University, Diss., 2001--Bonn.

Dans ce projet, nous nous sommes intéressés à l’invasion du nématode du pin, Bursaphelenchus xylophilus, un ver microscopique responsable de la maladie du dépérissement du pin et causant la perte de millions d’arbres annuellement à travers le monde. Notre objectif global était d’affiner nos connaissances sur ce cas d’invasion et particulièrement d’établir l’histoire d’invasion des populations européennes. Nous avons analysé la diversité génétique neutre d’échantillons de populations naturelles de nématode du pin de l’aire native et de différentes zones envahies à l’aide de méthodes de génétique des populations. Ces analyses ont essentiellement mis en évidence que (i) l’aire native du nématode du pin est fortement structurée à fines échelles spatiales et présente une diversité génétique faible à modérée, suggérant un rôle important de la dérive génétique, non compensée par la dispersion, (ii) les populations européennes présentent une diversité génétique extrêmement faible, suggérant un seul évènement d’introduction en Europe, et que (iii) l’Amérique du Nord est la source la plus probable des populations envahissantes européennes, non le Japon et la Chine. Ce projet souligne l’intérêt que les nématologistes et les généticiens des populations ont à collaborer. La génétique des populations a en effet permis de clarifier l’histoire de l’invasion des populations européennes et ce modèle nématode, du fait de son cycle de vie complexe résultant en un cas extrême de faible diversité génétique, a permis de s’interroger sur des méthodes et analyses couramment utilisées en génétique des populations. / In this project, we were interested in the invasion of the pinewood nematode, Bursaphelenchus xylophilus, a microscopic worm responsible for the pine wilt disease and causing the annual loss of millions of trees worldwide. Our global objective was to improve our knowledge on this case of invasion and particularly to clarify the invasion history of European populations. After developing the microsatellite markers needed for our study, we analysed the genetic diversity of samples of natural populations from both the native area and invaded areas thanks to population genetics methods. These analyses revealed that (i) the native area is strongly genetically structured at fine scales and displays a low to moderate genetic diversity, suggesting an important role of the genetic drift, not compensated by dispersal, (ii) the European populations exhibit an extremely low genetic diversity, indicating a unique event of introduction in Europe and (iii) North America is the most probable source of European populations compared to China and Japan. This project is finally a good example of the benefits of collaboration between nematologists and population geneticists. Population genetics allowed to clarify the invasion history of European populations and this “nematode” model, because of its complex life cycle resulting in an extreme case of low genetic diversity, provided the opportunity to question methodologies in population genetics that are routinely used.

Prostate cancer is the most commonly diagnosed malignancy among men, but few genetic factors that drive prostate cancer initiation have been identified. The WD repeat domain 77 (Wdr77) protein is essential for cellular proliferation when it localizes in the cytoplasm of epithelial cells at the early stage of prostate development. In the adult prostate, it is transported into the nucleus and functions as a co-regulator of the androgen receptor to promote cellular differentiation and prostate function. This developmental process is reversed during prostate tumorigenesis i.e., Wdr77 is translocated from the nucleus into the cytoplasm to drive proliferation of prostate cancer cells. In this study, we used in vivo genetic studies to investigate the role of Wdr77 in prostate tumorigenesis. We found that prostate-specific deletion of Wdr77 abolished prostate tumor initiation induced by loss of the tumor suppressor Pten. Mechanistically, Wdr77 ablation inhibited E2F3 activation and enhanced TGFb signaling, leading to attenuated cellular proliferation induced by loss of Pten. These findings establish an essential role of Wdr77 for prostate tumor initiation.

Branching is a highly plastic trait, enabling plants to adapt their growth form in response to environmental stimuli. In flowering plants, shoot branching is regulated through the activity of axillary buds, which grow into branches. Several classes of plant hormones have been shown to play pivotal roles in regulating bud outgrowth. Auxin derived from the primary shoot apex and active branches inhibits bud outgrowth, whereas cytokinin promotes it. Strigolactones also inhibit bud outgrowth, by changing properties of the auxin transport network, increasing the competition between buds. This occurs by modulating access to the polar auxin transport stream (PATS) in the main stem. The PATS provides directional, long distance transport of auxin down the stem, involving basal localisation of the auxin transporter PIN-FORMED1 (PIN1). Buds need to export their auxin across the stem towards the PATS in order to activate, but since PIN1 is mainly expressed in narrow files of cells associated with the stem vasculature, PIN1 itself it is unlikely to facilitate this connectivity. This thesis re-examines the role of auxin transport in the stem, showing that, besides the PIN1-mediated PATS, other auxin transport proteins constitute a more widespread and less polar auxin transport stream, allowing auxin exchange between the PATS and surrounding tissues. Disruption of this transport stream is shown to reduce bud-bud communication and to partially rescue the increased branching observed in strigolactone mutants. Furthermore, it is shown that distinct classes of auxin transport proteins within this stream can differentially affect bud outgrowth mediated by BRANCHED1 (BRC1). BRC1 is a transcription factor proposed to determine bud activation potential. Taken together, the data presented here provide a more comprehensive understanding of the shoot auxin transport network and its role in shoot branching regulation.

Background. Operative stabilisation of paediatric supracondylar elbow fractures is most commonly achieved through the use of percutaneous Kirschner wires. These implants are inert, cheap and simple to use. However, the requirement for removal and the possibility of pin site infection provides opportunity for the development of new techniques that eliminate these drawbacks. Bioabsorbable pins that remain in situ and allow definitive closure of skin at the time of surgery could provide such advantages. However, their ability to maintain fracture reduction and their effect on the growth plate has not been adequately evaluated. Hypotheses. The Acumed® Biotrak Helical Nail (a bioabsorbable fixation implant) has comparable strength to Kirschner wires and does not result in significant disruption of the growth plate or subsequent growth. Studies. Three complementary studies were performed. (1) A retrospective cohort analysis was performed to establish the prevalence of complications related to Kirschner wire fixation of paediatric supracondylar elbow fractures. (2) A saw-bone model was designed to compare the mechanical performance of the Helical Nail and Kirschner wires. (3) An ovine model was designed to assess the in vivo effects of the Helical Nail on limb growth and physeal morphology. The surgical practicalities of the device and its potential for use in the paediatric setting were evaluated. The primary outcome was femoral length six months after Helical Nail insertion. Micro-CT evaluation of growth plate thickness, percentage disruption and bony infiltration was undertaken – the first time this technique has been used in a large animal study. Traditional histopathological techniques complimented the Micro-CT analysis and offered comment on the microscopic appearance of the growth plate immediately adjacent to the bioabsorbable nails. Results. The infection rate within a large tertiary referral centre was 9.6%, which was marginally higher than previous cohort studies. Mechanical testing demonstrated that the Helical Nail had comparable strength in rotation, but inferior resistance to posterior translation, when compared to Kirschner wires. In the ovine model, the Helical Nail disrupted 3.4% of the physis. The nails had no effect on femoral growth during the six month study period. Micro-CT analysis of both the helical nail and Kirschner wire groups demonstrated multiple bony bridges, with two cases of physeal tethering in the Helical Nail group. There was no difference in physeal thickness or bony infiltration of the physis. Histopathology did not reveal any significant inflammatory or foreign body reaction adjacent to the nails. Conclusion. The Helical Nail demonstrated a number of encouraging attributes which indicate its potential. However, in its current state the device is not suitable for use in the stabilisation of paediatric supracondylar elbow fractures.

Triticale belongs to the amphiploid cereals and was derived by crossing wheat and rye. Its baking quality is substantially worse than in wheat. The baking quality is determined by a composition and a content of the storage proteins. Both high and low molecular glutenin subunits have a major effect on the final quality of dough. The secalins of rye belong amongst the storage proteins of triticale, which negatively influence the baking quality. These are the reasons why lineages having translocated chromosome 1R and containing subunit Glu-D1d, which positively influences the baking quality, were created. The thesis is focused on identification of the allelic composition of loci of high molecular glutenin subunits (HMW-GS), low molecular glutenin subunits (LMW-GS), loci Pina a Pinb and null alleles of Waxy genes. 23 selected genotypes of triticale were analysed by using DNA markers based on polymerase chain reaction (PCR). Allelic composition of loci HMW-GS (Glu-A1, Glu-B1, Glu-D1), LMW-GS (Glu-A3) and Pina-D1, Pinb-D1 was described and null alleles were detected in the loci Wx-A1 and Wx-B1.

Dentre os principais e mais efetivos tratamentos superficiais para a melhora das propriedades da superfície dos aços, encontra-se a nitretação e a nitrocarbonetação. Os benefícios da nitretação nos aços são o aumento da dureza, resistência ao desgaste, resistência à fadiga e resistência à corrosão. Por possuírem elementos como cromo, molibdênio e manganês, os aços ferramenta e aços baixa liga de ultra alta resistência são beneficiados pela nitretação. Neste trabalho, estudou-se o efeito da nitretação nos aços SAE 4140 e SAE H13 através de análises metalográficas, espectroscopia de emissão óptica, difração de raios-x, microdureza e ensaio pino-sobre-disco. Para efeito de comparação, amostras de aço SAE 1045 e ferro puro foram nitretadas juntamente com amostras dos dois materiais anteriores. Foram executados três tratamentos diferentes em cada um dos aços, nitretação com baixo potencial de nitrogênio, nitretação com alto potencial de nitrogênio e nitrocarbonetação. Os dois primeiros tratamentos foram realizados em três tempos diferentes de duas, quatro e seis horas e a nitrocarbonetação foi realizada em seis horas. Os resultados mostraram a formação de uma camada nitretada com de camada branca seguida de uma camada de difusão com gradiente de propriedades. Um aumento significativo de dureza superficial é observado com a aplicação dos tratamentos. A nitrocarbonetação junto com alto potencial de nitretação se mostrou não sendo benéfica para a formação da camada em relação à nitretação com mesmo potencial. Nos testes tribológicos realizados, a camada nitretada se mostrou eficiente em aumentar a resistência ao desgaste nos aços SAE 4140 e SAE H13. / Among the main and most effective surface treatments for improving the surface properties of steels are nitriding and nitrocarburizing. The benefits of nitriding in steels are the increase in hardness, wear resistance, fatigue resistance and corrosion resistance. Because they have elements such as chromium, molybdenum and manganese, tool steels and low alloy steels of ultra high strength are benefited by nitriding. In this work, the effect of nitriding on SAE 4140 and SAE H13 steels was studied through metallographic analysis, optical emission spectroscopy, x-ray diffraction, microhardness and pin-on-disc test. For comparison purposes, samples of SAE 1045 steel and pure iron were nitrided together with samples of the two former materials. Three different treatments were performed in each of the steels, nitriding with low nitrogen potential, nitriding with high nitrogen potential and nitrocarburizing. The first two treatments were performed at three different times of two, four and six hours and nitrocarburizing was performed in six hours. The results showed the formation of a nitrided layer with a white layer followed by a gradient layer of properties. A significant increase in surface hardness is observed with the application of the treatments. Nitrocarburizing together with high nitriding potential proved to be of no benefit to the formation of the layer in relation to nitriding with the same potential. In the tribological tests carried out, the nitrided layer proved efficient in increasing wear resistance in SAE 4140 and SAE H13 steels.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-28T10:50:36Z No. of bitstreams: 1 arquivototal.pdf: 800250 bytes, checksum: 42e76ab05ea580b4fd24a3312b9b4212 (MD5) / Made available in DSpace on 2016-03-28T10:50:36Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 800250 bytes, checksum: 42e76ab05ea580b4fd24a3312b9b4212 (MD5) Previous issue date: 2013-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this paper, we study Clifford algebras so universal and constructive as quantization of exterior algebra, we classify all Clifford algebras associated with the quadratic Minkowski spaces (Rp+q, p,q), where p,q(u) = u21 +...+u2 p −(u2 p+1 +...+u2 p+q), u = (u1, ..., up+q) ∈ Rp+q, which we denote by Clp,q, as well as their complexifications. To do so, we use important results as the periodicity theorem Carton / Bott. The, we study their representations, emphasizing the Twisted Adjoint Representataion, Spin Representation and the Spin-Half Representation moreover using the number of Radon-Hurwitz we study representations of the algebras Cl0,k. / Neste trabalho, estudamos as ´algebras de Clifford Cl(V, ) associadas aos espa¸cos quadr´aticos (V, ), de maneira universal, construtiva e como quantiza¸c˜ao da ´algebra exterior. Classificamos todas as ´algebras de Clifford associadas as espa¸cos quadr´aticos de Minkowski (Rp+q, p,q), onde p,q(u) = u21 + ... + u2 p − (u2 p+1 + ... + u2 p+q), u = (u1, ..., up+q) ∈ Rp+q, as quais denotamos por Clp,q, bem como suas complexifica¸c˜oes. Para tanto, usaremos resultados importantes como o teorema da periodicidade de Carton/Bott. Al´em disso, estudamos as suas representa¸c˜oes, destacando a Representa¸c˜ao Adjunta Torcida, as Representa ¸c˜oes Spin e Semi-Spin e por meio do n´umero de Radon-Hurwitz estudamos as representa¸c˜oes das ´algebras Cl0,k.

Made available in DSpace on 2015-05-15T11:46:09Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1473576 bytes, checksum: 7ed82fab94ed8434b60fff26580cd11e (MD5) Previous issue date: 2013-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we discuss the concepts and definitions that construct Clifford algebras focusing on a introduction the theory Spin Geometry. That s because the connection this two subject, enabling such algebras know the measure that helps to understand the definition of spin manifold, concept introductory the this special topic in Riemannian Geometry. We begin with the construction of Clifford algebras associated to infinite dimensional vector spaces, over any field, passing to associated with finite dimensional. we see the spinores groups, Pin and Spin, which characterize and show the relation with the twisted adjoint representation, homomorphism that, when restricted to these groups, has an important role in defining of a spin structure. As this definition works with representations of real Clifford algebras, restricted to spinors groups such algebras, we introduced them for soon afterwards consider such representations. We concluded approaching the necessary theory for us to show that those groups are also Lie groups (where we urged an intersection with the analysis) and double covering, to complete the concepts algebraic present in the definition of spin manifold. / No presente trabalho abordamos os conceitos e definições que constroem as álgebras de Clifford com foco em uma linha de estudo de quem se inicia na teoria de Geometria Spin. Isso devido a intima ligação desses dois assunto, permitindo conhecer tais álgebras à medida que se auxilia a compreensão da definição de variedade spin, conceito introdutório desse tópico especial em Geometria Riemanniana. Iniciamos com a construção das álgebras de Clifford associadas a espaços vetoriais de dimensão infinita, sobre um corpo qualquer, passando àquelas associadas aos de dimensão finita. Fazemos o mesmo com os grupos Pin e Spin, os quais caracterizamos e mostramos a relação com a representação adjunta torcida, aplicação que, quando restrita a esses grupos, tem papel importante na definição de uma estrutura spin. Como tal definição trabalha com representações das álgebras de Clifford reais, restritas aos grupos spinores dessas Cliffords, as apresentamos para em seguida conceituarmos tais representações. Finalizamos, para completar os conceitos algébricos presente na definição de variedade spin, abordando a teoria necessária para mostrarmos que esses grupos são também grupos de Lie (onde instigamos uma interseção com a análise, destacando os enlaces com outras teorias) e recobrimentos duplos.

Dentre os principais e mais efetivos tratamentos superficiais para a melhora das propriedades da superfície dos aços, encontra-se a nitretação e a nitrocarbonetação. Os benefícios da nitretação nos aços são o aumento da dureza, resistência ao desgaste, resistência à fadiga e resistência à corrosão. Por possuírem elementos como cromo, molibdênio e manganês, os aços ferramenta e aços baixa liga de ultra alta resistência são beneficiados pela nitretação. Neste trabalho, estudou-se o efeito da nitretação nos aços SAE 4140 e SAE H13 através de análises metalográficas, espectroscopia de emissão óptica, difração de raios-x, microdureza e ensaio pino-sobre-disco. Para efeito de comparação, amostras de aço SAE 1045 e ferro puro foram nitretadas juntamente com amostras dos dois materiais anteriores. Foram executados três tratamentos diferentes em cada um dos aços, nitretação com baixo potencial de nitrogênio, nitretação com alto potencial de nitrogênio e nitrocarbonetação. Os dois primeiros tratamentos foram realizados em três tempos diferentes de duas, quatro e seis horas e a nitrocarbonetação foi realizada em seis horas. Os resultados mostraram a formação de uma camada nitretada com de camada branca seguida de uma camada de difusão com gradiente de propriedades. Um aumento significativo de dureza superficial é observado com a aplicação dos tratamentos. A nitrocarbonetação junto com alto potencial de nitretação se mostrou não sendo benéfica para a formação da camada em relação à nitretação com mesmo potencial. Nos testes tribológicos realizados, a camada nitretada se mostrou eficiente em aumentar a resistência ao desgaste nos aços SAE 4140 e SAE H13. / Among the main and most effective surface treatments for improving the surface properties of steels are nitriding and nitrocarburizing. The benefits of nitriding in steels are the increase in hardness, wear resistance, fatigue resistance and corrosion resistance. Because they have elements such as chromium, molybdenum and manganese, tool steels and low alloy steels of ultra high strength are benefited by nitriding. In this work, the effect of nitriding on SAE 4140 and SAE H13 steels was studied through metallographic analysis, optical emission spectroscopy, x-ray diffraction, microhardness and pin-on-disc test. For comparison purposes, samples of SAE 1045 steel and pure iron were nitrided together with samples of the two former materials. Three different treatments were performed in each of the steels, nitriding with low nitrogen potential, nitriding with high nitrogen potential and nitrocarburizing. The first two treatments were performed at three different times of two, four and six hours and nitrocarburizing was performed in six hours. The results showed the formation of a nitrided layer with a white layer followed by a gradient layer of properties. A significant increase in surface hardness is observed with the application of the treatments. Nitrocarburizing together with high nitriding potential proved to be of no benefit to the formation of the layer in relation to nitriding with the same potential. In the tribological tests carried out, the nitrided layer proved efficient in increasing wear resistance in SAE 4140 and SAE H13 steels.