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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.
51

MOTIVATION FOR PARTICIPATION IN INTENSE, CHARITABLE ATHLETIC EVENTS

WESTRICH, KATE ANN 30 June 2003 (has links)
No description available.
52

Kan tuggning leda till träningsvärk i massetermuskulaturen – en experimentell studie

Domi, Ilir, Neziri, Besart January 2012 (has links)
Syfte: Målsättningen med studien är att hos friska kvinnor utvärdera om intensiv tuggning leder till en proprioceptiv allodyni i massetermuskulaturen. Följande hypoteser testades i studien: 30 minuters intensivt tuggande leder till (1) ökad trötthet och smärta, (2) sänkt smärttröskel, (3) ökad vibrotaktil känslighet (4) samt träningsvärk i massetermuskulaturen bilateralt. Material och Metod: 16 friska kvinnor (medelålder 25.8 ± 5.0 år) deltog i studien som bestod av två 60-minuters sessioner med 24-timmars uppföljning. Vid ena sessionen tuggade försökspersonerna på ett grekiskt tuggummi (Masticha Chios) i 5-minuters intervaller under 30 minuter, och vilade vid den andra sessionen. En vibrameter användes för att mäta vibrationströskel, upplevd vibrationsintensitet och upplevd vibrationsobehag. Upplevd trötthet och upplevd smärtintensitet värderades enligt en visuell analog skala 0-100 mm (VAS skala). Smärttröskeln mättes med en algometer som applicerades på massetermuskelns fäste. Två vägs variansanalys användes för att testa utfallsvariabler för upprepade mätningar och Dunnett’s posthoc-test. Resultat: En signifikant skillnad kunde ses mellan tuggning och icke tuggning för vibrationströskeln (P < 0.001); upplevda tröttheten (P < 0.001); smärttröskeln (P < 0.01); upplevda vibrationsobehaget (P < 0.05). Inga signifikanta skillnader observerades för upplevd smärta och upplevd vibrationsobehag. Däremot kunde en signifikant ökning ses över tid för vibrationströskeln och den upplevda tröttheten. Konklusion: Våra fynd indikerar att det ej finns något samband mellan intensiv tuggning och träningsvärk i massetermuskulaturen. Däremot resulterade tuggningen i ökad muskeltrötthet och vibrationsobehag, samt signifikant högre trösklar för smärta och vibration under försökets gång. Proprioceptiv allodyni kunde ej påvisas. / Aims: To evaluate if intense chewing leads to proprioceptive allodynia in the masseter muscle, and test if (1) pain and fatigue are increased after intense chewing, (2) pressure pain thresholds are decreased after intense chewing, (3) vibration thresholds are increased after intense chewing, (5) intense vibrations exacerbate pain after intense chewing. Materials and Methods: 16 healthy female volunteers (mean age 25.8 ± 5 years) participated in two 60-minute sessions, each with 24-hour follow-ups. In the first session, the subjects were instructed to chew on a viscous chewing gum (Masticha Chios). In the other session the participant were assigned a control task where no chewing was performed. Perceived intensity of vibration and perceived discomfort were assessed with a Vibrameter® on a 0-50-100 visual analog scale (VAS). Two 0-100 mm visual analog scales measured pain intensity and perceived fatigue. The pain threshold was measured with an electronic algometer. These variables were measured to assess delayed onset muscle soreness. All measurements were made on the masseter muscles. Two-way analysis of variance for repeated measures and Dunnett’s post hoc test was used to test for significant alterations in the outcome variables. Results: Significant differences were observed between chewing and no-activity for vibration threshold (P<0.001); perceived fatigue (P<0.001); pain threshold (P<0.01) and vibration discomfort (P<0.05). No significant differences were seen for perceived pain and perceived intensity of vibration. A significant increase over time could only be observed for vibration threshold (P<0.01) and perceived fatigue (P<0.05). Conclusion: Our findings suggest that there is no relation between intense chewing and delayed onset muscle soreness in the masseter muscles. Intense chewing evoked moderate levels of fatigue and discomfort, and a hypoalgesia to mechanical stimulation, and reduced vibrotactile sensitivity.
53

APPLICATION DE LA RESONANCE PARAMAGNETIQUE ELECTRONIQUE A CHAMP INTENSE A L'ETUDE DE RADICAUX ORGANIQUES DANS LES METALLOPROTEINES

Dorlet, Pierre 17 November 2000 (has links) (PDF)
Les observations de radicaux organiques dans les enzymes et de leur implication dans les cycles catalytiques n'ont cessé de croître ces dernières années. La spectroscopie de résonance paramagnétique électronique (RPE) à champ intense est un outil de choix pour l'étude de radicaux organiques car elle permet de résoudre la faible anisotropie du tenseur g pour ces espèces paramagnétiques. Un spectromètre fonctionnant à 285 GHz / 10.5 teslas a été construit dans la Section de Bioénergétique du centre d'études du CEA de Saclay. Le travail présentée dans ce mémoire de thèse a porté sur l'application de la RPE à champ intense à l'étude de radicaux organiques présents dans le photosystème II, qui est l'enzyme de dégagement d'oxygène, ainsi que dans les composés I de deux peroxydases, la cytochrome c peroxydase et la prostaglandine synthase.<br />Le premier chapitre présente la technique de RPE à champ intense de façon générale et introduit l'instrumentation. Les aspects généraux du photosystème II utiles dans la suite du mémoire sont également présentés.<br />Le second chapitre montre comment les propriétés anisotropes du tenseur g ont été utilisées pour obtenir des informations structurales quant à l'orientation de radicaux organiques dans le photosystème II.<br />Les enzymes étudiées dans ce travail de thèse sont des métalloprotéines. Les situations de couplages magnétiques entre les centres métalliques et les radicaux organiques présents sont souvent rencontrées dans ces cas-là. Les chapitres 3 à 5 portent sur l'étude de tels systèmes couplés.<br />Le dernier chapitre présente des situations pour lesquelles l'étude des valeurs de g permet d'obtenir des informations sur l'environnement électrostatique du radical étudié. Cette propriété déjà connue pour les radicaux tyrosyles et semiquinones est étendue aux radicaux anions de phéophytines.
54

Training, taper and recovery strategies for effective competition performance in judo

Papacosta-Kokkinou, Elena January 2015 (has links)
Post-exercise carbohydrate-protein consumption and tapering periods during training periodisation have been proposed as effective recovery strategies in several sports; however, limited attention has been given to judo. Apart from training and recovery, effective competition performance can also be influenced by several stimuli on the competition day, which may be manifested as distinct endocrine responses. The main objective of this thesis was to influence effective competition performance in judo, through examining strategies that can aid recovery from intense exercise/training and examining endocrine responses to competition. Three experimental studies on recovery were completed (chapters 3-5) followed by an observational study on a judo competition day (chapter 6) in elite, national level, male judo athletes. Studies 1 and 2 examined the effects 1000 ml of post-exercise chocolate milk (CM) consumption compared with water (W) following an intense judo training session (chapter 3) and five days of intense judo training with concomitant weight loss (chapter 4) on the recovery of salivary cortisol (sC), salivary testosterone (sT), salivary testosterone:cortisol (sT/C) ratio, salivary secretory IgA (SIgA) absolute concentrations and secretion rate, muscle soreness, mood state and judo-related performance. Study 1 (n=10) did not show any beneficial effects of acute CM consumption on aspects of recovery of any of the measured variables, except for a lower perception of soreness (p<0.05) and a tendency for better push-up performance (p=0.09). Study 2 (n=12) showed that post-exercise CM consumption resulted in significantly lower sC levels, a tendency for higher sT/C ratio (p=0.07), better judo-related performance, lower muscle soreness and reduced mood disturbance (p<0.05) with W. In addition, post-exercise consumption of CM resulted in a 1.1% decrease in body weight, indicating that CM is an effective recovery beverage during periods of intense judo training without affecting intentional weight loss. Study 3 (n=11) examined the effects of a 2-week exponential taper following 2 weeks of intense judo training on recovery of the aforementioned variables. Within 12 days of tapering there were evidence of enhanced performance, lower sC, higher sT and higher sT/C ratio, higher SIgA secretion rate, lower muscle soreness and reduced mood disturbance, indicating that a tapering period of ~10 days is an effective recovery strategy for optimising judo performance. Study 4 observed the responses of sC, sT, SIgA absolute concentrations and SIgA secretion rate and self-measured anxiety state in the winners (n=12) and losers (n=11) of a judo competition. Winners presented significantly higher morning sC levels and higher cognitive anxiety in anticipation of the competition, as well as a tendency for higher SIgA secretion rate (p=0.07) and significantly higher saliva flow rate mid-competition. These findings indicate that winners experienced higher arousal levels and that anticipatory sC might have some predictive value for winning performance in judo. This thesis concludes that nutrition and tapering are both important aspects of effective recovery; CM can be an effective nutritional recovery aid during periods of intense judo training and tapering for 7-12 days can optimise judo performance and can be implemented prior to competitions. In addition, elevated sC levels in anticipation of a judo competition and higher levels of arousal could have some predictive value for winning performance in judo. Further research could focus on strategies to increase levels of arousal in anticipation of competition.
55

Measurements of ultrashort intense laser-induced fragmentation of simple molecular ions

Sayler, A. Max January 1900 (has links)
Doctor of Philosophy / Department of Physics / Itzhak Ben-Itzhak / Present laser technology allows for the production of ultra short (&7 fs) intense (.1016 W/cm2)pulses, which are comparable in duration and interaction strength to the vibrational period and the interaction that binds the electron in molecules, respectively. In this intense-field ultra short-pulse regime one can both measure and manipulate dynamics on the femtosecond timescale. To probe the dynamics of laser-matter interactions in this regime, we have chosen to start from the simplest possible molecule - H+ 2 , which can either dissociate into H + p or ionize into p + p + e. We have designed and employ a coincidence three-dimensional momentum imaging technique which allows us to measure ionization and dissociation of a molecular ion beam target simultaneously, while completely separating the two channels from each other. By varying the laser intensity and the pulse duration, we measure the intensity and pulse length dependent momentum distributions for laser induced fragmentation of H+ 2 at 790 nm. These dissociation measurements are in agreement with the phenomena predicted using the adiabatic Floquet picture, e.g. bond softening, in addition to more sophisticated calculations done by solving the time-dependent Schrodinger equation in the Born-Oppenheimer representation. Furthermore, the structure seen in ionization in our measurements and soon after by others is explained via a unified diabatic Floquet picture, which includes both ionization and dissociation in a single intensity and wavelength dependent picture that includes nuclear motion. Additionally, we use the same experimental techniques and apparatus to probe the laser-induced dynamics of multi-electron diatomic molecules, e.g. O+2, N+2, and ND+. The most probable dissociation and ionization pathways producing the features seen in these measurements are discerned using the angular and kinetic-energy-release distributions in conjunction with the diabatic Floquet picture. Finally, we extend these experimental techniques and interpretive models to the simplest polyatomic molecule - H+ 3 , whose fragmentation presents challenges both in our first-of-their-kind experiments and in physical interpretation.
56

Avaliação da Terapia Fotodinâmica aplicada com luz intensa pulsada em pele sadia de suínos e diferentes fotossensibilizadores / Evaluation of Photodynamic Therapy using intense pulsed light on porcine healthy skin with different photosensitizers

Requena, Michelle Barreto 17 July 2015 (has links)
A Terapia Fotodinâmica (TFD) caracteriza-se por um conjunto de processos físicos, químicos e biológicos que ocorre após a administração de compostos fotossensibilizantes, que ficam retidos preferencialmente nos tecidos alterados, ao que se segue a irradiação com luz visível, ativando esses fotossensibilizadores (FS) por meio da absorção da luz. Nesta modalidade terapêutica, ocorrem mecanismos de transferência de energia entre o FS e o oxigênio molecular presente nos tecidos, gerando espécies reativas de oxigênio capazes de levar as células à morte. A TFD tem uma de suas principais aplicações no tratamento do câncer de pele, e este trabalho tem por objetivo otimizar tal aplicação utilizando a luz intensa pulsada (LIP) como sistema de irradiação. Na literatura, estudos demonstram a eficiência da aplicação de LIP na área dermatológica e estética na remoção de pelos, tratamento de lesões vasculares, acnes e no fotorejuvenescimento da pele, através de efeitos fotoquímicos e térmicos, mas não há relatos sobre aplicações terapêuticas para o câncer de pele. A aplicação da LIP em TFD leva a diferentes tipos de vantagens destacando-se a possibilidade de diminuição do tempo de tratamento, com consequente redução da dor durante o procedimento. Além disso a possibilidade de aplicação de misturas de FSs que absorvam em diferentes comprimentos de onda, promovendo a ativação simultânea de diferentes bandas de absorção que pode levar a potencialização do efeito da TFD. A ideia da irradiação com LIP é permitir a possibilidade de excitar diferentes bandas do FS simultaneamente, bem como reduzir os níveis de saturação do oxigênio dos tecidos devido a longos períodos de irradiação, minimizando também possíveis efeitos térmicos ocasionados pela irradiação prolongada. Neste trabalho, estudou-se a TFD com um equipamento comercial de LIP (Intense Pulse Light, HKS801) utilizando dois precursores do FS endógeno Protoporfirina (PpIX), 5-ácido aminolevulínico (ALA) e aminolevulinato de metila (M-ALA) e os FSs Photodithazine (PDZ) e Indocianina verde (ICV), em modelo de pele normal de suínos. As diferenças relativas à aplicação tópica de ALA e M-ALA por meio de creme e através da aplicação em sistema de injeção de alta pressão sem agulhas (SAFE INJECT) foram avaliadas. O sistema de injeção também foi utilizado para disponibilização dos FSs na pele. O estudo in vitro mostrou que a LIP interagiu com todos os FSs e levou à multiativação de suas bandas. Com relação aos estudos in vivo observou-se diferentes aspectos do uso da LIP para TFD. A avaliação de fluorescência mostrou que a distribuição por injeção foi mais homogênea, sugerindo a possibilidade de protocolos de TFD menos demorados. A análise termográfica mostrou que não ocorre aquecimento relevante do tecido nas aplicações de LIP em aplicações de TFD no protocolo utilizado. A avaliação histológicas das condições entre 24 e 48 horas permitiu observar as diferentes fases do processo cicatricial em função do tempo decorrido. O estudo possibilitou maior entendimento sobre os efeitos da LIP em tecido biológico, especialmente em associação à TFD. Também foi estabelecido, pela primeira vez, um modelo de protocolo para investigação do uso da LIP em modelo animal para TFD em pele, que pode ser extrapolado em futuros estudos para tratamentos oncológicos e dermatológicos. Consideradas as possibilidades oferecidas e a pronta disponibilidade do dispositivo para irradiação, a TFD com LIP torna-se viável técnica e comercialmente para uso clínico. / Photodynamic Therapy (PDT) is mainly composed of physical, chemical, and biological processes that occur after administration of photosensitizing compounds, which are selectively held in abnormal tissues. After visible light irradiation, those photosensitizers (PS) are activated by light absorption. During treatment, energy transfer mechanisms take place between PS and molecular oxygen that is available in tissues, promoting the generation of reactive oxygen species that bring cells to death. One of this technique´s main applications is skin cancer treatment, and this study aims to optimize such a PDT application by using intense pulsed light (IPL) as irradiation system. Literature shows IPL efficacy on dermatological aesthetic procedures, such as hair removal, treatment of vascular lesion, acne and skin photorejuvenation, promoted by photochemical and thermal effects. However, skin cancer treatment was never reported. Using IPL for PDT may bring advantages such as reducing the treatment sessions, which reduces pain during procedures, and the ability to use PS blends that will absorb in different regions of wavelengths, resulting in simultaneous activation of different absorption bands and improving PDT effect. Shorter irradiation may reduce oxygen depletion due to long irradiation periods, and major thermal effects. In this study, PDT was performed using an IPL commercial device (Intense Pulse Light, HKS801) with the application of two PpIX precursors (ALA and MAL) and the exogenous PS Photodithazine (PDZ) and Indocyanine Green (ICG) on porcine health skin model. Administration of the PS or PpIX precursors were investigated both by vehiculation via cream and by high pressure, needle-free injection (SAFE INJECT). The results obtained in this study showed that the damage induced by PDT using the needle-free injection is more expressive than for cream vehiculation. The in vitro study showed that IPL interacted with all PS and promoted absorption bands multi-activation. The in vivo studies showed different aspects of using IPL for PDT. Fluorescence investigation showed that the distribution by the needle-free injection was more homogeneous, suggesting that shorter PDT protocols are possible. Thermography imaging showed that no relevant heating was observed for IPL applications of PDT during the protocols of choice. Histological analysis of conditions between 24 and 48 hours allowed observing the different stages of the healing process as a function of time. This study provided deeper understanding of IPL effects in biological tissues, and particularly when associated to PDT. In addition, for the first time, an investigation protocol for the use of IPL-PDT in porcine healthy skin was designed, which can be extrapolated for future studies on cancer and skin lesions. Given the possibilities and the prompt availability of the irradiation device, IPL-PDT is readily available technically and commercially for clinical use.
57

Distribuição de freqüência e temporal de chuvas intensas.

Quadros, Luciana Espíndula de 24 July 2008 (has links)
Made available in DSpace on 2017-07-10T19:24:32Z (GMT). No. of bitstreams: 1 Luciana Espindula de Quadros.pdf: 521227 bytes, checksum: 7de1f8de229e20d0ac01c9f1aa7609c6 (MD5) Previous issue date: 2008-07-24 / This work aiming at contribute for the planning of activities that are influenced by the intensity of hasty water, in that the results condition technical or strategic decisions of order in activities as farming, civil construction and tourism. It was analizy historical series of maximum haste for different durations obtained of raingouge in the town of Cascavel-PR, planning an intense rain probability distribution model through the distribution generalized be adjusted Moments LH for estimate his parameters and the statistical test proposed by Wang (1998) for verification of the quality of the settlements developed in the environment Matlab. Beyond that, them referred series were adjusted through the distribution Gumbel for effect of comparison with the GEV. The results show that the distribution of the kind VEI of the GEV, that corresponds the distribution Gumbel, is not adequate for big periods of return therefore substime the values of the distribution kind VEII. As results are presented the estimates of the parameters of the GEV, the values of the rates for the time being LH, the period of each return duration of rain and the hydrographs of project. / Este trabalho visa contribuir para o planejamento de atividades que são influenciadas pela intensidade da água precipitada, em que os resultados condicionam decisões de ordem técnica ou estratégica em atividades como agropecuária, construção civil e turismo. O objetivo é ajustar um modelo de distribuição de probabilidades de chuva intensa pela distribuição generalizada de valores extremos (GEV), utilizando momentos LH para estimar seus parâmetros e o teste estatístico proposto por Wang (1998) para verificação da qualidade dos ajustes desenvolvidos no ambiente Matlab. Foram analisadas séries históricas de precipitação máximas para diferentes durações, obtidas de pluviográfos no município de Cascavel-PR. Além disso, as referidas séries foram ajustadas por meio da distribuição Gumbel para efeito de comparação com a GEV. Os resultados mostram que a distribuição do tipo VEI da GEV, que corresponde à distribuição Gumbel, não é adequada para grandes períodos de retorno, pois subestima os valores da distribuição tipo VEII. Como resultados são apresentados as estimativas dos parâmetros da GEV, os valores das taxas de momentos LH, o período de retorno para cada duração de chuva e o hietograma de projeto.
58

Distribuição de freqüência e temporal de chuvas intensas.

Quadros, Luciana Espíndula de 24 July 2008 (has links)
Made available in DSpace on 2017-05-12T14:47:53Z (GMT). No. of bitstreams: 1 Luciana Espindula de Quadros.pdf: 521227 bytes, checksum: 7de1f8de229e20d0ac01c9f1aa7609c6 (MD5) Previous issue date: 2008-07-24 / This work aiming at contribute for the planning of activities that are influenced by the intensity of hasty water, in that the results condition technical or strategic decisions of order in activities as farming, civil construction and tourism. It was analizy historical series of maximum haste for different durations obtained of raingouge in the town of Cascavel-PR, planning an intense rain probability distribution model through the distribution generalized be adjusted Moments LH for estimate his parameters and the statistical test proposed by Wang (1998) for verification of the quality of the settlements developed in the environment Matlab. Beyond that, them referred series were adjusted through the distribution Gumbel for effect of comparison with the GEV. The results show that the distribution of the kind VEI of the GEV, that corresponds the distribution Gumbel, is not adequate for big periods of return therefore substime the values of the distribution kind VEII. As results are presented the estimates of the parameters of the GEV, the values of the rates for the time being LH, the period of each return duration of rain and the hydrographs of project. / Este trabalho visa contribuir para o planejamento de atividades que são influenciadas pela intensidade da água precipitada, em que os resultados condicionam decisões de ordem técnica ou estratégica em atividades como agropecuária, construção civil e turismo. O objetivo é ajustar um modelo de distribuição de probabilidades de chuva intensa pela distribuição generalizada de valores extremos (GEV), utilizando momentos LH para estimar seus parâmetros e o teste estatístico proposto por Wang (1998) para verificação da qualidade dos ajustes desenvolvidos no ambiente Matlab. Foram analisadas séries históricas de precipitação máximas para diferentes durações, obtidas de pluviográfos no município de Cascavel-PR. Além disso, as referidas séries foram ajustadas por meio da distribuição Gumbel para efeito de comparação com a GEV. Os resultados mostram que a distribuição do tipo VEI da GEV, que corresponde à distribuição Gumbel, não é adequada para grandes períodos de retorno, pois subestima os valores da distribuição tipo VEII. Como resultados são apresentados as estimativas dos parâmetros da GEV, os valores das taxas de momentos LH, o período de retorno para cada duração de chuva e o hietograma de projeto.
59

Caractérisation de la variabilité phénotypique de ressources génétiques de Stevia rebaudiana (Bertoni) : analyse des composantes du rendement et critères de sélection en condition de production / Characterisation of the phenotypic variability within Stevia rebaudiana (Bertoni) genetic resources : analysis of yield components and selection criteria in field condition

Hastoy, Cécile 20 July 2018 (has links)
La consommation excessive de sucres conduit à l’augmentation de désordres métaboliques, tels que l’obésité et le diabète. Les consommateurs souhaitent une alimentation plus saine à base de produits d’origine naturelle. Stevia rebaudiana, l’herbe sucrée du Paraguay, accumule dans ses feuilles des glycosides de stéviol (SGs) considérés comme des édulcorants naturels intenses, dont le marché est en pleine expansion au niveau mondial. Dans ce contexte, la société Oviatis implante une filière BIO de Stevia rebaudiana en Nouvelle-Aquitaine. Les objectifs de cette thèse CIFRE sont de caractériser la variabilité phénotypique d’une collection de cette espèce en vue de la mise en place future d’un programme de sélection. Les composantes du rendement, de biomasse foliaire, de quantité et qualité des SGs et de la réponse à Septoria sp. ont été finement décrites en condition de production pluriannuelle et multi-sites ou en conditions contrôlées. Ces travaux ont permis de 1) développer des outils de phénotypage métabolique, pathologique et au champ, 2) évaluer la variabilité phénotypique de cette collection de Stevia rebaudiana en condition de production et identifier les descripteurs de cette variabilité, 3) identifier les facteurs ontogéniques, abiotiques et culturaux impliqués dans la variabilité de cette collection, 4) évaluer la variabilité de réponses face à la septoriose. Ces résultats permettent d’identifier les critères de sélection de cette espèce pour une production BIO en Nouvelle Aquitaine, ainsi que des génotypes d’intérêt. Ils constituent les bases de la mise en place d’un programme d’amélioration variétale. / Obesity and diabetes are consequences of metabolic disorders due to excessive sugar consumption. Consumers want a healthier diet with natural products. Stevia rebaudiana, the Paraguayan sweet herb, accumulates steviol glycosides (SGs) into its leaves. Considered as intense natural sweeteners, SGs represent a global market constantly increasing. In this context, Oviatis establishes a complete organic sector in the Nouvelle-Aquitaine region. The aims of this CIFRE thesis are to characterise the phenotypic variability within a collection of genetic resources, in order to implement a breeding program. Yield components, leaves biomass, SGs quality and quantity and responses against Septoria sp. were described in perennial and multi-site field conditions or in controlled conditions. This work allowed to: 1) develop tools for metabolic, pathology field-phenotyping, 2) evaluate the phenotypic variability of this Stevia rebaudiana collection in field conditions and identify variability descriptors, 3) identify ontogenic, abiotic and cultural factors implicated into phenotypic variability, and 4) evaluate response variability against septoria disease. These results led to the identification of genotypes of interest, as well as selection criteria for the organic production in Nouvelle-Aquitaine, which are the basis for the implementation of a breeding program.
60

Spectroscopies sous haute pression et champ magnétique intense

Millot, Marius 13 November 2009 (has links) (PDF)
Cette thèse présente des mesures de spectroscopie optique sous conditions extrêmes de pression et champ magnétique intense à basse température. L'objectif premier de ce travail de thèse était de développer et mettre au point un dispositif expérimental original permettant d'atteindre ces conditions extrêmes inédites. Nous avons étendu le domaine de pression, champ magnétique et température accessibles conjointement jusqu'à 56 T, 10 GPa et 4 K et étudié les propriétés de deux types de système pour lesquels les spectroscopies sous haute pression et champ magnétique intense sont particulièrement adaptées: les ions de métaux de transition et les semiconducteurs. L'étude du rubis par magnéto-photoluminescence nous a permis de mettre en évidence dans un domaine de champ magnétique inexploré l'effet Zeeman, i.e la levée de dégénérescence de spin des états électroniques de l'ion chrome, et l'effet Paschen-Back dû à une compétition entre le champ cristallin anisotrope et le champ magnétique appliqué. Une augmentation significative du champ trigonal induite par la pression a été ainsi détectée et interprétée. Nous avons également étudié la structure de bandes du séléniure d'indium, un semiconducteur lamellaire aux propriétés excitoniques remarquables par des mesures de magnéto-absorption. Le phénomène de magnéto-absorption oscillatoire, signature de la quantification de Landau des électrons et des trous, nous a permis d'explorer la structure de bandes dans une large gamme d'énergie autour du gap et de valider le modèle $k.p$ spécifique proposé pour ce composé. Enfin, une étude par magnéto-photoluminescence des propriétés électroniques de boîtes quantiques auto-organisées de phosphure d'indium encapsulées dans une matrice de phosphure de gallium nous a permis d'élucider l'origine de la forte luminescence caractéristique de ce système en déterminant clairement le confinement des porteurs et les effets induits par les fortes contraintes biaxiales inhérentes à la croissance par auto-assemblage.

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