Studies of nucleation in freezing nanoparticles usually assume that the embryo of the solid phase is completely wet by the liquid and forms in the core of the droplet. However, recent experiments and computer simulations have suggested that some nanoparticles start nucleating at the liquid-vapor interface of the drop in a pseudoheterogeneous process. The goal of the present work is to propose phenomenological models suitable for the study of surface nucleation in nanoparticle systems that can be used to understand the contributions of the various surface phenomena, such as surface and line tensions, to the nucleation barrier.<p/> The nucleation barrier for the freezing of a 276 atom gold cluster is calculated using Monte Carlo simulation techniques while previous simulation studies of a 456 atom gold cluster are extended in order to find the probability that the embryo forms in the surface or core of the nanoparticle. These calculations confirm that the crystal embryo forms at the liquid-vapor interface. Geometric studies measuring the liquid-solid and solid-vapor surface areas of the embryo suggest that it changes shape as it becomes larger and grows in towards the core of the droplet.<p/> Three phenomenological models that are based on the capillarity approximation and can account for surface nucleation are proposed. These models highlight the importance of accounting for the surface curvature contributions related to the Tolman length and the presence of the three phase contact line in calculating the nucleation free energy barrier. In some cases, the models are able to reproduce the qualitative properties of the free energy barriers obtain from simulation but numerical fits of the models generally result in estimates of the solid-liquid surface tension that are lower than the values expected on the basis of partial wetting in the bulk.<p/> Finally, a semi-phenomenological model approach to nucleation is proposed where the usual phenomenological expression for the free energy barrier is retained, but where the geometric prefactors are obtained from molecular simulation of the embryo. This method is applied to nucleation in the gold cluster and to the freezing of a bulk Lennard-Jones liquid.<p/>

The Pressure-Volume-Temperature (PVT) for polymer/gas solutions is an important fundamental property of which accurate data measurement has not been reported until recently. The diffusivity, solubility, and surface tension are critical physical properties of polymer/gas solutions in understanding and controlling polymer processing such as, foaming, blending, and extracting reaction. However, the determination of these properties relies on accurate PVT data as a prerequisite. Due to the difficulties involved in measuring the specific volume while maintaining a sufficiently high pressure and temperature to achieve a single-phase polymer/gas solution, accurate PVT data or volume swelling measurement of polymer/gas solutions is not yet available. In this research, a new methodology was proposed and developed for direct measuring the PVT properties of polymer melts saturated with high-pressure gas at elevated temperatures. The ultimate goal is to develop and construct an apparatus that would provide more accurate fundamental properties through PVT measurement to the foaming industry, which is heavily involved with polymer/gas mixtures.

Dramatic, in the sense of “highly intense,” is a quality we often associate with the music of Beethoven, but no theory has attempted to define drama in any systematic manner. This study therefore explores the idea by constructing a theory that distinguishes between dramatic and non-dramatic passages. At the core of the theory is the notion that drama is the result of several types of tension occurring simultaneously. Dramatic passages have a “High” tension level, whereas non-dramatic ones have a “Low” level. Individual tension types are divided into two categories: rhetorical and syntactical. Rhetorical tension types include such features as a loud dynamic, a fast rhythm, and a thick texture, which need no musical context to be expressed. By contrast, syntactical tension types include such features as chromaticism, metric irregularity, and phrase expansion, which always require a comparison of events to be expressed. Only tension types from the same category may combine to form drama. Because this study examines the relationships between drama and sonata form, the analysis of form is a key issue that receives a separate chapter and additional thought throughout. The methodology combines aspects of William E. Caplin’s theory of formal functions and James Hepokoski and Warren Darcy’s Sonata Theory, and is applied to all of Beethoven’s first-movement sonata forms, a total of eighty-seven movements. Each formal unit is analyzed as one of six dramatic “archetypes” that describe a basic outline of High and/or Low tension levels. These archetypes constitute the dramatic structure of the piece. Percentage frequencies of the archetypes were calculated for each formal unit in the movements as a whole, and as grouped by the categories of key, mode, genre, and style period. The greatest distinctions in dramatic structure occur among the three style periods of early, middle, and late, the early works showing a sectional approach with contrasting tension between phrases and the middle to late works gradually becoming more continuous, maintaining the same tension levels between units. A concluding analysis of Beethoven’s String Trio, op. 3, demonstrates the theory’s ability to enrich the interpretation of an individual work.

No description available.

La experimentación y posterior modelización de los procesos de transporte y transferencia de calor y de masa en medios poroso saturados encuentra un gran número de dificultades que se derivan fundamentalmente de la heterogeneidad del propio medio, de la metodología de su parametrización estructural y física para asimilarlo a un medio continuo.Los objetivos planteados en la presente tesis se han orientado hacia un mejor conocimiento de la influencia de diversos parámetros estructurales del medio poroso, así como de las propiedades de las substancias que constituyen la matriz sólida y la fase fluida saturante, en las características de ebullición de un medio poroso inicialmente saturado, calentado por su frontera inferior y limitado por una capa superior del mismo líquido saturante.A tal fin, se ha estudiado la influencia de la estructura del medio poroso (granular o fibrilar) y de la naturaleza de la sustancia que constituye la matriz sólida sobre la permeabilidad del medio poroso al agua y a una solución acuosa de tensioactivo, de baja concentración. Así mismo se ha estudiado la influencia respecto a la conductividad y difusividad térmicas efectivas en régimen no estacionario. Por último, utilizando la misma variedad de medios porosos saturados, se estudia el proceso de ebullición hasta que se alcanzan condiciones de "dryout", y se analizan las consecuencias que resultan de la variación de la estructura física del medio poroso, de la naturaleza de la sustancia que constituye su matriz sólida y de las propiedades del fluido saturante.En lo referente a las características fluidodinámicas y térmicas de los medios porosos estudiados se ha podido concluir:- La adición de un tensioactivo al agua saturante del medio poroso produce un comportamiento diferente según la naturaleza del sólido: en caso de inorgánica (arena) ocasiona un aumento de la permeabilidad intrínseca, mientras que en caso de orgánica (fibras de algodón) produce una reducción tanto mayor cuanto menor es la porosidad del medio poroso. Las causas de este diferente comportamiento, son las notables diferencias de absorción del tensioactivo según el tipo de sólido (orgánico o inorgánico) y la mejora substancial de la humectación de la superficie del sólido inorgánico por el fluido lo que activa la eficacia de desplazamiento de toda fase no acuosa adsorbida o retenida entre partículas.- La difusividad térmica efectiva promediada espacialmente tiende al valor de la difusividad del componente del medio poroso de menor difusividad térmica a medida que transcurre el tiempo de calentamiento.- La difusividad térmica efectiva de los medios porosos saturados en los que &#61548;s / &#61548;l < 1 se aproxima a la de la fase líquida; en los medios para los que &#61548;s / &#61548;l >> 1, dicha difusividad térmica efectiva es un grado de orden superior a la de la fase líquida.- La adición de tensioactivo a la fase líquida saturante provoca la disminución de la conductividad térmica efectiva de medio poroso saturado en aquellos en que la fase sólida es granular e inorgánica.En lo referente al proceso de calentamiento de un medio poroso saturado hasta ebullición-"dryout" de su fase líquida se ha descrito un modelo físico de comportamiento de los diferentes medios porosos que comporta las siguientes fases:i) Calentamiento del medio hasta la temperatura de saturación de su fase líquida, con evidente aumento de volumen de las fases sólida y líquida por dilatación térmica.ii) Proceso de evaporación con formación de una capa bifásica cuya frontera superior se desplaza a la velocidad del frente de vapor. Simultáneamente se produce una disminución de la presión fluidoestática en la frontera de la capa bifásica, lo que se traduce en una reducción del reflujo de líquido hacia la placa calefactora.iii) Total desaturación de la entrefase medio poroso-placa calefactora al recibir por reflujo menos líquido del que es capaz de evaporar la placa calefactora. Aparición del "dryout" y elevación progresiva de la temperatura de la placa.iv) Aparición, en algún caso, de un fenómeno de basculamiento de la fase líquida desde la capa subenfriada a la zona desaturada del medio poroso. / A large number of difficulties are found in the experimentation and later modelization of transport and transfer heat and mass process in saturated porous media, which basically derive from the heterogeneity of the medium, the methodology of structural and physic parameterization to assimilate it to a continuous medium.The raised aims in this doctoral thesis have been directed towards a better knowledge of the influence of several structural parameters of the porous medium, as well as of the properties of the solid matrix and the saturating fluid phase, in the characteristics of boiling of an initially saturated porous medium, heated by its lower boundary and limited by an upper layer of the same saturating liquid.For this, the influence of the structure of the porous medium (granular or fibrous) and the nature of the solid matrix on the permeability to water and to a surfactant solution of lower concentration have been studied. The influence in relation to effective thermal conductivity and diffusivity in unstationary regime has also been studied. Finally, the boiling process until to achieve dryout conditions has been studied, and the consequences result from the variation of the physical structure of the porous medium, the nature of the solid matrix and the properties of the saturating fluid have been analyzed.About the fluid dynamic and thermal characteristics of the porous media studied, the thesis concludes that:- The addition of a surfactant to the saturating water of the porous medium produces a different behaviour depending on the nature of the solid: in inorganic matrix (sand) occasions an increase in the intrinsic permeability, whereas in organic matrix (cotton fibres) produces a decrease as greater as smaller is the porosity of the porous medium. The reasons of this different behaviour are the notable differences of absorption of the surfactant depending on the sort of solid matrix (organic or inorganic) and the important increase of the wetting of the inorganic solid's surface by the fluid activating the displacement of all adsorbed or retained not watery phase between particles.- The spatially averaged effective thermal diffusivity tends to the value of the diffusivity of the component of the porous medium with lower thermal diffusivity throughout the boiling process.- The effective thermal diffusivity of the saturated porous media which have &#61548;s / &#61548;l < 1 approaches to of the liquid phase; in the media with &#61548;s / &#61548;l >> 1, the effective thermal diffusivity is a grade of upper order to the of liquid phase.- The addition of surfactant to the saturating liquid phase gives rise to the decrease of the effective thermal conductivity of the saturated porous medium with granular and inorganic solid phase. A physical model of behaviour of the different saturated porous media concerning heating process until to achieve dryout conditions has been described considering the next phases:i) Heating of the medium until the saturation temperature of its liquid phase, with evident increase of volume of the solid and liquid phases by thermal dilatation.ii) Evaporation process with creation of a biphasic layer whose upper boundary displaces to the velocity of the vapour front. Simultaneously a decrease of the fluid static pressure in the boundary of the biphasic layer is produced, what result in a reduction of the reflux of liquid towards the heating plate.iii) Total unsaturation of the porous medium-heating plate interphase caused by to receive less liquid by reflux that the heating plate is capable of evaporating.iv) Appearance, in some case, of a fast phenomenon of turn upside down of the liquid phase from subcooled layer to the unsaturated zone of the porous medium.

There is now ample evidence to support the notion that a lack of oxygen (hypoxia) within the tumour adversely affects the outcome of radiotherapy and whether a patient is able to remain disease free. Thus, there is increasing interest in accurately determining oxygen concentration levels within a tumour. Hypoxic regions arise naturally in cancerous tumours because of their abnormal vasculature and it is believed that oxygen is necessary in order for radiation to be effective in killing cancer cells. One method of measuring oxygen concentration within a tumour is the Eppendorf polarographic needle electrode; a method that is favored by many clinical researchers because it is the only device that is inserted directly into the tumour, and reports its findings in terms of oxygen partial pressure (PO2). Unfortunately, there are often anomalous readings in the Eppendorf measurements (negative and extremely high values) and there is little consensus as to how best to interpret the data. In this thesis, Bayesian methods are applied to estimate two measures commonly used to quantify oxygen content within a tumour in the current literature: the median PO2, and Hypoxic Proportion (HP5), the percentage of readings less than 5mmHg. The results will show that Bayesian methods of parameter estimation are able to reproduce the standard estimate for HP5 while providing an additional piece of information, the error bar, that quantifies how uncertain we believe our estimate to be. Furthermore, using the principle of Maximum Entropy, we will estimate the true median PO2 of the distribution instead of simply relying on the sample median, a value which may or may not be an accurate indication of the actual median PO2 inside the tumour. The advantage of the Bayesian method is that it takes advantage of probability theory and presents its results in the form of probability density functions. These probability density functions provide us with more information about the desired quantity than the single number that is produced in the current literature and allows us to make more accurate and informative statements about the measure of hypoxia that we are trying to estimate.

This study interprets the puzzling absence of war among the US, China, and Taiwan from 1990 to 2005, when identity politics across the Taiwan Strait caused high tensions. The application of realist constructivism theory to this case would produce a prediction of war there resulting from conflicting identities, which produce irreconcilable conflicts of interests over territorial claims. However, the application of four other, relevant international relations theories explains this absence of war during this period. A zero-sum game of competing identities was replaced by a positive-game resulting from three liberal theories promoting inter-state cooperation: complex interdependence; state trading identities; and issue-linkage functions and one alternative realist theory, offensive realism, which shows that the balance of power deters war. Assuming China’s increased defense spending does not alter the balance of power in its favor, the current relative peace will continue to prevail, at least in the short to medium term.

There is now ample evidence to support the notion that a lack of oxygen (hypoxia) within the tumour adversely affects the outcome of radiotherapy and whether a patient is able to remain disease free. Thus, there is increasing interest in accurately determining oxygen concentration levels within a tumour. Hypoxic regions arise naturally in cancerous tumours because of their abnormal vasculature and it is believed that oxygen is necessary in order for radiation to be effective in killing cancer cells. One method of measuring oxygen concentration within a tumour is the Eppendorf polarographic needle electrode; a method that is favored by many clinical researchers because it is the only device that is inserted directly into the tumour, and reports its findings in terms of oxygen partial pressure (PO2). Unfortunately, there are often anomalous readings in the Eppendorf measurements (negative and extremely high values) and there is little consensus as to how best to interpret the data. In this thesis, Bayesian methods are applied to estimate two measures commonly used to quantify oxygen content within a tumour in the current literature: the median PO2, and Hypoxic Proportion (HP5), the percentage of readings less than 5mmHg. The results will show that Bayesian methods of parameter estimation are able to reproduce the standard estimate for HP5 while providing an additional piece of information, the error bar, that quantifies how uncertain we believe our estimate to be. Furthermore, using the principle of Maximum Entropy, we will estimate the true median PO2 of the distribution instead of simply relying on the sample median, a value which may or may not be an accurate indication of the actual median PO2 inside the tumour. The advantage of the Bayesian method is that it takes advantage of probability theory and presents its results in the form of probability density functions. These probability density functions provide us with more information about the desired quantity than the single number that is produced in the current literature and allows us to make more accurate and informative statements about the measure of hypoxia that we are trying to estimate.

<p>Pediatric cervical spinal injuries are associated with high morbidity and mortality. Cervical injuries observed in the pediatric population appear to be age dependent with younger children experiencing more upper cervical level injuries compared to increased lower level cervical injury patterns to older children. The majority of pediatric cervical spinal injuries are motor vehicle crash related. Current progress in child occupant protection, including increased and proper restraint usage continues to reduce serious injury and fatalities to child occupants. However, improper restraint usage and incorrect child seating location, especially with children transitioning from rear-facing child restraints to forward-facing restraints is still a concern. Continued reductions in serious injury and fatalities to child occupants in survivable motor vehicle crashes will be based on continued education and improvements in child anthropometric test devices, child computational injury models and child restraint system design. Improvements in all of these categories are dependent on an improved understanding of the developmental biomechanics of the human cervical spine. Currently, limited data exist on human child neck biomechanics and none of the current cadaveric work has evaluated the biomechanical response over the entire age spectrum from birth to young adulthood. Numerous surrogate studies exist and have formed the basis of child injury criteria and developmental biomechanics, but have not been assessed in relation to the response of the pediatric human cervical spine. The current work investigates the biomechanics of the osteoligamentous human cervical spine from birth to young adulthood under tensile and bending loading environments. Tensile low-load and load-to-failure stiffness, load-to-failure, and flexion-extension bending stiffness increased with age. Tensile normalized displacement at failure and total bending low-load range of motion decreased with age. Viscoelastic rate effects are present in the pediatric cervical spine and are modeled with quasi-linear viscoelasticity. Peak load and loading energy increases with increased loading rate, while hysteresis energy is rate insensitive at lower loading rates, but increases at higher rates of loading. These data establish structural response behavior and injury thresholds for the osteoligamentous cervical spine by age. Additionally, they provide human data to assess the appropriateness of current surrogate models and current scaling techniques associated with these models. Finally, these data provide human response by age useful in progressing the biofidelity of computational and physical models for child occupant protection.</p> / Dissertation

Cartilage tissue engineering represents an exciting potential therapy for providing permanent and functional regeneration of healthy cartilage tissues, but these treatment options have yet to be successfully implemented in a clinical setting. One of the primary obstacles for cartilage engineering is obtaining a sufficient supply of cells capable of regenerating a functional cartilage matrix. Mesenchymal progenitors can easily be isolated from multiple tissues, expanded in vitro, and possess a chondrogenic potential, but it remains unclear what types or combinations of signals are required for lineage-specific differentiation and tissue maturation. The overall goal of this dissertation was to investigate how the coordination of biochemical stimuli with cues from mechanical forces and the extracellular matrix regulate the chondrogenesis of bone marrow stromal cells (BMSCs). These studies explored the potential for cyclic tensile loading and chondrogenic factors, TGF-1 and dexamethsone, to promote fibrochondrocyte-specific differentiation of BMSCs. The application of cyclic tensile displacements to cell-seeded fibrin constructs promoted fibrochondrocyte patterns of gene expression and the development of a fibrocartilage-like matrix. These responses were influenced by the specific loading conditions examined and the differentiation state of the BMSCs. Additionally, the roles of integrin adhesion and cytoskeletal organization in BMSC differentiation were examined within engineered hydrogels presenting controlled densities of biomimetic ligands. Adhesion to the arginine-glycine-aspartic acid (RGD) motif inhibited chondrogenesis in a density-dependent manner and was influenced by interactions with the f-actin cytoskeleton. Together, this research provided fundamental insights into the regulatory mechanisms involved in the chondrogenesis of mesenchymal progenitor cells.