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Underwater Optical Backscatter Communications using Acousto-Optic Beam Steering
No full textThis work introduces a novel, and high-speed underwater backscatter communication system based on acousto-optic light steering. The proposed approach enables underwater assets to achieve data transmission rates potentially reaching hundreds of megabits per second ( Mbps ), surpassing the performance of existing optical and acoustic backscatter techniques, which are typically limited to a few kilobits per second (kbps ). Communication is established by probing an underwater backscatter device with a pulsed laser from a base station, and detecting the retroreflected signal using an ultrafast photodetector. The backscatter device comprises a retroreflector and an ultrasound transducer, which generates pressure waves to modulate the refractive index of the surrounding medium spatio-temporally. This modulation steers the incident light either toward the detector (encoding bit 1 ) or away from it (encoding bit 0 ). A custom-built prototype incorporating a 2 MHz transducer demonstrates the technique’s feasibility. Utilizing a 3-bit redundancy scheme, the system achieves communication rates up to 0.66 Mbps, 60× greater than the current state-of-the-art. Extensive experiments, including multimedia data transmission from remote underwater assets under various environmental conditions, validate the system’s performance and robustnes
Motion Planning for a Flexible Modular Raft Robot
No full textThis thesis presents a hierarchical motion planning framework for SoftRafts, a modular and deformable aquatic robot capable of performing locomotion and manipulation tasks on water surfaces. SoftRafts consist of soft and rigid components that enable structural reconfiguration, offering adaptability in unstructured aquatic environments.
To address the complexity of planning in high-dimensional, deformable systems, the proposed method uses a bounding-shape abstraction, specifically, enclosing circles and rectangular bounding boxes to simplify motion planning. These enclosures abstract the robot\u27s overall shape, reducing the high-dimensional planning problem into a lower-dimensional problem. A global planner uses a probabilistic roadmap (PRM) to compute a collision-free path for the enclosing shape through environments with obstacles. At vertices along this path a local planner evaluates whether the current configuration can pass through the constrained space. If not, a deformation planner adjusts the robot\u27s shape to minimize the enclosure size while preserving locomotion capability. This process is repeated iteratively, with real-time coordination between global navigation goals and local deformation requirements
Black Women during the Great Migration: Transitions from Sharecropping to Black Metropolis
Full text linkThe origin of the dissertation came about as me being the only southerner within the group of individuals completing the MALS Program. While studying Cultural studies, I began to take a focus on the Great Migration of black Americans migrating from the South to other regions of the United States. As a southerner, I was aware of the migration patterns but never went in-depth on the subject because I felt no connection. While studying, I noticed the perception of black women who were being used as subjects. Women who were being forced out of their southern situations because of segregation, access to education, access to occupation, and abuse often left poverty to experience poverty in a different form. The lack of success stories was alarming as a researcher, once I expressed this concern to my family, historical information about women in my family began to arise. These women were successful, becoming entrepreneurs, educated, and exposed to a lifestyle where discrimination because of their sex or gender was almost non-existent. I began my research by interviewing my family members, mostly those who were senior to me and my parents, who would have experienced life during the times of migration. Only one of my subjects is still alive. Still, the other women left stories and evidence of their successful migration that allowed me to produce work to combat the information scholars had published. The results I discovered were that Black women achieved success at a high volume, which enabled them to hold positions of power within society and be financially free to provide for both immediate and distant family. Even though I focused on my family, I can conclude that Black Women were highly successful with migrating and that there’s still a lot of oral history that has not been documented that can support my claim
MULTI-LEVEL DIFFERENTIABLE MOVING PARTICLES WITH PARTITION OF UNITY
Full text linkRepresenting implicit geometry with intricate features has long been a challenge. Recent advances in Implicit Neural Representations (INRs) have shown great promise in applications such as 3D reconstruction, inverse rendering, and dynamic surface evolution. These methods leverage neural networks to model complex shapes continuously, offering advantages in resolution and flexibility over traditional discrete representations. Despite their success, efficiently handling fine geometric details and evolving dynamic scenes remains an open problem.
We introduce a differentiable moving particle representation based on the multi-level partition of unity (MPU) to model dynamic implicit geometries efficiently. Our approach employs two types of particles—feature particles and sample particles—that move in space and generate dynamic surfaces under external velocity fields or optimization gradients. These particles iteratively guide and refine each other by alternating roles as inputs and outputs. Feature particles encode local quadratic patches, which are assembled using partition-of-unity weights to construct a continuous implicit shape. Sample particles, carrying position and orientation, serve as dense surface samples for optimization. To enhance adaptability, we incorporate a multi-level background grid that adjusts particle distribution dynamically. Our fully differentiable framework enables high-fidelity implicit geometry inference and evolution across various inverse tasks. We validate its effectiveness through benchmark comparisons with state-of-the-art neural representations, demonstrating lower memory consumption, fewer training iterations, and orders-of-magnitude higher accuracy in handling complex topologies and dynamic tracking tasks
Feminist Fatalism: Subordination and Womanhood in 19th Century America
No full text“Feminist Fatalism: Subordination and Womanhood in 19th Century America” explores the history and concept of womanhood in United States society. From the nation’s founding to the early years of identity building and westward expansion to the country’s reconstruction after the Civil War and the rise of the Women’s Movement, this thesis considers how and why women often embraced their subordinate role. Building on the work of philosophers like Allison Jagger, Paula Rothenberg, and Charlotte Knowles, this piece considers the external and internal motivations of self-subordination across a variety of American women in the 19th century. For some, it was a fear of the unknown and an embrace of familiar societal norms; for others, it was a tool to weaponize in their push for change. For all, though, their acceptance of submission leads one to ask an important question: Are they complicit victims in an inescapable system of oppression or are they conspiratorial victims upholding that very system?
With the current turmoil of world events, many American women are embracing traditional notions of femininity yet again, leading to a surge in self-subordination across the nation. As such, this study is more relevant than ever, allowing us to look to the past to consider the roots of the nation’s gendered thinking and women’s embrace of that submissive role. Through this, one can discover that Americanism and womanhood have always been intimately entwined, making the fight for equality different than one might expect – it is not just a revolution of social norms but rather a revolution of national identity
Advancing The Functional Diversity of Hydrazone Photoswithces
No full textPhotochromic materials have drawn increasing interest for their ability to control functional systems and biological processes using light. Molecular switches enable precise, reversible regulation of the systems in which they are embedded. To achieve robust and versatile switching, careful tuning of molecular structure and activation conditions is essential. Hydrazones represent a promising class of photoswitches, offering synthetic accessibility, strong thermal and photochemical stability, and a modular framework that supports further development for materials and biological applications. This work begins by examining a family of heterocyclic hydrazones to determine how structural variations affect photoswitching efficiency and thermal half-lives. Comparisons with phenyl-based analogues help identify second-generation switches with enhanced bistability. These findings establish general design principles for improving the performance of hydrazone-based molecular switches. Next, the focus shifts to triazole-containing hydrazones, taking advantage of the triazole’s prominence in click chemistry. By varying the linkage pattern between the triazole and hydrazone core (1,4 vs. 1,5), the impact of steric and electronic effects on switching behavior is revealed. This part of the study introduces the first hydrazone photoswitch featuring a zero-length linker between electron-donating and -withdrawing groups, enabling a compact and highly modular design for integration into functional materials. The third section targets vibrational sensing applications by designing alkynefunctionalized hydrazones for Raman spectroscopy. Upon light-induced isomerization, these switches exhibit distinct and controllable shifts in alkyne stretching frequencies. Through structural refinement, a subclass of candidates is developed for use in optical data storage and Raman-based imaging platforms. Finally, this thesis explores the use of mechanical force as a stimulus for E/Z isomerization around the hydrazone C=N bond. Building on a fluorescent scaffold, new mechanophores are created to support reversible, dual-mode switching triggered by either light or mechanical input. These systems offer a pathway toward responsive materials capable of sensing and reporting mechanical stress in real time
Macrophage Heterogeneity and Function in the Lung
Full text linkMacrophages are critical custodians of the lung, orchestrating immune surveillance, maintaining tissue homeostasis, and coordinating both innate and adaptive responses. This dissertation examines their heterogeneity and specialized functions, focusing on IMs, which reside in the lung interstitium, and AMs, which occupy the airspace. Through comprehensive single-cell transcriptomic profiling of murine and human samples, we identify multiple IM and AM subsets defined by distinct chemokine, cytokine, receptor, and innate immune gene signatures. These subsets display clear divisions of labor, contributing to immune cell recruitment, tertiary lymphoid structure formation, and alveolar homeostasis.
In IMs, coordinated chemokine programs not only recruit inflammatory cells but also shape the architecture of tertiary lymphoid tissues, as shown by the depletion of specific IM subsets leading to reduced lymphoid organization. Further analyses reveal unique cytokine networks, innate immune pathways, and tissue-specific migratory cues, underscoring the complexity and adaptability of IMs. For AMs, single-cell RNA sequencing of bronchoalveolar lavage samples from healthy individuals and those with cystic fibrosis (CF) indicates the presence of multiple functionally specialized AM families, each harboring subclusters with distinct interferon, chemokine, lipid metabolism, and growth factor gene profiles. Notably, these subsets persist in relatively stable proportions under steady-state conditions but can shift in response to inflammatory challenges such as CF or viral infections like COVID-19.
The translational impact of these findings is underscored by studies in mild and severe CF, where persistent AM activation contributes to ongoing lung inflammation—even in the era of highly effective modulator therapies. Characterizing the crosstalk between macrophages and other immune cell types in CF provides insights into potential therapeutic targets aimed at mitigating chronic inflammation and improving disease outcomes. Finally, analyses in mouse models highlight both evolutionary conservation and divergence in AM subsets between species, revealing a shared “division of labor” that governs lung immunity and homeostasis and laying the groundwork for future translational studies
Collectively, these studies redefine our understanding of lung macrophage complexity, establishing a framework for how IM and AM heterogeneity underpins immune regulation, tissue maintenance, and disease pathogenesis. By illuminating the intricate interplay among macrophage subsets across health and disease states, this work opens new avenues for targeted interventions in pulmonary inflammation and other macrophage-involving pathologies
First-principles studies of electrical polarization effects in ferroelectrics, antiferroelectrics and defects
No full textOver the last few decades, density functional theory (DFT) has emerged as a formidable tool in the field of computational material science. Not only has it become a complementary method approach to experiments by rationalizing the many complex properties of materials but its formidable predictive power can also be used to identify the most promising candidates for specific applications. Point defects in semiconductors have become an important platform for the development of quantum networks due to their ability to act as spin-photon interfaces. Spectral diffusion, the broadening of the optical emission line, can significantly impact the performance of these defect-based quantum networks. One of the main sources of spectral diffusion is the Stark shift, which arises as the result of the coupling between the dipole moment change upon electronic transition and stray electric fields. In the first part of this thesis, I will discuss our work on the development of a methodological framework through which the Stark shift of defect can be evaluated directly from first principles. We benchmarked our approaches on the nitrogen-vacancy center in diamond and discuss the challenges associated with each method. Then, we demonstrate the effectiveness of our methodology by studying the Stark shift of the T center in silicon, a promising defect that has recently been integrated into photonic devices. In the second part of this thesis, I will present some of our work on the high-throughput search of new ferroelectrics. Ferroelectrics are materials with a spontaneous, switchable polarization and have many potential applications in electronic devices. We used the soft-mode theory of ferroelectricity to screen hundreds of materials in a phonon database. I discuss some of our findings and lessons from this work by presenting some of our candidates, among which some have been experimentally synthesized. We also demonstrate that this approach can be used to discover new antiferroelectrics, materials with a non-polar ground state that can be driven into a polar phase by an electric field induced transition. Finally, we provide some perspectives about the methodological challenge associated with the search of new ferroelectrics and antiferroelectric
Measuring Ancient Magnetic Data for Tectonic Plate Locations
No full textThere were supercontinents before Pangea known as Rodinia and Nuna. Because Laurentia (ancient North America) was central to Rodinia and Nuna, understanding its position is crucial to our knowledge of previous supercontinents. However, currently there is a gap in the record on Laurentia’s location from ~1.3 to 1.1 billion years ago (Ga). Donald Elston of the U.S. Geological Survey studied Mesoproterozoic (1.6 Ga - 1 Ga) red beds to help fill the gap in Laurentia’s record. However, his research faces several issues, including inadequate demagnetization methods and unpublished data (1). The purpose of this research is to analyze new samples from the Grinnell Formation and the Hakatai Shale that will allow for a new evaluation and modernization of Elston’s data.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1008/thumbnail.jp
Studies of Electrical Contacts with MnZn Ferrite Ceramics
No full textA poster summary of our findings regarding 3 methods to electrically contact MnZn ferrite ceramics with brass electrodes. In particular, a bare control, silver paint, indium foil, and a combined gold sputtering and indium foil contact. This study focused on the reproducibility, linearity, and stability of these contact methods, examined through DC and AC testing.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1009/thumbnail.jp