Des techniques d’exploration de la fonction respiratoire nécessitant une coopération minimale, réalisables en ventilation spontanée, sans anesthésie, sont nécessaires chez les jeunes enfants asthmatiques. De telles méthodes sont la mesure de l’impédance respiratoire par la technique des oscillations forcées, la mesure de la résistance spécifique des voies aériennes par pléthysmographie ou la capnographie qui mesure la concentration de CO2 dans le gaz expiré. L’objectif principal de travail a été l’amélioration du diagnostic de l’asthme infantile en utilisant des études cliniques et fondamentales. Une étude clinique incluant des enfants asthmatiques et témoins a montré que la spécificité de la résistance est améliorée en expiration par rapport à l’inspiration du au fait que la fermeture de la glotte à l’expiration est proportionnelle au degré de l’obstruction bronchique. Une autre étude a démontré que le diagnostic de l’asthme est amélioré par le calcul des variations d’admittance respiratoire à un bronchodilatateur, ce calcul n’étant pas influencé par l’artefact des voies aériennes supérieures. Une étude a montré que la mesure de la résistance spécifique des voies aériennes en ventilation spontanée est surestimée par rapport à la mesure en halètement. La capnographie est une méthode noninvasive qui donne des renseignements sur l’inhomogénéité de la ventilation pendant une obstruction bronchique aigue. Toutefois, elle peut être limitée chez le jeune enfant par une fréquence ventilatoire élevée. Une étude expérimentale a été menée chez le lapin pour valider les indices capnographiques à différentes fréquences ventilatoires pour identifier la présence d’une obstruction aigue / Shorter lung function testing methods are needed in young asthmatic children, requiring minimal cooperation, performed in spontaneous breathing, without anaesthesia. Such methods are measurement of respiratory impedance by forced oscillations technique, measurement of specific airway resistance by plethysmography or capnography, measurement of CO2 concentration in expired air. The main objective of this work was to improve pediatric asthma diagnosis by using clinical and experimental studies. A study including asthmatic and control children showed that the specificity of resistance was improved in expiration compared to inspiration due to the fact that the glottis closure during expiration was proportional to the degree of airway obstruction. Another clinical study demonstrated that asthma diagnosis was improved by computation of respiratory admittance response to a bronchodilator because this computation is not affected by upper airways artifact. A study showed that specific airway resistance measured during spontaneous breathing was overestimated compared to panting metthod. Capnography is a non invasive technique. The shape of the expired CO2 time course is altered by the non homogenous distribution of ventilation resulting from bronchoconstriction. But its clinical usefulness in young children may be limited by the relatively high respiratory rate. An experimental study was conducted in rabbits to validate capnogram shape indices at different rates of breathing during airway constriction by methacholine. The indices have detected the acute airway obstruction even at high frequencies, frequencies usually presented by infants during an acute bronchoconstriction

A impedância respiratória de entrada pode ser obtida pela Técnica das Oscilações Forçadas (FOT) através de dois métodos diferentes: convencional e de wavetube. Nessa dissertação, primeiramente realizamos uma revisão bibliográfica com enfoque nos assuntos de interesse para esse trabalho, como definições e modelagem de impedância, descrições e bases teóricas para a realização dos dois métodos e descrição dos equipamentos utilizados por cada um dos métodos. A partir de dados experimentais da impedância, em camundongos machos do tipo BALB/c normais, obtidos em dois equipamentos diferentes fez-se uma comparação utilizando como base o Modelo de Fase Constante, analisando possíveis divergências e buscando compreender os motivos de eventuais discrepâncias. Um dos equipamentos (flexiVent, SCIREQ, Canadá) emprega o método convencional enquanto o outro equipamento foi desenvolvido pelo grupo do professor Zoltán Hantos, da Universidade de Szeged, Hungria, e se utiliza do método de wavetube. Tal trabalho foi motivado pela ausência de referências bibliográficas que comparam os dois métodos. A análise dos resultados experimentais nos sugere que os parâmetros obtidos para o Modelo de Fase Constante nos dois equipamentos são diferentes e não comparáveis. / The input respiratory impedance can be obtained by two different methods of performing the Forced Oscillations Technique (FOT): conventional and wavetube method. In this dissertation, first we made a literature review focusing on issues of interest to this work, as definitions and models of impedance, description and theoretical basis for the realization of the two methods and description of the equipments used by each method. Using experimental data of impedance in BALB/c male mice, from two different equipments a comparison was made based on the Constant Phase Model, analyzing possible differences between them and trying to understand the reasons for any discrepancies. The first equipment (flexiVent, SCIREQ, Canada) uses the conventional method while the second one, developed by the research group of Professor Zoltán Hantos of the University of Szeged, Hungary, uses the wavetube method. This work was motivated by the lack of literature references comparing the model parameters obtained by both methods. The analysis of experimental results suggests that the equipments are different and not comparable.

A análise da mecânica respiratória em tempo real pela Técnica de OscilaçõesForçadas (FOT) Monofrequência é de interesse nos estudos clínicos e diagnósticos de doenças respiratórias. Entretanto, ainda é escassa a análise de asmáticos com esta técnica. O presente trabalho avalia a contribuição da FOT monofrequência na análise das alterações mecânicas ao longo do ciclo respiratório e da dinâmica da impedância do sistema respiratório (Zrs) de asmáticos. Na primeira fase do estudo, 14 voluntários sadios (GC) e 70 asmáticos foram incluídos. Destes, 13 asmáticos apresentaram espirometria normal (NE), e o restante apresentava obstrução leve (OL; n=26), moderada (OM; n=18) e acentuada (OA; n=13). Através da FOT foram analisadas a impedância total do sistema respiratório (Zt), a impedância inspiratória e expiratória (Zi e Ze), a impedância no início da inspiração e da expiração (Zii e Zie), a impedância pico-a-pico (diferença entre Zii e Zie) e a variação média da impedância (diferença entre Zi e Ze). Na segunda fase do estudo, a dinâmica do sistema respiratório foi analisada através da variabilidade da impedância, traduzida pelo desvio padrão da Zrs (sdZrs), pelo desvio-padrão do logaritmo da Zrs (sdlnZrs) e pela sua complexidade, analisada através da entropia aproximada da Zrs (EnApZ). Foram analisados 62 pacientes asmáticos da mesma amostra, divididos em NE (n=12), OL (n=20), OM (n=18) e OA (n=12). O GC foi composto por 12 voluntários. Testes de diferenças entre médias, correlações entre os parâmetros da FOT e da espirometria, além de curvas ROC, foram usados para avaliar o potencial da FOT monofrequência na detecção das alterações mecânicas em tempo real na asma. A impedância foi maior nos asmáticos em relação ao GC, sendo progressivamente maior entre os asmáticos de acordo com o grau de obstrução: Zt (p<0,0001), Zi (p<0,0001), Ze (p<0,0001), Zii (p<0,0001), Zie (p<0,0001), Zpp (p<0,0001) e &#916;Zrs (p<0,0001). A dinâmica do sistema respiratória sofreu diferenças significativas em asmáticos. Houve aumento significativo de sdZrs com o grau de obstrução brônquica (p<0,0001), enquanto a complexidade do sistema diminuiu (EnApZ; p<0,002). Correlações excelentes ocorreram entre VEF1/CVF e Zt (r=-0,76), Ze (r=-0,77) e Zie (r=-0,78), enquanto correlações razoáveis foram verificadas entre os parâmetros espirométricos com sdZrs e EnApZ. Os melhores parâmetros para uso diagnóstico na asma foram Zt, Zi, Ze, Zii e Zie com AUC adequada para identificar obstrução leve e de alta acurácia para identificar obstrução moderada e acentuada. O sdZrs foi adequado para identificar obstrução moderada e acentuada. Estes resultados estão em concordância com os fundamentos fisiopatológicos da asma. A FOTmonofrequência permite uma análise não invasiva e detalhada do sistema respiratório de asmáticos nas diferentes fases do ciclo respiratório. A impedância respiratória, principalmente na fase inspiratória, traduz as alterações mecânicas na asma. A dinâmica do sistema respiratório está alterada na asma, com maior variabilidade e menor complexidade do sinal de impedância respiratória, caracterizando um sistema com menor adaptabilidade a condições de maior demanda metabólica presentes na vida diária. Estes resultados confirmam o elevado potencial de uso clínico e científico desta metodologia na avaliação de pacientes com asma. / The analysis of respiratory mechanics in real time by Monofrequency FOT is of great interest in clinical and diagnosis studies of respiratory diseases. However, the use of this technique for the analysis of patients with asthma is still limited. The present study evaluates the contribution of the Monofrequency FOT in the analysis of changes in respiratory mechanics during the breathing cycle and the dynamics of the respiratory system of asthmatics. In the first phase of the study, 14 healthy volunteers (CG) and 70 asthmatics were included. Among them, 13 patients with asthma had normal spirometry (NE), and the others showed mild obstruction (n=26), moderate (n = 18) and severe (n=13). The parameters analyzed through FOT were the total impedance of the respiratory system (Zt), the inspiratory and expiratory impedance (Zi and Ze) and the impedance at the beginning of inspiration and expiration (Zii and Zie). The impedance peak-to-peak (Zii - Zie) and the mean of impedance (Zi - Ze) were also evaluated. In the second phase, the respiratory system dynamics was analyzed through the impedance variability, reflected by the standard deviation of Zrs (sdZrs), and the standard deviation of the Zrs logarithm (sdlnZrs), and an impedance complexity was analyzed through the approximated entropy of the Zrs (ApEnZ). 62 patients with asthma were analyzed, divided into NE (n=12), mild (n=20), moderate (n=18) and severe (n=12). The CG was composed by 12 volunteers. Tests of differences between means, correlations between the FOT parameters, spirometry, and ROC curves, were used to evaluate the potential of Monofrequency FOT in the detection of asthma mechanical changes in real-time. The respiratory impedance was higher in asthmatics than in CG, being progressively bigger among asthmatics according to obstruction degree: Zt (p<0.0001), Zi (p<0.0001), Ze (p<0.0001), Zii (p<0.0001), Zie (p<0.0001), Zpp (p<0.0001) and &#916;Zrs (p<0.0001). The dynamics of the respiratory system suffered significant differences in asthmatics. There was a significant increase in sdZrs with the bronchial obstruction degree in asthma (p<0.0001), while the complexity of the system decreased (ApEnZ, p<0.002). Excellent correlations occurred between FEV1/FVC and Zt (r=-0.76), Ze (r=-0.77) and Zie (r=-0.78), while reasonable correlations were found between spirometric parameters with sdZrs and ApEnZ. The best parameters to be used in asthma diagnosis were Zt, Zi, Ze, Zii Zie with adequate AUC to identify mild obstruction and high accuracy in identifying moderate and severe obstructions. The sdZrs was adequated to identify moderate and severe obstruction. These results are in close agreement with the pathophysiologic basis of asthma. The Monofrequency FOT allows a noninvasive analysis of the asthmatics respiratory system in the different phases. The respiratory impedance, especially during inspiration, reflects on the mechanical changes in asthma. The respiratory system dynamics is altered in asthma, with greater variability and less complexity of the respiratory impedance signal, characterizing a system with less adaptability to conditions of greater metabolic demand on the daily life. These results confirm the high potential of clinical and scientific use of this methodology to evaluate patients with asthma.

A análise da mecânica respiratória em tempo real pela Técnica de OscilaçõesForçadas (FOT) Monofrequência é de interesse nos estudos clínicos e diagnósticos de doenças respiratórias. Entretanto, ainda é escassa a análise de asmáticos com esta técnica. O presente trabalho avalia a contribuição da FOT monofrequência na análise das alterações mecânicas ao longo do ciclo respiratório e da dinâmica da impedância do sistema respiratório (Zrs) de asmáticos. Na primeira fase do estudo, 14 voluntários sadios (GC) e 70 asmáticos foram incluídos. Destes, 13 asmáticos apresentaram espirometria normal (NE), e o restante apresentava obstrução leve (OL; n=26), moderada (OM; n=18) e acentuada (OA; n=13). Através da FOT foram analisadas a impedância total do sistema respiratório (Zt), a impedância inspiratória e expiratória (Zi e Ze), a impedância no início da inspiração e da expiração (Zii e Zie), a impedância pico-a-pico (diferença entre Zii e Zie) e a variação média da impedância (diferença entre Zi e Ze). Na segunda fase do estudo, a dinâmica do sistema respiratório foi analisada através da variabilidade da impedância, traduzida pelo desvio padrão da Zrs (sdZrs), pelo desvio-padrão do logaritmo da Zrs (sdlnZrs) e pela sua complexidade, analisada através da entropia aproximada da Zrs (EnApZ). Foram analisados 62 pacientes asmáticos da mesma amostra, divididos em NE (n=12), OL (n=20), OM (n=18) e OA (n=12). O GC foi composto por 12 voluntários. Testes de diferenças entre médias, correlações entre os parâmetros da FOT e da espirometria, além de curvas ROC, foram usados para avaliar o potencial da FOT monofrequência na detecção das alterações mecânicas em tempo real na asma. A impedância foi maior nos asmáticos em relação ao GC, sendo progressivamente maior entre os asmáticos de acordo com o grau de obstrução: Zt (p<0,0001), Zi (p<0,0001), Ze (p<0,0001), Zii (p<0,0001), Zie (p<0,0001), Zpp (p<0,0001) e &#916;Zrs (p<0,0001). A dinâmica do sistema respiratória sofreu diferenças significativas em asmáticos. Houve aumento significativo de sdZrs com o grau de obstrução brônquica (p<0,0001), enquanto a complexidade do sistema diminuiu (EnApZ; p<0,002). Correlações excelentes ocorreram entre VEF1/CVF e Zt (r=-0,76), Ze (r=-0,77) e Zie (r=-0,78), enquanto correlações razoáveis foram verificadas entre os parâmetros espirométricos com sdZrs e EnApZ. Os melhores parâmetros para uso diagnóstico na asma foram Zt, Zi, Ze, Zii e Zie com AUC adequada para identificar obstrução leve e de alta acurácia para identificar obstrução moderada e acentuada. O sdZrs foi adequado para identificar obstrução moderada e acentuada. Estes resultados estão em concordância com os fundamentos fisiopatológicos da asma. A FOTmonofrequência permite uma análise não invasiva e detalhada do sistema respiratório de asmáticos nas diferentes fases do ciclo respiratório. A impedância respiratória, principalmente na fase inspiratória, traduz as alterações mecânicas na asma. A dinâmica do sistema respiratório está alterada na asma, com maior variabilidade e menor complexidade do sinal de impedância respiratória, caracterizando um sistema com menor adaptabilidade a condições de maior demanda metabólica presentes na vida diária. Estes resultados confirmam o elevado potencial de uso clínico e científico desta metodologia na avaliação de pacientes com asma. / The analysis of respiratory mechanics in real time by Monofrequency FOT is of great interest in clinical and diagnosis studies of respiratory diseases. However, the use of this technique for the analysis of patients with asthma is still limited. The present study evaluates the contribution of the Monofrequency FOT in the analysis of changes in respiratory mechanics during the breathing cycle and the dynamics of the respiratory system of asthmatics. In the first phase of the study, 14 healthy volunteers (CG) and 70 asthmatics were included. Among them, 13 patients with asthma had normal spirometry (NE), and the others showed mild obstruction (n=26), moderate (n = 18) and severe (n=13). The parameters analyzed through FOT were the total impedance of the respiratory system (Zt), the inspiratory and expiratory impedance (Zi and Ze) and the impedance at the beginning of inspiration and expiration (Zii and Zie). The impedance peak-to-peak (Zii - Zie) and the mean of impedance (Zi - Ze) were also evaluated. In the second phase, the respiratory system dynamics was analyzed through the impedance variability, reflected by the standard deviation of Zrs (sdZrs), and the standard deviation of the Zrs logarithm (sdlnZrs), and an impedance complexity was analyzed through the approximated entropy of the Zrs (ApEnZ). 62 patients with asthma were analyzed, divided into NE (n=12), mild (n=20), moderate (n=18) and severe (n=12). The CG was composed by 12 volunteers. Tests of differences between means, correlations between the FOT parameters, spirometry, and ROC curves, were used to evaluate the potential of Monofrequency FOT in the detection of asthma mechanical changes in real-time. The respiratory impedance was higher in asthmatics than in CG, being progressively bigger among asthmatics according to obstruction degree: Zt (p<0.0001), Zi (p<0.0001), Ze (p<0.0001), Zii (p<0.0001), Zie (p<0.0001), Zpp (p<0.0001) and &#916;Zrs (p<0.0001). The dynamics of the respiratory system suffered significant differences in asthmatics. There was a significant increase in sdZrs with the bronchial obstruction degree in asthma (p<0.0001), while the complexity of the system decreased (ApEnZ, p<0.002). Excellent correlations occurred between FEV1/FVC and Zt (r=-0.76), Ze (r=-0.77) and Zie (r=-0.78), while reasonable correlations were found between spirometric parameters with sdZrs and ApEnZ. The best parameters to be used in asthma diagnosis were Zt, Zi, Ze, Zii Zie with adequate AUC to identify mild obstruction and high accuracy in identifying moderate and severe obstructions. The sdZrs was adequated to identify moderate and severe obstruction. These results are in close agreement with the pathophysiologic basis of asthma. The Monofrequency FOT allows a noninvasive analysis of the asthmatics respiratory system in the different phases. The respiratory impedance, especially during inspiration, reflects on the mechanical changes in asthma. The respiratory system dynamics is altered in asthma, with greater variability and less complexity of the respiratory impedance signal, characterizing a system with less adaptability to conditions of greater metabolic demand on the daily life. These results confirm the high potential of clinical and scientific use of this methodology to evaluate patients with asthma.

A impedância respiratória de entrada pode ser obtida pela Técnica das Oscilações Forçadas (FOT) através de dois métodos diferentes: convencional e de wavetube. Nessa dissertação, primeiramente realizamos uma revisão bibliográfica com enfoque nos assuntos de interesse para esse trabalho, como definições e modelagem de impedância, descrições e bases teóricas para a realização dos dois métodos e descrição dos equipamentos utilizados por cada um dos métodos. A partir de dados experimentais da impedância, em camundongos machos do tipo BALB/c normais, obtidos em dois equipamentos diferentes fez-se uma comparação utilizando como base o Modelo de Fase Constante, analisando possíveis divergências e buscando compreender os motivos de eventuais discrepâncias. Um dos equipamentos (flexiVent, SCIREQ, Canadá) emprega o método convencional enquanto o outro equipamento foi desenvolvido pelo grupo do professor Zoltán Hantos, da Universidade de Szeged, Hungria, e se utiliza do método de wavetube. Tal trabalho foi motivado pela ausência de referências bibliográficas que comparam os dois métodos. A análise dos resultados experimentais nos sugere que os parâmetros obtidos para o Modelo de Fase Constante nos dois equipamentos são diferentes e não comparáveis. / The input respiratory impedance can be obtained by two different methods of performing the Forced Oscillations Technique (FOT): conventional and wavetube method. In this dissertation, first we made a literature review focusing on issues of interest to this work, as definitions and models of impedance, description and theoretical basis for the realization of the two methods and description of the equipments used by each method. Using experimental data of impedance in BALB/c male mice, from two different equipments a comparison was made based on the Constant Phase Model, analyzing possible differences between them and trying to understand the reasons for any discrepancies. The first equipment (flexiVent, SCIREQ, Canada) uses the conventional method while the second one, developed by the research group of Professor Zoltán Hantos of the University of Szeged, Hungary, uses the wavetube method. This work was motivated by the lack of literature references comparing the model parameters obtained by both methods. The analysis of experimental results suggests that the equipments are different and not comparable.

<p>Theoretical studies of dusty plasmas have been performed by focusing attention principally on collective phenomena and on grain motion. This thesis consists of a collection of seven published papers that explore both the collective behavior of a complex plasma system as well as the dynamics of grains in plasmas. In paper 1, a mechanism that explains the energy gain which leads to the self excited grain oscillations is theoretically formulated. The newly developed mechanism explains the observed self excited oscillations through the coupling of plasma sheath fluctuations with the electrostatic force, which holds the dust grain. In paper 2, theoretical and simulation studies have been conducted to study the vertical oscillations of dust grains that are levitated in plasma sheaths, under low pressure conditions. The oscillations were driven either by an external force or by a plasma number density modulation. The proposed model gives a full picture of the dust grains dynamics and is capable of successfully explaining the experimental observations. Paper 3 explores both theoretically and numerically the origin of the nonlinearities that lead to the observed oscillation resonances. The feature of the confining potential well which traps the grain, the influence of an electrode voltage modulation on the trapping well, and hence on the grain dynamics, and the resulting nonlinear resonances are analyzed in detail. The numerical simulations presented successfully reproduce a broad range of dynamical phenomena, including the self excited oscillations, for a range of different parameters. Paper 4 is dedicated to the analysis of the propagation of Dust Acoustic Waves (DAW) in a medium with an equilibrium dust density distribution. It has been theoretically shown that only some harmonics of the dust density distribution will influence the propagation of the DAW, thus modifying its frequency. Paper 5 presents a theoretical and numerical analysis of the excitation of higher harmonics of electrostatic dust cyclotron waves. The instability is driven by the ion and electron currents flowing along the magnetic field. The dispersion relation and the wave instability conditions have been derived, and a detailed numerical analysis has been performed. In Paper 6, we explore theoretically some cross field instabilities of low frequency, long wavelength electrostatic modes in fully and weakly ionized plasmas. It is shown that in a magnetoplasma with a transverse equilibrium dc electric field, the energy associated with the cross field motion of the plasma particles can be coupled to low frequency electrostatic waves. Paper 7 explores the properties and instabilities of low frequency electrostatic waves propagating in a current carrying magnetoplasma with equilibrium density and field aligned ion flow with a transverse gradient. The paper contains previous results as limiting cases, together with additional instabilities related to the equilibrium plasma density distribution. </p>

Theoretical studies of dusty plasmas have been performed by focusing attention principally on collective phenomena and on grain motion. This thesis consists of a collection of seven published papers that explore both the collective behavior of a complex plasma system as well as the dynamics of grains in plasmas. In paper 1, a mechanism that explains the energy gain which leads to the self excited grain oscillations is theoretically formulated. The newly developed mechanism explains the observed self excited oscillations through the coupling of plasma sheath fluctuations with the electrostatic force, which holds the dust grain. In paper 2, theoretical and simulation studies have been conducted to study the vertical oscillations of dust grains that are levitated in plasma sheaths, under low pressure conditions. The oscillations were driven either by an external force or by a plasma number density modulation. The proposed model gives a full picture of the dust grains dynamics and is capable of successfully explaining the experimental observations. Paper 3 explores both theoretically and numerically the origin of the nonlinearities that lead to the observed oscillation resonances. The feature of the confining potential well which traps the grain, the influence of an electrode voltage modulation on the trapping well, and hence on the grain dynamics, and the resulting nonlinear resonances are analyzed in detail. The numerical simulations presented successfully reproduce a broad range of dynamical phenomena, including the self excited oscillations, for a range of different parameters. Paper 4 is dedicated to the analysis of the propagation of Dust Acoustic Waves (DAW) in a medium with an equilibrium dust density distribution. It has been theoretically shown that only some harmonics of the dust density distribution will influence the propagation of the DAW, thus modifying its frequency. Paper 5 presents a theoretical and numerical analysis of the excitation of higher harmonics of electrostatic dust cyclotron waves. The instability is driven by the ion and electron currents flowing along the magnetic field. The dispersion relation and the wave instability conditions have been derived, and a detailed numerical analysis has been performed. In Paper 6, we explore theoretically some cross field instabilities of low frequency, long wavelength electrostatic modes in fully and weakly ionized plasmas. It is shown that in a magnetoplasma with a transverse equilibrium dc electric field, the energy associated with the cross field motion of the plasma particles can be coupled to low frequency electrostatic waves. Paper 7 explores the properties and instabilities of low frequency electrostatic waves propagating in a current carrying magnetoplasma with equilibrium density and field aligned ion flow with a transverse gradient. The paper contains previous results as limiting cases, together with additional instabilities related to the equilibrium plasma density distribution.

Ce travail présente une étude de la dynamique interfaciale de gouttes oscillantes dans une plage étendue de fréquences, en particulier dans le domaine des hautes fréquences. Nous avons développé une méthode de caractérisation de la dynamique des oscillations de gouttes, en présence d’un forçage externe imposé, sous la forme de variations de volume périodiques de faible amplitude sur une goutte attachée à l’extrémité d’un capillaire. Cette méthode permet d’identifier les modes d’oscillation des gouttes et d’en mesurer les fréquences et les taux d’amortissement. Cette méthode a été appliquée à différents systèmes liquide-liquide, en l’absence ou en présence de surfactants. Dans ce dernier cas, elle permet d’évaluer l’effet du comportement viscoélastique des interfaces sur la dynamique des oscillations. Ainsi 3 types d’interfaces ont été identifiés. Pour les interfaces de premier type (heptane/eau sans ajout de surfactant), chaque mode propre est modélisé par un oscillateur linéaire peu amorti. Les fréquences propres et les taux d’amortissement sont bien prédits par la théorie linéaire. Les interfaces de types 2 et 3 sont obtenues en ajoutant du pétrole brut à la phase dispersée. Les surfactants naturellement présents dans le pétrole (asphaltènes, résines) s’adsorbent à l’interface et lui confèrent des propriétés viscoélastiques. Pour les interfaces jeunes (type 2, moins de 20 minutes de vieillissement), les fréquences propres mesurées restent bien prédites par la théorie, qui considère des interfaces non contaminées, tandis que les taux d’amortissement sont de loin supérieurs aux valeurs théoriques. D’autre part, les interfaces vieillies (type 3) présentent des modes propres différents avec des fréquences de résonance supérieures à celles des interfaces jeunes. Dans ce cas, la dynamique de l’interface à haute fréquence est régie par l’élasticité du réseau formé par les espèces amphiphiles du pétrole brut. Les oscillations libres d’une goutte en ascension dans une phase externe stagnante, pour un système liquide-liquide sans ajout de surfactants, ont été étudiées. Les valeurs mesurées de la fréquence d’oscillation des 4 premiers modes sont en adéquation avec la théorie linéaire. Cependant les valeurs mesurées du taux d’amortissement sont très élevées par rapport aux valeurs théoriques, pour une interface non contaminée. En effet, des espèces résiduelles adsorbées à l’interface provoquent l’apparition d’un gradient de tension interfaciale par effet Marangoni et par suite une production de vorticité plus intense dans les couches-limites, ce qui conduit à l’augmentation de l’amortissement des oscillations. / We present an experimental study of oscillating drop interfacial dynamics at a wide frequency range, especially at high frequency. A characterization method of drops oscillation dynamics has been developed. The oscillations are generated by imposing low amplitude periodic variation of volume to a drop which is attached to a capillary tip. The present method is based on the identification of the drop eigenmodes and the determination of their frequencies and damping rates. It has been applied to characterize several liquid-liquid systems. Three types of interface have been identified. For interfaces of type 1 (heptane/water without added surfactant), each eigenmode is modelled by a weakly damped linear oscillator. Eigenfrequencies and damping rates are well predicted by the linear theory. Interfaces of Types 2 and 3 are obtained by adding crude oil to the disperse phase. Oil native surfactants (asphaltenes, resins) adsorb on the drop interface and provide the latter with viscoelastic behaviour. For young interfaces (type 2 with aging time below 20 minutes), eigenfrequencies remain well predicted by the theory, which deals with non contaminated interfaces, whereas the measured damping rates are significantly higher than the theoretical values. On the other hand, aged interfaces (type 3) exhibit different eigenmodes, of which eigenfrequencies are much higher than the resonance frequencies measured for the young interfaces. At high frequency, the dynamics of aged interfaces are governed by the elasticity of the network constituted by the crude oil amphiphilic species, while the dynamics of young interfaces are governed by interfacial tension. Freely decaying oscillations of a rising drop in a liquid at rest without added surfactant were also considered. Measured frequencies for the first four eigenmodes are in good agreement with the linear theory. However, measured damping rates are much higher than the theoretical rates for non contaminated interfaces. In fact, residual adsorbed species at the heptane/water interface induce Marangoni effects and thus gradients of interfacial tension. Therefore, vorticity production within the boundary layers is enhanced, which explains the observed increase of the oscillation damping rates.

Pour les roches saturées, la comparaison entre les mesures ultrasoniques (1 MHz) au laboratoire et les mesures sismiques (100 Hz) ou de diagraphie (10 kHz) sur le terrain n’est pas directe à cause de la dispersion des vitesses des ondes. Les mécanismes impliqués dans la dépendance en fréquence sont les écoulements de fluides à différentes échelles provoqués par le passage de l’onde. La dispersion et l’atténuation des modules élastiques de roches carbonatées ont été étudiées expérimentalement. Les calcaires étudiés sont : un Lavoux, un Indiana intact et craqué thermiquement, un calcaire Urgonien de Provence (Rustrel), et un coquina pré-sel du Congo. Les mesures ont été faites sur une large gamme de fréquence, en combinant les techniques d’oscillations forcées (10-3 to 102 Hz) et ultrasoniques (1 MHz) dans une presse triaxiale, pour différentes pressions effectives. Le forçage peut être hydrostatique pour mesurer un module d’incompressibilité, ou axial pour mesurer le module de Young et le coefficient de Poisson. Pour étudier l’effet de la viscosité, les mesures ont été faites en condition sèche, puis saturée en glycérine et en eau. Le drainage global et le mécanisme d’écoulement crack-pore ont été caractérisés, en termes d’amplitude de dispersion, d’atténuation viscoélastique, et de fréquence de coupure. Pour nos échantillons, la théorie de Biot-Gassmann s’est montrée valide pour les fréquences sismiques (10-100 Hz) sauf pour l’Indiana craqué thermiquement. La dispersion liée à des écoulements crackspores a été observée pour tous les échantillons sauf le Lavoux. Les fréquences de coupures de ceux-ci sont toutes dans la gamme des fréquences des diagraphies (10 kHz) pour des conditions de saturation en eau. Un modèle simple, combinant poroélasticité et milieux effectifs, a été développé pour prédire la dispersion des modules sur toute la gamme de fréquence, et s’est montré généralement en accord avec les résultats expérimentaux. / For fluid-saturated rocks, comparing ultrasonic measurements (1 MHz) in the laboratory and seismic (100 Hz) or logging (10 kHz) measurements in the field is not straightforward due to dispersion of the bodywave velocities. The frequency-dependent mechanisms involved are wave-induced fluid flows that occur at different scales. The dispersion and the attenuation of the elastic moduli of four fluid-saturated carbonate rocks have been studied experimentally. The selected limestones were a Lavoux, an intact and thermally cracked Indiana, a Urgonian limestone from Provence (Rustrel), and a presalt coquina from offshore Congo. Measurements were done over a large frequency range, by the combination of forced oscillations (10-3 to 102 Hz) and ultrasonic measurements (1 MHz) in a triaxial cell, at various effective pressures. The forced oscillations were either hydrostatic to deduce the bulk modulus, or axial to deduce Young’s modulus and Poisson’s ratio. The measurements were done in dry-, glycerinand water-saturated conditions to investigate the effect of viscosity. For all our samples, the global drainage and the squirt-flow mechanisms were characterized experimentally, in terms of amplitude of dispersion, amount of viscoelastic attenuation, and cut-off frequencies. Biot- Gassmann’s theory was found to be valid at seismic frequencies (10-100 Hz) for all the samples except the thermally cracked Indiana. Squirt-flow transitions were observed for all the samples, except the Lavoux. The cut-off frequencies were all in the range of logging frequencies (10 kHz), for watersaturated conditions. A simple model, combining poroelasticity and the noninteraction approximation effective medium, was developed to predict the dispersion of the moduli over the whole frequency range, and was generally in agreement with the experimental results.

Auto-fluorescence emission of plant tissues can be a powerful reporter on plant biochemistry and physiology since it originates in substances inherent to primary or secondary metabolism. Plant bodies contain a plethora of intrinsic fluorescent compounds emitting practically all wavelengths of visible light. Moreover, the spectrum of fluorescent reporter signals was recently extended by a variety of fluorescent proteins that provide a new tool to mark whole cells or sub-cellular structures, study protein localization and monitor gene expression and molecule interactions. The imaging of such fluorescence signals reveals a possibility to acquire the information from as many as millions of points simultaneously, in vivo and in a non-invasive way thereby preserving integrity of cells and whole organisms. Imaging is particularly suited to visualize heterogeneity such as a localized immune response to invading pathogens. It can be applied both at macro- as well as micro-scales in two and three dimensions. The recent advancement in microscopy, the multi-photon microscopy, has made possible to monitor fluorescence signals, such as NAD(P)H fluorescence from intact leaf interior, that have been hidden to single-photon techniques.