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- Creators: Arizona State University
Description
In the face of the sixth mass extinction on Earth, with the flowering plant family Cactaceae assessed as the fifth most endangered plant or animal family by the International Union for the Conservation of Nature (IUCN), it is imperative that all available tools be used to understand the biodiversity, habitat suitability, climate change impacts and population viability of cacti. Within the Cactaceae, Mammillaria Haw and the closely related genus Cochemiea (K. Brandegee) Walton of Baja California, Mexico, are species-rich, with 46 regionally endemic taxa, 12 of which have been assessed as threatened or endangered by the IUCN. This study clarifies the evolutionary relationships in the Mammilloid clade, a complex and species-rich clade in tribe Cacteae, and generic circumscription of the genera Mammillaria Haw. and Cochemiea (K. Brandegee) Walton, estimates divergence times, diversification rates and ancestral ranges and explores habitat suitability and the risk of extinction of a representative species within these genera. The r species, Cochemiea halei (K. Brandegee) Walton, a narrowly distributed island endemic, is assessed using species distribution modeling (SDM) and population viability analysis (PVA). SDM in this study includes projections to two climate change scenarios over the next century, using four representative particle concentration pathways, and the PVA uses habitat-specific deterministic and stochastic models. The results of molecular phylogenetic analyses of the Mammilloid cladde restore the genus Mammillaria to monophyly via new combinations in the genus Cochemiea. The taxa in this study are shown to be of recent origin resulting from rapid diversification and radiation. Geological and climatic forces at multiple scales appear to be responsible for the high degree of biodiversity and endemism of these cacti. SDM shows that C. halei is likely to be stranded in its fragmented island habitat, has a facultative adaptation to ultramafic soils, and faces a 21%–53% contraction of its range on the islands under climate change scenarios. PVA suggests that C. halei is at increased risk of extinction in response to slight decreases in fecundity and persistence. In general, the perspectives in this dissertation fill several gaps in our prior knowledge of the evolution, biogeography, and conservation pressures of an important, species-rich group of cacti, occurring in a region of high biodiversity and endemism.
ContributorsBreslin, Peter (Author) / Wojciechowski, Martin F (Thesis advisor) / Albuquerque, Fabio (Committee member) / Fehlberg, Shannon (Committee member) / Majure, Lucas (Committee member) / Rebman, Jon (Committee member) / Arizona State University (Publisher)
Created2020
DescriptionUnderstanding the evolution of opinions is a delicate task as the dynamics of how one changes their opinion based on their interactions with others are unclear.
ContributorsWeber, Dylan (Author) / Motsch, Sebastien (Thesis advisor) / Lanchier, Nicolas (Committee member) / Platte, Rodrigo (Committee member) / Armbruster, Dieter (Committee member) / Fricks, John (Committee member) / Arizona State University (Publisher)
Created2021
Description
Cryogenic Electron Microscopy (Cryo-EM) is a method that can be used for studying the structure of biological systems. Biological samples are frozen to cryogenic temperatures and embedded in a vitreous ice when they are imaged by electrons. Due to its ability to preserve biological specimens in near-native conditions, cryo-EM has a significant contribution to the field of structural biology.Single-particle cryo-EM technique was utilized to investigate the dynamical characteristics of various protein complexes such as the Nogo receptor complex, polymerase ζ (Polζ) in yeast and human integrin ⍺vβ8-pro-TGFβ1-GARP complex. Furthermore, I proposed a new method that can potentially improve the sample preparation for cryo-EM. The Nogo receptor complex was expressed using baculovirus expression system in sf9 insect cells and isolated for structural studies. Nogo receptor complex was found to have various stoichiometries and interactions between individual proteins. A structural investigation of the yeast apo polymerase ζ holoenzyme was also carried out. The apo Polζ displays a concerted motions associated with expansion of the Polζ DNA-binding channel upon DNA binding. Furthermore, a lysine residue that obstructs the DNA-binding channel in apo Polζ was found and suggested a gating mechanism. In addition, cryo-EM studies of the human integrin ⍺vβ8-pro-TGFβ1-GARP complex was conducted to assess its dynamic interactions. The 2D classifications showed the ⍺vβ8-pro-TGFβ1-GARP complex is highly flexible and required several sample preparation techniques such as crosslinking and graphene oxide coating to improve protein homogeneity on the EM grid. To overcome challenges within the cryo-EM technique such as particle adsorption on air-water interface, I have documented a collaborative work on the development and application of lipid monolayer sandwich on cryo-EM grid. Cryogenic electron tomography (cryo-ET) along with cryo-EM were used to study the characteristics of lipid monolayer sandwich as a potential protective layer for EM grid. The cryo-ET results demonstrated that the thickness of lipid monolayer is adequate for single-particle cryo-EM processing. Furthermore, there was no appearance of preferred orientations in cryo-EM and cryo-ET images. To establish that this method is actually beneficial, more data must be collected, and high-resolution structures of protein samples must be obtained using this methodology.
ContributorsTruong, Chloe Du (Author) / Chiu, Po-Lin (Thesis advisor) / Liu, Wei (Committee member) / Mazor, Yuval (Committee member) / Arizona State University (Publisher)
Created2021
Description
Nonlinguists’ attitudes towards language are a major factor in the process of language change. Therefore, linguists are interested in examining how language varieties are perceived. Several studies around the world have demonstrated that ideologies play a major role in shaping how people perceive certain dialects, how social meanings are associated with these varieties, and how linguistic communities are shaped in part by these beliefs. However, little attention has been given to language attitude in the Arab region, and in the Saudi context particularly. Moreover, none of the attitudinal studies in the region have tried to investigate Najdis’ attitudes towards their own dialects. Using a conceptually presented attitudinal approach, this study bridges the literature gap by examining 1041 Najdis’ language attitudes towards two of the main dialects there: The Najdi Urban and Najdi Bedouin varieties. The study answers the following questions: How do Najdis perceive the Najdi Urban and Bedouin dialects, and what are the frequently associated characteristics with these varieties? The results of the quantitative analysis show that Najdis’ language attitudes can be discussed with and reduced to two themes: modernity and traditionality. The Urban Najdi dialect was perceived as modern. Contrarily, the Bedouin Najdi dialect was considered traditional. Each social group tended to rate their dialect higher than the other group did in both factors, indicating in-group loyalty. Also, both groups showed high levels of linguistic security.
ContributorsAlothman, Ayoub (Author) / Adams, Karen (Thesis advisor) / Van Gelderen, Elly (Committee member) / Prior, Matthew (Committee member) / Arizona State University (Publisher)
Created2021
Climate Sensitivity in Mature Versus Pre-Reproductive Saguaro Determined from Spine Isotopic Signals
Description
The saguaro cactus is vital to the unique biodiversity of the Sonoran Desert. Many animals rely on it for survival and shelter. Due to its thick waxy exterior, it is able to retain a massive amount of water in its succulent stems, making it an ideal habitat for many birds that are native to the region. It also holds a large cultural significance for many native tribes of this region. Thus, it is important to understand how these magnificent plants are affected by changing environmental conditions in order to protect them in the future. Measurements of carbon isotope (13C) signals in saguaros spine tissues have been shown to be a robust approach for evaluating plant responses to climate variation over multiple seasons and years. This study investigated growth and 13C signals in young saguaros (< 2.5 m tall) at a location north of Phoenix to compare with large saguaros (> 4 m tall) that actively flower in the spring. Adolescent saguaros were examined to determine how they responded to variation in moisture between the years 2012 through 2016. As with a previous study by Hultine et al. (2018), this research demonstrated a strong relationship between height growth and precipitation. Stem growth was also highly correlated with the number of areoles produced across both young and old plants. Winter and late summer moisture from the previous year had a significant effect on stem growth, and a legacy effect could be seen in the low growth rates in 2014 which may be a result of low precipitation during the previous fall and winter. This study also established that the adolescent saguaro may be less sensitive to seasonal changes than the mature saguaro. When comparing the large plants with the adolescent plants, spine 13C values were similar between mature and adolescent plants, indicating that perhaps flower does not impose a significant added cost to saguaro water budgets. However, identifying the cost of flowering requires more investigation than that from only spine carbon isotope measurements and coarse measurements of plant productivity.
ContributorsDe Leon, Isabella (Author) / Hultine, Kevin (Thesis advisor) / Pigg, Kathleen (Thesis advisor) / Maienschein, Jane (Committee member) / Arizona State University (Publisher)
Created2021
Description
Students with disabilities are entering higher-education institutions at increasing rates, but they are not being adequately prepared for this transition. Transition plans have been created by Special Education teams in the K-12 system, but oftentimes, the student is not an active participant in the development of these plans for their futures. A huge gap in preparing for the transition to post-secondary education is a student’s self-determination skills. Self-determination is a belief that you control your own destiny and are motivated to create your own path in life. This study explores how students with disabilities can improve their self-determination skills through guided practice and small group collaboration. Participants included (n=4) freshmen students with disabilities who were actively engaged with their institution’s Disability Resource Center at a 4-year public research institution in the West. A qualitative practical action research study was designed to explore the impact of implementing a self-determination innovation to support college students with disabilities in improving their self-determination skills. The innovation developed for this study was adapted from Field and Hoffman’s Steps to Self-Determination curriculum. Findings from this study illustrate the need to support transitioning college students with disabilities in understanding their disabilities and how it can and will impact them in the college environment and beyond. Providing students with a safe space to explore their disabilities and the challenges they have encountered in their lives, allows them to identify the barriers to their growth and build a support system of similarly situated students that provide them with a sense of belonging and camaraderie they have not usually experienced in their lives. This study demonstrates how supporting students in improving their self-determination skills can help them build their confidence and self-advocacy skills to persist in higher education institutions.
ContributorsVioli, Patricia Kathryn (Author) / Markos, Amy (Thesis advisor) / Rotheram-Fuller, Erin (Committee member) / Thierfeld-Brown, Jane (Committee member) / Arizona State University (Publisher)
Created2021
Description
In this dissertation, the surface interactions of fluorine were studied during atomic layer deposition (ALD) and atomic layer etching (ALE) of wide band gap materials. To enable this research two high vacuum reactors were designed and constructed for thermal and plasma enhanced ALD and ALE, and they were equipped for in-situ process monitoring. Fluorine surface interactions were first studied in a comparison of thermal and plasma enhanced ALD (TALD and PEALD) of AlF3 thin films prepared using hydrogen fluoride (HF), trimethylaluminum (TMA), and H2-plasma. The ALD AlF3 films were compared ¬in-situ using ellipsometry and X-ray photoelectron spectroscopy (XPS). Ellipsometry showed a growth rate of 1.1 Å/ cycle and 0.7 Å/ cycle, at 100°C, for the TALD and PEALD AlF3 processes, respectively. XPS indicated the presence of Al-rich clusters within the PEALD film. The formation of the Al-rich clusters is thought to originate during the H2-plasma step of the PEALD process. The Al-rich clusters were not detected in the TALD AlF3 films. This study provided valuable insight on the role of fluorine in an ALD process.
Reactive ion etching is a common dry chemical etch process for fabricating GaN devices. However, the use of ions can induce various defects, which can degrade device performance. The development of low-damage post etch processes are essential for mitigating plasma induced damage. As such, two multistep ALE methods were implemented for GaN based on oxidation, fluorination, and ligand exchange. First, GaN surfaces were oxidized using either water vapor or O2-plasma exposures to produce a thin oxide layer. The oxide layer was addressed using alternating exposures of HF and TMG, which etch Ga2O3 films. Each ALE process was characterized using in-situ using ellipsometry and XPS and ex-situ transmission electron microscopy (TEM). XPS indicated F and O impurities remained on the etched surfaces. Ellipsometry and TEM showed a slight reduction in thickness. The very low ALE rate was interpreted as the inability of the Ga2O3 ALE process to fluorinate the ordered surface oxide on GaN (0001).
Overall, these results indicate HF is effective for the ALD of metal fluorides and the ALE of metal oxides.
ContributorsMessina, Daniel C (Author) / Nemanich, Robert J (Thesis advisor) / Goodnick, Stephen (Committee member) / Ponce, Fernando A (Committee member) / Smith, David (Committee member) / Arizona State University (Publisher)
Created2021
Description
Human operators are more prone to errors under high-workload conditions. However, error-commission research in cognitive science has been limited to studying behavior in single-choice reaction time tasks, which do not represent the complex multitasking scenarios faced in the real-world. In the current paper, prior evidence for a cognitive error-monitoring mechanism was applied toward predictions for how humans would react after making errors in a more ecologically valid multitasking paradigm. Previous work on neural and behavioral indices of error-monitoring strongly supports the idea that errors are distracting and can deplete attentional resources. Therefore, it was predicted that after committing an error, if a subject is subsequently presented with two simultaneously initiated task alerts (a conflict trial), they would be more likely to miss their response opportunity for one task and stay tunneled on the other task that originally caused the error. Additionally, it was predicted that this effect would dissipate after several seconds (under different lag conditions), making the error cascade less likely when subsequent tasks are delayed before presentation. A Multi-Attribute Task Battery was used to present the paradigm and collect post-error and post-correct performance measures. The results supported both predictions: Post-error accuracy was significantly lower as compared to post-correct accuracy (as measured through post-trial error rates). Post-trial error rates were also higher at shorter lags and dissipated over time, and the effects of pre-conflict performance on post-trial error rates was especially noticeable at shorter lags (although the interaction was not statistically significant). A follow-up analysis also demonstrated that following errors (as opposed to following correct trials), participants clicked significantly more on the task that originally caused the error (regardless of lag). This continued task-engagement further supports the idea that errors lead to a cognitive tunneling effect. The study provides evidence that in a multitasking scenario, the human cognitive error-monitoring mechanism can be maladaptive, where errors beget more errors. Additionally, the experimental paradigm provides a bridge between concepts originating in highly controlled methods of cognitive science research and more applied scenarios in the field of human factors.
ContributorsLewis, Christina Mary (Author) / Gutzwiller, Robert S (Thesis advisor) / Becker, David V (Committee member) / Gray, Robert (Committee member) / Arizona State University (Publisher)
Created2021
Description
This manuscript option dissertation elucidates the role of patient-provider interactions in keeping HIV positive Black women in medical care. Since 2012, the Arizona State Department of Health has acknowledged that women of African descent are disproportionately affected by HIV and die at higher rates from AIDS-related complications than other women. The dissertation includes three manuscripts covering a feature of this topic. The first paper is a scoping review of literature on what is known about the influence of patient-provider relationships on adherence and viral suppression among Black women living with HIV in Arizona. The second is an empirical study built upon interviews with Black women living with HIV analyzed through constructivist grounded theory to understand women’s perspectives of provider actions that keep them in care. The third offers practice recommendations based on the interviews with Black women living with HIV, dialog with HIV advocates, and proceedings of the Phoenix Fast Track Cities ad hoc committee to end HIV as an epidemic. Together, the three manuscripts integrate the voices of women, advocates, and past research to support best practices and future steps for HIV retention strategies.
ContributorsHassan, Kenja (Author) / Coon, David W. (Thesis advisor) / McCarthy, Marianne (Committee member) / Uriri-Glover, Johannah (Committee member) / Arizona State University (Publisher)
Created2021
Description
Stress and anxiety are on the rise in children and adolescents, which may adversely impact their social and emotional development, learning, mental health, level of functioning, and educational success. Compounding this issue is that teachers often lack the preparation to best meet their students’ mental health needs. These associated factors constitute the problem of practice that prompted this action research study, whose purpose is to examine the effectiveness of Stress on Students (SOS)—a series of professional development modules designed to educate teachers on student stress and anxiety. SOS was developed with input from teachers through previous cycles of action research. The modules focus on identifying stress and anxiety among students and intervention strategies to increase teachers’ knowledge and perceived levels of self-efficacy. This study was grounded in the theoretical frameworks of andragogy and self-efficacy theory and employed a concurrent, mixed-methods design. Data were collected through a quantitative pre- and post-test survey instrument and qualitative semi-structured individual interviews. Analytic strategies included paired samples t-tests, descriptive statistics of the pre- and post-test, and multiple coding cycles of the individual interviews. Triangulation of the quantitative and qualitative data confirmed SOS’ effectiveness on teacher participants (n = 6) and provided complementary evidence. Teachers showed an increase in their actual and perceived knowledge about student stress and anxiety post-SOS with similar results pertaining to their perceived levels of self-efficacy in working with students who exhibit stress and anxiety. Additionally, teachers fully participated in SOS and deemed the topic and content to be relevant and valuable.
ContributorsJukins, Brian (Author) / Gee, Elisabeth (Thesis advisor) / Oakes, Wendy P (Committee member) / Rotheram-Fuller, Erin (Committee member) / Arizona State University (Publisher)
Created2021