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Interaktion und Vermischung kompositionell unterschiedlicher Silikatschmelzen treten im gesamten Spektrum magmatischer Aktivität auf. Dabei kann es sowohl zu Magma mingling-, als auch zu Magma mixing-Prozessen kommen. Magmatische Enklaven und Dispersionen sind dabei Zeugen der ehemaligen Interaktion und Vermischung der beteiligten Schmelzen. Diese Arbeit präsentiert ein neuartiges Modell zur Genese magmatischer Dispersionen, das auf hydrodynamischen Mischungsprozessen der beteiligten Schmelzen beruht. Es geht davon aus, dass es bei geeigneten, an der Grenzfläche zwischen zwei Schmelzen wirkenden Scherkräften zu mechanischen Mischungsprozessen unter Ausbildung von Dispersionen kommen kann. Die dafür relevanten Parameter umfassen die jeweiligen Viskositäten der Schmelzen, die zwischen ihnen herrschende Grenzflächenspannung, die anliegenden Scherraten bzw. Fließgeschwindigkeiten und die zur Verfügung stehende Zeitspanne. Die praktische Anwendbarkeit und die generelle Gültigkeit für georelevante Silikatschmelzen des Modells zur hydrodynamischen Genese magmatischer Dispersionen wurde experimentell durch Laborversuche und durch die Anwendung auf natürliche Fälle magmatischer Mischungsprozesse bestätigt. Somit steht auch ein tool im Sinne der Geospeedometrie zur Verfügung, mit dem die damaligen Temperaturen, Viskositäten und relativen Strömungsgeschwindigkeiten der beteiligten Magmen zum Zeitpunkt ihrer Vermischung berechnet und rekonstruiert werden können. Es liefert wichtige Daten zur Erfassung der kinematischen Eigenschaften von Silikatschmelzen und trägt so zur weiteren Aufklärung der komplexen magmatischen Systeme bei. / Interaction and comingling of contrasting silicate magmas is a frequent phenomenon occurring in the entire spectrum of magmatic activity. Thereby both magma mingling and mixing processes are to be found. Magmatic enclaves and dispersions appear as a witness for the former interaction and mingling of the involved melts. This work presents a new model for the genesis of magmatic dispersions, which is based on hydrodynamic mingling processes of the participating melts. It is due to the attempt that under suitable shear rates mechanical mingling processes at the interface of two melts can be initiated to form dispersions. The parameters relevant to this process include the viscosities, the interacting interfacial tension, the applied shear rates resp. flow velocities and the available time span. The practical applicability and the general validity for geo-relevant silicate melts of the proposed model was confirmed by experimental laboratory tests and by the application on natural cases of magmatic mingling processes. Thus a tool in the sense of geo-speedometry is available which allows calculation and reconstruction of the former temperatures, viscosities and relative flow velocities of the melts at the time of their conjunction. In doing so it provides important data on the kinematic features of silicate melts and provides insights into the complex magmatic systems.

Un cristal phononique est un arrangement périodique de matériaux dont les propriétés élastiques différent selon une, deux ou trois dimensions, conduisant à la formation de bandes interdites omnidirectionnelles. Ces matériaux artificiels présentent des propriétés physiques nouvelles comme la réfraction négative ou les isolants topologiques et concernent différents domaines de la physique comme l’acoustique, l’optomécanique, la thermique… Leur réalisation à l’échelle submicronique permet de placer ces propriétés dans la gamme hypersonique. Le travail présenté dans cette thèse porte sur l’étude théorique et numérique de la propagation des ondes élastiques dans des cristaux phononiques hypersoniques à base de matériaux hybrides en relation étroite avec des expériences de diffusion de la lumière, effectuées au Max Planck de Mainz. Les principales quantités étudiées sont les courbes de dispersion, les champs de déplacement élastique et le spectre de diffusion de la lumière. Les chapitres successifs abordent les cas de rainures à haut facteur d’aspect déposés sur un substrat, ainsi que ceux de cristaux structurés à 1D et 2D. Au-delà de la compréhension des structures de bandes dans ces matériaux, la comparaison avec les résultats expérimentaux permet de discuter et de caractériser les propriétés physiques des matériaux constituants et aussi de leur évolution vis à vis du vieillissement et des techniques de fabrication. Enfin, un dernier chapitre est consacré au développement d’une méthodologie numérique nouvelle pour le calcul des spectres Brillouin, avec des retombées potentielles dans les calculs optomécaniques. / A phononic crystal is a periodic arrangement of materials whose elastic properties differ in one, two or three dimensions, leading to the formation of omnidirectional forbidden bands. These artificial materials present new physical properties such as negative refraction or topological insulators and concern different areas of physics such as acoustics, optomechanics, thermal management... Their realization on the submicron scale allows to place these properties in the hypersonic range. The work presented in this thesis deals with the theoretical and numerical study of the propagation of elastic waves in hypersonic phononic crystals based on hybrid materials closely related to light scattering experiments at Max Planck in Mainz. The main quantities studied are the dispersion curves, the elastic displacement fields and the scattering spectrum of the light. Successive chapters deal with cases of high aspect ratio grooves deposited on a substrate, as well as those of 1D and 2D structured crystals. Beyond the understanding of the band structures in these materials, the comparison with the experimental results makes it possible to discuss and characterize the physical properties of the constituent materials and also their evolution with respect to aging and manufacturing techniques. Finally, a final chapter is devoted to the development of a new numerical methodology for calculating Brillouin spectra, with potential spin-offs in optomechanical calculations.

Kiel, University, Diss., 2005.

Polymer nanocomposites have garnered incredible promise in the field of material science due to the excellent mechanical strength, thermal and electrical conductivities of the nanoparticles and the extension of these properties to the processing flexibility inherent to plastics. However, practical realization of these nanoparticle-based materials has been hindered by the tendency of these nanoparticles to aggregate as a result of strong inter-particle forces. In this dissertation, we investigate the formation of non-covalent charge transfer interactions between polymers and single-walled carbon nanotubes (SWNTs) with the goal of optimizing interfacial adhesion and homogeneity of nanocomposites without modifying the SWNT native surface. Nanocomposites of SWNTs and three sets of polymer matrices with varying composition of electron donating or electron accepting functional groups were prepared. In the first part of this dissertation, quantitative characterization by optical microscopy and Raman spectroscopy and qualitative results through thick film composite visualization show that the existence of a moderate amount of interacting moieties along the polymer chain results in an enhanced intermolecular interaction with SWNT, which translates to an optimum nanoparticle homogeneity. Calculations from density functional theory and Flory-Huggins theory correlate with the experimental results, which illustrate that chain connectivity is critical in controlling the accessibility of the functional groups to form intermolecular interactions. Thus, controlling the amount of interacting functional groups throughout the polymer chain such that an adequate distance between them is realized will direct the extent of charge transfer interaction, which enables tuning the SWNT dispersion. The second part of this dissertation focuses on the elucidation of the morphology of these nanoparticle entities in a polymer matrix. The observance of microphase-separated peaks in the scattering patterns of polyacrylonitrile (PAN) nanocomposites indicate an ordering of the PAN polymer induced by the carbon nanotube cage, which could either be due to a thermodynamically bound layer around the SWNT or the occurrence of SWNT-induced PAN crystallization. Finally, UV-Vis measurements were performed on SWNT-polymer suspension in order to comprehend the interactions that occur during nanocomposite fabrication. These results demonstrate that SWNT dispersions in pure N,N-dimethyl formamide (DMF) are stabilized by the adsorption of polymers onto the SWNTs.

The advent of the internet has revolutionized the way people buy and sell. The internet is characterized by increased access to information. This increased information should foster convergence to the “law of one price,” for homogenous goods. The surge of electronic markets has motivated a stream of research focusing on comparing the efficiency of the internet market to the traditional one. This dissertation contributes to the existing literature of consumer search behavior in electronic markets and its effects on the price level and dispersion in the market more generally. A part of this dissertation assesses the direct and indirect effect of increased internet usage on the prices of airline tickets, using a unique contemporaneous online and offline transaction data for airline tickets, covering the final quarter of 2004. The study also investigates the relationship between increased internet usage and price dispersion in the market for airline tickets. This study also includes an exhaustive set of controls for airline ticket characteristics, namely refundability, advance purchase requirements, travel and stay restrictions, class of travel, departure and return day of the week and time, flight level load factor along with other market structure data used in the standard airlines literature. The existing theoretical literature in consumer search extended to the electronic markets assumes, for simplicity, that all consumers in the internet markets are the “searchers,” looking for the lowest price. The internet, however, also plays the role of a convenient shopping medium for a group of consumers whose primary motivation is not to search for the lowest price. The contemporary literature incorrectly categorizes these consumers as the traditional searchers. The remaining part of this dissertation provides a modification to the existing theoretical models of consumer search to accommodate both searchers and non-searchers in each of the electronic and traditional markets and derive the implications of the increased internet usage on the average level of prices and price dispersion in a market selling a homogenous good.

SUMMARY Mangrove ecosystems thrive in (sub)tropical, intertidal areas where adaptations like vivipary and the hydrochorous dispersal of propagules become an absolute necessity. As propagule dispersal and early growth allow for the replenishment of existing stands and colonization of new habitats, many authors recognize the importance of these stages in structuring mangrove populations and communities. However, when it comes to the actual propagule dispersal and recruitment mechanisms, there is an apparent lacuna in the current understanding of mangrove ecology. The period between the mature propagule falling from the parental mangrove tree and the early growth of the established seedling, under various possible circumstances, remains in the dark. In this study we focus on this particular period by investigating both the places where these propagules end up as the pathways their dispersal units follow. And we go one step further. Mangrove forests are being destroyed worldwide at a threatening pace despite their tremendous asset to coastal human communities and associated biological species. The effect of human-induced (cutting and mangrove conversion to aquaculture ponds) as well as indirectly and/or ‘naturally’ evolving disturbances (sea level rise) on propagule hydrochory occupies an important place in this study. Dispersal of water-buoyant propagules of the family Rhizophoraceae and Acanthaceae (now including the Avicenniaceae) was studied in Gazi Bay (Kenya), Galle and the Pambala-Chilaw Lagoon Complex (Sri Lanka). The study sites differ both in tidal regime and vegetation structure, covering an interesting variety of ecological settings to examine propagule dispersal. Field data and experiments ranging from micro/ mesotopographical measurements and successive propagule counts to hydrodynamic and propagule dispersal experiments were collected or executed in situ. Two main methodological approaches were employed. Firstly, the question on mechanisms of propagule recruitment was addressed by statistically investigating the effect of microtopography, top soil texture and above-ground-root complexes on the stranding and self-planting of propagules (Chapter 2&3). Afterwards, suitability maps were created using Geographical Information Systems (GIS) to assess whether a particular mangrove stand has the ability to succesfully rejuvenate. Furthermore, the effect of degradation (tree cutting) (Chapter 2&3), sea level rise (Chapter 2&4) and microtopography-altering burrowing activities of the mangrove mud lobster Thalassina anomala (Chapter 3), was incoporated in the GIS-analyses. Secondly, the combined set-up of hydrodynamic modelling and ecological dispersal modelling was developed to simulate propagule dispersal pathways influenced by dispersal vectors (tidal flow, fresh water discharge, wind), trapping agents (retention by vegetation or aerial root complexes) and seed characteristics (buoyancy, obligated dispersal period) (Chapter 5&6). This type of approach provided the possibility to explore propagule dispersal within its ecological context, but was also applied to an implication of shrimp pond area restoration (Pambala-Chilaw Lagoon Complex, Sri Lanka) (Chapter 5) and to evaluate changes in propagule dispersal when sea level rises (Gazi Bay, Kenya) (Chapter 6). The main findings regarding propagule recruitment indicate that propagules are not distributed equally or randomly within a mangrove stand, yet species-specific distribution for anchorage occurs. Characteristics of the environment (microtopography, top soil texture and above-ground root complex) influence propagule recruitment in a way that complex root systems (e.g. pencil roots and prop roots) facilitate the entanglement of dispersal units and a more compact soil texture (like clay and silt) and a predominant flat topography creates suitable areas for stranding and self-planting of propagules. This combines effects of existing vegetation and abiotic factors on mangrove propagule establishment. Since propagule dispersal is not solely determined by species-specific propagule characteristics (e.g. buoyancy, longevity, etc.), I emphasize that propagule sorting by hydrochory has to be viewed within its ecological context. Propagule retention by vegetation and wind as a dispersal vector, deserve a prominent role in studies on propagule dispersal. The significance of dense vegetation obstructing long distance dispersal (LDD in its definition of this work), mainly in inner mangrove zones, supports our main finding that propagule dispersal is largely a short distance phenomenon. ‘Largely’ is here understood as quantitatively, not excluding epic colonization events of rare but important nature. In accordance with the Tidal Sorting Hypothesis (TSH) of Rabinowitz (1978a), smaller, oval-shaped propagules were found to disperse over larger distances than bigger, torpedo-shaped propagules. We can however not fully support the TSH because (1) these differences are no longer valid when comparing between torpedoshaped propagules of different sizes and (2) propagule dispersal is not always directed towards areas more inland, but can be strongly concentrated towards the edges of lagoons and channels Anthropogenic pressure on mangrove ecosystems, more specifically clear-felling or mangrove conversion to aquaculture ponds, imposes limitations on propagule recruitment due to reduced propagule availability and a decrease in suitable stranding areas where the architecture of certain root complexes, like prop roots and pencil roots, function as propagule traps. These types of pressure appear to have more severe consequences on propagule dispersal than the effect of sea level rise on mangroves. Mangrove forests, which are not situated in an obviously vulnerable setting, can be resilient to a relative rise in sea level if a landward shift of vegetation assemblages and successful early colonization is not obstructed by human-induced pressures. Also, and this renders mangrove forests vulnerable in spite of their intrinsic resilience, when the ‘capital’ of forest is severely reduced or impoverished as happens extensively worldwide, the ‘interest’ on this capital, understood as propagule availability, delivery and trapping, will not allow them to efficiently cope with sea level rise, putting sustainability of mangrove ecosystem services and goods at risk. In a larger framework of mangrove vegetation dynamics, knowledge on propagule dispersal will benefit management strategies for the conservation of mangroves worldwide, besides its fundamental interest to fully fathom the ecology of this particular marine-terrestrial ecotone formation.

The public nuisance and health concerns caused by odours from livestock facilities are among the key issues that affect neighbouring communities and the growth of the livestock industry across Canada. A setback distance is the common regulatory practice to reduce odour impact on the neighbouring areas. The air dispersion modeling method may be a more accurate tool for establishing setback distances since it considers site-specific airborne emissions, such as odour and gases from the animal production site as well as weather conditions and then estimates a concentration of the pollutant (odour, ammonia, etc.). Although various dispersion models have been studied to predict odour concentration from agricultural sources, limited field data exist to evaluate their applicability in agricultural odour dispersion. Thus, the purpose of this project was to evaluate the selected commercial air dispersion models with field plume measurements from swine operations. <p>Firstly, this thesis describes a sensitivity analysis of how the climatic parameters affect model simulations for four selected air dispersion models, ISCST3, AUSPLUME, CALPUFF, and CALPUFF. Under the steady state weather condition, mixing height had no effect on the livestock odour dispersion, while atmospheric stability, wind speed and wind direction had great effect on the livestock odour dispersion. Ambient temperature had a moderate effect compared with other parameters. Under variable weather conditions, the predicted odour concentrations were much lower than the results under steady state weather conditions. <p>A series of comparisons between model predictions of the same four models and field odour measurements were conducted. When using the livestock odour plume measurement data from University of Manitoba, three equations were used to convert the model predicted odour concentration to field measured odour intensity. The equations did not predict odour intensity very well. No model showed obvious better performance than the others. Scaling factors did not improve the results considerably. When using the odour plume measurement data from University of Minnesota, INPUFF2 performed better than CALPUFF. Scaling factors did improve the modeled results. When using the odour plume measurement data from University of Saskatchewan, INPUFF2 also performed better than CALPUFF. Scaling factors were still useful for the results improvements.<p>Finally, because CALPUFF is the US EPA preferred model and predicted the highest values under variable weather conditions in the sensitivity study, we used it to simulate odour plumes on selected three swine sites using hourly weather data from 1993 to 2002 in Yorkton, Saskatchewan. The maximum predicted distance were 2.9 km for 1 OU, which was lower than the recommended maximum setback distance of 3.2 km. <p>It is recommended that the variable weather conditions be used in the setback distance determination. CALPUFF is the preferred model and INPUFF2 is another option for field odour plume simulation, however scaling factors are needed to bring the model predictions close to the field measured results. Because the models evaluated were not developed for odour dispersion simulation, a model that can accurately predict livestock odour dispersion should be developed to take into account of the difference between odour and gas and wind direction shifts within the simulation time interval.

The public nuisance and health concerns caused by odours from livestock facilities are among the key issues that affect neighbouring communities and the growth of the livestock industry across Canada. A setback distance is the common regulatory practice to reduce odour impact on the neighbouring areas. The air dispersion modeling method may be a more accurate tool for establishing setback distances since it considers site-specific airborne emissions, such as odour and gases from the animal production site as well as weather conditions and then estimates a concentration of the pollutant (odour, ammonia, etc.). Although various dispersion models have been studied to predict odour concentration from agricultural sources, limited field data exist to evaluate their applicability in agricultural odour dispersion. Thus, the purpose of this project was to evaluate the selected commercial air dispersion models with field plume measurements from swine operations. <p>Firstly, this thesis describes a sensitivity analysis of how the climatic parameters affect model simulations for four selected air dispersion models, ISCST3, AUSPLUME, CALPUFF, and CALPUFF. Under the steady state weather condition, mixing height had no effect on the livestock odour dispersion, while atmospheric stability, wind speed and wind direction had great effect on the livestock odour dispersion. Ambient temperature had a moderate effect compared with other parameters. Under variable weather conditions, the predicted odour concentrations were much lower than the results under steady state weather conditions. <p>A series of comparisons between model predictions of the same four models and field odour measurements were conducted. When using the livestock odour plume measurement data from University of Manitoba, three equations were used to convert the model predicted odour concentration to field measured odour intensity. The equations did not predict odour intensity very well. No model showed obvious better performance than the others. Scaling factors did not improve the results considerably. When using the odour plume measurement data from University of Minnesota, INPUFF2 performed better than CALPUFF. Scaling factors did improve the modeled results. When using the odour plume measurement data from University of Saskatchewan, INPUFF2 also performed better than CALPUFF. Scaling factors were still useful for the results improvements.<p>Finally, because CALPUFF is the US EPA preferred model and predicted the highest values under variable weather conditions in the sensitivity study, we used it to simulate odour plumes on selected three swine sites using hourly weather data from 1993 to 2002 in Yorkton, Saskatchewan. The maximum predicted distance were 2.9 km for 1 OU, which was lower than the recommended maximum setback distance of 3.2 km. <p>It is recommended that the variable weather conditions be used in the setback distance determination. CALPUFF is the preferred model and INPUFF2 is another option for field odour plume simulation, however scaling factors are needed to bring the model predictions close to the field measured results. Because the models evaluated were not developed for odour dispersion simulation, a model that can accurately predict livestock odour dispersion should be developed to take into account of the difference between odour and gas and wind direction shifts within the simulation time interval.