archives@tulane.edu / Despite great progress in the treatment viral illnesses, epidemics of emerging infectious diseases often have no specific treatments, leaving most patients to be treated with only supportive care. Broad-spectrum antiviral drugs could help ease this burden especially in situations where diagnostics are limited. Recently, many antiviral peptides have been discovered to inhibit a wide array of viruses using the Wimley-White interfacial hydrophobicity scale to predict inhibitory peptides, some of which were found to possess broad-spectrum activity. These broad-spectrum peptides share some common characteristics: they are moderately hydrophobic and have a propensity to disrupt membranes. We hypothesize that there are general molecular characteristics that these peptides possess, such as a propensity for membrane interaction, that drive broad-spectrum antiviral activity, which we can utilize for the design of novel potent antiviral peptides. To test this hypothesis, we first selected membrane-active peptides with no previously known antiviral activity. We screened these peptides against multiple diverse viruses and found that a majority possess antiviral activity with little cytotoxicity. We next explored the mechanism of action and found that peptides bind virus and cause rapid aggregation. We then used this information to guide the design of novel gain-of-function antiviral peptides. We sequentially designed peptides to test specific hypotheses about sequence motifs that may alter antiviral activity and/or cytotoxicity. Through our screenings we uncovered sequence motifs that led to greater antiviral activity, lower cytotoxicity, and potent broad-spectrum activity. More optimization is needed to turn these peptides into viable drug candidates, but we believe our findings identified important design aspects of antiviral peptides that could lead to the creation of potent broad-spectrum antiviral therapeutics. / 1 / Andrew Hoffmann

A well-known challenge in vehicle dynamics is to design a vehicle that will not only keep the occupants comfortable, but will also ensure safe and stable operation during various manoeuvres over multiple driving surfaces. A soft and compliant suspension is generally required for good ride comfort, while a stiff suspension with a low centre of mass is required for improved handling. These contradicting factors in the design process is commonly referred to as the ride comfort versus handling compromise. A newly developed semi-active hydropneumatic suspension system is proposed to reduce or negate this compromise by being able to change its characteristics according to the dynamic state of the vehicle. The unit is equipped with two proportional solenoid valves that can provide continuously variable damping. In addition, the valves are able to completely close off flow to compressible gas volumes to provide four discrete stiffness characteristics. This suspension system is based on a previously developed suspension that had only two state (open or closed) valves, which provided discrete damping characteristics. A thorough investigation of the older system proved that the system was capable of addressing the ride comfort versus handling compromise. The purpose of this study was to investigate whether the updated design could deliver improved performance and to recommend focus areas for future research initiatives. The suspension system’s characteristics were determined experimentally by actuating the unit on a test bench. Results indicated that the unit produced the desired stiffness, low damping and response time characteristics. A mathematical model of the suspension unit was developed and validated against experimental data. The model was used in single degree of freedom simulations to investigate both passive and semi-active controlled performance. Results indicated that the suspension could be semi-actively controlled for improve ride comfort. However, the magnitude of improvements with semi-active control, which includes a suitable response time, proved to be rather insignificant compared to the optimum passive suspension. / Dissertation (MEng)--University of Pretora, 2019. / Mechanical and Aeronautical Engineering / MEng (Mechanical) / Unrestricted

Indoor occupant localization is a key component of location-based smart-space applications. Such applications are expected to save energy and provide productivity gains and health benefits. Many traditional camera-based indoor localization systems use visual information to detect and analyze the states of room occupants. These systems, however, may not be acceptable in privacy-sensitive scenarios since high-resolution images may reveal room and occupant details to eavesdroppers. To address visual privacy concerns, approaches have been developed using extremely-low-resolution light sensors, which provide limited visual information and preserve privacy even if hacked. These systems preserve visual privacy and are reasonably accurate, but they fail in the presence of noise and ambient light changes. This dissertation focuses on two-dimensional localization of an occupant on the floor plane, where three goals are considered in the development of an indoor localization system: accuracy, robustness and visual privacy preservation. Unlike techniques that preserve user privacy by degrading full-resolution data, this dissertation focuses on an array of single-pixel light sensors. Furthermore, to make the system robust to noise, ambient light changes and sensor failures, the scene is actively illuminated by modulating an array of LED light sources, which allows algorithms to use light transported from sources to sensors (described as light transport matrix) instead of raw sensor readings. Finally, to assure accurate localization, both principled model-based algorithms and learning-based approaches via active scene illumination are proposed. In the proposed model-based algorithm, the appearance of an object is modeled as a change in floor reflectivity in some area. A ridge regression algorithm is developed to estimate the change of floor reflectivity from change in the light transport matrix caused by appearance of the object. The region of largest reflectivity change identifies object location. Experimental validation demonstrates that the proposed algorithm can accurately localize both flat objects and human occupants, and is robust to noise, illumination changes and sensor failures. In addition, a sensor design using aperture grids is proposed which further improves localization accuracy. As for learning-based approaches, this dissertation proposes a convolutional neural network, which reshapes the input light transport matrix to take advantage of spatial correlations between sensors. As a result, the proposed network can accurately localize human occupants in both simulations and the real testbed with a small number of training samples. Moreover, unlike model-based approaches, the proposed network does not require modeling assumptions or knowledge of room, sources and sensors.

There has been much recent research on the control of complex sound fields in enclosed vibrating structures via active control techniques. Active Structural Acoustic Control (ASAC) has shown much promise for reducing interior cabin noise in aircraft by applying control forces directly to the fuselage structure. Optimal positioning of force actuators for ASAC presents a challenging problem however, because a detailed knowledge of the structural-acoustic coupling in the fuselage is required. This work is concerned with the development of a novel experimental technique for examining the forced harmonic vibrations of an aircraft fuselage and isolating the acoustically well-coupled motions that cause significant interior noise. The developed system identification technique is itself based upon an active control system, which is used to approximate the disturbance noise field in the cabin and apply an inverse excitation to the fuselage structure. The resulting shell vibrations are recorded and used to optimally locate piezoelectric (PZT) actuators on the fuselage for ASAC testing. Experiments for this project made use of a Cessna Citation III aircraft fuselage test rig. Tests were performed at three harmonic disturbance frequencies, including an acoustic resonance, an off-resonance, and a structural resonance case. In all cases, the new system identification technique successfully isolated a simplified, low-magnitude vibration pattern from the total structural response caused by a force disturbance applied at the fuselage's rear engine mount. These measured well-coupled vibration components were used for positioning candidate piezoelectric actuators on the fuselage shell. A genetic algorithm search provided an optimal subset of actuators for use in an ASAC system. ASAC tests confirmed the importance of actuator location, as the optimal sets outperformed alternate groupings in all test cases. In addition, significant global control was achieved, with sound level reductions observed throughout the passenger cabin with virtually no control spillover. / Master of Science

Lightweight cellular concrete (LCC) is a mixture of cement, water and foam, with a density less than 50 pcf. This material is being used increasingly often in a variety of construction applications due to its self-leveling, self-compacting, and self-consolidating properties. LCC may be used as a backfill or structural fill in areas where traditional granular backfill might normally be used. This material may be especially advantageous in areas where the underlying soil may not support the weight of a raised earth embankment. Testing on the behavior of LCC when used as backfill behind retaining walls is relatively limited. The effects of surcharge on the development of active pressure material are unknown. Two large-scale active pressure tests were conducted in the structures laboratory of Brigham Young University. Each test was performed within a 10-ft x 10-ft x 12-ft box that was filled with four lifts of LCC. Hydraulic jacks mounted to a steel reaction frame provided a surcharge load to the LCC surface. In the first test, the LCC was confined on three sides by the reaction frame, while the fourth side was confined by a reinforced concrete cantilever (RCC) wall. Both vertical and horizontal pressures and deflections were measured to determine the effect of the surcharge load on the development of active pressure behind the wall. In the second test, the LCC was confined on three sides and exposed on the fourth. Surcharge was applied to this sample in a similar fashion until the LCC reached ultimate failure. Vertical pressures and displacements, along with horizontal displacements, were measured in this test. Sample cylinders of LCC were cast at the time the test box was filled. These samples were tested periodically to determine the material strength and density. It was observed that the LCC backfill developed active pressure most similarly to a granular soil with a friction angle of 34º and a cohesion between 700 and 1600 psf. The RCC wall was seen to add vertical bearing capacity to the LCC, as well as prevent the catastrophic and brittle failure seen in the free-face test. It was also observed that an induced shear plane in the material dramatically decreased the total bearing capacity when compared to a uniformly loaded specimen with no induced shear plane. The results of this study were compared with design parameters given in previous research, and new design suggestions are presented herein.

Philosophiae Doctor - PhD / The faint radio population consisting of star forming galaxies (SFG) and radio-quiet active galactic nuclei (AGN) is important in the study of galaxy evolution. However, the bulk of the faint population is below the detection threshold of the current radio surveys. I study this population through a Bayesian-stacking technique that I have adapted to probe the radio luminosity function (RLF) below the typical 5σ detection threshold. The technique works by fitting RLF models to radio flux densities extracted at the position of galaxies selected from an auxiliary catalogue. I test the technique by adding Gaussian noise (σ) to simulated data and the RLF models are in agreement with the simulated data for up to three orders of magnitude (3 dex) below the detection threshold (5σ). The source of radio emission from radio quiet quasars (subset of AGN) is widely debated. I apply the technique to 1.4-GHz flux densities from the Faint Images of the Radio Sky at Twenty-cm survey (FIRST) at the positions of the optical quasars from the Sloan Digital Sky Survey (SDSS). The RLF models are constrained to 2 dex below the FIRST detection threshold. I found that the radio luminosity where radio-quiet quasars emerge coincides with the luminosity where SFGs are expected to start to dominate the RLF. This Implies that the radio emission of radio-quiet quasars and radio-quiet AGN, in general, could have a significant contribution from star formation in the host galaxies.

Learner mobility and active school travel (AST) has been proposed to improve school attendance and academic performance. In South Africa, approximately 86% of learners have been reported as walking to and from school. AST in Africa is becoming less common in urban areas, and this may be a contributing factor to the increased risk and frequency of noncommunicable diseases due to decreased physical activity. The aim of this wait-list controlled evaluation was to assess the physiological and cognitive changes of access to a bicycle versus walking on adolescents. Specifically, changes adolescent's physical activity levels and executive function in a South African low-income community. Two schools were recruited, with the evaluation school receiving bicycles and the control a school who were yet to receive bicycles. Significant differences were observed across the physiological and executive function assessments. Most notably in the executive function tests, the evaluation group showed significant time to completion decreases across all three tests (N-Back, Arrow Flanker, WCST: p< 0.001). The results from this study are significant, as they are the first to assess anthropometric, physiological and executive function in South African adolescents from low-socioeconomic regions. It is evident that there are potential improvements in working memory, inhibition and shifting due to cycling as a mode of AST or during leisuretime. Further research needs to determine the specific mechanisms associated with these improvements.

Background: There is limited data on active play both in terms of perceived competence and actual motor performance in children living in low- and middle-income countries. Promotion of active play in children is crucial for enhancing participation in physical activity and reducing the burden of obesity. Regular engagement in active play is important for promoting optimal development and increasing physical activity levels in children. Despite the increased interest in active play and physical fitness worldwide, many children in low-resource settings are thought to be physically inactive due to the lack of physical activity-promoting resources and programmes. The 2018 Ghana Report Card on physical activity reports that a high proportion of Ghanaian children do not achieve recommended physical activity levels and a high percentage of these children have poor motor skills. To date, no published study has examined active play among school-aged children in Ghana. Investigating the nature of active play by assessing perceived and actual motor performance among Ghanaian children can serve to increase our understanding of activity deficits, movement difficulties and associated factors in this population. Aim: The aim of this study was to investigate the nature of active play in children aged 6-12 years in Ghana. Specific Objectives: 1. To determine children and caregivers' perceptions of children's motor performance in active play using the Motor Coordination Questionnaire (MCQ). 2. To determine children and caregivers' perceptions of the importance of active play. 3. To identify additional forms of active play and games (which are not listed on the MCQ) that children and caregivers perceive to be important and meaningful. 4. To determine the relationship between MCQ ratings by caregivers and children. 5. To determine the relationship between children's MCQ and actual motor performance. 6. To determine the relationship between caregivers' MCQ and actual motor performance. Methodology: A cross-sectional descriptive and analytical design was used. Three primary schools were purposively selected for this study. The study recruited 406 children and their caregivers for this study. Ethical approval was sought from the Ethics Review Committee of the Ghana Health Service (GHS-ERC 052/05/19) and the University of Cape Town Faculty of Health Sciences Human Research Ethics Committee (HREC REF: 112/2020). Data was collected from both caregivers and children (aged 6-12 years) using questionnaires and the Performance and Fitness (PERF-FIT) test battery. The MCQ-caregivers and MCQ-children were used to assess perceived motor performance, and the PERF-FIT test was used to measure children's actual motor performance. In using the Statistical Package for Social Sciences (SPSS) version 24.0 (SPSS Inc, IBM Company, Armonk, NY), Pearson or Spearman's correlation coefficient was calculated to determine the relationship between children and caregivers' perceptions as well as the relationship between the perceptions and the actual motor performance of the children. Results: Both children (75.6%-94.2%) and their caregivers (69.3%-95.4%) perceived good motor performance of the children during active play. Children (82.8%-96%) and their caregivers (83.2%-94.4%) also regarded active play as very important. Twenty-four additional games were found to be of importance to Ghanaian children and their caregivers. Weak negative, weak positive and sometimes moderate positive correlation between MCQ items and the PERF-FIT items were found. Conclusions: This study shows that we can't rely solely on perceptions, but need actual motor performance, to accurately measure motor performance during active play. We found that parents and children do not accurately estimate the actual level of motor performance. Further studies should be done to understand confounding variables that may have caused poor relationship between perceived and actual motor performance. There is a need for a valid tool like the PERF-FIT to help in accurate measurement of motor performance.

Presently, there is no standard testing procedure for piezoelectric actuators. It is then very difficult for a very specific given application to design the most efficient actuator in terms of blocked force, displacement, power consumption, weight, cost, etc. Piezoelectric actuator suppliers would like to have the possibility to fully characterize their actuators to be able to guide their customers on selection of the most suitable actuator based on their utilization. However, this is not an easy goal to reach since performance of a given actuator depends on the specific dynamic conditions under which it is applied. In order to characterize an actuator, it is therefore necessary to recreate similar conditions to those experienced in the real application. Because of the infinite variety of possible applications for piezoelectric actuators, physically recreating those conditions could take an enormous amount of time, means and money. The aim of the research is then to develop the technology required in order to test an actuator under a various range of dynamic load conditions using a single automated test set-up. To do so, a second actuator will be used with a suitable sensing apparatus (impedance head) and an active control system. Using data from the sensing apparatus (force and velocity signals), the active control system will drive the second actuator to recreate any load condition the first actuator would be supposed to experience in a real application. <i>[Vita removed May 14, 2012. Gmc]</i> / Master of Science

Community college leaders face challenges due to a lack of persistence data concerning 2-year colleges, especially in rural settings, prompting these leaders to turn to national data sets to drive local institutional changes. The purpose of this study was to identify variables associated with student place-frame and academic integration which are predictive of student persistence from the first to the second year in a small, residential community college in a rural frontier setting. Guided by Tinto's institutional departure theory, the theory of social representation, and Bassett's work in ruralism, a nonexperimental, correlational, quantitative research design was used to examine predictive relationships between student place-frame variables (age, sex, and intent to transfer), academic integration variables (student effort, collaborative learning, active learning, and academic challenge), and student persistence. Archival Community College Survey of Student Engagement data collected in 2013–2016 from 332 student participants were used for the study. Regression analysis showed a significant predictive relationship between student age and student intent to transfer with active learning. Additional binary logistical regression showed a significant positive relationship between active learning scores and student persistence. These findings informed development of evidence-based recommendations for programmatic changes to increase active learning practices, which could increase students' academic integration and persistence over time. By improving students' academic integration and persistence, positive social change may result through more students completing their degrees and their 2-year colleges gaining access to more substantial resources that are tied to student performance.