GLASS-CLAD SEMICONDUCTOR CORE OPTICAL FIBERS

Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. As research into these fibers has progressed, it has become evident that excessive losses are limiting performance and so greater understanding of the underlying materials science, coupled with advances in fiber processing, is needed. More specifically, the semiconductor core fibers possess three performance-limiting characteristics that need to be addressed: (a) thermal expansion mismatches between crystalline core and glass cladding that lead to cracks, (b) the precipitation of oxide species in the core upon fiber cooling, which results from partial dissolution of the cladding glass by the core melt, and (c) polycrystallinity; all of which lead to scattering and increased transmission losses. This dissertation systematically studies each of these effects and develops both a fundamental scientific understanding of and practical engineering methods for reducing their impact. With respect to the thermal expansion mismatch and, in part, the dissolution of oxides, for the first time to our knowledge, oxide and non-oxide glass compositions are developed for a series of semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding to minimize cracking and (2) matching the viscosity-temperature dependences, such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor in order to minimize dissolution and improve the fiber draw process. The x[Na2O:Al2O3] + (100 - 2x)SiO2 glass compositional family was selected due to the ability to tailor the glass properties to match the aforementioned targets through slight variations in composition and adjusting the ratios of bridging and non-bridging oxygen; experimental results show a decrease in fiber core oxygen content in the fibers drawn with the tailored glass composition. In a further attempt to reduce the presence of oxide species in the core, a reactive molten core approach to semiconductor optical fibers are developed. Specifically, the addition of silicon carbide (SiC) into a silicon (Si) core provides an in-situ reactive getter of oxygen during the draw process to achieve oxygen-free silicon optical fibers. Elemental analysis and x-ray diffraction of fibers drawn using this reactive chemistry approach show negligible oxygen concentration in the highly crystalline silicon core, a significant departure from the nearly 18 atom percent oxygen in previous fibers. Scattering of light out of the core is shown qualitatively to have been reduced in the process. The role of the cross-sectional geometry on the resultant core crystallography with respect to the fiber axis is explored in a continued effort to better understand the nature of the crystal formation and structural properties in these semiconductor core optical fibers. A square cross-sectional geometry was explored to determine if core non-circularity can enhance or promote single crystallinity, as the semiconductors studied have a preference to form cubic crystals. Resultant crystallography of the non-circular core showed a significant improvement in maintaining a preferred crystallographic orientation, with the square core fibers exhibiting a 90% preference for the \u3c 1 1 0 \u3e family of directions occurring closest to the longitudinal direction of the fiber. The ability to orient the crystallography with respect to the fiber axis could be of great value to future nonlinear optical fiber-based devices. In summary, this dissertation begins to elucidate some of the microstructural features, not present in conventional glass optical fibers, which could be important for future low-loss single crystalline semiconductor optical fibers. Additionally, this dissertation offers novel insight into the various aspects of materials science of non-conventional glass optical fibers, such as crystallization and solidification under highly non-equilibrium and confined conditions, phase equilibria and in-situ reactions, and the interplay between thermodynamics and kinetics

Audre Lorde and the Power of Provocative Imagery

This essay is an examination of Audre Lorde\u27s use of graphic imagery in her poems to create awareness of injustice in America and promote healing and survival. Lorde incorporates this element in her poetry to evoke emotions that will remain with readers even after reading her work

Engendering meaning within the high school experience: A consideration of movement and dance

Dance, movement, and kinesthetic learning are among the most powerful ways in coming to know, yet they are amid the most ignored processes at the high school level. Dance has the power to change lives as it offers aesthetic ways of viewing and connecting with the world through its creative, reflective, and imaginative embodied experiences. I have observed these valuable outcomes and address the nature and power of them with the following questions: (1) How has dance and movement influenced my journey? (2) How has this influence affected the high school experience of my students? The heuristic method of qualitative research is utilized to analyze data such as my personal narrative and reflections, observations, and analysis of existing lessons plans, scope and sequence descriptions, assignments, assessments, and existing student work. The data supports a clear evolution of my definition of dance, the design and implementation of its curriculum, and the valuable experiences of my students. Through this research it is evident that dance engenders meaning in dynamic ways at the high school level and that experiences like those offered through dance education play an integral part in meeting the needs of the 21 st century and the Conceptual Age

Understanding the place and meaning of physical activity in the lives of young people: An ethnographic study with two youth centres in a low-income urban area of Northern England

This study was conducted in response to the low levels of physical activity in young people in the UK (and elsewhere) that are considered a major public health challenge. Adopting a critical ethnographic approach, this study explores how physical activity fits into the daily lives of young people (13-21-year-olds) from two youth centres in an urban area of Northern England. This approach enabled the exploration of young people’s physical activity perceptions and practices within the context, complexities, and contingencies of their wider lives, rather than as a compartmentalised phenomenon. Drawing on recent re-conceptualisations of the life-course and anthropological theories of childhood, I show that changes in physical activity over time were enmeshed within life-phase expectations and experiences, but were also non-linear and contingent. Social expectations of adolescence limited some young people’s physical activity practices, and yet many etched out ways of being mobile and physically active, including re-living childhood games on the streets, parks, and at youth centres. Employing spatial theories, I explain how the young people negotiated their sense of safety in their local environments in order to be mobile; created places of their own for sociality; and used spaces and props in the material environment to engage in informal physical activity practices such as “hardcore parkour”. I lastly use Foucauldian and gender theories to re-think how understandings and practices of physical activity were gendered, and centred around the self and the body’s appearance and capability. Many of the young men in particular engaged in ‘self-bettering’ practices: some took up boxing to deal with challenges in their lives and some shaped muscular, fit, and ‘healthy’ bodies. This thesis critically challenges the dominant discourses that shape young people’s individualistic understandings of themselves, their lives, and their physical activity practices. Engaging closely with the young people’s actions and experiences helps to reveal how the socioeconomic and material environments, that young people negotiate in daily life, interact with their physical activity and mobility practices

The Experience of Music Therapy During the Weaning Process of Patients Receiving Invasive Mechanical Ventilation

Mechanical ventilation (MV) is a medical intervention used to assist the respiratory function of someone who is medically compromised. Patients need to wean from the ventilator in order to resume breathing on their own. A spontaneous breathing trial (SBT) is used to determine one’s readiness to be liberated from the ventilator. Music therapy is the use of music interventions, facilitated by a board-certified music therapist, to address patient-specific goals within a therapeutic relationship. Music therapists working in an intensive care unit (ICU) may focus their clinical work to address the stressors, fears, and medical complications associated with vent weaning. The goal of the present study was to determine if one 30-minute music therapy session during an SBT would decrease the patient’s perceived level of anxiety and improve physiologic metrics related to the SBT, specifically, respiratory rate, blood pressure, oxygen saturation, and heart rate. In addition to evaluating the physiological response to music therapy, this study sought to understand the impact from the perspective of the patient. The research question was: What does the patient experience related to music therapy during their spontaneous breathing trial? Data collected from 20 patients revealed that measurements of heart rate and systolic and diastolic blood pressure significantly increased pre- to post-music therapy session. Data analyzed in the interviews suggested that music therapy may assist patients in coping with the physical, emotional, and spiritual stressors of weaning from MV

Gene Therapy for Neurological Disease: State of the Art and Opportunities for Next-generation Approaches

Gene therapy for rare monogenetic neurological disorders is reaching clinics and offering hope to families affected by these diseases. There is also potential for gene therapy to offer new and effective treatments for common, non-genetic disorders. Treatments for Parkinson's Disease are in clinical trials, and treatments for refractory epilepsies are due to enter first-in-human clinical trials in 2022. Gene therapies for these disorders are based on delivering genes that address the mechanism of the disease, not repairing a mutated gene. Similar 'mechanistic' gene therapies could offer treatments to a wide range of neurological and neuropsychiatric diseases where there is a known mechanism that could be restored using gene therapy. However, the permanent nature of most gene therapies is a serious drawback for translation of gene therapies to a wide-range of diseases because it could present risk of irreversible adverse effects. Several lines of research are aimed at developing gene therapy approaches that allow for the treatment to be turned on and off, including: using proteins activated by exogenous ligands, and promoters turned on by activators. We review these approaches and propose an overall de-risking strategy for gene therapy for common neurological and psychiatric diseases. This approach is based on using a temporary mRNA-based treatment to initially assess efficacy and safety of the planned manipulation, and only following with permanent, virally-delivered treatment if the approach appears safe and effective

Studien zum SELMA-Mechanismus

Diatomeen beherbergen eine komplexe Plastide rhodophytischen Ursprungs, vermutlich hervor-gegangen aus einer Endosymbiose höherer Ordnung (polyphyletisches Ereignis). Eine Rotalge wurde als Endosymbiont sukzessive zu einer semiautonomen komplexen Plastide mit vier Hüll-membranen etabliert. Anders als bei Crypto- und Chlorarachniophyta wurden essenzielle Sym-bionten-spezifische Gene vollständig ins Wirtsgenom in Heterokonto-, Haptophyta, Apicomplexa integriert und der frühere symbiontische Nukleus eliminiert. Die auf dem Wirts-Kern kodierten plastidären Präproteine bedurften der Etablierung neuer Translokationsmechanismen inklusive spezifischer Zielsteuerungssequenzen. Für die äußerste Plastidenmembran der komplexen „roten“ Plastiden wurde postuliert, dass die plastidären Präproteine über Sec61 ins Plastiden-Lumen (cER) transloziert werden. Der Transport entlang der zweiten Plastidenmembran (PPM) ist weitestge-hend ungeklärt. Es konnte gezeigt werden, dass der Transport plastidärer Präproteine anhand der Symbiont-specific ERAD-like machinery (SELMA) stattfinden kann. Für dieses aus der ER-assoziierten Degradation abgeleitete System wurden ERAD-Homologe identifiziert und teilweise spezifische Interaktionen gezeigt. SELMA stellt vermutlich ein während der Evolution rezykliertes und an neue Aufgaben adaptiertes System dar. Ein postulierter noch unbekannter Importrezeptor könnte als lösliches cER- oder als PPM-ständiges Protein plastidäre Präproteine im cER erkennen und an der zweiten Plastidenmembran für die weitere Translokation mittels SELMA-Komplex rek-rutieren. Im Rahmen dieser Arbeit wurden durch zwei gerichtete in silico Ansätze und einem proteinbio-chemischen Ansatz Kandidaten für den postulierten Importrezeptor gesucht und davon 32 eGFP-Fusionsproteine in der pennaten Diatomee Phaeodactylum tricornutum in vivo lokalisiert. Davon lokalisieren acht Fusionsproteine möglicherweise im sekretorischen Weg und drei weitere Kandi-daten mutmaßlich in den Mitochondrien. Zwei mutmaßlich PPM-lokalisierte, neun möglicher-weise cER lokalisierte Fusionsproteine und acht potenzielle PPC-Fusionsproteine wurden in dieser Arbeit identifiziert. Für zwei Kandidaten konnten eine PPC-Lokalisation in dieser Arbeit verifiziert werden. Ein möglicherer ER-Lumen-Rezeptor mit plastidärer Lokalisation wird als mutmaßlicher Importrezeptor im cER der komplexen Plastide postuliert. Für ein PPC-residentes TPR-Fusionsprotein wurden spezifische Interaktionen mit zwei mitochondrial carrier Proteinen der komplexen Plastide und dem in der zweiten Plastidenmembran-lokalisierten Protein sDer1-1 in vivo gezeigt

A Permutation Test for Compound Symmetry with Application to Gene Expression Data

The development and application of a permutation test for compound symmetry is described. In a simulation study the permutation test appears to be a level-α test and is robust to non-normality. However, it exhibits poor power, particularly for small samples