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Block copolymers are an ideal solution for a wide variety of nanolithographic opportunities due to their tendency to self-assemble on nanoscopic length scales. High etch selectivity and thin-film orientation are crucial to the success of this technology. Most conventional block copolymers have poor etch selectivity; however, incorporating silicon into one block produces the desired etch selectivity. A positive side effect of the silicon addition is that the χ value (a block-to-block interaction parameter) of the block copolymer increases. This decreases the critical dimension of potential features. Unfortunately, one negative side effect is the increase in the surface energy difference between the blocks. Incorporating silicon decreases the surface energy of that block. Typically, annealing is used to induce the chain mobility that is required for the block copolymer to reach its minimum thermodynamic energy state. Thermal annealing is the easiest annealing technique; however, if the glass transition temperature (Tg) of one block is above the thermal decomposition temperature of the other block, the latter will degrade before the former can reorient. In addition, annealing silicon-containing block copolymers usually results in a wetting layer and parallel orientation since the lower surface energy block favors the air interface, minimizing the free energy. Solvent annealing replaces the air interface with a solvent, thereby changing the surface energy. The solvent plasticizes the block copolymer, effectively decreasing the Tgs of both blocks. Another benefit is the ability to reversibly alter the orientation by changing the solvent or solvent concentration. The challenge with solvent annealing is that it depends on a number of parameters including: solvent selection, annealing time, and vapor concentration, which generate a very large variable space that must be searched to find optimum screening conditions. / text

Metabolic Syndrome (MetS), the clustering of obesity, high blood pressure, and disordered glucose and lipid/lipoprotein metabolism within a single individual, is associated with poorer cognitive function and dementia in later life. It has been hypothesized that cognitive impairment in MetS occurs primarily within the context of inflammation. MetS risk factors are also associated with thinning of the cerebral cortex. However, the mechanisms by which MetS and inflammation affect the brain are poorly understood. The present study used statistical mediation to examine the relationship between MetS risk factors, cortical thickness in a priori regions of interest (ROIs) and inflammation. ROIs in the inferior frontal, superior temporal, middle frontal, supra marginal, anterior cingulate and middle occipital regions were chosen from the previous literature. Serum levels of pro-inflammatory markers (interleukin 1, interleukin 2, interleukin 6 and C-Reactive Protein) were measured using enzyme-linked immunosorbent assays. Forty-three adults between the ages of 40 and 60 years underwent a health screen, neuropsychological testing and structural magnetic resonance imaging. A higher number of MetS risk factors was associated with thinning in the inferior frontal ROI (β=-0.35, p = 0.019). A higher number of MetS risk factors was also associated with higher levels of serum interleukin 2 (β=0.31, p=0.04). A higher level of serum interleukin 2 was also associated with reduced thickness in the inferior frontal ROI (β=-0.41, p=0.013). After accounting for the effects of interleukin 2, the number of MetS risk factors was no longer associated with cortical thickness in the inferior frontal ROI indicating successful statistical mediation and pointing towards a potentially important role for imflammation in linking MetS to cortical thinning and cognitive vunlerability. / text

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Thickness distributions of sea ice (g(h)) display a ubiquitous exponential decay (’tail’) in ice above approximately 2 meters thick. This work uses idealised models to examine the root causes of the exponential tail of the sea ice thickness distribution. The ice of thickness greater than 2 meters is formed through the fracture and piling of ice caused by interactions between floes, driven by winds and currents. The material properties of sea ice are complex and mathematical descriptions of the relationship between force and deformation of a floe are still a topic of study. Smoluchowski Coagulation Models (SCMs) are used to develop an abstract representation of redistribution dynamics. SCMs describe populations whose members of fixed size combine at size-dependent rates. SCMs naturally produce exponential or quasi-exponential distributions. An SCM coupled with a thermodynamic component produces qualitatively realistic g(h) under a wide range of conditions. Using the abstract representation of redistribution dynamics from SCMs, a model developed from physical processes specific to sea ice is introduced. Redistribution events occur at rates dependent on the change in potential energy. This model is demonstrated to produce qualitatively realistic g(h). Sensitivity analysis shows that primary model sensitivities are to the relative strengths of the dynamic and thermodynamic components of the model; and to the relative occurrence of ice ridging, shearing and rafting. The exact relationship between the rate of redistribution events and the energy they consume is shown to be of lesser importance. We conclude that the exponential tail of g(h) is a mathematical consequence of the coagulative nature of the ice thickness redistribution process, rather than the material properties of sea ice. These model results suggest the strongest controls on the form of the tail are the relative strengths of thermodynamic and dynamic action, and the relative occurrence of ice ridging, shearing and rafting. / Graduate / 0415 / 0768

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Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Vita. Includes bibliographical references.

Thesis (M.Sc. (Biostatistics))--Mahidol University, 1984.

Thesis (M.S.)--Marshall University, 2002. / Title from document title page. Document formatted into pages; contains vii, 46 p. Includes bibliographical references (p. 43-46).