Nanocomposites with shape memory behavior based on a segmented polyurethane and magnetic nanostructures

Shape-memory composites based on a commercial segmented polyurethane and magnetite (Fe⁠3O⁠4) nanoparticles(NPs) were prepared by a simple suspension casting method. The properties of the resulting nanocomposites,containing 1 to 10 nominal wt.% magnetic particles, were evaluated by thermogravimetric tests, contact anglemeasurements, differential scanning calorimetry, infrared and X-ray spectroscopy, static and thermal cyclic tensiletests, dynamic mechanical analysis and experiments of alternating-magnetic-field heating. It was found thatmost of the suspended NPs could be successfully incorporated into the polyurethane matrix, and thus compositesamples with up to 7 wt.% actual concentration were obtained. On the other hand, the incorporation of magnetitenanoparticles to the shape memory polyurethane did not significantly affect most of the matrix properties,including its shape memory behavior, while added magnetic response to the nanocomposites. Thus, nanocompositeswere able to increase their temperature when exposed to an alternating magnetic field, which allowedthem to recover their original shape quickly by an indirect triggering method.Fil: Soto, Guillermo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Meiorin, Cintia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Actis, Daniel Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Mendoza Zélis, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Mosiewicki, Mirna Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Marcovich, Norma Esther. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Disruption of Hydrogen Bonds between Major Histocompatibility Complex Class II and the Peptide N-Terminus Is Not Sufficient to Form a Human Leukocyte Antigen-DM Receptive State of Major Histocompatibility Complex Class II

Peptide presentation by MHC class II is of critical importance to the function of CD4+ T cells. HLA-DM resides in the endosomal pathway and edits the peptide repertoire of newly synthesized MHC class II molecules before they are exported to the cell surface. HLA-DM ensures MHC class II molecules bind high affinity peptides by targeting unstable MHC class II:peptide complexes for peptide exchange. Research over the past decade has implicated the peptide N-terminus in modulating the ability of HLA-DM to target a given MHC class II:peptide combination. In particular, attention has been focused on both the hydrogen bonds between MHC class II and peptide, and the occupancy of the P1 anchor pocket. We sought to solve the crystal structure of a HLA-DR1 molecule containing a truncated hemagglutinin peptide missing three N-terminal residues compared to the full-length sequence (residues 306–318) to determine the nature of the MHC class II:peptide species that binds HLA-DM. Here we present structural evidence that HLA-DR1 that is loaded with a peptide truncated to the P1 anchor residue such that it cannot make select hydrogen bonds with the peptide N-terminus, adopts the same conformation as molecules loaded with full-length peptide. HLA-DR1:peptide combinations that were unable to engage up to four key hydrogen bonds were also unable to bind HLA-DM, while those truncated to the P2 residue bound well. These results indicate that the conformational changes in MHC class II molecules that are recognized by HLA-DM occur after disengagement of the P1 anchor residue

Analysis of radiopacity, pH and cytotoxicity of a new bioceramic material

AbstractObjective RetroMTA® is a new hydraulic bioceramic indicated for pulp capping, perforations or root resorption repair, apexification and apical surgery. The aim of this study was to compare the radiopacity, pH variation and cytotoxicity of this material to ProRoot® MTA.Material and Methods Mixed cements were exposed to a digital x-ray along with an aluminum stepwedge for the radiopacity assay. pH values were verified after incubation period of 3, 24, 48, 72 and 168 hours. The cytotoxicity of each cement was tested on human periodontal ligament fibroblasts using a multiparametric assay. Data analysis was performed using ANOVA and Tukey’spost hoc in GraphPad Prism.Results ProRoot® MTA had higher radiopacity than RetroMTA®(p;0.05) although pH levels of both materials reduced over time. Both ProRoot® MTA and RetroMTA® allowed for significantly higher cell viability when compared with the positive control (

Le rôle social des bibliothèques dans la ville

Organisé, avec le soutien de l’ABF, par l’Ecla Aquitaine, la ville de Floirac et le pôle des Métiers du livre de l’IUT Michel-de-Montaigne de Bordeaux, ce colloque a démontré avec succès l’intérêt toujours soutenu manifesté pour ce sujet à l’urgence grandissante

La responsabilité de l’avenir

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Le patrimoine bien modéré

Depuis leur apparition sur les réseaux Internet, les listes de discussion professionnelles ont facilité les échanges entre spécialistes et largement contribué à les aider dans l’exercice de leur métier. Entretien – en forme de coup de chapeau – avec la modératrice de la liste des bibliothécaires chargés du patrimoine

Classe Patrimoine

Jouer le Patrimoine, c’est inscrire la bibliothèque dans un parcours complet qui, du passé au présent, de l’école aux archives, du local à l’universel, inscrit le jeune public dans un espace élargi. Reconnaissance, fréquentation, transversalité, communication : un résultat gagnant-gagnant. À Viroflay comme à Saint- Deni

Pour un patrimoine électif

Récente et confuse, la notion de patrimoine recouvre – contradictoirement ? – une réalité et une exigence. Non content de lui demander d’embrasser la mémoire du passé, on lui demande encore de construire celle de l’avenir. Comment tant embrasser sans mal étreindre