of C-Mg ... [more ▼]

The poor wettability of carbon substrates by liquid Mg and, in the case of carbon nanotubes (CNTs), their strong tendency to agglomerate, are major obstacles to the large-scale production of C-Mg composites by classical ‘liquid-state’ processing routes such as squeeze casting. As an innovative ‘solid state’ process, Friction Stir Processing (FSP) hence appeared as a very promising alternative for the production of C-Mg composites, although the method for inserting the reinforcing phase - in grooves or holes machined in the matrix material - remained time-consuming and labour-intensive. More recently, the present authors proposed a new and easier technique for the insertion of C fibres in FSPed Mg-matrix composites i.e. FSP of a C fabric stacked between two metal sheets. In the current work, the feasibility of extending this latter method to the production of CNTs-Mg composites has been assessed. “Bucky papers” – thin disks made from agglomerated CNTs, thus ensuring for their safe handling – were stacked between two sheets of Mg alloy AZ31B, and the resulting sandwich was FSPed. The effect of FSP experimental parameters such as the rotational and advancing speeds or the number of passes on the microstructural changes occuring upon processing has been studied and compared with the case of C fibres-Mg composites. Moreover, a particular attention has been given to the distribution of the reinforcements in the Mg matrix and to the characterization of the resulting mechanical properties. [less ▲]

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See detailLe volontariat, quelle(s) professionalisation(s) ?
Mouchamps, Hugues ULg

Conference given outside the academic context (2013)

Detailed reference viewed: 17 (7 ULg)
See detailLa précision dans les mesures RTK
Wautelet, Gilles ULg

Conference given outside the academic context (2013)

Detailed reference viewed: 15 (0 ULg)
Peer Reviewed
See detailLa recherche et la formation doctorales au XXIe siècle
Winand, Jean ULg

Conference (2013, December 04)

Detailed reference viewed: 19 (5 ULg)
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See detailEvaluation de la Teneur Sanguine en Sélénium dans le Sang des Vaches en Wallonie (Belgique)
Mehdi, Youcef ULg; Cabaraux, Jean-François ULg; Hornick, Jean-Luc ULg et al

in 20ième Rencontre Recherches Ruminants (2013, December 04)

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See detailDétermination de la teneur en équol dans les laits commercialisés en Wallonie (Belgique)
Daems, Frédéric ULg; Jasselette, Christophe; Franckson, Delphine et al

Poster (2013, December 04)

Detailed reference viewed: 25 (6 ULg)
See detail3D ERT monitoring of the reactivation of waste biodegradation with fresh leachate injection
Dumont, Gaël ULg; Robert, Tanguy ULg; Pilawski, Tamara et al

Conference (2013, December 04)

The aim of this study is to monitor (bio) physical processes occurring in a landfill. The experiment consists in injecting leachate towards a drain in unsaturated and not yet digested waste to reactivate ... [more ▼]

The aim of this study is to monitor (bio) physical processes occurring in a landfill. The experiment consists in injecting leachate towards a drain in unsaturated and not yet digested waste to reactivate (or activate) waste biodegradation. The target is the first 15 meters of the studied landfill subsurface. The visualization of the wet front arrival (short term effect) is crucial because we want to ensure that waste is entirely humidified to allow the reactivation of waste digestion. The second process is a long term effect consisting in the increase of the internal temperature of the landfill which is synonymous of the reactivation of biodegradation processes. We use 3D time-lapse ERT on a monthly basis to capture the decrease of electrical resistivity related to the increasing temperature. We also collect ground truth data, including distributed temperatures in a borehole to validate results. For short term effects, we monitored the wet front arrival with three 2D ERT profiles composing the 3D image, during an entire day. Preliminary results, corroborated by ground truth data, show that leachate flow in anisotropic (more rapid horizontally than vertically). So far, waste was completely humidified and slight changes of temperature occurred. [less ▲]

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See detailPotentiel d'utilisation de la spectrometrie moyen infrarouge pour prédire le rendement fromager du lait et étudier sa variabilité génétique
Colinet, Frédéric ULg; Troch, Thibault ULg; Abbas, O. et al

Conference (2013, December 04)

Providing a quick, reliable and cheap indication of the expected cheese yield for a milk sample by avoiding (empirical or theoretical) formulas based on previously determined milk constituents would be an ... [more ▼]

Providing a quick, reliable and cheap indication of the expected cheese yield for a milk sample by avoiding (empirical or theoretical) formulas based on previously determined milk constituents would be an economically valuable tool useful for farmers and the dairy industry. In order to study the genetic variability of cheese yield on a large scale, mid-infrared (MIR) chemometric methods were used to predict fresh or dry Individual Laboratory Cheese Yield (RdFF and RdFS, respectively). RdFF and RdFS were determined on a total of 258 milks samples also analyzed by a MIR spectrometer. Equations to predict RdFF and RdFS from milk MIR spectra were developed using partial least square regression (PLS) after first derivative pre-traitment applied to the spectra. The cross-validation coefficients of determination (R²cv) of the two equations were equal to 0.81 for the prediction of RdFF and 0.82 for the prediction RdFS. The ratios of performance to deviation (RPD) of the two equations were both equal to 2.3. Therefore, these results suggest a practical utility of these two equations, i.e. for genetic research. Both equations were applied on the spectral database generated during the Walloon routine milk recording. The variances components were estimated using univariate random regressions animal test-day model. The dataset included 51 537 predicted records from 7 870 Holstein first-parity cows. Estimated daily heritabilities ranged from 0.31 (at 5th day in milk (DIM)) to 0.59 (at 279th DIM) for RdFF and from 0.31 (at 5th DIM) to 0.57 (at 299th DIM) for RdFS. Those moderate to high daily heritabilities indicated potential of selection for both traits. [less ▲]

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