Dissertations / Theses: 'DltX'

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Kamar, Rita. "Mécanismes de résistance aux peptides antimicrobiens chez Bacillus thuringiensis : rôle de dltX dans la D-alanylation des acides téichoïques." Electronic Thesis or Diss., Paris, AgroParisTech, 2014. http://www.theses.fr/2014AGPT0029.

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Le groupe Bacillus cereus est très hétérogène du point de vue toxicité et il est difficile de prédire le potentiel pathogène d'une souche. Dans ce travail, nous avons étudié les différents phénotypes de colonisation/adaptation à l'hôte, et analysé la corrélation entre ces phénotypes et les maladies humaines, pour une collection de souches représentatives de la diversité pathologique de B. cereus chez l'homme. L'analyse statistique a révélé des corrélations entre plusieurs phénotypes, et une analyse en composante principale a permis de regrouper les souches en deux sous-populations distinctes. Notre étude a ainsi permis de montrer qu'un ensemble de caractères phénotypiques liés au pouvoir pathogène permet de discriminer les souches présentant un historique en maladies infectieuses des souches sans historique. Nous pensons que ces résultats faciliteront l'identification d'un phénotype ou d’une combinaison de phénotypes qui pourraient être utilisés dans le développement de stratégies de prévention des infections par B. cereus. Le résultat de cette étude suggère que B. cereus n'est pas exclusivement un pathogène opportuniste et pourrait plutôt être considéré comme un véritable agent pathogène en soi.Cependant, la virulence est un phénomène multifactoriel impliquant de nombreux facteurs du côté de l'hôte ainsi que de celui de l'agent pathogène envahisseur. Les peptides antimicrobiens (PAMs) cationiques constituent les principales molécules effectrices de l’immunité innée. La résistance des microorganismes vis à vis de ces composés est donc nécessaire pour qu’ils puissent se développer dans l’hôte et exercer leur pouvoir pathogène. Par conséquent, de nombreuses bactéries pathogènes ont développé des stratégies de résistance impliquant la réduction des charges négatives de l’enveloppe bactérienne, réduisant ainsi l'interaction et la fixation de ces PAMs. L'incorporation de résidus D-alanine aux acides téichoïques (ATs) représente l'un des mécanismes les plus courants de résistance bactérienne qui dépendent de telles modifications. Ce processus de D-alanylation est accompli par les produits des gènes de l’opéron dlt. Celui-ci contient cinq gènes dltXABCD dont les séquences sont très conservées dans la quasi-totalité des bactéries à Gram-positif. La première ORF, dltX, code pour une protéine dont la fonction est inconnue. Le but de la seconde partie de ce travail était donc de déterminer si cette protéine est impliquée dans le processus de D-alanylation chez Bacillus thuringiensis. Pour cela, nous avons procédé à une délétion en phase du gène dltX, qui n’affecte pas l’expression des autres gènes de l'opéron. Les caractéristiques de croissance du mutant dltX et celles de la souche de type sauvage se sont avérées similaires in vitro. Cependant la délétion de dltX affecte considérablement la résistance de B. thuringiensis aux PAMs et atténue significativement sa virulence chez deux espèces d’insectes: Galleria mellonella et Drosophila melanogaster. En outre, une analyse HPLC montre que la paroie du mutant dltX est dépourvue de D-alanine, et la mesure de la mobilité électrophorétique indique que cette absence de D-alanylation est associée à un changement de la charge globale à la surface bactérienne. Des expériences de microscopie électronique à balayage montrent aussi des modifications morphologiques du mutant dltX, ce qui suggère que l'absence de D-alanine affecte également la structure de la paroi cellulaire. Nos résultats montrent que DltX est essentiel pour l'incorporation de la D-alanine aux acides téichoïques. Par ailleurs nous avons également démontré que dltX n’affecte pas l’expression de l’opéron dlt. Par conséquent nos résultats indiquent clairement que DltX joue un rôle direct dans la résistance aux PAMs, contribuant ainsi à la survie et la virulence de B. thuringiensis chez les insectes. Ce travail est le premier qui étudie la participation de dltX dans la D-alanylation des ATs
The Bacillus cereus pathogenic spectrum ranges from strains used as probiotics to human-lethal strains (causing gastrointestinal disorders or local and severe systemic infections). However, prediction of the pathogenic potential of a strain remains difficult. In this work, we studied different phenotypes of colonization/adaptation to the host (adhesion, cytotoxicity, motility, biofilm formation, resistance to antimicrobial peptides and virulence), analyzing the correlation between these phenotypes and human disease in a collection of strains representative of the pathological diversity of B. cereus in humans. Statistical analysis revealed correlations between several phenotypes, and principal component analysis grouped the strains into two distinct subpopulations. We found that strains differed in pathogenic potential and that virulent strains could be differentiated from non-pathogenic strains. We believe that these findings will facilitate the identification of a phenotype or a combination of phenotypes of potential use in the development of effective prevention strategies and/or diagnostic tools for distinguishing between pathogenic and non-pathogenic B. cereus strains. Our result suggests that B. cereus is not an exclusively opportunistic pathogen and could instead be considered a real pathogen per se. However, virulence is a multifactorial phenomenon involving numerous factors from both the host and the invading pathogen. As cationic antimicrobial peptides (CAMPs) are the primary defense mechanism against invading organisms, virulence of pathogens like B. cereus requires bacterial resistance to such compounds. Consequently, many pathogens have developed resistance strategies involving the reduction of the cell envelope negative charge, thereby influencing the binding and interaction of these CAMPs. The incorporation of Dalanine esters into teichoic acids (TAs) represents one of the most common bacterial resistance mechanisms that depend on such charge modifications. That D-alanylation process is accomplished by the gene products of an operon containing five genes, dltXABCD, that is highly conserved among nearly all gram-positive bacteria. The small first ORF, dltX, encodes a protein of unknown function. The aim of the other part of this work was then to establish whether this protein is involved in the D-alanylation process in Bacillus thuringiensis. We therefore constructed an in frame deletion mutant of dltX, without affecting the expression of the other genes of the operon. The growth characteristics of the dltX mutant and those of the wild type strain were similar under standard in vitro conditions. However disruption of dltX drastically impaired the resistance of B. thuringiensis to CAMPs and significantly attenuated its virulence in two insect species: Galleria mellonella and Drosophila melanogaster. Moreover, HPLC studies showed the dltX mutant was devoid of D-alanine, and electrophoretic mobility measurements indicated that the cells carried a higher negative surface charge. Scanning electron microscopy experiments showed morphological alterations of these mutant bacteria, suggesting that depletion of D-alanine from TAs affects cell wall structure. Our findings suggest that DltX is essential for the incorporation of D-alanyl esters into teichoic acids. Moreover, we found that DltX does not affect the expression of the operon. We therefore conclude that dltX is translated into a functional protein that plays a direct biosynthetic, transport or addresser role. Altogether, our results clearly indicate that DltX plays a direct role in the resistance to CAMPs, thus contributing to the survival and virulence of B. thuringiensis in insects. The exact function of that protein remains to be elucidated. This work is the first report examining the involvement of dltX in the Dalanylation of TAs

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Pfennig, Sabrina [Verfasser], Milton T. [Akademischer Betreuer] Stubbs, Ralph P. [Akademischer Betreuer] Golbik, and Norbert [Akademischer Betreuer] Sträter. "Strukturelle und thermodynamische Charakterisierung der DltA-DltC-Interaktion und kinetische Analyse der DltA katalysierten D-Alanylierung des DltC / Sabrina Pfennig. Betreuer: Milton T. Stubbs ; Ralph P. Golbik ; Norbert Sträter." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2015. http://d-nb.info/1073150704/34.

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Allen, Darin. "Transcriptional regulation of the dlt operon in Enterococcus faecalis and further characterization of a dlta mutant." Thesis, Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/783.

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Zimmermann, Stephan [Verfasser], Milton T. [Akademischer Betreuer] Stubbs, J. [Akademischer Betreuer] Balbach, and H. D. [Akademischer Betreuer] Mootz. "Strukturelle Untersuchungen der Wechselwirkungen zwischen DltA und DltC / Stephan Zimmermann. Betreuer: Milton T. Stubbs ; J. Balbach ; H. D. Mootz." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/1025231376/34.

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Gurimskaya, Yana. "Comportement de quelques impuretés métalliques dans le germanium : une étude par les techniques capacitives DLTS-MCTS-LAPLACE DLTS." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00734375.

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Ce travail consiste en une tentative de ré-examiner les propriétés électroniques du Fe, Cr et Au au sein de Ge, qui ont déjà été étudiées classiquement par DLTS (Deep Level Transient Spectroscopy). L'image générale qui en découle est que les métaux de transition dans Ge forment de manière prépondérante des centres accepteurs multiples, introduisant plusieurs niveaux profonds dans la bande de gap. A partir d'un modèle de liaison de valence simple, cette conclusion est en accord avec une survenue des impuretés sur des sites de substitution. Cependant, plusieurs questions demeurent ouvertes, comme le rôle de l'hydrogène en tant que contaminant dans l'élargissement des spectres DLTS. Notre contribution se base sur l'utilisation d'une approche plus performante nommée Laplace DLTS, en ce sens qu'elle autorise une meilleure résolution du signal. Nous présentons une analyse extensive par DLTS, MCTS et Laplace DLTS, afin d'étudier les propriétés électroniques des états accepteurs multiples, induits par les 4 métaux de transition sus-nommés. On distingue, parmis les paramètres étudiés, les barrières de capture des porteurs, les vraies sections efficaces de capture de sporteurs majoritaires (déterminées directement par la méthode de variation du pulse de remplissage), L'effet Pool-Frenkel (en lien avec la détermination de l'état de charge du niveau concerné). Ceci permet d'indiquer avec précision la position exacte des niveaux dans la bande interdite. Nous confirmons la plupart des résultats mis en évidence précédemment, tout en ajoutant quelques précisions sir le rôle de l'hydrogène dans la formation de nouveaux complexes. Une mise en parallèle avec le silicium. Dans le cas de Au, de nouveaux niveaux attribués aux complexes Au-Hn et Au-Sb sont observés. De manière générale, l'analyse des porteurs majoritaires et minoritaires par MCYS est toujours sujette à étude. En ce qui concerne le cas du Fe, la faible différence d'énergie entre ses deux niveaux soulève la possibilité d'un caractère de type U-négatif. L'ensemble de ses points devraient faire l'objet d'un travail approfondis dans un avenir proche.

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Djebbar, El-hocine. "A DLTS study of copper indium diselenide." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391312.

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Marklund, Daniel. "Control of a high temperature DLTS setup." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328710.

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This thesis deals with a DLTS-setup and how this can be controlled. The controlling program is constructed in LABVIEW, where a previous built program measuring transients at varying pulses been handled and tried to be implemented for this setup. Parts of the program was implemented successfully, other part needs more work. The heater in the setup has further been connected directly to the sample. This one has been tested to see that the setup can handle the heat and that the difference between the temperature at the sample and the setup did not differ too much. The result showed that the difference was not so big. Finally, DLTS tests was performed at samples of silicon carbide as well as on diamond, where transients could be measured up to 723 °C on the silicon carbide sample, while the tests of diamond only gave noise.

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Jin, Gongjiu. "DLTS studies of surface state effects in GaAsFETs." Thesis, Lancaster University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316292.

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Tabata, Americo Sheitiro. "Estudo de níveis profundos em GaAs usando DLTS." [s.n.], 1988. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278298.

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Orientador: Marcio A.A. Pudensi
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-07-17T14:01:56Z (GMT). No. of bitstreams: 1 Tabata_AmericoSheitiro_M.pdf: 727451 bytes, checksum: 6f553ad446b36fbefaabb37c21ce3d4a (MD5) Previous issue date: 1988
Resumo: Não informado
Abstract: Not informed.
Mestrado
Física
Mestre em Física

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Hellig, Kay. "Untersuchung tiefer Störstellen in Zinkselenid." [S.l. : s.n.], 1997. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10324521.

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Nyamhere, Cloud. "Characterization of process and radiation induced defects in Si and Ge using conventional deep level transient spectroscopy (DLTS) and Laplace-DLTS /." Access to E-Thesis, 2009. http://upetd.up.ac.za/thesis/available/etd-02022010-134937/.

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Stübner, Ronald. "Electrical characterization of carbon-hydrogen complexes in silicon and silicon-germanium alloys." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-233055.

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In this thesis, a comprehensive study of the electrical properties of carbon-hydrogen (CH) complexes in silicon (Si) and silicon-germanium (SiGe) alloys is presented. These complexes form by the reaction of residual carbon impurities with hydrogen that is introduced either by wet chemical etching or a dc hydrogen plasma. The complexes were detected and characterized by the deep level transient spectroscopy (DLTS), Laplace DLTS, and minority carrier transient spectroscopy (MCTS) technique. With this approach, properties like the activation enthalpy for carrier emission, the capture cross section, the charge state, and the thermal stability of the complexes were determined. The composition of the complexes was derived from the analysis of their depth profiles in samples with different impurity concentrations. Using these methods, eight carbon-hydrogen related defect levels (E42, E65, E75, E90, E90', E262, H50, H180) and one hydrogen related level (E150) were detected in Si, SiGe alloys and Ge. Hydrogen plasma treatment at temperatures around 373 K introduces four dominant traps in Si at about Ec-0.06 eV (E42), Ec-0.52 eV (E262), Ev+0.33 eV (H180), and Ev+0.08 eV (H50). E42 and E262 are shown to be two charge states of the same defect. The characteristic field dependence of their emission rate links E42 with the double acceptor level and E262 with the single acceptor level of a CH complex. By comparison of their properties with calculations they are assigned to the anti-bonding configuration of the CH complex (CH_1AB). H180 was previously suggested to be the donor state of the CH_1AB configuration. This hypothesis could not be confirmed. Instead, it is shown that H180 exhibits a barrier for hole capture of about 53 meV, which hinders the reliable determination of its charge state from the field dependence of the emission rate. However, its activation enthalpy is in reasonable agreement with the predicted level position of the acceptor state of the CH_T configuration of CH, where H sits on the tetrahedral interstitial (T) position next to carbon. Therefore, H180 is tentatively assigned to CH_T. H50 is reported for the first time and it appears with concentrations close to the detection limit of the DLTS technique (~1E11 cm^-3). This complicates the determination of its charge state. Nevertheless, theory predicts the acceptor level of the CH_2AB configuration at about Ev+0.07 eV, which is remarkably close to the experimental value of H50. Therefore, H50 is tentatively assigned to the acceptor level of CH_2AB. In contrast, hydrogenation of silicon by wet chemical etching introduces three dominant levels at Ec-0.11 eV (E65), Ec-0.13 eV (E75), and Ec-0.16 eV (E90). Previously, E90 was contradictorily assigned by different authors to the donor and to the acceptor state of the bond-centered configuration of the CH complex (CH_1BC). In this work, this contradiction is resolved. It is shown that two different defect levels (E90 and E90') appear in the DLTS spectra at about 90 K in samples with a low oxygen concentration (< 1E17 cm^-3). The acceptor state of the CH_1BC configuration (E90) can be observed directly after hydrogenation by wet chemical etching or a dc hydrogen plasma treatment at temperatures below 373 K. In contrast, the donor state of a CH_n complex (E90', Ec-0.14 eV), that involves more than one hydrogen atom, is formed by a reverse bias annealing of samples with a net donor concentration of Nd > 1E15 cm^-3. By comparison with theory it is concluded that n > 2. In samples with a high oxygen concentration (> 1E17 cm^-3) E65 and E75 are dominant. Both levels belong to the CH_1BC configuration disturbed by a nearby oxygen atom. The appearance of two levels is the result of two inequivalent positions of the oxygen atom in respect to the CH bond. E42, E90, E262, and H180 are also investigated in diluted SiGe alloys to analyze the influence of alloying on their electrical properties. The presence of Ge atoms in the closest environment of the defects leads to the appearance of additional defect levels close to those observed in pure Si. The relative concentration of these additional defects is in agreement with models of the proposed defect structure of E42, E90, E262, and H180. An increase of the Ge content in SiGe alloys leads to a shift of the defect levels in the band gap of SiGe. An extrapolation of this shift predicts the appearance of E90 and E262 also in pure Ge. A hydrogen related level E150 (Ec-0.31 eV) is indeed observed in hydrogenated n-type Ge. Its concentration is significantly higher after hydrogen plasma treatment than after wet chemical etching. It is shown that E150 contains a single hydrogen atom and involves an unknown impurity, most likely carbon, oxygen, or silicon. E150 represents a reasonable candidate for a CH complex in Ge
In dieser Arbeit werden die elektrischen Eigenschaften von Kohlenstoff-Wasserstoff-Komplexen in Silizium (Si) und Silizium-Germanium-Legierungen (SiGe) studiert. Diese Komplexe bilden sich durch Reaktion von Kohlenstoff-Verunreinigungen mit Wasserstoff, welcher durch nasschemisches Ätzen oder eine Wasserstoffplasma-Behandlung eingebracht wird. Der Nachweis und die Charakterisierung der Defekte erfolgte mit den Methoden der Kapazitätstransientenspektroskopie (DLTS), Laplace DLTS und der Minoritätsladungsträgertransientenspektroskopie (MCTS). Damit wurden Eigenschaften wie die Aktivierungsenergie der Ladungsträgeremission, die Einfangquerschnitte, der Ladungszustand und die thermische Stabilität der Komplexe bestimmt. Die Zusammensetzung der Komplexe wurde durch eine Analyse der Tiefenprofile ermittelt, welche in Proben mit verschiedenen Verunreinigungskonzentrationen gemessen wurden. Mit diesen Methoden wurde acht Kohlenstoff-Wasserstoff-korrelierte Defektniveaus (E42, E65, E75, E90', E90, E262, H50, H180) in Si und SiGe und ein Wasserstoff-korreliertes Niveau in Ge nachgewiesen. Eine Wasserstoffplasma-Behandlung bei Temperaturen um 373 K erzeugt vier dominante Defektniveaus in Si bei Ec-0.06 eV (E42), Ec-0.52 eV (E262), Ev+0.33 eV (H180) und Ev+0.08 eV. Es wird gezeigt, dass E42 und E262 zwei Ladungszustände desselben Defektes sind. Die charakteristische Feldabhängigkeit der Emissionsrate zeigt, dass E42 der Doppel-Akzeptor- und E262 der Einfach-Akzeptor-Zustand eines CH-Komplexes ist. Durch Vergleich der beobachteten Eigenschaften mit theoretischen Berechnungen werden beide Niveaus der antibindenden Konfiguration des CH-Komplexes (CH_1AB) zugeordnet. Das Niveau H180 wurde in der Literatur bisher mit dem Donator-Zustand der CH_1AB-Konfiguration in Verbindung gebracht. Diese Hypothese konnte nicht bestätigt werden. Es wird gezeigt, dass H180 eine Barriere für den Löchereinfang von etwa 53 meV besitzt, was die Bestimmung des Ladungszustandes aus der Feldabhängigkeit der Emissionsrate erschwert. Die Aktivierungsenergie von H180 stimmt jedoch befriedigend mit der berechneten Aktivierungsenergie des Akzeptorzustandes der CH_T-Konfiguration überein, bei der H auf der T-Zwischengitterposition sitzt. Daher wird H180 vorläufig dem CH_T-Komplex zugeordnet. Das Niveau H50, welches zum ersten Mal hier beschrieben wird, wird nur mit sehr geringen Konzentrationen nachgewiesen. Dies erschwert die Bestimmung des Ladungszustandes. Die Aktivierungsenergie von H50 stimmt jedoch auffallend gut mit dem von der Theorie vorhergesagten Akzeptorniveau von CH_2AB (Ev+0.07 eV) überein. Daher wird H50 vorrübergehend CH_2AB zugeordnet. Das Einbringen von Wasserstoff in Silizium durch nasschemisches Ätzen führt zu drei dominanten Defektniveaus bei Ec-0.11 eV (E65), Ec-0.13 eV (E75) und Ec-0.16 eV (E90). E90 wurde bisher widersprüchlich von verschiedenen Autoren dem Donatorzustand und dem Akzeptorzustand der bindungszentrierten Konfiguration (CH_1BC) des CH-Komplexes zugeordnet. Dieser Widerspruch konnte aufgelöst werden. Es wird gezeigt, dass in Silizium mit niedrigem Sauerstoffanteil (< 1E17 cm^-3) zwei verschiedene Defektniveaus (E90 und E90') bei etwa 90 K in den DLTS-Spektren erscheinen, welche nur mit der Laplace DLTS-Technik aufgelöst werden können. Der Akzeptorzustand der CH_1BC-Konfiguration kann direkt nach nasschemischem Ätzen oder einer Wasserstoffplasma-Behandlung bei 373 K beobachtet werden. Im Gegensatz dazu wird durch eine Sperrspannungs-Temperung in Proben mit einer Donatorkonzentration von Nd > 1E15 cm^-3 der Donatorzustand eines CH_n-Komplexes (E90', Ec-0.14 eV), welcher mehr als ein Wasserstoffatom enthält, gebildet. Durch Vergleich mit theoretischen Berechnungen wird n > 2 geschlussfolgert. Die Niveaus E65 und E75 sind in Proben mit einem hohen Sauerstoffanteil (> 1E17 cm^-3) dominant. Beide Niveaus gehören zu einer durch ein O-Atom verzerrten CH_1BC-Konfiguration. Das Auftreten von zwei Niveaus wird durch zwei nicht-äquivalente Positionen des O-Atoms bezüglich der CH-Bindung erklärt. Die Eigenschaften von E42, E90, E262 und H180 wurden ebenfalls in verdünnten SiGe-Legierungen untersucht. Es wird gezeigt, dass Ge-Atome in der direkten Umgebung der Defekte zusätzliche Defektniveaus erzeugen, die in der Bandlücke nahe zu den Si-Defektniveaus liegen und von durch Ge-Atomen verzerrten Defekten stammen. Die beobachteten relativen Konzentrationen dieser Ge-korrelierten Niveaus kann mit Modellen der atomaren Struktur der Defekte erklärt werden. Eine Verschiebung der Defektniveaus proportional zum Ge-Anteil in der Legierung wurde beobachtet. Eine Extrapolation dieser Verschiebung legt den Schluss nahe, dass E90 und E262 auch in reinem Ge beobachtbar sein sollten. Tatsächlich wurde ein Wasserstoff-korrelierter Defekt E150 (Ec-0.31 eV) in n-Typ Germanium beobachtet. Die Konzentration von E150 ist nach einer Wasserstoffplasma-Behandlung wesentlich höher als nach nasschemischen Ätzen. Es wird gezeigt, dass E150 ein einzelnes Wasserstoffatom und ein noch unbekanntes Verunreinigungsatom enthält, höchstwahrscheinlich Kohlenstoff, Sauerstoff oder Silizium. Damit ist E150 ein sehr wahrscheinlicher Kandidat für einen CH-Komplex in Germanium

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Morselli, Enrico. "Radix DLT: un'alternativa scalabile alle Blockchain." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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La tecnologia Blockchain, introdotta inizialmente come registro distribuito per le transazioni della moneta digitale Bitcoin nel 2008, ha suscitato grande interesse nel corso degli ultimi anni. In poco tempo si è capito come tale tecnologia potesse essere applicata ai campi più disparati, e non soltanto alle monete elettroniche. Fra le tante applicazioni che si prospettano per le blockchain vi sono, ad esempio, il settore energetico, il sistema sanitario, e la tracciabilità delle catene di fornitura di beni, servizi o prodotti alimentari. Il futuro insomma, sembra orientato verso un'adozione delle blockchian su scala globale. Tuttavia, è necessario risolvere una serie di problematiche affinchè ciò possa avvenire. Il difetto forse più importante da questo punto di vista, è che la tecnologia blockchain, per come è stata progettata, non è scalabile. Non sarebbe pertanto capace di supportare un volume di transazioni pari o superiore a quello di circuiti di pagamento globali come Visa o MasterCard (si pensi ad esempio che Visa ha circa 736 milioni di utenti attivi, contro i circa 5,8 milioni di Bitcoin). Mentre vengono studiate possibili soluzioni per aggirare il problema nelle blockchain esistenti, sono nate piattaforme alternative alle blockchain che promettono una maggiore scalabilità, nonchè facilità nel costruire applicazioni basate su esse. E' il caso di Radix DLT. In questa tesi ho deciso di concentrarmi su Radix DLT e di realizzare una piccola applicazione per provare con mano gli strumenti di sviluppo a disposizione.

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Schlenker, Thomas. "Redesign eines DLX-Prozessormodells mit Pipeline." [S.l.] : Universität Stuttgart , Fakultät Informatik, 1998. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB6783562.

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Bains, S. K. "DLTS and A.C. hopping conductivity studies on electron irradiated silicon." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356128.

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Navet, Benjamin. "Homéogènes Dlx, signalisation RANK/RANKL et ostéosarcomes." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT1018/document.

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L’ostéosarcome (OS), plus fréquente des tumeurs osseuses primitives malignes, se caractérise par une croissance ostéoïde parfois associée à une ostéolyse. Malgré les avancées thérapeutiques, le taux de survie reste faible (30 % à 5 ans si métastases ou chimiorésis-tances). De nouvelles approches thérapeutiques ciblant la cellule tumorale et son environnement sont néces-saires. Les travaux présentés se sont intéressés aux poten-tiels facteurs pro-tumoraux que sont les gènes Dlx et à une signalisation clé de l’environnement osseux (RANKL/RANK) susceptible d’influer l’agressivité tumo-rale. L’OS étant une tumeur ostéoblastique, la famille Dlx a été choisie, car impliquée dans l’ostéoblasto-genèse, et la signalisation RANKL/RANK, car voie car-dinale du couplage entre ostéoblastes et ostéoclastes. De plus un lien entre Dlx et signalisation RANK était suspecté. Les gènes Dlx1, Dlx4 et Rank non-exprimés dans l’ostéoblaste sain le sont dans les lignées d’OS. Des modulations d’expression des Dlx et de Rank ont été réalisées afin d’en évaluer l’impact sur les cellules tumo-rales. L’implication de la signalisation RANK/RANKL dans le microenvironnement tumoral a été analysée. La perturbation du remodelage est en faveur de la tumeur en participant à l’établissement d’un cercle vicieux entre la tumeur et l’environnement. Les travaux ont établi l’implication des Dlx, surtout Dlx4 pour lequel un nouveau transcrit codant a été ca-ractérisé. Cependant des études supplémentaires sont nécessaires. Concernant la signalisation RANK/RANKL, il s’avère qu’au-delà du cercle vicieux, important au stade d’initiation tumorale, l’expression de RANK par la tumeur s’avère être un facteur pro-métastatique
Osteosarcoma (OS), the most common malignant primary bone tumor, is characterized by an osteoid formation occasionally associated with osteolysis. De-spite therapeutic advances, the 5-years survival rate remains low (30% in case of metastasis or drug-resistance). New therapeutic approaches targeting the tumor cell and its environment are needed. Presented studies focused on potential pro-tumor factors namely Dlx genes and a key signaling pathway of the bone environment (RANKL / RANK) that may influence tumor aggressiveness. The OS is an osteo-blastic tumor and Dlx family was chosen due to its in-volvement in osteoblastogenesis. RANKL / RANK path-way was selected as it constitutes a main element in the coupling between osteoblasts and osteoclasts. A link between Dlx genes and RANK signaling was suspected. Dlx1, Dlx4 and Rank genes are not normally ex-pressed in osteoblasts but are present in the OS cell lines. Dlx and Rank expression modulations were real-ized to assess the impact on tumor cells. RANK / RANKL signaling involvement in the tumor microenvi-ronment was analyzed. Disruption of remodeling is in favor of the tumor taking part in the establishment of a vicious circle between tumor and environment. This work established the involvement of Dlx, espe-cially DLX4 to which a new coding transcript has been characterized. However, additional studies are needed. Regarding the RANK / RANKL signaling, it turns out that beyond the vicious circle, leading to tumor initiation stage, the RANK expression by the tumor proves to be pro-metastatic elements

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Iaconianni, Sara. "Caratterizzazione di dispositivi a giunzione tramite Deep Level Transient Spectroscopy (DLTS)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14216/.

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I semiconduttori in equilibrio termodinamico sono caratterizzati dalla presenza di stati difettivi, che perturbano la periodicità del reticolo cristallino e di conseguenza alterano la struttura a bande del materiale, introducendo stati energetici disponibili nel gap di energie proibite. Tali stati si dividono in due categorie: shallow levels e deep levels. Gli shallow levels devono il loro nome al fatto che gli stati elettronici ad essi associati hanno energie dell'ordine del meV, si collocano quindi vicino al bordo della banda di valenza o conduzione. I deep levels, al contrario, sono così chiamati poiché gli stati elettronici associati hanno energie vicine al centro dell’energy gap del materiale. I deep levels influenzano alcune importanti proprietà dei materiali (ad esempio il tempo di vita medio τ dei portatori minoritari), inoltre possono essere introdotti volontariamente in un semiconduttore, ad esempio per renderlo semi-isolante. In questo lavoro di tesi è stato implementato l'apparato sperimentale necessario ad effettuare misure di Deep Level Transient Spectroscopy (DLTS), la principale tecnica per caratterizzare i deep levels; è stato inoltre sviluppato un software per controllare gli strumenti ed acquisirne le misure. La DLTS si basa sullo studio delle variazioni della capacità associata alla zona di svuotamento di dispositivi a giunzione dovute ai processi di cattura ed emissione di portatori di carica da parte dei deep levels. Le fasi di cattura sono indotte applicando al campione impulsi di tensione, e si alternano alle fasi emissione: tale alternanza origina una serie di transienti di capacità, che vengono acquisiti (mentre il campione è sottoposto a un riscaldamento costante) e poi opportunamente elaborati al fine di produrre gli spettri di DLTS veri e propri. Utilizzando i metodi descritti nel presente elaborato, gli spettri sono stati infine sfruttati per caratterizzare i deep levels di un campione di Si n-type e di uno di GaAs n-type.

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Shi, Yi. "An investigation of defects in gallium arsenide using the DLTS technique." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/28061.

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A well-known technique—Deep level Transient Spectroscopy (DLTS)—was used for investigating deep levels in Gallium Arsenide (GaAs) semiconductor material. Eight deep levels, among them the most important deep level EL2, were found in Liquid-Encapsulated Czochralski (LEC) grown semi-insulating GaAs substrates. Two of these deep levels, one electron deep level and one hole deep level, were observed for the first time in DLTS studies. Both have large thermal activation energy. A study in understanding the formation of deep levels in the GaAs substrate was actively undertaken. The cause of four deep levels present in the LEC-grown GaAs substrate were identified. The chief effects on electronic devices and integrated circuits due to the presence of these deep levels in the GaAs substrate were partially characterized. Other contributions include: firstly, a computer-assisted method was used to profile the spatial distribution of deep traps. Deep traps act as free carrier traps when deep levels are present in semiconductor bulk material. Secondly, the author, through experiments, made clear that the increasing capacitance of a Schottky diode increasing with temperature was due to the Schottky diode's barrier height decreasing with rising temperature. Thirdly, the author, by experimental results, supported the point that shallow donor with very high concentration in the bulk material is the major cause of annihilation of EL2 deep traps.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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Jansson, Rasmus. "Completion of the software required for a high-temperature DLTS setup." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-205076.

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The main purpose of this thesis was to examine the communication problems with the DLTS set up in the Division for Electricity at Ångström Laboratory in Uppsala, Sweden, and to make the DLTS software complete. The set up consisted of a C/V meter, a pulse generator, a temperature controller and a PC with a control program written in LabVIEW. It was found that the software had been constructed to fit another set of instruments than the set up currently used at Ångström Laboratory. The task was therefore to properly integrate the correct control commands of those instruments into the software.
DLTS investigation of wide bandgap materials
Diamond electronics

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Hartnett, S. J. "Uniaxial stress/DLTS studies on deep level defects in n-GaAs." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361362.

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21

Ma, Wenqian. "Dlx Gene Regulation of Zebrafish GABAergic Interneuron Development." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19970.

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Abstract The Dlx genes play an important role in the differentiation and migration of gamma-aminobutyric acid (GABA) interneurons of mice. GABAergic interneurons are born in the proliferative zones of the ventral telencephalon and migrate to the cortex early during mouse development. Single Dlx mutant mice show only subtle phenotypes. However, the migration of immature interneurons is blocked in the ventral telencephalon of Dlx1/Dlx2 double mutant mice leading to reduction of GABAergic interneurons in the cortex. Also, Dlx5/Dlx6 expression is almost entirely absent in the forebrain, most probably due to cross-regulatory mechanisms. In zebrafish, the role of dlx genes in GABAergic interneuron development is unknown. By injecting Morpholino, we double knocked down dlx1 and dlx2 genes in wildtype zebrafish to investigate the function of the two genes in zebrafish GABAergic interneuron development. By comparing different subsets of GABAergic interneuron development in wildtype and dlx1/2 morphant zebrafish forebrain, we found out that at 3dpf, 4dpf and 7dpf, double knockdown of dlx1 and dlx2 genes in zebrafish remarkably reduced the number of Calbindin-, Somatostatin- and Parvalbumin-positive GABAergic neurons, whereas the development of Calretinin-positive neurons is slightly affected. These results suggest that in zebrafish, dlx1a and dlx2a genes are important for the development of certain subtypes of GABAergic interneurons (Calbindin-, Somatostatin- and Parvalbumin-positive neurons) and may have minor influence on Calretinin-positive neuron development. This also suggests that different regulatory mechanisms are involved in the development of the different subtypes of GABAergic interneurons.

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Abboud, Nadine. "Etude et caractérisation des structures à base du silicium." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20103/document.

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Le but de ce travail est l'étude et la caractérisation des structures à base du silicium. La première partie de cette thèse traite le sujet des composants de puissance du type VDMOSFET en fonctionnement sous conditions extrêmes. Le comportement électrique des composants étudiés ainsi que l'évolution des temps de commutation sont bien étudiés en fonction de la température qui varie linéairement de 25 à 180ºC. Des contraintes électriques sont appliquées de manière à simuler expérimentalement les conditions réelles de fonctionnement. Les défauts sont ensuite caractérisés par des mesures de capacité et conductance grille-source permettant ainsi le calcul des densités des états d'interface induits par le stress. Les résultats expérimentaux montrent que les densités des états d'interface augmentent avec la durée du stress électrique appliqué. Les défauts induits et activés par le stress électrique sont aussi étudiés par la technique CDLTS qui se repose sur un balayage en largeur de l'impulsion appliquée sur la grille. Le balayage du gap a été assuré par la variation du niveau bas de l'impulsion. Différents défauts ont été détectés et les impuretés dopantes ainsi que les états d'interface ont été distingués des niveaux profonds situés au sein de la bande interdite. La deuxième partie de la thèse concerne la caractérisation et la modélisation des cellules à émetteurs dopés bore. La caractérisation électrique a été assurée par la caractérisation SIMS et la mesure des caractéristiques C(V) et I(V). La modélisation vient accompagner les résultats obtenus expérimentalement afin de tirer tout les paramètres caractéristiques de la cellule étudiée. Par la technique DLTS, un piège ayant une énergie d'activation de 0.029 eV et une section efficace de capture de 1.41 10-24 cm2 a été identifié
The aim of this work is to study and characterize silicon based structures. The first part of this thesis deals with the operation of VDMOSFET power devices under extreme conditions. The electrical behavior of studied devices and the evolution of switching times were studied as a function of temperature (25 to 180ºC). Electrical stressing was applied in order to simulate real operating conditions. Defects are then characterized by gate-source capacitance and conductance measurements allowing the calculation of interface states densities induced by stress. Experimental results show that interface states densities increase with the stress duration. Defects induced and activated by the electrical stress are also studied by the CDLTS technique based on gate pulse width scan. The band gap was scanned by varying the pulse base level. Different defects were detected and we have distinguished the doping levels and interface states from deep levels located in the forbidden band gap. The second part of the thesis concerns the characterization and modeling of boron-doped emitter photovoltaic cells. The electrical characterization was carried out by SIMS characterization and the measurement of C(V) and I(V) characteristics. Experimental results are supported by modeling in order to estimate all the characteristic parameters of the studied cell. By the DLTS technique, a trap with activation energy of 0.029 eV and capture cross section of 1.41 10-24 cm2 has been identified

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Meyer, Walter Ernst. "Digital DLTS studies on radiation induced defects in Si, GaAs and GaN." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-06182007-143820.

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Mari, Ruaz Hussain. "DLTS characterisation of defects in III-V compound semiconductors grown by MBE." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/14211/.

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The interest in the growth of III-V compound semiconductors such as GaAs and AlGaAs on high index planes has increased tremendously over the last few years. The structural, optical and electrical properties III-V based structures are found to improve by, growing on (nil) planes. For example the amphoteric nature of silicon (Si) facilitates the Molecular Beam Epitaxy (MBE) growth of p-type GaAs/AlGaAs heterostructures on (311)A that have higher hole mobilities than those based on the conventional Be-doped p-type on (100) GaAs plane. The incorporation of intentional impurities, such as Si or Be in III-V semiconductors, have desirable effects in terms of controlling the electrical conductivity of the materials. However, other unintentionally incorporated impurities and defects have deleterious effects on the electrical and optical properties of III-V based devices. In this thesis, current-voltage-temperature (I-V-T), capacitance-voltage (C-V) Deep Level Transient Spectroscopy (DLTS) and Laplace DLTS techniques have been used to investigate defects in several MBE III-V epilayers and modulated structures grown both on the conventional (100) and non-(100) GaAs substrates. These include: (i) n-type silicon-doped (n11)B (n = 2-5) GaAs epitaxial layers; (ii) n-type silicon-doped (100) and (311)B GaAs/AlGaAs multi-quantum well (MQW); (iii) n-type silicon-doped (100) MQWs grown at different substrate temperatures, arsenic overpressures and arsenic species (As2 and As4); (iv) p-type Be-doped (100) and (311)A AlGaAs epitaxial layers; (v) GaAs/AlGaAs two dimensional electron gas (2DEG); (vi) commercially grown high electron mobility transistors (HEMT). The main findings of the experimental results are given in the following: 1. n-type silicon-doped (n11)B (n = 2-5) GaAs: the overall density of defects is highest in (211)B and lowest in (511)B. The number of detected defects is minimum in (511)B. The common carbon background impurity in MBE is observed only in (100) substrates. 2. n-type silicon-doped (100) and (311)B GaAs/AlGaAs MQWs: the concentration of the only trap is higher in (100) than in (311)B orientation. Furthermore, in (100) the observed trap electrically charged, while it has neutral nature in (311)B. 3. n-type silicon-doped (100) MQWs grown at different substrate temperatures, arsenic overpressures and arsenic species (As2 and As4): the average trap concentration for As2 samples is lower than Asa samples. In addition, the concentration of the common VAs-related point defect decreases with increasing growth temperature and arsenic overpressure. 4. p-type Be-doped (100) and (311)A AlGaAs: the number of hole traps in (311)A decreases from five to one when the Be-doping level varies from 1 x 1016 cm-3 to 1 x 1017 cm3. For (100) the detected hole levels are three, four and two for Be-concentrations of 1ix 016 cm -3 , 3x1016 cm-3 and 1x1017 cm 3, respectively. In addition, an electron emitting level is observed only in (100) samples doped to 1 x1017 cm 3. 5. GaAs/AlGaAs 2DEG and HEMT devices: one major defect, assigned to the DX center, is common in both in-house grown 2DEG and commercially HEMT devices. It behaves as a generation-recombination center, and its concentration is directly related to the silicon doping level in the AlGaAs layer. The HEMT devices which showed poor frequency response are found to have the highest concentration of the DX center.

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Thienprasit, Jeanne A. (Jeanne Athya). "DLTS characterization of aluminum gettering of iron contaminants in boron-doped silicon." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10613.

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Leonard, Simon. "An investigation into metallic impurities in silicon for solar cells." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/an-investigation-into-metallic-impurities-in-silicon-for-solar-cells(4519e1a6-56bc-47ee-ac13-9459470a86ac).html.

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Photovoltaics is an exciting area of research with the potential to completely change the world's energy landscape. Silicon still dominates the photovoltaics market and shows no sign of being overtaken by other materials systems for large scale manufacture. Huge strides have been made in recent years to reduce the cost of solar modules, mainly through the introduction of mass production solar panel plants. However producing very pure single crystalline silicon is still a relatively expensive, energy intensive process. If cheaper less pure silicon could be cast into multi-crystalline ingots, without significant losses to the conversion efficiency this could be a game changer in the photovoltaics industry. For this to happen we need to have greater knowledge and understanding of the role of metallic impurities in solar silicon. If we can find ways to passivate or getter these impurities in cost effective processes that lend themselves to mass production then this would be the key to cost effective solar energy. In the work in this thesis I have investigated some of the most common and most harmful metallic impurities in silicon solar cells using a combination of Deep Level Transient Spectroscopy (DLTS), Capacitance Voltage (CV) measurements, Secondary Ion Mass Spectroscopy and Tunnelling Electron Microscopy (TEM). The specific transition metals I studied were iron, as it is one of the most common impurities and also titanium and molybdenum, because they are very harmful, have slow diffusivities and hard to get rid of with traditional gettering techniques. I have then looked at using hydrogen to electrically passivate these defects, and show evidence that hydrogen passivation is possible for interstitially incorporated titanium in silicon, but is unlikely to happen for interstitially incorporated iron. Another important part of this thesis was the observation and characterisation of molybdenum nano-precipitates in silicon. We have observed the nano-precipitates both electrically in DLTS, and physically in TEM. The precipitates have very interesting electrical properties, and appear to be very strong minority carrier recombination centres, which would have a very negative effect on solar cell performance. It is possible that these nano-precipitates could form from any of the slow diffusing transition metals, and could be a key reason to explain the efficiency gap between low purity cast silicon and high purity single crystal silicon.

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Canimoglu, A. "Studies of lattice defects in as-grown and irradiated n-InP." Thesis, University of Sussex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264561.

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Chartrand, Nathalie. "Functional analysis of Dlx homeodomain proteins from the zebrafish." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0018/MQ48141.pdf.

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29

Esau, Crystal. "Characterization of the Dlx Enhancers in the Developing Mouse." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30201.

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The Distal-less homeobox (Dlx) genes encode homeodomain transcription factors found in all animals of the phylum Chordata. These genes are involved in early vertebrate development of limbs, sensory organs, branchial arches and the forebrain (telencephalon and diencephalon). The mouse and human genomes each have six Dlx genes organized into convergently transcribed bigene clusters (Dlx1/2, Dlx3/4 and Dlx5/6). In the forebrain, Dlx1/2 and Dlx5/6 genes play essential roles in GABAergic neuron proliferation, migration and survival. Each bigene cluster includes a short intergenic region (~3.5-16kb) harboring cis-regulatory elements (CREs) that control expression of the Dlx genes. The Dlx1/2 intergenic region harbors the I12b/I12a CREs, while Dlx5/6 includes I56i/I56ii. In determining the regulatory roles of the CREs on Dlx activity and forebrain development, I have characterized the phenotypic changes that occur in mice that have an I56i enhancer deletion. I have also characterized mice with double deletions of I56i and I12b as well as mice that harbored an I12b deletion and have a SNP in the I56i enhancer (vI56i). Mutant mice with a single targeted deletion of I56i are viable, fertile and do not show obvious developmental defects. These mice have significant decreases in Dlx5/6, Gad1/Gad2 and Evf-2 expression in the forebrain and have defects related to GABAergic neuron development. The ΔI56i mutants demonstrate a behavioral phenotype related to anxiety and learning deficits. Mice that lack the I12b enhancer and have the vI56i do not show morphological abnormalities but have severely disrupted Dlx expression. When mice are homozygous for the I56i and I12b enhancer deletion, they do not survive past post natal day 5 and exhibit a dwarfed body size. These mice look weak and seem to have limited motor ability. In characterizing mice with targeted deletions of highly conserved Dlx enhancers, we will have a better understanding of forebrain development.

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El, Bouabdellati Mohamed. "Etude par spectroscopie DLTS des structures formées sur InP(n) par oxydation plasma." Metz, 1994. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1994/El_Bouabdellati.Mohamed.SMZ9464.pdf.

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Le but principal de ce travail de thèse est l'étude par spectroscopie DLTS des diodes Schottky et Schottky oxydées formées sur des substrats InP de type n. Le procédé de passivation choisi est l'oxydation en milieu plasma, on distingue principalement deux cas : 1) oxydation dans un plasma multipolaire d'oxygène en adoptant deux types d'excitation : a) excitation avec une cathode chaude. B) excitation avec micro-onde (rce). 2) oxydation hors plasma rf. Cette étude a permis la localisation de la distribution en énergie des défauts ainsi que leur localisation, à l'interface entre l'InP et son oxyde natif, dans l'isolant ou dans le volume du semiconducteur. Les spectres DLTS mesurés sur toutes les structures présentent un pic large à température ambiante. Ces spectres font apparaître des anomalies. Pour les expliquer deux méthodes ont été utilisées: i) un modèle à deux composantes. Ii) un modèle à défaut unique tenant compte des fuites de courant et de la variation des sections efficaces de capture
The topic of this thesis was the study of Schottky and oxided Schottky diodes formes on n-InP substrate. The passivation process used was the oxidation in plasma environment, we distinguish principally two cases : 1°) oxidation in multipolar plasma using two types of excitation : i) hot cathode excitation ; ii) microwave excitation (ECR). 2°) oxidation downstream the RF plasma region under and without illumination. This study leads to investigate the enrgy distribution of defects, their localisation at the interface between InP and its native oxide, inside the oxide or in the bulk of the semiconductor. DLTS spectra measured on all strucutres shows a wide peak at room temperature. Some anomalies appears on these spectra. Two methods were used to explain these anomalies : i) a two components model ; ii)a single component model which takes into account the leakage current and the variation of the capture cross sections

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EL, BOUABDELLATI MOHAMED LEPLEY B. "ETUDE PAR SPECTROSCOPIE DLTS DES STRUCTURES FORMEES SUR INP(N) PAR OXYDATION PLASMA /." [S.l.] : [s.n.], 1994. ftp://ftp.scd.univ-metz.fr/pub/Theses/1994/El_Bouabdellati.Mohamed.SMZ9464.pdf.

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32

Malonis, Andrew C. "Quantitative defect spectroscopy on operating AlGaN/GaN high electron mobility transistors." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259597046.

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Zhao, Pengcheng. "Phenotype Characterization of Mice with Targeted Deletions of Dlx Enhancers." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36904.

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The Distal-less homeobox (Dlx) genes encode a group of transcription factors that are involved in early vertebrate development of limbs, sensory organs, branchial arches and the forebrain. In the forebrain, four Dlx genes, Dlx1, Dlx2, Dlx5, Dlx6, play essential role in the differentiation and proper migration of GABAergic interneurons to the cortex. Dlx genes are organized in convergently transcribed bigene clusters and each cluster includes a short intergenic region harboring cis-regulatory elements (CREs): specifically, the Dlx1/2 cluster includes I12b and I12a CREs, while Dlx5/6 harbors I56i and I56ii. In an effort to determine the regulatory role of the CREs on Dlx expression and forebrain development, I characterized mice with an I56i deletion and both I12b and I56i deletions. At late embryonic stage (E18.5) and the adult stage (P35), both mutants had similar expression levels of Dlx2 and Gad2 gene, encoding enzyme glutamic acid decarboxylase that is responsible for synthesis of GABA. Mutant mice showed impaired expression levels of Dlx5. The expression levels of Gad1 were decreased in ΔI56i mutants but increased in ΔI12b/I56i mutants at E18.5, and both adult mutants had comparable expression of Gad1 as wildtype mice. Together with previous in situ hybridization results of mice at earlier stages (E11.5, E14.5), my data show that Dlx CREs have different levels of activity in regulating the expression of Dlx genes at different developmental stages. The mutations of I56i and I12b CREs did not affect the development of two subtypes of GABAergic neurons (calbindin and calretinin expressing neurons) in the forebrain. Compared to wildtype mice, both mutants had hypersociability and deficits of memory and learning ability. This opens the possibility that the deletions of Dlx intergenic CREs caused some developmental abnormalities and, therefore affected the behavior of the mice. Through studying the mice lacking Dlx intergenic CREs, I gained a better understanding of the role that I56i and I12b play in the regulation of the expression of Dlx genes, the development of GABAergic neurons, and the social and cognitive behavior.

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Burton, Lindsay. "Dlx regulation in zebrafish brain development via I56iI56ii and I12aI12b." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27754.

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Dlx genes are involved in the formation of the forebrain, branchial arches, sensory organs, and limbs. In the forebrain, Dlx genes are expressed in restricted domains in the telencephalon and diencephalon. The telencephalon is one of the most complex structures in the vertebrate central nervous system, but despite variable morphologies of the adult telencephalon, the patterning and basic organization is conserved amongst vertebrates. Cis-acting regulatory sequences (CREs) that contribute to Dlx expression in the telencephalon were previously identified in the intergenic region between Dlx5 and Dlx6 (I56i and I56ii), between Dlx1 and Dlx2 (I12b), and upstream of Dlx1 (URE2) in zebrafish, mouse, and human. I hypothesize that these CREs contribute to defining distinct subtypes of interneurons during forebrain development. In this study, we have investigated the differential activity of intergenic CREs in the developing zebrafish brain using the established transgenic lines Tg(6kb-dlx1a/dlx2a: EGFP) and Tg(1.4kb-dlx5a/dlx6a:EGFP) in which the green fluorescent protein gene (GFP) was used as a reporter whose expression was controlled by dlx CREs. The two intergenic fragments target reporter transgenes with overlapping patterns of expression in the telencephalon but also show differential activity in the dorsal region of the brain at the level of the pallium. These results suggest that the dlx1a/2a CREs are involved in dlx regulation in a set of cells occupying the subpallium, whereas the dlx5a/6a CREs are involved in dlx regulation in a set of cells that migrate out of the subpallium and travel in a ventral to dorsal manner to occupy the pallium. Co-localization of GFP with GAD65/67 and with molecular markers of the interneuron subtype, calretinin, indicates that the dlx CREs target the reporter constructs to GABAergic interneurons, with at least one subtype expressing calretinin. Results from this study reflect a dynamic regulation of dlx gene expression in the developing zebrafish forebrain through several regulatory elements with distinct and overlapping functions.

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Thames, Fred. "A NEW GENERATION OF DATA RECORDERS BASED ON DLT TECHNOLOGY." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/607371.

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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California
As the performance of inexpensive commercial off-the-shelf (COTS) data storage devices continues to increase, the temptation to use them as the basis for data capture products for military and industrial applications becomes ever more compelling. For example, the Digital Linear Tape (DLT) format now offers a 270 Gigabits per cassette capacity at a sustained transfer rate of 40 Mbits/s – performance which would have cost tens or even hundreds of thousands of dollars per system just a few years ago. But to transplant such a device from its benign office habitat into a data capture product which will function reliably and consistently in a wide range of field and platform environments is an engineering task fully as difficult and complex as designing an environmentally robust recorder from scratch. This paper discusses the problems which typically have to be overcome; environmental protection, reliability, data integrity, power supplies, software issues, control and data interfacing, etc., citing practical examples of analog and digital DLT-based data recorders which are now entering service for telemetry, intelligence gathering, anti-submarine warfare and related applications

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Debiasi, Paula. "Ortorretificação de imagens CCD CBERS 2 atravás da transformação DLT." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/13763.

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Este trabalho avalia a potencialidade da geração de ortoimagens advindas do sensor CCD do CBERS 2 produzidas através de um modelo matemático generalizado, a Transformação Linear Direta (DLT). O modelo de transformação foi implementado na linguagem Delphi 4.0 por alunos de pós-graduação da Universidade Federal do Paraná (UFPR), sendo gerado um utilitário para adaptar a leitura do Modelo Digital de Elevação (MDE) do SRTM (Shuttle Radar Topography Mission) no programa. A área utilizada como teste é uma região de relevo variando de plano a acidentado com variação de até 700m de altura, localizada no Centro Oriental Paranaense e abrangendo o cânion do Guartelá. Para a geração das ortoimagens utilizou-se de duas fontes de informação altimétrica, um MDE gerado pela missão SRTM e outro MDE gerado por curvas de nível e pontos contados de cartas topográficas na escala 1:50.000. Foi realizado o processo de ortorretificação de um recorte da cena CBERS utilizando os diferentes MDE’s, sendo as ortoimagens analisadas por testes estatísticos, e classificadas pelo Padrão de Exatidão Cartográfica (PEC) com o uso de pontos de verificação. Para a avaliação da necessidade de ortorretificação da cena CCD CBERS 2 o mesmo recorte foi também corrigido geometricamente por um polinômio de 2°. Os resíduos planimétricos gerados pela simples correção através do polinômio de 2° demonstram que há necessidade do processo de ortorretificação, ou seja, correção de erros devido à topografia do relevo nesta cena. E a comparação entre as ortoimagens geradas pelos diferentes MDE’s demonstra que é satisfatória a utilização do MDE do SRTM na ortorretificação de imagens advindas do sensor CCD do CBERS 2.
This work evaluates the orthoimages generation potentiality of the CCD sensor from the CBERS 2, by using a generalized mathematical model, say, the “Direct Linear Transformation (DLT)”. The transformation model was implemented by the pos graduated students from the Federal University of Paraná using the Delphi 4.0 language, and in this task an utilitarian software to adapt the Digital Elevation Model (DEM) from the Shuttle Radar Topography Mission (SRTM) function, on the program was produced. The land area surface used for trial is localized at the Paraná Oriental Centre and comprising the Guartelá canyon, varies in shape from an irregular to a plane embossment where variations up to 700m in height are found.Two DEM sources of altimetry information data for the orthoimages generations were used: The first generated from SRTM mission and the another one developed from contour lines and topographic points counted in a 1:50.000 scale. A orthorretification process, of a cutting out scene from the CBERS, was realized utilizing both MDE´s. The images were analyzed by statistics inferences and classified according to the Padrão de Exatidão Cartográfica (PEC) using check points. To evaluate the CCD CBERS 2 scene orthorefications necessity, the same cutting out was also object of geometric corrections having a second degree polynomial as a tool. The planimetrics residues generated by the second degree polynomial simplified corrections were just enough to demonstrate the necessity of the orthoretification process, it is, corrections of errors due to the embossment topography at the considered scene. The comparison of the images produced by the differents DEM´s demonstrate that the utilization of the DEM from the SRTM is a satisfactory tool for images orthoretifications of the CBERS 2.

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Weinschutz, Mendes Hellen. "Dlx Genes, Neurogenesis and Regeneration in the Adult Zebrafish Brain." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40047.

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The Dlx homeobox genes encode homeodomain transcription factors that are involved in multiple developmental aspects. In the brain, these genes take part in neuronal migration and differentiation, more precisely in the migration and differentiation of GABAergic neurons. Dysfunctions in the GABAergic system can lead to various pathological conditions, where impaired inhibitory function is one of the main causes of several neuropathies characterized by neuronal hyperexcitability. The Dlx genes are organized as bi-gene clusters and highly conserved cis-regulatory elements have been previously characterized to be fundamental for the regulation of Dlx expression in developing embryos of different vertebrates. The activity of these regulatory elements and the Dlx genes has been well studied in developmental stages of mice and zebrafish, but little is known about their activity in the adult brain. The extensive neurogenesis that takes place in the adult zebrafish brain provides an ideal platform for the visualization of mechanisms involving dlx genes during adulthood and their possible involvement in adult neurogenesis. Here we show novel information concerning the expression of dlx1a, dlx2a, dlx5a and dlx6a in the adult zebrafish brain and provide insight into the identity of cells that express dlx. We also demonstrate the involvement of dlx genes in brain regeneration and through lineage tracing, their fate determination in the adult zebrafish brain. Analyses in the adult zebrafish has revealed that all four dlx paralogs are expressed in the forebrain and midbrain throughout adulthood and expression is found in almost all areas presenting continuous proliferation. Most dlx-expressing cells present GABAergic neuronal identity in the adult forebrain where, in some areas they were identified as the Calbindin subtype. In some areas of the midbrain, especially within the hypothalamus, many dlxexpressing cell co-localized with a marker for neural stem cells. However, cells expressing dlx iii genes did not co-localize with markers for proliferating cells or for glia. Investigations during brain regeneration in response to injury in the adult zebrafish brain has revealed that dlx5a expression decreases shortly after lesion and that the dlx5a/6a bi-gene cluster, more specifically, dlx5a, is up regulated during the peak of regeneration response proposing a possible role for dlx during regeneration in adults. Studies of lineage tracing have shown the progeny of dlx1a/2a-expressing cells in adults are located within small clusters in different areas of the adult brain where they seem to become mature neurons. Our observations provide a better understanding about the role of dlx genes during adulthood, further contributing to the general knowledge of the molecular pathways involved in adult neurogenesis and regeneration in the zebrafish adult brain.

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Pellegrino, Paolo. "Point Defects in Silicon and Silicon-Carbide." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3133.

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Nouaille, Sébastien. "Facteurs d'hôtes influençant la sécrétion de protéines hétérologues chez Lactococcus lactis." Paris 11, 2003. http://www.theses.fr/2003PA112064.

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Les bactéries lactiques présentent une parfaite innocuité hygiénique et sont de bons candidats pour le développement de nouvelles utilisations. Dans le développement de vaccins vivants, la sécrétion peut être préférable à une production cytoplasmique. Nous avons étudié la sécrétion de protéines hétérologues chez Lactococcus lactis en employant la nucléase de S. Aureus comme protéine sécrétée modèle. Nous avons agi sur les facteurs intrinsèques de Nuc par l'utilisation d'un peptide signal de L. Lactis pour diriger la sécrétion et sur l'équilibre des charges de la partie N-terminale pour augmenter l'efficacité de sécrétion. Pour mieux comprendre la sécrétion chez L. Lactis, nous avons identifié des facteurs d'hôtes qui sont impliqués directement ou non dans la sécrétion. Par mutagenèse insertionnelle aléatoire nous avons identifié, puis analysé, deux nouveaux facteurs d'hôtes, dltA et ybdD. L'inactivation de dltA modifie les charges à la surface de la cellule et entraîne la rétention de Nuc sécrétée. L'inactivation de ybdD dérégule l'expression de gènes pouvant contrôler la sécrétion. Tous les composants de la machinerie Sec sont présents, à l'exception de SecDF. Chez B. Subtilis, SecDF maintient une forte capacité de sécrétion. La complémentation du sécrétome de L. Lactis par SecDF de B. Subtilis augmente la sécrétion. Afin d'évaluer la possible utilisation de L. Lactis comme vecteur de protéines immunogènes pour déclencher une réponse immune chez la souris, nous avons construit des souches de L. Lactis produisant une fusion entre Nuc et un épitope immunogène de la beta-lactoglobuline (Blg). La Blg est l'allergène majeur chez les nourrissons allergiques au lait de vache et constitue un bon modèle d'allergie alimentaire. L'administration orle des souches de L. Lactis produisant l'epitope declenche chez la souris une réponse immunitaire mucosale, non allergique, spécifique de la Blg
Lactic acid bacteria (LAB) are Gram-positive bacteria generally considered as safe (GRAS) and they are therefore excellent potential candidates for the development of new uses such as live vectors for the delivery of immunogenic proteins. To this purpose, secretion of heterologous proteins could be more advantageous than cytoplasmic production. We studied the heterologous protein secretion in Lactococcus lactis with the staphylococcal nuclease (Nuc) as secretory model protein. By the use of a lactococcal signal peptide to drive Nuc secretion and a synthetic propeptide to maintain an optimal charge balance at the N-terminal end of Nuc, the Nuc secretion efficiency was strongly improved. To better understand secretion, we identified by random insertional mutagenesis two new host factors indirectly involved in secretion. Inactivation of dltA unbalances charges present at the cell surface and leads to Nuc entrapment into the cell wall. Inactivation of ybdD up-regulates expression of several genes of which products might control secretion in L. Lactis. The analysis of the so-called secretome in L. Lactis reveals that all components of the Sec machinery are present except SecDF. In B. Subtilis, SecDF is necessary in late secretion stages. Introduction of SecDF from B. Subtilis into the L. Lactis secretome improves secretion of several heterologous proteins. To evaluate the potential use of L. Lactis as vector of an allergen to trigger an immune response in mice, we developed L. Lactis strains secreting a fusion between Nuc and an immunogenic epitope of β-lactoglobulin (Blg). Blg is the major cow milk allergen in childhood and a good model for study of food allergy. Oral administration of L. Lactis secreting this fusion protein triggers a specific mucosal immune and non allergic type response in mice, against both the epitope and the entire Blg

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Paez-Sierra, Beynor Antonio. "Raman spectroscopy of metal-organic-inorganic heterostructures and pentacene-based OFETs." [S.l. : s.n.], 2008.

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Kuang, Li-chao. "Deep-level transient spectroscopy, DLTS, for the determination of trap parameters in semiconductor devices." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq23373.pdf.

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Chen, Peter. "Investigation of ZnO / CdS / CuInSe2 solar cells using a custom built I-DLTS system." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116990.

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The principles and theory behind deep level transient spectroscopy (DLTS) are examined in this thesis. Different DLTS methods and techniques are surveyed and investigated to determine the viability of making an economical DLTS system using modern data acquisition (DAQ) hardware. An isothermal current DLTS (I-DLTS) technique was chosen for its simplicity of implementation. The finalized system was then tested using ZnO/CdS/CuInSe2 solar cells fabricated in this laboratory. Characterization of these solar cells were also investigated using current-voltage and capacitance-voltage techniques to show the existence of deep levels and determine primary device parameters necessary for I-DLTS calculations. Deep levels with activation energies between 0.16 eV to 0.28 eV, and 0.35 eV to 0.38 eV were found.
Cette thèse a pour but d'examiner les principes et la théorie derrière la spectroscopie des niveaux profonds (DLTS: Deep Level Transient Spectroscopy). Différentes méthodes et techniques DLTS sont étudiées pour déterminer la possibilité de concevoir un system DLTS économique en utilisant du matériel informatique moderne d'acquisition de données (DAQ: Data Acquisition). Une technique de courant isothermique DLTS (I-DLTS) a été choisie pour sa simplicité d'implémentation. Le système final a été testé en utilisant des cellules solaires ZnO/CdS/CuInSe2 fabriquées en laboratoire pendant cette étude. La caractérisation de ces cellules solaires a aussi été investigué en utilisant des techniques courant-tension et capacité-tension pour démontrer l'existence des niveaux profonds et de déterminer les paramètres primaires nécessaires au calculs d'I-DLTS. Des niveaux profonds avec activation d'énergies entre 0.16 eV à 0.28 eV ainsi qu'entre 0.35 eV et 0.38 eV ont été découverts.

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Fazel, Darbandi Siavash. "Functional Analysis of Dlx Intergenic Enhancers in the Developing Mouse Forebrain." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31079.

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The Distal-less homeobox (Dlx) genes encode a group of transcription factors that are involved in various developmental processes including forebrain development. Dlx genes are arranged in convergently transcribed bigene clusters with enhancer sequences located in the intergenic region of each cluster. The expression patterns of Dlx1/Dlx2 and of Dlx5/Dlx6 are attributed in part to the activity of I12a/I12b and I56i/I56ii intergenic enhancers, respectively. In an effort to determine how Dlx intergenic enhancers interact with the promoter regions of each cluster, I employed the Chromosome Conformation Capture (3C) technique on developing forebrain at E13.5 and E15.5. My 3C analysis provided potential enhancer-promoter interaction, in cis, that are consistent with previously known regulatory mechanisms. Furthermore, trans interactions may exist between Dlx1/Dlx2 and Dlx5/Dlx6 clusters in the developing forebrain at E13.5, thus providing a possible novel cross-regulatory mechanism between these two loci. I have also investigated the phenotypic consequences of Dlx enhancer deletion(s) on forebrain development by characterizing mice with I56ii and I56ii/I12b enhancer deletions. Enhancer deletions significantly impair Dlx expression as well as that of Evf2, Gad2 and of the striatal markers Islet1 and Meis2. Enhancer deletion(s) also reduce the expression of ISLET1 and CTIP2 proteins and Semaphorin 3A, Slit1 and Ephrin A5 that are thought to provide guidance cues in the corridor cells. Overall, these changes may disrupt the guidance of the thalamocortical axons. The data presented here further our understanding of the interactions between Dlx intergenic enhancers and promoter regions. Enhancer deletion(s) furthers our understanding of Dlx regulatory networks necessary that ensure proper Dlx expression, which, in turn may be involved in a genetic pathway underlying the synthesis of GABA, which may be further essential in maintaining the GABAergic phenotype.

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Jowett, Simon. "A novel photogrammetric technique using DLT to measure golf shaft dynamics." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272754.

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STEINER, BENEDIKT, and VINCENT NEIDLINGER. "Impact of the Distributed Ledger Technology (DLT) IOTA on Smart Cities." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301276.

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This article analyses the impact of the IOTA distributed ledger technology (DLT) on smart cities. The world population is rapidly increasing while at the same time trends such as urbanization shape future demographics. Thus, fast-growing cities face the challenge of increasing demands in resources such as energy, water, transportation, while at the same time aiming to increase life quality by reducing burdens such as pollution and waste. The concept of a “Smart City” emerged with the ambition to solve a city’s issues by creating social and economic advantages while providing efficient resource allocation processes. Nevertheless, current information communication technologies tend to underperform a smartcities systems requirement since the quantity of connected devices increases which slows down the transition of a city becoming smart. The distributed ledger technology IOTA promises to enable automated, feeless transactions and processes with a high level of integrity, which may impact the development of smart cities. In this research the IOTA technology is introduced and investigated. The advantages of IOTA compared to conventional information communication technologies and the blockchain technology are highlighted. Thereafter, the current state of IOTA in smart cities is reviewed by analysing current research and use cases. To investigate the concept of a smart city the smart city initiative framework, including its subcategories is introduced. Additionally, different experts working on IOTA integrations related to smart city initiatives were interviewed giving insights into their field ofexpertise. Finally, an analysis and discussion of the IOTA technology use cases are put into relation with the multi-level perspective framework (Geels, 2006) highlighting the positive impact of IOTA on the development of smart cities.
I den här artikeln analyseras effekterna av IOTA:s teknik för distribuerade huvudböcker (DLT) på smarta städer. Världens befolkning ökar snabbt samtidigt som trender som urbanisering formar framtidens demografi. Snabbt växande städer står därför inför utmaningen att öka kraven på resurser som energi, vatten och transporter, samtidigt som de strävar efter att öka livskvaliteten genom att minska belastningar som föroreningar och avfall. Begreppet smart stad uppstod med ambitionen att lösa stadensproblem genom att skapa sociala och ekonomiska fördelar och samtidigt tillhandahålla effektiva processer för resursfördelning. Den nuvarande informations- och kommunikationstekniken tenderar dock att inte uppfylla kraven på system för smarta städer, eftersom mängden anslutna enheter ökar, vilket gör att övergången till en smart stad blir långsammare. Den distribuerade huvudbokstekniken IOTA lovar att möjliggöra automatiserade, felfria transaktioner och processer med en hög grad av integritet, vilket kan påverka utvecklingen av smarta städer. I den här forskningen introduceras och undersöks IOTA-tekniken. Fördelarna med IOTA jämfört med konventionell informationskommunikationsteknik och blockkedjetekniken lyfts fram. Därefter granskas det nuvarande läget för IOTA i smarta städer genom att analysera aktuell forskning och användningsfall. För att undersöka begreppet smart stad introduceras ramverket för initiativet för smarta städer, inklusive dess underkategorier. Dessutom intervjuades olika experter som arbetar med IOTA-integrationer isamband med initiativ för smarta städer för att ge en inblick i deras expertisområde. Slutligen analyseras och diskuteras IOTA-teknikens användningsområden i förhållande till ramverket för flernivåperspektivet (Geels, 2006), där IOTA:s positiva inverkan på utvecklingen av smarta städer lyfts fram.

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TELIA, AZZEDINE LEPLEY BERNARD. "ETUDE PAR SPECTROSCOPIE DLTS DES TRANSITOIRES DE CAPACITE SUR LES INTERFACES OXYDES NATIFS (N) INP /." [S.l.] : [s.n.], 1990. ftp://ftp.scd.univ-metz.fr/pub/Theses/1990/Telia.Azzedine.SMZ9012.pdf.

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Pollack, Jacob N. "Activity of Dlx Transcription Factors in Regulatory Cascades Underlying Vertebrate Forebrain Development." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23655.

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The temporal and spatial patterning that underlies morphogenetic events is controlled by gene regulatory networks (GRNs). These operate through a combinatorial code of DNA – binding transcription factor proteins, and non – coding DNA sequences (cis-regulatory elements, or CREs), that specifically bind transcription factors and regulate nearby genes. By comparatively studying the development of different species, we can illuminate lineage – specific changes in gene regulation that account for morphological evolution. The central nervous system of vertebrates is composed of diverse neural cells that undergo highly coordinated programs of specialization, migration and differentiation during development. Approximately 20% of neurons in the cerebral cortex are GABAergic inhibitory interneurons, which release the neurotransmitter gamma-aminobutyric acid (GABA). Diseases such as autism, schizophrenia and epilepsy are associated with defects in GABAergic interneuron function. Several members of the distal-less homeobox (Dlx) transcription factor family are implicated in a GRN underlying early GABAergic interneuron development in the forebrain. I examined the role played by orthologous dlx genes in the development of GABAergic interneurons in the zebrafish forebrain. I found that when ascl1a transcription factor is down-regulated through the micro-injection of translation – blocking morpholino oligonucleotides, Dlx gene transcription is decreased in the diencephalon, but not the telencephalon. Similarly, gad1a transcription is also decreased in this region for these morphants. As gad1a encodes an enzyme necessary for the production of GABA, these genes are implicated in a cascade underlying GABAergic interneuron development in the diencephalon.

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Choudhury, Anuradha. "The regulation and function of DLX genes in the first branchial arch." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420629.

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Vieux-Rochas, Maxence. "Evolution de la régulation des gènes Dlx au cours de la morphogenèse." Paris, Muséum national d'histoire naturelle, 2009. http://www.theses.fr/2009MNHN0003.

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La morphogenèse des mâchoires est un processus complexe impliquant la migration et la différenciation des cellules de la crête neurale (CCNCs) ainsi que des cellules mésodermiques qui vont coloniser le premier arc branchial (AB1). Avant d'atteindre leur destination finale, les CCNCs ne sont pas encore engagées dans des voies morphogénétiques spécifiques. Des signalisations moléculaires et des interactions cellulaires vont avoir lieu au cours de la colonisation de l'AB1 permettant l'engagement des CCNCs vers une voie de signalisation donnée. La voie de signalisation à l'Edn1 est nécessaire et suffisante pour induire l'identité de la mâchoire inférieure; cependant le mécanisme par lequel la spécification a lieu n'est pas totalement élucidé. De plus, l'absorption d'acide rétinoïque (AR) ou de son précurseur, la vitamine A, durant la grossesse est associée à une augmentation de l'incidence des lésions craniofaciales. Au début de ma thèse, l'origine de ces effets tératogènes était énigmatique car la transduction de la signalisation à l'AR n'est pas active dans les CCNCs. Dans les deux premières études, nous avons pu montrer, chez la souris et Xenopus laevis, que l'action de l'AR s’exerce au niveau des signalisations Edn1 et Fgf8 provenant des épitheliums de l'AB1. L'AR va réduire l'expression de ces deux signaux moléculaires de façon graduelle selon le temps d’administration, la dose utilisée et la durée du traitement. L’Edn1 et Fgf8 induisent l'activation des gènes Dlx dans les CCNCs, permettant le déclenchement de programmes morphogénétiques donnant naissance aux différents éléments squelettiques constituant les mâchoires. Ainsi, un bref traitement à l'AR provoque des malformations craniofaciales différents selon l’age exact de l’embryon lors de l’administration. L’action tératogène de l’AR au niveau craniofacial s’exerce dans une fenêtre temporelle réduite correspondant à la colonisation de l'AB1 par les CCNCs. La troisième étude ouvre de nouvelles perspectives sur la dynamique spatio-temporelle et le dosage génique du processus permettant la morphogenèse des mâchoires proposant ainsi un lien entre les altérations de ce processus et l'origine de malformations humaines appelées "syndromes du premier arc". Cette thèse a permis de contribuer à cinq autres études impliquant la fonction et la régulation de Dlx5 et Dlx6 dans l’ostéogenèse, le développement des membres et du tubercule génital et la différenciation des cellules de Leydig
Jaw morphogenesis is a complex process involving the migration and differentiation of cephalic neural crest cells (CNCCs) and mesodermal cells to the first pharyngeal arch (PA1). Before reaching their destination CCNCs are not yet engaged in specific morphogenetic pathways. Molecular signalling and cellular interactions occurring during PA1 colonization determine the genesis of facial structures. Endothelin-1 (Edn1) signaling is necessary and sufficient to specify “lower jaw” identity; the mechanism through which this specification takes place is not yet completely elucidated. Intake of retinoic acid (RA) or of its precursor, vitamin A, during early pregnancy is associated with increased incidence of craniofacial lesions. Before my thesis, the origin of these teratogenic effects was enigmatic as in cranial neural crest cells (CNCCs), the RA-transduction pathway is not active. In the first two articles we show that, in mouse and Xenopus laevis, RA acts on the signalling epithelium of PA1 reducing the expression of Edn1 and Fgf8. Depending on the time of administration and on the dose and length of treatment, RA reduces progressively the expression of these two molecular signals. Edn1 and Fgf8 are instrumental in activating Dlx genes in incoming CNCCs, thereby triggering the morphogenetic programs, which specify different jaw elements. We report that, RA treatments provokes dramatically different craniofacial malformations when administered at slightly different developmental times within a narrow temporal interval corresponding to the colonization of the 1st PA by CNCCs. The third article provides new insight into the spatio-temporal and gene-dosage dynamics of the jaw morphogenetic process proposing a link between the alteration of this process and the origin of human malformation collectively known as "First Arch Syndromes". This thesis contributed also to five other studies on the role and regulation of Dlx5 and Dlx6 during osteogenesis, limb development, genital tubercle morphogenesis and Leydig cells differentiation

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Burguière, Eric. "Rôle de la DLT cérébelleuse hétérosynaptique des fibres parallèles dans la navigation." Paris 6, 2006. https://tel.archives-ouvertes.fr/tel-00129346.

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Récemment, il a été proposé que le cervelet participe à l’acquisition de fonctions cognitives telle que la navigation. Un des mécanismes de plasticité synaptique du cervelet, la Dépression synaptique à Long Terme hétérosynaptique des fibres parallèles (DLT), est déjà connu pour être impliqué dans les apprentissages moteurs. L’objectif de ce travail de thèse était de déterminer si cette DLT participe également à l’acquisition d’une tâche de navigation. A l’aide de tests de navigation développés dans l’équipe, j’ai étudié les performances de souris transgéniques L7-PKCI dont ce mécanisme de DLT est altéré. Dans ces tests, les souris L7-PKCI étaient déficientes dans la capacité à élaborer une trajectoire efficace pour rejoindre leur but. Ces résultats suggèrent qu’un rôle essentiel du cervelet dans la navigation, et plus particulièrement de la DLT, est d’adapter en permanence la sortie motrice afin d’effectuer une trajectoire optimale.

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