Macromolecular engineering of CO2-philic (co)polymers through RAFT/MADIX polymerization

Cette thèse s'inscrit dans le cadre de la recherche sur l'utilisation du dioxyde de carbone supercritique comme alternative aux solvants organiques usuels. Afin de proposer de nouveaux tensioactifs macromoléculaires stabilisants d'émulsions inverses eau/dioxyde de carbone, le travail s'est porté sur la recherche et l'étude de familles originales de (co)polymères CO2-philes et de nouveaux copolymères à blocs amphiphiles. Les résultats présentés dans ce manuscrit de thèse incluent la synthèse, la caractérisation et les études des propriétés de ces (co)polymères, en particulier, leur solubilité dans le CO2 supercritique. La structure et la composition de ces macromolécules ont été variées en s'appuyant sur la polymérisation RAFT/MADIX de monomères CO2-philes tels que l'acétate de vinyle, les esters vinyliques fluorés et les oléfines fluorées. L'influence des paramètres macromoléculaires des copolymères CO2-philes et amphiphiles sur leur solubilité, dont la longueur de chaîne, le groupe terminal et la balance hydrophile/CO2-phile, a ensuite été étudiée par spectroscopie infrarouge et par des mesures de points de troubles, afin d'établir des relations structure-propriété.The work presented in this manuscript describes the development of original families of CO2-philic (co)polymers in a context of an increasing promotion of green solvents such as supercritical carbon dioxide. In this respect, innovative amphiphilic block copolymers which may act as macromolecular surfactants for water/carbon dioxide emulsions are also studied. This thesis encompasses the synthesis, the characterization and the property studies of such (co)polymers, with a particular emphasis on their solubility in supercritical CO2. Building on RAFT/MADIX polymerization, the structure and the composition of these macromolecules were varied using vinyl acetate, fluorinated vinyl esters and fluorinated olefins as CO2-philic monomers. The influence of macromolecular characteristics of CO2-philic and amphiphilic copolymers including chain length, chain end group and CO2-phobic/CO2-philic balance on their solubility was then studied through infrared spectroscopy and cloud point measurements, in order to draw structure-property relationships

DUAL-ANNULAR SLOT PHASE-SHIFTING CELL LOADED WITH MEMS SWITCHES FOR RECONFIGURABLE REFLECTARRAYS

International audienceReconfigurable reflectarrays require low-loss and lowdispersion active cells in order to achieve efficient beam scanning or beam shaping on a large bandwidth. The low-loss constraint is the more stringent as the introduction of tunable components (such as MEMS) in resonant phase-shifting cells may dramatically decrease their quality factor. In this paper, a comprehensive review of recent developments at IETR and TAS is carried out with the objective to dynamically control complementary resonant modes in a reconfigurable phase-shifting cell. The new topology consists of a dualannular slot loaded with 8 MEMS switches. It operates around 12 GHz and can provide four equidistributed phase states with low dispersion and low losses

A Patch-Slot Combination Approach for Large Band Reflectarrays

International audienceThis paper presents a new passive phase-shifting cell for reflectarray. It permits to loop back to its initial state after a whole theoretically 360° phase cycle. After optimization, a nearly 360° phase range is provided with a frequency dispersion less than 45°/GHz over a nearly 57% bandwidth. A complete analysis of the cycle is given supported with an equivalent electrical circuit

Phase-Shifting Cell for Dual Linearly Polarized Reflectarrays With Reconfigurable Potentialities

International audienceThis letter presents a new phase-shifting cell topology for dual linearly polarized reflectarrays. It consists of two orthogonal sets of straight slots etched in a metallic plane and loaded with four capacitances in order to control the phase of the reflected wave. Measurements have demonstrated that the convenient capacitive loading of the central slots permits to provide 331 ° of phase range at 12.5 GHz with linear and parallel dispersions for the different phase states

Assessing Wind Impact on Semi-Autonomous Drone Landings for In-Contact Power Line Inspection

In recent years, the use of inspection drones has become increasingly popular for high-voltage electric cable inspections due to their efficiency, cost-effectiveness, and ability to access hard-to-reach areas. However, safely landing drones on power lines, especially under windy conditions, remains a significant challenge. This study introduces a semi-autonomous control scheme for landing on an electrical line with the NADILE drone (an experimental drone based on original LineDrone key features for inspection of power lines) and assesses the operating envelope under various wind conditions. A Monte Carlo method is employed to analyze the success probability of landing given initial drone states. The performance of the system is evaluated for two landing strategies, variously controllers parameters and four level of wind intensities. The results show that a two-stage landing strategies offers higher probabilities of landing success and give insight regarding the best controller parameters and the maximum wind level for which the system is robust. Lastly, an experimental demonstration of the system landing autonomously on a power line is presented

Scan-Chain Intra-Cell Aware Testing

This paper first presents an evaluation of the effectiveness of different test pattern sets in terms of ability to detect possible intra-cell defects affecting the scan flip-flops. The analysis is then used to develop an effective test solution to improve the overall test quality. As a major result, the paper demonstrates that by combining test vectors generated by a commercial ATPG to detect stuck-at and delay faults, plus a fragment of extra test patterns generated to specifically target the escaped defects, we can obtain a higher intra-cell defect coverage (i.e., 6.46% on average) and a shorter test time (i.e., 42.20% on average) than by straightforwardly using an ATPG which directly targets these defects

Regulation of reinforcement learning parameters captures long-term changes in rat behaviour

In uncertain environments in which resources fluctuate continuously, animals must permanently decide whether to stabilise learning and exploit what they currently believe to be their best option, or instead explore potential alternatives and learn fast from new observations. While such a trade-off has been extensively studied in pretrained animals facing non-stationary decision-making tasks, it is yet unknown how they progressively tune it while learning the task structure during pretraining. Here, we compared the ability of different computational models to account for long-term changes in the behaviour of 24 rats while they learned to choose a rewarded lever in a three-armed bandit task across 24 days of pretraining. We found that the day-by-day evolution of rat performance and win-shift tendency revealed a progressive stabilisation of the way they regulated reinforcement learning parameters. We successfully captured these behavioural adaptations using a meta-learning model in which either the learning rate or the inverse temperature was controlled by the average reward rate

Immunomodulatory effects of Amblyomma variegatum saliva on bovine cells: Characterization of cellular responses and identification of molecular determinants

The tropical bont tick, Amblyomma variegatum, is a tick species of veterinary importance and is considered as one of major pest of ruminants in Africa and in the Caribbean. It causes direct skin lesions, transmits heartwater, and reactivates bovine dermatophilosis. Tick saliva is reported to affect overall host responses through immunomodulatory and anti-inflammatory molecules, among other bioactive molecules. The general objective of this study was to better understand the role of saliva in interaction between the Amblyomma tick and the host using cellular biology approaches and proteomics, and to discuss its impact on disease transmission and/or activation. We first focused on the immuno-modulating effects of semi-fed A. variegatum female saliva on bovine peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages in vitro. We analyzed its immuno-suppressive properties by measuring the effect of saliva on PBMC proliferation, and observed a significant decrease in ConA-stimulated PBMC lymphoproliferation. We then studied the effect of saliva on bovine macrophages using flow cytometry to analyze the expression of MHC-II and co-stimulation molecules (CD40, CD80, and CD86) and by measuring the production of nitric oxide (NO) and pro- or anti-inflammatory cytokines. We observed a significant decrease in the expression of MHC-II, CD40, and CD80 molecules, associated with decreased levels of IL-12-p40 and TNF-α and increased level of IL-10, which could explain the saliva-induced modulation of NO. To elucidate these immunomodulatory effects, crude saliva proteins were analyzed using proteomics with an Orbitrap Elite mass spectrometer. Among the 336 proteins identified in A. variegatum saliva, we evidenced bioactive molecules exhibiting anti-inflammatory, immuno-modulatory, and anti-oxidant properties (e.g., serpins, phospholipases A2, heme lipoprotein). We also characterized an intriguing ubiquitination complex that could be involved in saliva-induced immune modulation of the host. We propose a model for the interaction between A. variegatum saliva and host immune cells that could have an effect during tick feeding by favoring pathogen dissemination or activation by reducing the efficiency of host immune response to the corresponding tick-borne diseases. (Résumé d'auteur