Physical Sciences and Mathematics Commons^™

An Instrument For Experimental Secondary Electron Emission Investigations, With Application To The Spacecraft Charging Problem, Robert Davies

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Secondary electron emission (SEE) and incident-particle backscattering are important processes accompanying the impact of energetic electrons and ions on surfaces. The phenomena play a key role in the buildup of electrical charge on spacecraft surfaces. and are therefore of particular interest to scientists attempting to model spacecraft charging. In response to a demonstrated need for data, techniques for determining total secondary electron (SE) and backscatter (BS) yields S and n, and associated scattering-angle-resolved, scattering-energy-resolved, and simultaneous angle-energy-resolved yields have been developed. Further, an apparatus capable of making the necessary measurements for experimental determination of these quantities-for conducting materials in …

The Effect Of Salinity Level Upon The Yield, Root Growth, And Water Extraction Of Contrasting Rooting Subpopulations Of Alfalfa (Medicago Sativa) Under Conditions Of Zero Leaching, Laura A. Vincent

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth and thus plant yield is limited in these soils due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase plant yield and water extraction, in an irrigated saline soil.

Soil profiles for a control …

Spatial And Temporal Dynamics Of Plant Populations In Salt-Desert Shrub Vegetation Grazed By Sheep, Humberto Alzérreca-Angelo

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

I studied the effect of moderate sheep grazing on a shadscale plant community at the Desert Experimental Range, southwestern Utah, USA, using a 61-yr data set with two grazing treatments (yes vs. no), two seasons (spring vs. winter), and two soil types (loamy-skeletal vs. coarse-loamy). I studied precipitation, total species cover, annuals, shrub survival, seedling recruitment, plant succession, and plant spatial relationships.

Precipitation showed high variability (CV=31%) masking on short-term cycles, resulting in study intervals with average (1935-58), dry (1958-69), driest (1969-75), and wet (1980-94[5]) regimes. Total cover in both grazed and ungrazed pastures increased between 1935 and 1975 before …

Second Growth Forest As Potential Marten Habitat In Western Newfoundland: An Examination Of Forest Habitat Structure And Microtine Abundance, Brian R. Sturtevant

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The American marten (Martes americana) is associated with large tracts of relatively undisturbed, mature coniferous forests. I examined coarse woody debris (CWD) structure and small mammal abundance with respect to forest age and stem structure within second-growth forests, in comparison with old-growth stands in western Newfoundland. Results suggest that a critical change in marten habitat quality may occur at stand senescence, due to decreased tree competition, more complex subcanopy structure, and increased meadow vole (Microtus pennsylvanicus) abundance.

Analysis of stem structure within a chronosequence of 19 second-growth stands indicated high intertree competition, with dense canopy closure …

Mule Deer Highway Mortality In Northeastern Utah: An Analysis Of Population-Level Impacts And A New Mitigative System, Mark E. Lehnert

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rerouting highways to accommodate construction of the Jordanelle Reservoir in northeastern Utah caused a dramatic increase in vehicle collisions with mule deer (Odocoileus hemionus). I evaluated the effectiveness of a new system of highway crosswalk structures installed to reduce deer losses and preserve seasonal migrations. In addition, I constructed computer simulation models to investigate how highway mortality has impacted the Jordanelle deer population.

The crosswalk system restricted deer crossings to specific, well-marked areas along highways where motorists could anticipate them. Subsequent to installation, mortality declined 42.3% and 36.8% along a four-lane and two-lane highway, respectively. I was unable …

A Survey Of Employees Of The United States Department Of Agriculture's Animal Damage Control Program, Susan A. Schroeder

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This study examined the attitudes of employees of the United States Department of Agriculture's Animal Damage Control (ADC) Program. This research examined ADC employees' attitudes about wildlife, the ADC program and ADC employment, wildlife damage management methods, euthanasia and the killing process, and the role of various public and private groups on ADC policy. This study also applied the theory of organizational capture to the ADC program to test its utility in explaining the attitudes and behaviors of employees. Results were based on a survey of ADC employees conducted in January 1995.

Survey responses were analyzed to explore associations between …

Livestock As Seed Disseminators For Reseeding Degraded Rangelands: The Role Of Dung In Gap Formation And Plant Establishment, Brian S. Auman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Livestock (cattle and sheep) were examined as seed disseminators for reseeding degraded Intermountain rangelands. "Hycrest" crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult. X A. cristatum (L.) Gaert.] seed was fed to yearling Holstein steers and Suffolk ewes. Dung was collected from each animal type and deposited on plots of high and low densities of an annual [cheatgrass (Bromus tectorum L.)] and perennial [squirreltail (Sitanion hystrix Nutt.)] grass species. The experiment evaluated the ability of the dung to suppress the resident vegetation, and the recruitment and establishment of Hycrest seedlings emerging from the dung.

Sheep dung had …

Aminostratigraphy Of Thatcher Basin, Se Idaho: Reassessment Of Pleistocene Lakes, Amy Hochberg

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Quaternary geologic history of Lake Thatcher, southeastern Idaho, is pivotal in determining when the Bear River carved its through-flowing channel into the Bonneville Basin. Bright's reconstruction of the history of Lake Thatcher was based on ¹⁴C dates that are now known to be inaccurate. Lava Creek B ash found interbedded with lacustrine sediment suggests that Thatcher Basin contained a lake well before Bright's original estimate of 34 ka.

D/L ratios, which measure the extent of racemization in fossil gastropods, in conjunction with paleosols and tephra, were used to correlate between four localities across Thatcher Basin to reassess lake-level …

Adaptive Density Estimation Based On The Mode Existence Test, Nizar Sami Jawhar

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The kernel persists as the most useful tool for density estimation. Although, in general, fixed kernel estimates have proven superior to results of available variable kernel estimators, Minnotte's mode tree and mode existence test give us newfound hope of producing a useful adaptive kernel estimator that triumphs when the fixed kernel methods fail. It improves on the fixed kernel in multimodal distributions where the size of modes is unequal, and where the degree of separation of modes varies. When these latter conditions exist, they present a serious challenge to the best of fixed kernel density estimators. Capitalizing on the work …

Thermodynamics And Kinetics Of Small Molecule Binding To [Cyclopentadienyl-Ru-No] And [Rh-Co] Electrophilic Centers, Anna Svetlanova

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This work is concentrated on the thermodynamic and kinetic aspects of water, alcohols, alkyl halides, ethers, and lactones bound and activated by the electrophilic [Cp'Ru(N0)]⁺² and [Cp’Ru (NO)(CH₃)] + centers (Cp' = cyclopentadienyl group). Counterions in these systems include OSO₂CF₃- (OTf`) and [(3, 5-(CF₃)₂C₆H₃)₄B]- ([BAr₄']-). The displacement of OTf- in Cp'Ru(N0) (0Tf)2 by H20 in dichloromethane is exothermic but entropically unfavorable due to the required reorganization of the solvent cage around released triflate ions. Thermodynamic parameters are also determined for OTf …

Habitat Selection And Movement Of A Stream-Resident Salmonid In A Regulated River And Tests Of Four Bioenergetic Optimization Models, Mark D. Bowen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A bioenergetics model was constructed for stream-resident drift-feeding salmonids. Model predictions of surplus power (energy available per unit time for growth and reproduction) were not statistically distinguishable from observations of surplus power in three laboratory studies. Of 40 experimental trials in these three studies, the model correctly predicted surplus power in 39 cases (p < 0.05).

I collected observations of rainbow trout (Oncorhynchus mykiss) focal velocity and physical habitat availability in the Green River of northeastern Utah, USA (1988-1990). In the winter of 1988, Flaming Gorge Dam generated hydropower and delivered an lJDStable discharge regime with a higher mean discharge …

An Ecological History Of Tintic Valley, Juab County, Utah, Jeffrey A. Creque

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This work was a case study of historical ecological change in Tintic Valley, Juab County, Utah, an area historically impacted by mining and ranching activities common to much of the American West. The temporal framework for the study was approximately 120 years, the period of direct Euroamerican influence. In recognition of the ecological implications of cultural change, however, the impacts of prehistoric and protohistoric human activity on study area landscape patterns and processes were also explicitly addressed.

The study included a narrative description of historic land uses and ecological change in Tintic Valley, and examined the changes in landscape patterns …

Evaluation Of The Delta Waterfowl Foundation's Adopt-A-Pothole Project, Daniel S. Vice

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The establishment of dense nesting cover (DNC) for breeding waterfowl is a common management practice on large blocks of former agricultural land. The Delta Waterfowl Foundation's Adopt-A-Pothole (AAP) program establishes DNC adjacent to small wetland complexes to increase waterfowl use and productivity. I evaluated waterfowl use and nesting success on AAP lease sites in southwestern Manitoba in 993- 94 and compared the relative amount and success of overwater and upland nesting by mallards using these sites.

Diving duck breeding pair densities were higher on treatment sites in both 1993 and 1994 (P = 0.02 and 0.02, respectively). Dabbling duck …

The Influence Of Forest Fragmentation And Landscape Pattern On American Martens And Their Prey, Christina D. Hargis

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Habitat fragmentation occurs when large tracts of an orginal habitat are replaced by smaller patches of two or more habitat types, largely through human activities. I studied the behavior of six measures of landscape pattern that seemed appropriate for quantifying fragmentation, and used these measures to investigate the effects of forest fragmentation on American martens (Martes americana) and their prey. The measures I selected were edge density, contagion, mean nearest neighbor distance between patches, mean proximity index, perimeter-area fractal dimension, and mass fractal dimension. To test the behavior of these measures with a variety of landscape patterns, I …

Visitor Use Of Interpretive Facilities At Fossil Butte National Monument, Wyoming, Rizal Bukhari

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Visitors expect to a gain high-quality outdoor experiences at any recreation site they visit. In order to support that effort, most recreation managers utilize interpretive facilities to educate and inform visitors about the site. It is important for interpretive managers to be aware of what kind of interpretive media could best be used in a given setting for the type of visitor anticipated. To accomplish this goal, it is necessary to understand visitors' behavior and incorporate that understanding into the interpretive planning process.

This study looks at visitor use of interpretive facilities provided at Fossil Butte National Monument, Wyoming. The …

Structural Analysis Of The Mitten Park Reverse Fault And Related Deformation In Dinosaur National Monument, Northwestern Colorado And Northeastern Utah, Clint M. Brown

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

An integrated field and structural analysis of the Mitten Park fault-fold structure, northwestern Colorado and northeastern Utah, examines its structural origin. The Mitten Park structure is a modified fault-propagation-fold. This new model incorporates faulting, folding, and fracturing in one deformational event to produce the Mitten Park fault and associated monocline.

The largest structure in the study area is the Mitten Park fault and associated monocline. The Mitten Park fault has approximately 127 meters (415 feet) of net slip, strikes S28°W and dips 55°WNW. In the footwall, net shortening was accommodated by reverse and normal faulting. Faulting was the result of …

Hydrochemical Definition Of Ground Water And Surface Water, With An Emphasis On The Origin Of The Ground-Water Salinity In Southern Juab Valley, Juab County, Utah, Heidi K. Hadley

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

As part of a U.S. Geological Survey study in Juab Valley in central Utah from 1991 to 1994, the chemistry of ground - and surface -water samples was determined. Total dissolved solids in the ground water of southern Juab Valley have historically been higher, in general, than ground water in other areas of Utah. Total dissolved solids for ground-water samples from this study ranged from 623 to 3,980 milligrams/liter. High-sulfate chemical data of previous studies suggested that the major source of ground-water salinity is the dissolution of gypsum (hydrous calcium sulfate ) from the Arapien Shale. Sulfur-34 to sulfur-32 isotopic …

Pre-Late-Wisconsin Glacial History Of The Naknek River Valley, Southwestern Alaska, Caleb H. Thompson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The lower Naknek River in southwestern Alaska dissects thick (~20m) exposures of Pleistocene glaciogenic sediments. The stratigraphy of the deposits and their physical, geochemical, mineralogical, and geochronological properties were studies to determine the number and timing of glacial advances represented. Multivariate data reduction methods (cluster and principal component analyses) were applied to the data to differentiate diamicton beds. The results show a clear separation of drift of the lower Naknek River valley from drift of northern Bristol Bay and from younger, moraine-comprising drift up valley. Within the Naknek River valley, however, there is no stratigraphic trend to the clusterings. The …

Paleoenvironmental And Stratigraphic Interpretation Of The Middle Cambrian Ute Formation, Northern Utah, Keith E. Eagan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Middle Cambrian Ute Formation includes some 200 m of cyclically alternating carbonates and mud rocks. These are arranged in eight to nine, meter-scale, shallowing-upwards packages, representing deposition under predominantly subtidal conditions. The packages consist of vertical sequences of shale, silty limestone, oncolitic packstone, and oolitic grainstone that exhibit little variance in this general pattern. Small-scale unconformities separate the packages. The inferred depositional environment consists of an intrashelf basin that has a peritidal platform near its margins. The craton, which supplied most of the terrigenous sediment, was situated to the south (Cambrian orientation), and located near the equator. One cycle …

A Study Of The Gradient Drift Instability In The High-Latitude Ionosphere Using The Utah State University Time Dependent Ionospheric Model, Mahesh Subramanium

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Research over the years has established that the Gradient Drift Instability process causes small-scale irregularities, mostly along the edges of the high-latitude polar cap patches. Studying these irregularities will help in the development of a Global Scale Ionospheric model, which is a central part of a global space weather forecast system. Much theoretical work has been done with varying degrees of complexity to study this instability in the high latitude patches.

In this work we have used the Utah State University Time Dependent Ionospheric Model to model the high-latitude patches, calculate the growth rate of the instability, and perform a …