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In-plane gradient permittivity materials by shadow mask molecular beam epitaxy
No full textLaw, StephanieInfrared spectroscopy currently relies on the use of expensive, bulky, and/or fragile spectrometers. For environmental monitoring, gas sensing and additional applications, an inexpensive, compact, sturdy on-chip spectrometer is a much-required technology. One way to attain this is through in-plane gradient permittivity materials (GPMs), in which the material permittivity varies as a function of position in the lateral direction. In this dissertation, I demonstrate the synthesis of infrared GPMs in silicon doped indium arsenide (Si:InAs) thin film samples using shadow mask molecular beam epitaxy (SMMBE) technique. Each of my resulting samples via SMMBE develops in-plane permittivity gradients on two opposite sides: on the flat mesa on one side, and on the film slope on the other side, leading to confining varying wavelengths of infrared light at varying horizontal locations. My first demonstration of in-plane GPM synthesis in Si:InAs using SMMBE exhibited an electric field enhancement corresponding to wavenumbers :650 cm-1 to 900 cm-1 over an in-plane width of 13 μm on the flat mesa; 900 cm-1 to 1250 cm-1 over an in-plane width of 13 μm on the film slope. ☐ In order to be useful, the permittivity gradient requires to be of high crystalline quality and its properties need to be tunable. With this in mind, I have dived further and demonstrated that the permittivity gradient length and steepness can be controlled by varying the shadow mask thickness. Samples synthesized with similar growth parameters but with mask thicknesses of 200 μm and 500 μm show permittivity gradient lengths of 18 μm and 39 μm on the flat mesa on one side and 11 μm and 23 μm on the film slope on the other side, respectively. The resulting gradient steepnesses are 23.3 cm-1/μm and 11.3 cm-1/μm on the flat mesa and 21.8 cm-1/μm and 9.1 cm- 1/μm on the film slope, for samples developed with the 200 μm and 500 μm masks, respectively. This work clearly displays the ability to control the in-plane permittivity gradient in Si:InAs thin films, setting the platform for the creation of a variety of miniature infrared devices. ☐ Overall, this dissertation presents the detailed information on how in-plane permittivity gradients in Si:InAs thin films can be created using SMMBE, which overcomes the shortcomings of the existing GPM synthesis methods that result in film damage and contamination. It also presents a thorough description on how the in-plane permittivity gradients can be controlled utilizing SMMBE and explains how the GPMs can work as the building blocks of optoelectronic infrared devices.University of Delaware, Department of Materials Science and EngineeringPh.D
Evaluating routine agronomic soil tests for coastal soil salinity detection in the mid-Atlantic
No full textThis article was originally published in Soil Science Society of America Journal. The version of record is available at: https://doi.org/10.1002/saj2.70075
© 2025 The Author(s). Soil Science Society of America Journal published by Wiley Periodicals LLC on behalf of Soil Science Society of America.
This is an open access article under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0 International License, which permits use and distribution in any medium, provided
the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Coastal salinity is a growing concern for managing agricultural soils in the eastern United States, including the Delmarva Peninsula. The saturated paste (SP) extraction, which is the standard method for measuring soil salinity in arid climates, is not widely available in the eastern United States and its effectiveness in humid coastal soils is unknown. We evaluated the Mehlich-3 (M3) routine agronomic soil test as an alternative to SP and ammonium acetate (AA) extractions on samples from 13 Delmarva agricultural fields with known salinity issues. Soils were analyzed for electrical conductivity (EC) by SP extract (ECe) or deionized water (1:2 and 1:5 soil-to-water ratios; EC1:2 and EC1:5). Extractable cations (Na, Ca, Mg, and K by SP, M3, and AA) were used to calculate exchangeable sodium percentage (ESP), sodium cation ratio (SCR), and sodium adsorption ratio (SAR). We noted significant positive relationships between SP-extractable Na and both M3-extractable and AA-extractable Na (r2 = 0.81 and 0.77, respectively). Soil SCR values calculated from M3 and AA exhibited significant linear relationships (r2 = 0.82–0.88) with ESPSAR and SAR. Strong positive linear relationships were also noted between M3-extractable Na and ECe (r2 = 0.81). Reclassification of salinity using predicted ECe from M3-Na and SCRM3 were similar to standard classification methods. We suggest M3 as a cost-effective and accessible option for salinity assessment in coastal soils of the Eastern United States. Further field studies linking soil salinity to crop health and yields are needed to validate soil salinity interpretations prior to widespread adoption of M3-based salinity assessments.We thank Shawn Tingle for assisting soil sample collection
and University of Delaware soil testing laboratory staffs for
processing and analyzing samples. We also acknowledge the
work of Georgia Angeletakis and DukeWilliams who assisted
in sample preparation and laboratory analysis as undergraduate
student interns. We thank all the farmers for granting
permission to collect soil samples from their fields. This
project is funded by USDA NIFA award #2022-68008-36647
and 2018-68002-27915
Data Privacy Made Easy: Enhancing Applications with Homomorphic Encryption
No full textThis article was originally published in ACM Transactions on Design Automation of Electronic Systems. The version of record is available at: https://doi.org/10.1145/3715877
This work is licensed under a Creative Commons Attribution 4.0 International License. ©2025 Copyright held by the owner/author(s).Homomorphic encryption is a powerful privacy-preserving technology that is notoriously difficult to configure and use, even for experts. The key difficulties include restrictive programming models of homomorphic schemes and choosing suitable parameters for an application. In this tutorial, we outline methodologies to solve these issues and allow for conversion of any application to the encrypted domain using both leveled and fully homomorphic encryption.
The first approach, called Walrus, is suitable for arithmetic-intensive applications with limited depth and applications with high throughput requirements. Walrus provides an intuitive programming interface and handles parameterization automatically by analyzing the application and gathering statistics such as homomorphic noise growth to derive a parameter set tuned specifically for the application. We provide an in-depth example of this approach in the form of a neural network inference as well as guidelines for using Walrus effectively.
Conversely, the second approach (HELM) takes existing HDL designs and converts them to the encrypted domain for secure outsourcing on powerful cloud servers. Unlike Walrus, HELM supports FHE backends and is well-suited for complex applications. At a high level, HELM consumes netlists and is capable of performing logic gate operations homomorphically on encryptions of individual bits. HELM incorporates both CPU and GPU acceleration by taking advantage of the inherent parallelism provided by Boolean circuits. As a case study, we walk through the process of taking an off-the-shelf HDL design in the form of AES-128 decryption and running it in the encrypted domain with HELM.National Science Foundatio
Identifying the sources of dissolved inorganic carbon (DIC) and carbon isotopes (delta13C) in the Roosevelt Inlet (Lewes, DE, US)
No full textCai, Wei-JunLuther, George W.Over the past decade, researchers have studied how climate change alters the oceans, which has made oceans sinks of carbon dioxide (CO2). The release of hydrogen ions (H+) that results from the oceanic absorption of anthropogenic CO2 causes long-term decreases in pH; otherwise known as ocean acidification (OA). Despite its local importance, few studies examine the impacts of tidal variability on the biogeochemistry, particularly CO2 signals, of various endmember waters mixing. Here, we investigate the Roosevelt Inlet (Lewes, DE, USA), where endmembers namely Broadkill River (freshwater), Canary Creek (marsh water), Lewes and Rehoboth Canal (brackish) and Delaware Bay (seawater) mix. Two in situ autonomous biogeochemical sensors (SeapHOx V2 and SeaFET V2, Sea-Bird Scientific) were deployed to collect high resolution timeseries of coastal ocean biogeochemical data coupled with dissolved oxygen to identify biological influences during tidal events along with timeseries of light measured as Photosynthetically Active Radiation (EPAR). On five separate occasions, discrete samplings coinciding with the high resolution time series were also conducted to determine dissolved inorganic carbon (DIC), δ13C(DIC), total alkalinity (TA) and pH. ☐ Results revealed during the August and October sampling periods that low tide DIC was elevated by biological organic matter decomposition from the freshwater and marsh endmembers, producing high values of PCO2, low pH and O2 values while high tide produced lower values of DIC, PCO2, and higher pH and O2 values. In contrast, the sampling periods of December and February showed low values in DIC, PCO2, and high pH and O2 values, indicating the major processes were carbonate dissolution/precipitation, dilution/evaporation and summation of all aerobic processes. The DIC production in the April sampling period was impacted by an influence from photosynthesis that caused a source of higher pH, O2, and lower DIC and PCO2 values that originated from the freshwater endmember. Once endmembers were identified, the Fry (2002) mixing model for the conservative mixing of DIC and δ13C-DIC was applied to indicate the organic carbon source (decomposition) for the DIC. The modeled data resulted in a seasonal effect on δ13C and DIC, where the high-resolution and high and low tide discrete sampling in August and October had values of δ13C driven by S. alterniflora (-13 ‰) decomposition through marshland aerobic respiration rather than sulfate reduction. The December high resolution sampling period was also driven by values of δ 13C from S. alterniflora (-13 ‰) decomposition, while the high and low tide discrete sampling period had δ13C isotopic values driven by the freshwater endmember of Delaware Bay (-10 ‰, Deng et al., 2022) as noted in Fry (2002). The February discrete and high-resolution sampling pointed towards a dampened effect from marshlands with δ13C isotopic values that were driven by the freshwater endmember of Delaware Bay (-10 ‰, Deng et al., 2022). As such, the Fry (2002) conservative mixing model provides the science community another way to predict the source of organic carbon for DIC to other estuaries with similar characteristics. Overall, the present work utilized sensor and discrete sampling of carbon parameters to facilitate an assessment of the performance of the autonomous biogeochemical sensors and to elucidate the source of carbon parameters (DIC, TA, PCO2, pH, δ13C) to the Roosevelt inlet, driven by both tidal and seasonality effects. The high and low tide discrete sampling helped identify endmembers and high-resolution sampling identified daily and seasonal drivers of biogeochemical variability at the Roosevelt inlet, DE using continuous data logging with emphasis on the carbon dioxide system.University of Delaware, School of Marine Science and PolicyM.S
Boron-Containing Analogs of Fosmidomycin: Benzoxaborole Derivatives Exhibit Promising Activity Against Resistant Pathogens
No full textThis article was originally published in ACS Omega. The version of record is available at: https://doi.org/10.1021/acsomega.5c02701
© 2025 The Authors. Published by American Chemical Society
This work is licensed under a Creative Commons Attribution CC-BY 4.0 . (https://creativecommons.org/licenses/by/4.0/).The rise of antimicrobial resistance presents an urgent challenge that necessitates the development of novel therapeutic agents with distinct mechanisms of action. This research explores boron-containing compounds as potential neutral phosphate/phosphonate isosteres of fosmidomycin, a potent inhibitor of 1-deoxy-d-xylulose-5-phosphate reductoisomerase (IspC) within the nonmevalonate isoprenoid biosynthesis (MEP) pathway, with limited clinical utility due to poor pharmacokinetics. We report the synthesis of a library of 15 boron-containing analogs of fosmidomycin and their comprehensive evaluation as IspC inhibitors and antimicrobial agents. The compounds did not demonstrate significant activity against the intended IspC target, thus providing evidence that these boron moieties may have limited utility as phosphonate isosteres in this system. However, our investigation yielded unexpected and valuable antimicrobial discoveries. Several benzoxaborole compounds demonstrated significant activity against pathogenic microbes, including methicillin-resistant Staphylococcus aureus (MRSA), E. coli, and C. albicans. Mechanistic studies confirmed that these compounds operate through alternative pathways distinct from MEP pathway inhibition. These results provide a foundation for the rational design of next-generation boron-containing antimicrobials with enhanced potency and selectivity against resistant pathogens, including MRSA.This work was supported by the University of the Sciences in Philadelphia Department of Chemistry & Biochemistry. JMG was a Robert D. Spiers Graduate Research Fellow at the University of the Sciences in Philadelphia. The antimicrobial screening performed by CO-ADD (The Community for Antimicrobial Drug Discovery) was funded by the Wellcome Trust (UK) and The University of Queensland (Australia). The authors would like to thank Prof. Caren Freel Meyers, Johns Hopkins University, for plasmids for and technical assistance with the IspC assay. The authors would like to thank Amanda Vangieri for critical review of the manuscript prior to submission
Innovative Compact Vibrational System with Custom GUI for Modulating Trunk Proprioception Using Individualized Vibration Parameters
No full textThis article was originally published in Bioengineering. The version of record is available at: https://doi.org/10.3390/bioengineering12101088
© 2025 by the authors.Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/
licenses/by/4.0/).Conventional vibrational systems associated with proprioception are mostly equipped with a single standard frequency and amplitude. This feature often fails to show kinesthetic illusion on different subjects, as different individuals respond to different frequencies and amplitudes. Additionally, different muscle groups may also require the flexibility of frequencies and amplitudes. We developed a custom vibrational system that is equipped with flexible frequency and amplitude, adapted to a custom graphical user interface (GUI). Based on the user’s criteria, the proposed vibrational system enables a wide range of frequencies and amplitudes that can be swept under a single platform. In addition, the system uses small linear actuators that are wearable and attach to the subject without the need for restrictive straps. The vibrational system was used to model trunk proprioceptive impairment associated with low back pain. Low back pain is the leading cause of disability worldwide. It is mostly associated with impaired postural control of the trunk. For postural control, the somatosensory system transmits proprioceptive (position sense) information from the sensors in the skin, joints, muscles, and tendons. Proprioceptive studies on trunk muscles have been conducted where the application of vibration at a set amplitude and frequency across all participants resulted in altered proprioception and a kinesthetic illusion, but not in all individuals. To assess the feasibility of the system, we manipulated the trunk proprioception of five subjects, demonstrating that the vibrational system is capable of modulating trunk proprioception and the value of customizing parameters of the system to obtain maximal deficits from individual subjects.This publication was made possible in part by Grant Number T32-GM081740 from NIH-NIGMS (J.R.G.). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIGMS, or NIH. This research was funded in part by a Promotion of Doctoral Studies (PODS) II Scholarship from the Foundation for Physical Therapy Research (J.R.G.). This work was partially supported by a SPARC Graduate Research Grant from the Office of the Vice President for Research at the University of South Carolina (J.R.G.). This publication was supported by the University of Florida Partnerships Across Interdisciplinary Networks: Training through Engineering, Epidemiology & Addiction Medicine (UF PAIN TEAM) NIH grant T90AR085527 and the University of Florida Pain Research & Intervention Center of Excellence (J.R.G.)
Atomistic insights into highly dispersed catalysts for selective shale-gas chemistry
No full textVlachos, Dionisios G.Caratzoulas, StavrosThis thesis demonstrates the critical role of atomistic modeling in accessing catalytic length and timescales that are challenging to probe experimentally, and bridging the gap between experimental observations and fundamental mechanistic understanding. ☐ Light olefins such as ethylene and propylene are essential building blocks in the chemical industry and are traditionally produced through energy-intensive processes like steam and fluid catalytic cracking of petroleum-based feedstocks. The emergence of shale gas extraction offers a lower-cost, alternative feedstock rich in ethane and methane. Ethane can be upgraded to ethylene via catalytic ethane dehydrogenation (EDH), while methane, which accounts for roughly 25% of global warming, poses an environmental challenge. Its effective utilization is critical to realizing the full potential of shale gas. Dry reforming of methane (DRM) offers a pathway to convert both CH4 and CO2 into syngas. While EDH and DRM present economically and environmentally attractive reactions, they are challenged by high operating temperatures, undesirable side reactions, catalyst deactivation, and in some cases, the use of toxic materials like Cr-based catalysts. Thus, there is a growing interest in developing selective, non-toxic, and stable catalysts for these reactions. ☐ Supported single-atom catalysts (SACs) and subnanometer metal clusters offer a promising solution by combining the high selectivity of homogeneous catalysts with the thermal stability of heterogeneous systems. These atomically dispersed catalysts exhibit unique electronic properties due to strong metal-support interactions, which can be fine-tuned via support composition or defects. However, their structural heterogeneity and dynamic behavior under reaction conditions make experimental characterization difficult. This thesis addresses these challenges by developing multiscale computational frameworks that systematically explore the active site landscape and link atomic-scale structure to experimental catalytic performance. ☐ In Chapter 2, we investigate the EDH mechanism on Co/SiO2 catalysts using electronic structure calculations and microkinetic modeling. The catalyst comprises paramagnetic Co2+ sites anchored on an amorphous silica support. Both monomeric (Co2+) and dimeric (-Co2+-O-Co2+-) sites are considered to assess the influence of site nuclearity on catalytic activity. The dominant reaction mechanism is shown to involve spin-crossing, and a methodology is developed to incorporate the probability of spin-crossing events into the microkinetic model. ☐ Chapters 3 and 4 expand this framework to examine how cobalt’s coordination environment and crystallinity of the support influence reactivity. In Chapter 3, an ensemble of Co2+ sites is generated from an amorphous SiO2 surface, and a workflow is developed to compute site-averaged apparent activation energies for comparison with experimental kinetics. This analysis also reveals key geometric descriptors of the catalytic sites that govern activity. Chapter 4 extends the mechanistic study to Co/BEA catalysts, in collaboration with experimentalists, to explore the role of support defects and crystallinity in modulating EDH activity. ☐ Chapter 5 focuses on active site heterogeneity in Pt-CHA catalysts for EDH. Ab initio molecular dynamics simulations are employed to identify stable monomeric and dimeric Pt motifs associated with framework Sn4+ and silanol defects. The coordination environments that disperse Pt atoms are identified, and the interaction of Pt with the zeolite framework is analyzed using electronic structure calculations. A kinetic ranking of the active sites is constructed to assess their relative catalytic relevance. ☐ Chapter 6 investigates metal-support interactions in atomically dispersed Ni on ceria–zirconia mixed oxides (CZO), a catalyst known for high activity and coke resistance in the DRM reaction. Using electronic structure methods and statistical thermodynamics, the influence of reaction conditions on support reducibility and Ni stability is elucidated.University of Delaware, Department of Chemical and Biomolecular EngineeringPh.D
Situating the Yao's heritage within chinese cultural preservation: Bapai Yao history, heritage, and tourism in Liannan, China
No full textRujivacharakul, VimalinSince the early 2000s, China has shifted its heritage preservation approach, expanding beyond a focus on architecture to include cultural practices and the lives of local people, particularly among ethnic minorities. This approach aims to bridge the urban-rural divide and leverages tourism as a means of economic growth, reshaping minority identities to align with a diverse, modern national image. Central and local governments play a significant role in this process, using cultural heritage as a tool for economic and political control, which profoundly impacts local communities. However, this centralized model often overlooks the tensions it creates with local communities, especially among ethnic minorities. ☐ This dissertation addresses these issues through a case study of the Bapai Yao, examining the preservation of cultural heritage, ethnic identity, and the power dynamics between the Yao community and the Chinese government. It first contextualizes Yao’s historical interactions with the Han majority, emphasizing the evolution of policies and perceptions that shape Yao’s identity. It then explores the architecture and social structures of Nangang Pai, a Bapai Yao settlement, illustrating the resilience of Yao culture amid external pressures, with a critical examination of government policies since 1949 and the balance between development and cultural preservation. ☐ Key chapters discuss tensions between government policies and local practices, the complexities of tourism, and the state’s role in recasting Yao’s culture within a socialist vision. Key findings include the paradoxical nature of cultural preservation in the context of tourism-driven development, where the celebration of ethnic diversity coexists with the commodification and exoticization of minority cultures. ☐ By exploring how the state’s portrayal of the Yao perpetuates stereotypes, reflects elite narratives, and marginalizes Yao perspectives, and by highlighting the government’s dual objectives—utilizing tourism as an economic catalyst while shaping ethnic identities to align with a modern, diverse, and progressive national narrative—this dissertation argues that the new approach to heritage preservation in China serves to “Other” minority cultures, strategically framing them within a national narrative that promotes a highly uniform set of values. This operation of official discourse shapes how the Bapai Yao’s cultural heritage and identity are represented. Identifying this discursive construction may reveal conflicting power/knowledge relations between authorities and minority communities. This identification presents an opportunity to resolve conflicts in pursuit of equitable dialogues and social inclusion, contributing to ongoing discussions on the complexities of cultural heritage preservation, economic sustainability, and identity politics in contemporary China.University of Delaware, Department of Art ConservationPh.D
Characterizing Storm-Induced Coastal Flooding Using SAR Imagery and Deep Learning
No full textThis article was originally published in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. The version of record is available at: https://doi.org/10.1109/JSTARS.2025.3530255.
© 2025 The Authors. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/Flooding is among the most common yet costly worldwide annual disasters. Previous studies have proven that synthetic aperture radar (SAR) is an effective tool for flooding observation due to its high-resolution and timely observations, and deep learning-based models can accurately extract water bodies from SAR imagery. However, many previous flood analyses do not account for influences of tides and permanent water bodies, and the comprehensive characteristics of coastal storm flooding are still not fully understood. This study therefore presents a novel approach for isolating storm-induced flood waters in coastal regions from SAR imagery through the identification and removal of permanent water bodies and tidal inundation. This methodology is applied to the Delaware Bay region, with ancillary geospatial data used to determine resulting landcover impacts. Results indicate that flooding primarily impacts agricultural and marsh regions, as well as urban areas like airports and road systems adjacent to rivers or large inland bays. The sensitivity impacts of tides on flood estimates reveals that estimates significantly increase if included in analysis, highlighting the importance of their removal prior to flood identification. Finally, exploration into intense coastal storm events in the Delaware Bay region reveal the importance of storm characteristics like high water levels, wind, and precipitation in generating extreme flooding conditions. The case study presented here has important implications for other coastal regions and provides an innovative and comprehensive approach to coastal storm flood identification and characterization which can benefit coastal managers, emergency responders, coastal communities, and researchers interested in coastal flood hazards.This work was supported in part by the Delaware Space Grant College and Fellowship Program under NASA Grant 80NSSC20M0045, in part by the National Aeronautics and Space Administration under Grant NASA-80NSSC20M0220, and in part by the National Science Foundation under Grant NSF-IIS-484 2123264
Sustainable protein and waste management using insects
No full textCrossley, MichaelInsects are often viewed as pests in conventional agricultural production but have the opportunity to become farmed commodities and allies in solving persistent agricultural challenges. The growing global population will require sustainable and innovative protein sources to meet rising nutritional demands. An option for protein that requires little space, water, and inexpensive feed could be insects. Insects such as Tenebrio molitor (yellow mealworm), Alphitobius diaperinus (lesser mealworm), Hermetia illucens (black soldier fly), and Acheta domesticus (house cricket) have shown promise as efficient consumers and could be waste upcyclers which turn agricultural and municipal waste products into high-protein biomass suitable for livestock, aquaculture, and potentially human consumption. Despite their potential, challenges remain in optimizing rearing practices, particularly with respect to feed type, density, and environmental conditions, to scale insect production effectively. In Chapter 1, I explored a quantitative literature review to examine the influence of density-dependent and -independent factors on farmed insect mass and survival. The lesser mealworm has been the most recent insect of interest as a waste upcycler. While widely known as a significant pest of poultry, their association with animal manure may offer a pathway for sustainable waste reduction and protein generation. In Chapter 2, using agricultural and municipal waste as feed substrates, I studied the growth performance of the lesser mealworm at different rearing scales, bridging gaps in knowledge between scaling up production and optimizing rearing conditions in controlled environments. In addition to converting waste into insect biomass, insects may alter their waste substrates in ways that are beneficial for agriculture. For instance, parasites often spread through animal manures, yet the role of manure-feeding insects, like black soldier fly larvae, in reducing these parasite loads may be underappreciated. In Chapter 3, I conducted controlled feeding bioassays to examine the effect of black soldier fly larvae on nematode parasites in horse manure. Ultimately, my work presents a snapshot of the potential solutions that insects offer to address global challenges in food security, waste management, and parasite control, building toward sustainable and scalable agricultural practices.University of Delaware, Department of Entomology and Wildlife EcologyM.S