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DEGRADATION OF POLYMERS AND POLYMER COMPOSITES IN EXTREME ENVIRONMENTS
No full textPolymeric materials are widely used in engineering applications due to their high strength-to-weight ratio, easy manufacturability, and cost-effectiveness. When incorporated into composites, they provide further performance enhancements, enabling use in demanding structural applications. However, long-term exposure to harsh environments including elevated temperatures, UV radiation, harsh chemicals, and radiation, can drive degradation processes that alter the material’s network structure, and in turn, degrade its mechanical performance. Exposure to thermo-oxidative conditions is one of the most common environments driving polymer degradation, leading to chain scission and crosslinking events, with the resulting oxidative products causing discoloration, reduced ductility, and changes in glass transition behavior. Much of the existing literature has focused on reaction-limited oxidation in thin films. In contrast, bulk materials typically experience diffusion-limited oxidation, which produces steep gradients in chemical and mechanical properties across the cross-section. Recognizing these differences and their impact on mechanical behavior is critical for predicting the long-term performance of load-bearing applications.
This work presents a series of preliminary studies aimed at characterizing the effects of high-temperature oxidative aging in bulk polymers and polymer composites. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and mechanical testing were utilized to link physical and chemical changes with alterations in thermal and mechanical response. Three systems were examined: polypropylene with and without antioxidants, unidirectional glass fiber reinforced polymers with 0° and 90° fiber orientations, and carbon fiber reinforced polymers with varying fiber volume fractions. Results highlight the interaction between polymer microstructure, composite architecture, and oxidative mechanisms, providing insight into how local chemical degradation propagates to influence macroscopic material performance. Together, these findings establish a foundation for understanding long-term durability in structural polymer systems
Experimental Evaluation Of The Impact Of Floating Treatment Wetlands On The Performance Of A Lagoon-Based Wastewater Treatment System In Copper Harbor, Michigan
No full textLagoon-based wastewater treatment systems are common in small, rural communities. Because of the large number of lagoon treatment systems in the U.S., they have the potential to substantially impact the water quality in surface water bodies. Although lagoon systems have many advantages, it can be difficult to meet standards for total suspended solids and total biochemical oxygen demand due to the growth of algae, and increasing demand for wastewater nutrient removal creates an additional challenge for lagoon-based treatment systems. These problems are exacerbated in cold climates. In this study, the impact of floating treatment wetlands (FTWs) on the performance of an aerated lagoon wastewater treatment system in Copper Harbor, MI, was evaluated as part of an overall project focusing on improving methods for monitoring and treating wastewater in lagoons in cold climates. This was achieved by monitoring key wastewater constituents throughout the treatment train, which includes two lagoons operated in series. The system was monitored both with (2024 and 2025) and without (2023) FTWs installed in the secondary lagoon. In 2024, the FTWs appeared to increase nitrification in the secondary lagoon, and a noticeable increase in nutrient and suspended solids concentrations occurred following harvesting of the plants. In 2025, effluent total nitrogen and total phosphorus concentrations decreased and reached the lowest concentrations measured during the three-year period. Other factors, including improved management of the wastewater treatment plant, may have contributed to the observed changes, but it appears that the FTWs had a modest and positive impact on the performance of the lagoons in Copper Harbor, MI
Indigenous-Industrial Heritage: Centering Indigenous Voices in Minnesota\u27s Iron Range
No full textIndustrial heritage refers to the material remains, sites, landscapes, and practices associated with industrial and extractive activities. As a field, it has historically been concerned with the conservation, management, and interpretation of industrial sites and activities and forms a central narrative within Minnesota\u27s museums. Yet such accounts often privilege object-centered narratives while silencing the presence, knowledge, and contributions of Indigenous and Descendant communities, obscuring their enduring relationships to extractive landscapes. In recent decades, critiques of traditional industrial heritage approaches have identified gaps in the discipline related to the exclusion of marginalized populations, including Indigenous Peoples. Minnesota is home to eleven federally recognized Tribes who have maintained deep ties to the lands and waters. This study focuses on Minnesota’s ‘Iron Range,\u27 a settler name for a region defined by more than a century of iron ore mining.
This dissertation centers the complex, enduring relationships Indigenous and Descendant communities hold with extractive industries and landscapes. It introduces the concept of authorized industrial heritage discourse to show how dominant accounts erase Indigenous presence, voices, and lived experiences, while perpetuating settler colonial narratives of “discovery” and progress.
It further demonstrates how Indigenous storywork, guided by ethical principles of the Two-Row Wampum (Gaswéñdah), reframes and centers Indigenous knowledge systems and lived experiences in industrial heritage contexts. The Gaswéñdah principles serve as an ethical framework that provides a relational basis for interpreting industrial heritage and histories while ensuring relational accountability and cultural competence throughout the research design.
Employing a Feminist-Indigenous research approach, the study engages with co-researchers through semi-structured interviews and oral histories. Drawing on these narratives, the study identifies examples of Ojibwe labor in the historic underground mines of Ely, MN, and the complex relationships with resource extraction. These stories highlight how communities balance the economic security provided by mining jobs with profound concerns over environmental impact and treaty rights, including maintaining ties to lands through labor.
The findings unsettle dominant narratives, restore the voices of those who long carried relationships with these lands, and lead to the articulation of an Indigenous-Industrial Heritage, a framework that prioritizes community voices to re-story industrial landscapes through multi-vocality. It proposes that the systematic inclusion and amplification of long-hidden community narratives can serve as a critical form of restorative justice and offer pathways toward repair, reciprocity, and reconciliation in contexts where the physical return of land (#landback) is not yet possible. This dissertation provides a practical and theoretical model for heritage institutions to adopt, to support ongoing efforts to advance more collaborative and equitable interpretation practices
OVERCOMING OBSTACLES TO EQUITABLE ENERGY TRANSITIONS AND PROMOTING ENERGY SOVEREIGNTY FOR US TRIBAL NATIONS
No full textThis dissertation explores the potential of equitable energy transitions guided by the tenets of energy justice with a focus on Tribal energy sovereignty through renewable energy development. It contributes to the literature on the social acceptance of energy systems, public perceptions of renewable energy transitions, the ramifications of US federal Tribal law on Tribal energy development and sovereignty, and the implications of conforming to capitalist logics in the energy justice literature.
To understand the importance of building reciprocal and collaborative relationships, our team of researchers and Tribal members collaborated on the development of a methodology to survey respondents in a culturally appropriate forum to learn about Tribal perceptions of energy planning outside of typically rigid and hierarchal energy planning processes. The results demonstrate a desire to prioritize energy systems that protect the environment, decrease costs, and advance Tribal energy sovereignty. This methodology and resulting analyses reinforce the importance of collaboration, engagement, and transparency in the energy planning process to build trust and increase participation, leading to more authentic and informed decision making, to inform the development of values-based energy policies.
Through a legal analysis of US federal Tribal law using the divergent lenses of Western and Indigenous concepts of sovereignty, this work explores whether federal laws have supported or impeded Tribal energy development in ways that promote energy sovereignty. The impact of federal law on tribal energy sovereignty was analyzed in the context of de recto (by right), de facto (in fact), or de jure (by law) sovereignty, to identify whether and how federal policy has advanced or has the potential to advance Tribal sovereignty. This work also engages with the divergence between Western and Indigenous concepts of sovereignty. The research demonstrates the usefulness of the energy justice framework in guiding the development of values-based emancipatory policies that advance equitable energy transitions and Tribal energy sovereignty.
Finally, this work proposes an energy justice research agenda that asserts commodified energy as the root cause of injustices identified in the literature. Failure to acknowledge this assertion creates barriers to overcoming the obstacles to equitable energy transitions. This chapter asserts that decommodified energy should be considered a prerequisite to energy justice and that centering alternatives to capitalist logics, which include decommodification and post-growth models, can help energy justice scholars create alternate imaginaries outside of the capitalist agenda and overcome obstacles to equitable energy transitions
EFFECTIVENESS, COHERENCE, AND JUSTICE IMPLICATIONS OF CLEAN ENERGY POLICIES IN THE UNITED STATES
No full textPublic policies have been adopted and implemented at various government levels in the United States, aiming to facilitate the clean energy transition process. This dissertation examines three distinct but related dimensions of clean energy policies: policy effectiveness, policy coherence, and distributional policy impact. First, I evaluate the impact of the American Reinvestment and Recovery Act (ARRA) on clean energy adoption at the utility level using a quasi-experimental design: the Difference-in-Difference estimation. Secondly, I use the state of California as a case study to investigate the role of policy coherence in public policy success. Thirdly, I investigate whether communities with different demographic and socio-economic characteristics have equal access to modern energy services (e.g., dynamic pricing). The preliminary findings from the third paper suggest that certain populations, particularly low-income and minority groups, are disproportionately disadvantaged in accessing modern energy services. This dissertation will contribute to the scholarly debates on energy justice, clean energy policy evaluation, and policy coherence by employing a mixed methods approach of geographical information systems (GIS), statistics, and document review
MULTISCALE COMPUTATIONAL CHEMISTRY STUDIES OF THE CATALYTIC MECHANISMS OF NON-HEME FE(II)/2-OXOGLUTARATE-DEPENDENT OXYGENASES
No full textEnzymes catalyze complex biological transformations. Non-heme Fe(II)/2-oxoglutarate (2OG)–dependent enzymes are highly versatile catalysts capable of selective C–H oxidation, enabling transformations such as hydroxylation, halogenation, desaturation, demethylation, ring rearrangements, epoxidation, and electrophilic aromatic substitution. These enzymes are involved in various biological processes, including fatty acid metabolism, hypoxic signaling, collagen maturation, and transcriptional regulation. Computational Modeling provides detailed knowledge of the enzymes including atomistic details of the important catalytic species, conformational and electronic effects, which are crucial to enzyme engineering and drug design efforts. This dissertation implements advanced multi-scale molecular modelling techniques including Molecular dynamics and Quantum Mechanic / Molecular Mechanics calculations to comprehend the dynamics and catalytic reaction mechanisms of non-heme Fe(II)/2-oxoglutarate (2OG) dependent oxygenases. Chapter 2 describes the role of synergy between non-heme Fe(II) center, second coordination sphere (SCS) and long-range (LR) interactions in the catalytic mechanism of KDM6 family of enzymes, focusing on similarities and differences in dynamics and the reaction mechanism of KDM6A and KDM6B in the demethylation of tri-methylated H3 histone lysine. The results identified differences in the SCS interactions of the Fe-chelating glutamate influences the hydrogen atom transfer reactivity of KDM6A and KDM6B. Chapter 3 describes the mechanism of consecutive oxidations catalyzed by KDM6B enzyme with higher alkylated H3 Lysine substrates. The results identified the role of SCS residues N344 and Y239 in conformational positioning of different alkylation marks of the lysine substrate to access the Fe(IV)=O intermediate, thereby influencing the regio- and chemo-selectivity. Chapter 4 unravels the second branchpoint in the catalytic mechanism of ethylene forming enzyme, which determines the product distribution of ethylene and 3-hydroxypropionate (3HP). The results suggest that the propion-3-yl radical acts as the branchpoint between ethylene and 3HP rather than previously proposed carboxyethyl carbonato-Fe(II) intermediate. Chapter 5 explores the catalytic mechanism of Adev halogenases in achieving regio- and stereo-specific chlorination of nucleosides and determines the reactive intermediate among the two ferryl intermediates identified experimentally. The QM/MM reaction path calculations and Mossbauer calculations complements the experimental observation by suggesting the offline Fe(IV)=O as the reactive intermediate for C-H activation. Chapter 6 describes the reaction mechanism of free amino acid halogenase BesD and halogenase variants derived from homologous hydroxylase. The results suggest an isomerization pathway involving swapping of -OH and -Cl groups at the Cl-Fe(III)-OH intermediate which helps in achieving chlorination selectivity. Overall, the insights presented in this dissertation deepens the fundamental understanding of the catalysis by non-heme Fe(II)/2OG dependent enzymes, which could help in design of drugs and enzyme engineering efforts
Analysis of a saline dust storm from the Aralkum Desert – Part 2: Atmospheric flow precursors in the Euro-Atlantic region
No full textWind-blown dust emissions from the man-made Aralkum Desert pose significant environment and human health risks across Central Asia. Yet, little is known about the atmospheric circulation patterns favoring dust outbreaks from the region. This study examines the role of upstream atmospheric blocking and recurrent transient Rossby wave packets (RWPs) in initiating a severe dust storm from the Aralkum Desert in May 2018. Results show that the dust event was triggered by an unusual early-summer cold air outbreak and attendant postfrontal northerly winds reaching 24–31 m/s. The compound cold air and dust outbreaks were preceded by repeated meridional flow amplification linked to recurrent RWPs across the North Atlantic, persistent blocking over Scandinavia, and the subsequent development of a pronounced ridge-trough couplet that facilitated cold intrusions into Kazakhstan. This study underscores the importance of Euro-Atlantic blocking systems in shaping surface weather hazards in the downstream Central Asia region
BIMW: Blockchain-Enabled Innocuous Model Watermarking for Secure Ownership Verification
No full textThe integration of artificial intelligence (AI) and edge computing gives rise to edge intelligence (EI), which offers effective solutions to the limitations of traditional cloud-based AI; however, deploying models across distributed edge platforms raises concerns regarding authenticity, thereby necessitating robust mechanisms for ownership verification. Currently, backdoor-based model watermarking techniques represent a state-of-the-art approach for ownership verification; however, their reliance on model poisoning introduces potential security risks and unintended behaviors. To solve this challenge, we propose BIMW, a blockchain-enabled innocuous model watermarking framework that ensures secure and trustworthy AI model deployment and sharing in distributed edge computing environments. Unlike widely applied backdoor-based watermarking methods, BIMW adopts a novel innocuous model watermarking method called interpretable watermarking (IW), which embeds ownership information without compromising model integrity or functionality. In addition, BIMW integrates a blockchain security fabric to ensure the integrity and auditability of watermarked data during storage and sharing. Extensive experiments were conducted on a Jetson Orin Nano board, which simulates edge computing environments. The numerical results show that our framework outperforms baselines in terms of predicate accuracy, p-value, watermark success rate (WSR), and harmlessness H. Our framework demonstrates resilience against watermarking removal attacks, and it introduces limited latency through the blockchain fabric
CortenMM: Efficient Memory Management with Strong Correctness Guarantees
No full textModern memory management systems suffer from poor performance and subtle concurrency bugs, slowing down applications while introducing security vulnerabilities. We observe that both issues stem from the conventional design of memory management systems with two levels of abstraction: a software-level abstraction (e.g., VMA trees in Linux) and a hardware-level abstraction (typically, page tables). This design increases portability but requires correctly and efficiently synchronizing two drastically different and complex data structures, which is generally challenging.We present CortenMM, a memory management system with a clean-slate design to achieve both high performance and synchronization correctness. Our key insight is that most OSes no longer need the software-level abstraction, since mainstream ISAs use nearly identical hardware MMU formats. Therefore, departing from prior designs, CortenMM eliminates the software-level abstraction to achieve sweeping simplicity. Exploiting this simplicity, CortenMM proposes a transactional interface with scalable locking protocols to program the MMU, achieving high performance by avoiding the extra contention in the software-level abstraction. The one-level design further enables us to formally verify the correctness of concurrent code operating on the MMU (correctness of basic operations and locking protocols), thereby offering strong correctness guarantees. Our evaluation shows that the formally verified CortenMM outperforms Linux by 1.2× to 26× on real-world applications
Unveiling exosomal biomarkers in neurodegenerative diseases: LC-MS-based profiling
No full textExosomes, small extracellular vesicles secreted by various cell types, play a critical role in intercellular communication and are increasingly recognized as key players in the progression of neurodegenerative diseases (NDs). Their ability to carry and propagate pathogenic proteins such as amyloid-beta, tau, and alpha-synuclein have established exosomal biomarkers as both key players in disease pathology and promising indicators for early diagnosis. Liquid chromatography-mass spectrometry (LC-MS) has emerged as a powerful tool for the comprehensive analysis of exosomal cargo, enabling the identification of proteins, metabolites, and other molecules associated with neurodegeneration. This review explores the structural composition, biogenesis, and role of exosomes in the propagation of pathogenic proteins in NDs such as Alzheimer\u27s disease (AD), Parkinson\u27s disease (PD), and amyotrophic lateral sclerosis (ALS). It highlights the potential of exosomal biomarkers for disease diagnosis and monitoring. The foundation for LC-MS-based analyses is discussed, focusing on isolation, purification, and characterization techniques essential for reliable proteomic and metabolomic studies. The LC-MS workflow, from protein and metabolite identification to quantitative proteomics, is detailed alongside the advantages of LC-MS in uncovering exosomal biomarkers. We delve into the application of LC-MS/MS in NDs research, showcasing its contributions to decoding disease pathology in AD, PD, and ALS by identifying specific exosomal biomarkers. Challenges such as the heterogeneity of exosome populations, variability in biofluid samples, and technical limitations in LC-MS analysis are critically examined. Finally, we discuss the future potential of LC-MS in advancing the diagnosis and treatment of NDs, emphasizing its transformative impact on biomarker discovery and personalized medicine