Search

A zenodo library associated to the publication : Improving crosstalk assessment in multicolor Single Molecule Localization Microscopy&nbsp

Many studies show that mixed species stands can have higher gross growth, or so-called overyielding, compared with monocultures. However, much less is known about mortality in mixed stands. Knowledge is lacking, for example, of how much of the gross growth is retained in the standing stock and how much is lost due to mortality. Here, we addressed this knowledge gap of mixed stand dynamics by evaluating 23 middle-aged, unthinned triplets of monospecific and mixed plots of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) repeatedly surveyed over 6–8 years throughout Europe. For explanation of technical terms in this abstract see Box 1. First, mixed stands produced more gross growth (+10%) but less net growth (−28%) compared with the weighted mean growth of monospecific stands. In monospecific stands, 73% of the gross growth was accumulated in the standing stock, whereas only 48% was accumulated in mixed stands. The gross overyielding of pine (2%) was lower than that of beech (18%). However, the net overyielding of beech was still 10%, whereas low growth and dropout of pine caused a substantial reduction from gross to net growth. Second, the mortality rates, the self- and alien-thinning strength, and the stem volume dropout were higher in mixed stands than monospecific stands. The main reason was the lower survival of pine, whereas beech persisted more similarly in mixed compared with monospecific stands.Third, we found a 10% higher stand density in mixed stands compared with monospecific stands at the first survey. This superiority decreased to 5% in the second survey.Fourth, the mixing proportion of Scots pine decreased from 46% to 44% between the first and second survey. The more than doubling of the segregation index (S) calculated by Pielou index (S increased from 0.2 to 0.5), indicated a strong tendency towards demixing due to pine. Fifth, we showed that with increasing water supply the dropout fraction of the gross growth in the mixture slightly decreased for pine, strongly increased for beech, and also increased for the stand as a whole. We discuss how the reduction of inter-specific competition by thinning may enable a continuous benefit of diversity and overyielding of mixed compared with monospecific stands of Scots pine and European beech., The study received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No952314 and under the Marie Skłodowska-Curie grant agreement No 778322. The first author also wishes to thank the German ScienceFoundation (Deutsche Forschungsgemeinschaft) for funding the project “Structure and dynamics of mixed-species stands of Scots pine and European beech compared with monospecific stands; analysis along an ecological gradient through Europe” (# DFG PR 292/15-1). Felipe Bravo is grateful for Funds by the Junta de Castilla y León through the projects “CLU-2019-01 and CL-EI-2021-05 - iuFOR Institute Unit of Excellence” of the University of Valladolid and the co-financing by the European Regional Development Fund (ERDF “Europe drives our growth”). Miren del Río thanks for the support by the Spanish Ministerio de Ciencia e Innovación (# PID2021-126275OB-C21/C22). Dejan Stojanović thanks the Ministry of Education, Science and Technological Development of the Republic of Serbia for funding. Tzvetan Zlatanov thanks the Ministry of Education and Science of the Republic of Bulgaria (# DO1-405/18.12.2020 LTER-BG).

International audience; A mixed hyperbolic-parabolic, non conservative, Reynolds Stress Model (RSM), is studied. It is based on an underlying set of Langevin equations, and allows to describe turbulent mixing, including transient demixing effects as well as incomplete mixing. Its mathematical structure is analysed, and specific regimes, related to acoustic-like, Riemann-type, or self-similar solutions, are identified. A second-order accurate numerical scheme is proposed in arbitrary curvilinear geometry. Its accuracy and convergence behaviour are tested by comparison with analytical solutions in the different regimes. The numerical scheme can be generalized to multi-dimensional configurations, with potentially cylindrical symmetry, on unstructured meshes.

Demixing is an everyday life phenomenon that takes place when different species with strong enough repulsive interactions are brought together: because the mixed state is unstable, a hydrodynamical instability develops, which tends to spatially segregate the two immiscible species. From the separation of oil and vinegar in a vinaigrette, to the tears of wine observable in a glass filled with alcohol, hydrodynamical instabilities are encountered in many mundane situations. However, the description of cold atoms gases by hydrodynamic-like equations shows that these phenomena are also relevant for such systems. In this thesis, we explore the dynamics of such phenomena in 2D Bose gases confined in box potentials, both in a square and ring configuration, and we compare our results to theoretical predictions. We also develop a method to spatially tailor the optical potential applied on our cloud in order to have more control on our sample.; La démixtion est un phénomène facilement observé dans la vie de tous les jours, et se produit quand deux espèces, ayant l’une pour l’autre une force d’interaction suffisamment répulsive, sont réunies. Comme l’état mélange est instable, une instabilité hydrodynamique se développe, et tend à séparer spatialement ces deux espèces immiscibles. De la séparation de l’huile et du vinaigre dans un vinaigrette, à la formation des larmes de vin dans un verre rempli d’alcool, les instabilités hydrodynamiques se rencontrent dans beaucoup de situations de la vie de tous les jours. Cependant, la possibilité de décrire les ensembles de gaz ultrafroids par des équations de type hydrodynamiques montre que ce genre de phénomènes peut également concerner ce type de systèmes. Dans cette thèse, nous explorerons les dynamiques reliées à ces phénomènes dans des gaz de Bose bidimensionnels confinés dans des boîtes de géométries carrées ou circulaires, et nous comparerons nos résultats à un modèle théorique. Nous développerons également une méthode consistant à tailler sur mesure le potentiel optique appliqué à notre nuage afin de raffiner le contrôle que nous avons de notre échantillon.

Demixing is an everyday life phenomenon that takes place when different species with strong enough repulsive interactions are brought together: because the mixed state is unstable, a hydrodynamical instability develops, which tends to spatially segregate the two immiscible species. From the separation of oil and vinegar in a vinaigrette, to the tears of wine observable in a glass filled with alcohol, hydrodynamical instabilities are encountered in many mundane situations. However, the description of cold atoms gases by hydrodynamic-like equations shows that these phenomena are also relevant for such systems. In this thesis, we explore the dynamics of such phenomena in 2D Bose gases confined in box potentials, both in a square and ring configuration, and we compare our results to theoretical predictions. We also develop a method to spatially tailor the optical potential applied on our cloud in order to have more control on our sample.; La démixtion est un phénomène facilement observé dans la vie de tous les jours, et se produit quand deux espèces, ayant l’une pour l’autre une force d’interaction suffisamment répulsive, sont réunies. Comme l’état mélange est instable, une instabilité hydrodynamique se développe, et tend à séparer spatialement ces deux espèces immiscibles. De la séparation de l’huile et du vinaigre dans un vinaigrette, à la formation des larmes de vin dans un verre rempli d’alcool, les instabilités hydrodynamiques se rencontrent dans beaucoup de situations de la vie de tous les jours. Cependant, la possibilité de décrire les ensembles de gaz ultrafroids par des équations de type hydrodynamiques montre que ce genre de phénomènes peut également concerner ce type de systèmes. Dans cette thèse, nous explorerons les dynamiques reliées à ces phénomènes dans des gaz de Bose bidimensionnels confinés dans des boîtes de géométries carrées ou circulaires, et nous comparerons nos résultats à un modèle théorique. Nous développerons également une méthode consistant à tailler sur mesure le potentiel optique appliqué à notre nuage afin de raffiner le contrôle que nous avons de notre échantillon.

The decay of the Convective Boundary Layer (CBL) is studied using large-eddy simulations of free and advective CBLs, in which surface heat supply is suddenly cut off. After the cutoff, coherent convective circulations last about one convective time scale and then fade away. In the mixed layer, the decay time scale increases with height, indicating that nonlocal eddies decay slower than near-surface local eddies. The slower decay of turbulence in the middle of CBL than near-surface turbulence is reconfirmed from the analysis of pattern correlations of perturbations of vertical velocity. Perturbations of potential temperature and scalar concentration decay faster and slower than vertical velocity perturbations, respectively. A downward propagation of negative heat flux and its oscillation are found and a quadrant analysis reveals that warmer air sinking events are responsible for the downward propagation. The fourth quadrant events seem to be induced by demixing of air parcels, entrained from above the CBL. The advective CBL simulation with geostrophic wind illustrates that near-surface eddies are mechanically generated and they decelerate flow from the bottom up in the CBL/residual layer. The two-dimensional spectra show the height- and scale-dependent characteristics of decaying convective turbulence again in the free and advective boundary layer simulations.

The behaviour of minerals under high pressure affects the bulk properties of exoplanets and planets with rocky components, possibly influencing their observable radii. Obtaining a wide range of experimental data is key to understanding observations and informing planetary interior models.

A contactor is an electromechanical device designed to establish or disconnect anelectrical current in a circuit by closing or opening contacts. During each operation, anelectric arc is created, due to the enormous power density involved to reach and locallyexceed the melting temperature of the material. As a result, the repeated action of thearcs during the life of the device (up to several hundred thousand closing/opening cycles)gradually leads to the ruin of the contact pads and the malfunction of the contactor. Thethesis work aims to propose tools for modelling the damage of contact pads under the effectof repeated impacts, with the longer-term objective of predicting the life of the contactoraccording to its operating conditions. The material considered is a pseudo-alloy made ofsilver and tin oxide SnO 2 . As a first step, several experimental campaigns were carried outto collect all the input data required for modelling : determination of the thermomechanicalproperties of the material, characterization of damage – surface and bulk – produced by asingle arc and by an accumulation of arcs, estimation of the power density provided by anarc to the contact material. Many experimental techniques have been used : monotonoustensile tests and cyclic loading, indentation (microhardness), 3D profilometry, opticalmicroscopy and scanning electron microscopy, EDS and EBSD analysis, thermal imagingcamera, high speed camera. Then two types of models were successively developed. Thefirst one uses the Zset finite element code. Developped in an axisymmetric geometry, itaims to describe within the material the evolution of temperatures, stresses and strainsresulting from an arc (assumed fixed), then the initiation of cracks after a few hundredof impacts at the same point. A 3D variant was then discussed to approach the case ofmoving arcs. The second model, of a phenomenological nature, is based on simplifieddescriptions of topography and tensile strength in silver in the vicinity of the surface, aswell as on rules of occurrence and spatial distribution, taken as much as possible fromexperimental observations. It is intended to simulate in a manageable calculation time thedamage resulting from the accumulation of a very large number of arcs over the entiresurface of the pellets.; Un contacteur est un dispositif électromécanique destiné à établir ou couper un courantélectrique dans un circuit par la fermeture ou l’ouverture de contacts. Lors de chaquemanœuvre, un arc électrique est créé entre les «pastilles» des contacts, conduisant parl’énorme densité de puissance mise en jeu à atteindre et dépasser localement la températurede fusion du matériau. De ce fait, l’action répétée des arcs durant la vie de l’appareil (jusqu’àplusieurs centaines de milliers de cycles ouverture/fermeture) mène progressivement à la«ruine» des pastilles des contacts et au dysfonctionnement du contacteur. Le travail de thèsevise à proposer des outils de modélisation de l’endommagement des pastilles de contact sousl’effet des arcs, dans l’objectif à plus long terme de prédire la durée de vie du contacteurselon ses conditions d’utilisation. Le matériau considéré est un pseudo-alliage en argent etoxyde d’étain. Dans un premier temps, plusieurs campagnes expérimentales ont été menéespour réunir toutes les données d’entrée indispensables aux modélisations : déterminationdes propriétés thermomécaniques du matériau, caractérisation des endommagements – ensurface et en profondeur – produits par un arc unique et par une accumulation d’arcs,estimation de la densité de puissance apportée par un arc au matériau de contact. Denombreuses techniques ont ainsi été mises en œuvre : essais de traction monotone et dechargement cyclique, indentation (microdureté), profilométrie 3D, microscopies optiqueet électronique à balayage, analyses EDS et EBSD, imagerie par caméras thermique etultrarapide. Puis deux types de modèles ont été successivement développés. Le premierutilise le code de calcul par éléments finis Zset. Développé en géométrie axisymétrique, ilvise à décrire au sein du matériau l’évolution des températures, contraintes et déformationsrésultant d’un arc (supposé fixe), puis l’amorçage de fissures au terme de quelques centainesd’impacts au même point. Une variante 3D a ensuite été abordée pour approcher le casd’arcs mobiles. Le second modèle, de nature phénoménologique, repose sur des descriptionssimplifiées de la topographie et de la teneur en argent au voisinage de la surface, ainsique sur des règles d’occurrence et de distribution spatiale, issues autant que possible desobservations expérimentales. Il est destiné à simuler dans un temps de calcul raisonnableles dommages résultant du cumul d’un très grand nombre d’arcs sur toute la surface despastilles.

A contactor is an electromechanical device designed to establish or disconnect anelectrical current in a circuit by closing or opening contacts. During each operation, anelectric arc is created, due to the enormous power density involved to reach and locallyexceed the melting temperature of the material. As a result, the repeated action of thearcs during the life of the device (up to several hundred thousand closing/opening cycles)gradually leads to the ruin of the contact pads and the malfunction of the contactor. Thethesis work aims to propose tools for modelling the damage of contact pads under the effectof repeated impacts, with the longer-term objective of predicting the life of the contactoraccording to its operating conditions. The material considered is a pseudo-alloy made ofsilver and tin oxide SnO 2 . As a first step, several experimental campaigns were carried outto collect all the input data required for modelling : determination of the thermomechanicalproperties of the material, characterization of damage – surface and bulk – produced by asingle arc and by an accumulation of arcs, estimation of the power density provided by anarc to the contact material. Many experimental techniques have been used : monotonoustensile tests and cyclic loading, indentation (microhardness), 3D profilometry, opticalmicroscopy and scanning electron microscopy, EDS and EBSD analysis, thermal imagingcamera, high speed camera. Then two types of models were successively developed. Thefirst one uses the Zset finite element code. Developped in an axisymmetric geometry, itaims to describe within the material the evolution of temperatures, stresses and strainsresulting from an arc (assumed fixed), then the initiation of cracks after a few hundredof impacts at the same point. A 3D variant was then discussed to approach the case ofmoving arcs. The second model, of a phenomenological nature, is based on simplifieddescriptions of topography and tensile strength in silver in the vicinity of the surface, aswell as on rules of occurrence and spatial distribution, taken as much as possible fromexperimental observations. It is intended to simulate in a manageable calculation time thedamage resulting from the accumulation of a very large number of arcs over the entiresurface of the pellets.; Un contacteur est un dispositif électromécanique destiné à établir ou couper un courantélectrique dans un circuit par la fermeture ou l’ouverture de contacts. Lors de chaquemanœuvre, un arc électrique est créé entre les «pastilles» des contacts, conduisant parl’énorme densité de puissance mise en jeu à atteindre et dépasser localement la températurede fusion du matériau. De ce fait, l’action répétée des arcs durant la vie de l’appareil (jusqu’àplusieurs centaines de milliers de cycles ouverture/fermeture) mène progressivement à la«ruine» des pastilles des contacts et au dysfonctionnement du contacteur. Le travail de thèsevise à proposer des outils de modélisation de l’endommagement des pastilles de contact sousl’effet des arcs, dans l’objectif à plus long terme de prédire la durée de vie du contacteurselon ses conditions d’utilisation. Le matériau considéré est un pseudo-alliage en argent etoxyde d’étain. Dans un premier temps, plusieurs campagnes expérimentales ont été menéespour réunir toutes les données d’entrée indispensables aux modélisations : déterminationdes propriétés thermomécaniques du matériau, caractérisation des endommagements – ensurface et en profondeur – produits par un arc unique et par une accumulation d’arcs,estimation de la densité de puissance apportée par un arc au matériau de contact. Denombreuses techniques ont ainsi été mises en œuvre : essais de traction monotone et dechargement cyclique, indentation (microdureté), profilométrie 3D, microscopies optiqueet électronique à balayage, analyses EDS et EBSD, imagerie par caméras thermique etultrarapide. Puis deux types de modèles ont été successivement développés. Le premierutilise le code de calcul par éléments finis Zset. Développé en géométrie axisymétrique, ilvise à décrire au sein du matériau l’évolution des températures, contraintes et déformationsrésultant d’un arc (supposé fixe), puis l’amorçage de fissures au terme de quelques centainesd’impacts au même point. Une variante 3D a ensuite été abordée pour approcher le casd’arcs mobiles. Le second modèle, de nature phénoménologique, repose sur des descriptionssimplifiées de la topographie et de la teneur en argent au voisinage de la surface, ainsique sur des règles d’occurrence et de distribution spatiale, issues autant que possible desobservations expérimentales. Il est destiné à simuler dans un temps de calcul raisonnableles dommages résultant du cumul d’un très grand nombre d’arcs sur toute la surface despastilles.

The solution phase behaviour of poly(2, 6-diphenyl-p-phenylene oxide) (PPPO) is investigated by a combination of turbidimetry, infrared spectroscopy, dynamic light scattering and densitometry, combined with calorimetry and X-ray scattering. We select dichloromethane (DCM) and heptane as, respectively, representative good and poor solvents for the polymer. This ternary system results in a miscibility gap which can be utilised for the design and fabrication of PPPO porous materials, membranes and scaffolds via phase inversion. We establish the phase diagram and resolve the kinetic solidification condition arising from the intersection between the coexistence and glass transition curves. PPPO exhibits a high T g ≈ 230 ∘C and is found to crystallise at T c ≈ 336 ∘C, and melt at T m ≈ 423, 445 ∘C with a double endotherm. The kinetics of demixing and (buoyancy-driven) stratification are quantified by optical imaging and the PPPO-rich phase analysed by SAXS/WAXS to resolve both amorphous and crystalline phases. Equipped with this knowledge, we demonstrate the controlled formation of nodular, bicontinuous and cellular morphologies by non-solvent induced demixing.

We investigate the phase separation mechanism of bosonic binary mixtures in spatially-fragmented traps, evidencing the emergence of phases featuring a different degree of mixing. The analysis is initially carried out by means of a semiclassical approach which transparently shows the occurrence of critical phenomena. These predictions are actually corroborated by the study of genuinely quantum indicators, including, but not limited to, the energy levels' structure and the entanglement between the species. The scope of our work goes also beyond the ground state's properties, as it comprises excited states and the dynamical evolution thereof. In particular, after introducing an indicator to monitor the degree of mixing, we show that several dynamical regimes feature persistent demixing in spite of their remarkably chaotic character., 11 pages, 8 figures

Polyphosphoinositides (PPIns) are a family of seven lipid messengers that regulate a vast array of signalling pathways to control cell proliferation, migration, survival and differentiation. PPIns are differentially present in various sub-cellular compartments and, through the recruitment and regulation of specific proteins, are key regulators of compartment identity and function. Phosphoinositides and the enzymes that synthesise and degrade them are also present in the nuclear membrane and in nuclear membraneless compartments such as nuclear speckles. Here we discuss how PPIns in the nucleus are modulated in response to external cues and how they function to control downstream signalling. Finally we suggest a role for nuclear PPIns in liquid phase separations that are involved in the formation of membraneless compartments within the nucleus.

The description and analysis of spatial data is an omnipresent task in both science and industry: In the food industry the distribution and size of pores in baked goods plays a role in their taste. In chemistry, biology and physics spatial data arises in manifold disciplines and on all length scales. On large scales one finds them in the structure of the universe or in earth surveillance data. On small scales one observes highly structured data in inner bones or on minute scales in the deformation of nucleons in nuclear pasta, which is theorized to form during the cooling of a neutron star. In particular in statistical physics many-body-systems have a tendency to collectively form complex structures by self-organization. These complex structures often allow to draw conclusions about the underlying physics. In order to formulate a quantitative relation between the physics of many-body-systems and their morphology, i.e. the spatial structure they assume, a quantitative description of this structure is essential. In this dissertation the spatial structure of phase transitions (crystallization and demixing) in many-body-systems is quantitatively described and analyzed in order to achieve an improved understanding of the physics involved. Regarding the analysis methods applied in this thesis we go beyond conventional linear measures based on two-point correlation functions or the power spectrum. Instead, the aim is a full nonlinear morphological characterization of the spatial data with measures derived from the family of Minkowski functionals and tensors. They are additive, morphological measures related to, not only geometrical concepts like volume, area and curvature, but also to topological aspects such as connectivity and are sensitive to higher order correlation. Complex plasmas (dielectric microparticles immersed in a plasma) are a well suited model system for the particle resolved investigation of many-body processes. Their optical thinness allows for the optical imaging and tracking of the fully resolved trajectories of hundreds of particle layers. Additionally interactions can be tuned over a large range allowing to manipulate the shape and magnitude of the interparticle potential. Since the gas density is typically very low, the particle motion is practically undamped resulting in a direct analogy to the atomistic dynamics in solids or fluids. Liquid-solid phase transition have been considered impossible for a long time since the Mermin-Wagner theorem forbids long-range order in two (or less) dimensions. However, Kosterlitz and Thouless (Nobel prize 2016) circumvented this by replacing the long-range order with a quasi-long-range order and by introducing a topological phase transition mediated by defects. The well accepted KTHNY theory predicts an intermediate anisotropic phase, the hexatic phase. In the first part of this thesis the KTHNY theory is tested for experiments and a simulation of the crystallization of two-dimensional complex plasma sheets. For the same experiments the hypothesis and prediction of the recently developed fractal-domain-structure (FDS) theory is tested. The FDS theory is based on the Frenkel kinetic theory of melting. It postulates a fractal relationship between crystalline domains separated by boundaries of defect lines and predicts a scale-free relation between the system energy and the defect fraction. It is found that the KTHNY theory is not applicable to the liquid-solid phase transition in complex plasmas. The FDS theory however, is validated. The other focus of this thesis is the morphological characterization of fluid-fluid demixing dynamics. The generally accepted mechanism for fluid-fluid demixing is spinodal decomposition. Spinodal decomposition is achieved by a quench deep inside the spinodal curve of the phase diagram. It is characterized by the exponential growth of longwavelength density fluctuations. However the mean-field theory predictions of spinodal decomposition are not consistent with experiments and simulations. This shows the need for particle resolved studies with tunable interactions. To this end complex plasma simulations in flat three-dimensional space and density-functional theory calculations on the two-dimensional sphere are analyzed. In both cases different stages of demixing are identified with distinct domain growth rates during spinodal decomposition. Most importantly, universal demixing behavior is found for different interaction potentials, respectively for different mixture fractions and sphere sizes. These universal features could only be resolved by applying nonlinear measures, going beyond conventional methods based on the power spectral density. This suggests that nonlinear features in the demixing kinetics play an important role and that it is crucial to address this issue in future works., Räumliche Daten zu beschreiben und zu analysieren ist eine allgegenwärtige Problemstellung sowohl in der Wissenschaft als auch in der Industrie: So spielt beispielsweise in der Nahrungsmittelindustrie die räumliche Verteilung und die Größe von Poren in Backwaren eine Rolle für deren Geschmack. In den wissenschaftlichen Gebieten der Chemie, Biologie und der Physik liefern räumlich strukturierte Systeme Grundlage vieler Forschungsbereiche und sind in allen Größenordnungen aufzufinden: Auf großen Skalen z.B. bei der Struktur des Universums oder bei Erdbeobachtungsdaten. Auf kleinen Skalen bei der Struktur im inneren von Knochen oder im kleinsten bei der Verformung von Nukleonen zu nuklearer Pasta, die z.B. beim Abkühlen von Neutronensternen entstehen soll. Insbesondere in der statistischen Physik neigen Vielteilchensysteme dazu, sich in komplexen Strukturen selbst anzuordnen. Diese komplexen räumlichen Strukturen lassen oft Rückschlüsse auf die zugrunde liegende Physik zu. Um einen quantitativen Zusammenhang zwischen der Physik von Vielteilchensystemen und ihrer Morphologie, also der Struktur die diese annehmen, herzustellen, ist eine quantitative Beschreibung dieser Struktur unerlässlich. In dieser Dissertation werden daher die räumlichen Strukturen bei Phasenübergängen (Kristallisation und Entmischung) in Vielteilchensystemen beschrieben und analysiert, um damit Rückschlüsse auf die zugrundeliegende Physik ziehen zu können. Im Hinblick auf die Methoden, die zur Analyse der in dieser Dissertation untersuchten Systeme genutzt werden, gehen wir über konventionelle Methoden, die auf dem Leistungsspektrum oder auf zwei-Punkt Korrelationsfunktionen beruhen, hinaus. Das Ziel ist es die räumlichen Daten vollständig morphologisch zu charakterisieren. Zu diesem Zweck werden Metriken basierend auf der Familie der Minkowski Funktionale und Tensoren abgeleitet. Das sind additive morphologische Maße, die auch Korrelationen höherer Ordnung detektieren können. Sie sind nicht nur mit geometrischen Konzepten wie Volumen, Fläche und Krümmung verwandt, sondern stellen auch Aspekte der Topologie wie z.B. Verbundenheit dar. Komplexe Plasmen (dielektrische Mikropartikel eingebracht in ein Plasma) stellen ein überaus geeignetes Modellsystem für die Untersuchung von Vielteilchenprozessen auf der kinetischen Ebene individueller Teilchen dar, da durch ihre optische Dünnheit die Bildgebung mehrerer hundert Lagen von Teilchen und die volle Auflösung der Teilchentrajektorien ermöglicht wird. Darüber hinaus können die Teilchenwechselwirkungen in Komplexen Plasmen auf vielfältige Art und Weise manipuliert werden. Da der Gasdruck meist sehr gering ist, sind die Teilchenbewegungen praktisch ungedämpft. Dies stellt eine direkte Analogie zur Dynamik von Atomen in Flüssigkeiten oder Festkörpern dar. Flüssig-fest Phasenübergänge in zwei-dimensionalen Systemen wurden lange Zeit als unmöglich erachtet, da das Mermin-Wagner Theorem langreichweitige Ordnung in zwei (oder weniger) Dimensionen verbietet. Kosterlitz und Thouless umgingen diese Problem jedoch, indem sie die langreichweitige Ordnung durch eine quasi-langreichweitige Ordnung ersetzten und einen topologischen Phasenübergang vorstellten, der durch Interaktionen von Kristalldefekten vonstatten geht. Diese allgemein akzeptierte KTHNY Theorie sagt eine anisotrope Zwischenphase vorher, die so genannte hexatische Phase. Im ersten Teil dieser Dissertation werden die Vorhersagen der KTHNY Theorie, anhand von Experimenten und einer Computer Simulation an einzelnen zwei-dimensionalen Komplexen Plasma Kristall-Lagen getestet. Anhand selbiger Experimente wird eine kürzlich neu entwickelte fraktale-Domänen-Struktur (FDS) Theorie getestet. Die FDS Theorie basiert auf der kinetischen Theorie des Schmelzens von Frenkel. Sie postuliert einen fraktalen Zusammenhang zwischen der eingeschlossenen Fläche von kristallinen Domänen und der Länge deren Begrenzung durch Linien aus Kristalldefekten. Es wird gezeigt, dass die KTHNY Theorie nicht auf flüssig-fest Phasenübergänge in zwei-dimensionalen Komplexen Plasmen angewandt werden kann. Die FDS Theorie wird hingegen validiert. Desweiteren wird in dieser Dissertation die morphologische Beschreibung der Entmischungsdynamik von Flüssigkeiten behandelt. Der allgemein anerkannte Mechanismus, der für die Flüssigkeitsentmischung verantwortlich ist, ist die spinodale Dekomposition. Diese wird durch das quenchen (z.B. abkühlen) in den inneren Bereich der spinodalen Kurve im Phasendiagramm ausgelöst. Das charakteristische Merkmal der spinodalen Dekomposition ist der Beginn der Entmischung durch das exponentielle Wachstum von Dichtefluktuationen mit großen Wellenlängen. Die Vorhersagen der Molekularfeldtheorie der spinodalen Dekomposition sind jedoch nicht mit experimentellen Beobachtungen und Simulationen vereinbar. Diese Tatsache zeigt den Bedarf an Studien auf, die es vermögen einzelnen Teilchen zu folgen und bei denen man die Interaktionen zwischen den Teilchen beeinflussen kann. Deshalb werden in dieser Doktorarbeit sowohl Simulationen von Komplexen Plasmen (in drei-dimensionaler Euklidscher Geometrie) als auch Dichtefunktionaltheorie Berechnungen auf der zwei-dimensionalen Sphäre untersucht. In beiden Fällen können verschiedene Stadien in der Dynamik der Entmischung unterschieden werden. Das interessanteste Ergebnis ist die Entdeckung von universellem Verhalten im Entmischungsprozess. Universalität kann in dieser Arbeit im Hinblick auf verschiedene Interaktionspotentiale, bzw. im Hinblick auf verschiedene Mischungsverhältnisse und Sphärenradien gezeigt werden. Um diese universellen Eigenschaften zu entdecken, ist die Anwendung nicht-linearer Maße zwingend erforderlich, konventionelle auf dem Leistungsspektrum basierende Maße sind hierfür unzureichend. Dies zeigt, dass die nicht-linearen Eigenschaften des Entmischungsprozesses eine wichtige Rolle spielen und ist deshalb ein Fokus künftiger Arbeitenzu diesem Thema.

This cumulative dissertation discusses the experimental observation and description of crystallization and demixing processes in a three-dimensional complex plasma. Complex plasmas are low temperature plasmas to which well-defined microparticles have been added deliberately. These particles are charged by electron and ion fluxes toward their surfaces. Charged particles can then create regular structures similar to a crystal or arrange comparable to fluids. The typical size and time ranges in a complex plasma allow for observations of changes in form of distinct phases on a single-particle level. This is why they are often used as model systems for phase transitions.In the first publication, the influence of neutral gas pressure on the crystallization of a three-dimensional complex plasma under gravity conditions was considered. The ´scalar product of the Minkowski structure metric´ was developed in this publication to identify the particles´ state of aggregation. Besides this method, various well-known crystallization criteria were applied. All criteria revealed the same picture: the system was in the crystalline state at low pressure and in the liquid state at high pressure. This stands in contrast with previous experiments under gravity as well as under microgravity conditions. The increasing role of collisions between ions and neutrals in the vicinity of the particles as well as a decreased Debye length were identified as responsible for this observation.The second publication is a logical extension of the first one. In this publication, the scalar product of the Minkowski structure metric was applied to visualize the location of the particles in the solid state and in the liquid state at different pressure rates. Hereby, it could be shown additionally that the degree of crystallization was decreasing from the lower to the upper part of the particle cloud.After the first two publications, the detailed conditions under which complex plasmas are highly ordered were determined. This knowledge facilitated the third publication. In this publication, the crystallization process of a complex plasma under gravity conditions was analyzed in a time-resolved manner. During crystallization, tomographic scans were performed to identify the evolution of solid clusters. The calculated fractal dimension of these clusters showed that the solidification process was dominated by epitaxial growth and diffusion-limited growth.The fourth publication deals with the demixing of two particle types in a complex plasma. Due to the mass discrepancies, the particles would levitate at different heights in the plasma under gravity conditions. This is why the experiments were performed under milligravity during a parabola flight. The transition from a single phase into a two-phase system was observed and described., Das Thema dieser kumulativen Dissertation ist die experimentelle Beobachtung und die Beschreibung der Kristallisation und der Entmischung von dreidimensionalen komplexen Plasmen. Komplexe Plasmen sind Niedertemperaturplasmen, in denen genau definierte Mikropartikel hinzugefügt wurden. Die Partikel laden sich durch Elektronen- und Ionenflüsse auf ihre Oberfläche elektrisch auf. Aufgrund ihrer Ladung können die Teilchen regelmäßige Strukturen vergleichbar mit Kristallen ausbilden. Eine Ordnung analog zu Fluiden ist ebenfalls möglich. Die typische Größen- und Zeitskalen in einem komplexen Plasma, erlauben es Übergänge zwischen unterschiedlichen Phasen auf einer Partikelebene direkt zu beobachten. Aus diesem Grund werden sie oft als Modellsysteme für Phasenübergänge genutzt.In der ersten Veröffentlichung wird der Einfluss des Gasdruckes auf die Kristallisation eines dreidimensionalen komplexen Plasmas unter Gravitation untersucht. Das "Skalarprodukt der Minkowski Struktur Metrik" wurde hier entwickelt, um den Aggregatzustand in dem sich die Partikel befinden zu bestimmen. Daneben wurden zahlreiche weitere bekannte Kristallisationskriterien eingesetzt. Alle Kriterien zeigten das gleiche Bild: Bei niedrigem Druck war das System im kristallinen, bei hohem Druck im flüssigem Zustand. Das steht im Gegensatz zu bisherigen Experimenten sowohl unter Gravitation als auch unter Mikrogravitation. Als Grund für diese Beobachtung wurden die zunehmende Bedeutung von Stößen zwischen Ionen und Neutralgas in der direkten Umgebung der Partikel sowie eine verringerte Debye Länge identifiziert.Die zweite Veröffentlichung ist eine logische Erweiterung der Ersten. In dieser Publikation wird bei unterschiedlichen Gasdrücken das Skalarprodukt der Minkowski Struktur Metrik genutzt, um den Ort der Partikel, die sich im festen bzw. im flüssigen Zustand befinden, zu visualisieren. Hierdurch konnte zusätzlich gezeigt werden, dass der Kristallisationsgrad der Partikelwolke von unten nach oben abnimmt.In den ersten beiden Veröffentlichungen wurden die genauen Bedingungen, unter denen sich ein komplexes Plasma in einem kristallinen Zustand befindet, bestimmt. Dieses Wissen erlaubte die dritte Publikation, in der der Kristallisationsvorgang eines komplexen Plasmas unter Gravitation zeitaufgelöst analysiert wurde. Während des Kristallizationsprozesses wurden tomographische Scans durchgeführt, um die Entwicklung fester Domänen zu identifizieren. Die berechnete fraktale Dimension dieser Domänen ergab, dass der Erstarrvorgang durch epitaktisches Wachstum und diffusions begrenztes Wachstum dominiert wurde.Die vierte Publikation handelt von dem Entmischen zweier Partikelsorten innerhalb eines komplexen Plasmas. Unter Gravitation würden die Partikelsorten aufgrund der Massendifferenzen in unterschiedlichen Höhen innerhalb des Plasmas levitieren. Aus diesem Grund wurden die Experimente unter Milligravitation während eines Parabelfluges durchgeführt. Der Übergang zwischen einem Ein-Phasen zu einem Zwei-Phasen System konnte beobachtet und beschrieben werden.

This cumulative dissertation discusses the experimental observation and description of crystallization and demixing processes in a three-dimensional complex plasma. Complex plasmas are low temperature plasmas to which well-defined microparticles have been added deliberately. These particles are charged by electron and ion fluxes toward their surfaces. Charged particles can then create regular structures similar to a crystal or arrange comparable to fluids. The typical size and time ranges in a complex plasma allow for observations of changes in form of distinct phases on a single-particle level. This is why they are often used as model systems for phase transitions. In the first publication, the influence of neutral gas pressure on the crystallization of a three-dimensional complex plasma under gravity conditions was considered. The ´scalar product of the Minkowski structure metric´ was developed in this publication to identify the particles´ state of aggregation. Besides this method, various well-known crystallization criteria were applied. All criteria revealed the same picture: the system was in the crystalline state at low pressure and in the liquid state at high pressure. This stands in contrast with previous experiments under gravity as well as under microgravity conditions. The increasing role of collisions between ions and neutrals in the vicinity of the particles as well as a decreased Debye length were identified as responsible for this observation. The second publication is a logical extension of the first one. In this publication, the scalar product of the Minkowski structure metric was applied to visualize the location of the particles in the solid state and in the liquid state at different pressure rates. Hereby, it could be shown additionally that the degree of crystallization was decreasing from the lower to the upper part of the particle cloud. After the first two publications, the detailed conditions under which complex plasmas are highly ordered were determined. This knowledge facilitated the third publication. In this publication, the crystallization process of a complex plasma under gravity conditions was analyzed in a time-resolved manner. During crystallization, tomographic scans were performed to identify the evolution of solid clusters. The calculated fractal dimension of these clusters showed that the solidification process was dominated by epitaxial growth and diffusion-limited growth. The fourth publication deals with the demixing of two particle types in a complex plasma. Due to the mass discrepancies, the particles would levitate at different heights in the plasma under gravity conditions. This is why the experiments were performed under milligravity during a parabola flight. The transition from a single phase into a two-phase system was observed and described. Das Thema dieser kumulativen Dissertation ist die experimentelle Beobachtung und die Beschreibung der Kristallisation und der Entmischung von dreidimensionalen komplexen Plasmen. Komplexe Plasmen sind Niedertemperaturplasmen, in denen genau definierte Mikropartikel hinzugefügt wurden. Die Partikel laden sich durch Elektronen- und Ionenflüsse auf ihre Oberfläche elektrisch auf. Aufgrund ihrer Ladung können die Teilchen regelmäßige Strukturen vergleichbar mit Kristallen ausbilden. Eine Ordnung analog zu Fluiden ist ebenfalls möglich. Die typische Größen- und Zeitskalen in einem komplexen Plasma, erlauben es Übergänge zwischen unterschiedlichen Phasen auf einer Partikelebene direkt zu beobachten. Aus diesem Grund werden sie oft als Modellsysteme für Phasenübergänge genutzt. In der ersten Veröffentlichung wird der Einfluss des Gasdruckes auf die Kristallisation eines dreidimensionalen komplexen Plasmas unter Gravitation untersucht. Das "Skalarprodukt der Minkowski Struktur Metrik" wurde hier entwickelt, um den Aggregatzustand in dem sich die Partikel befinden zu bestimmen. Daneben wurden zahlreiche weitere bekannte Kristallisationskriterien eingesetzt. Alle Kriterien zeigten das gleiche Bild: Bei niedrigem Druck war das System im kristallinen, bei hohem Druck im flüssigem Zustand. Das steht im Gegensatz zu bisherigen Experimenten sowohl unter Gravitation als auch unter Mikrogravitation. Als Grund für diese Beobachtung wurden die zunehmende Bedeutung von Stößen zwischen Ionen und Neutralgas in der direkten Umgebung der Partikel sowie eine verringerte Debye Länge identifiziert. Die zweite Veröffentlichung ist eine logische Erweiterung der Ersten. In dieser Publikation wird bei unterschiedlichen Gasdrücken das Skalarprodukt der Minkowski Struktur Metrik genutzt, um den Ort der Partikel, die sich im festen bzw. im flüssigen Zustand befinden, zu visualisieren. Hierdurch konnte zusätzlich gezeigt werden, dass der Kristallisationsgrad der Partikelwolke von unten nach oben abnimmt. In den ersten beiden Veröffentlichungen wurden die genauen Bedingungen, unter denen sich ein komplexes Plasma in einem kristallinen Zustand befindet, bestimmt. Dieses Wissen erlaubte die dritte Publikation, in der der Kristallisationsvorgang eines komplexen Plasmas unter Gravitation zeitaufgelöst analysiert wurde. Während des Kristallizationsprozesses wurden tomographische Scans durchgeführt, um die Entwicklung fester Domänen zu identifizieren. Die berechnete fraktale Dimension dieser Domänen ergab, dass der Erstarrvorgang durch epitaktisches Wachstum und diffusions begrenztes Wachstum dominiert wurde. Die vierte Publikation handelt von dem Entmischen zweier Partikelsorten innerhalb eines komplexen Plasmas. Unter Gravitation würden die Partikelsorten aufgrund der Massendifferenzen in unterschiedlichen Höhen innerhalb des Plasmas levitieren. Aus diesem Grund wurden die Experimente unter Milligravitation während eines Parabelfluges durchgeführt. Der Übergang zwischen einem Ein-Phasen zu einem Zwei-Phasen System konnte beobachtet und beschrieben werden.

The effects of hydrocarbon dissociation and subsequent diamond precipitation on the internal structure and evolution of icy giant planets like Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, gravity compresses mixtures of light elements to densities of several grams per cubic centimeter while the temperature reaches thousands of Kelvins resulting in thermal energies on the order of chemical bonding and above. Under these conditions, simple hydrocarbons like methane, which are highly abundant in the atmospheres of these planets, are believed to undergo structural transitions that release molecular hydrogen from deeper layers and may lead to compact stratified cores. Indeed, the isentropes of Uranus and Neptune intersect temperature-pressure conditions where first polymerization occurs, and then, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene samples dynamically compressed to 150GPa and 5000 K, which resembles the environment ~10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon-hydrogen demixing and imply that diamond precipitation may require ~10x higher pressures than previously suggested by experiments investigating non-isolated hydrocarbons. Besides underlining the general importance of chemical processes inside giant planets, these results will inform evolutionary models of Uranus and Neptune, where carbon-hydrogen demixing can be a significant source for the convection necessary to explain their unusual magnetic fields. Additionally, our experiment demonstrates an alternative path for producing nanodiamonds for scientific and industrial applications that may be superior to current methods using oxygen-deficient explosives.

The manuscript focuses on the demixing of hyaluronan and alginate in the hydrogel state. Binary solutions of the two polysaccharides have been treated with Ca2+ as the alginate cross-linking ion and the radial distribution of the two components in the hydrogels was measured by means of 1H NMR. These results revealed the presence of alginate-enriched and hyaluronan-enriched domains stemming from a polysaccharide demixing. The hydrogels were characterized by means of uniaxial compression and creep-compliance measurements which showed that the demixing increased the overall resistance of the hydrogel to stress. In addition, due to the viscoelastic properties of hyaluronan, a marked increase of the Newtonian viscosity of the constructs was noticed. The peculiarity of the effect of hyaluronan was demonstrated by the use of an alginate unable to form gel by binding non-calcium binding alginate, i.e. mannuronan, ruling out the effect of viscosity over the time-dependent behavior of the mixed hyaluronan-alginate hydrogels.

We investigated various aspects of colloidal dispersions. In this study we not only emphasized the tunability of the particle properties (rods versus spheres, charging properties of the particle surface), but also the properties of the medium in which they reside (oil and/or water). These properties can impact the phase behaviour of colloidal dispersions, and the effective colloid-colloid or colloid-interface interactions. We applied concepts like (long-range) ionic screening, charge regulation, many-body effects, and anisotropy in particle shape, to various dispersions of charged colloidal spheres and hard needles. For the phase behaviour, we studied reentrant melting of colloidal Wigner crystals as function of colloid density, the spontaneaous demixing in binary mixtures of positively charged colloidal spheres, and the formation of string-like structures consisting of charged colloidal particles. Charge regulation, the way how colloidal particles acquire their charge by adsorption or desorption of ions, turned out to be essential not only on the level of the macroscopic phase diagram (such as the occurrence of reentrant fluid phases), but also on the type of structures that could be formed (strings or clusters). Colloid-interface interactions were studied in the context of colloidal particles in a medium that consists of two immiscible solvents, namely oil and water. We showed that so-called non-touching colloids experience an effective interaction potential with the oil-water interface, that is tunable by the Donnan potential and colloidal charge. These colloid-ion forces can not only be tuned in range and strength, but also in being repulsive or attractive at sufficiently large distances from the interface, and should be added to the well-known image-charge and van der Waals potential. Furthermore, we investigated lateral colloid-colloid interactions for colloids that can penetrate the oil-water interface. We suggested that the colloid-colloid lateral interaction is dominated by the small, weakly screened bound charges at the oil-exposed side of the colloidal surface, and these are probably more important than the many highly screened charges at the water-exposed side. Finally, we considered the anisotropy in the particle shape in the context of hard needles. These needles were described by a novel Landau-de Gennes theory that accurately mimicks Onsager theory. We tested this theory, which is based on the grand-canonical ensemble, in bulk and for the isotropic-nematic interface. We applied it subsequently to the hedgehog defect and showed that colloidal systems have an isotropic core size that is on the order of the particle size. This should be contrasted to molecular (thermotropic) systems where the core size is much larger than the molecular size. Furthermore, we investigated the density dependence of director field textures and their defects for confined rods. Ultimately, we applied our theory to tactoids: liquid crystalline droplets in an isotropic background. The experimentally observed large size aspect ratios of these droplets are, however, not explained in our theory, if we use the surface tensions from Onsager theory, revealing the need of additional ingredients in our model.

We investigated various aspects of colloidal dispersions. In this study we not only emphasized the tunability of the particle properties (rods versus spheres, charging properties of the particle surface), but also the properties of the medium in which they reside (oil and/or water). These properties can impact the phase behaviour of colloidal dispersions, and the effective colloid-colloid or colloid-interface interactions. We applied concepts like (long-range) ionic screening, charge regulation, many-body effects, and anisotropy in particle shape, to various dispersions of charged colloidal spheres and hard needles. For the phase behaviour, we studied reentrant melting of colloidal Wigner crystals as function of colloid density, the spontaneaous demixing in binary mixtures of positively charged colloidal spheres, and the formation of string-like structures consisting of charged colloidal particles. Charge regulation, the way how colloidal particles acquire their charge by adsorption or desorption of ions, turned out to be essential not only on the level of the macroscopic phase diagram (such as the occurrence of reentrant fluid phases), but also on the type of structures that could be formed (strings or clusters). Colloid-interface interactions were studied in the context of colloidal particles in a medium that consists of two immiscible solvents, namely oil and water. We showed that so-called non-touching colloids experience an effective interaction potential with the oil-water interface, that is tunable by the Donnan potential and colloidal charge. These colloid-ion forces can not only be tuned in range and strength, but also in being repulsive or attractive at sufficiently large distances from the interface, and should be added to the well-known image-charge and van der Waals potential. Furthermore, we investigated lateral colloid-colloid interactions for colloids that can penetrate the oil-water interface. We suggested that the colloid-colloid lateral interaction is dominated by the small, weakly screened bound charges at the oil-exposed side of the colloidal surface, and these are probably more important than the many highly screened charges at the water-exposed side. Finally, we considered the anisotropy in the particle shape in the context of hard needles. These needles were described by a novel Landau-de Gennes theory that accurately mimicks Onsager theory. We tested this theory, which is based on the grand-canonical ensemble, in bulk and for the isotropic-nematic interface. We applied it subsequently to the hedgehog defect and showed that colloidal systems have an isotropic core size that is on the order of the particle size. This should be contrasted to molecular (thermotropic) systems where the core size is much larger than the molecular size. Furthermore, we investigated the density dependence of director field textures and their defects for confined rods. Ultimately, we applied our theory to tactoids: liquid crystalline droplets in an isotropic background. The experimentally observed large size aspect ratios of these droplets are, however, not explained in our theory, if we use the surface tensions from Onsager theory, revealing the need of additional ingredients in our model.

We investigated various aspects of colloidal dispersions. In this study we not only emphasized the tunability of the particle properties (rods versus spheres, charging properties of the particle surface), but also the properties of the medium in which they reside (oil and/or water). These properties can impact the phase behaviour of colloidal dispersions, and the effective colloid-colloid or colloid-interface interactions. We applied concepts like (long-range) ionic screening, charge regulation, many-body effects, and anisotropy in particle shape, to various dispersions of charged colloidal spheres and hard needles. For the phase behaviour, we studied reentrant melting of colloidal Wigner crystals as function of colloid density, the spontaneaous demixing in binary mixtures of positively charged colloidal spheres, and the formation of string-like structures consisting of charged colloidal particles. Charge regulation, the way how colloidal particles acquire their charge by adsorption or desorption of ions, turned out to be essential not only on the level of the macroscopic phase diagram (such as the occurrence of reentrant fluid phases), but also on the type of structures that could be formed (strings or clusters). Colloid-interface interactions were studied in the context of colloidal particles in a medium that consists of two immiscible solvents, namely oil and water. We showed that so-called non-touching colloids experience an effective interaction potential with the oil-water interface, that is tunable by the Donnan potential and colloidal charge. These colloid-ion forces can not only be tuned in range and strength, but also in being repulsive or attractive at sufficiently large distances from the interface, and should be added to the well-known image-charge and van der Waals potential. Furthermore, we investigated lateral colloid-colloid interactions for colloids that can penetrate the oil-water interface. We suggested that the colloid-colloid lateral interaction is dominated by the small, weakly screened bound charges at the oil-exposed side of the colloidal surface, and these are probably more important than the many highly screened charges at the water-exposed side. Finally, we considered the anisotropy in the particle shape in the context of hard needles. These needles were described by a novel Landau-de Gennes theory that accurately mimicks Onsager theory. We tested this theory, which is based on the grand-canonical ensemble, in bulk and for the isotropic-nematic interface. We applied it subsequently to the hedgehog defect and showed that colloidal systems have an isotropic core size that is on the order of the particle size. This should be contrasted to molecular (thermotropic) systems where the core size is much larger than the molecular size. Furthermore, we investigated the density dependence of director field textures and their defects for confined rods. Ultimately, we applied our theory to tactoids: liquid crystalline droplets in an isotropic background. The experimentally observed large size aspect ratios of these droplets are, however, not explained in our theory, if we use the surface tensions from Onsager theory, revealing the need of additional ingredients in our model.

A molecular dynamics simulation of the demixing process of a binary complex plasma is analysed and the role of distinct interaction potentials is discussed by using morphological Minkowski tensor analysis of the minority phase domain growth in a demixing simulated binary complex plasma. These Minkowski tensor methods are compared with previous results that utilized a power spectrum method based on the time-dependent average structure factor. It is shown that the Minkowski tensor methods are superior to the previously used power spectrum method in the sense of higher sensitivity to changes in domain size. By analysis of the slope of the temporal evolution of Minkowski tensor measures qualitative differences between the case of particle interaction with a single length scale compared to particle interactions with two different length scales (dominating long range interaction) are revealed. After proper scaling the graphs for the two length scale scenario coincide, pointing towards universal behaviour. The qualitative difference in demixing scenarios is evidenced by distinct demixing behaviour: In the long range dominated cases demixing occurs in two stages. At first neighbouring particles agglomerate then domains start to merge in cascades. However in the case of only one interaction length scale only agglomeration but no merging of domains can be observed. Thus, Minkowski Tensor analysis are likely to become a useful tool for further investigation of this (and other) demixing processes. It is capable to reveal (nonlinear) local topological properties, probing deeper than (linear) global power spectrum analysis, however still providing easily interpretable results founded on a solid mathematical framework., 12 pages, 10 figures, Phys. Rev. E, accepted for publication, http://journals.aps.org/pre

Phase separation process is important as it determines the structure of the final materials. There are many systems that have more than one phase such as foams and gels. Aqueous foams are dispersions of gas bubbles in a water phase and gels appear when some basic microscopic unit starts to aggregate forming a large solid network that spans macroscopic space. They have many applications in industry and daily life. In the present thesis, firstly, I focus on studying different types of phase separation. Secondly, I studied the ion specific effects on the aggregation of colloidal particles and surfactant, the purpose is to make stable foams. In the miscibility gap there are two types of phase separation: Nucleation growth and spinodal decomposition, they have different growth mechanisms and kinetics. Therefore, my first p project is to investigate the evolution process of them and their effects to the final structure of material. Gels can be made by adding salt to the dispersion of colloidal particles, they have a large number of applications such as in food and material science. In this dissertation, we use different types of salts to compare gel properties from both macroscopic and microscopic aspects. Obtaining stable foams is significant in the view of their plenty of applications, but the ways to make them are mostly complicated. In this thesis, we can obtain stable foams via two ways. One is simply by adding salts to surfactant solutions, through which we can make ultrastable foam. Another way is using the gel phase we have studied as the continuous phase in foams to arrest the foam aging., Le procédé de séparation de phase est importante car elle détermine la structure des matériaux finaux. Il existe de nombreux systèmes qui ont plus d'une phase tels que des mousses et des gels. Les mousses sont des dispersions aqueuses de bulles de gaz dans une phase aqueuse et gels apparaissent lorsque certains microscopique unité de base commence à se rassembler formant un grand réseau solide qui enjambe l'espace macroscopique. Ils ont de nombreuses applications dans l'industrie et la vie quotidienne. Dans cette thèse, tout d'abord, je me concentre sur l'étude de différents types de séparation de phase. Deuxièmement, je étudié les effets spécifiques d'ions sur l'agrégation des particules colloïdales et tensioactif, le but est de faire des mousses stables. Dans la lacune de miscibilité il existe deux types de séparation de phase: la croissance nucléation et la décomposition spinodale, ils ont différents mécanismes et de la cinétique de croissance. Par conséquent, mon premier projet est d'étudier le processus d'évolution d'eux et de leurs effets sur la structure finale du matériau. Les gels peuvent être préparés par l'ajout de sel à la dispersion de particules colloïdales, ils ont un grand nombre d'applications telles que dans les aliments et la science des matériaux. Dans cette thèse, nous utilisons différents types de sels de comparer les propriétés de gel à partir de deux aspects macroscopiques et microscopiques. Obtenir des mousses stables est significatif dans la vue de leur beaucoup d'applications, mais les moyens de les faire sont pour la plupart compliqué. Dans cette thèse, nous pouvons obtenir des mousses stables par l'intermédiaire de deux façons. On est tout simplement en ajoutant des sels de solutions de tensioactifs, à travers lequel nous pouvons faire la mousse ultra-stable. Une autre façon est d'utiliser la phase de gel, nous avons étudié en tant que phase continue dans les mousses à arrêter le vieillissement de la mousse.

Con el propósito de esclarecer los fenómenos que tienen lugar durante la síntesis del poliestireno de alto impacto (HIPS), se prepararon mezclas poliméricas utilizando poliestireno (PS) o polibutadieno (PB) y un copolímero tipo estrella estireno- butadieno (BC), empleando etilbenceno (EB) como solvente. Se varió la masa molar del PS, la concentración de BC y la fracción másica total de PS. Las morfologías de algunas de las mezclas o fases aisladas, se observaron por microscopía electrónica de transmisión. Se encontró que las mezclas homopolímero/BC/EB fueron más estables cuanto mayores fueron su viscosidad y la afinidad entre sus componentes. Tanto la afinidad como el reparto de los componentes cuando ocurrió desmezclado, fueron función de la concentración de BC y de la relación entre las masas molares de los bloques de BC y cada uno de los homopolímeros investigados. Las mezclas PS/BC fueron estables, excepto para el caso de PS con alta masa molar y la mayor concentración de BC. En este caso y también para la fase aislada rica en PS, BC exhibió microdominios lamelares dispersos en una fase continua rica en PS. El número y el diámetro de estos microdominios fueron dependientes de la concentración de BC en la matriz de PS. With the objective of clarifying the phenomena taking place during the synthesis of high impact polystyrene (HIPS), polymeric mixtures between polystyrene (PS) or polybutadiene (PB) and a star-shaped poly(styrene-butadiene) copolymer (BC) were prepared using ethylbenzene (EB) as a solvent. The molar mass of PS, the BC concentration and the total mass fraction of the PS were varied. The morphology of some of the mixtures or isolated phases was observed by transmission electron microscopy. It was found that the stability of the homopolymer/BC/EB blends increased when their viscosity and affinity between its components were higher. Both, the affinity and the distribution of the components when demixing occurred, were dependent upon the concentration of BC and the relationship between the molar masses of the blocks in BC and each one of the homopolymers investigated. The mixtures PS/BC were stable, except for the case with the high PS molar mass and the highest BC concentration. In this case and also for the PS - rich isolated phase, BC exhibited lamellar microdomains dispersed in a continuous PS-rich phase. The number and diameter of these microdomains were dependent upon the BC concentration in the PS matrix.

We study the interface evolution of a series of periodic Co/Mo2C multilayers as a function of the annealing temperature up to 600{\textdegree}C. Different complementary techniques are implemented to get information on the phenomenon taking place at the interfaces of the stack. The periodical structure of Co/Mo2C multilayer is proven by Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles which demonstrate the formation of an oxide layer at both air/stack and stack/substrate interfaces. From Nuclear magnetic resonance (NMR) spectra, we observed the intermixing phenomenon of Co and C atoms for the as-deposited sample, and then at annealing temperature above 300{\textdegree}C Co and C atoms separate from their mixed regions. Comparison of NMR results between Co/Mo 2 C and Co/C references confirms this phenomenon. This is in agreement with x-ray emission spectroscopy (XES) measurements. Furthermore the calculation of the Co-C, Co-Mo and Mo-C mixing enthalpy using Miedema's model gives a proof of the demixing of Co and C atoms present within the stacks above 300{\textdegree}C. From the transmission electron microscopy (TEM) analysis, we found the presence of some crystallites within the as-deposited sample as well as the mainly amorphous nature of all layers. This is confirmed using x-ray diffraction (XRD) patterns which also demonstrate the growth of crystallites induced upon annealing., Published in Applied Surface Science 331, 8-16 (2015). http://dx.doi.org/10.1016/j.apsusc.2014.12.055

International audience; The sintering behaviour of Pd or Pt loaded ceria-zirconia solid solutions of nominal composition Ce0.50Zr0.50O2 and Ce0.68Zr0.32O2 was studied under oxidising conditions. Calcination treatments were carried out under controlled oxidising atmosphere for periods of up to 96 h. Powder X-ray diffraction and BET nitrogen adsorption-desorption derived surface area data are reported for the bare materials and for those loaded with low (

During the preparation of multi-component model membranes, a primary consideration is that compositional homogeneity should prevail throughout the suspension. Some conventional sample preparation methods pass the lipid mixture through an intermediary, solvent-free state. This is an ordered, solid state and may favor the demixing of membrane components. A new preparative method has been developed which is specifically designed to avoid this intermediary state. This novel strategy is called rapid solvent exchange (RSE) and entails the direct transfer of lipid mixtures between organic solvent and aqueous buffer. RSE liposomes require no more than a minute to prepare and manifest considerable entrapment volumes with a high fraction of external surface area. In phospholipid/cholesterol mixtures of high cholesterol content, suspensions prepared by more conventional methods reveal evidence of artifactual demixing, whereas samples prepared by rapid solvent exchange do not. The principles which may lead to artifactual demixing during conventional sample preparation are discussed.

The linearized cloudpoint curve correlation presented by Boom et al. [Polymer, 1993, 34, 2348] is revised. Boundaries for the validity of the linearized cloudpoint correlation are given for which an interpretation from the Flory-Huggins theory is possible. The distinction between liquid-liquid and solid-liquid demixing by this correlation must also be subjected to some constraints, although the slope in the correlation still offers a good way to distinguish between solid-liquid and liquid-liquid demixing. The statement, however, that concentration-dependent interaction parameters can be derived from this correlation must be rejected. The empirical rule found by Li et al. [Desalination, 1987, 62, 7955] can be rationalized on the basis of the LCC correlation.

Isothermal phase diagrams for the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA) in combination with several solvent-nonsolvent combinations (dioxane/water, dioxane/methanol, chloroform/methanol, and NMP/water) have been determined. The locations of the liquid-liquid miscibility gap, the solid-liquid miscibility gap and the vitrification boundary in the isothermal phase diagrams at 25°C were identified. The liquid-liquid miscibility gap for the systems with PLLA was located in the same composition range as the corresponding systems with PDLLA. For the systems containing PLLA solid-liquid demixing was thermodynamically preferred over liquid-liquid demixing. Attempts were made to correlate the experimental findings with predictions on the basis of the Flory-Huggins theory for ternary solutions using interaction parameters derived from independent experiments. Qualitative agreement was found between the theoretical predictions and the experimentally obtained liquid-liquid miscibility gap. No good agreement was found for the solid-liquid miscibility gap.

Demixing is the task of identifying multiple signals given only their sum and prior information about their structures. Examples of demixing problems include (i) separating a signal that is sparse with respect to one basis from a signal that is sparse with respect to a second basis; (ii) decomposing an observed matrix into low-rank and sparse components; and (iii) identifying a binary codeword with impulsive corruptions. This thesis describes and analyzes a convex optimization framework for solving an array of demixing problems. Our framework includes a random orientation model for the constituent signals that ensures the structures are incoherent. This work introduces a summary parameter, the statistical dimension, that reflects the intrinsic complexity of a signal. The main result indicates that the difficulty of demixing under this random model depends only on the total complexity of the constituent signals involved: demixing succeeds with high probability when the sum of the complexities is less than the ambient dimension; otherwise, it fails with high probability. The fact that a phase transition between success and failure occurs in demixing is a consequence of a new inequality in conic integral geometry. Roughly speaking, this inequality asserts that a convex cone behaves like a subspace whose dimension is equal to the statistical dimension of the cone. When combined with a geometric optimality condition for demixing, this inequality provides precise quantitative information about the phase transition, including the location and width of the transition region.

Nowadays, CO2 capture by amines solvents is the most advanced technology to reduce CO2 industrial emissions. However, this technology presents some concerns. The major problem of this process, using monoethanolamine (MEA), is the high energy needed to regenerate the solvent and makes the process of CO2 capture very expensive. In order to reduce the high cost associated to the energy of regeneration, various breakthrough processes have been studied within the framework of FUI «ACACIA» which include several companies (IFPEN, RHODIA/SOLVAY, ARKEMA, LAFARGE, Gas of France, VEOLIA) and four academic laboratories (LMOPS, LSA, LTIM (ex-LTSP), IRCELyon): - CO2 Capture with gas hydrate formation. - Use of enzymes leading to process of less energy-consuming. - Use of multiamines to increase the quantity of CO2 absorbed or demixing amines which only allow the regeneration of the rich phase in CO2 (low cost for regeneration energy). Our contribution into the consortium has been the study of seven demixing amines or multiamines: - Three commercial amines (the N-Methylpiperidine, 2-Methylpiperidine and the molecule A). - Four « multiamines » with confidentiel structures synthesized by LMOPS and denoted by the initials B, D, E, F. The demixing phenomenon is influenced by many factors such as temperature, the loading of the acid gas and the amine concentration of the solution. The understanding of this phenomenon is one of the objectives of this thesis. The essential data to estimate the potentials efficiency of solvent to capture CO2 is the isotherm of absorption. We have determined these isotherms at temperatures close to the absorber and regenerator units (respectively 40°C and 80°C) at different concentrations of amine ((26%, 30%, 50% and 66%) and pressures of CO2varying between 10 kPa et 200 kPa. The thermodynamic modelling of the isotherms of absorption allows to deduce important operating parameters of the process (cyclic capacity, average enthalpy of reaction, solvent flow...) and to dimension the absorption unit and to estimate its energy consumption. The experimental study has been completed by the determination of vapor-liquid equilibrium of pure amines and of different aqueous solutions of amines with the static method. These data allow anticipating the possible loss in amine in the regenerator. Among the studied amines, the one denoted with the initial « F » is a potential candidate for an industrial application energy-efficient (good CO2 absorption capacity, low regeneration energy, low volatility), Actuellement, le captage du CO2 par lavage aux amines est la technique la plus avancée et la plus adaptée pour répondre au besoin de tous les types d'installations industrielles émettrices de CO2. Cependant, cette technique présente un certains nombre de problèmes. Le problème principal est la forte énergie associée à la régénération du solvant qui rend le procédé de captage très couteux. Afin de réduire ce coût, différents procédés en rupture ont été étudiés dans le cadre du FUI « ACACIA » regroupant plusieurs entreprises (IFPEN, RHODIA/SOLVAY, ARKEMA, LAFARGE, Gaz de France, VEOLIA) et quatre laboratoires académiques (LMOPS, LSA, LTIM (ex-LTSP), IRCELyon): - Captage par formation d'hydrates de gaz . - Utilisation d'enzymes conduisant à des procédés moins énergivores. - Utilisation de « multiamines » en vue d'accroitre la quantité de CO2 absorbé ou d'amines « démixantes » permettant de régénérer uniquement la phase riche en CO2 (d'où minimisation de l'énergie de régénération). Notre contribution à ce consortium a été l'étude de sept amines ou multiamines démixantes : - Trois amines commerciales (la N-Méthylpipéridine, la 2-Méthylpipéridine et la molécule A). - Quatre « multiamines » de structures confidentielles synthétisées par LMOPS représentées par les sigles B, D, E, F. Le phénomène de démixtion est influencé par de nombreux facteurs tels que la température, le taux de charge et la concentration en amine de la solution. La compréhension et l'explication de ce phénomène est l'un des objectifs de cette thèse. La donnée essentielle qui permet d'évaluer les performances potentielles d'une solution absorbante est l'isotherme d'absorption du CO2. Nous avons déterminé ces isothermes aux températures proches de l'absorbeur et du régénérateur (respectivement 40°C et 80°C) pour différentes concentrations en amine (26%, 30%, 50% et 66%) et pour des pressions en CO2 variant entre 10 kPa et 200 kPa. La modélisation thermodynamique des isothermes d'absorption permet de déduire les paramètres opératoires importants du procédé qui mettraiten ouvre ces amines (capacité cyclique, enthalpie moyenne de réaction, débit de solvant…etc.) permettant ainsi le dimensionnement de l'unité d'absorption et l'estimation de sa consommation énergétique. L'étude expérimentale a été complétée par la détermination des équilibres liquide-vapeur des amines pures et des différentes solutions aqueuses d'amines au moyen de la méthode statique. Ces données permettent de prévoir les pertes possibles en amine dans le régénérateur donc le coût des appoints dans le procédé. Parmi les sept amines étudiées, l'amine nommée « F » est un bon candidat pour une application industrielle économe en énergie (bonne capacité d'absorption, faible énergie de régénération, faible volatilité)

The thesis describes how demixing of binary colloidal mixtures could be used to design new kinds of amorphous structures. We show that a rich phase behavior emerges, dependent on density (colloidal concentration) and composition (species relative populations). A simple model is adopted for the colloidal particles, which are assumed to be hard spheres interacting via an effective short-ranged attractive square-well (SW) potential. We show that demixing - due to composition fluctuations - can strongly interfere with typically dominating condensation mechanism - due to density fluctuations,- if the inter-species attraction is significantly reduced with respect to intra-species one. Thermodynamic perturbation theory (TPT) calculations and extensive numerical simulations have been performed on binary mixtures of the SW model. In the whole range of compositions and densities, we demonstrate how the enhancement of demixing over condensation brings to distinctive properties of the arrested structures. If the population of one colloidal species largely exceeds the other (asymmetric composition), the typical condensation mechanism dominates and brings to the percolation of only the main species. Instead, demixing separation prevails approaching the symmetric composition, and results in two interpenetrating sub-gels, both percolating. We name this structure a BiGel. The formation of BiGels has been analyzed in the thesis, pointing out structural differences and similarities with the usual one-component gel. In particular, we implemented a novel method that enables an explicit topological characterization. Despite the sub-gel branches of a BiGel present longer and thinner arms, we quantified the resemblance of gels and BiGels at large length-scales in light of their congruent porosities. Furthermore, we propose an experimental exploration of the dominant demixing scenario. The possibility is offered by the fine tuning of inter-species interactions that can be achieved in DNA-coated colloids (DNACCs). Thus, the numerical investigation is complemented with experiments on symmetric mixtures of DNACCs and the proof of BiGel’s actual realization. The main result of the thesis is the demonstration that, in presence of tunable inter-particle interactions, phase separation driven by the demixing mechanism can be arrested in the same fashion as condensation. We show how to enhance the demixing and demonstrate, by simulations and experiments, the possibility of multi-component gelation. Notably, complex structures result without requiring complex architectures of the single particles, nor anisotropic potentials, as isotropic spherical colloids already constitute suitable building blocks. Hence, the results and ideas here presented may find application in the design and development of novel types of materials.

We study fluid-fluid phase separation in a colloid-polymer mixture adsorbed in a colloidal porous matrix close to the \theta -point. For this purpose we consider the Asakura-Oosawa model in the presence of a quenched matrix of colloidal hard spheres. We study the dependence of the demixing curve on the parameters that characterize the quenched matrix, fixing the polymer-to-colloid size ratio to 0.8. We find that, to a large extent, demixing curves depend only on a single parameter f, which represents the volume fraction which is unavailable to the colloids. We perform Monte Carlo simulations for volume fractions f equal to 40% and 70%, finding that the binodal curves in the polymer and colloid packing-fraction plane have a small dependence on disorder. The critical point instead changes significantly: for instance, the colloid packing fraction at criticality increases with increasing f. Finally, we observe for some values of the parameters capillary condensation of the colloids: a bulk colloid-poor phase is in chemical equilibrium with a colloid-rich phase in the matrix., Comment: 26 pages, 8 figures. In publication in Molecular Physics, special volume dedicated to Luciano Reatto for his 70th birthday

Thermal properties of CoCl2, MnCl2 and their mixed crystals are investigated by means of temperature dependent neutron powder diffraction and time-resolved small angle neutron scattering. The coefficients of thermal expansion of these crystals have been determined as a function of temperature. The temperature-induced structural variations can be explained by distortions of CoCl5/MnCl6 octahedra and changes in Co/Mn-Cl bond lengths. CoCl2 and MnCl2 form homogeneous solid solutions in the entire temperature range between the solidus and 50 K. There is no indication of any miscibility gap as predicted from thermodynamic calculations.

Refereed/Peer-reviewed

8 pages; International audience; We present a system for under-determined source separation of non-stationary audio signals from a stereo 2-channel linear instantaneous mixture. This system is dedicated to isolate the different instruments/voices of a piece of music, so that an end-user can separately manipulate those source signals. The problem is addressed with a specific informed approach, that is implemented with a coder corresponding to the step of music production, and a separate decoder corresponding to the step of signal restitution. At the coder, source signals are assumed to be available, and are used to i) generate the stereo 2-channel mix signal, and ii) extract a small amount of distinctive features embedded into the mix signal using an inaudible watermarking technique. At the decoder, extracting and exploiting the watermark from the transmitted mix signal enables an end-user who has no direct access to the original source signals to separate these source signals from the mix signal. In the present study, we propose a new hybrid system that merges two techniques of informed source separation: a subset of the source signals are encoded using a "sources-channel coding" approach, and another subset are selected for local inversion of the mixture. The respective codes and indexes are transmitted to the decoder using a new high-capacity watermarking technique. At the decoder, the encoded source signals are decoded and then subtracted from the mixture signal, before local inversion of the remaining sub-mixture signal leads to the estimation of the second subset of source signals. This hybrid separation technique enables to efficiently combine the advantages of both coding and inversion approaches. We report experiments with 5 different source signals separated from stereo mixtures, with a remarkable quality, enabling separate manipulation during music restitution.

Ankara : The Department of Physics and the Institute of Engineering and Science of Bilkent University, 2009. Thesis (Ph. D.) -- Bilkent University, 2009. Includes bibliographical references leaves 131-148. In this thesis we study many-body effects in three distinct two-dimensional systems. The two dimensional electron gas is a model system yielding to basic analytical and computational theoretical ideas of many-body physics and at the same time allows faithful experimental realizations. In connection to the recently observed metal-insulator transition in this system, the spin susceptibility is a relevant observable. The behavior of the spin polarization in a parallel magnetic field is studied using a parametrized ground-state energy expression from accurate quantum Monte Carlo simulations and compared with approximate theories. The critical field to fully polarize the system is calculated. A qualitative difference for the ferromagnetic transition is found for an interval of density values. Next, we consider exciton condensation in an electron-hole bilayer system with density imbalance. Electrons and holes attracting via Coulomb interaction pair up to form spatially separated excitons and condense at low temperatures. Using mean- field theory we establish the phase diagram at zero temperature for different electron and hole densities by comparing the energy of the normal phase with that of the condensed phase. In the last chapter, the two-dimensional Bose-Fermi atomic gas mixture which is composed of a condensed boson component and a spin polarized Fermi component at zero temperature is studied. Confinement in the third direction affects the density profiles and can induce collapse of the mixture and spatial separation of components. Subaşı, A Levent Ph.D.

When aqueous potato starch suspensions were heated into the solution state and cooled, spreadable particle gels were obtained with a spherulite morphology and a cream-like texture. This so-called superheated starch (SHS) exhibits more effective gelling properties than maltodextrin, which is currently applied as a fat mimetic. In addition, a gel-like texture is immediately obtained when mixing dry SHS with cold water. Other starch types showed similar properties. Gel moduli were higher as amylose content increased. A large-scale preparation procedure based on jet cooking and spray drying with or without intermediate gelation was devised. SHS was identified as a slightly to moderately degraded starch. The formation of particle gels with spherulitic morphology was observed over at least two decades of Mw from 0.06 to 16×106 g/mol. At higher molar mass, demixing between amylose and amylopectin was observed. These phenomena are tentatively explained by assuming a competition between demixing and crystallization. © 2008 Elsevier Ltd. All rights reserved.

When aqueous potato starch suspensions were heated into the solution state and cooled, spreadable particle gels were obtained with a spherulite morphology and a cream-like texture. This so-called superheated starch (SHS) exhibits more effective gelling properties than maltodextrin, which is currently applied as a fat mimetic. In addition, a gel-like texture is immediately obtained when mixing dry SHS with cold water. Other starch types showed similar properties. Gel moduli were higher as amylose content increased. A large-scale preparation procedure based on jet cooking and spray drying with or without intermediate gelation was devised. SHS was identified as a slightly to moderately degraded starch. The formation of particle gels with spherulitic morphology was observed over at least two decades of Mw from 0.06 to 16×106 g/mol. At higher molar mass, demixing between amylose and amylopectin was observed. These phenomena are tentatively explained by assuming a competition between demixing and crystallization. © 2008 Elsevier Ltd. All rights reserved.

Spinodal decomposition is observed in a variety of materials, such as metal alloys, oxide glasses, mineral solid solutions, steels, gels, ceramics and mixtures of polymers and liquids. It’s an irreversible process in which the transition of solid or liquid solutions is not triggered by nucleation and growth from a sudden concentration peak, but by local sinusoidal fluctuations in the concentration of the components. It occurs, when rapidly quenched, in the thermodynamically unstable region of the demixing area, beyond the spinodal. The spinodal which leads to spontaneous decomposition is the spinodal of the coherent free energy curve of the metastable coherent phase diagram. The early-stage kinetics of spinodal decomposition of a binary alloy A-B can be obtained with a nonlinear diffusion equation, the Cahn-Hilliard-Cook equation, with constant mobility. The equation with variable mobility, describes the later-stage and the coarsening process. In this report the process of spinodal decomposition is discussed phenomenological and mathematically. Also two examples of materials in which decomposition takes place are given, i.e. computer simulations in solids and mineral alkali feldspar solid solution in geology.

Spinodal decomposition is observed in a variety of materials, such as metal alloys, oxide glasses, mineral solid solutions, steels, gels, ceramics and mixtures of polymers and liquids. It’s an irreversible process in which the transition of solid or liquid solutions is not triggered by nucleation and growth from a sudden concentration peak, but by local sinusoidal fluctuations in the concentration of the components. It occurs, when rapidly quenched, in the thermodynamically unstable region of the demixing area, beyond the spinodal. The spinodal which leads to spontaneous decomposition is the spinodal of the coherent free energy curve of the metastable coherent phase diagram. The early-stage kinetics of spinodal decomposition of a binary alloy A-B can be obtained with a nonlinear diffusion equation, the Cahn-Hilliard-Cook equation, with constant mobility. The equation with variable mobility, describes the later-stage and the coarsening process. In this report the process of spinodal decomposition is discussed phenomenological and mathematically. Also two examples of materials in which decomposition takes place are given, i.e. computer simulations in solids and mineral alkali feldspar solid solution in geology.

In this report a phase diagram is determined by heat flux DSC of the binary mixture Ethyl undecanoate and Ethyl tridecanoate. Our hypothesis for equilibrium phase behaviour is that the components Ethyl undecanoate and Ethyl tridecanoate do have the same crystal form and they have restricted miscibility in that form. However, the results of the DSC measurements are complex and are not unambiguous. We determined a simple phase diagram and calculated it with the program Winifit. The calculated phase diagram with the program shows good similarity with the one obtained by the experiments. The excess Gibbs energy parameters of the solid state are determined with Winifit, being A = 5000 J.mol-1 and B = 0,1. The mole fraction of the critical point XC is calculated as XC =0,43. The critical temperature C T at XC =0,43 is also calculated, being C T = 307,2 K. For better understanding the crystal structures have to be examined in greater detail. On the left-hand side and on the right-hand side of the phase diagram they have to be the same.

This thesis presents the derivation of the theory leading to the determination of the governing equations of chemically reacting flows under local thermodynamic equilibrium, which rigorously takes into account effects of elemental (de)mixing. As a result, new transport coefficients appear in the equations allowing a quantitative predictions and helping to gain deeper insight into the physics of chemically reacting flows at and near local equilibrium. These transport coefficients have been computed for both air and carbon dioxide mixtures allowing the application of this theory to both Earth and Mars entry problems in the framework of the methodology for the determination of the catalytic activity of Thermal Protections Systems (TPS) materials.Firstly, we analyze the influence of elemental fraction variations on the computation of thermochemical equilibrium flows for both air and carbon dioxide mixtures. To this end, the equilibrium computations are compared with several chemical regimes to better analyze the influence of chemistry on wall heat flux and to observe the elemental fractions behavior along a stagnation line. The results of several computations are presented to highlight the effects of elemental demixing on the stagnation point heat flux and chemical equilibrium composition for air and carbon dioxide mixtures. Moreover, in the chemical nonequilibrium computations, the characteristic time of chemistry is artificially decreased and in the limit the chemical equilibrium regime, with variable elemental fractions, is achieved. Then, we apply the closed form of the equations governing the behavior of local thermodynamic equilibrium flows, accounting for the variation in local elemental concentrations in a rigorous manner, to simulate heat and mass transfer in CO2/N2 mixtures. This allows for the analysis of the boundary layer near the stagnation point of a hypersonic vehicle entering the true Martian atmosphere. The results obtained using this formulation are compared with those obtained using a previous form of the equations where the diffusive fluxes of elements are computed as a linear combination of the species diffusive fluxes. This not only validates the new formulation but also highlights its advantages with respect to the previous one :by using and analyzing the full set of equilibrium transport coefficients we arrive at a deep understanding of the mass and heat transfer for a CO2/N2 mixture.Secondly, we present and analyze detailed numerical simulations of high-pressure inductively coupled air plasma flows both in the torch and in the test chamber using two different mathematical formulations: an extended chemical non-equilibrium formalism including finite rate chemistry and a form of the equations valid in the limit of local thermodynamic equilibrium and accounting for the demixing of chemical elements. Simulations at various operating pressures indicate that significant demixing of oxygen and nitrogen occurs, regardless of the degree of nonequilibrium in the plasma. As the operating pressure is increased, chemistry becomes increasingly fast and the nonequilibrium results correctly approach the results obtained assuming local thermodynamic equilibrium, supporting the validity of the proposed local equilibrium formulation. A similar analysis is conducted for CO2 plasma flows, showing the importance of elemental diffusion on the plasma behavior in the VKI plasmatron torch.Thirdly, the extension of numerical tools developed at the von Karman Institute, required within the methodology for the determination of catalycity properties for thermal protection system materials, has been completed for CO2 flows. Non equilibrium stagnation line computations have been performed for several outer edge conditions in order to analyze the influence of the chemical models for bulk reactions. Moreover, wall surface reactions have been examined, and the importance of several recombination processes has been discussed. This analysis has revealed the limits of the model currently used, leading to the proposal of an alternative approach for the description of the flow-surface interaction. Finally the effects of outer edge elemental fractions on the heat flux map is analyzed, showing the need to add them to the list of parameters of the methodology currently used to determine catalycity properties of thermal protection materials., Doctorat en sciences appliquées, info:eu-repo/semantics/nonPublished

Complex coacervation between proteins and polysaccharides is a demixing process mainly driven by electrostatic interactions. During this process many structural transitions occur, involving the formation of soluble complexes, aggregated complexes, and coacervates. The dynamic mechanism of complexation/coacervation was studied on β-lactoglobulin (BLG)/Acacia gum (AG) mixed dispersions (0.1 wt% total concentration; BLG:AG ratio of 2:1) using small angle static light scattering (SALS). Acidification of BLG/AG dispersions was induced by dissolution of 0.11 wt% glucono-δ-lactone, allowing in situ SALS measurements. Time evolution of turbidity, scattered light intensity at 46° scattering angle ( I 46 ) or slope of scattering functions at high q range revealed the existence of six pH-induced structural transitions. During BLG/AG complexation and before coacervation took place, scattering profiles displayed a monotonic decrease of I ( q ) as a function of q. A correlation peak in the scattering functions was only observed when coacervates appeared in the system. The wave vector q max corresponding to the maximum in scattered intensity first shifted toward larger q values, indicating an increasing number of coacervates, then shifted toward smaller q values, as a consequence of the system coarsening. The power laws q max ∼ t − α and I max ∼ t − β gave values of 1.9 and 9.2, respectively, values much larger than those expected for intermediate and late stages of spinodal decomposition. From these results, it was concluded that complex coacervation between BLG and AG was a nucleation and growth type process. In addition, the temporal evolution of I 46 followed power laws with two different exponents. First exponent corresponding to BLG/AG complexation was 3.0 ± 0.3 and indicated a diffusion-controlled growth mechanism. Second exponent corresponding to the initiation of phase separation to the coacervation process was 6.5 ± 0.3 and revealed an interfacially-controlled growth mechanism.

This paper describes the synthesis of two tri-phenylamine monomers (hole conducting) and one triazine monomer (electron conducting) which differ in their copolymerization parameters because of their styrene and vinyl ester nature. A blend of triphenylamine monomer and poly-(ethylene glycol) and mixtures of both types of monomers (triphepylamine and triazine) were illuminated through a line mask, creating laterally modulated radicals, thus leading to lateral demixing. The experiments with mixtures of triphenylamine and triazine monomers show that the concentration of p- or n-type polymers can be modulated laterally in a controlled way.