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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

A Dental Microwear Texture Analysis of the Early Pliocene African Ursid Agriotherium africanum (Mammalia, Carnivora, Ursidae)

Stynder, Deano D., DeSantis, Larisa R.G., Donohue, Shelly L., Schubert, Blaine W., Ungar, Peter S. 01 December 2019 (has links)
The craniodental morphology of the early Pliocene ursid Agriotherium africanum has been studied extensively to reveal aspects of its dietary ecology. Results suggest that this large-bodied, long-legged, short-faced African native primarily consumed vertebrate matter. While many carnivoran families exhibit a clear functional relationship between craniodental form and performance on the one hand, and dietary behavior on the other, this is not always the case with Ursidae. Because of uncertainties regarding the appropriateness of using craniodental form to investigate ursid diets, questions still linger about the dietary ecology of Ag. africanum. Here, we report on a dental microwear texture analysis of six Ag. africanum lower second molars from the South African fossil site of Langebaanweg. Results support morphological evidence that suggests a diet focused on vertebrate soft tissue and bone. Unfortunately, results cannot clarify questions about mode of acquisition.
192

Locomotory Adaptations in Entoptychine Gophers (Rodentia: Geomyidae) and the Mosaic Evolution of Fossoriality

Calede, Jonathan J.M., Samuels, Joshua X., Chen, Meng 01 June 2019 (has links)
Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene-aged deposits of the western United States and Mexico. Their postcranial remains, however, are much rarer and little studied. Yet, they offer the opportunity to investigate the locomotion of fossil gophers, shed light on the evolution of fossoriality, and enable ecomorphological comparisons with contemporaneous rodents. We present herein a quantitative study of the cranial and postcranial remains of eight different species of entoptychine gophers as well as many contemporary rodent species. We find a range of burrowing capabilities within Entoptychinae, including semifossorial scratch-digging animals and fossorial taxa with cranial adaptations to burrowing. Our results suggest the repeated evolution of chisel-tooth digging across genera. Comparisons between entoptychine gophers and contemporaneous rodent taxa show little ecomorphological overlap and suggest that the succession of burrowing rodent taxa on the landscape may have had more to do with habitat partitioning than competition.
193

New Insights Into Prehispanic Urban Organization at Tiwanaku (NE Bolivia): Cross Combined Approach of Photogrammetry, Magnetic Surveys and Previous Archaeological Excavations

Vella, M. A., Ernenwein, E. G., Janusek, J. W., Koons, M., Thiesson, J., Sanchez, C., Guérin, R., Camerlynck, C. 01 February 2019 (has links)
The prehispanic site of Tiwanaku, located in northeastern Bolivia, was the focus of many studies during the past few decades. However, much of the site remains unexplored, leaving many questions unanswered about the location of dense archaeological deposits, the nature of urban organization, and water management strategies—specifically those located in the eastern sector of the Akapana Pyramid. Orthophoto mosaics and Digital Elevation Models derived from drone imagery helped identify archaeological features and anthropogenic mounds. New magnetic survey produced with a cesium gradiometer was merged with previous surveys (fluxgate and cesium gradiometer). The integration of maps and plans from six areas of a previous archaeological investigation within a common Geographical Information System helped relate geophysical anomalies to archaeological features. Our results demonstrate a high level of urban organization associating monumental buildings to open ritual spaces and to densely populated areas during Tiwanaku IV (500–800 CE) and V (800–1100 CE). The complexity of the urban organization is also demonstrated by landscape modifications such as a complex water management system and at least three terraces that augmented the monumentality of the Akapana Pyramid This interdisciplinary approach, innovative in Bolivia, provides new insight into one of the most significant archaeological sites in the Andes.
194

Seasonal Denning Behavior and Population Dynamics of the Late Pleistocene peccary Platygonus Compressus (Artiodactyla: Tayassuidae) From Bat Cave, Missouri

Woodruff, Aaron L., Schubert, Blaine W. 01 January 2019 (has links)
The late Pleistocene faunal assemblage from Bat Cave, central Ozarks, Missouri provides an opportunity to assess specific aspects of behavior, ecology, and ontogeny of the Rancholabrean species Platygonus compressus. All identifiable elements referable to this taxon were catalogued and examined, and a minimum number of individuals of 73 was determined for the sample. Evidence of seasonal behavioral patterns are reported for the first time in a fossil peccary. Maturation of individuals was assessed using the tooth eruption sequence and occlusal wear patterns for all tooth-bearing mandibular elements and isolated lower dentition. Approximate ages were established through comparison with the extant collared peccary. The presence of distinct, developmentally non-overlapping age groups suggests that P. compressus was seasonally present at the Bat Cave locality, with the cave functioning as seasonal shelter in which individuals would occasionally die. The study also suggests the peccaries engaged in synchronous, seasonal breeding behaviors. Demographic assessment of the Bat Cave peccary population suggests that younger individuals formed the bulk of the population at a given time with progressively older individuals becoming scarcer until the age of about 10 years, which matches the typical demographic patterns and life expectancy of extant peccaries.
195

Forensic Assessment of the 1999 Mount Cameroon Eruption, West-Central Africa

Wantim, Mabel N., Bonadonna, Costanza, Gregg, Chris E., Menoni, Scira, Frischknecht, Corine, Kervyn, Matthieu, Ayonghe, Samuel N. 01 June 2018 (has links)
The 28 March to 22 April 1999 eruption of Mount Cameroon volcano in southwest Cameroon occurred from multiple vents along fissures at two sites. Vents opened first at the upper site 1 (2650 m) and were more explosive than vents at the lower site 2 (1500 m), which were more effusive. Earthquakes, lava flows, tephra fall, ballistics and gas emissions affected the volcano's west and south flanks, including forests, plantations, stock animals, water supplies, coastal communities and their people. Through an analysis of existing published data and new interview data, we provide an overview of the environmental, social and economic consequences of these hazards on infrastructure, human health, and socio-economic and agricultural activities of the four coastal communities most affected by the eruption: Batoke, Bakingili, Debundscha and Idenau. The collected data provide a more detailed description of the short- and long-term direct and indirect effects of the eruption and response than has been provided to date. Sedimentation of tephra and ballistics from site 1 produced both short-term and long-lasting impacts on people, through the contamination of plants and water supplies, which induced impacts on human health and commercial activities. A ~9.2 km long lava flow erupted from site 2 received significant short-term attention as it severed the only arterial coastal highway, forced the evacuation of some 600 residents of Bakingili, and interrupted commerce between communities. The agricultural sector also suffered due to burning of crops and soils. The only obvious significant benefit of the eruption appears to be that the long lava flow has become a tourist attraction, responsible for bringing in money for food, drink and lodging. However, the long-term cascading effects caused by the hazards have proven to be more severe than the immediate direct and indirect effects during the eruption.
196

Ash Resuspension Related to the 2011–2012 Cordón Caulle Eruption, Chile, in a Rural Community of Patagonia, Argentina

Forte, Pablo, Domínguez, Lucia, Bonadonna, Costanza, Gregg, Chris E., Bran, Donaldo, Bird, Deanne, Castro, Jonathan M. 15 January 2018 (has links)
The 2011–2012 Cordón Caulle eruption emitted about 1 km3 of rhyodacitic tephra. Dominant westerly winds in the region caused most of the primary tephra to deposit in neighboring Argentina. In addition to the impact of widespread dispersal and fallout of primary tephra during the eruption, Argentina was also significantly affected by remobilization of the primary ash even several years after the climactic phase of the eruption. In this mixed methods study, we combine aspects of natural and social sciences to characterize the ash resuspension events associated with the 2011–2012 Cordón Caulle deposits and assess the impacts on the Argentinian farming community of Ingeniero Jacobacci in the Patagonian Steppe. Our findings show the primary importance of wind, rainfall and ash availability in controlling the occurrence and persistence of ash resuspension events. The role played by these variables was also reflected in the seasonal distribution of events observed. Regarding the impacts, our results complement those of earlier studies and demonstrate that ash resuspension events can exacerbate the negative impact of primary tephra fallout events from the time of deposition to many years after the eruption. Only after five years has the environment and the farming community begun to show signs of recovery. Our findings also highlight the importance of assessing ash resuspension events in multi-hazard scenarios involving volcanic and hydrometeorologic hazards.
197

Challenges and Benefits of Standardising Early Warning Systems: A Case Study of New Zealand’s Volcanic Alert Level System

Potter, Sally H., Scott, Bradley J., Fearnley, Carina J., Leonard, Graham S., Gregg, Christopher E. 01 January 2018 (has links)
Volcano early warning systems are used globally to communicate volcano-related information to diverse stakeholders ranging from specific user groups to the general public, or both. Within the framework of a volcano early warning system, Volcano Alert Level (VAL) systems are commonly used as a simple communication tool to inform society about the status of activity at a specific volcano. Establishing a VAL system that is effective for multiple volcanoes can be challenging, given that each volcano has specific behavioural characteristics. New Zealand has a wide range of volcano types and geological settings, including rhyolitic calderas capable of very large eruptions (>500 km 3 ) and frequent unrest episodes, explosive andesitic stratovolcanoes, and effusive basaltic eruptions at both caldera and volcanic field settings. There is also a range in eruption frequency, requiring the VAL system to be used for both frequently active ‘open-vent’ volcanoes, and reawakening ‘closed-vent’ volcanoes. Furthermore, New Zealand’s volcanoes are situated in a variety of risk settings ranging from the Auckland Volcanic Field, which lies beneath a city of 1.4 million people; to Mt. Ruapehu, the location of popular ski fields that are occasionally impacted by ballistics and lahars, and produces tephra that falls in distant cities. These wide-ranging characteristics and their impact on society provide opportunities to learn from New Zealand’s experience with VAL systems, and the adoption of a standardised single VAL system for all of New Zealand’s volcanoes following a review in 2014. This chapter outlines the results of qualitative research conducted in 2010–2014 with key stakeholders and scientists, including from the volcano observatory at GNS Science, to ensure that the resulting standardised VAL system is an effective communication tool. A number of difficulties were faced in revising the VAL system so that it remains effective for all of the volcanic settings that exist in New Zealand. If warning products are standardised too much, end-user decision making and action can be limited when unusual situations occur, e.g., there may be loss of specific relevance in the alert message. Specific decision-making should be based on more specific parameters than the VAL alone, however wider VAL system standardisation can increase credibility, a known requirement for effective warning, by ensuring that warning sources are clear, trusted and widely understood. With a credible source, user groups are less likely to look for alternatives or confirmation, leading to faster action. Here we consider volcanic warnings within the wider concept of end-to-end multi-hazard early warning systems including detection, evaluation, notification, decision-making and action elements (based on Carsell et al. 2004).
198

Isotropic and Anisotropic Kriging Approaches for Interpolating Surface-Level Wind Speeds Across Large, Geographically Diverse Regions

Friedland, Carol J., Joyner, T. Andrew, Massarra, Carol, Rohli, Robert V., Treviño, Anna M., Ghosh, Shubharoop, Huyck, Charles, Weatherhead, Mark 15 December 2017 (has links)
Windstorms result in significant damage and economic loss and are a major recurring threat in many countries. Estimating surface-level wind speeds resulting from windstorms is a complicated problem, but geostatistical spatial interpolation methods present a potential solution. Maximum sustained and peak gust weather station data from two historic windstorms in Europe were analyzed to predict surface-level wind speed surfaces across a large and topographically varied landscape. Disjunctively sampled maximum sustained wind speeds were adjusted to represent equivalent continuously sampled 10-minute wind speeds and missing peak gust station data were estimated by applying a gust factor to the recorded maximum sustained wind speeds. Wind surfaces were estimated based on anisotropic and isotropic kriging interpolation methodologies. The study found that anisotropic kriging is well-suited for interpolating wind speeds in meso- and macro-scale areas because it accounts for wind direction and trends in wind speeds across a large, heterogeneous surface, and resulted in interpolation surface improvement in most models evaluated. Statistical testing of interpolation error for stations stratified by geographic classification revealed that stations in coastal and/or mountainous locations had significantly higher prediction errors when compared with stations in non-coastal/non-mountainous locations. These results may assist in mitigating losses to structures due to excessive wind events.
199

Channel Geomorphic Evolution After Dam Removal: Is Scale Important?

Land, Timothy, Nandi, Arpita, Luffman, Ingrid 01 August 2017 (has links)
Post-dam removal geomorphologic adjustment of a stream channel has been documented in the scientific literature at watershed, hillslope, and laboratory scales. Hillslope-scale studies in channel cross sections are most common and add significant value in the dam-removal literature. This study examines geomorphic stream channel adjustment following dam removal at the hillslope scale under natural climatic conditions. A sedimentfilled silt fence dam (1 m tall, 12.65 m wide) was removed in three stages, and the width and depth of the upstream developing channel was monitored at six transects for 15 months. Headcut retreat and changes in channel sinuosity were also recorded. After the silt fence dam was removed, channel development was initiated by headcut formation, which migrated upstream at a rate of 4 cm/d for about 10 months and then gradually reached attenuation. The channel progressed through four distinct stages: Stage 1 (Initial conditions); Stage 2 (Downcutting)-wide, shallow, meandering channel incised to a maximum depth of 0.52 m, and sinuosity decreased; Stage 3 (Floodplain development)-upon reaching base level, surface runoff began to meander within the channel, widening it through bank slumps and erosion; and Stage 4 (Quasi-equilibrium)-channel development reached dynamic (quasi-) equilibrium with only minor widening at downstream transects (maximum width of the incised channel reached 0.46 m), accompanied by sediment aggradation. The stages of upstream channel development and headcut retreat pattern in this study are consistent with the findings of other studies at the laboratory and watershed scales, indicating that channel development after dam removal is scale independent.
200

Reconciling Phylogenetic and Morphological Trends in North American Mammuthus

Widga, Chris, Saunders, Jeff, Enk, Jacob 02 July 2017 (has links)
The morphology of mammoth upper third permanent molars (M3) is used to address regional- and continental-scale patterns in the structure of mammoth populations. Recent refinements to the understanding of Mammuthus phylogenetic diversity south of the Laurentide ice show extensive overlap between regional populations. We assess the underlying geographic structure in Mammuthus tooth morphology in light of these new genetic data. Comparison of regional trends in dental morphology show a single, morphologically variable, population of Mammuthus was present in North America during the Wisconsin glaciation. Within this population, there are no significant differences in degree of hypsodonty or molar shape however, there is a geographic pattern of lower enamel:dentin ratios in Mammuthus from the Channel Islands, West Coast, and Southwest/Mexico as measured by the number of molar lamellae and the standardized thickness of lamellae. These results contrast with historical perspectives of Mammuthus population structure suggesting at least four species of North American mammoths but are consistent with recent phylogeographic analyses of mitochondrial ancient DNA.

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