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See detailA study of composite laminates failure using an anisotropic gradient-enhanced damage mean-field homogenization model
Wu, Ling ULg; Sket, Federico; Molina-Aldareguia, Jon M et al

in Composite Structures (2015), 126

The failure of carbon fiber reinforced epoxy laminates is studied using an anisotropic gradient-enhanced continuum damage model embedded in a mean-field homogenization scheme. In each ply, a homogenized ... [more ▼]

The failure of carbon fiber reinforced epoxy laminates is studied using an anisotropic gradient-enhanced continuum damage model embedded in a mean-field homogenization scheme. In each ply, a homogenized material law is used to capture the intra-laminar failure. The anisotropy of the homogenized material model results from the homogenization method and from the reformulation of the non-local continuum damage theory to account for the material anisotropy. As a result the damage propagation direction in each ply is predicted with accuracy as compared to the experimental results, while the problems of losing uniqueness and strain localization, which occur in classical finite element simulations when strain softening of materials is involved, can be avoided. To model the delamination process, the hybrid discontinuous Galerkin/extrinsic cohesive law method is introduced at the ply interfaces. This hybrid method avoids the need to propagate topological changes in the mesh with the propagation of the delamination while it preserves the consistency and stability in the un-cracked interfaces. As a demonstration, open-hole coupons with different stacking sequences are studied numerically and experimentally. Both the intra- and inter-laminar failure patterns are shown to be well captured by the computational framework. [less ▲]

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See detailCharacterizing activity sequences using Profile Hidden Markov Models
Liu, Feng; Janssens, Davy; Cui, JianXun et al

in Expert Systems with Applications (2015), 42(13), 57055722

In literature, activity sequences, generated from activity-travel diaries, have been analyzed and classified into clusters based on the composition and ordering of the activities using Sequence Alignment ... [more ▼]

In literature, activity sequences, generated from activity-travel diaries, have been analyzed and classified into clusters based on the composition and ordering of the activities using Sequence Alignment Methods (SAM). However, using these methods, only the frequent activities in each cluster are extracted and qualitatively described; the infrequent activities and their related travel episodes are disregarded. Thus, to quantify the occurrence probabilities of all the daily activities as well as their sequential orders, we develop a novel process to build multiple alignments of the sequences and subsequently derive profile Hidden Markov Models (pHMMs). This process consists of 4 major steps. First, activity sequences are clustered based on a pre-defined scheme. The frequent activities along with their sequential orders are then identified in each cluster, and they are subsequently used as a template to guide the construction of a multiple alignment of the cluster of sequences. Finally, a pHMM is employed to convert the multiple alignment into a position-specific scoring system, representing the probability of each frequent activity at each important position of the alignment as well as the probabilities of both insertion and deletion of infrequent activities. By applying the derived pHMMs to a set of activity-travel diaries collected in Belgium as well as a group of mobile phone call location data recorded in Switzerland, the potential and effectiveness of the models in capturing the sequential features of each cluster and distinguishing them from those of other clusters, are demonstrated. The proposed method can also be utilized to improve activity-based transportation model validation and travel survey designs. Furthermore, it offers a wide application in characterizing a group of any related sequences, particularly sequences varying in length and with a high frequency of short sequences that are typically present in human behavior. [less ▲]

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See detailSedimentological and geochemical evidence to detect arid periods recorded in wadi deposits: a case study from northern Morocco
El Ouahabi, Meriam ULg; Bartz, Melanie; Rixhon, Gilles et al

Poster (2015, July 27)

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See detailIdentification of VZV ORF9p potential cellular partners that could be important for the viral egress.
Lebrun, Marielle ULg; riva, laura; Rambout, Xavier ULg et al

Poster (2015, July 26)

ORF9p (homologous to HSV-1 VP22) is a VZV tegument protein essential for the viral replication. During the lytic cycle it is the mostly expressed gene. We have recently demonstrated that it is a substrate ... [more ▼]

ORF9p (homologous to HSV-1 VP22) is a VZV tegument protein essential for the viral replication. During the lytic cycle it is the mostly expressed gene. We have recently demonstrated that it is a substrate of the viral kinase ORF47p and that its ORF47p-dependent phosphorylation is important for the secondary envelopment process. We also have identified an acidic cluster (AC) within the protein that is important for its correct localization in the infected cells and for the interaction with ORF47p. The recombinant VZV expressing ORF9p-ΔAC presents an accumulation of capsids in the perinuclear space. ORF9p seems then to play an important role in several steps of the egress process. In this context, we sought to identify cellular partners of ORF9p that might be important for these functions. We performed a yeast two hybrid screen against the human ORFeome 5.1. and picked out 44 candidates among which 5 proteins playing roles in membrane organization and targeting. We currently are trying to confirm these interactions in infected cells and to assess the role of these interactions for the viral lytic cycle. [less ▲]

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See detailSpatio‑temporal dynamics of β‑tubulin isotypes during the development of the sensory auditory organ in rat
Renauld, Justine ULg; Johnen, Nicolas; Thelen, Nicolas ULg et al

in Histochemistry & Cell Biology (2015)

There are different β-tubulin isoforms in microtubules of vertebrate tissues. However, their functional significance is still largely unknown. In the present study, we investigated the localization of ... [more ▼]

There are different β-tubulin isoforms in microtubules of vertebrate tissues. However, their functional significance is still largely unknown. In the present study, we investigated the localization of five β-tubulin isotypes (β1– 5) within the hearing organ during development in rat. By using confocal microscopy, we showed that with the exception of the β3-tubulin isoform that was specific to nerve fibres, all the different β-tubulin isoforms were mainly present in the supporting cells. Contrary to β1–4-tubulins, we also found that the β5-tubulin isoform appeared only at a key stage of the post-natal development in specific cell types (pillar cells and Deiters’ cells). By using transmission electron microscopy, we revealed further that this developmental stage coincided with the formation of two separate bundles of microtubules from a unique one in these supporting cells. Together, these results suggest that the β5-tubulin isoform might be involved in the generation of new microtubule bundles from a pre-existing one. [less ▲]

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See detailPrediction of the excavation damaged zone in Callovo-Oxfordian claystone using a coupled second gradient model
Collin, Frédéric ULg; Pardoen, Benoît ULg

Scientific conference (2015, July 23)

The solution currently studied in France for long-term management of radioactive waste is the repository in deep argillaceous geological media with low permeability. The drilling of underground galleries ... [more ▼]

The solution currently studied in France for long-term management of radioactive waste is the repository in deep argillaceous geological media with low permeability. The drilling of underground galleries in these clayey rocks induces damage propagation in the surrounding medium. This excavation process creates a damaged zone, in which the material properties are modified. The prediction of the fracture structure and material properties evolution within this zone is a major issue especially in the context of underground disposal. Experimental works have highlighted that the damage around galleries in Callovo-Oxfordian claystone is localized and develops mainly as extensional and shear fractures. We propose to model these shear fractures as a strain localisation process in the mode of a shear band. In order to properly represent the shear strain localisation behaviour, an enhanced model introducing a regularization method and an internal length scale is needed. Among the different regularization methods, the coupled second gradient local model is chosen. To illustrate the development of the damaged zone, a two-dimensional plane strain state hydro-mechanical modelling of a gallery excavation is performed (Lagamine code, ULg) for two orientations of the gallery in the Callovo-Oxfordian claystone. Firstly, a gallery oriented along the minor horizontal principal stress is considered. In this direction, the anisotropy of the stress state in the plane perpendicular to the gallery is the predominant factor leading to the elliptical shape of the damaged zone, with a significantly larger extent in the vertical direction. Secondly, a gallery oriented along the major horizontal principal stress is modelled. The stress state in the plane perpendicular to the gallery is quasi-isotropic and does not lead to shear strain localisation unless the material anisotropy is considered. Moreover, the modelling provides information about the fracture structure and evolution around the gallery. It exhibits a chevron fracture pattern corresponding to in situ experimental measurements of shear fractures for both considered gallery orientations. [less ▲]

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See detailImpact of phenotypic heterogeneity and metabolic specialisation on metabolic engineering strategies: case of study of E.coli as a representative microbial cell factory
Brognaux, Alison ULg; Delepierre, Anissa ULg; Pecheux, Hélène ULg et al

Conference (2015, July 21)

The goal of this research is to directly highlight the simultaneous occurrence of several phenotypes with distinct metabolic function among clonal population of E. coli., often used for recombinant ... [more ▼]

The goal of this research is to directly highlight the simultaneous occurrence of several phenotypes with distinct metabolic function among clonal population of E. coli., often used for recombinant protein and pDNA production in bioprocesses. This phenotypic heterogeneity, first due to the noise, is reinforced by environmental heterogeneities occurring at large scale during fed-batch processes. This phenotypic heterogeneity has been tracked according to GFP reporter strains (biosensors) that circulate in the bioreactor and encounter environmental heterogeneities. First, we have highlighted the simultaneous occurrence of several phenotypes with distinct metabolic functions. Indeed, a diversity of glucose uptake strategies has recently been noticed with the PtsG and MglABC transporters. Moreover, when E.coli encounters zones of glucose excess, acetate is produced through the overflow metabolism. Only the sub-population with high acs expression (acetate transporter) could consume this acetate. GFP reporter strains have thus been constructed for PtsG, MgIABC and acs genes. In addition of the stable GFP, two destabilized GFP variants for each gene have been used to obtain more instantaneous responses. The response of these biosensors have been followed by on-line flow cytometry. In the end, this experimental strategy for direct phenotyping at the single cell level will also be used to investigate the impact of metabolic engineering strategies on phenotypic heterogeneity, robustness and fitness of microbial population in industrial conditions. [less ▲]

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See detailExploratory study of narratives in children with attention deficit hyperactivity disorder
Boulard, Aurore ULg; Pignatiello, Laure ULg; Leclercq, Cédric

Poster (2015, July 21)

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See detailA viscoelastic-viscoplastic-damage constitutive model based on a large strain hyperelastic formulation for amorphous glassy polymers
Nguyen, Van Dung ULg; Morelle, Xavier; Lani, Frédéric et al

in proceedings of the 20th International Conference on Composite Materials, Copenhagen, Denmark, 19-24th July 2015 (2015, July 20)

The aim of this work is to develop an efficient large-strain hyperelastic constitutive model for amorphous polymers in the glassy state. These materials exhibit a complex rate- and pressure-sensible ... [more ▼]

The aim of this work is to develop an efficient large-strain hyperelastic constitutive model for amorphous polymers in the glassy state. These materials exhibit a complex rate- and pressure-sensible behavior in both elastic and plastic regimes. After an initial linear elastic region, a nonlinear stage continues until reaching a peak stress, which is followed by a softening stage. At large strains, when the softening is saturated, a re-hardening stage is reached. The viscoelastic effect is captured using the generalized Maxwell model. The viscoplastic effect is considered using a Perzyna-type flow rule incorporating a pressure sensitive yield surface and a non-associated flow potential. This yield surface is extended from the Drucker-Prager one. The saturated softening phenomenon is modelled using an isotropic numerical damage variable progressed by a saturated softening law. With the introduction of the damage parameter, a non-local implicit gradient damage model is used to avoid the loss of the solution uniqueness. Through experimental comparisons, it is shown that the proposed model has the ability to model the complex mechanical responses of amorphous glassy polymers. [less ▲]

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See detailFunctionality of microbial phenotypic heterogeneity in bioprocessing conditions: an analysis based on the use of on-line flow cytometry
Delepierre, Anissa ULg

Conference (2015, July 20)

Microbial phenotypic heterogeneity is known to be naturally present in isogenic population and can be attributed to the stochastic nature of the biochemical reactions. An important question at this level ... [more ▼]

Microbial phenotypic heterogeneity is known to be naturally present in isogenic population and can be attributed to the stochastic nature of the biochemical reactions. An important question at this level was to determine whether such stochastic behavior exhibits some functionality, i.e. how single cell heterogeneity leads to population level strategies. One of this strategies, called bet-hedging, is known to give a competitive advantage to the population, by leading for example to a persistent phenotype able to survive to antibiotics exposure. Among the single cell toolbox available for the analysis of phenotypic heterogeneity, flow cytometry present the advantage of being compatible with bioprocess cultivation tools. In this work, we present an on-line analytical workflow based on automated flow cytometry that can be used to monitor simultaneously several bioreactors, testing different bioreactor operating conditions, in combination with fluorescent transcriptional reporter strategies: promoter involved in metabolism fused to a gene expressing an unstable variant of GFP , and viability fluorescent tagging: propidium iodide uptake, correlated with membrane permeability. [less ▲]

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See detailGlobally significant greenhouse-gas emissions from African inland waters
Borges, Alberto ULg; Darchambeau, François ULg; Teodoru, Cristian R. et al

in Nature Geoscience (2015), advance online publication

Carbon dioxide emissions to the atmosphere from inland waters[mdash]streams, rivers, lakes and reservoirs[mdash]are nearly equivalent to ocean and land sinks globally. Inland waters can be an important ... [more ▼]

Carbon dioxide emissions to the atmosphere from inland waters[mdash]streams, rivers, lakes and reservoirs[mdash]are nearly equivalent to ocean and land sinks globally. Inland waters can be an important source of methane and nitrous oxide emissions as well, but emissions are poorly quantified, especially in Africa. Here we report dissolved carbon dioxide, methane and nitrous oxide concentrations from 12 rivers in sub-Saharan Africa, including seasonally resolved sampling at 39 sites, acquired between 2006 and 2014. Fluxes were calculated from published gas transfer velocities, and upscaled to the area of all sub-Saharan African rivers using available spatial data sets. Carbon dioxide-equivalent emissions from river channels alone were about 0.4 Pg carbon per year, equivalent to two-thirds of the overall net carbon land sink previously reported for Africa. Including emissions from wetlands of the Congo river increases the total carbon dioxide-equivalent greenhouse-gas emissions to about 0.9 Pg carbon per year, equivalent to about one quarter of the global ocean and terrestrial combined carbon sink. Riverine carbon dioxide and methane emissions increase with wetland extent and upland biomass. We therefore suggest that future changes in wetland and upland cover could strongly affect greenhouse-gas emissions from African inland waters. [less ▲]

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See detailCombining mindfulness and ACT to learn how to manage emotions and to engage in valued activities: Assessment of the feasibility of a training group and its efficiency
Wagener, Aurélie ULg; Dierickx, Christophe; Blairy, Sylvie ULg

Poster (2015, July 18)

BACKGROUND Managing painful emotions could be an issue for a lot of adults. Indeed, learning how to manage painful emotions is an often-requested demand in psychotherapy. Mindfulness-based programs and ... [more ▼]

BACKGROUND Managing painful emotions could be an issue for a lot of adults. Indeed, learning how to manage painful emotions is an often-requested demand in psychotherapy. Mindfulness-based programs and acceptance and commitment therapy (ACT) offer useful tools which aim to guide in this learning process. ACT also provide guidelines to engage in valued activities. In order to help community adults to manage their painful emotions and to engage themselves in valued activities, we offer training group cycles combining tools of mindfulness-based programs and ACT. This study aims to assess the feasibility of such training groups and their efficiency. METHODS A longitudinal design with three assessment-times (T0, T1 and T2) is employed. Participants to the training group attend to three three-hours training sessions on a six-weeks period. They are assessed before the training sessions (T0), directly after (T1) and at three-months follow-up (T2). Questionnaires assess these variables: sociodemographic data, mood, mindfulness, psychological flexibility, cognitive coping strategies and behavioural activation. Student t tests for paired samples are conducted. RESULTS Fifty-four adults participated to four training cycles (the cycles are all identical). Until now, 28 participants (21 women) completed the T0 and the T1 (mean age = 41.43, SD = 11.83). Student t test indicate a significant decrease of depression (t(25) = 4.53, p < 0,001), anxiety (t(25) = 6.23, p < 0.001) and non-adaptive cognitive coping strategies (t(24) = 3.76, p < 0.001). Student t test also indicate a significant increase in mindfulness (t(26) = -3.87, p < 0.001), psychological flexibility (t(26)) = -5.48, p < 0.001) and behavioural activation (t(26) = -4.86, p < 0.001). DISCUSSION Preliminary results indicate the feasibility of training groups combining tools of mindfulness-based programs and ACT. Results show a decrease in several variables (depression, anxiety and non-adaptive cognitive coping strategies) and an increase in other variables (mindfulness, psychological flexibility and behavioural activation). These results seem to indicate that participants benefit from the training groups. Data collection is still ongoing and a control group (waiting-list) is currently being composed. Results and clinical implications will be further discussed during the congress. [less ▲]

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See detailJustice énergétique pour tous!
Bauwens, Thomas ULg

Article for general public (2015)

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See detailTowards an "African Stylistics": Apprehending Cross-Cultural Creativity in the Works of Chris Abani
Tunca, Daria ULg

Conference (2015, July 18)

Anglophone African literatures have often been praised for their linguistic originality. More often than not, critics interested in the stylistic inventiveness of works from the continent have focused ... [more ▼]

Anglophone African literatures have often been praised for their linguistic originality. More often than not, critics interested in the stylistic inventiveness of works from the continent have focused their attention on these texts’ specifically “African” features, from the use of proverbs to the presence of words from indigenous languages. While these scholarly studies have done much to demonstrate the richness of African aesthetic standards, they have also tended to obscure other facets of the creativity of African writers who, just like their counterparts all over the world, make ample use of such devices as metaphor, irony, and unreliable narration. After a brief examination of the methodological and epistemological issues that have shaped the elusive field of “African stylistics”, I propose to investigate how contemporary stylistic theories may contribute to the understanding of the multiple forms of creativity found in the works of the US-based Nigerian writer Chris Abani. A self-proclaimed “global Igbo” (after the name of his father’s ethnic group), Abani boldly combines in his work African cosmology with influences from the Catholic and Buddhist traditions, also using formal devices – such as minor sentences and poetic metaphors – whose significance can only be fully appreciated through extensive stylistic analysis. Mainly focusing on Abani’s novella Becoming Abigail (2006), I will suggest that a combination of traditional culture-oriented approaches to African literatures and more typically “mainstream” stylistic techniques is needed to apprehend the Nigerian writer’s complex cross-cultural worldview. [less ▲]

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See detailMetabolomics analysis of Galium odoratum (L.) Scop.: impact of the plant population origin and growth conditions.
Ledoux, Allison ULg; Martin, Bertrand; De Tullio, Pascal ULg et al

Poster (2015, July 16)

Galium odoratum is a plant used in traditional medicine and to prepare beverages. This work aimed at studying the impact of plant origin and growth conditions on the metabolite content of the plant ... [more ▼]

Galium odoratum is a plant used in traditional medicine and to prepare beverages. This work aimed at studying the impact of plant origin and growth conditions on the metabolite content of the plant. Material and methods- Aerial biomass of Galium odoratum was collected from five natural populations (in situ conditions) and from controlled environment (ex situ conditions). Results- Quantitative analysis of selected phytochemicals including phenylpropranoids and iridoids showed clear differences between the plants from nature and those of controlled growth conditions as well as internal variation within the group. The metabolomic approach emphasized the decrease of the secondary metabolites pool paralleled by an increase of the carbohydrates in ex situ conditions. Conclusion- Metabolomics approaches using 1H-NMR and HPLC is worth to consider for studying the impact of climate factors on the regulation of the phytochemical profile in relation to the origin of the plant material. [less ▲]

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See detailDevelopmental profiles of GFAP-positive astrocytes in sheep cerebellum
Salouci, Moustafa ULg; Antoine, Nadine ULg; Shikh Al Sook, Mohamad Khir ULg et al

Poster (2015, July 16)

Astroglial cells make up the largest glial population in the brain and play a variety of vital functions in the development of the CNS. Defects in the development of these cells may induce various ... [more ▼]

Astroglial cells make up the largest glial population in the brain and play a variety of vital functions in the development of the CNS. Defects in the development of these cells may induce various neurodegenerative disorders and result in neural disease. The aim of this study is to investigate the normal development of astrocytes in sheep in various zones of the cerebellum during the different stages of gestation. 19 ovine fetuses, one lamb in the first postnatal week and three adult sheep. Sections of the cerebellum were embedded in paraffin and processed for immunohistochemistry for GFAP. The current study indicates that the first appearance of astrocytes occurs around the 8th week of gestation from restricted zones in the cerebellum. Bergmann cells were present around the 15th week of gestation. Our findings suggest that the maturation of astrocytes begins in the caudal parts of the cerebellum from their initial ventral regions to dorsal regions radially within the white matter followed by the more rostral parts of the cerebellum and that the astrocytes proliferate in the vermis before the cerebellar hemispheres. Our study provide a bases for future studies focusing on the pathological changes in the CNS of both human and sheep. [less ▲]

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See detailEffective segmentation of green vegetation for resource-constrained real-time applications
Krishna Moorthy Parvathi, Sruthi Moorthy ULg; Boigelot, Bernard ULg; Mercatoris, Benoît ULg

Scientific conference (2015, July 15)

This paper describes an improved algorithm for segmentation of green vegetation under uncontrolled illumination conditions and also suitable for resource-constrained real-time applications. The proposed ... [more ▼]

This paper describes an improved algorithm for segmentation of green vegetation under uncontrolled illumination conditions and also suitable for resource-constrained real-time applications. The proposed algorithm uses a naïve Bayesian model to effectively combine various manually extracted features from two different color spaces namely RGB and HSV. The evaluation of 100 images indicated the better performance of the proposed algorithm than the vegetation index-based methods with comparable execution time. Moreover, the proposed algorithm performed better than the state-of-the-art EASA-based algorithms in terms of processing time and memory usage. [less ▲]

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