The purpose of this thesis is to describe the development of an anatomically based, young adult eye model, which includes a crystalline lens with a gradient refractive index (GRIN). This model will then be used to investigate the effect of laser refractive surgery. The first step in this process involved developing a symmetrical eye model that was found to be a better predictor of empirical longitudinal spherical aberration than any previous model. Myopia was simulated by either a purely axial or refractive technique. While these models were found to be good predictors of the spherical aberration measured in young adults, they did not predict the total amount of high-order aberrations. The techniques used to simulate a single type of myopia caused the myopic models to become anatomically inaccurate. To improve the eye models a biconic surface was used to quantify the anterior corneal shape as a function of myopia. A method to describe the refractive error and biconic shape parameters in Jackson Cross Cylinder terms was implemented to determine correlations. Results indicate that a biconic accurately models the average shape of the anterior corneal surface as a function of myopia. Adopting the biconic model for the anterior corneal surface and adding average misalignments of the ocular components transformed the models from symmetrical to asymmetrical. Refractive error was now simulated by the anatomically accurate changes in both the anterior corneal shape and axial length. The asymmetrical aberrations resulted from the misalignment of the ocular components and provided a good prediction of average empirical aberrations but underestimated the aberrations of individual subjects. Photorefractive keratectomy, a form of laser refractive surgery, was simulated by theoretically calculated and by empirically measured changes in the shape of the anterior corneal surface. Applying the change in anterior corneal shape to the asymmetrical models was used to develop postoperative models. Changes in corneal shape and model aberrations attributed to theoretical calculations do not match empirical observations. The prediction of increased high-order aberrations in postoperative models based on empirically measured changes in the anterior corneal topography was similar to clinical results. Average anatomically based, GRIN eye models have been developed that accurately predict the average aberrations of emmetropic and myopic young adults. These models underestimate the asymmetrical and total high-order aberrations that have been measured in individual subjects but are still useful for investigating the average effects of procedures like refractive surgery.

<strong>Purpose:</strong> Although orthokeratology (non-surgical corneal reshaping, Corneal Refractive Therapy, CRT®) has been used for almost a half century, contemporary CRT's outcomes and mechanisms still require investigation. A series of studies was designed to examine different aspects of non-surgical corneal reshaping for myopic and hyperopic corrections, including the efficacy and stability of this procedure, the effect of the lens material characteristics (Dk/t), and the corneal or superficial structural change (e. g. corneal/epithelial thickness) in corneal reshaping. <br /> <strong>Methods:</strong> In the CRT® for myopia (CRT1) study, 20 myopes wore CRT® lenses on one eye and control lenses on the contralateral eye (eye randomized) for one night while sleeping. Corneal topography and refractive error were measured the night prior to lens insertion, immediately after lens removal on the following morning and at 20 and 60 minutes and 3, 6 and 12 hours later. In the CRT® for hyperopia (CRTH) study, 20 ametropes wore CRT®H lenses on one eye for one night while sleeping, the contralateral eye (no lens wear) served as control (eye randomized). Corneal topography, aberrations and refractive error were measured the night prior to lens insertion, immediately after lens removal on the following morning and at 1 and 3, 6, 12 and 28 hours later. In the relatively long term (4 weeks) CRT® for myopia (CRT2) study, 23 myopes wore CRT® lenses overnight and removed their lenses on awakening. Visual Acuity (VA), subjective vision, refractive error, aberrations, and corneal topography were measured at baseline, immediately after lens removal on the first day and 14 hours later, and these measurements were repeated on days 4, 10, and 28. The treatment zone size was demarcated by the change in corneal curvature from negative to positive and vice versa, using tangential difference maps from the corneal topographer. In the study of effects of Dk/t on CRT® for myopia (CRTHDK), 20 myopic subjects were fit with Menicon Z (MZ) lenses (Dk/t=90. 6, Paragon CRT®) on one eye and an Equalens II (EII) CRT® lenses (Dk/t=47. 2) on the contralateral eye (eye randomized). Corneal topography, refractive error and aberrations were measured before lens insertion (baseline), and the following day after overnight lens wear, on lens removal and 1, 3, 6, 12 hours later. In the study of short term effects of CRT® for myopia and hyperopia (STOK), 20 ametropes wore CRT® and CRT®H lenses in a random order on one eye (randomly selected). The lenses were worn for 15, 30 and 60 minutes (randomly ordered, with each period taking place on a different day). Refractive error, aberrations, corneal topography, and corneal/epithelial thickness (using OCT) were measured before and after lens wear. The measurements were performed on the control eyes at 60 minutes only. <br /> <strong>Results:</strong> In the CRT1 study, after one night of CRT® for myopia, the central cornea flattened and the mid-periphery steepened, and myopia reduced. In the CRTH study, after one night of CRT® for hyperopia, the central cornea steepened and the para-central region flattened, myopia was induced or hyperopia was reduced, all aberrations except for the astigmatism increased and signed spherical aberration (SA) shifted from positive to negative. In the CRT2 study, after 4 weeks of CRT® lens wear, in general, the treatment zones stabilized by day 10, vision improved, myopia diminished, total aberration and defocus decreased and higher order aberrations (HOAs) including coma and SA increased. The visual, optical and subjective parameters became stable by day 10. In the CRTHDK study, after one night of CRT® (MZ vs. EII) lens wear, the central corneal curvature and aberration were similar with a slight exception: The mid-peripheral corneal steepening was greater in the EII (lower Dk/t) lens-wearing eyes compared to the MZ (higher Dk/t) eyes. In the STOK study, after brief CRT® and CRT®H lens wear, significant changes occurred from the 15 minutes time point: The corneal shape and optical performance changed in a predictable way; the central cornea swelled less than the mid-periphery after CRT® lens wear, whereas the central cornea swelled more than the para-central region after CRT®H lens wear; the central epithelium was thinner than the mid-periphery after CRT® lens wear and was thicker than the para-central region after CRT®H lens wear. <br /> <strong>Conclusion:</strong> After one night of lens wear, CRT® and CRTH® lenses were effective for myopia and hyperopia correction, respectively. In the 4 week CRT study, the treatment zone size changed during the first 10 days. Its size was associated with VA, refractive error, aberrations, and subjective vision. In the CRTHDK study, after one night of lens wear, changes in corneal shape were slightly different, with more mid-peripheral steepening in the lower Dk lens-wearing eyes compared to the higher Dk lens-wearing eyes. Changes in central corneal shape and optical performance were similar in both eyes. In the STOK study, CRT® lenses for myopia and hyperopia induced significant structural and optical changes in as little as 15 minutes. The cornea, particularly the epithelium, is remarkably moldable, with very rapid steepening and flattening possible in a small amount of time.

A major challenge to cold regions hydrology and northern water resources management lies in predicting runoff dynamically in the context of warming-induced changes to the rates and patterns of ground thaw and drainage. Meeting this challenge requires new knowledge of the mechanisms and rates of ground thaw and their implications to water drainage and storage patterns and processes. The study carries out to evaluate the concept of energy-based runoff in the perspective of ground heat flux, soil thaw and liquid moisture content, tortuosity of snow-free area, preferential flow and discharge of the hillslope. Based on field measurements, coupled energy and water flow is simulated in the Area of Interest (AOI) with a half-hour time interval by the distributed hydrological model, GEOtop. In the field, the saturated hydraulic conductivity varies exponentially between the superficial organic layer and the underlying mineral layer. In the simulation, the parameters of the soil physical properties are input by fourteen uneven layers below the ground surface. Starting from the initially frozen state, the process of soil thaw is simulated with dynamic variables such as soil liquid moisture and ice content, hydraulic conductivity, thermal conductivity and heat capacity. The simulated frost table depths are validated by 44-point measurements and the simulation of point soil temperature is also compared to data measured in an excavated soil pit. As a result, the frost table topography is dominated by both the snow-free pattern and the energy fluxes on the ground surface. The rate and magnitude of runoff derived from snow drift and the ice content of frozen soil is greatly influenced by the frost table topography. According to the simulation, the frost table depth is closely regressed with the ground surface temperature by a power function. As soil thawing progresses, ground heat flux reduces gradually and the rate of soil thaw becomes small when the frost table descends. Along with the snow-free area expanding, the average soil moisture of the AOI increases prior to that time when the average frost table is less than 25 cm deep. The snow-free patches expand heterogeneously in the AOI, which causes the spatial and temporal variation of hydraulic conductivity due to the non-uniform frost table depth. According to the simulation, the transit time of the flow through the AOI decreases to the shortest span on May 13 with the average frost table of 10 cm. Before this date, the time lag between snowmelt percolation and slope runoff is about 8-10 hours; while after this date, the time lag is no more than 5 hours. The pattern of the preferential flow in the AOI highly depends on the frost table topography. When the snow-free patches are widely scattered and the average frost table is between 0 and 10 cm, the preferential flow paths are inhibited. With soil thaw progresses, the preferential flow paths are prominent with the largest single contributing area occurring when the average frost table is between 10 cm to 15 cm. When the average frost table reaches 25 cm, the importance of preferential flow is not apparent, and matrix flow prevails.

Field-scale transport through unsaturated soil is influenced by surface and subsurface boundary conditions, and the spatial variability of state soil variables. The objective of this thesis is to examine the relative importance of the spatial redistribution of surface water versus spatial variability of soil properties on long-term transient water flow and transport under semi-arid conditions. The field-scale transport (34 yr) of a surface applied tracer (chloride), spatial variability of other pedogenic tracers, and surface water redistribution over a 19 mo fallow period were measured in a catchment basin. In 1966 and 1971, a chloride tracer (KCl) was surface applied to plots (6.1 m x 90 m, Chernozemic soil) near Saskatoon, Saskatchewan. In 2000 and 2001, 262 soil cores were taken along and perpendicular to one KCl strip. Soil layering at each core was recorded and samples were analysed for chloride concentration, electrical conductivity, bulk density and water content. Sulphate and nitrate concentrations were measured on selected cores. The site is level by common definitions, with a very slight concave depression (1.8% grade) midway along the KCl strip and a slight grade (¡Ü2.1%) perpendicular to the KCl strip. Measured water recharge indicated slight differences in surface slope had a marked effect on redistribution of water and spatial distribution of the chloride tracer. An estimated 90% of redistributed water was subsequently used by plants and 10% resulted in an increase in deep drainage. A varved layer had a strong influence on the subsurface redistribution of water and chloride below the root zone. There were sharp horizontal transitions between areas of slow and faster transport, which corresponded to sharp increases in catchment area and water recharge. Small surface depressions, which controlled pedogenic transport and soil formation, have been filled in by tillage translocation. Spatial variability of soil horizon thickness (and associated hydraulic properties) had little effect on transport of chloride after 34 yr. Computer simulations also suggest substantial surface redistribution of precipitation and snowmelt. In contrast to the measured chloride data, the model was sensitive to changes in hydraulic properties and horizon thickness in the root zone. Surface water redistribution was the primary factor controlling long-term transport.

<p>Regenerative medicine holds the promise of providing relief for people suffering from diseases where treatment has been unattainable. The research is advancing rapidly; however, there are still many hurdles to overcome before the therapeutic potential of regenerative medicine and cell therapy can be realized. Low in frequency in all tissues, stem cell number is often a limiting factor. Approaches that can control the proliferation and direct the differentiation of stem cells would significantly impact the field. Developing an adequate environment that mimics in vivo conditions is an intensively studied topic for this purpose. Collaboratively, researchers have come close to incorporating nearly all biological cues representative of the human body. Arguably the most overlooked aspect is the influence of electrical stimulation. In this dissertation, we examined polyvinylidene fluoride (PVDF) as a new biomaterial and developed a 3D scaffold capable of providing mechanical and electrical stimuli to cells in vitro. </p><p>The fabrication of a 3D scaffold was performed using electrospinning. To obtain highly aligned fibers and scaffolds with controlled porosity, the set-up was modified by incorporating an auxiliary electrode to focus the electric field. Highly aligned fibers with diameters ranging from 500 nm to 15 µm were fabricated from colorless polyimide (CP2) and polyglycolic acid (PGA) and used to construct multilayer scaffolds. This experimental set-up was used to electrospin &#945;-phase PVDF into the polar &#946;-phase. We demonstrated the transition to the &#946;-phase by examining the crystalline structure using x-ray diffraction (XRD), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR) and polarized light optical microscopy (PLOM). We confirmed these results by observing a polarization peak at 80°C using the thermally stimulated current (TSC) method. Our results proved the electrospinning process used in our investigation poled the PVDF polymer in situ. </p><p>TThe influence of architecture and topographical cues was examined on 3D scaffolds and films of CP2 polyimide and PVDF. Culture of human mesenchymal stem cells (hMSCs) for 7 and 14 days demonstrated a significant difference in gene expression. The fibers upregulated the neuronal marker microtubule associated protein (MAP2), while downregulation of this protein was observed on films. Gap junction formation was observed by the expression of connexin-43 after 7 days on PVDF films attributed to its inherent pyroelectric properties. Connexin-43 expression on fibers showed cell-cell contact across the fibers indicating good communication in our 3D scaffold. </p><p>A scaffold platform was designed using PVDF fibers that allowed us to apply electrical stimulation to the cells through the fibers. The electrically stimulated PVDF fibers resulted in enhanced proliferation compared to TCPS as evidenced by a 10% increase in the uptake of EdU. Protein expression revealed upregulation of neuronal marker MAP2. Our findings indicate this new platform capable of delivering mechanical, electrical, topographical and biochemical stimuli during in vitro culture holds promise for the advancement of stem cell differentiation and tissue engineering.</p> / Dissertation

With the changing perceptions in coastal engineering in recent time, creation of bay beach for recreation by combining artificial headlands with nourishment has become one of the favorable options for mitigating erosion and shore protection in several foreign countries advanced in coastal engineering. To achieve this goal, hydraulic model tests and numerical simulations have been applied for the planning and design of stable bay beaches. While using the latter approach, numerical computation includes four major components, these being the waves, topography changes, flow field and sediment transport. This study utilizes the so-called Modified Hsu3D model developed by Serizawa et al. (1996) and Kumada et al. (2002) in Japan for the bathymetry within a static equilibrium bay beach defined by Hsu and Evans (1989). This model enables the direct calculation of bottom bathymetry within a static bay without using not only iterative numerical steps for wave transformation and current distribution, but also the continuity equation for total sediment transport. The results of this simplified approach can be used to estimate the distribution of erosion and accretion within a static bay, hence, suitable for pre-assessment of an artificial beach nourishment project. Prior to applying the Modified Hsu3D model to a bay beach undertaken in this study, sensitivity tests are performed on the setting of several key parameters associated with this model, such as limiting slope on land , limiting slope in the water , height of the berm , alignment angle at downdrift of the bay beach, and wave incident angle . The verification results are then adopted to compare with that reported in Serizawa et al. (2000), as well as to investigate the effects of each parameters on the accuracy of the modeling, in order to enhance the reliability of this model and the setting of the parameters. Finally, the Modified Hsu3D model is applied to simulate the changes in the shoreline and bathymetry for the Sizihwan Bay in Kaohsiung, under the action of normal incident waves during summer monsoon. This study also takes the advantage of the Modified Hsu3D model to explore the effect of oblique wave incidence on the deviation of downdrift control point of a static bay, in order to assist the prediction of downdrift control point for beach changes on an artificially nourished bay beach. The results reveal that the downdrift control point does not shift, under normal incident waves with different for the breaker. On the other hand, under oblique wave action within from the external boundary line of 20 m depth offshore of a bay beach comprising sediment 0.2~0.5 mm, the offset of point (i.e., and coordinates from the original origin) versus wave incident angle can be established. By establishing a regression equation between and versus , the result can be used to assist the determination, more precisely without guess work, on locating the downdrift control point of a bay beach, while working on the MEPBAY (Klein, et al., 2003) on computer screen to assess its stability.

This dissertation focuses on the challenge of soil hydraulic parameter scaling in soil hydrology and related applications in general; and, in particular, the upscaling of these parameters to provide effective values at coarse scales. Soil hydraulic properties are required for many hydrological and ecological models at their representative scales. Prediction accuracy of these models is highly dependent on the quality of the model input parameters. However, measurement of parameter data at all such required scales is impractical as that would entail huge outlays of finance, time and effort. Hence, alternate methods of estimating the soil hydraulic parameters at the scales of interest are necessary. Two approaches to bridge this gap between the measurement and application scales for soil hydraulic parameters are presented in this dissertation. The first one is a stochastic approach, based on artificial neural networks (ANNs) applied within a Bayesian framework. ANNs have been used before to derive soil hydraulic parameters from other more easily measured soil properties at matching scales. Here, ANNs were applied with different training and simulation scales. This concept was further extended to work within a Bayesian framework in order to provide estimates of uncertainty in such parameter estimations. Use of ancillary information such as elevation and vegetation data, in addition to the soil physical properties, were also tested. These multiscale pedotransfer function methods were successfully tested with numerical and field studies at different locations and scales. Most upscaling efforts thus far ignore the effect of the topography on the upscaled soil hydraulic parameter values. While this flat-terrain assumption is acceptable at coarse scales of a few hundred meters, at kilometer scales and beyond, the influence of the physical features cannot be ignored. anew upscaling scheme which accounts for variations in topography within a domain was developed to upscale soil hydraulic parameters to hill-slope (kilometer) scales. The algorithm was tested on different synthetically generated topographic configurations with good results. Extending the methodology to field conditions with greater complexities also produced good results. A comparison of different recently developed scaling schemes showed that at hill-slope scales, inclusion of topographic information produced better estimates of effective soil hydraulic parameters at that scale.

Disputats. Rheinische Friedrick-Wilhelms-Universität, 2001.

This dissertation advances our understanding of how turbidity currents interact with three-dimensional (3-D) minibasin topography and the resulting deposits that form. Conceptual Gulf of Mexico-centric models of minibasin fill development have become the foundation for exploring and identifying strategic deep-water hydrocarbon reserves on continental slopes around the world. Despite the abundance of subsurface data, significant questions remain about the 3-D physical processes through which minibasins fill and the relationship between these processes and the topography of the basin. To overcome this problem, I utilize techniques in physical laboratory modeling to query established models of the role that turbidity currents play in minibasin fill development, and observe the relationships between fill from the Lobster minibasin located in a proximal continental slope position in the Gulf of Mexico and from the Safi Haute Mer (SHM) minibasin located in the distal continental slope of offshore western Morocco. First, existing published literature are reviewed and assessed for the known state of minibasin development and fill processes, and the strengths and weaknesses of our current knowledge base. Second, results are presented from two series of experiments that document the interaction between steady, depletive turbidity currents and 3-D minibasin topography. Experimental results suggest that turbidity currents produce deposits that are more likely to drape pre-flow topography than pond within it. Turbidity current velocity data show a strong 3-D physical component in minibasin fill sedimentation that also influences extra-basinal sedimentation patterns. Details of these results provide insight into processes that have not been previously considered in published conceptual models of minibasin fill. Third, a comparison of the two subsurface datasets show that the types and abundance of architectural elements vary depending on the location of the minibasin on the continental slope (i.e. proximal vs. distal), and suggests key differences in the processes responsible for their infilling. Finally, a comparison of experimental results to preserved deposit architectures in the Lobster and SHM datasets suggest a more complex relationship of process-driven sedimentation than that derived primarily from suspension fallout. This improved understanding of minibasin fill is applicable to industry for increasing confidence in subsurface interpretations and reducing risk while exploring for quality reservoirs in deepwater regions. / text

A dehydrogen is an ‘under-wrapped’ hydrogen bond in a protein that is purported to be a hot spot for binding due to the favorable replacement of water with hydrocarbon upon binding of another protein. A model at the level of dielectric constants is used to test the validity of the claim that moving a hydrogen bond from high dielectric (i.e. a dehydron) to low dielectric (i.e. after binding of another protein) is actually a thermodynamically favorable process. In simulation, several proteins have been shown to undergo a dewetting transition when fixed components are separated a small distance. A new atomic-level hydrophobicity scale is combined with topographical information to characterize protein interfaces. The relationship between hydrophobicity and topography for protein surfaces known to be involved in binding is examined. This framework is then applied to identify surface characteristics likely to have an affect on the occurrence of a dewetting transition. Cadmium selenide (CdSe) nanoparticles form nanospheres or nanorods when grown in solutions of varying concentrations of the surfactants hexylphosphonic acid (HPA) and trioctylphosphine oxide (TOPO). Relative binding free energies are calculated for HPA and TOPO to the solvent-accessible faces of CdSe crystals. Binding free energies calculated with a Molecular Mechanics-Generalized Born model are used to identify a set of low free energy structures for which the solvation free energy is refined with the solution to the Poisson equation. These relative binding free energies provide information about the relative growth rates of these crystal faces in the presence of surfactants. Relative growth rates are then used to help understand why nanoparticles form certain shapes in the presence of specific surfactants. / text