Dissertations / Theses on the topic 'Collins Function'

2010/2011
The transversity distribution function can be studied in inclusive one- and two-hadrons production in DIS off a transversely polarized target. The measurement of the spin asymmetries in the azimuthal distribution of the one- or two-hadrons, and of the Collins or di-hadron fragmentation functions, allows to access the transversity distribution function. In this thesis the measurements of the one- and two-hadron transverse spin asymmetries performed by the COMPASS experiment is discussed. Finally the first extraction of the transversity PDF from two-hadron asymmetries is perfomed.
XXIV Ciclo
1976

A complete, fundamental understanding of the proton must include knowledge of the underlying spin structure. The transversity distribution, h1(x), which describes the transverse spin structure of quarks inside of a transversely polarized proton, is only accessible through channels that couple h1(x) to another chiral odd distribution, such as the Collins fragmentation function (ΔN Dπ/q↑(z,jT)). Significant Collins asymmetries of charged pions have been observed in semi-inclusive deep inelastic scattering (SIDIS) data. These SIDIS asymmetries combined with e+e- process asymmetries have allowed for the extraction of h1(x) and ΔN Dπ/q↑(z,jT). However, the current uncertainties on h1(x) are large compared to the corresponding quark momentum and helicity distributions and reflect the limited statistics and kinematic reach of the available data. In transversely polarized hadronic collisions, Collins asymmetries may be isolated and extracted by measuring the spin dependent azimuthal distributions of charged pions in jets. This thesis will report on the first statistically significant Collins asymmetries extracted from √ s = 200 GeV hadronic collisions using 14 pb-1 of transversely polarized proton collisions at 57% average polarization.

In this thesis, computer simulations are used to study the properties of new colloidal systems with structured interactions. These are pair interactions that include both attraction and repulsion. Structured colloids differ from conventional colloids in which the interactions between particles are either strictly attractive or strictly repulsive. It is anticipated that these novel interactions will give rise to new microscopic structure and dynamics and therefore new material properties. Three classes of structured interactions are considered: radially structured interactions with an energetic barrier to pair association, Janus surface patterns with two hemispheres of different surface charge, and striped surface patterns. New models are developed to capture the structured interactions of these novel colloid systems. Dynamical computer simulations of these models are performed to quantify the effects of structured interactions on colloid properties. The results show that structured interactions can lead to unexpected particle ordering and novel dynamics. For Janus and striped particles, the particle order can be captured with simpler isotropic coarse-grained models. This relates the static properties of these new colloids to conventional isotropically attractive colloids (e.g. depletion attracting colloids). In contrast, Janus and striped particles are found to have substantially slower dynamics than isotropically attractive colloids. This is explained by the observation of longer-duration reversible bonds between pairs of structured particles. Dynamical mapping methods are explored to relates the dynamics of these structured colloids to isotropically attractive colloids. These methods could also facilitate future nonequilibrium simulation of structured colloids with computationally efficient coarse-grained models.

Nanostructuring has led to materials with novel and improved materials properties driving innovation across fields as varied as transportation, computing, energy and biotechnology. However, the benefits of nanostructured material have not widely been extended into large-scale, three-dimensional applications as deterministic pattern techniques have proven too expensive for devices outside of high value products. This thesis explores how colloidal self-assembly can be used to form macroscopic functional materials with short-range order for electronic, photonic and electrochemical applications at scale. DNA-functionalized nanoparticles are versatile models for exploring colloidal self-assembly due to the highly specific, tunable and thermally reversible binding between DNA strands. Gold nanoparticles coated with DNA were used to investigate the temperature-dependent interaction potentials and the gel formation in DNA-colloidal systems. The electronic conductivity and the plasmonic response of the DNA-gold gels were studied to explore their applicability as porous electrodes and SERS substrates, respectively. Subsequently, silica nanoparticles were assembled into nanostructures that preferentially scatter blue light using both DNA and polymer-colloid interactions. Finally, rod-sphere structures made from DNA-coated gold nanoparticles and viruses were explored, demonstrating how high-aspect ratio building blocks can create composite structures with increased porosity. The gold-virus gel structures inspired the design and assembly of a silicon-carbon nanotube composite material using covalent bonds that shows promise for high energy density anodes.

Syftet med undersökningen är att studera hur grammatiska konstruktioner av Katniss, Gale, Prim, Cinna, Rue, Peeta, och Haymitch i Suzanne Collins ungdomsroman Hungerspelen (2012) kan bidra till karaktärernas görande av manligt eller kvinnligt genus. Frågeställningen som ska besvaras är på vilket sätt framställs Katniss och de sex andra utvalda karaktärerna grammatiskt utifrån den systemisk-funktionella grammatikens transitivitetssystem processer och deltagare? Och på vilket sätt kan framställningen tolkas ur ett genusperspektiv? Genom att analysera sex utvalda delar ur boken med systemisk-funktionell grammatiks transitivitetssystem och se till processer och deltagare gjordes en grammatisk analys. Analysen tolkades sedan utifrån ett genusperspektiv gällande vilka föreställningar det finns kring manligt och kvinnligt beteende. Resultaten visar att de grammatiska konstruktionerna av Katniss och Peeta kan tolkas som görande av både manligt och kvinnligt genus, Gales och Haymitchs konstruktioner som görande av manligt genus och Cinnas, Rues och Prims grammatiska realiserande som görande av kvinnligt genus. Tillsammans visar resultaten på att karaktärernas grammatiska konstruktioner bidrar till görandet av manligt eller kvinnligt genus som inte behöver avspegla deras ”naturliga kön”.
The aim of this thesis is to study how grammatical constructions of the characters Katniss, Gale, Prim, Cinna, Rue, Peeta and Haytmich, from Suzanne Collins The Hunger Games (2012), contribute to their doing of gender. The thesis set to explore this using two research questions: How is Katniss and the six other characters presented grammatically and accordingly to systemic functional grammars transitivity system’s processes and participants? And, how can the grammatical analysis be interpreted from a gender perspective? By analysing six selected excerpts from the book with systemic functional grammars transitivity system’s processes and participants a grammatical analysis was done. The grammatical analysis was then interpreted from a gender perspective regarding the conceptions of what is considered as a doing of male or female gender behaviour. The result show that the grammatical constructions of Katniss and Peeta can be understood as a doing of both male and female gender. Futhermore, Gale’s and Haymitch’s constructions can be understood as a doing of male gender and Cinna’s, Rue’s and Prim’s constructions as a doing of female gender. Together these results show that the grammatical constructions in The Hunger Games (2012) affect the characters’ doing of gender and that their doing of gender does not have to reflect their sex.

Les modifications du paysage engendrées par les activités humaines sont une des causes majeures du déclin de la biodiversité. En générant une perte de la connectivité fonctionnelle du paysage, elles limitent les déplacements des individus et entraînent la rupture des flux de gènes, processus clés dans le maintien et la persistance des populations. Cependant, le lien entre ces processus et la structure du paysage est encore mal compris. Dans ce contexte, nous avons conduit une étude sur la Martre des pins, une espèce a priori forestière, bien que capable de s’installer durablement dans des paysages fragmentés. A partir de l’analyse de la variabilité génétique de groupes échantillonnées sur 13 sites forestiers à l’échelle de la région Champagne-Ardenne, et du suivi des déplacements d’individus à fine échelle, en milieu continu et fragmenté, nous avons estimé la résistance du paysage aux différents déplacements, c’est-à-dire dans quelle mesure ceux-ci sont freinés ou facilités par les éléments du paysage. Nous avons mis en évidence que les déplacements sont freinés, d’une part par la présence d’une large plaine agricole, et d’autre part, par certaines infrastructures de transport. Nous avons également mis en évidence que les déplacements des martres entre les taches d’habitats sont facilités par la présence de haies et que la hauteur du couvert végétal des habitats non boisés pourrait jouer un rôle dans ces déplacements. Cette étude apporte d’importantes connaissances sur l’écologie des déplacements de la Martre des pins et souligne la nécessité de la prise en compte de la réponse des organismes dans l’établissement des futurs réseaux écologiques
Landscape changes, generated by anthropogenic activities, are widely recognised as one of the main causes of global biodiversity decline. Leading to a loss of functional landscape connectivity, they disrupt movements and gene flow which play a primordial role for the persistence of populations. However, the relationship between these processes and landscape structure remains unclear. In this context, we studied landscape connectivity in European pine marten, a forest species present in fragmented landscapes. We evaluated landscape resistance, i.e. how landscape features impede or facilitate movements and gene flow, analysing genetic variability of groups sampled in 13 forest sites of the Champagne-Ardenne regional area, and studying individual fine-scale movements in both continuous and fragmented areas. We showed that intensive agricultural plain and certain linear infrastructures could impede movements. In addition, we showed that hedgerows facilitate movements between forest patches and we suggested that vegetation height of open habitats could play a role for these movements. This study provides important insights on movement ecology of the European pine marten and underlines the need to take into account responses of organisms in the establishment of ecological networks

Carbon nanotubes are known as one of the strongest materials in nature and since their discovery; they have triggered the scientific interest for fabricating multi-functional polymer composites. However, a well-known problem associated to the incorporation of nanoparticulate materials in polymer matrices is their tendency to agglomerate in order to reduce their surface energy, and the extreme increase of the polymer viscosities (i.e melts, solutions, etc), which makes it very difficult to process them. Polymers can be efficiently reinforced by fibers for applications where high strength and stiffness are required. Micro-scale short fiber reinforced polymer composites have been an alternative way to obtain fiber reinforced composites since the long fiber incorporation is a painful job and not always feasible and easy to produce composites in big scale. Therefore, use of long glass fibers as the support for depositing CNTs as well as CNTs+other kind of nanoparticles was made, and the resulting interfaces were investigated in detail by single fiber model composites. This approach can bring the CNT functionality, fiber strength and toughness to the final composite, and simultaneously alleviate the manufacturing process from increase of the polymer high viscosities. Finally, very logically the question of whether to improve or destroy the interface integrity comes before implementing the hybrid hierarchical reinforcements in bigger scales, and an output out of this work will be given. Furthermore, several information and functionalities arising from the CNTs at the interphase region will be elucidated like cure monitoring of the epoxy resin matrix, UV-sensing ability, and thermoelectric energy harvesting, giving rise to multi-functional structural composites. CNT-modified natural fibers also have been utillised to fabricate short fiber reinforced composites, and have shown a promising reinforcement effect due to the CNT nanostructured interfaces. The ‘interface’ in fiber reinforced polymer composites (FRPCs) is known as a very crucial parameter that has to be considered in the design of a composite with desired properties. Interfaces are often considered as surfaces however, they are in fact zones or areas with compositional, structural, and property gradients, typically varying from that of the fiber and the matrix material. Characterization of the mechanical properties of interfaces is necessary for understanding the mechanical behavior of scaled-up composites. In fact, the mechanical characteristics of a fiber/resin composite depend mainly on i) the mechanical properties of the component materials, ii) the surface of the fiber, and iii) the nature of the fiber/resin bonding as well as the mode of stress transfer at the interface. Among the many factors that govern the characteristics of composites involving a glass, carbon, natural or ceramic fiber, and a macromolecular matrix, the adhesion between fiber and matrix plays a predominant role. In specific, the stress transfer at the interface requires an efficient coupling between fiber and matrix. Therefore, it is important to optimize the interfacial bonding since a direct linkage between fiber and matrix gives rise to a rigid, low impact resistance composite material.

Trypanosoma brucei, un parasite flagellé unicellulaire, est responsable de la trypanosomiase humaine africaine aussi connue comme la maladie du sommeil.Les microtubules (MTs) sous-pelliculaires, le quartet de MTs (MTQ), le flagelle (F) et le collier de la poche flagellaire (CPF) sont les principaux composants du cytosquelette dutrypanosome. À ce jour, une seule protéine du CPF, BILBO1, a été identifiée et caractérisée.Dans cette étude, nous montrons in vivo que BILBO1 forme des polymères capables deconstruire un échafaudage qui permet l’ancrage de protéines partenaires. Ainsi, un crible en double hybride chez la levure a identifié plusieurs protéines partenaires de BILBO1,notamment une nouvelle protéine appelée FPC4. Nous démontrons que FPC4 est une protéine spécifique des kinétoplastides, localisée au CPF mais aussi au hook-complex, une structure proche du CPF. L’interaction FPC4 – BILBO1 est démontrée in vitro et in vivo, etles domaines d'interaction identifiés. En outre, nous démontrons in vivo et in vitro que FPC4est une protéine associée aux microtubules. Nos données suggèrent fortement que FPC4est impliquée dans le processus de séparation des CPFs au cours du cycle cellulaire. Nos résultats mettent en évidence un lien étroit entre le MtQ et le CPF et l'implication probable duhook-complex. Enfin, nous mettons en évidence une structure analogue au hook-complex chez les Leishmanies. L’interaction BILBO1 – FPC4 représente une nouvelle cible thérapeutique et sera caractérisée plus avant
Trypanosoma brucei, a unicellular flagellated parasite, is responsible for the human African trypanosomiasis also known as sleeping sickness. Sub-pellicular microtubules (MT), the MT quartet (MtQ), the flagellum (F) and the Flagellar Pocket Collar (FPC) are the main components of the T. brucei cytoskeleton. To date, only a single FPC protein, BILBO1, has been identified and characterized. In this study we demonstrate in vivo that BILBO1 forms polymers able to build a scaffold structure that anchors partner proteins. As such, a yeast-2-hybrid screen identified several BILBO1 interacting protein partners. We demonstrate that FPC4 is a kinetoplastid-specific protein, which is localized at the FPC and at the hook complex. Its specific interaction with BILBO1 has been demonstrated in vitro and in vivo, and the interacting domains identified. Furthermore, we demonstrate that FPC4 is a microtubule binding protein. Our data strongly suggest that FPC4 is involved in the separation of the old and the newly formed FPC during the cell cycle. Altogether, our results demonstrate a tight connection and interplay between the MtQ and the FPC and the likely involvement of an adjacent third structure, the hook complex. Finally, we highlight a structure similar to the hook-complex in Leishmania. The BILBO1 – FPC4 interaction represents a new therapeutic target and will be characterized further

The work developed during this PhD has embraced several topics that I divide in three blocks. Each block contains two chapters in this dissertation. Additionally, a general introduction of the different topics is provided (Chapter 1). The first block corresponds to the study of colloidal synthetic routes to produce functional nanoparticles (Chapter 2 and 3). In the second block the developed nanoparticles are used to produce bulk nanostructured materials. The functional properties of the nanomaterials are also characterized in this second block. As the paradigmatic application for such bottom-up assembled nanostructured materials I considered thermoelectricity (Chapter 4 and 5). In the last block, I go one step beyond and design and prepare multiphase nanoparticles as building blocks for the bottom up production of nanocomposites with improved thermoelectric performance (Chapter 6 and 7).
El treball desenvolupat durant aquesta tesi doctoral engloba diverses temàtiques que s’han dividit en tres blocs. Cada bloc conté dos capítols. A més a més, com a Capítol 1 s’ha inclòs una introducció general de cadascuna de les temàtiques tractades. En el primer bloc, Capítols 2 i 3, s’estudien diferents síntesis col·loïdals per produir nanopartícules funcionals. En el segon bloc, Capítols 4 i 5, les nanopartícules desenvolupades s'utilitzen per produir materials nanoestructurats en bulk a partir del seu assemblatge. Les propietats funcionals d’aquests nanomaterials es caracteritzen també en aquest segon bloc. Com a aplicació paradigmàtica s’ha considerat la termoelectricitat. En l'últim bloc, Capítols 6 i 7, es va un pas més enllà i es dissenyen nanopartícules heterogènies com blocs de construcció per a la producció de nanocompostos amb millor rendiment termoelèctic.

A range of microgels with two different functionalities were synthesized, and their utility in novel bioapplications was examined. Cationic microgels with varying properties were developed by tuning synthesis conditions. Their size and primary amine content was analyzed, and one microgel system was selected as a model construct. Its primary amine groups were conjugated to two dyes with properties favorable for utilization as contrast agents in photoacoustic imaging. The concentration of contrast agent in single particles was determined. The implications of a high local dye concentration in the generation of high intensity photoacoustic signals, are discussed. The second bioapplication involved the targeted delivery of fibrinolytics to fibrin clots, in order to bring about dissolution of abnormal thrombi. For this purpose, core/shell microgels with carboxylic acid groups in their shells were synthesized in three size ranges. Following this, their dimension based differential localization in and around porous fibrin clots was examined. Fibrin-specific peptides were then conjugated onto the shells of these particles and the conjugates were shown to demonstrate strong interactions with the fibrin clots. The microgels conjugated to the peptide with the highest binding affinity to fibrin, were observed to bring about disruption of fibrin clots, merely through interference in the dynamic interactions among clot fibers, due to the equilibrium nature of the fibrin polymer. The implications of these novel results and future studies required to facilitate a better understanding of the phenomena involved, are discussed.

Particle dispersions provide a promising tool for the engineering of functional materials that exploit self-assembly of complex structures. Dispersion made from magnetic colloidal particles is a great choice; they are biocompatible and remotely controllable among many other advantages. However, their dominating dipolar interaction typically limits structural complexity to linear arrangements. This paper shows how a magnetostatic equilibrium state with noncollinear arrangement of the magnetic moments, as reported for ferromagnetic Janus particles, enables the controlled self-organization of diverse structures in two dimensions via constant and low-frequency external magnetic fields. Branched clusters of staggered chains, compact clusters, linear chains, and dispersed single particles can be formed and interconverted reversibly in a controlled way. The structural diversity is a consequence of both the inhomogeneity and the spatial extension of the magnetization distribution inside the particles. We draw this conclusion from calculations based on a model of spheres with multiple shifted dipoles. The results demonstrate that fundamentally new possibilities for responsive magnetic materials can arise from interactions between particles with a spatially extended, anisotropic magnetization distribution.

Systems of interacting colloidal particles are ideal tools for studies of pattern formation and collective non-equilibrium dynamics on the mesoscopic scale. These processes are governed by the interaction between the particles, which can be tuned by sophisticated fabrication. In this thesis, self-assembly of artificially designed magnetic spheres dispersed in water has been studied via video microscopy. The particles are based on silica microspheres with hemispherical ferromagnetic coating of [Co/Pd] multilayers with perpendicular magnetic anisotropy. These particles are exceptional in that they exhibit an off-centered net magnetic moment and yet obey rotational and mirror symmetry. It has been demonstrated how these magnetic properties provide innovative flexibility in pattern formation and collective dynamics based on magnetostatic interactions on the mesoscopic scale. The results are supported by analytical and numerical calculations of interacting spheres with radially shifted point dipoles (sd-particles). In two dimensions, the particles spontaneously self-assemble into branched structures as a result of a bistable assembly behavior where neighboring particles exhibit a non-collinear magnetic orientation. It has been shown that these features, which are atypical for homogeneous systems of magnetic particles, can be reproduced by simulation. It employs a theoretical model of a sphere that contains a distribution of three radially shifted point dipoles in analogy to the magnetization distribution in the coated particles. The stability of the assembly has been examined further by external manipulation using optical tweezers and homogeneous magnetic fields. A rich variety of stable structures with diverse spatial and magnetic ordering has been found. Particularly, the collective alignment of the specially designed particles in external fields opens completely new possibilities for the remote control over reversible pattern formation on the micrometer scale. In time-dependent fields, the collective dynamics of the anisotropic particles has revealed a novel approach for magnetically actuated translation. The variety of stable structures particularly enables control over this motion
Kolloidale Suspensionen sind geeignete Systeme zur Untersuchung von Strukturbildung und kollektiver Nichtgleichgewichtsdynamik in mesoskopischen Größenskalen. Diese Vorgänge werden durch die Wechselwirkung zwischen den Teilchen bestimmt, welche durch geeignete Partikelherstellung angepasst werden kann. In der vorliegenden Arbeit wird ein System von künstlich hergestellten magnetischen Partikelsuspensionen mittels Videomikroskopie untersucht. Quarzglas-Mikrokugeln wurden halbseitig mit einer ferromagnetischen Dünnschicht aus [Co/Pd] Multilagen mit senkrechter Anisotropie beschichtet. Solche Partikel sind ausgezeichnet durch ein resultierendes magnetisches Moment mit Rotations- und Spiegelsymmterie, welches zusätzlich vom Mittelpunkt der Kugel verschoben ist. Die vorliegende Arbeit zeigt, dass diese Besonderheit zu einer bisher unbekannten Flexibilität bei der mesoskopischen Strukturbildung und der kollektiven Dynamik auf der Basis magnetostatischer Wechselwirkung führt. Die vorgestellten Ergebnisse werden durch analytische und numerische Berechnungen unterstützt, denen ein Modell einer idealen Kugel mit verschobenem Dipol zugrunde liegt. Die zweidimensionale Selbstanordnung der Partikel zeigt experimentell zwei stabile Formen der Verknüpfung, welche zu verzweigten Strukturen mit unterschiedlich magnetischer Ausrichtung benachbarter Partikel führen. Diese für ein homogenenes System magnetischer Partikel außergewöhnlichen Eigenschaften konnten in Simulationen durch ein Modellsystem aus Kugeln mit drei verschobenen Punktdipolen reproduziert werden. Darüber hinaus wurde die spontante Anordnung unter externer Manipulation mittels optischer Pinzette und magnetischen Feldern untersucht. Es konnte eine Vielfalt an stabilen Strukturen mit verschiedenen magnetischen und strukturellen Anordnungen gefunden werden. Insbesondere die kollektive Ausrichtung dieser Partikel in externen Feldern eröffnet neuartige Möglichkeiten, kontrolliert und reversibel Mikrostrukturen zu erzeugen. In zeitabhängigen Feldern zeigen die anisotropen Partikel zusätzlich eine kollektive Dynamik welche eine neue Möglichkeit zum magnetischen Antrieb von Partikelagglomeraten eröffnet. Die Vielfalt der möglichen stabilen Strukturen erlaubt es in besonderer Weise diese Bewegung zu steuern

Cette thèse est consacrée à la modélisation de la turbulence avec des approches hybrides RANS-LES. Ces approches permettent d’assurer le meilleur compromis entre, d’une part, la capacité de la LES à capturer les structures instationnaires dans les régions d'intérêt de l’écoulement, et, d’autre part, un coût de calcul abordable en activant le mode RANS lorsque la résolution LES n’est pas nécessaire ou trop coûteuse, notamment en paroi. L’objectif industriel pour EDF est d’utiliser ces méthodes pour estimer les efforts instationnaires qui s’exercent sur certains gros composants (GMPP) des réacteurs à eau pressurisée.En premier lieu, une nouvelle formulation du modèle hybride HTLES (Hybrid Temporal Large-Eddy Simulation) est développée, dans le but d’améliorer ses fondations théoriques, en utilisant le critère de H-Equivalence. L'intérêt de ce modèle réside dans l'utilisation du filtrage temporel pour contrôler la répartition d’énergie entre les échelles résolues et modélisées, permettant de garantir la consistance entre les opérateurs RANS et LES. L’approche hybride est appliquée à différents modèles de fermeture RANS, et la calibration est effectuée sur la décroissance d'une turbulence homogène isotrope. De plus, des développements analytiques similaires permettent de proposer, pour la première fois, un modèle hybride fondé sur une modification d’échelle dans une formulation RANS qui tend explicitement vers un modèle LES préexistant.Le contrôle de la transition RANS-LES dans les régions de proche paroi est une problématique majeure de cette thèse. Afin d’améliorer le comportement du modèle HTLES, une fonction de protection double (dépendante à la fois de paramètres physiques et de critères liés aux maillages) et une contrainte de consistance interne sont proposées pour imposer le mode RANS en paroi lorsque la résolution LES n’est pas appropriée. Le modèle amélioré est validé sur les écoulements en canal plan et sur les collinespériodiques, avec des résultats très satisfaisants et robustes vis-à-vis du raffinement du maillage. Il est de plus montré pour le cas test des collines périodiques que des fluctuations turbulentes résolues dans la zone LES pénètrent dans la région RANS de proche paroi sans être trop altérées. Cela permet de capturer correctement les basses fréquences des spectres d'énergie turbulente et de pression en paroi, ce qui s'avère décisif dans le but d'estimer les efforts instationnaires sur des composants. Finalement, la HTLES offre une méthode de résolution alternative au coût numérique réduit par rapport à un modèle LES résolu en paroi.Enfin, la thèse s'intéresse à une version zonale de la HTLES (imposant le mode RANS dans les régions où la résolution LES n'est pas nécessaire), en appliquant le ALF (Anisotropic Linear Forcing) au niveau des interfaces RANS-HTLES afin de promouvoir l'apparition de fluctuations turbulentes résolues. Cette première étude de faisabilité offre des résultats prometteurs.Résumé en
This work is devoted to turbulence modelling using hybrid RANS-LES approaches. These approaches offer the best potential to reach the compromise between the capability of LES to capture the large-scale structures in regions of interest, and the low-computational cost of RANS calculations in regions where LES resolution is not required or too CPU-demanding, notably in near-wall regions. The industrial objective for EDF is to use these methods to predict unsteady loads on large components (reactor coolant pumps) of pressurized water reactors.In this regard, a new formulation of HTLES (Hybrid Temporal Large-Eddy Simulation) is developed, in order to improve the theoretical foundation of the model, applying the Hybrid-Equivalence criterion. The interest of this model lies in the use of temporal filtering, to control the energy partition between resolved and modeled scales, ensuring a consistent bridging between RANS and LES models. The HTLES approach is applied to several RANS models, and the model is calibrated in decaying isotropic turbulence. In addition, a similar analysis shows for the first time that it is possible, from theoretical considerations, to derive a hybrid RANS-LES model based on scale modifications in a RANS model, which explicitly tends towards a standard LES model in LES regions.The control of the RANS-to-LES transition in near-wall regions is a major concern in this work. In order to improve the behavior of the HTLES model, a two-fold shielding function (depending on physical parameters and mesh criteria) and an internal consistency constraint are introduced, aiming at enforcing the RANS mode when the activation of the LES mode is not suitable. The validation process of the upgraded version of the model is carried out on channel and periodic-hill flows, reaching the expected outcomes: accuracy of the predictions and robustness of HTLES to grid coarsening. Moreover, it is shown that resolved vortices coming from the LES zone penetrates into the near-wall RANS region down to the wall, enabling the hybrid model to fairly reproduce the low frequencies. The capacity of HTLES to provide information on energy and pressure spectra at the wall is assessed, which is decisive to predict unsteady loads. Hence, HTLES offers a cost-saving alternative to a wall-resolved LES.Finally, the work focuses on a zonal control of HTLES (enforcing the RANS mode in large portions of the domain where the LES mode is not required), applying the ALF (Anisotropic Linear Forcing) at the RANS-to-HTLES interfaces to promote turbulent fluctuations. This feasibility study offers promising results

膠體顆粒吸附在油水介面的現象最近幾年引起極大的關注。一方面，受限在油水介面的膠體顆粒可以用作一個很好的模型體系來研究一些基本物理問題，例如二維結晶，擠壓以及其它相轉變問題。另一方面，在許多工業產品和處理過程中，例如食品，抗沫劑製備，以及原油乳液處理中膠體顆粒在油水介面的行為扮演著極為重要的角色。
微凝膠，一種軟膠體顆粒，也可以作為乳化劑用來穩定製備乳液。微凝膠在許多方面和普通膠體顆粒有著相同的行為。但是，微凝膠顆粒，作為一種三維交聯的高分子網狀鏈，在良性溶劑裡會膨脹。之前已經有報導明確指出這種微凝膠顆粒可以用來穩定的乳液。並且這些乳液的穩定性可控，此性質在小分子乳化劑和普通膠體顆粒體系是無法實現的。但是，這些微凝膠顆粒製備的乳液的穩定以及不穩定的作用機制至今尚有許多爭論。具體來說，這些微凝膠是如何吸附到油水面，什麼因素控制著這些吸附行為，微凝膠在油水介面如何行為，吸附在油水介面的微凝膠如何動態的回應外界條件的改變，統統不清楚。
本論文首先旨在深入瞭解微凝膠在油水介面的動態行為，然後用這些微凝膠穩定的乳液作為範本製備出多功能材料。本論文一共包括八部分，這八部分全部圍繞著微凝膠在油水介面的行為而展開。第一部分將介紹微凝膠應用在油水介面的研究已經取得的進展。第二部分將介紹彎曲的油水介面以及本論文主要用到的儀器。在第三部分，我們將會介紹微凝膠的製備與表徵。第四部分，我們集中於微凝膠是如何吸附到油水介面。我們發現微凝膠的柔軟，稀鬆，以及可變形決定了微凝膠的吸附過程。第五部分，我們探討為什麼油水介面動態張力在微凝膠的相轉變溫度附近有個最低值。通過對介面張力，溫度還有時間進行三維作圖，我們發現介面張力在微凝膠相轉變溫度附近(308.1K) 存在一個峰穀。這個峰谷的形成是由微凝膠的變形性以及它們之間相互作用所導致的。這些微凝膠吸附在油水介面之後形成一個新的微凝膠膜隔離開水與油，這層微凝膠險主導著油水介面的性質。第六部分，基於以上理解，我們在相轉變溫度附近創建了一個微凝膠未鋪滿的油水介面來研究微凝膠顆粒在一個受限的環境下的溫敏性行為。降低溫度，微凝膠在油水介面經歷一個極慢的舒張過程。但是升高溫度，微凝膠並沒有塌縮。第仁部分，我們首先應用微凝膠作為唯一穩定劑製備了一種高內相乳液，然後以此乳液為範本製備了多功能材料。最後一部分，縱觀全文，我們的結論是微凝膠的變形性以及它們之間的相互作用對於微凝膠在油水介面的行為起著非常重要的角色:包括微凝膠在油水介面的吸附行為，微凝膠在油水介面的溫敏性行為，油水介面的流變性能以及多功能材料的性能。
The adsorption phenomena of colloidal particles at the liquid-liquids interfaces have received tremendous interests in recent years. On the fundamental side, interest stems from the fact that colloidal particles confined to the interfaces can serve as an elegant system for fundamental studies of physical processes, such as two-dimensional crystallization, jamming and other phase transitions. On the practical side, interest arises as a result of demonstrated importance of the behavior of colloidal particles at the interfaces for applications in many industrial products and processes such as the production of food, anti-foam formulations, and crude oil.
In recent years, soft particles, like microgels are also employed as emulsifiers for making emulsions. These microgel particles resemble colloidal particles in many aspects. However, structurally, microgel particles constitute a three-dimensional covalently crosslinked network and can swell up in good solvents. It has been reported that emulsions stabilized by these soft microgel particles can offer an unprecedented degree of control of emulsion stability, well beyond what can be achieved by using small molecular surfactants or conventional particles. However, the stabilization and destabilization mechanism involving such soft and deformable microgels is still a matter of debate. Specifically, how microgels adsorb onto the oil-water interfaces; what parameters control the microgel adsorption; how these microgels behave at the interfaces; and how these microgels respond to environmental triggers after adsorption, are unclear.
This thesis aims at first gaining a fundamental understanding of the microgels dynamic behaviors at the oil-water interfaces, and then using this system to fabricate functional materials. This thesis contains eight parts; all of them are connected with soft microgels at the oil-water interfaces. The first part of this thesis introduces the soft microgels’ performance at the oil-water interfaces. The second part focuses on the curved oil-water interfaces and the instrument we will use in this thesis. In the third part, we will present the preparations and characterizations of microgels. The fourth part addresses the microgels adsorption behaviors at the oil-water interfaces. Our results clearly show that deformability of microgel particles plays a vital role in their adsorption behaviors at the oil-water interfaces. In the fifth part, we discuss why interfacial tension (γ) exhibits a minimum in the vicinity of PNIPAM-related microgel volume phase transition temperature (VPTT). Our results suggest that, this observed minimum can be attributed to highest deformability of microgels around VPTT as well as the interactions among the adsorbed microgels. Moreover, our results reveal that unlike conventional solid particles, the adsorbed microgels are not wetted by both oil and water. On the contrary, they will form an intruding microgel layer separating the oil and water phases, which ultimately dominates the oil-water interfacial properties. Based on the above understanding, in the sixth part, we create microgels partially covered oil-water interfaces, and investigate the microgels thermal behaviors under a confined condition. Our results show that microgels undergo an extremely slow swelling process at the oil-water interfaces. In addition, microgels would not collapse upon heating. In the seventh part of this thesis, we present the preparation of high internal phase emulsions (HIPEs) by solely using soft microgels as emulsifiers. Furthermore, we demonstrate that these microgels-stabilized HIPEs can be good templates for the preparation of hierarchical porous functional materials. Based on our investigations, in the final part, we summary the importance of microgel deformability and their interactions on microgels behaviors at the oil-water interfaces: including their adsorption dynamics, thermal-responsive behaviors, oil-water interfacial rheology properties and functional materials properties.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Li, Zifu.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
摘要 --- p.I
ABSTRACT --- p.III
ACKNOWLEDGEMENT --- p.V
TABLE OF CONTENTS --- p.VII
Chapter CHAPTER 1 --- INTRODUCTION AND BACKGROUND --- p.1
Chapter 1.1 --- Introduction --- p.1
Chapter 1.1.1 --- Surfactant-stabilized emulsions --- p.1
Chapter 1.1.2 --- Particle-stabilized emulsions --- p.3
Chapter 1.2 --- Microgels as particulate emulsifiers in Pickering Emulsions --- p.6
Chapter 1.2.1 --- Literature survey of microgels at interfaces --- p.7
Chapter 1.2.2 --- Discussions and conclusions --- p.16
Chapter 1.3 --- Theme of this thesis --- p.18
Chapter 1.4 --- References and Notes --- p.19
Chapter CHAPTER 2 --- THE FUNDAMENTALS OF CURVED OIL-WATER INTERFACE --- p.21
Chapter 2.1 --- Introduction --- p.21
Chapter 2.2 --- Pendant drop tensiometer --- p.22
Chapter 2.3 --- The dynamic interfacial tension --- p.26
Chapter 2.3.1 --- Two surfactant adsorption mechanisms --- p.27
Chapter 2.4 --- Investigation of one single interface --- p.29
Chapter 2.4.1 --- Pure heptane-water interface --- p.30
Chapter 2.4.2 --- Heptane-BSA protein solution interface --- p.35
Chapter 2.5 --- Dilatation rheology --- p.41
Chapter 2.6 --- Conclusions --- p.42
Chapter 2.7 --- References and Notes --- p.43
Chapter CHAPTER 3 --- SYNTHESIS AND CHARACTERIZATION OF PNIPAM-RELATED MICROGELS --- p.45
Chapter 3.1 --- Introduction --- p.45
Chapter 3.2 --- Microgels preparation and characterization --- p.56
Chapter 3.2.1 --- Preparation of microgel samples used in this thesis --- p.57
Chapter 3.2.2 --- Microgels characterization --- p.59
Chapter 3.3 --- Conclusions --- p.63
Chapter 3.4 --- References and Notes --- p.63
Chapter CHAPTER 4 --- MICROGEL ADSORPTION BEHAVIORS AT THE OIL-WATER INTERFACES: THE KINETIC STUDY --- p.65
Chapter 4.1 --- Introduction --- p.65
Chapter 4.2 --- Results and discussions --- p.67
Chapter 4.2.1 --- The effect of microgel concentration: below VPTT --- p.68
Chapter 4.2.2 --- Microgel concentration effect on dynamic interfacial tension: above VPTT of microgels --- p.73
Chapter 4.2.3 --- Temperature effect on dynamic interfacial tension well above VPTT --- p.78
Chapter 4.2.4 --- Diffusion controlled process --- p.81
Chapter 4.2.5 --- Kinetic controlled process --- p.85
Chapter 4.3 --- Conclusions --- p.93
Chapter 4.4 --- References and Note --- p.95
Chapter CHAPTER 5 --- ANOMALOUS INTERFACIAL TENSION VALLEYS DURING THE VOLUME PHASE TRANSITION OF PNIPAM MICROGELS AT THE OIL-WATER INTERFACE --- p.96
Chapter 5.1 --- Introduction --- p.96
Chapter 5.2 --- The interfacial tension valleys --- p.97
Chapter 5.3 --- Discussions --- p.106
Chapter 5.4 --- Conclusions --- p.115
Chapter 5.5 --- References and Notes --- p.115
Chapter CHAPTER 6 --- THE THERMAL BEHAVIOR OF MICROGELS CONFINED AT THE OIL-WATER INTERFACES: REVERSIBLE OR IRREVERSIBLE? --- p.117
Chapter 6.1 --- Introduction --- p.117
Chapter 6.2 --- Microgels thermal behaviors confined at interfaces --- p.118
Chapter 6.3 --- Conclusions --- p.137
Chapter 6.4 --- References and Notes --- p.138
Chapter CHAPTER 7 --- FUNCTIONAL MATERIALS FROM MICROGELS AT INTERFACES --- p.139
Chapter 7.1 --- High internal phase emulsions (HIPEs) --- p.139
Chapter 7.2 --- Microgels stabilized HIPEs --- p.140
Chapter 7.2.1 --- Preparations --- p.140
Chapter 7.2.2 --- Characterizations --- p.141
Chapter 7.3 --- Materials from microgels stabilized emulsions --- p.144
Chapter 7.3.1 --- Porous membranes --- p.144
Chapter 7.3.2 --- Hierarchical porous materials --- p.145
Chapter 7.4 --- Conclusions --- p.146
Chapter 7.5 --- References and Notes --- p.147
Chapter CHAPTER 8 --- OVERVIEW OF MICROGELS AT INTERFACES --- p.148
Chapter 8.1 --- Summary of microgels at interfaces --- p.148
Chapter 8.2 --- Outlook and further experiments --- p.150
CURRICULUM VITAE --- p.152

Carbon nanotubes are known as one of the strongest materials in nature and since their discovery; they have triggered the scientific interest for fabricating multi-functional polymer composites. However, a well-known problem associated to the incorporation of nanoparticulate materials in polymer matrices is their tendency to agglomerate in order to reduce their surface energy, and the extreme increase of the polymer viscosities (i.e melts, solutions, etc), which makes it very difficult to process them. Polymers can be efficiently reinforced by fibers for applications where high strength and stiffness are required. Micro-scale short fiber reinforced polymer composites have been an alternative way to obtain fiber reinforced composites since the long fiber incorporation is a painful job and not always feasible and easy to produce composites in big scale. Therefore, use of long glass fibers as the support for depositing CNTs as well as CNTs+other kind of nanoparticles was made, and the resulting interfaces were investigated in detail by single fiber model composites. This approach can bring the CNT functionality, fiber strength and toughness to the final composite, and simultaneously alleviate the manufacturing process from increase of the polymer high viscosities. Finally, very logically the question of whether to improve or destroy the interface integrity comes before implementing the hybrid hierarchical reinforcements in bigger scales, and an output out of this work will be given. Furthermore, several information and functionalities arising from the CNTs at the interphase region will be elucidated like cure monitoring of the epoxy resin matrix, UV-sensing ability, and thermoelectric energy harvesting, giving rise to multi-functional structural composites. CNT-modified natural fibers also have been utillised to fabricate short fiber reinforced composites, and have shown a promising reinforcement effect due to the CNT nanostructured interfaces. The ‘interface’ in fiber reinforced polymer composites (FRPCs) is known as a very crucial parameter that has to be considered in the design of a composite with desired properties. Interfaces are often considered as surfaces however, they are in fact zones or areas with compositional, structural, and property gradients, typically varying from that of the fiber and the matrix material. Characterization of the mechanical properties of interfaces is necessary for understanding the mechanical behavior of scaled-up composites. In fact, the mechanical characteristics of a fiber/resin composite depend mainly on i) the mechanical properties of the component materials, ii) the surface of the fiber, and iii) the nature of the fiber/resin bonding as well as the mode of stress transfer at the interface. Among the many factors that govern the characteristics of composites involving a glass, carbon, natural or ceramic fiber, and a macromolecular matrix, the adhesion between fiber and matrix plays a predominant role. In specific, the stress transfer at the interface requires an efficient coupling between fiber and matrix. Therefore, it is important to optimize the interfacial bonding since a direct linkage between fiber and matrix gives rise to a rigid, low impact resistance composite material.