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Attentive Optimism in the Face of Uncertainty: Balancing Exploration-Exploitation in Multi-Armed Bandits
No full textSequential decision-making is the process of making a sequence of decisions over time, where each decision can impact future outcomes. This framework is critical in many real-world scenarios, where decisions must be adapted based on the observed results. Within this context, contextual multi-armed bandit (CMAB) models have emerged as a powerful tool, aiming to balance exploration of new actions and exploitation of known rewards. These models are employed under uncertainty and have been proven to be efficient in different domains such as recommendation systems, adaptive clinical trials, and dynamic resource allocation. However, many existing methods rely on strong assumptions, which limit their effectiveness in real-world settings characterized by complex reward structures, evolving user preferences, and high-dimensional feature spaces. As a result, such models often suffer from inadequate exploration or an inability to accurately estimate rewards in non-linear or temporally drifting environments. To address these limitations, this work proposes a novel model that enhances traditional bandit algorithms through two key innovations: (1) an attention-based exploration mechanism that modulates exploration adaptively over time for each arm, and (2) an adaptive k-Nearest Neighbors (k-NN) regression module that captures local reward variations to better model non-linear relationships. We enhance the classic Linear UCB (LinUCB) structure with these two components, leading to development of a new algorithm called LNUCB-TA. LNUCB-TA combines global linear estimation of expected rewards with a non-parametric k-NN adjustment, where the number of neighbors is dynamically selected based on the reward variance of each arm. This allows the model to flexibly respond to both stable and volatile conditions. The exploration component is enhanced by a temporal attention mechanism that balances global and local reward trends, ensuring that arms with promising but underexplored behavior receive appropriate attention. This design enables LNUCB-TA to adaptively navigate dynamic environments, balancing the exploration-exploitation trade-off more effectively than existing models. Theoretical analysis confirms that LNUCB-TA maintains sublinear regret bounds, while incorporating non-linear estimation and dynamic exploration. Empirical results on a wide range of benchmark datasets and real-world news recommendation tasks further validate its effectiveness. LNUCB-TA consistently outperforms existing baselines in terms of both average regret and stability across hyperparameter configurations. In addition, this thesis explores how a proposed attention-based exploration mechanism can be integrated into other bandit models, demonstrating consistent performance gains. Finally, ablation studies and error analyses highlight the individual contributions of the k-NN and attention components and reinforce the robustness of the proposed model
Neuroendocrine Regulation of the Luteinizing Hormone Surge and Puberty Onset in Sheep
Full text linkGonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle stimulating hormone (FSH) are essential for the reproduction of all mammalian species, including both sheep and humans. GnRH is secreted by hypothalamic neurons into the hypophyseal portal vasculature in a pulsatile manner, which then acts within the anterior pituitary to elicit the release of LH and FSH into wider systemic circulation. In females LH and FSH act on the ovaries to promote estradiol (E2) production, follicular development, and under certain conditions in regard to LH, ovulation. Furthermore, while E2 inhibits GnRH and subsequent LH secretion under most conditions, at high concentrations E2 acts as a positive regulator in the hypothalamus to generate an elevated and prolonged release of GnRH, and thus LH, termed the GnRH/LH surge, which culminates in ovulation. However, hypothalamic GnRH neurons lack estrogen receptors, thus E2-mediated feedback must occur upstream of GnRH neurons.
Arcuate nucleus (ARC) located kisspeptin-, neurokinin B-, and dynorphin A-containing neurons, known as KNDy neurons, are thought to mediate E2-negative feedback, but their possible role in E2-postive feedback was not completely understood. Within this dissertation we demonstrate that the ablation of KNDy neurons significantly blunted the amplitude of the GnRH/LH surge, suggesting a role in E2-positive feedback as well. Additional hypothalamic neuronal populations are thought to contribute to the GnRH/LH surge, such as retrochiasmatic area neurokinin 3 receptor- (NK3R) and galanin-containing neurons, and ARC kisspeptin receptor-containing (Kiss1R) neurons. By blocking the action of galanin within the ARC and on the KNDy neurons located there, we subtly but significantly reduced the amplitude of the GnRH/LH surge, while ablating ARC Kiss1R-containing neurons prevented the occurrence of the surge out right.
In females, puberty relies on both increased pulsatile GnRH/LH secretion as well as the emergence of the E2 induced GnRH/LH surge. While KNDy neuron number does not change during ovine puberty, other neurons contribute to this physiological process as well. ARC Kiss1R-containing neurons, which are crucial for the GnRH/LH surge, were ablated in prepubertal female lambs and significantly delayed puberty onset. The mechanism for this is not clear, but GnRH/LH surge amplitude was significantly reduced, but not blocked as seen in adults, suggesting a possible disruption to the generation of the preovulatory surge. Additionally, preoptic area NK3R-containing neurons, which contribute to the GnRH/LH surge in adult ewes, were ablated in prepubertal female lambs as well. This significantly accelerated puberty onset but had no effect on the timing or amplitude of the GnRH/LH surge and, surprisingly, no reduction in cell number was observed. Further studies are needed in characterizing preoptic NK3R-containing neurons and to determine whether they are truly inhibitory to puberty onset in sheep.
Body weight and metabolism are tightly linked to reproduction and fertility, as well as to puberty onset. The melanocortin system, consisting of pro-opiomelanocortin (POMC) and agouti-related peptide (AgRP) neurons located in the ARC, act to integrate metabolic cues into the reproductive axis. POMC, through its cleavage product alpha-melanocyte stimulating hormone, acts as an excitatory stimulus, while AgRP plays an inhibitory role. We examined both the number of POMC and AgRP neurons and their activation throughout pubertal development in female lambs. POMC cell numbers did not change, but their activation, as measured by c-Fos, was elevated at the postpubertal time point. In contrast, AgRP cell numbers obviously and significantly decreased from the pre- to postpubertal time point and their activation significantly decreased as well. Thus, puberty onset in sheep may in part be mediated through the withdrawal of inhibitory AgRP signaling and an increase in stimulation via POMC neurons
VITAL RATES AND NEST SITE SELECTION OF MERRIAM’S WILD TURKEYS (MELEAGRIS GALLOPAVO MERRIAMI) IN SOUTH-CENTRAL, SOUTH DAKOTA
Full text linkWild turkeys (Meleagris gallopavo) are an economically and culturally significantly game species throughout much of the United States. Within South Dakota, spring turkey hunting generates approximately $20 million in expenditures annually to local economies. Merriam’s wild turkeys (Meleagris gallopavo meriami) were reintroduced to the Missouri River Breaks of Gregory County, South Dakota, USA, between the 1950s and 1980s, and was one of the most successful reintroductions in the state. However, a recent decline in gobbler harvest suggests a potential decline in this population. To estimate survival and reproduction and evaluate nest site selection, we captured 121 wild turkey hens and fitted them with VHF transmitters during the winters of 2023 and 2024. We monitored wild turkey hens from January 2023-December 2024. We used Bayesian methods to model hen survival, nest survival, poult survival, clutch size, and nest site selection as a function of covariates. Annual survival probabilities were 0.28 for adults and 0.55 for yearlings during our study period. Adult hen survival was lower than previous studies in the Midwest and throughout much of the United States. We recorded 119 nesting attempts across 2023 and 2024, with 25 successful nests. The survival probability for nests incubated by adults was 0.22 and 0.18 for nests incubated by yearlings. The survival probability for poults reared by adults was 0.14 and 0.12 for poults reared by yearlings. The average clutch size for this study area was 9.87 eggs. We found that nest site selection for deciduous land cover decreased later in the nesting season. Managers may seek to improve hen and nest survival by carrying out activities that improve nesting habitat
Litigating \u3cem\u3eLoper Bright\u3c/em\u3e: Interpretive Challenges and Solutions for the Post-\u3cem\u3eChevron\u3c/em\u3e Era
No full textThis Article arrives at a critical juncture in Administrative Law and comprehensively answers two burning questions about Loper Bright Enterprises v. Raimondo, the case that overturned Chevron deference. First, what did Loper Bright change about review of agency action? Second, how should lower courts implement the decision? This Article engages in a first-of-its-kind, exhaustive review of the major circuit court decisions citing Loper Bright and analyzes how influential judges, scholars, and justices have characterized the impact of the decision. The Article defines what role Skidmore “deference” and the major questions doctrine should play in judicial review—while seriously questioning the long-term viability of the latter. Using this study and foundational administrative law methodologies, I propose a three-step formulation on how judges should tackle statutory interpretation and related constitutional issues in the post-Chevron era. This approach will be helpful to courts, academics, and litigants because it is simple enough to quickly understand but contains the depth necessary to engage some of the hardest textual challenges. This Article also soundly rebuts the argument made by influential scholars that Loper Bright is simply a rebranded Chevron that does not mark a significant change in administrative law. The Article engages directly with these scholars and, through its analytical proposal, stands as a rebuke of this criticism—showing, through both real-world and hypothetical application, just how significantly Loper Bright changed things. Finally, the Article proposes that if Congress responds to the decision by expanding its grants of discretionary authority to agencies, the Supreme Court will have no choice but to both revive a robust non-delegation doctrine and more broadly apply void for vagueness to civil cases
Perceived Unmet Needs and Barriers to Services Associated with Traumatic Brain Injury in Rural Populations
Full text linkThis study investigated unmet needs of individuals with traumatic brain injury (TBI) and of their caregivers living in rural communities. The objective of this research study was to identify occupational therapy’s role and intervention priorities for individuals with TBI and their caregivers in rural settings. Descriptive statistics were generated from quantitative survey responses obtained from 84 community-dwelling individuals with TBI and 40 caregivers ranging in age from 18 to 80 years. The most identified “barriers” were poor awareness of the ways to receive services (TBI Survivors = 65%, Caregivers = 61%), inadequate professional/provider knowledge about available supports and services (TBI Survivors = 63%, Caregivers = 52%), and difficulty finding healthcare providers who understand brain injury (TBI Survivors = 55%). Needs reported as being most frequently “unmet” among individuals with TBI were cognition (43%), establishing relationships (39%), and opportunities to socialize (37%). Caregiver’s most identified “unmet” needs were financial assistance (43%), behavior services for the individual with TBI (52%), services to increase the independent living skills of the individual with TBI (49%), help with developing/maintaining friendships and relationships (33%), and help finding/accessing recreational or leisure activities (40%). Participants prioritized unmet needs that were consistently within the occupational therapy scope of practice. Findings indicate a lack of services and support related to cognition and social aspects of TBI recovery. Study findings support the need to ensure that OT practitioners have the knowledge and skills to support client cognitive performance and to facilitate meaningful social networks. Discharge considerations should consider higher-level cognitive and social rehabilitation needs
From Creek to Community:Restoring Deckers Creek Watershed
Full text linkThis project was conducted out of the Center for Resilient Communities in partnership with local non-profit Friends of Deckers Creek. This research explored the impacts of industrialization and water contamination on the health and well-being of community members in the Deckers Creek Watershed. West Virginia’s rolling mountains, steep slopes, and low hollers are a place where many families and individuals call home. Our beautiful landscape is full of mountains and rivers that continue to be a source of joy for many of the people living within the region. When West Virginians reflect on what makes them feel connected to this place, it is often the people and the landscape that come to mind. The Appalachian landscape is distinctive, but it has suffered from significant environmental degradation due to various economic industries. More specifically, the Deckers Creek watershed has experienced the boom and bust of coal mining along the banks of its streams. Stretching 24.6 miles through Monongalia and Preston Counties, the watershed touches the lives of tens of thousands of residents. Unfortunately, pollution from historical mining and other sources has compromised the health of the creek, leading to the loss of natural beauty, recreational opportunities, and, most critically, access to clean water. Through a historical analysis of newspaper archives, community mapping exercise, community surveys, and water sampling, this research focuses on the benefits of conducting a holistic assessment of watersheds and how to build more just, vibrant, and resilient communities
