Scholarworks

ScholarWorks is an open access repository for the capture of the intellectual work of Montana State University (MSU) in support of its teaching, research and service missions. MSU ScholarWorks is a central point of discovery for accessing, collecting, sharing, preserving, and distributing knowledge to the Montana State University community and the world.

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Scholarship & Research

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Bridging the reptilian-avian reproductive continuum through analysis of maniraptoran dinosaur nesting physiology
(Montana State University - Bozeman, College of Letters & Science, 2026) Hogan, Jason Douglas; Chairperson, Graduate Committee: David J. Varricchio; This is a manuscript style paper that includes co-authored chapters.
While it has been the general scientific consensus that the dominant avian practice of thermoregulatory contact incubation of fully exposed eggs evolved from a prior habit of crocodilian-like nest guarding of fully buried eggs, the efficacy of specific intermediate behaviors and the role of associated selective pressures is not well understood. Troodon formosus, a late Cretaceous theropod from North America, has provided fossils illuminating this period of transition from reptilian to avian reproductive strategies. Unfortunately, this species has long been plagued by taxonomic and nomenclatural concerns. We believe these issues would be significantly alleviated by the designation of a neotype. Our biological understanding of T. formosus is further bolstered via investigation of behavior and ecology. Daily growth lines in an embryonic tooth attributed to T. formosus suggest an incubation period of around 74 days, a value between what would be expected for a reptilian (107 days) and avian (44 days) egg of the same mass. Experimental analysis of maniraptoran nesting practices indicates that their partially buried eggs (as evidenced in the fossil record) likely could have benefited more from contact incubation than previously believed. Additionally, experimental results suggest that an attending, endothermic adult might have been able to warm even a fully buried clutch through a barrier of sediment. Egg asymmetry is another feature that appears at this junction, and while it has been well studied in modern birds, most of the suggested benefits are inapplicable to the asymmetric eggs of T. formosus. Actualistic and virtual experimentation indicates that elongate, asymmetric egg-shapes could have reduced the likelihood of displacement and provided increased resistance to vertical compression; two concerns that might have accompanied early contact incubation. Given information gleaned from the studies described herein, it seems possible that the gap between modern avian and crocodilian-style reproduction could have been bridged by stages described as indirect contact incubation (fully buried eggs warmed by an attending adult) and weak contact incubation (partially buried eggs warmed by an attending adult)--changes driven by a selective pressure for increased clutch temperatures.
Content-based recommendation via topic modeling and social network analysis
(Montana State University - Bozeman, College of Engineering, 2025) Noor, Md Asaduzzaman; Chairperson, Graduate Committee: John Sheppard
The exponential growth of digital information and scholarly output has increased the need for intelligent systems that can identify relevant, interpretable, and equitable connections among entities. Traditional content-based recommender systems focus on item similarity but often overlook the relational structures that govern how knowledge and expertise are organized. This dissertation advances content-based recommendation by integrating topic modeling and social network analysis into a unified framework that represents semantic similarity as a network. The framework models relationships among entities through their topical proximity, enabling recommendations that are not only accurate but also transparent and structurally grounded. The research is organized around four interrelated questions. The first investigates how topic modeling can be combined with network analysis to construct topic-based collaboration graphs that reveal latent research communities. By transforming document-level topic distributions into author-level profiles, this approach defines weighted network edges through topical similarity, producing networks that balance cohesion and diversity. The second question extends this representation to hierarchical community detection, introducing Nested Hierarchical Louvain (NH-Louvain) and Spectral Hierarchical Agglomerative Clustering (Spectral-HAC). These methods uncover multilevel community structures, allowing recommendations to operate at different granularities, from tightly focused collaborators within a subcommunity to broader interdisciplinary groups. The third question addresses a broader data imbalance problem, demonstrated through the case of publication imbalance, where prolific authors dominate the content space and bias recommendation outcomes. A cloning-based strategy was developed to represent such authors by multiple topical instances, each reflecting a distinct research direction. Clone- LDA and Clone-BERT variants reduce dominance effects, improve thematic diversity, and enhance background representation in the generated networks. The fourth question evaluates the framework's accuracy, stability, and its content-based explainability, assessed through hold-out and perturbation experiments. Results show that topic-based similarity remains stable under missing information and that hierarchical and cloned models yield balanced, semantically coherent communities. To operationalize these findings, the ScholarNode prototype system was developed, providing an interactive, explainable interface that links recommendations to their underlying topical and community evidence. Together, these contributions establish a principled foundation for topic-driven, network- aware recommender systems. The integrated framework advances understanding of how semantic and relational information interact, while the ScholarNode implementation shows its practical feasibility. Beyond the scholarly domain, the same design principles, representing content similarity as a network, detecting hierarchical communities, addressing imbalance, and supporting content-based explanations, can generalize to other content-rich environments. This research thus lays the groundwork for recommender systems that emphasize clarity, diversity, and balanced representation.
Individual differences of working memory capacity in Stroop performance with reactive support and incremental proactive support of attentional control
(Montana State University - Bozeman, College of Letters & Science, 2026) Charbonneau, Brooke Zauner; Chairperson, Graduate Committee: Keith A. Hutchison
Working memory capacity (WMC) differences in Stroop task performance reflect differences in attentional control ability. However, support for preparing to control attention for each trial (proactive control support via low list congruency) or support for attentional control when a trial appears (reactive control via low item congruency) may additively or redundantly support the attentional control to minimize Stroop performance differences. Although previous literature has shown differences interact with list and item congruency effects in the Stroop task (Hutchison, 2011), some of the effects were marginal and the list congruency was manipulated between groups. This limits that ability to see how the need for reactive control support changes as proactive support changes. Therefore, the current study examined WMC difference in Stroop performance for mostly congruent and mostly incongruent items (which provide reactive support) as list congruency incrementally decreased (therefore incrementally increasing proactive list support). Results replicated Hutchison (2011) by showing that WMC differences are larger for mostly congruent items within mostly congruent lists, indicating that WMC is redundant with both proactive and reactive support. Further, our reaction time results suggested that those with lower WMC benefit from reactive support when proactive support is absent but benefit less when proactive support is present. In contrast, those with higher WMC have a consistent benefit of reactive support whether proactive support is present or not. Future studies should consider disentangling whether proactive and reactive control work separately or simultaneously interact with WMC.
Towards lignin valorization from diverse biomass feedstocks
(Montana State University - Bozeman, College of Engineering, 2024) Becsy-Jakab, Villo Eniko; Chairperson, Graduate Committee: David B. Hodge; This is a manuscript style paper that includes co-authored chapters.
The biorefinery concept shows great promise for renewable energy and bioproducts. However, achieving economic viability remains a key challenge, particularly in realizing high- value applications for lignin. In this dissertation we investigated three key aspects of processing that affect lignin valorization: extraction, recovery, and solubilization. In Chapter Two, lignin was extracted from biorefinery hydrolysis residue using organosolv, alkaline, and ionic liquid methods and recovery yields were determined for each approach. Recovered lignin solubility was then screened with a range of organic solvents, and the fractional solubility of lignin was successfully predicted by using a novel method, which assumes lignin exhibits a distribution of solubility parameters, given its polydispersity. In Chapter Three, the alkaline extraction of lignin from corn stover and hybrid poplar was scaled and implemented to a 20-L scale by prioritizing the purity of lignin and throughput of lignin production. Lignin was recovered from the pretreatment black liquor by precipitation. The final lignin products were sent to collaborators for research on lignin fractionation and potential high-value applications. Due to inconsistent physical properties, especially color, we conducted a variable screening to determine which recovery condition impacts the physical properties of lignin. The filtering temperature had a significant impact on lignin recovery. In Chapter Four, the filtering temperature during lignin recovery was investigated in detail. A transition temperature was identified for lignin recovery marking a change in processability and color, from dark, slow-filtering lignin to light, easily filterable lignin. Chemical and physical differences between dark and light lignins were identified, such as particle morphology, surface roughness, chemical composition, and solubility. Finally, we proposed a theoretical framework based on colloid science to explain the observed differences by the kinetics of lignin aggregation.
Bio-inspired propulsion: vortex ring formation from varied flexibility nozzles and modal dynamics of plunging tapered hydrofoils
(Montana State University - Bozeman, College of Engineering, 2024) Mitchell, Brysen James; Chairperson, Graduate Committee: Sarah E. Morris; This is a manuscript style paper that includes co-authored chapters.
Many aquatic animals and flying insects rely on flexible bodies and appendages for efficient locomotion. The flexibility inherent in these organisms has been linked to increased thrust and efficiency across diverse operating conditions. In this work, two bio-inspired propulsion mechanisms are examined: the first investigates pulses of fluid ejected through nozzles of varying flexibility, and the second explores a tapered flexible foil subjected to varied heaving amplitudes. Jellyfish, squid, and siphonophores move by periodically contracting and expanding their bodies to expel and refill fluid from a flexible orifice, producing a series of vortex rings and stopping vortices. In this study, different volumes of fluid are ejected into a quiescent water tank through nozzles of varied stiffness to create vortex rings. Particle Image Velocimetry (PIV) is used to quantify thrust, and Finite-time Lyapunov Exponent (FTLE) fields are calculated to determine vortex ring pinch-off. It is found that the flexible nozzle stores and imparts elastic energy to the fluid, increasing the impulse of the ejected vortex ring. Impulse per unit volume is maximized at an optimal nozzle stiffness, wherein the damped natural frequency of the nozzle matches the fluid acceleration time. When the fluid decelerates, the more compliant nozzles collapse, suppressing unfavorable negative pressure regions from forming and instead eject additional fluid. Upon reopening, beneficial stopping vortices form within the nozzle, with circulation increasing with nozzle stiffness, indicating a second optimal stiffness criterion for a full expulsion-refill cycle analysis of this propulsion mechanism. The flexural rigidity observed in insect wings and fish fins is commonly nonuniform and typically decreases from leading to trailing edge. This variation in stiffness encourages the propagation of traveling waves along the structure, increasing propulsive performance over a wider frequency range. In this study, rectangular foils undergo a sinusoidal heaving motion with varied amplitude and frequency. 2D mode shapes and resonant frequencies are measured using a scanning laser vibrometer. PIV is used to quantify the thrust from the wake of the foil. The traveling wave behavior is quantified and correlated with the thrust measured in the foil wake.