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See detailOrganometallic-mediated radical synthesis of well-defined ethylene-vinyl acetate statistical and block copolymers
Demarteau, Jérémy ULg; Kermagoret, Anthony; Jérôme, Christine ULg et al

Poster (2015, May 18)

The copolymerization of ethylene (E) and vinyl acetate (VAc) is of high interest for polymer industry. Nevertheless, the control of the macromolecular parameters of ethylene-vinyl acetate copolymers (EVAs ... [more ▼]

The copolymerization of ethylene (E) and vinyl acetate (VAc) is of high interest for polymer industry. Nevertheless, the control of the macromolecular parameters of ethylene-vinyl acetate copolymers (EVAs) is difficult to achieve. Herein, we report the controlled radical copolymerization of these monomers by organometallic-mediated radical polymerization (OMRP) using Co(acac)2 as controlling agent. The ethylene pressure is varied from 10 to 100 bar and we discuss the effect of this parameter on kinetics, level of control and copolymer composition. EVAs are synthetized accordingly with low dispersities and ethylene content reaches up to 57 mol%. The precision design of EVA-containing block copolymers, i.e. PVAc-block-EVA, is also addressed. [less ▲]

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See detail"Psycho" d'Alfred Hitchcock, un thriller matriciel
Tomasovic, Dick ULg

Scientific conference (2015, May 18)

Analyse des motifs structurants du film "Psycho" et de leurs avatars dans le cinéma hollywoodien.

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See detailTests in vitro pour l’évaluation des substituts du Bisphenol A
Simon, Coraline ULg; Scippo, Marie-Louise ULg

Scientific conference (2015, May 18)

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See detailDémocratie et populisme: quelle réalité pour quelle légitimité?
Biard, Benjamin; Debras, François ULg

Conference (2015, May 18)

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See detailAl-Maqrīzī at Work
Bauden, Frédéric ULg

Scientific conference (2015, May 17)

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See detailClassical analogy for the deflection of flux avalanches by a metallic layer
Silhanek, Alejandro ULg

Conference (2015, May 17)

Motivated by the experimental observation of the exclusion of magnetic flux avalanches in a superconducting sample partially covered by a conducting capping layer, we have investigated the simpli fied ... [more ▼]

Motivated by the experimental observation of the exclusion of magnetic flux avalanches in a superconducting sample partially covered by a conducting capping layer, we have investigated the simpli fied case of the interaction of a magnetic charge (monopole and dipole) with a semi-in finite conducting plane. We have found that early theoretical descriptions for the damping enhancement due to the metallic sheet needed a correction at large vortex velocities where a decrease of the damping coe fficient is expected. We also demonstrate that vortex trajectories are strongly modi fied when penetrating into the area covered by the metallic sheet and may even be fully diverted from that area thus providing a qualitative explanation for the bending of the trajectories of flux avalanches. Our fi ndings may be extended to study the damping of Larkin-Ovchinnikov vortex instabilities and phase-slip lines in current driven systems. [less ▲]

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See detailInfluence of substrate nature and β-lactoglobulin on cleanability after soiling by suspension spraying and drying
Toure, Yetioman ULg; Sindic, Marianne ULg; Dupont-Gillain, C. Christine et al

in Chemical Engineering Science (2015), 134

Glass and stainless steel (StSteel, AISI304-2R), previously cleaned with ethanol (-Eth) or with ethanol and UV–Ozone treatment (-UVO), were soiled with quartz suspensions in water and in a β-lactoglobulin ... [more ▼]

Glass and stainless steel (StSteel, AISI304-2R), previously cleaned with ethanol (-Eth) or with ethanol and UV–Ozone treatment (-UVO), were soiled with quartz suspensions in water and in a β-lactoglobulin (β-LGB) solution, and dried. The cleanability (ease of quartz particle detachment) in water was evaluated using a radial-flow cell. The soiling suspension containing β-LGB was used as such or after heating for 4h at 75°C, which provoked coagulation of about 75% of β-LGB. The substrate–solution interfaces were characterized by X-ray photoelectron spectroscopy (XPS) analysis of conditioned substrates and by contact angle measurements. The substrate surfaces are covered by a layer of organic contaminants which are not removed by pre-cleaning or are adsorbed from the surroundings. The presence of β-LGB in the soiling suspension leads to protein adsorption, but a significant amount of contaminants remains at the surface. For three of the substrates tested (Glass-Eth, Glass-UVO, StSteel-UVO) the increase of cleanability when the soiling suspension contained β-LGB may be explained by lower capillary forces acting upon drying. Capillary forces are proportional to the liquid surface tension and depend in a less important way on substrate contact angle. However the order of cleanability observed for the substrates soiled with a suspension of quartz particles in water (Glass-Eth≅Glass-UVO<StSteel-UVO<StSteel-Eth) and the influence of β-LGB on the cleanability of StSteel-Eth may not be explained only by computed capillary forces. The contact angle may exert a direct influence on droplet spreading and particle–substrate contact. The organic contaminants present on the surfaces, which are often neglected by supposing model solid surfaces, may have a significant influence on cleanability through physico-chemical processes which remain to be appreciated. [less ▲]

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See detailPolarization holography for vortex retarders recording: laboratory demonstration
Piron, Pierre ULg; Blain, Pascal ULg; Décultot, Marc ULg et al

in Applied Optics (2015), 54(15), 4765--4770

This paper will present a prototype of the first set of vortex retarders made of liquid crystal polymers recorded by polarization holography. Vortex retarders are birefringent plates characterized by a ... [more ▼]

This paper will present a prototype of the first set of vortex retarders made of liquid crystal polymers recorded by polarization holography. Vortex retarders are birefringent plates characterized by a rotation of their fast axis. Liquid crystals possess birefringent properties and they are locally orientable. Their orientation is defined by the perpendicular to the local orientation of the recording field. Polarization holography is a purely optical recording method. It is based on the superimposition of coherent and differently polarized beams. It is used to shape the electric field pattern to enable the recording of vortex retarders. The paper details the mathematical model of the superimposition process. The recording setup is exposed; it is characterized by a nearly common path interferometer. Two sets of measurements allowing the prediction of the retarder’s features are presented and compared. Finally, the experimentally recorded retarder is shown, its characteristics are investigated and compared to the predicted ones. [less ▲]

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See detailRheological behavior of β-Ti and NiTi powders produced by atomization for SLM production of open porous orthopedic implants
Yablokova, G.; Speirs, M.; Van Humbeeck, J. et al

in Powder Technology (2015)

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion ... [more ▼]

The growing interest for Selective Laser Melting (SLM) in orthopedic implant manufacturing is accompanied by the introduction of novel Ti alloys, in particular β-Ti for their excellent corrosion resistance as well as favorable combination of high mechanical strength, fatigue resistance and relatively low elastic modulus. As part of the SLM process for producing quality β-Ti parts powder flowability is essential to achieve uniform thickness of powder layers. In this work the flowability of different gas atomized β-Ti, including NiTi, powders has been studied. Their rheological properties were compared to those of commercially available plasma-atomized Ti–6Al–4V powder using a newly developed semi-automatic experimental set-up. Not only the particle size, shape and size distribution of the powders display a large influence on the powder flowability but also particle surface properties such as roughness, chemical composition and the presence of liquid on the surface of the particles. It was found that plasma or gas atomization production techniques for SLM powder have a considerable effect on the particle topography. Among the powders studied regarding SLM applicability only rheological properties of the fine size fraction (25–45 μm) of Ti–45Nb didn't conform to SLM processing requirements. To improve flowability of the Ti–45Nb powder itwas annealed both in air and argon atmosphere at 600 °C during 1 h, resulting in an improved rheological behavior suitable for SLM processing. [less ▲]

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See detailLe cycle sexuel de la femelle des petits camélidés sud-américains
Hanzen, Christian ULg; Cucho Dolmos, Hernan; Ampuero Casquino, Enrique et al

E-print/Working paper (2015)

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See detailJupiter’s aurora, ultraviolet, visible and infrared views: what can we learn?
Gérard, Jean-Claude ULg

Scientific conference (2015, May 15)

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See detailMAVEN's Imaging Spectrograph and the Legacy of Charles Barth
Schneider, Nick; McClintock, W; Stewart, I et al

Scientific conference (2015, May 15)

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See detailVaricella-Zoster Virus (VZV) assemblons interplay with PML bodies
Lebrun, Marielle ULg; Thiry, Marc ULg; Sadzot, Catherine ULg

Poster (2015, May 15)

Using a virus expressing the small capsid protein fused to an eGFP tag (eGFP-ORF23 VZV), we recently identified, in the nuclei of infected cells, the presence of dynamic capsid aggegrates. Because we ... [more ▼]

Using a virus expressing the small capsid protein fused to an eGFP tag (eGFP-ORF23 VZV), we recently identified, in the nuclei of infected cells, the presence of dynamic capsid aggegrates. Because we believe that these structures might represent sites of preferential caspid assembly and by analogy with HSV-1, we referred to them as “VZV assemblons”. Structures resembling these assemblons and identified as capsids entrapped in some “PML-cages” were recently described in the nuclei of wild-type VZV infected cells (Reichelt et al., 2011). We then wonder if there was a link between these independent observations. When we infected MeWo cells in which the expression of each PML subunit is downregulated by shRNA, VZV assemblons still formed. Immunostaining of MeWo cells infected by eGFP-ORF23 VZV with an antibody against the PML protein showed that VZV assemblons only partially colocalize with PML bodies. However, overexpression of PML-I-eGFP in HEK293 cells followed by infection with a tagRFP-T-ORF23 VZV, where the ORF23 protein is fused to a red tag, showed a complete colocalization is complete. The same result was obtained with all tested PML isoforms. This suggests that the partial colocalization in normal cells could be due to the expression level of PML proteins. Altogether, these results suggest that rather than a progressive accumulation of newly formed capsids within PML cages, it is likely that PML protein is recruited to the sites where VZV assemblons develop. It correlates with the fact that the number of PML bodies decreases with the infection. Obviously, even if this phenomenon might impede the egress of a substantial amount of capsids and, in this regard, limit the infection progression, all the tested cell lines are permissive to VZV. It would then be interesting to investigate the relationship between VZV assemblons and PML bodies in latent or non permissive VZV infection models. [less ▲]

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See detailMeasurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay
Fagnard, Jean-François ULg; Kirsch, Sébastien; Morita, Mitsuru et al

in Physica C: Superconductivity (2015), 512

Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be ... [more ▼]

Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz–20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect. [less ▲]

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See detailWhy are flux avalanches deflected by a metallic layer?
Brisbois, Jérémy ULg

Conference (2015, May 15)

Sudden avalanches of magnetic flux bursting into a superconducting sample are deflected from their trajectories when they encounter a conductive layer deposited on top of the superconductor. Remarkably ... [more ▼]

Sudden avalanches of magnetic flux bursting into a superconducting sample are deflected from their trajectories when they encounter a conductive layer deposited on top of the superconductor. Remarkably, in some cases the flux is totally excluded from the area covered by the conductive layer. Even if this phenomenon has been known for a few years, there is currently no theoretical model describing it. Moreover, the question whether the deflection would also be observed for a single vortex entering the region covered by a metallic layer is still unanswered. In this work we use the magneto-optical imaging (MOI) technique, based on the Faraday effect, to show that a conductive layer (Cu) can repel flux avalanches triggered in an underlying superconducting film (Nb) (see figure). We present a simple classical model that accounts for the deflection of a single vortex and considers a magnetic monopole approaching a semi-infinite conductive plane. This model suggests the important role played in the avalanche deflection by electromagnetic braking, arising from the eddy currents induced by the moving vortex in the metal. Moreover, we have found a decrease of the vortex damping coefficient due to the metallic sheet at large vortex velocities, correcting early theoretical descriptions where a linear behaviour was proposed. [less ▲]

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See detailWhat makes the invasive Harmonia axyridis so successful? Six years of research in Gembloux provide additional answers
Fassotte, Bérénice ULg; Durieux, Delphine ULg; Vandereycken, Axel ULg et al

Conference (2015, May 14)

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been ... [more ▼]

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been involved in the characterization of the behavioral traits making this lady beetle species so successful. The main conclusions of two PhD works will be shortly presented: (1) Through a six-year inventory performed in Belgian agroecosystems, we have demonstrated that H. axyridis has become well established and was among the most abundant aphidophagous predatory species, causing a severe depression of biodiversity, even if communities of aphid predators are still quite diversified. (2) The social issues associated with the establishment of overwintering aggregations in human constructions were also carefully investigated. We have demonstrated the importance of social interactions on the establishment and cohesion of the aggregates. Finally, we have demonstrated that the deposition of a set of saturated and non-saturated hydrocarbons on the surfaces where the lady beetles were settling on, allowed their conspecifics to follow their markings and join the group. [less ▲]

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See detailChristianisme et paideia dans l'Égypte byzatine : l'apport des papyrus scolaires grecs à contenu composite profane et chrétien (fin du IIIe-début du VIIIe s.)
Carlig, Nathan ULg

Conference (2015, May 14)

Documentée par des milliers de papyrus, restes de livres ou de documents, dont les plus anciens remontent à la fin du IIe siècle de notre ère, la christianisation de l’Égypte a profondément modifié le ... [more ▼]

Documentée par des milliers de papyrus, restes de livres ou de documents, dont les plus anciens remontent à la fin du IIe siècle de notre ère, la christianisation de l’Égypte a profondément modifié le rapport des populations à la paideia hellénique, sans pour autant se substituer à elle. L’examen du matériau, de la forme, de la mise en page, du contenu, ainsi que de la provenance des papyrus scolaires grecs à contenu composite profane et chrétien (fin IIIe – 1e moitié VIIIe s.), permettra d'illustrer cette problématique en relevant les continuités et les ruptures dans les stratégies d'enseignement par rapport à la paideia de tradition hellénique. [less ▲]

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See detailMasculinités et migrations chinoises
Florence, Eric ULg

in La vie des idées.fr (2015)

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See detailAuroral emissions at Jupiter and Saturn, at the crossroads of Astrophysics Geophysics and Plasma Physics
Grodent, Denis ULg

Conference (2015, May 13)

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow ... [more ▼]

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow rotating pulsars. For these two planets, there is a direct link between this pulsar-like behaviour and the auroral processes that are taking place in their atmosphere. We will take the example of Jupiter to illustrate haw the aurora is generated in the magnetosphere as a result of the volcanic activity of the moon Io. [less ▲]

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