Circle Packings on Affine Tori

This thesis is a study of circle packings for arbitrary combinatorial tori in the geometric setting of affine tori. Certain new tools needed for this study, such as face labels instead of the usual vertex labels, are described. It is shown that to each combinatorial torus there corresponds a two real parameter family of affine packing labels. A construction of circle packings for combinatorial fundamental domains from affine packing labels is given. It is demonstrated that such circle packings have two affine side-pairing maps, and also that these side-pairing maps depend continuously on the two real parameters

Inventory and analysis of the Black Vermillion river system riparian corridors

Master of Landscape ArchitectureDepartment of Landscape Architecture/Regional and Community PlanningTimothy D. KeaneThe purpose of the investigation was to inventory and analyze riparian corridor vegetation changes throughout the Black Vermillion watershed from approximately 1857 through 2007. Three sub-watersheds were studied; North Fork, Irish Creek and Black Vermillion Main Stem. Research questions investigated were: 1) What changes in riparian corridor width have taken place since the original territory surveys done in 1857 and why? 2) How has land cover adjacent to riparian corridors changed since the original territory surveys? 3) Has woody species composition in the riparian corridors changed? The research questions were addressed using a variety of techniques and tools including aerial photography, basic GIS, and vegetation survey techniques. Territory of Kansas survey maps and notes that were completed in 1857 were used as baseline reference conditions concerning corridor width and woody species present in the riparian corridors. Inventory and analysis of the riparian vegetation change over time and adjacent land cover will aid in understanding the present ecology of these riparian corridors and are important to stream and riparian ecosystem rehabilitation. Woody riparian corridors increased in width throughout the watershed from 1857 until about 1956 (probably due to a decrease in prescribed burning and lack of grazing), which is the pre-channelization period for this watershed. After channelization (late 1960's & early 1970's), average corridor widths dropped significantly as the stream was shortened a total of 15.8 miles (25.4Km). Most often, the land cover changed from native, tallgrass prairie to cultivated cropland or pasture. Woody species composition has changed over time from established mature woodland to a pioneer successional stage. The findings of this study can influence beginning stages of design for natural habitat rehabilitation purposes in this watershed. Design decisions for land rehabilitation purposes should consider reference conditions (historic), and to understand reference conditions we must study the history of land use and land change. This study provides a template for studying the history of land use and land use change of riparian corridors for Midwestern, agricultural landscapes

Rapid development of anoxic niches in supraglacial ecosystems

Microorganisms play a significant role in changing the physical properties of the surface of the Greenland Ice Sheet. Cryoconite holes are a hotspot for this microbial activity, yet little is known about the REDOX conditions that develop within them. In this study, we used oxygen microelectrodes and microoptodes to measure for anoxic conditions at the microscale, for the first time revealing a potential niche for anaerobic microorganisms and anaerobic processes. The development of an anoxic zone 2 mm deep within a 6 mm-thick layer of cryoconite sediment was observed within an hour of disturbance, showing rapid acclimation to changing physical conditions. Long-term (half year) incubations of cryoconite material showed a peak of oxygen production and consumption after forty days and reached a low-activity, steady state by day 116, with a persisting anoxic zone beginning between 2 mm and 4 mm deep. Anaerobic microorganisms, which have received little attention to date, should therefore be considered an important component of the cryoconite ecosystem. We discuss the possible dynamics of oxygen concentrations in the supraglacial system and infer that anoxic zones are an important factor in the development of cryoconite sediment communities

Probabilistic assessment of deep geothermal resources in the Cornubian Batholith and their development in Cornwall and Devon, United Kingdom

Geothermal energy could play a pivotal role in decarbonisation as it can provide clean, constant base-load energy which is weather independent. With a growing demand for clean energy and improved energy security, geothermal resources must be quantified to reduce exploration risk. This study aims to quantify the untapped resource-potential of the Cornubian Batholith as a geothermal resource for power generation and direct heat use. Recent field work, laboratory measurements and petrophysical characterization provides a newly compiled dataset which is inclusive of subsurface samples taken from the production well of the United Downs Deep Geothermal Power Project. Deterministic and probabilistic calculations are undertaken to evaluate the: total heat in place, recoverable resource, technical potential and potential carbon savings. The Cornubian Batholith is considered a petrothermal system which may require stimulation as an enhanced geothermal system. This study shows the batholith has significant heat stored of 8988 EJ (P50), corresponding to 366 EJ recoverable and a technical potential of 556 GWth. When evaluating the potential for power generation (i.e., electricity) the P50 is 31 GWe. The total carbon savings when generating electricity (P50) equates to 106 Mt

Uncertainty of ICESat-2 ATL06- and ATL08-Derived Snow Depths for Glacierized and Vegetated Mountain Regions

Seasonal snow melt dominates the hydrologic budget across a large portion of the globe. Snow accumulation and melt vary over a broad range of spatial scales, preventing accurate extrapolation of sparse in situ observations to watershed scales. The lidar onboard the Ice, Cloud, and land Elevation, Satellite (ICESat-2) was designed for precise mapping of ice sheets and sea ice, and here we assess the feasibility of snow depth-mapping using ICESat-2 data in more complex and rugged mountain landscapes. We explore the utility of ATL08 Land and Vegetation Height and ATL06 Land Ice Height differencing from reference elevation datasets in two end member study sites. We analyze ∼3 years of data for Reynolds Creek Experimental Watershed in Idaho\u27s Owyhee Mountains and Wolverine Glacier in southcentral Alaska\u27s Kenai Mountains. Our analysis reveals decimeter-scale uncertainties in derived snow depth and glacier mass balance at the watershed scale. Both accuracy and precision decrease as slope increases: the magnitudes of the median and median of the absolute deviation of elevation errors (MAD) vary from ∼0.2 m for slopes \u3c 5° to \u3e 1 m for slopes \u3e 20°. For glacierized regions, failure to account for intra- and inter-annual evolution of glacier surface elevations can strongly bias ATL06 elevations, resulting in under-estimation of the mass balance gradient with elevation. Based on these results, we conclude that ATL08 and ATL06 observations are best suited for characterization of watershed-scale snow depth and mass balance gradients over relatively shallow slopes with thick snowpacks. In these regions, ICESat-2 elevation residual-derived snow depth and mass balance transects can provide valuable watershed scale constraints on terrain parameter- and model-derived estimates of snow accumulation and melt

Physiological capabilities of cryoconite hole microorganisms

Cryoconite holes are miniature freshwater aquatic ecosystems that harbor a relatively diverse microbial community. This microbial community can withstand the extreme conditions of the supraglacial environment, including fluctuating temperatures, extreme and varying geochemical conditions and limited nutrients. We analyzed the physiological capabilities of microbial isolates from cryoconite holes from Antarctica, Greenland, and Svalbard in selected environmental conditions: extreme pH, salinity, freeze-thaw and limited carbon sources, to identify their physiological limits. The results suggest that heterotrophic microorganisms in cryoconite holes are well adapted to fast-changing environmental conditions, by surviving multiple freeze-thaw cycles, a wide range of salinity and pH conditions and scavenging a variety of organic substrates. Under oxic and anoxic conditions, the communities grew well in temperatures up to 30°C, although in anoxic conditions the community was more successful at colder temperatures (0.2°C). The most abundant cultivable microorganisms were facultative anaerobic bacteria and yeasts. They grew in salinities up to 10% and in pH ranging from 4 to 10.5 (Antarctica), 2.5 to 10 (Svalbard), and 3 to 10 (Greenland). Their growth was sustained on at least 58 single carbon sources and there was no decrease in viability for some isolates after up to 100 consecutive freeze-thaw cycles. The elevated viability of the anaerobic community in the lowest temperatures indicates they might be key players in winter conditions or in early melt seasons, when the oxygen is potentially depleted due to limited flow of meltwater. Consequently, facultative anaerobic heterotrophs are likely important players in the reactivation of the community after the polar night. This detailed physiological investigation shows that despite inhabiting a freshwater environment, cryoconite microorganisms are able to withstand conditions not typically encountered in freshwater environments (namely high salinities or extreme pH), making them physiologically more similar to arid soil communities. The results also point to a possible resilience of the most abundant microorganisms of cryoconite holes in the face of rapid change regardless of the location

Neural correlates of suspiciousness and interactions with anxiety during emotional and neutral word processing

Suspiciousness is usually classified as a symptom of psychosis, but it also occurs in depression and anxiety disorders. Though how suspiciousness overlaps with depression is not obvious, suspiciousness does seem to overlap with anxious apprehension and anxious arousal (e.g., verbal iterative processes and vigilance about environmental threat). However, suspiciousness also has unique characteristics (e.g., concern about harm from others and vigilance about social threat). Given that both anxiety and suspiciousness have been associated with abnormalities in emotion processing, it is unclear whether it is the unique characteristics of suspiciousness or the overlap with anxiety that drive abnormalities in emotion processing. Event-related brain potentials were obtained during an emotion-word Stroop task. Results indicated that suspiciousness interacts with anxious apprehension to modulate initial stimulus perception processes. Suspiciousness is associated with attention to all stimuli regardless of emotion content. In contrast, anxious arousal is associated with a later response to emotion stimuli only. These results suggest that suspiciousness and anxious apprehension share overlapping processes, but suspiciousness alone is associated with a hyperactive early vigilance response. Depression did not interact with suspiciousness to predict response to emotion stimuli. These findings suggest that it may be informative to assess suspiciousness in conjunction with anxiety in order to better understand how these symptoms interact and contribute to dysfunctional emotion processing

The ribosome stabilizes partially folded intermediates of a nascent multi-domain protein

Co-translational folding is crucial to ensure the production of biologically active proteins. The ribosome can alter the folding pathways of nascent polypeptide chains, yet a structural understanding remains largely inaccessible experimentally. We have developed site-specific labelling of nascent chains to detect and measure, using 19F nuclear magnetic resonance (NMR) spectroscopy, multiple states accessed by an immunoglobulin-like domain within a tandem repeat protein during biosynthesis. By examining ribosomes arrested at different stages during translation of this common structural motif, we observe highly broadened NMR resonances attributable to two previously unidentified intermediates, which are stably populated across a wide folding transition. Using molecular dynamics simulations and corroborated by cryo-electron microscopy, we obtain models of these partially folded states, enabling experimental verification of a ribosome-binding site that contributes to their high stabilities. We thus demonstrate a mechanism by which the ribosome could thermodynamically regulate folding and other co-translational processes

Neural correlates of suspiciousness and interactions with anxiety during emotional and neutral word processing

Suspiciousness is usually classified as a symptom of psychosis, but it also occurs in depression and anxiety disorders. Though how suspiciousness overlaps with depression is not obvious, suspiciousness does seem to overlap with anxious apprehension and anxious arousal (e.g., verbal iterative processes and vigilance about environmental threat). However, suspiciousness also has unique characteristics (e.g., concern about harm from others and vigilance about social threat). Given that both anxiety and suspiciousness have been associated with abnormalities in emotion processing, it is unclear whether it is the unique characteristics of suspiciousness or the overlap with anxiety that drive abnormalities in emotion processing. Event-related brain potentials were obtained during an emotion-word Stroop task. Results indicated that suspiciousness interacts with anxious apprehension to modulate initial stimulus perception processes. Suspiciousness is associated with attention to all stimuli regardless of emotion content. In contrast, anxious arousal is associated with a later response to emotion stimuli only. These results suggest that suspiciousness and anxious apprehension share overlapping processes, but suspiciousness alone is associated with a hyperactive early vigilance response. Depression did not interact with suspiciousness to predict response to emotion stimuli. These findings suggest that it may be informative to assess suspiciousness in conjunction with anxiety in order to better understand how these symptoms interact and contribute to dysfunctional emotion processing