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See detailRecent progresses in the nonsmooth contact dynamics method for flexible multibody systems
Bruls, Olivier ULg

Scientific conference (2014, January 10)

This talk will start with a brief overview of the current research activities undertaken at the Multibody & Mechatronic Systems Laboratory with a number of applications in the fields of wind turbines ... [more ▼]

This talk will start with a brief overview of the current research activities undertaken at the Multibody & Mechatronic Systems Laboratory with a number of applications in the fields of wind turbines, deployable space structures, robotics and human motion analysis. Then, the presentation will focus on some recent results related with the modelling of dynamic contact conditions in multibody systems. Typical applications include the modelling of non-ideal joints with backlash and friction, the analysis of mechanical transmission systems and gearboxes, the modelling of grasping tasks or the description of the foot-ground contact in gait analysis. The proposed formalism relies on the nonsmooth contact dynamics method. Accordingly, the condition of impenetrability of the bodies in contact is expressed as a unilateral constraint, with the consequence that impacts and/or instantaneous changes in the velocities may arise in the dynamic response. Also, the resulting set of equations is solved in the time domain using a time-stepping strategy, which is known its robustness and its ability to deal with a large number of events in an efficient way. After a review of the time-stepping method originally proposed by Moreau and Jean, a number of improvements are addressed during the talk. Firstly, a splitting method is introduced to isolate the contributions of impacts, which can only be integrated with first-order accuracy, from smooth contributions, which can be integrated using a higher order scheme. Secondly, following the idea of Gear, Gupta and Leimkuhler, the equation of motion is reformulated so that the bilateral and unilateral constraints appear both at position and velocity levels. This strategy leads to an algorithm which exactly satisfies the constraints at both levels, i.e., no penetration is allowed in the numerical response. After time discretization, the equation of motion involves two complementarity conditions and it can be solved at each time step using a monolithic semi-smooth Newton method. The numerical behaviour of the proposed scheme is studied and compared to other approaches for a number of numerical examples. It is shown that the formulation offers a unified and valid approach for the description of contact conditions between rigid bodies as well as between flexible bodies. [less ▲]

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See detailDes répertoires en dialogue. Gemmes et monnaies à types isiaques
Veymiers, Richard ULg

Conference (2014, January 10)

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See detailAgricultural spray measurement by high-speed shadow imagery
De Cock, Nicolas ULg; Massinon, Mathieu ULg; Lebeau, Frédéric ULg

Scientific conference (2014, January 10)

Spray characteristics determine treatment performance and environmental contamination. Shadowgraphy associated with high-speed imaging presents an attractive option for measuring drop velocity and size ... [more ▼]

Spray characteristics determine treatment performance and environmental contamination. Shadowgraphy associated with high-speed imaging presents an attractive option for measuring drop velocity and size simultaneously. This study presents an overview of the contrast problems occurring when using backlighted images and proposes appropriate solutions for reliable and quality measurements. Drop diameter measurement is based on the area inside the sub-pixel contour assuming a circular shape. Drop velocity is determined by tracking a drop on two successive images taking into account the drop size, speed limits and the general flow direction. Then, the drop size distribution is corrected taking in account the sampling rate of each drop. Finally, a comparison between PDA and shadowgraphy measurements realized simultaneously on the same spray location is presented. [less ▲]

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See detailL’analyse des sensations en contexte intentionnel : l’approche brentanienne
Dewalque, Arnaud ULg

Scientific conference (2014, January 09)

Mon intention est d’examiner la position de Franz Brentano et de certains brentaniens sur le statut des sensations et de ce que l’on appelle communément les "données sensibles" (couleurs, sons, odeurs ... [more ▼]

Mon intention est d’examiner la position de Franz Brentano et de certains brentaniens sur le statut des sensations et de ce que l’on appelle communément les "données sensibles" (couleurs, sons, odeurs, qualités tactiles et gustatives). À mon sens, l’une des spécificités de l’approche brentanienne est d’avoir abordé le problème de l’analyse des sensations comme un cas particulier d’un problème plus général, soit l’analyse descriptive du mental. Le problème de l’analyse des sensations est donc essentiellement connecté à la question de savoir dans quelle mesure un état mental – et, en l’occurrence, un état sensoriel – peut être considéré comme un état composé de "données sensorielles". La réponse affirmative à cette question tient dans une thèse que je propose d’appeler, par commodité, la thèse de la composition sensorielle. Je suggère ici qu'il y a de bonnes raisons de défendre une certaine version de cette thèse et, partant, de réhabiliter la notion de "donnée sensible". [less ▲]

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See detailCritique et modernité
Filipucci, Alexis ULg; Pieron, Julien ULg

Conference (2014, January 09)

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See detailWASP-103b: a new planet at the edge of tidal disruption
Gillon, Michaël ULg; Anderson, D. R.; Collier-Cameron, A. et al

in Astronomy and Astrophysics (2014)

We report the discovery of WASP-103b, a new ultra-short-period planet (P=22.2 hr) transiting a 12.1 V-magnitude F8-type main-sequence star (1.22+-0.04 Msun, 1.44-0.03+0.05 Rsun, Teff = 6110+-160 K). WASP ... [more ▼]

We report the discovery of WASP-103b, a new ultra-short-period planet (P=22.2 hr) transiting a 12.1 V-magnitude F8-type main-sequence star (1.22+-0.04 Msun, 1.44-0.03+0.05 Rsun, Teff = 6110+-160 K). WASP-103b is significantly more massive (1.49+-0.09 Mjup) and larger (1.53-0.07+0.05 Rjup) than Jupiter. Its large size and extreme irradiation (around 9 10^9 erg/s/cm^2) make it an exquisite target for a thorough atmospheric characterization with existing facilities. Furthermore, its orbital distance is less than 20% larger than its Roche radius, meaning that it might be significantly distorted by tides and might experience mass loss through Roche-lobe overflow. It thus represents a new key object for understanding the last stage of the tidal evolution of hot Jupiters. [less ▲]

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See detailWind collisions in three massive stars of Cygnus OB2
Cazorla, Constantin ULg; Nazé, Yaël ULg; Rauw, Grégor ULg

in Astronomy and Astrophysics (2014), 561

Aims. We wish to study the origin of the X-ray emission of three massive stars in the CygOB2 association: CygOB2#5, Cyg OB2 #8A, and Cyg OB2 #12. Methods. To this aim, dedicated X-ray observations from ... [more ▼]

Aims. We wish to study the origin of the X-ray emission of three massive stars in the CygOB2 association: CygOB2#5, Cyg OB2 #8A, and Cyg OB2 #12. Methods. To this aim, dedicated X-ray observations from XMM-Newton and Swift are used, as well as archival ROSAT and Suzaku data. Results. Our results on Cyg OB2 #8A improve the phase coverage of the orbit and confirm previous studies: the signature of a wind- wind collision is conspicuous. In addition, signatures of a wind-wind collision are also detected in Cyg OB2 #5, but the X-ray emission appears to be associated with the collision between the inner binary and the tertiary component orbiting it with a 6.7 yr period, without a putative collision inside the binary. The X-ray properties strongly constrain the orbital parameters, notably allowing us to discard some proposed orbital solutions. To improve the knowledge of the orbit, we revisit the light curves and radial velocity of the inner binary, looking for reflex motion induced by the third star. Finally, the X-ray emission of Cyg OB2 #12 is also analyzed. It shows a marked decrease in recent years, compatible with either a wind-wind collision in a wide binary or the aftermath of a recent eruption. [less ▲]

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See detailLa capacité critique du renard. Althusser lecteur de Machiavel
Mancuso, Eva ULg

Scientific conference (2014, January 09)

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See detailSpray retention assment combining high-speed shadow imagery and fluorescence techniques
Massinon, Mathieu ULg; Boukhalfa, Hassina dite Hafida ULg; Lebeau, Frédéric ULg

in International Advances in Pesticide Application: Aspects of Applied Biology 122, 2014 (2014, January 08)

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and ... [more ▼]

Droplet behaviour during impact affects retention by leaves. The increase of droplet adhesion to plant leaves is the objective when applying crop protection products, while droplet bouncing and fragmentation are usually seen as detrimental to spray retention. However, observation of droplet impacts on barley using high speed imaging showed that fragmentation impact outcome can occur in two different wetting regimes: Cassie-Baxter or Wenzel’s regime. In the latter, a fraction of the droplet is anchored in the surface roughness, what contributes to retention. Three mixtures were sprayed on excised barley leaves with an 11003 flat-fan nozzle operating at 0.2 MPa. Simultaneous measurements were performed using high speed imaging for droplet impact characterisation. A fluorescent tracer was added to the spray mixture for retention assessment. Retention was related to impact type considering the fraction of the droplet remaining on the leaf surface after a droplet splashing occurring in Wenzel’s wetting regime. This fraction varied from 28‒46% depending on the spray mixture and was correlated to the Volume Median Diameter DV0.5 of the impacting droplets. [less ▲]

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See detailThe Tax protein and the minichromosome maintenance protein complex MCM2-7 affect cell replication and viral transcription
Barez, Pierre-Yves ULg; Carpentier, Alexandre ULg; Boxus, Mathieu et al

in Retrovirology (2014), 11(S1), 96

The Tax oncoprotein plays a key role in the mechanisms of transformation, viral persistence and pathogenicity. Recently, we showed that Tax interacts with the minichromosome maintenance MCM2-7 helicase ... [more ▼]

The Tax oncoprotein plays a key role in the mechanisms of transformation, viral persistence and pathogenicity. Recently, we showed that Tax interacts with the minichromosome maintenance MCM2-7 helicase and binds to origins of DNA replication (Boxus et al, 2012 Blood 119:151). In fact, Tax modulates the spatiotemporal program of origin activation during the S phase of cell cycle. By this mechanism, Tax accelerates S phase progression through early firing of late replication origins. By interacting with the 5’ LTR, the MCM2-7 complex also modulates Tax transactivation. Together, our data thus demonstrates that interaction between Tax and MCM2-7 modulates reprogramming of replication origins as well as viral transcription. [less ▲]

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See detailOn the Vedic Yajamâna-
Swennen, Philippe ULg

Conference (2014, January 07)

When he is consecrated, the Vedic Yajamâna symbolically becomes an embryo because he originally had the become a new Mârtânda in order to conquer the same divine status obtained by Vivasvant thanks to the ... [more ▼]

When he is consecrated, the Vedic Yajamâna symbolically becomes an embryo because he originally had the become a new Mârtânda in order to conquer the same divine status obtained by Vivasvant thanks to the realization of the first sacrifice. [less ▲]

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See detailRain-operated Foliar Disease Transmission
Gilet, Tristan ULg

Conference (2014, January 07)

Plant diseases are a major cause of crop loss worldwide. They are known to be triggered by rainfalls. We here combine high-speed visualizations and physical modelling to elucidate the causal link between ... [more ▼]

Plant diseases are a major cause of crop loss worldwide. They are known to be triggered by rainfalls. We here combine high-speed visualizations and physical modelling to elucidate the causal link between rain impact on foliage and pathogen spreading. We identify two dominant scenarios by which the pathogens get ejected from leaves. The leaf compliance is shown to strongly affect these mechanisms. The laws of fluid dynamics set tight limits on this epidemiological problem. They suggest a revision of the current agricultural practices in order to contain the spread of foliar diseases. [less ▲]

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See detailOrigin and evolution of metal P-type ATPases in Plantae (Archaeplastida)
Hanikenne, Marc ULg; Baurain, Denis ULg

in Frontiers in Plant Science (2014), 4

Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two ... [more ▼]

Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialisation into either monovalent (Cu) or divalent (Zn, Cd…) metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterised in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms. [less ▲]

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See detailCheckpoints modulation by the Human T-lymphotropic virus type 1 Tax protein
Carpentier, Alexandre ULg; Barez, Pierre-Yves ULg; Boxus, Mathieu et al

in Retrovirology (2014), 11(S1), 90

HTLV-1 is responsible for two main diseases, Adult T-cell Leukemia/Lymphoma and HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis, for which there is currently no satisfactory treatment. Among the ... [more ▼]

HTLV-1 is responsible for two main diseases, Adult T-cell Leukemia/Lymphoma and HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis, for which there is currently no satisfactory treatment. Among the proteins encoded by HTLV-1, Tax appears to play an important role in the mechanisms leading to pathogenicity. We are interested in the mechanisms of cell transformation by Tax and more particularly in the interplay between the viral Tax oncoprotein and the DNA damage response (DDR). We demonstrated that transient expression of Tax results in DNA damage, cell cycle arrest and activation of the DDR. In fibroblasts, cell cycle arrest occurs at the G1 and G2 phases depending on the p53 background. Although Tax induces apoptosis and senescence in fibroblasts, HTLV-1 infected lymphocytes proliferate continuously and appear to be adapted to the checkpoint control. This mechanism allows infected lymphocytes to proliferate despite the presence of genomic lesions. With these observations, we propose a novel therapeutic approach based on the principle of synthetic lethality. [less ▲]

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See detailHyper-replicative bovine leukemia virus by mutation of an envelope N-linked glycosylation site
De Brogniez, Alix ULg; Bouzar, Amel-Baya; Jacques, Jean-Rock ULg et al

in Retrovirology (2014), 11(1), 141

Reverse genetics can be used in the bovine leukemia virus (BLV) system to characterize mechanisms of viral persistence and pathogenesis. The question addressed here pertains to the role of glycans bound ... [more ▼]

Reverse genetics can be used in the bovine leukemia virus (BLV) system to characterize mechanisms of viral persistence and pathogenesis. The question addressed here pertains to the role of glycans bound to the BLV envelope glycoprotein (SU). A commonly accepted hypothesis is that addition of carbohydrates to the SU protein potentially creates a structure called « glycan shield » that confers resistance to the virus against the host immune response. On the other hand, glycosylation can also modulate attachment of the virus to the cell membrane. To unravel the role of SU glycosylation, three complementary strategies were developed: pharmacological inhibition of different glycosylation pathways, interference with glycan attachment and site-directed mutagenesis of N-glycosylation sites in an infectious BLV provirus. The different approaches show that glycosylation is required for cell fusion, as expected. Simultaneous mutation of all 8 potential N-glycosylation sites destroys infectivity. Surprisingly, mutation of the asparagine residue at position 230 creates a virus having an increased capacity to form syncytia in vitro. Compared to wild-type BLV, mutant N230 also replicates at accelerated rates in vivo. Collectively, this data thus illustrates an example of a N-glycosylation site that restricts viral replication, contrasting with the hypothesis supported by glycan shield model. [less ▲]

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See detailReversibly crosslinked thermo- and redox-responsive nanogels for controlled drug release
Liu, Ji ULg; Detrembleur, Christophe ULg; Hurtgen, Marie ULg et al

in Polymer Chemistry (2014), 5(1), 77-88

Reversibly crosslinked poly(vinyl alcohol)-b-poly(N-vinylcaprolactam) PVOH-b-PNVCL nanogels were prepared by using a redox-responsive crosslinking agent, 3,30-dithiodipropionic acid (DPA), to crosslink ... [more ▼]

Reversibly crosslinked poly(vinyl alcohol)-b-poly(N-vinylcaprolactam) PVOH-b-PNVCL nanogels were prepared by using a redox-responsive crosslinking agent, 3,30-dithiodipropionic acid (DPA), to crosslink the PVOH corona, above the lower critical solution temperature (LCST) of the PNVCL block. The stability of the as-prepared nanogels against heating and diluting with water was studied by dynamic light scattering (DLS) to follow the evolution of the hydrodynamic diameter and size distribution. Stability under reductive conditions was also studied by DLS and transmission electron microscopy (TEM) after exposure to dithiothreitol (DTT) buffer solutions at different pH. The reversibility of the crosslinking was evaluated by treating the de-crosslinked nanogels with hydrogen peroxide (H2O2) above the LCST. As a hydrophobic drug model, Nile red (NR) was loaded into the nanogels, and triggered release behaviours were studied after exposure to the same DTT buffer solutions. Moreover, two PVOH-b-PNVCL copolymers with different compositions and LCST were used to evaluate the effect of the LCST on the release behaviours of the nanogels. The cytotoxicity of the nanogels against a mouse fibroblast-like L929 cell line was assessed via the MTS assay, and preliminary studies on cellular uptake of the nanogels within human melanoma MEL-5 cells were also carried out by fluorescence microscopy and fluorescence-activated cell sorting. [less ▲]

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See detailHeat-triggered drug release systems based on mesoporous silica nanoparticles filled with a maghemite core and phase-change molecules as gatekeepers
Liu, Ji ULg; Detrembleur, Christophe ULg; De Pauw-Gillet, Marie-Claire ULg et al

in Journal of Materials Chemistry B (2014), 2(1), 59-70

Core–shell nanoparticlesmade of a maghemite core and a mesoporous silica shell were developed as drug delivery systems (DDS). Doxorubicin® (DOX, DNA intercalating drug) was loaded within the mesoporous ... [more ▼]

Core–shell nanoparticlesmade of a maghemite core and a mesoporous silica shell were developed as drug delivery systems (DDS). Doxorubicin® (DOX, DNA intercalating drug) was loaded within the mesoporous cavities, while phase-change molecules (PCMs), e.g. 1-tetradecanol (TD) with a melting temperature (Tm) of 39 °C, were introduced as gatekeepers to regulate the release behaviours. An overall loading amount of ca. 20 wt% (TD/DOX ca. 50/50 wt/wt) was confirmed. Heat-triggered release of DOX evidenced a “zero premature release” (<3% of the entire payload in 96 h release) under physiological conditions (37°C), and however, a sustainable release (ca. 40% of the entire payload in 96 h) above Tm of TD (40 °C). It also demonstrated the possibility to deliver drug payloads in small portions (pulsatile release mode) via multiple heating on/off cycles, due to the reversible phase change of the PCMs. In vitro heattriggered release of DOX within cell culture of the MEL-5 melanoma cell line was also tested. It was found that DOX molecules were trapped efficiently within the mesopores even after internalization within the cytoplasm of MEL-5 cells at 37 °C, with the potential toxicity of DOX strongly quenched (>95% viability after 72 h incubation). However, continuous cell apoptosis was detected at cell culture temperature above Tm of TD, due to the heat-triggered release of DOX (<50% viability after 72 h incubation at 40 °C). Moreover, due to the presence of a maghemite core within the DDS, T2-weighted magnetic resonance imaging performance was also confirmed. These as-designed core–shell nanoparticles are envisaged to become promising DDS for “on-demand” heat-triggered release. [less ▲]

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See detailBi-directional Modulation of Somatosensory Mismatch Negativity with Transcranial Direct Current Stimulation: An event Related Potential Study
Chen, Jui-Cheng; Hammerer, Dorothea; D'Ostilio, Kevin ULg et al

in The journal of Physiology (2014)

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