Digital Commons Network^™

Ai-Enabled Robotic Nitrogen Management, Ankita Kalra

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Nitrogen management in corn agriculture faces economic and environmental challenges, motivating development of precision, site-specific solutions. This dissertation presents AIR-N (AI-Enabled Robotic Nitrogen Management), a novel system that integrates cloud-based artificial intelligence with an autonomous field robot (Flex-Ro) to optimize nitrogen fertilizer application in real time. The research is driven by the need to improve nitrogen use efficiency while reducing leaching and emissions.

Comprehensive architecture (Cloud-E) was designed using Amazon Web Services to ingest multi-modal agronomic data (soil sensors, crop reflectance, weather) and host machine learning models. A Random Forest-based model was trained on historical field data to predict spatially …

Evaluating Fall And Spring Planted Cover Crops For Integrated Management Of Herbicide Resistant Palmer Amaranth And Effect On Soil Health, Vipin Kumar

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Herbicide-resistant Palmer amaranth (Amaranthus palmeri S. Watson) pose a severe threat to agronomic crop productivity in the United States, including corn and soybean production in Nebraska. Therefore, there is an urgent need for diversified and sustainable management approaches. Integrating cover crops (CCs) with herbicide programs represents a promising strategy to achieve Palmer amaranth suppression, sustain crop yields, and contribute to long-term soil health in irrigated corn–soybean production systems in Nebraska.

A meta-analysis of 41 studies and 595 paired observations demonstrated that CCs reduced Amaranthus spp. density and biomass by 37–59% depending on the growing season, with grasses and mixtures …

Synthesis And Study Of Stable Organic Radicals For Mri Contrast Agents And New Materials, Sabina Dhakal

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

The first part of this dissertation focuses on the design, synthesis, and characterization of a thermally robust S =1/2 phototetrazolinyl monoradical and the development of synthetic methodologies for a high-spin (S = 1) phototetrazolinyl diradical. Electrochemical studies of the phototetrazolium cation (precursor to the monoradical) revealed a remarkably narrow electrochemical band gap (Ecell ≈ 0.82 V), suggesting promising electrical conductivity. Thermal analysis of the monoradical demonstrated excellent stability, with the onset of decomposition at 232 °C. Building on the excellent thermal stability and promising properties for electrical conductivity of the monoradical, we developed two condensation-based synthetic routes that provide viable …

Investigating Preservice Elementary Teachers’ Stem Teaching Self-Efficacy And Goal Orientation, Derek Scott Cox

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

In the context of teacher education, self-efficacy and goal orientation can have an impact on one’s motivation, desire to improve, and maintaining a growth mindset in teachers. This study utilized an explanatory mixed methods design to investigate how and why preservice elementary science, technology, engineering, and mathematics (STEM) teachers’ confidence and views on competency changes after completing an array of courses built around integrated STEM.

Sixty-five preservice teachers participated in the pre- post-test quantitative data collection to determine changes in integrated STEM self-efficacy and achievement goal orientations (mastery-approach, mastery-avoidance, performance-approach, performance-avoidance). Data collection measures include Self-Efficacy for Teaching Integrated STEM …

Large-Scale Experimental Study On The Impact Of Air Cleaning & Ventilation On Indoor Air Quality And Student Illness-Related Absenteeism, Daud Nosham

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

This large-scale randomized experimental field study investigated the effect of portable air purifiers (PAPs) on classroom’s air quality and student’s illness related absenteeism. PAPs were installed in 317 classrooms from various school districts located in Eastern Nebraska. The classrooms were randomly assigned into four conditions: three treatment conditions (T1, T2 & T3) and one control condition (device without any filter). T1 was equipped with HEPA filters, T2 added Activated Carbon (AC) layer to HEPA, and T3 further integrated Germicidal Ultraviolet (GUV) alongside HEPA and AC filters. The measured variables were carbon dioxide (CO2), fine particles (PN2.5) and coarse particles (PNcoarse), …

Assessing Crop Rotation Productivity, Soil Health, And Fertility, And Economic Performance, To Enhance Semi-Arid High Plains Cropping Systems Sustainability, Ezequiel Maria Villamil

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Sustainable crop production in the semi-arid High Plains of Nebraska faces challenges from limited precipitation, high interannual variability, and economic risk. This dissertation investigates the long-term productivity, water use, soil health, and economic sustainability of dryland crop rotations, with emphasis on the role of pulses as alternatives to fallow.

Chapter 1 analyzes nearly three decades (1995–2023) of on-farm data from the High Plains Agricultural Laboratory (Sidney, Nebraska) to compare seven crop rotations, including wheat, corn, millet, sunflower, and field peas. Results showed that wheat–corn–fallow (W–C–F) consistently outperformed traditional wheat–fallow (W–F) and more intensified four-year rotations, providing the highest grain yields, …

Development Of Databases For Glycan Utilization And Anti-Prokaryotic Defense In Microbiomes, Yuchen Yan

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Microbiomes in humans, animals, plants, and other environments are necessary components of the biosphere for global nutrient cycling and maintaining ecosystem balance. In particular, the gut microbiome plays an essential role in modulating human health through glycan utilization. Carbohydrate-active enzymes (CAZymes), CAZyme gene clusters (CGCs), and polysaccharide utilization loci (PULs) are key genomic features that determine microbial capacities for carbohydrate metabolism. Meanwhile, the arms race between phages and prokaryotes has led to the evolution of various anti-prokaryotic immune systems (APIS) in phages to counteract prokaryotic immune systems (PIS).

As bioinformatics methods used to analyze microbiome information advance rapidly, there is …

Advancing Precision Agriculture Through The Application Of Remote Sensing Technologies In Plant Health Assessment, Thomas Wilbur Davis

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

Monitoring plant health, including nutritional status assessment, is an important component of crop management decisions. This doctoral document addresses the use of agricultural remote sensing through focused investigations of plant disease detection and nutrient status assessment technologies that advance precision agriculture. The first chapter provides a comprehensive overview of remote sensing technologies in agriculture and examines current capabilities, limitations, and future directions. The final two chapters address studies that evaluated the virus-nitrogen interaction in wheat and compared methods to determine the nitrogen status of midseason field corn.

The first study evaluated the wheat streak mosaic virus (WSMV) × nitrogen interaction …

The Role Of Peroxisomal Acot4 And Acot8 In Modulating Lipid Metabolism And Stress Pathways In Steatotic Hepatocytes, Sylwia Miekus

Department of Nutrition and Health Sciences: Dissertations, Theses, and Student Research

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by excessive lipid accumulation in hepatocytes and the development of lipotoxic stress that disrupts cellular homeostasis. Peroxisomal lipid metabolism plays an important role in maintaining acyl-CoA balance during fatty acid overload, yet the contribution of peroxisomal acyl-CoA thioesterases to early lipotoxic responses remains insufficiently understood. The aim of this study was to investigate the functional involvement of the peroxisomal enzymes acyl-CoA thioesterase 4 (ACOT4) and acyl-CoA thioesterase 8 (ACOT8) in hepatocyte lipid handling under acute lipotoxic conditions. An in vitro model of steatosis was established in AML12 cells through exposure to a …

Pfos And Lung Injury: A Review Of Human And Experimental Evidence, Farzana Hakim

Theses and Dissertations

Human epidemiological research has shown the adverse health consequences of long-term accumulation of per- and polyfluoroalkyl substances (PFAS) in human tissue. Specifically, this review will examine the relationship between PFAS exposure, impaired immune system functioning, and an elevated risk of respiratory disease using both human and experimental data. Research on human populations indicates that children exposed to PFAS have lower levels of antibodies to vaccines; those children prenatally exposed to PFAS are more susceptible to upper respiratory infections; and that adult humans have a higher incidence of chronic obstructive pulmonary disease (COPD). Additionally, experimental studies demonstrate that PFOS and PFOA …

Assessing Native Tallgrass Prairie Species As Main Roadside Vegetation In Arkansas, Sarah Paschal

Graduate Theses and Dissertations

Tallgrass prairies are among the most endangered ecosystems in North America, with Arkansas having lost over 99% of its native grasslands. This research evaluated the potential for using native tallgrass prairie species in Arkansas roadside vegetation. Two field experiments were conducted from 2022 to 2024. The first assessed seven native seed mixtures at three roadside locations (Clarksville, Huntsville, and Newport). Seed mixture composition significantly influenced establishment outcomes, with early-establishing forbs such as black-eyed Susan, partridge pea, and Illinois bundleflower performing well, though establishment varied by location. A second trial compared planting date (Autumn, Winter, Spring) and planting method (broadcast, drill …

Solar Powered Conservation: The Effects Of Solar Photovoltaic Facilities On Avian Community Composition, Michael Christopher Ferrara

Graduate Theses and Dissertations

The expansion of solar photovoltaic energy infrastructure is transforming landscapes worldwide. Increasingly, facilities are planted with native vegetation, yet how vegetation characteristics and landscape variables shape wildlife communities in solar facilities remains poorly understood. Because avian populations have been in decline and are sensitive to habitat changes, understanding how solar facilities influence avian communities is important. In Chapter 1, we used autonomous recording units, local vegetation measurements, and land use and land cover data to quantify how avian community occupancy is influenced by solar cover in solar facilities and comparable reference sites. We used a Bayesian multi-species occupancy model to …

A Prevalence Study Of Iron Deficiency Anemia Among Children In Elbasan, Albania: Directions For Health Care Policy, Artilda Lala

All Dissertations

Iron deficiency anemia (IDA) is one of the most prevalent disorders worldwide, especially in children from low-income and underdeveloped countries. In Albania, anemia is a major public health concern with many unstudied regions (prefectures and rural municipalities). Childhood IDA can impair cognitive development, immunity and overall well-being, so early diagnosis and prevention of anemia is critical. This study examined the prevalence of IDA in children aged 0-10 years in the district of Elbasan, Albania. The data were additionally analyzed for relationships with demographic (age, gender, education, parental education and child academic performance) and nutrition variables.

A cross-sectional study design was …

Moon Moth, Britain Noelle Powers

Open Access Theses & Dissertations

No abstract provided.

Copula-Based Tests For Assessing The Association Between Genetic Variants And Mixed Phenotypes, Martin Amoah

Open Access Theses & Dissertations

High-dimensional omics studies increasingly involve heterogeneous data types and phenotypes, which traditional association methods struggle to model jointly due to incompatible marginal distributions and complex dependence structures. This thesis develops a unified copula-based framework for assessing associations between genetic variants and mixed phenotypes by decoupling flexible marginal models from their joint dependence structure. While previous copula-based approaches in this setting have focused largely on continuous and binary traits, we extend these methods to a broader class of phenotype pairs. Specifically, we introduce new association tests for bivariate outcomes involving ordinal–continuous, nominal–continuous, and survival–continuous combinations. The proposed methodology derives joint density …

Multi-Hop Hybrid Graph Neural Network, James Arthur

Open Access Theses & Dissertations

Graph-structured data appear across diverse domains, such as social networks, citation graphs, biological systems, and knowledge bases. Graph Neural Networks (GNNs) have emerged as a powerful framework for learning on such data, yet existing architectures face significant challenges. Graph Convolutional Networks (GCNs) suffer from over-smoothing as depth increases, Graph Attention Networks (GATs) introduce computational and statistical instabilities, and naïve multi-hop propagation inflates memory and computation while failing to adapt to topology. These limitations motivate the development of a new framework that is both expressive and scalable. This dissertation proposes the Multi-Hop Hybrid Graph Neural Network (MHHGNN), a novel architecture that …

Evaluation And Identification Of Risk Factors For Stress Among Maquiladora Workers Based On The Mexican Official Standard 035 Survey Tool, Andrea Baca Melendez

Open Access Theses & Dissertations

Background and significance: Occupational psychosocial risk factors are workplace conditions that can trigger physiological, emotional, cognitive, and behavioral changes. They are strongly associated with mental health issues such as anxiety and depression, as well as non-mental health conditions like myocardial infarction, stroke, and occupational injuries. Analyzing these risks from a sociodemographic perspective provides valuable insights for improving work environments and workers’ well-being. Purpose: This study aimed to identify and determine the levels of occupational psychosocial risk factors among workers in a manufacturing company in Cd. Juárez, Chihuahua, and to examine their relationship with sociodemographic variables to inform future interventions in …

Machine Learning And First-Principle Approach To The Stability And Properties Of Iron-Based Materials Under Extreme Conditions., Blaise Awola Ayirizia

Open Access Theses & Dissertations

This dissertation investigates the stability and physical properties of iron-based materials under extreme conditions, utilizing a combination of machine learning techniques and first principles calculations. In the first study, we employ Gaussian Process Regression (GPR) with a Marginalized Graph Kernel to analyze the mechanical stability of non-magnetic body-centered cubic (BCC) iron at high temperatures and pressures, similar to those found in Earth’s core. Our model, trained on data derived from ab initio molecular dynamics (AIMD) simulations, predicts the energy landscape, atomic forces, and potential pathways for instability in BCC iron. The findings suggest that BCC iron remains stable in extreme …

Ai-Facilitated Abuse & Misogyny: A Feminist Response To Non-Consensual Intimate Image Deepfakes, Lizbeth Carmona

Open Access Theses & Dissertations

The creation of non-consensual intimate images utilizing AI deepfake technology has been demonstrated to overwhelmingly target women. The harms of non-consensual intimate image deepfakes are similar to other forms of misogynistic abuse, including intimate image abuse and online objectification. This project seeks to contextualize this phenomenon within feminist accounts of misogyny and its role in regulating women's behavior. In particular, this project highlights that the accessibility of this technology has lowered the threshold of abuse, despite the individual woman's preventive measures. Furthermore, this project argues that the dissemination of non-consensual intimate image deepfakes is a morally problematic situation because it …

Intelligent Predictive Frameworks Under Data Scarcity And Uncertainty, Solayman Hossain Emon

Open Access Theses & Dissertations

Modern predictive systems frequently operate under conditions of limited annotated data, high uncertainty, and the need for reliable decision-making. When the predictive models expand across heterogeneous data types (e.g., spatial, temporal streams), the challenge lies not only in accurate prediction but also in adapting in data distributions shifts or label scarcity. To address these issues, this thesis explores an Intelligent Predictive Framework that operates robustly under data scarcity and uncertainty across two distinct domains: medical imaging (spatial) and time-series forecasting (temporal). In the first part of this work, a semi-supervised mean teacher (MT) paradigm is tailored for medical image segmentation …

Hydrological Responses To Rainfall Pulses In Desert Vadose Zones: A Multi-Scale Approach Integrating Geophysical, Isotopic, And Eddy-Covariance Measurements, Alfredo Dagda-Torres

Open Access Theses & Dissertations

Drylands are shaped by natural episodic precipitation, where short, intense rainfall pulses interrupt prolonged drought and drive most hydrological and ecological activity. Yet the mechanisms that determine how pulse water infiltrates, is redistributed, stored, evaporated, and ultimately used by desert vegetation remain under quantified in landscapes underlain by shallow petrocalcic horizons. This dissertation integrates three complementary approaches 1) three-dimensional electrical resistivity tomography, 2) eddy-covariance evapotranspiration partitioning, and 3) stable-isotope tracing to improve a mechanistic understanding of pulse-driven water movement and plant water use in a caliche-rich piedmont at the Jornada Experimental Range. The first component characterizes how infiltration pulses interact …

Triply Periodic Minimal Surface Design And Resin Engineering For Hybrid Piezoelectric Ceramic Composites, Joshua Zahn Renaldo Dantzler

Open Access Theses & Dissertations

Chapter I:This chapter investigates Barium Titanate (BTO)-epoxy composites reinforced with 3D-printed zirconia triply periodic minimal surface (TPMS) scaffolds. Gyroid and Primitive lattices fabricated by digital light processing (DLP) were compared with a bulk composite. The Primitive architecture showed the greatest improvement, with an elastic modulus ~ 20% higher than the Gyroid and ~ 5% higher than the bulk. Normalized piezoelectric coefficients increased substantially, with d33 enhanced by ~ 2750% and g33 enhanced by ~ 120% relative to the bulk. Under cyclic loading, the Primitive lattice generated specific voltages ~ 575% greater than the bulk and ~ 60% greater than the …

Exploring The Impact Of Stem Degree Attainment On Intragenerational Social Mobility Among Hispanic Students And Graduates In Two Texas-Mexico Border Universities, Pilar Gonzalez

Open Access Theses & Dissertations

This research employed a two-phase, sequential, explanatory, mixed-methods design to answer the research questions. The first research question examined how obtaining a Science, Technology, Engineering, and Mathematics (STEM) higher education degree affects the socioeconomic advancement of current Hispanic students and alumni of the Louise Stokes Alliance for Minorities in Participation (LSAMP) within the context of two higher education institutions located along the Texas-Mexico border. The second research question explored the determinants shaping the professional pathways of Hispanic STEM students and graduates in the geographic vicinity of the Texas-Mexico border. For this study, STEM degrees refer to those recognized by the …

From Morphology To Machine Learning And Genomics: Understanding Phenotypic Variation In Wild Ducks, Sara Gonzalez

Open Access Theses & Dissertations

Understanding the genetic underpinning and distribution of phenotypic variation within and between divergent groups is core towards shedding light into how populations diverge and adapt, as well as how hybridization breaks or builds on these scenarios; and thus, central to evolutionary biology. In wild organisms, however, quantifying and linking phenotypic traits to underlying genetic processes, like mutation, gene expression, epigenetics and allele interactions, remains challenging. This difficulty arises from the complex interplay between morphology, environment, and gene regulation, as well as the logistical barriers of collecting and standardizing large-scale data across individuals and populations. As a result, researchers are increasingly …

Calibration Of Low-Cost Pm2.5 Sensors Using Data Continuously Generated At A Reference Station In El Paso, Texas, Brenda Lizbeth Hernandez

Open Access Theses & Dissertations

Low-cost sensors (LCS) offer a cost-effective way to expand air-quality monitoring networks, but they require strong calibration methods to ensure reliable performance under changing environmental conditions. In this study, Clarity LCSs were co-located with a state reference monitor for 6 months to evaluate fixed-time (2-, 3-, 4-, and 6-week) and rolling (2- and 3-week) calibration approaches. A multivariate regression model using PM1, PM2.5, PM10, and relative humidity was used to generate calibration coefficients for a “base sensor.” Data from two additional sensors were normalized to the base unit using linear regression, and their calibration coefficients were applied across the network. …

The Misadventures Of Popcorn And Zelda, Lori Lynne Kullberg

Open Access Theses & Dissertations

The Value of Animal Protagonists for Young Readers in Children’s Literature. This series is about my rescue cat and dog, Popcorn and Zelda, who are brought together at different ages and stages of their life. Witnessing their sweet interaction, mischievous playfulness, and close bond, I am immediately provided the inspiration for the early reader series of my thesis, The Misadventures of Popcorn and Zelda. My animals offer a constant stream of entertainment in watching how they interact with not only one another, but with me, as well. Oftentimes, Popcorn and Zelda’s behavior mirrors how I think a person would act …

Exploring Intersectional Risks Of Substance Use Disorder, Mental Health, Hiv/Aids, And Hepatitis C Among Hispanic Adults On The Tx-Mx Border: A Mixed-Methods Study, Md Mohsin

Open Access Theses & Dissertations

Purpose: The purpose of this study was to explore intersectional risks of substance use disorders, mental health, HIV/AIDS, and HCV among Mexican-origin Hispanic adults on the Texas-Mexico border. Methods: The study employed an exploratory sequential mixed-methods approach, which involved collecting and analyzing qualitative data first, followed by quantitative data collection. Selected purposively, 15 in-depth interviews were conducted among the target population. Using convenient sampling, 106 cross-sectional surveys were conducted. Qualitative interview data were analyzed manually using thematic analysis. Quantitative data analyses included univariate descriptive analysis, bivariate, and multivariable penalized logistic regression, negative binomial, and zero-inflated negative binomial regression. Results: The …

A Half Century Of Biophysical Change In Polygonized Tundra On The Coastal Plain Of Northern Alaska, Mariana Mora

Open Access Theses & Dissertations

Climate change is amplified in the Arctic. As a result, Arctic tundra landscapes are undergoing physical changes through accelerated thaw and ice-wedge degradation. Understanding the magnitude and direction of these changes in the Arctic is a necessary step toward understanding the response of the Arctic to climate change and feedbacks to the Climate System. Through repeat measurements collected from 1973 through 2018, we were able to assess decadal time scale changes in polygon geomorphology, thaw depth, land surface compression and expansion, and vertical elevation within a highly polygonized tundra system, and their implications when scaled to a regional level. This …

Applying The Quadruple Process Model To A Measure Of Implicit Bias Towards Individuals With Alcohol Use Disorder, Erin Marie Portillo

Open Access Theses & Dissertations

Alcohol use disorders is one of the major burdens of disease, yet it remains one of the disorders with the lowest treatment prevalence. For individuals who seek treatment for their alcohol use disorder, they may experience higher levels of social disintegration, guilt, shame, and stigmatization. Stigma is a multistep process that makes way for stereotypes, prejudice, and acts of discrimination to take place. With labels such as “alcoholic” implying negative connotation and being frequently used, the fear of being stigmatized and negatively labeled often results in delayed or entirely avoided care. Research has turned to the use of implicit measures …

Spatial Patterns In Plant Structural Diversity Across A Shrub Encroachment–Native Grassland Landscape Mosaic In The Northern Chihuahuan Desert, Bindu Poudel

Open Access Theses & Dissertations

Drylands are heterogeneous landscapes that provide important ecosystem services, but they are threatened by global change factors that may influence aspects of their diversity and function. Environmental factors may influence the three-dimensional physical characteristics of vegetation structure (structural diversity) across spatial scales in arid ecosystems. This study investigated how environmental factors, including shrub cover, landform, and elevation, are related to vegetation structural diversity metrics across different spatial scales and scopes across the Jornada Experimental Range, a long-term ecological research site located in the northern Chihuahuan Desert. A canopy height model generated by Airborne Observation Platform (AOP) LiDAR data and collected …