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Novel Method for Pure Polymer Vagus Nerve Stimulators
Full text linkVagus nerve stimulation (VNS) has become a promising treatment for epilepsy, depression, obesity, and more. However, the state-of-the-art nerve cuffs use metal conductors, limiting the implanted VNS devices’ biocompatibility, electronic properties, and ultimately the device lifetime. Because the benefits of VNS treatment increase over time, and metal limits the lifetime of devices, a transition to non-metallic conductors with a better match to tissue material properties and safer electronic properties promises to increase the lifetime of VNS devices. To demonstrate the replacement of metal with a conductor with properties closer to that of body tissue, a novel fabrication scheme was designed using a consumer pattern cutter to create a fully polymeric neural stimulator. Kapton was used as insulation around the conductive element, PEDOT:PSS. Electrodes with 1 mm pad diameters were successfully fabricated and characterized by electrochemical impedance spectroscopy, cyclic voltammetry, transient voltammetry, and tensile testing. Devices with 1 mm pad diameters were found to have an average impedance at 1k Hz of a 7.83 ± 263 kW and charge injection capacity of 356.52 ± 216.08 μC/cm2. The results found in this thesis demonstrate the potential for fully polymeric nerve stimulators
“Untraditional Intimacies:” Re-Pairing American Narratives of Racialization and Settler Colonialism in Ocean Vuong’s On Earth We’re Briefly Gorgeous (2019) and Gerald Vizenor’s Hiroshima Bugi: Atomu 57 (2003)
No full textRecent scholarship on contemporary American literature has asked how representations of cross-racial relationships can restore the blotted-out stories and experiences of minoritized individuals in the United States. This essay incorporates and expands upon the theorization of cross-racial relationships to read across several fields, developing a macroscopic framework around relationships represented in contemporary multiethnic literature that confront the oppressive systems embedded in the American nation-building process. Drawing upon the work of scholars like Lisa Lowe, I define the concept of “untraditional intimacies” as relationships between people who share similarly lived experiences as those who have been most directly affected by America\u27s racialization and settler colonialism. These untraditional intimacies may extend across race, across colonial borders, across time, and/or beyond heteronormativity to challenge prominent representations of relationships in America that segregate and erase racialized peoples. I apply this concept to Anishinaabe Gerald Vizenor’s Hiroshima Bugi: Atomu 57 (2003) and to Vietnamese American Ocean Vuong’s On Earth We’re Briefly Gorgeous (2019) to analyze how the untraditional intimacies in these novels-in-verse are relationships that “re-pair” ongoing narratives of racialization and settler colonialism across the contemporary United States and beyond. This essay also theorizes the American “Frontier” as any space that reinforces American narratives of racialization and settler colonialism. When the Frontier becomes a moveable space no longer tethered to the nineteenth-century American West, it creates a way scholars can analyze, track, and compare how these narratives have had similar or different impacts from nation to nation, region to region, relationship to relationship, or person to person. In a “reverse American expansion,” I argue Vuong’s work situated in New England takes readers back to a region where American colonization began centuries earlier, revealing how it has only continued to function as this Frontier space. On the other hand, Vizenor’s work speaks to how the American West continues to exist as this Frontier at the same time Japan has also become an American Frontier with American imperialism
The Ecophysiology of the Enigmatic Namib Succulent, Lithops ruschiorum
No full textWater availability is the primary constraint for plant survival and reproduction in hyper-arid ecosystems. In such environments, plant fitness depends on an alignment between physiological traits and limited water resources. The Namib Desert of Namibia exemplifies this extreme selection pressure. Within the Namib Desert, Lithops ruschiorum, a succulent endemic to the gravel plains, exhibits habitat specificity and numerous physiological adaptations to cope with the hyper-aridity.
This research explores the intersection of two fitness strategies for L. ruschiorum: habitat selection and exploitation of alternative moisture sources. The first chapter explores the population dynamics and micro-site habitat conditions preferred by L. ruschiorum. Our population surveys between 2007 and 2024 revealed a significant decline in abundance of L. ruschiorum, with several populations approaching local extinction. The habitat distribution analysis indicated that topographic position and substrate type best predict habitat occupancy for L ruschiorum possibly due to the potential for fog capture and retention. Our second chapter investigates the hypothesis that fog, as opposed to rain or groundwater, serves as the primary water source used by L. ruschiorum. Stable isotope analyses, foliar capacity tests and fluorescent microscopy indicated that L. ruschiorum supplements its water budget through the foliar uptake of fog. These findings suggest that the species’ survival depends on highly specific microhabitats and fog water inputs. With the growing threats of climate change and poaching, L. ruschiorum is vulnerable to irreparable population loss. An understanding of the environmental factors determining the species’ distribution and its primary water source inform conservation and restoration strategies for the long-term survival of the species
Application-Driven Materials Development of Solid-State Conductive Composites of Ultra-High Molecular Weight Polyethylene
Full text linkUltra-high molecular weight polyethylene (UHMWPE) is a linear long chain homopolymer valued for its toughness, wear resistance, and chemical inertness. In the medical field, these properties make it the material of choice for bearing surfaces despite recognized tradeoffs between wear resistance, toughness, and oxidation resistance. Electrically conductive composites of UHMWPE show promise to enable new types of smart and active load-bearing implants in a future of personalized medicine, if beneficial properties can be maintained with the addition of solid-state additives.
Clinical need-finding conducted through Dartmouth’s Training Program in Surgical Innovation revealed several potential applications for conductive, load-bearing polymers. These include: (1) conductive knee bearings for electrochemical treatment of prosthetic joint infection, (2) strain sensors for arthroplasty and spinal applications, and (3) electrodes for embedded sensors in orthopedic bearings. Each application area demands specific material properties, requiring a framework for producing a tough, conductive polymer composite with adjustable parameters while considering property tradeoffs.
Carbon black nanoparticles were added to UHMWPE to confer conductive properties while providing good interphase adhesion. A range of carbon black concentrations were tested to understand the effect of additive concentration on certain mechanical and electrical properties relevant to highly-loaded applications. Mechanical toughness measures indicated that tensile and impact toughness properties were more affected by the presence of the additive than fatigue properties. Comparisons to neat void-filled materials demonstrated that this effect could be explained in part by the presence of intergranular defects in the material. Electrical results demonstrated that resistive properties were predictable in the plastic regime at lower strains, but deviated from theoretical behaviors at higher strains. These results provided a key understanding of the deformation behavior of conductive nanoparticles in these materials. Furthermore, results showed that these composites can simultaneously meet mechanical and electrical requirements for the applications of interest. Overall, this work demonstrated mechanical and electrical viability of these materials for clinical applications while providing a deeper understanding of structure-property relationships in solid-state, electrically conductive composites of UHMWPE
A Realizability Approach to Constructing Higher Types via Classifiers
Full text linkWe construct an interpretation of higher types into Peano arithmetic, showing in particular that every model of PA is a model of higher types. This is a reversal of Gödel’s Dialectica construction. We also define the classifier degrees, a degree structure which subsumes the Turing degrees, the enumeration degrees, and the many-one degrees. The classifier degrees boast a rich structure and many well-behaved operations
Functional Morphology of the Primate Knee and its Implications for Hominin Bipedal Mechanics
Full text linkBipedal locomotion is central to the human condition, having shaped our evolutionary trajectory since its early emergence in the hominin lineage. Despite its importance, key questions remain about its origins and evolutionary trajectory. While many studies have focused on locomotor-related anatomies, comparatively less attention has been paid to the knee joint – a structure critical to the primate locomotor repertoire. This dissertation aims to clarify the form-function relationship of the knee in extant primates to better infer the locomotor behaviors of Miocene hominoids and Plio-Pleistocene hominins. To address these questions, this research employs a multifaceted analytical approach, integrating linear measurements, three-dimensional shape analysis, modern kinematic data, and virtual musculoskeletal modeling. Chapter One reviews linear measurements of the distal femur within the hominin genus Australopithecus. Chapter Two presents a 3D shape analysis of the distal femur and proximal tibia across modern humans, extant primates, and fossil hominins, linking variation in shape to patterns of knee flexion during gait. Chapter Three extends the shape analysis to the Miocene apes Sivapithecus, Morotopithecus bishopi, and Danuvius guggenmosi, contextualizing their knee functional morphology within that of extant primates. Chapter Four integrates these datasets using virtual musculoskeletal simulations to evaluate a novel model of early hominin gait: the extended-hip-bent-knee (EHBK) hypothesis. Together, these dissertation findings support a mosaic pattern of knee morphology among Miocene fossil hominoids and highlight variability in bipedal gait mechanics among Plio-Pleistocene hominins, including the presence of moderate knee flexion in early hominin locomotion
Benchmarking Low-Power Line-Frequency Transformers
No full textThis poster presents research from the First-Year Research in Engineering Experience (FYREE) at Dartmouth\u27s Thayer School of Engineering, focused on benchmarking low-power line-frequency transformers (LFTs). The study examined 19 commercial transformers used in HVAC units, doorbells, and similar systems, assessing performance in terms of power loss, efficiency, and power factor under varying input conditions.
To streamline testing, the team developed a semi-automated system integrating a programmable resistor array, Arduino-controlled switching, and MATLAB-compatible data acquisition using a Voltech PM6000 analyzer. These hardware and software improvements reduced transformer testing time from over an hour to just 15 minutes per unit. The resulting data—over 4000 points—revealed trends across transformer models and identified trade-offs between price, size, and efficiency.
The benchmarking process was also applied to test a small solid-state transformer designed by co-author Allen T. Nguyen, which aims to improve standby power efficiency through high-frequency switching.
This work lays the foundation for future research into more efficient, compact transformer technologies and supports broader energy-saving applications in residential and industrial electronics.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1005/thumbnail.jp
The effects of a geopolitical policy—Case Study of “Korea Limitation Order” upon the Cultural Entertainment Industry in China
Full text linkThis paper examines the impact on the South Korean Cultural Entertainment Indus- try(CEI) of China’s “Korea Limitation Order”. In November 2016, Beijing restricted South Korean artists from holding concerts and the broadcast of South Korean TV dramas and banned cooperation between the two countries in the entertainment in- dustries. This paper focuses on the effect this had on exports of cultural products and relating industries from Korea, and how Korea was able to adjust to this geopolitical shock. I examine exports from Korea to China, Japan, and the United States using data from Cultural Entertainment Industry Products Exports, such as Korean mu- sic and filming industries, and South Korean inbound foreign tourism statistics from 2011 to 2019. Utilizing the deviation from an estimated autoregressive moving average (ARMA) model specification of exports from Korea after the “Korea Limitation Order” and a Difference-in-Difference (DID) Model, I found that South Korea’s tourism indus- try was particularly affected, with the most significant decline relative to the other two countries. The film and broadcasting industries saw similar but less dramatic declines. There is no evidence that sectors of the cultural industry that are not included in this restriction category, such as the cartoon industry, were impacted by this shock
High-Accuracy Soybean Yield Prediction Using Multispectral Satellite Data
No full textModern agriculture generates vast volumes of satellite and environmental data, yet the tools used to forecast crop outcomes often fail to integrate these inputs into accurate, scalable predictions. In soybean production—a sector where yield forecasts underpin hundreds of billions of dollars in commodity trading, insurance, and supply chain activity—current methods typically rely on delayed government reports, aggregated seasonal summaries, or localized proprietary surveys. These limitations restrict both the timeliness and the geographic scalability of traditional forecasting systems.
This thesis presents a machine learning framework designed to predict county-level soybean yields by leveraging satellite imagery and environmental data collected over daily timescales. The system processes high-frequency time series inputs through a learnable model architecture capable of recognizing dynamic crop development pat terns across time and space. By directly modeling environmental dynamics at fine temporal resolution, the framework enables automated, high-accuracy forecasts with out the need for ground surveys or region-specific calibration.
Experimental results demonstrate test R-squared values between 0.87 and 0.91, with root mean squared error (RMSE) values between 3.02 and 3.37 bushels per acre on held out years—substantially outperforming published academic benchmarks. These out comes demonstrate that scalable, real-time yield forecasting can be achieved through advanced deep learning approaches, offering significant potential for earlier, more geographically resolved agricultural intelligence