Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2007. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1951.

abstract: The characteristics of the wintertime 500hPa height surface, the level of non-divergence and used for identifying/observing synoptic-scale features (ridges and troughs), and their impact on precipitation are of significance to forecasters, natural resource managers and planners across the southwestern United States. For this study, I evaluated the location of the 500hPa mean Pacific ridge axis over the winter for the period of 1948/49 to 2011/12 and derived the mean ridge axis in terms of location (longitude) and intensity (geopotential meters) from the NCEP/NCAR Reanalysis dataset. After deriving a mean ridge axis climatology and analyzing its behavior over time, I correlated mean location and intensity values to observed wintertime precipitation in select U.S. Climate Divisions in Arizona, Colorado, Nevada, Utah and New Mexico. This resulted in two findings. First specific to the 500hPa ridge behavior, the ridge has been moving eastward and also has been intensifying through time. Second, results involving correlation tests between mean ridge location and intensity indicate precipitation across the selected Southwest Climate Divisions are strongly related to mean ridge intensity slightly more than ridge location. The relationships between mean ridge axis and observed precipitation also are negative, indicating an increase of one of the ridge parameters (i.e. continued eastward movement or intensification) lead to drier winter seasons across the Southwest. Increased understanding of relationships between upper-level ridging and observed wintertime precipitation aids in natural resource planning for an already arid region that relies heavily on winter precipitation. / Dissertation/Thesis / M.A. Geography 2013

The influence water levels have on CO2 and CH4 efflux were investigated at the Loxahatchee Impoundment Landscape Assessment (LILA) research facility, located in Boynton Beach, FL, USA. Measurements of CO2 efflux were taken for 24 h periods four times for one year from study plots. Laboratory incubations of intact soil cores were sampled for CO2, CH4, and redox potential. Additionally, soil cores from wet and dry condition were incubated for determination of enzyme activity and macronutrient limitation on decomposition of organic matter from study soils. Water levels had a significant negative influence on CO2 efflux and redox, but did not significantly influence CH4 efflux. Study plots were significantly different in CH4 efflux and redox potential. Labile carbon was more limiting to potential CO2 and CH4 production than phosphorus, with the effect significantly greater from dry conditions soils. Enzyme activity results were variable with greater macronutrient responses from dry condition soils.

Wind-induced external and internal pressures on tiles installed on a low-rise building model with gable roof were investigated by using a full-scale wind testing facility generically named Wall of Wind (WoW). Emphasis was given to ridge tile where a failure usually initiates during extreme wind events. Three different profiles field tiles namely high, medium, and low were investigated in combination with two types of ridge tiles namely rounded and three-sided. Effect of weather block on the pressure was examined. The study produced a unique high resolution pressure data in the form of pressure coefficients (Cpmin, Cpmax and Cpmean) for field and ridge tiles. These tests revealed high pressure coefficients for the ridge tile compared to the field tiles including those at the corners. Ridge tiles at the middle of the roof saw slightly lower wind pressure compared to those close to the gable end. Weather blocking of clay tiles while useful preventing water intrusion, increased the wind loads on the field tiles. The case without weather blocking produced significant pressure underneath the field tiles that resulted in lower net pressures.

Semiconductor corrugated ridge waveguide (CRW) distributed feedback (DFB) lasers offer compelling advantages over standard DFB lasers. Indeed, the use of surface gratings etched on the ridge waveguide sidewalls in CRW-DFB devices avoids any epitaxial overgrowth. This provides a considerable simplification in the fabrication process, reducing cost and time of manufacturing, and ultimately increasing yield. It offers also the potential for monolithic integration with other devices, paving the way towards low-cost and mass-production of photonics integrated circuits. In recent years, the re-consideration of growth-free DFB lasers has drawn considerable attention, particularly with the current state-of-the-art photolithography machines. In this work, we present an experimental investigation on two generations of InGaAsP/InP multiple-quantum-well (MQW) CRW-DFB lasers that have been fabricated using stepper lithography. An early developed 1310 nm CRW-DFB laser showed stable single mode with high side-mode suppression ratios (SMSR) (>50 dB), albeit with thresholds higher than anticipated. A subsequent single-mode 1550 nm CRW-DFB laser showed stable operation with SMSR (>50 dB) and narrow spectral linewidths (≤250 kHz), observed for a wide range of current injection. Besides, novel multi-electrode CRW-DFB lasers have been tested. The experimental investigation showed that narrower linewidth (<150 kHz) and wide wavelength tunability (>3 nm) have been recorded using different multi-electrode current injection configurations. The application of a time-domain modeling approach for semiconductor CRW-DFB lasers is then described for the first time. We numerically studied the effect of the radiation modes on CRW-DFB laser properties by using time-domain coupled wave equations. High-order corrugated gratings with λ/4 phase-shit were analyzed, where the degree of longitudinal spatial hole burning (LSHB) can be effectively reduced by means of fine tuning of the grating duty cycle. Additionally, we showed how the side-mode suppression ratio can be predicted depending on the device geometry.

A stratigraphic framework for altered volcanic rocks assigned to the Late Jurassic - Early Cretaceous Gambier Group (Heah et al., 1986) is proposed that correlates units from the abandoned Britannia Mine with strata along the eastern section of Britannia Ridge and the Furry Creek valley. Geological mapping defines three packages, interpreted as volcanic sequences, that represent a continuous succession of mainly mafic to felsic volcanics. From north to south, packages 1, 2 and 3 dip moderately and face consistently southwest. Package 1 is characterized by a mafic flow sequence intruded by rhyolite domes. Package 2 is dominated-by a felsic dome complex and a sedimentary basin, both blanketed by a thick pyroclastic flow unit. Package 3 is characterized by felsic lavas and ash flow tuffs gradational upwards to a thick argillite unit. Developed orebodies occur at two major horizons that are close to the lower and upper contacts of package 2. Sulphides associated with chert horizons occur within altered sheared equivalents of crystal lithic tuff and felsic breccia related to felsic dome complexes. Whole rock analyses define an altered calc-alkaline volcanic suite. Alteration, attributed to hydrothermal solutions accompanying massive sulphides, is most intense in packages 1 and 2 where rocks are MgO-rich, CaO-poor and enriched or depleted in alkalis compared to normal subalkaline rocks. Rocks in package 3 and from later crosscutting dykes are relatively unaltered. Rb-Sr values tentatively define a Jurassic to Early Cretaceous age of 167 ± 37 Ma for the altered volcanic suite. K-Ar dates of 90.5 ± 3.2 Ma and 81.4 ± 3 Ma are interpreted as reset by Coast Plutonic Intrusions surrounding the volcanic pendant and a later deformational or undocumented intrusive event. Massive sulphides associated with felsic volcanic rocks on Britannia Ridge are similar to volcanogenic massive sulphide deposits described in the Canadian Archean greenstone belts and the Miocene Kuroko deposits of Japan. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Accompanied by two oversized thesis maps / Graduate

East Fork Poplar Creek (EFPC) in Oak Ridge, TN was highly contaminated with elemental mercury in the 1950 and 1960. The area is still experiencing the effects of mercury contamination, and researchers are searching for ways to remediate the EFPC. One possible mechanism for bioremediation is the use of biogenic Mn oxides to remove heavy metals from water systems. Native Pseudomonas bacteria species were isolated from EFPC in order to examine biogenic Mn oxides production and bioremediation of Oak Ridge slurries. Pseudomonas isolates did produce Mn oxides which bound to mercury, and mercury bound to organic matter significantly decreased. However, after a significant decrease of dissolved mercury, dissolved mercury was cycled back into the water system on day 10. Given a longer experimental timeline, biogenic Mn oxides have the potential to decrease mercury cycling.

The soil seed bank plays a dynamic role in the regeneration of plant communities after natural and anthropogenic disturbance. In this thesis, I addressed how disturbances influence the vegetation and seed bank of Florida rosemary scrub. In Chapter One I evaluated changes in species composition and spatiotemporal pattern of the vegetation and seed bank along a gradient of disturbance. During the summers and winters of 2007-2009 percent ground cover and seed bank species composition were assessed among replicates of three vegetation types subjected to minimal, moderate, and extreme anthropogenic disturbance (native rosemary scrub, degraded scrub, and agriculturally improved pasture, respectively). These vegetation types shared the same soil and topographic characteristics but differed in disturbance history. I found that species composition and spatial pattern varied with disturbance. In pastures the compositional and structural characteristics of rosemary scrub were lost and only native scrub species able to evade herbivory persisted in this community. Native and degraded scrub differed most from each other in species abundances and spatial pattern. Degraded scrub showed highest abundance of subshrubs and a spike moss species, while rosemary scrub was dominated by shrubs. The seed banks of scrub herbs in degraded scrub had a tendency towards a random spatial distribution that lacked association with aboveground cover. Conversely, rosemary scrub seed banks tended to have an aggregated distribution and were associated with occurrence of conspecific species aboveground, litter, and shrub cover. These results indicated a change in the spatial heterogeneity of the seed banks of scrub herbs in degraded scrub. In Chapter Two I evaluated changes in seed bank density with time-since-fire in native rosemary scrub. Due to large pulses of recruitment immediately after fire and population decline iii with time-since-fire, I predicted seed density with time-since-fire would follow a unimodal function with low density in early and late years post-fire, and highest density at intermediate time-since-fire. I compared seed density data among sites with different time-since-fire: two sites each of three, six, ten and 24 years time-since-fire and three long-unburned sites ( > 24 years). Variability in seed bank composition and density increased with time-since-fire and only recently burned stands were distinctly different from the other time-since-fire age classes. Some species and functional groups did exhibit a quadratic or cubic association to time-since-fire (ruderal herbs, subshrubs, Ceratiola ericoides, Lechea cernua, Paronychia chartacea, Phyllanthus tenellus); however, timing of the peak in seed density varied depending on life span and age of reproductive maturity. Scrub herbs were the most abundant functional group in the seed bank and showed highest density in the first ten years post-fire. This pattern corresponds to the pattern of aboveground species abundance and suggests abundances above- and belowground are closely linked. Understanding the dynamics of the seed bank in both naturally and anthropogenically disturbed communities in Florida rosemary scrub is important for the restoration of scrub habitat and management of existing populations of endangered and threatened scrub species endemic to the Lake Wales Ridge in central Florida.

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