AUETD (Auburn University)
Not a member yet
9771 research outputs found
Sort by
Migration Energetics and Mitochondria: Modulation and Underpinning of Seasonal Flexibility in Mitochondrial Respiration in Migratory and Non-migratory Species
No full textThe migratory phenotype consists of a suite of adaptations to support short- and long-distance movements. Numerous species make annual movements to and from more northern latitudes, taking advantage of the longer daylight hours and a high abundance of seasonal food resources during the summer. In eastern North America, many species face the challenge of the major geographic barrier posed by the Gulf of Mexico. Millions of birds maintain flapping flight across a roughly 800km stretch of water. For decades, researchers have studied migration to understand orientation and navigation, stopover biology, physiology, and energetics; however, despite significant advances in fundamental understanding of migration, many questions remain.
From a plethora of studies, it is known that physiological adaptations serve as critical underpinnings of migration energetics supporting increased energetic output and efficiency. These adaptations can be observed across numerous hierarchical levels of biology from metabolic rates and whole-body respiration, tissue- and organ- specific changes, and cellular and even subcellular level adjustments. Nevertheless, gaps in the literature remain especially pertaining to organelle functionality within cells. Notably, the mitochondrion, which is responsible for producing over 90% of cellular energy in the form of ATP has received very little study in the context of migration. My goal was to investigate this critical gap in the literature to add to our current understanding of the migratory phenotype to further elucidate trait adaptation and migration energetics.
My approach was to compare the mitochondrial physiology of closely related populations of birds that differed in migratory behavior. In Chapter 1, I first compared migrant and non-migrant populations of sparrows in genus Zonotrichia. In Chapter 2, I compared two species belonging to the family Mimidae. These comparative studies provided critical baseline information. For the Zonotrichia pair, mitochondrial respiration was seasonally flexible and played a critical role in migration energetics. For the Mimidae pair, results were likely confounded due to the migrants exhibiting mixed migratory strategies and due to other life history differences in the non-migrant. In Chapter 3, I investigated pectoralis ultrastructure and mitochondrial morphology as a potential mechanism underpinning patterns observed with Zonotrichia and found that mitochondrial size, number, and area are likely key mechanisms in the patterns reported in Chapter 1.
Lastly, in Chapter 4, I expanded the Zonotrichia comparison to include another seasonal comparison within this genus. Unlike my initial predictions though, seasonal effects in this additional group were limited and variables such as ketones, demographics, and species-specific behavior likely played a larger role in the mitochondrial respiratory patterns reported. Collectively, this research provides some of the first documentation of seasonal flexibility in mitochondrial respiration and evidence of underpinning mechanisms
Three-Body Noncovalent Interactions: Insights from Energy Decomposition and their influence on Halogen Bonding
No full textAccurate models are crucial to predict noncovalent interactions, which govern complex struc-
ture, energetics, material self-assembly and reaction dynamics in complex environments. While
there exist ample datasets of accurate interaction energies for bimolecular complexes, benchmark
data for nonadditive three-body interactions are quite scarce, limiting the development and valida-
tion of methods that capture many-body contributions. This work introduces two datasets to study
two and three−body noncovalent interactions in heteromolecular trimers. The 3BHET benchmark
dataset comprises 20 equilibrium noncovalent interaction energies for a small but diverse selec-
tion of 10 heteromolecular trimers that combine different interactions including π − π, anion−π,
cation−π and various motifs of hydrogen and halogen bonding. The 3BXB datastet in contrast,
features a diverse selection of 107 heteromolecular trimers in 214 structures formed by augmenting
halogen−bonded dimers with either methane or water. It presents complexes that model σ − hole
interactions within each trimer, focusing on the magnitude and influence of three-body effects on
the halogen bonds. Both datasets are constructed using the same level of theory and subjected to
the same analysis process. The benchmark interaction energies were computed using the com-
posite CCSD(T)/CBS method and a detailed energy decomposition of the two- and three-body
interaction energies performed using various flavors and variants symmetry-adapted perturbation
theory (SAPT). Additionally, we develop a six-dimensional potential energy surface (6D PES) for
the OH-H2 system using RCCSD(T) and CCSDT corrections for the symmetric geometires and
MRCI-F12 for asymmetric configurations. This PES allows for the quantum scattering calcula-
tions for the computation of elastic and inelastic cross-sections
Stormwater Recharged: Innovating with Electrical Flocculation
No full textThe construction, operation, and maintenance of public infrastructure systems generate a variety of pollutants such as sediment, heavy metals, and nutrients, which are contaminants the U.S. Environmental Protection Agency (EPA) identifies as the most widespread in affecting the beneficial uses of the Nation’s rivers and streams. These contaminants degrade aquatic habitat, impair water quality, and reduce channel capacity, often requiring costly dredging or remediation. Growing urban development and increasingly severe storm events place additional strain on traditional drainage infrastructure, which must contend with both high flow volumes and elevated pollutant concentrations. In response, construction sites located near Waters of the United States, impaired waterbodies, or areas served by municipal separate storm sewer systems are required to implement stormwater pollution prevention plans, incorporating best‐management practices to minimize downstream impacts.
Although conventional erosion and sediment control measures, such as sediment basins, check dams, and silt fences effectively capture coarse, gravitationally settleable solids, they are not necessarily designed to reduce turbidity from colloidal particles. Currently, chemical flocculants remain the primary enhancement method for turbidity control in the field of stormwater. However, these chemical flocculants typically require manual dosing, generate large sludge volumes, and require tailored products for specific soils. These challenges highlight the need for additional solutions to address high turbidity environments to improve downstream water quality.
To address these limitations, this dissertation details the design, fabrication, and evaluation of a portable electrical flocculant generator, which employs in situ electrocoagulation to aggregate fine particulates without added chemicals. While electrocoagulation is well established in municipal and industrial water treatment, its application to construction and post‐construction stormwater has been limited. By branding the technology as “electrical flocculation,” this work introduces a familiar concept to stormwater practitioners and provides a foundation for broader field adoption.
Research began with a comprehensive literature review to distinguish between chemical coagulation and electrical flocculation, identify common stormwater contaminants, and the parameters affecting electrical flocculation performance. Leveraging these insights, three prototypes (A, B, and C) were developed and tested in an intermediate-scale system across five evaluation categories, including fundamental performance evaluations, aluminum‐coagulant release, mixing, electrode longevity, and pollutant loading. Fundamental performance evaluations that compared series versus parallel electrode wiring (prototypes A and B), showed no significant difference in turbidity removal performance. Subsequently, aluminum release trials demonstrated that under conditions of 54.1 L/min (14.3 GPM), 750 Nephelometric Turbidity unit (NTU) influent, and 37 A/m2 (3.4 A/ft2), prototype C released 0.19 mg/L Al3+, which is below the EPA’s secondary drinking‐water standard of 0.20 mg/L. This indicated preliminary compliance; however, toxicity analysis must be completed to confirm this finding in future testing. Mixing experiments demonstrated that two minutes of mechanical stirring at 360 rotations per minute (RPM) optimizes settlement, and specific passive mixers can offer equal performance. Electrode‐longevity trials revealed a 33% performance decline over 100 hours without polarity reversal and showed that a 5-hour reversal interval did not improve current density or performance within a 30-hour test. Pollutant‐loading evaluations conducted under testing parameters of 37.9 L/min (10.0 GPM) and 38 A/m2 (3.5 A/ft2) achieved removals of 60% of cadmium, below detection limits for copper, 73% for iron, 82% for lead, 68% for phosphorus, and 33% for zinc. Field‐scale tests with prototypes C and D confirmed that performance is strongly influenced by both influent temperature and anodic surface area.
These results establish a baseline performance for the retrofit electrical flocculant generator, demonstrating its lab‐ and field‐scale efficacy in removing turbidity and non‐sediment pollutants and quantifying its kinetics, energy use, and optimal current densities. This research provides a new approach to improving stormwater treatment by introducing a chemical-free, portable device that uses electrical flocculation to remove suspended solids and pollutants. By effectively reducing turbidity, heavy metals, and nutrients, the technology can help prevent the degradation of downstream waterbodies and support cleaner, healthier aquatic ecosystems. Its ability to operate without added chemicals also reduces the risk of harmful byproducts and makes it easier to implement at construction sites and other areas with stormwater challenges. Overall, this research offers a practical alternative solution to enhance water quality and advance sustainable stormwater management practices
Characterization of Soil Macropores Using X-ray Computed Tomography and Hydro-physical Properties Under Different Soil Management Practices
No full textThe goal of this study was to quantify changes in soil macropore characteristics by X-ray Computed Tomography (CT) and soil hydro-physical properties as influenced by different soil management practices, such as, cover crops, crop rotations, and addition of biochar.
The first objective quantified the impact of long-term cover crop (CC) vs. no cover crop (NC) treatment on soil planted with cotton. X-ray CT scanning of undisturbed soil cores collected from 400 mm deep soil profile indicated that CC improved macropore volume descriptors (macroporosity, macropore number density, and surface area density) in the surface soil layer (0-100 mm). Macropore geometry descriptors exhibited higher pore circularity, tortuosity, and lower degree of anisotropy under CC treatment than NC. Cover crops increased soil organic carbon levels (SOC), wet aggregated stability (WAS), water content at field capacity, plant available water, and reduced bulk density (ρb) in the surface soil layer. Enhanced root volume and root surface area exhibited higher root activity under the CC treatment. The results suggested that CC contributed to higher root activity in the soil and enhanced soil hydro-physical properties, and improved macropore characteristics.
The second objective investigated the impact of long-term (> 125 years old) crop rotation treatments: continuous cotton (C) and 2-year cotton-corn rotation (CCR) on X-ray CT-derived macropore characteristics and soil hydro-physical properties in a 400 mm deep soil profile. Cotton-corn rotation had higher X-ray CT-derived macropore number density, macroporosity of medium-sized pores (pore diameter: 1-2 mm), and lower anisotropy values in the top 100 mm of the soil layer, indicating more dense and stable macropore networks under CCR as compared to C. The depth-wise distribution exhibited a reduction in macroporosity and interconnectivity values from 0-100 to 300-400 mm soil layer, indicating less disturbance at the lower depths by field and root activities. The investigation of soil hydro-physical properties (ρb, SOC, WAS, and water retention characteristics) revealed no significant difference among treatments due to long-term adoption of soil conservation practices (cover crops and conservation tillage).
The third objective evaluated the short-term impact of biochar incorporation in the sandy-textured soil at different application rates: (i) BC0: 0-Mg/ha, (ii) BC7.5: 7.5-Mg/ha, (iii) BC15: 15-Mg/ha, and (iv) BC30: 30-Mg/ha. The biochar addition at the given application rates exhibited no significant impact on X-ray CT-derived pore indices, except on pore circularity and macroporosity fraction of different-sized macropores for the top 0-50 mm depth, where biochar was incorporated. The macroporosity fraction under the two size groups of macropores (1-10 and 10-100 mm3) was lower under BC15 at 0-50 mm and 50-100 mm depth classes. Lower macropore density under BC15 at the 50-100 mm soil layer indicates preferential movement of biochar particles below their application depth. The reduction in macropore indices with increase in application rates indicates the occupying effect of biochar. The higher application rate (BC30) showed comparable results with BC0, demonstrating that the higher biochar application rates can shift its effect from occupying to expansion. Soil hydro-physical properties revealed no significant differences among biochar treatments at both depth classes, indicating that the higher amount of sand particles and low organic matter may have diminished any improvement in soil hydro-physical properties by biochar addition.
The results of this study will contribute to the understanding of soil macropore characteristics and their relationship with soil hydro-physical properties, providing meaningful insights for sustainable agricultural production and various structural and hydrological dynamics controlling pollutant leaching and greenhouse gas emissions
End-to-end Framework for Pavement Crack Severity Classification
No full textPavement infrastructure forms the critical foundation of supply chains in both developing and developed nations. Maintaining optimal pavement performance is essential for effective transportation networks and economic functionality. Over time, pavement conditions deteriorate due to multiple interconnected factors, including climatic conditions, temperature variations, traffic loading, and seismic activity. Effective pavement management systems depend on accurate distress identification and assessment. Among various forms of pavement deterioration, cracking represents the most common and structurally significant distress type. While federal and local agencies continuously invest in data collection and pavement condition monitoring, traditional manual assessment methods remain labor-intensive, time-consuming, and prone to inconsistencies. This challenge necessitates the development of automated approaches for efficient and reliable pavement condition evaluation.
Recent decades have witnessed the development of diverse pavement crack detection methodologies, ranging from traditional image processing techniques to shallow machine learning algorithms and advanced deep learning approaches. Deep learning-based methods have demonstrated superior accuracy and enhanced generalizability compared to conventional image processing and shallow machine learning techniques. Nevertheless, these advanced solutions typically require significant computational resources, limiting their practical deployment.
In this study, we develop a comprehensive end-to-end framework for automated pavement crack severity classification, combining deep learning algorithms with image processing techniques to enable crack recognition, detection, and severity assessment. The proposed system emphasizes resource optimization, particularly regarding computational processing and memory utilization, to ensure practical deployment in pavement management applications.
The first study develops a lightweight deep learning solution for pavement crack recognition using a convolutional neural network architecture. The proposed model is evaluated across three public benchmark datasets and one private dataset, demonstrating effective crack pattern recognition in pavement imagery. Explainability analysis reveals that the model focuses on relevant morphological features for crack identification rather than relying on spurious correlations.
The second study addresses the challenge of developing a computationally efficient deep learning solution for pavement crack segmentation. We propose LiteCrackNet, a U-Net-based convolutional neural network that incorporates atrous convolution and multi-scale supervision for enhanced feature extraction. Evaluation across three public benchmark datasets demonstrates that LiteCrackNet outperforms existing state-of-the-art lightweight models, achieving superior precision-recall balance with reduced computational requirements. Cross-dataset evaluation further validates the model's enhanced generalizability compared to competing approaches. Notably, LiteCrackNet achieves state-of-the-art performance with only 0.043 million parameters, demonstrating exceptional parameter efficiency.
The final study implements image processing techniques to measure crack width from segmented images and categorize cracks into three severity levels: low, medium, and high. The classification system defines low-severity cracks as those with widths less than 3 mm, medium-severity cracks as those ranging from 3 mm to less than 6 mm, and high-severity cracks as those with widths of 6 mm or greater.
The proposed end-to-end framework delivers a computationally efficient solution for pavement crack classification while maintaining state-of-the-art performance levels, as demonstrated through comprehensive benchmark evaluations
Utilizing Farm Savings to Reduce Income Volatility for Southern Row Crop Producers
No full textAmerican farmers continue to operate in a financially volatile industry, experiencing high revenue variability from year to year. A variety of elements, including erratic weather patterns, variable production costs, and deflated market prices, create financial uncertainty on an annual basis. Farm savings accounts have been discussed at various times over the past thirty years, although they have not been enacted at the federal level. Recently, the need for one-time economic assistance programs has been evident, giving reason to investigate the potential addition of a new risk management tool. The Reducing Farm Income Volatility Account (RFIVA) is a tax-deferred savings account designed to provide income stabilization by encouraging farmers to manage risk through deposits in high-income years, while making withdrawals during low-income years. RFIVA allows farmers to make tax-deductible deposits to lower tax liability during high-revenue years and smooth out their income stream during low-revenue years. This account does not replace existing risk management strategies, such as tax deduction methods, marketing tools, or crop insurance policies. It provides an additional financial management tool for farmers to minimize income volatility and create a personal safety net reserve
Embedded Imaging of Internal Shock Boundary Layer Interactions
No full textRamjets and scramjets continue to be a central developmental focus spurred by both offensive and defensive needs on the battlefield. The development of field-able versions of these supersonic and hypersonic air-breathing propulsion systems will rely on improving the collective physical understanding of inlet flow physics enabled by the continued development of improved non-intrusive measurement systems. Present experimental methods of characterizing these internal, shock-dominated flows largely rely on the use of pressure taps in practical, optically-inaccessible geometries. The present work offers a solution in the form of a miniature embedded camera system which is designed to perform non-intrusive measurements which is then applied to the measurement of wall-bounded, incident/reflecting shock boundary layer interactions.
The camera system developed in this work leverages recent developments in the field of board-mounted camera systems to produce a packaged camera with integrated illumination which is capable of performing oil flow visualization (OFV) and pressure-sensitive paint (PSP) experiments. The system was fielded in the University of Tennessee Space Institute Mach 4.0 Ludwieg Tube, obtaining direct optical measurements at the throat of a custom-built Busemann streamline-traced inlet model. The camera system obtained pressure and shear fields while surviving the harsh tunnel environment. Following this initial success, the Auburn University variable Mach number tunnel was modified by adding an extension to enable the main experimental effort. The data from these tests suggest that corner flow/shock interaction is primarily driven by the swept shock interaction on the sidewall rather than Free-Interaction Theory (FIT). PSP and OFV results indicate that the corner region interaction length increases with Mach number, and decreases with wedge angle and shock strength. This trend is explained by comparison to the swept shock upstream interaction measurements of Settles and Lu. An interaction length scaling is proposed based on this work which acts synergistically with FIT to produce the scaled interaction
Applications of charcoal morphometry and morphology during the Cretaceous Period
No full textWildfire regimes are intensifying globally due to anthropogenic climate change, necessitating improved methods for reconstructing past fire activity to inform future mitigation strategies. The Cretaceous period, particularly the Campanian stage, serves as a valuable analog for future greenhouse climates due to its elevated atmospheric CO₂ levels and absence of polar ice caps. This thesis refines the use of sedimentary charcoal as a proxy for paleofire and paleoecological reconstructions by conducting novel experimental and in situ analyses. We present novel data morphometrics based on aspect ratio (L:W), circularity, rectangularity, and feret diameter, revealing that charcoal morphology varies significantly at the tissue and component levels. Our findings indicate that Cretaceous wildfires were predominantly low-intensity surface fires fueled by ferns and small angiosperms, with taphonomic processes influencing charcoal preservation. These insights improve fire history reconstructions and underscore the importance of modern fuel reduction strategies, such as controlled burns, to mitigate future wildfire risks in warming climates
Effect of thermal variation during late-stage incubation on broiler chicken post-hatch growth performance, Pectoralis major muscle growth characteristics, and satellite cell activity
No full textThermal variation (TV) occur in both multi-stage and single-stage incubators under commercial settings, and slight variation from optimal during late-stages of incubation (LSI), while embryonic muscle fibers and satellite cells (SC) are being established, result in detrimental effects on body weight (BW), body weight gain (BWG), feed conversion ratio (FCR) and carcass characteristics. Additional reductions in average Pectoralis major (PM; breast) weight and responses in breast meat yield highlight the economic importance of optimal incubation temperatures. Therefore, to better understand the cellular and molecular mechanisms behind these post-hatch responses in muscle growth, an experiment was conducted applying TV during LSI (embryonic day (ED) 11 to 18). In which growth performance, PM muscle growth characteristics and SC activity were assessed over time post-hatch. Yield Plus × Ross 708 broiler breeder eggs (n = 2,160) were incubated at 37.5 °C from ED 0 to 11. On ED 11 COLD incubator setpoints were decreased to 36.4 °C, CTRL incubators remained 37.5 °C, and HOT incubator setpoints were increased to 38.6 °C (n = 2 incubators per treatment). At transfer (ED 18), all incubators were set to 36.7 °C until hatch. Chicks were pulled simultaneously from hatchers by treatment and were allotted to floor pens with 45 birds per pen (n = 2 pens per TV treatment). On d 7, 14, 21, and 28, Bird BW was recorded and the whole left PM and muscle sample tissue from the right PM muscle were collected and stored for cryohistological and immunofluorescence analysis. Data were analyzed as a 1-way (TV) or 2-way (TV × sex) ANOVA with the GLIMMIX procedure of SAS (v9.4). Means were separated with the PDIFF option at P ≤ 0.05. Tendencies were declared when 0.0501 ≤ P ≤ 0.10. No interaction between TV treatment and sex were observed, therefore only results for TV treatment as a main effect are reported. Birds from COLD incubators were the lightest compared to the HOT group on d 7 (P = 0.015) and tended to be lighter than the CTL on d 14 (P = 0.069). Similarly, both COLD and CTL birds gained the least weight at 7 d of age compared to the HOT treatment (P < 0.001) and tended to gain the least weight compared to CTL birds on d 14 (P = 0.075). PM muscle weight was reduced by COLD temperatures during LSI at 7 d post-hatch compared to HOT temperatures (P = 0.022). On d 21 COLD birds continued to have the smallest PM muscle weight compared to CTL and HOT groups (P = 0.033). When looking at PM growth characteristics, the average PM muscle fiber cross sectional area (CSA) of COLD birds tended to be smaller than those from the HOT group (P = 0.056). Similarly, both COLD and CTL birds had smaller fibers compared to HOT birds at d 21 post-hatch (P = 0.027). As expected, inversely proportional to these results, birds incubated under hypothermic conditions had higher fiber densities compared to HOT birds at 14 (P = 0.0049) and 21 (P = 0.0044) d of age. These changes in average PM fiber CSA also reflected in fiber size distribution, with HOT birds having lower proportion of small fibers on d 7 (P = 0.010) and higher proportion of big fibers on d 21 (P = 0.047). No differences amongst TV treatments were observed on total nuclei, MRF+ SC, mitotically active MRF- cells, total MRF+ mitotically-active, total MRF+ SC, and total mitotically active cell population densities at any sampling point (d 7, 14, 21, and 28). Higher densities of mitotically active SC expressing Pax7 (Pax7+:BrdU+) were observed in PM muscle tissue from HOT birds at 28 d of age, both on a per mm2 (P = 0.038) and a per 1000 fibers (P = 0.036), while the rest of mitotically-active MRF+ SC categories remained similar amongst TV treatment over time. TV during LSI result in changes on post-hatch PM muscle growth characteristics. However, these results present no evidence for these changes to be SC-mediated
Systematics of the Riffle Dace with Special Emphasis on the Blacknose Daces (Leuciscidae: Rhinichthys)
No full textThe freshwater fish genus Rhinichthys (Agassiz 1849) has a complex taxonomic history and extensive geographic distribution across North America. In this dissertation, I used multiple molecular and morphological approaches to resolve taxonomic uncertainties and understand evolutionary relationships within this genus. Multi-locus phylogenetic analysis using Bayesian Inference revealed three major clades within Rhinichthys: R. atratulus, R. cataractae, and R. osculus clades. Widespread species were found to be non-monophyletic due to misidentifications and local endemic populations recovered within broader species complexes. Restriction site-associated DNA sequencing (3RAD) analyses of the Eastern Blacknose Dace (R. atratulus) and Western Blacknose Dace (R. obtusus) revealed three distinct evolutionary lineages with strong phylogenomic support: R. atratulus, R. obtusus A, and R. obtusus B (potentially R. meleagris). The distribution of R. obtusus B in predominantly glaciated regions versus R. obtusus A in non-glaciated regions suggests distinct evolutionary histories tied to glacial refugia and subsequent recolonization patterns. Despite their genetic distinctiveness, geometric morphometric analysis demonstrated that the Eastern and Western Blacknose Dace species are morphologically indistinguishable. Principal component analysis revealed no significant differences, though canonical variate analysis did differentiae the species, although the differences are not likely diagnostic. When focusing on R. obtusus populations within Alabama, a biogeographic study focused on populations in the Black Warrior River system of the Mobile Basin revealed multiple independent movements between the Tennessee River Drainage and the Mobile River Basin. Phylogenomic analysis recovered two separate, monophyletic clades that are not each other’s closest relatives, with variable gene flow recovered across systems. These findings suggest that R. obtusus was likely never fully extirpated from the Black Warrior River despite previously suggested. Overall, this dissertation highlights the complex evolutionary relationships of Rhinichthys and demonstrates the values of combining multiple molecular and morphological approaches to better resolve intricate relationships. My dissertation not only addresses key questions but also opens new areas for exploring evolutionary patterns within this diverse genus of North American freshwater fishes