[pt] Inúmeros estudos têm sido realizados para melhor entender a formação e estabilidade de emulsões. Em algumas situações, é desejável ter emulsões estáveis; em outros, a separação de fases por coalescência de gotas é benéfica. Em ambos os casos, é importante entender os mecanismos associados ao processo de coalescência. O presente trabalho investiga a relação entre as propriedades reológicas das interfaces óleo-água e o tempo de drenagem de um filme fino de óleo entre duas gotas aquosas. A tensão interfacial e a reologia dilatacional interfacial foram medidas usando a análise axissimétrica da forma da gota. Foram avaliadas diferentes concentrações de um tensoativo não iônico (Span 80) dissolvido em óleo mineral (Primol 352). Os resultados indicam uma relação direta entre as propriedades da estrutura formada na interface óleo-água e a ausência de coalescência das gotas. Para concentrações de surfactante abaixo da concentração micelar crítica (CMC), a interface é fracamente elástica (fluid-like) e o processo de coalescência sempre ocorre; o tempo de drenagem não está relacionado ao tempo de envelhecimento da interface. Para concentrações de surfactante acima da CMC, os módulos elástico e viscoso mostraram mudanças significativas com o envelhecimento, levando à formação de um filme sólido na interface, impedindo a coalescência entre as gotas. Usamos experimentos de coalescência gota/gota para avaliar o efeito da reologia interfacial na dinâmica de coalescência. Para entender melhor o fenômeno da não coalescência, estudamos microscopicamente a estrutura do filme interfacial e observamos o aparecimento de pequenas gotas de água formadas na interface através de emulsificação espontânea. Descobrimos que a taxa de surgimento dessas microgotículas está diretamente relacionada à concentração de surfactante. À medida que a concentração de surfactante aumenta, mais rápido ocorre o processo de emulsificação espontânea, o que confirma os resultados obtidos com a reologia interfacial. Finalmente, um novo método para promover a desestabilização da emulsão impondo uma perturbação do filme interfacial pelo escoamento das gotas através de capilares constritos é proposto e testado. / [en] Several studies have been conducted to understand emulsions formation and stability. In some situations, it is desirable to have stable emulsions; in others, phase separation through drop coalescence is beneficial. In both cases, it is important to understand the mechanisms associated to the coalescence process. The present work investigates the relationship between rheological properties of oil-water interfaces and the drainage time of a thin oil film between two aqueous drops. Interfacial tension and dilatational rheology were measured using the axisymmetric drop shape analysis. We evaluated different concentrations of a nonionic surfactant (Span 80) dissolved in mineral oil (Primol 352) phase. The results indicate a direct relationship between the properties of the structure formed at the oil-water interface and the absence of droplet coalescence. For low surfactant concentrations, below the critical micelle concentration (CMC), the interface is weakly elastic (fluid-like) and the coalescence process always occurs; the draining time is not to related to the aging time of the interface. For surfactant concentrations above CMC, the elastic and viscous moduli showed significant changes with aging leading to the formation of a solid-like film at the interface preventing further coalescence. We used a drop/drop coalescence experiments to evaluate the effect of interfacial rheology on the coalescence dynamics. To better understand the phenomenon of non-coalescence, we study the structure of interfacial film microscopically and observe the appearance of small water droplets formed at the interface by spontaneous emulsification. We found that the emergence rate of these microdroplets is directly related to the surfactant concentration. As the surfactant concentration increases, faster the spontaneous emulsification process occurs, which confirms the results obtained with the interfacial rheology. Finally, a new method to promote emulsion destabilization by imposing a perturbation of the interfacial film by flowing the drops through constricted capillaries is proposed and tested.

La domestication du mil (Pennisetum glaucum), dans le Sahel, a engendré une large gamme de variétés, très diversifiées pour de nombreuses caractéristiques agronomiques. En particulier, la diversité de la durée du cycle des variétés locales de mil est une composante essentielle des stratégies mises en œuvre par les agriculteurs pour faire face aux fluctuations des précipitations et assurer une certaine stabilité de la production. Au cours des dernières décennies, des évolutions dans les pratiques agricoles ont été observées, en réponse à des changements écologiques et sociaux. Une des conséquences de ces évolutions pourrait être l’existence de flux de gènes entre variétés à cycle court et variétés à cycle long du fait de l’émergence de situations de parapatrie entre ces deux types de variétés, naguère isolées. Par ailleurs, l’existence de recouvrement des périodes des floraisons de ces deux types variétaux a déjà été préalablement observée. Une telle situation amène donc à s’interroger sur la dynamique évolutive passée et actuelle de la diversité de la longueur du cycle du mil dans le Sahel. Dans la première partie de ma thèse, j’ai évalué les possibilités d’occurrence de flux de gènes entre variétés précoces et tardives de mil dans le Sud-ouest du Niger, en utilisant une approche comparative entre situations contrastées pour la distribution spatiale de ces deux types de variétés. J’ai réalisé : 1) une étude des périodes de floraison de deux variétés de mil (précoce (Haïni Kiré) : 75 à 95 jours entre le semis et la maturité et tardive (Somno) : 105 à 125 jours de durée de cycle) dans plusieurs champs paysans, et dans deux villages. 2) une analyse moléculaire à l’aide de 15 marqueurs microsatellites qui a permis l’estimation des niveaux de différenciation génétique entre populations de mils précoces et tardifs échantillonnés dans 4 villages (incluant les deux villages déjà cités) de la même région.Les résultats ont montré la possibilité effective de flux de pollen et l’existence d’introgressions génétiques entre variétés précoces et tardives. Les mécanismes qui pourraient permettre un maintien sur le long terme d’une différenciation phénologique entre les deux types variétaux malgré l’existence de ces flux de gènes, sont discutés.Dans la deuxième partie, j’ai utilisé une approche « gène candidat » combinée à une démarche de génétique des populations, pour tenter d’identifier des gènes qui auraient pu contribuer à la diversité de la durée de cycle chez le mil. Je me suis focalisé sur trois gènes du contrôle de la transition florale PgHd3a, PgDwarf8 et PgPHYC. Leur implication dans la diversité de la durée de cycle chez plusieurs espèces a déjà été montrée. J’ai estimé les niveaux de différenciation génétique entre les mils domestiques et sauvages, précoces et tardifs pour ces trois gènes J'ai aussi cherché à mettre en évidence, au sein de ces gènes, les empreintes éventuelles d’évènements sélectifs passés. Afin de prendre en compte l’histoire démographique des mils dans les tests de neutralité sélective, j’ai utilisé les données de polymorphisme nucléotidiques de 8 séquences témoins dans le cadre d’une approche Bayésienne.Les résultats obtenus suggèrent fortement que PgHd3a et PgDwarf8 ont été ciblés par la sélection durant la domestication. Cependant, les données ne soutiennent pas l’hypothèse d’un rôle potentiel des trois gènes candidats dans la différenciation de la durée de cycle entre les variétés locales précoces et tardives. L’approc / Domestication of pearl millet (Pennisetum glaucum) in the Sahel of Africa has produced a wide range of diversity in cycle duration of landraces. This diversity allows Sahelian farmers to outface the precipitation fluctuation and to ensure regularity in grain production. Due to ecological and social recent changes, modifications of farmer’s practices could be a factor promoting gene flow between the early and late flowering varieties by increasing the opportunity of neighboring and flowering overlap between them. Such a situation raises questions about the past and current evolutionary dynamics of phenological diversity in this crop.In the first part of my thesis I tried to evaluate the possibility of gene flow between pearl millet varieties in South-West Niger, through a comparative approach among contrasting situations pertaining to the spatial distribution of early and late landraces. Therefore I conducted: 1) a field study where we observed flowering periods, for two types of varieties (early type (Haïni Kiré): 75 to 95 days and late type (Somno): 105 to 125 days of cycle length) in several pearl millet fields, and in two villages 2) a molecular study that allows the assessment of the level of genetic differentiation between late and early flowering populations sampled from four villages (including the two where the field study was conducted) of the same region (Dallol Bosso), using microsatellite markers. I was able to demonstrate the occurrence of pollen flow between the two types of landraces and I also showed evidence of genetic introgression between early and semi-late landraces. Potential mechanisms that would allow for the maintenance of the phenological differentiation between these two varieties and despite the gene flow are discussed.In the second part of this work I used a candidate gene and a population genetics approach, to try to identify genes that may have contributed to the cycle length diversity in pearl millet. I focused on three flowering candidate genes, PgHd3a, PgDwarf8 and PgPHYC which have been shown to be involved in the cycle length genetic diversity in several species, in order to estimate the differentiation between wild and domestic pearl millets and between early and late landraces, on the basis of theses candidate genes. I also tried to track for the fingerprint of eventual past selective events within these candidate genes. To be able to distinguish the effects of selection from the effect of demographic events that occurred during the domestication process, I used 8 neutral STS loci and an Approximate Bayesian Computation approach.My results strongly suggest that PgHd3a and PgDwarf8 were likely targeted by selection during domestication. However, a potential role of any of the three candidate genes in the phenological differentiation between early and late landraces was not supported by our data. The Bayesian approach confirmed the idea, suggested by many authors, that the gene flow from the wild to the domestic genetic pool has contributed significantly to the genetic diversity of the domestic pearl millet.

Cette thèse se compose de quatre chapitres:Le chapitre 1 étudie la distribution du temps de coalescence (plus récent ancêtre commun) de deux individus tirés au hasard (uniformly) dans la génération actuelle d'un processus de Bienaymé-Galton-Watson en temps continu.Dans le chapitre 2, nous obtenons une représentation de la diffusion de Feller logistique en termes des temps locaux d'un mouvement brownien réfléchi H avec une dérive qui est affine en le temps local accumulé par H à son niveau actuel.Le chapitre 3 considère la diffusion de Feller avec compétition générale. Nous donnons des conditions précises sur le terme de la concurrence, pour le but de décider si le temps d'extinction (qui est aussi la hauteur du processus) reste borné ou non lorsque la taille initiale de la population tend vers l'infini, et de même pour la masse totale du processus.Dans le chapitre 4, nous généralisons les résultats du chapitre 3 pour le cas du processus de branchement à espace d'état continu avec compétition à trajectoires discontinues. / This thesis consists of four chapters:Chapter 1 investigates the distribution of the coalescence time (most recent common ancestor) for two individuals picked at random (uniformly) in the current generation of a continuous time Bienaymé-Galton-Watson process.In chapter 2 we obtain a Ray-Knight representation of Feller's branching diffusion with logistic growth in terms of the local times of a reflected Brownian motion H with a drift that is affine in the local time accumulated by H at its current level.Chapter 3 considers the Feller's branching diffusion with general competition. We give precise conditions on the competition term, in order to decide whether the extinction time (which is also the height of the process) remains or not bounded as the initial population size tends to infinity, and similarly for the total mass of the process.In chapter 4 we generalize the results of chapter 3 to the case of continuous state branching process with competition which has discontinuous paths.

This dissertation is an analysis of the segmental phonology of the Shangani language as spoken in the South Eastern parts of Zimbabwe. It starts by presenting the language situation in Zimbabwe and comparing the language’s status in Zimbabwe with that of its sister varieties in South Africa where it is referred to as Tsonga and in Mozambique where it is referred to as XiChangana or Changana. The dissertation is based on data collected from the speakers of Shangani using a variety of research techniques. The dissertation identifies and characterizes the language’s distinctive phonemes using the minimal pair and set tests. It presents the language’s consonants, which include aspirated, breathy-voiced, pre-nasalized, labialized and palatalized consonants. It shows that in Shangani, voiceless consonants cannot be pre-nasalized and that there is an incompatibility between that labio-velar glide /w/ and most labial consonants excpt /m/. The phonemes are analysed using Chomsky and Halle’s (1968) distinctive feature theory. The study uses Clements and Keyser’s (1983) CV phonology of the syllable structure to analyse the language’s syllable structure. The language’s canonical syllable structure is CV. It is also shown that consonant clusters are gaining their way into the language through borrowing from English, Afrikaans and other languages that have consonant clusters in their inventories. Onsetless Vs are marginally attested word-initially. In agent nouns, VV sequences are in most cases retained. These sequences are not analysed as diphthongs since they occupy different V slots on the syllable tier. The second vowel in the sequence is the onsetless syllable. Affricates, NCs, Cws and Cjs are presented as unitary segments that occupy a single C slot of the CV tier. Phonological processes that are attested in the language are also presented. Secondary articulation, vowel deletion, feature spreading, vowel coalescence and nasalization are shown to be the most common phonological process in the language. Since Shangani has the CV syllable typology, most of the phonological processes are there to resolve hiatus that would have been induced by suffixation of vowel commencing stems or suffixes to vowel final prefixes or stems. The notion of domains is shown to be a diagnostic tool for identifying a process in a hiatus situation. The study shows that vowel deletion is the least preferred strategy when secondary articulation, feature spreading, vowel coalescence have been blocked by some constraints like syllable structure processes or the language’s phonotactics / African Languages / D. Litt. et Phil. (African Languages)

This dissertation is an analysis of the segmental phonology of the Shangani language as spoken in the South Eastern parts of Zimbabwe. It starts by presenting the language situation in Zimbabwe and comparing the language’s status in Zimbabwe with that of its sister varieties in South Africa where it is referred to as Tsonga and in Mozambique where it is referred to as XiChangana or Changana. The dissertation is based on data collected from the speakers of Shangani using a variety of research techniques. The dissertation identifies and characterizes the language’s distinctive phonemes using the minimal pair and set tests. It presents the language’s consonants, which include aspirated, breathy-voiced, pre-nasalized, labialized and palatalized consonants. It shows that in Shangani, voiceless consonants cannot be pre-nasalized and that there is an incompatibility between that labio-velar glide /w/ and most labial consonants excpt /m/. The phonemes are analysed using Chomsky and Halle’s (1968) distinctive feature theory. The study uses Clements and Keyser’s (1983) CV phonology of the syllable structure to analyse the language’s syllable structure. The language’s canonical syllable structure is CV. It is also shown that consonant clusters are gaining their way into the language through borrowing from English, Afrikaans and other languages that have consonant clusters in their inventories. Onsetless Vs are marginally attested word-initially. In agent nouns, VV sequences are in most cases retained. These sequences are not analysed as diphthongs since they occupy different V slots on the syllable tier. The second vowel in the sequence is the onsetless syllable. Affricates, NCs, Cws and Cjs are presented as unitary segments that occupy a single C slot of the CV tier. Phonological processes that are attested in the language are also presented. Secondary articulation, vowel deletion, feature spreading, vowel coalescence and nasalization are shown to be the most common phonological process in the language. Since Shangani has the CV syllable typology, most of the phonological processes are there to resolve hiatus that would have been induced by suffixation of vowel commencing stems or suffixes to vowel final prefixes or stems. The notion of domains is shown to be a diagnostic tool for identifying a process in a hiatus situation. The study shows that vowel deletion is the least preferred strategy when secondary articulation, feature spreading, vowel coalescence have been blocked by some constraints like syllable structure processes or the language’s phonotactics / African Languages / D. Litt. et Phil. (African Languages)

Agitated dispersions of one liquid in another immiscible liquid are widely used in chemical industry in operations such as liquid-liquid extraction, suspension polymerisation, and blending of polymers. When holdup of the dispersed phase is increased, in an effort to increase the productivity, at a critical holdup, the dispersed phase catastrophically becomes the continuous phase and vice versa. This phenomenon is known as phase inversion. Although the inversion phenomenon has been studied off and on over the past few decades, the mechanism of phase inversion (PI) has yet not become clear. These studies have however brought out many interesting aspects of PI, besides unravelling the effect of physical and operational variables on PL Experiments show that oil-in-water (o/w) and water-in-oil (w/o) dispersions behave very differently, e.g water drops in w/o dispersions contain oil droplets in them, but oil drops in o/w dispersions contain none, dispersed phase hold up at which inversion occurs increases with agitation speed for w/o dispersions but decreases for o/w dispersions. A common feature of both types of dispersions however is that as agitation speed is increased to high values, inversion holdups reach a constant value. A further increase in agitation speed does not change inversion hold up. Although this finding was first reported a long time ago, the implications it may have not received any attentions. In fact, the work reported in the literature since then does not even mention it. The present work shows that this finding has profound implications. Starting with the finding that at high agitation speed inversion hold up does not change with agitation speed, the present work shows that inversion hold up also does not change with agitator diameter, type of agitator and vessel diameter. In these experiments, carried out in agitated vessel, energy was introduced as a point source. The experiments carried out with turbulent flow in annular region of two coaxial cylinders, inner one rotating, in which energy is introduced nearly uniformly throughout the system, show that the inversion holdup remains unchanged. These results indicate that constant values of inversion holdups for a given liquid-liquid systems (o/w and w/o) are properties of the liquid-liquid systems alone, independent of geometrical and operational parameters. A new hypothesis is proposed to explain the new findings. Phase inversion is considered to occur as a result of imbalance between breakup and coalescence of drops. Electrolytes, which affect only coalescence of drops, were therefore added to the system to investigate the effect of altering coalescence of drops on phase inversion. The experiments performed in the presence of electrolyte KI at various concentrations indicate that addition of electrolyte increases the inversion holdup for both o/w and w/o dispersions for three types of systems: non polar-water, polar-water and immiscible organic-organic. Higher the concentration of electrolyte used, higher was the holdup required for phase inversion. These findings indicate that while the addition of electrolyte increases coalescence of drops in lean dispersions, it has exactly opposite effect on imbalance of breakage and coalescence of drops at high holdups near phase inversion point. The opposite effect of electrolytes in lean and concentrated dispersions could be explained qualitatively, but only in part in the light of a new theory, involving multi-particle interactions. The phase inversion phenomenon is quantified in a simple manner by testing the breakage and coalescence rate expressions available in literature. It has been found that, equilibrium drop size (where breakage and coalescence events are in dynamic equilibrium) approaches infinity near phase inversion holdup which is not an ex perimentally observed fact. To capture the catastrophic nature of phase inversion, two steady state approach is proposed. The two steady states namely the stable steady state and unstable steady state, are achieved by modifying the expression for coalescence frequency on the basis of (i) shear coalescence mechanism and, (ii) recognising the fact that at high dispersed phase holdup the droplets are already in contact with each other at all times and hence rendering the second order coales cence process to a first order one. Using two steady states approach, catastrophic phase inversion is shown to occur at finite drop size.

The failure mechanism in ductile materials involves void nucleation, their growth and subsequent coalescence to form the fracture surface. The voids are generated due to fracture or debonding of second phase particles or at slip band intersections. The triaxial stress field prevailing around a crack tip and in the necking region strongly influences the growth of these voids. In the initial stages of deformation, these microscale voids are often sufficiently small so that they exist entirely within a single grain of a polycrystalline material. Further, single crystals are used in high technology applications like turbine blades. This motivates the need to study void growth in a single crystal while investigating ductile fracture. Thus, the objectives of this work are to analyze the interaction between a notch tip and void as well as the growth and coalescence of a periodic array of voids under different states of stress in ductile FCC single crystals. First, the growth of a cylindrical void ahead of a notch tip in ductile FCC single crystals is studied. To this end, 2D plane strain finite element simulations are carried out under mode I, small scale yielding conditions, neglecting elastic anisotropy. In most of these computations, the orientation of the FCC single crystal is chosen so that notch lies in the (010) plane, with notch front along the [101] direction and potential crack growth along [101]. This orientation has been frequently observed in experimental studies on fracture of FCC single crystals. Three equivalent slip systems are considered which are deduced by combining three pairs of 3D conjugate slip systems producing only in-plane deformation. Attention is focused on the effects of crystal hardening, ratio of void diameter to spacing from the notch on plastic flow localization in the ligament connecting the notch and the void as well as their growth. The results show strong interaction between slip shear bands emanating from the notch and angular sectors of single slip forming around the void leading to intense plastic strain development in the ligament. However, the ductile fracture processes are retarded by increase in hardening of the single crystal and decrease in ratio of void diameter to spacing from the notch. In order to examine the effect of crystal orientation, computations are performed with an orientation wherein the three effective slip systems are rotated about the normal to the plane of deformation. A strong influence of crystal orientation on near-tip void growth and plastic slip band development is observed. Further, in order to study the synergistic, cooperative growth of multiple voids ahead of the notchtip, an analysis is performed by considering a series of voids located ahead of the tip. It is found that enhanced void growth occurs at higher load levels as compared to the single void model. Next, the growth and coalescence of a periodic array of cylindrical voids in a FCC single crystal is analyzed under different stress states by employing a 2D plane strain, unit cell approach. The orientation of the crystal studied here considers [101] and [010] crystal directions along the minor and major principal stress directions, respectively. Three equivalent slip systems, similar to those in the notch and void simulations are taken into account. Fringe contours of plastic slip and evolution of macroscopic hydrostatic stress and void volume fraction are examined. A criterion for unstable void growth which leads to onset of void coalescence is established. The effects of various stress triaxialities, initial void volume fraction and hardening on void growth and coalescence is assessed. It is observed that plastic slip activity around the void intensifies with increase in stress triaxiality. The macroscopic hydrostatic stress increases with deformation, reaches a peak value and subsequently decreases rapidly. An increase in stress triaxiality enhances the macroscopic hydrostatic stress sustained by the unit cell and promotes void coalescence. The stress triaxiality also has a profound effect on the shape of the void profile. The values of critical void volume fraction and critical strain, which mark onset of void coalescence, decrease within crease in stress triaxiality. However, the onset of void coalescence is delayed by increase in hardening and decrease initial void volume fraction.

In dieser Arbeit wird eine neue Methode und ein neuartiges FET -Sensorelement zum Nachweis von Flüssigkeitsbewegungen vorgestellt, das zudem bei Bedarf auch als Chemo- oder Biosensor fungieren kann. Das Einsatzspektrum von FET-basierten Sensoren in Lab on a Chip-Systemen wird dadurch entscheidend erweitert. Bei dem entwickelten FET-Sensor Bauelement handelt es sich um einen normally-on n-leitenden Dünnschichtfeldeffekttransistor mit Ti-Au-Kontakten, basierend auf Silicon-on-Insulator- Substraten, wobei das natürliche Oxid des Siliziumfilms als Schnittstelle zum Elektrolyten bzw. zur Flüssigkeit verwendet wird. Der mit 10exp16 Bor Atomen pro cm³ p-dotierte Siliziumdünnfilm hat eine Dicke von nur 55 nm und ist durch eine 95 nm dicke Siliziumdioxidschicht vom darunterliegenden Siliziumsubstrat von 600 µm Dicke elektrisch isoliert. Aufgrund der geringen Schichtdicke durchdringt die feldempfindliche Raumladungs- bzw. Verarmungszone die gesamte Dünnschicht, so dass durch Anlegen einer Backgatespannung am Substrat der spezifische Widerstand und die Empfindlichkeit des Bauelements eingestellt werden können. Grundlegende ISFET-Funktionalitäten wie die Empfindlichkeit auf Änderungen der Ionenstärke und des pH-Wertes werden nachgewiesen und ein ENFET-Glukosesensor realisiert. Zudem wird im Hinblick auf die Separation von Emulsionen der Nachweis erbracht, dass die Benetzung mit Hexan und Toluol eine Änderung der spezifischen Leitfähigkeit bewirkt, und die Empfindlichkeit des Bauelements nach Beschichtung mit einem hydrophoben Methacrylatcopolymerfilm erhalten bleibt. Hinsichtlich der Verwendung des FET-Sensor Bauelements zum Nachweis von Flüssigkeitsbewegungen wird zunächst ein theoretisches Modell entwickelt, dessen Kernaussage ist, dass sich in einem rechteckigen Kanal der relative Bedeckungsgrad mit Flüssigkeit direkt proportional zum Drainstrom des FET-Sensors verhält. Basierend auf diesem theoretischen Modell, welches experimentell belegt wird, können mittels eines einzelnen FET-Sensors Füllstand und Füllgeschwindigkeit bzw. bei bekannter Füllgeschwindigkeit Kapillarvolumen und Kapillargeometrie bestimmt werden. Abweichungen von der direkten Proportionalität erlauben zudem, Rückschlüsse auf die Benetzungseigenschaften der Kapillaren und die Dynamik an der Halbleitergrenzfläche zu ziehen. Ist ein Sensorelement vollständig mit Flüssigkeit bedeckt, wird mittels Lösungsmitteltropfen als Markerobjekten die Strömungsgeschwindigkeit bestimmt. Ändert sich die Ionenkonzentration im Elektrolyten als Funktion der Strömungsgeschwindigkeit, so kann die Strömungsgeschwindigkeit durch Messung der Ionenkonzentration mittels FET-Sensor ebenfalls ermittelt werden. Als wichtigster Demonstrator für die Verwendung des FET-Sensors wird ein komplexes Lab on a Chip-System zur Separation von Emulsionen auf chemisch strukturierten Oberflächen entwickelt, bei dem der Separationsvorgang mittels FET-Sensorarray verfolgt werden kann. Zur einfachen Herstellung chemisch modifizierter Oberflächen für die Separationsexperimente werden die Abscheidung von nanoskaligen hydrophoben Methacrylatcopolymerfilmen und die selektive Fluorsilanisierung von Oberflächen sowie deren Lösungsmittelbeständigkeit in Wasser, Toluol und Aceton untersucht. Dabei zeigt sich, dass die Hydrophobie nach Lösungsmittelbehandlung weitestgehend erhalten bleibt, Wasserrückstände im Methacrylatfilm aber zu einer reversiblen Schichtdegradation führen können. Als Modellsystem werden Hexan-Wasser- bzw. Toluol-Wasser-Emulsionen verwendet, die auf Oberflächen getrennt werden, deren eine Seite hydrophil, und deren andere Seite hydrophob ist (Stufengradient). Der Separationsprozess beruht auf der großen Affinität des Wassers hin zu polaren Oberflächen, wobei das wenig selektive Lösungsmittel zur unpolaren Seite gedrängt wird. Zur Erlangung eines tieferen Verständnisses des Prozesses werden die Tropfenkoaleszenz und der Einfluss geometrischer Beschränkungen untersucht. Die Versuche werden sowohl auf offenen Oberflächen als auch im Spalt, unter Verwendung von hydrophilen und hydrophoben Oberflächen, durchgeführt. Es zeigt sich, dass sich die Dynamik der Tropfenkoaleszenz im Spalt umgekehrt zur Dynamik auf offenen Oberflächen verhält. Dies wird mittels eines hierzu entwickelten theoretischen Modells erklärt, welches die Minimierung der Oberflächenenergie und Hystereseeffekte einbezieht. Das Lab on a Chip-System schließlich besteht aus einem mit Siliziumnitrid beschichteten FET-Sensorchip, auf den eine Separationszelle aufgeklebt ist. Neben dem Einlass für die Emulsion ist ein weiterer Einlass vorhanden, durch den Salzsäure für eine pH-Reaktion zugegeben werden kann. Der gesamte Separationsprozess sowie die anschließende pH-Reaktion, lassen sich bequem am PC anhand der Änderung der Stromstärke der einzelnen Sensoren verfolgen und analysieren. Wichtige Ergebnisse hier sind: 1) Mittels eines quasi 1-dimensionalen Sensorarrays kann der Verlauf einer Flüssigkeitsfront in einem 2-dimensionalen Areal überwacht bzw. dargestellt werden. 2) Anhand der Signatur des Signalverlaufs bei pH-Änderung und Flüssigkeitsbewegung, können beide Prozesse unterschieden werden. Der Sensor kann also zum Nachweis von Flüssigkeitsbewegungen und zugleich als Chemosensor eingesetzt werden. Es wurde also nicht nur ein neuartiges, äußerst robustes, chemikalienbeständiges und biokompatibles Multifunktionssensorelement mit Abmessungen im Mikrometer- bis Millimeterbereich entwickelt, sondern auch eine neue Methode entwickelt, mit der es möglich ist, sowohl (bio-)chemische Reaktionen als auch die Bewegung von Flüssigkeiten in Lab on a Chip-Systemen nachzuweisen.

No description available.

L'information quantique et ses protocoles de cryptographie, de téléportation et de calcul ont trouvé dans les sources quantiques de lumière un ensemble d'outils à très fort potentiel. Les sources de photons uniques déclenchées en font évidement partie, tout comme les sources de photons jumeaux, sur lesquelles reposent l'émission de photons annoncés ou la production de paires de photons intriqués en polarisation. Les sources quantiques de lumière ne cessent de trouver de nouvelles applications comme par exemple l'intrication conditionnelle d'émetteurs de photons uniques par la mesure conjointe des photons qu'elles émettent, l'augmentation d'intrication de faisceaux EPR ou encore le stockage de photons uniques dans des vapeurs atomiques.<br /><br />L'ensemble de mes activités de recherche s'inscrit dans ce mouvement. Mes travaux ont porté en grande partie sur les sources de photons uniques et les sources de paires de photons, ainsi que leurs applications à la cryptographie quantique, à la téléportation quantique et au calcul quantique. Mes travaux s'ouvrent maintenant sur la suite: variables continues, mémoires quantiques et téléportation d'états non classiques sont probablement les prochaines étapes.