Physical Sciences and Mathematics Commons^™

Investigations Of Low-Frequency Vibrations In Crystalline Organic Semiconductors And Their Impact On Material Properties, Peter Alexander Banks

Graduate College Dissertations and Theses

An increasing amount of attention has been dedicated to small-molecule based crystalline organic semiconducting materials, with regular reports of newly-designed molecules that are specifically engineered to produce high-performance organic devices. Commonly, these molecules contain distinct chemical characteristics that are specifically incorporated to inhibit the large-amplitude, low-frequency vibrational motions that occur about intermolecular van der Waals contacts. These molecular motions have been historically considered a primary factor that uniquely limits the semiconducting performance of these materials, as the large displacements induced by these vibrations strongly diminish the electronic coupling between molecules in the lattice. This phenomenon is denoted as electron-phonon coupling, …

Relationships Between Deformation, Magmatism, And Sedimentary Geology Along The Mongol-Okhotsk Suture Zone: Ulz Gol Region, Mongolia, Jarret William Pidgeon

Graduate College Dissertations and Theses

The Mongol-Okhotsk Suture Zone (MOSZ) is a continental-scale structure that signifies the closure of a Paleozoic ocean basin. Though suturing of the Siberian Craton and southern Mongolian terranes is thought to have occurred in the Mesozoic Era, the exact timing and mechanisms remain debated. This prolonged period of orogenic activity is believed to be responsible for forming much of the Central Asian Orogenic Belt (CAOB) that encompasses essentially all of Mongolia, part of China, Siberia, and Kazakhstan. Also permeated throughout the CAOB are intra-continental, post-suturing structures. In the Late Jurassic–Early Cretaceous, a significant, crustal-scale extensional episode affected central and eastern …

Applications Of Bayesian Hierarchical Detection Models, Emily Beasley

Graduate College Dissertations and Theses

Bayesian hierarchical detection models are useful for addressing uncertainty in datasets in the form of detection error and can be adapted to a variety of research questions. This dissertation uses three case studies to highlight advantages of Bayesian hierarchical detection models: 1) using prior information to model undetected species, 2) efficiently modeling a naturally hierarchical system, and 3) correcting for observation bias in two interconnected ecological metrics for effective disease management.Detection error can bias ecological observations, especially when a species is never detected during sampling. In many communities, the probable identity of these species is known from previous research, but …

Weathering Gradients In Podzols Of The Northeastern U.S., Jenny Bower

Graduate College Dissertations and Theses

Soil formation has long been framed as a vertical process because of the historical emphasis on agricultural areas, which tend to be low relief. This framing fails in areas where steep topography, a restrictive soil horizon, or shallow bedrock leads to lateral flow. In the glaciated Northeast, lateral podzolization is the dominant process forming shallow-bedrock soils on hillslope summits and shoulders, in contrast to deeper soils on backslopes that are influenced by vertical podzolization. These patterns are accompanied by gradients in hydrologic regime and solution chemistry which imply the existence of mineral weathering gradients. This work aimed to understand weathering …

Forest Management Tradeoffs: Examining Relationships Between Timber Harvest, Carbon Sequestration And Storage, Bioenergy, And Wildlife, Michelle L. Brown

Graduate College Dissertations and Theses

Timber harvesting is the leading cause of adult tree mortality in forests of the northeastern United States. While current rates of harvest are generally sustainable, there is considerable pressure to increase harvest to meet timber production, climate, and energy goals. Maximizing one of these values may compromise other forest resources, including a wide range of ecosystem services and the conservation of native species. This dissertation investigates the effects of timber harvest on carbon sequestration and storage, bioenergy, and wildlife. First, I estimated current harvest regimes for different forest types and regions across the U.S. states of New York, Vermont, New …

Paleolimnological Data Synthesis To Assess Long-Term Ecological Change In Vermont Lakes, Ismar Biberovic

Graduate College Dissertations and Theses

Lakes are excellent early indicators of environmental change on a landscape scale. Due to their connectedness in the landscape, any alteration of land-cover extends beyond a single watershed and can only be amplified by the effects of climate change. These processes can reflect differently across lakes of various characteristics, however, combined, they can leave a lasting impact on biogeochemical processes of a lake, resulting in profound effects on biological communities residing in it. Lake sediments are terrific archives that integrate and preserve this evidence, which then allows us to investigate the extent to which a lake has changed given its …

Socio-Ecological Economic Impact Analysis Of Food Systems Initiatives Using Mixed Methods And Community-Based Research Approaches, Josiah J. Taylor

Graduate College Dissertations and Theses

Many NGO and government community development programs seek to alleviate complex problems related to food systems and agriculture. Yet, without integrated social, ecological, and economic impact analysis we cannot understand or communicate the value of such interventions. For this research, we partnered with food and agriculture organizations using participatory action research approaches to co-develop and test tools for holistic program analysis. We then used these tools to conduct and co-produce a holistic analysis and evaluation of program impacts. The first chapter provides background and context for the body of the dissertation. Chapter two details work with Hunger Free Vermont to …

Leveraging A Machine Learning Based Predictive Framework To Study Brain-Phenotype Relationships, Sage Hahn

Graduate College Dissertations and Theses

An immense collective effort has been put towards the development of methods forquantifying brain activity and structure. In parallel, a similar effort has focused on collecting experimental data, resulting in ever-growing data banks of complex human in vivo neuroimaging data. Machine learning, a broad set of powerful and effective tools for identifying multivariate relationships in high-dimensional problem spaces, has proven to be a promising approach toward better understanding the relationships between the brain and different phenotypes of interest. However, applied machine learning within a predictive framework for the study of neuroimaging data introduces several domain-specific problems and considerations, leaving the …

Anaerobic Soil Disinfestation And Vermicompost To Manage Rhizoctonia Solani In Organic Lettuce, Anna Rissland Brown

Graduate College Dissertations and Theses

Rhizoctonia solani Kühn is an aggressive saprophytic soilborne fungal plant pathogen that is distributed globally and infects many crops including Solanaceae, Fabaceae, and Asteraceae. The lack of effective organic methods to control R. solani and the resulting yield losses contribute to the economic insecurity of farms and farmers. The overall aim of this study was to compare two organic certifiable approaches to manage bottom rot caused by R. solani (subspecies AG1-IB) in field-grown organic lettuce: anaerobic soil infestation (ASD) and thermophilic compost cured by vermicompost (vermicompost). A commercially available biocontrol product and an untreated control were used as references.

Two …

Developing Muscle Synergy Functions For Remote Gait Analysis, Nicole Marie Donahue

Graduate College Dissertations and Theses

Digital medicine promises to improve healthcare and enable its delivery to rural and underserved communities. A key component of digital medicine is accurate and robust remote patient monitoring. For example, remote monitoring of biomechanical measures of limb impairment during daily life could allow near real-time tracking of rehabilitation progress and personalization of rehabilitation paradigms in those recovering from orthopedic surgery. Wearable sensors have long been suggested as a means for quantifying muscle and joint loading, which can provide a direct measure of limb impairment. However, current approaches either do not provide these measures or require unwieldy wearable sensor arrays and/or …

Assessing The Drivers Of Legacy Phosphorus Loading And Distribution In Shallow Eutrophic Lake Sediments And The Impacts Of Intervention, Ashton P. Kirol

Graduate College Dissertations and Theses

The eutrophication of freshwater lakes from excessive nutrient runoff leads to decreased water quality and worsening cyanobacteria blooms. Water quality improvements in shallow eutrophic lakes can be delayed by decades due to the seasonal recycling of legacy phosphorus (P) enriched lake sediments, even when external nutrient loads are addressed. It is critical to understand the drivers of internal P loading to suppress this source of P through intervention to meet water quality goals. This study contrasts two shallow eutrophic systems, Lake Carmi and Missisquoi Bay in Lake Champlain, impacted by legacy P loading driven by the occurrence of low dissolved …

Forest Management In The Context Of Global Change: Impacts Of Disturbance, Adaptive Management, And Invasive Species On Northeastern Forests, Jennifer Santoro

Graduate College Dissertations and Theses

Climate change is predicted to have variable and uncertain effects on forested ecosystems globally. In the northeastern US, natural disturbances have historically been a central driver of forest successional dynamics, but as climate warming is projected to alter the frequency and severity of these events, post-disturbance management strategies to sustain biodiversity and ecosystem services must adaptively change to promote forest resilience. A suite of adaptive silvicultural actions has been proposed to promote forest resilience in the face of uncertainty, but due to the multi-decadal scale of forest management, initial field experiments are only beginning to show results. To address these …

Estimating Particle Velocity From Dual-Camera Mixed Reality Video Images Using 3d Particle Tracking Velocimetry, Thomas Chivers

Graduate College Dissertations and Theses

Mixed reality (MR) systems integrate diverse sensors, allowing users to better visualize and quantify surrounding environmental processes. Some existing mixed reality headsets include synchronized front-facing cameras that, among other things, can be used to track naturally occurring tracer particles (such as dust or snowflakes) to estimate particle velocity field in real time. The current work presents a 3D particle tracking velocimetry (PTV) method for use with MR systems, which combines various monocular cues to match particles between corresponding stereo images. Binocular disparity is used to estimate particle distance from an observer. Individual particles are tracked through time and used to …

Imaginaries Of The Great Outdoors: Comparing Facebook Postings Across Resource Places, Frances Hoag

Graduate College Dissertations and Theses

Communication across agencies, interested audiences, and the public is central to resource management. While social media expands agencies’ communication options, it also may present opportunities for constructing and presenting “imaginaries” – collectively imagined discourses that that shape understandings of place and influence the world views of followers. Imaginaries are “socially constructed, taken-for-granted meanings about reality that make everyday social and cultural practices seem obvious and sensible to people” (Stokowski et al., 2021). Extending prior research, we sought to understand whether/how resource management agencies used social media to construct and deploy imaginaries. Data were collected during 2021-2022 from resource management agencies …

Applications Of Centrality Measures And Extremal Combinatorics, Hunter Dane Rehm

Graduate College Dissertations and Theses

Centrality measures assign numbers or rankings to network nodes that reflect their importance. There are many types of centrality measures, each suitable for different types of networks and applications. In Chapter 2, we consider a model of astronaut health during a space mission. Katz centrality is commonly used to measure the influence of nodes in social and biological networks. We motivate its use in this application to estimate the expected quality time lost due to the progression of medical conditions. In Chapter 3, we find dominating sets in satellite networks. To do this, we use the Shapley value, a centrality …

In-Situ Weathering Of Calcium Bearing Minerals In Forested Ecosystems, Victoria Treto

Graduate College Dissertations and Theses

Timber harvests in the northeastern United States are integral to its economy but shifts in land management, biotic stresses, and nutrient limitations are diminishing forest productivity levels. The effects of harvesting severity and repeated harvests result in net losses of base cation nutrients which decreases woody biomass, potentially as much as 20%. Calcium (Ca) serves to regulate critical processes linked to tree growth and ecosystem health, but it is the quickest depleting base cation from northeastern forest soils. As a result, the quantification of nutrient-bearing minerals in forest soils is fundamental in predicting long-term sustainability of wood production. Further, the …

Estimation In Generalized Estimating Equation Measurement Error Models Using Instrumental Variables/ Estimating The Cardinality Of Latent Defective Edges In Hypergraphs, Damin Zhu

Graduate College Dissertations and Theses

This dissertation consists of two studies. The first develops theory for a new method for estimating regression parameters using generalized estimating equations (GEE) with panel data prone to covariate measurement error. The focus is on logistic regression, though the method is applicable to other models. The method requires availability ofinstrumental variables (IV) to identify model parameters. Simulations are performed to assess the performance of the proposed estimator. The method, abbreviated GEEIV, is able to accurately estimate logistic regression parameters masked by measurement error in a variety of population configurations.

In the second study, an algorithm is proposed to estimate the …

Understanding The Connections Between Cross-Sector Collaboration And Service Delivery For Charitable Organizations Using Mixed Methods, Kristin Elizabeth Darby

Graduate College Dissertations and Theses

Two of the most pressing challenges in the world today are food and water access. Charitable organizations frequently use cross-sector collaboration to address food and water access. Cross-sector collaboration is grounded in knowledge, relationships, communication, action, and trust, which cultivate innovation and resilience. However, very few studies have discussed the connections between collaboration, service delivery, and perceptions. Using a convergent design of mixed methods, this thesis examined how cross-sector collaboration enhances service delivery and resilience in charitable organizations. Specifically, the project is guided by three research questions: (1) What communication practices support effective cross-sector collaborations for impactful service delivery for …

Metagenomic Insights Into Landfill Intermediate Cover Soil Microbiomes And Their Potential Role In Mitigating Greenhouse Gas Emissions, Peyton Lienhart

Graduate College Dissertations and Theses

Landfills are the third largest source of anthropogenic methane emissions in the United States and have also been found to produce nitrous oxide, an even more potent greenhouse gas than methane. Intermediate cover soils (ICS) play a major role in reducing greenhouse gas emissions from landfills because they harbor methanotrophic bacteria that degrade methane. However, the extent of methanotrophs in landfill cover soils and the roles of microbial communities in these complex ecosystems is only beginning to be understood. Additionally, the role of ICS in producing nitrous oxide is poorly understood. While methane consumption is a desirable trait, genes involved …

Timeseries Analysis To Characterize Complex Phenomena In Environmental And Human Health Applications, Jeremy Ernest Matt

Graduate College Dissertations and Theses

Studying and evaluating time series signals that emerge when monitoring complex phenomena requires fusing, visualizing, and often reducing the dimensionality of large amounts of data to reveal the patterns and relationships that appear at different scales. In this work, we develop methods for monitoring, visualizing, and identifying the complex relationships that appear in time series data collected from two very different domains – health care conversations and river networks – to facilitate large-scale understanding of these systems. Fostering connection between clinicians and patients and their families in the context of serious illness is a fundamental component of good clinical communication …

How To Analyze Parental Conversation Online: A Computational Stack For Studying Vaccine Hesitancy., Carter Willets Ward

Graduate College Dissertations and Theses

Despite national and international organizations such as the CDC and WHO recognizing the value of vaccines and their importance in addressing public health concerns, there has been a decline in coverage for even the most established vaccines over the past three years. The global COVID-19 pandemic has contributed to this decline via decreases in medical resource accessibility and an increase in vaccine hesitancy. Even before the COVID-19 pandemic, WHO had recognized vaccine hesitancy as one of the top ten threats to public health. In the present work, we introduce a background account of (1) vaccine hesitancy and (2) anti-vax activism, …

An Analysis Of A Linear Algebra Based Group Key Exchange Protocol, Annie Zhang

Graduate College Dissertations and Theses

Group key exchange protocols are used to establish session keys, which can then be used as encryption keys to set up secure channels of communication, between more than two parties simultaneously. Many different group key exchange protocols exist and require security proofs in order to determine the strength of the protocol and answer the following questions: does the protocol provide authentication, and if so, to what degree? Does the protocol provide key secrecy? In this thesis we examine a particular group key exchange protocol that we call the \textit{vector space projection protocol} as first described in “A Group Key Establishment …

Deep Reinforcement Machine Learning As A Driver Of Agent Decision-Making In Agent-Based Models Of Coupled Natural And Human Complex Systems, Kevin Allen Andrew

Graduate College Dissertations and Theses

Agent-based models are becoming increasingly useful in studying the behavior of real-world complex multi-agent systems; however, one of the outstanding challenges in the modeling of coupled natural and human systems is the dearth of techniques for creating agents that are able to learn from their past failures and successes, as well as compounded environmental and social uncertainties. This research has been focused on the integration of traditional agent-based modeling with machine learning methodologies for modeling agent decision-making and its recursive impacts on economic, environmental, and societal outcomes, feeding into the dynamic co-evolution of the coupled natural and human system state …

Performance Of A Low-Reynolds Discrete Swirl Injection Method Under A Range Of Design Parameters, Owen Brandriss

Graduate College Dissertations and Theses

In recent years, the industry of small-satellite technology has experienced massive growth. In 2020, the value of the global smallsat market was valued at $3.2 billion, and is projected to reach $13.7 billion by 2030, with thousands of successful smallsat launches already completed as of 2022. While these satellites are typically inserted into orbit via rideshare on large rockets, maneuvers such as attitude correction, station-keeping, and deorbiting of these sattelites - which often have masses under 10kg - requires the development of very small propulsion systems, with thrust levels as low as individual micro-Newtons. These propulsion systems often use hypergolic …

Investigating The Mechanical Properties Of Different Types Of Phospholipids, A Molecular Dynamics Study, Atena Farhangian

Graduate College Dissertations and Theses

Around 54.4 million ) of the US population is suffering from arthritis. It is one of the main contributors to activity limitations and is imposing a great cost on society. The main reason behind the lack of a cure for arthritis is the incomplete understanding of the lubrication of the joint. A critical question is the role of phospholipids, especially their mechanical role in relation to cartilage and other molecules present in synovial fluid.

The main type of load a joint like a knee endures is compressive forces. The present work is an effort to better understand the molecular-level interactions …

Groundwater Governance And Agricultural Sustainability: Examining Farmer Interactions With California’S Sustainable Groundwater Management Act, Zachary Matthew Goldstein

Graduate College Dissertations and Theses

Climate change has exacerbated groundwater depletion globally, and policymakers have struggled to effectively manage groundwater resources. California enacted the Sustainable Groundwater Management Act (SGMA) in 2014 to restore groundwater to sustainable levels.

The first paper of this thesis examines the drivers associated with uptake of groundwater conservation practices in agriculture. While a rich body of research has explored farmers’ conservation practice adoption, understanding of groundwater conservation practices is more limited. This study explores how information sources influence the actual and intended adoption of groundwater management practices in California. Using survey data from farmers (n = 553) in three largely agricultural …

Riparian Buffer Establishment Using Different Management Techniques, Stever H. Bartlett

Graduate College Dissertations and Theses

ABSTRACT

In riparian areas of the northeastern United States, well-established reed canary grass (Phalaris arundinacea) stands are common and have proven to be a challenge for the success of tree plantings during riparian forest restoration projects. The impacts of reed canary grass (RCG) on the habitats it invades are numerous. Reed canary grass reduces biological diversity by homogenizing habitat structure, richness, and environmental variability. Its rapid growth rate and invasive nature limits tree regeneration in riparian forests by shading and crowding out seedlings. Riparian forests improve water quality, wildlife habitat, flood control, and provide a variety of other ecosystem services. …

Drivers Of Soil Organic Carbon In Rich Northern Hardwood Forests, Sophia Rebecca Marinace

Graduate College Dissertations and Theses

Forests are increasingly being managed for their carbon sequestration potential. As such, an understanding of the factors controlling carbon dynamics across and within sites is becoming increasingly important for guiding carbon management strategies. Given that much of a forest’s carbon is stored in soils, identifying the factors that control how much carbon is stored in soils is critical. This study used detailed vegetation and soil measurements across a rich northern hardwood forest in Corinth, Vermont to identify factors that drive soil carbon storage in a northern hardwood forest, a common type in New England, and investigated how multiple non-native species …

Data Science And Mathematical Modeling For Humanitarian Response, Ollin Demian Langle Chimal

Graduate College Dissertations and Theses

This dissertation focuses on the exploration of societal responses to crises, with a par-ticular interest in existing socio-economic disparities, using tools of data science and mathematical modeling. The scope of the research is comprised predominantly around the COVID-19 pandemic, incorporating an in-depth analysis across six middle-income countries; Brazil, Colombia, Indonesia, Mexico, Philippines, and South Africa. With GPS data of approximately three million users, we found significant differences in the adherence to stay-at-home guidelines, revealing a great contrast between individuals in high-wealth and low-wealth areas, showing the disparities of who were more able to stay at home without risking their livelihood. …

Analyzing The Impact Of Cultural Factors On Happiness Levels In Arabic Language Tweets, Parisa Suchdev

Graduate College Dissertations and Theses

Culture is a fundamental force shaping our view of the world. Filtered through the stories we share on social media, our collective behavior both reflects and amplifies cultural impacts. The present study seeks to describe the effect of cultural factors, such as religion, on happiness scores in Arabic language tweets from January 2010 to June 2023. Our methodology involves using present tools called Hedonometer (https://hedonometer.org/) to study happy and sad events and StoryWrangler (https://storywrangling.org/) to study the usage of keywords related to those events. Our findings reveal a notable pattern of Twitter happiness declining following the start of the Arab …