Les tests d'écoute subjectifs permettent d'évaluer la fiabilité de reproduction des systèmes de codage audio (codecs). Le projet présenté ici vise à évaluer la possibilité d'utiliser les réactions physiologiques (activité électrodermale, cardiaque, musculaire et cérébrale) à la place d'une note donnée par l'auditeur, afin de caractériser la performance d'un codec. Ceci permettrait d'avoir une méthode d'évaluation plus proche de la perception réelle de qualité audio du sujet. Des tests d'écoute mettant en oeuvre des dégradations audio bien connues en concours avec la mesure des réactions physiologiques ont été réalisés pour 4 auditeurs. L'analyse des résultats montre que certaines caractéristiques physiologiques permettent d'avoir une information fiable sur la qualité audio perçue, et ce de manière répétable pour près de 70% des signaux audio testés chez un sujet, et près de 60% des séquences audio testées chez tous les sujets. Ceci permet de postuler sur la faisabilité d'une telle méthode d'évaluation subjective des codecs audio.

La récupération et la valorisation des rejets thermiques industriels à basse température et leur conversion en électricité constituent un moyen efficace pour la diminution de la consommation énergétique et l'augmentation de l'efficacité énergétique industrielle. Parmi les technologies actuelles et potentiellement utilisées pour la valorisation de l'énergie thermique rejetée par les différents secteurs industriels, on cite les cycles de Rankine utilisant des fluides de travail organiques. La plupart des études qui ont été faites sur ces derniers ne considèrent que l'aspect de l'analyse énergétique interne. Ce projet propose une étude détaillée d'une configuration de cycle de Rankine sans régénérateur et présente une méthodologie permettant la comparaison de cinq fluides de travail (R134a, R123, R141b, NH[indice inférieur 3] et H[indice inférieur 2]O). Ainsi, plusieurs études sont présentées dans ce projet. La première utilise la première loi de la thermodynamique et l'analyse énergétique interne permettant la détermination du rendement thermique et le travail spécifique du cycle. La deuxième considère l'analyse exergétique qui détermine le rendement de la deuxième loi ainsi que les irréversibilités présentes dans chaque composant du cycle. La troisième analyse se penche sur l'optimisation du cycle et la détermination de la plage de la pression d'évaporation. Cela consiste à minimiser la conductance thermique totale des échangeurs thermiques et maximiser la puissance nette du cycle. Il s'en suit une analyse permettant le dimensionnement de la turbine. Dans ce contexte, le paramètre de la taille de la turbine ainsi que le rapport des débits volumiques à l'entrée et à la sortie de la turbine pour chaque fluide de travail sont déterminés. Des valeurs optimales de ces paramètres sont ensuite obtenues dans les conditions qui minimisent la conductance thermique totale des échangeurs de chaleur. De plus, une autre analyse permet la critique des résultats apparus dans une récente publication et prouve l'efficacité du modèle implémenté dans ce projet de recherche. Finalement, une analyse a été réalisée pour obtenir des corrélations généralisées aux conditions de la puissance nette maximale. Les résultats obtenus ont montré la nécessité d'une étude économique qui se base sur le calcul des surfaces d'échange et les coûts d'installation du cycle.

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Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The experimental observation of the quantum Hall effect in a two-dimensional electron gas posed an intriguing question to theorists: Why is the quantization of conductance so precise, given the imperfections of the measured samples? The question was answered a few years later, when a connection was uncovered between the quantum Hall effect and topological quantities associated with the band structure of the material in which it is observed. The Hall conductance was revealed to be an integer topological invariant, implying its robustness to certain perturbations. The topological theory went further than explaining only the usual integer quantum Hall effect in a perpendicular magnetic field. Soon it was realized that it also applies to certain systems in which the total magnetic flux is zero. Thus it is possible to have a quantized Hall effect without Landau levels. We study a carbon nanotube in a magnetic field perpendicular to its axial direction. Recent studies suggest that the application of an electric field parallel to the magnetic field would induce a gap in the electronic spectrum of a previously metallic carbon nanotube. Despite the quasi onedimensional nature of the carbon nanotube, the gapped state supports a quantum Hall effect and is associated with a non zero topological invariant. This result is revealed when an additional magnetic field is applied parallel to the axis of the carbon nanotube. If the flux due to this magnetic field is varied by one flux quantum, exactly one electron is transported between the ends of the carbon nanotube. / AFRIKAANSE OPSOMMING: Die eksperimentele waarneming van die kwantum Hall effek in ’n twee-dimensionele elektron gas laat ’n interessante vraag aan teoretiese fisikuste: Waarom sou die kwantisasie van die geleiding so presies wees al bevat die monsters, waarop die meetings gedoen word, onsuiwerhede? Hierdie vraag word ’n paar jaar later geantwoord toe ’n konneksie tussen die kwantum Hall effek en topologiese waardes, wat verband hou met die bandstruktuur van die monster, gemaak is. Dit is aan die lig gebring dat die Hall geleiding ’n heeltallige topologiese invariante is wat die robuustheid teen sekere steurings impliseer. Die topologiese teorie verduidelik nie net die gewone kwantum Hall effek wat in ’n loodregte magneetveld waargeneem word nie. Dit is ook moontlik om ’n kwantum Hall effek waar te neem in sekere sisteme waar die totale magneetvloed nul is. Dit is dus moontlik om ’n gekwantiseerde Hall effek sonder Landau levels te hˆe. Ons bestudeer ’n koolstofnanobuis in ’n magneetveld loodreg tot die aksiale rigting. Onlangse studies dui daarop dat die toepassing van ’n elektriese veld parallel aan die magneetveld ’n gaping in die elektroniese spektrum van ’n metaliese koolstofnanobuis induseer. Ten spyte van die een-dimensionele aard van die koolstofnanobuis ondersteun die gapings-toestand steeds ’n kwantum Hall effek en hou dit verband met ’n nie-nul topologiese invariante. Hierdie resultaat word openbaar wanneer ’n bykomende magneetveld parallel tot die as van die koolstofnanobuis toegedien word. Indien die vloed as gevolg van hierdie magneetveld met een vloedkwantum verander word, word presies een elektron tussen die twee kante van die koolstofnanobuis vervoer.

Regional differences in sweat gland output, skin temperature and thermoreceptor distribution can account for variations in regional perceptions of temperature, thermal comfort and wetness sensation. Large cohorts of studies have assessed these perceptual responses during sedentary activity but the findings are typically applied to a multitude of conditions, including exercise. Increases in sweat gland output, redistribution of blood flow and changes in skin and core temperature are basic responses to exercise in most conditions and these ultimately influence our perceptual responses. The primary aim of this thesis is to determine factors that influence regional differences in thermal sensation, thermal comfort and wetness sensation during exercise in moderate to hot conditions. The secondary aim is to develop and understand an additional variable, galvanic skin conductance (GSC) that can be used to predict thermal comfort and wetness sensation. The aim of the first study (Chapter 4) was to determine the influence of exercise on thermal sensitivity and magnitude sensation of warmth to a hot-dry stimulus (thermal probe at 40°C) and assess if any gender-linked differences and/or regional differences exist. From the data, body maps indicating sensitivity were produced for both genders during rest and exercise. Females had more regional differences than males. Overall sensitivity was greatest at the head, then the torso and declined towards the extremities. The data showed that exercise did not cause a significant reduction in thermal sensitivity but magnitude estimation was significantly lower after exercise for males and selected locations in females. The cause of a reduced magnitude sensation is thought to be associated with exercise induced analgesia; a reduction in sensitivity due to exercise related increases in circulating hormones. As the literature suggests that thermal comfort in the heat is influenced by the presence of sweat, the next study and all proceeding studies were concerned with this concept. In Chapter 5, building on earlier studies performed in our laboratories, the influence of local skin wettedness (wlocal) on local thermal comfort and wetness sensation was investigated in a neutral dry condition (20.2 ± 0.5°C and 43.5 ± 4.5% RH) whilst walking (4.5 km∙hr-1). Regional differences in wlocal were manipulated using specialised clothing comprising permeable and impermeable material areas. Strong correlations existed between local thermal comfort and local wetness sensation with the various measured wlocal (r2>0.88, p<0.05 and r2>0.83, p<0.05, respectively). The thermal comfort limit was defined as the wlocal value at which the participants no longer felt comfortable. Regional comfort limits for wlocal were identified (in order of high-low sensitivity); lower back (0.40), upper legs (0.44), lower legs (0.45), abdomen (0.45), chest (0.55), upper back (0.56), upper arms (0.57) and lower arms (0.65). The maximum degree of discomfort and wetness sensation experienced during the investigation was kept deliberately low in an attempt to determine the threshold values. Therefore comfort scores and wetness scores rarely reached a state of uncomfortable or wet so the next step was to assess these relationships when sweat production is high and the sensations worsened. However, pilot testing indicated that a ceiling effect would occur for wlocal at high levels of sweat production whilst thermal discomfort increased indicating wlocal was not the determining parameter in that case. Thus an additional parameter was required. The chosen parameter was galvanic skin conductance (GSC) due to its alleged ability to monitor pre-secretory sweat gland activity, skin hydration and surface sweat. In Chapter 6, the reliability, reproducibility and validity of GSC were confirmed in a series of pilot tests. Moderate to strong correlations were found between GSC and regional sweat rate (RSR) (r2>0.60, p<0.05) and wlocal (r2>0.55, p<0.05). The literature suggests standardising GSC relative to a minimum and maximum GSC value; however uncertainties arise when attempting to achieve maximum GSC. Therefore a change from baseline (∆GSC) was chosen as the proposed method of standardisation for further use. Additional results (from Chapter 9) revealed that ∆GSC also reflects pre-secretory sweat gland activity as it increased prior to sweat being present on the skin surface and prior to an increase in RSR. In Chapter 9, also hydration of the stratum corneum was measured using a moisture meter and the results revealed that it has an upper limit; indicating maximal hydration. From this point of full skin saturation ∆GSC and RSR markedly increase though sensations did not. It was also found that ∆GSC is only influenced by surface sweat that is in direct contact with the electrode and is not influenced by sweat elsewhere on the skin surface between electrodes. Higher levels of thermal discomfort have rarely been explored and neither has its relationship with wlocal. The ability of ∆GSC and wlocal to predict local thermal comfort and wetness sensation were compared in two different conditions to elicit low and high sweat production. Unlike Chapter 5, the body sites were not manipulated to control wlocal but allowed to vary naturally over time. The test was carried out on males (Chapter 7) and females (Chapter 8) to compare any gender linked differences and the results suggest that females are more sensitive than males to the initial presence of sweat. For both genders, wlocal and ∆GSC are strong predictors of thermal comfort and wetness sensation. More importantly, wlocal can only be used to predict local thermal comfort in conditions of low sweat production or low levels of thermal discomfort. However, once sweat production increases and thermal discomfort worsens ΔGSC (and not wlocal) can predict thermal comfort. Due to low sweat production observed in females indicates that this is only relevant for females. It appears that epidermal hydration has an important role on influencing thermal comfort. Receptors influencing our perceptual responses are located in the epidermis and when sweat is produced and released onto the skin surface, this epidermis swells and the sensitivity of receptors are said to increase. wlocal indicates the amount of moisture present on the skin surface, yet ∆GSC indicates presecretory sweat gland activity and epidermal hydration where the receptors are located. This may explain why on numerous occasions thermal comfort had a stronger relationship with ∆GSC than wlocal. Where Chapter 5 indicated the true local comfort limits for each respective zone, Chapter 7 and 8 provided a global picture of how local regions interact and influence local thermal comfort across the body. When wlocal varies naturally, the torso areas naturally produce more sweat than the extremities and it seemed that these areas produce so much more sweat than the extremities that they dominate local thermal comfort across the whole body. This is referred to in this thesis as a model of segmental interaction. As with thermal comfort, wetness sensation had strong relationships with wlocal and ∆GSC. The results also revealed a strong relationship between wetness sensation and thermal comfort. In contrast to the widely supported claim, a drop in skin temperature is not required to stimulate a wetness sensation. The point at which we detect sweat and when it becomes uncomfortable occurs at different wlocal values across the body. Thermal comfort is shown to be influenced by sweat during exercise in moderate-to-hot conditions. As w has an upper limit the findings suggest that it cannot predict thermal comfort during high sweat rates. Galvanic skin conductance monitors the process of sweat production more closely and thus is a better predictor of thermal comfort during all conditions and particularly during high sweat production. The strong relationship between thermal comfort and wetness sensation confirm the role of sweat production on thermal comfort. Gender differences to perceptual responses were observed, with females generally being more sensitive to sweat and a warm thermal stimulus than males. Regional differences to sweat and a warm stimulus generally suggest that the torso area is more sensitive than the extremities. This is important not only for sports clothing design but also protective clothing at the work place.

<p>Over an extended period of time there have been plans to establish a shared facility in Lennheden to extract groundwater from the Badelunda esker to provide drinking water for the cities of Borlänge and Falun. The city of Falun is dissatisfied with the quality of its drinking water and the city of Borlänge is concerned about the risk of contamination of its existing groundwater supply at its current location. To provide a basis for a decision on this issue, the company Midvatten AB has been commissioned to perform hydrogeological investigations in the area of Lennheden.</p><p>The purpose of this thesis is to design a functional groundwater model of the area between Lennheden, place of planned extraction, and Övre Tjärna, place of existing extraction, to get a better understanding of the groundwater situation in the area. A groundwater model enables simulations of different scenarios in risk assessment and contaminant transport. The aim of the thesis is that the model can be used as an aid in Midvatten’s investigations in Lennheden and that it also can be used in future projects in the area.</p><p>The model has been made in Processing Modflow 5.3 and encompasses an area of 19,5 × 11 km along the Badelunda esker and the river Dalälven between Djurmo and Frostbrunnsdalen. The model has 6 layers and a cell resolution of 50 × 50 meters and 50 × 100 meters. The physical parameters of the model are comprised from different hydrological and geological investigations in the area.</p><p>The Badelunda esker and the river Dalälven totally dominate the groundwater situation in the area. A large part of the work in the thesis has been focused on the calibration of the horizontal hydraulic conductivity in the esker and the vertical hydraulic conductivity in the riverbed of Dalälven. The calibration of the model implies a vertical hydraulic conductivity of 0,01 – 0,1 md-1 in the riverbed of Dalälven, depending on the riverbed thickness.</p><p>Between Bäsna and Övre Tjärna, simulated and observed groundwater levels correspond well. The transport time of the water in the esker, simulated in PMPATH, also corresponds well with estimated transport times. The model can be used for simpler studies of contaminant transport.</p><p>Simulation of the pumping test in Lennheden gives a good correspondence eastward in the esker from Lennheden to Övre Tjärna. Westward in the esker, from Lennheden to Bäsna, the draw down is sharper than observed. Possible reasons for the sharper draw down is an underestimation of the bulk of the esker and that the vertical hydraulic conductivity of the riverbed is set too low between Lennheden and Bäsna.</p><p>In order to improve the model, the most important step should be to thoroughly investigate the river Dalälven with regards to vertical hydraulic conductivity in the riverbed and riverbed thickness.</p> / <p>Under en längre tid har det funnits planer på att upprätta en ny, gemensam vattentäkt för Borlänge och Falu kommun i Badelundaåsen i Lennheden nordväst om Borlänge stad. Falu kommun är missnöjd med vattenkvaliteten i sin ytvattentäkt och Borlänge är oroad över riskerna med att ha sin nuvarande vattentäkt i Badelundaåsen lokaliserad i nära anslutning till riksväg 70 och järnvägen. Beslut i frågan ska tas under 2006 och Midvatten AB har fått i uppdrag att genomföra geohydrologiska undersökningar i och runt Lennheden som underlag till beslutet.</p><p>Syftet med det här examensarbetet är att skapa en fungerande grundvattenmodell för området mellan Lennheden, plats för planerat vattenuttag, och Övre Tjärna, plats för befintligt vattenuttag, för att få en större förståelse för grundvattenmagasinet. En grundvattenmodell möjliggör simulering av olika scenarion så som föroreningstransport i grundvattnet och bestämning av skyddsområden. Målet är att modellen ska kunna användas som ett komplement i Midvattens undersökningar och även användas i framtida projekt i området.</p><p>Modellen är gjord i Processing Modflow 5.3 och omfattar ett 19,5 × 11 km stort område längs Badelundaåsen och Dalälven mellan Djurmo och Frostbrunnsdalen. Modellen består av 6 lager där cellernas upplösning är 50 × 50 meter och 50 × 100 meter. De fysiska parametrar som modellen är uppbyggd av är sammanställda från olika hydrologiska och geologiska undersökningar som har utförts i området de senaste 30 åren.</p><p>Badelundaåsen och Dalälven är de två komponenter som totalt dominerar grundvattensituationen i området. En stor del av arbetet har fokuserats på kalibreringen av den horisontella hydrauliska konduktiviteten i åsen och den vertikala hydrauliska konduktiviteten i Dalälvens botten. I modellen är den vertikala hydrauliska konduktiviteten i Dalälvens botten kalibrerad till intervallet 0,01 – 0,1 md-1 beroende på bottnens mäktighet.</p><p>På sträckan mellan Bäsna och Övre Tjärna så fungerar modellen bra. Simulerade och observerade grundvattennivåer stämmer väl överens. Även vattnets transporttider i åsen, simulerade i PMPATH, stämmer väl överens med uppskattade transporttider. Modellen kan användas för enklare studier av ämnestransport.</p><p>Vid simulering av provpumpningen i Lennheden så är överensstämmelsen god österut i åsen, från Lennheden till Övre Tjärna. Västerut i åsen, från Lennheden till Bäsna, är avsänkningen av grundvattennivån för kraftig. Möjliga orsaker till den för kraftiga avsänkningen är att åsens utbredning är underskattad och att Dalälvens botten har en för lågt ansatt vertikal hydraulisk konduktivitet längs sträckan Lennheden – Bäsna.</p><p>Den klart viktigaste åtgärden för att förbättra modellen skulle vara att grundligt undersöka Dalälven, särskilt längs sträckan Djurmo – Båtsta, med avseende på dess bottens vertikala hydrauliska konduktivitet och mäktighet.</p>

As a result of manufacturing processes, real surfaces have roughness and surface curvature. The real contact occurs only over microscopic contacts, which are typically only a few percent of the apparent contact area. Because of the surface curvature of contacting bodies, the macrocontact area is formed, the area where microcontacts are distributed randomly. The heat flow must pass through the macrocontact and then microcontacts to transfer from one body to another. This phenomenon leads to a relatively high temperature drop across the interface. Thermal contact resistance (TCR) is a complex interdisciplinary problem, which includes geometrical, mechanical, and thermal analyses. Each part includes a micro and a macro scale sub-problem. Analytical, experimental, and numerical models have been developed to predict TCR since the 1930's. Through comparison with more than 400 experimental data points, it is shown that the existing models are applicable only to the limiting cases and none of them covers the general non-conforming rough contact. The objective of this study is to develop a compact analytical model for predicting TCR for the entire range of non-conforming contacts, i. e. , from conforming rough to smooth sphere-flat in a vacuum. The contact mechanics of the joint must be known prior to solving the thermal problem. A new mechanical model is developed for spherical rough contacts. The deformation modes of the surface asperities and the bulk material of contacting bodies are assumed to be plastic and elastic, respectively. A closed set of governing relationships is derived. An algorithm and a computer code are developed to solve the relationships numerically. Applying Buckingham Pi theorem, the independent non-dimensional parameters that describe the contact problem are specified. A general pressure distribution is proposed that covers the entire spherical rough contacts, including the Hertzian smooth contact. Simple correlations are proposed for the general pressure distribution and the radius of the macrocontact area, as functions of the non-dimensional parameters. These correlations are compared with experimental data collected by others and good agreement is observed. Also a criterion is proposed to identify the flat surface, where the influence of surface curvature on the contact pressure is negligible. Thermal contact resistance is considered as the superposition of macro and micro thermal components. The flux tube geometry is chosen as the basic element in the thermal analysis of microcontacts. Simple expressions for determining TCR of non-conforming rough joints are derived which cover the entire range of TCR by using the general pressure distribution and the flux tube solution. A complete parametric study is performed; it is seen that there is a value of surface roughness that minimizes TCR. The thermal model is verified with more than 600 data points, collected by many researchers during the last 40 years, and good agreement is observed. A new approach is taken to study the thermal joint resistance. A novel model is developed for predicting the TCR of conforming rough contacts employing scale analysis methods. It is shown that the microcontacts can be modeled as heat sources on a half-space for engineering applications. The scale analysis model is extended to predict TCR over the entire range of non-conforming rough contacts by using the general pressure distribution developed in the mechanical model. It is shown that the surface curvature and contact pressure distribution have no effect on the effective micro thermal resistance. A new non-dimensional parameter is introduced as a criterion to identify the three regions of TCR, i. e. , the conforming rough, the smooth spherical, and the transition regions. An experimental program is designed and data points are collected for spherical rough contacts in a vacuum. The radius of curvature of the tested specimens are relatively large (in the order of m) and can not be seen by the naked eye. However, even at relatively large applied loads the measured joint resistance (the macro thermal component) is still large which shows the importance of surface out-of-flatness/curvature. Collected data are compared with the scale analysis model and excellent agreement is observed. The maximum relative difference between the model and the collected data is 6. 8 percent and the relative RMS difference is approximately 4 percent. Additionally, the proposed scale analysis model is compared/verified with more than 880 TCR data points collected by many researchers. These data cover a wide range of materials, surface characteristics, thermal and mechanical properties, mean joint temperature, directional heat transfer effect, and contact between dissimilar metals. The RMS difference between the model and all data is less than 13. 8 percent.

The research in this thesis focuses on the ways in which participants represent highly charged negative emotional experiences in narrative form through vocal disclosures, and the relationships between disclosure style and psychophysiological activity. This thesis also attempts to theorise some of the psychophysiological mechanisms that may be associated with the effects of emotional disclosure. Participants were randomly assigned to an emotion (disclosure) group (n = 16) in which they talked about a particular highly charged negative experience, or a neutral (control) group (n = 16) in which they talked about their typical morning. Participants undertook these tasks on three separate occasions, each separated by one week. Skin conductance levels (SCLs) were measured throughout. Statistical analyses were conducted to look at possible SCL differences between the two groups and associations between the disclosure style and SCL variations. Although there were no statistically significant differences between the two groups' SCLs, there were significant differences in SCLs with regard to disclosure style. Qualitative narrative and discourse analyses were undertaken on 4 selected participants, chosen on the basis of clinically significant SCL moves. These analyses revealed that neutral participants also engaged in forms of emotional disclosure through forms of identity negotiation that were constructed within their talk concerning their typical mornings. The qualitative analysis also identified disclosure styles that may be associated with variations in psychophysiological activity.

This thesis addresses the tunnelling of charge carriers in different materials. First looking at the simplest case of electron tunnelling in metals at zero, then finite temperature, the current is obtained using the Fermi-Dirac golden rule and then the conductance is obtained. This is extended to take into account the spatial dependence of one of the metals being a tip since experimentally this is done by scanning tunnelling microscopy where a tip traces over the surface of a sample. The next step is to look at tunnelling between a metal and a semiconductor, again the current is found. Semiconductors can be doped and the effect this has on tunnelling is examined. Next superconductors are introduced. The purpose of my research has been to look at the tunnelling spectra of high-temperature superconducting cuprates for both extrinsic (metal-superconductor) and intrinsic (superconductor-superconductor) tunnelling. The main features seen experimentally with cuprate tunnelling are identified and then a theory capable of explaining these features is discussed. The theory is compared to experimental results and we find good agreement.

Le travail présenté dans ce manuscrit décrit quelques-uns des mécanismes qui régissent les échanges de CO2 et d’eau dans le mésophylle. Nous présentons dans une première partie une méthode originale qui utilise une technique de traçage isotopique et une modélisation deséchanges gazeux pour décrire le transfert du CO2 et la concentration de CO2 aux sites catalytiques des anhydrases carboniques. Dans une deuxième partie, cette approche nous permet de caractériser la diffusion de CO2 intra-mésophylienne et d’aborder l’étude du rôle des anhydrases carboniques et des aquaporines dans la facilitation du transport de CO2. Cette étude est basée sur une analyse fonctionnelle de mutants d’insertions d’Arabidopsis affectésdans l’expression des anhydrases carboniques (ACs) ou des aquaporines. La contribution fonctionnelle d’une AC, bCA4 localisée à la membrane plasmique et récemment identifiée estanalysée plus spécifiquement. Dans une troisième partie, nous montrons par un travail de modélisation que l’approche de traçage isotopique précédemment introduite pour étudier le transfert de CO2 peut être utilisée pour étudier la compartimentation de l’eau mésophyllienne et les flux associés. Cette approche nous permet de démontrer l’existence d’une compartimentation fonctionnelle de l’eau foliaire. La signification de cette compartimentation est discutée, et une nouvelle méthode de suivi quantitatif des flux d’eau entre l’apoplasme etle symplasme est proposée. Enfin, dans une dernière partie nous abordons expérimentalement les effets de l’acide abscissique sur la transpiration foliaire et la régulation stomatique. / N this study, mechanisms that govern CO2 and water fluxes in the mesophyll are investigated. In a first part, an original approach based on isotopic tracing and modeling of gas exchange is presented to describe the CO2 transfer towards sites of carbonic anhydrases catalysis that are used to probe the intracellular CO2 concentration. In a second part, this approach allows to characterize the intracellular diffusion of CO2 and to address the implication of carbonicanhydrases and aquaporins in the facilitation of the CO2 transfer. The functional analysis is based on the characterization of Arabidopsis mutants in which the expression of some carbonic anhydrases (CAs) or aquaporins is impaired. The implication of a recently identified CA, bCA4 located at the plasma membrane, is studied in detail. In a third part a modeling approach is used to show that the method of isotopic tracing introduced to probe the CO2 fluxes can also be used to study the compartmentation of the mesophyll water and the associated fluxes. The basis of this functional compartmentation is analyzed and a newmethod is proposed to quantitatively monitor the water fluxes between the apoplasm and the symplasm. In a last part, the effects of abscissic acid on the leaf transpiration and on the stomatal aperture regulation are addressed.