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- Creators: Baumel, Katie
- Member of: ASU Electronic Theses and Dissertations
- Status: Published
Description
Craniofacial morphology in primates can vary on the basis of their diet because foods are often disparate in the amount and duration of force required to break them down. Therefore diet has the potential to exercise considerable selective pressure on the morphology of the masticatory system. The zygomatic arch is a known site of relatively high masticatory strain and yet the relationship between arch form and load type is relatively unknown in primates. While the relative position and robusticity of the arch is considered a key indicator of craniofacial adaptations to a mechanically challenging diet, and central to efforts to infer diet in past species, the relationships between morphology and diet type in this feature are not well established.
This study tested hypotheses using two diet categorizations: total consumption percent and food material properties (FMPs). The first hypothesis that cortical bone area (CA) and section moduli (bone strength) are positively correlated with masticatory loading tests whether CA and moduli measures were greatest anteriorly and decreased posteriorly along the arch. The results found these measures adhered to this predicted pattern in the majority of taxa. The second hypothesis examines sutural complexity in the zygomaticotemporal suture as a function of dietary loading differences by calculating fractal dimensions as indices of complexity. No predictable pattern was found linking sutural complexity and diet in this primate sample, though hard object consumers possessed the most complex sutures. Lastly, cross-sectional geometric properties were measured to investigate whether bending and torsional resistance and cross-sectional shape are related to differences in masticatory loading. The highest measures of mechanical resistance tracked with areas of greatest strain in the majority of taxa. Cross-sectional shape differences do appear to reflect dietary differences. FMPs were not correlated with cross-sectional variables, however pairwise comparisons suggest taxa that ingest foods of greater stiffness experience relatively larger measures of bending and torsional resistance. The current study reveals that internal and external morphological factors vary across the arch and in conjunction with diet in primates. These findings underscore the importance of incorporating these mechanical differences in models of zygomatic arch mechanical behavior and primate craniofacial biomechanics.
This study tested hypotheses using two diet categorizations: total consumption percent and food material properties (FMPs). The first hypothesis that cortical bone area (CA) and section moduli (bone strength) are positively correlated with masticatory loading tests whether CA and moduli measures were greatest anteriorly and decreased posteriorly along the arch. The results found these measures adhered to this predicted pattern in the majority of taxa. The second hypothesis examines sutural complexity in the zygomaticotemporal suture as a function of dietary loading differences by calculating fractal dimensions as indices of complexity. No predictable pattern was found linking sutural complexity and diet in this primate sample, though hard object consumers possessed the most complex sutures. Lastly, cross-sectional geometric properties were measured to investigate whether bending and torsional resistance and cross-sectional shape are related to differences in masticatory loading. The highest measures of mechanical resistance tracked with areas of greatest strain in the majority of taxa. Cross-sectional shape differences do appear to reflect dietary differences. FMPs were not correlated with cross-sectional variables, however pairwise comparisons suggest taxa that ingest foods of greater stiffness experience relatively larger measures of bending and torsional resistance. The current study reveals that internal and external morphological factors vary across the arch and in conjunction with diet in primates. These findings underscore the importance of incorporating these mechanical differences in models of zygomatic arch mechanical behavior and primate craniofacial biomechanics.
ContributorsEdmonds, Hallie Margaret (Author) / Reed, Kaye (Thesis advisor) / Schwartz, Gary (Committee member) / Vinyard, Chris (Committee member) / Arizona State University (Publisher)
Created2017
Description
Sexual minorities use social media platforms at higher rates than heterosexual individuals, often to find and connect with other sexual minorities and the broader online LGBTQ+ community. These online connections may help normalize feelings and experiences as a sexual minority in a heterosexual-normed society by increasing exposure to more meaningful reference groups and helping to mitigate the negative impact of heterosexist norms. There has been relatively little research investigating online social connectedness (OSC) among sexual minority adults, the relation between OSC and positive psychological outcomes, and the role of OSC in lessening the impact of heterosexist norms. The goal of the present thesis was to examine the relation between OSC and positive psychological outcomes, and whether such a relation is mediated by compulsory heterosexuality (CH; i.e., heterosexist norms) and internalized heterosexism (IH; i.e., internalizing and accepting heterosexist norms). A sample of 298 sexual minority adults in the U.S. completed an online survey that included measures of OSC, CH, IH, and positive psychological outcomes including resilience, well-being, self-acceptance, and self-esteem. The hypothesized model, with CH and IH as serial mediators of the relation between OSC and positive psychological outcomes, along with a series of alternative models, were tested using structural equation modeling. Support was found for the hypothesized model, such that greater OSC predicted lower CH, which then predicted lower IH, which in turn predicted greater positive psychological outcomes. While several alternative models had adequate fit, the hypothesized model was best supported statistically and by previous literature. These findings provide insights into the psychological benefits of social media connections for sexual minorities and the potential for OSC to lessen the impact of heterosexist norms. This study also adds to the existing literature regarding OSC and sexual minority adults, expanding the literature from primarily focusing on sexual minority youth. Future studies should be more socio-demographically diverse and longitudinal in nature in order to help better understand the directionality of the relationship between CH and IH. The present findings may also inform the development of interventions aimed at decreasing CH and IH, which future studies should investigate more fully.
ContributorsBaumel, Katie (Author) / Hall, Deborah (Thesis advisor) / Mickelson, Kristin (Committee member) / Salerno, Jessica (Committee member) / Arizona State University (Publisher)
Created2021