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Impact of Facial Divergence on Post-Treatment Settling in Patients Retained With Clear-Overlay Retainers
No full textVertical growth patterns are well-recognized by the orthodontic community as being impactful on function, form, and subsequent treatment. The hyperdivergent phenotype is characterized by smaller masticatory muscles, lower bite forces, and thinner cortical bone compared to hypodivergent subjects. As occlusion depends on dentition, muscle function, and periodontium, facial divergence plays a role in establishing occlusion. Just as orthodontics aims to improve a patient���s occlusion, a goal of orthodontics is to retain the occlusion after debonding but to allow for the vertical movement of teeth into better intercuspation, known as settling. With the determinants of occlusion being influenced by factors affected by facial divergence, there is the possibility that different facial divergence patterns have different capacities to experience settling.
The purpose of the study is to investigate and compare the changes in areas of contact and near contact in hypodivergent and hyperdivergent patients retained with a clear overlay retainer.
This study is a retrospective cohort study with patients recruited from a single private practice. 7 hyperdivergent and 11 hypodivergent patients were identified. All patients were retained with upper and lower clear overlay retainers and a lower bonded retainer. Initial lateral cephalograms were used to categorize patients as hyperdivergent or hypodivergent. Intraoral scans from debond and first retention check appointments were compared. Changes in areas of contact (AC) and areas of contact and near contact (ACNC) were used to characterize settling.
Hyperdivergent patients had a statistically significantly higher number of AC as compared to hypodivergent patients at the time of debond (T0) but not at first retention check (T1). There was no statistical difference between AC or ACNC at T0 or T2 between the two groups. There were no statistical differences detected within each group for either AC or ACNC when doing pairwise comparisons.
Without adequate power, this study instead serves to justify the benefits of repeating this study with a larger sample size. It indicates the potential for different facial divergence patterns to respond differently with the same retention protocol which could therefore impact the settling that can be achieved
From Remote Work to Virtual Collaboration: Toward the Design of Collaborative Virtual Reality Environments
No full textRecently the world was hit by the COVID-19 pandemic, during this time mandatory social distancing went into effect to stop the spread of the virus. Due to the social distancing mandates many schools and businesses were forced to close their doors for an undisclosed amount of time, opening the door for online and remote work. Individuals who worked on collaborative teams during this time were forced to adopt new methods of collaboration. Although teleconferencing applications such as Zoom, Google Hangouts and Microsoft Teams provided online support for collaboration the human-human social interaction was lacking. Like these teleconferencing applications Virtual Reality (VR) has taken off during these unprecedented times. Recent developments into VR have created immersive applications that allow users to meet socially and professionally in virtual environments, bringing back the human-human social interaction. This research seeks to understand how and to what extent collaborative VR environments can support interdisciplinary team collaboration. A series of five studies was conducted to first explore how collaborative teams work with each other in different environments (face-to-face vs virtual). The following studies will investigate user preferences of Virtual Characters (VCs) in immersive VR environments. A final study will observe an interdisciplinary team to compare team collaboration face-to-face, virtually and in a commercially available collaborative VR application. From these five studies this body of work will contribute a set of design guidelines to be used in the development of collaborative VR environments
A New Galerkin Quadrature Method Without the Requirement of Matrix Inverse
No full textA new method of forming the scattering source of the Boltzmann neutron transport equation for anisotropic scattering is proposed through the use of Grahm-Schmidt orthogonalization. This new method builds upon two previous methods but differentiates itself by lowering the computational burden of the calculation and potentially admitting more general types of quadratures. It is hoped that this method will gain greater traction in codes solving the Boltzmann neutron transport because of its lower cost and wider applicability. The Galerkin Quadrature method is required for highly anisotropic scattering, which characterizes charged particle transport, and was originally developed for this purpose. This thesis presents the sum of research into the new Galerkin Quadrature method in the form of a paper submitted to the Journal of Nuclear Science and Engineering, 2024. The derivation of all 3 Galerkin Quadrature methods are defined, the test problems are stated with their results, and conclusions drawn. An additional summary section details the conclusions of the overall work
Using Stimuli-Responsive Material for the Design and Fabrication of Artificial Muscles
No full textStimuli-responsive materials that change shape (i.e., elongate, contract, and/or twist) when exposed to an appropriate stimulus are promising candidates to replace traditional machines in biomedical devices. This dissertation explores the innovative use of stimuli-responsive materials in addressing the challenges of treating stress urinary incontinence (SUI), a condition that affects nearly 50% of women during their lifetime. Current treatments for SUI are associated with complications leading to undesirable outcomes such as postoperative voiding dysfunction. The research, divided into four key chapters, focuses on the development and application of artificial muscle devices based on two distinct stimuli-responsive materials ��� Liquid Crystal Elastomers (LCEs) and Magnetoactive Elastomers (MAEs) for the potential treatment of SUI.
In Chapter I, the dissertation commences with a comprehensive introduction to stimuli-responsive materials, elucidating their pivotal role in the design and fabrication of artificial muscles. Emphasizing the versatility of two materials (LCEs and MAEs), the chapter provides a foundation for their application in the subsequent chapters. Chapter II delves into the pathophysiology of SUI, providing a thorough overview of the condition, including its causes, prevalence, and impact. This section establishes the contextual framework for the subsequent exploration of the subsequent development of LCE and MAE-based devices for urethral support. We also provide relevant information that must be considered when designing in vitro models of the urinary tract and selecting appropriate animal models to evaluate devices. Chapter III focuses on the design, fabrication, and in vitro and in vivo evaluation of a dynamic urethral support device based on LCEs. In Chapter IV, I extend the exploration to MAEs and investigate their integration into a dynamic urethral support device. MAE-based devices were fabricated, characterized, and then evaluated using a simple in vitro urinary system simulating the effects of stress or cough.
Collectively, this dissertation contributes to the interdisciplinary field of biomedical engineering by integrating stimuli-responsive materials with innovative solutions for SUI. Investigating the potential of LCEs and MAEs in providing adaptive and customizable support, this dissertation presents a novel approach to addressing SUI through advanced materials. The findings presented herein pave the way for further advancements in the design and fabrication of artificial muscles, offering hope for improved therapeutic interventions for complex healthcare challenges
Allocation of Peptidoglycan Resources Between the Rod System and Class-A Penicillin-Binding Proteins in Myxococcus xanthus
No full textPeptidoglycan (PG) is a polymer scaffolding surrounding the cell membrane of bacteria and is key to survival as it aids in preserving cell structure and protects against harmful stresses. It is composed of alternating N-acetylglucosamine and N-acetylmuramic acid strands that are crosslinked through peptide chains. The synthesis of PG is a highly dynamic and tightly regulated process, spanning across the cytoplasm, inner membrane, and periplasm in gram-negative bacteria. PG synthesis is vital for cell survival and remodeling of the sacculus is required during cell elongation and division as well as during PG repair. PG synthesis has been heavily studied, however, it is still unknown how the allocation of PG precursors are portioned between the two PG synthase systems of the class-A penicillin-binding proteins and the Rod system. Here we take advantage of the monomer-dimer characteristic of the phospho-MurNAc-pentapeptide translocase protein, MraY, as a proxy for PG precursor usage of PG synthases. Using single particle tracking photoactivatable localization microscopy, we show that the Rod system is the main synthase system active in vegetative growth while aPBP���s are responsible for PG repair. This study aims to further understand the properties of PG synthesis and how the cell divides its resources during vegetative growth and repair
Data: Trypanosoma cruzi DTU TcI disproportionately associated with fatal T. cruzi myocarditis in dogs in Texas, USA
No full textComparing Single-Level Regression Based Methods for Analyzing Nested Data When the Extent and Location of Clustering Are Systematically Varied
No full textCollecting and analyzing clustered data is inevitable in educational research. Often, applied researchers will use traditional multilevel modeling to account for the non-independence of observations that result from clustering. However, multilevel models are more complex and have additional data requirements or assumptions relative to a single-level model that applies a correction to the standard errors. Using Monte Carlo Simulations, this work examines the efficacy of various single-level regression-based alternatives for analyzing clustered data when the data-generating model assumes predictors at the lowest level of clustering have both within and between-level variance as well as the effect of different centering choices ��� aspects missing from many contemporary works. The results of this study indicate that correcting standard errors using Taylor Series Linearization or the CR2 correction are the most flexible single-level regression-based methods for analyzing clustered data, as long as within-level predictors are group-mean centered, and the group mean for each cluster is re-introduced. Under these conditions, unbiased standard errors for within and between level estimates are recovered, even with few clusters. However, if within-level predictors are not centered, these corrections lead to increasingly negatively biased standard errors for the within-level estimate as the extent of clustering in the predictors increases, especially when the number of clusters is small. Next, fixed-effects modeling always recovered unbiased standard errors as long as slopes could be assumed to be non-randomly varying; even slight violations of this assumption lead to negatively biased standard errors for within-level estimates. Finally, examining nested data without correcting the standard errors (regular ordinary least squares regression) or using the DEFT correction is not recommended. These methods only lead to unbiased standard errors for within or between-level estimates under conditions that are not likely to be satisfied in real data analysis
Experimental Studies on Measurements in Oil-Gas-Water Flow and Turbulent Flow Field in Wind Generated Water Waves
No full textThis thesis presents experimental studies in multiphase flows with two main topics: (1) measurements in oil-gas-water flow using the fiber optic reflectometer (FOR) technique; (2) turbulent flow field in wind generated water waves.
The application of the single-probe fiber optic reflectometer (FOR) technique has been investigated to determine the velocities and size of oil droplets rising in a static water column. The droplet velocity, residence time, and chord length measurements were validated by comparing with the results from high-speed images using the bubble image velocimetry (BIV) technique and the image gradient method. Subsequently, the application of the FOR technique has been extended to oil-gas-water three-phase flows by investigating the accuracy of phase discrimination and measuring the velocity and size of bubbles and droplets. The technique was expanded to identify water, air bubbles, and oil droplets and to quantify the velocity and size of bubbles and droplets in an oil-gas-water three-phase flow through the processing of acquired signals.
In the second part of this thesis, the turbulent flow field in wind generated waves has been studied. The experiments were performed in a wind-wave-current flume with three freestream wind speeds using a particle image velocimetry (PIV) technique. The Bond number and the shear velocity-fetch based Reynolds number were found to correlate the wind wave regimes well. The turbulent dissipation rates were determined based on spatial gradient of instantaneous velocities and one-dimensional velocity spectrum in temporal space. In addition, the turbulent kinetic energy (TKE) budget including its production, dissipation, advection, and turbulent transport was presented. The production-dissipation ratio increased significantly as the wind speed increased, likely attributed to the increased roughness over the substantial coverage of micro-breaking waves. Subsequently, the turbulent flow filed beneath the water surface has also been investigated under the same experimental conditions used for airflow measurements. The friction velocities were estimated from both air- and water- side measurements with the mean velocity profile and the eddy-correlation methods. The result from the comparison of different methods is useful in determining the scaling of water side turbulence such as dissipation rate of turbulence kinetic energy with the air side velocity measurements, or vice versa
Optical Distortion in Hypersonic True Flight Enthalpy Flows
No full textA simplified, blunt-nose wedge model was tested over a range of realistic hypersonic flight conditions to evaluate several aero-optic diagnostic measurement techniques. A two-dimensional 10��� half angle wedge of width 0.47 m and blunt-nose radius 1 cm test article was designed and tested in an experimental campaign in Texas A&M University���s hypervelocity expansion wind tunnel. The aero-optic diagnostic techniques employed in this work included schlieren photography, linear array focused laser differential interferometry, Michelson interferometry, and optical emission spectroscopy. Experimental test conditions comprised Mach numbers of 6, 9, 12, and 15, realistic-flight flow enthalpy, and static temperatures between 200 K and 270 K. Hypersonic flow features such as bow shocks, natural light emission, and boundary layers were captured in schlieren recordings. Index of refraction fluctuation power spectral density data were recorded between frequencies of 100 kHz and 10 MHz at multiple points near the surface of the test arti-cle. The data suggested that eddies causing density fluctuations at rates greater than 2 MHz and between 7.30 mm and 10.63 mm tall developed in the boundary layer for unit Reynolds numbers between 11 �� 106 m���1 and 12 �� 106 m���1
Computational Fluid Dynamics Analysis of the Blockage Accident in Wire-Wrapped Fuel Rod Bundles
No full textThe purpose for reducing CO2 emissions and enhancing the safety of nuclear reactors have led to increased interest in Liquid Metal Fast Reactors (LMFRs). These reactors offer high power density, low-pressure operation, and the ability to breed fissile material. However, LMFR fuel assemblies, comprising fuel pins enclosed in hexagonal ducts with wire-wrapped spacers, are susceptible to coolant flow blockages due to debris buildup, potentially leading to reduced heat transfer and fuel cladding damage. This PhD dissertation aims to conduct a comprehensive computational fluid dynamics (CFD) analysis of blockage accidents in wire-wrapped fuel rod bundles. The objectives include the preparation and validation of CFD models for both nominal (unblocked) conditions and various blockage scenarios, considering solid and porous blockages. Conjugate heat transfer modeling is also incorporated to simulate the cladding temperature. The proposed research activities encompass analyzing fluid flow behavior, pressure drop, velocity, turbulent structures, and temperature profiles for the different blockage configurations. Experimental data from wire-wrapped test facilities is used to validate the CFD models. These facilities have provided high-fidelity data of velocity and pressure drop for transition and turbulent flow regimes at nominal conditions, as well as for blockage scenarios with solid and porous obstructions. The CFD methodology involves solving the incompressible Navier-Stokes equations with the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) methods. The results demonstrate the accuracy of the proposed methodology in predicting friction factors and velocity profiles in both unblocked and blocked bundles after the comparison with the experimental data. The findings reveal that the presence of blockages in wire-wrapped fuel rod bundles significantly impact the thermal-hydraulic performance of LMFRs. The analyses show that solid blockages cause an increase in pressure drop and a decrease in velocity, while porous blockages have a lesser impact. The turbulence analysis reveals that the blockages lead to the formation of vortices and eddies, which can further impact the flow behavior and heat transfer. This research yields valuable insights into blockage accidents and contribute to gain more reliability in the use of CFD models for safety assessments of LMFRs