L'irritation mécanique de la peau entraîne une vasodilatation sur la ligne de la griffure suite à la libération de l'histamine des mastocytes et une vasodilatation dans les alentours liée à la stimulation des récepteurs de douleurs. Le réseau vasculaire est décrit par un modèle continu et un modèle discret. Les modèles consistent en trois couches. Le modèle continu décrit la première et la troisième couche (irrigation et drainage) comme milieux poreux bidimensionnels horizontaux. Le modèle discret tient compte de la structure de l'arbre vasculaire. La couche intermédiaire est décrite comme modèle de compartimentation. La vasodilatation a été mesurée en utilisant la Vélocimétrie Laser Doppler. Les résultats expérimentaux et numériques ont été comparés à l'aide du modèle de Bonner et al., qui est basé sur le spectre de fréquence du signal Doppler.

Les modèles de comportement issus des théories "moléculaires" permettent de faire le lien entre structure moléculaire et comportement dans des écoulements rhéométriques. Cependant, ces modèles peuvent être mis en défaut dès que l'écoulement est complexe ou fortement non-linéaire. Dans cette thèse, nous avons présenté des résultats expérimentaux permettant d'identifier les paramètres non linéaires constitutifs de ces lois de comportement viscoélastique pour les polymères fondus, en utilisant des mesures de champ telles que la Vélocimétrie Laser Doppler (LDV) et la Biréfringence Induite par Écoulement (FIB) pour un polystyrène (PS) et un polyéthylène basse densité (PEBD). Pour ces deux matériaux, nous avons réalisé des mesures de champ de contraintes et des mesures de champ de vitesses dans un écoulement convergent (pour le PS) et une contraction (pour le PEBD). Nous avons développé une méthode d'évaluation et d'identification d'une loi de comportement viscoélastique (modèle de Marrucci et Ianniruberto pour le PS, modèle de type " Pom-Pom " pour le PEBD) à partir de ces mesures de champs. Pour le PEBD nous avons en outre analysé l'influence de la température et du débit sur la taille des recirculations d'un écoulement secondaire. La taille de ces dernières dépend de l'importance relative des propriétés rhéologiques en cisaillement et en élongation de ce matériau.

<p>Patients with idiopathic anal fistula (n=85) were compared with 215 control subjects, matched for age and sex, through a 180-item questionnaire. Obesity, smoking, constipation and bowel symptoms associated with IBS were more common in the patients.</p><p>Endoanal ultrasound (EUS) and magnetic resonance imaging (MRI) were compared in the preoperative evaluation of anal fistula in 23 patients. For classifying the primary tract, EUS and surgical findings agreed in 14 cases, and MRI and surgery for 11: for identifying an internal opening, the corresponding figures were 17 and 10.</p><p>Healing and sphincter function were studied in 42 patients operated with fistula excision and closure of the internal opening. Twenty-three patients healed primarily and another 10 after one re-operation, whereas nine required further surgery until healed. Anal resting pressure was reduced after three and 12 months, and squeeze pressure after 12 months.</p><p>Eighty-three patients were randomised to surgery with or without application of gentamicin-collagen underneath the flap: 26/42 of patients randomised to gentamicin-collagen healed primarily compared with 21/41 of patients randomised to surgery only (n.s).</p><p>Micro perfusion in the flap was studied by laser Doppler flowmetry during surgery in 16 patients. No correlation was seen between change in blood flow during surgery and non-healing/recurrence of the fistula.</p><p>In conclusion, obesity, functional bowel symptoms and possibly smoking are more common in patients with idiopathic anal fistula than in the general population. Endoanal ultrasound is a useful tool in the preoperative evaluation of anal fistula. Advancement flap repair has a reasonably high primary recurrence rate and healing is not significantly improved by local application of gentamicin-collagen: impaired intraoperative blood perfusion of the flap is an unlikely reason for non-healing. A decrease in continence occurs also after this kind of surgery, probably due to an impaired internal anal sphincter function.</p>

Patients with idiopathic anal fistula (n=85) were compared with 215 control subjects, matched for age and sex, through a 180-item questionnaire. Obesity, smoking, constipation and bowel symptoms associated with IBS were more common in the patients. Endoanal ultrasound (EUS) and magnetic resonance imaging (MRI) were compared in the preoperative evaluation of anal fistula in 23 patients. For classifying the primary tract, EUS and surgical findings agreed in 14 cases, and MRI and surgery for 11: for identifying an internal opening, the corresponding figures were 17 and 10. Healing and sphincter function were studied in 42 patients operated with fistula excision and closure of the internal opening. Twenty-three patients healed primarily and another 10 after one re-operation, whereas nine required further surgery until healed. Anal resting pressure was reduced after three and 12 months, and squeeze pressure after 12 months. Eighty-three patients were randomised to surgery with or without application of gentamicin-collagen underneath the flap: 26/42 of patients randomised to gentamicin-collagen healed primarily compared with 21/41 of patients randomised to surgery only (n.s). Micro perfusion in the flap was studied by laser Doppler flowmetry during surgery in 16 patients. No correlation was seen between change in blood flow during surgery and non-healing/recurrence of the fistula. In conclusion, obesity, functional bowel symptoms and possibly smoking are more common in patients with idiopathic anal fistula than in the general population. Endoanal ultrasound is a useful tool in the preoperative evaluation of anal fistula. Advancement flap repair has a reasonably high primary recurrence rate and healing is not significantly improved by local application of gentamicin-collagen: impaired intraoperative blood perfusion of the flap is an unlikely reason for non-healing. A decrease in continence occurs also after this kind of surgery, probably due to an impaired internal anal sphincter function.

The human stomach normally contains high levels of bioactive nitric oxide (NO). This NO derives from salivary nitrate (NO3-) that is converted to nitrite (NO2-) by oral bacteria and thereafter non-enzymatically reduced in the acidic gastric lumen to NO. Nitrate is a common component in vegetables, and after ingestion it is absorbed in the small intestine. Interestingly, circulating nitrate is then concentrated by the salivary glands. Hence, intake of nitrate-rich vegetables results in high levels of NO in the stomach. The physiological effects of the high concentration of NO gas normally present in the gastric lumen have been hitherto unknown, and the present investigations were therefore conducted to address this issue. NO produced in the gastric lumen after nitrate ingestion increased gastric mucosal blood flow and the thickness of the firmly adherent mucus layer in the stomach. The blood flow and mucus layer are essential defense mechanisms that protect the mucosa from luminal acid and noxious agents. Nonsteroidal antiinflammatory drugs (NSAID) are commonly prescribed and effective drugs for treating pain and inflammation, but are associated with severe gastrointestinal side effects. We demonstrated that a nitrate-rich diet protects against NSAID-induced gastric damage, as a result of the increased formation of NO in the stomach. We also showed that the gastroprotective effect attributed to nitrate depended completely on conversion of nitrate to nitrite by the bacterial flora colonizing the tongue, and that the oral microflora is therefore important in regulating physiological conditions in the stomach. In summary, this thesis challenges the current dogma that nitrate intake is hazardous, and on the contrary suggests that dietary nitrate plays a direct role in regulating gastric homeostasis. It is likely that a sufficient supply of nitrate in the diet together with the oral microflora is essential for preventing pathological conditions in the gastrointestinal tract.

Laser Doppler Vibrometry (LDV) is a non-contact technique for sensing surface vibrations. Traditionally, LDV uses one or more fixed beams to measure the vibrational velocity of specific points and orientations. In order to measure an angular velocity at least two laser beams are required. Instead, this research proposes to develop a Continuous Scanning Laser Doppler Vibrometer (CSLDV) technique, based on a single laser beam continuously sweeping the area of interest using a scanning mirror. Linear scans allow the measurement of normal and angular velocity while circular scans allow the measurement of normal velocity and two angular velocities. The first part of the study analyzes the performance of rigid body models of both the short line and circular scans (< 1 cm) for measuring low broadband frequency vibrations of gel samples. This thesis focused on low frequency broadband vibration since natural human body vibrations (such as tremor or breathing) are typically below a few hundred hertz. Results for normal and angular velocity measurements are validated against conventional method of using two fixed LDVs. The second part of this research investigates the CSLDV technique for longer scans (< 5 cm). These long scans will be used to act as an array of virtual transducers at multiple points along the scanning path of the single laser beam; thus yielding similar information obtained using an array of several real fixed LDVs. A practical challenge encountered when using CSLDV is speckle noise, that is generated when a coherent light source is reflected back from an optically rough surface. The effect of speckle noise will be quantified by varying different parameters such as scan lengths, scanning frequency, target to sensor distance and the amplitude of excitation. These parameters will be optimized in order to reduce the error of vibration measurements obtained from the CSLDV. Such systems will be used to monitor multiple degrees of freedom of human skeletal muscle vibrations for elastography purposes. The forced vibration of human muscles will be analyzed using these CSLDV techniques. Overall contributions of this work include: (1) Validation of rigid body models of both short line and circular scans CSLDV for broadband low frequency linear and angular velocity measurements; (2) application to sensing natural human body vibrations (e.g., hand tremors); (3) replacement of an array of vibration sensors by a single long line scan CSLDV. (4) development of a dynamic elastography technique for skeletal muscles using CSLDV.

La réduction des nuisances sonores est un enjeu permanent pour les acteurs de l'aéronautique. L'optimisation de la réduction de bruit apportée par les traitements acoustiques tapissant la nacelle des réacteurs turbofan passe par une caractérisation précise des matériaux employés dans l'environnement aéroacoustique d'utilisation, qui met en jeu un écoulement rasant de vitesse importante combiné à de forts niveaux sonores. L'objectif de cette thèse est de développer une méthode inverse pour la détermination de l'impédance acoustique de liners soumis à un écoulement rasant, basée sur des mesures non intrusives du champ de vitesse acoustique au-dessus du matériau par Vélocimétrie Laser Doppler (LDV). L'impédance de liner est obtenue par minimisation de l'écart entre le champ de vitesse acoustique mesuré et le champ simulé numériquement en résolvant les équations d'Euler linéarisées bidimensionnelles harmoniques, discrétisées par un schéma Galerkin discontinu. Le gradient de la fonction objectif minimisée est calculé via la résolution, à chaque itération, des équations directes et adjointes. Une première étape de validation du solveur est effectuée sur des cas-tests académiques, puis sur des cas expérimentaux impliquant des mesures de pression acoustique en paroi rigide opposée au liner. Dans un second temps, la méthode est appliquée à des mesures de vitesse acoustique obtenues par LDV dans le banc B2A de l'ONERA en l'absence d'écoulement. La dernière étape consiste à prendre en compte l'effet d'un écoulement rasant de profil cisaillé. Les impédances identifiées à partir de mesures LDV en présence d'écoulement ont notamment permis de gagner en compréhension sur les phénomènes d'absorption intervenant dans le banc B2A.

Flow past circular cylinders with stepwise discontinuities in diameter was investigated experimentally and numerically for the diameter ratio D/d = 2 and three Reynolds numbers, Re = 150, 300, and 1050. The investigation was focused on the vortex shedding phenomena occurring in the wake of the cylinders. In the first series of experimental and numerical studies, the flow development past a single step cylinder was investigated. The single step cylinder model is comprised of a small diameter cylinder (d) attached coaxially to a large diameter cylinder (D). The results show that three distinct spanwise vortex cells form in the step cylinder wake: a single vortex shedding cell in the wake of the small cylinder (the S-cell) and two vortex shedding cells in the wake of the large cylinder, one in the region downstream of the step (the N-cell) and the other away from the step (the L-cell). Due to the differences in vortex shedding frequencies between the three cells, complex vortex connections occur in two vortex-interaction regions located between the adjacent cells. The region at the boundary between the S-cell and the N-cell is relatively narrow and its spanwise extent does not fluctuate significantly. In this region, vortex dislocations manifested as half-loop connections between two S-cell vortices of opposite sign. In contrast, the region at the boundary between the N-cell and the L-cell exhibits a transient behavior, with large scale vortex dislocations causing cyclic variation in the extent of N-cell vortices. For Re = 300 and 1050, small scale streamwise vortices forming in the wake complicate the vortex dynamics within the adjacent S-cell and L-cell. There is no significant Reynolds number effect on the average spanwise extent of the vortex cells and the two transition regions between neighboring cells. Finally, formation of N-cell vortices is linked to downwash fluctuations near the step. The flow development past a dual step cylinder was studied experimentally for Re = 1050. The dual step cylinder model is comprised of a small diameter cylinder (d) and a large diameter cylinder (D) mounted at the mid-span of the small cylinder. The experiments were completed for a range of large cylinder aspect ratios 0.2 ≤ L/D ≤ 17. The flow development is highly dependent on the aspect ratio of the large cylinder, L/D. The results identify four distinct flow regimes: (i) for L/D = 17, three vortex shedding cells form in the wake of the large cylinder, one central cell and two cells of lower frequency extending over about 4.5D from the large cylinder ends, (ii) for 7 < L/D ≤ 14, a single vortex shedding cell forms in the wake of the large cylinder, whose shedding frequency decreases with decreasing L/D, (iii) for 2 ≤ L/D ≤ 7, vortex shedding in the wake of the large cylinder is highly three-dimensional, with vortices deforming in the near wake, (iv) for 0.2 ≤ L/D ≤ 1, only small cylinder vortices are shed in the wake and can form vortex connections across the wake of the large cylinder.

In der vorliegenden Arbeit wird eine Methode zur Charakterisierung von Mikrosystemen mit beweglichen Komponenten dargestellt. Sie erlaubt, funktionsrelevante Parameter und deren Schwankungen produktionsbegleitend auf Waferlevel zu ermitteln. Dabei wird vorausgesetzt, dass die Sollform der Struktur und die Abweichungsarten bekannt sind. Die Methode beruht auf dem Vergleich von numerisch berechneten mit experimentell ermittelten Eigenfrequenzen der untersuchten Mikrosysteme. Dazu wird die Abhängigkeit verschiedener Eigenfrequenzen von den gesuchten Parametern mittels einer Parametervariationsanalyse berechnet und durch eine geeignete Funktion angenähert. Die Messung der dynamischen Eigenschaften erfolgt mit Hilfe eines Bewegungsanalysators, der auf einem Laser-Doppler-Vibrometer basiert. Im letzen Schritt werden die gesuchten Parameter berechnet. Kernpunkt der entwickelten Methode sind Messungen auf der Basis von speziellen Teststrukturen, die im Waferlayout neben den eigentlichen Nutzstrukturen platziert sind und parallel mit den Nutzstrukturen prozessiert werden. Es werden Algorithmen zur Generierung des Designs der Teststrukturen und ihrer Platzierung im Waferlayout entwickelt. Dabei werden das Design der Nutzstruktur und deren funktionsrelevante Parameter, der technologische Ablauf und materialspezifische Kennwerte berücksichtigt. Im Ergebnis liegt eine Bibliothek von Standard-Teststrukturen vor, die für produktionsbegleitende Messungen sowie für die Übertragbarkeit der Ergebnisse geeignet sind. Außerdem werden allgemeingültige Richtlinien zur Durchführung der Messungen an den Standard-Teststrukturen abgeleitet. Das Messverfahren wurde an unterschiedlichen Mikrosystemen mit beweglichen Komponenten überprüft und zu einer allgemeinen Messmethode für diese Klasse von Mikrosystemen erweitert. / In this work a method for the characterization of microsystems with movable components is presented. The method allows to determine the relevant parameters and their variations on wafer level if the nominal shape of the structure and the type of deviations are known. The method is based on a comparison of the numerically calculated and experimentally measured Eigenfrequencies of the microsystems. For that purpose, the relationships between various Eigenfrequencies and the searched parameters are calculated by parameter variation analysis and the results of this analysis are approximated with appropriate functions. A Laser Doppler vibrometer based motion analyzer is used to determine the frequency response function of the micromechanical structure and extract Eigenfrequencies. The comparison of the measured and the calculated frequencies provides values for the searched parameters. The key element of the developed method is the measurement on special test structures that are placed in the wafer layout next to the actual microsystems and processed in the same technological process parallel to the actual microsystems. Algorithms for designing the test structures and their placement in the wafer layout are shown, taking into account the design of the actual microsystems and the function parameters of the technological process as well as material characteristics. As a result, a library of standard test structures for function relevant parameters is available. A general guideline for the measurement on the test structures is presented. The presented method is verified on various microsystems and extended to a whole class of microsystems with movable components.

Flow past circular cylinders with stepwise discontinuities in diameter was investigated experimentally and numerically for the diameter ratio D/d = 2 and three Reynolds numbers, Re = 150, 300, and 1050. The investigation was focused on the vortex shedding phenomena occurring in the wake of the cylinders. In the first series of experimental and numerical studies, the flow development past a single step cylinder was investigated. The single step cylinder model is comprised of a small diameter cylinder (d) attached coaxially to a large diameter cylinder (D). The results show that three distinct spanwise vortex cells form in the step cylinder wake: a single vortex shedding cell in the wake of the small cylinder (the S-cell) and two vortex shedding cells in the wake of the large cylinder, one in the region downstream of the step (the N-cell) and the other away from the step (the L-cell). Due to the differences in vortex shedding frequencies between the three cells, complex vortex connections occur in two vortex-interaction regions located between the adjacent cells. The region at the boundary between the S-cell and the N-cell is relatively narrow and its spanwise extent does not fluctuate significantly. In this region, vortex dislocations manifested as half-loop connections between two S-cell vortices of opposite sign. In contrast, the region at the boundary between the N-cell and the L-cell exhibits a transient behavior, with large scale vortex dislocations causing cyclic variation in the extent of N-cell vortices. For Re = 300 and 1050, small scale streamwise vortices forming in the wake complicate the vortex dynamics within the adjacent S-cell and L-cell. There is no significant Reynolds number effect on the average spanwise extent of the vortex cells and the two transition regions between neighboring cells. Finally, formation of N-cell vortices is linked to downwash fluctuations near the step. The flow development past a dual step cylinder was studied experimentally for Re = 1050. The dual step cylinder model is comprised of a small diameter cylinder (d) and a large diameter cylinder (D) mounted at the mid-span of the small cylinder. The experiments were completed for a range of large cylinder aspect ratios 0.2 ≤ L/D ≤ 17. The flow development is highly dependent on the aspect ratio of the large cylinder, L/D. The results identify four distinct flow regimes: (i) for L/D = 17, three vortex shedding cells form in the wake of the large cylinder, one central cell and two cells of lower frequency extending over about 4.5D from the large cylinder ends, (ii) for 7 < L/D ≤ 14, a single vortex shedding cell forms in the wake of the large cylinder, whose shedding frequency decreases with decreasing L/D, (iii) for 2 ≤ L/D ≤ 7, vortex shedding in the wake of the large cylinder is highly three-dimensional, with vortices deforming in the near wake, (iv) for 0.2 ≤ L/D ≤ 1, only small cylinder vortices are shed in the wake and can form vortex connections across the wake of the large cylinder.