Physical Sciences and Mathematics Commons^™

The Black-To-White Hole Transition, Farshid Soltani

Electronic Thesis and Dissertation Repository

Classically, an isolated black hole is a stable gravitational object. If however semiclassical effects are taken into account, an isolated black hole can be shown to slowly radiate its mass away in a process called evaporation. At the end of the evaporation process, when the size of the horizon becomes Planckian, the quantum nature of the gravitational field can no longer be neglected and the dynamics of the horizon is governed by quantum gravity. The main objective of this thesis is the systematic investigation of a tentative scenario for the “end of the life” of a black hole: the black-to-white …

Luminescence And Structural Properties Of Silicon-Germanium Quantum Structures Fabricated By Ion Implantation, Matheus Coelho Adam

Electronic Thesis and Dissertation Repository

The advancement of semiconductor materials has played a crucial role in driving positive technological breakthroughs that impact humanity in numerous ways. The presence of defects significantly alters the physical properties of semiconductors, making their analysis essential in the fabrication of semiconductor devices. I presented a new method to quantify surface and near-surface defects in single crystal semiconductors. Epitaxially-grown silicon was measured by low energy electron diffraction (LEED) to obtain the surface Debye temperature (θ_D). The results showed the surface θ_D of bulk Si (001), 1.0 μm, and 0.6 μm Si on sapphire of 333 K, 299 K, …

Modeling Thermosyphon And Heat Pipe Performance For Mold Cooling Applications, Dwaipayan Sarkar

Electronic Thesis and Dissertation Repository

Thermosyphons are enhanced heat transfer devices that can continuously transfer very large amounts of heat rapidly over long distances with small temperature differences. The high heat transfer rate is achieved through simultaneous boiling and condensation of the working fluid and the continuous heat transfer is achieved through recirculation of the working fluid in its liquid and vapor phase. A potentially important application of the thermosyphons has been towards reducing the cycle times of the mold cooling processes which would provide economic incentives to the automotive industry.

Different operational and geometrical parameters such as the input heating power, fill ratio (FR), …

High-Performance Computing In Covariant Loop Quantum Gravity, Pietropaolo Frisoni

Electronic Thesis and Dissertation Repository

This Ph.D. thesis presents a compilation of the scientific papers I published over the last three years during my Ph.D. in loop quantum gravity (LQG). First, we comprehensively introduce spinfoam calculations with a practical pedagogical paper. We highlight LQG's unique features and mathematical formalism and emphasize the computational complexities associated with its calculations. The subsequent articles delve into specific aspects of employing high-performance computing (HPC) in LQG research. We discuss the results obtained by applying numerical methods to studying spinfoams' infrared divergences, or ``bubbles''. This research direction is crucial to define the continuum limit of LQG properly. We investigate the …

Patterned Heating Induced Propulsion, Saajid A. Aman

Electronic Thesis and Dissertation Repository

This study explores propulsion effects generated by patterned heating acting on smooth and corrugated surfaces. The model problem assumes that the upper plate moves freely, and the lower plate is stationary, equipped with grooves, and exposed to spatially distributed heating. Our findings identify two distinct propulsion effects: thermal streaming and thermal drift. Thermal streaming occurs when given sufficient heating intensity with net flow in the left or right direction characterized by a pitchfork bifurcation. The efficiency of this technique can be controlled using the wavelength of heating. Thermal drift represents a pattern interaction effect. Its strength depends on the relative …

Interplay Of Forces In Impinging Jet Flow And Circular Hydraulic Jump, Abdelkader Baayoun

Electronic Thesis and Dissertation Repository

The circular liquid jet impingement with subsequent hydraulic jump formation is studied theoretically using boundary-layer and thin-film approaches. Three different scenarios are tackled, namely, an accelerated Newtonian jet impinging on a stationary disk, a steady Newtonian jet impinging on a rotating disk, and a steady viscoelastic liquid jet impinging on a stationary disk. Accordingly, the effects of jet acceleration, gravity, centrifugal forces, and fluid elasticity on the flow behaviour and the jump are examined. The results are validated against numerical simulation and existing measurements. The findings show that the thickness of the boundary layer developing near impingement diminishes with jet …

Feasibility Of Functional Mri On Point-Of-Care Mr Platforms, Arjama Halder

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a clinically valuable tool that can produce anatomical and functional images with improved soft tissue contrast compared to other imaging modalities. There has recently been a surge in low- and mid-field scanners due to hardware developments and innovative acquisition techniques. These compact scanners are accessible, offer reduced siting requirements and can be made operational at a reduced cost.

This thesis aims to implement blood-oxygen-level-dependent (BOLD) resting-state functional MRI (fMRI) at such a mid-field point-of-care scanner. The availability of this technique can be beneficial to get neurological information in cases of traumatic brain …

Towards Clinical Microscopic Fractional Anisotropy Imaging, Nico Jj Arezza

Electronic Thesis and Dissertation Repository

Microscopic fractional anisotropy (µFA) is a diffusion-weighted magnetic resonance imaging (dMRI) metric that is sensitive to neuron microstructural features without being confounded by the orientation dispersion of axons and dendrites. µFA may potentially act as a surrogate biomarker for neurodegeneration, demyelination, and other pathological changes to neuron microstructure with greater specificity than other dMRI techniques that are sensitive to orientation dispersion, such as diffusion tensor imaging. As with many advanced imaging techniques, µFA is primarily used in research studies and has not seen use in clinical settings.

The primary goal of this Thesis was to assess the clinical viability of …

Effect Of Morphology And An Upstream Tall Building On A Street Canyon Flow, Haoran Du

Electronic Thesis and Dissertation Repository

The effects of the morphological model and the existence of an upstream tall building on the turbulent street canyon flow and the overlying boundary layer are investigated in a wind tunnel, using Stereoscopic Particle Image Velocimetry (S-PIV) measurements. The velocity variances, Reynolds shear stress, and turbulent kinetic energy are found to be larger than in a similar idealized street canyon model. Increasing building height results in a decrease in vertical mass fluxes across the opening of the canyon, at least in the canyon portion directly downstream of the building. The interaction between the large-scale structures in the overlying boundary layer …

The Magnetic Field Of Protostar-Disk-Outflow Systems, Mahmoud Sharkawi

Electronic Thesis and Dissertation Repository

Recent observations of protostellar cores reveal complex magnetic field configurations that are distorted in the innermost disk region. Unlike the prestellar phase, where the magnetic field geometry is simpler with an hourglass configuration, magnetic fields in the protostellar phase are sculpted by the formation of outflows and rapid rotation. This gives rise to a significant azimuthal (or toroidal) component that has not yet been analytically modelled in the literature. Moreover, the onset of outflows, which act as angular momentum transport mechanisms, have received considerable attention in the past few decades. Two mechanisms: 1) the driving by the gradient of a …

Modelling Cell Population Growth, Mahmood Mazarei

Electronic Thesis and Dissertation Repository

The growth of biological matter, e.g., tumor invasion, depends on various factors, mainly the tissue’s mechanical properties, implying elasticity, stiffness, or apparent viscosity. These properties are impacted by the characteristics of the tissue’s extracellular matrix and constituent cells, including, but not limited to, cell membrane stiffness, cell cytoskeleton mechanical properties, and the intensity and distribution of focal adhesions over the cell membrane. To compute and study the mechanical properties of tissues during growth and confluency, a theoretical and computational framework, called CellSim3D, was developed in our group based on a three-dimensional kinetic division model.

In this work, CellSim3D is …

A Highly Charged Topic: Intrinsically Disordered Proteins And Protein Pka Values, Carter J. Wilson

Electronic Thesis and Dissertation Repository

Intrinsically disordered proteins (IDPs) are known not only for their roles in disease but also for their conformational flexibility, which makes them elusive for experimentation. We consider the role played by theory and simulation in resolving important questions pertaining to IDP structure and dynamics, as well as the nature of the charged residues (e.g., glutamate, lysine, etc.) that enrich them. Specifically, we investigated how the deep learning trained AlphaFold2 (AF2) predictor estimates disorder content, revealing both strong performance in relation to conventional approaches and an important relationship between the AF2 confidence metric and IDP dynamics. We also assessed how modern …

New Aspects Of Scattering Amplitudes, Higher-K Amplitudes, And Holographic Quark Gluon Plasmas, Bruno Giménez Umbert

Electronic Thesis and Dissertation Repository

We present new results on different aspects of quantum field theory, which are divided into three main parts. In part I, we find and prove a new behavior of massless tree-level scattering amplitudes, including the biadjoint scalar theory, the U(N) non-linear sigma model, and the special Galileon, within specific subspaces of the kinematic space. We also derive new formulas for the double-ordered biadjoint scalar and $\phi^p$ amplitudes, which can be obtained as integrals over the positive tropical Grassmannian and under limiting procedures on the kinematic invariants. This reveals surprising connections with cubic amplitudes. We also present alternative versions of the …

Pressure-Induced Modifications To The Structural And Optoelectronic Properties Of 2d Hybrid Organic-Inorganic Perovskites, Jesse Ratte

Electronic Thesis and Dissertation Repository

Recently, 2D hybrid organic-inorganic perovskites (HOIP) have garnered lots of research interest for their applications in optoelectronic devices, especially in solar cells. The optoelectronic properties of 2D HOIPs have yet to be optimized for these applications. High external pressure is well known to induce structural modifications to 2D HOIPs, and thus modify their optoelectronic properties. Herein, we report a study of the effects of high pressure (HP) on the structures and optoelectronic properties of cyclohexane methylamine (CMA) lead iodide (CMA2PbI4) and the structures of N,N-dimethylphenylene-p-diammonium (DPDA) lead iodide (DPDAPbI4).

High pressure measurements of CMA2PbI4 were performed using Raman spectroscopy, Fourier-transform …

Wideband And Relativistic Superradiance In Astrophysics, Christopher M. Wyenberg

Electronic Thesis and Dissertation Repository

In the quantum phenomenon of superradiance (SR) a population of inverted particles evolves, through its interaction with the quantized vacuum radiation field, into a highly entangled state capable of generating much greater radiative emission than predicted by the independent spontaneous decay of its constituent particles. The phenomenon has recently been applied to transient astrophysical processes but has thus far been restricted to particles sharing a common velocity. This thesis researches the effects of astrophysical velocity distributions upon SR, which are distinct from conventional regimes of the quantum optics literature in that they may possess extremely wide bandwidths, turbulent statistical properties, …

Magnetic Resonance Systems Development For Point-Of-Care Mri Platforms, Eric J. Lessard

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging utilizes electromagnets to produce anatomical images in both clinical and research settings. In the race towards increasing performance head-optimized scanners have begun playing a significant role in providing high quality imaging of the head. However, they are implemented using smaller geometries and as such fail to allow entrance of the patient past their shoulders. This is overcome by designing asymmetric gradient coils which have their imaging region located towards one end of the gradient coil, as opposed to the geometric center, allowing brain imaging. There exists interest in compact configurations which allow imaging further into the cervical …

Electrical And Mechanical Properties Of Polymer Nanocomposites, Nuwansiri N.K. Getangama

Electronic Thesis and Dissertation Repository

This thesis consists of three projects concerning the electrical and mechanical properties of polymer nanocomposites. We study the effect of nanoscale filler particles on the polymer dynamics at different length and time scales. In the first study, poly(ethylene oxide) (PEO)-multiwalled carbon nanotubes (MWCNT) nanocomposites with a MWCNT concentration ranging from 0 to 5 wt\% were prepared by both melt-mixing and twin-screw extrusion. Their electrical properties were studied over a wide range of frequency and temperature using a dielectric spectrometer. A percolation transition is observed at which the electrical conductivity of the nanocomposites increases by several orders of magnitude. The percolation …

A Molecular Dynamics Study Of Polymer Chains In Shear Flows And Nanocomposites, Venkat Bala

Electronic Thesis and Dissertation Repository

In this work we study single chain polymers in shear flows and nanocomposite polymer melts extensively through the use of large scale molecular dynamics simulations through LAMMPS. In the single polymer chain shear flow study, we use the Lattice Boltzmann method to simulate fluid dynamics and also include thermal noise as per the \emph{fluctuation-dissipation} theorem in the system. When simulating the nanocomposite polymer melts, we simply use a Langevin thermostat to mimic a heat bath. In the single polymer in shear flow study we investigated the margination of a single chain towards solid surfaces and how strongly the shear flow …

Physical Investigation Of Downburst Winds And Applicability To Full Scale Events, Federico Canepa

Electronic Thesis and Dissertation Repository

Thunderstorm winds, i.e. downbursts, are cold descending currents originating from cumulonimbus clouds which, upon the impingement on the ground, spread radially with high intensities. The downdraft phase of the storm and the subsequent radial outflow that is formed can cause major issues for aviation and immense damages to ground-mounted structures. Thunderstorm winds present characteristics completely different from the stationary Gaussian synoptic winds, which largely affect the mid-latitude areas of the globe in the form of extra-tropical cyclones. Downbursts are very localized winds in both space and time. It follows that their statistical investigation, by means of classical full scale anemometric …

Non-Circular Hydraulic Jumps Due To Inclined Jets, Ahmed Mohamed Abdelaziz

Electronic Thesis and Dissertation Repository

When a laminar inclined circular jet impinges on a horizontal surface, it forms a non-circular hydraulic jump governed by a non-axisymmetric flow. In this thesis, we use the boundary-layer and thin-film approaches in the three dimensions to theoretically analyse such flow and the hydraulic jumps produced in such cases. We particularly explore the interplay among inertia, gravity, and the effective inclination angle on the non-axisymmetric flow.

The boundary-layer height is found to show an azimuthal dependence at strong gravity level only; however, the thin film thickness as well as the hydraulic jump profile showed a strong non-axisymmetric behaviour at all …

Functional Nanoparticles: Tin Monoxide And Molybdenum Disulfide Quantum Dots On Graphene Nanosheets, Denys Vidish

Electronic Thesis and Dissertation Repository

Light harvesting can be referred to the use of an ensemble of different nanoparticles, or quantum dots, or other absorbers to optimize the ability to capture a given spectrum of electromagnetic radiation (for example the solar spectrum under specific atmospheric conditions) in a light-absorbing system. To this end, different nanoparticles play complementary functions within the system and absorb or scatter light at different wavelength intervals. Light harvesting finds applications in fields as diverse as solar cells, photosynthesis and photocatalysis. Graphene supporting a set of different semiconducting nanoparticles has often been proposed as light harvesters. To further this concept, my thesis …

Symphas: A Modular Api For Phase-Field Modeling Using Compile-Time Symbolic Algebra, Steven A. Silber

Electronic Thesis and Dissertation Repository

The phase-field method is a common approach to qualitative analysis of phase transitions. It allows visualizing the time evolution of a phase transition, providing valuable insight into the underlying microstructure and the dynamical processes that take place. Although the approach is applied in a diverse range of fields, from metal-forming to cardiac modelling, there are a limited number of software tools available that allow simulating any phase-field problem and that are highly accessible. To address this, a new open source API and software package called SymPhas is developed for simulating phase-field and phase-field crystal in 1-, 2- and 3-dimensions. Phase-field …

Heat Flow In The Core Of Ganymede: High Pressure-Temperature Electrical Resistivity Measurements Of Solid And Liquid Ag And Fe-S Alloys, Joshua A.H. Littleton

Electronic Thesis and Dissertation Repository

Experimental investigations of materials at high pressures (P) and temperatures (T) provide insight into the properties and behaviours expected within the inaccessible interiors of planetary bodies. Using a four-wire electrical resistance technique, the electrical resistivity (ρ) of 4d transition metal (Ag) and 3d transition metal alloys (Fe-S) were measured in the solid and molten states at high P. The thermal conductivity (κ) of these materials is inversely proportional to ρ, as described by the Wiedemann-Franz Law. When applied to planetary cores, κ is an important parameter that regulates heat transport mechanisms and magnetic field production.

A hypothesis of ‘resistivity invariance’ …

Field Theories From Physical Requirements: Noether's First Theorem, Energy-Momentum Tensors And The Question Of Uniqueness, Mark Robert Baker

Electronic Thesis and Dissertation Repository

An axiomatic approach to physics is proposed for obtaining classical gauge theories from a common set of physical requirements based on standard features of special relativistic field theories such as gauge invariance, conformal invariance and being in four dimensions. This approach involves the use of Noether's first theorem to directly obtain a unique, complete set of equations from the symmetries of the action. However, implementation of this procedure is obstructed by issues of ambiguity and non-uniqueness associated with the conserved tensors in the majority of special relativistic field theories. In the introductory chapter, we outline the three major problems which …

Studies Of The Tilts Of Atmospheric Scatterers By Windprofiler Radars, Farnoush Attarzadeh

Electronic Thesis and Dissertation Repository

MST (Mesosphere–Stratosphere–Troposphere) radars are powerful instruments for observing the differences in refractive indexes in the air. By tracking refractive index perturbations, these radars can determine wind speeds and turbulence strengths in the atmosphere from the ground up to 15 km altitude. In this project, we used 6 Doppler Radars to study the correlation between horizontal and vertical winds in the Troposphere to find scatterer tilts. However, instrumental effects due to small tilts in the radar beam can also cause such correlations, thus our studies cover that as well. Scatterers are best known for being the result of turbulence and waves …

Fundamental Transport Properties In Silicon Quantum Structures, Nazban M. Darukhanawalla

Electronic Thesis and Dissertation Repository

In the field of silicon photonics, there is an effort to bridge the gap between electrical and optical signals on a single platform, creating a need for Si-based light sources. In this project, Si quantum structures – Si quantum wells and quantum dots in SiO2 were fabricated via solid state precipitation methods. Their properties were studied using X-ray photoelectron spectroscopy, photoluminescence and I-V measurements. Rutherford backscattering spectroscopy was used for depth analysis in monitoring the Si distribution. Different electrical transport mechanisms were explored to understand how an ensemble of silicon QD’s or a silicon quantum well behaves in an SiO2 …

Improving Hydrid Pet/Mri Cardiovascular Imaging With Improved Hardware Design And Attenuation Correction Coefficient, Adam Helmy Farag

Electronic Thesis and Dissertation Repository

According to the World Health Organization (WHO) report in 2019, cardiovascular diseases (CVD) cause 52% of all illness-related deaths globally and are considered to be the second most common cause of death in Canada. CVD is also estimated to cost the Canadian economy about $21.2 billion in direct and indirect costs. With these figures, it is vital to develop the most effective and accurate methods and tools to diagnose accurately CVD and their causes. One of the promising tools for accurate diagnostic and therapeutic of CVD is the integrated Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) PET/MRI technology, …

Cfd Simulations Of Bubble Column Equipped With Bundles Of Concentric Tubes, Glen C. Dsouza

Electronic Thesis and Dissertation Repository

Bubble column reactors are multiphase contactors that have found several industrial applications owing to various attractive features including excellent thermal management, low maintenance cost due to simple construction and absence of moving parts. In order to attain desired performance for a given application, these reactors are usually equipped with internals such as vertical tube bundles to facilitate heat transfer. The column hydrodynamics and turbulence parameters are altered when the column is occluded with internals which adds to the complexity of the problem. The use of Computational Fluid Dynamics (CFD) tools for the study of multiphase flows has gained a lot …

Yield-Stress Fluids In Confined Geometries, Thalia Magyar

Electronic Thesis and Dissertation Repository

A yield-stress fluid is a material that has properties of both solids and conventional liquids that only begins to flow when subject to a finite stress. The behaviour of yield-stress fluids is interesting and important in many applications. It is expected that the rheological properties of a yield-stress fluid will change when confined to a region with a length scale comparable to the characteristic scale of its microstructure. The particle size and polydispersity of two yield-stress fluids, Carbopol and poly(N-isopropylacrylamide), were determined using dynamic light scattering. A rheological characterization was performed on these two yield-stress fluids. Flow of …

Electronic And Local Structures Of Pt-Based Bimetallic Alloy And Core-Shell Systems, Jiatang Chen

Electronic Thesis and Dissertation Repository

This thesis investigates the electronic structure of Pt for catalysis applications. The importance of the Pt 5d band is discussed in terms of the bonding capability of Pt. The oxygen reduction reaction in proton exchange membrane fuel cells is chosen as the catalytic reaction model to illustrate the effect of Pt 5d states on Pt-O interaction. Pt-based bimetallic systems are introduced as a solution for the high price and limited resources of Pt. Despite lower usage of Pt, the tuning capability to optimize the Pt 5d band in bimetallic catalysts is supposed to provide superior catalytic activity. Advanced synchrotron X-ray …