Previous studies have shown the importance of cricothyroid muscle activation in altering fundamental frequency in the human voice. Other studies have investigated the non-linear properties of vocal fold tissue and the impact of this non-linearity on frequency response. Several physical models of the vocal folds have been made for research purposes. However, all have been isotropic in nature with linear stress-strain properties. The purpose of this study was to create a physical model with non-linear stress-strain properties to investigate the frequency response of the model as cricothyroid muscle activation was simulated (in other words, as the vocal folds were stretched in an anterior-posterior dimension). In this study the physical models of the vocal folds were stretched in 1 mm increments and the fundamental frequency (F0) was recorded at each position. Subglottal pressure was also monitored and phonation threshold pressures were recorded for each adjustment in length and vocal fold tension, because this can influence F0. Results were obtained for models with and without non-linear properties for comparison. Tensile tests were also conducted for the linear and non-linear synthetic vocal folds. Results indicate that non-linear models demonstrated a more substantial frequency response than linear vocal fold models and a more predictable F0 increase with respect to increasing vocal fold length. Phonation threshold pressures also increased with increasing vocal fold length for non-linear vocal fold models. This trend was reversed for linear vocal fold models, with phonation threshold pressures decreasing with increasing vocal fold length. These results indicate that the non-linear vocal fold models more accurately represent the human vocal folds than do linear models. This study serves as the foundation for future research to quantify the impact of non-linear tissue properties versus active tensioning (through antagonistic thyroarytenoid muscle activation) on F0 response and phonation threshold pressure.

Approximations made in the traditional signal model for synthetic aperture radar (SAR) processing cause defocusing of the radar images when the system operates under conditions where the approximations lose validity. This dissertation investigates a number of these approximations and presents algorithmic improvements based on generalizations of the approxmations of the SAR signal model. These improvements result in better focused imagery from SAR systems with varied designs and parameters. Among the advancements presented is the development of a generalized chirp-scaling algorithm and a generalized frequency scaling algorithm to address the problems caused by approximations based on a Taylor series expansion of the SAR signal for both pulsed SAR and linear frequency modulated continuous wave (LFM-CW) SAR systems. These generalized algorithms extend the ability of frequency-domain algorithms to process SAR data from systems with a low frequency, a wide beamwidth, and a large bandwidth. Image formation algorithms are developed that account for the continuous platform motion and compensate for translational position errors due to the continuous non-ideal motion of real-world LFM-CW SAR systems, including a backprojection algorithm that does not rely upon the traditional stop-and-go approximation for platform motion.

Prosody plays an important role in speech communication. Many individuals with motor speech disorders have decreased prosodic control and thus lower overall intelligibility. Few studies have examined the effect of a flattened prosodic contour on the intelligibility of dysarthric speech, and little is known about the role that listener gender plays in understanding disordered speech. The purpose of this study was to quantify the impact of artificial prosodic manipulation on the intelligibility of dysarthric speech as a function of the extent of fundamental frequency (F0) contour flattening. A further goal was to examine the influence of listener gender on intelligibility. Speech recordings from two speakers (one with mild dysarthria and one with severe dysarthria) were synthetically altered by reducing F0 variability by 50%, 75%, and 100%. Fifty listeners transcribed the sentences and rated the perceived difficulty of the task. Results of the study indicated that a flattened F0 contour led to decreases in the intelligibility of both speakers with dysarthria, both in terms of transcription accuracy and ratings of listener confidence. All altered conditions resulted in poorer intelligibility than the unaltered utterances. For the mild speaker, scores and ratings decreased predictably in proportion to the extent of F0 flattening, whereas for the severe speaker, there was not a steady decrease in intelligibility as the F0 was progressively flattened. The utterances were more intelligible to female than male listeners.

Synthetic aperture radar (SAR) is a type of radar capable of high-resolution coherent imaging. In order to produce coherent imagery from raw SAR data, an image formation algorithm is employed. The various image formation algorithms have strengths and weaknesses. As this work shows, time-domain backprojection is one algorithm whose strengths are particularly well-suited to use at low-altitudes. This work presents novel research in three areas regarding time-domain backprojection. The first key contribution of this work is a detailed analysis of SAR time-domain backprojection. The work derives a general form of backprojection from first principles. It characterizes the sensitivities of backprojection to the various inputs as well as error sources and performance characteristics. This work then shows what situations are particularly well-suited to use of the backprojection algorithm, namely regimes with turbulent motion and wide variation in incidence angle across the range swath (e.g., low-altitude, airborne SAR).The second contribution of this work is an analysis of geometric signal correlation for multi-static, sometimes termed multiple-input and multiple-output (MIMO), imaging. Multi-static imaging involves forming multiple images using different combinations of transmitters and receivers. Geometric correlation is a measure of how alike observations of a target are from different aspect angles. This work provides a novel model for geometric correlation which may be used to determine the degree to which multi-static images are correlated. This in turn determines their applicable use: operating in the highly correlated regime is desirable for coherent processing whereas operating in a lower-correlation regime is desirable for obtaining independent looks. The final contribution of this work is a novel algorithm for interferometry based on backprojected data. Because of the way backprojected images are formed, they are less suited to traditional interferometric methods. This work derives backprojection interferometry and compares it to the traditional method of interferometry. The sensitivity and performance of backprojection interferometry are shown, as well as where backprojection interferometry offers superior results. This work finds that backprojection interferometry performs better with longer interferometric baseline lengths or systems with large measurement error in the baseline length or angle (e.g., low-altitude, airborne SAR).

A Synthetic Learning Environment (SLE) the Virtual Field Trip (VFT) was designed to increase vocabulary acquisition and knowledge by utilizing simulation based technologies and leveraging sound educational findings. Vocabulary acquisition is considered a prerequisite to becoming a good reader and therefore a critical predictor of academic and lifelong success for early learners, however, teachers report that students lack the real world knowledge required for vocabulary knowledge. The VFT provides a meaningful context for anchored and situated instruction. Second grade students were assigned to either use the VFT or to listen to stories read aloud by a researcher on a video tape. While results did not indicate significant vocabulary acquisition on a series of 3 vocabulary tests; students who used the VFT did use significantly more words in a post exposure writing sample than students in the story group indicating an increase of words known at a level of depth sufficient to warrant their use in a writing sample. Students who used the VFT also reported increased motivation to use SLEs like the VFT for future learning objectives and that VFTs were fun. Findings related to the self-efficacy of students as measures immediately following each vocabulary test did not reveal a significant increase for VFT users. Students using the VFTs did not report learning more words than those students assigned to the story group. Limitations of the current study and directions for future research are discussed.

The push to further the use of technology in learning has broadened the attempts of many to find innovated ways to aid the new, technologically savvy generation of learners, in acquiring the knowledge needed for their education and training. A critical component to the success of these initiatives is the proper application of the science of learning (Cannon-Bowers and Bowers, 2009). One technological initiative that can benefit from this application is the use of synthetic learning environments (SLEs). SLEs are instructional systems embedded within virtual worlds. These worlds can be simulations of some task, for instance a simulation that may be completed as part of a military training to mimic specific situations, or they could be in the form of a video game, for example, a game designed to maintain the attention of school children while teaching mathematics. The important components to SLEs are a connection to the underlying task being trained and a set of goals for which to strive toward. SLEs have many unique characteristics which separate them from other forms of education. Two of the most salient characteristics are the instructorless nature of SLEs (most of the learning from SLEs happens without instructor interaction) and the fact that in many cases SLEs are actually fun and engaging, thus motivating the learner to participate more and allowing them to experience a more immersive interaction. Incorporating the latter of these characteristics into a model originally introduced by Davis (1989) and adapted by Yi and Hwang (2003) for use with web applications, an expanded model to predict the effects of enjoyment, goal orientation, ease of use, and several other factors on the overall use of SLEs has been created. Adapting the Davis and Yi and Hwang models for the specific use of SLEs provides a basis understanding how each of the critical input variables effect the use and thus effectiveness of learning tools based on SLEs. In particular, performance goal orientation has been added to the existing models to more accurately reflect the performance characteristics present in games. Results of this study have shown that, in fact, performance goal orientation is a significant factor in the SLE Use and Learning model. However, within the model it is important to distinguish that the two varieties of performance goal orientation (prove and avoid) play different roles. Prove performance goal orientation has been shown to have significant relationships with several other critical factors while avoid performance goal orientation is only accounted for in its significant correlation with prove performance goal orientation. With this understanding, training developers can now have a better understanding of where their resources should be spent to promote more efficient and effective learning. The results of this study allow developers to move forward with confidence in the fact that their new learning environments will be effective in a number of realms, not only limited to classroom, business, or military training.

Eukaryotic genes are often regulated by multivalent transcription factor (TF) complexes. Through the process of cooperative self-assembly, these complexes carry out non-linear regulatory operations involved in cellular decision-making and signal processing. In this thesis, we apply this natural design principle to artificial networks, testing whether engineered cooperative TF assemblies can be used to program non-linear synthetic circuit behavior in yeast. Using a model-guided approach, we show that specifying strength and number of interactions in an assembly enables predictive tuning between regimes of linear and non-linear regulatory response for single- and multi-input circuits. We demonstrate that synthetic assemblies can be adjusted to control circuit dynamics, shaping the timing of activation. We harness this capability to engineer circuits that perform dynamic filtering, enabling frequency-dependent decoding in cell populations. Thru this work, we find that cooperative assembly provides a versatile way to tune nonlinearity of network connections, dramatically expanding the range engineerable behaviors available to synthetic circuits. We then extend our modeling-framework to predict genome-wide binding of our TF assemblies and find that cooperative complexes made of weakly-interacting proteins can reduce unintended activation of endogenous genes. Thus, we are able to introduce synthetic regulatory components with low fitness costs on the cell, ensuring long-term stability of our integrated circuits over time. Taken together, this dissertation outlines a synthetic framework for building cooperative transcriptional complexes in vivo in order to engineer complex regulatory behaviors that are functionally orthogonal to the host cell. / 2019-10-22T00:00:00Z

Legalizing marijuana for recreational use has been a hot political topic in recent years. Different conclusions have been drawn from the literature on this subject, but one conclusion is that the tactic is an effective instrument in combating the black market. On the other side, it has also been demonstrated that it has a negative effect on neighbouring regions that still view marijuana as an illicit drug.  This study examines the evidence of any causal link between the legalization of marijuana for recreational use and its consequences on neighbouring regions. The legalization of marijuana in Washington state in 2012 and spillover effects on drug-related crime rates in British Columbia served as the foundation for this study. With the help of nine Canadian provinces, a synthetic British Columbia has been created that attempts to simulate how crime rates may have developed had Washington not legalized marijuana.  The legalization of marijuana has had both positive and negative spillover impacts on the neighbouring territory, according to empirical data. As a "gateway" substance, marijuana possession rates rose after the implementation of the policy. Results on the supply side show that because of increased competition and legal supply from the neighbouring region, marijuana suppliers are switching to other drugs. This essay also addresses other potential social effects of marijuana legalization, such as a decline in the prevalence of sexual assault and marijuana possession among young people. Based on the empirical data, the study offers improvements in aiding neighbouring regions who are considering the implementation of RML in creating preventative measures against illicit usage of marijuana.

Yes / Membrane computing is a new natural computing paradigm inspired by the functioning and structure of biological cells, and has been successfully applied to many different areas, from biology to engineering. In this paper, we present kPWorkbench, a software framework developed to support membrane computing and its applications. kPWorkbench offers unique features, including modelling, simulation, agent-based high performance simulation and verification, which allow modelling and computational analysis of membrane systems. The kPWorkbench formal verification component provides the opportunity to analyse the behaviour of a model and validate that important system requirements are met and certain behaviours are observed. The platform also features a property language based on natural language statements to facilitate property specification. / EPSRC

Natural cellular networks are very good at processing diverse inputs, generating complicated responses, and confounding researchers with their complexities. As an alternative to traditional cellular engineering approaches, the field of synthetic biology attempts to avoid the complexities of natural systems by focusing on the bottom-up construction of artificial cellular circuits. By rationally building up circuit complexity, synthetic biologists hope to both create novel systems capable of programming unique cellular responses, and gain insights into the design principles of natural systems. Circuits that allow for the programming of intercellular responses are of particular interest, and researchers have focused on the use of bacterial communication mechanisms (quorum sensing) to construct such circuits. At their most basic, quorum-sensing systems are composed of three main components, making them amenable to genetic manipulation. These components, however, have properties that have been finely tuned through evolution to function in very specific ways, and repurposing them for our own uses requires methods to overcome their naturally evolved properties. This thesis details our work in the construction and engineering of synthetic circuits based on components of the LuxI-LuxR quorum-sensing system. Using these components, we demonstrate methods for altering both the sensitivity and the form of the quorum-sensing response through the creation of three unique systems: an ultrasensitive positive feedback loop, a logical AND gate, and a coupled feedback loop oscillator. Construction and tuning of each circuit's properties were achieved through a mixture of rational and evolutionary approaches, with particular emphasis on the directed evolution of the LuxR transcriptional activator. Mathematical modeling was also used during the construction of the more complex circuits to predict the properties that were essential to their functionalities. With the construction and characterization of these circuits, we have provided both well-defined modules that can be used in the construction of more complex systems, and developed methods that will allow for the creation and engineering of additional synthetic circuits.