Les comètes se sont formées dans des régions froides du disque protoplanétaire. Elles sont considérées comme porteuses du matériau le plus primitif du système solaire, témoin de la composition et des conditions physico-chimiques de la nébuleuse en formation. L’objectif de cette thèse est de caractériser des échantillons de la comète Wild2 rapportés sur Terre en 2006 par la mission spatiale Stardust de la NASA. Une centaine de picogramme de matière a été analysée en microscopie électronique en transmission. L’étude de la minéralogie des particules nous renseigne sur les conditions de formation des constituants et sur leur évolution. Il s’agit également de décrypter dans les microstructures observées les effets associés à la collecte du matériau cométaire. Nous avons caractérisé deux familles de grains, l’une étant constituée de gros cristaux (5-10 µm en moyenne), principalement des silicates, bien préservés par la collecte. La composition chimique des grains ainsi que leur microstructure se révèlent très variées. L’autre famille est constituée de matière à grains fins (<500 nm) ayant subi de fortes interactions avec l’aérogel de silice utilisé pour la capture des particules. Une méthodologie particulière a été mise en place pour comprendre les mécanismes de modifications associés à la collecte. Il nous a été ensuite possible de déduire des observations les propriétés initiales des particules. On montre alors que les poussières cométaires étaient composées à l’origine d'un assemblage de grains relativement gros, cimentés entre eux par une matrice à grains fins d’une composition typique des objets très primitifs observés dans certaines météorites chondritiques. / Cometary dust particles are believed to be relics of the primitive material of the early solar system. This material is now available for studies in the laboratories since the Stardust mission (NASA) brought to Earth samples from the comet 81P/Wild 2.The aim of this PhD work is to characterize Wild2 samples by TEM. Approximately one hundred picograms of cometary material have been studied. The mineralogy gives information about the formation and evolution conditions of the grains in order to reconstruct their histories. The aim is also to characterize the thermal induced modification due of the collect into the silica aerogel under hypervelocity conditions. We have characterized two categories of grains. The first consists of relatively large grains (5-10µm in average), mainly well preserved silicates. These silicates display a wide range of compositions and microstructures. The second category consists of fine grain material (<500nm). The microstructure is characteristic of thermally modified particles that have suffered strong interaction with the silica aerogel during the hypervelocity impact. A specific method has been developed to quantify the data and to understand the physical and chemical mechanisms that occurred during the deceleration into aerogel. This fine grain material has a composition close to solar abundance, showing that it did not been chemically fractionated in the protoplanetary disk before the incorporation on comet Wild2. We deduce that cometary material is made of an assemblage of relatively large grains stick together by a fine grained material with the characteristic composition of the most primitive material found into the chondritic meteorites.

The discovery of Ni-, Cu-, and Zn-bearing Fe-sulfides from comet 81P/Wild 2 represents the strongest evidence, in the Stardust collection, of grains that formed in an aqueous environment. Crystalline sulfide assemblages from Wild 2 and the hydrothermally altered CI chondrite Orgueil were investigated. Structural and compositional characterizations of the sulfide grains from both collections reveal similarities. The Stardust samples include a cubanite (CuFe₂S₃) grain, a pyrrhotite [(Fe,Ni)₁₋ₓS]/pentlandite [(Fe,Ni)₉S₈] assemblage, and a pyrrhotite/sphalerite [(Fe,Zn)S] assemblage. Similarly, the CI-chondrite sulfides include individual cubanite and pyrrhotite grains, cubanite/pyrrhotite assemblages, pyrrhotite/pentlandite assemblages, as well as possible sphalerite inclusions within pyrrhotite grains. The cubanite is the low temperature orthorhombic form, which constrains temperature to a maximum of 210°C. The Stardust and Orgueil pyrrhotites are the 4C monoclinic polytype, which is not stable above ~250°C. The combinations of cubanite and pyrrhotite, as well as pyrrhotite and pentlandite, signify even lower temperatures. The crystal structures, compositions, and petrographic relationships of these sulfides constrain formation and alteration conditions. Taken together, these constraints attest to low-temperature hydrothermal processing. The hydrothermal conditions under which cubanite forms were investigated through thermodynamic modeling and experimental synthesis. A thermodynamic model for cubanite was developed to constrain its formation environment. Cubanite was synthesized under hydrothermal conditions consistent with those predicted for the CI-chondrite parent body. The similarity between Stardust and CI-chondrite sulfides suggest similar fluid conditions may have existed on the comet at some point in its history. The presence of cubanite in the Stardust collection has implications for large scale issues such as: heat sources in the comet-forming region; aqueous activity on cometary bodies; and the extent and mechanisms of radial mixing of material in the early nebula. The Wild 2 sulfides are most likely the products of low-temperature aqueous alteration and provide evidence of radial mixing of material from the inner solar system to the comet-forming region and possible secondary aqueous processing on the cometary body.

Les cellules épithéliales fournissent différentes fonctions biologiques: elles servent de barrière entre l'extérieur et l'intérieur d'un organisme et forment un continuum mécanique à travers les jonctions adhérentes qui les connectent. Au cours du développement, elles subissent des modifications extrêmes pour former l'embryon: elles changent de forme, modifient leur position relative ou perdent leur intégrité épithéliale. La plus part de ces changement se basent sur la modulation de l'actomyosine corticale et jonctionale, et sur la modulation des protéines qui définissent et maintiennent la polarité apico basale. Neuralized (Neur) est une E3 ubiquitine ligase qui est conservée des nématodes jusqu'aux mammifères. Elle a été découverte pour son rôle dans la régulation de la signalisation Delta/Nocth. Dans ce travail on décrit deux autres functions Notch-indépendantes de Neur dans le remodelage des épithéliums. En premier temps, on montre que Neur régule négativement la protéine apicale Crumbs à travers une isoforme de Stardust, ce qui permet le remodelage de l'intestin postérieur de la Drosophile et favorise la migration trans-epithéliale des cellules germinales primordiales. Puis, on présente que, pendant la gastrulation, Neur module la contractilité de l'actomyosine dans le mésoderme, et indirectement dans l'ectoderme, pour contrôler la formation du sillon ventral. / Epithelial cells serve many biological functions: they act as a barrier to separate the interior from the exterior, and form a mechanical continuum through the junctions that interconnect them. During development, they undergo dramatic changes to shape the embryo: they change their shape, modify their relative position or lose their epithelial integrity. Most of these changes rely on the modulation of cortical and junctional actomyosin, and the regulation of the proteins that define and maintain the epithelial apical/basal polarity. Neuralized (Neur) is an E3 ubiquitin ligase conserved from nematodes to mammals. It was first discovered for its role in the regulation of Delta/Notch signalling. Here we describe two Notch independent roles of Neur in epithelial remodelling. First, we show that Neur negatively regulates the apical protein Crumbs though a specific isoform of Stardust. This allows the remodelling of the drosophila posterior midgut and favours the trans-epithelial migration of the primordial germ cells. Finally, we present that Neur modulates actomyosin contractility in the mesoderm, and indirectly in the ectoderm, to control ventral furrow formation during gastrulation.

Ma thèse porte sur l'analyse par SXRM (Synchrotron X-Ray Microscopy) et spectroscopie µ-FTIR (micro Fourier Transformed InfraRed) des échantillons de la comète Wild 2 collectés par la mission Stardust. Les analyses SXRM ont permis de déterminer la composition élémentaire des grains de Wild 2, tout en étudiant leur ralentissement dans l'aérogel. Une étude XANES (X-Ray Absorption Near Edge Structure) au seuil du fer d'analogues des échantillons Stardust a permis de valider la méthode de collecte des grains en se basant sur l'état d'oxydation du fer. Malgré l'élévation de température subie par la particule lors de son entrée dans l'aérogel, les informations concernant la particule incidente, en particulier concernant sa minéralogie, sont préservées dans la particule finale. Des cartographies de µ-fluorescence X ont permis de déterminer la composition élémentaire des grains de Wild 2. Les abondances élémentaires, normalisées au fer, sont chondritiques pour Ca, Ti, Cr, Mn, Ni, Ge, et Se. Un enrichissement en Cu, Zn et Ga est en revanche observé et indiquerait qu'au moins une partie de la matière réfractaire de Wild 2 s'est formée tardivement, à partir d'un gaz appauvri en les éléments les plus réfractaires. Le soufre semble quant à lui sous-abondant, ce qui signe sans doute un processus de condensation incomplet, stoppé avant que la totalité du soufre ait pu se condenser. L'analyse par µ-FTIR, complétée par de la spectroscopie Raman, de grains extraits de l'aérogel montre que la matière organique de Wild 2 est dominée par la présence d'îlots de carbone aromatique reliés entre eux par des ponts aliphatiques. L'étude de la bande à 3.4 µm montre que les chaînes aliphatiques sont plus longues (ou moins ramifiées) que dans les IDPs et les grains du milieu interstellaire (MIS). La comparaison avec les observations du MIS diffus montre que la matière organique de Wild 2 n'est clairement pas interstellaire et semble plus simple que celle contenue dans les grains du MIS.

Made available in DSpace on 2016-05-17T16:51:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-28. Added 1 bitstream(s) on 2016-05-17T16:55:05Z : No. of bitstreams: 1 000864001.pdf: 2233983 bytes, checksum: 74437cf2aac5fed38f87fd02fcb64d8b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho tem o objetivo de analisar o modo como a figura do herói é construída em um romance contemporâneo e, a partir dos dados obtidos nesse estudo, entender a maneira como esse herói é traduzido para o suporte fílmico. Como base para meu trabalho, utilizo o romance Stardust (1999), do escritor inglês Neil Gaiman, e sua adaptação cinematográfica Stardust (2007), lançada no mesmo ano no Brasil sob o título de Stardust: o mistério da estrela. Como aporte teórico utilizo, principalmente, os textos de Campbell (2007), Propp (1978) e Simonsen (1987) no que concerne ao herói, sua jornada e como ele a enfrenta. Utilizarei também, especialmente, as teorias de Hutcheon (2006), Sanders (2006), Stam (2000) e Leitch (2007, 2008) no que refere-se ao estudo da adaptação de obras literárias; e os textos de Martin (2003), Xavier (2005) e Vanoye e Goliot-Lété (1994), sobretudo, ao comentar sobre o cinema, suas características e o modo como produz suas obras. Proponho aqui uma visão da adaptação enquanto obra artisticamente autônoma, bem como do herói como uma figura que, apesar de beber dos grandes clássicos, apresenta-se com novas características / This study aims at analysing the way the figure of the hero is built in a contemporary novel and, from the data obtained, understanding the way the hero is translated to the filmic media. The corpus of the research was constituted by the novel Stardust (1999), by the English writer Neil Gaiman, and its film adaptation Stardust (2007), released in Brazil, in the same year, under the title Stardust: o mistério da estrela. As theoretical contribution I use, mainly, the texts by Campbell (2007), Propp (1978) and Simonsen (1987) regarding the hero, his journey and how he faces it. I will also use, specially, the theories of Hutcheon (2006), Sanders (2006), Stam (2000) and Leitch (2007, 2008) for the study of the adaptation of literary works; and the texts of Martin (2003), Xavier (2005) and Vanoye and Goliot-Lété (1994) to comment on film, its characteristics and the way it produces its works. I propose here a vision of the adaptation as an artistically independent work, and the hero as a figure that, despite the recurrent dialogue with the great classics, shows himself with new characteristics

The sculptural environments I create immerse the viewer in a decrepit vaudevillian past. The sculptures allude to narratives within Community Theater as well as the Drag Show. Making becomes an act; manipulating materials such as synthetic hair and paint are associated with the guise of the makeup artist. Frantic rehearsal logic prevails as a dress is repurposed into a male giant's costume and window blinds are used to construct a boat's deck. This collusion asks the viewer to transgress the boundary of the stage, becoming a voyeur privileged to the world of exiled props and role reversal.

The purpose of my dissertation is to conduct an intertextual study of two fantasy texts — Alice in Wonderland by Victorian author Lewis Carroll, and Stardust by postmodern fantasy author Neil Gaiman — and their filmic re-visionings by Tim Burton and Matthew Vaughn respectively. In scrutinising these texts, drawing on insights from feminist, children’s literature and intertextual theorists, the actions of ‘growing up’ and ‘falling down’ are shown to be indicative of a paradoxical becoming of the text’s central female protagonists, Alice and Yvaine. The social mechanisms of the Victorian age that educate the girl-child into becoming accepting of their domestic roles ultimately alienate her from her true state of being. While she may garner some sense of importance within the imaginary realms of fantasy narratives, as these female protagonists demonstrate, she is reduced to the position of submissive in reality – in ‘growing up’, she must assume a ‘fallen down’ state in relation to the male. / English Studies / M.A. (English)

The purpose of my dissertation is to conduct an intertextual study of two fantasy texts — Alice in Wonderland by Victorian author Lewis Carroll, and Stardust by postmodern fantasy author Neil Gaiman — and their filmic re-visionings by Tim Burton and Matthew Vaughn respectively. In scrutinising these texts, drawing on insights from feminist, children’s literature and intertextual theorists, the actions of ‘growing up’ and ‘falling down’ are shown to be indicative of a paradoxical becoming of the text’s central female protagonists, Alice and Yvaine. The social mechanisms of the Victorian age that educate the girl-child into becoming accepting of their domestic roles ultimately alienate her from her true state of being. While she may garner some sense of importance within the imaginary realms of fantasy narratives, as these female protagonists demonstrate, she is reduced to the position of submissive in reality – in ‘growing up’, she must assume a ‘fallen down’ state in relation to the male. / English Studies / M.A. (English)