Social Anxiety (SAD) increases in prevalence as children enter adolescence. Adolescents with Autism Spectrum Disorder (ASD) are diagnosed with comorbid SAD at higher rates than these individuals are diagnosed with other clinical disorders, including depression and other anxiety disorders. However, there is little research on whether the presentation and neural underpinning of comorbid SAD within the context of ASD is the same as SAD alone. Individual and diagnostic differences exist in neural and biological mechanisms of fear conditioning. Characterization of whether neural mechanisms of fear are different within ASD with comorbid SAD and SAD alone may better inform clinical treatments. Accordingly, the present study characterizes neural responses during a fear-inducing experiment, as measured by fMRI. Fifty-seven adolescents participated in this study, with adolescents with ASD and SAD (n=17), SAD alone (n=20), and typically developing adolescents (n=20). All participants completed two fear conditioning and reversal paradigms while completing an fMRI scan. The paradigm consisted of a Social condition and Nonsocial condition. An ANOVA for fear conditioning was conducted. Results revealed significant activation in the Inferior Temporal Gyrus (ITG) during fear conditioning. No between group differences were observed, but within-group differences indicated differential modulation of the ITG in the ASD with SAD group in the Social condition compared to the Nonsocial condition. The SAD group demonstrated differential activation between conditioning stimuli in the Nonsocial condition, but not in the Social condition. Results indicate that adolescents with ASD and SAD may display different neural mechanisms for acquiring fear compared to typically developing peers. Results have potential to inform treatment approaches. / Doctor of Philosophy / Based on the 2012 international energy agency (IEA) report, global waste heat energy is estimated to be in the range of 246 Exajoule (1 EJ = 10¹⁸ J). Tapping even small fraction of this wasted energy through thermal energy harvesting techniques will allow us to generate significant magnitude of green energy. Thermoelectrics (TEs) are one of the most promising thermal energy conversion materials as they offer cost-effective and environmentally friendly option with solid-state silent operation and scalability. Among many different options for high temperature TE materials, half-Heusler system is one of the leading candidates as it has the potential to provide high performance and thermal stability at temperatures as high as 873 K.
The progress in developing practical half-Heusler materials has been limited for last two decades. Despite many publications, the maximum figure of merit (zT) of n-type half-Heusler materials has been stagnant (zT ~ 1.0). Further, there has been a lack of focus towards module development that can operate under realistic conditions. This dissertation provides comprehensive studies on novel thermoelectric compositions and nanocomposites that are suitable for manufacturing of high temperature modules. Microstructural architectures proposed here provide the ability to tailor electronic transport and phonon scattering beyond the commonly demonstrated regimes. Optimized materials were successfully implemented in efficient and stable thermoelectric generator exhibiting power density on the order of 13.81 W⸱cm⁻² , which is 1400 % higher than that of the fuel cell (~1 W⸱cm⁻² ).
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/102409 |
| Date | 28 August 2019 |
| Creators | Coffman, Marika C. |
| Contributors | Psychology, Richey, John A., Ollendick, Thomas H., Kim-Spoon, Jungmeen, White, Susan W. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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