Stabilité thermique de la couche active d’une cellule solaire organique par réticulation

Date du colloque : 11/2012</p

UV activation of polymeric high aspect ratio microstructures: Ramifications in antibody surface loading for circulating tumor cell selection

The need to activate thermoplastic surfaces using robust and efficient methods has been driven by the fact that replication techniques can be used to produce microfluidic devices in a high production mode and at low cost, making polymer microfluidics invaluable for in vitro diagnostics, such as circulating tumor cell (CTC) analysis, where device disposability is critical to mitigate artifacts associated with sample carryover. Modifying the surface chemistry of thermoplastic devices through activation techniques can be used to increase the wettability of the surface or to produce functional scaffolds to allow for the covalent attachment of biologics, such as antibodies for CTC recognition. Extensive surface characterization tools were used to investigate UV activation of various surfaces to produce uniform and high surface coverage of functional groups, such as carboxylic acids in microchannels of different aspect ratios. We found that the efficiency of the UV activation process is highly dependent on the microchannel aspect ratio and the identity of the thermoplastic substrate. Colorimetric assays and fluorescence imaging of UV-activated microchannels following EDC/NHS coupling of Cy3-labeled oligonucleotides indicated that UV-activation of a PMMA microchannel with an aspect ratio of ???3 was significantly less efficient toward the bottom of the channel compared to the upper sections. This effect was a consequence of the bulk polymer&apos;s damping of the modifying UV radiation due to absorption artifacts. In contrast, this effect was less pronounced for COC. Moreover, we observed that after thermal fusion bonding of the device&apos;s cover plate to the substrate, many of the generated functional groups buried into the bulk rendering them inaccessible. The propensity of this surface reorganization was found to be higher for PMMA compared to COC. As an example of the effects of material and microchannel aspect ratios on device functionality, thermoplastic devices for the selection of CTCs from whole blood were evaluated, which required the immobilization of monoclonal antibodies to channel walls. From our results, we concluded the CTC yield and purity of isolated CTCs were dependent on the substrate material with COC producing the highest clinical yields for CTCs as well as better purities compared to PMMA.close9

Atlas of marine bony fish otoliths (Sagittae) of Southeastern - Southern Brazil Part I: Gadiformes (Macrouridae, Moridae, Bregmacerotidae, Phycidae and Merlucciidae); Part II: Perciformes (Carangidae, Sciaenidae, Scombridae and Serranidae)

The drawings, detailed pictures, precise descriptions and measurements that characterize otoliths must be made available for studies in various areas, including taxonomy, phylogeny, ecology, fisheries, paleontology, diversity, predator-prey relationships and modeling. The Collection of Teleostei Fish Otoliths of Southeastern-Southern Brazil (COSS-Brasil) of IOUSP contains 45,000 pairs of otoliths from 210 species. This publication is the first in a series that will constitute an atlas of Teleostei otoliths for southeastern-southern Brazil and presents the results of the morphologic and morphometric analyses of 11 Gadiformes and 36 Perciformes species by means of the most commonly used features, measurements and indices. Three otoliths of each species were illustrated and photographed whenever possible. The frequency of occurrence was calculated for each characteristic by total length classes (TL), and the ontogenetic differences were analyzed (multiple χ2 test; significance 0.05). Morphometric analyses were conducted for each characteristic per total length (TL) class and for the whole sample, and the ontogenetic differences were analyzed

Structural modifications of polymers under the impact of fast neutrons

International audienceFast neutron irradiations were performed at room temperature on a series of 13 polymer matrixes having great practical and academic interest. Polymers were irradiated with very low doses of 14 MeV neutrons deposited at reduced dose rate. The modifications of chemical structure of the polymeric matrixes resulting from irradiation were analyzed at the molecular scale by infrared and UV-visible spectroscopy. Particular attention was given to the oxidation occurring in irradiated matrixes during storage in the absence of light at room temperature. In addition the effects of irradiation on the chain arrangements in the polymers were analyzed by Differential Scanning Calorimetry. The most significant result obtained in this preliminary work was evidence that neutron irradiation with very low doses in the range ≈130-320 cGy could provoke structural changes. Indeed, depending on the matrixes, the formation of oxidation products along the macromolecular chains or the evolution of the polymer architecture, evidenced by changes of the Tg or of the crystallinity, was observed. The perspectives of this preliminary work are discussed

Influence of the chemical structure of polycarbonates on the contribution of crosslinking and chain scissions to the photothermal ageing

International audienceThe relative importance of crosslinking and chain scissions reactions involved in the photothermal ageing of polycarbonates is shown to depend on the chemical structure of the polymer. The orientation of these reactions is linked to the modifications of the chemical structure resulting from photolysis, photooxidation and thermooxidation. In this paper, the effects of crosslinking and chain scission of tetramethyl bisphenol-A polycarbonate (TMPC) are determined by size exclusion chromatography (SEC) and gel fraction measurements. These evolutions are correlated to the modifications of the chemical structure observed by FTIR spectroscopy.The presence of the four ortho-methyl substituants on the aromatic rings accounts for the difference in the photothermal ageing of TMPC compared to bisphenol-A polycarbonate (PC). Tetramethyl substitution inhibits photo-Fries rearrangements in TMPC, but in contrast these methyl groups involve crosslinks under irradiation and are the source of a higher oxidizability of TMPC compared to PC. A proposal for the various routes accounting for the crosslinking and the formation of the oxidation products in TMPC is reported in this paper