Phononic crystals are structures composed of periodically arranged scatterers in a background medium that affect the transmission of elastic waves. They have garnered much interest in recent years for their macro-scale properties that can be modulated by the micro-scale components. The elastic properties of the composite materials, the contrast in the elastic properties of the composite materials, and the material arrangement all directly affect how an elastic wave will behave as it propagates through the sonic structure. The behavior of an elastic wave in a periodic structure is revealed in its transmission bandstructure, and modification of any the elastic parameters will result in tuning of the band structure. In this dissertation, a phononic crystal with properties that can be modulated using electromagnetic radiation, and more specifically, radio-frequency (RF) light will be presented.

This paper approaches The House of Fame through the emerging lens of sound studies and discusses how Chaucer used the developing sonic theories of his day and other literary works as a catalyst for his discussion of fame in his dream vision. Chaucer's poem shows the fragile and uncontrollable characteristics of lasting fame by comparing it to the Boethian metaphor of sound functioning similarly to rippling water. The construction of The House of Fame ultimately becomes an example of this medieval sonic theory as it engages with, incorporates, and echoes themes and ideas from other texts. In exploring the process of fame throughout the narrative and by engaging in that same process as he translates the works of Boethius, Virgil, Ovid and Dante, Chaucer steps into the precarious shoes of his own character, becoming the goddess Fame, by molding his literary predecessors into his own text.

The Utah State University Aerolab developed and tested a set of tools for rapid prediction of the loudness of a sonic boom generated by supersonic transport aircraft. This work supported a larger effort led by Texas A&M to investigate the use of adaptive aerostructures in lowering sonic boom loudness at off design conditions. Successful completion of this effort will improve the feasibility of supersonic commercial transport over land. Funding was provided by a NASA University Leadership Initiative grant to several universities, including Utah State University, as well as industry partners to complete this work over a five year period. The work presented in this thesis was done over the first year of the grant. The Aerolab team was specifically tasked with developing a set of tools for rapidly predicting the sonic boom loudness of supersonic aircraft. Specifically, this work included an assessment of the existing analysis tools available followed by the planning, development, and testing of a framework of tools for performing the needed calculations. Results of the framework were compared against high fidelity solutions available from the 2017 AIAA Sonic Boom Prediction Workshop. These comparisons revealed that panel methods perform well for simple geometries. However, localized errors appear when modeling more complex geometries that reduce the accuracy of the predicted sonic boom loudness. It was found that these localized errors were a consequence of the inherent assumptions built into panel methods. Consequently, in future work, it may be necessary to develop techniques for combining the results of panel methods with higher fidelity methods or to revisit the panel method formulation.

Indiana University-Purdue University Indianapolis (IUPUI) / Recently, the concept of “bulk-fill” resin-based composites (RBCs) has been re-emphasized, with claimed improvements in depth of cure (DOC) with similar mechanical properties and comparable adaptation to walls and margins relative to conventional composite. More research is needed to carefully examine the properties of these new materials. The objective of this study was to measure the light energy, microhardness (VHN), and elastic modulus across the depth of one conventional and three bulk-fill RBCs. Materials and Methods: Three commercially available bulk-fill RBCs (Tetric EvoCeram Bulk Fill [TE], SonicFill [SF], X-tra fill[XF]) and one conventional RBC (Premise [PR]) were evaluated (n = 10). DOC (using Vickers’s microhardness), elastic modulus (using atomic force microscopy), and the mean irradiance and total light energy transmitted through different thicknesses of RBC were measured by a spectrometer. The effects of group, location, and curing depth on VHN were analyzed using mixed-model ANOVA. Elastic modulus and light energy comparisons were made using two-way ANOVA, with a significance level of 5 percent. Results: There was a significant difference in the depths for the mean irradiance and total energy between different depths in all materials. All materials achieved the manufacturers’ claimed DOC. XF had the highest DOC with 7 mm and a light energy of 0.56± 0.02 J/cm2 at 7 mm. PR had the lowest DOC with 3 mm and a light energy of 0.84 ±0.12 J/cm2 at 3 mm. The elastic modulus showed significant variation in depth profiles that were different than the DOC. Significance: The manufacturers’ claims for bulk-fill DOC were achieved using a microhardness method. However, this method failed to detect the quality of the polymerization. Assessment of the elastic modulus using AFM is a promising method for greater understanding of the polymerization.

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The application of digital elements to traditional playgrounds can enhance children’s outdoor play and counteract the growing trend of sedentary activities. This work reports the implementation and evaluation of a playground installation which looks at sound as the modality that can provide new and engaging play experiences. The design of this system follows an open-ended approach that let the children create their own emerging game goals and rules. The sound design is first tested in a lab setting and later on in a Swedish preschool, with a particular focus on the stages of play (invitation, exploration, and immersion). 38 children between 2 and 6 years old participated in a field study that lasted for three days. Children’s engagement over time was quantified and field notes were taken during the whole evaluation. None of the children between 2 and 3 years old reached the immersion stage. On the other hand, children between 4 and 6 years old created their own rules showing parallel and collaborative play and, in some occasions, solitary play. The sound modality chosen proved to be effective to encourage children’s play in a first place. In a longer engagement perspective, the soundscape partly supported an immersive play. The selection of the sounds to be integrated in the system demonstrated to be as fundamental as the physical appearance of the playground installation. The results of this study show how the visual and auditory modalities can be effective in an open-ended interactive playground and report the limitations of this design. / Additionen av digitala element till traditionella lekplatser kan förstärka barns utomhuslek och motverka den växande trenden av stillasittande aktiviteter. Detta arbete beskriver genomförandet och utvärderingen av en lekplatsinstallation med ljud i fokus som den modalitet som kan tillhandahålla nya och engagerande lekupplevelser. Utformningen av denna lekplatsinstallation skedde ur ett fri lek-perspektiv där barn skapar egna mål och regler till sin lek. Ljuddesignen är först testad i en laboratoriemiljö och senare i en svensk förskola, med särskilt fokus på lekfaserna (invit-fasen, utforskande-fasen och uppslukad-fasen). 38 barn mellan 2 och 6 år deltog in en fältstudie som varade i tre dagar. Barns engagemang över tid kvantifierades och noteringar togs under hela utvärderingen. Inga av barnen mellan 2 och 3 år nådde uppslukad-fasen. Å andra sidan skapade barn mellan 4 och 6 år egna regler som visar på parallell och samspelslek och i några fall ensamlek. Den valda ljudmodaliteten visade sig vara effektiv för att uppmuntra barns lek till en början. På längre sikt understödde ljudlandskapet delvis lek av uppslukad karaktär. Valet av ljud integrerat i systemet visade sig vara lika fundamental som den fysiska uppenbarelsen av lekplatsinstallationen. Resultaten av denna studie visar hur de visuella och auditoriska modaliteterna effektivt kan vara designade i en interaktiv lekplats för öppen lek, och begränsningarna av denna design rapporteras.

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Traumatic brain injury (TBI) is a major cause of disability worldwide. No effective treatment is currently available to restore function to the injured brain. After injury, massive neuronal death occurs which can result in long-lasting cognitive dysfunction. Following immediate mechanical damage, a series of secondary effects of injury occur including evolving neuronal damage, inflammation, astrocyte reactivation, blood brain barrier disruption and other physiological effects. Additionally, neural stem cell (NSC) proliferation has been observed following TBI, suggestive of an endogenous attempt to repair the brain. Stimulating proliferation of NSCs is a promising strategy to facilitate recovery following TBI, but the mechanisms underlying NSC proliferation remain unknown. In this work, we have addressed the following specific aims. In the first aim, we determined the role of Shh signaling in NSC proliferation after TBI. Using a fluid percussion model of TBI and conditional transgenic animal models, we investigated the role astrocytes play in NSC proliferation. Using a Sonic hedgehog (Shh) pathway inhibitor, we found that NSC proliferation after TBI relies on Shh signaling. In the second aim, we determined the role of astrocyte activation in NSC proliferation after TBI. Using transgenic tools, we determined that astrocytes are a major cellular source of Shh and that astrocyte-specific deletion of Shh inhibited NSC proliferation. This indicates that NSC proliferation relies on Shh signaling and that astrocytes represent the key cellular source. In the final aim, we sought to define the functional requirement of Nestin in NSC proliferation. Recent studies in our lab found that Nestin, an intermediate filament protein predominantly expressed by NSCs, played a role in Shh signaling in the setting of medulloblastoma cells. Here, we found that knockdown of Nestin impaired Shh signal transduction and Shh-driven proliferation in NSCs. Further, we generated a new mouse model allowing conditional deletion of Nestin in NSCs to determine whether Nestin played a similar role a non-neoplastic setting. Conditional deletion of Nestin in NSCs abolished the proliferation of hippocampal NSCs after TBI. These findings reveal the critical role of Nestin in Shh signaling and proliferation in NSCs following TBI. Our studies elucidate the cellular and molecular basis for NSC proliferation after TBI, which pave the road for development of therapeutic approaches to treat TBI by augmenting endogenous NSC regeneration. / Cancer Biology & Genetics

Axons of retinal ganglion cells (RGCs) send visual information to a number of retinorecipient regions in the brain. In rodents, visual thalamus receives dense innervations from RGC axons and is important for both image-forming and nonimage-forming visual functions. Retinal inputs invade visual thalamus during embryonic development, before the arrival of non-retinal inputs (such as local interneurons and axonal inputs from other brain regions). In this dissertation, I explore how early innervation of RGC axons affects circuitry in visual thalamus and the role of visual experience, neural activity, and molecular cues in the development. While the development of astrocytes in cortex has been well-described, they have been largely overlooked in visual thalamus. Using immunohistochemical, functional, and ultrastructural analysis, I show that astrocytes in visual thalamus reach adult-like morphological properties and functionality at retinogeniculate synapses early in development, by eye-opening and before visual experience. These studies reveal that while experience-dependent visual activity from RGC axons is critical for many aspects of visual thalamus development, astrocytic maturation occurs independent of that information about our visual environment. As with astrocytes, little progress has been made in understanding the development of interneurons in the visual thalamus. Here, I show that retinal inputs interact with thalamic astrocytes to influence the recruitment of GABAergic interneurons into visual thalamus. I found that this interaction between RGC axons and astrocytes is not dependent on neural activity of RGCs. Using transcriptomic analysis, in situ hybridization, and reporter lines, I observed thalamus-projecting RGCs express SHH and astrocytes in visual thalamus express SHH signaling molecules. My results reveal that SHH signaling between RGC axons and astrocytes is critical for astrocytic fibroblast growth factor 15 (FGF15) expression in developing visual thalamus. Ultimately, FGF15 serves as a potent motogen that is essential for thalamic interneuron migration. These data identify a novel morphogen-dependent and activity-independent mechanism that mediates crosstalk between RGCs and astrocytes to facilitate the recruitment of interneurons into the developing visual thalamus. / Doctor of Philosophy / The most dominant sense in human is the sight, which we need to interact with our environment efficiently. The retina takes up the information about our visual world and sends it to the brain, which ultimately puts everything together, for us to see properly. The visual information from the retina goes to the brain via nerves (which are essentially cables/wires of brain cells). These nerves from the retina go to many places in the brain, including a region called visual thalamus, which is the focus of my PhD work. For the past five years, I have been trying to understanding if nerves from the retina play a role in the brain formation during early development. To study this, I have used mice as a model system, as their brain regions that process visual information have very similar structural architecture to those in humans. My research shows that retinal nerves are indeed important for the development of visual thalamus. Here, I show that information from the eye is critical for migration (a process during development where brain cells move from their place of origin to their final location) of cells in visual thalamus. Discoveries made in this dissertation are important because they highlight how different cells in the central nervous system communicate with each other at the level of molecules and how these interactions are important for building circuits that are important for vision.