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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.
251

Magma Envelopes, Enclaves and Rogue Crystals in the Atascosa Lookout Lava Flow: Magma Communication Across a Range of Crustal Levels

Burrill, Christine 25 October 2018 (has links)
The Atascosa Lookout lava flow is a mid-Tertiary trachyandesite flow that caps the rhyolitic to dacitic volcanic sequence exposed in the Atascosa Mountains of southern Arizona. The flow erupted near the beginning of extension in the southern Basin and Range following the floundering of the Farallon plate and during the development of the San Andreas fault. The flow hosts a variety of disequilibrium crystals and textures including resorbed and overgrown feldspar phenocrysts with inclusion-rich zones, quartz-bearing enclaves, and clusters of plagioclase +/- chromium diopside, magnesian augite, quartz, hornblende, and orthopyroxene crystals and envelopes of contrasting composition with both the groundmass and the enclaves. Current evidence suggests that magma generation and differentiation commonly take place mainly in the lower crust and batches of magma are emplaced and equilibrate across a range of crustal levels. Crystallization depths and temperatures of various phases in the flow were obtained with new and revised geothermometers and geobarometers to examine the petrogenesis of the lava flow. Major elements of parental melts for most of the mineral phases were estimated using thermobarometry equilibrium tests and rare earth and trace element concentrations of parental melts of hornblendes and clinopyroxenes were calculated using known partition coefficients elements. Thermobarometry shows distinct ranges of temperatures and pressures for each component of the flow and calculated parental melts of various phases are distinct from one another. Orthopyroxenes crystallized at depths greater than 25 km, at the highest temperatures from the most mafic parent, estimated to be a picro-basalt. Clinopyroxenes crystallized at 11.5 – 30 km, lower temperatures and a more evolved parent of basalt or trachybasalt composition. Plagioclase crystallized throughout the crust from a range of intermediate melts and hornblendes crystallized 12 – 13 km from a parental melt similar in composition to the groundmass. This study demonstrates the lava flow hosts minerals that crystallized from different parent melts at various crustal levels. Extension and previous magmatism provided a rapid path for magma to ascend, subduing crustal assimilation and enhancing the probability of a diverse crystal cargo that retains the record of the plumbing system beneath a volcanic complex.
252

Impacts of Prescribed Fire and Grazing on Northern Great Plains Rangelands

Johnson, Haley Mae Ann January 2018 (has links)
Prescribed burning was utilized as a management tool on grasslands of the Northern Great Plains. We analyzed the use of fire to manipulate encroaching and unpalatable western snowberry (Symphoricarpos occidentalis), to promote browsing and improve nutritive quality. Fire was successful at altering the nutrient quality of western snowberry and selectivity of grazing livestock from plant specific to patch specific. Additionally, we evaluated the difference between burn season and frequency on plant community dynamics of an ungrazed tallgrass prairie invaded by Kentucky bluegrass (Poa pratensis). Fire promoted native forb and grass species, stressing that native species are well adapted to the historical disturbance. Our research emphasizes the need for restored fire regimes in the Northern Great Plains to benefit numerous aspects of prairie ecosystem function, stability, services, and productivity. / U.S. Forest Service / Central Grasslands Research and Extension Center
253

Investigating the effect of a weak lower crust on Basin and Range extensional history

Christopher Calvelage (10897515) 22 July 2021 (has links)
The deformation mechanisms responsible for the extension and rifting in Basin and Range extension over the past ~36 Ma, and their relative importance remain debated. Slab rollback, lithospheric body forces, and relative plate motions have all been shown to contribute, but the relative importance of each mechanism is not fully understood. Here, we build three-dimensional (3D) steady state geodynamic models to simulate the full tectonic reconstruction of Basin and Range extension and compare these results with known geologic field observations and other detailed reconstructions of surface deformation. Our modeling approximates lithospheric deformation through Stokes flow in a spherical cap of variable viscosities. By applying reconstructed boundary conditions, crustal thickness, and surface elevation at 17 Ma, and varying lithospheric viscosity we map out the predicted response of the surface motions and lower crustal flow for different assumed lithospheric viscosity contrasts and investigate the origin of core complex formation. Comparisons between predicted model deformation and geologic field observations from metamorphic core complexes and exposed fluorite deposits indicate: (1) The primary driving force of the formation of geologic features in the western US is regional gravitational collapse focused in the lower crust. Plate motions are second order by comparison at this time period and act to rotate velocities near the plate boundary. (2) A weak lower crust facilitates metamorphic core complex formation and extension in the Nevadaplano. Lateral extrusion of the lower crust serves as a mechanism for both core complex formation and the flattening of the Moho that is observed at present day. (3) Lower crustal flow is a contributes to the rotation and tilt of the Colorado Plateau and formation of the Rio Grande Rift.
254

Reconfigurable Snapshot HDR Imaging Using Coded Masks

Alghamdi, Masheal M. 10 July 2021 (has links)
High Dynamic Range (HDR) image acquisition from a single image capture, also known as snapshot HDR imaging, is challenging because the bit depths of camera sensors are far from sufficient to cover the full dynamic range of the scene. Existing HDR techniques focus either on algorithmic reconstruction or hardware modification to extend the dynamic range. In this thesis, we propose a joint design for snapshot HDR imaging by devising a spatially varying modulation mask in the hardware combined with a deep learning algorithm to reconstruct the HDR image. In this approach, we achieve a reconfigurable HDR camera design that does not require custom sensors, and instead can be reconfigured between HDR and conventional mode with very simple calibration steps. We demonstrate that the proposed hardware-software solution offers a flexible, yet robust, way to modulate per-pixel exposures, and the network requires little knowledge of the hardware to faithfully reconstruct the HDR image. Comparative analysis demonstrated that our method outperforms the state-of-the-art in terms of visual perception quality. We leverage transfer learning to overcome the lack of sufficiently large HDR datasets available. We show how transferring from a different large scale task (image classification on ImageNet) leads to considerable improvements in HDR reconstruction
255

A 10-Week Stretching Program Increases Strength in the Contralateral Muscle

Nelson, Arnold G., Kokkonen, Joke, Winchester, Jason B., Kalani, Walter, Peterson, Karen, Kenly, Michael S., Arnall, David A. 01 March 2012 (has links)
It was questioned whether a unilateral stretching program would induce a crosstraining effect in the contralateral muscle. To test this, 13 untrained individuals participated in a 10-week stretching program while 12 other untrained individuals served as a control group. For the experimental group, the right calf muscle was stretched 4 times for 30 seconds, with a 30-second rest between stretches, 3 d·wk -1 for 10 weeks. Strength determined via 1 repetition maximum (1RM) unilateral standing toe raise, and range of motion (ROM) were measured pre-post. In the treatment group, the stretched calf muscle had a significant (p < 0.05) 8% increase in ROM, whereas the nonstretched calf muscle had a significant 1% decrease in ROM. The 1 RM of the stretched calf muscle significantly increased 29%, whereas the 1RM of the nonstretched calf muscle significantly increased 11%. In the control group, neither 1RM nor ROM changed for either leg. The results indicate that 10 weeks of stretching only the right calf will significantly increase the strength of both calves. Hence, chronic stretching can also induce a crosstraining effect for strength but not for the ROM. This study also validates earlier findings suggesting that stretching can elicit strength gains in untrained individuals.
256

Survival, Home Range and Spatial Relationships of Virginia's Exploited Black Bear Population

Higgins, Jennifer C. 02 September 1997 (has links)
Eighty-three (21M, 62F) of 194 black bears captured during 1994-1996 were equipped with radio collars. Annual survival rates estimated with Kaplain-Meier staggered entry approach for radio collared adult females, adult males, subadult females, and subadult males were 95.3, 100.0, 90.4 and 50.0% respectively. Hunting, handling, vehicle collisions, and natural causes accounted for 81.0, 11.1, 3.2, and 1.6% of mortality. Twenty, 9.8, and 70.6 % of bears harvested were harvested in the deer firearm season, the deer archery season, and the bear firearm season, respectively. Twenty-three cubs were equipped with expandable radio collars (11M,10F) or transmitters implanted subcutaneously (2M,0F) in 1995-1996. Six cubs (4M, 2F) died, 6 (3M,3F) survived their first year, and the status of 11 cubs (6M, 5F) was unknown. Survival rates (date marked until 4 December) estimated with Kaplain-Meier and Heisey-Fuller were 64.3 and 64.7% respectively. Interval survival rates were 71% (15 March to 31 May), 100% (1 June to 31 July), 92% (1 August to 31 August), and 100% (1 September to 4 December). Intraspecific aggression (33.3%), starvation (16.7%), unknown causes (16.7%) and predation (16.7%) were the causes of mortality. Total home range size for males and adult, subadult, and transitional age females were 7.2, 5.5, 5.6 and 7.2 km2 (95% MCP) and 11.2, 6.8, 9.0, and 10.0 km2 (95% normal kernel). Females with cubs had larger fall ranges than spring and summer ranges. Seasonal ranges of solitary females did not differ when estimated with MCP. Bears exhibited home range overlap among and within sex classes. / Master of Science
257

Learning and Application of Range Management Innovations Among Ranchers in West-Central Colorado

Kennedy, Caroline A. 01 May 2005 (has links)
Like many ranchers in the West, ranchers in West-Central Colorado are reevaluating their management strategies in the face of forces like drought, rising land prices, and encroaching development. While ranchers seek answers on alternative management strategies, research and Extension personnel search for adequate means of diffusing needed information. Relative to many rural western communities, ranchers in West-Central Colorado show high interest in alternative range management ideas, and many implement changes to their ranch management based on these ideas. This can partially be attributed to a unique support system of Extension and agency personnel with effective, untraditional outreach and land-management approaches. A survey was mailed to all 647 persons on the mailing list for the CSU Tri-River Extension Office, including Forest Service and BLM permittees in Mesa, Delta Montrose, San Miguel, Ouray, Hinsdale, Saguache, and Gunnison counties. The survey was designed to gain insight on how ranchers perceive current Extension efforts, how they learn new management information from peers and Extension/agency personnel, and how they apply these new ideas to their operations. Subsequent qualitative interviews with respondents gathered information on the process of adapting and implementing range management innovations into individual operations. This paper presents the findings of the survey and interviews, and implications for future outreach efforts.
258

Geology of the West-Central Part of the Malad Range, Idaho

Wach, Phillip H. 01 May 1967 (has links)
The west central part of the Malad Range is located in south-eastern Idaho. This area was the site of thick marine deposition in the early Paleozoic period. In the Tertiary and Quaternary periods continental deposition occurred, covering the Paleozoic rocks. Quartzite and shale units of the Brigham Quartzite are found near the base of the Cambrian section. Carbonate with shale interbeds is found in the middle and late Cambrian units. Limestone and silty limestone are found in the early and middle Ordovician time overlain by the middle Ordovician Swan Peak Quartzite. The Laketown Dolomite includes units of late Ordovician and Silurian age. Paleozoic units younger than Silurian and and Mesozoic units are not found in the mapped area. Red conglomerates mark early Tertiary deposition, and water-lain tuff, fresh-water limestone, conglomerate and sandstone are of middle and late Tertiary age. Tertiary-Quaternary rocks, found in the mapped area, are composed of deposits of boulders resting on older Tertiary and Paleozoic rocks. These deposits show rough polygonal structures and stone stripes. Quaternary deposits are composed of sediment from the Late Pleistocene Lake Bonneville and Quaternary alluvium. Northwest-trending faults, northeast-trending faults, and north-trending faults are found in the mapped area, with northwest-trending faults predominating. The northwest-trending faults are high-angle faults and have resulted in Tertiary rocks being faulted against lower Paleozoic rocks. Northeast-trending faults are roughly parallel and predate the middle and late Tertiary rocks. North-trending faults are high-angle faults involving both Paleozoic and Tertiary rocks. One northwest-trending fault has evidence of horizontal movement. The structures are assigned to three periods of movement: 1. early Cretaceous to early Tertiary, 2. late Tertiary to middle Tertiary, 3. middle Tertiary to Recent.
259

Simulated Browsing Impacts On Aspen Suckers' Density, Growth, and Nutritional Responses

Tshireletso, Koketso 01 May 2008 (has links)
Heavy and repeated ungulate browsing on reproductive suckers has limited trembling aspen (Populus tremuloides Michx.) regeneration on many Western landscapes. However, little is known about the specific effects of season and intensity of browsing. My objectives were to determine the effects of season and intensity of clipping (simulated browsing) on suckers’ (1) density and growth characteristics, and (2) nutritional quality and quantity. Three randomly selected stands were clear-felled in mid-July, 2005, and fenced. Simulated browsing treatments of 0%, 20%, 40%, and 60% removal of current year’s growth were randomly applied in early, mid-, and late summers of 2006 and 2007. Sucker density, height, leader length, twig numbers, bud numbers, basal area, and biomass harvested were monitored in each quadrat. Harvested material was analyzed for crude protein and in vitro true dry matter digestibility. Early summer clipped suckers suffered no winter mortality compared to mortalities of 41% and 42% for mid- and late summer clipped suckers, respectively. However, even at the highest mortality, there were still ample numbers of suckers for stand regeneration. Sucker height was restricted by all early summer treatments. Clipping at 20% and 40% in mid- and late summer, respectively, did not reduce sucker height, but suckers clipped 60% were ≤ 40 cm shorter than controls. Twig and bud density both declined with increasing intensity of clipping. By the study’s end, basal area of early summer clipped suckers was higher than for those clipped in late summer. Crude protein of clipped biomass decreased with season’s advance and clipping intensity. Levels ranged from 12.8% to 22.9% and 10.6% to 16.5% in 2006 and 2007, respectively. Digestibility ranged from 80.1% to 93.4% and 75.2% to 90.7% in 2006 and 2007, respectively. Biomass (260 vs. 181 kg/ha) and total digestible dry matter (197 vs. 142 kg/ha) harvested were higher in mid-summer clipped plots in 2007 than in 2006, respectively. Apart from early summer, total nitrogen harvested was not affected differently by season of clipping. Clear-felling programs that allow browsing of ≤ 40% in mid- and late summer would ensure sustained aspen stand density and growth. (184 pages)
260

Differential Behavior of Coyotes with Regard to Home Range Limits

Harris, Charles E. 01 May 1983 (has links)
This study was conducted to examine coyote behavioral responses to novel stimuli in familiar and unfamiliar environments and the implications of this behavior with regard to specific coyote management and research techniques. A series of pen studies with captive coyotes was undertaken at the U.S. Fish and Wildlife Service's Predator Ecology and Behavior Project research site, Logan, Utah, to observe the range and type of behaviors coyotes showed towards small novel objects and standard scent stations in familiar and unfamiliar 1-ha enclosures. The initial response to these novel stimuli in familiar environments was one of neophobia and caution, whereas in the unfamiliar environment these same stimuli were readily approached and investigated. Field studies were undertaken at the Idaho National Engineering Laboratory and Freer, Texas, to examine coyote visitation to scent stations inside, peripheral to, and outside their defined home ranges. Radio-collared coyotes were monitored to determine home range use and movement patterns, with relocations plotted on computer graphic maps and gridded base maps. Modified scent-station survey lines were run and visitations by marked coyotes plotted with respect to home range zone. Marked coyotes visited a greater percentage of scent stations peripheral to and outside their home ranges than inside. The socio-spatial distribution of coyotes, home range size, and percentage of road comprising home range zones influenced differential scent-station visitation rates. The importance of understanding the influences of animal behavior on wildlife management and research techniques is discussed.

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