Cells respond to chemical, mechanical and topographical cues both in vivo and in vitro. Much research has been carried out into the effects of chemical signals and to a lesser degree, mechanical. However, less is known about cell responses to topographical cues, particularly to topographies with nanoscale dimensions. Understanding how cells respond to topography is of particular interest to the field of tissue engineering, where it is crucial to characterise the effects that biomaterial surfaces have on the cells that they come into contact with. Observations of the impact that topographic signalling has on cells, within two tissue engineering systems, are discussed in this thesis. These systems are: polymer conduits for peripheral nerve regeneration and thin films for the replacement of the retinal pigment epithelium. Understanding the effects that micro and nano scaled topographies have on nerve and retinal cell regeneration is important for successful development and implementation of appropriate tissue engineered devices. In order to fabricate topographical patterns on biomaterial surfaces, a number of fabrication techniques were investigated. The fundamental requirement of these techniques was for reliable production of uniform nano and micro scale topographical patterns over large lateral areas (millimeter scale). Initially, the suitability of electrohydrodynamic lithography (EHDL) was assessed. EHDL is a relatively new technique, first published in 2000, which employs electrostatic forces to pattern thin polymer films. Subsequently, techniques traditionally associated with the computing industry, such as e-beam lithography and reactive ion etching, were evaluated. Following successful pattern fabrication, NG108-15 and ARPE-19 cells were cultured on grooved topographies. Against a baseline parameter of elapsed time, the cell morphologies and their propensity for alignment with the grooves was rigorously assessed and compared. ARPE-19 and NG108-15 cell responses differed from one another, and were sensitive to varying groove dimensions. Ultimately, the developing morphologies (for both cell types) proved to be clearly dependent on groove dimensions and elapsed time.

The Gray Fossil Site, Washington County, Tennessee, has produced a remarkable Mio-Pliocene fauna and flora with no known correlative in the Appalachian region. After its discovery in 2000, a series of auger holes were drilled by the Tennessee Department of Transportation (TDOT) to determine the areal extent of the site. Drilling indicated that the fossils occurred in fill material within a paleokarst basin, but the distribution of boreholes does not permit details of sinkhole topography, and therefore its formation and fill history, to be adequately resolved. To better image the sinkhole basin, a high-resolution gravity survey, which included 1104 gravity measurement stations, was conducted. These data were used to create complete Bouguer and residual gravity anomaly maps and a 3D density model via inversionmethods. The residual gravity anomaly map compares favorably with 29 TDOT auger holes drilled to basement, but contains significantly more detail. The residual gravity anomaly map reveals the presence of seven separate sinkholes. However, 3D inverse modeling constrained by drill-hole depths and density data indicates that there are 11 separate sinkholes formed within the Knox Group carbonates. These sinkholes, which range between 20 and 44 m in depth, are aligned along northwest and northeast trending linear features that correlate to structural features formed during the Appalachian orogenies. It is possible that the overall sinkhole basin formed as the result of partial coalescence of multiple sinkhole structures controlled by a joint system and that the sinkholes then acted as a natural trap for the Gray Fossil Site fauna and flora.

No abstract provided. / Thesis / Bachelor of Arts (BA)

Agricultural productivity, ecosystem health, and wetland restoration rely on soil organic carbon (SOC) as vital for microbial activity and plant health. This study assessed: (1) accuracy of topographic-based non-linear models for predicting SOC; and (2) the effect of analytic strategies and soil condition on performance of spectral-based models for predicting SOC. SOC data came from 28 agriculturally converted Delmarva Bays sampled down to 1 meter. R2 was used as an indicator of model performance. For topographic-based modeling, correlation coefficients and condition indices reduced 50 terrain-related values to three datasets of 16, 11, and 7 variables. Five types of non-linear models were examined: Generalized Linear Mondel (GLM) ridge, GLM LASSO, Generalized Additive Model (GAM) non-penalized, GAM cubic splice, and partial least-squares regression. Carbon stocks varied widely, 50 to 219 Mg/ha, with the average around 93 Mg/ha. Topography shared a weak relationship to SOC with most attributes showing a correlation coefficient less than 0.3. GLM ridge and both GAMs achieved moderate accuracy at least once, usually using the 16 or 11 variable datasets. GAMs consistently performed the best. Prior to carbon analysis, hyperspectral signatures were recorded for the topmost soil horizons under different conditions: moist unground, dry unground, and dry ground. Twenty-four math treatment and smoothing technique combinations were run on each hyperspectral dataset. R2 varied greatly within datasets depending on analytic strategy, but all datasets returned an R2 greater than 0.9 at least twice. Moist unground soil models outperformed the others when comparing the best models among datasets. / Master of Science

The architecture and morphology of a mountain range is fundamentally controlled by the combination of rock uplift and distribution of precipitation. This relationship attributes fluctuations in climate to the erosion of orogens, sedimentation rates, and geodynamics of the crust. Glaciers are the most effective climate driven erosive processes, where the frequency of glacial periods has a direct impact on the structure of mountain ranges through time. The late Cenozoic global cooling period was the beginning of a series of many glaciations which increased erosion in orogens experiencing fast rock uplift. We characterize the threshold for the onset of effective glacial erosion and record the increase in erosion rate during the late Cenozoic in the Chugach and Kenai Mountains of Alaska. We utilized low temperature thermochronometry and cosmogenic dating to constrain the spatial and temporal distribution of exhumation and glacial history in order to characterize the net effect of glaciers on an orogen that experiences slow rock uplift. We constrain the spatial distribution of exhumation and characterize the landscape along the Kenai Peninsula, underlain by the transition from flat slab to normal subduction. The region is characterized by old AHe ages which mimic the subduction angle of the down going plate and decrease away from an exhumational hotspot at a syntax in the Chugach Mountains. We attribute the long term exhumational characteristic of the Kenai Peninsula to subduction and underplating of sediment shed from the accreting Yakutat microplate to the east. A delineation of the glacial history using 10Be cosmogenic dating depict a series of glacial advances which date to the early and late Wisconsin. We find that the asynchronuity of glaciation across maritime and continental Alaska is controlled by steep orographic precipitation gradients which result from upper plate deformation. Finally, we observe an increase in erosion since the late Cenozoic using both AHe and cosmogenic dating and conclude that it is possible for the onset of effective glacial erosion in regions that experience slow to moderate rock uplift and that climate drives erosion rates in these regions. / Ph. D.

This thesis is an investigation of how to achieve walkability over steep urban topography greater than Americans with Disabilities Act accessible 8.33% standard. I studied how landscape architects and architects have overcome challenging topography in a variety of international cities and how to increase connectivity in the steep terrain of Washington D.C.'s Anacostia neighborhood. Specifically, this thesis explores the roles of staircases in the city and how staircases can enhance the experience of moving through the city. Topographic changes can be an obstacle to walk on: the steeper the path the harder it is to move through it, which in turn may encourage a person to use a car to travel between low and high points in the city. My hypothesis is that steep topography can be an enhancement to walkability in the city. The experience of traveling through steep terrain is unique as it can provide visually engaging environment of walking, including expansive views of the city, engaging architecture, and physical exercise. To test this hypothesis, I designed two distinct routes over steep topography to connect the Frederick Douglass National Historic Site, the Smithsonian's Anacostia Community Museum, a sports field, and the Fort Stanton Recreation Center. The paths respond to L'Enfant's method for laying out the city in "diagonal avenues superimposed over a grid system" (Nps.gov, 2018) and the very steep terrain of Anacostia, which seems to defy in places the orthagonal and axial relationships underlying L'Enfant's plan. Drawing on both L'Enfant's ordering scheme of the city and the given form of the two hundred foot escarpment above Anacostia, the design demonstrates that paths through steep terrain can be a great asset, revealing the larger order of the city through views to the monumental core, bringing people through the native forest, making more direct connections between the civic infrastructure, including the Frederick Douglass National Historic Site and the Smithsonian's Anacostia Community Museum. It shows that expanding the notion of walkability to include terrain that is not ADA accessible is important, and can be the impetus for the strategic inclusion of accessible paths where the topography permits. / Master of Landscape Architecture / This thesis is an investigation of how to create walkable spaces over steep topography in Washington, D.C. By steep topography, I concentrated on grade changes that are greater than the steepest slopes allowed in construction so that anyone can access the site. I studied how landscape architects and architects have overcome challenging topography in a variety of international cities and how to increase connectivity in the steep terrain of Washington D.C.’s Anacostia neighborhood. Specifically, this thesis explores the roles of staircases in the city and how staircases can enhance the experience of moving through the city. Walkscore’s walkability map presents a unique view of the city where walkable parts follow the topography of the city. Topographic changes can be an obstacle to walk on: the steeper the path the harder it is to move through it, which in turn may encourage a person to use a car to travel between low and high points in the city. My hypothesis is that steep topography can be an enhancement to walkability in the city. The experience of traveling through steep terrain is unique as it can provide visually engaging environment of walking, including expansive views of the city, engaging architecture, and physical exercise. To test this hypothesis, I designed two distinct routes over steep topography to connect the Frederick Douglass National Historic Site, the Smithsonian’s Anacostia Community Museum, a sports field, and the Fort Stanton Recreation Center. The paths respond to the method for laying out the city in “diagonal avenues superimposed over a grid system” (Nps.gov, 2018) established by Pierre L’Enfant, the designer of Washington, D.C., over the steep terrain of Anacostia, which seems to defy in places the orthagonal and axial relationships underlying L’Enfant’s plan. Drawing on both L’Enfant’s ordering scheme of the city and the given form of the two hundred foot escarpment above Anacostia, the design demonstrates that paths through steep terrain can be a great asset, revealing the larger order of the city through views to the monumental core, bringing people through the native forest, making more direct connections between the civic infrastructure, including the Frederick Douglass National Historic Site and the Smithsonian’s Anacostia Community Museum. It shows that expanding the notion of walkability to include terrain that is not universally accessible is important, and can be the impetus for the strategic inclusion of accessible paths where the topography permits.

X-ray diffraction topography, using both conventional and synchrotron sources, has been employd t reveal, to a resoltuoon of 1um, internal structural imperfections in diamonds from Brazil. Many of these diamonds were found to be twinned; and X-ray studies have been made of twinned diamonds from Brazil and elsewhere, in order to elucidate the mechanisms of twinning in diamond. Numerous X-ray topographs have been taken of contact twins (mcles), interpenetrant cubes and mulitple twins. The well collimated beam of synchrotron radiation at the SERV Daresbury Laboratory has proved most useful in revealing, in the forward reflexion Laue photographers, small twinned regions of diamons: the presence of which would have been mised by conventioanl methods.

Internal waves are generated in stratified fluids, like the ocean, where density increases with depth. Tides are one of the major generation mechanisms of internal waves. As the tides move water back and forth over underwater topography, internal waves can be generated. Topography slope and amplitude are major factors in the behavior of the generated internal wave field. In order to further understand the effects topographic shape plays, the effect of asymmetry on internal waves is investigated. This research investigates internal waves generated by dual-ridge topographies. Four cases of symmetric topographies, T, M, W, and W2, with three different peak spacings are compared to their singular ridge counter parts at three oscillation frequencies, ω = 0.6N, ω = 0.75N, and ω = 0.9N. Both subcritical and supercritical symmetric ridges were investigated. Experiments were also performed for subcritical, asymmetric dual ridges at the middle oscillation frequency. The internal wave fields were captured with synthetic schlieren and analyzed with the Hilbert transform and sum of kinetic energy in wavenumber space. It is found that for wave fields from substantially separated ridges, mixing and wave interference occurs that decreases total kinetic energy of the system.

This thesis explores the embodied topography of Mount Athos, emphasizing the conditions of liminality – the nature of different kinds of boundaries and intermediate zones within it. Mount Athos is a valuable case study of sacred topography, as it is one of the largest monastic communities and an important pilgrimage destination. Its phenomenological examination in this study highlights the importance of embodiment in the experience of religious places advocating also for a deeper understanding of the boundaries in it. The thesis seeks to convey a more primary insight into the phenomena found there, examining also how ritual and pre-reflective embodied movements explore the topography in a meaningful way. Combining elements of different disciplines (philosophy, theology, anthropology, and architectural history and theory) with primary sources from archives and fieldwork, the thesis constitutes an original contribution to both Athonian studies and sacred topography scholarship. By focusing on the spatial, temporal and aural boundaries and intermediate zones as perceptual phenomena of an embodied topography, it suggests an alternative to the usual art-historical, objectifying examination of the case study. Liminality refers to the intermediate zones between two or more components of a sacred place. It allows the reciprocal communication between them, carrying the character of both departure and return. In using liminality as a focus of investigation, the thesis provides a new understanding of the way religious places are interconnected through cyclical rituals, the strangers’ travel and silent meditation. Following the archetype of the journey, these movements are also studied according to their particular power to “map” places in a more primary way than the modern cartographic method. Starting from the periphery of Athos, the study presents a variety of in-between zones, the passage through which contributes to the sensual realization of a multi-layered meaningful topography. Annual pilgrimages to the peak of the mountain, silent meditation in isolated caves, wandering asceticism and walking along the footpaths provide different ways to narrate the natural landscape of the peninsula. Moreover, ritual choreographies being inscribed in the courtyard and church of a coenobitic monastery, meals and death services ritually perform the place. Through their investigation, this study illuminates important aspects of the topography, such as its multi-sensual aural environment in which silence plays a key role. The analysis concludes that the different liminal zones of Mount Athos are always undergoing a condition of penetration, alteration, and even violation, allowing the integrity of the topography to be enacted.

<p>The purpose of this thesis was to study the influence of manufacturing variations on gear performance. The manufacturing variations inherent in different manufacturing methods were studied to include the effect of real surfaces. Real surfaces have surface irregularities at least on some scale, which can significantly influence how loads are transmitted at the gear contact. To some extent, the lubricant design can help to prevent contact that could lead to tooth failures by forming a protective surface boundary layer. An experimental study was used to consider the compositions of these layers with a surface analysis method.</p><p>In Paper <strong>A</strong> a robust design approach was used to find out to what extent the current standard for calculation of surface durability treats manufacturing variations and the choice of lubricant. The results show that the simplest calculation method used is not enough to predict the effect of these on surface durability. Additionally, the standard quality levels are poorly incorporated in the standard calculating procedures for surface durability, and the quality of the gear tooth is restricted to include only a few parameters.</p><p>In Paper <strong>B</strong> a pin-on-disc machine was used to evaluate the tribofilm formation by the additives and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants. Studies of the additive and base fluid interaction were carried out using glow discharge-optical emission spectroscopy. It was found that the chemically reacted surface boundary layers played an important role in terms of wear. More specifically, the oxide layer thickness had significant influence on wear. The findings also demonstrate the complexity of lubrication design formulations coupled to these layers. For example, it was found that the pre-existing surface boundary layer (before any lubricant had been added) played an important role in allowing the lubricant to react properly with the surfaces.</p><p>The aim of Paper <strong>C</strong> was to contribute to the knowledge of how different surface topographies, tied to manufacturing methods, influence the early life contact conditions in gears. Topographical measurements of differently manufactured tooth flanks were used as data input to a contact analysis program. The variation in surface topography inherent in the manufacturing method was found to have a strong influence on the contact area ratio.</p>