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A review of characteristics influencing lake mercury dynamics, and drivers of variation in mercury concentration within stocked lake fish
No full textMercury (Hg) is a pollutant released naturally and anthropogenically, depositing in waterways, where it accumulates in organisms such as plants and animals. Above certain concentrations, Hg causes health, particularly neurological, effects. Within my thesis, I addressed knowledge gaps in Hg dynamics within lake food webs. In the first chapter, I conducted a literature review on how characteristics such as elevation or pH, climate stressors, and mitigation techniques influence Hg food web dynamics in lakes. I compiled information from scientific journal articles, and ran statistical analyses to assess whether lake characteristics were significant predictors of Hg biomagnification within food webs. I found that no single variable was strongly correlated with TMS or TMF within lakes. Additionally, I found that environmental stressors have complicated influences on Hg cycling, which can increase or decrease Hg biomagnification within lake food webs. Fortunately, mitigation techniques approach water systems from various angles such as lake water and sediment, fish stocking, and industrial activities.
In the second chapter, I narrowed the focus of study to one lake. I investigated total Hg (THg) dynamics within the food web of Benka Lake, a stocked lake in subarctic Alaska, USA, and I studied drivers of variation within rainbow trout (Oncorhynchus mykiss) in Benka Lake. I used a dataset with information on fish THg concentrations and other variables. I ran univariate statistical analyses to assess whether variables such as length, age, stable isotope ratios, and collection date were significant predictors of THg concentration in individual rainbow trout. I found that standard length and length:age ratio were positively correlated with THg concentration in rainbow trout, while carbon isotope ratio was negatively correlated with THg concentration in rainbow trout
Patient-specific modeling of the biomechanics of vulnerable coronary artery plaques
Get PDFCoronary artery atherosclerosis is a local, multifactorial, complex disease, and the leading cause of death in the US. Complex interactions between biochemical transport and biomechanical forces influence disease growth. Wall shear stress (WSS) affects coronary artery atherosclerosis by inducing endothelial cell mechanotransduction and by controlling the near- wall transport processes involved in atherosclerosis. The current management guidelines for detection of atherosclerotic plaques focus on morphological characterizations and the blockage percentage of the stenosis based on coronary computed tomography angiography (CCTA). Despite the progress achieved in therapeutics, the relation between hemodynamic environment and the composition of atherosclerotic plaques remains unexplored. This dissertation is divided into two main sections: the association between hemodynamics/biotransport and longitudinal changes in the plaque vulnerability characteristics and developing a 1D automatic vascular network generation package with the ability to be coupled with a 3D patient-specific model.
Biochemical-specific mass transport models were developed to study low-density lipoprotein, nitric oxide, adenosine triphosphate, oxygen, monocyte chemoattractant protein-1, and monocyte transport. The transport results were compared with WSS vectors and WSS Lagrangian coherent structures (WSS LCS). High WSS magnitude protected against atherosclerosis by increasing the production or flux of atheroprotective biochemicals and decreasing the near-wall localization of atherogenic biochemicals. Low WSS magnitude promoted atherosclerosis by increasing atherogenic biochemical localization.
To find the association between hemodynamics/biotransport and longitudinal changes in the atherosclerotic plaque characteristics, a plaque quantification software was developed with the aim of performing a segment-specific assessment to accurately calculate the volumes of low attenuation plaque (LAP), fibrous plaque (FP), calcium plaque (CP), and vessel wall and identify the quantitative plaque characteristics including spotty calcification, presence of napkin-ring sign, and positive remodeling. The changes in the different plaque characteristics were compared against the hemodynamic/biotransport parameters. The results showed that WSS magnitude is moderately correlated with the longitudinal changes in LAP, FP, and vessel wall volumes. Also, WSS magnitude and local concentration of nitric oxide (NO) showed a meaningful correlation with the presence of positive remodeling in the follow-up.
A hybrid 1D-3D solver was developed in Simvascular software and validated against the existing data in the literature. The results of our coupled 1D-3D solver showed a good agreement with the 3D, deformable wall models. This solver can be used to solve the blood flow in a large network of 1D vessels coupled with a patient-specific 3D model. Finally, an automatic vascular network generation framework was developed using the Constraint Constructive Optimization (CCO) algorithm to study the generation of arterial trees based on theoretical perfusion maps. The algorithm simulated angiogenesis by optimizing the total vessel volume governed by physiological and geometrical constraints
Constraining planet location through gravitational modeling
Get PDFThroughout history, tracking the location of planets has been at the forefront of astronomy. Modern computational resources allow for extreme precision in tracking planets and other objects through their orbits with the use of gravitational modeling. The classical planets in the solar system have well-known orbits, but there are several types of planets that require further orbital analysis in order to develop a solid understanding of these worlds and their impact on the solar system and beyond.
In this dissertation we discuss our efforts to gravitationally model three separate systems. The first of these is the relationship between a hypothetical distant giant planet in the outer reaches of our solar system and the distant objects that provide evidence for its existence. This population of distant dwarf planets has orbits that are clustered together in a way that is suggestive of another large planet, which we refer to in this work as Planet X, orbiting beyond Neptune. Here we explore another orbital feature related to these objects, a gap between two sub-populations of distant dwarf planets that cannot form under the gravitational influence of the known planets alone. By including Planet X in the solar system, we show that both the gap and this population of distant objects are formed naturally over the age of the solar system.
The second group of systems analyzed in this work centers on exoplanets, planets orbiting other stars. One major challenge for direct imaging studies of exoplanets is the large amount of telescope observation time that must be allocated to orbit determination. We have developed a method for reducing the telescope observing time required to determine the orbits of these exoplanets by reducing the number of revisit observations required to constrain directly imaged exoplanet orbits. This will allow for a sizeable fraction of observing time to be repurposed for further study of the surfaces and atmospheres of these worlds.
Our final study is focused on a minor planet in the solar system, 282P. This object shows signs of comet-like activity and it clearly has close encounters with Jupiter both in the last few hundred years, and in the next few hundred as well. These close approaches cause the orbit of 282P to be chaotic beyond the time of these encounters, so we employ statistical techniques to determine likely outcomes and histories of 282P. We find that 282P is in the Quasi-Hilda region, which likely serves as an intermediate zone between comets and active asteroids.
These related projects all focus on constraining the orbital parameters of the planet in question in order to better understand the system as a whole. By improving our understanding of the gravitational influence exerted by and on these bodies, we can develop a more complete picture of the formation, composition, and evolution of the solar system and other planetary systems as well
A mixed method evaluation of a culturally grounded after-school arts intervention on Native youth
No full textA critical component of resilience for many Native American communities is their ability to sustain their culture and identity through deep connections with homelands, Native language, ceremonial practices, and tribal communities. Native American youth living off of tribal lands, often in urban regions, are faced with unique pressure to negotiate and adapt their culture and values while navigating nonnative settings. After-school programming centering Native culture has shown promise in strengthening Native youth resilience, yet few empirically based prevention programs exist, especially programming using developmentally appropriately art programming. To address the lack of empirical evidence for the use of culturally grounded after-school art programming for Native American youth living in urban areas, the current study will extend an earlier pilot study (Pepić et al., 2022) by using a mixed-methods design across three time points to evaluate the impact of a virtual culturally oriented art therapy curriculum on youth resilience, perceived stress, connection to culture, and mood while considering coronavirus pandemic related fears and experiences. No statistically significant results were found across time points, although qualitative results indicated individual, cultural, and ecological protective factors for Native resilience. The results of this study provide examples of how culturally centered Native after school programming can provide protective factors for Native American youth living in urban settings, but also highlight stories of resilience for youth navigating challenging pandemic times
Protected areas conserved forests from fire and deforestation in Vietnam’s central highlands: 2001-2020
No full textNature conservation and poverty alleviation should not be mutually exclusive. REDD+ is a United Nations initiative that was designed to facilitate payments from wealthy to developing countries for forest protection and carbon monitoring. As one of the first UN-REDD partner countries, case studies from Vietnam’s REDD+ pilot programs can give insights of common successes and failures, to guide future program success. We searched for REDD+ case studies from Vietnam in Open-Access journals and reviewed six REDD+ case studies from five provinces. We analyzed REDD+ applications funded by USAID, UN-REDD Programme and NGO operations. In our review, we found illegal logging and agricultural conversion were two major drivers of deforestation and degradation in Vietnam. Additionally, we compared payments from REDD+ to the opportunity cost to prevent deforestation from timber exploitation or agricultural land use. Although Vietnam’s REDD+ programs have garnered millions of US dollars in support, there was a large gap in funds paid to voluntary participants of REDD+, thereby compromising the long-term sustainability and support of the system. Future initiatives should take a bottom-up approach to address the root drivers of poverty, rather than a top-down approach that prioritizes carbon benefits to wealthy countries and has been plagued by elite-capture in developing nations. Knowledge co-production with local and indigenous communities can improve the success of REDD+ projects by including marginalized and vulnerable communities. As a biodiversity hotspot with ~40% forested land area and 290 protected areas, Vietnam is a global conservation priority. Vietnam’s forests have faced a complex history of change, including anthropogenic impacts from warfare, development, and global warming. Vietnam is one of few tropical countries to reverse trends in forest loss, has shown a net gain in forest cover since the 1990s, and was one of the first countries to take part in UN-REDD programs. However, a considerable amount of Vietnam’s forest gain has been from plantation forestry, as Vietnam’s policy has promoted economic development to support the population. Natural resource intensification, expansion, and residential development in the historically agrarian Central Highlands region has favored forest conversion to croplands and timber plantations. We selected a key region of the Central Highlands to ask four questions in our study: (1) How has forest cover changed in the Da Lat Plateau from 2001-2020? (2) How has fire affected the same landscape? (3) How are forest loss and fire linked spatially and temporally? And (4) how do these patterns vary between areas with legal protection status and those without? To answer these questions, we integrated the Global Forest Change (Hansen et al., 2013) and FIRED VIETNAM datasets (Balch et al., 2020; Mahood et al., 2022) to investigate forest cover change, fire, and fire-linked deforestation in the region from 2001-2020. Our study area is 1,524,783 ha near the Da Lat Plateau and roughly equivalent areas of legally protected areas (802,791 ha) and surrounding landscape (721,992 ha) without formal protection status. We used five spatial categories for analysis: Cat Tien National Park, Bidoup Nui-Ba N.P., Dong Nai Biosphere Reserve, the total area of smaller protected areas, and the land matrix outside protected areas. Between 2001 and 2020, 3,794 fires burned 132,216 ha (8.7% total area), and 208,356 ha of deforestation occurred (13.6% total area). Nearly half of all fires overlapped with forest loss in the same year, but fire-linked deforestation only accounted for 6,692 ha, 3.2% forest loss, and 0.4% of the study area. Fifty-four percent of fire-linked deforestation occurred in natural forests and 46% in plantations. Fire ignitions were almost exclusively in the regional dry season, December to April. Long-term climate data, 1971-2020, showed statistically significant increasing trends in minimum, mean, and maximum temperatures. However, the total area burned does not show significant increasing trends between 2001-2020 or from 2001 to the peak in 2010. Between 2001 to 2020, 70% of fires, 57% of forest loss, and 74% of fire-linked forests occurred outside formally protected areas. Overall, protected areas in the Central Highlands have effectively achieved national and international conservation goals, while adjacent land use and land cover change contributed to Vietnam’s development
Examining Mars, near and far: using rover and orbiter data to constrain ancient histories of Mars
No full textSedimentary structures are incredibly useful in planetary studies as their characteristics are diagnostic of the environmental conditions experienced during their formation. The effects of water and climate on a surface are intricately recorded in their morphology, composition, and thermophysical character. Observations from orbiting spacecraft, landers, and rovers are critical in elucidating how we view planetary surfaces beyond our own. This dissertation utilizes passive remote sensing techniques, computational modeling, and geologic analyses to determine the evolution of surfaces and surface features on Mars. We used a wide variety of instruments and techniques to successfully constrain surface conditions and environments on ancient Mars. We accomplished this by first characterizing the thermophysical and compositional properties of a class of ancient, lithified sedimentary structures – or paleobedforms – found across Mars. We determined paleobedforms on Mars likely formed in an environment with low water-rock ratio by applying cement volume modeling to each paleobedform site. During this study we generated a novel technique to determine the thermophysical heterogeneity of planetary surfaces. We built on this study by conducting a ground truth experiment in which we applied the novel technique to rover observations at the Mars Science Laboratory landing site in Gale crater. During this ground truth experiment we characterized the thermophysical properties of a feature known as the Greenheugh pediment, the surface of which is a candidate paleobedform field. This characterization sheds light on the environmental conditions during a potentially life-sustaining period on Mars. Finally, we continue to build on our work by using all previously established remote sensing and computational techniques to determine the influence of regional geology on the fluvial history of a unique valley network on Mars called Licus Vallis. This region was investigated through geologic mapping, incorporating both thermal and visible datasets, to determine why Licus Vallis has uniquely preserved fluvial terraces. We discovered prolonged overland flow was required to explain the geomorphology and thermophysical properties of Licus Vallis, indicating more water in the region than previously suggested
The COVID-19 pandemic and social-emotional learning in Arizona elementary schools
No full textThe COVID-19 pandemic has caused schools to close in an effort to prevent the further spread of the disease. This has impacted teachers and students around the world. This mixed-methods research study examines if social and emotional learning has a statistically significant relationship between teachers’ participation in SEL training and teachers’ self-reporting regarding their social and emotional competencies; the relationship between teachers’ experience and teachers’ self-reporting regarding their social and emotional competencies; and teachers’ perceptions of students’ social and emotional wellbeing following the global pandemic
Maximum Entropy Predictive Modeling of Open-Air Basketmaker II Sites on Black Mesa and the Grand Staircase-Escalante National Monument
Get PDFUsing Lolomai phase, open-air Basketmaker II archaeological site locations and environmental variables representing resource distribution, climate, and landscape, I created a predictive model for Early Agricultural period cultural manifestations on Black Mesa in northeastern Arizona. I project the Black Mesa model to the Grand Staircase-Escalante National Monument region in southern Utah to locate high probability areas that are likely to contain Early Agricultural period cultural manifestations. The sites used in this pilot project were identified and recorded during the Black Mesa Archaeological Project and represent the most complete set of open-air Basketmaker II sites in the Southwest. Environmental data include relatively standard data sets used extensively in predictive modeling throughout the world. I use geographic information system software and MaxEnt software to create the predictive model. Maximum entropy modeling has been used extensively to model the distribution of species in ecology and is ideal for archaeological data. While the technique has not been used extensively in an archaeological context, maximum entropy modeling has been shown to be the best approach for modeling archaeological data. This pilot project adds to the predictive modeling literature with the ultimate goal of preserving cultural resources and adding to archaeologists’ understanding of the past
On the discourse of activism: the Navajo Vietnam veteran and The Navajo Times
No full textThis thesis examines the role that activism by the Navajo Vietnam veteran and The Navajo Times has had in creating a historical discontinuity in the dynamics of the relationship between white, Western culture and the culture of Navajo society. It situates the Navajo Vietnam veteran and The Navajo Times in the midst of this process by highlighting both of their contributions to the politics of activism. It also traces the exposure that the Navajo Vietnam veteran has received in the Navajo Times from 1962 to 2016. This exposure ranges from the early years of the Vietnam war, the “In Country,” period, 1962 to1975, through “Back to the World,” period from 1975 to 1984, to the period of “Recognition and Demanding Their Rights,” from 1985 to 2016. The roles of both the Navajo Vietnam veteran and The Navajo Times are examined in detail in Chapter 4; Content Analysis: The Navajo Times.
Theoretically, this thesis starts with the hegemony that white, Western culture enjoyed over Navajo culture in the late 1950s and early 1960s. This is exemplified by the coverage that Navajo Vietnam veterans had during the early years of the war. Their voices were minimalized, at least until 1968, when dissent about the war became evident in the Navajo Times.
This thesis also covers the transition in The Navajo Times between the 1980s and 2016, after the war in Vietnam, when the voice of the Navajo Vietnam veteran becomes activated and gained the support of reporters from The Navajo Times. The content analysis methodology employed in this thesis allows for both quantitative and qualitative analysis of the coverage contained in The Navajo Times. It covers such issues as Agent Orange, PTSD, the POW and MIA, legislative responses to the Navajo Vietnam veteran and his activism, medals received by veterans during the war, ceremony, the Vietnam Veterans Memorial, the Run for the Wall, and activism and the Veteran’s Administration.
The thesis concludes with a discussion of the concepts of colonization, discontinuity, and hegemony. It looks at the important role that the discourse of activism of the Navajo Vietnam veteran and the Navajo people as presented in The Navajo Times in countering the hegemonic view of the dominant culture. Finally, new concerns have been raised in the process of this research. I elaborate on them in the last section of this thesis called: Implications for Further Research
Synergistic interactions of ecosystem stressors and mitigation by mycorrhizal fungi on the foundation species, Fremont cottonwood
Get PDFThe combined ecological stressors of climate change and invasive species are threatening native ecosystems, each independently and may interact in unpredictable ways. My greenhouse study examined the potentially synergistic interaction of climate change and invasive species legacy soil on the fitness and performance of a foundation tree species in the threatened riparian ecosystems in the southwestern United States. I also examine methods for improving restoration outcomes for the foundation tree species, Fremont cottonwood (Populus fremontii), when planted in invasive tamarisk (Tamarix spp.). The first study found that increased temperature and invasive tamarisk legacy soils had a synergetic negative interaction on cottonwood survivorship, but a positive synergistic interaction on cottonwood root investment. Root investment typically positively correlates with fitness in arid environments; therefore, the combination of higher temperatures and tamarisk legacy soil may allow surviving cottonwoods to perform well in these novel environmental conditions. The second study found that the addition of whole soil inoculum, including important root symbionts known as mycorrhizal fungi, from a nearby reference site increased cottonwood dry biomass by 45% compared to those given sterile inoculum and increased mycorrhizal colonization by 53%. I found that cottonwoods from sites with co-occurring tamarisk (experienced) showed better performance than cottonwoods from sites without tamarisk (naïve) when grown in tamarisk legacy soil. However, when given live whole soil inoculum from a reference site, there were no longer differences between experienced and naïve cottonwoods. Although I expected to see experienced cottonwoods respond less to inoculation than naïve cottonwoods, I found no difference. I was surprised to find that cottonwoods, independent of source, responded more positively to inoculation when grown in tamarisk legacy soil than in agricultural legacy soil. The results from this greenhouse study suggest that Fremont cottonwood restored in tamarisk legacy soil will show increased root investment, especially when given whole soil inoculum from a reference site, which may make them better suited to the increasing aridity in the American southwest due to climate change