Ce travail a eu pour objectif la création de matériaux composites à base de nanocharges de carbonate de calcium. L'étude des phénomènes interfaciaux qui régissent ces systèmes, ainsi que leurs impacts sur les propriétés fonctionnelles du matériau et plus particulièrement des propriétés de transport, ont été réalisées. Pour ce faire, nous avons considéré deux matrices polymères de nature chimique différente : le polylactide et le polyfluore de vinylidène. Les nanocomposites ont été élaborés par deux voies de mise en œuvre : la voie fondu et la voix solvant. Une analyse fine des relations structure/morphologie/propriétés des composites a été réalisée. Nous avons mis en évidence, quelle que soit la matrice polymère choisie, l'importance du traitement de surface des charges afin d'améliorer leurs états de dispersion dans le matériau et d'augmenter la qualité de l'interface charge/polymère. Ces paramètres ont été corrélés aux propriétés de transport de ces matériaux composites. / The aim of this PhD work is to elaborate composites based on calcium carbonate nanoparticles. Polylactide and polyvinylidene fluoride were used as polymer matrix and nanocomposite were elaborated either by melting process and either by casting method. The interfacial behaviour between polymer and calcium carbonate were studied and we especially focused on their impact on the composite gas barrier properties. The importance of filler surface treatment had been highlighted on the filler dispersion state improvment and filler/polymer interface reinforcement. Both parameters were important in the improvement of composite gas barrier properties.

The study of impurity diffusion in semiconductor hosts is an important field that has both fundamental appeal and practical applications. Ion implantation is a good technique to introduce impurities deep into the semiconductor substrates at relatively low temperature and is not limited by the solubility of the dopants in the host. However ion implantation creates defects and damages to the substrate. Annealing process was used to heal these damages and to activate the dopants. In this study, we introduced several species such as alkali metals (Li, Na, K), alkali earth metals (Be, Ca,), transition metals (Ti, V, Cr, Mn) and other metals (Ga, Ge) into semiconductor substrates using ion implantation. The implantation energy varies form 70 keV to 200 keV and the dosages vary between ~ 1.0x1012 and ~5.0x1015 atoms/cm2. The samples are annealed at different temperatures from 300°C to 1000°C and for different time intervals. The redistribution behaviors of the implanted ions are studied experimentally using secondary ion mass spectrometry (SIMS). We observed some complex distribution behaviors due to the defects created during the process of ion implantation. The diffusivities of some impurities are calculated and compared to previous data. It was found that the diffusivities of implanted impurities is related to the dosages, annealing temperatures and the defects and damages caused by ion implantation. Additionally, as we go from one type of semiconductor to another, the diffusion behavior of the impurities shows a different trend.

Passivating-contact technologies fabricated from polycrystalline-silicon (poly-Si) are increasingly considered by the crystalline silicon (c-S) PV industry to be key enablers towards record performance. This is largely thanks to their ability to provide excellent carrier collection and surface passivation, while being compatible with industrial scale production. Poly-Si based passivating contacts consist of a stack of an ultrathin silicon oxide (SiOx) film on the surface of crystalline silicon (c-Si), covered by a doped silicon film. Thin films of SiOx can be grown by several different methods: chemically, thermally, or via UV-ozone exposure. However, each of these methods presents challenges towards industrial implementation. Here, we report an alternative method to grow SiOx films using an in-situ plasma process, where we subsequently deposit the doped poly-Si layer in the same process chamber by plasma enhanced chemical vapor deposition (PECVD). This process presents several advantages, such as ease of fabrication, inherently single-side oxide growth and poly-Si deposition, and the combined deposition in one chamber, lowering capital expenditure. Subsequently, we studied the structure of the SiOx films and the doped poly-Si(p+) capping layers using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) in order to determine the films’ elemental composition, and the band alignment at the semiconductor/oxide interfaces. A less p-type polysilicon was observed grown on top of a wet SiOx/c-Si with the origin tentatively attributed to depletion of the boron dopant via pin holes evidenced by AFM. A surface photo-voltage (SPV) was observed by XPS under in-situ light bias (AM 1.5) and a representation of the band alignment of the c-Si/SiOx/p-polysilicon under illumination is derived. The SPV was attributed to the photo accumulation of holes at the p-polysilicon and a splitting of quasi-fermi levels with its magnitude correlated to the device measured iVoc . Finally, a valuable application for this contact technology is the integration of silicon with perovskite solar cells, in the so-called monolithic tandem configuration. This approach is very promising to develop a new generation of PV with unmatched performances. Here, poly-Si contacts offer a variety of advantages, thanks to their broader material selection and to the stability at high processing temperature.

Proper functioning of instruments requires precise calibration and routine quality assurance. In a clinical setting, this is achieved through the use of phantoms, which mimic the physical characteristics of tissues. Polyvinyl alcohol (PVA), a non-toxic, water-soluble polymer is well-suited for use as clinical phantom material. Through successive freezing and thawing, solutions of PVA in water can be solidified into rigid cryogels (PVA-C). The number of freeze-thaw cycles affects the properties of the material, including its optical characteristics. A double integrating sphere system was used in conjunction with the Inverse Adding Doubling (IAD) algorithm to characterize the optical properties of thin slab samples. The setup was evaluated using liquid phantoms. Liquid emulsion and food colouring were used to impart scattering and absorbing properties in the range characteristic of human tissue. Measured values of normalized reflectances and transmittances were entered into IAD, and a set of optical properties (μ′s,μa,g) retrieved. The reduced scattering coefficient was found to increase linearly with increasing lipid concentration, while a consistent overestimation of the absorption coefficient was observed. Measurements of PVA cryogels revealed a linear increase in the reduced scattering coefficient with an increasing number of freeze-thaw cycles up to five cycles. Scattering was also observed to increase with concentration up to PVA concentrations of 15%, and to spontaneously increase during the lifetime of the slab samples. These findings suggest it is possible to tune the optical scattering of PVA-C via different purely physical mechanisms. / Thesis / Master of Science (MSc)

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No description available.

The adhesion of poly(dimethyl siloxane) (PDMS) to silica substrates was measured by 90 degree peel testing of PDMS strips cast on silica substrates. The objective of this work was to investigate the effects of silica surface chemistry on the adhesion between PDMS and silica substrate. Silica substrates with different surface chemistry were prepared by both chemical modification and physical adsorption. Silane coupling agents were used to provide octyl chains and primary amino groups on the silica surfaces. Also silica surfaces were coated with cetyltrimethylammonium bromide (CTAB), polyvinylamine (PVAm) or poly(N-isopropylacrylamide) (PNIPAM) by physical adsorption. The adhesion samples were prepared by casting Sylgard® 184 silicone elastomers on silica surfaces followed by thermal curing. Water contact angle measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared microscopy (FTIR) were performed to measure the surface properties of the peel test samples. It is believed that hydrogen bonding between siloxane bonds in PDMS and silanol groups on silica substrate contributes to the strong adhesion of PDMS and silica surface. The adhesion forces significantly reduced by the adsorption of PVAm and PNIPAM onto silica surfaces. In addition, the introduction of primary amino groups on silica surface would poison the catalyst during the curing of PDMS, which causes the formation of low crosslinking PDMS in the outer surface and is expected to decline the adhesion force. Lastly, the slightly reduce of adsorbed PVAm (340 kDa) on the silica substrate after peel test is considered to be useful for long-term lubrication. / Thesis / Master of Applied Science (MASc)

Copolymer-cobalt complexes have been formed by thermolysis of dicobalt octacarbonyl in solutions of copolysiloxanes. The copolysiloxane-cobalt complexes formed from toluene solutions of PDMS-b-[PMVS-co-PMTMS] block copolymers were annealed at 600-700 °C under nitrogen to form protective siliceous shells around the nanoparticles. Magnetic measurements after aging for several months in both air and in water suggest that the ceramic coatings do protect the cobalt against oxidation. However, after mechanical grinding, oxidation occurs. The specific saturation magnetization of the siliceous-cobalt nanoparticles increased substantially as a function of annealing temperature, and they have high magnetic moments for particles of this size of 60 emu g⁻¹ Co after heat-treatment at temperatures above 600 °C. The siliceous-cobalt nanoparticles can be re-functionalized with aminopropyltrimethoxysilane by condensing the coupling agent onto the nanoparticle surfaces in anhydrous, refluxing toluene. The concentration of primary amine obtained on the surfaces is in reasonable agreement with the charged concentrations. The surface amine groups can initiate L-lactide and the biodegradable polymer, poly(L-lactide), can be polymerized directly from the surface. The protected cobalt surface can also be re-functionalized with poly(dimethylsiloxane) and poly(ethylene oxide-co-propylene oxide) providing increased versatility for reacting polymers and functional groups onto the siliceous-cobalt nanoparticles.Phthalonitrile containing graft copolysiloxanes were synthesized and investigated as enhanced oxygen impermeable shell precursors for cobalt nanoparticles. The siloxane provided a silica precursor whereas the phthalonitrile provided a graphitic precursor. After pyrolysis, the surfaces were silicon rich and the complexes exhibited a substantial increase in Ms. Early aging data suggests that these complexes are oxidatively stable in air after mechanical grinding. Aqueous dispersions of macromolecule-magnetite complexes are desirable for biomedical applications. A series of vinylsilylpropanol initiators, where the vinyl groups vary from one to three, were prepared and utilized for the synthesis of heterobifunctional poly(ethylene oxide) oligomers with a free hydroxy group on one end and one to three vinylsilyl groups on the other end. The oligomers were further modified with carboxylic acids via ene-thiol addition reactions while preserving the hydroxyl functionality at the opposite terminus. The resulting carboxylic acid heterobifunctional PEO are currently being investigated as possible dispersion stabilizers for magnetite in aqueous media. / Ph. D.

L'intégrité de l'ADN génomique humain est maintenue par des systèmes de réparation de l'ADN qui protègent les cellules des dommages causés par des agents environnementaux ou des lésions spontanées de l'ADN. Chaque cellule peut subir jusqu'à 10⁵ lésions par jour, y compris les cassures double-brin de l'ADN (CDB). La poly(ADPribosyl)ation (PARylation) est l'un des premiers événements de signalisation moléculaire survenant aux CDBs. Il est catalysé par les poly(ADP-ribose)polymérases (PARP) qui sont directement activées par ces lésions d'ADN. Le fait de ne pas générer de poly(ADP)ribosyl (pADPr) en réponse à des dommages à l'ADN par une inhibition chimique ou par l'absence de PARP-1 augmente la sensibilité cellulaire au stress génotoxique, indiquant que la pADPr elle-même est une molécule clé de signalisation des dommages à l'ADN. L'inhibition de l'enzyme de signalisation des dommages à l'ADN, la poly(ADP-ribose) polymérase-1 (PARP-1) est l'une des nouvelles thérapies les plus prometteuses contre le cancer. Les inhibiteurs de PARP sensibilisent les cellules cancéreuses aux agents endommageant l'ADN et tuent efficacement les cellules cancéreuses du sein, des ovaires et du pancréas déficientes en BRCA1 (Breast Cancer gene 1) et BRCA2 (Breast Cancer gene 2), ce qui suggère que les cellules déficientes en réparation des CDBs sont extrêmement sensibles à l'inhibition de PARP. Pourtant, les mécanismes sous-jacents à cette létalité synthétique entre le déficit de réparation du CDB et l'inhibition de PARP restent mal définis. Il y a un débat considérable sur le mécanisme par lequel l'inhibition de PARP tue les cellules déficientes en réparation de l'ADN, et le plein potentiel des inhibiteurs de PARP dans le traitement du cancer ne peut être obtenu que par une compréhension claire des voies de réponse aux dommages de l'ADN (DDR) aux CDB et comment ils sont affectés par les inhibiteurs de PARP. L'objectif général de ma thèse est d'étudier le rôle de PARP-1 dans la réparation DSB et d'identifier les interacteurs de PARP-1 qui jouent également un rôle dans ce processus. Les cellules eucaryotes réparent les CDBs par deux voies principales, la jonction d'extrémité non homologue (NHEJ) et la recombinaison homologue (HR). La HR est initiée par la liaison des CDBs par BRCA1 et le complexe MRE11-RAD50-NBS1 et des nucléases EXO1/DNA2 pour générer de l'ADN simple-brin, qui est ensuite utilisé par la recombinase RAD51 et le complexe BRCA1-PALB2-BRCA2. Une question clé dans notre domaine concerne les facteurs critiques pour réguler le choix de la voie CDB. HR est initiée à partir d'extrémités DSB hautement résectées, tandis que dans le NHEJ, la résection est empêchée par des facteurs de réparation clés incluant RIF1 et 53BP1. En utilisant des cellules déficientes en PARP-1, nous avons observé que deux inhibiteurs de la résection de l'ADN et des régulateurs de choix de voie, RIF1 et 53BP1, la formation de foyers induits par des dommages à l'ADN sont fortement altérés. Cela confirme notre hypothèse selon laquelle PARP-1 participe à la réparation du DSB en influençant la résection de l'ADN. Afin de mieux comprendre le mécanisme de résection et le rôle que PARP-1 y joue, nous avons identifié d'autres protéines qui interagissent avec PARP-1 et modulent ce processus. Pour ce faire, nous avons utilisé des données sur les protéines de liaison au pADPr générées à la fois dans notre laboratoire et celui de notre collaborateur Ted Dawson de Johns Hopkins. Les candidats sélectionnés à partir de ces listes ont été criblés pour identifier une seule cible qui démontrerait un phénotype similaire à la perte de PARP-1. Deux cibles initiales ont été explorées et finalement une seule protéine à doigt de zinc a été choisie comme cible principale. Nous devons relever la fonction de ce doigt de zinc en HR, dans l'espoir qu'il permettra de découvrir davantage les mécanismes de PARP-1 en résection. En résumé, cette thèse élucide le rôle de PARP-1 dans la résection de l'ADN et identifie une protéine à doigt de zinc non étudiée auparavant qui interagit avec PARP-1 et partage une fonction similaire à PARP-1 dans la résection de l'ADN. / The integrity of human genomic DNA is maintained by DNA repair systems that will protect cells from damage by environmental agents or spontaneous DNA lesions. Each cell can experience up to 10⁵ lesions daily, including DNA double-strand breaks (DSB)s. Poly(ADP-ribosyl)ation (PARylation) is one of the earliest molecular signalling events occurring at DNA DSBs. It is catalysed by poly(ADP-ribose) polymerases (PARPs) that are directly activated by those DNA lesions. Failure to generate pADPr in response to DNA damage by either chemical inhibition or absence of PARP-1 increases the cellular sensitivity to genotoxic stress, indicating that pADPr itself is a key DNA damage signalling molecule. Inhibition of the DNA damage signalling enzyme poly(ADP-ribose) polymerase-1 (PARP-1) is among the most promising new therapies in cancer. PARP inhibitors sensitize cancer cells to DNA damaging agents and efficiently kill BRCA1- and BRCA2-deficient breast, ovarian and pancreatic cancer cells, suggesting that cells deficient in DSB repair are exquisitely sensitive to PARP inhibition. Yet, the mechanisms underlying this synthetic lethality between DSB repair deficiency and PARP inhibition remain poorly defined. There is considerable debate about the mechanism through which PARP inhibition kills DNA repair-deficient cells, and the full benefit of PARP inhibitors in cancer therapy can only be achieved by a clear understanding of the DNA damage response (DDR) pathways to DSBs and how these are affected by PARP inhibitors. The overall aim of my PhD is to investigate the role of PARP-1 in DSB repair and identify interactors of PARP-1 which also play a role in this process. Eukaryotic cells repair DSBs by two major pathways, non-homologous end-joining (NHEJ) and homologous recombination (HR). HR is initiated by the binding of DSB by BRCA1 and the end resection of the DSB by MRE11 (and the associated NBS1, RAD50, CtIP, and EXO1) to generate single-stranded DNA, which is further processed by RAD51 and BRCA1-PALB2-BRCA2. A key question in our field regards which factors are critical for regulating the DSB pathway choice. HR is initiated from highly resected DSB ends, whereas in NHEJ, resection is prevented by key repair factors that include RIF1 and 53BP1. Using PARP-1-deficient cells, we have observed that two inhibitors of DNA resection and regulators of pathway choice, RIF1 and 53BP1, are strongly impaired in forming DNA damage-induced foci. This supports our hypothesis that PARP-1 participates in DSB repair by influencing DNA resection. In order to further understand the mechanism of resection and the role that PARP-1 plays in it we also aim to identify other proteins which interact with PARP-1 and modulate this process. To accomplish this, we made use of data on PAR binding proteins generated both in our lab and that of our collaborator Ted Dawson. The candidates selected from these lists were screened to identify a single target that would demonstrate a similar phenotype to PARP-1 loss. Two initial targets were further explored and finally a single zinc finger protein was selected as our primary target. We aim to characterize the function of this zinc finger in HR, in the hopes that it will further uncover the mechanisms of PARP-1 in resection. In summary this thesis elucidates the role of PARP-1 in DNA resection and identifies a previously unstudied zinc finger protein which interacts with PARP-1 and shares a similar function to PARP-1 in DNA resection.

L'ADN, support de l'information génétique, subit chaque jour de nombreuses attaques pouvant induire différents types de lésions. Que ce soit d'origine environnementale (agents chimiques), rayonnements ionisants) ou d'origine endogène (métabolisme de L'ADN, radicaux libres), chacun de ces agents peut provoquer des cassures simple ou double-brin dans la molécule d'ADN. Ces lésions doivent être détectées rapidement et réparées fidèlement, afin d'éviter d'engendrer une mutation pouvant déclencher une maladie telle le cancer, ou encore éviter de se transmettre à la descendance. Au cours de l'évolution, la cellule eucaryote a développé différentes voies spécifiques pour répondre à un stress génotoxique. Ainsi il existe un véritable réseau de surveillance et d'évaluation des dommages permettant à la cellule lésée de réparer l'ADN ou d'entrer en apoptose si les dommages sont trop importants. La poly(ADP-ribosyl)ation des protéines est une modification post-traductionnelle qui intervient rapidement dès qu'une cassure dans la molécule d'ADN est détectée. Le polymère est synthétisé à partir du NAD+ par une famille d'enzymes appelées PARP (poly(ADP-ribose)polymérase), dont le rôle principal est la maintien de l'intégrité du génome. Cette modification affecte les propriétés physico-chimiques ainsi que la fonction des protéines cibles. Celle-ci permet, entre autre, le recrutement des enzymes de réparation de l'ADN. Ce signal demeure toutefois transitoire, le polymère formé étant rapidement dégradé par la PARG (poly(ADP-ribose)glycohydrolase. Ce travail présente une analyse structurale de la PARP-3, un membre peu caractérisé de la famille PARP, ainsi qu'une analyse fonctionnelle de mutants de phosphorylation de la PARP-1 (premier article) qui montre que la phosphorylation du premier doigt de zinc de cette protéine altère son recrutement et sa persistance aux sites de cassure de l'ADN. Par ailleurs, de nombreuses évidences montrent que que la poly(ADP-ribosyl)ation des protéines peut survenir dans un contexte autre que les dommages à l'ADN, le second article présente les métabolismes qui peuvent être associés aux PARP-1 et 2 ainsi qu'à la PARG et monte un possible nouveau rôle biologique pour la PARP-1.