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1
Qureshi, Fahad. "Optimization of Rotations in FFTs." Doctoral thesis, Linköpings universitet, Elektroniksystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-74702.
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The aims of this thesis are to reduce the complexity and increasethe accuracy of rotations carried out inthe fast Fourier transform (FFT) at algorithmic and arithmetic level.In FFT algorithms, rotations appear after every hardware stage, which are alsoreferred to as twiddle factor multiplications. At algorithmic level, the focus is on the development and analysisof FFT algorithms. With this goal, a new approach based on binary tree decompositionis proposed. It uses the Cooley Tukey algorithm to generate a large number ofFFT algorithms. These FFT algorithms have identical butterfly operations and data flow but differ inthe value of the rotations. Along with this, a technique for computing the indices of the twiddle factors based on the binary tree representation has been proposed. We have analyzed thealgorithms in terms of switching activity, coefficient memory size, number of non-trivial multiplicationsand round-off noise. These parameters have impact on the power consumption, area, and accuracy of the architecture.Furthermore, we have analyzed some specific cases in more detail for subsets of the generated algorithms. At arithmetic level, the focus is on the hardware implementation of the rotations.These can be implemented using a complex multiplier,the CORDIC algorithm, and constant multiplications. Architectures based on the CORDIC and constant multiplication use shift and add operations, whereas the complex multiplication generally uses four real multiplications and two adders.The sine and cosine coefficients of the rotation angles fora complex multiplier are normally stored in a memory.The implementation of the coefficient memory is analyzed and the best possible approaches are analyzed.Furthermore, a number of twiddle factor multiplication architectures based on constant multiplications is investigated and proposed. In the first approach, the number of twiddle factor coefficients is reduced by trigonometric identities. By considering the addition aware quantization method, the accuracy and adder count of the coefficients are improved. A second architecture based on scaling the rotations such that they no longer have unity gain is proposed. This results in twiddle factor multipliers with even lower complexity and/or higher accuracy compared to the first proposed architecture.
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Rodrigues, Letícia Jenisch. "Fatores de Dancoff de celulas unitarias em geometria Cluster com absorção parcial de nêutrons." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/28965.
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O fator de Dancoff, em sua formulação clássica, corrige a corrente de nêutrons incidente na superfície de uma vareta combustível devido à presença das demais varetas da célula. Alternativamente, esse fator pode ser interpretado como a probabilidade de um nêutron oriundo de uma vareta de combustível entrar em outra vareta sem colidir no moderador ou no revestimento. Para combustíveis perfeitamente absorvedores essas definições são equivalentes. Entretanto, quando se assume a hipótese de absorção parcial no combustível, essa equivalência não se verifica. Então, os fatores de Dancoff devem ser determinados em termos de probabilidades de colisão. Ao longo dos últimos anos, vários trabalhos, usando ambas as definições, vêm relatando melhorias no cálculo dos fatores Dancoff. Neste trabalho, esses fatores são determinados através do método de probabilidades de colisão para células em geometria cluster com contorno externo quadrado, assumindo-se absorção total (Black Dancoff Factors) e parcial (Grey Dancoff Factors) no combustível. A validação dos resultados é feita através de comparações com a célula cilíndrica equivalente. O cálculo é realizado considerando-se reflexão especular, para a célula quadrada, e condição de contorno difusa (white) para a célula cilíndrica equivalente. Os resultados obtidos, com o aumento do tamanho das células, evidenciam o comportamento assintótico da solução. Além disso, são computados fatores de Dancoff para as células canadenses CANDU-37 e CANFLEX por ambas as metodologias de cálculo, direta e probabilística. Finalmente, os fatores de multiplicação efetivo, keff, para as células com contorno externo quadrado e a cilíndrica equivalente, são determinados e as diferenças registradas para os casos onde se assumem as hipóteses de absorção total e parcial.In its classical formulation, the Dancoff factor for a perfectly absorbing fuel rod is defined as the relative reduction in the incurrent of resonance neutrons into the rod in the presence of neighboring rods, as compared to the incurrent into a single fuel rod immersed in an infinite moderator. Alternatively, this factor can be viewed as the probability that a neutron emerging from the surface of a fuel rod will enter another fuel rod without any collision in the moderator or cladding. For perfectly absorbing fuel these definitions are equivalent. In the last years, several works appeared in literature reporting improvements in the calculation of Dancoff factors, using both the classical and the collision probability definitions. In this work, we step further reporting Dancoff factors for perfectly absorbing (Black) and partially absorbing (Grey) fuel rods calculated by the collision probability method, in cluster cells with square outer boundaries. In order to validate the results, comparisons are made with the equivalent cylindricalized cell in hypothetical test cases. The calculation is performed considering specularly reflecting boundary conditions, for the square lattice, and diffusive reflecting boundary conditions, for the cylindrical geometry. The results show the expected asymptotic behavior of the solution with increasing cell sizes. In addition, Dancoff factors are computed for the Canadian cells CANDU-37 and CANFLEX by the Monte Carlo and Direct methods. Finally, the effective multiplication factors, keff, for these cells (cluster cell with square outer boundaries and the equivalent cylindricalized cell) are also computed, and the differences reported for the cases using the perfect and partial absorption assumptions.
3
Guillouet, Stéphane. "Étude cinétique et physiologique de Corynebacterium glutamicum sous stress osmotique." Vandoeuvre-les-Nancy, INPL, 1996. http://docnum.univ-lorraine.fr/public/INPL_T_1996_GUILLOUET_S.pdf.
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L’objectif général de ce travail est l'étude du comportement cinétique et physiologique de Corynebacterium glutamicum en croissance dans des conditions de stress osmotique. Cette étude comporte quatre parties au cours desquelles les cinétiques de croissance et d'accumulation des métabolites intracellulaires sont présentées pour différents modes et conditions de culture. Nous avons mis en évidence les événements physiologiques successifs à un choc hyperosmotique lors de cultures discontinues et continues. Ainsi l'élévation de la pression osmotique externe entraine une diminution de la vitesse spécifique de la croissance et du rendement de croissance sur glucose. À la suite du choc osmotique, une accumulation transitoire d'ions sodium ou potassium a été observée suivant l'osmolyte dépresseur utilisé. Par la suite, Corynebacterium glutamicum accumule de manière importante de la proline. Nous avons montré que le contenu cellulaire en proline varie proportionnellement avec l'osmolarité du milieu et avec la vitesse spécifique de croissance. Une accumulation intracellulaire de tréhalose a également été observée en réponse au choc osmotique lors des cultures continues. Cette synthèse de tréhalose est augmentée lorsque la voie de biosynthèse de la proline est affectée, par exemple, lors de cultures continues sous limitation ammonium et potassium ou lors de cultures discontinues d'une souche génétiquement modifiée bradytrophe pour la proline. L’accumulation de ces différents métabolites entraine une augmentation de la pression osmotique intracellulaire proportionnelle à l'osmolarité du milieu. Par ailleurs, nous avons observé que la pression de turgescence (différence entre la pression osmotique intracellulaire et extracellulaire) est liée à la vitesse spécifique de croissance et non pas à l'osmolarité du milieu. Ces résultats suggèrent que la pression de turgescence est la force motrice de la croissance bactérienne sous stress osmotique. Enfin, l'établissement de bilans osmotiques a permis de vérifier que les principaux intervenants dans la réponse osmotique ont été identifiés
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Morrison, Vivienne Frances. ""You have to find a way to glue it in your brain": children's views on learning multiplication facts." Thesis, University of Canterbury. Education, 2007. http://hdl.handle.net/10092/1059.
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While there has been research on development of multiplicative reasoning, and how to teach multiplication facts, there is little research on how children consider they learn these. This study explores the children's learning as they consider how they commit their multiplication facts to memory, discover calculation strategies and develop multiplicative thinking. A group of eleven Year 4 children (8 years old) participated in a series of 13 lessons where they became coresearchers in the exploration of their learning. A contextually based thematic approach was provided through 'Crocodilian Studies'. The mixed-method approach to this study included formal assessment, participant observation, individual interviews, the children's written ideas, and individual case studies. The most significant finding of this study was the powerful influence of peer learning. The children enriched and directed each other's learning as they shared ideas and reflected on their own mathematical learning as they observed and critiqued the thinking of peers. As the children were involved in thinking about how they learn they were able to identify gaps and construct their own learning pathways. A significant finding was that children can develop their multiplicative strategies while they commit their multiplication facts to memory, in a relatively short time provided that the learning process facilitates strategy development and understanding. By exposing the children to multiplication facts in sequenced clusters provided them with a manageable number of facts to be learnt at one time. Another finding related to how children develop calculation strategies through lesson activities rather than being explicitly taught them. The children considered practice important for memorisation. Parental support was significant in enriching the children's learning.
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Maarri, Khalil al. "Micropropagation in vitro du pommier (M9), du poirier ("williams" et "passe crassane") et du cognassier de Provence : problèmes posés par l'état physiologique du matériel." Paris 6, 1986. http://www.theses.fr/1986PA066057.
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Au cours du travail présenté dans ce mémoire, nous sommes parvenus à obtenir, de façon systématique, la micropropagation in vitro et l'acclimatation ex vitro non seulement des poiriers juvéniles issus de pépins de "passe crassane", mais aussi du cognassier de Provence et de deux cultivars de poirier, "williams" et "passe crassane". Les conditions de culture concernant les différentes phases de la micropropagation et l'acclimatation ont été étudiées. Plusieurs problèmes d'ordre physiologique (dormance des bourgeons in vitro, anomalie des pousses formées, nécrose des apex) ont pu être surmontés ou limités.
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Khoza, Samukelisiwe Nozipho Purity. "Characteristic behaviour of pebble bed high temperature gas-cooled reactors during water ingress events / Samukelisiwe Nozipho Purity Khoza." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8706.
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The effect of water ingress in two pebble bed high temperature gas-cooled reactors
i.e. the PBMR-200 MWthermal and the PBMR-400 MWthermal were simulated and
compared using the VSOP 99/05 suite of codes.
To investigate the effect of this event on reactivity, power profiles and thermal
neutron flux profiles, the addition of partial steam vapour pressures in stages up to
400 bar into the primary circuit for the PBMR-400 and up to 300 bar for the PBMR-
200 was simulated for both reactors. During the simulation, three scenarios were
simulated, i.e. water ingress into the core only, water ingress into the reflectors only
and water ingress into both the core and reflectors. The induced reactivity change
effects were compared for these reactors.
An in-depth analysis was also carried out to study the mechanisms that drive the
reactivity changes for each reactor caused by water ingress into the fuel core only,
the riser tubes in the reflectors only and ingress into both the fuel core and the riser
tubes in the reflectors.
The knowledge gained of these mechanisms and effects was used in order to
propose design changes aimed at mitigating the reactivity increases, caused by
realistic water ingress scenarios. Past results from simulations of water ingress into
Pebble Bed Reactors were used to validate and verify the present simulation
approach and results. The reactivity increase results for both reactors were in
agreement with the German HTR-Modul calculations.Thesis (MSc (Engineering Sciences in Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013
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Besnard, François. "Culture et caracterisation des oligodendrocytes de rat : effets des facteurs de croissance." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13179.
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Luciani-Sentier, Nathalie. "Optimisation d'un système de traduction in vitro : rôle des molécules oxydantes sur la synthèse protéique acellulaire." Nancy 1, 1994. http://www.theses.fr/1994NAN10340.
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Ce travail a été réalisé dans le but d'optimiser le système de traduction in vitro de germe de blé. L'arrêt prématuré de la synthèse protéique dans un tel système est lié à une limitation en oxygène du milieu réactionnel, puisque l'augmentation de la surface d'échange entre milieu de traduction et atmosphère augmente la synthèse protéique. La quantité de protéines synthétisées ainsi que la vitesse de traduction sont augmentées lorsqu'on enrichit le milieu en oxygène. Lorsqu'on ajoute du peroxyde d'hydrogène au milieu de traduction, on observe le même effet qu'avec l'oxygène, on peut donc penser que la stimulation de la synthèse protéique observée est liée aux propriétés oxydantes communes aux deux molécules. Lorsque les molécules oxydantes participent à des réactions d'oxydoréduction, des radicaux libres sont formés. Ces radicaux libres, et principalement l'anion superoxyde, sont impliqués dans la traduction in vitro, hypothèse renforcée par l'inhibition de la synthèse protéique en présence d'agents chélateurs de fer, ainsi que par l'effet positif d'un ajout de système générateur de radicaux libres et par l'effet négatif de celui d'enzymes bloquant les radicaux libres
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Mičian, Peter. "Bezpečnost skladování paliva ve vodním prostředí." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377026.
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This diploma thesis deals with storing the spent nuclear fuel and reviewing its safety. The theoretical part analyzes the processes taking place while the fuel is being used, such as fission, isotopic changes, fission gas release, cracking, swelling and densification of fuel pellet. The thesis is also focused on handling the spent fuel and on the way it makes from the reactor, through the spent fuel pool, the transportation, various kinds of storing, till the reprocessing and final deep geological repository. Furthermore, this part of the thesis briefly discusses computing code MCNP, its main characteristics, input files and using. The practical part of the work is focused on creating the model of the spent fuel pool located next to the nuclear reactor WWER 440/V213. This type was chosen, because it is the most used type of nuclear reactor in Czech Republic and Slovakia. With the help of the code MCNP, the multiplication factor of the main configurations of the fuel in the pool was calculated, and then the required safety regulations to ensure sufficient subcriticality, so its safety, were checked. Next, several analysis were performed using this model. These analyses were concerning the temperature of coolant, fuel and the use of various nuclear data libraries. In the future this model can be used to realize new analyses with new kinds of fuels, materials and data libraries.
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Perraud, Frédéric. "Effets des facteurs de croissance fibroblastiques (fgf) et d'autres facteurs de croissance sur la proliferation et la maturation des cellules astrogliales de rat." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13091.
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Mackenbach, Loue Petra. "Translocation nucléaire de la protéine kinase CK2 induite par les facteurs de croissance et surexpression d'une forme anormale de la kinase dans les tumeurs du sein." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10164.
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La proteine kinase ck2 est une serine/threonine proteine kinase exprimee dans toutes les cellules eucaryotes. Elle est composee de deux sous-unites catalytiques (alpha et alpha') et deux sous-unites regulatrices beta. Des observations convergentes suggerent qu'elle doit jouer un role important dans le controle de la division cellulaire. Le but de notre travail etait de tenter de determiner la facon dont les facteurs de croissance peuvent reguler la ck2 dans la cellule. Dans un premier temps nous avons caracterise les differentes isoformes de la ck2 mais aucune distinction n'a ete detectee concernant leur distribution dans la cellule et leurs activites catalytiques respectives. Par des etudes en immunofluorescence, nous avons pu mettre en evidence que la translocation nucleaire de la ck2 est dependante de l'activite tyrosine kinase du recepteur a l'egf et de l'activite de ras et concerne donc avant tout la reponse cellulaire a une signalisation mitogene. La biosynthese de la ck2 semble egalement etre sensible aux facteurs de croissance. En effet, des la premiere heure de stimulation, une augmentation de biosynthese est detectable. L'ensemble de ces resultats montre que les facteurs de croissance regulent a la fois la biosynthese et la localisation de la ck2 dans la cellule. La poursuite de cette etude par une approche de biologie moleculaire pourrait permettre de determiner l'importance des differents domaines des sous-unites de la ck2 dans le controle de la localisation subcellulaire de la kinase. Dans une deuxieme partie nous avons etudie la ck2 dans les tumeurs du sein. Ce tissu exprime six fois plus d'activite ck2 que le tissu normal et cette situation est correlee avec une surexpression de la sous-unite catalytique. De plus, une sous-unite regulatrice anormale, associee a la ck2 alpha a ete mise en evidence : la proteine est deletee de ses deux derniers acides amines c-terminaux. L'existence de cette forme de ck2 dans les coupes de tumeurs nous permet de conclure que la presence de cette sous-unite tronquee est une realite dans les tumeurs. Le defi est maintenant de poursuivre de telles recherches par une approche cellulaire afin de determiner la relation entre la proteolyse de la ck2 beta et la tumorigenese. La quantification de la ck2 beta anormale dans les tumeurs devrait nous permettre de determiner si cette proteine est un nouveau marqueur tumoral.
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Eckhart, Victoria Ann. "Effects of Peer Tutoring on the Acquisition of Basic (0-9) Multiplication Facts by Sixth Grade Students with Math Deficits." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268239873.
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Maurin, Aurélie. "Etude des implications du facteur cellulaire Ku dans le cycle de multiplication du VIH-1." Paris 11, 2010. http://www.theses.fr/2010PA11T021.
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Puccio, François. "Influence de l'hydrocortisone, de l'egf, de la bombesine et du grf sur la proliferation cellulaire et la maturation du tractus gastrointestinal et du pancreas chez le jeune rat non sevre." Paris 6, 1988. http://www.theses.fr/1988PA066497.
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Listerman, Kelsey E. "Examining the Impact of Play on the Multiplication Fluency of Third Graders." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1552668939543415.
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Godet, Xavier. "Biologie du colchique (colchicum autumnale l. ) : multiplication vegetative par voie traditionnelle et in vitro." Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF2D189.
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Examen des cycles biologiques de la plante adulte et de la plante juvenile: les exigences thermiques, les potentialites du bourgeon vegetatif accessoire, variabilite individuelle pour la production de graines et d'alcaloides. Une methode de multiplication vegetative est recherchee: en pepiniere ou in vitro, possibilite de fragmenter les cornus; caulogenese in vitro. La possibilite d'une biosynthese d'alcaloides par des cellules de colchique cultivees in vitro est evoquee
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Goudout, Elie. "Étude de la fonction ω : petits intervalles et systèmes translatés." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC040.
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Dans cette thèse, on s’intéresse à l’interaction entre les structures multiplicative et additive des entiers. Pour cela, on étudie notamment la fonction « nombre de facteurs premiers distincts », notée ω, dans de très petits intervalles, mais aussi sur des systèmes translatés. Ce projet est né suite à une importante percée de Matomäki & Radziwiłł dans l’étude des petits intervalles, en 2015. Dans un premier temps, on démontre que le théorème d’Erdős-Kac est vérifié dans presque tous les petits intervalles, dès lors que leur taille tend vers l’infini. On s’intéresse ensuite aux lois locales de la fonction ω. On parvient à démontrer, lorsque , que presque tous les intervalles de longueur h contiennent des entiers n6x vérifiant ω(n) = k, dès que h est suffisamment grand. Lorsque , la condition sur h est optimale. On obtient un résultat analogue, bien que non optimal, sur les entiers x1/u-friables pour u6 (logx)1/6−ε, où ε> 0 peut être fixé arbitrairement petit. Les méthodes employées dans le deuxième chapitre invitent naturellement à étudier le comportement de certaines fonctions additives sur des systèmes d’entiers translatés. On démontre alors, dans un troisième temps, une version multidimensionnelle d’un théorème de 1975 dû à Halász, relatif à la concentration maximale des valeurs d’une seule fonction additive. Enfin, dans le quatrième chapitre, on démontre que ω(n−1) vérifie un théorème d’ErdősKac lorsque ω(n) = k est fixé. Cela généralise un résultat d’HalberstamIn this thesis, we study the interactions between the multiplicative and additive structures of integers. As such, we particularly investigate the function “number of distinct prime factors”, noted ω, on short intervals and shifted systems. This project originates from an important breakthrough of Matomäki & Radziwiłł regarding the study of small intervals, in 2015. As a first step, we show that the Erdős-Kac theorem is valid in almost all short intervals, as long as their length goes to infinity. We then consider the local laws of ω. We prove that, for x> 3 and , almost all intervals of length h contain integers n 6 x satisfying ω(n) = k, when h is large enough. For , the condition on h is optimal. A similar result, albeit non optimal, is obtained for x1/u-friable integers with u 6 (logx)1/6−ε, where ε > 0 is fixed, arbitrarily small. The techniques used in the second chapter naturally invite us to consider the behavior of a wide class of additive functions on shifted systems. In the third chapter, we prove a multidimensional version of a theorem from Halász in 1975, regarding the maximum concentration of the values of one additive function. In the last chapter, we show that ω(n− 1) satisfies an Erdős-Kac theorem whenever ω(n) = k is fixed. This generalizes a theorem of Halberstam
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IRISH, CHERYL L. "THE EFFECTS OF PEG- AND KEYWORD MNEMONICS AND COMPUTER-ASSISTED INSTRUCTION ON FLUENCY AND ACCURACY OF BASIC MULTIPLICATION FACTS IN ELEMENTARY STUDENTS WITH LEARNING AND COGNITIVE DISABILITIES." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin997209845.
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Li, Tangchen. "The Comparative Effects of Interspersal Drill and Cover-Copy-Compare on the Math Performance of Students with Autism." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523448676139087.
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Shi, Wei. "Essays on Spatial Panel Data Models with Common Factors." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461300292.
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Balghonaim, Abir A. "Effect of platelet factors and thrombin on multiplication of human bone marrow mesenchymal stem cells cultured in low and high oxygen level in vitro." Scholarly Commons, 2012. https://scholarlycommons.pacific.edu/uop_etds/210.
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Background: In the bone marrow, hematopoietic and mesenchymal stem cells form a unique niche, in which oxygen tension is low. Hypoxia may have a role in maintaining stem cell capacity for self-renewal and multipotency. We have shown previously a positive influence of platelet-derived growth factors (PDF) on increase of multiplication rate of human mesenchymal stem cells cultured in normal atmosphere. Objective: The goal of this study is to examine effects of platelet-derived factors and thrombin on multiplication of adult human mesenchymal stem cells derived from bone marrow (hBMMSC) in a low or in a high oxygen environment in vitro. Hypothesis: It is hypothesized that PDF will have no effect on multiplication of BMMSC cultured in a low oxygen environment and that thrombin will have no effect on multiplication of BMMSC in either low or high oxygen atmosphere. Materials and methods: Adult human mesenchymal stem cells isolated from bone marrow aspirate (Lonza) were used. Cells were grown in plastic flasks or dishes. The human mesenchymal stem cell basal medium (Lonza) was supplemented with adult human serum with or without PDF or with or without thrombin. High and low oxygen environment (Biospherix) was applied during expansion of hBMMSC. Results: Cultivation medium containing PDF in 5% oxygen increased multiplication rate of hBMMSC. Thrombin addition to the cultivation medium had a positive influence on cell multiplication in 21% oxygen atmosphere, but not in presence of 5% oxygen. Conclusions: PDF enhanced proliferation of hBMMSC grown in 5% oxygen when compared to controls. Thrombin had a stimulatory effect in 21% oxygen environment. These findings will be utilized in an optimized protocol used for cultivation of hBMMSC preceding their clinical application. The hBMMSC need to be grown in physiological conditions and for the shortest cultivation period possible. 6
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CALDEIRA, ALEXANDRE D. "Solucoes Psubn para os problemas da moderacao e do calculo de celula em geometria plana." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10730.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Wehbi, Houssein. "Study of the genetic factors controlling early stages of somatic embryogenesis in Brachypodium distachyon." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS049.
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L'embryogenèse somatique (ES) est la voie de développement par laquelle les cellules somatiques changent d'identité et recouvrent la capacité de se diviser et de produire des structures embryonnaires, en l'absence de reproduction sexuelle. Les méthodes de culture in vitro basées sur l'ES sont couramment appliquées pour la transformation génétique et l'édition du génome de nombreuses plantes, y compris les principales céréales cultivées, même si les processus cellulaires impliqués sont encore mal compris. Nous avons caractérisé les premiers événements conduisant à la production d'embryons somatiques dans des tissus dérivés d'embryons zygotiques immatures de Brachypodium distachyon et traités par une auxine exogène, le 2,4-D. Nous avons observé, en accord avec des travaux antérieurs, que certaines cellules du scutellum reprennent leurs divisions mitotiques quelques jours après application du 2,4-D, préfigurant ainsi les nouvelles régions méristématiques formées à des stades ultérieurs. Grâce à l'analyse des domaines réactifs dans les explants qui étaient soit fixés (colorants, hybridation in situ), soit vivants (expression de protéines fluorescentes), nous avons identifié les gènes qui marquent ces premiers changements cellulaires. En combinant les informations recueillies avec une haute résolution spatiale et temporelle, nous avons également identifié quels types de cellules somatiques évoluent en tissus embryogènes. Nos résultats indiquent que ces lignées cellulaires peuvent également être identifiées par inférence sur la base des transcriptomes de cellules individuelles préparées à partir des mêmes explants. Notre étude met en évidence les gènes et les modules fonctionnels associés - et potentiellement moteurs - de la transition cellulaire entre état somatique et embryogène. Ce travail fournit des données originales pour étudier plus en détail les mécanismes qui contrôlent la totipotence des cellules végétales. L'implication des gènes candidats dans ce processus sera confirmée par des analyses fonctionnelle et phénotypique de la réponse in vitro des explantsSomatic embryogenesis (SE) is the developmental pathway through which somatic cells change fate and acquire the ability to divide and yield embryonic structures, in the absence of sexual reproduction. In vitro culture methods based on SE are routinely applied for the genetic transformation and genome editing of many plants, including all major cereal crops, despite the limited understanding of the cellular processes involved. We have characterized the early events leading to the production of somatic embryos in tissues derived from immature zygotic embryos of Brachypodium distachyon, a cereal crop model, treated with an exogenous auxin (2,4-D). As previously reported, we observed that cells within the scutellum resume mitotic division within days of 2,4-D induction, prefiguring the new meristematic regions formed at later stages. Through the analysis of the reactive domains in explants that were either fixed (dyes, in situ hybridization) or alive (expression of fluorescent reporter proteins), we identified genes that mark these early cellular changes. Combining information collected with high spatial and temporal resolution, we also tracked which somatic cell types evolve into embryogenic tissues. We will present evidence that these cell lineages could also be inferred based on the transcriptomes of single cells prepared from the same explants. Our study points to genes and functional modules associated with - and potentially driving - the transition from the somatic towards the embryogenic cell fate. It provides original data to further investigate the mechanisms that control plant cell totipotency. The involvement of candidate genes in this process will be confirmed through functional analyses, together with the phenotypic characterization of the explant's in vitro response
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Lengronne, Catherine. "Etude du facteur neuroendocrinien mitogène, responsable des multiplications cellulaires dans la gonade et le tentacule en régénération chez Crepidus fornicata Linné 1758." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37599124h.
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PERRIN, CHRISTELE. "Methodologie pour l'analyse quantitative en imagerie microscopique conventionnelle et a fluorescence. Application a l'etude de la proliferation et de l'expression du recepteur a l'egf dans des cellules tumorales mammaires." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10198.
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L'utilisation accrue des methodes d'imagerie microscopique dans le domaine de la cancerologie, et les developpements recents des marqueurs specifiques utilises dans ce contexte ont fait naitre un besoin urgent en ce qui concerne le developpement de procedures de multi-marquages enzymatiques ou fluorescents, et leur quantification cellule a cellule. C'est dans ce contexte de mise au point methodologique qu'ont ete realises les travaux presentes dans cette these. Ils incluent les divers aspects de la standardisation de methodes de multi-marquages, l'adaptation des methodes d'imagerie pour la quantification du marquage in situ du recepteur a l'egf, et la normalisation des mesures. Les techniques developpees pour la quantification par cytometrie en image sont detaillees, faisant apparaitre les limites et les problemes eventuels rencontres, ainsi que la facon de les contourner ou de les resoudre. Ces developpements methodologiques ont ete appliques a l'etude de l'analyse quantitative in situ des recepteurs a l'egf dans les tissus animaux et humains (tumeurs mammaires), en relation avec la cinetique de proliferation de chacune des cellules (marquages ki67, brdu, agnor). L'etude de marquages simultanes des proteines ki67-agnors-egfr associes au marquage de l'adn montre qu'il devrait etre possible de preciser pour chaque cellule en cycle, dans un tissu normal ou tumoral, la relation entre la vitesse du cycle et l'expression des recepteurs a l'egf
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Lengronne, Catherine. "Etude du facteur neuroendocrinien mitogene responsable des multiplications cellulaires dans la gonade et le tentacule en regeneration chez crepidula fornicata l. (mollusque mesogasteropode)." Caen, 1986. http://www.theses.fr/1986CAEN2018.
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Etude experimentale du facteur mitogene cerebroide responsable des multiplications cellulaires dans la gonade et le tentacule en regeneration realisee chez crepidula fornicata. Un test biologique a permis de montrer la nature neuroendocrine de ce facteur mitogene
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Philippe, Géraldine. "Influence de la température sur le métabolisme du toluène chez des souches bactériennes psychrotrophes." Rouen, 1998. http://www.theses.fr/1998ROUES057.
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Les bactéries psychrotrophes représentent une part importante de la microflore des sols des régions tempérées, soumis a des fluctuations de température. De plus si ces souches sont capables de dégrader des composés xénobiotiques, elles présentent un grand intérêt pour la dépollution des sols. Dans le cadre d'une approche physiologique de ce type de souches, une étude de la croissance et de la toxicité du toluène a été réalisée, en fonction de la température. L'étude de l'effet de la température sur la croissance de ces souches psychrotrophes sur différents substrats (citrate, toluène et benzoate) nous a permis de mettre en évidence, grâce à l'utilisation de la représentation d'Arrhénius, l'existence d'une température « Critique »(comprise entre 17°C et 20°C) définissant deux domaines de températures. La variation de l'effet de la température sur la croissance de part et d'autre de cette température critique, semble dépendre non seulement de la souche, mais également du substrat utilisé pour la croissance. L'étude de l'effet de la température sur la toxicité du toluène sur ces souches, a montré que cette toxicité dépend non seulement de la température de croissance, et est plus faible à 28°C qu'à 8°C, et maximale à 17°C. Elle dépend également de la capacité des souches à métaboliser ce composé. La capacité de ces souches à s'adapter au toluène, a également pu être mis en évidence, indépendamment de la capacité à le dégrader. Cette adaptation des souches semble être affectée par la température de croissance et est probablement liée à des modifications au niveau des protéines membranaires, induites lors de l'adaptation.
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Sola, Brigitte. "Transformation in vitro des cellules de la lignee myeloblastique par le virus leucemogene murin de friend (f-mulv) : analyse des mecanismes moleculaires de cette transformation." Paris 7, 1987. http://www.theses.fr/1987PA077242.
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Le retrovirus leucemogene murin f-mulv, competent pour la replication, entraine des leucemies myeloblastiques apres un temps de latence de plusieurs mois. L'infection de culture de cellules medullaires par ce virus entraine la transformation des cellules de la lignee myeloblastique apres une latence equivalente. En utilisant une sonde specifique du f-mulv, l'analyse du spectre d'integration des provirus dans les lignees obtenues in vitro a montre qu'il y a proliferation d'un clone cellulaire tres tot pendant le processus de leucemogenese. Une banque d'adn genomique a ete construite a partir d'une lignee ayant 5 provirus integres; les f-mulvs s'integrent preferentiellement dans 3 regions appelees fim-1, fim-2 et fim-3, fim-2 est la partie 5' de l'oncogene c-fms qui code pour le recepteur au csf1. L'integration d'un f-mulv dans la gene fim-2/cfms entraine sa surexpression sans apparente modification de structure. Role possible d'un recepteur a facteur de croissance physiologique dans un processus leucemogene
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Da, Silva Vieira Maria-Roseli. "Recherches sur la levure schwanniomyces occidentalis (Castellii) et sa réponse à l'élévation de température." Compiègne, 1996. http://www.theses.fr/1996COMP9705.
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Apres un examen cytologique de schwanniomyces occidentalis (castellii) plusieurs aspects de la physiologie de ce micro-organisme eucaryote et de sa reponse a l'accroissement de temperature sont precises. Une comparaison est etablie sur plusieurs points entre cette levure (classee comme petite negative par bulder) son mutant dr12 deficient en cytochrome b (mais developpant la respiration alternative existant chez schw. Occidentalis) et egalement l'espece petite positive saccharomyces cerevisiae, representee par la souche sauvage de laboratoire km91rho#+ et son mutant km91 rho#0 depourvu d'adnmt. La croissance a 28c et a 37c est analysee chez les souches sauvages des deux especes ainsi que la variation des teneurs en cytochromes. Les syntheses proteiques sont etudiees apres des cultures a 23c ou 28c suivies ou non d'un choc des cellules a une temperature testee jusqu'a 45c mais generalement limitee ensuite a 37c. Deux niveaux sont consideres: d'une part les syntheses chez les cellules entieres ; d'autre part les syntheses chez les mitochondries isolees. Schw. Occidentalis est plus sensible au choc thermique. La comparaison des proteines apparaissant ou augmentant (hsps d'environ 97 kda a 14 kda) ou diminuant, est effectuee. Par ailleurs les mitochondries isolees de cellules choquees montrent des modifications quantitatives de synthese de certains polypeptides codes par l'adnmt. Apres le choc thermique des cellules de schw. Occidentalis leur respiration diminue et notamment celle sensible au sham. L'inhibition par la rotenone de la respiration des mitochondries confirme l'existence d'un premier site de phosphorylation fonctionnel chez cette levure. Les mesures de l'activite de l'atpase mitochondriale effectuees a differents ph, a 28c et 37c apres un choc thermique, ou non, des cellules, suggerent des changements de conformation de l'enzyme. Des elements nouveaux sont apportes sur l'action de l'oligomycine
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Ehlinger, Frédéric. "Fermenteurs a cellules fixees en fermentation methanique : facteurs intervenant dans la colonisation du support, caracterisation des biofilms." Toulouse, INSA, 1988. http://www.theses.fr/1988ISAT0015.
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Etude de l'adherence initiale d'une biomasse methanogene sur un support, en flacons agites, en faisant varier les facteurs du milieu (ph, rapport carbone-azote, calcium exopolymere) afin d'optimiser l'adherence de cette biomasse
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Azemi, Ghasem. "Mobile Velocity Estimation Using a Time-Frequency Approach." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15807/.
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This thesis deals with the problem of estimating the velocity of a mobile station (MS)in a mobile communication system using the instantaneous frequency (IF) of the received signal at the MS antenna. This estimate is essential for satisfactory handover performance, effective dynamic channel assignment, and optimisation of adaptive multiple access wireless receivers. Conventional methods for estimating the MS velocity are based either on the statistics of the envelope or quadrature components of the received signal. In chapter 4 of the thesis, we show that their performance deteriorates in the presence of shadowing. Other velocity estimators have also been proposed which require prior estimation of the channel or the average received power. These are generally difficult to obtain due to the non-stationary nature of the received signal. An appropriate window which depends on the unknown MS velocity must first be applied in order to accurately estimate the required quantities. Using the statistics of the IF of the received signal at the MS antenna given in chapter 3, new velocity estimators are proposed in chapter 4 of this thesis. The proposed estimators are based on the moments, zero-crossing rate, and covariance of the received IF. Since the IF of the received signal is not affected by any amplitude distortion, the proposed IF-based estimators are robust to shadowing and propagation path-loss. The estimators for the MS velocity in a macro- and micro-cellular system are presented separately. A macro-cell system can be considered as a special case of a micro-cell in which there is no line-of-sight component at the receiver antenna. It follows that those estimators which are derived for micro-cells can be used in a macro-cell as well. In chapter 4, we analyse the performance of the proposed velocity estimators in the presence of additive noise, non-isotropic scattering, and shadowing. We also prove analytically that the proposed velocity estimators outperform the existing methods in the presence of shadowing and additive noise. The proposed IF-based estimators need prior estimation of both the IF of the received signal and Ricean K-factor. The IF estimation in a typical wireless environment, can be considered as a special case of a general problem of IF estimation in the presence of multiplicative and additive noise. In chapter 5, we show that current time-frequency approaches to this problem which are based on the peak of a time-frequency distribution (TFD) of the signal, fail because of the special shape of the power spectral density of the multiplicative noise in a wireless environment. To overcome this drawback, the use of the first-order moment of a TFD is studied in chapter 5. Theoretical analysis and simulations show that the IF estimator based on the first-order moment of a TFD exhibits negligible bias when the signal-to-additive noise ratio is more than 10 dB. The Ricean K-factor is not only necessary for velocity estimation in micro-cells, but also is a measure of the severity of fading and a good indicator of the channel quality. Two new methods for estimating the Ricean K-factor based on the first two moments of the envelope of the received signal, are proposed in chapter 6. Performance analysis presented in chapter 6, prove that the proposed K estimators are robust to non-isotropic scattering. Theoretical analysis and simulations which are presented in chapters 4 and 7 of this thesis, prove that the proposed velocity and K estimators outperform existing estimators in the presence of shadowing and additive noise.
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Derelle, Sophie. "Eléments d'orientation des photodiodes à avalanches pour l'infrarouge : application à la filière HgCdTe." Paris 11, 2009. http://www.theses.fr/2009PA112335.
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Le développement actuel des mosaïques infrarouge (IR) se traduit par l'intégration de nouvelles fonctionnalités optiques et électroniques pour répondre aux besoins des applications comme l'imagerie active ou hyperspectrale. Ces évolutions s'accompagnent d'une réduction du nombre de photons incidents par pixel d'où la question de préservation de l'intégrité du signal photonique. Une réponse possible à cette problématique est l'emploi de détecteurs à gain peu bruyants. Le phénomène d'amplification sans excès de bruit a été mis en évidence pour la première fois dans des photodiodes à avalanche (APD) en HgCdTe pour le moyen IR en 2001. Ce travail de thèse, réalisé à rOnera en collaboration avec le CEA/LETI, a pour objectif de fournir des éléments d'orientation de cette nouvelle filière de détecteurs. Pour cela, j'ai mis au point des bancs de caractérisation pour mesurer les performances électro-optiques (gain M, facteur d'excès de bruit F, courant d'obscurité, etc) de différents composants et j'ai développé un outil de simulation Monte Carlo afin de mieux comprendre le mécanisme d'ionisation par impact dans l'alliage HgCdTe et notamment l'influence de différents paramètres physiques et technologiques sur M et F. Ceci a permis de démontrer l'existence d'une amplification sans excès de bruit dans les APD pour le lointain IR de la filière française. Ces détecteurs souffrent cependant d'un courant tunnel élevé qui limite leur utilisation. Les simulations ont montré que M et F sont peu affectés par les variations de la largeur de la zone de multiplication ce qui nous a conduit à réaliser de nouveaux composants, à zone de multiplication élargie, pour réduire le courant tunnelThe current development of infrared focal plane arrays results in the integration of new optical and electronic functionalities to meet the needs for emergent applications like hyperspectral and active imaging. These evolutions are accompanied by a reduction of the incident photon number per pixel what raises the question of the preservation of photonic signal integrity. A possible response to that issue is the use of detector with gain and low associated noise. The phenomenon of electronic amplification without excess noise has been demonstrated for the frrst time in 2001 in mid¬wavelength infrared HgCdTe avalanche photodiodes (APDs). This work, made at Onera in collaboration with CEA/LETI, aims at providing elements of guiding for this new detector technology. To reach this goal, 1 realized experimental test benches in order to measure electro-optical performance (gain M, excess noise factor F, dark current) of several devices and 1 developed a Monte Carlo simulation tool in order to better understand the mechanism of impact ionization in the HgCdTe alloy and particularly the effect of various physical and technological parameters on M and F. This work makes it possible to demonstrate an amplification without excess noise in the French technology for long wavelength infrared APDs. These detectors nevertheless suffer from a high tunnelling current which limits their use. Monte Carlo simulations show that the gain and the excess noise factor are little modified by variations of the multiplication region thickness which leads us to carry out new long wavelength infrared devices, with thicker multiplication region, in order to reduce tunnelling current
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Lévêque, Catherine. "Etude de l'expression des récepteurs des cytokines par les cellules hématopoïétiques : aspects cellulaires et moléculaires." Rouen, 1998. http://www.theses.fr/1998ROUES047.
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La différenciation et la prolifération des cellules souches hématopoïétiques sont modulées par différents facteurs de croissance. Ces facteurs agissent par l'intermédiaire de récepteurs membranaires pour transmettre un signal intracellulaire. L'expression d'un récepteur rend la cellule qui l'exprime sensible au facteur correspondant. Pendant la maturation cellulaire, l'acquisition de l'expression de certains récepteurs est le reflet de ce phénomène. Mais, est-ce la différenciation cellulaire qui engendre l'expression des récepteurs des cytokines et/ou est-ce l'expression des récepteurs des cytokines qui entraîne la différenciation cellulaire? Les cellules des lignées TF-1 et U-937 ont permis la mise au point des techniques de biologie cellulaire (cytométrie en flux, immunocytochimie) et moléculaire (RT-PCR) pour la détection des récepteurs de l'IL-3 et du G-CSF. Une première étude sur les monocytes du sang périphérique a mis en évidence la modulation de l'expression du récepteur de l'IL-3 sous l'effet de différentes cytokines. L'IL-4 et l'IL-13 augmentent l'expression de ce récepteur sur les monocytes. Pour l'IL-4, cette expression est dépendante du temps d'incubation et de la concentration en cytokine. L'IL-10 et le TGF-β diminuent cette expression. En revanche, l'OSM et le LIF n'ont pas d'effet. L'expression de ce récepteur peut être régulée positivement ou négativement sous l'effet de différentes cytokines, rendant les cellules plus ou moins sensibles à l'IL-3. Une seconde étude sur les cellules souches hématopoïétiques CD34 + du sang de cordons ombilicaux n'a pas montré de variations significatives dans l'expression du récepteur de l'IL-3 en présence ou absence d'IL-4 avec la technique de cytométrie en flux. L'IL-4 sur les cellules souches hématopoiétiques ne fait pas apparaître de récepteur de l'IL-3 à la surface cellulaire. Pourtant, elle augmente le nombre absolu de cellules CD34 +, comme l'IL-6 et le SDF-1.
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Lecron, Jean-Claude. "Caractérisation biologique et physico-chimique d'un facteur "prothymocyte differentiating activity" (ptda) capable de promouvoir la différenciation et l'activation de lymphocytes T humains." Poitiers, 1988. http://www.theses.fr/1988POIT2270.
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La differenciation lymphocytaire t obeit a des mecanismes complexes faisant extervenir des interactions cellulaires de contact et des facteurs solubles. Les techniques de clonage lymphocytaire t en milieu semi solide ont permis de mettre en evidence un facteur doue d'une activite differenciatrice vis a vis de prothymoxytes medullaires humains (ptda). Ce facteur est produit, par les cellules b + nulles du sang peripherique stimulees par la phytohemagglutinine. Des etudes sequentielles suggerent que la ptda agit non comme un facteur de proliferation mais comme un signal de differenciation des prothymocytes et de preactivation des lymphocytes t cd4+
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Buchon, Laurent. "Influence de la température sur la physiologie de la croissance et la production d'enzymes exocellulaires chez des bactéries adaptées aux basses températures." Rouen, 2000. http://www.theses.fr/2000ROUES046.
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Des bactéries adaptées au froid ont été sélectionnées pour leur capacité à dégrader des polysaccharides naturels. L'influence de la température de croissance, sur la régulation de la production des enzymes exocellulaires, a été étudiée. Nous avons mis en évidence l'existence de cinq profils de régulation qui ne sont corrélés ni a l'origine taxonomique des souches, ni au type d'activité produite. D'autre part, chez une même souche, le profil de production d'une activité donnée peut varier suivant la composition du milieu de culture, notamment en substrat carboné, ainsi qu'en fonction de la présence d'inducteur spécifique. La dépendance des profils de production à l'égard des conditions nutritionnelles, démontre également qu'aucune loi générale ne peut être établie quant à l'influence de la température sur la production des enzymes exocellulaires, chez les bactéries adaptées au froid. Cependant des comportements différents peuvent être observés suivant le groupe thermique des souches. En utilisant la représentation selon Arrhénius, du taux de croissance en fonction de la température, nous avons démontré l'existence d'une température critique de rupture de pente chez toutes les souches psychrotrophes, celle-ci étant absente chez les psychrophiles. Sur la base de ce critère distinctif nous avons établi que, chez les psychrotrophes, la production des enzymes exocellulaires varie de façon discontinue sur l'ensemble de la gamme de températures suboptimales de croissance, ce qui se traduit par l'existence de deux domaines thermiques de production. En revanche chez les psychrophiles la production varie de façon monotone sur la gamme de températures inférieures à l'optimum de croissance. Ces profils pourraient résulter d'adaptation en réponse aux différentes amplitudes de température caractérisant les environnements d'origine des représentants de chacun de ces deux groupes thermiques.
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BRANCO, ISABELA S. L. "Estudo dos efeitos na dose devido à heterogeneidade em braquiterapia com fontes de I125." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28045.
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A braquiterapia de baixas taxas de dose realizada com sementes de 125I tem sido amplamente usada por décadas em variados sítios anatômicos, com bons resultados clínicos. O advento de algoritmos para cálculo de dose baseados em modelos (MBDCAs) permitiu aprimorar oestudo de deposição da dose considerando heterogeneidades como diferentes tecidos, órgãos,aplicadores com composições diferentes da água, proporcionando a análise em geometriascomplexas. As simulações matemáticas realizadas através destes algoritmos possibilitam odesenvolvimento de modelos fisicamente mais acurados que estendem sua aplicabilidade àverificação de sistemas de planejamento em braquiterapia. Neste trabalho foram estudadasconfigurações de objetos simuladores confeccionados para medidas experimentais e simuladosatravés do código MCNP de Monte Carlo a fim de observar as diferenças ocasionadas pelaintrodução de heterogeneidades quando presentes fontes de 125I de baixa taxa de dose. Para estepropósito, distintas as vertentes do tema foram abordadas, entre elas o estudo da influênciaexercida pelos parâmetros de densidade e composição dos materiais tecido equivalentes. Osresultados obtidos demonstraram que, o efeito que a composição de cada um dos materiaisexerce sobre a deposição de dose é mais expressivo que o efeito de sua densidade. Em outroestudo, foi estabelecida uma relação para estimar, de maneira simples, a dose de atenuação detecidos heterogêneos a partir da aferição ou simulação da dose obtida num objeto simuladorconstituído por PMMA, metodologia que pode ser desenvolvida e implementada na rotina clínica.Para complementação das análises dos estudos dosimétricos com a presença deheterogeneidades, foi realizada a validação da geometria simulada da semente de 125I, onde sereproduziu a metodologia de cálculo dosimétrico presente no TG-43 da AAPM. Além disto, foirealizado o estudo teórico da dependência energética dos dosímetros termoluminescentes paraanalisar a variação de sua resposta conforme a energia. A metodologia desenvolvida para oestudo dos efeitos da heterogeneidade na deposição de dose é recomendada na avaliação desistemas de planejamento computadorizados que possuem algoritmos de cálculo de dosebaseados em modelos, quando utilizadas fontes de 125I com baixa taxa de dose, de forma acontribuir na incorporação de novas estimativas de doses com maior acurácia.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Voll, Sarah. "Functional Genetic Analysis Reveals Intricate Roles of Conserved X-box Elements in Yeast Transcriptional Regulation." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30168.
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Understanding the functional impact of physical interactions between proteins and
DNA on gene expression is important for developing approaches to correct disease-associated gene dysregulation. I conducted a systematic, functional genetic analysis of protein-DNA interactions in the promoter region of the yeast ribonucleotide reductase
subunit gene RNR3. I measured the transcriptional impact of systematically
perturbing the major transcriptional regulator, Crt1, and three X-box sites on the
DNA known to physically bind Crt1. This analysis revealed interactions between
two of the three X-boxes in the presence of Crt1, and unexpectedly, a significant
functional role of the X-boxes in the absence of Crt1. Further analysis revealed Crt1-
independent regulators of RNR3 that were impacted by X-box perturbation. Taken
together, these results support the notion that higher-order X-box-mediated interactions
are important for RNR3 transcription, and that the X-boxes have unexpected roles in the regulation of RNR3 transcription that extend beyond their interaction with Crt1.
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Iferroudjene, Djedjiga. "Complément et réponse immune : effet comitogénique du composant C3 et du facteur H sur les lymphocytes T." Rouen, 1988. http://www.theses.fr/1988ROUES011.
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Kurz, Terri L., H. Bahadir Yanik, and Jorge Garcia. "Helping a Young Child Connect Fact Family Addition and Subtraction using Tools." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-80491.
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In order to help children become effective at addition and subtraction, it is important to provide them with an opportunity to investigate and discover the interconnectedness of the two operations. Fact families are one method teachers use to try and help children develop and understand how the operations relate to one another. This paper documents a strategy that was used with a seven year old boy to help him connect addition to subtraction. The strategy incorporated flash card tools to help him create logical problems to discover the mathematical relationship of fact families. With just a few trials, the child was able to create and explain problems that demonstrated the interconnectedness of fact families through addition and subtraction. The model was successful in helping the child advance his understanding. Additionally, it can be extended to more complex addition and subtraction problems as well as multiplication and division
fact families.
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Silva, Luis Henrique Pereira da. "Uma aplicação da congruência na determinação de critérios de divisibilidade." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/4600.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This work aims to demonstrate in a practical way the divisibility criteria 2-97 in sieve Eratostenes with cutting the right and the left, based on the method of multiplication and division Egyptian. The entire process is demonstrated using the divisibility to whole numbers, greatest common divisor, prime numbers, decomposition in prime factors and matching.
Este trabalho tem como objetivo demonstrar de modo prático os critérios de divisibilidade de 2 a 97 no crivo de Eratóstenes com os corte a direita e a esquerda, baseando-se no método de multiplicação e divisão egípcia. Todo processo é demostrado utilizando a divisibilidade para números inteiros, máximo divisor comum, números primos, decomposi ção em fatores primos e congruência.
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Mazibas, Murat. "Dynamic portfolio construction and portfolio risk measurement." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3297.
Full textAbstract:
The research presented in this thesis addresses different aspects of dynamic portfolio construction and portfolio risk measurement. It brings the research on dynamic portfolio optimization, replicating portfolio construction, dynamic portfolio risk measurement and volatility forecast together. The overall aim of this research is threefold. First, it is aimed to examine the portfolio construction and risk measurement performance of a broad set of volatility forecast and portfolio optimization model. Second, in an effort to improve their forecast accuracy and portfolio construction performance, it is aimed to propose new models or new formulations to the available models. Third, in order to enhance the replication performance of hedge fund returns, it is aimed to introduce a replication approach that has the potential to be used in numerous applications, in investment management. In order to achieve these aims, Chapter 2 addresses risk measurement in dynamic portfolio construction. In this chapter, further evidence on the use of multivariate conditional volatility models in hedge fund risk measurement and portfolio allocation is provided by using monthly returns of hedge fund strategy indices for the period 1990 to 2009. Building on Giamouridis and Vrontos (2007), a broad set of multivariate GARCH models, as well as, the simpler exponentially weighted moving average (EWMA) estimator of RiskMetrics (1996) are considered. It is found that, while multivariate GARCH models provide some improvements in portfolio performance over static models, they are generally dominated by the EWMA model. In particular, in addition to providing a better risk-adjusted performance, the EWMA model leads to dynamic allocation strategies that have a substantially lower turnover and could therefore be expected to involve lower transaction costs. Moreover, it is shown that these results are robust across the low - volatility and high-volatility sub-periods. Chapter 3 addresses optimization in dynamic portfolio construction. In this chapter, the advantages of introducing alternative optimization frameworks over the mean-variance framework in constructing hedge fund portfolios for a fund of funds. Using monthly return data of hedge fund strategy indices for the period 1990 to 2011, the standard mean-variance approach is compared with approaches based on CVaR, CDaR and Omega, for both conservative and aggressive hedge fund investors. In order to estimate portfolio CVaR, CDaR and Omega, a semi-parametric approach is proposed, in which first the marginal density of each hedge fund index is modelled using extreme value theory and the joint density of hedge fund index returns is constructed using a copula-based approach. Then hedge fund returns from this joint density are simulated in order to compute CVaR, CDaR and Omega. The semi-parametric approach is compared with the standard, non-parametric approach, in which the quantiles of the marginal density of portfolio returns are estimated empirically and used to compute CVaR, CDaR and Omega. Two main findings are reported. The first is that CVaR-, CDaR- and Omega-based optimization offers a significant improvement in terms of risk-adjusted portfolio performance over mean-variance optimization. The second is that, for all three risk measures, semi-parametric estimation of the optimal portfolio offers a very significant improvement over non-parametric estimation. The results are robust to as the choice of target return and the estimation period. Chapter 4 searches for improvements in portfolio risk measurement by addressing volatility forecast. In this chapter, two new univariate Markov regime switching models based on intraday range are introduced. A regime switching conditional volatility model is combined with a robust measure of volatility based on intraday range, in a framework for volatility forecasting. This chapter proposes a one-factor and a two-factor model that combine useful properties of range, regime switching, nonlinear filtration, and GARCH frameworks. Any incremental improvement in the performance of volatility forecasting is searched for by employing regime switching in a conditional volatility setting with enhanced information content on true volatility. Weekly S&P500 index data for 1982-2010 is used. Models are evaluated by using a number of volatility proxies, which approximate true integrated volatility. Forecast performance of the proposed models is compared to renowned return-based and range-based models, namely EWMA of Riskmetrics, hybrid EWMA of Harris and Yilmaz (2009), GARCH of Bollerslev (1988), CARR of Chou (2005), FIGARCH of Baillie et al. (1996) and MRSGARCH of Klaassen (2002). It is found that the proposed models produce more accurate out of sample forecasts, contain more information about true volatility and exhibit similar or better performance when used for value at risk comparison. Chapter 5 searches for improvements in risk measurement for a better dynamic portfolio construction. This chapter proposes multivariate versions of one and two factor MRSACR models introduced in the fourth chapter. In these models, useful properties of regime switching models, nonlinear filtration and range-based estimator are combined with a multivariate setting, based on static and dynamic correlation estimates. In comparing the out-of-sample forecast performance of these models, eminent return and range-based volatility models are employed as benchmark models. A hedge fund portfolio construction is conducted in order to investigate the out-of-sample portfolio performance of the proposed models. Also, the out-of-sample performance of each model is tested by using a number of statistical tests. In particular, a broad range of statistical tests and loss functions are utilized in evaluating the forecast performance of the variance covariance matrix of each portfolio. It is found that, in terms statistical test results, proposed models offer significant improvements in forecasting true volatility process, and, in terms of risk and return criteria employed, proposed models perform better than benchmark models. Proposed models construct hedge fund portfolios with higher risk-adjusted returns, lower tail risks, offer superior risk-return tradeoffs and better active management ratios. However, in most cases these improvements come at the expense of higher portfolio turnover and rebalancing expenses. Chapter 6 addresses the dynamic portfolio construction for a better hedge fund return replication and proposes a new approach. In this chapter, a method for hedge fund replication is proposed that uses a factor-based model supplemented with a series of risk and return constraints that implicitly target all the moments of the hedge fund return distribution. The approach is used to replicate the monthly returns of ten broad hedge fund strategy indices, using long-only positions in ten equity, bond, foreign exchange, and commodity indices, all of which can be traded using liquid, investible instruments such as futures, options and exchange traded funds. In out-of-sample tests, proposed approach provides an improvement over the pure factor-based model, offering a closer match to both the return performance and risk characteristics of the hedge fund strategy indices.
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Hossaert-McKey, Martine. "Des fleurs comment et à quoi bon ? : Données et réflexions sur la reproduction sexuée de deux espèces pérennes affines, à propagation végétative, Lathyrus latifolius et Lathyrus sylvestris (légumineuses, papilionaceae)." Pau, 1988. http://www.theses.fr/1988PAUU3013.
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La coexistence de la reproduction sexuée et de l'apomixie chez certaines espèces végétales permet de comparer leurs effets respectifs sur la dynamique et le maintien des populations. Une telle étude a été réalisée chez deux espèces affines de légumineuses pérennes à propagation végétative : Lathyrus latifolius et L. Sylvestris, à l'intérieur de populations reparties dans le nord de la France, l'Anjou, et le Béarn. Une étude spatio-temporelle de l'apparition des rejets et des plantules a montré que le recrutement annuel et la survie des plantules restent faibles. Cependant, suite à une étude génétique, ces populations paraissent résulter de l'installation de plusieurs génotypes. La production de graines semblerait, donc, nécessaire au développement de nouvelles populations. La "surproduction" de fleurs semble être une réponse diffuse à une succession de contraintes externes imprévisibles
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陳君柔. "Criticality Analysis of Burnup Effect on Multiplication Factor." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/10346858534087785055.
Full textAbstract:
碩士國立清華大學
核子工程與科學研究所
99
During all process of nuclear fuel cycle, criticality safety analysis is indispensable. Burnup effect dominates the result of criticality analysis. In this study, we evaluated the effect of burnup credit on the k-eff of a spent fuel dry storage transfer cask system, and performed core neutronics analysis for a generation IV lead-cooled fast reactor SSTAR(Small Secure Transportable Autonomous Reactor). The computer software systems SCALE 5.1 and 6.0 were used in this thesis. We modeled complex geometries by taking advantage of the 3D Monte Carlo code KENO, which is a functional module for criticality evaluation in SCALE. Several sequences consisting of cross section processing, depletion modules and KENO were used to complete the assessments. We consider a transfer cask loaded with 24 PWR fuel assemblies with 4.2 % 235U enrichment. For fresh fuels, k-eff was calculated to be 0.9227. For fuel assemblies with 45,000MWD/MTU burnup, k-eff kept decreasing as actinides and fission products being added into the fuel batch by batch. When all available actinides and fission products are included, k-eff was reduced to 0.6270. The SSTAR lead-cooled fast reactor is characterized by its long core life. The fuel composition is transuranium nitride, and the specific power is 21.19 MW/MTHM. The calculated result shows that the reactor can last for 20 years without refueling. During operation, the total flux of each core region varies from 5.07×1014 neutrons/cm2-sec to 1.70×1015 neutrons/cm2-sec. The average energy of low-enriched fuel region is about 3.35×105 eV to 4.41×105 eV, and the trend is increasing or fixed; in high-enriched fuel region the average energy decreases from 6.00 × 105 eV to 4.80 × 105 eV. The amount of U-235 and U-238 consumed with time; Pu-239 is bred in low-enriched region but consumed in high-enriched region with time.
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Waddle, C. Allen. "Fast spectral multiplication for real-time rendering." Thesis, 2018. https://dspace.library.uvic.ca//handle/1828/9332.
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In computer graphics, the complex phenomenon of color appearance, involving the interaction of light, matter and the human visual system, is modeled by the multiplication of RGB triplets assigned to lights and materials. This efficient heuristic produces plausible images because the triplets assigned to materials usually function as color specifications. To predict color, spectral rendering is required, but the O(n) cost of computing reflections with n-dimensional point-sampled spectra is prohibitive for real-time rendering.
Typical spectra are well approximated by m-dimensional linear models, where m << n, but computing reflections with this representation requires O(m^2) matrix-vector multiplication. A method by Drew and Finlayson [JOSA A 20, 7 (2003), 1181-1193], reduces this cost to O(m) by “sharpening” an n x m orthonormal basis with a linear transformation, so that the new basis vectors are approximately disjoint. If successful, this transformation allows approximated reflections to be computed as the products of coefficients of lights and materials. Finding the m x m change of basis matrix requires solving m eigenvector problems, each needing a choice of wavelengths in which to sharpen the corresponding basis vector. These choices, however, are themselves an optimization problem left unaddressed by the method's authors.
Instead, we pose a single problem, expressing the total approximation error incurred across all wavelengths as the sum of dm^2 squares for some number d, where, depending on the inherent dimensionality of the rendered reflectance spectra, m <= d << n, a number that is independent of the number of approximated reflections. This problem may be solved in real time, or nearly, using standard nonlinear optimization algorithms. Results using a variety of reflectance spectra and three standard illuminants yield errors at or close to the best lower bound attained by projection onto the leading m characteristic vectors of the approximated reflections. Measured as CIEDE2000 color differences, a heuristic proxy for image difference, these errors can be made small enough to be likely imperceptible using values of 4 <= m <= 9.
An examination of this problem reveals a hierarchy of simpler, more quickly solved subproblems whose solutions yield, in the typical case, increasingly inaccurate approximations. Analysis of this hierarchy explains why, in general, the lowest approximation error is not attained by simple spectral sharpening, the smallest of these subproblems, unless the spectral power distributions of all light sources in a scene are sufficiently close to constant functions. Using the methods described in this dissertation, spectra can be rendered in real time as the products of m-dimensional vectors of sharp basis coefficients at a cost that is, in a typical application, a negligible fraction above the cost of RGB rendering.Graduate
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Huang, Wen-Ming, and 黃文明. "An ADPLL Clock Generator with Large Frequency Multiplication Factor for Video Application." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/47484094175765669069.
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碩士國立交通大學
電機學院碩士在職專班電子與光電組
95
In this thesis, an all-digital phase-locked loop with large multiplication factor is presented. This circuit can be applied to the video system as a clock generator. It receives the horizontal synchronous signal from the graphics card and then generates a high frequency pixel clock according to the monitor resolution setting to acquire the video signal data. The stability of this sampling clock affects the display image quality directly. If the pixel clock is not stable, the display image will be glittering or jittering. Therefore, how to design a stable clock generator with large multiplication factor is the point of this thesis. This chip is implemented with standard cell library by synthesis and auto place-and-route tools, and realized using 90nm 1P9M standard CMOS process.
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Chang, Hsiu-Ju, and 張琇茹. "A Fast Phase-Tracking ADPLL for Video Applications with Large Frequency Multiplication Factor." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/33619577450669114680.
Full textAbstract:
碩士國立交通大學
電子工程系所
97
In this thesis, a fast phase-tracking all-digital phase-locked loop with large multiplication factor is presented. This circuit can be applied to the video system as a clock generator. It receives the horizontal synchronous signal from the graphics card and then generates a high frequency pixel clock according to the monitor resolution setting to acquire the video signal data. The phase error between sampling clock and video data affects the display image quality directly. If the phase of pixel clock is not stable, the display image will be glittering or jittering. Therefore, how to design a fast phase-tracking clock generator with large multiplication factor is the point of this thesis. In the proposed architecture, a sigma-delta modulator is used to enhance the equivalent digital-controlled oscillator resolution, and a time-to-digital converter loop is applied to compensate the phase error immediately, and the glitch of DCO is also analyzed and prevented. This chip is implemented with standard cell library by synthesis and auto place-and-route tools, and realized using 0.18�慆 1P5M standard CMOS process.
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Ko, Chiun-Yao, and 柯鈞耀. "Fast Phase Tracking and High Frequency Multiplication Factor All-Digital Phase-Locked Loop and Its Applications." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/91419033887713251833.
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碩士國立中正大學
資訊工程所
98
An All-Digital Phase-Locked Loop (ADPLL) for video capture application is presented in this dissertation. The major function of this ADPLL is to generate the high speed pixel clock from the horizontal synchronization signal (HSYNC) of the Person Computer (PC) graphics card according to the user-defined video resolution. When it is compared with conventional Phase-Locked Loop (PLL), the proposed design have better phase tracking ability than conventional PLLs in high frequency multiplication factor applications. And it can accept large reference clock jitter and still have fast phase tracking ability. The advantages of digital design can overcome the leakage problem in advanced CMOS process, reduce chip area and avoid to use external components (such as external capacitor and oscillator). The digital loop filter was developed to resist the jitter effects of reference clock and to reduce the period jitter of pixel clock. The stability of sampling clock (pixel clock) will have large effects on video quality. Thus how to generate a very stable, and small phase drift pixel clock, is the major design challenge in this dissertation. And the proposed ADPLL was implemented with standard cells on a standard 65nm CMOS process to verify the performance of the proposed architecture.
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Gopinath, M. "Rinderpest Virus Transcription : Functional Dissection Of Viral RNA Polymerase And Role Of Host Factor Ebp1 In Virus Multiplication." Thesis, 2009. http://hdl.handle.net/2005/627.
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Rinderpest virus (RPV) belongs to the order Mononegavirale which comprises non segmented negative sense RNA viruses including human pathogens such as Measles, Ebola and Marburg virus. RPV is the causative agent of Rinderpest disease in large ruminants, both domesticated and wild. The viral genome contains a non segmented negative sense RNA encapsidated by nucleocapsid protein (N-RNA). Viral transcription/replication is carried out by the virus encoded RNA dependent RNA polymerase represented by the large protein L and phosphoprotein P as (L-P) complex. Viral transcription begins at the 3’ end of the genome 3’le-N-P-M-F-H-N-tr-5’ with the synthesis of 55nt leader RNA followed by the synthesis of other viral mRNAs. A remarkable feature common to all members of Paramyxoviridae family is the gradient of transcription from 3’ end to the 5’ end of the genome due to attenuation of polymerase transcription at each gene junction.
The present study aims at functional characterization of Rinderpest virus transcription and the associated activities required for viral mRNA capping. In addition, an attempt has been made to understand the novel role of a host factor, Ebp1, playing a key role in virus multiplication in infected cells. The specific aims of the study are presented in detail below.
1. Development of in vitro transcription system for RPV mRNA synthesis and role of phosphorylation of P protein in transcription.
The transition of viral polymerase from transcription to replication in infected cells has been a long standing puzzle in all paramyxoviruses. Earlier work carried out using RPV minigenome with a CAT reporter gene and studies with phosphorylation null mutant P, has revealed the importance of P phosphorylation for viral transcription in vivo. However, the contribution of other cellular factors in the viral transcription/replication switch could not be ruled out in these assays. In order to understand the specific role of P protein in transcription/replication, it was necessary to develop a cell free transcription system for viral mRNA synthesis. Hence, viral genomic RNA (N-RNA) was purified from RPV infected cells using CsCl density gradient centrifugation. The viral RNA polymerase consisting of L-P complex was separately expressed in insect cells and partially purified by glycerol gradient centrifugation. Glycerol gradient fraction containing the L-P complex was found to be active in viral transcription. Notably, the gradient of transcription of viral mRNA was observed in vitro with the partially purified recombinant L-P complex similar to in vivo. However, the recombinant polymerase complex failed to synthesis the 55nt leader RNA, in agreement with the recent finding in VSV that the transcriptase complex was unable to synthesize leader RNA and viral transcription is initiated at the N gene start site unlike the conventional 3’ entry mode. The newly developed in vitro reconstituted transcription system was used to analyze the effect of P phosphorylation on viral transcription. The results presented in chapter 2, indicate that phosphorylated P supports transcription whereas unphosphorylated P transdominantly inhibits the transcription in vitro suggesting the possible role of the status of P protein phosphorylation in determining transcription/replication switch.
2. Enzymatic activities associated with RPV L protein- role in viral mRNA capping.
Post transcriptional modification of mRNA such as capping and methylation determines the translatability of viral mRNA by cellular ribosome. In negative sense RNA viruses, synthesis of viral mRNA is carried out by the viral encoded RNA polymerase in the host cell cytoplasm. Since the host capping and methylation machinery is localized to the nucleus, viruses should either encode their own mRNA modification enzymes or adopt alternative methods as has been reported for orthomyxoviruses (cap snatching) and picornaviruses (presence of IRES element). In order to test, if RPV RNA polymerase possesses any of the capping and methylation activities, both virus as well as the RNP complex containing the viral N-RNA and RNA polymerase (L-P) were purified from infected cells. Using the purified virus and RNP complex, the first two activities required for mRNA capping vis-à-vis, RNA triphosphatase and guanylyltransferase were tested and the results are described in chapter 3 and 4. Purified virus as well as the RNP complex showed both RNA triphosphatase (RTPase) and Nucleotide triphosphatase activities. Neither purified N-RNA or recombinant P proteins show these activities suggesting that it is indeed mediated by viral L protein. By the metal dependency of the reaction and by the motif conservation with other reported RTPases, RPV L protein was assigned to the metal dependent RTPase tunnel family. Capping activity was also seen with the L protein present in RNP complex by its ability to form a covalent complex with GMP moiety of GTP. The specificity of the reaction with GTP, inhibition of Enzyme-GMP complex formation by the inorganic pyrophosphate and the susceptibility of Enzyme-GMP complex under acidic conditions clearly indicated that RPV L represents the viral guanylyl transferase. Further confirmation was obtained by the indirect capping assay in which Enzyme-GMP complex was formed when recombinant L protein was incubated with the cap labeled RNA due to the reversible nature of capping reaction.
Owing to the large size of L protein (240 KDa), it is conceivable that the L protein functions in a modular fashion for different activities pertaining to RNA synthesis and modification. Sequence comparison of L proteins from different morbilliviruses revealed the presence of three conserved domains namely domain I (aa 1-606), domain II (aa 650-1694) and domain III (aa 1717-2183). Since domain II has already been assigned as the viral RNA dependent RNA polymerase, domain I and domain III were chosen for further characterization. Both domains were cloned, expressed and purified to homogeneity using recombinant baculovirus expression system. However, the recombinant domain III alone showed the NTPase activity where as neither domain I or III showed RTPase activity. This is expected since a part of the conserved RTPase motif was located in domain II in the multiple sequence alignment with other viral and yeast RTPases. In addition, the recombinant domain III also showed the characteristic enzyme-GMP complex formation but failed to be active in the indirect capping assay. Therefore, both domain II and domain III are likely to be involved in the co-transcriptional capping of viral mRNA. In support of this view, recent report in VSV suggests the presence of additional motif in domain II which is essential for viral mRNA capping. Preliminary evidence has been presented in the appendix section for the presence of N7 guanine methyl transferase activity with L protein although further experiments are needed to confirm this activity.
3. Role of host factor Ebp1 in negative sense RNA virus replication - a possible antagonist
In recent years, many cellular factors such as actin, tubulin and profilin have been shown to be involved in viral transcription. Ebp1-ErbB3 binding protein was initially isolated as a cellular protein which binds to Influenza viral polymerase subunit PB1. Ebp1 selectively inhibits the influenza virus transcription in vitro whereas the cap binding and endonuclease activity of PB1 subunit of viral polymerase is unaffected. Till now there are no reports of the role of Ebp1 in non segmented negative sense RNA virus infection. The fifth chapter describes the role of Ebp1 in RPV infection and vice versa. RPV infection leads to down regulation of Ebp1 mRNA levels which in turn leads to decreased protein synthesis. Subsequently, it was found that Ebp1 interacts presumably with viral N protein, being a part of the viral RNP complex in both infected cells as well as in purified virion. Further, over expression of Ebp1 inhibits viral transcription and as a consequence the virus multiplication in vivo suggesting a mutual antagonism between virus and the host cell through Ebp1 protein.
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Wang, Yun-Hsin, and 王芸馨. "Part I: Functional analysis of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) binding to HDV RNA in the multiplication of hepatitis delta virus;Part II: Characterization and functional analysis of a cellular factor NESI interacting with the nuclear exp." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/69770453548400918982.
Full textAbstract:
博士國立臺灣大學
生物化學暨分子生物學研究所
93
Heaptitis virus (HDV) is the causative agent of acute and chronic liver diseases including fulminant hepatitis and accelerated liver cirrhosis. HDV particles contain a single-stranded circular RNA genome of 1.7 kilobases. The HDV antigenomic RNA contains an open reading frame which encodes delta antigens( HDAgs). There are two forms of HDAgs, the small HDAg (HDAg-S, 24 kDa) and the large HDAg (HDAg-L, 27 kDa). The two HDAgs are identical in the amino acid sequence, except that the HDAg-L contains an additional 19 amino acids at it C terminus. Nevertheless, functions of two forms of HDAgs are quite different. The HDAg-S is required for the HDV replication, whereas the HDAg-L has negative effects on genome replication is required for HDV assembly. The HDV genome RNA is associated with delta antigen to form ribonucleoprotein. Previous results have shown that a cellular factor, GAPDH interacted with HDV RNA. In addition, nuclear export signal that located in the C-terminus of HDAg-L from amino acid residues 198-210, designated NES(HDAg-L), has been identified. To investigate the biological role of GAPDH in HDV life cycle, cells were transfected with plasmid pSVD2 representing the dimeric HDV cDNA and proceeded to fluorescence in situ hybridization/immunofluorescence staining. In the presence of HDV replication, GAPDH relocalized from the cytoplasm to the nucleus. The biological significance of the interaction between GAPDH and HDV RNA was further elucidate by examing the possible role of GAPDH on the catalysis of HDV ribozyme. This cis-cleavage activity of the HDV anigenomic RNA increase from 34 to 62 % following a 40-min incubation with 50 ng/ l of GAPDH. The enhancing effect of GAPDH on the catalysis of HDV ribozyme was reproducible and was not observed with bovine serum albumin (BSA). These results suggest a possible role of GAPDH involved in HDV multiplication. The process of host factor-mediated nucleocytoplasmic transport is critical for diverse cellular events in eukaryotes and the life cycle of viruses. A previously identified chromosome region maintenance 1 (CRM1)-independent nuclear export signal (NES) at the C-terminus of the large form of hepatitis delta antigen (HDAg), designated NES(HDAg-L) is required for the assembly of hepatitis delta virus (HDV) To look for interacting proteins of the NES(HDAg-L), yeast two-hybrid screening was applied using GAL4 binding domain fused to NES(HDAg-L) as bait. Among the positive clones, one encodes a protein, designated NESI (NES-interacting protein) that specifically interacted with the wild-type NES(HDAg-L), but not with the export/package-defective HDAg-L mutant, NES*(HDAg-L) in which Pro-205 has been replaced by Ala. Northern blot analysis revealed NESI as the gene product of a 1.9 kb endogenous mRNA transcript that is present predominantly in human liver tissue. NESI consists of 467 amino acid residues and bears a putative actin-binding site and a bipartite nuclear localization signal. Specific interaction between HDAg-L and NESI was further confirmed by coimmunoprecipitation and immunofluorescence staining. Overexpression of an antisense NESI RNA abolished HDAg-L-mediated assembly of HDV genomic RNA into virus-like particles. These data indicate a critical role of NESI, through the interaction of HDAg-L, involved in the assembly of HDV.
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Lee, Chieh-Wen, and 李介文. "The Design and Analysis of Frequency Synthesizers with Large Multiplication Factors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/65946639401783345152.
Full textAbstract:
碩士國立臺灣大學
電子工程學研究所
101
In general, noise in PLLs can be sorted into two categories, reference noise and VCO noise. It is known that reference noise can be suppressed with a low bandwidth while VCO noise would be cleaned up more efficiently with a high bandwidth. Thus, it has a tradeoff in the choice of bandwidth. However, loop bandwidth should be kept below approximately one tenth of the reference frequency in practice to ensure the stability of the system. With some standard pre-defining the bandwidth mandatorily, it is hard to choose the loop bandwidth arbitrarily. The situation is getting more serious when designing the frequency synthesizer with low reference frequency and large multiplication factors. For instance, when the PLL is applied into a control circuit in an LCD device, the input frequency is around 15 KHz ~ 100 KHz while the output frequency is almost around 30 MHz ~ 100 MHz. Therefore, limited by the reference frequency, the loop bandwidth in this application will be lower than 10 KHz, which make VCO noise hard to be suppressed. In this scenario, how to suppress the VCO noise efficiently becomes an important issue. Furthermore, low bandwidth will make loop filter capacitor too large to be integrated on-chip. To overcome the problems mentioned above, this thesis proposes a hybrid frequency synthesizer based on a combination of PLL and multiplying DLL. It can achieve the best noise responses of key noise sources among all the proposed multi-loop architectures. Besides, a compact digital loop filter is utilized to save large area. However, with such a long reference period, it is hard for TDC to cover its full range. The limited tracking range of the P2D will result in long lock time. Therefore, we adopt a fast lock approach. By this approach, 4 bit TDC can be employed without sacrificing the setting time. Last not but least, we take the multiphase compensation method to suppress the quantization noise in high frequency offset. This proposed hybrid frequency synthesizer operates from 350 MHz to 850 MHz with reference frequency equal to 32.768 KHz. It is fabricated in a 0.18μm CMOS technology with an core area of 1 x 0.7 mm2. The power consumption is 30 mW from 1.8-V power supply.