2020 MU theses - Freely available online
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Item A flexible speech feature converter based on an enhanced architecture of U-net(University of Missouri--Columbia, 2020) Yue, Yanghao; Zhao, YunxinIn order to analyze speech or audio, many methods are applied to transform the time domain signals into various features such as the mel spectral features and WORLD vocoder features. These two types of features can both be extracted from speech or used to synthesize speech. On the other hand, certain applications call for conversion between different types of features. To convert mel spectral features to WORLD vocoder features, one possible method is to first synthesize time domain signal from mel spectrogram and then do the feature extraction by WORLD vocoder. The goal of this project is to develop a direct way to achieve this transformation, i.e., convert mel spectrogram output of text-to-speech (TTS) system to WORLD vocoder features. In this project, a feature converter is designed to accomplish our aim. The converter has an enhanced neural network architecture based on the U-net. In our design, except for the basic architecture of U-net, the Res Path composed of residual blocks and linear transformations are added on the skip connection. Our flexible system can complete feature conversion directly at feature level without processing in the time domain. In addition to the function of converting mel spectrogram to WORLD features, the reverse transformation from WORLD features to mel spectrogram is also attainable by a few adjustments. The transformed feature has achieved good performance in objective metrics and the converter generalized well to different speakers, which can be applied to produce high quality speech via vocoder resynthesis.Item A geochemical, taxonomic, and phylogenetic investigation of Paleozoic arthropods : case studies on the Cambrian spice event and the Silurian Waukesha Lagerstatte(University of Missouri--Columbia, 2020) Pulsipher, Mikaela A.; Schiffbauer, James D.This thesis details two stand-alone projects: Chapters 1 and 2 comprise a quantitative investigation of controls on the [delta]13C record of the Steptoean Positive Carbon Isotope Excursion (SPICE); Chapter 3 describes a taxonomic and phylogenetic assessment of a previously unnamed arthropod from the Silurian Waukesha Lagerstatte. Despite the disparate nature of these projects, they are united by an underpinning theme of Paleozoic arthropods. The SPICE event is a prominent, global disturbance in the [delta]13C record of the Cambrian that is temporally linked to trilobite biomere turnover at the Marjuman--Steptoean and equivalent Guzhangian--Paibian stage boundaries. The SPICE has been used as a tool for global chemostratigraphic correlation despite the fact that individual [delta]13C records display marked variability. To quantitatively evaluate its utility as a chemostratigraphic marker, we constructed the Steptoean Positive Carbon Isotope Excursion repository for quantitative analysis (the SPICEraq) containing [delta]13C values and associated metadata from known records of the SPICE. Results from Wilcoxon Rank Sum and x2 tests indicate that regional/local conditions do have a statistically significant impact on the expression of the SPICE, with paleolatitude and approximate water depth bearing the most appreciable impact. Furthermore, this investigation confirms that the SPICE event is immediately preceded by a short-lived negative [delta]13C excursion which potentially has bearing on the associated trilobite extinction event.Item Single molecule imaging of DNA on nanogap embedded plasmonic gratings with enhanced fluorescence and improved level of detection(University of Missouri--Columbia, 2020) Pathak, Avinash; Gangopadhyay, ShubhraOne of the most commonly used detection tools in clinical diagnostics, life science research, chemical, and biological sensors is fluorescence. Because of its cost effective, sensitive, and specific nature fluorescence has emerged as one of the key techniques used for detection of analytes in many biological applications like cell imaging, DNA amplification, and sequencing etc. However, there has been a growing need to detect weak signals and improve the contrast levels in fluorescence images. This is essential for detecting single fluorophores and improving the limit of detection for fluorescence based biosensing. In recent years, researchers have developed many methods like total internal reflection microscopy (TIRF), confocal microscopy, and two-photon excitation microscopy (TPEM), which improve the fluorescence emission, thereby increasing the detection sensitivity. To further enhance the output of this technique, a number of nano-patterned structures like plasmonic gratings, photonic crystals and metallic bowtie nano-antennas have been developed. These nano-structures enhance the electric field intensity which can be used to couple light to the surface-bound fluorescent dye molecules thereby providing extreme signal amplification necessary for detecting low quantities of biomolecules tagged with fluorophores. In this thesis, a cheap and simple fabrication technique is presented for producing polymethylsilsesquioxane (PMSSQ) based gratings embedded with nano-gaps using micro-contact printing where a commercially available high-definition (HD) DVD-R is used as the mold to obtain the starting PDMS stamps. The nano-gaps are formed spontaneously within the grating structure as a result of tensile strain in the elastomeric PDMS stamp during the printing process. This method overcomes all the shortcomings of conventional lithography, e-beam lithography and reactive ion-etching (RIE) procedures, as the nano-structured substrates can be fabricated relatively quickly, easily and at a low production cost. These nano-gap embedded PMSSQ gratings can then be used as a base pattern for depositing metal layers to form plasmonic gratings. Using this approach, nano-gap embedded silver gratings were fabricated for enhanced fluorescence emission. Because of the enhancement on these nano-structured substrates, several applications can be thought of in bio-sensing area as it can lower the detection limit of analytes, single molecule imaging, and other diffraction-limited optics. In addition, this technique coupled with another deposition regime, called GLAD (Glancing Angle Deposition) produces further improvement of fluorescence and level of detection. Glancing angle deposition or GLAD is a well-known technique that is most often utilized to produce very unique surface features by extremely simple techniques. In most cases, little or no lithographic process is needed in order to produce columnar structures on surfaces when GLAD is used by itself. In its most basic form, GLAD represents the deposition of metallic vapors or metallic atoms at an extremely oblique angle with respect to the surface over which such deposition takes place. In addition, several other techniques such as a horizontal or vertical rotation may be combined with the angled deposition process to produce features which are symmetric and repeatable. This not only produces a more streamlined process for the fabrication of such devices, but also offers tunability to ensure the highest improvement in the level of detection of a given species.Item The guerrilla in town : influences on content production in exiled media(University of Missouri--Columbia, 2020) Gelan, Edom; Cropp, FritzOn 21 June 2011 Reeyot Alemu was detained by the Federal Police and later was charged with terrorism and sentenced for five years. Her detention is one of the several incidents in Ethiopia that illustrate how journalists function in their daily routine ever since the Ethiopian People Democratic Revolutionary Front party took power in 1991. Her detention generated waves of protest among press freedom advocates and human rights groups. She was freed after four years of imprisonment. Just like many journalists before her, Reeyot fled her country and join Ethiopian exiled media institution. Ethiopia has vibrant exiled media organizations working from Europe and North America. This study examines factors that influence content creation on mass media especially in Ethiopian Satellite Television and Radio (ESAT) and Oromia Media Network (OMN). Findings show even if governmental pressure impacts all exiled media at the same time the content production process both in ESAT and OMN take sharp edge on ideological lineage. In addition, both institutions depend on anonymous reporters or stringers while leveraging on their media content credibility. The result suggests that influences that shape exiled media content production also impacted the Ethiopian media culture.Item The significance of mothers' attachment for vagal responding during interactions with infants(University of Missouri--Columbia, 2020) Xu, Nanxi; Groh, AshleyLittle is known about the significance of mothers' attachment for neurobiological responding during interactions with infants, as research has primarily examined neurobiological responding to unfamiliar infant stimuli. To advance knowledge of the real-world significance of mothers' attachment for autonomic physiological responding during interactions with offspring, we examined links between mothers' (N=139) attachment representations and change in respiratory sinus arrhythmia (RSA)--an index of physiological regulation--while interacting with infants in the Still-Face Procedure (SFP). Mothers higher (vs. lower) on secure base script knowledge (SBSK) exhibited greater change in RSA from rest over the course of the SFP characterized by decreases in RSA during normal play, increases in RSA during the still-face episode, and decreases in RSA upon reunion. Findings indicate that mothers' higher (vs. lower) on SBSK exhibit RSA responding reflective of physiological regulation during normal play and reunion-- consistent with the need to engage infants in social interaction--and RSA responding during the still-face episode suggesting that becoming unresponsive to infants is physiologically dysregulating. Findings advance knowledge of the significance of adult attachment for the neurobiology of caregiving, by indicating that mothers' higher on SBSK exhibit flexible shifts in RSA while interacting with infants according to caregiving context.