Preliminary design of the wavefront sensor for CCAT

CCAT1 is a submillimeter telescope currently under development that will be located at an altitude of 5600 meters in the Andes mountains of northern Chile. The atmospheric transmission at this site will allow CCAT to achieve high sensitivity over a wide field of view and a broad wavelength range to provide an unprecedented capability for deep, large area multicolor submillimeter surveys. In order to achieve high aperture efficiencies out to frequencies of ~ 1 THz, the 162 individual panels that form the 25 meter aperture of CCAT must be aligned to a tolerance of a few microns rms. The design of a wavefront sensor to achieve this goal is presented

Preliminary design of the wavefront front sensor for CCAT

CCAT is a submillimeter telescope currently under development that will be located at an altitude of 5600 meters in the Andes mountains of northern Chile. The atmospheric transmission at this site will allow CCAT to achieve high sensitivity over a wide field of view and a broad wavelength range to provide an unprecedented capability for deep, large area multicolor submillimeter surveys. In order to achieve high aperture efficiencies out to frequencies of ~ 1 THz, the 162 individual panels that form the 25 meter aperture of CCAT must be aligned to a tolerance of a few microns rms. The design of a wavefront sensor to achieve this goal is presented

Hydrogels physiques et chimiques à propriétés amphiphiles à base de polysaccharides aux échelles nano et microscopiques

La synthèse et la caractérisation d hydrogels amphiphiles à base de carboxyméthylpullulane et d un agent réticulent hydrophobe, le dibromohexane, ont fait l objet de ce travail. La cinétique de gélification est rapide et chaque dibromohexane donne un lien de réticulation. Ces hydrogels possèdent deux fractions : une fraction gel et une fraction sol dont les proportions varient avec les paramètres de synthèse. Ces systèmes présentent un caractère métastable en étant très sensibles au temps et à la température pour donner des objets dont les tailles varient de quelques nanomètres à quelques microns. Leur structure est complexe et provient de la création de liens chimiques (irréversibles) mais aussi d associations hydrophobes (réversibles). Une étude préliminaire de séquestration de colorants hydrophobes montre un potentiel intéressant.The aim of this work is the synthesis and the characterization of amphiphilic hydrogels based on carboxymethylpullulan and on a hydrophobic cross-linking agent : the dibromohexan. The kinetics of gelification is fast and every incorporated dibromohexan molecule gives a cross-link. These hydrogels possess two fractions : a gel fraction and a sol fraction whose proportions vary with the synthesis parameters. These systems present a metastable character and are very sensitive to time and temperature to give objects with a size from some nanometers to some micrometers. Their structure is complex and is constituted from chemical crosslinks (irreversible) and hydrophobic associations (reversible). The preliminary study of the entrapment of hydrophobic dyes shows an interesting potential.ROUEN-BU Sciences (764512102) / SudocSudocFranceF

Investigation of an Organogel by Micro-Differential Scanning Calorimetry: Quantitative Relationship between the Shapes of the Thermograms and the Phase Diagram

International audienceThe phase diagrams of organogels are necessary for applications and fundamental aspects, for instance to understand their thermodynamics. Differential scanning calorimetry is one of the techniques implemented to map these diagrams. The thermograms of organogels upon heating show broad endotherms, increasing gradually to a maximum, at a temperature Tmax, and decreasing back to the baseline, sometimes 10 °C above. This broadening can lead to uncertainty in determining the molar enthalpies and the melting temperatures Tm of the gels. Herein, we have measured the thermograms of the 12-hydroxystearic acid/nitrobenzene gels for weight fractions ranging from 0.0015 to 0.04. Compared with transition temperatures measured by other techniques, the inflection points of the thermograms provide a measurement of Tm with less bias than Tmax. The phase diagram explains why the molar melting enthalpies derived from the thermograms for samples of low concentration are lower than expected. The shapes of the heat flows below the peak correlate quantitatively with the diagrams: after suitable correction and normalization, the integral curves superimpose with the phase diagram in their ascending branch and reach a plateau when the gel is fully melted. The shape of the thermograms upon cooling is also qualitatively explained within the frame of the diagrams

New Polysaccharide-based Microparticles Crosslinked with Siloxane: Interactions with Biologically Active Substances

International audienceThe interaction of microparticles of carboxymethyl pullulan crosslinked with siloxane (provided by a new crosslinking agent: 3-(glycid oxypropyl) trimethoxysilane) with biologically active molecules, such as enzymes (lysozyme) and drugs (propranolol, quinidine) was studied. The anionic amphiphilic supports retained through electrostatic and/or hydrophobic forces, variable amounts of the substances as a function of their structure, such as crosslinking degree and amount of uncrosslinked alkylsilane chains. The absorption of lysozyme on the supports followed the Langmuir isotherm, which allowed the calculation of constants k1 and k2. Both retention and in vitro release behavior of these support potential applications in controlled drug release as well as immobilization and purification of enzymes

Self-organization of Water Soluble and Amphiphile Crosslinked Carboxymethylpullulan

International audienceThe soluble state of amphiphile and crosslinked derivatives of carboxymethylpullulan was investigated by physicochemical analyses. This soluble state also called infinite sol was obtained from hydrogels after a short-time temperature treatment. The analyses show a large distribution in size for the species in solution (from some nanometers to some micrometers). Furthermore, they also reveal the presence of hydrophobic associations (intra and/or intermolecular) in addition to the chemical links. The nature of these hydrophobic interactions will depend on the polymer concentration and on the solvent used