Site-controlled quantum dots integrated with photonic crystal waveguides and cavities

Quantum mechanics did not only deeply transform our world view down to a philosophical level, it is also expected to be key ingredient of future so-called quantum technologies. Indeed, quantum properties of matter such as isolated single particles or entanglement, can provide a technological resource for faster computers or perfectly secure communication protocols. In this new paradigm, arbitrary quantum states of light and matter would be deterministically controlled to perform operations that are not feasible in the realm of classical physics. A promising platform proposed for quantum technologies consists of quantum dots (QD) embedded in photonic crystal (PhC) circuits. While QDs exhibit high oscillator strengths, and are a promising solution as single photon sources, PhCs represent an ideal platform for light processing due to their capacity to enhance light-matter interactions. However, most previous experiments relied on self-assembled QDs nucleating at random position, which prevents their scaling to larger systems with multiple QDs. The subject of this thesis is the study of site-controlled quantum dots and their interaction with photonic crystal systems made of cavities and waveguides. A first challenge lies in the free propagation of light in simple PhC waveguides. Elongated PhC cavities were first harnessed to measure the mode reflectivity at the edge of the linear cavities, and the propagation losses in PhC waveguides. The impact of disorder on the density of states, mode localization and dispersion in long linear PhC cavities was then investigated. The direct imaging of the modes permitted to identify localized modes. A statistical analysis of the measured group index clarified the boundary between the diffusive and dispersive regime. The site-control of the QDs permitted the in-situ probing of the the local density of states, from which the weak field distortions in the dispersive regime were analyzed. In a second part, the integration of five site controlled QDs in a PhC waveguide is demonstrated together with the corresponding on-chip single photon transfer over macroscopic distances. The efficiency of coupling QDs to waveguides in these structures is measured while taking into account the statistical variations of the QDs intrinsic properties. Broad fluctuations of the coupling efficiencies were observed and attributed to the formation of Fabry-Pérot modes in the waveguides. An optimal design to reach reproducibly a broadband high efficiency of coupling is then proposed. The final part focuses on a system in which a QD is embedded in a cavity, itself coupled to a PhC waveguide. First, a design for coupling light out of plane from a PhC waveguide with reduced back-reflection in the waveguide is presented. This coupler is then used for collecting light from the QD-cavity-waveguide system. The existence of a cavity to waveguide coupling which optimizes the coupling efficiency of single photons to the waveguide is then shown theoretically. The parameters controlling the coupling between the QD cavity and waveguide are measured, from which we infer a single photon collection efficiency close to its optimal value. This work represents the first experimental implementation of site-controlled QDs in PhC circuits beyond simple cavities. It focuses on the limitations and possibilities opened by such QD systems as on-chip efficient single photon sources, useful for on-chip quantum circuits

SIV(SM)/HIV-2 Vpx proteins promote retroviral escape from a proteasome-dependent restriction pathway present in human dendritic cells

BACKGROUND: Vpx is a non-structural protein coded by members of the SIV(SM)/HIV-2 lineage that is believed to have originated by duplication of the common vpr gene present in primate lentiviruses. Vpx is incorporated into virion particles and is thus present during the early steps of viral infection, where it is thought to drive nuclear import of viral nucleoprotein complexes. We have previously shown that Vpx is required for SIV(MAC)-derived lentiviral vectors (LVs) infection of human monocyte-derived dendritic cells (DCs). However, since the requirement for Vpx is specific for DCs and not for other non-dividing cell types, this suggests that Vpx may play a role other than nuclear import. RESULTS: Here, we show that the function of Vpx in the infection of DCs is conserved exclusively within the SIV(SM)/HIV-2 lineage. At a molecular level, Vpx acts by promoting the accumulation of full length viral DNA. Furthermore, when supplied in target cells prior to infection, Vpx exerts a similar effect following infection of DCs with retroviruses as divergent as primate and feline lentiviruses and gammaretroviruses. Lastly, the effect of Vpx overlaps with that of the proteasome inhibitor MG132 in DCs. CONCLUSION: Overall, our results support the notion that Vpx modifies the intracellular milieu of target DCs to facilitate lentiviral infection. The data suggest that this is achieved by promoting viral escape from a proteasome-dependent pathway especially detrimental to viral infection in DCs

Community structure of woody plants on islands along a bioclimatic gradient

Peer reviewe

Global Island Monitoring Scheme (GIMS) : a proposal for the long-term coordinated survey and monitoring of native island forest biota

Islands harbour evolutionary and ecologically unique biota, which are currently disproportionately threatened by a multitude of anthropogenic factors, including habitat loss, invasive species and climate change. Native forests on oceanic islands are important refugia for endemic species, many of which are rare and highly threatened. Long-term monitoring schemes for those biota and ecosystems are urgently needed: (i) to provide quantitative baselines for detecting changes within island ecosystems, (ii) to evaluate the effectiveness of conservation and management actions, and (iii) to identify general ecological patterns and processes using multiple island systems as repeated 'natural experiments'. In this contribution, we call for a Global Island Monitoring Scheme (GIMS) for monitoring the remaining native island forests, using bryophytes, vascular plants, selected groups of arthropods and vertebrates as model taxa. As a basis for the GIMS, we also present new, optimized monitoring protocols for bryophytes and arthropods that were developed based on former standardized inventory protocols. Effective inventorying and monitoring of native island forests will require: (i) permanent plots covering diverse ecological gradients (e.g. elevation, age of terrain, anthropogenic disturbance); (ii) a multiple-taxa approach that is based on standardized and replicable protocols; (iii) a common set of indicator taxa and community properties that are indicative of native island forests' welfare, building on, and harmonized with existing sampling and monitoring efforts; (iv) capacity building and training of local researchers, collaboration and continuous dialogue with local stakeholders; and (v) long-term commitment by funding agencies to maintain a global network of native island forest monitoring plots.Peer reviewe

The CEP5 Peptide Promotes Abiotic Stress Tolerance, As Revealed by Quantitative Proteomics, and Attenuates the AUX/IAA Equilibrium in Arabidopsis.

Peptides derived from non-functional precursors play important roles in various developmental processes, but also in (a)biotic stress signaling. Our (phospho)proteome-wide analyses of C-TERMINALLY ENCODED PEPTIDE 5 (CEP5)-mediated changes revealed an impact on abiotic stress-related processes. Drought has a dramatic impact on plant growth, development and reproduction, and the plant hormone auxin plays a role in drought responses. Our genetic, physiological, biochemical, and pharmacological results demonstrated that CEP5-mediated signaling is relevant for osmotic and drought stress tolerance in Arabidopsis, and that CEP5 specifically counteracts auxin effects. Specifically, we found that CEP5 signaling stabilizes AUX/IAA transcriptional repressors, suggesting the existence of a novel peptide-dependent control mechanism that tunes auxin signaling. These observations align with the recently described role of AUX/IAAs in stress tolerance and provide a novel role for CEP5 in osmotic and drought stress tolerance

GENERATION, CARACTERISATION, ET IMMUNOMODULATION DES CELLULES DENDRITIQUES ISSUES DE MONOCYTES HUMAINS

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Gérénétion de cellules T CD4+CD25+ suppressives, induite par des lymphocytes T CD8+CD28- au cours de réactions leucocytaires mixtes autologues

La réaction mixte lymphocytaire autologue (aMLR) permet l'étude des circuits de régulation du système immunitaire et correspond à la prolifération des lymphocytes T CD4+ suite à une stimulation par des cellules dendritiques autologues (aMLRs déficientes dans: maladie de Hodgkin, syndrome de Down, lupus érythémateux systématique, arthrite rhumatoïde, cirrhose biliaire primitive, etc). Les lymphocytes T CD8+CD28- sont des cellules régulatrices capables de suppression directe de l'allo- et la xéno-réactivité de lymphocytes T CD4+ et de rendre tolérogènes des cellules dentritiques. L'objectif de notre étude est de développer un système de co-culture in vitro permettant l'étude des rôles suppresseurs des lymphocytes T CD8+CD28-. Ce sont les MLR autologues de 5 jours: (Mo-DCs . cellules T CD4+ . cellules T CD8+CD28-). Les résultats montrent une forte réponse proliférative des cellules T CD4+, qui est inhibée par des anticorps monoclonaux dirigés contre HLA DR, CD2, CD11a, CD54 et CD86 et s'accompagne d'une sécrétion d'IFN-g et d'IL-12, reflétant une réponse de typeTh1. De plus, on observe l'émergence d'une population cellulaire de phénotype CD4+ CD25+ CTLA4+ (expression intracellulaire et membranaire) CD45RA- 45RO+ au cours de l'aMLR : ces cellules, dotées par ailleurs de faibles capacités prolifératives, sont capables de supprimer par contact cellulaire la réactivité de lymphocytes T CD4+ vis-à-vis d'auto- et d'allo-antigènes présentés par des DCs matures. Notre étude montre que cette population cellulaire T CD8+CD28- pourraitégalement exercer des fonctions régulatrices indirectes en générant une population de lymphocytes T aux fonctions suppressives. Nous montrons donc qu'il est possible de générer in vitro, et dans un modèle syngénique, des lymphocytes T régulatrices CD4+CD25+. S'agit-il ici de lymhocytes générés de novo? Ou alors la MLR autologue a-t-elle permis d'amplifier une population régulatrice existante et quiescente? Ce système pourrait refléter un mécanisme intervenant dans le maintien de la tolérance périphérique, par génération de cellules T régulatrices.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Les Anticorps anti-polynucléaires neutrophiles et le syndrome de détresse respiratoire aigüe post-transfusionnelle (TRALI (Transfusion Related Acute Lung Injury))

LYON1-BU Santé (693882101) / SudocSudocFranceF

Génération in vitro et caractérisation immunophénotypique des cellules dendritiques canines obtenues à partir de monocytes

Actuellement, les cellules dendritiques (DCs) sont très étudiées chez l'homme et chez la souris. Cependant, les travaux expérimentaux restent assez pauvre pour la majorité des autres espèces animales. Le chien présente des pathologies cancéreuses et auto-immunes spontanées comparables à celles de l'homme. De ce fait, il paraît être un bon modèle animal potentiel pour évaluer la validité de l'immunomodulation par l'intermédiaire des cellules dendritiques. Dans un premier temps, nous avons développé une méthode visant à purifier les monocytes canins. Dans ce travail, nous avons pu mettre au point une méthode de purification des monocytes canins en combinant une technique d'élutriation et d'immunopurification complémentaire par des billes magnétiques. Ensuite, nous avons produit et caractérisé des Mo-DCs en utilisant de l'IL-4 et du GM-CSF de chien. Nous avons établi que la molécule CD86 était un marqueur spécifique de ces cellules dans cette espèce. Ces cellules dendritiques canines sont très fortement stimulantes en MLR et expriment aussi de façon importante les molécules CMH de Classe II et le CD32. Le marquage spécifique CD86 permettra de mieux purifier et analyser les fonctions de ces cellules chez le chien. Ces travaux permettrons de mieux caractériser et produire des cellules dendritiques canines pour envisager leur utilisation en immunothérapie et ouvrir les perspectives de recherche thérapeutiques chez cette espèceLYON1-BU.Sciences (692662101) / SudocSudocFranceF