Étude des propriétés dynamiques de mélanges d'elastomère chargés en relation avec la nature des interactions polymère-charge

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

MOTION OF ACTIVE FLUIDS: DIFFUSION DYNAMICS OF CYANOBACTERIA

Cyanobacteria are photosynthetic micro-organisms colonizing all aquatic and terrestrial environments. The motility of such living micro-organisms should make their diffusion distinct from typical Brownian motion. This diffusion can be investigated in terms of global behavior (Fickian or not) and in terms of displacement probabilities, which provide more detail about the motility process. Using cyanobacterium Synechocystis sp. PCC 6803 as the model micro-organism, we carry out time-lapse video microscopy to track and analyze the bacteria\u27s trajectories, from which we compute the mean squared displacement (MSD) and the distribution function of displacement probabilities. We find that the motility of Synechocystis sp. PCC 6803 is intermittent: high-motility run phases are separated by low motility tumble phases corresponding to trapped states. However, this intermittent motility leads to a Fickian diffusive behavior, as shown by the evolution of the MSD with time

Fabrication of ZnO micro- and nano-structures by electrodeposition using nanoporous and lithography defined templates

International audienceWereport in this work the fabrication of ZnO nanowires and nano-pillars by electrodeposition using three types of micro- and nano-structured templates. First, ZnO nanowires were synthesized in a nanoporous polycarbonate template and their morphology and monocrystalline structure were checked by conventional transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) techniques. The optical properties of the monocrystalline ZnO nanowires were also studied by measuring the photo-fluorescence spectra of the sample. Then, the micro-structured template was made by optical lithography and the electrodeposited ZnO micro-rods were analysed by scanning electron microscopy (SEM) imaging and X-ray diffraction (XRD). Finally, UV-nanoimprint templates were used for the fabrication of regular ZnO nano-pillar array. SEM images showed quite homogenous ZnO nano-pillar array on which the collective I–V characteristic has been carried out in order to determine the nature of the Au/ZnO contact. SEM images also revealed an effect of size increase of the ZnO microrods and nano-pillars with respect to that of the PMMA template. XRD patterns showed the hexagonal Wurtzite crystalline structure with cell parameters slightly larger than the literature ones