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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
851

A teoria pulsional freudiana à luz da leitura de Green: uma alternativa ao biologismo mítico / Freuds drive theory in the light of Greens readings: an alternative to mythical biologism

Cano, Tatiana Monreal 15 May 2015 (has links)
Diante da explicação freudiana para o fenômeno da compulsão à repetição através da tese da pulsão de morte concebida enquanto retorno ao estado inorgânico, formula-se a seguinte questão: seria possível, por um lado, recusar a explicação freudiana pautada em seu biologismo mítico e, por outro lado, aceitar a tese de que a pulsão de morte seja uma força de desligamento? Para responder a essa pergunta encontramos um vasto material na obra publicada por André Green ao longo de sua carreira de mais de quarenta anos sob a rubrica trabalho da pulsão de morte, mais tarde, substituída por trabalho do negativo. Este texto tem como objetivo sistematizar a leitura e os aportes de Green à teoria das pulsões freudiana, sobretudo em relação ao segundo dualismo pulsional. Ele se divide em duas partes. Na primeira, destaca-se a análise de Green sobre as relações entre a pulsão de morte e a teoria do narcisismo na obra freudiana; na segunda, sua crítica em relação ao solipsismo freudiano e a necessidade de sua superação através das teorizações contemporâneas em torno às noções de objeto e de espaço potencial. Estas são complementadas por uma teoria da temporalidade do psiquismo. O trabalho defende a tese de que Green aceita o conceito freudiano de pulsão de morte enquanto força de desligamento, mas recusa o biologismo mítico subjacente à ideia do retorno ao estado inorgânico. Além disso, se Green concorda com a explicação freudiana para a pulsão de morte enquanto força de desligamento expressada no narcisismo negativo , ele se recusa a conceber que o processo de desligamento possa se instaurar de maneira espontânea ou automática. Para ele, este processo deve ser pensado mediante a articulação do funcionamento pulsional e da reposta do objeto que, neste caso, falha no estabelecimento do princípio do prazer; em outras palavras, o fracasso na instalação da espera institui a compulsão à des-fazer e des-ligar. De tal modo, a compulsão à repetição mortífera, ao contrário de repetir o desejo inconsciente e, portanto, estar referida à intemporalidade do inconsciente e à lógica da esperança é, na verdade, um anti-tempo. Nesse sentido, presente, passado e futuro ficam reduzidos ao instante da descarga completa de toda tensão, impossibilitando qualquer projeto. Dado o anterior, resulta que as teorizações de Green em relação ao trabalho do negativo, ainda que avessas à tese freudiana do retorno ao estado inorgânico, aceitam, não obstante, a tese da pulsão de morte enquanto processo de desligamento desde que esta seja pensada através da articulação das dimensões intrapsíquica e intersubjetiva. Isso implica pensar na resposta do objeto e fazê-lo responsável pelo malogro na instalação da heterocronia no psiquismo. 8 Conclui-se que a obra de Green oferece uma alternativa original ao biologismo mítico para a explicação da pulsão de morte / Given the Freudian explanation for the phenomenon of compulsion to repeat based on the death drives thesis, conceived as a return to the inorganic state, one formulates the following question: would it be possible, on the one hand, to refuse the Freudian explanation guided by its mythical biologism, and on the other hand accept the thesis that the death drive is a disengagement force? To answer this question we find a vast amount of material on the work published by André Green throughout his career of more than forty years under the title \"work of the death drive\", later renamed \"work of the negative\". This thesis aims to systematize Greens reading and contributions to the Freudian drive theory, especially regarding the second drive dualism. It is divided into two parts. The first one is Green\'s analysis of the relationship between death drive and theory of narcissism on Freud\'s work; the second one is about his criticism of Freud\'s solipsism and the need to its overcome through contemporary theories around the notions of object and potential space. These will be complemented by a theory of the temporality of the psyche. The present work supports the thesis that Green accepts the Freudian concept of death drive as a disengagement force, but refuses the mythical biologism subjacent to the return to the inorganic states idea. Furthermore, if Green agrees with the Freudian explanation of the death drive as a disengagement force expressed in the negative narcissism he will refuse to conceive that the disengagement process will be established spontaneously or automatically. To him, this process should be thought through the articulation of instintual functioning and the objects response that in this case fails in establishing the principle of pleasure; in other words, the failure of the waiting installation establishes the compulsion to disengage and to disconnect. Insomuch, the deadly compulsion to repeat, instead of repeating the unconscious desire and therefore be referred to the intemporality of the unconscious and to the logic of hope is actually an anti-time. In this sense, present, past and future are reduced to the instant of total discharge of all tension, precluding any project. Given the above it follows that Greens theorization regarding the work of the negative, though averse to the Freudian thesis of the return to the inorganic state, accept however the thesis of death drive as a shutdown process provided that this is thought through the articulation of the intrapsychic and intersubjective dimensions. This implies thinking of the objects response and make it responsible for the failure in the installation of heterochrony in the psyche. It concludes that the work of Green offers an original alternative to the mythical biologism regarding the explanation of the death drive
852

Interação da onda híbrida inferior com os íons rápidos no Tokamak JET / Interaction of Lower Hybrid Waves with Fast Ions in JET

Andrade, Maria Celia Ramos de 10 June 1994 (has links)
As tentativas de se conseguir um funcionamento contínuo para o tokamak e as perspectivas de estabilização de oscilações MHD através do controle do perfil de corrente, motivaram pesquisas que levassem a uma forma de geração de corrente não indutiva. Uma das possíveis alternativas para atingir esta meta é a injeção de ondas de alta freqüência como, por exemplo, ondas na freqüência híbrida inferior ou Lower Hybrid (LH), que impulsionam elétrons através do amortecimento de Landau na direção paralela ao campo magnético toroidal, tomando-os capazes de transportar corrente. Nos futuros reatores, entretanto, a absorção da onda pelas partículas de 3.5 MeV, conforme o que é previsto, e que ocorre através do amortecimento de Landau na direção perpendicular ao campo magnético, pode diminuir a eficiência do método descrito acima. Nosso objetivo, neste trabalho, é simular a interação LH-partículas com a interação entre a onda LHe os íons rápidos do plasma, que atingem até alguns MeV de energia e que são provenientes do aquecimento de íons de minoria pela onda ciclotrônica de íons (IC). Estes fenômenos podem ser descritos através de uma equação de Fokker-Planck uni-dimensional, no espaço de velocidades, onde os termos de difusão quase-linear, correspondentes à injeção das ondas IC e LH, estão presentes juntamente com os termos colisionais, que representam a termalização dos íons rápidos sobre um plasma maxwelliano. Apresentamos, aqui, as primeiras evidências experimentais da interação LH-íons rápidos no tokamak JET. A análise de dados foi baseada na observação do conteúdo energético dos íons de minoria e das taxas de emissão de raios e de nêutrons no plasma, toda vez que a onda LH estava presente simultaneamente ao aquecimento com ondas IC. Observamos, nesta situação, que há um aumento de cerca de 20% do conteúdo energético dos íons rápidos, que corresponde a uma potência da onda absorvida de até, aproximadamente, 25%, dependendo dos parâmetros do plasma. O aumento de emissão de raios e de nêutrons, provenientes das reações de fusão, também confrrmou o aumento de energia dos íons rápidos quando a onda LH estava presente. Análises com FFT em experimentos onde a potência da onda estava 100% modulada, propiciaram o estudo da absorção de potência da onda LH de acordo com os níveis de superposição dos dois perfis de deposição sobre o plasma (ICe LH). / Attempts to achieve a steady-state operation in a reactor regime and the possibilities of stabilising MHD oscillations by controlling the plasma current density profile motivated studies of different methods of generating non-inductive current in reactor scenarios. The injection of Lower Hybrid waves (LH) in tokamak plasmas is considered as a possible route to reach this goal and has been successfully employed to generate plasma current by transferring momentum to the electrons in the direction parallel to the magnetic field through Electron Landau Damping (ELD). However, in a reactor operation regime, LHCD (Lower Hybrid Current Drive) efficiency can be affected, as it is predicted, by the damping of the wave on the 3.5 MeV particles, produced during fusion reactions. This interaction occurs through perpendicular Landau Damping since the particles can be considered as unmagnetized. In this work, the interaction of LH waves with particles is simulated through the interaction between the LH wave and ICRH driven minority íons, that can reach energies up to few MeV. Both phenomena can be described by a 1-D Fokker-Planck equation in velocity space that includes both quasi-linear diffusion coefficients due to ICRH and LH waves and collision terms which represent the fast ions slowing-down over a maxwellian plasma Once this Fokker-Planck equation is solved, the fast ion distribution function can be obtained in order to provide information on the fast minority íons. The first experimental evidence of the interaction of LH waves with ICRH minority íons in the MeV energy range is presented in this work. This interaction was detected in JET through measurements of the fast ion energy, ray and neutron ernission rates and by means of Fast Fourier Transform (FFT) analysis in experiments with 100% LH power modulation. An increase has been observed of approximately 20% in the fast ion energy content which corresponds about to 25% of LH power absorbed by the fast minority ions, depending on the plasma parameters. The increase of ray and neutron rates ernitted in the plasma and the FFT analysis confirm, respectively, the fast ion energy increase and a better damping of the wave when the overlap between IC and LH deposition profiles is maxirnized.
853

Música e invocação: uma oficina terapêutica com crianças com transtornos de desenvolvimento / Music and invocation: a therapeutic workshop with children with developmental disorders

Lima, Tiago de Moraes Tavares de 25 May 2012 (has links)
A presente pesquisa visa acompanhar os efeitos de uma oficina de música sobre um grupo de crianças com transtornos de desenvolvimento. O objetivo foi o de estabelecer algumas hipóteses sobre a compreensão que a atenção à dimensão da musicalidade pode fornecer sobre esses casos, bem como que tipo de contribuição é capaz de proporcionar em termos de tratamento. Diversas pesquisas constataram que há, na primeira infância, uma relação do bebê com o outro, cuidador, da qual é possível depreender certas qualidades musicais. Além disso, pela via da psicanálise, é desenvolvida a tese de que a voz e a música podem ser abordadas como uma porta de entrada para a relação arcaica entre o sujeito e o Outro, em especial através da noção de pulsão invocante termo cunhado por Jacques Lacan, mas aprofundado principalmente por autores posteriores. A leitura de alguns trabalhos em torno dessa questão conduziu a uma consideração sobre a importância da musicalidade da voz, bem como da sincronia temporal na relação entre o infans e o outro, para a constituição do sujeito. Apesar da potência invocadora da música, o circuito da pulsão invocante não se completa enquanto a dimensão diacrônica e a alternância entre presença/ausência não engendrarem a falta cujo destino na constituição do sujeito for o do recalque originário. O que coloca a questão de se, em primeiro lugar, em casos de psicose e autismo, a sensibilidade à musicalidade está preservada e, em segundo lugar, se uma intervenção terapêutica pela via da música produziria efeitos positivos na qualidade do laço social estabelecido por essas crianças. Os resultados obtidos na pesquisa alinham-se com os de outras pesquisas que mostram que a sensibilidade ao manhês e à musicalidade está preservada em casos de autismo. Os efeitos que a dimensão de surpresa envolvida na música produz em diferentes crianças apresentaram uma aproximação possível com as hipóteses diagnósticas e com a orientação da intervenção no tratamento desses casos. Por fim, pareceu-nos que a atenção à dimensão musical, seja presente na fala ou nos movimentos, é profícua para o trabalho com crianças com distúrbios de desenvolvimento como o autismo e a psicose, seja num enquadre institucional em grupo ou não / The present dissertation aims to verify the effects of a music workshop on a group of children with developmental disorders. The goal was to establish some hypotheses related to what an attention to the dimension of musicality may provide in terms of understanding to these cases, as well as the kind of contribution it may offer in terms of treatment. Several researches have established that there is, in early childhood, a relationship of the infans with the caring other from which it is possible to infer musical qualities. Furthermore, through psychoanalytical theory, we develop the thesis that voice and music may represent a doorway to the archaic relationship between the subject and the Other, specially through the notion of invocative drive a term coined by Jacques Lacan, but which was further developed by subsequent authors. The reading of some works related to this issue has lead to a reflection on the importance of the musicality of voice, as well as the temporal synchrony present in the relationship between infans and other, to the subjects constitution. Despite the invocative power of music, the circuit of the invocative drive cannot complete itself as long as the diachronic dimension and the alternating cycle of presence/absence produce the lack that is, in the constitution of the subject, destined for the original repression. Which raises the question, first of all, if the sensibility to music is preserved in cases of autism and child psychosis and, secondly, if a therapeutic intervention based on music would produce any positive effects in the quality of the social bonds established by these children. The results obtained line up with other researches which show that the sensibility to the motherese and musicality is preserved in cases of autism. Also, the effects that the surprise inherent to music have on different children present us with a possible approach to the diagnostic hypotheses and to the orientation of intervention in the treatment of these cases. Finally, we had indications that the attention to the musical qualities present in speech or movement is fertile in work with children with developmental disorders such as autism and psychosis, whether in an institutional context or not
854

Habitat structure drives the evolution of aerial displays in birds / Estrutura do hábitat influencia a evolução de displays aéreos em aves

Menezes, João Carnio Teles de 22 February 2019 (has links)
Physical properties of the environment may shape signalling traits by determining how effective signals are in influencing the behaviour of other individuals. Evidence abounds of signalling environment driving the evolution of colours and sounds, yet little is known about its influence upon gestural displays. Here, we performed a continent-wide phylogenetic comparative analysis to test the hypothesis that habitat structure drives the evolution of aerial sexual displays in passerine birds. We found that aerial displays are seven times more likely to evolve in open-habitat passerines than in forest ones, likely as a result of physical properties that allow aerial displays to transmit more broadly in open habitats. Our results provide an emblematic example of how environmental factors may help predict the direction of evolution of otherwise unpredictable sexual traits. The broader range of aerial displays in open habitats may also mean that females can sample more males, potentially leading to more intense sexual selection in open-habitat, aerial-displaying males / Propriedades físicas do ambiente podem influenciar a evolução de sinais ao determinar quão efetivos eles são em influenciar o comportamento de outro indivíduo. Diversos estudos mostram a influência do ambiente sobre a evolução de cores e sons. Entretanto, pouco se sabe de sua influência sobre sinais motores (i.e., displays). Nesse trabalho, conduzimos uma análise comparativa filogenética para testar a hipótese de que a estrutura do hábitat influencia a evolução de displays sexuais aéreos em aves Passeriformes. Descobrimos que display aéreos têm uma probabilidade sete vezes maior de evoluir em passeriformes de ambiente aberto do que nos florestais, provavelmente decorrente de propriedades físicas que permitem que displays aéreos sejam transmitidos mais amplamente em ambientes abertos. Nossos resultados são um exemplo emblemático de como fatores ambientais podem ajudar a prever a direção de evolução de caracteres sexuais, frequentemente tidos como imprevisíveis. O raio mais amplo de displays aéreos em ambientes abertos também pode permitir que fêmeas consigam amostrar mais machos da população, potencialmente intensificado a seleção sexual sobre machos de ambiente aberto que exibem displays aéreos
855

Contribution à la commande sans capteur mécanique d' actionneurs électriques motorisés par des machines synchrones à aimants permanents / Contribution to mechanical sensorless control of electric actuators motorized by permanent magnet synchronous machines

Zaim, Sami 12 July 2013 (has links)
Grace à leur forte densité de puissance et leur facilité de commande, les machines synchrones à aimants permanents (MSAP) sont fréquemment utilisées pour motoriser les actionneurs aéronautiques. Afin de pouvoir assurer le pilotage de ces moteurs, une information précise sur la position du rotor est nécessaire. Des capteurs de position sont utilisés pour mesurer la position et calculer la vitesse du rotor. Les inconvénients inhérents à l'utilisation de ces capteurs sont la diminution de la fiabilité du système et l'augmentation du poids, du volume, et du coût total du celui-ci. Dans ce travail, nous présentons une commande ne nécessitant pas le capteur de position à l'aide d'algorithmes d'estimation des variables mécaniques uniquement à partir de la mesure des courants statoriques. Après avoir abordé les méthodes de commande sans capteur adaptées aux hautes vitesses et basées sur l'estimation de la force électromotrice, nous établissons un état de l'art des méthodes de contrôle à basses vitesses basées sur la saillance du rotor. Une nouvelle méthode de commande sans capteur en basses vitesses et à l'arrêt, indépendante des paramètres du moteur et très simple à implanter est ensuite proposée et validée en simulation (sur un modèle de MSAP prenant en compte les effets de saturation) puis sur banc d'essais. Une étude analytique sur la convergence de l'algorithme et sa robustesse est également réalisée. Enfin, un processus d'initialisation ainsi qu'une méthode de transition sans à-coups entre les méthodes basses et hautes vitesses sont proposées et validées par simulation et expérimentation / For their high power density and ease of control, permanent magnet synchronous motors (PMSM) are widely used in more electric aircraft. In order to control PMSMs, precise information on the rotor position is required. This information is provided by position sensors which have inherent drawbacks despite their good precision: these sensors decrease reliability and increase weight, volume, and cost of the whole system. In this thesis, we present a mechanical sensorless control method by estimating the rotor speed and position only from the phase currents measurements. Sensorless control methods suitable for high speeds and based on back-EMF estimation are first discussed. Then, a state of the art in sensorless methods for low speeds operations is presented. A new sensorless control, independent from the motor parameters, is presented for operating at low speeds and standstill. Both simulations (on a PMSM model taking into account the saturation phenomenon) and experimental results show the effectiveness of this model-independent method. A convergence analysis and a robustness study of the proposed algorithm are also made. Finally, an initialization process and a method for smooth transition between low and high speeds methods are proposed and validated on an experimental test-bench
856

Protocole de diagnostic des entraînements asynchrones par références : application à la détection des déséquilibres mécaniques et des défauts de courroies / Diagnosis protocol of induction machines by references : application to the detection of mechanical unbalances and belts faults

Fournier, Etienne 26 November 2015 (has links)
Les applications entrainées par des moteurs asynchrones consomment à elles seules la majorité de l’énergie électrique utilisée dans le secteur industriel. Des défauts, majoritairement d’origine mécanique, sont susceptibles de se développer au cours du fonctionnement de ces systèmes et rendent nécessaires la mise en place d’une maintenance souvent onéreuse. Afin de réduire ces coûts et d’optimiser la disponibilité des matériels, des méthodes de diagnostic peuvent être développées afin de détecter au plus tôt l’apparition d’un défaut. Cependant, la fiabilité de ces algorithmes et l’automatisation du diagnostic sont complexifiées par la diversité des systèmes alimentés par les variateurs de vitesse industriels ainsi que par le changement de leur point de fonctionnement. Afin de répondre à ces problématiques, un protocole de diagnostic permettant de réaliser une détection sensible et robuste des défaillances mécaniques est développé dans ce travail. Cette méthode consiste à segmenter le plan couple-vitesse du moteur surveillé et à réaliser des références statistiques caractérisant son fonctionnement sain sur chacune des zones de fonctionnement. Des indicateurs de défaut peuvent ensuite être définis statistiquement afin de quantifier l’écart du système vis-à-vis de son comportement sain. Ces indicateurs sont ainsi indépendants du système surveillé et de son point de fonctionnement. Les principales applications ciblées par ce protocole sont les systèmes de compression, de pompage et de ventilation qui représentent une part importante de l’énergie électrique consommée dans le secteur industriel. Le protocole de diagnostic développé dans cette étude est validé expérimentalement dans le cadre de la détection de différentes niveaux de déséquilibre mécanique mais également pour la surveillance d’un système de transmission de type poulies-courroies. De plus, les campagnes expérimentales sont effectuées sur plusieurs systèmes électromécaniques dont les propriétés sont foncièrement différentes afin de valider les performances de normalisation de ce protocole. / Systems driven by induction motors consume most of the industrial electric supply. Mechanical faults may develop over time and disrupt their proper functioning, resulting in high maintenance expenditure. In order to reduce these costs and to improve machines availability, diagnosis methods can be developped to perform the early detection of incipient faults. However, the variety of industrial applications driven by induction motors complicates the automation of fault detection. To resolve these issues, a sensitive and robust diagnosis protocol has been developed in two stages. First, the torque-speed plane of the monitored motor is segmented in different functioning areas. Then, a statistical reference is achieved on each operating zone in order to characterize the healthy working of the system. Statistic-based indicators may then quantify the system deviation from its healthy behaviour. These indicators are therefore independent of the monitored system and of its functioning point. The applications targeted by this study are fans, pumps and compressors which are widely used in industrial processes. This diagnosis protocol is experimentally validated on the detection of several levels of mechanical unbalance and for the monitoring of V-belts drive health state. Moreover, test campaigns are achieved on varied electromechanical systems in order to validate the normalization performances of the developed protocol.
857

"Jogo patológico: análise por neuroimagem, neuropsicológica e de personalidade" / Pathological gambling: neuroimaging, neuropsychology and personality analyses

Moreira, Daniel Fuentes 24 August 2004 (has links)
Há evidências de comportamentos associados à impulsividade e prejuízos de funções de lobo frontal, sobretudo das funções executivas, em jogadores patológicos. Na tentativa de melhor caracterizar o fenômeno do jogo patológico, este estudo teve por objetivo verificar a utilidade de diferentes medidas de personalidade, desempenho em testes neuropsicológicos e análise das estruturas, na discriminação entre amostras jogadores patológicos e voluntários normais. Foram avaliados, em dois estudos, 50 jogadores patológicos e 50 controles normais, pareados por sexo, idade e anos de escolaridade formal. A bateria de testes neuropsicológicos consistiu de testes clássicos e computadorizados, avaliando funções atencionais e executivas. A personalidade foi avaliada através de inventários de auto-preenchimento desenvolvidos a partir de diferentes referenciais teóricos. Os dados de neuroimagem foram obtidos através de exames de ressonância magnética e foram analisados através do método automático de morfometria baseada no voxel. As pontuações obtidas nos testes neuropsicológicos e os resultados das diferentes medidas de personalidade revelaram que jogadores patológicos apresentam disfunção executiva e exacerbação de traços impulsivos e compulsivos. Os achados de ressonância magnética indicaram menor volume do núcleo caudado à esquerda e maior volume das porções dorsolaterais do córtex pré-frontal esquerdo na amostra de jogadores em relação aos controles. Estes achados, associados à relação encontrada entre impulsividade e compulsividade com as porções posteriores e anteriores do giro cingulado, respectivamente e sub-regiões dos gânglios da base, indicam que jogadores patológicos apresentam falhas das circuitarias cerebrais implicadas na regulação do comportamento. / High impulsivity and neuropsychological deficits associated to frontal lobes, specifically executive dysfunction, are reported among pathological gamblers (PG). In order to better understand the pathological gambling phenomena, the aim of this study was to verity the ability of personality measures, neuropsychological tests and brain structures to discriminate a sample of pathological gamblers from a sample of normal volunteers. A two-study format was adopted evaluating 50 pathological gamblers matched to 50 healthy volunteers according to gender, age and years of formal education. The neuropsychological measures consisted of classic and computerized tests that evaluate attentional and executive functions. Personality traits were measured by self-report scales developed under different theoretical approaches. Neuroimage data were analyzed using an optimized Voxel-Based Morphometric protocol. The scores obtained on the neuropsychological tests and self-report inventories showed that pathological gamblers present executive dysfunction and high personality traits of impulsivity and compulsivity. The magnetic resonance imaging of pathological gamblers showed smaller caudate volume on the left hemisphere and larger prefontal dorsolateral areas on left frontal cortex than the control group. An association between posterior and anterior cingulated, basal ganglia sub regions and compulsivity and impulsivity was also found too. These data suggest that pathological gamblers have dysfunctional brain circuits implicated in behavioural regulation.
858

Implication du système nerveux central dans la faiblesse musculaire périphérique du patient atteint de broncho-pneumopathie chronique obstructive / Involvement of central nervous system in peripheral muscle weakness of patients with chronic obstructive pulmonary disease

Alexandre, François 03 July 2015 (has links)
La faiblesse des muscles périphériques, définie par une diminution de la force maximale volontaire en dehors de tout état de fatigue neuromusculaire, est une complication fréquente de la broncho-pneumopathie chronique obstructive (BPCO). La force maximale volontaire dépend à la fois des propriétés musculaires périphériques (i.e. volume et architecture musculaire, qualités contractiles) et de la capacité du système nerveux à activer le muscle maximalement. Dans la BPCO, plusieurs travaux ont souligné l'existence paradoxale d'une perte de force maximale volontaire sans altérations musculaires périphériques et sans qu'un déficit d'activation volontaire n'ait clairement été identifié. Pourtant, les patients atteints de BPCO présentent de nombreuses altérations du système nerveux, compatibles avec une capacité d'activation volontaire altérée.L'objectif de ce travail de thèse était donc de tester l'implication du système nerveux dans la faiblesse musculaire de la BPCO et d'en déterminer les mécanismes sous-jacents. Au cours de nos travaux, nous avons mis en évidence une activité corticale diminuée dans la BPCO lors de contractions maximales et sous-maximales volontaires. Nous avons par ailleurs rapporté une perte d'excitabilité du cortex moteur et un déficit d'activation volontaire spécifique aux patients atteints de faiblesse musculaire. Ces résultats sont en accord avec une implication des altérations cérébrales dans la faiblesse musculaire périphérique de la BPCO. Nous sommes ensuite parvenus à identifier une origine potentielle des altérations cérébrales : les désaturations en O2 au cours du sommeil avec mouvements non-rapides des yeux (NREM). Cette hypothèse a été corroborée par l'observation d'un niveau d'activation volontaire réduit chez les patients désatureurs en sommeil NREM. En revanche, aucune répercussion significative n'a pu être observée sur la force maximale volontaire de ces patients, suggérant l'existence d'un mécanisme compensatoire. In fine, nos résultats constituent une avancée importante dans la compréhension du phénomène de faiblesse musculaire, classiquement attribué à la seule perte de masse musculaire. L'implication du système nerveux central dans la faiblesse musculaire ouvre notamment la voie à de nouvelles modalités de prise en charge par des approches spécifiques, dans l'optique de lutter contre la faiblesse musculaire et ses multiples répercussions négatives dans la vie du patient atteint de BPCO. / Peripheral muscle weakness, as defined by a reduced voluntary strength outside any state of neuromuscular fatigue, is a common complication of chronic obstructive pulmonary disease (COPD). Maximal voluntary strength is determined by both peripheral muscle properties (i.e. muscle volume and architecture, contractile quality) and the nervous system's ability to activate the muscle maximally. In COPD, many studies highlighted the paradoxical existence of maximal voluntary strength loss without any peripheral muscle impairment, and without a clearly identified voluntary activation deficit. However, patients with COPD exhibited several nervous system alterations compatible with a reduced maximal voluntary activation capacity. The aim of this thesis was to test the nervous system implication in COPD muscle weakness and to determine the involved mechanisms. As major results, we found a reduced cortical activity in COPD during maximal and sub-maximal voluntary contractions. Furthermore, we reported reduced motor cortex excitability and voluntary activation deficit, specifically in patients with muscle weakness. These results are in accordance with an involvement of cortical alterations in COPD muscle weakness. Then, we indentified a potential origin for cortical alterations: O2 desaturation during non-rapid eye movement (NREM) sleep. This hypothesis has been corroborated by the observation of a reduced voluntary activation in patients with NREM sleep desaturation. However, no significant repercussion could have been observed on maximal voluntary strength in these patients, suggesting a compensatory mechanism.Our results are an important step forward in understanding the COPD muscle weakness that was classically attributed to loss of muscle mass only. The involvement of the central nervous system in COPD muscle weakness also brings about new patient care opportunities via tailored approaches, in order to fight against muscle weakness and its deleterious consequences on a patient's life.
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飲食剝奪操弄與鋰鹽去價值程序對大白鼠舔舐行為的影響 / The Effects of Food Deprivation and Lithium Chloride-Induced Devaluation on Licking Behavior

藍丞弘, Lan, Churng-Horng Unknown Date (has links)
本研究操弄受試的食物剝奪程度以及鋰鹽(LiCl)去價值程序,觀察此兩種實驗操弄對於大白鼠舔舐行為的影響,以探討飢餓驅力調節完結行為的機制。實驗一連續觀察8天大白鼠舔舐15%蔗糖液的表現,結果顯示初期兩天剝奪受試和自由吃食受試的舔舐表現並沒有顯著差異,第三天起剝奪組才顯著高於自由吃食組。實驗二待大白鼠習於食物剝奪狀態下舔舐15%蔗糖液之後,進行僅舔舐空管的消除情境測試。實驗結果顯示將剝奪狀態改為自由吃食,不論有無接受誘因學習都不能降低受試舔舐空管的表現。實驗三則待大白鼠習於食物剝奪狀態下舔舐25%蔗糖液之後,接受空管測試(實驗三A、B、C)與舔水消除情境測試(實驗三B、C)。實驗三結果如同實驗二,將剝奪狀態改為自由吃食,不論有無接受誘因學習都不能降低受試舔舐空管或舔水的表現。實驗四使用柳橙香料配加蔗糖液(20%)進行舔舐訓練,以僅含柳橙香料水進行消除情境測試。實驗結果顯示受試不論是由剝奪狀態轉為自由吃食,或由自由吃食轉為剝奪,都顯示出當驅力高舔舐表現高或驅力低表現低的現象。實驗五進行鋰鹽去價值實驗,大白鼠先擁有舔飲柳橙香料糖精液(實驗五A)或草莓香料食鹽水(實驗五B)的經驗後,再進行鋰鹽去價值程序。實驗結果顯示大白鼠唯有舔舐香料糖精液或香料食鹽水後接受鋰鹽注射才能降低其舔舐香料水的表現;糖精-鋰鹽配對、糖精-鋰鹽配對後再舔飲一次糖精液,以及香料水-鋰鹽配對都無法降低受試舔飲香料水的表現。糖精或食鹽水只要和鋰鹽配對過,便能產生味覺嫌惡。本研究結論如下:(1)飢餓驅力調節舔舐行為的能力只顯現在舔飲蔗糖液以及舔舐柳橙香料水的消除情境測試中;(2)香料與糖精或香料與食鹽必須同時呈現與鋰鹽配對才能降低香料引發舔舐行為的能力。 / The effects of food deprivation and lithium chloride (LiCl)-induced devaluation on licking behavior were studied for the regulatory mechanism of hunger drive on licking behavior. The first experiment for measuring the licking of 15% sucrose solution for 8 days and found that deprived subjects did not lick more than non-deprived ones until the third day. In the second experiment, the rats trained to lick 15% sucrose in a food-deprivation state were shifted to a non-deprivation state and tested under extinction procedure by using the empty tube. This shift in deprivation did not suppress licking in empty tube test for subjects with or without incentive learning experiences. In the third experiment, the rats trained to lick 25% sucrose in a food-deprivation state were shifted to a non-deprivation state and tested in empty tube (Exp. 3A, B, C) or water-licking test (Exp. 3B, C) conditions. Independent of incentive learning, the shift in deprivation did not suppress licking in these two kinds of extinction conditions although the concentration of sucrose was increased. In the fourth experiment, rats were trained to lick 20% sucrose mixed with orange flavor and tested in orange flavor water-licking test condition. Deprived rats licked more than non-deprived ones in the test condition whether they were trained under deprivation or non-deprivation. In the fifth experiment, rats were trained to lick orange flavor saccharin solution (Exp. 5A) or strawberry flavor sodium chloride (NaCl) solution (Exp. 5B) and then tested by the LiCl devaluation procedure. Flavored saccharin or flavored NaCl paired with LiCl suppressed rats to lick flavored water. But none of saccharin paired with LiCl, incentive learning after saccharin devaluation, and flavored water paired with LiCl had any significant effect. Saccharin or NaCl paired with LiCl could induce taste aversion. In conclusion, hunger drive modulating licking behavior was only found in licking sucrose or the flavored water-licking test condition. Further, only flavored saccharin or flavored NaCl solutions paired with LiCl could suppress licking flavored water.
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Fast wave heating and current drive in tokamaks

Laxåback, Martin January 2005 (has links)
This thesis concerns heating and current drive in tokamak plasmas using the fast magnetosonic wave in the ion cyclotron range of frequencies. Fast wave heating is a versatile heating method for thermonuclear fusion plasmas and can provide both ion and electron heating and non-inductive current drive. Predicting and interpreting realistic heating scenarios is however difficult due to the coupled evolution of the cyclotron resonant ion velocity distributions and the wave field. The SELFO code, which solves the coupled wave equation and Fokker-Planck equation for cyclotron resonant ion species in a self-consistent manner, has been upgraded to allow the study of more advanced fast wave heating and current drive scenarios in present day experiments and in preparation for the ITER tokamak. Theoretical and experimental studies related to fast wave heating and current drive with emphasis on fast ion effects are presented. Analysis of minority ion cyclotron current drive in ITER indicates that the use of a hydrogen minority rather than the proposed helium-3 minority results in substantially more efficient current drive. The parasitic losses of power to fusion born alpha particles and beam injected ions are concluded to be acceptably low. Experiments performed at the JET tokamak on polychromatic ion cyclotron resonance heating and on fast wave electron current drive are presented and analysed. Polychromatic heating is demonstrated to increase the bulk plasma ion to electron heating ratio, in line with theoretical expectations, but the fast wave electron current drive is found to be severely degraded by parasitic power losses outside of the plasma. A theoretical analysis of parasitic power losses at radio frequency antennas indicates that the losses can be significantly increased in scenarios with low wave damping and with narrow antenna spectra, such as in electron current drive scenarios. / QC 20100506

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