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- Creators: Arizona State University
- Resource Type: Text
- Status: Published
Description
Waste plastic is considered an environmental pollutant because it is not biodegradable. Therefore, there is increased interest in the use of recycled plastic in pavement construction. Polyethylene terephthalate (PET) is a thermoplastic polymer that is commonly used in the manufacturing of containers and bottles. Waste PET is a durable material that has shown enhancement in performance when introduced into asphalt binder and asphalt mixtures. However, PET particles tend to separate from asphalt because of differences in density, molecular structure, molecular weight, and viscosity, leading to inadequate dispersion of PET particles in the asphalt. This incompatibility between PET and asphalt causes segregation, where storage stability becomes an issue. To solve this problem, applying a surface activation on the PET using another abundant urban waste (waste vegetable oil) was examined in this study, showing this method can be effective to enhance PET-asphalt interactions and consequently the storage stability of PET-modified asphalt. To ensure proper surface activation, it is important to thoroughly understand the chemo-mechanics of asphalt containing PET particles as well as the underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using computational modeling based on density functional theory along with laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface-activated PET and asphalt. To do so, the efficacy of bio-oil treatment was examined in terms of both the surface-activation capability and the durability of the resulting PET-modified asphalt. It was found that the grafted bio-oil on the PET particles can make a strong interaction with bituminous composites, leading to enhancing the durability and extending the service life of asphalt pavement by reducing the diffusion of free radicals and moisture into the bulk. The study was further extended to study the effect of coating the PET with biochar, showing the latter coating can improve the mechanical properties of the PET-modified asphalt and the adsorption behavior of the PET for volatile organic compounds. The performance of the waste PET was compared with another widely used modifier, crumb rubber.
ContributorsAldagari, Sand (Author) / Fini, Elham (Thesis advisor) / Kaloush, Kamil (Committee member) / Ozer, Hasan (Committee member) / Arizona State University (Publisher)
Created2024
Description
Research demonstrates that maladaptive eating (e.g., restriction, disinhibition) and persistent depressive symptoms often co-occur and may reinforce each other over time. However, little is known regarding the etiology of early maladaptive eating and depressive symptoms among Mexican American children and how cultural orientation impacts co-occurrence. This study aimed to map the emerging structure of maladaptive eating–depression symptom networks, identify early dysfunctional mechanisms (i.e., symptoms) that maintain network structure, and explore how cultural orientation influences mechanisms. The sample included 263 low-income Mexican American children, assessed at 6-, 7.5-, and 9-years-old via maternal report. Mothers completed surveys on child eating, depressive symptoms, and cultural orientation. Data was analyzed using regularized partial correlation, Ising, and mixed graphical network models. Results showed that maladaptive eating networks were invariant over time. Central maladaptive eating symptoms were related to food responsiveness. Depressive symptom and combined networks were not stable enough for interpretation. Sadness and thoughts of worthlessness/inferiority emerged as central depressive symptoms at age 9. No bridge symptoms or moderated effects were large enough for interpretation. This study is the first of its kind to examine associations between eating and depressive symptoms among Mexican American children using network analysis. Results provide etiological information on the structure of co-occurring eating and depressive symptoms across late childhood and provide direction towards optimal prevention targets among this group.
ContributorsHernandez, Juan Carlos (Author) / Perez, Marisol (Thesis advisor) / Luecken, Linda (Committee member) / Berkel, Cady (Committee member) / Cruz, Rick (Committee member) / Arizona State University (Publisher)
Created2024
Description
A lack of public trust in governance institutions such as governments, federal agencies, and public health organizations limits national capacities to mitigate climate-related risks. Trustworthy sources of risk information are theorized to be more persuasive and more likely to motivate adaptive behaviors. Accordingly, this dissertation addresses relational and translational challenges of risk communication to support public health and safety by making climate science more accessible to communities at risk from extreme heat. This project developed and applied a theory-driven model of trust determination to understand how United States residents evaluate the trustworthiness of state governments and emergency management agencies. Using confirmatory factor analysis, a two-factor model of trustworthiness as self-reliability and source reliability was strongly empirically supported. This measurement model of trustworthiness was translated into experimental trustworthiness manipulations capable of creating statistically significant differences in perceptions of source reliability. The dissertation then tested the persuasive efficacy of trust-building risk messaging using randomized controlled trials, finding that when controlling for political ideology, message trust condition had a significant effect on attitudes toward extreme heat risk and preparedness as well as intentions to prepare for extreme heat events. Practical and theoretical implications are discussed.
ContributorsMattson, LD (Author) / Adame, Bradley (Thesis advisor) / Corman, Steven R (Committee member) / Eakin, Hallie (Committee member) / Arizona State University (Publisher)
Created2024
Description
This project aims to tackle two perspectives: to design and express an enzyme that can perform single-molecule modifications for identification, and to determine the inclusion of the last adenosine in mature mRNAs within the metazoan, Caenorhabditis elegans. Starting with the first perspective, the enzymatic group that was utilized was methyltransferases. Methyltransferases have gained great interest in biotechnology and academia due to their ability to make single-molecule modifications to a wide variety of biomolecules, ranging from proteins to RNA. Of these methyltransferases, the subset that has the greatest interest for this study are RNA methyltransferases. Of the known RNA methyltransferases, human METTL16 was chosen for this project, due to its ability to modify adenosines at the N6 position (m6A), specificity for its consensus motif, and its promise in chimeric enzymatic complexes. As a result of these properties, this study looks to design METTl16-based complexes for the purpose of identifying single nucleotides in RNA.
The second perspective involves pre-mRNA cleavage and polyadenylation of the 3’ untranslated region (3’UTR). Cleavage of pre-mRNAs within C.elegans appears to prefer an adenosine, leading to the term “terminal adenosine” (terminal-A). Since RNA cleavage and polyadenylation is highly conserved across metazoans, we can utilize the model system, C. elegans, to apply our findings to humans. Utilizing METTL16’s ability to modify adenosines, it is theorized that it may be possible to modify the terminal-A in vivo within C. elegans. To confirm the functionality and utilization of METTL16, a novel methodology is currently being developed called the terminal adenosine methylation (TAM) assay. The TAM assay takes advantage of METTL16’s N-terminal RNA binding domain (RBD) and methyltransferase domain – called the “core” – to methylate the terminal adenosine of probe mRNA transcripts prior to cleavage in vivo. To determine if the adenosine is present within mature mRNAs, sequencing will determine if there is a m6A present, confirming that CPSF-3 cleaves either upstream or downstream of the terminal-A.
Ultimately, this project focuses on designing METTL16 complexes for mRNA modification, testing the functionality of these constructs in vitro, and developing transgenic C. elegans strains to express the METTL16 complexes. The bioconjugation capabilities of RNA methyltransferases allow for concepts such as the TAM assay to be viable, as well as make way for future prospects of methyltransferases as a biotechnical tool.
ContributorsMurray, Jillian (Author) / Mangone, Marco (Thesis director) / Lapinaite, Audrone (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Molecular Sciences (Contributor)
Created2024-05