331 research outputs found
Quand un vocabulaire de spécialité emprunte au langage courant : le nucléaire, étude de cas
http://www.eila.univ-paris-diderot.fr/_media/recherche/clillac/ciel/cahiers/2007-2008/05bis-calberg.pdf?id=recherche%3Aclillac%3Aciel%3Acahiers%3A2007-2008&cache=cach
“One-pot” dispersion ATRP and alkyne-azide Huisgen’s 1,3-dipolar cycloaddition in supercritical carbon dioxide: towards the formation of functional microspheres
Functional polymers were successfully prepared in scCO2 by combining alkyne-azide 1,3-dipolar Huisgen’s cycloaddition and dispersion ATRP in a “one pot” process using new perfluorinated polymeric amino-based ligands that had a dual role, i.e. the complexation of the copper catalyst and the stabilization of growing particles
Atom transfer radical polymerization of MMA with a macromolecular ligand in a fluorinated solvent and in supercritical carbon dioxide
Macromolecular fluorinated ligands were prepared according to a three-step strategy that consists of the random copolymerization of heptadecafluorodecyl acrylate and 2-hydroxyethylacrylate, followed by the esterification of the pendant hydroxyl groups with acryloyl chloride and the Michael-type addition of tetraethyldiethylenetriamine onto the acrylic double bonds of the polymeric chains. These fluorinated macroligands were successfully used in the atom transfer radical polymerization of MMA catalyzed by a copper salt in a fluorinated solvent. The polymerization control was analyzed in relation to the copper salt, the initiator and the molecular weight and composition of the macroligand before being extended to the heterogeneous ATRP of MMA in scCO2
Ontoterminology: A new paradigm for terminology
International audienceToday, collaboration and the exchange of information are increasing steadily and players need to agree on the meaning of words. The first task is therefore to define the domain‟s terminology. However, terminology building remains a demanding and time-consuming task, even in specialised domains where standards already exist. While reaching a consensus on the definition of terms written in natural language remains difficult, we have observed that in specialised technical domains, experts agree on the domain conceptualisation when it is defined in a formal language. Based on this observation, we have introduced a new paradigm for terminology called ontoterminology. The main idea is to separate the linguistic dimension from the conceptual dimension of terminology and establish relationships between them. The linguistic component consists of terms (both normalised and non-normalised specialised words) linked by linguistic relationships such as hyponymy and synonymy. The term definition, written in natural-language, is considered a linguistic explanation. The conceptual component is a formal ontology whose concepts are linked by conceptual relationships like the is-a (kind of) and part-of relations. The concept definition, written in a formal language, is viewed as logical specification. An ontoterminology enables us to link these two non-isomorphic networks in a global and coherent system
Supercritical carbon dioxide as an efficient solvent for the manufacture of specialty organoclays: from lab preparation to pre-industrial production
audience: researche
Polyester layered silicate nanohybrids by controlled grafting polymerization
peer reviewedPoly( epsilon-caprolactone) (PCL) layered silicate nanohybrids were synthesized by ring opening polymerization of epsilon-caprolactone according to a well-controlled coordination-insertion mechanism. Montmorillonites were surface-modified by non functional (trimethylhexadecylammonium) and hydroxy functional alkylammonium cations, i.e., (2-hydroxyethyl) dimethylhexadecylammonium. The hydroxy functions available at the clay surface were activated into tin( II or IV) or Al(III) alkoxide initiators for lactone polymerization, thus yielding surface-grafted PCL chains. The surface-grafted PCL chains were recovered by an ionic exchange reaction with lithium chloride and they were analyzed by size exclusion chromatography. The PCL molar mass was measured as a function of the hydroxy content of the clay that was modulated by exchanging the Na cations with mixtures of non-functional and hydroxy functional ammonium cations of different compositions. Nanohybrids were also characterized by small-angle X-ray diffraction, transmission electron microscopy and thermogravimetry. The PCL molar mass and the nanocomposite morphology (i.e., exfoliation and/or intercalation) were readily tuned by the content of the hydroxy groups available at the clay surface. Surface-grafted aluminium trialkoxide species proved highly efficient in initiating polymerization that leads to PCL chains of controlled molar mass and narrow molecular weight distribution with polydispersity indices as low as 1.2
Silica-based ionogels as a promising solution for all-solid-state Lithium-ion microbatteries
The emerging market of the Internet of Things, smart objects, wearables and others increases the demand for micro energy sources. Rechargeable lithium-ion batteries are a well-known technology for energy storage. However, safety issues and high production costs constrain progress. Electrolyte solutions based on ionic liquids (ILs) with dissolved lithium salts can be confined into inorganic porous networks forming so-called ionogels, which are investigated as solid electrolytes. Ionogels combine low hazard and good ionic conductivity. However, the growth of lithium dendrites may be observed during cycling, which reduce battery lifetime. In this project, we try to prepare a silica-ionogel to prevent dendritic growth by mechanical hindrance. The ionogel composition was studied to obtain a fast gelation and the correlation between the physical properties of the silica matrix and the electrochemical performances of the ionogel was evaluated
Supernovae observations and cosmic topology
Two fundamental questions regarding our description of the Universe concern
the geometry and topology of its 3-dimensional space. While geometry is a local
characteristic that gives the intrinsic curvature, topology is a global feature
that characterizes the shape and size of the 3-space. The geometry constrains,
but does not dictate the the spatial topology. We show that, besides
determining the spatial geometry, the knowledge of the spatial topology allows
to place tight constraints on the density parameters associated with dark
matter () and dark energy (). By using the
Poincar\'e dodecahedral space as the observable spatial topology, we reanalyze
the current type Ia supenovae (SNe Ia) constraints on the density parametric
space . From this SNe Ia plus cosmic topology
analysis, we found best fit values for the density parameters, which are in
agreement with a number of independent cosmological observations.Comment: 5 pages, 2 figures. Minor changes and a ref. added. To appear in A&A
(2006
Characterization of the porous structure of biodegradable scaffolds obtained with supercritical CO2 as foaming agent
Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed under a high CO2 saturation pressure (higher than 250 bars)
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