Dissertationen zum Thema „Effet tampon“
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Cardona, Echeverry Andres Hernan. „Tri sélectif et rôle tampon des condensats ARNm dans le contrôle stoichiométrique du transcriptome“. Electronic Thesis or Diss., Université Côte d'Azur, 2022. http://www.theses.fr/2022COAZ6029.
Der volle Inhalt der QuelleCellular homeostasis requires the robust control of biomolecule concentrations. Gene regulation alone necessitates millions of mRNA molecules to coordinate their stoichiometry in the face of dynamic translational changes. RNAs can co-assemble into liquid droplets, semi-liquid hydrogels, or solidify into glass or crystal-like forms to concentrate and phase separate into bio-condensates that tolerate large stoichiometric variations in their composition. Their ability to buffer protein accumulations has been recently debated, and their impact on mRNA fluxes and concentrations remains elusive despite the transcriptome-wide association of translation repression with cytosolic condensation. From single mRNAs to macroscopic condensates, the various structural scales of RNA organization are yet to be uncovered and mapped to functionalities. Here, we combined the purification-sequencing of RNA super-assemblies with single-molecule RNA imaging in C. elegans germlines. We quantitatively modeled the cytosolic reorganization of the transcriptome upon oogenesis arrest. Tightly repressed mRNA copies of same sequence identity self-assembled into nanoclusters that, upon quiescence, further co-assembled into super-compacted multiphase condensates. Self-assemblies not only sorted through phase separations, but also buffered, accumulating repressed mRNAs through sequestration. At mesoscale, the cooperative sharing of limiting translation repressors between mRNAs prevented the disruption of RNA:regulator stoichiometry in the cytosol, where translation control occurs. Transcriptome-wide stoichiometric control emerges from mRNA self-sorting and buffering in multiphase super-assemblies. Self-sorting autonomy coupled to co-assembly cooperativity provides selective and robust stoichiometric control, we term stoichiostasis. We define a new transcriptome organization scale, the nanocluster. Nanoclusters regulate RNA-RNA relative stoichiometry, while mesoscale condensates provide RNA-protein stoichiometric control
Lippé, Catherine. „Conservation génétique du chevalier cuivré (Moxostoma hubbsi) : effet tampon du temps de génération sur l'érosion de la diversité génétique“. Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/23329/23329.pdf.
Der volle Inhalt der QuelleIncreasing human activities have caused destruction and fragmentation of natural habitats, leading to the extinction of many species. Since genetic diversity plays an important role in the evolutionary potential of a species, conservation genetics is increasingly providing adequate tools needed towards the preservation of biodiversity. The Copper redhorse (Moxostoma hubbsi), an endangered species of Québec, has an extremely restricted distribution, limited to the Richelieu River and a short section of the St.Lawrence River. Surprisingly, this unique and ageing remaining population exhibits a high level of genetic diversity without sign of inbreeding, where recent demographic history and effective population size estimates suggest a gradual demographic decline scaled on a large time period. Our results clearly demonstrate the potential of genetic data towards effective conservation, as well suggesting that long generation times may act as a buffering effect contributing to reduce the pace of genetic diversity erosion in threatened species.
BOUYER, PATRICE. „Pouvoir tampon et effet de l'atp extracellulaire sur le calcium intracellulaire et sur la conductance chlore dans les cellules proximales du rein d'amphibien (doctorat : science de la vie et de la sante)“. Paris 5, 1998. http://www.theses.fr/1998PA05N026.
Der volle Inhalt der QuelleHernandez, Pauline. „Effet d'une sécheresse extrême sur le fonctionnement de l'écosystème prairial : évaluation du rôle tampon de la composition et de la diversité végétale par approche expérimentale“. Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22752/document.
Der volle Inhalt der QuellePermanent grasslands are one of the main forms of land use in Europe. In France, permanent grasslands represent around 40% of Utilised Agricultural Land and support many animal-based farming systems. Current climate change scenarios predict increased climate variability that could result in an increase in extreme events such as drought episodes. These extreme events can significantly alter the structure and functioning of grasslands, with implications for their capacity to provide agricultural, ecological and environmental services. Improved understanding of the resistance and resilience mechanisms of grassland plant communities exposed to extreme drought is therefore critical in order to assess the stability of grassland functions, in particular that of biomass production. This thesis aims at assessing the capacity of permanent grasslands to sustain their production when exposed to an extreme drought event. The study uses an experimental approach and semi-controlled conditions to investigate the role of community composition and functional diversity for drought resistance and resilience in grassland mixtures. Monocultures and mixtures combining grasses and legumes were selected to test the importance of composition and functional diversity for plant community responses during drought and up to a year after the end of water stress. The originality of this work is the use of a functional ecological approach to assess the impacts of species’ interactions via measurements of plant morphological and physiological traits both above- and below-ground. This study demonstrates the importance of white clover (Trifolium repens) in modulating the impact of extreme droughts on biomass production of grassland mixtures. Community composition did not have a buffering effect on biomass production during the drought event but the presence and abundance of white clover in mixtures was linked to higher recovery of biomass production in the long-term. After the extreme drought event, overyielding in mixtures combining grass and white clover could be attributed to mechanisms of nitrogen facilitation and vertical root complementarity for water uptake. Results also show the importance of deep root growth for the establishment of functional complementarity between species and the maintenance of biomass production under extreme drought. Drought had lasting effects on the root system patterns and thus on the underlying mechanisms of the positive effect of white clover on aboveground production. Moreover, this work highlights the key role of heterospecific interactions in the expression of intraspecific traits related to resource acquisition strategies. Heterospecific interactions are thus an important driver of the species performance under extreme drought.We show that the structure and functional composition of the plant community in simplified mixtures are critical for modulating grassland responses to an extreme drought event. In our study, the recovery of aboveground biomass production is mainly related to the presence of white clover and the establishment of positive interactions between species. Changes of species behaviour in response to heterospecific interactions should be taken into account to better predict grassland biomass production under future climatic conditions. From an applied perspective, accounting for the key role of white clover and the inherent variability or neighbour-induced plasticity of intraspecific traits appears important to adapt mixtures of species or varieties to more intense and frequent drought events
Duszynski, Isabelle. „Réalisation et caractérisation électrique de transistors HEMTs AlInAs/GaInAs de longueur de grille sub-50 nanomètres et de transistors sans couche tampon“. Lille 1, 2005. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2005/50376-2005-346.pdf.
Der volle Inhalt der QuelleAinsi, en augmentant ce rapport à 1,5 (cas des transistors sur barrière fine), on obtient une fréquence ft de 253GHz et une fréquence fmax de 380GHz. La dernière structure, à barrière fine et mixte, nous a permis d'obtenir des fréquences ft de l'ordre de 270GHz rien qu'en augmentant légèrement l'épaisseur de la barrière (puisque la grille a été déposée sur la Couche d'InP). Ces premiers résultats indiquent les potentialités offertes par l'utilisation d'une barrière Schottky mixte. Ces résultats pourraient être améliorés par l'utilisation d'un "double recess", ce qui permettrait de diminuer les zones trop importantes d'extensions de recess, à l'origine de la dégradation des performances fréquentielles de ces composants ultimes. L'amélioration de certains paramètres électriques liée à l'utilisation d'un recess mieux adapté permettrait d'aboutir à une fréquence ft de 520GHz, proche de l'état de l'art. Néanmoins, la réduction des dimensions atteint des limites, c'est pourquoi nous avons envisagé d'étudier des composants en rupture technologique avec les précédents transistors appelés "transistors sans couche tampon". L'idée est de venir supprimer la couche tampon qui est à l'origine d'une augmentation de la conductance de sortie par l'injection de porteurs dans cette couche. La réalisation technologique de ces composants est basée sur la technique de report de substrat, qui a été mise au point et adaptée à la réalisation d'un HEMT sans couche tampon. Les premiers résultats électriques indiquent que la technique de report de substrat affecte peu les caractéristiques de la couche active. Bien que nous ayons réalisé les premiers transistors sans couche tampon de longueur de grille 100nm, les caractéristiques électriques observées ne sont pas celles escomptées. Toutefois l'origine de ces faibles performances a été identifïée, et des solutions d'amélioration sont proposées
Prat, Denis. „Epoxydations stereoselectives d'alcools olefiniques par l'eau oxygene a 30% catalysees par l'acide tungstique en milieu tamponne“. Paris 6, 1988. http://www.theses.fr/1988PA066493.
Der volle Inhalt der QuelleVarache, Renaud. „Développement, caractérisation et modélisation d'interfaces pour cellules solaires à haut rendement à base d'hétérojonctions de silicium“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00781937.
Der volle Inhalt der QuelleLahreche, Hacène. „Croissance de nitrures d'éléments III par épitaxie en phase vapeur à base d'organo-métalliques sur substrats 6H-SiC et Si(111) : application aux transistors à effet de champ“. Grenoble INPG, 2000. http://www.theses.fr/2000INPG0124.
Der volle Inhalt der QuelleAg, Atteynine Solimane. „Changement climatique et rongeurs ravageurs des cultures : effet attractif des cultures de saison sèche sur les espèces du genre Arvicanthis au Mali“. Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0130.
Der volle Inhalt der QuelleIn Mali, during the dry season, there is the issue of the attractive effect of dry season crops on rodent pests, which would be all the more marked in the latitudinal gradient of Sudan-Sahel aridity GECS (1100 mm to 200 mm). These hypotheses are tested in the genus Arvicanthis (A.ansorgei, A. niloticus). The results of the previous cytogenetic survey 1994-1999 and an expanded survey 2009-2014 reveal recent changes in the distribution areas of both species; suggesting a strong role of their chronobiological adaptation in the determinism of their distribution. This horizontal approach followed by a vertical approach (2009-2016) compares four indicators of the attractiveness of the CSS vs. the MNC in the five climatic regions of GECS (Sikasso, Koulikoro, Ségou, Mopti, Gao). The population densities of both species are higher in the CSS vs. the MNC; and this attractiveness of the CSS increases with aridity in the area of A. niloticus. The ratio of "migratory strategists" within populations demonstrates the buffering effect of the CSS and confirms the frequency of these episodes. The diet study confirms their phytophagous diet. In a natural environment, aridity induces a decrease in the consumption of plants compensated by that of non-orthopterous Arthropods; and the diversity of plants consumed decreases with aridity in A.ansorgei vs increases with aridity in A. niloticus. The buffering effect of CSS "neutralizes" inter-specific differences, and in both species, in the CSS, the diversity of weeds consumed decreases to the detriment of crops, especially rice and the consumption in the Orthoptera increases
Varache, Renaud. „Development, characterization and modeling of interfaces for high efficiency silicon heterojunction solar cells“. Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112279/document.
Der volle Inhalt der QuelleThe interface between amorphous silicon (a-Si:H) and crystalline silicon (c-Si) is the building block of high efficiency solar cells based on low temperature fabrication processes. Three properties of the interface determine the performance of silicon heterojunction solar cells: band offsets between a-Si:H and c-Si, interface defects and band bending in c-Si. These three points are addressed in this thesis.First, an analytical model for the calculation of the band bending in c-Si is developed. It assumes a constant density of states (DOS) in the a-Si:H band gap. The influence of most parameters of the structure on the band bending is studied: band offsets, DOS in a-Si:H, interface defects, etc. The presence of quantum confinement at the interface is discussed. Analytical calculations and temperature dependent planar conductance measurements are compared such that the band offsets on both (p)a-Si:H/(n)c-Si and (n)a-Si:H/(p)c-Si can be estimated: the valence band offset amounts 0.36 eV while the conduction band offset is 0.15 eV. In addition, it is shown that the valence band offset is independent of temperature whereas the conduction band offset follows the evolutions of c-Si and a-Si:H band gaps with temperature. A discussion of these results in the frame of the branch point theory for band line-up leads to the conclusion that the branch point in a-Si:H is independent of the doping.Then, analytical calculations are developed further to take into account the real solar cell structure where the a-Si:H/c-Si structure is in contact with a transparent conductive oxide and an undoped buffer layer is present at the interface. Measurements of the planar conductance and of the interface passivation quality are interpreted in the light of analytical calculations and numerical simulations to open a way towards a method for the optimization of silicon heterojunction solar cells. It is particularly shown that a trade-off has to be found between a good passivation quality and a significant band bending. This can be realized by tuning the buffer layer properties (thickness, doping), the TCO-contact (high work function) and the emitter (defect density and thickness). Interestingly, an emitter with a high DOS leads to better cell performances.Finally, a new type of interface has been developed, that was not applied to heterojunction solar cells so far. The c-Si surface has been oxidized in deionized water at 80 °C before the (p)a-Si:H emitter deposition such that (p)a-Si:H/SiO2/(n)c-Si structures were obtained. A tunneling current model has been developed, implemented in the 1D numerical device simulator AFORS-HET and used to study the effect of a wide band gap interfacial layer (as it is the case for SiO2) on cell performance: the fill-factor and the short-circuit current are dramatically reduced for thick and high barriers. However, a SiO2 layer has only little impact on optical properties. Fabricated samples show a passivation quality halfway between samples with no buffer layer and with an (i)a-Si:H buffer layer: this is explained by the presence of a negative fixed charge in the oxide. The band bending in (n)c-Si is higher with an oxide layer than with an (i)a-Si:H buffer layer. Solar cells demonstrate that this new concept has the potential to achieve high power conversion efficiencies: for non-optimized structures, an open-circuit voltage higher than 650 mV has been demonstrated, while the oxide does not seem to create a barrier to charge transport
Mirzoyan, Rafayel. „Study of the coherent effects in rubidium atomic vapor under bi-chromatic laser radiation“. Phd thesis, Université de Bourgogne, 2013. http://tel.archives-ouvertes.fr/tel-00934648.
Der volle Inhalt der QuelleKozlova, Olga. „Caractérisation d'une horloge à piégeage cohérent de population dans une vapeur thermique de césium. Principaux effets pouvant affecter la stabilité de fréquence à moyen-long terme“. Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00669784.
Der volle Inhalt der QuelleHakhumyan, Hrant. „Study of optical and magneto processes in Rb atomic vapor layer of nanometric thickness“. Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00764958.
Der volle Inhalt der QuelleRichardson, Jason. „The Effect of Mortgage Liberalization on Housing Patterns in Tampa Bay“. Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4213.
Der volle Inhalt der QuelleJaren, Sophie. „Étude de TbFe2 épitaxié par dépot laser pulsé : des couches minces aux nanostructures magnétiques“. Université Joseph Fourier (Grenoble ; 1971-2015), 1998. http://www.theses.fr/1998GRE10064.
Der volle Inhalt der QuelleRothman, Johan. „Etude des propriétés structurales, électroniques et magnétiques des couches minces épitaxiées de cerium“. Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10019.
Der volle Inhalt der QuelleSantana, Mark Vincent Eli. „The Effect of Urbanization on the Embodied Energy of Drinking Water in Tampa, Florida“. Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5772.
Der volle Inhalt der QuellePark, Jin Young. „A critical assessment of moist tamping and its effect on the initial and evolving structure of dilatant triaxial specimens“. Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/23949.
Der volle Inhalt der QuelleChang, Hsin-Pei Nicol. „The effect of fabric on the behaviour of gold tailings“. Thesis, Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-04072009-184620.
Der volle Inhalt der QuelleAdam, Fatima. „Quantification of the effect of air traffic on terminal precinct ground traffic and the corresponding ground traffic effect on kerbside and parking infrastructure requirements at O.R. Tambo International Airport“. Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/9991.
Der volle Inhalt der QuelleBona, Melissa Ellen. „The effect of straightening and grinding of welds on track roughness“. Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16180/7/Thesis_Melissa_Bona.pdf.
Der volle Inhalt der QuelleBona, Melissa Ellen. „The effect of straightening and grinding of welds on track roughness“. Queensland University of Technology, 2005. http://eprints.qut.edu.au/16180/.
Der volle Inhalt der QuelleGirard, Antoine. „Nouveaux substrats métalliques à texture biaxiale pour câbles supraconducteurs à haute température critique“. Phd thesis, Chambéry, 2006. http://tel.archives-ouvertes.fr/tel-00118093.
Der volle Inhalt der QuelleDes essais sur des laminoirs différents, avec ou sans lubrification et en modifiant le taux d'écrouissage ont permis de mettre en évidence des effets de peau et d'optimiser le procédé de déformation.
Les températures de recuit ont été choisies à la suite de caractérisations de texture avant et après le recuit ainsi que de mesures in-situ par diffraction de rayons X durs durant la montée en température.
Des laminages supérieurs à 98% et des recuits entre 900°C et 950°C en atmosphère protectrice ont permis d'obtenir des rubans ayant une forte texture cubique : désorientations hors du plan (DT) de 5° et dans le plan de 8°. Une partie de la surface est cependant maclée (entre 8% et 10%). Celle-ci entraîne localement de fortes désorientations.
L'état de surface a été contrôlé et amélioré par l'utilisation de rouleaux polis miroirs, l'optimisation des conditions de recuit (atmosphère et durée du palier) ainsi que l'ajout d'une étape d'électropolissage.
Des essais mécaniques et magnétiques ainsi qu'une étude d'oxydation ont été pratiqués pour vérifier le comportement du ruban dans les conditions d'utilisation comme dans les conditions rencontrées pendant les différents étapes de la réalisation du câble.
Le dépôt d'une couche d'oxyde protectrice LZO, sur le substrat a été réalisé avec succès. Les conditions d'un prétraitement sous atmosphère sulfurée, nécessaire à une bonne épitaxie de la couche, ont été déterminées : 1 h à 600°C avec un flux à 0,2 ppm d'H2S.
Enfin des essais sur le développement d'un alliage à barrière de diffusion in situ Cu Ni Y permettant de s'affranchir de la première couche tampon ont été menés.
Veldsman, Tamrin. „Effect of long-term physical activity intervention on the functional capacity of persons with intellectual disability : a Potchefstroom cohort / Tamrin Veldsman“. Thesis, 2014. http://hdl.handle.net/10394/15145.
Der volle Inhalt der QuelleMSc (Biokinetics), North-West University, Potchefstroom Campus, 2015