Tesis sobre el tema "Recombinaison de défauts"
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Ait, Saada Anissia. "Mécanismes par lesquels la recombinaison homologue prévient les défauts mitotiques induits par le stress réplicatif". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS167/document.
Texto completoAt each cell cycle, cells undertaking the DNA replication process face several sources of replication stress (RS) compromising the progression of the replicating forks and threatening both chromosome duplication fidelity and their correct segregation during mitosis. Replication stresses emerged as a major source of genetic instability and cancer development. Several mechanisms, among which homologous recombination (HR), operate to buffer the deleterious effects of RS. HR acts as an escort to fork progression and prevents mitotic defects. Nonetheless, the molecular connection between replication stress and mitotic defects remains elusive. A conditional replication fork barrier (RFB) acting in a polar manner was developed in the lab to terminally-arrest fork progression. In this system, HR functions handling replication stress can be assessed independently of its well-known function in double strand break repair. The work described here aims to understanding the mechanism that HR performs to ensure genetic stability in response to replication stress. In general, blocked replication forks can be rescued either by fork convergence or by active HR-mediated fork restart. However, in absence of Rad51 recombinase or it loader Rad52, a single activated RFB is sufficient to induce mitotic abnormalities including anaphase bridges. The involvement of HR factors in fork protection was explored at the molecular and cellular levels. It turns out that terminally-arrested forks are extensively resected by the Exo1 nuclease in the absence of Rad51/Rad52. Interestingly, the excess of ssDNA accumulation at the fork triggers sister chromatid non-disjunction in mitosis despite the arrival of an uncorrupted converging fork to rescue replication. Thus, unprotected replication forks are prone to pathological termination threatening chromosome segregation. HR being involved in fork protection and restart, the use of a Rad51 mutant showed that these two functions are genetically separable. Indeed, protected forks unable to restart by HR do not show any pathological termination. Thus, beyond their ability to restart inactivated forks, HR factors ensure replication completion by maintaining the forks in a suitable conformation for a fusion with the converging fork. Overall, these results shed light on the molecular events engaged by RH to ensure genome stability in response to replication stress
Alabert, Constance. "Étude des liens entre les défauts de réplication et la recombinaison chez la levure S. Cerevisiae". Montpellier 1, 2008. http://www.theses.fr/2008MON1T045.
Texto completoRéaux, David. "Cellules photovoltaïques à hétérojonctions de silicium (a-Si˸H/c-Si) : modélisation des défauts et de la recombinaison à l'interface". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS174/document.
Texto completoSilicon heterojunction (Si- HET) solar cells are based on an n-doped (p-doped) crystalline silicon (c-Si) substrate, a very thin (a few nanometers) passivation layer of undoped hydrogenated amorphous silicon (a-Si:H) and a layer of p-doped (n-doped) a-Si:H, approximately 10 nanometer- thick. These cells currently lead the performance of silicon solar cells with conversion efficiencies in the order of 26% (with a record of 26.6% being achieved by the Kaneka company in 2017). One of the major focal points of research in Si- HET cells is the study of the c-Si/a-Si:H interface, which is a key factor in the cells' efficiency. In particular, this efficiency is strongly dependent on the recombination states at the interface between c-Si and a-Si:H. We therefore focused on developing a model of recombination through interface defects, which were evaluated based on the Defect-Pool Model (DPM) in a-Si:H. We calculated the effective lifetime vs excess carrier density curves and their dependence on the undoped a-Si:H passivation layer thickness and compared them to experimental results.In order to determine the characteristics of the c-Si/a-Si:H interface, we proceeded as follows: (1) Calculation of the volumic density of states (DOS) in a-Si:H layers (doped and undoped) using the DPM. In this model, the DOS varies as a function of the position of the Fermi level in relation to the band edge. The band bending at the a-Si:H/c-Si interface thus implies a spatial variation of the DOS in a-Si:H. (2) Calculation of the surface DOS at the interface by projection from the volumic states present in a-Si:H at the interface. (3) Calculation of the recombination rates and of the effective lifetime curves for symmetrical a-Si:H/c-Si/a-Si:H structures and comparison with experimental results. Thus we were able to study the impact of material parameters of a-Si:H on the effective lifetime curves. The change in lifetime as a function of a-Si:H parameters is sometimes counter-intuitive because two passivation mechanisms, namely passivation by field-effect or by the reduction of the DOS at the a-Si:H/c-Si interface, have opposed behavior in relation to the position of the Fermi level at the interface. A simple calculation of the DOS at the interface is not, therefore, sufficient to explain variations in lifetime, and a complete calculation of effective lifetime under illumination is required and has been performed. We demonstrate that the impact of certain DPM parameters may have a significant effect on the DOS but only a minor effect on the effective lifetime due to the compensation by the field-effect passivation. Moreover we have studied both types of silicon heterojunctions, (p)a-Si:H/(i)a-Si:H/(n)c-Si(PIn), and (n)a-Si:H/(i)a-Si:H/(n)c-Si(NIn) that are used as front emitter and back surface field junctions, respectively, in double-side contacted silicon Si-HET solar cells. Our simulations allowed us to emphasize that NIn interfaces are less critical in terms of recombination than PIn interfaces. We demonstrate that recombination at PIn interfaces is dominated by the capture of electrons by positively charged silicon dangling bonds. We further show that the Urbach energy is the major a-Si:H parameter that determines the effective lifetime in Si-HET solar cells and that the use of fixed values for this Urbach energy in the passivation layer whatever the layer thickness does not permit the experimental trends of PIn interfaces to be reproduced. Instead, we propose a model featuring that the Urbach energy decreases with the thickness of the passivation layer, which does allow experimental trends to be reproduced for very thin passivation layers (< 10 nm), but which requires further elaboration for larger thicknesses, for instance with a combined bandgap variation
Nemar, Noureddine. "Génération-recombinaison en régime de porteurs chauds dans le silicium de type P". Montpellier 2, 1990. http://www.theses.fr/1990MON20151.
Texto completoSibille, Alain. "Etude des défauts créés par irradiation électronique dans InP". Paris 7, 1985. http://www.theses.fr/1985PA077083.
Texto completoFekecs, André. "Élaboration de photoconducteurs d’InGaAsP par implantation d'ions de fer pour des applications en imagerie proche-infrarouge et spectroscopie térahertz". Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6840.
Texto completoDarga, Arouna. "Etude des défauts électriquement actifs et des mécanismes de recombinaison des cellules solaires à base de Cu(In1-xGax)(Se1-ySy)2 co-évaporé ou électrodéposé". Paris 6, 2007. http://www.theses.fr/2007PA066413.
Texto completoVera, Gabriella. "Défauts de la réparation de l’ADN et développement lymphoïde : Analyse de situations pathologiques chez l’homme et la souris". Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05T028/document.
Texto completoThroughout their development, hematopoietic cells are exposed to many DNA damages of either exogenous or endogenous origin. Living organisms evolved a variety of DNA repair mechanisms in order to face those threats, and their impairment leads to rare but severe diseases in human. Of the two mechanisms involved in the repair of DNA double-strand break (DSB) repair, one plays a major role in mammal’s Immune System (IS). The non-homologous end joining (NHEJ) pathway is essential for the correct proceeding of V(D)J recombination in lymphocyte progenitors from bone marrow and thymus. Indeed, the formation of DNA DSB is a key step of the rearrangement. In similar fashion, though to a lesser degree, NHEJ is involved in repair of AID induced breaks during immunoglobulin class switch recombination (Ig-CSR). Our team previously identified a new NHEJ factor, Cernunnos (or XLF), as being responsible for a human syndrome of severe combined immunodeficiency (SCID) associated with ionizing radiation (IR) sensitivity (RS-SCID) and microcephaly. To better understand Cernunnos role in the hematopoietic system and particularly in lymphocyte development, we engineered a knock-out (KO) mouse model for this gene. Surprisingly, lymphocyte development is almost normal in these mice, the only defect observed being a decrease of lymphocyte number. However, a refined analysis of T cell repertoire allowed us to uncover a bias in the use of V and J segments from the receptor’s α chain (TCRα). This is the signature of a survival defect in thymocytes, caused by chronic activation of the p53 dependent apoptosis pathway in response to DNA damage. Some discrete T cell populations, such as iNKTs and MAITS, would be affected. In the meantime, our team pursues the uncovering of genetic diseases and their functional description in patients showing signs of immune or hematopoietic deficiency combined to impaired DNA repair. We focused on a patient harboring clinical signs of genomic instability and hematopoietic defects with strong evidence for genetic cause. Thanks to high-throughput DNA sequencing technology and whole genome association study (WGAS), we identified several mutations, one of them striking us as pertinent
Oulmane, Mohamed. "Transport dans les composants en présence de centres profonds : modélisation numérique et analytique". Montpellier 2, 1999. http://www.theses.fr/1999MON20210.
Texto completoChapelon, Olivier. "Transport en régime de porteurs chauds dans le silicium de type n". Montpellier 2, 1993. http://www.theses.fr/1993MON20066.
Texto completoJiang, Xianwu. "Hydrocarbon molecules databases for waste treatment applications". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST039.
Texto completoIn this thesis, we investigate the vibronic (de-) excitation and dissociative recombination of CH+ by low-energy electron impact. We first develop a theoretical approach for the electron-impact vibronic (de-) excitation of CH+. In this approach, the fixed-nuclear R-matrix method is employed to compute electron-ion scattering matrices in the Born-Oppenheimer approximation. A vibronic frame transformation and the closedchannel elimination procedure in a spirit of molecular quantum defect theory are employed to construct an energy-dependent scattering matrix describing interactions between vibronic channels of the target ion induced by the incident electron. The obtained scattering matrix accounts for Rydberg series of vibronic resonances in the collisional spectrum. Cross sections for vibronic excitation for different combinations of initial and final vibronic states are computed. A good agreement between electronic-excitation cross sections, obtained using the quantum defect theory and in a direct R-matrix calculation, demonstrates that the present approach provides a reliable tool for determination of vibronic (de-) excitation cross sections for targets with low-energy electronic resonances. Such targets were difficult to treat theoretically using earlier methods. Within the same framework applied for the vibronic (de-) excitations, we further compute the cross section for low-energy dissociative recombination of CH+ coupling the outgoing-wave basis function defined by complex absorbing potential. The contribution of the three lowest X 1Σ +, a 3Π and A 1Π ionic states and the Rydberg series converging to those states are taken into account. The obtained DR cross sections are quantitatively in good agreement with the experimental measurements and exhibit a resonanc feature analogous to the experimental cross-section curve. The origination of the prominant resonances in the computed results are analyzed through computing the DR probabilities for the partial waves of the incident electron. The d-type partial waves including dσ, dπ and dδ are found considerably contributing to the DR of the ground-state CH+. This may explain the discrepancies observed between thoery and experiment in the preceeding studies
Luo, Yandi. "Development of new buffer layers and rapid annealing process for efficient Sb₂Se₃ thin-film solar cells". Electronic Thesis or Diss., Université de Rennes (2023-....), 2024. http://www.theses.fr/2024URENS039.
Texto completoIn this thesis, heterojunction interface behavior, grain growth process and alternative buffer layer of Sb₂Se₃ based solar cells were investigated. The absorber quality and the band alignment are identified as key parameters for reducing defect density and for facilitating the separation and the transport of photogenerated charge carriers. A strategy of Al³⁺ doping into the CdS buffer layer was introduced in Sb₂Se₃ solar cells. The band alignment and the interface quality have been significantly improved. A “spike-like” structure was obtained for the best device with an efficiency of 8.41%. Secondly, a rapid thermal annealing process has also been developed and optimized in order to improve the quality of Sb₂Se₃ absorber film with reduced defect density. The efficiency of the Sb₂Se₃ solar cells is increased to 9.03%. In addition, we have tried to replace the toxic CdS buffer layer with an environmentally friendly ZnSnO film with moreover a wider band gap. An interesting power conversion efficiency of 3.44% was achieved for the Cd-free Sb₂Se₃ thin-film solar cells
Backodissa, Kiminou Roscelin Davy. "Recombinaison dissociative dans les plasmas froids et dans la combustion : mécanismes et calcul de vitesses". Le Havre, 2013. http://www.theses.fr/2013LEHA0012.
Texto completoThe study of the collisions between charged particles is a challenging subject for fundamental and applied physics. The electrons and positive molecular ions treated in this thesis are present in various astrophysical media (stars and interstellar clouds), in plasmas and in combustion flames. Dissociative recombination and electron/molecular cation scattering are important for these environments. We evaluate in this work the probabilities of occurrence of these physico-chemical reactions as cross sections and rate coefficients, by underlining the basic mechanisms and the relevant energy ranges (dissociative recombination at low energies and dissociative excitation at higher energies) and by presenting the main steps of the multichannel quantum defect theory (MQDT), on which our approach is based. We present in this thesis results obtained for H2+/H2, HD+/HD and CO+/CO systems, in comparison with storage ring experiments and other theoretical results. We notice a good agreement, which has certainly to be improved. The rate coefficients which we produced are used in the modeling of the kinetics of cold reactive ionized media
Nana, Ngassam Valéry. "Collisions électrons-ions moléculaires : états résonnants et dynamique de dissociation". Paris 11, 2004. http://www.theses.fr/2004PA112284.
Texto completoDissociative recombination and related processes are specially effective in interstellar media where the very low density and temperature favour exothermic reactions. They also play an important role in various types of “cold” plasmas. This work reports the study of dissociative recombination of H2+, Ne2+ and HCNH+ molecular ions. The molecular states and their mutual interactions (for Ne2+ + e- and HCNH+ + e- systems) are calculated by ab initio methods: CI calculations for the bound part of the energy spectrum and electron-molecule scattering within the framework of the complex Kohn variational method for the continuous part. The low-energy dynamics (H2+ et Ne2+) is then treated by the multichannel quantum defect method. Several extensions of the formalism were developed in order to take account of the “off the energy shell” effects and to explicitly include the non-adiabatic couplings of the Rydberg states open to dissociation either between them or with the ion continuum
Niyonzima, Sébastien. "Collisions réactives dans les gaz d'intérêt énergétique". Thesis, Le Havre, 2013. http://www.theses.fr/2013LEHA0021/document.
Texto completoThis thesis devoted to the study of reactive collisions in gases of energetic interest concerns two aspects. Firstly, a Multichannel-Quantum-Defect-Theory-type approach [Giusti 1980, Nakashima 1987] is used in the treatment of the dissociative recombination (DR), vibrational excitation (VE), and vibrational de-excitation (VdE) of BeH+ in their four lowest vibrational states (X1Σ+,v i+ =0,1,2,3). The molecular structure data previously computed [Roos 2009] have been employed in the calculations of cross sections and rate coefficients of DR, VE and VdE including three electronic symmetries of BeH (2Π, 2Σ+ et 2∆ ). The vibrational dependence [Niyonzima 2013] and the isotopic effects in these collisional processes are highlighted – Figure (V.7) – in order to be used in the modeling of the edge fusion plasma [Celiberto 2012]. Satisfactory agreement with results computed with the wave packet method [Roos 2009] is reached at intermediate energies [Niyonzima 2013]. Thereby, this part of the thesis work extends the previous study of [Roos 2009]. The MQDT-based approach, able to fully account for the temporary captures of electrons in Rydberg bound states, as well as the vibronic coupling between ionization channels, provides the first results (reliable) at low energies [Niyonzima 2013]. Lastly, an approximate analytical formulation of DR, VE and VdE cross section for the prediction and interpretation of results of numerical calculations has been provided. This formulation is usefull in the understanding of different intramolecular interactions and explains the sensibility of rate coefficients with respect to dominant interactions
Wane, Sada Taminou. "Systématique de la photoionisation et de la recombinaison radiative dans les séquences isoélectroniques du potassium, du rubidium, du cuivre et de l'argent". Paris 11, 1988. http://www.theses.fr/1988PA112007.
Texto completoIn the framework of a non-relativistic single electron model, photoionisation cross sections from ground and excited n. T states have been computed for the K, Rb, Cu and Ag isoelectronic sequences, by the use of a parametric central potential. The evolution of the non-hydrogenic behaviour of photoionisation cross sections near threshold is studied along Rydberg series and along the isoelectronic sequences, and emphasis is put on the occurrence of minima and maxima in the photoïonisation cross section curves. Systematic trends along an isoelectronic sequence and in addition along the sequence of neutral alkali atoms Li through Cs, and the comparison of the behaviour along the different K, Rb, Cu and Ag isoelectronic sequences are analysed in terms of the quantum defect theory. Through the principle of the detailed balance radiative recombination rate coefficients have been obtained along the isoelectronic sequences, rather for relatively low temperatures. Markedly and peculiar non-hydrogenic features are outlined and the systematics of recombination along the isoelectronic sequences are analysed. Comparisons for bath photoïonisation and recombination results are made with mainly those of the hydrogenic model, and with other available theoretical or experimental results
Quintart, Anne. "Mise au point d'un test de réparation des cassures double-brin de l'ADN, application au déficit immunitaire T(-) B(-) caractérisé par un défaut de recombinaison V(D)J avec radiosensibilité accrue". Paris 5, 2001. http://www.theses.fr/2001PA05P019.
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