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See detailMicrophase separation at the surface of block copolymers, as studied with atomic force microscopy
Rasmont, A.; Leclère, Philippe; Doneux, C. et al

in Colloids and Surfaces B : Biointerfaces (2000), 19(4), 381-395

Atomic force microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. The simultaneous measurement of the amplitude and the phase of the oscillating ... [more ▼]

Atomic force microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. The simultaneous measurement of the amplitude and the phase of the oscillating cantilever in the tapping mode operation provides the surface topography along with the cartography of the microdomains of different mechanical properties. This technique thus allows to characterize the size and shape of those microdomains and their organization at the surface (e.g. cubic lattice spheres, hexagonal lattice of cylinders, or lamellae). In this study, a series of symmetric triblock copolymers made of a inner elastomeric sequence (poly(butadiene) or poly(alkylacrylate)) and two outer thermoplastic sequences (poly(methylmethacrylate)) is analyzed by AFM in the tapping mode. The microphase separation and their morphology are essential factors for the potential of these materials as a new class of thermoplastic elastomers. Special attention is paid to the control of the surface morphology, as observed by AFM, by the molecular structure of the copolymers (volume ratio of the sequences, molecular weight, length of the alkyl side group) and the experimental conditions used for the sample preparation. The molecular structure of the chains is completely controlled by the synthesis, which relies on the sequential living anionic polymerization of the comonomers. The copolymers are analyzed as solvent-cast films, whose characteristics depend on the solvent used and the annealing conditions. The surface arrangement of the phase-separated elastomeric and thermoplastic microdomains observed on the AFM phase images is discussed on the basis of quantitative information provided by the statistical analysis by Fourier transform and grain size distribution calculations. [less ▲]

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See detailCharacterization of porous polylactide foams by image analysis and impedance spectroscopy
Maquet, Véronique; Blacher, Silvia ULg; Pirard, René ULg et al

in Langmuir (2000), 16(26), 10463-10470

The texture of highly porous polylactide foams prepared by freeze-drying of poly-L-lactide (L-PLA) and poly-DL-lactide (DL-PLA) solutions of various concentrations was investigated by two novel ... [more ▼]

The texture of highly porous polylactide foams prepared by freeze-drying of poly-L-lactide (L-PLA) and poly-DL-lactide (DL-PLA) solutions of various concentrations was investigated by two novel methodologies, image analysis and impedance spectroscopy. Image analysis of scanning electron micrographs of transverse cross-sections at two different magnifications gave information on both the macroporosity (1 mum < width 10 <mu>m) and ultramacroporosity (width > 10 mum). Impedance spectroscopy was used to investigate the transport properties of the three-dimensional porous matrices by measurement of ionic conduction. Image analysis showed that: (a) the macroporosity, which mainly contributes to porosity, is independent of the sample composition; (b) when the concentration of the polymer solution is increased, the density of the ultramacropores decreases and their average diameter increases; (c) the distribution of the ultramacropores is more homogeneous in the semicrystalline L-PLA. foams than in the amorphous DL-PLA counterparts, in which the ultramacropores tend to make clusters. The dielectric properties changed at low frequency, in relation to modifications in the ultramacroporosity. Ultramacropores of the L-PLA foams were found to be more open and more sensitive to the concentration of the polymer solutions compared with DL-PLA. Expectedly, the mechanical properties of the PLA foams changed with the structure of the ultramacroporous network. These results encourage further investigations on the texture of porous supports, to collect pertinent information on the physical macro- and ultramacroenvironment in which cells will reside. [less ▲]

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See detailSystème de positionnement universel (GPS)
Debouche, Charles ULg

Scientific conference (2000, December 20)

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See detailCyclic esterketone compounds, processes for the synthesis thereof
Wautier, Henri; Latere, Jean-Pierre; Lecomte, Philippe ULg et al

Patent (2000)

Cyclic esterketone compounds, and in particular, 2-oxepane-1,5-dione, which are useful as a monomer for the production of polymers, and in particular for the production of poly(2-oxepane-1,5-dione ... [more ▼]

Cyclic esterketone compounds, and in particular, 2-oxepane-1,5-dione, which are useful as a monomer for the production of polymers, and in particular for the production of poly(2-oxepane-1,5-dione). Processes are also disclosed for both the synthesis of this new compound and for the use (polymerization) thereof for the preparation of poly(2-oxepane-1,5-dione). The poly(2-oxepane-1,5-dione) polymers and copolymers which are obtained by use of the polymerization processes with the monomer compounds are also disclosed. [less ▲]

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See detailCyclic esterketone compounds, processes for the synthesis thereof and process for the preparation of poly(esterketone)polymers
Wautier, Henri; Latere, Jean-Pierre; Lecomte, Philippe ULg et al

Patent (2000)

Unsubstituted oxepane-diones useful as monomers for the production of polymers, process for the synthesis thereof by oxidation of unsubstituted cyclohexanediones, process for the preparation of ... [more ▼]

Unsubstituted oxepane-diones useful as monomers for the production of polymers, process for the synthesis thereof by oxidation of unsubstituted cyclohexanediones, process for the preparation of polyesterketone polymers by polymerisation of cyclic esterketones and polyesterketone polymers so obtained. [less ▲]

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See detailPrise en charge des troubles de la mémoire dans la maladie d'Alzheimer
Adam, Stéphane ULg

Conference given outside the academic context (2000)

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See detailType Iv Collagen Induces Matrix Metalloproteinase 2 Activation in Ht1080 Fibrosarcoma Cells
Maquoi, Erik ULg; Frankenne, F.; Noël, Agnès ULg et al

in Experimental Cell Research (2000), 261(2), 348-59

Matrix metalloproteinase 2 (MMP-2) activation has been described as a "master switch" which triggers tumor spread and metastatic progression. We show here that type IV collagen, a major component of ... [more ▼]

Matrix metalloproteinase 2 (MMP-2) activation has been described as a "master switch" which triggers tumor spread and metastatic progression. We show here that type IV collagen, a major component of basement membranes, promotes MMP-2 activation by HT1080 cells. When plated on plastic, HT1080 cells constitutively processed the 66-kDa pro-MMP-2 into a 62-kDa intermediate activated form, most probably through a membrane type (MT) 1 MMP-dependent mechanism. In the presence of type IV collagen, part of this intermediate form was further processed to fully activated 59-kDa MMP-2. This activation was prevented by tissue inhibitor of MMP (TIMP)-2 and a broad-spectrum hydroxamic acid-based synthetic MMP inhibitor (GI129471). Type IV collagen-mediated pro-MMP-2 activation did not involve either a transcriptional modulation of MMP-2, MT1-MMP, or TIMP-2 expression nor any alteration of MT1-MMP protein synthesis or processing. An inverse relationship between MMP-2 activation and the concentration of secreted TIMP-2 was observed. This is consistent with our previous report that TIMP-2 degradation is probably linked to the MT1-MMP-dependent MMP-2 activation mechanism. Because invasive tumor cells must breach basement membranes at different steps of the metastatic dissemination, the ability of HT1080 cells to activate pro-MMP-2 in the presence of type IV collagen might represent a key regulatory mechanism for the acquisition of an invasive potential. [less ▲]

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See detailPeripheral Nerve Regeneration Using Bioresorbable Macroporous Polylactide Scaffolds
Maquet, Véronique; Martin, Didier ULg; Malgrange, Brigitte ULg et al

in Journal of Biomedical Materials Research, Part A (2000), 52(4), 639-51

The ability of DRG-derived neurons to survive and attach onto macroporous polylactide (PLA) foams was assessed in vitro. The foams were fabricated using a thermally induced polymer-solvent phase ... [more ▼]

The ability of DRG-derived neurons to survive and attach onto macroporous polylactide (PLA) foams was assessed in vitro. The foams were fabricated using a thermally induced polymer-solvent phase separation. Two types of pore structures, namely oriented or interconnected pores, can be produced, depending on the mechanism of phase separation, which in turn can be predicted by the thermodynamics of the polymer-solvent pair. Coating of the porous foams with polyvinylalcohol (PVA) considerably improved the wettability of the foams and allowed for cell culture. The in vitro biocompatibility of the PVA-coated supports was demonstrated by measuring cell viability and neuritogenesis. Microscopic observations of the cells seeded onto the polymer foams showed that the interconnected pore networks were more favorable to cell attachment than the anisotropic ones. The capacity of highly oriented foams to support in vivo peripheral nerve regeneration was studied in rats. A sciatic nerve gap of 5-mm length was bridged with a polymer implant showing macrotubes of 100 microm diameter. At 4 weeks postoperatively, the polymer implant was still present. It was well integrated and had restored an anatomic continuity. An abundant cell migration was observed at the outer surface of the polymer implant, but not within the macrotubes. This dense cellular microenvironment was found to be favorable for axogenesis. [less ▲]

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See detailThe Second generation in Belgium
Martiniello, Marco ULg

Scientific conference (2000, December 14)

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See detailAccréditation et agrément des laboratoires de Biologie clinique
Chapelle, Jean-Paul ULg

Conference (2000, December 12)

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See detailTraumatismes médullaires, quelles possibilités de réparation
Martin, Didier ULg

Conference (2000, December 12)

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See detailWater-soluble complexes formed by sodium poly(4-styrenesulfonate) and a poly(2-vinylpyridinium)-block-poly(ethyleneoxide) copolymer
Gohy, Jean-François; Varshney, Sunil K; Antoun, Said et al

in Macromolecules (2000), 33(25), 9298-9305

Formation of interpolyelectrolyte complexes (IPEC) between sodium poly(4-styrenesulfonate) (PSSO3Na) and a diblock copolymer consisting of a protonated poly(2-vinylpyridine) (P2VP) block and a neutral ... [more ▼]

Formation of interpolyelectrolyte complexes (IPEC) between sodium poly(4-styrenesulfonate) (PSSO3Na) and a diblock copolymer consisting of a protonated poly(2-vinylpyridine) (P2VP) block and a neutral poly(ethylene oxide) (PEO) one was investigated in water. The main experimental variables were the molecular weight (MW) of the PSSO3Na polyanion, the molar ratio of the cationic and anionic species (i.e., the stoichiometry of the complex), and the pH of the aqueous solution. It was observed that (i) the interpolyelectrolyte complexes self-assemble at least at low pH into the core of monodisperse spherical micelles surrounded by a corona of PEO blocks and possibly of uncomplexed PSSO3Na segments, (ii) their stability depends on the pH in relation to the degree of protonation of the P2VP block, whatever the MW of the PSSO3Na polyanion and the cation/anion stoichiometry, (iii) the complexes are dissociated above a critical pH and are salt-sensitive, falling apart above a critical salt concentration, and (iv) a cooperative mechanism operates, which is completely reversible. [less ▲]

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See detailAdsorption of Poly(vinylpyrrolidone)/Surfactant(s) mixtures at the silica/water interface: a calorimetric investigation
Thibaut, Anne; Misselyn-Bauduin, Anne-Marie; Broze, Guy ULg et al

in Langmuir (2000), 16(25), 9841-9849

The adsorption of binary mixtures of poly(vinylpyrrolidone) (PVP) and sodium dodecyl sulfate (SDS) and of ternary mixture of PVP, SDS, and pentaethylene glycol monodecyl ether (C10E5) onto silica has been ... [more ▼]

The adsorption of binary mixtures of poly(vinylpyrrolidone) (PVP) and sodium dodecyl sulfate (SDS) and of ternary mixture of PVP, SDS, and pentaethylene glycol monodecyl ether (C10E5) onto silica has been studied by the measurements of the adsorbed amount of PVP and the heat of adsorption. The amount of PVP adsorbed from the binary mixtures decreases as the SDS concentration is increased, whereas the enthalpy change passes through a maximum at SDS concentration of ca. 4 g/L. The chain conformation of PVP adsorbed on silica has been estimated from the adsorption data in relation to the surfactant concentration. It changes from loops and tails to trains upon increasing SDS concentration. At SDS concentrations higher than 4 g/L, a comblike conformation is observed. The adsorption of PVP/SDS/C10E5 ternary mixtures depends on the polymer concentration regime. [less ▲]

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See detailComment lire entre les lignes? Les secrets de l’interprétation
Dawans, Stéphane ULg

Conference given outside the academic context (2000)

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See detailSpecific Passive Immunity Reduces the Excretion of Glycoprotein E-Negative Bovine Herpesvirus Type 1 Vaccine Strain in Calves
Lemaire, Mylène; Hanon, E.; Schynts, Frédéric et al

in Vaccine (2000), 19(9-10), 1013-7

We investigated the excretion of either a glycoprotein E (gE)-negative bovine herpesvirus type 1 (BHV1) vaccine strain or a conventional modified-live vaccine strain in both naive and passively immunised ... [more ▼]

We investigated the excretion of either a glycoprotein E (gE)-negative bovine herpesvirus type 1 (BHV1) vaccine strain or a conventional modified-live vaccine strain in both naive and passively immunised calves. The replication of gE-negative strain was considerably reduced in the maternally immunised calves, in comparison with the non-immune calves. On the other hand, the excretion of the gE-positive conventional vaccine strain was not reduced and even seemed to be prolonged in the presence of maternal antibodies. These results suggest that BHV1 gE may play a role in virus survival in the presence of antibodies. [less ▲]

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