1925 research outputs found
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Field data analysis, laboratory experimentation, and mapping Cassini radar images to characterize fluvial sediments on Titan
No full textThe icy surface of Saturn’s largest moon, Titan, has been modified by fluvial processes, as evidenced in flyby radar images from the Cassini spacecraft and near-surface images from the Huygens lander. Some features interpreted as gravel-bed braided rivers on Titan exhibit anomalously high radar backscatter, which may be due to the particular size, shape, and distribution of rounded fluvial sediments. In this dissertation, I characterize fluvial sediment on Titan and related processes by exploring the sedimentological controls on radar backscatter using ground truth for Earth-observing radar images, tracking the evolution of icy clasts in Titan-analog abrasion mill experiments, and assessing downstream variations in radar backscatter in Titan’s fluvial features that may indicate sedimentary processes.
To provide ground truth for a coarse-grained sedimentary environment, sediment properties were measured at field sites on alluvial fans in the Mojave Desert. These hand measurements were compared to radar backscatter at C-band (λ = 5.6 cm) and L-band (λ = 23.5 cm) wavelengths to find strong correlations with median grain size, and little or no effect from shape or sorting. Differences with expectations from theoretical models support the importance of empirical evaluations.
To observe how sediment properties may change in transport on Titan, water ice clasts were tumbled at cryogenic temperatures. The measured abrasion rates are comparable to that of weak terrestrial materials and rounding occurs very rapidly, indicating that clast comminution may occur over comparatively short distances on Titan. The dominance of fragmentation over attrition produces relatively few fine particles, suggesting fluvial abrasion is unlikely to be a significant source of Titan’s dune sands.
The field study of radar backscatter and laboratory tests of fluvial abrasion are synthesized to assist interpretation of backscatter variations occurring in Titan’s radar-bright fluvial features. The measured backscatter trends are frequently found to be non-monotonic, both increasing and decreasing over a feature’s length, in contrast to the steady decrease in backscatter expected for simple downstream fining. Causes for local variation are explored and a typical fining rate is proposed that is most consistent with the lowest abrasion rates of the Titan Tumbler, indicating Earth-like downstream fining that may be explained by fluvial sediment more durable than pure water ice
Simulator-based training for logging equipment operators
No full textLogging equipment simulators offer opportunities for new operators to become familiar with operating logging machines as well as a promising solution to the high costs of training. These simulators are fairly new to the market, and we were unable to find much research regarding whether they can be effective training tools. In chapter one, we introduce the motivation behind the studies presented in this manuscript. In chapter two, we conduct a literature review with the goal of identifying effective ways to incorporate logging equipment simulators into an equipment operator training curriculum. While we were able to draw some important conclusions from the literature review, we found that no studies have directly quantified the extent to which skills transfer between simulated and real logging equipment. In chapter three, we present a summary of our controlled experiments to evaluate the effectiveness of simulator training compared to machine training for equipment operators in terms of operator performance, subjective operator experience, and cost effectiveness. In chapter four, we briefly summarize and synthesize what we learned in chapters two and three and discuss the broader impacts of the research completed for this thesis
Contextualizing attitudes, framing disability: Universal Design and structural violence through the lens of the Accessibility Expedition
Get PDFUsing a framework of structural violence (Farmer 2005), this thesis examines the ways in which the United States education system maintains stereotypical tropes about disability through enculturation (Spindler 1963, 1965). A lack of awareness and understanding of the cultural beliefs that create real barriers for disabled people is prevalent and replicated within our education system and larger society. I draw upon ideas of how disability and disabled people are viewed through two lenses borrowed from disability studies, the medical model and the social model (Linton 1998) and Universal Design. Finally, an intervention, the Accessibility Expedition is explained and discussed as a way to change attitudes toward disability by providing experiences that allow engagement with disabled people and encounters with the barriers cultural norms create for them
Navigating intergenerational ocean identity and well-being: third wave Kānaka `Ōiwi diaspora to the continental United States
No full textMy `ohana is a member of the third wave diasporic Kānaka `Ōiwi to the continental
United States. This study explores the stories of third wave diasporic Kānaka `Ōiwi as
they forge, cultivate, and create Indigenous spaces; foster and maintain `Ōiwi identities;
and remember and engage within cultural protocols and practices over generations
within their family system. The significance of the study documents the lived
experiences of third wave diasporic Kānaka `Ōiwi through the broader scope of
education: a`o- teaching and na`auao- learning, within the family system and the home
environment. Kūpuna- elders and mākua- parents/adults serve as the leaders, teachers,
guides to nā `ōpio children/youth essential for personal and cultural identity
formation. As time passes, the children mature and become mākua, the youth/students
become the next generation of alaka`i- leaders/teachers within the `ohana and greater
community. I center `ike kupuna- Kānaka `Ōiwi ancestral knowledge alongside of
Western scholarship and analyze data- stories with Indigenous Autoethnography,
Critical Kānaka Geographies, and Decolonizing Methodologies
Eau claire de la lune: clarifying the origin and distribution of water on the moon
No full textWater is an essential resource to life as we know it. On the Moon, water is scarce and should not be able to survive on its harsh airless surface. However, several spacecraft measurements and samples returned from the Moon indicate that water exists across the entire lunar surface. There is active debate surrounding the origin, location, and abundance of water on the Moon. Using a three-pronged approach centered on spacecraft observations and computational modeling, the work presented here seeks to answer fundamental questions about where water is found on the Moon and how it got there. One hypothesis suggests that water could be produced by space weathering, the combination of processes that alter the lunar surface due to its exposure to space. I use spacecraft imagery to investigate the rate of space weathering on the Moon to investigate it as a possible source of lunar hydration. I then test whether the spacecraft-observed widespread hydroxyl (OH) / water (H₂O) signature migrates across the surface daily. Finally, I update a simulation of ice delivery to the lunar polar regions to predict where and how deep ancient ice may be buried near the south pole. I find that space weathering alters the lunar surface at a predictable rate for the first 1 billion years of exposure to space. However, the widespread OH / H₂O signature is inherent, or develops on much shorter timescales, and I find no evidence of its daily migration. Finally, I show that the majority of ice that may be buried near the poles has likely been disrupted by impact events and that any remaining ice is most likely 10s to 100s of meters below the surface. I discuss these findings in the context of active and future lunar space exploration. With a new era of lunar exploration on the horizon, the three investigations herein provide key constraints on the origin and distribution of water on the Moon
Understanding and supporting women’s participation in open source software
No full textWomen represent less than 24% of employees in the software development industry and experience various types of prejudice and bias. Despite various efforts to increase diversity and multi-gendered participation, women are even more underrepresented in Open Source Software (OSS) projects. Many OSS communities are aware of the importance of correcting this imbalance and spend significant resources on a variety of onboarding and outreach programs targeted to women. However, these programs are insufficient if those who onboard do not feel that they belong to the community and ultimately abandon the project---a frequent occurrence in OSS. Previous research in psychology, health care, and education has shown that a sense of belonging is a basic human need that affects a broad variety of behaviors and has implications for long-term engagement and job satisfaction. Nevertheless, the investigation of a sense of belonging in OSS so far has been under-explored. It is still unclear what environmental factors contribute to a (lack of a) sense of belonging and how to improve it in practice. In my PhD, I investigate the following questions: How do women participate in OSS projects? How do different forces affect women’s participation in a large and community-oriented OSS project? I worked with the Linux Kernel managers on a case study that has the ultimate goal to increase women's participation. Some problems surpass the organization and are related to the local culture of the OSS communities. There are problems that go beyond the company's gates and permeate society, which often contributes to this cultural legacy. However, there is also space for improvement. The results of this research include a theoretical framework that describes open-source-specific factors that can impact women's participation in OSS projects
Action recognition in intelligent systems
No full textAction recognition is an emerging topic in artificial intelligence, which aims to automatically detect and recognize actions of human and intelligent nodes (vehicles, UAVs) by processing video recordings and data provided by other sensing platforms. Action recognition has been used in a wide range of applications including but not limited to surveillance systems, health-care, athlete training, human-computer interaction modeling, and autonomous vehicles. Action recognition, based on the utilized information acquisition method, can be categorized into three main areas: video-based, radar-based (node-based), and wearable-sensor-based action recognition. However, the definitions are not exclusive and these methods can be overlapping. Developed algorithms are diverse to meet the requirement and constraints of different applications. An important challenge is developing real-time action recognition, which can prohibitively increase the computational cost of the system. In addition, technical implementation challenges can be different in data acquisition based on the utilized platforms. In video-based action recognition, developing highly accurate algorithms requires accommodating different view angles, illumination conditions, camera motions, and background contrast. In the radar-based target tracking method, as an important variant of action recognition, the intrinsic variations among the motion patterns of different species should be taken into account by developing type-specific or customizable models. In wearable-sensor-based action recognition systems, the sensor position can be sensitive for different actions.
This project will mainly focus on these three types of action recognition. The aims of this project are developing efficient and fast algorithms for video-based action recognition in different applications, proposing a unified algorithm for radar-based action recognition, and developing novel architecture methods with higher accuracy for wearable-sensor-based action recognition
Formerly used defense sites on islands in the Bering Sea: hotspots of contamination and health risks to local communities and wildlife
Get PDFThe Arctic is an important indicator region for assessing properties and effects of persistent organic pollutants (POPs). The Arctic is subject to atmospheric deposition of globally distilled POPs, acting as a hemispheric sink for POPs that are transported from lower latitudes. Additionally, the Arctic contains thousands of contaminated formerly used defense (FUD) sites dating from World War II and the Cold War, many of which are co-located with rural communities and remain significant sources of POPs. The Arctic is therefore a repository of persistent chemicals that are readily transported through the atmosphere or that are released from FUD sites. Once POPs enter the Arctic, low temperatures and low intensity sunlight slow their deterioration, which makes them available for long-term incorporation into biological systems, especially in lipid-rich arctic food webs. As a result, concentrations of some POPs, including polychlorinated biphenyls (PCBs), in the blood of people in certain arctic regions continue to be higher than in general populations of North America and Europe. The Arctic is the home of many Indigenous peoples who rely on a traditional subsistence diet that includes a high proportion of lipid-rich foods such as fish and marine mammals; thus, they may be chronically exposed to dangerous levels of POPs. Because POPs are often endocrine disruptors, carcinogenic, and/or neurotoxic, exposures present important public health concerns for Arctic Indigenous Peoples. My dissertation research focused on health risks posed by FUD sites on Sivuqaq (St. Lawrence Island) and Unalaska Island, Alaska. These islands were used extensively by the U.S. military during WWII and the Cold War, and FUD sites on the islands may contribute to health disparities reported by residents, including high incidence of cancers, thyroid diseases, and reproductive disorders. My dissertation research on Sivuqaq followed a community-based participatory research (CBPR) approach and utilized sentinel fishes living near two FUD sites to examine contaminant concentrations and health effects at multiple levels of biological organization. My results demonstrate that FUD site contamination continues to pose a health risk to local wildlife and Sivuqaq residents despite large-scale remediation efforts. I found that PCB and Hg concentrations in a subsistence fish collected near the Northeast Cape FUD site exceed the Environmental Protection Agency’s regulatory guidelines for safe consumption of fish. I found differential expression of genes related to ribosomal and metabolic functions in sentinel fish collected near Sivuqaq FUD sites. At the Gambell FUD site, I demonstrated that ninespine stickleback exposed to FUD site contamination exhibit suppressed gonadal maturation and two distinct liver phenotypes, indicating that some fish may be more resistant to POP toxicity. On Unalaska Island, I modelled distributions of contaminants to identify hotspots of contamination at FUD sites remediated by the Army Corps of Engineers. I found that contaminant concentrations remain above state cleanup thresholds at more than half of Unalaska FUD sites and that the City of Unalaska is a pollution hotspot. Collectively, the results of my dissertation research demonstrate that Alaskan FUD sites continue to serve as point sources of pollution and potentiate the risk of disease for local wildlife and rural communities living near these sites
Caches in the court: the ideological significance of eccentric lithics from Ballcourt 2, Xunantunich
No full textXunantunich was a prominent Maya city in the Belize River Valley during the Late (600-800 AD) and Terminal (800-900 AD) Classic periods. Excavations in 2018 by the Xunantunich Archaeology and Conservation Project (XACP), a branch of the Belize Valley Archaeological Reconnaissance Project (BVAR), revealed a total of four caches containing over 80 eccentric lithics, three (3) stingray spines, several freshwater snail shells, and two (2) ceramic vessels, placed lip-to-lip, that were deposited along the playing alley of Ballcourt 2. Eccentric lithics are stone objects that the Classic Maya knapped into unusual, nonutilitarian forms. Their shapes represent human, animal and celestial figures and they are not used in domestic or utilitarian settings. This research analyzed the eccentrics and associated artifacts from the Ballcourt 2 caches to determine their ideological significance. My research provides evidence that the eccentrics at Ballcourt 2 were cached in groups of deified numbers, and were arranged as cosmograms, or physical and symbolic representations of the layout of the Maya universe. My research contends that eccentrics were important symbols that act as characters in retelling the story of the Maya cosmos, and that their purpose was to materialize concepts of Maya cosmology, religion, and political power into the physical world. The act of caching eccentrics provided life-sustaining substances to the monumental architecture under which they lay, protecting and memorializing them, connecting them to the past and present, and opening portals to the Otherworlds
Ecology and eco-physiology of mycorrhizal symbioses in arid riparian areas
Get PDFMy dissertation consists of three related research topics focused on translating previous research on mycorrhizal fungi into best practices for natural regeneration, replanting and habitat restoration. In the first chapter, I highlight the ecosystem services known to be provided by mycorrhizal fungi (symbiotic with plant roots), and examine whether utilization of diverse mixes of native mycorrhizal fungi, a potentially crucial tool in land managers’ toolboxes to alleviate restoration challenges, has made the translation from academia to restoration practice. In the second chapter, I examine crucial questions surrounding the need for restoring diverse mixes of native mycorrhizal fungi alongside plant communities, and the implications of research on the co-adaptation of mycorrhizal fungi with their symbiont plant hosts for assisted migration. In the final chapter, I investigate whether mycorrhizal restoration and assisted migration can be conducted successfully in tandem with mycorrhizal restoration under by conducting a common garden experiment with reciprocal plantings of local and migrant plant provenances and a migrant mycorrhizal inoculum treatment under harsh, post-Tamarix spp. (tamarisk) invasion and drought conditions.
In combination, these three chapters have built on previous research and advanced knowledge of the following. 1) Although the separate, intentional step of mycorrhizal restoration has been shown to have clear benefits if conducted appropriately, and mycorrhizae clearly support many ecosystem services that are often part of the goals of land management plans, they are still overwhelmingly left out of management planning. 2) Even under ideal circumstances with adjacent natural sources, natural regeneration two-years post planting fails to achieve ectomycorrhizal colonization rates similar to that in natural tree source populations after agricultural disturbance. 3) Natural regeneration of local mycorrhizal colonization is poorer in assisted migrant plant provenances, and concurrent with trends in other ecotype differences such as survival and growth. 4) Under multiple stressors in the field, assisted migrant plant provenances given an appropriate mycorrhizal inoculum can survive at higher rates than local plant provenances. 5) Inoculation with a contrasting ecotype’s live mycorrhizae can have neutral to negative effects that interact with site conditions. 6) The afterlife of an invasive species in the soil once the invasive plants have been removed can have dire consequences for native plants after restoration. Below is a summary of each of the three chapters.
Chapter 1: During the coming decade, planting material shortages are expected to constrain restoration. Climate change will reduce recruitment and exacerbate the need for restoration and natural regeneration. Concurrently, research shows that native mycorrhizal fungi optimized to plant provenance and site conditions significantly and meaningfully accelerate restoration, support crucial ecosystem services, and provide natural climate solutions (sequestering carbon), and nature-based solutions for climate change (providing climate adaptation). We reviewed 130 systematically available management plans for natural areas in the United States to evaluate whether the science-based innovation of restoring native mycorrhizal communities has translated into implementation. Results are notable: management plans frequently discussed the ecosystem services mycorrhizal fungi provide, but nearly one half (46%) viewed fungi solely as pathogens or ignored them altogether. Only 8% of plans mentioned mycorrhizae. Only one plan mentioned that mycorrhizae were potentially helpful to natural regeneration, and one mentioned utilizing soil as a restoration tool. Our examination of publicly available data and case studies suggests that relatively meager protections and research funding, research difficulty and data paucity, and limited access to mycology experts and training characterize this gap between science and implementation. A database of literature showcasing mycorrhizal ecosystem services and benefits is provided to highlight when and why mycorrhizae should be considered in management, regeneration, and restoration. Three action items are recommended to safeguard native mycorrhizal communities and accelerate restoration and regeneration. Ten implementation tips based on scientific literature are provided to clarify the need and methods for mycorrhizal restoration.
Chapter 2: Many factors deplete and shift the mycorrhizal fungal communities upon which native plants depend, and consequently their often sizable and meaningful benefits to plant survival and growth, and a variety of ecosystem services. Yet, as the UN Decade on Ecosystem Restoration begins, active restoration of native mycorrhizal fungal communities is often overlooked as a strategy to enhance and sustain ecosystem restoration. Few studies focus specifically on implementation questions, such as the success and timeliness of natural mycorrhizal regeneration in disturbed soils and its effect on replanting success. Simultaneously, assisted migration of plant species or provenances has been suggested to hasten ecosystem climate change adaptations, but the consequences of assisted migration for mycorrhizal regeneration and associations remain poorly described. To determine the success of natural mycorrhizal regeneration, its interaction with plant provenance, and the consequences for restoration success, we evaluated naturally regenerating mycorrhizal colonization of Populus fremontii (Fremont cottonwood), a foundation riparian tree, in trees from one local and two assisted migrant source populations two years after planting. Three main lessons emerged. 1) Ectomycorrhizal colonization rates two years post-planting were considerably lower than those found in source populations, even under ideal conditions with an adjacent source of mycorrhizal host trees. 2) Within the planting site, proportions of dedicated exchange sites between plants and mycorrhizal fungi closely followed plant provenance, with trees from greater distances demonstrating fewer EMF root tips and AMF arbuscules. 3) For the plant provenance struggling the most, a close association between tree survival rates and mycorrhizal colonization was found. Results suggest that active mycorrhizal restoration and optimizations of pairings between fungal, plant, and site provenances could maximize investments in restoration and natural area management, and help offset challenges posed by shortages in planting material and climate change.
Chapter 3: Under climate change, the need for and importance of natural regeneration, replanting, and restoration is expected to grow while planting and recruitment success decrease, and planting material shortages continue to constrain replanting efforts. Thus, strategies to optimize restoration effectiveness seem increasingly important. Assisted migration and the restoration of native mycorrhizal communities appear promising. However, intraspecies assisted migrations often still show reduced survival compared to local provenances, and mycorrhizal inoculation, effective if well-matched to plants and site conditions, can have neutral to negative results with poor pairings. Few studies examine the interaction between these two strategies and invasive species soil legacies, particularly under drought conditions exacerbated by a warming, drying climate. To evaluate these interactions, we planted Populus fremontii (Fremont cottonwoods) from two ecoregions (local and warmer) in soils with and without legacies of invasion by Tamarix spp. (tamarisk), and with and without restoration of native mycorrhizal fungi. Four main lessons emerged. 1) The soil legacies left behind after tamarisk invasion reduced survival by 85%. 2) Actively restoring a diverse, native community of mycorrhizal fungi after tamarisk invasion doubled and then tripled survival during the first and second field seasons, respectively. 3) Inoculation sometimes had neutral and even negative effects, interacting with timing, pairing between tree and inoculum sources, and site conditions. 4) During the second field season, assisted migrants survived at twice the rate of trees from the local ecoregion, if inoculated with an appropriate and diverse native mix of mycorrhizal fungi. Results emphasize the detrimental effects of soil legacies left behind after tamarisk invasion, the beneficial effects of appropriate mycorrhizal restoration, and the need to thoughtfully optimize pairings between plants, fungi, and site conditions