Dissertations / Theses on the topic 'Spectrin'
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1
McCubbin, T. Paul. "Novel #Beta#-spectrin isoforms." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279964.
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North, Alison Jane. "Spectrin localisation in mammalian striated muscle." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276872.
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Chen, Tony W. Nam Sang-Chul. "The role of spectrin in Drosophila photoreceptor development." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5209.
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Hill, Stephanie. "Folding and association of spectrin tetramer domains : a study of intrinsically disordered proteins from a protein folding perspective." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648579.
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Taupin, Hazel Lindsay. "Tyrosine phosphorylation of spectrin and its relation to neurite growth." Thesis, University of Kent, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497697.
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Bignone, Paola A. "Studies on the phosphorylation and tetramerisation of βII spectrin." Thesis, University of Kent, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252538.
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Godi, Anna. "Regulation and molecular composition of the Golgi-associated spectrin skeleton." Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393189.
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Fan, Jun. "The functional studies of a novel Golgi specific spectrin protein /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
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Gough, Lisa Lucio. "Dissecting the functions of the Golgi localized spectrin Syne-1 /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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O'Toole, Peter John. "Spectrin-lipid interactions : investigations by fluorescence spectroscopy and digital fluorescence microscopy." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242333.
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Sarri, Barbara Claire Mireille Annick. "Spectrin-lipid interactions and their effect on the membrane mechanical properties." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15976.
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This thesis presents the experimental work performed on the spectrin protein. The aim of the work was to study the direct interactions of spectrin, the cytoskeleton of RBCs, with membrane lipid to determine its effects on the mechanical properties of the lipid bilayer. Motivation for this work came from a lack of unanimity in the field of spectrin, and the hypothesized potential of the protein to perforate giant unilamellar vesicles. The work aimed to investigate and determine how spectrin-lipid interactions influence membrane mesoscopic morphology and biophysics in ways that could ultimately be important to cellular function. For this purpose, a protocol was implemented to take into account the different aspects of the binding. Direct visualisation of the spectrin-lipid interaction and distribution was achieved using confocal fluorescence microscopy. Changes in the mechanical properties of the membrane were investigated using the micropipette aspiration technique. Finally the thermodynamics of the interaction were considered with isothermal titration calorimetry experiments. This allowed evaluation of the protein-lipid interaction in a complete and coherent manner. Experiments were also performed on another elastic protein, alpha-elastin, for comparison. In addition to its similarities with spectrin (both possess hydrophobic domains and entropy elasticity), elastin is auto-fluorescent which makes it an attractive model protein. Elastin was also used as a sample model to implement new techniques using nonlinear optics microscopy.
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GALLI, CAMILLA. "DYNAMIC INTERPLAY BETWEEN SPECTRIN, ACTIN AND PLASMA MEMBRANE DURING CELL MECHANORESPONSE." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/697440.
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The spectrin cytoskeleton is a major component of the mammalian cell cortex. While long known and ubiquitously expressed, its dynamic behaviour and cooperation with other major components of the cell cortex is poorly understood. Here we investigated spectrin reactions upon different mechanical cues, such as cell-driven perturbations, like cell adhesion, spreading and contraction, or environmentally driven ones, like compression, stretch and osmotic changes. Upon all of these challenges we observed that spectrin meshwork spatially adapts and reorganizes under the plasma membrane together with the acto-myosin cytoskeleton. Working together to maintain cell integrity, both cytoskeletons define specific membrane territories. Actin-rich regions control protrusions, adhesions and stress fibers, whereas spectrin-rich regions concentrate in retractile zones, covering low actin density territories of the cortex. Given this interplay, we wondered if spectrin could be potentially involved in the spatial and temporal regulation of membrane trafficking. We followed spectrin, actin and clathrin dynamics through live TIRF microscopy and observed an inverted correlation between spectrin and actin densities and endocytic capacities, suggesting a spectrin contribution to clathrin-mediated endocytosis. Our results pinpoint a role for spectrin in the support of the lipid bilayer in regions where actin cytoskeleton is not established, creating a fencing mechanism for actin remodelling and cargoes internalization. All these mechanisms potentially unveil why the spectrin family of protein is evolutionary highly conserved and ubiquitously expressed in eukaryotic cells, and might explain its involvement in a broad range of pathological condition.
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Virel, Ana. "Molecular characterization and evolution of alpha-actinin : from protozoa to vertebrates." Doctoral thesis, Umeå University, Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-931.
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alpha-actinin is a ubiquitous protein found in most eukaryotic organisms. The ability to form dimers allows alpha-actinin to cross-link actin in different structures. In muscle cells alpha-actinin is found at the Z-disk of sarcomeres. In non-muscle cells alpha-actinin is found in zonula adherens or focal adhesion sites where it can bind actin to the plasma membrane.
alpha-actinin is the shortest member of the spectrin superfamily of proteins which also includes spectrin, dystrophin and utrophin. Several hypotheses suggest that alpha-actinin is the ancestor of this superfamily.
The structure of alpha-actinin in higher organisms has been well characterized consisting of three main domains: an N-terminal actin-binding domain with two calponin homology domains, a central rod domain with four spectrin repeats and a C-terminal calcium-binding domain. Data mining of genomes from diverse organisms has made possible the discovery of new and atypical alpha-actinin isoforms that have not been characterized yet.
Invertebrates contain a single alpha-actinin isoform, whereas most of the vertebrates contain four. These four isoforms can be broadly classified in two groups, muscle isoforms and non-muscle isoforms. Muscle isoforms bind actin in a calcium independent manner whereas non-muscle isoforms bind actin in a calcium-dependent manner.
Some of the protozoa and fungi isoforms are atypical in that they contain fewer spectrin repeats in the rod domain. We have purified and characterized two ancestral alpha-actinins from the parasite Entamoeba histolytica. Our results show that despite the shorter rod domain they conserve the most important functions of modern alpha-actinin such as actin-bundling formation and calcium-binding regulation. Therefore it is suggested that they are genuine alpha-actinins.
The phylogenetic tree of alpha-actinin shows that the four different alpha-actinin isoforms appeared after the vertebrate-invertebrate split as a result of two rounds of genome duplication. The atypical alpha-actinin isoforms are placed as the most divergent isoforms suggesting that they are ancestral isoforms. We also propose that the most ancestral alpha-actinin contained a single repeat in its rod domain. After a first intragene duplication alpha-actinin with two spectrin repeats were created and a second intragene duplication gave rise to modern alpha-actinins with four spectrin repeats.
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Herring, Tammy. "Calcium, actin and the spectrin skeleton, responses to swelling and shrinking perturbations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28427.pdf.
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Lubbers, Ellen R. "Defining New Mechanistic Roles for αII Spectrin in Cardiac Function and Excitability." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1554998846437076.
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Ringger, Nancy C. "A novel biomarker for traumatic brain injury csf alphaii-spectrin breakdown product levels /." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006487.
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Thesis (Ph.D.)--University of Florida, 2004.Typescript. Title from title page of source document. Document formatted into pages; contains 119 pages. Includes Vita. Includes bibliographical references.
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Rammé, Stephanie [Verfasser]. "Mutationssuche im α-Spectrin-Gen bei Patienten mit einer autosomal-dominanten Ataxie / Stephanie Rammé." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2012. http://d-nb.info/1026430607/34.
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Ragnauth, Cassandra Divika. "Characterisation and functional analysis of nesprins : a novel family of spectrin repeat containing proteins." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615228.
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Armiger, Travis J. "Force Propagation in Mammalian Cell Systems and the Relevance of the Mechanically Integrated Cell." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1143.
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Mammalian cells are known to respond to both extra- and intra- cellular forces as well as the physical properties of the surrounding tissue. There is increasing evidence to support the fundamental role of force, applied to or generated within cells, in maintaining proper tissue function. The mechanical integration from the exterior of a cell to the interior of the nucleus is crucial for cellular sensing of, and response to, the physical environment. Further, misregulation of this mechanosensitive ability can lead to the development or propagation of many diseases such as cancers, cardiovascular diseases, and tissue fibrosis. In this thesis, we investigate the role of various proteins in regulating the mechanical properties of mammalian cells. We also develop techniques to examine the propagation of forces through cells and multicell systems with the aim of elucidating critical biophysical factors involved in regulating cell function. The idea that the genome can be regulated through changes in forces applied to cells or changes in the propagation of forces through a cell, (i.e. mechanotransduction) is becoming widely accepted. The complex interplay between biochemical and biophysical mechanisms that ultimately control mechanotransduction are beginning to be uncovered; however, a true understanding of this remarkable cellular process has not yet been achieved. By investigating multiple factors which impact mechanosensitivity (such as protein expression, cell-cell and cell-environment connections, cell generated contractions, and physical connections through the cellular interior), we aim to further the understanding of potential pathways of mechanotransduction. Through novel studies and technological advances, the field of cellular biomechanics will continue to grow as we hope to uncover the physical mechanisms that regulate cell function or lead to disease.
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Marra, Pierfrancesco. "Role of the spectrin-based cytoskeleton in the function and dynamics of the Golgi complex." Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393199.
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Tardy, Philippe. "Caractérisation du trafic cellulaire du canal potassique à deux domaines P UNC-58 par la protéine UNC-44 chez le nématode C. elegans." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1157.
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Les canaux potassiques à deux domaines P (K2P) contrôlent l’excitabilité cellulaire et jouent un rôle central dans l’établissement et le maintien du potentiel de repos membranaire dans la majorité des cellules animales. Depuis leur identification dans les années 90, ces canaux ont été impliqués dans de nombreuses fonctions comme la modulation de l’activité neuronale, l’activité du muscle cardiaque ou encore la physiologie rénale. Malgré l’importance de ces canaux, peu de données existent sur les processus cellulaires qui contrôlent leur fonction in vivo. Au cours de ma thèse, j’ai utilisé des approches génétiques, d’imagerie et d’électrophysiologie pour comprendre comment l’expression, la distribution et l’activité du canal K2P UNC-58 sont contrôlés chez le nématode modèle C. elegans.Pour cela, j’ai effectué un crible suppresseur du phénotype locomoteur du mutant gain de fonction unc-58(e665). J’ai ainsi obtenu 133 mutants présentant une large gamme de niveaux de suppression, suggérant l’implication de plusieurs gènes dans les processus de régulation du canal. En utilisant les technologies de reséquençage complet de génome, j’ai pu cloner six nouveaux gènes requis pour la fonction d’unc 58.J’ai ensuite caractérisé en détail le rôle d’unc-44/ankyrine dans le contrôle du trafic d’unc 58. Ce travail a conduit à 4 conclusions majeures : (1) UNC-58, malgré sa structure de canal potassique, possède en réalité une sélectivité ionique altérée favorisant le passage des ions sodium, (2) l’addition à UNC 58 de protéine fluorescente par approche CRISPR/Cas9 nous a permis pour la première fois d’observer directement la distribution du canal UNC-58 in vivo, (3) l’ankyrine est nécessaire à l’adressage du canal UNC-58 à la surface des muscles et dans les axones des neurones mécanosenseurs ALM. Cette fonction fait intervenir une poche d’interaction lipidique localisée au sein du module Zu5N-Zu5C-UPA d’UNC-44, (4) ce mécanisme est hautement sélectif puisqu’il n’est pas requis pour l’adressage de 6 autres canaux potassiques musculaires. Mon crible a également identifié une interaction génétique entre unc-70/ß-spectrine et unc-44/ankyrine. Toutefois, la nature moléculaire de cette interaction reste encore à préciserTwo-pore potassium channels (K2P) control cell excitability and play a central role in the establishment and the maintenance of the resting membrane potential of almost all animal cells. Since their identification in the late 90s, these channels have been implicated in a large number of functions ranging from neuronal and cardiac activity to kidney physiology. Despite the crucial functions of these channels, comparatively little is known about the cellular processes controlling their function in vivo. During my PhD, I used a wide range of strategies including genetics, microscopy and electrophysiology to understand how the expression, the distribution and the activity of the K2P channel UNC-58 are controlled in the model nematode C. elegans. I have first performed a genetic suppressor screen targeting the locomotion phenotype of the gain of function mutant unc-58(e665). The screen yielded 133 mutants, displaying a wide range of suppression level, suggesting that several genes may be implicated in the channel regulation process. By using whole genome sequencing technologies, I’ve been able to clone six new genes required for the function of UNC-58.Then, I’ve characterized in detail the role of unc-44/ankyrin in the trafficking of UNC 58. This project led to 4 main conclusions : (1) UNC-58, despite its potassium channel structure, has an altered ionic selectivity, allowing preferably sodium ions to pass through the channel (2) the addition of a fluorescent protein to UNC-58 by CRISPR/Cas9 approaches allowed us for the first time to directly observe the addressing of the UNC-58 channel to the muscle surface and axons of ALM mechanosensory neurons. This function involves a lipid binding pocket located within the Zu5N-Zu5C-UPA module of UNC-44, (4) this mechanism is highly selective since it is not required for the addressing of 6 other muscular channels.My screen also identified a genetic interaction between unc-70/ß-spectrin and unc-44/ankyrin. However, the exact molecular nature of this interaction remains to be elucidated
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Wong, Simon Yuk Chun. "A spectrin-like protein in bovine retinal rod photoreceptor outer segments as defined by monoclonal antibodies." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29217.
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Biochemical and immunological studies indicate that rod outer segments (ROS) of bovine photoreceptor cells contain a Mr 240,000 polypeptide related to the ∝-subunit of red blood cell (RBC) spectrin. With the use of sodium dodecyl sulfate gel electrophoresis in conjunction with the immunoblotting technique, monoclonal antibody 4B2 was found to bind to a Mr 240,000 polypeptide in ROS that is distinct from the prominent Mr 220,000 concanavalin A binding glycoprotein. The Mr 240,000 polypeptide is highly susceptible to degradation by endogenous proteases. It does not appear to be an integral membrane protein but is tightly membrane associated since it can be partially extracted from ROS membranes with urea in the absence of detergent.
The 4B2 antibody cross-reacted with RBC ghost membranes and bovine brain microsomal membranes. Radioimmune assays and immunoblotting analysis of purified bovine RBC spectrin further revealed that the 4B2 antibody predominantly labelled the ∝-chain of RBC spectrin having an apparent Mr of 240,000. Monoclonal antibody 3A6 was found to bind to a polypeptide with a slightly lower Mr than the 4B2-specific polypeptide. It is also highly susceptible to degradation by endogenous proteases, but unlike the 4B2 antibody, it predominantly labelled the β-chain of RBC spectrin having an apparent M of 220,000. Polyclonal anti-spectrin antibodies that bound to both the ∝ - and β-chain of RBC spectrin predominantly labelled a Mr 240,000 polypeptide of ROS membranes. Two faintly labelled bands in the Mr range of 210,000-220,000 were also observed. These components may represent variants of the β -chain of spectrin that are weakly cross-reacting or present in smaller quantities than the ∝-chain.
Immunocytochemical labelling studies using the 4B2 antibody and immunogold-dextran markers indicated that the ROS spectrin-like protein is preferentially localized in the region where the discs come in close contact to the plasma membrane of ROS. Immunoblotting analysis indicated that rhodopsin and peripherin which constitute over 90% of total disc membrane proteins were selectively solubilized in Triton X-100, whereas a set of polypeptides including the 4B2-specific polypeptide and the Mr 220,000 concanavalin A-binding glycoprotein was only partially soluble. Electron microscopy of a negatively stained Triton-extracted ROS pellet revealed a filamentous network.
These studies indicate that ROS contain a protein related to RBC spectrin, which may constitute a major component of a filamentous network lining the inner surface of the ROS plasma membrane as previously seen by electron microscopy. This membrane skeletal system may serve to stabilize the ordered ROS structure and maintain a constant distance between the rim region of the discs and the plasma membrane.Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
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Mariani, Mariagabriella. "Purification and characterization of a red blood cell spectrin fraction which is tightly bound to the membrane /." [S.l.] : [s.n.], 1989. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8982.
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Cortese, Matteo. "Cellular and molecular mechanisms of Usher syndrome pathogenesis." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066390/document.
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Le syndrome d’Usher (USH) cause une surdité-cécité chez l’homme. Au moins neuf gènes responsables ont été identifiés. L’origine de l’atteinte auditive a été dévoilée par l’analyse de souris mutantes, mais les causes de la cécité sont encore obscures. Néanmoins, unes des protéines de Usher, la myosine VIIa, a été impliquée dans le transport intracellulaire dans les photorécepteurs. Pour mieux comprendre le rôle dans la rétine, j’ai étudié l’un de ses partenaires, la spectrine βV. Nous avons conclu que cette spectrine, en collaboration avec les protéines USH1, est impliquée dans le trafic cellulaire: elle couple les moteurs (myosine VIIA, kinesine II et le complexe dynéine/dynactine) à leurs cargos en route vers le segment externe des photorécepteurs. La combinaison d’études comparatives dans les cellules ciliées (CC) de l'oreille interne de grenouille et de souris, de tests biochimiques et d’analyses phylogénétiques indique que le transport vers et depuis la surface apicale des cellules est la fonction ancestrale de cette spectrine. Chez les mammifères, une pression évolutive a engendré le recrutement de la spectrine βV à la paroi latérale des CC externes auditives, probablement pour participer à une nouvelle fonction: l’électromotilité. Enfin, j’ai étudié l’origine de la surdité dans le syndrome d’Usher III. Le seul gène causal connu est CLRN1, qui code pour la clarine-1. Nous avons conclu que la clarine-1 est nécessaire à la maturation et le maintien des touffes ciliaires des CC. De plus, la clarine-1 est essentielle pour le regroupement des canaux calciques voltage-dépendants au voisinage immédiat de la machinerie exocytotique de la synapse à ruban des CC internesUsher syndrome (USH) causes a combined deafness-blindness in humans. At least nine causative genes are known. While the analysis of USH knockout mice has shed light on the origin of the auditory deficit, the causes of vision loss are still unclear. Nevertheless, USH1B protein, myosin VIIa, appears to contribute to intracellular traffic in photoreceptor cells. To better understand the role of this myosin in the retina, I studied the functions of its interacting partner, spectrin βV. We found that spectrin V, along with USH1 proteins, participates in intracellular transport by coupling motor proteins (myosin VIIa, kinesin II, dynein/dynactin complex) to the cargoes en route towards the outer segment of photoreceptor cells. Evidence from comparative studies in frog and mouse inner ear, biochemical assays and phylogenetic analyses point to cargo trafficking to and from the apical cell region, as the likely ancestral function of this spectrin. Our analyses also suggest that evolutionary pressures in the mammalian lineage drove the recruitment of spectrin βV to the lateral wall of auditory outer hair cells, probably to support a new function: electromotility. Finally, I explored the origin of hearing loss in Usher syndrome of type III (USH3). So far, the only causal gene known is CLRN1, which codes for clarin-1. The comparative characterization of two Clrn1 mouse mutants revealed that clarin-1 is required for the maturation and maintenance of the hair bundle in the hair cells. Moreover, our results indicate that clarin-1 is also essential to cluster the voltage-gated Ca2+ channels in close proximity to the exocytotic machinery of the ribbon synapse of inner hair cells
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Wilson, Gina Nicole. "PRE-DEGENERATIVE CHANGES IN THE RETINOFUGAL PROJECTION OF DBA/2J GLAUCOMATOUS MICE." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1501466545809801.
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Tak, Saurabh. "Les voies de mécanotransduction entre muscles et épiderme impliquées dans l'élongation embryonnaire de C. elegans." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ054/document.
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L'élongation embryonnaire de C. elegans a lieu en deux étapes. La première phase est permise par les contractions d’actomyosine et régulée par les kinases let-502 et pak-1. La seconde dépend des contractions musculaires (après le stade 1,7-fold). La tension fournie par ces contractions permet le recrutement de GIT-1 aux hémidesmosomes, facilitant la poursuite de l’élongation via l’activation de PAK-1 (Nature, 2011). Étonnamment, en l'absence de git-1 ou pak-1, l'élongation se poursuit, nous conduisant à émettre l'hypothèse de voies de régulation parallèles. Un crible ARNi a été réalisé pour rechercher les candidats impliqués. La majorité des candidats interagissant fortement avec git-1 appartenait au complexe dynéine-dynactine. En utilisant des allèles sensibles à la température et des protéines affectant les microtubules, nous avons décrit un rôle de la dynactine indépendant des microtubules dans l'épiderme ainsi que son interaction avec la spectraplakine vab-10 et la spectrine spc-1C. elegans embryonic elongation is driven by 2 forces: Actomyosin contractility and Muscle contraction (after 1.7-fold). Actomyosin contraction is regulated by the Rho kinase and the serine/threonine p21 activated kinase pak-1. Tension provided by muscle contraction recruits GIT-1 to hemidesmosomes (HD), which in turn facilitates further elongation by activating proteins such as PAK-1 (Nature 2011). Surprisingly in absence of git-1/pak-1, elongation still continues, which led us to hypothesize parallel pathways. An RNAi screen was performed to get the candidates in the parallel pathway/s. Candidates interacting strongly with git-1 belonged to the Dynein Dynactin complex. By use of temperature sensitive alleles and microtubule severing proteins, we found a microtubule independent role of Dynactin in epidermis and that dynactin functionally interacts with spectraplakin vab-10 and spectrin spc-1, which allows us to portray the role of Dynein Dynactin complex during embryonic elongation
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Pasti, Gabriella. "Etude du rôle des propriétés mécaniques des cellules de l'épiderme au cours de l'allongement des embryons de C. elegans." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ068.
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Mon travail se concentre sur la morphogenèse épithéliale pendant l’élongation embryonnaire de C. elegans. Ce processus s’appuie sur la transmission de signaux mécaniques, jouent un rôle essentiel également au cours de l’homéostasie tissulaire. Le gène pak-1 joue un rôle essentiel au cours des tels processus à la fois chez l’homme et dans l’élongation chez C. elegans. Nous avons montré que α-spectrine (SPC-1) est un nouveau partenaire de la kinase PAK-1. Pendant mon doctorat, j’ai confirmé que la perte simultanée de PAK-1 et de SPC-1 induit des défauts sévères d’élongation, impliquant une rétractation et un collapse général de l’embryon et suggèrent la présence de défauts biomécaniques. Mon travail était destiné à déterminer comment la perte de PAK-1 et SPC-1 influence le comportement mécanique des cellules épidermales. Cette étude permettra de mieux d’établir le rôle de SPC-1 et de PAK-1 dans la morphogenèse épithéliale et de mieux comprendre la régulation des propriétés mécaniques des cellules dans un contexte vivantI study epithelial morphogenesis during C. elegans embryonic elongation. This process depends on mechanical cues that also influence tissue homeostasis. The pak-1 gene plays an essential role equally during such processes in human and during C. elegans elongation. Our work identified α-spectrin (SPC-1) as a new interactor of the kinase PAK-1. During my PhD I confirmed that the simultaneous lack of PAK-1 and SPC-1 induces serious elongation defects, including a retraction and general collapse of the embryo and suggests that the mechanical properties of the epidermis are modified. My work aimed to determine how the simultaneous lack of PAK-1 and SPC-1 could influence these processes. Such studies would allow to better establish the role of SPC-1 and PAK-1 during epithelial morphogenesis and to better understand the regulation of cellular mechanical properties in the living organisms
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Cortese, Matteo. "Cellular and molecular mechanisms of Usher syndrome pathogenesis." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066390.pdf.
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Le syndrome d’Usher (USH) cause une surdité-cécité chez l’homme. Au moins neuf gènes responsables ont été identifiés. L’origine de l’atteinte auditive a été dévoilée par l’analyse de souris mutantes, mais les causes de la cécité sont encore obscures. Néanmoins, unes des protéines de Usher, la myosine VIIa, a été impliquée dans le transport intracellulaire dans les photorécepteurs. Pour mieux comprendre le rôle dans la rétine, j’ai étudié l’un de ses partenaires, la spectrine βV. Nous avons conclu que cette spectrine, en collaboration avec les protéines USH1, est impliquée dans le trafic cellulaire: elle couple les moteurs (myosine VIIA, kinesine II et le complexe dynéine/dynactine) à leurs cargos en route vers le segment externe des photorécepteurs. La combinaison d’études comparatives dans les cellules ciliées (CC) de l'oreille interne de grenouille et de souris, de tests biochimiques et d’analyses phylogénétiques indique que le transport vers et depuis la surface apicale des cellules est la fonction ancestrale de cette spectrine. Chez les mammifères, une pression évolutive a engendré le recrutement de la spectrine βV à la paroi latérale des CC externes auditives, probablement pour participer à une nouvelle fonction: l’électromotilité. Enfin, j’ai étudié l’origine de la surdité dans le syndrome d’Usher III. Le seul gène causal connu est CLRN1, qui code pour la clarine-1. Nous avons conclu que la clarine-1 est nécessaire à la maturation et le maintien des touffes ciliaires des CC. De plus, la clarine-1 est essentielle pour le regroupement des canaux calciques voltage-dépendants au voisinage immédiat de la machinerie exocytotique de la synapse à ruban des CC internesUsher syndrome (USH) causes a combined deafness-blindness in humans. At least nine causative genes are known. While the analysis of USH knockout mice has shed light on the origin of the auditory deficit, the causes of vision loss are still unclear. Nevertheless, USH1B protein, myosin VIIa, appears to contribute to intracellular traffic in photoreceptor cells. To better understand the role of this myosin in the retina, I studied the functions of its interacting partner, spectrin βV. We found that spectrin V, along with USH1 proteins, participates in intracellular transport by coupling motor proteins (myosin VIIa, kinesin II, dynein/dynactin complex) to the cargoes en route towards the outer segment of photoreceptor cells. Evidence from comparative studies in frog and mouse inner ear, biochemical assays and phylogenetic analyses point to cargo trafficking to and from the apical cell region, as the likely ancestral function of this spectrin. Our analyses also suggest that evolutionary pressures in the mammalian lineage drove the recruitment of spectrin βV to the lateral wall of auditory outer hair cells, probably to support a new function: electromotility. Finally, I explored the origin of hearing loss in Usher syndrome of type III (USH3). So far, the only causal gene known is CLRN1, which codes for clarin-1. The comparative characterization of two Clrn1 mouse mutants revealed that clarin-1 is required for the maturation and maintenance of the hair bundle in the hair cells. Moreover, our results indicate that clarin-1 is also essential to cluster the voltage-gated Ca2+ channels in close proximity to the exocytotic machinery of the ribbon synapse of inner hair cells
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Stubberfield, Lisa Marie. "Interactions of Plasmodium falciparum proteins at the membrane skeleton of infected erythrocytes." Monash University, Dept. of Microbiology, 2003. http://arrow.monash.edu.au/hdl/1959.1/9433.
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Reasor, Daniel Archer. "Numerical simulation of cellular blood flow." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42760.
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In order to simulate cellular blood, a coarse-grained spectrin-link (SL) red blood cell (RBC) membrane model is coupled with a lattice-Boltzmann (LB) based suspension solver. The LB method resolves the hydrodynamics governed by the Navier--Stokes equations while the SL method accurately models the deformation of RBCs under numerous configurations. This method has been parallelized using Message Passing Interface (MPI) protocols for the simulation of dense suspensions of RBCs characteristic of whole blood on world-class computing resources.
Simulations were performed to study rheological effects in unbounded shear using the Lees-Edwards boundary condition with good agreement with rotational viscometer results from literature. The particle-phase normal-stress tensor was analyzed and demonstrated a change in sign of the particle-phase pressure from low to high shear rates due to RBCs transitioning from a compressive state to a tensile state in the flow direction. Non-Newtonian effects such as viscosity shear thinning were observed for shear rates ranging from 14-440 inverse seconds as well as the strong dependence on hematocrit at low shear rates. An increase in membrane bending energy was shown to be an important factor for determining the average orientation of RBCs, which ultimately affects the suspension viscosity. The shear stress on platelets was observed to be higher than the average shear stress in blood, which emphasizes the importance of modeling platelets as finite particles.
Hagen-Poiseuille flow simulations were performed in rigid vessels for investigating the change in cell-depleted layer thickness with shear rate, the Fåhraeus-Linqvist effect, and the process of platelet margination. The process of platelet margination was shown to be sensitive to platelet shape. Specifically, it is shown that lower aspect ratio particles migrate more rapidly than thin disks. Margination rate is shown to increase with hematocrit, due to the larger number of RBC-platelet interactions, and with the increase in suspending fluid viscosity.
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Régnier, David. "Contribution à l'étude des gammas prompts de fission." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI065.
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Cette thèse a essentiellement été motivée par la montée en puissance de la thématique des échauffements nucléaires en réacteurs. Elle avait pour objectif la mise en place de méthodes permettant la simulation de l'émission des gammas prompts de fission. Pour répondre à cette attente, différents algorithmes de désexcitation d'un noyau ont été implémentés. Ils ont été testés avec succès via plusieurs calculs d'application (rapport d'embranchement isomérique, largeur radiative totale, etc). Ces méthodes ont ensuite été mises en oeuvre dans le cadre du code de fission FIFRELIN. L'outil qui en résulte, permet la détermination d'un grand nombre d'observables de fission, dans le cadre d'un modèle unique. Une étude de sensibilité des résultats à différents éléments du calcul a été réalisée. Enfin, des simulations de la fission spontanée du 252Cf, et des fissions induites par neutrons thermiques sur l' 235U et le 239Pu ont été menées. Les spectres des gammas prompts pour ces trois systèmes fissionnants ont pu être déterminés. Les résultats obtenus sont en très bon accord avec les données expérimentales disponibles, dont certaines ont été publiées récemment (2012 et 2013)This PhD thesis has essentially been motivated by the nuclear heating problematic in reactors. The main goal of this work was the production of methods capable of simulating the prompt gamma emission from fission. First of all, several algorithms for the treatment of the nucleus deexcitation were implemented. They have been succesfully tested through various calculations (isomeric branching ratio, total radiative width, etc). These methods were then incorporated in the frame of the fission code FIFRELIN. The tool which results from this work, enables the determination of numerous fission observables in the frame of a single consistent model. A sensitivity study of the results to several numerical and nuclear models has been realized. At last, calculation have been lead for the 252Cf spontaneous fission and the thermal neutron induced fission of 235U and 239Pu. The prompt gamma spectra obtained for those three fissionning systems have been determined. The results are in good agreement with available experimental data, including recent measurements published in 2012 and 2013
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Martin, Alexandre. "Théorie de Mourre et opérateurs de Schrödinger : De nouvelles classes d'opérateurs conjugués." Thesis, Cergy-Pontoise, 2018. http://www.theses.fr/2018CERG0978/document.
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Dans cette thèse, nous nous intéressons à l’étude du spectre essentiel d’opérateurs de Schrödinger et tout particulièrement à l’obtention d’un Principe d’Absorption Limite pour ces opérateurs. Ce Principe d’Absorption Limite consiste en l’existence d’une limite de l’opérateur résolvante lorsque le paramètre spectral se rapproche du spectre essentiel et permet de connaitre des informations sur le groupe engendré par l’Hamiltonien de Schrödinger. Une méthode pour montrer ce Principe d’Absorption Limite est d’utiliser la théorie de Mourre. Cette théorie nécessite l’utilisation d’un autre opérateur appellé opérateur conjugué. Lorsqu’on veut appliquer la théorie de Mourre aux opérateurs de Schrödinger, on utilise habituellement un opérateur conjugué nommé le générateur des dilatations. Cet opérateur implique que les dérivées du potentiel doivent avoir une certaine décroissance ce qui peut être gênant dans certains cas.Dans cette thèse, nous appliquerons le théorème de Mourre avec d’autres types d’opérateurs conjugués, dont certains n’impliquent pas de conditions de dérivabilité. Dans une première partie, nous nous intéresserons aux opérateurs de Schrödinger sur l’espace euclidienpour lesquels nous montrerons un Principe d’Absorption Limite à énergie strictement positive, un Principe d’Absorption Limite à énergie nulle et l’absence de valeurs propres plongées dans le spectre essentiel. Dans une seconde partie, nous nous intéresserons aux opérateurs de Schrödinger sur des guides d’ondes pour lesquels nous montrerons un Principe d’Absorption Limite loin des seuils et un Principe d’Absorption Limite près des seuilsIn this thesis, we are interested in the study of the essential spectrum of Schrödinger operators and more particulary in the obtention of a Limiting Absorption Principle for these operators. This Limiting Absorption Principle consists on the existence of a limit for the resolvent operator when the spectral parameter is near the essential spectrum and permits to know some properties about the group generated by the Schrödinger Hamiltonian we study. A technique to prove this Limiting Absorption Principle is to use the Mourre theory. This theory needs to use an other operator called the conjugate operator. When we want to apply the Mourre theory to Schrödinger operators, we usually used a conjugate operatornamed the generator of dilations. This operator implies some conditions of decay on the derivatives of the potentials which can be a problem in certain cases. In this thesis, we will apply the Mourre theory with other types of conjugate operators wich, for some of them, does not imply any conditions on the derivatives of the potential.In a first part, we will be interested in Schrödinger operators on the euclidian space. We will show a Limiting Absorption Principle at positive energy, a Limiting Absorption principle at zero energy and the absence of eigenvalue embedded in the essential spectrum. In a second part, we will be interested in Schrödinger operators on wave guides for which we will prove a Limiting Absorption Principle far thresholds and near thresholds
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Rozario, Hoimonti Immaculata. "Spectroscopic study of acetylene and hydrogen cyanide." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2012, 2012. http://hdl.handle.net/10133/3415.
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High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213–333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters.
The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results.
We have studied the line intensities of the 1νl20←0νl20 band system from the HCN emission spectrum. The infrared emission spectrum of H12C14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.viii, 112 leaves : ill. ; 29 cm
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Mohan, Anusha. "Neural Correlates of Spectral, Temporal and Spectro-temporal Modulation." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5078.
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Natural sounds are characterized by the distribution of acoustic power over different frequency regions and/or time. This is termed spectral, temporal or spectro-temporal modulation. The auditory system is equipped with banks of filters tuned to different spectral, temporal and spectro-temporal modulation frequencies (SM, TM, STM). The sensitivity of the peripheral system to these modulations can be measured by undertaking a linear systems approach. In addition to understanding the psychophysical sensitivity, studying the neural patterns of their processing is also critical. The current study is an attempt to understand the relationship between the behavioral and neural correlates of spectral, temporal and spectro-temporal processing in ten normal hearing subjects (age range 21-27 years; mean = 23.7 years). In the behavioral experiment, sensitivity to SM, TM and STM frequencies was estimated using a 3-interval, 3-alternative, forced-choice paradigm with a 3-down-1-up tracking algorithm. In the electrophysiological experiment, Electroencephalographs (EEGs) were recorded in a change-detection paradigm in response to the same set of modulation stimuli used in the behavioral experiment presented at 20 dB sensation level (SL). The EEG data were analyzed to determine the global field power and latencies of the N1and P2 components and the amplitude of the N1-P2 complex. Although an overall parietal dominance was observed for all of the components, the N1-P2 complex was strongly lateralized to the right hemisphere in the frontal region, but the hemispheric asymmetry decreased at central and parietal regions. A highly significant but weak to moderate negative correlation between individual behavioral thresholds and N1-P2 amplitudes was observed, and this relationship also was observed when behavioral spectro-temporal transfer functions and N1-P2 amplitude transfer functions were examined together. Thus the current project reveals that a relationship exists between the behavioral measures and neural correlates and gives us hope to work towards establishing this relationship.
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Dahl, Jason F. "Time Aliasing Methods of Spectrum Estimation." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd157.pdf.
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Deepak, G. C. "Spectrum sharing systems for improving spectral efficiency in cognitive cellular network." Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/85771/.
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Since spectrum is the invisible infrastructure that powers the wireless communication, the demand has been exceptionally increasing in recent years after the implementation of 4G and immense data requirements of 5G due to the applications, such as Internet-of-Things (IoT). Therefore, the effective optimization of the use of spectrum is immediately needed than ever before. The spectrum sensing is the prerequisite for optimal resource allocation in cognitive radio networks (CRN). Therefore, the spectrum sensing in wireless system with lower latency requirements is proposed first. In such systems with high spatial density of the base stations and users/objects, spectrum sharing enables spectrum reuse across very small regions. The proposed method in this Thesis is a multi-channel cooperative spectrum sensing technique, in which an independent network of sensors, namely, spectrum monitoring network, detects the spectrum availability. The locally aggregated decision in each zone associated with the zone aggregator (ZA) location is then passed to a decision fusion centre (DFC). The secondary base station (SBS) accordingly allocates the available channels to secondary users to maximize the spectral efficiency. The function of the DFC is formulated as an optimization problem with the objective of maximizing the spectral efficiency. The optimal detection threshold is obtained for different cases with various spatial densities of ZAs and SBSs. It is further shown that the proposed method reduces the spectrum sensing latency and results in a higher spectrum efficiency. Furthermore, a novel power allocation scheme for multicell CRN is proposed where the subchannel power allocation is performed by incorporating network-wide primary system communication activity. A collaborative subchannel monitoring scheme is proposed to evaluate the aggregated subchannel activity index (ASAI) to indicate the activity levels of primary users. Two utility functions are then defined to characterize the spectral efficiency (SE) and energy efficiency (EE) as a function of ASAI to formulate a utility maximization problem. The optimal transmit power allocation is then obtained with the objective of maximizing the total utility at the SBS, subject to maximum SBS transmit power and collision probability constraint at the primary receivers. Since optimal EE and SE are two contradicting objectives to obtain the transmit power allocation, the design approach to handle both EE and SE as a function of common network parameter, i.e., ASAI, is provided which ultimately proves the quantitative insights on efficient system design. Extensive simulation results confirm the analytical results and indicate a significant improvement in sensing latency and accuracy and a significant gain against the benchmark models on the rate performance, despite the proposed methods perform with lower signalling overhead.
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Makara, Michael A. "Molecular physiology of ankyrin-G in the heart:Critical regulator of cardiac cellular excitability and architecture." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1455812677.
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Bandeira, Nuno Filipe Cabrita. "Spectral networks algorithms for de novo interpretation of tandem mass spectra." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274510.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 141-152).
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Kharroubi, Hassane. "Étude du pouvoir réflecteur de monocristaux uniaxes et biaxes dans l'infrarouge lointain." Nancy 1, 1994. http://www.theses.fr/1994NAN10108.
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L'étude du pouvoir réflecteur (r) et de la transmission (t) des milieux anisotropes et absorbants dans l'infrarouge lointain nous a conduit a présenter des expressions directement programmables des relations permettant la détermination des constantes optiques, l'indice de réfraction n et l'indice d'absorption k à partir des mesures expérimentales de r et de t. Nous avons établi les expressions des facteurs de réflexion et de transmission pour les deux polarisations possibles de l'onde, en fonction de l'angle d'incidence. L'étude est limitée au cas de la propagation d'une onde plane dans les plans principaux du cristal. Nous abordons ensuite le cas de la lame à faces parallèles qui représente physiquement nos échantillons. Les facteurs de réflexion et de transmission sont mesurés dans l'infrarouge lointain de 10 à 600 cm##1 en lumière polarisée pour des températures comprises entre 7 et 300 k. Pour cette étude nous avons choisi un cristal biaxe, le nitrite de sodium et deux cristaux uniaxes, la cassitérite et le quartz. La comparaison des résultats expérimentaux et des valeurs calculées nécessite la connaissance de la fonction diélectrique. Nous utilisons la forme factorisée de la fonction diélectrique. Les valeurs initiales des paramètres d'ajustage sont déterminées par une analyse de Kramers-Kronig du spectre de réflexion sous incidence normale. La mesure simultanée du pouvoir réflecteur et de la transmission de la lame nous permet d'apporter une correction pour déterminer la valeur vraie du pouvoir réflecteur des cristaux, valeur nécessaire pour les calculs de physique du solide
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Mekler, A. A., Christine Böckmann, and N. Sokolovskaia. "Particle distribution from spectral Mie-scattering: kernel representation and singular-value spectrum." Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2007/1494/.
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This paper deals with the Mie scattering kernels for multi-spectral data. The kernels may be represented in form of power series. Furthermore, the
singular-value spectrum and the degree of ill-posedness in dependence on the refractive index of the particles are numerically approximated. A special hybrid
regularization technique allows us to determine via inversion the particle distributions of different types.
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鄧愛紅 and Aihong Deng. "Some studies towards improving positron lifetime spectroscopy for semiconductors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31214083.
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Bing, Zhou. "Crosshole resistivity and acoustic velocity imaging : S.5-D helmholtz equation modeling and inversion /." Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phb613.pdf.
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Berge, Léonie. "Contribution à la modélisation des spectres de neutrons prompts de fission .Propagation d'incertitudes sur un calul de fluence cuve." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI039/document.
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Le spectre des neutrons prompts de fission (PFNS) est une donnée très importante pour diverses applications de la physique nucléaire. Cependant, en dehors du spectre de la fission spontanée du 252Cf, qui est reconnu comme un standard international et est utilisé pour la métrologie, le PFNS reste mal connu pour la plupart des noyaux fissionnants. En particulier, pour la fission rapide (induite par un neutron de plus de 100 keV environ), il existe peu de mesures, et les évaluations internationales présentent de fortes contradictions. De plus, il existe très peu de données sur les covariances associées aux diverses évaluations du spectre. Dans cette thèse, trois aspects de l'évaluation du PFNS sont abordés. Le premier aspect est la modélisation du spectre via le code FIFRELIN, développé au CEA Cadarache, qui simule la chaine de désexcitation des fragments de fission par émissions successives de neutrons et gammas prompts par la méthode de Monte-Carlo. Ce code a pour vocation de calculer les observables de fission dans un même calcul cohérent, à partir des distributions en masse, en énergie cinétique et en spin des fragments de fission. FIFRELIN a donc un caractère prédictif que n'ont pas les modèles analytiques utilisés pour décrire le PFNS. Une étude des paramètres de modèle influents, notamment le paramètre de densité de niveaux, est mené afin de tenter de mieux reproduire le spectre. Le deuxième aspect de la thèse concerne l'évaluation du PFNS et de sa matrice de covariance. On propose une méthodologie pour évaluer le spectre et sa matrice de covariance de manière rigoureuse, à travers l'outil CONRAD du CEA Cadarache. Ceci implique la modélisation du spectre à travers des modèles simples, notamment celui de Madland-Nix qui est le plus utilisé dans les évaluations, en ajustant les paramètres de ces modèles afin de reproduire les données expérimentales. La matrice de covariance provient de la propagation rigoureuse des sources d'incertitude qui interviennent dans le calcul. En particulier, les incertitudes systématiques liées au dispositif expérimental sont propagées par des techniques de marginalisation. La marginalisation permet de propager ces incertitudes sur le spectre calculé, en obtenant des incertitudes réalistes sans besoin d'être artificiellement rehaussées comme c'est souvent le cas dans le cadre d'ajustements bayésiens. La propagation de ces incertitudes expérimentales impacte aussi la matrice de corrélation du spectre calculé. On présente les résultats pour la fission induite par neutron thermique de l'235U et du 239Pu. Pour le modèle de Madland-Nix avec section inverse constante, l'énergie moyenne des neutrons prompts obtenue est de 1.979 MeV pour l'235U, et de 2.087 MeV pour le 239Pu. Le dernier aspect de la thèse est l'étude de l'impact du PFNS et de ses covariances sur le calcul du flux neutronique sur la cuve d'un réacteur. L'enjeu est de taille, car l'estimation de la fluence au niveau de la cuve d'un réacteur détermine l'intégrité de celle-ci, et donc la durée de vie du réacteur. On observe l'importance des termes de corrélations du spectre pour calculer notamment l'incertitude sur le flux intégré au-dessus de 1 MeV, de l'ordre de 6% (incertitude due seulement au spectre)The prompt fission neutron spectrum (PFNS) is very important for various nuclear physics applications. Yet, except for the 252Cf spontaneous fission spectrum which is an international standard and is used for metrology purposes, the PFNS is still poorly known for most of the fissionning nuclides. In particular, few measurements exist for the fast fission spectrum (induced by a neutron whose energy exceeds about 100 keV), and the international evaluations show strong discrepancies. There are also very few data about covariances associated to the various PFNS evaluations. In this work we present three aspects of the PFNS evaluation. The first aspect is about the spectrum modeling with the FIFRELIN code, developed at CEA Cadarache, which simulates the fission fragment de-excitation by successive emissions of prompt neutrons and gammas, via the Monte-Carlo method. This code aims at calculating all fission observables in a single consistent calculation, starting from fission fragment distributions (mass, kinetic energy and spin). FIFRELIN is therefore more predictive than the analytical models used to describe the spectrum. A study of model parameters which impact the spectrum, like the fragment level density parameter, is presented in order to better reproduce the spectrum. The second aspect of this work is about the evaluation of the PFNS and its covariance matrix. We present a methodology to produce this evaluation in a rigorous way, with the CONRAD code, developed at CEA Cadarache. This implies modeling the spectrum through simple models, like the Madland-Nix model which is the most commonly used in the evaluations, by adjusting the model parameters to reproduce experimental data. The covariance matrix arises from the rigorous propagation of the sources of uncertainty involved in the calculation. In particular, the systematic uncertainties arising from the experimental set-up are propagated via a marginalization technique. The marginalization allows propagating these uncertainties on the calculated spectrum, and obtaining realistic uncertainties without having to artificially raise them, as it is sometimes necessary in Bayesian adjustments. The experimental uncertainty propagation also impacts the spectrum correlation matrix. We present the result for thermal neutron-induced fission of 235U and 239Pu. For the Madland-Nix model with constant inverse cross-section, the prompt neutron mean energy is 1.979 MeV for 235U and 2.087 MeV for 239Pu. The last aspect of this work is the calculation of the impact of the PFNS and its covariance matrix on a reactor vessel flux. This calculation is of major importance, since the vessel fluence estimation determines the vessel integrity, and therefore determines the reactor lifetime. We observe the importance of the PFNS correlation terms, to compute in particular the vessel flux uncertainty above 1 MeV, which is of the order of 6% (uncertainty only due to PFNS)
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Lu, Lu. "Spectral-efficient design in modern wireless communications networks." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53902.
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We investigate spectral-efficient design and develop novel schemes to improve spectral efficiency of the modern wireless communications networks. Nowadays, more and more spectrum resources are required to support various high-data-rate applications while spectrum resources are limited. Moreover, static allocation and exclusive access in current spectrum assignment policy caused a lot of licensed spectrum bands to be underutilized. To deal with the problem, cognitive radio (CR) has been developed, which allows unlicensed/secondary users to transmit with licensed/primary users as long as the former ones do not generate intolerable interference to the latter ones. The coexistence of users and networks requires careful and dynamic planning to mitigate interference. Otherwise, the network performance will be severely undermined. We study both spectrum sensing and spectrum access techniques and propose several transmit schemes for different types of cognitive ratio networks, including spectrum overlay and spectrum underlay systems. The proposed algorithms can improve spectral efficiency of the networks efficiently and have potentials to be used in future wireless communications networks.
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Akkouche, Sofiane. "Sur la theorie spectrale des opérateurs de Schrödinger discrets." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14098/document.
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Cette thèse traite de la théorie spectrale des opérateurs de Schrödinger discrets H(λ) := - Δ + b sur Zd et plus généralement sur des graphes pondérés infinis. Plus précisément, nous étudions le comportement des fonctions spectrales qui représentent les bornes du spectre de ces opérateurs. Un des principaux résultats est l'obtention d'une condition nécessaire et suffisante sur le potentiel b pour que le bas du spectre soit strictement positif. L'étude du haut du spectre est également considérée.Nous étudions tout d'abord ces questions pour les opérateurs de Schrödinger discrets sur Zd. La régularité de cet espace permet alors d'obtenir des résultats spécifiques dans ce cas particulier. Nous généralisons ensuite nos travaux au cas des graphes infinis pondérés. Les techniques développées dans ce cadre nous permettent également d'étudier le comportement asymptotique du bas du spectre pour les grandes valeurs de λThis thesis deals with the spectral theory of discrete Schrödinger operators H(λ) := - Δ + b on Zd and more generally on in#nite weighted graphs. Precisely, we study the behavior of the spectral functions which represent the spectral bounds of these operators. One of the main results is the obtention of a necessary and sufficient condition on the potential b such that the bottom of the spectrum is stricly positive.The study of the top of the spectrum is also treated.We first study these questions for discrete Schrödinger operators on Zd. The regularity of this space provides specific results in this particular case. Then we extend our work to the case of infinite weighted graphs. Moreover, the technics developed in this framework allow us to study the asymptotic behavior of the bottom of the spectrum for large values of λ
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Harvey, Pierre Dominique. "Applications of vibrational spectroscopy and NMR spin-lattice relaxation time measurements to organometallic and organic molecular crystals." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73986.
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Borde, Arnaud. "One-Dimensional Power Spectrum and Neutrino Mass in the Spectra of BOSS." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01023004.
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The framework of the studies presented in this thesis is the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forests. The Lyman-alpha forest is an an absorption pattern seen in the spectra of high redshift quasars corresponding to the absorption of the quasar light by the hydrogen clouds along the line of sight. It is a powerful cosmological tool as it probes relatively small scales, of the order of a few Mpc. It is also sensible to small non-linear effects such as the one induced by massive neutrinos.First, we have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from =2.2 to =4.4, and scales from 0.001 (km/s)^−1 to 0.02 (km/s)^−1. We carefully determined the methodological and instrumental systematic uncertainties of our measurements.Then, we present a suite of cosmological N-body simulations with cold dark matter, baryons and neutrinos aiming at modeling the low-density regions of the IGM as probed by the Lyman-alpha forests at high redshift. The simulations are designed to match the requirements imposed by the quality of BOSS and eBOSS data. They are made using either 768^3 or 192^3 particles of each type, spanning volumes ranging from (25 Mpc/h)^3 for high-resolution simulations to (100 Mpc/h)^3 for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 3072^3 = 29 billion particles of each type in a (100 Mpc/h)^3 box size, i.e. a mean mass per gas particle of 1.2x10^5 solar masses. We show that the resulting power spectrum is accurate at the 2% level over the full range from a few Mpc to several tens of Mpc. We explore the effect on the one-dimensional transmitted-flux power spectrum of 4 cosmological parameters (n_s, sigma_8, Omega_m ,H_0), 2 astrophysical parameters (T_0, gamma) related to the heating rate of the IGM and the sum of the neutrino masses. By varying the input parameters around a central model chosen to be in agreement with the latest Planck results, we built a grid of simulations that allows the study of the impact on the flux power spectrum of these seven relevant parameters. We improve upon previous studies by not only measuring the effect of each parameter individually, but also probing the impact of the simultaneous variation of each pair of parameters. We thus provide a full second-order expansion, including cross-terms, around our central model. We check the validity of the second-order expansion with independent simulations obtained either with different cosmological parameters or different seeds for the initial condition generation. Finally, a comparison to the one-dimensional Lyman-alpha forest power spectrum obtained in the first part with BOSS data shows an excellent agreement.Eventually, even if there are still some potential biases and systematic errors that need to be studied in our simulation, we performed cosmological fits combining our measurement of the one-dimensional power spectrum and other cosmological probes such as the CMB results provided by Planck. These preliminary results are very encouraging as they lead to some of the tighest cosmological constraints as of today, especially on the sum of the neutrino masses with an upper limit of 0.1 eV.
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Rosenmann, Laurence. "Etudes théorique et expérimentale de l'élargissement par collisions des raies de CO2 perturbé par CO2, H2O, N2 et O2 : constitution d'une base de données infrarouge et Raman appliquée aux transferts thermiques et à la combustion." Châtenay-Malabry, Ecole centrale de Paris, 1988. http://www.theses.fr/1988ECAP0071.
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Etude systématique des coefficients d'élargissement par collisions des raies infrarouge et Raman de dioxyde de carbone perturbé par dioxyde de carbone, eau, diazote et dioxygène. Les résultats obtenus dans la gamme de température 300-3000 K sont utiles pour modéliser les transferts radiatifs en particulier dans les systèmes de combustion, et pour les diagnostics infrarouge et Raman.
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Mambrini, Thomas. "Caractérisation de panneaux solaires photovoltaïques en conditions réelles d’implantation et en fonction des différentes technologies." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112380/document.
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Dans un contexte de fort déploiement du Photovoltaïque (PV), de plus en plus de recherches sont menées pour assurer une certaine fiabilité et prédictibilité de la production provenant du PV. Les investisseurs se plaignent d’un manque de visibilité dans cette filière et hésitent à investir dans le PV (surtout avec les baisses régulières des tarifs de rachats). Il est donc nécessaire pour le développement de la filière PV de faire des efforts pour étudier, comprendre les systèmes PV en fonctionnement et ainsi donner plus de visibilité pour l’amélioration des systèmes, leur monitoring, une plus grande fiabilité et pouvoir prédire plus précisément le productible PV en améliorant les modèles de prédiction du productible PV déjà existants.C’est dans ce cadre que s’inscrit cette thèse qui a pour but de caractériser les modules PV en conditions réelles d’utilisation en fonction des différentes technologies. Nous étudions, dans cette thèse, les facteurs extérieurs qui influent sur le comportement des modules de différentes filières, pour tenter de rendre le PV plus fiable et prédictible. C’est donc un axe de recherche qui vient en complément de la caractérisation en laboratoire qui a pour objectif l’amélioration des rendements des cellules.Pour y parvenir il est nécessaire, dans un premier temps, de connaitre les paramètres extérieurs qui influent sur le fonctionnement du module et savoir comment les étudier. Une partie de la thèse est par conséquent consacrée à l'étude des facteurs météorologiques et atmosphériques ayant un impact sur le comportement électrique du module ainsi que la mise en place d'instruments et méthodes pour les mesurer. On présente également les avantages et inconvénients de la caractérisation en extérieur.Après avoir exposé tous les paramètres à prendre en compte, on décrit l'installation de plusieurs plateformes de caractérisation de modules PV entièrement automatisées que l'on a monté au cours de cette thèse au LGEP ainsi qu'à l'École Polytechnique et qui ont toutes un objectif particulier.Ce manuscrit montre par la suite les différentes applications et utilités que peuvent avoir de telles plateformes en analysant les données enregistrées régulièrement (toutes les minutes en moyenne) sur des périodes allant de quelques jours à plusieurs mois. On compare, par la même occasion, les données constructeur prises en conditions standard de test et les performances mesurées dans de nombreuses conditions de modules PV. Les résultats obtenus peuvent servir à la fois pour la recherche, l'aide à la compréhension du comportement des modules, par conséquent aide à la prévision du productible d'installation PV et peuvent avoir un rôle pédagogique dans l'enseignement du PV.Enfin, une dernière partie est dédiée à la description et à la démonstration de faisabilité d'une carte qui permet d'obtenir les caractéristiques principales de n'importe quel module PV en les extrayant de la courbe I(V) mesurée. Cette carte, développée au LGEP, a d'autres utilités telles que la recherche du point de fonctionnement maximale du module (MPPT)Nowadays, photovoltaic (PV) keeps growing fast and an increasing number of studies is require in order to assure the reliability and predictability of the PV-produced electricity. The lack of visibility concerning this field is a continuous source of complaints from the investors who hesitate to commit to PV projects (especially after the decrease of buying prices in Europe). Therefore, to assure the successful increase of PV energy, it is necessary to provide studies aiming at better understanding PV systems in real operations conditions, that means in outdoor conditions.The goal of this doctoral work has been to characterize different PV module technologies in their real use conditions. The outdoor parameters that influence the behavior of different module technologies have been investigated. The goal was to obtain useful information which could make PV-produced electricity more reliable. Therefore, these studies can efficiently complete standard laboratory characterization tests made under a single condition, the purpose of which is usually to determine the efficiency of the different solar cells technologies.To achieve this goal, first it has been necessary to define the outdoor parameters that mainly influence the modules and the most suitable methods to be used for their investigation. For this reason, part of this doctoral work has been devoted to the study of weather and atmospheric factors affecting the electrical behavior of the modules, as well as setting up instruments and methods to measure them. Additionally, advantages and disadvantages of outdoors characterizations have been addressed.Then, after multiple fully automated PV platforms, mounted at the LGEP and at Ecole Polytechnique, thanks to a collaboration with the Laboratoire de Méteorologie Dynamique (LMD). The different applications and uses of these platforms have been highlighted by analyzing data recorded periodically (every minute on average) over periods ranging from days to several months. Manufacturer data, which are acquired in standard test conditions, and the performance measured in several conditions are compared. These results can be used for both research, understanding the behavior of the modules, help in predicting the energy yield of PV system and also to stress the educational role in teaching PV.Finally, the feasibility of an electric card that provides the main characteristics of any PV module by extracting the measured I(V) curve is described. Such electric card, developed at the LGEP, has other uses such as the determination of the maximum operating point
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Brett, Caroline. "Spectral theory using linear systems and sampling from the spectrum of Hill's equation." Thesis, Lancaster University, 2015. http://eprints.lancs.ac.uk/79286/.
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This thesis, entitled Spectral Theory Using Linear Systems and Sampling from the Spectrum of Hill’s Equation is submitted by Caroline Brett, Master of Science for the degree of Doctor of Philosophy, September 2015. It uses linear systems to solve various problems connected with Hill’s equation, −f + qf = λf for q ∈ C2, real-valued and π-periodic. Introducing a new operator, Rx constructed from a linear system, (−A, B, C) allows us to solve Hill’s equation and the inverse spectral problem. We use Rx to construct a function, T(x, y) that satisfies a Gelfand–Levitan integral equation and then derive a PDE for T(x, y). Solving this PDE recovers q. Extending Hill’s work in [28], we show that there exist Hilbert–Schmidt operators, Rp and Rc analogous to Rx, such that the roots of their Carleman determinants are elements of the periodic spectrum of Hill’s equation. The latter half concerns sampling from entire functions in Paley–Wiener space. From the periodic spectrum of Hill’s equation we derive a sampling sequence, (tn)n∈Z. Whittaker, Kotel’nikov and Shannon give a sampling result for (n)n∈Z where samples occur at a constant rate. Samples taken from the periodic spectrum do not occur at a constant rate, nevertheless we provide analogous results for this case. From (tn)n∈Z we also construct Riesz bases for L2[0, π] and L2[−π, π], the Fourier transform space of PW(π). In L2[0, π] we construct the dual Riesz basis using linear systems. Furthermore, we show that the determinant of the Gram matrix associated with the Riesz basis is a Lipschitz continuous function of (tn)n∈Z. Finally, we look at an integral, Ia associated with Ramanujan and use it to create a basis for PW π2. We conclude with an evaluation of various determinants associated with Ia.