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Mapping Groundwater Discharge Seeps with Thermal UAS Imaging on a Wetland Restoration Site
No full textOne of the key metrics for the effectiveness of wetland restoration is whether a restored wetland behaves hydrologically like a natural wetland. Restoration is designed to increase the water residence time on the surface of the site in order to capture and process nutrients, mitigate the impact of local flooding and drought, and provide a habitat for wetland species abundance and biodiversity. Quantifying the change in groundwater presence at the wetland’s surface will inform future freshwater wetland restorations across New England. The ability to produce a comprehensive map of the locations of groundwater discharge over a large area has the potential to provide insight into restoration practice, its success, and its effects on individual seeps over time. Identification, mapping, and measurement of groundwater discharge sites have long been a challenge, but new methodologies are developing with the advances in unmanned aerial systems (UAS). This study uses a UAS -mounted thermal infrared camera to map groundwater seeps on a 25-ha (62-acre) site in Plymouth, Massachusetts, before and after it underwent restoration to a freshwater wetland. Using the thermal map, we located and quantified the spatial extent of groundwater seeps pre-restoration and the changes after restoration. The location and size of these seeps show that existing groundwater seeps remained immobile through restoration, but the area of their surface expression grew, indicating that restoration removed barriers to surface expression and successfully increased residence time. This analysis using a thermal camera -enabled UAS allows for a temporal comparison over large spatial scales and provides insight into restoration impacts to groundwater expression on the surface of post-agricultural wetland sites.Master of Science (M.S.
Unmanned Aerial Vehicles for Communication and Civil Applications
No full textThis dissertation focuses on using unmanned aerial vehicles (UAVs) for communication and civil applications. Nowadays, UAVs have found numerous applications across a proliferation of fields, such as aerial inspection, photography, precision agriculture, traffic control, search and rescue, package delivery, and telecommunications.
While most related works use UAVs for single-task operations, an interesting idea is to design UAVs capable of simultaneously performing multiple tasks. This approach could significantly improve system efficiency. For example, consider a residential area where drones are used as last-mile delivery tools. However, it is unclear whether such mobility patterns for package delivery can provide uniform coverage within the area of interest. In this dissertation, we aim to design UAV trajectories that efficiently perform transportation operations (e.g., package delivery) while simultaneously providing uniform coverage over a neighborhood area. Such coverage is essential for applications like network coverage, Internet of Things (IoT) data collection, wireless power transfer, and surveillance.
We first consider multi-task UAVs in a simplified scenario where the neighborhood area is a circular region. In this case, UAV missions start from the center, with destinations assumed to be uniformly distributed along the circle's boundary. We propose a trajectory planning process that achieves uniform coverage while preserving delivery efficiency. Subsequently, we explore a more practical scenario where transport destinations are arbitrarily distributed in an irregularly shaped region. We demonstrate that simultaneous uniform coverage and efficient transport trajectories (e.g., package delivery) are achievable in such realistic settings. This is substantiated through rigorous analysis and simulations.\\
Additionally, this dissertation examines the use of UAVs in disaster management. UAVs offer significant advantages in disaster response, search and rescue operations (SAR), and wildfire detection. For instance, in critical scenarios such as wildfires, avalanches, or searches for missing persons, UAVs can expedite disaster management and SAR efforts. Search efficiency is crucial in such operations because the likelihood of survival diminishes over time, and wildfire containment becomes increasingly challenging.
In this work, we aim to optimize flight paths that maximize the probability of locating missing persons or detecting wildfires. The path optimization algorithm ensures full coverage of the area of interest by leveraging prior knowledge of target distribution. In the case of finding missing persons, this knowledge may be derived from behavioral analyses, while for wildfire detection, it can be obtained through expert assessment of terrain and emergency factors. The UAV follows the optimized flight path, collecting data for processing. We employ machine learning techniques to quickly and accurately identify targeted objects or detect fires. Specifically, we use residual neural networks (ResNet) to detect fire and smoke in wildland areas and to locate missing persons in snow-covered regions.Doctor of Philosophy (Ph.D.
Scalable fabrication of an array-type fixed-target device for automated room temperature X-ray protein crystallography.
No full textX-ray crystallography is one of the leading tools to analyze the 3-D structure, and therefore, function of proteins and other biological macromolecules. Traditional methods of mounting individual crystals for X-ray diffraction analysis can be tedious and result in damage to fragile protein crystals. Furthermore, the advent of multi-crystal and serial crystallography methods explicitly require the mounting of larger numbers of crystals. To address this need, we have developed a device that facilitates the straightforward mounting of protein crystals for diffraction analysis, and that can be easily manufactured at scale. Inspired by grid-style devices that have been reported in the literature, we have developed an X-ray compatible microfluidic device that can be used to trap protein crystals in an array configuration, while also providing excellent optical transparency, a low X-ray background, and compatibility with the robotic sample handling and environmental controls used at synchrotron macromolecular crystallography beamlines. At the Stanford Synchrotron Radiation Lightsource (SSRL), these capabilities allow for fully remote-access data collection at controlled humidity conditions. Furthermore, we have demonstrated continuous manufacturing of these devices via roll-to-roll fabrication to enable cost-effective and efficient large-scale production
Source Data for Architected Dual-Network Solvent-free Adhesives for Stretchable Fabrics
No full textSource Data for Architected Dual-Network Solvent-free Adhesives for Stretchable FabricsNatural systems, such as tendons and spider silk, demonstrate how the combination of strength and stretchability can be effectively achieved by integrating stiff and flexible network structures. Inspired by these systems, we developed a novel, solvent-free dual-network adhesive based on a self-assembling ABA triblock copolymer, poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) (PMMA-b-PnBA-b-PMMA), designed for applications requiring both high strength and stretchability. The triblock copolymer forms a physically crosslinked network through microdomains of PMMA end-blocks that provide structural integrity, while the PnBA mid-block forms a soft, stretchable matrix. To further enhance mechanical performance, a second poly(n-butyl acrylate) (PnBA) network is polymerized in situ, locking the PMMA microdomains in place and creating a load-bearing system. By varying the crosslinking density of the secondary network, we tailor the adhesive’s mechanical properties (Young’s modulus: 0.17 – 1.18 MPa) to suit different substrates, creating a mechanically transparent seam. The resulting dual-network system combines different strategies to achieve high strength and stretchability, with adhesive performance comparable to industrial methods such as sewing, particularly in bonding neoprene fabric composites and sealing the joints. Our solvent-free approach also eliminates the need for lengthy solvent evaporation steps, offering an eco-friendly and more efficient alternative for flexible adhesive applications in fields such as soft robotics, flexible electronics, and sports apparel.The authors thank Sheico Group and CUMIRP for financial support of this work, and Dr. David Waldman for his assistance in facilitating industrial collaborations
Defiant Grace: Brazil and the São Francisco River (1799 – 1955)
No full textThis dissertation examines the long and complex relationship between the Brazilian state and the São Francisco River from the late colonial period through the construction of the Paulo Afonso hydroelectric plant in the 1950s. It investigates how this major river basin came to be reimagined as a crucial axis of national integration, modernization, and development. Drawing on government reports, engineering surveys, travel narratives, political discourse, local newspapers, and Brazilian social thought literature, the study traces the evolving role of the São Francisco in shaping political ideologies, state policies, and regional economies.
The research demonstrates how early interactions between colonial authorities and riverine societies laid the groundwork for later economic exploitation and infrastructural ambitions. It explores nineteenth-century efforts by provincial governments and private actors to introduce steam-powered navigation as a symbol of progress and a tool for economic growth, followed by the state’s increasing intervention during the Republican era. In the early twentieth century, events such as the War of Canudos and successive state-sponsored expeditions redefined the river’s symbolic and practical significance, contributing to its portrayal as a vehicle for redeeming Brazil’s drought-prone Northeast from “backwardness.”
By analyzing the convergence of local elite interests, nationalist rhetoric, and federal development agendas, the dissertation reveals how the São Francisco became “the river of national unity” and a cornerstone of modern Brazilian statecraft. Ultimately, this work argues that the history of the São Francisco basin reflects broader tensions in Brazilian development: between center and periphery, tradition and modernity, and environmental constraint and infrastructural ambition.Potash Travel Grant to Latin America (Umass, Department of History)
Predissertation Grant (Umass, Graduate School)
Dissertation Fieldwork Grant (Umass, Graduate School)Doctor of Philosophy (Ph.D.)2026-09-0
Sustainable crop protection: essential oil as a biocidal drift reduction adjuvant
No full textCrop protection through application of agrichemicals such as pesticides continues to be a reliable and cost-effective method to maintain high crop yields. However, usage of synthetic ingredients and losses from spray droplet drift and bouncing cause environmental contamination and human health risks. A promising solution is to substitute synthetic ingredients with essential oils, which are plant-derived compounds that exhibit pesticidal properties while being harmless to the environment and humans. However, the short environmental persistence and phytotoxicity of essential oils at relatively low concentrations limit their use. An alternative strategy is to utilize them as dilute oil-in-water emulsions, a common type of spray adjuvant used to reduce losses from spray drift by increasing spray droplet size. The objective of this project is to evaluate the feasibility of essential oil emulsions as spray drift reduction adjuvants and advance the understanding of the spray atomization mechanism. Emulsion formulations with various oil compositions and surfactants were sprayed and spray droplet size distributions were measured using the shadow sizing method as an indicator for spray drift potential; smaller spray droplets are likely to drift with the surrounding airflow and miss the target application area. Results demonstrate that relatively polar essential oils such as carvacrol have anti-drift abilities comparable to the traditional methylated seed oil (MSO) used in the field. Meanwhile, other oils with different physicochemical properties do not increase the spray droplet size compared to a water spray. The selection of the surfactant is also important to influence relevant properties such as surface charge. High-speed images reveal differences in the dominating spray atomization mechanism for each oil-surfactant system. Emulsified oil droplets must be able to enter the water-air interface to atomize the spray into larger droplets. Dimensionless numbers such as capillary number were used to quantify an emulsion’s ability to alter the spray droplet size based on its properties. These findings present ways to optimize essential oil emulsion formulations for agriculture sprays to minimize losses from spray drift and improve safety and sustainability.U.S. Department of Agriculture, National Institute of Food and Agriculture, AFRI project 2022-67021-37603;
Lotta Crabtree FellowshipDoctor of Philosophy (Ph.D.
Exploring the Role of Cryptochrome in Phase Resetting: From SCN to Behavior
No full textThe mammalian circadian system must balance stability with flexibility to maintain reliable timekeeping while adapting to environmental changes. This thesis investigates the molecular basis of accelerated circadian re-entrainment in the duper hamster, a naturally occurring Cry1-null mutant, at the level of the suprachiasmatic nucleus (SCN). Through immunohistochemical analysis of core clock proteins (PER1 and PER2) across the rostro-caudal extent of the SCN, I demonstrated distinct patterns of molecular adaptation between genotypes following an 8-hour phase advance of the light cycle. While duper hamsters exhibit rapid behavioral adaptation to shifted light schedules, wild-type animals display prolonged adjustment periods. By the third day post-shift, when duper hamsters had largely completed behavioral adaptation, wild-type SCN showed severe disruption of PER1 rhythms with altered temporal patterns and regional uncoupling. In contrast, duper SCN maintained coherent molecular rhythms similar to unshifted conditions throughout all rostro-caudal regions. Duper hamsters exhibited consistently lower PER1 protein levels, consistent with the absence of their normal binding partner CRY1. Colocalization analysis revealed distinct PER1/PER2 ratio dynamics that were maintained in duper but disrupted in wild-type following phase shifts. Additional studies of VIP neurons demonstrated that in shifted wild-type, PER1 rhythmicity persisted but with a phase delay, while PER2 showed no apparent rhythm. The importance of cryptochromes in circadian plasticity was further confirmed through targeted knockout models, as both Cry1-/-and Cry2-/-mice demonstrated remarkably accelerated adaptation to phase shifts despite their opposing period phenotypes. Surprisingly, this enhanced entrainment occurred without corresponding alterations in phase response curves to brief light pulses, suggesting a mechanistic dissociation between acute phase shifting and entrainment rate. These findings establish cryptochromes as key constraints on the speed of circadian entrainment, with their absence creating a more malleable clock that rapidly adapts to environmental timing cues, revealing unexpected complexity in the molecular mechanisms governing circadian plasticity.Doctor of Philosophy (Ph.D.)2026-09-0
ON-WAFER NOISE MEASUREMENT AND OPTIMIZATION OF CRYOGENIC SILICON-BASED LOW NOISE AMPLIFIERS
No full textThis dissertation investigates on-wafer noise measurement and noise optimization of cryogenic low-noise amplifiers (LNAs) based on Silicon Germanium (SiGe) heterojunction bipolar transistors (HBTs), as well as a tunable cryogenic LNA aimed at increasing system flexibility for a particular application. To accomplish these goals, two state-of-the-art HBT technologies are first characterized and modeled at cryogenic temperatures. A low-power cryogenic LNA is designed and implemented with the extracted small signal and noise models. Second, a novel noise measurement method using HBT as a shot noise source at cryogenic temperature is described and analyzed. At last, the first reconfigurable cryogenic LNA with a programmable RLC resonator is researched, designed, and implemented.Doctor of Philosophy (Ph.D.
EXAMINING DEFEAT AND ENTRAPMENT AS MEDIATORS BETWEEN SOCIAL COMPARISON AND SUBJECTIVE SOCIAL RANK AND SUICIDAL THOUGHTS ACROSS RACIAL BACKGROUNDS
No full textSocial comparison is a socio-cognitive process that can increase risk for suicidal thoughts through feelings of defeat and entrapment. However, its role as a risk factor for Asian, Black, and multiracial individuals remains unclear. This study examined whether social comparison and subjective social rank (one’s perceived position derived from social comparison) predict suicidal thoughts via defeat and entrapment, particularly for racially minoritized college students. College students from predominantly White institutions completed online surveys at baseline and one-month follow-up. Using data from 409 participants, path analyses showed that perceived social rank is a risk factor for suicidal thoughts across racial groups, leads to defeat and entrapment only for White students.Doctor of Philosophy (Ph.D.)2026-09-0
Energetic Materials for Biological and Electronic Applications
No full textConjugated polymeric materials represent a promising next step for electronic applications. As organic semiconductors (OSCs), they offer key advantages over their inorganic counterparts, including solution-processability, mechanical flexibility, and compatibility with low-cost fabrication techniques. To enable efficient charge transport, OSCs typically require doping to generate charge carriers. However, this creates instabilities and changes within the material. In this dissertation, I investigate the doping mechanism of an n-type dopant and in parallel, I explore strategies to improve charge transport in amorphous p-type conjugated polymers, where disordered morphology poses a significant challenge. Additionally, I examine a biological application that employs abiotic triphosphate compounds to modulate muscle function, expanding the potential of synthetic systems in bioelectronic contexts. Collectively, this work advances the understanding of doping mechanisms in n-type polymers and proposes new methods to enhance electrical performance in disordered systems, paving the way toward cost-effective synthesis and broader application of conjugated polymers.Doctor of Philosophy (Ph.D.)2026-09-0