Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1931. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 1, 2010) Includes index (p. [iii-iv]).

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A systematic study of the properties of ion-exchanged float glass has been carried out by a.c. impedance spectroscopy. The measurement of electrical parameters allows the ionic mobility within the surface region to be investigated separately from the bulk glass. The correlation of a.c. impedance measurements with electron probe micro analysis, infrared reflectance spectroscopy, differential scanning calorimetry and dynamic mechanical thermal analysis has lent some new insights into anomalous behaviour of ionic transport under these circumstances. A highly resistive layer is found to exist as a result of the ion-exchange process in float glass. This is not attributable to compressive stress alone nor does the mixed alkali effect (MAE) operate within this diffusion zone. Glasses of the same composition prepared by homogeneous mixed-melting, however, indicate a strong mixed alkali effect. Infrared reflectance spectroscopic measurements clearly illustrate a more uniform distribution of non-bridging oxygen ions (and therefore some structural relaxation) as a result of ion-exchange. This also holds true for the comparison of ion-exchanged glass and mixed-melted glass. This result clearly shows that a different structure is generated depending on whether alkali cations are mixed homogeneously or via the ion-exchange process. It is proposed that some type of foreign ion repulsion effect (FIRE) operates when the larger cation is substituted into the glass below T_g. The repulsion of such foreign cations, and their search to find their own new sites causes their immobilisation (and a slow ion-exchange process) via the break up of conduction pathways, and thus the conductivity continues to decrease without any recovery, as more K⁺ ions are introduced. In contrast, only a weak mixed alkali effect is apparent in melt-grown lithium-alumino-silicate compositions and no high resistance (or cation immobilisation effect) is found in the ion-exchanged alumino-silicate system.

abstract: Swarms of animals, fish, birds, locusts etc. are a common occurrence but their coherence and method of organization poses a major question for mathematics and biology.The Vicsek and the Attraction-Repulsion are two models that have been proposed to explain the emergence of collective motion. A major issue for the Vicsek Model is that its particles are not attracted to each other, leaving the swarm with alignment in velocity but without spatial coherence. Restricting the particles to a bounded domain generates global spatial coherence of swarms while maintaining velocity alignment. While individual particles are specularly reflected at the boundary, the swarm as a whole is not. As a result, new dynamical swarming solutions are found. The Attraction-Repulsion Model set with a long-range attraction and short-range repulsion interaction potential typically stabilizes to a well-studied flock steady state solution. The particles for a flock remain spatially coherent but have no spatial bound and explore all space. A bounded domain with specularly reflecting walls traps the particles within a specific region. A fundamental refraction law for a swarm impacting on a planar boundary is derived. The swarm reflection varies from specular for a swarm dominated by kinetic energy to inelastic for a swarm dominated by potential energy. Inelastic collisions lead to alignment with the wall and to damped pulsating oscillations of the swarm. The fundamental refraction law provides a one-dimensional iterative map that allows for a prediction and analysis of the trajectory of the center of mass of a flock in a channel and a square domain. The extension of the wall collisions to a scattering experiment is conducted by setting two identical flocks to collide. The two particle dynamics is studied analytically and shows a transition from scattering: diverging flocks to bound states in the form of oscillations or parallel motions. Numerical studies of collisions of flocks show the same transition where the bound states become either a single translating flock or a rotating (mill). / Dissertation/Thesis / Doctoral Dissertation Applied Mathematics 2015

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The Effective Fragment Potential (EFP) is a quantum-mechanical based model used to describe non-covalent interactions of small molecules or fragments. It can be used along with fully <i>ab initio</i> methods to study the electronic properties of complex systems, such as solvated chromophores or proteins. For this purpose, the system is divided into two regions: one modeled with quantum mechanics and the other with EFP. The interaction between the QM region and the effective fragments has popularly been described through electrostatics and polarization only. This thesis focuses on the development of the QM/EFP exchange-repulsion term, as well as the evaluation of the dispersion term and a charge-penetration correction. The goal of is to determine how these terms can increase the accuracy of QM/EFP calculations without an increase in their computational cost.

<p> The material presented in this thesis is an attempt to obtain an increased understanding of the electronic structure and chemical binding in molecular systems. The one-electron charge distribution in methane, which is derived by considering only one-electron dependent properties of the system, is used to analyze the chemical binding in this molecule. A theoretical method, which allows one to determine the effect of the Pauli exclusion principle on the one-electron density distribution, is used to test the concepts underlying the electron pair repulsion theory as applied to H2O and NH3. Kinetic energy distributions are defined in order to examine the relationship between the topographical features of the molecular one-electron charge distribution and the kinetic energy of the system.</p> / Thesis / Doctor of Philosophy (PhD)

INTRODUCTION: Pancreatic Ductal Adenocarcinoma (PDAC) is an aggressive form of cancer with a high mortality rate, primarily due to lack of effective treatment options. Current therapeutic approaches are limited to surgical resection of the pancreas during early stages of the disease and to the use of non-specific chemotherapeutic drugs such as gemcitabine, neither of which has successfully improved the 5-year survival rate of PDAC. Both the lack of effective treatments and the high mortality of the disease call for the urgent need to develop new therapeutic options. OBJECTIVES: This thesis project focuses on an endogenous inhibitor of the neuropilin 2 receptor (NRP2) called semaphorin 3F (SEMA3F) and its use as a potential new drug in the fight against pancreatic cancer. By binding the transmembrane receptor neuropilin 2 (NRP2), SEMA3F can inhibit angiogenesis and cellular proliferation. Interestingly, given its role as a guidance molecule, it is also a potent mediator of cellular repulsion. All three of these effects will be analyzed in the context of this study. METHODS: Syngeneic pancreatic cancer cells were injected orthotopically in two separate groups of mice. One group involved the use of transgenic Nrp2-/- mice, and served as a way to analyze the absence of the receptor on the vasculature and how that affects the growth of the primary tumor and the formation of metastases in the liver. The other group received intravenous injections of SEMA3F-expressing and control adenovirus, and served to explore the effect of SEMA3F as a potential therapy against the growth of the primary tumor in the pancreas and distant metastases in the liver. RESULTS: We observed a decrease in pancreatic tumor and metastatic growth in the absence of Nrp2 in our transgenic mouse model compared to the WT control. Mice injected with SEMA3F-expressing adenovirus also showed a decrease in primary tumor growth as well as a reduction in the formation of metastases in the liver compared to the control. CONCLUSION: Nrp2 mediates angiogenesis in pancreatic cancer, which facilitates the growth of the primary tumor as well as the formation of metastases. Our results indicate that the anti-angiogenic, anti-proliferative and repulsive actions of SEMA3F could be used to develop an effective treatment option for PDACpancreatic ductal adenocarcinoma. / 2020-07-24T00:00:00Z

The characterization of fine particles is an area of immense significance to many industrial endeavors. It has been estimated that 70% of all industrial processes deal with fine particles at some point in the process. A natural phenomenon occurring in these processes is colloidal aggregation. This study examines aggregation in colloidal systems in order to characterize, examine, and control this occurrence in industrial processes. The study of particle aggregation has been broken into many different areas, such as collision mechanisms, interaction energy etc, but a complete model that integrates these different aspects has never been fully realized. A new model is required to accurately predict the aggregation behavior of colloidal particles. In this work, a new model is developed that integrates Smoluchowski kinetics, total interaction energy between particles, and stability ratios for perikinetic and orthokinetic collision mechanisms. The total particle interaction energy necessary for the calculation of stability ratios is represented by the summation of electrostatic and van der Waals interactions. The electrostatic interactions are modeled using DLVO theory, the linear Poisson-Boltzmann equation, and a numerical solution for the non-linear Poisson-Boltzmann Equation, while the van der Waals interactions are represented by Hamaker theory. The mathematical model is solved using an adjustable discretion technique, which is tested against a specific analytic solution, and yields an assessment of the error intrinsic in the discretization method. The basis of the mathematical model is a population balance framework. The model developed in this study is general in many respects, but could be readily applied to many different aggregation systems with minor modification. A comparison of the mathematical model with previous experiments conducted by Scott Fisher (1998) is carried out for the perikinetic and orthokinetic transport-limited aggregation regimes. The fractal nature of solid-sphere aggregates is considered when comparing the mathematical model predictions with experimental measurements. The previous experiments that are used for comparison utilized polystyrene particles ranging from 100 nm to 500 nm in initial diameter, several initial particle concentrations, and various stirring rates. Zeta potential measurements are presented in order to set the range of transport-limited aggregation. An assessment of the results of the mathematical model with the experimental results show good agreement for transport-limited aggregation within the perikinetic and orthokinetic transport-limited aggregation, with average particle sizes ranging from 100 nm to well over 2 microns.