Spectroscopie optique et propriétés de spin des boîtes quantiques uniques de GaAs/AlGaAs formées par épitaxie par gouttelettes.

Ce travail de thèse, essentiellement expérimental, porte sur l'étude par photoluminescence résolue spatialement, temporellement et en polarisation des propriétés de spin des\ud boîtes quantiques uniques de GaAs/Al GaAs formées par épitaxie par gouttelettes. Les travaux présentés sont organisés autour de trois parties.\ud Une première partie dédiée à l'étude expérimentale de la corrélation temporelle des photons émis par les boîtes quantiques incorporées dans une membrane bidimensionnelle\ud de cristaux photoniques. Une dépendance en puissance de la probabilité de coïncidence lors de la corrélation croisée entre les transitions excitonique et biexcitonique de la même boîte est observée et modélisée en fonction du taux d'occupation de la boîte.\ud Une deuxième partie porte sur les règles de sélection optique dans ces structures, point de départ pour des expériences de pompage optique. L'observation de l'orientation de la polarisation des photons émis par les différentes transitions de la boîte quantique nous\ud permet de mettre en évidence un couplage entre les états de trous lourds et de trous légers.\ud Ce couplage est modélisé en fonction de la forme et de l'orientation de la boîte quantique par rapport aux axes cristallographiques. La dernière partie porte sur des expériences de polarisation du spin des noyaux de\ud la boîte quantique par transfert de la polarisation du spin de l'électron. Ce transfert de polarisation, dû à l'interaction hyperfine entre électron et noyaux, dépend de différents paramètres temporels que nous pouvons ajuster avec notre modèle. Nous présentons également une mesure directe du temps de construction de cette polarisation nucléaire.---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------This thesis present experimental studies of spin properties in GaAs/AlGaAs quantum dots grown by droplet epitaxy by spatially and temporally resolved photoluminescence measurements. This studies are presented in three different parts. The first part is dedicated to the study of the temporal correlation of the photons emitted by a quantum dot embdedded in two-dimensional photonic crystal membrane. We observe the power dependance of the coincidence probability by cross-correlation measurements between the biexcitonic and the excitonic transitions into a single quantum dot. Our findings are qualitatively understood with a statistic model. The second part focuses on optical selection\ud rules in these structures, starting point for spin injection experiments. We evidence the mixing between heavy holes and light holes states by analysing the polarisation direction of the luminescence from a single quantum dot. We explain the states mixing by a model that takes into account the shape and the tilting of the quantum dot with respect to the crystallographic axes. The last part presents optical pumping experiments. We inject spin\ud polarised electrons and observe the creation of a dynamical nuclear polarisation. This polarisation transfert, due to hyperfine interaction, depends on caracteristic times that we can extract thanks to our model. We also present a direct measurement of the creation time of the nuclear spins polarisation

Optically monitored nuclear spin dynamics in individual GaAs quantum dots grown by droplet epitaxy

We report optical orientation experiments in individual, strain free GaAs quantum dots in AlGaAs grown by droplet epitaxy. Circularly polarized optical excitation yields strong circular polarization of the resulting photoluminescence at 4K. Optical injection of spin polarized electrons into a dot gives rise to dynamical nuclear polarization that considerably changes the exciton Zeeman splitting (Overhauser shift). We show that the created nuclear polarization is bistable and present a direct measurement of the build-up time of the nuclear polarization in a single GaAs dot in the order of one second.Comment: 7 pages, 3 figure

Aptamer-modified polymer nanoparticles for targeted drug delivery

The purpose of this study was to develop a model system for targeted drug delivery. This system should enable targeted drug release at a certain tissue in the body. In conventional drug delivery systems, drugs are often delivered unspecifically resulting in unwarranted adverse effects. To circumvent this problem, there is an increasing demand for the development of intelligent drug delivery systems allowing a tissue-specific mode of delivery. Within this study, nanoparticles consisting of two biocompatible polymers are used. Because of their small size, nanoparticles are well-suited for effective drug delivery. The small size affects their movement through cell and tissue barriers. Their cellular uptake is easier when compared to larger drug delivery systems. Paclitaxel was encapsulated into the nanoparticles as a model drug, and to achieve specific targeting an aptamer directed against lung cancer cells was coupled to the nanoparticles surface. Nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), and nanotracking analysis (NTA). Also their surface charge was characterized from ζ-potential measurements. Their preparation was optimized and subsequently specificity of drug-loaded and aptamer-functionalized nanoparticles was investigated using lung cancer cells. © 2016 by De Gruyter

Controlling the polarization eigenstate of a quantum dot exciton with light

We demonstrate optical control of the polarization eigenstates of a neutral quantum dot exciton without any external fields. By varying the excitation power of a circularly polarized laser in micro-photoluminescence experiments on individual InGaAs quantum dots we control the magnitude and direction of an effective internal magnetic field created via optical pumping of nuclear spins. The adjustable nuclear magnetic field allows us to tune the linear and circular polarization degree of the neutral exciton emission. The quantum dot can thus act as a tunable light polarization converter.Comment: 5 pages, 3 figure

Copy number variants as modifiers of breast cancer risk for BRCA1/BRCA2 pathogenic variant carriers

The risk of germline copy number variants (CNVs) in BRCA1 and BRCA2 pathogenic variant carriers in breast cancer is assessed, with CNVs overlapping SULT1A1 decreasing breast cancer risk in BRCA1 carriers.The contribution of germline copy number variants (CNVs) to risk of developing cancer in individuals with pathogenic BRCA1 or BRCA2 variants remains relatively unknown. We conducted the largest genome-wide analysis of CNVs in 15,342 BRCA1 and 10,740 BRCA2 pathogenic variant carriers. We used these results to prioritise a candidate breast cancer risk-modifier gene for laboratory analysis and biological validation. Notably, the HR for deletions in BRCA1 suggested an elevated breast cancer risk estimate (hazard ratio (HR) = 1.21), 95% confidence interval (95% CI = 1.09-1.35) compared with non-CNV pathogenic variants. In contrast, deletions overlapping SULT1A1 suggested a decreased breast cancer risk (HR = 0.73, 95% CI 0.59-0.91) in BRCA1 pathogenic variant carriers. Functional analyses of SULT1A1 showed that reduced mRNA expression in pathogenic BRCA1 variant cells was associated with reduced cellular proliferation and reduced DNA damage after treatment with DNA damaging agents. These data provide evidence that deleterious variants in BRCA1 plus SULT1A1 deletions contribute to variable breast cancer risk in BRCA1 carriers.Peer reviewe

Metabolic constituents of grapevine and grape-derived products

The numerous uses of the grapevine fruit, especially for wine and beverages, have made it one of the most important plants worldwide. The phytochemistry of grapevine is rich in a wide range of compounds. Many of them are renowned for their numerous medicinal uses. The production of grapevine metabolites is highly conditioned by many factors like environment or pathogen attack. Some grapevine phytoalexins have gained a great deal of attention due to their antimicrobial activities, being also involved in the induction of resistance in grapevine against those pathogens. Meanwhile grapevine biotechnology is still evolving, thanks to the technological advance of modern science, and biotechnologists are making huge efforts to produce grapevine cultivars of desired characteristics. In this paper, important metabolites from grapevine and grape derived products like wine will be reviewed with their health promoting effects and their role against certain stress factors in grapevine physiology

Outcomes of elective liver surgery worldwide: a global, prospective, multicenter, cross-sectional study

Background: The outcomes of liver surgery worldwide remain unknown. The true population-based outcomes are likely different to those vastly reported that reflect the activity of highly specialized academic centers. The aim of this study was to measure the true worldwide practice of liver surgery and associated outcomes by recruiting from centers across the globe. The geographic distribution of liver surgery activity and complexity was also evaluated to further understand variations in outcomes. Methods: LiverGroup.org was an international, prospective, multicenter, cross-sectional study following the Global Surgery Collaborative Snapshot Research approach with a 3-month prospective, consecutive patient enrollment within January–December 2019. Each patient was followed up for 90 days postoperatively. All patients undergoing liver surgery at their respective centers were eligible for study inclusion. Basic demographics, patient and operation characteristics were collected. Morbidity was recorded according to the Clavien–Dindo Classification of Surgical Complications. Country-based and hospital-based data were collected, including the Human Development Index (HDI). (NCT03768141). Results: A total of 2159 patients were included from six continents. Surgery was performed for cancer in 1785 (83%) patients. Of all patients, 912 (42%) experienced a postoperative complication of any severity, while the major complication rate was 16% (341/2159). The overall 90-day mortality rate after liver surgery was 3.8% (82/2,159). The overall failure to rescue rate was 11% (82/ 722) ranging from 5 to 35% among the higher and lower HDI groups, respectively. Conclusions: This is the first to our knowledge global surgery study specifically designed and conducted for specialized liver surgery. The authors identified failure to rescue as a significant potentially modifiable factor for mortality after liver surgery, mostly related to lower Human Development Index countries. Members of the LiverGroup.org network could now work together to develop quality improvement collaboratives

Optical spectroscopy and spin properties of single GaAs / AlGaAs quantum dots grown by droplet epitaxy

Ce travail de thèse, essentiellement expérimental, porte sur l'étude par photoluminescence résolue spatialement, temporellement et en polarisation des propriétés de spin des boîtes quantiques uniques de GaAs/Al GaAs formées par épitaxie par gouttelettes. Les travaux présentés sont organisés autour de trois parties.Une première partie dédiée à l'étude expérimentale de la corrélation temporelle des photons émis par les boîtes quantiques incorporées dans une membrane bidimensionnelle de cristaux photoniques. Une dépendance en puissance de la probabilité de coïncidence lors de la corrélation croisée entre les transitions excitonique et biexcitonique de la même boîte est observée et modélisée en fonction du taux d'occupation de la boîte.Une deuxième partie porte sur les règles de sélection optique dans ces structures, pointde départ pour des expériences de pompage optique. L'observation de l'orientation de la polarisation des photons émis par les différentes transitions de la boîte quantique nous permet de mettre en évidence un couplage entre les états de trous lourds et de trous légers.Ce couplage est modélisé en fonction de la forme et de l'orientation de la boîte quantique par rapport aux axes cristallographiques.La dernière partie porte sur des expériences de polarisation du spin des noyaux de la boîte quantique par transfert de la polarisation du spin de l'électron. Ce transfert de polarisation, dû à l'interaction hyperfine entre électron et noyaux, dépend de différents paramètres temporels que nous pouvons ajuster avec notre modèle. Nous présentons également une mesure directe du temps de construction de cette polarisation nucléaireThis thesis present experimental studies of spin properties in GaAs/AlGaAs quantumdots grown by droplet epitaxy by spatially and temporally resolved photoluminescence measurements. This studies are presented in three different parts. The first part is dedicated to the study of the temporal correlation of the photons emitted by a quantumdot embdedded in two-dimensional photonic crystal membrane. We observe the power dependanceof the coincidence probability by cross-correlation measurements between the biexcitonic and the excitonic transitions into a single quantum dot. Our findings are qualitatively understood with a statistic model. The second part focuses on optical selection rules in these structures, starting point for spin injection experiments. We evidence the mixing between heavy holes and light holes states by analysing the polarisation direction of the luminescence from a single quantum dot. We explain the states mixing by a model that takes into account the shape and the tilting of the quantum dot with respect to the crystallographic axes. The last part presents optical pumping experiments. We inject spinpolarised electrons and observe the creation of a dynamical nuclear polarisation. This polarisation transfert, due to hyperfine interaction, depends on caracteristic times that we can extract thanks to our model. We also present a direct measurement of the creation time of the nuclear spins polarisatio