Made available in DSpace on 2016-06-02T19:22:56Z (GMT). No. of bitstreams: 1 4404.pdf: 1810111 bytes, checksum: 6d3d450fd7a8a81c835b1a82a6176dba (MD5) Previous issue date: 2012-03-02 / Financiadora de Estudos e Projetos / The central nervous system (CNS) has an important role in maintaining the composition and volume of body fluids for the appropriate tissue perfusion. An important area of the CNS that receives cardiorespiratory afferents is the nucleus of the solitary tract (NTS) that has several types of neurotransmitters, includingL-glutamate and adenosine 5'-triphosphate (ATP). Neuroendocrine changes that occur during sodium depletion could change glutamatergi c and purinergic neurotransmissions into the NTS. Thus, in this study, we investigated : 1) the effects of sodium depletion on cardiorespiratory responses before and after injections of L -glutamate and α,β-methyleneadenosine 5′-triphosphate (α,β-methyl ATP, a selective P2X purinergic receptor agonist) into the NTS of unanesthetized and sodium depleted rats; 2) the cardiorespiratory responses of the injection of α,β-methyl ATP before and after the blockade of P2 receptor purinergic antagonist with suramin (non-selective P2 purinergic receptor antagonist) into NTS of unanesthetized and normovolemic rats and 3) to describe the autonomic components involved with the cardiovascular responses after injection of α,β-methyl ATP into the NTS. Male Holtzman rats with a cannula implanted into the NTS and catheters inserted into the femoral artery and vein were used. Ventilation (VE) was measured by whole body plethysmograph method. In relation to objective 1, the cardiorespiratory parameters were measured in normovolemic (before sodium depletion), depleted (24 h after sodium depletion) and repleted rats (two hours after free access to 0.3 M NaCl and water). Sodium depletion was induced by the treatment with the diuretic furosemide (20 mg/kg of body weight) injected subcut aneously (s.c.) followed by 24 h of sodium -deficient diet. Sodium depletion did not modify baseline MAP (104 ± 4 mmHg, vs. normovolemic: 105 ± 4 mmHg) or HR (334 ± 20 bpm, vs. normovolemic: 379 ± 13 bpm) but increased the VE (708 ± 107 ml/min/kg, vs. normovolemic: 478 ± 60 ml/min/kg). This effect was due to increase on tidal volume (VT, 7 ± 0.6 ml/kg, vs. normovolemic: 5 ± 0.4 ml/kg) without effect on the respiratory frequency (fR, 99 ± 8 cpm, vs. normovolemic: 85 ± 6 cpm). In repleted rats, VE did not return to normal level (640 ± 33 ml/min/kg, vs. normovolemic: 478 ± 60 ml/min/kg). Unilateral injections of L-glutamate (1 and 5 nmol/100 nl) into the NTS produced pressor response (17 ± 3 and 36 ± 3 mmHg, respectively, vs. saline: 3 ± 1 mmHg), bradycardia (-130 ± 15 and -169 ± 10 bpm, respectively, vs. saline: -13 ± 6 bpm) and the hyperventilation (233 ± 44 and 495 ± 114 ml/min/kg, respectively, vs. saline: 32 ± 26 ml/min/kg). Sodium depletion reduced pressor responses (4 ± 3 mmHg and 13 ± 4 mmHg, respectively) and hyperventilation (-112 ± 112 and 7 ± 115 ml/min/kg, respectively) and did not change bradycardia (-116 ± 30 and -156 ± 18 bpm, respectively). Unilateral injections of α,β-methyl ATP (2 nmol/100 nl) into the NTS also produced pressor response (36 ± 5 mmHg, vs. saline: 3 ± 1 mmHg), bradycardia (-194 ± 18 bpm, vs. saline: -13 ± 6 bpm) and did not change VE (54 ± 96 ml/min/kg, vs. saline: 32 ± 26 ml/min/kg). Sodium depletion reduced pressor response (24 ± 5 mmHg), VE ( -147 ± 184 ml/min/kg) and did not change bradycardia (-168 ± 22 bpm). In relation to objective 2, the results showed that injection of α,β-methyl ATP (2 nmol/100 nl) into NTS produced pressor response (24 ± 4 mmHg e -187 ± 39 bpm, respectively) and these responses were reduced 15 min after injection of suramin into NTS ipsilateral (13 ± 2 mmHg e -80 ± 18 bpm). Injection of α,β-methyl ATP into NTS produced no significantly change in VE. In relation to objective 3, the results showed that injection of α,β-methyl ATP (2 nmol/100 nl) into NTS promote pressor and bradycardic response (32 ± 5 mmHg and -183 ± 21 bpm). The pre-treatment with the alpha1 -adrenoceptor antagonist prazosin (1 mg/kg bw, i.v.) attenuated the increase in MAP (+10 ± 3 mmHg) without changing the bradycardic response (-192 ± 21 bpm) evoked by injection of α,β-methyl ATP into NTS. The pre-treatment with the cholinergic muscarinic antagonist, methyl-atropine (1 mg/kg bw, i.v.) did not changed the pressor response (+31 ± 6 mmHg) and abolished the bradycardic response (+21 ± 6 bpm) induced by injection of α,β-methyl ATP into the NTS. The results suggest that neuroendocrine changes produced by sodium depletion (increased level of circulating ANG II, aldosterone and the desactivation of the volume receptors and baroreceptors) may change the glutamatergic and purinergic neurotransmissions into the NTS. Furthermore, activation of P2X receptors in the NTS activates both the sympathetic and parasympathetic nervous system to produce pressor and bradycardic responses, respectively, without changing ventilation / O sistema nervoso central (SNC) possui um papel fundamental na manutenção da composição e do volume dos líquidos corporais, para a adequada perfusão tecidual. Uma importante área do SNC que recebe aferências cardiorrespiratórias é o núcleo do trato solitário (NTS) que possui vários tipos de neurotransmissores, dentre eles o L-glutamato e adenosina-5´-trifosfato (ATP). Mudanças neuroendócrinas que ocorrem durante a depleção de sódio poderiam alterar as neurotransmissões glutamatérgica e purinérgica no NTS. Assim, neste estudo, tivemos 3 objetivos: 1) investigar os efeitos da depleção de sódio nas respostas cardiorrespiratórias antes e após a injeção de L-glutamato e α,β-metileno adenosina 5’ trifosfato (α,β-metil ATP, agonista seletivo de receptor purinérgico P2X) no NTS de ratos não anestesiados; 2) investigar as respostas cardiorrespiratórias à injeção de α,β-metil ATP no NTS antes e após o bloqueio dos receptores purinérgicos P2 com o suramin (antagonista não-seletivo de receptores P2) no NTS de ratos não anestesiados e normovolêmicos e 3) caracterizar os componentes autonômicos envolvidos nas respostas cardiovasculares após a injeção de α,β-metil ATP no NTS. Foram utilizados ratos Holtzman com cânulas implantadas no NTS e com cateter inserido na artéria e veia femoral. As medidas de ventilação (VE) foram obtidas pelo método de pletismografia de corpo inteiro. Com relação ao objetivo 1, os parâmetros cardiorrespiratórios foram medidos em ratos normovolêmicos (antes da depleção de sódio), depletados (24 h após a depleção de sódio) e ratos repletos (2 h após o livre acesso a NaCl 0,3 M e água). A depleção de sódio foi induzida pelo tratamento com o diurético furosemida (20 mg/Kg do peso corporal) injetado subcutaneamente (s.c.) acompanhado de uma dieta deficiente em sódio por 24 h. A depleção de sódio não modificou a PAM basal (104 ± 4 mmHg, vs. normovolêmicos: 105 ± 4 mmHg) nem a FC (334 ± 20 bpm, vs. normovolêmico: 379 ± 13 bpm) mas aumentou a VE (708 ± 107 ml/min/kg, vs. normovolêmico: 478 ± 60 ml/min/kg). Este efeito ocorreu devido a um aumento do volume corrente (VC, 7 ± 0,6 ml/kg, vs. normovolêmico: 5 ± 0,4 ml/kg) sem alterar a frequência respiratória (fR, 99 ± 8 cpm, vs. normovolêmicos: 85 ± 6 cpm). Em ratos repletos, a VE não retornou ao nível normal (640 ± 33 ml/min/kg vs. normovolêmico: 478 ± 60 ml/min/kg). Injeções unilaterais de Lglutamato (1 e 5 nmol/100 nl) no NTS produziu resposta pressora (17 ± 3 e 36 ± 3 mmHg, respectivamente, vs. salina: 3 ± 1 mmHg), bradicardia (-130 ± 15 e -169 ± 10 bpm, respectivamente, vs. salina: -13 ± 6 bpm) e hiperventilação (233 ± 44 e 495 ± 114 ml/min/kg, respectivamente, vs. salina: 32 ± 26 ml/min/kg). A depleção de sódio reduziu a resposta pressora (4 ± 3 mmHg e 13 ± 4 mmHg, respectivamente) e hiperventilação (-112 ± 112 e 7 ± 115 ml/min/kg, respectivamente) e não alterou a bradicardia (-116 ± 30 e -156 ± 18 bpm, respectivamente). Injeção unilateral de α,β-metil ATP (2 nmol/100 nl) no NTS também produziu resposta pressora (36 ± 5 mmHg, vs. salina: 3 ± 1 mmHg), bradicardia (- 194 ± 18 bpm, vs. salina: -13 ± 6 bpm) e não modificou a VE (54 ± 96 ml/min/kg, vs. salina: 32 ± 26 ml/min/kg). A depleção de sódio reduziu a resposta pressora (24 ± 5 mmHg), a VE (-147 ± 184 ml/min/kg) e não alterou a bradicardia (-168 ± 22 bpm). Com relação ao objetivo 2, os resultados mostraram que a injeção de α,β-metil ATP (2 nmol/100 nl) no NTS promoveu resposta pressora e bradicárdica (24 ± 4 mmHg e -187 ± 39 bpm, respectivamente) e estas respostas foram reduzidas aos 15 minutos após a injeção de suramin no NTS ipsilateral (13 ± 2 mmHg e -80 ± 18 bpm). A injeção de α,β-metil ATP no NTS não promoveu alterações significativas na VE. Com relação ao objetivo 3, os resultados mostraram que as injeções de α,β-metil ATP (2 nmol/100 nl) no NTS promoveu resposta pressora e bradicardia (+32 ± 5 mmHg e -183 ± 21 bpm). O pré-tratamento com o antagonista de receptor alfa-1 adrenérgico, prazosin (1 mg/kg de peso corporal, i.v.), atenuou o aumento da PAM (+10 ± 3 mmHg) sem alterar a bradicardia (-192 ± 21 bpm) provocada pela injeção de α,β-metil-ATP no NTS e o pré-tratamento com o antagonista colinérgico muscarínico, metil-atropina (1 mg/kg de peso corporal, i.v.) não alterou a resposta pressora (+31 ± 6 mmHg) e aboliu a bradicardia (+21 ± 6 bpm) induzida pela injeção de α,β-metil ATP no NTS. Os resultados sugerem que alterações neuroendócrinas produzidas pela depleção de sódio (aumento dos níveis de ANG II e aldosterona circulantes e a desativação de receptores de volume e dos barorreceptores) podem alterar as neurotransmissões glutamatérgica e purinérgica no NTS. Além disso, a ativação dos receptores purinérgicos P2X no NTS ativa simultaneamente o sistema nervoso simpático e parassimpático para produzir respostas pressora e bradicárdica, respectivamente, sem alterar a ventilação pulmonar.

In this work, carbonaceous deposits on spent HTFT catalysts were investigated. This research was required in order to better understand the observed loss in productivity observed in the industrial reactors, with the aim of improving the economy of the HTFT process. A host of complementary techniques were employed to systematically determine the composition of a typical catalyst recovered from a reactor. Spent HTFT catalysts are comprised of magnetite and a mixture of iron carbides as well as adsorbed hydrocarbon products (soft carbon) and hard carbon. Reaction initiates at the particle surface and along the promoter-rich grain boundaries toward the core of the grains. A partially reacted particle would therefore have a core-shell structure, with magnetite representing the unreacted region of the catalyst. The reacted region consists of a porous carbonaceous matrix with soft carbon and carbide crystallites nestled in this matrix. The hard carbonaceous species is a mixture of polymeric carbon and polycyclic aromatic hydrocarbons. The particle structure is linked to the sample preparation method and an alternative method yielding catalyst particle with uniformly distributed promoter elements could be beneficial. Investigating carbonaceous species is a complex process, and development of a fresh methodology would aid in the quest for insight into the nature of carbonaceous species in various systems. A new approach which entails a combination of the traditional techniques combined with MALDI-TOF MS enabled a deeper investigation. Additional aspects such as the molecular weight distributions along with known information about crystallinity and morphology of the catalyst provide a comprehensive study of carbonaceous material. Polymeric carbon and very large polycyclic aromatic hydrocarbons constitute hard carbon and can be observed with minimal sample preparation procedures. The evolution of the HTFT catalysts was investigated as a function of time-on-stream. This enabled us to study the effects of increasing amounts of hard carbon on the activity and the chemical and physical properties of the catalysts. The catalyst activity was found to decrease with increasing hard carbon content, although the effect of carbon deposition cannot be distinguished from phase transformation (oxidation) which occurs simultaneously. A method to quantify the amount of hard carbon, which progressively builds up on the catalyst, was demonstrated. This required a great deal of method development, which provides a platform for future investigations of these catalysts. Importantly, it allows predictions of the amounts of carbon that will be deposited after a certain reaction time. This allows more efficient regulation of catalyst replacement. The production of fine carbon-rich particles in the industrial reactor poses a major problem in the process. Carbon deposition leads to an increase in particle diameter with time on-stream. Permissible levels of hard carbon were identified, beyond which the mechanical strength of the catalyst particles deteriorate. This leads to break-up of the particles and therefore fines formation. The surface area and pore volume generally increase with progressive deposition of hard carbon, while the bulk density of the catalyst material exhibits a linear decrease with carbon build-up. A mechanism is proposed for hard carbon formation which apparently occurs through the dissociative adsorption of CO to form a carbon monolayer. This is followed by polymerisation of the carbon atoms. Meta-stable interstitial carbides are formed at the iron-carbon interface. Owing to a carbon concentration gradient between the top of the surface and the bottom of the metal or carbide particle, carbon diffusion across the crystal (carbide decomposition) and grows as a PAH molecule lifting the iron carbide away from the particle. As this corrosion process is intrinsic to iron-based catalysts, a catalyst that contains sulphur is proposed for future development.

Palladium complexes of bis(di-tert-butylphosphinomethyl)benzene (DTBPMB) show remarkably high activity as alkene methoxycarbonylation catalysts, in addition to numerous other catalytic conversions, and are currently being commercialised by Lucite in ethene methoxycarbonylation to methyl propanoate. Any large-scale exploitation of this catalyst system for heavier products, however, is likely to be hindered by catalyst-product separation problems common to homogeneous catalysts; hence modification of this catalyst system to allow facile product separation was investigated. Tethering of DTBPMB residues onto polystyrene via Suzuki-type coupling of suitable precursors onto bromopolystyrene and boronic acid functionalised polystyrene resins was investigated and the phosphine was successfully immobilised. Phosphination of the resins was not complete however and as such there is concern that other phosphine residues may be present which do not exhibit a bidentate binding motif. The synthesis of a potassium sulfonate derivative of DTBPMB (KBPMBS) was successful and immobilisation of this onto ion exchange resins was also investigated. Some preliminary results from studies into 1-octene methoxycarbonylation using palladium complexes of these resins were obtained. Supporting of this diphosphine onto silica via a sol-gel co-condensation methodology was also investigated; the synthesis of a suitably functionalised precursor containing a sulfonamide linkage was successful via protection of the diphosphine using borane. Although formation of the silica support was successful, attempts to deprotect the phosphine-borane resulted in cleavage of the ligand from the support. An alternative route to this supported ligand was attempted and others discussed. Synthesis of a suitable sol-gel precursor via alkene hydrosilation was also attempted and is discussed. Supporting of the sulfonated phosphine, KBPMBS onto silica functionalised with imidazolium tethered residues was also investigated, although complete leaching of the phosphine from the support by methanol washing was observed. Immobilisation of the synthesised KBPMBS ligand in an ionic liquid (IL) phase was investigated. Complex formation and catalytic activity were demonstrated and a positive effect on conversion was observed upon addition of carbon dioxide to the system; possibly due to the increased CO solubility within the IL phase. Efficient product separation from the IL-immobilised catalyst system was demonstrated, both by organic extraction and using supercritical carbon dioxide flow. However, poor catalyst stability under these conditions appears to present a barrier to recycling this system, with loss of conversion observed on catalyst recycling. Other attempts to immobilise the DTBPMB ligand are discussed and reduction of the sulfide derivative of DTBPMB was demonstrated using hexachlorodisilane, which could be used as a general synthetic strategy for protecting highly electron rich phosphines. It is possible that increasing the bulk of the DTBPMB ligand may increase catalyst stability and result in catalyst systems with higher turnover numbers. Therefore syntheses of bulky ligands based on the DTBPMB backbone were investigated. 1,2,4,5-tetrakis(di(tert-butyl)phosphinomethyl)benzene was successfully synthesised although palladium complexes of this showed no activity in catalytic methoxycarbonylation. Attempts to synthesise a related biphenyl-based tetraphosphine is also discussed, although isolation of this in a pure form was not achieved. Routes toward tetraphenyl and dimethyl-diphenyl functionalised derivatives of DTBPMB have also been explored, although only a monophosphine was isolated due to difficulties in obtaining an intermediate di(chloromethyl) precursor in both synthetic pathways, although this now appears to have been overcome.

Behavioural scientists argue that ‘social learning' provides the link between biological phenomena and cultural phenomena because of its role in the ‘cultural transmission' of knowledge among individuals within and across generations. However, leading authors within the social sciences have proposed alternative ways of thinking about social life not founded on the Modern oppositions including nature-culture, biology-culture, body-mind, and individual-society. Similarly, the distinction between a domain of nature and a domain of nurture has also been extensively criticized within biology. Finally, advocates of ‘radical embodied cognitive science' offer an alternative to the representational-computational view of the mind which supports the conventional notion of culture and cultural information. This thesis attempts to integrate developmental systems theory, radical embodied cognitive science, and relational thinking, with the goal to bring the field of social learning closer to these critical theoretical developments. In Chapter 2, I find no justification for the claim that the genome carries information in the sense of specification of biological form. Chapter 3 presents a view of ontogeny as a historical, relational, constructive and contingent process. Chapter 4 uses the notions of environmental information, abilities, affordances, and intentions to make sense of behaviour and learning. In Chapter 5, I argue that the notion of social learning can be understood in terms of relational histories of development rather than in terms of transmission of information. I then report empirical studies investigating behavioural coordination and social learning consistent with this theoretical framework. Chapter 6 presents evidence that dyads in a joint making activity synchronize their attention constrained by their changing situation and that coordination of attention is predictive of implicit and explicit learning. Chapter 7 presents evidence that joint attention does not require gaze following and that attentional coordination is predictive of learning a manual task. Together, these theoretical and empirical studies suggest a new way of thinking about how humans and other animals live and learn socially, one that is consistent with critical theoretical and philosophical developments that are currently neglected in the literature on social learning.

Behavioral perceptions and cortical auditory evoked potentials (CAEPs) from native English (N=10) and Spanish speakers (N=10) were recorded for speech stimuli that constitute phonetically relevant categories of voicing. The stimuli were synthesized bilabial stop consonant-vowel syllables in a continuum ranging from/ba/to/pa/that varied in voice onset time (VOT) from 0 to 60ms. Different behavioral perceptions were evidenced by significantly different categorical phonetic boundaries between the two groups (p.05). Peak P1, N1, and P2 response latencies and P1–N1 and N1–P2 amplitudes increased significantly with increasing VOTs (p

The mechanical properties of boron carbide (B4C) with 10 and 20 vol% particulate inclusions of commercially available nano-sized alpha-phase silicon carbide (a-SiC) or micron-sized titanium diboride (TiB2) were investigated so as to produce a fine-grained material with high hardness, toughness, and overall strength in order to increase the effectiveness of B4C as a structural ceramic, whose use in the field has been limited because of the extreme brittle nature of the material. Full density sintering of the ceramics (≥99% theoretical) was completed using the novel Plasma Pressure Compaction (P²C®) technique, which limited grain growth due to a reduced processing temperature and a significantly reduced consolidation time. The reinforced ceramic composites had particulate grains homogeneously distributed within the B4C matrix. X-ray diffraction patterns confirmed that the constituents did not interdiffuse. The four-point flexure strength for the monolithic B4C ceramic was found to be significantly larger than any recorded value found in scientific literature, and was most likely attributed to the fine-grained microstructure resulting from the P²C® processing. The mechanical properties of the nano-sized a-SiC-B4C ceramics showed a slight increase in the Chevron-notched four-point bend fracture toughness due to the crack deflection toughening mechanism. A slight decrease in the Vickers microhardness and the static elastic modulus values were also observed. A significant increase in the fracture toughness as well as a slight increase in the microhardness and elastic modulus of the micron-sized TiB2-B4C materials was found. The toughening mechanism of this composite was attributed to the slight chemical bond between the B4C matrix and the ultra-small, ultra-tough TiB2 particulates, which forced a propagating crack to completely rip apart the TiB2 reinforcing particles. This cleaving nature resulted in significant amounts of energy being absorbed by the micron-sized particulates. It was concluded that the composite with 20 vol% TiB2 allowed for the largest gain in toughness because it possessed the largest number of ultra small, ultra tough particulate-cracktip interactions.

This report describes the aim, scope, underlying literature and results of the research project "The Nexus between the Financial and the Real Sector". We studied the contribution of the financial sector as a whole and its individual segments (bank credits, the issuance of bonds and shares) to real economic growth in EU Member and Candidate Countries, the United States and Japan. We supplement existing approaches with the inclusion of the bond market and of foreign direct investment in the banking sector, wherein for the first time, we provide empirical evidence for slightly positive effects thereof. Methodically, we extend previous research by the production-function approach and document the importance of the market microstructure. We recommend to include liberalisation and integration effects, the bond and insurance sector, and effects of foreign bank entry and investment into future research on the Finance-Growth-Nexus. (author's abstract) / Series: EI Working Papers / Europainstitut

La division cellulaire est un événement fondamental, indispensable au développement embryonnaire animal et à l’homéostasie des organismes adultes. Il s’agit d’un processus complexe qui doit être précisément contrôlé dans le temps et l’espace pour permettre la formation de deux cellules filles, au contenu génétique identique à celui de la cellule mère. Ceci requiert une coordination entre la ségrégation des chromosomes, opérée par les microtubules, et le clivage de la cellule, engageant une réorganisation dynamique du cytosquelette d’Actine. La modification de la forme des cellules en cours de division est en effet due au remodelage du cortex cellulaire, incluant la membrane plasmique et le réseau de filaments d’Actine sous-jacent. Bien que cette série de modifications du cortex soit indispensable au déroulement correct de la division cellulaire, les mécanismes moléculaires du contrôle l’organisation corticale en mitose restent mal caractérisés. Le PI(4,5)P2 est un phosphoinositide constituant de la membrane plasmique, notamment nécessaire à la division cellulaire. Nos travaux chez la drosophile mettent en évidence que ce phospholipide présente une distribution dynamique, homogène sur l’ensemble du cortex à l’entrée en mitose, puis se concentrant à l’équateur des cellules après la séparation des deux lots de chromosomes. Nous montrons que le PI(4,5)P2 est nécessaire au contrôle de la stabilité corticale et du fuseau mitotique, au moins en partie par son rôle favorisant l’activation de la dMoésine. La dMoésine régule l’interaction entre les filaments d’Actine et la membrane plasmique, jouant un rôle clé dans l’organisation locale du cortex des cellules en mitose et ses propriétés mécaniques. Nous montrons que l’interaction PI(4,5)P2/dMoésine participe à la contraction cellulaire à l’entrée en mitose, puis à l’élongation cellulaire caractéristique des étapes plus tardives de la division. A la fin de la mitose, nous montrons que la phosphatase pP1-87B inhibe l’activation de la dMoésine, indispensable à la relaxation du cortex des cellules en interphase. Par un crible fonctionnel systématique, nous avons recherché l’ensemble des facteurs indispensables à la production et à l’enrichissement localisé du PI(4,5)P2 au cortex mitotique. Nous montrons le rôle majeur de deux voies de biosynthèse, qui collaborent pour produire localement le PI(4,5)P2 à la membrane plasmique au cours de la mitose. Leur absence prévient l’activation et le recrutement membranaire de la dMoésine, et conduit à une instabilité corticale associée à des défauts du fuseau mitotique. Une troisième voie, nécessitant l’activité de la protéine dOcrl, contribue à l’homéostasie de ce phosphoinositide, en dégradant le PI(4,5)P2 présent sur les membranes internes de la cellule. L’inactivation de dOcrl empêche la formation normale et l’ingression du sillon de clivage. Ensemble, ces résultats identifient donc des régulateurs importants de la membrane plasmique et de son interaction avec le cytosquelette, permettant de mieux comprendre les mécanismes de la réorganisation de la forme cellulaire au cours de la mitose. / Cell division must be accurately controlled in time and space to permit the formation of two daughter cells whose genetic content is identical to that of the mother cell. This process requires successive modifications of cell shape, induced by cortical remodelling. Molecular mechanisms controlling cortical reorganization during mitosis remain partially uncharacterized. Our work in Drosophila cells demonstrates that PI(4,5)P2, a phosophoinositide of the plasma membrane, is enriched at the equatorial region at the onset of anaphase. This PI(4,5)P2 is necessary for the cortical stability of mitotic cells, and requires dMoesin activation. The dMoesin, linking actin to the plasma membrane, plays a critical role in the cortical organization of mitotic cells and in the regulation of its mechanical properties. We show that the interaction PI(4,5)P2/dMoesin participates in cellular contraction at the beginning of mitosis, then in cell elongation characteristic of subsequent steps. At the end of mitosis, the Pp1-87B phosphatase inactivates the dMoesin. By a systematic functional screen, we characterize the key role of two pathways acting in synergy to locally produce PI(4,5)P2, Skittles- and Pten-dependent, and the role of a third pathway requiring dOcrl activity to control PI(4,5)P2 homeostasis. Altogether, these results allow us to better understand the mechanisms controlling cortical remodelling and modifications of cell shape that occur during mitosis. / Doctorat réalisé en cotutelle avec le laboratoire de François Payre au Centre de Biologie du Développement à Toulouse, France (Université de Toulouse III - Paul Sabatier)

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George MacDonald (1824-1905) is one of the most complex and significant Scottish writers of the nineteenth century, especially as a writer of children's fiction and literary fairy tales. His works, however, have seldom been studied as Scottish literature. This dissertation is the first full-length analysis of his writings for children in their Scottish context, focusing particularly on his use of Scottish folklore in his literary fairy tales. MacDonald wrote in the Scottish Romantic tradition of Robert Burns, Walter Scott, and James Hogg; by close reading his works alongside similar texts by his compatriots, such as Andrew Lang, MacDonald's own idiosyncratic contribution to that tradition becomes more apparent. His profound knowledge of and appreciation for Christian mysticism is in evidence throughout his work; his use of folklore was directly informed by his exploration of mystical ideas. Hogg is recast as a second Dante, and ‘bogey tales' become catalysts for spiritual awakening. MacDonald's fairy tales deal sensitively and profoundly with the theme of child death, a tragedy that held personal significance for him, and can thus be read as his attempt to come to terms with the reality of bereavement by using Scottish folklore to explain it in mystical terms. Traditional figures such as Thomas Rhymer, visionary poets, and doubles appear in his fairy tales as guides and pilgrims out of the material world toward mystical union with the Divine.