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STUDYING THE HADRONIC NATURE OF ULTRA-HIGH-ENERGY GAMMA-RAY EMISSION USING WIDE-FIELD-OF-VIEW INSTRUMENTS
Get PDFSince the discovery of cosmic rays, i.e., protons, electrons, and atomic nuclei originating from space, and the birth of astroparticle physics, scientists have searched for the most energetic particle accelerators in our galaxy. PeVatrons are astrophysical objects capable of accelerating cosmic rays to peta-electronvolt energies. Studying the nature of PeVatrons allows scientists to study particle physics at energies three orders of magnitude higher than those achievable with Earth-based particle accelerators. While PeVatrons can accelerate both electrons and protons, it is thought that searching for hadronic PeVatrons is more fruitful, given the limitations of accelerating electrons to such high energies. In this dissertation, I will probe the nature of ultra-high-energy gamma-ray emission (UHE; \u3e10s TeV) from hadronic PeVatrons using the High-Altitude Water Cherenkov (HAWC) observatory and the Southern Wide-field Gamma-ray Observatory (SWGO).
The HAWC observatory is located in Puebla, Mexico. It is a wide-field-of-view survey instrument sensitive to gamma rays in the 300 GeV to 100s TeV range and utilizes single-layer water Cherenkov detectors (WCDs). For UHE gamma-ray emission to be produced by protons from hadronic PeVatrons, some type of matter, like molecular clouds, must be nearby. This has made molecular clouds a promising tracer for hadronic PeVatrons. This dissertation details a study of the believed PeVatron supernova remnant (SNR) G106.3+2.7. The molecular cloud template fit performed on UHE data from HAWC reveals that the SNR is fully capable of producing a population of \u3e560 TeV protons that have an energy budget of 7.62x1044 erg. In an attempt to probe more galactic hadronic PeVatrons, I also present HAWC\u27s second catalog of UHE gamma-ray sources: the 2eHC catalog. In the 2eHC catalog, a total of 27 sources are detected above 56 TeV, where 19 sources have a nearby SNR, 18 have a nearby pulsar wind nebula, 10 have a nearby binary system, and 1 has a nearby star-forming region.
There is currently no wide-field-of-view instrument in the southern hemisphere, leaving a large fraction of our southern sky unobserved in the 100s TeV range. SWGO is a next-generation, ground-based, gamma-ray observatory that will be built in Chile. With a sensitivity up to 1 PeV, SWGO will be ideal for surveying the southern gamma-ray sky for hadronic PeVatrons. SWGO evaluated a phase space encompassing many tank variations and array layouts using background rejection capabilities to determine the optimal WCD for SWGO\u27s science objectives. This dissertation details the implementation of background rejection algorithms, adopted from HAWC, into SWGO\u27s reconstruction chain. The results presented herein show that the double-layered WCDs have superior background rejection capability compared to the single-layered detectors. The final part of this dissertation details a successful prototyping effort to build a double-layered WCD at the HAWC site. These prototyping efforts are crucial for validating the technical feasibility of the detector technology
THE ANIMATED FRONTIER: FLUCTUATIONS OF POWER ACROSS TIME AND SPACE IN FLOWS OF U.S. AND JAPANESE ANIMATED MEDIA
Get PDFThis project critiques the historical and contemporary relationships between the U.S., Japan, and marginalized groups through the lens of animation. The U.S. and Japan share a complex history, from the opening of Japan during the Edo period to events like Pearl Harbor and the atomic bombings, which shaped their present-day alliance. Furthermore, the U.S. and Japan are the central nodes in flows of animation, where both nation states have dominated the global market at various points in animationβs history. Today, Japan\u27s soft power in media is significant, and the flow of power between these nations has influenced media forms and depictions of marginalized groups. In this dissertation, I trace the flows of the medium of animation from its inception in the United States, to its rise in Japan to understand and intervene in the representations of stereotyped groups. Using the dual concepts of the crystal-image from Gilles Deleuze, and visual dualisms from Michelle Raheja, within the framework of the virtual reservation, I analyze two specific case studies of stereotyped groups within global flows of animation: North American Indigenous peoples, and Asian peoples. Especially with the rise of new technologies which shape animation production, and the flow of images within the medium of animation, such as artificial intelligence, these flows become dislocated from space and time. I argue that this disruption of flow, and the un-anchoring to geopolitical contexts and national cinemas, creates a crisis of the time-image, under which the crystal-image operates.
The project explores five key areas: the evolution of animation as a medium; the U.S.-Japan historical relationship; how the Hollywood Western\u27s portrayal of Indigenous people influenced Japanese media; the portrayal of Asian and Asian-American groups in U.S. adult animation as model minorities ; and the Space Western genre in anime, which offers hopeful visions of interstellar frontiers.[1] [2] [3] By beginning with an understanding of the medium as it is deeply connected to factors of space, time, and material, we can in turn examine how flows of images within the medium are produced, consumed, disrupted, and redirected. The project then argues that media depictions of Indigenous and Asian groups have been historically harmful and hegemonic. Transnational media flows have perpetuated stereotypes, but the potential for adaptation and transformation in genres like animation can offer more hopeful representations. In the end, the final chapter of the project seeks to offer an understanding of frontiers, on the virtual reservation, such that dislocations from space and time may be constructive components of image-production, rather than negative and harmful ones. The project concludes that we are experiencing a time-image crisis, with the rise of artificial intelligence and new media forms reshaping how we perceive and construct worlds, moving away from traditional geopolitical narratives toward image production and consumption which is becoming unanchored by space and time. This project asks how can we understand the time-image crisis in the wake of stereotyping AI-generated images through the tracing of historical, transnational flows of animation between the U.S. and Japan from World War II to the present day
Leveraging Product and Process Characteristics Across the Concrete Pavement Life Cycle to Integrate Global Warming Potential into Project Procurement Processes
Get PDFThe objective of this research is to support sustainable procurement of concrete pavements by linking materials-level global warming potential (GWP) to the project-level. Infrastructure owners require reliable environmental product declarations (EPDs) and methodologies for integrating GWP into the procurement process to ensure equitable decision-making. This work provides insights into current EPD reliability by assessing the sensitivity of concrete GWP to materials-level contributors to recommend a level of supply chain specificity needed to effectively communicate GWP. A benchmarking methodology was developed and implemented to establish reference values for procuring sustainable products. Having provided evidence towards EPD reliability, this work presents a framework that integrates GWP with pay items in project specifications. Linking incentives within infrastructure owner specifications to desired performance characteristics encourages all involved stakeholders to prioritize achievement of those performance characteristics. This same concept can be applied using GWP as the desired performance characteristics. A data collection protocol and life cycle information model (LCIM) for concrete pavement construction were developed to facilitate GWP integration into current project procurement practices. The LCIM methodology was developed and implemented to estimate the production and construction environmental impacts of six real-world concrete pavement construction projects. Applying the LCIM methodology allowed this work to map GWP to pay items and incentives in specifications and provide a pathway to extend a LCIM across the life cycle. The LCIM was further demonstrated on a real-world joint repair project, as well as for a concrete pavement reconstruction, demolition, and waste hauling. The culmination of this research demonstrated that the LCIM can be used to estimate the embodied environmental impacts of a concrete pavement across its life cycle and provided a framework for integrating environmental impacts into the procurement process, facilitating sustainable project procurement for infrastructure owners
Synthesis of Sensitive RNAs Using Fluoride-Cleavable Groups as Linkers and Amino-Group Protection
No full textA chemical method suitable for the synthesis of RNAs containing modifications such as N4-acetylcytidine (ac4C) that are unstable under the basic and nucleophilic conditions used by standard RNA synthesis methods is described. The method uses the 4-((t-butyldimethylsilyl)oxy)-2-methoxybutanoyl (SoM) group for the protection of exo-amino groups of nucleobases and the 4-((t-butyldimethylsilyl)oxy)-2-((aminophosphaneyl)oxy)butanoyl (SoA) group as the linker for solid phase synthesis. RNA cleavage and amino deprotection are achieved using fluoride under the same conditions used for the removal of the 2\u27-OH silyl protecting groups. Using this method, a wide range of electrophilic and base-sensitive groups including those that play structural and regulatory roles in biological systems and those that are artificially designed for various purposes are expected to be able to be incorporated into any position of any RNA sequences. As a proof of concept, several RNAs containing the highly sensitive ac4C epitranscriptomic modification was synthesized and purified with RP HPLC. MALDI MS analysis indicated that the ac4C modification is completely stable under the fluoride deprotection conditions. The sensitive RNA synthesis method is expected to be able to overcome the long-lasting obstacle of accessing various modified sensitive RNAs to projects in areas such as epitranscriptomics, molecular biology and the development of nucleic acid therapeutics
Per- and Polyfluoroalkyl Substances Removal Using Carbonaceous Adsorbents in a Brackish Water Circular Economy
No full textCircular economy concepts are becoming increasingly attractive in a world with limited resources. This study proposed one that would exist at the intersection of two pressing issues, per- and polyfluoroalkyl substances (PFAS) contamination and dwindling freshwater resources. The concept was developed around treating PFAS-contaminated, brackish irrigation water (BIW) using unconventional carbonaceous adsorbents, including an evaluation of realistic implementation hurdles. PFAS would be removed from BIW, halting their environmental cycling, using powdered bone char (PBC) or powdered halophyte biochar (PHB), while their production would be integrated with livestock grazing and halophyte cultivation, respectively. Halophytes would be irrigated with treated BIW, potentially paired with reverse osmosis for freshwater production, while cattle would use halophytes for fodder/forage. Using a PFAS-contaminated brackish groundwater (BGW) as a representative BIW, higher doses of PBC and PHB relative to powdered activated carbon (PAC) (200-500 mg/L vs. 10-50 mg/L) were required to achieve \u3e50% PFAS removal. Though results highlighted inferior performance, PBC and PHB did achieve comparable PFAS loadings to PAC on a surface area basis, indicating adsorption deficiencies were more related to the lack of specific surface area than surface properties. Increasing PBC- and PHB-specific surface areas by at least 3.5-4.0 times would be required to match PAC performance. Cattle and land requirements were projected to be βΌ6,700 animals and 35 ha, respectively, assuming either a 500 mg/L (PBC) or 350 mg/L (PHB) dose to achieve substantial perfluorooctane sulfonic acid (PFOS) removal from 1,000 L/min of BIW. In addition, a simple approach using PFOS dose-response data and the homogeneous surface diffusion model was developed to predict kinetic curves without testing
Role of Pyrolysis Wax on Enhancing the Performance of Waste Plastic Modified Asphalt Prepared with the Wet Modification Process
No full textUsing waste plastics in pavement construction has been attracting significant attention because of its ability to increase the sustainability of the road infrastructure, economic benefits, and superior performance with regard to resistance against rutting. However, poor compatibility, mainly because of differences between the properties of plastics and asphalt with regard to density, molecular weight, polarity, and solubility, has been one of the major drawbacks that has been limiting their successful application. As a result, this study aims to use a wax-based product, which is a by-product of the pyrolysis of waste polyethylene, to enhance the compatibility between asphalt and two main types of polyolefins: polyethylene and polypropylene. The main objective was to use pyrolysis wax to enhance the compatibility between asphalt and plastics, as well as eliminating two of the primary downsides of plastic-modified asphalt: poor resistance to cold weather and fatigue-related cracks. To achieve this, after the incorporation of pyrolysis wax to plastic-modified asphalt during the wet modification process, the rheological performance of the asphalt containing plastics was evaluated by conducting different laboratory testing. The results indicate that a proper ratio between pyrolysis wax additive and plastic asphalt binder containing 2% polyolefins and 1.5% pyrolysis wax overall can demonstrate a superior performance with regard to the different aspects of performance, including resistance against rutting, thermal cracking, and fatigue, without sacrificing any other aspects of the performance when compared with base PG 58-28 binder and plastic-modified binder
Connecting Landscapes of Extraction: Sustainable Educational Tourism and Experiential Learning in the YucatΓ‘n
No full textCritical scholars often draw connections between the boom and bust of large-scale extractive industries such as mining and agriculture with the equally extractive tourism industries which often replace them in the name of economic development. Labor exploitation, volatile markets, and the risk of a singular economic base too often accompany large-scale shifts toward tourism. From the perspective of a former school of mines and a university context situated deep within a deindustrialized landscape-turned tourist destination, we seek to understand how best to implement sustainable and experiential programs from which our students can externalize many of the ongoing concerns of our community. Using the YucatΓ‘n Peninsula and a 10-day study abroad as our case study, we explore the potential for students to draw connections between the Keweenaw and YucatΓ‘n Peninsulas as both former and transformed landscapes of industrial extraction (copper and henequen, respectively). Building upon Houston and Langeβs βGlobal/Localβ community-engaged framework for experiential learning, we aim to similarly trouble not only the notion of βthe classroomβ but of development as an assumed force of positive change within many community-engaged experiences. Furthermore, this framework is structured around the context of our home institution, the former Michigan School of Mines, with the goal of speaking towards other educators working critically within technological institutions. Combining the self-exploration of educational tourism with intersectional landscapes of industrial, cultural, and ecological heritage, we utilize student surveys, landscape analysis, and autoethnography to illustrate the potential praxis of sustainable educational tourism and its challenges
Early life high fructose impairs microglial phagocytosis and neurodevelopment
No full textDespite the success of fructose as a low-cost food additive, epidemiological evidence suggests that high fructose consumption during pregnancy or adolescence is associated with disrupted neurodevelopment1, 2β3. An essential step in appropriate mammalian neurodevelopment is the phagocytic elimination of newly formed neurons by microglia, the resident professional phagocyte of the central nervous system4. Whether high fructose consumption in early life affects microglial phagocytosis and whether this directly affects neurodevelopment remains unknown. Here we show that offspring born to female mice fed a high-fructose diet and neonates exposed to high fructose exhibit decreased phagocytic activity in vivo. Notably, deletion of the high-affinity fructose transporter GLUT5 (also known as SLC2A5) in neonatal microglia completely reversed microglia phagocytic dysfunction, suggesting that high fructose directly affects neonatal development by suppressing microglial phagocytosis. Mechanistically, we found that high-fructose treatment of mouse and human microglia suppresses phagocytosis capacity, which is rescued in GLUT5-deficient microglia. Additionally, we found that high fructose drives significant GLUT5-dependent fructose uptake and catabolism to fructose 6-phosphate, rewiring microglial metabolism towards a hypo-phagocytic state in part by enforcing mitochondrial localization of the enzyme hexokinase 2. Mice exposed to high fructose as neonates develop anxiety-like behaviour as adolescentsβan effect that is rescued in GLUT5-deficient mice. Our findings provide a mechanistic explanation for the epidemiological observation that high-fructose exposure during early life is associated with increased prevalence of adolescent anxiety disorders
Polycaprolactone-chitosan-based scaffolds with nanostructured cuprorivaite fabricated via 3D printing for bone tissue engineering
No full textRecently, there has been significant interest in using three-dimensional (3D) printed scaffolds for tissue engineering. In this study, scaffolds were created using a combination of polycaprolactone, chitosan, and cuprorivaite (PCL/CS/5β30 wt% Cup) through a 3D printing process. The resulting PCL/CS/5β30 wt% Cup scaffolds exhibited a rectangular, porous, and interconnected structure, with contact angle ranging from 68 Β± 2Β° to 80 Β± 4Β°. The addition of cuprorivaite only slightly affected the pore sizes. The compressive strength of the PCL/CS/Cup scaffolds reached approximately 22 Β± 3 MPa, compared to 17 Β± 2 MPa for the PCL/CS scaffolds. Additionally, the composite scaffolds demonstrated improved antibacterial performance against both Gram-positive and Gram-negative bacteria, as well as enhanced hydrophilicity and bioactivity. These findings suggest that 3D bioprinting has considerable potential for producing PCL/CS/Cup composite scaffolds suitable for bone tissue engineering (BTE), with enhanced bioactivity and antibacterial properties
Unveiling a New Class of Quasi-One-Dimensional van der Waals Crystal with Tunable Electronic and Magnetic Properties
No full textThe success in exfoliating quasi-one-dimensional van der Waals (vdW) magnets to produce one-dimensional nanostructures with a stable long-range magnetic ordering at finite temperatures has ignited significant interest in exploring vdW crystals with unique electronic and magnetic properties. Here in, using a predictive density functional theory, we investigated a new class of vdW magnet, Cr1-xMnxSbSe3 (x = 0, 0.5, 1), and revealed the mechanisms underlying their distinct magnetic behaviors. Our findings show that CrSbSe3 is a ferromagnetic semiconductor with a Curie temperature of βΌ70 K, in agreement with experimental observations. The indirect exchange mechanism mediated by selenium atoms is identified as the driver of its ferromagnetic ordering. For Cr0.5Mn0.5SbSe3, we observe half-metallic ferromagnetism with a Curie temperature of βΌ40 K, while MnSbSe3 exhibits an antiferromagnetic metallic behavior. The magnetic ordering in these systems is attributed to Ruderman-Kittel-Kasuya-Yosida interaction mediated by itinerant electrons from selenium. In addition, CrSbSe3 features a Dirac cone-like band dispersion at the high-symmetry R-point for the spin majority channel, βΌ0.80 eV below the Fermi energy, with a maximum quasiparticle velocity of 1.49 Γ 105 m/s, which is comparable to the Fermi velocity in graphene. Upon 50% substitution of Cr by Mn, the Dirac-cone shifts closer to the Fermi energy, with the quasiparticle velocity increasing to 4.2 Γ 105 m/s. Further, the observation of nonlinear dispersion away from the R-point indicates that the quasiparticles transition from a massless behavior in one region of the Brillouin zone to a massive behavior in other regions. These tunable electronic behaviors and exchange mechanisms underscore the potential of compositional modifications for engineering novel low-dimensional magnets, paving the way for their future applications in next-generation spintronics