Digital Commons Network^™

Separating Signal From Noise In High-Density Diffuse Optical Tomography, Arefeh Sherafati

Arts & Sciences Graduate Student Theses and Dissertations

High-density diffuse optical tomography (HD-DOT) is a relatively new neuroimaging technique that detects the changes in hemoglobin concentrations following neuronal activity through the measurement of near-infrared light intensities. Thus, it has the potential to be a surrogate for functional MRI (fMRI) as a more naturalistic, portable, and cost-effective neuroimaging system. As in other neuroimaging modalities, head motion is the most common source of noise in HD-DOT data that results in spurious effects in the functional brain images. Unlike other neuroimaging modalities, data quality assessment methods are still underdeveloped for HD-DOT. Therefore, developing robust motion detection and motion removal methods in …

Flux Variability In Gamma-Ray Blazars, Benjamin Groebe

Arts & Sciences Graduate Student Theses and Dissertations

Blazars, among the most luminous objects in the sky, are extreme members of the class of active galactic nuclei featuring powerful outflows of relativistic particles in the form of jets pointed towards the observer. They display strong flux variability in all observed wavebands and on all observed timescales, with significant changes in flux observed in some sources over periods of as short as minutes. These remarkable observations have led to open questions regarding the nature of particle acceleration in the jets, location of the radiating particles along the jet, and the connection between jet emission and rate of accretion onto …

Peer-Led Team Learning In Calculus-Based Introductory Physics: Implementation And Evaluation, Siera Maia Stoen

Arts & Sciences Graduate Student Theses and Dissertations

Robust evidence shows that Peer-led Team Learning (PLTL) improves the academic success of college students in introductory Science, Technology, Engineering, and Mathematics (STEM) courses. However, further research is needed to gain a fuller understanding of the benefits of PLTL and the aim of this dissertation is to explore two key and understudied questions surrounding the effects of PLTL. First, does deviating from the optimal implementation of PLTL change its effectiveness? Second, what specific outcomes, in addition to academic success (e.g., exam scores), does PLTL improve? This dissertation will provide a fuller picture of the impact of PLTL by examining its …

Modifications To Gravitational Wave Equation From Canonical Quantum Gravity, Andrea Dapor, Klaus Liegener

Faculty Publications

It is expected that the quantum nature of spacetime leaves its imprint in all semiclassical gravitational systems, at least in certain regimes, including gravitational waves. In this paper we investigate such imprints on gravitational waves within a specific framework: space is assumed to be discrete (in the form of a regular cubic lattice), and this discrete geometry is quantised following Dirac's canonical quantisation scheme. The semiclassical behavior is then extracted by promoting the expectation value of the Hamiltonian operator on a semiclassical state to an effective Hamiltonian. Considering a family of semiclassical states representing small tensor perturbations to Minkowski background, …

Evidence For A Supergalactic Structure Of Magnetic Deflection Multiplets Of Ultra-High-Energy Cosmic Rays, Rasha U. Abbasi

Physics: Faculty Publications and Other Works

Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire …

Studies Of Two-Phase Flow With Soluble Surfactant, Ryan Peter Atwater

Dissertations

Numerical methods are developed for accurate solution of two-phase flow in the zero Reynolds number limit of Stokes flow, when surfactant is present on a drop interface and in its bulk phase interior. The methods are designed to achieve high accuracy when the bulk Péclet number is large, or equivalently when the bulk phase surfactant has small diffusivity

In the limit of infinite bulk Péclet number the advection-diffusion equation that governs evolution of surfactant concentration in the bulk is singularly perturbed, indicating a separation of spatial scales. A hybrid numerical method based on a leading order asymptotic reduction in this …

H-Atom Ladder Operator Revisited, Carl W. David

Chemistry Education Materials

An error laden note (Am. J. Phys., 34, 984,(1966)) concerning the ladder operator solution to the hydrogen atom electronic energy levels is corrected.

Problems With Lorentz Violation Originating From A Cosmologically Varying Pseudoscalar Field, Sapan Karki, Brett David Altschul

Faculty Publications

Lorentz- and CPT-violating models of electrodynamics with Chern-Simons terms are typically plagued by various sorts of instabilities. However, when the Chern-Simons term arises from a slow time variation in a pseudoscalar field with an axionlike electromagnetic coupling, the total energy of the theory is bounded below. We examine the behavior of such a theory, finding that in a systematic power series expansion of the magnetic and pseudoscalar fields, singularities appear in the field profiles. Some of the questionable behavior can be cured by taking a fully nonperturbative approach, but other problematic terms remain. This may be an indication that Cerenkov-like …

Investigation Of The Chemical Kinetics In An Atmospheric Cold Plasma Towards Co2 Conversion, Daniel Piatek

Seton Hall University Dissertations and Theses (ETDs)

Hydrogenation of carbon dioxide (CO2) to methanol (CH3OH) is a promising route for utilization of excess and residual CO2. The conversion of CO to methanol is a well-developed process but the ability to use CO2 as a feed gas still requires high pressures (30-300 atm) to attain conversion. In this work, the hydrogenation of CO2 is explored using H2O as well as H2 in an atmospheric pressure nonthermal (cold) plasma created with a dielectric barrier discharge (DBD) reactor. Different gas mixtures such as argon (Ar) and helium (He) are used to understand their interactions in the process of CO2 hydrogenation. …

Qwasi: The Quantum Walk Simulator, Warren V. Wilson

Theses and Dissertations

As quantum computing continues to evolve, the ability to design and analyze novel quantum algorithms becomes a necessary focus for research. In many instances, the virtues of quantum algorithms only become evident when compared to their classical counterparts, so a study of the former often begins with a consideration of the latter. This is very much the case with quantum walk algorithms, as the success of random walks and their many, varied applications have inspired much interest in quantum correlates. Unfortunately, finding purely algebraic solutions for quantum walks is an elusive endeavor. At best, and when solvable, they require simple …

Artificial Neural Network Discovery Of A Switchable Metasurface Reflector, J. R. Thompson, J. A. Burrow, P. J. Shah, Jonathan E. Slagle, E. S. Harper, A. Van Rynbach, I. Agha, M. S. Mills

Student Publications

Optical materials engineered to dynamically and selectively manipulate electromagnetic waves are essential to the future of modern optical systems. In this paper, we simulate various metasurface configurations consisting of periodic 1D bars or 2D pillars made of the ternary phase change material Ge2Sb2Te5 (GST). Dynamic switching behavior in reflectance is exploited due to a drastic refractive index change between the crystalline and amorphous states of GST. Selectivity in the reflection and transmission spectra is manipulated by tailoring the geometrical parameters of the metasurface. Due to the immense number of possible metasurface configurations, we train deep neural networks capable of exploring …

Separability Of The Planar 1/Ρ2 Potential In Multiple Coordinate Systems, Richard Decosta, Brett David Altschul

Faculty Publications

With a number of special Hamiltonians, solutions of the Schrödinger equation may be found by separation of variables in more than one coordinate system. The class of potentials involved includes a number of important examples, including the isotropic harmonic oscillator and the Coulomb potential. Multiply separable Hamiltonians exhibit a number of interesting features, including “accidental” degeneracies in their bound state spectra and often classical bound state orbits that always close. We examine another potential, for which the Schrödinger equation is separable in both cylindrical and parabolic coordinates: A z-independent V ∝ 1/ρ² = 1/ (x² + y^{2 …}

A Hybrid Achromatic Metalens, Fatih Balli, Mansoor A. Sultan, Sarah K. Lami, J. Todd Hastings

Electrical and Computer Engineering Faculty Publications

Metalenses, ultra-thin optical elements that focus light using subwavelength structures, have been the subject of a number of recent investigations. Compared to their refractive counterparts, metalenses offer reduced size and weight, and new functionality such as polarization control. However, metalenses that correct chromatic aberration also suffer from markedly reduced focusing efficiency. Here we introduce a Hybrid Achromatic Metalens (HAML) that overcomes this trade-off and offers improved focusing efficiency over a broad wavelength range from 1000-1800 nm. HAMLs can be designed by combining recursive ray-tracing and simulated phase libraries rather than computationally intensive global search algorithms. Moreover, HAMLs can be fabricated …

Nonlocal Complex Potential Theory Of Dissociative Electron Attachment: Inclusion Of Two Vibrational Modes, H. B. Ambalampitiya, Ilya I. Fabrikant

Department of Physics and Astronomy: Faculty Publications

The process of dissociative electron attachment (DEA) to molecules with several vibrational degrees of freedom is usually treated in the approximation of the local potential for the description of the nuclear motion. We develop the nonlocal complex potential theory to treat the dissociation dynamics when there is more than one vibrational mode in the neutral molecule. We demonstrate the application of the multimode nonlocal theory to a generic molecule of the type CY₃X, where Y denotes the H or F atom and X denotes the halogen atom, with the inclusion of symmetric C–X stretch and CY₃ deform …

A Twist On Broken U(3) × U(3) Supersymmetry, Scott Chapman

Mathematics, Physics, and Computer Science Faculty Articles and Research

What symmetry breaking would be required for gauginos from a supersymmetric theory to behave like left-handed quarks of the Standard Model? Starting with a supersymmetric SU(3)xSU(3)xU(1)xU(1) gauge theory, the 18 adjoint-representation gauginos are replaced with 2 families of 9 gauginos in the (3,3*) representation of the group. After this explicit breaking of supersymmetry, two-loop quadratic divergences still cancel at a unification scale. Coupling constant unification is supported by deriving the theory from an SU(3)xSU(3)xSU(3)xSU(3) Grand Unified Theory (GUT). Sin² of the Weinberg angle for the GUT is 1/4 rather than 3/8, leading to a lower unification scale than usually …

Investigation Of Nanostructures For Highly Sensitive Surface Plasmon Resonance Sensors, Hussein Akafzade

Physics Dissertations - Archive

An extensive study of Surface Plasmon Polaritons (SPPs) and their applications has been undertaken in this work. Highly sensitive surface plasmon resonance sensors, made of noble metals, as well as multilayer nanostructures, are investigated. Detailed simulations are performed to optimize and improve the structure of these sensors. Evanescent fields created on the surface of the sensor are evaluated. It is demonstrated theoretically and experimentally that sensor sensitivity can be increased significantly by choosing the right index of the prism used in our Kretschmann and Fixed Detector Kretschmann Spectrometers. The interaction of the SPPs and CdSe/ZnS quantum dots that leads to …

Ns2-Md0 Post-Transition Metal Oxides For Solar Energy Applications, Edan Bainglass

Physics Dissertations - Archive

Meeting the growing global energy demand while mitigating the deterioration of the global climate requires the rapid introduction of clean, renewable, and sustainable fuels. Solar energy output at daytime provides more than enough to satiate global demands. However, to utilize solar energy at night would require the development of efficient materials for solar energy storage. Photoelectrochemical (PEC) water-splitting is regarded as one of the most promising solar storage technologies. The material properties necessary to drive both O2 and H2 evolution reactions may be decoupled by designing a photoanode-photocathode PEC cell, with each half reaction respectively handled by an n-type and …

Refinements To Data Acquired By 2-Dimensional Video Disdrometers, Michael L. Larsen, Christopher K. Blouin

Michigan Tech Publications, Part 1

The 2-Dimensional Video Disdrometer (2DVD) is a commonly used tool for exploring rain microphysics and for validating remotely sensed rain retrievals. Recent work has revealed a persistent anomaly in 2DVD data. Early investigations of this anomaly concluded that the resulting errors in rain measurement were modest, but the methods used to flag anomalous data were not optimized, and related considerations associated with the sample sensing area were not fully investigated. Here, we (i) refine the anomaly-detecting algorithm for increased sensitivity and reliability and (ii) develop a related algorithm for refining the estimate of sample sensing area for all detected drops, …

Synthesis And Characterization Of Carbon Coated Barium Titanate Core-Shell Nanoparticles, Moudip Nandi

Graduate Theses/Dissertations

Core-shell nanoparticles (CSNP) with fascinating ferroelectric properties have diverse applications in biotechnology and the electronic field of studies. Among so many perovskites, barium titanate (BTO) nanoparticles draw much interest due to their distinct electronic and ferroelectric features. Additionally, the incorporation of carbon in the shell of CSNP makes it suitable for application in many fields due to its innocuous nature. Carbon not only increases the biocompatible properties of an element but also gives mechanical stability to the CSNP. This thesis is targeted towards the synthesis of oxide-carbide CSNP, where the core is made of BTO and the shell is made …

Modeling The Obscuring Features In Active Galactic Nuclei: An X-Ray Analysis Of Ngc 1052, Samantha E. Cabral

Graduate Masters Theses

We present a multi-epoch analysis of the X-ray spectrum of NGC 1052, a nearby galaxy notorious for its well-studied spectral variability. We utilize observations from NuSTAR, XMM-Newton, Chandra, Swift, Suzaku, BeppoSAX, and ASCA to create a comprehensive set of data that spans roughly 20 years. Organizing our data by observation date and grouping into specific epochs allows us to explore a model allowed to flex and accommodate any spectral changes that occur over time in the X-ray spectrum of NGC 1052. We find that the spectrum takes on a relatively flat nature and is best modeled with two neutral absorption …

Investigation Of Range Verification In Carbon Ion Therapy Using Monte Carlo Simulation, Ananta Chalise

Physics Dissertations - Archive

Carbon ion therapy is one of the advanced forms for radiotherapy and currently only available in few developed countries. Unlike conventional radiation therapy methods, carbon ion therapy has high potential in treating deep-seated and photon-radiation resistant tumors owing to its unique dose-conformality, higher relative biological effect and lower oxygen enhancement ratio. However, due to the lack of precise range verification tools in routine clinic, carbon ion therapy has not been used to its full potentiality. In this work, we used a Monte Carlo simulation tool, Geant4, to investigate range verification for carbon ion therapy. Geant4 is one of the well-stablished …

Searching For A Pair-Produced Supersymmetric Top Partner Using Recursive Jigsaw Variables And Boosted Decision Trees With 139 Fb⁻¹ Of Data From The Atlas Detector, Jared David Little

Physics Dissertations - Archive

The Standard Model of Particle Physics is the most comprehensive theory describing how fundamental particles and three of the four fundamental forces are related. However, the Standard Model is known to be an incomplete theory with several limitations. Supersymmetry is an extension of the Standard Model of Particle Physics, introducing supersymmetric partners to every fermion and boson in the Standard Model. Supersymmetry gives a diverse collection of theoretical models providing solutions to these phenomenological inconsistencies. It contains a mechanism for stabilizing the Higgs boson mass while predicting the existence of several new particles, including a suitable Dark Matter candidate. The …

Searching For Low Frequency Fast Radio Bursts With Vlite, Suryarao Bethapudi

Theses and Dissertations

The VLITE (VLA Low Band Ionosphere and Transient Experiment; http://vlite.nrao.edu) program performs commensal observations using 16 antennas of the Very Large Array radio telescope from 320-384 MHz. The VLITE-Fast program searches for short time-scale (<100ms) transients, such as Fast Radio Bursts (FRBs), in real time and triggers recording of baseband voltages for offline imaging. Searches are made possible by a 12 node cluster, each housing GPUs for digital signal processing. A real-time Message Passing Interface (MPI)-based co-adder incoherently sums the data streams from all the antennas to boost the signal-to-noise. To undo the dispersion effects of signal propagation through the ionized interstellar medium, the co-added stream is de-dispersed and matched-filtered to search for transients. This operation is completely performed on GPUs by the software package Heimdall . A selection logic is applied to the candidates and interesting candidates with their corresponding data are processed and packaged in a binary file along with a diagnostic plot. Furthermore, a Machine Learning classification is applied on the reduced data product and, based on its decision, baseband voltages are recorded. Reduced data products collected over 126 days of on-sky operation form the VLITE-Fast Pathfinder Survey (VFPS). This pipeline has triggered on single pulses from 7 known radio pulsars. Lastly, the pipeline capabilities are tested against pure random noise and simulated injected signals.

Searching For Pulsars Using The Long Wavelength Array Telescope, Keeisi A. Caballero Valdez

Theses and Dissertations

Radio pulsars are fascinating celestial objects known to display both periodic and transient behavior. Pulsars are characterized by narrow electromagnetic radiation beams which restrict the number of pulsars visible from Earth due to the necessary alignment of the radiation beam across an observer’s line of sight. Pulsars are useful tools for a broad range of applications and provide important information about the process of stellar evolution, tests for relativistic theories of gravity and the search for low-frequency gravitational waves. Over 2,500 pulsars have been observed since their initial discovery in 1967 but the search for these objects is continuously warranted. …

Toward Background-Free Methods To Search For Majorana Neutrinos In Xenon Gas, Austin Mcdonald

Physics Dissertations - Archive

Since the observation of double beta decay 33 years ago the search for neu- trinoless double beta decay has been underway. This is due to the fact that a robust observation of neutrinoless double beta decay is currently the most sen- sitive method to determine the Majorana nature of the neutrino. Such searches have been at the forefront for developing new methods and techniques that are required for observing such rare processes. The detection of the single barium ion produced as a result of the double beta decay of 136Xe would enable a new class of ultra-low background neutrinoless double …

Simulation And Development Of The Radial Time Projection Chamber For The Bonus12 Experiment In Clas12, Nathan M. Dzbenski

Physics Theses & Dissertations

Knowledge of the structure of nucleons (i:e: protons and neutrons) is a central topic of interest to nuclear/particle physicists. Much more is known about the structure of the proton than the neutron due to the lack of high-density free neutron targets. The Barely Off-shell Nucleon Structure experiment (BONuS12) at Jefferson Lab (JLab) is a second generation experiment upgraded/optimized to advance our knowledge of the neutron's structure using the deep-inelastic scattering of electrons off deuterium. Typically, since deuterium is a nuclear target, corrections for off-shell and nuclear binding effects must be taken into account in order to extract results on the …

Direct Measurement Of The Muonic Content Of Extensive Air Showers Between 2× 1017 And 2×1018 Ev At The Pierre Auger Observatory, A. Aab, P. Abreu, M. Aglietta, J. M. Albury, I. Allekotte, A. Almela, J. Alvarez Castillo, J. Alvarez-Muñiz, G. A. Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, P. R. Araújo Ferreira, H. Asorey, P. Assis, G. Avila, A. M. Badescu, A. Bakalova, A. Balaceanu, F. Barbato, R. J. Barreira Luz, K. H. Becker, J. A. Bellido, C. Berat, M. E. Bertaina, X. Bertou, P. L. Biermann, T. Bister, J. Biteau, A. Blanco, J. Blazek, B. Fick, D. F. Nitz, A. Puyleart

Michigan Tech Publications, Part 1

The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between 2 × 10 17 and 2 × 10 18 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We …

Characterization Of Treatment Planning System Photon Beam Modeling Errors In Iroc Houston Phantom Irradiations, Mallory Glenn

Dissertations and Theses (Open Access)

In radiation therapy, proper commissioning of the treatment planning system’s (TPS) dose calculation algorithm is critical because any errors in this process impact all treatment plans prepared in the system. Previously, TPS errors have been identified as a major cause for poor phantom irradiation performance, which may also mean that patients are treated suboptimally. The purpose of this work was to investigate the TPS beam modeling developed by the radiotherapy community to understand where inconsistencies may arise, which variables are most susceptible to variations, and in what way changing these variables can alter dose calculations.

Using the Imaging and Radiation …

Active Magnetic Radiation Shielding For Long-Duration Human Spaceflight, Kristine Ferrone

Dissertations and Theses (Open Access)

Exploration of interplanetary space presents dramatic hazards to human survival.

Space radiation hazards outside the protection of the Earth’s magnetosphere can

produce both acute and chronic health risks and thus become limiting factors for

NASA’s planned mission to Mars by the 2030s. Radiation exposure on a Mars mission

is delivered primarily by high energy ions from galactic cosmic rays and moderate

energy protons from solar particle events. The chronic radiation dose due to galactic

cosmic rays on a typical Mars mission is on the order of 1 Sv, and additional acute

radiation dose from solar flares can reach over 4 …

A Structural Study Of Correlated Materials: Incipient Mott Insulators And Low-Dimensional Systesm., Alaa Alfailakawi

Electronic Theses and Dissertations

Current theories of high-temperature superconductivity suggest that electrons must organize into Cooper pairs in order for a material to exhibit a superconducting phase. Electrons in insulators experience significant repulsive interactions that tend to keep electrons localized at atomic positions. In contrast, electrons in metals are delocalized, interact weakly, and are free to conduct electricity. Therefore, the formation of Cooper pairs should have different mechanisms for metals compared to insulators. This contrast raises the debate about the origin of high-temperature superconductivity in iron-based material, whether it depends on the strong or weak coupling. Many iron-based materials are metallic in the normal …