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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.
201

Variability in Bioavailable<sup>87</sup>Sr/<sup>86</sup>Sr in the North American Midcontinent

Widga, Chris, Douglas Walker, J., Boehm, Andrew 01 January 2017 (has links)
Strontium (Sr) isotope tracers are useful for understanding provenance and mobility in biological materials across multiple disciplines. However, the impact of these techniques is highly dependent on the construction of appropriate comparative baselines (i.e., an isoscape). We present the results of a systematic survey of87Sr/86Sr values from grasses in the North American Midcontinent with a particular emphasis on sedimentary systems. Although87Sr/86Sr values are highly variable across the region, the Sr isoscape shows ­multi-scalar patterns that are dependent on local-to-regional trends in surficial geology. High values are found in bedrock-dominated areas such as the Black Hills (SD) and Ozark Uplift (MO), or formerly glaciated areas where surface deposits are dominated by ice-transported Precambrian clasts. The lowest values are found in river valleys that incorporate eroded Neogene sediments into terrace formation. Intermediate values are found in upland loess and alluvial deposits which blanket much of the study area. We demonstrate trends in large-scale variability of the Midcontinent’s87Sr/86Sr isoscape and suggest that future refinement focus on sub-regional trends in Sr isotope variability.
202

Kusterosion på sydvästra Gotland : En undersökning i GIS och berggrundsgeologi / Coastal Erosion on Southwestern Gotland : A Survey in GIS and Bedrock Geology

Andersson, Colin, Hoset, Andreas January 2021 (has links)
Southwestern Gotland has a relatively diverse bedrock where both sandstone, limestone and marl areexposed. The purpose of the survey has been to investigate differences in coastal erosion regarding thecontent of the bedrock. This was done by taking samples from 9 different locations which were laterexamined in point load tests and a slake durability test. A GIS-analysis was also done where the coastalarea in old aerial images and modern orthophotos were compared. The results showed that the sandstoneand marl samples were approximately equally prone to break and that limestone was less prone. Theslake durability test showed that sandstone from one site had the least resistance to abrasion, sandstonefrom the marl areas had greater resistance and that the limestone area had marginally greater resistancethan the marl areas. The GIS analysis indicated that the sandstone and marl areas had a relatively highsensitivity to coastal erosion and that the limestone area was not particularly exposed to coastal erosion. / Sydvästra Gotland har en relativt mångfaldig berggrund där både sandsten, kalksten och märgelstenexponeras. Arbetets syfte har varit att undersöka skillnader i kusterosion med avseende på berggrundensinnehåll. Detta utfördes genom att ta prov från 9 olika lokaler som senare undersöktes i punktlasttestoch nötningstest. En GIS-analys utfördes även där kustområdet i äldre flygfoton och modernaortofotona jämfördes. Resultatet indikerade att sandstens- och märgelstensproverna hade ungefärligenlika stor benägenhet att brytas och att kalksten har mindre benägenhet. Nötningstester visade attsandsten från en lokal hade minst motståndskraft mot nötning, att sandsten från märgelstensområdenahade större motståndskraft och att kalkstensområdet hade marginellt större än märgelstensområdena.Enligt GIS-analysen hade sandstens- och märgelstensområdena en relativt stor känslighet förkusterosion och att kalkstensområdet inte var särskilt utsatt för kusterosion.
203

A New Species of Ceratogaulus From Nebraska and the Evolution of Nasal Horns in Mylagaulidae (Mammalia, Rodentia, Aplodontioidea)

Calede, Jonathan J.M., Samuels, Joshua X. 01 September 2020 (has links)
Members of the Mylagaulidae have been known for over a century to bear nasal horns; the only rodents, extinct or extant, ever to have done so. This striking feature is known from five of the over 30 species of mylagaulid rodents discovered across North America and Eurasia, all relatively large animals that were likely less fossorial than their relatives. We describe herein a sixth new species of horned mylagaulid. This new taxon from Sioux County, Nebraska, offers the opportunity to reassess the phylogenetic relationships of Mylagaulidae and test several evolutionary hypotheses. Our analyses demonstrate that horns evolved only once in Mylagaulidae, in the common ancestor of Ceratogaulus, first as short horns exapted from the thickened nasals of fossorial ancestors, and later as taller horns. The horns evolved following a positive allometric scaling with body mass that suggests a response to predation pressure in these nearly blind animals. The evolution of tall horns also corresponds to a jump in body mass. The largest mylagaulids are not horn-bearing species, however. Additional analyses of the complex pattern of body mass evolution we reveal will be necessary to explain the evolution of the largest head-lift digging rodents in Earth history. https://zoobank.org/urn:lsid:zoobank.org:pub:81FE999A-F79E-4BD4-9A81-2C7D3D5D81CD.
204

Community Preparedness for Volcanic Hazards at Mount Rainier, USA

Vinnell, Lauren J., Hudson-Doyle, Emma E., Johnston, David M., Becker, Julia S., Kaiser, Lucy, Lindell, Michael K., Bostrom, Ann, Gregg, Chris, Dixon, Maximilian, Terbush, Brian 01 December 2021 (has links)
Lahars pose a significant risk to communities, particularly those living near snow-capped volcanoes. Flows of mud and debris, typically but not necessarily triggered by volcanic activity, can have huge impacts, such as those seen at Nevado Del Ruiz, Colombia, in 1985 which led to the loss of over 23,000 lives and destroyed an entire town. We surveyed communities around Mount Rainier, Washington, United States, where over 150,000 people are at risk from lahar impacts. We explored how factors including demographics, social effects such as perceptions of community preparedness, evacuation drills, and cognitive factors such as risk perception and self-efficacy relate to preparedness when living within or nearby a volcanic hazard zone. Key findings include: women have stronger intentions to prepare but see themselves as less prepared than men; those who neither live nor work in a lahar hazard zone were more likely to have an emergency kit and to see themselves as more prepared; those who will need help to evacuate see the risk as lower but feel less prepared; those who think their community and officials are more prepared feel more prepared themselves; and benefits of evacuation drills and testing evacuation routes including stronger intentions to evacuate using an encouraged method and higher self-efficacy. We make a number of recommendations based on these findings including the critical practice of regular evacuation drills and the importance of ongoing messaging that focuses on appropriate ways to evacuate as well as the careful recommendation for residents to identify alternative unofficial evacuation routes.
205

Evaluating Spatial Regression-Informed Cokriging of Metals in Soils Near Abandoned Mines in Bumpus Cove, Tennessee, USA

Magno, Melissa, Luffman, Ingrid, Nandi, Arpita 01 November 2021 (has links)
Inorganic contaminants, including potentially toxic metals (PTMs), originating from un-reclaimed abandoned mine areas may accumulate in soils and present significant distress to environmental and public health. The ability to generate realistic spatial distribution models of such contamination is important for risk assessment and remedial planning of sites where this has oc-curred. This study evaluated the prediction accuracy of optimized ordinary kriging compared to spatial regression-informed cokriging for PTMs (Zn, Mn, Cu, Pb, and Cd) in soils near abandoned mines in Bumpus Cove, Tennessee, USA. Cokriging variables and neighborhood sizes were system-atically selected from prior statistical analyses based on the association with PTM transport and soil physico-chemical properties (soil texture, moisture content, bulk density, pH, cation exchange capacity (CEC), and total organic carbon (TOC)). A log transform was applied to fit the frequency histograms to a normal distribution. Superior models were chosen based on six diagnostics (ME, RMS, MES, RMSS, ASE, and ASE-RMS), which produced mixed results. Cokriging models were preferred for Mn, Zn, Cu, and Cd, whereas ordinary kriging yielded better model results for Pb. This study determined that the preliminary process of developing spatial regression models, thus enabling the selection of contributing soil properties, can improve the interpolation accuracy of PTMs in abandoned mine sites.
206

Geophysical Survey Techniques

Ernenwein, Eileen G. 01 May 2023 (has links)
Book summary: In the newly revised Second Edition of the Handbook of Archaeological Sciences, a team of more than 100 researchers delivers a comprehensive and accessible overview of modern methods used in the archaeological sciences. The book covers all relevant approaches to obtaining and analyzing archaeological data, including dating methods, quaternary paleoenvironments, human bioarchaeology, biomolecular archaeology and archaeogenetics, resource exploitation, archaeological prospection, and assessing the decay and conservation of specimens [...]
207

What Do We Gain From High-rate Digital Stacking?

Kruske, Montana L., Ernenwein, Eileen G. 01 June 2020 (has links)
Ground penetrating radar (GPR) is limited by the depth of penetration and signal-to-noise ratio (SNR), which both impact the ability to resolve subsurface features. GPR antennas are known to have limited depth penetration due to the noise and signal attenuated. The noise floor is the depth at which there is no discernable signal (Stec and Susek 2018). SNR is the comparison of desired signal to background noise, understanding that noise is any unwanted signal. Different objects in the environment can transmit frequencies that are recorded in data as background noise; this noise is considered to be external noise. Internal noise is noise which is generated by the internal components of the GPR system. Data processing such as filtering can reduce noise. Noise that occurs at the same frequency as the signal of interest, however, cannot be filtered out without also removing the signal of interest.
208

Acervos que escrevem a história: a trajetória do Museu de Geociências do IGc-USP contada pelas suas coleções / Collections that tell history: the trajectory of Museum of Geosciences of USP told by its collections.

Azevedo, Miriam Della Posta de 17 August 2018 (has links)
Este trabalho compreende um estudo sobre utilização de coleções museológicas para a composição de trajetórias históricas institucionais, mais especificamente, coleções geológicas e a recomposição da trajetória institucional do Museu de Geociências do Instituto de Geociências da Universidade de São Paulo. O uso de coleções como fonte primária é uma tendência internacional nos estudos sobre História da Ciência, mas no Brasil ainda é pouco explorado. O presente estudo é dividido em quatro partes, que versam sobre a importância do estudo das coleções para as Ciências da Terra, apresentação de metodologias sobre o uso de coleções como fontes documentais e descrição das coleções do Museu de Geociências da USP, recuperando assim sua trajetória histórica. O objetivo dessa pesquisa é criar instrumentos para que os acervos de unidade de ensino da USP (com atividades museológicas, porém que não são considerados museus pelo Estatuto da Universidade de São Paulo), semelhantes ao Museu de Geociências no tocante à constituição de seus acervos, possam recuperar seus processos de formação, enxergando seus acervos também como fontes históricas. Com o estudo de uma das partes, o Museu de Geociências do IGc-USP, é possível colaborar para um estudo do todo universitário, no que diz respeito à formação das coleções em posse da USP, cuja variedade de patrimônios científicos é metodologicamente pouco explorada. Conhecer a história desses acervos é conhecer e respeitar a história da própria Universidade de São Paulo. / This work comprises a study on the use of museological collections for the composition of historical institutional events, more specifically, geological collections and a reconstitution of the institutional trajectory of the Museum of Geosciences of the Institute of Geosciences of the University of São Paulo. The use of collections as a primary source is an international trend in studies on the History of Science, but in Brazil it is still little explored. The current study is divided in four parts that deal with the importance of the study of collections for the Earth Sciences, presentation of tools on the use of sources as documents and description of the collections of the Museum of Geosciences of USP, thus recovering its trajectory. The purpose of this research is to create instruments for the other collections of the University of São Paulo, along with the Museum of Geosciences in relation to the constitution of their collections, the use of their training processes, viewing their collections as historical sources. With the study of one of the parts of the USP - the Museum of Geosciences of the IGC-USP - it is possible to collaborate in the study of the entire university, regarding to the formation of collections in the variety of USP faculties and graduation courses. Getting in touch with history of USP Collections is getting to know and respect the history of the University of São Paulo.
209

Expanding the pathway: The role of a residential STEM program for high school students in shifting perceptions and personal relevance of scientists and science

Carlton, Caleb 30 April 2021 (has links)
STEM (Science, Technology, Engineering, and Mathematics) academic programs and career fields continue to lack representation among females and minorities. STEM learning programs that engage youth in culturally relevant and personally meaningful experiences in STEM have been shown to develop participant self-concept as a scientist, as well as increase interest in related careers. This study uses the Draw-a-Scientist Checklist (DAST-C) instrument, as well as the Draw-a-Scientist Growth (DAST-G) instrument, which was developed and implemented by the author as part of this research. The DAST-C and DAST-G instruments were used to examine the science-related perceptions of youth before and after participation in a residential STEM geosciences program. An analysis found that the program produced statistically significant (p<.05) reductions to the DAST-C scientist stereotype scores in all twelve cycles of the program between 2018 and 2019, and statistically significant gains to the DAST-G scientist perception growth scores in eleven of the cycles.
210

Case Studies on Fractal and Topological Analyses of Geographic Features Regarding Scale Issues

Ren, Zheng January 2017 (has links)
Scale is an essential notion in geography and geographic information science (GIScience). However, the complex concepts of scale and traditional Euclidean geometric thinking have created tremendous confusion and uncertainty. Traditional Euclidean geometry uses absolute size, regular shape and direction to describe our surrounding geographic features. In this context, different measuring scales will affect the results of geospatial analysis. For example, if we want to measure the length of a coastline, its length will be different using different measuring scales. Fractal geometry indicates that most geographic features are not measurable because of their fractal nature. In order to deal with such scale issues, the topological and scaling analyses are introduced. They focus on the relationships between geographic features instead of geometric measurements such as length, area and slope. The scale change will affect the geometric measurements such as length and area but will not affect the topological measurements such as connectivity.   This study uses three case studies to demonstrate the scale issues of geographic features though fractal analyses. The first case illustrates that the length of the British coastline is fractal and scale-dependent. The length of the British coastline increases with the decreased measuring scale. The yardstick fractal dimension of the British coastline was also calculated. The second case demonstrates that the areal geographic features such as British island are also scale-dependent in terms of area. The box-counting fractal dimension, as an important parameter in fractal analysis, was also calculated. The third case focuses on the scale effects on elevation and the slope of the terrain surface. The relationship between slope value and resolution in this case is not as simple as in the other two cases. The flat and fluctuated areas generate different results. These three cases all show the fractal nature of the geographic features and indicate the fallacies of scale existing in geography. Accordingly, the fourth case tries to exemplify how topological and scaling analyses can be used to deal with such unsolvable scale issues. The fourth case analyzes the London OpenStreetMap (OSM) streets in a topological approach to reveal the scaling or fractal property of street networks. The fourth case further investigates the ability of the topological metric to predict Twitter user’s presence. The correlation between number of tweets and connectivity of London named natural streets is relatively high and the coefficient of determination r2 is 0.5083.   Regarding scale issues in geography, the specific technology or method to handle the scale issues arising from the fractal essence of the geographic features does not matter. Instead, the mindset of shifting from traditional Euclidean thinking to novel fractal thinking in the field of GIScience is more important. The first three cases revealed the scale issues of geographic features under the Euclidean thinking. The fourth case proved that topological analysis can deal with such scale issues under fractal way of thinking. With development of data acquisition technologies, the data itself becomes more complex than ever before. Fractal thinking effectively describes the characteristics of geographic big data across all scales. It also overcomes the drawbacks of traditional Euclidean thinking and provides deeper insights for GIScience research in the big data era.

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