Physics Commons^™

Static Magnetic Field Interactions Of Medical Devices In The Mri Environment, Spencer Baird Parent

Electronic Thesis and Dissertation Repository

Background: The current procedures and guidelines for testing medical devices require that conservative testing be carried-out using the “worst-case” device or device configuration for each interaction (force, torque, heating, et cetera) of importance, and the results of those tests be used to inform regulatory labeling for that device. One of the most difficult elements of carrying out the above procedure is the determination of what represents a “worst-case” device or device configuration. A simulation “pipeline” would enable a systematic procedure for identification of the worst-case device or device configuration for magnetic force from an otherwise impossibly large set of options. …

Novel Simulation To Avoid Bias In Measurement Of Hyperpolarized Pyruvate: Demonstrated In Phantom And In Vivo, Christopher M. Walker

Dissertations & Theses (Open Access)

Dynamic nuclear polarization creates a transient hyperpolarized nuclear state that can dramatically increase the signal detected by magnetic resonance imaging. This signal increase allows real-time spectroscopic imaging of specific metabolites in vivo by magnetic resonance. Real-time imaging of both the spatial and chemical fate of hyperpolarized metabolites is showing great promise to meaningfully benefit clinical care of cancer patients. Imaging of hyperpolarized agents will have a larger clinical impact if it can function as a quantitative modality upon which clinical decisions can be made. However, quantitative measurement of hyperpolarized agents is currently difficult due to the restrictions imposed by the …

Measuring Nonlinear Properties Of Graphene Thin Films Using Z-Scan Technique, Thekrayat Hassan Al Abdulaal

Graduate Theses and Dissertations

The nonlinear studies of two-dimensional (2D) nanomaterials, specifically graphene, are very significant since graphene is finding its usefulness in handling the enormous heat in nanoscale high-density power electronics. Graphene has emerged to be a promising nanomaterial as an excellent heat spreader due to its high thermal conductivity. However, the experimental nonlinear study of graphene materials and their application in developing future optoelectronic devices demands for more developed research.

The research objective is first to build a precise, and sensitive technique to investigate and understand the thermal nonlinear properties, including nonlinear refractive index (n2), nonlinear absorption coefficient (β), and thermo-optic coefficient …

Assessing The Potential Clinical Impact Of Variable Biological Effectiveness In Proton Radiotherapy, Christopher R. Peeler Ph.D.

Dissertations & Theses (Open Access)

It has long been known that proton radiotherapy has an increased biological effectiveness compared to traditional x-ray radiotherapy. This arises from the clustered nature of DNA damage produced by the energy deposition of protons along their tracks in medium. This effect is currently quantified in clinical settings by assigning protons a relative biological effectiveness (RBE) value of 1.1 corresponding to 10% increased effectiveness compared to photon radiation. Numerous studies have shown, however, that the RBE value of protons is variable and can deviate substantially from 1.1, but experimental data on RBE and clinical evidence of its variability remains limited.

The …

Effect Of Void Fraction On Transverse Shear Modulus Of Advanced Unidirectional Composites, Jui-He Tai

USF Tampa Graduate Theses and Dissertations

In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.

Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, …

Photonic Crystals With Alternate Arrays Of Rods And Holes In A Low Dielectric-Index Material, Dimitar L. Dimitrov

Dissertations, Theses, and Capstone Projects

This thesis theoretically deals with the propagation of electromagnetic waves (light beams) in periodically modulated dielectric material structures based on Maxwell’s equations. We are interested in novel light propagation characteristics in these man-made dielectric material structures for practical applications, especially on optical communications and computations. Since the wavelength range of light is on the same order of magnitude as the modulation periods of dielectric materials, an analogy of the light propagation in dielectric-constant modulated structures with the electron transport in solid-state crystals is used throughout my thesis by using a term “photonic crystals (PhCs)” referring to these dielectric structures. I …

3d Post-Stack Seismic Inversion Using Global Optimization Techniques: Gulf Of Mexico Example, Elijah A. Adedeji

University of New Orleans Theses and Dissertations

Seismic inversion using a global optimization algorithm is a non-linear, model-driven process. It yields an optimal solution of the cost function – reflectivity/acoustic impedance, when prior information is sparse. The inversion result offers detailed interpretations of thin layers, internal stratigraphy, and lateral continuity and connectivity of sand bodies. This study compared two stable and robust global optimization techniques, Simulated Annealing (SA) and Basis Pursuit Inversion (BPI) as applied to post-stack seismic data from the Gulf of Mexico.

Both methods use different routines and constraints to search for the minimum error energy function. Estimation of inversion parameters in SA is rigorous …

Ultracold Quantum Scattering In The Presence Of Synthetic Spin-Orbit Coupling, Su-Ju Wang

Open Access Dissertations

Two-body scattering constitutes one of the most fundamental processes in various physical systems ranging from ultracold dilute quantum gases to energetic quark- gluon plasmas. In this dissertation, we study the low-energy atomic collision physics in the presence of synthetic gauge fields, which are generated by atom-light interaction. One category of synthetic gauge fields is the artificial spin-orbit coupling. We discuss three different aspects in scattering theory: ultracold collision, scattering resonance, and bound state formation from a few-body perspective when the atomic spin states are coupled with their center-of-mass motion. The understanding of the spin-orbit effects on the modification of the …

Identifying Treatment Planning System Errors In Iroc-Houston Head And Neck Phantom Irradiations, James Kerns

Dissertations & Theses (Open Access)

Treatment Planning System (TPS) errors can affect large numbers of cancer patients receiving radiation therapy. Using an independent recalculation system, the Imaging and Radiation Oncology Core-Houston (IROC-H) can identify institutions that have not sufficiently modelled their linear accelerators in their TPS model. Linear accelerator point measurement data from IROC-H’s site visits was aggregated and analyzed from over 30 linear accelerator models. Dosimetrically similar models were combined to create “classes”. The class data was used to construct customized beam models in an independent treatment dose verification system (TVS). Approximately 200 head and neck phantom plans from 2012 to 2015 were recalculated …

Measurement Of The Electron Return Effect Using Presage Dosimeter, Gye Won Choi

Dissertations & Theses (Open Access)

MR-guided radiation therapy (MRgRT) provides benefits such as superior soft tissue contrast, no imaging dose, and functional imaging capacities, but it also has concerns to be addressed. The electron return effect (ERE) refers to dose enhancement at the interface between different media, caused when radiation is delivered in the magnetic field. The ERE poses clinical concerns in MRgRT because it significantly enhances the dose at interfaces, and the intensity and pattern of the dose enhancement depends on many factors. The ERE results in a complex pattern of dose enhancement over a three-dimensional (3D) volume around tissue interfaces inside the patient …

Utilizing Computed Tomography Image Features To Advance Prediction Of Radiation Pneumonitis, Shane P. Krafft

Dissertations & Theses (Open Access)

Improving outcomes for non-small-cell lung cancer patients treated with radiation therapy (RT) requires optimizing the balance between local tumor control and risk of normal tissue toxicity. In approximately 20% of patients, severe acute symptomatic lung toxicity, termed radiation pneumonitis (RP), still occurs. Identifying the individuals at risk of RP prior to or early during treatment offers tremendous potential to improve RT by providing the physician with information to assist in making clinical decisions that enhance therapy. Our central goal for this work was to demonstrate the potential gain in predictive accuracy of normal tissue complication probability models for RP by …

Designing Active Granular Squares, Christopher C. Olson

Masters Theses

The goal of this thesis has been to find a means of i) designing an active square particle, and ii) continuously varying its degree of activity with the objective of understanding the effects of activity on the various phases of granular matter. The motivations, results and limitations of our methods of creating active particles are discussed in this thesis. The applicability of a stochastic model based on the Langevin equation in 2D as well as implications for future experiments are also discussed.

Optimizing Respiratory Gated Intensity Modulated Radiation Therapy Planning And Delivery Of Early-Stage Non-Small Cell Lung Cancer, Ilma Xhaferllari

Electronic Thesis and Dissertation Repository

Stereotactic ablative body radiotherapy (SABR) is the standard of care for inoperable early-stage non-small cell lung cancer (NSCLC) patients. However, thoracic tumours are susceptible to respiratory motion and, if unaccounted for, can potentially lead to dosimetric uncertainties. Respiratory gating is one method that limits treatment delivery to portions of the respiratory cycle, but when combined with intensity-modulated radiotherapy (IMRT), requires rigorous verification. The goal of this thesis is to optimize respiratory gated IMRT treatment planning and develop image-guided strategies to verify the dose delivery for future early-stage NSCLC patients.

Retrospective treatment plans were generated for various IMRT delivery techniques, including …

Atomic Force Microscopy Of Poly(Ethylane-Oxide) Crystalization, Xavier Capaldi

Honors Theses

Polymer crystallization is a complex process which is influenced by a variety of factors. Atomic force microscopy is used to explore the material properties of polymer crystals. Poly(ethylene-oxide) is used in a variety of molecular weights as the sample. In addition, a variety of sample preparation methods and microscopy modes were tested. A relatively new imaging technique was identified for the characterization of polymer crystals: amplitude modulation-frequency modulation viscoelastic mapping. This mode was used to measure material properties such as stiffness and dissipation.

Magnetic Reconnection In Small And Large Scales On The Sun, Xin Chen

Dissertations

Almost all solar activities observed are related to the solar magnetic field, especially the topological restructuring of magnetic fields, the so-called magnetic reconnection in solar physics. They are occurring at different scales related to various phenomena, during minimum or maximum of the solar cycle, from the photosphere to the solar corona.

For small-scale activities, type II spicules which display high velocity upflows observed at the limb, have the most possible underlying driving mechanism of magnetic reconnection. A set of tools is developed for detecting small-scale solar magnetic cancellations and the disk counterpart of type II spicules (the so-called Rapid Blueshifted …

New Facet Of Solar Activities Revealed By High-Resolution Imaging At He I 10830 Å, Zhicheng Zeng

Dissertations

Major solar activities such as major flares and associated coronal mass ejections (CMEs), have a great impact on space weather, which requires us to develop the ability to predict them. Despite the extensive studies already made, however, many basic processes, such as energy accumulation processes in solar active regions and the triggering mechanism of solar activities, are still not well understood.

One reason why the basic processes are hard to be understood is that the large-scale activities are complicated, involving many small-scale energy releases, making it hard to understand the basic picture of the events. Small-scale solar activities, such as …

Radiative Properties Of Silicon Related Materials, Scott Sanowitz

Theses

The objective of this thesis is to study the optical properties of silicon, as a function of temperature, in the infrared range of wavelengths. The wavelength range, considered in this study, is between 1 micron and 20 microns. The temperature range observed is from 50 degrees Celsius to 1000 degrees Celsius. Varying wafer thickness and doping are taken into account. The thickness of the native oxide, silicon dioxide, must be taken into account as well as its orientation (front side versus back side). The effect of layering wafers one onto another is investigated. It is shown that all these parameters …

Automated Sea State Classification From Parameterization Of Survey Observations And Wave-Generated Displacement Data, Jason A. Teichman

University of New Orleans Theses and Dissertations

Sea state is a subjective quantity whose accuracy depends on an observer’s ability to translate local wind waves into numerical scales. It provides an analytical tool for estimating the impact of the sea on data quality and operational safety. Tasks dependent on the characteristics of local sea surface conditions often require accurate and immediate assessment. An attempt to automate sea state classification using eleven years of ship motion and sea state observation data is made using parametric modeling of distribution-based confidence and tolerance intervals and a probabilistic model using sea state frequencies. Models utilizing distribution intervals are not able to …

Particle Image Velocimetry Design & Installation, Zach Ritchie

Mechanical Engineering Undergraduate Honors Theses

This work will mainly focus on the design, construction, and installation of the Particle Image Velocimetry (PIV) system in the Chemical Hazards Research Center wind tunnel. The PIV system utilizes a Class IV (double pulsed) laser, optics to produce a light sheet, timing circuitry, and a high-resolution camera (with buffered output) to measure a system’s velocity (two-dimensional) field by determining the displacement of particles over the time between laser pulses. For maximum mobility and functionality, the PIV system was installed in the center of the tunnel on a moveable cart with the laser and camera mounted to an adjustable support. …

Electromagnetic Properties Of Metal-Dielectric Media And Their Applications, Shravan Rakesh Animilli

Doctoral Dissertations

The main objective of this dissertation is to investigate nano-structured random composite materials, which exhibit anomalous phenomena, such as the extraordinary enhancements of linear and non-linear optical processes due to excitation of collective electronic states, surface plasmons (SP). The main goal is to develop a time and memory efficient novel numerical method to study the properties of these random media in three dimensions (3D) by utilization of multi core processing and packages such as MPI for parallel execution. The developed numerical studies are then utilized to provide a comprehensive characterization and optimization of a surface plasmon enhanced solar cell (SPESC) …

Novel Electrolytes For Use In New And Improved Batteries: An Nmr Study, Marc B. Berman

Dissertations, Theses, and Capstone Projects

This thesis focuses on the use of nuclear magnetic resonance (NMR) spectroscopy in order to study materials for use as electrolytes in batteries. The details of four projects are described in this thesis as well as a brief theoretical background of NMR. Structural and dynamics properties were determined using several NMR techniques such as static, MAS, PFG diffusion, and relaxation to understand microscopic and macroscopic properties of the materials described within. Nuclei investigate were 1H, 2H, 7Li, 13C, 19F, 23Na, and 27Al. The first project focuses on an exciting new material to be used as a solid electrolyte membrane. T. …

Terahertz Wireless Communication Through Atmospheric Atmospheric Turbulence And Rain, Jianjun Ma

Dissertations

This dissertation focusses on terahertz (THz) wireless communication technology in different weather conditions. The performance of the communication links is mainly studied under propagation through atmospheric turbulence and rain. However, as real outdoor weather conditions are temporally and spatially varying, it is difficult to obtain reproducible atmospheric conditions to verify results of independent measurements making it a challenge to measure and analyze the impact of outdoor atmospheric weather on communication links. Consequently, dedicated indoor weather chambers are designed to produce controllable weather conditions to emulate the real outdoor weather as closely as possible. To emulate turbulent air conditions, an enclosed …

Opto-Mechanical Design Of Synchrotron Radiation-Based Far-Infrared Spectroscopic Ellipsometer With Strong Magnetic-Field, Ahmad Abbas Chaudhry

Theses

The objective of this dissertation is to present opto-mechanical design of a synchrotron radiation based far-infrared spectroscopic ellipsometer with a strong external magnetic-field capability. Since high magnetic field has enabled major breakthrough in science such instrument will be highly important to the field of condensed matter physics and characterization of advanced electronic materials. This instrument will be installed at the multi-User facility with the most advanced synchrotron light source: Natonal Synchrotron Source (NSLS-II) at Brookhaven National Laboratory (BNL).The proposed here instrument is capable to measure full Mueller matrix spectroscopic ellipsometry spectra in high magnetic fields of up to 9 Tesla. …

Complex Semiclassics: Classical Models For Tunneling Using Complex Trajectories, Max Edward Meynig

Senior Projects Spring 2017

This project is inspired by the idea that black holes could explode due to a quantum process somewhat analogous to quantum mechanical tunneling. This idea was presented in recent research that also proposed that semiclassical physics could be used to investigate the so called black hole fireworks. Semiclassical physics connects quantum and classical physics and because of this it is a powerful tool for investigating gravity where the classical theory is known but there is no complete quantum theory. Unfortunately, the traditional tools in semiclassics that are needed fail to treat tunneling. However, if classical mechanics is extended to complex …

Calculating The Observable Properties Of Mass Accreting Black Holes, Heather Lee

Undergraduate Research Symposium Posters

My goal is to generalize Chandrasekhar’s formulas to include partial Rayleigh Scattering. In my summer research, I successfully recalculated key tables and solutions from his book and I am working in generalizing his results for use in an infinitely deep electron atmosphere. Here, I will summarize how Chandrasekhar derived his formulas and how to potentially generalize them to include absorption.

Understanding And Design Of An Arduino-Based Pid Controller, Dinesh Bista

Theses and Dissertations

This thesis presents research and design of a Proportional, Integral, and Derivative (PID) controller that uses a microcontroller (Arduino) platform. The research part discusses the structure of a PID algorithm with some motivating work already performed with the Arduino-based PID controller from various fields. An inexpensive Arduino-based PID controller designed in the laboratory to control the temperature, consists of hardware parts: Arduino UNO, thermoelectric cooler, and electronic components while the software portion includes C/C++ programming. The PID parameters for a particular controller are found manually. The role of different PID parameters is discussed with the subsequent comparison between different modes …

Analogy: A Decomposition Of Space And Time, David Gordon Shoemaker Jr

Senior Projects Spring 2016

The written part of this project is divided into two sections, with the first section focusing on the human eye as a biological tool for gathering and processing physical information. The second section strives to provide a model of human vision by utilizing Fourier Analysis. Out of this model came a focus on Fourier Analysis as not only a model, but as a methodology that can be applied in a variety of ways. The Fourier methodology provided a conceptual bridge that allowed me to more thoroughly explore art, physics, and how these two fields can contribute to each other.

Polarization Charge Density In Strained Graphene, Noah Wilson

Graduate College Dissertations and Theses

Graphene, the world's first truly two-dimensional material, is unique for having an electronic structure described by an effective Lorentz invariant theory. One important consequence is that the ratio or Coulomb energy to kinetic energy is a constant, depending only on conditions within the lattice rather than on the average charge density as in a typical Galilean invariant material. Given this unusual property, a natural question would be how do phenomena, such as screening of a Coulomb impurity, happen in graphene? Moreover, how does the addition of uniaxial strain enhance or diminish this behavior? Here I discuss our work to calculate …