Last 7 days
Bookmark and Share    
Full Text
See detailStreamable Laguerre-Voronoi Tessellation Model for Tomographic Images
Leblanc, Christophe ULg; Nguyen, Van Dung ULg; Wan, Fangyi et al

Conference (2014, July 25)

Introduction. Nowadays, the interest in foam materials is growing in several engineering fields [1]. Foams can exhibit a nonlinear mechanical behavior [2], which is highly depen- dent on their ... [more ▼]

Introduction. Nowadays, the interest in foam materials is growing in several engineering fields [1]. Foams can exhibit a nonlinear mechanical behavior [2], which is highly depen- dent on their microstructure [3]. Thus designing foams with specific mechanical properties can be very challenging. The present contribution is part of the ARC-Bridging project [4], whose objective is to predict the mechanical behavior of complex microstructured mate- rials via numerical simulations. A possible classification of foam models into two groups is: random models and deterministic models [5]. The random models frequently require statistical estimations of their parameters [6], whereas the deterministic models generally require numerically expensive image analyse. Indeed, classical analysis steps involve a distance tranform, a watershed and, optionally, a h-minima transform [5, p. 22], which can be computationally demanding [7, 8, 9]. Contribution. In the present Laguerre–Voronoi tessellation model, the image analysis part neither involes the watershed transform, nor the h-minima transform. Instead, fol- lowing the original idea of A.M. Lopez-Reina et E. Béchet [10], these two transforms are respectively replaced by a Hessian-based removal of spurious extrema and a clustering of the remaining maxima. This substitution allows the processing of large 3D-images by slices, i.e. “streaming”. The only limitation is enforced by the distance transform: the “feature” voxel of a given voxel should belong to the same slice. For foam images, this condition is fulfilled as long as the slice’s thickness is larger than the maximal foam cell’s size. Conclusion and perspectives. The aim of this contribution is to provide an efficient tessellation model for tomographic images of foams. From input tomographic images, this model provides a geometry model which will be used as an input for finite element simulations under the ARC-Briding project [4]. Simulation results will be compared with experimental measures. [less ▲]

Detailed reference viewed: 21 (13 ULg)
Full Text
See detailQuelle histoire pour les forêts d'Afrique centrale ?
Morin-Rivat, Julie ULg

Scientific conference (2014, July 24)

Conférence grand public sur les indicateurs de perturbations climatiques et anthropiques dans les forêts d'Afrique centrale.

Detailed reference viewed: 11 (4 ULg)
See detailBrokers and intermediaries in environmental governance, Southern Sri Lanka
Rosillon, Caroline ULg

Conference (2014, July 23)

Since the end of the civil war in 2009, rural Southern Sri Lanka is facing growing tensions between fast economic development and the conservation of biodiversity, which contributes to the notoriety of ... [more ▼]

Since the end of the civil war in 2009, rural Southern Sri Lanka is facing growing tensions between fast economic development and the conservation of biodiversity, which contributes to the notoriety of the island. In order to preserve the green areas of the country, both the government and international institutions have made great efforts to implement projects combining biodiversity protection and poverty reduction as their objectives. Within that context, this paper focuses on a specific category of stakeholders, emerging from the implementation of the aforementioned projects: a wide range of intermediaries between local communities and the State, or international institutions. Based on an ethnographic study of two protected areas in Southern Sri Lanka, the paper will examine the role of those intermediaries in the implementation of environmental governance models and ideologies in local arenas. I will also analyze the complex relationships between those brokers and other categories of individuals or groups within the community: people living in protected areas, traditional figures of power, social and political elites, etc. Using fieldwork illustrations, I will stress how the emergence of brokers and intermediaries in the context of nature conservation may lead to the reorganization of social and political relationships at the local scale. [less ▲]

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailRécits de vie d’adolescents. Humeur dépressive et figures parentales
Poudat, Céline; Boulard, Aurore ULg

in 4ème Congrès Mondial de Linguistique Française (2014, July 22)

Detailed reference viewed: 7 (1 ULg)
Full Text
Peer Reviewed
See detailDetection of differential item functioning using the lasso approach
Magis, David ULg; Tuerlinckx, Francis; De Boeck, Paul

Conference (2014, July 22)

The purpose of this talk is to present a novel approach to detect differential item functioning (DIF) among dichotomously scored items. Unlike standard DIF methods that perform an item-by-item analysis ... [more ▼]

The purpose of this talk is to present a novel approach to detect differential item functioning (DIF) among dichotomously scored items. Unlike standard DIF methods that perform an item-by-item analysis, we consider a logistic regression model including item-group interaction (i.e. DIF) effects of all items simultaneously. The method is based on penalized maximum likelihood estimation of a model with a lasso penalty on all possible DIF parameters. Optimal penalty parameter selection is investigated through several known information criteria (such as AIC and BIC) as well as a newly developed weighted alternative. A simulation study was conducted to compare the global performance of the suggested “lasso DIF” method to the logistic regression and Mantel-Haenszel methods, and to evaluate the different optimal penalty parameter selection methods. It is concluded that for small samples the lasso DIF approach globally outperforms the logistic regression method, and also the Mantel-Haenszel method, especially in the presence of item impact, while it yields similar results with larger samples. [less ▲]

Detailed reference viewed: 46 (3 ULg)
Full Text
Peer Reviewed
See detailLiver proteomic response to hypertriglyceridemia in human-apolipoprotein C-III transgenic mice at cellular and mitochondrial compartment levels
Ehx, Grégory ULg; Gerin, Stéphanie ULg; Mathy, Grégory et al

in Lipids in Health and Disease (2014), 13

Background: Hypertriglyceridemia (HTG) is defined as a triglyceride (TG) plasma level exceeding 150 mg/dl and is tightly associated with atherosclerosis, metabolic syndrome, obesity, diabetes and acute ... [more ▼]

Background: Hypertriglyceridemia (HTG) is defined as a triglyceride (TG) plasma level exceeding 150 mg/dl and is tightly associated with atherosclerosis, metabolic syndrome, obesity, diabetes and acute pancreatitis. The present study was undertaken to investigate the impact of hypertriglyceridemia on the mitochondrial, sub-mitochondrial and cellular proteomes in the hepatocytes of a hypertriglyceridemic transgenic mouse model overexpressing the human apolipoproteinC-III. Methods: Quantitative comparative proteomics (2D-DIGE) was carried out in both “low-expressor” (LE) and “high-expressor” (HE) mice, respectively exhibiting moderate and severe HTG, to characterize the effect of the TG plasma level on the proteomic response. Results: The mitoproteome analysis revealed the occurrence of a large-scale adaptation in transgenic mice consisting of a general down-regulation of matricial proteins and up-regulation of inner membrane proteins. Remarkably, the magnitude of these proteomic changes appears to strongly depend on the TG plasma level. Altogether, our different analyses indicate that, in HE mice, the capacity of several metabolic pathways is altered to promote the availability of acetyl-CoA, glycerol-3-phosphate, ATP and NADPH for de novo TG biosynthesis. The up-regulation of several cytosolic ROS detoxifying enzymes also tend to confirm that the cytoplasm of HTG mice is subjected to oxidative stress as previously stated. The up-regulation of cytosolic ferritin indicates that iron over-accumulation could take place in the cytosol of HE mice hepatocytes and contribute to (i) enhance oxidative stress and (ii) promote cellular proliferation. Conclusions: The present analyses demonstrate that important TG dose-responsive metabolic adaptations are set up in human apolipoproteinC-III-overexpressing mice. Our results indicate that these adaptations could support the higher TG production rates which have been previously reported in this HTG model, and also suggest that cytosolic oxidative stress may result from FFA over-accumulation, iron overload and enhanced activity of some ROS-producing catabolic enzymes. [less ▲]

Detailed reference viewed: 19 (5 ULg)
Full Text
See detailSeed dispersal by western lowland gorillas: what about gut passage effect?
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2014, July 21)

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of ... [more ▼]

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of an effective seed disperser. WLG preferentially disperses species of various seed-size into open canopy habitats suitable for seedling growth. However, few studies have addressed the effects of the passage through the digestive tract on germination. Thus, the effectiveness of WLG in ecological processes governing forest dynamics and regeneration is still poorly known. Seed dispersal by WLG was studied in Central Gabon and Southeast Cameroon. Dispersed seed were identified from fresh fecal samples. Comparative germination trials based on 5 treatments (seeds from fresh fruits, seeds from fresh fruits surrounded by pulp, seeds from fresh fruits with fecal matrix, seeds from feces and seeds from feces with fecal matrix) were realized for 13 species. We recorded germination success for all species and germination delay for 6 species. Our results suggest a neutral gut passage effect for 54% and positive effect for 40% of tested species. Germination success enhancement was linked to another factor than pulp suppression. For two species, pulp suppression enhanced germination success, but not gut passage. The presence of pulp or fecal matrix surrounding the seed seemed to longer germination delay, while gut passage would not fasten germination. Globally, we conclude that WLG dispersed seeds are not damaged by gut passage. Consequently, WLG is thought to provide effective ecological services that could be essential to the maintenance and the recovery of forest ecosystems. [less ▲]

Detailed reference viewed: 9 (1 ULg)
Full Text
See detailShort Prime Quadratizations of Cubic Negative Monomials
Crama, Yves ULg; Rodriguez Heck, Elisabeth ULg

E-print/Working paper (2014)

Pseudo-Boolean functions naturally model problems in a number of different areas such as computer science, statistics, economics, operations research or computer vision, among others. Pseudo-Boolean ... [more ▼]

Pseudo-Boolean functions naturally model problems in a number of different areas such as computer science, statistics, economics, operations research or computer vision, among others. Pseudo-Boolean optimization (PBO) is NP-hard, even for quadratic polynomial objective functions. However, much progress has been done in finding exact and heuristic algorithms for the quadratic case. Quadratizations are techniques aimed at reducing a general PBO problem to a quadratic polynomial one. Quadratizing single monomials is particularly interesting because it allows quadratizing any pseudo-Boolean function by termwise quadratization. A characterization of short quadratizations for negative monomials has been provided. In this report we present a proof of this characterization for the case of cubic monomials, which requires a different analysis than the case of higher degree. [less ▲]

Detailed reference viewed: 17 (6 ULg)
Full Text
Peer Reviewed
See detailResorcinol-Formaldehyde Carbon Xerogels as Lithium-Ion Battery Anodes: Synthesis, Grinding, Coating on current collector and Electrochemical characterization
Piedboeuf, Marie-Laure ULg; Léonard, Alexandre ULg; Pirard, Jean-Paul ULg et al

Poster (2014, July 17)

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However ... [more ▼]

Rechargeable lithium-ion batteries show great advantages over traditional batteries and are extensively used for consumer electronic devices due to their high energy density and long cycle life. However, the improvement of performance of current lithium-ion batteries requires the optimization of the materials used (electrolyte and electrodes). Therefore, tremendous efforts have been dedicated to exploring new materials with high capacity, excellent cycling performance, low cost and high safety features [1-4]. As an example, carbon xerogels are promising candidates in the development of new high performance C-based anode materials for Li-ion batteries, since such carbonaceous materials show very small changes of volume during the charge/discharge process, providing an improved cycle life. Nevertheless, hard carbons also exhibit quite high irreversible capacity losses due to their intrinsic high microporosity and, compared to graphite, a poor rate performance related to slow diffusion of Li in the internal structure [5-6]. To reduce these disadvantages, the structural and textural characteristics need to be carefully controlled. Also, due to the different morphology of these materials compared to graphite, the deposition of carbon xerogels on current collectors needs to be studied in detail. In this work, porous carbon xerogels were synthetized from Resorcinol-Formaldehyde mixtures by adjusting the pH of the solution in order to obtain different mesopore sizes. Monoliths of carbon xerogels were obtained after drying of the polymer gel and pyrolysis [7]. Mercury intrusion porosimetry and nitrogen adsorption techniques (BET) was used to characterize the pore texture of the carbon xerogels. These monoliths were ground to particles around 10 µm for all the samples. The resulting powders were then mixed with a binder and a solvent to form slurries and then cast on copper foil using a bar coater. After evaporation of the solvent, the resulting coatings were analyzed using scanning electron microscopy (SEM) for the morphology and their thickness was monitored by profilometry. The resulting electrodes were subjected to electrochemical characterization. Since the particle sizes and the method of coating was the same for all the samples, it was possible to evaluate selectively the influence of the textural and structural parameters of the different carbon materials on their performances. Electrochemical characterizations were performed using charge-discharge galvanostatic curves and cyclic voltammetry in Li/C half cells between 0.005 and 1.5 V vs. Li+/Li. References 1) Goodenough J.B., Kim Y. J. Power Sources 2011; 196(16): 6688-6694. 2) Bruce P.G. Solid State Ionics 2008; 179: 752-760. 3) Armand M., Tarascon J.-M., Nature 2008; 451: 652-657. 4) Scrosati B., Garche J., J. Power Sources 2010 ; 195 : 2419-2430. 5) Yuan X., Chao Y.-J., Ma Z.-F., Deng X., Electrochemistry Communications 2007 ; 9 : 2591-2595. 6) Zanto E.J., Ritter J.A., Popov B.N., Proceedings - Electrochemical Society 1999; 98-16: 71-8. 7) Job N., Théry A., Pirard R., Marien J., Kocon L., Rouzaud J., Béguin F., Pirard J. Carbon 2005; 43: 2481-2494. [less ▲]

Detailed reference viewed: 21 (1 ULg)
Peer Reviewed
See detailFrom variability to stability: The acquisition of phonemes in French speaking children aged 30 to 53 months.
MacLeod, Andrea; Maillart, Christelle ULg

Poster (2014, July 16)

When children first begin to produce the phonemes of their language, their productions are characterized by a high degree of variability (e.g., Ferguson & Farwell, 1975). As children’s phonological ... [more ▼]

When children first begin to produce the phonemes of their language, their productions are characterized by a high degree of variability (e.g., Ferguson & Farwell, 1975). As children’s phonological representations become more defined, their productions become more stable. In fact, the observation of variability beyond the early-word stage has been used as a diagnostic criteria for sub-types of phonological disorders (Dodd et al. 2005). Despite the clinical significance of phonological variability, there exists no normative data that can be used to objectively describe this variability in French. The goal of the present study was to describe variability and stability among French-speaking children between the ages of 30 and 53 months. A total of 153 children participated in the present study and were equally distributed in four groups (aged 30-35, 36-41, 42-47, and 48-53 months). We created a picture identification task with 65 target words, which contained the consonants of French in word initial, medial and final position. The children were asked to produce this series of words three times. Two measures of variability were used. (1) A consonant level analysis that investigated the stability of consonants regardless of word or syllable position. (2) A word level analysis that investigated the consistency of productions across the three series (Holm et al., 2007). The preliminary analysis focused on the consonant level analysis and revealed that the youngest group of children aged 30 to 35 months were significantly more variable than the oldest group aged 48-53 months. This shift from variability to stability will be discussed in terms of the development phonological representations. In addition, the clinical significance of variability will be discussed in light of these findings. [less ▲]

Detailed reference viewed: 15 (1 ULg)
Peer Reviewed
See detailDo tree species influence community structure and richness of Ammonia Oxidizing Bacteria at three temperate forest sites?
Malchair, Sandrine ULg; Carnol, Monique ULg

Poster (2014, July 15)

Introduction: The relationship between biodiversity and ecosystem function remains a controversial subject with numerous open questions. In Europe, the conversion of coniferous monocultures into ... [more ▼]

Introduction: The relationship between biodiversity and ecosystem function remains a controversial subject with numerous open questions. In Europe, the conversion of coniferous monocultures into broadleaved or mixed stand is considered to face ecological and economical risks posed by coniferous monocultures. Belowground effects of such a change in the dominant tree species is however largely unknown, although bacteria regulate many soil processes and some groups, like ammonia oxidizing bacteria (AOB) are highly sensitive to environmental stress. Objectives: The aims of this study were to investigate (i) AOB community structure and richness under several tree species, (ii) microbial/environmental factors related to AOB diversity, (iii) the relationship between AOB diversity and the nitrification process. Materials and methods: Forest floor (Of, Oh) was sampled under European beech, sessile oak, Norway spruce and Douglas fir at three sites. AOB community structure and richness was assessed by PCR-DGGE and sequencing. Samples were analysed for net N mineralization, potential nitrification, basal respiration, microbial biomass, microbial or metabolic quotient, pH, total nitrogen, extractable ammonium, organic matter content and exchangeable cations. Results: AOB community structure and tree species effects on AOB diversity were site-specific. Factors regulating ammonium availability, i.e. net N mineralization or microbial biomass, were related to AOB community structure. AOB richness was not related to nitrification. Conclusions: Our research revealed that, at larger spatial scales, site specific characteristics may be more important that tree species in determining AOB richness and community structure. Within sites, tree species influence AOB diversity. The absence of a relation between AOB richness and nitrification points to a possibly role of AOB abundance, phenotypic plasticity or the implication of ammonia oxidizing archaea in this process. [less ▲]

Detailed reference viewed: 20 (1 ULg)
Peer Reviewed
See detailAre expectancies and peers involved in the relation between depressive mood, anxiety and cannabis use in adolescence?
Schmits, Emilie ULg; Quertemont, Etienne ULg; Boulard, Aurore ULg

Poster (2014, July 15)

Background: Cannabis is the most commonly used illicit drug among teenagers and depression is one of the most common psychopathologies in adolescence. The specific symptom of depressive mood is present in ... [more ▼]

Background: Cannabis is the most commonly used illicit drug among teenagers and depression is one of the most common psychopathologies in adolescence. The specific symptom of depressive mood is present in 30% to 40% of adolescents in regular school settings. Links between cannabis use and depression have been highlighted, especially in adolescence. But questions remain about the strength of the association between lifetime cannabis use, depressive mood and anxiety, and about the mechanism underpinning the link. Aim: The aim of this study was to clarify the relationship between depressive mood and lifetime cannabis use in adolescents, particularly through the mediating role of anxiety and cannabis use effect expectancies, and the moderating role of peer cannabis use. Methods: A questionnaire was administered to 1,246 Belgian teenagers aged 16–17 years. ANOVA, chi-square, logistic regressions and mediation/moderation analyses were carried out to model lifetime cannabis use. Results: Depressive mood was positively correlated with lifetime cannabis use. Social anxiety, trait-anxiety and cognitive impairment effect expectancies mediated the effect of depression on lifetime cannabis use. The direct effect of depression on lifetime cannabis use increased when mediators were introduced into the relation, revealing their suppressive effects. The number of peer cannabis users moderated this model. Conclusion: Findings are discussed in terms of potential risk factors (depressive mood) or protective factors (anxiety and expectancies) for lifetime cannabis use, including the self-medication hypothesis. [less ▲]

Detailed reference viewed: 13 (3 ULg)
Full Text
See detailNumerical modelling of mirror nozzle flow
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Mercatoris, Benoît ULg et al

Conference (2014, July 15)

Detailed reference viewed: 49 (27 ULg)
Full Text
Peer Reviewed
See detailAssessing spatiotemporal variability and trends (2000-2013) of modeled and measured Greenland Ice Sheet albedo
Alexander, P.; Tedesco, M.; Fettweis, Xavier ULg et al

in Cryosphere Discussions (The) (2014), 8

Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the crucial role of surface albedo in modulating the amount of absorbed solar radiation and ... [more ▼]

Accurate measurements and simulations of Greenland Ice Sheet (GrIS) surface albedo are essential, given the crucial role of surface albedo in modulating the amount of absorbed solar radiation and meltwater production. In this study, we assess the spatio-temporal variability of GrIS albedo (during June, July, and August) for the period 2000–2013. We use two remote sensing products derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS), as well as outputs from the Modèle Atmosphérique Régionale (MAR) regional climate model (RCM) and data from in situ automatic weather stations. Our results point to an overall consistency in spatiotemporal variability between remote sensing and RCM albedo, but reveal a difference in mean albedo of up to ~0.08 between the two remote sensing products north of 70° N. At low elevations, albedo values simulated by the RCM are positively biased with respect to remote sensing products and in situ measurements by up to ~0.1 and exhibit low variability compared with observations. We infer that these differences are the result of a positive bias in simulated bare-ice albedo. MODIS albedo, RCM outputs and in situ observations consistently point to a~decrease in albedo of −0.03 to −0.06 per decade over the period 2003–2013 for the GrIS ablation zone (where there is a net loss of mass at the GrIS surface). Nevertheless, satellite products show a~decline in albedo of −0.03 to −0.04 per decade for regions within the accumulation zone (where there is a net gain of mass at the surface) that is not confirmed by either the model or in situ observations. [less ▲]

Detailed reference viewed: 8 (0 ULg)
Peer Reviewed
See detailStudies of early interactions among infants aged 4 to 6 months furtherly diagnosed with autistic spectrum disorder and their developmental trajectories and outcome at 4 years old.
Boulard, Aurore ULg; Wolff, Marion; Morange-Majoux, Françoise et al

Poster (2014, July 14)

The purpose of this study is to observe and analyze the social skills of infants aged 4 to 6 months later diagnosed with autism. Through the family films collected, we compared 28 children later diagnosed ... [more ▼]

The purpose of this study is to observe and analyze the social skills of infants aged 4 to 6 months later diagnosed with autism. Through the family films collected, we compared 28 children later diagnosed with autism to 28 typically developing children strictly matched on chronological age and sex. To do this, we used the social behavior assessment scale (SBAS). This scale measures the behavior of the infant (turning his head, looking, smile, vocalize ...) in response to 5 parental stimuli (1.calling by her / his name, 2.saying peek-a-boo, a vocal sound 3.Producing , 4.filmed in silent 5.simultaneous interactions with one or more persons). Then we analyzed the responses behaviors of these children with the software "the observer". Results show evidence that, contrary to infants with typical development, infants later diagnosed as autistic made less visual contact, smile or vocalize less in response to parental stimuli. However, even if the responses of autistic children are statistically different in quantity (compared to the control group), responses to parental stimuli are still present. In a second step, we studied the developmental trajectories of children with autism. Our hypothesis was that children with a low score at the SBAS would have a lower global development score than the children with a high score at the SBAS at 3 years old. Our results validate our hypothesis. [less ▲]

Detailed reference viewed: 30 (3 ULg)
Full Text
See detailHigher Symmetries of the conformal Laplacian
Radoux, Fabian ULg

Conference (2014, July 14)

Detailed reference viewed: 9 (0 ULg)
Full Text
Peer Reviewed
See detailSelf broadening coefficients and improved line intensities for the ν7 band of ethylene near 10.5 µm, and impact on ethylene retrievals from Jungfraujoch spectra
Vander Auwera, J; Fayt, A; Tudorie, M et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2014), 148

Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self broadening coefficients for the nu7 band of ... [more ▼]

Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self broadening coefficients for the nu7 band of 12C2H4. The measured self broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10 % for high J lines in the P branch and lower by about 5 % for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrievals of atmospheric ethylene in the 949.0-952.0 cm-1 microwindow was evaluated using a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The use of HITRAN 2012 with line intensities modified to match the present measurements led to a systematic reduction of the measured total columns of ethylene by -4.1+/-0.1 %. [less ▲]

Detailed reference viewed: 11 (1 ULg)