MS Theses - DO NOT EDIT
http://hdl.handle.net/10106/11756
2024-03-28T18:52:10ZRelation Between Solitary Wave Occurrence and Solar Wind Parameters During the Kelvin-Helmholtz Instability
http://hdl.handle.net/10106/31718
Relation Between Solitary Wave Occurrence and Solar Wind Parameters During the Kelvin-Helmholtz Instability
The Kelvin-Helmholtz instability (KHI) is an important mechanism whereby the solar wind transports energy and momentum into the magnetosphere. One unresolved topic is the role of kinetic phenomena and turbulence in mediating this energy transport. Previous studies hypothesized that the prevalence of electrostatic solitary waves, an artifact of kinetic turbulence, decreased along the flanks as the instability grew. These previous studies had been conducted using 3 KHI events. For this study, we test the hypothesis and further investigate how these solitary waves affect the local plasma with an expanded list of 15 KHI events. A combination of solar wind data from OMNI and in-situ plasma measurements from the NASA Magnetospheric Multiscale (MMS) mission was taken for the duration of these events. Analysis of the findings show that solitary wave occurrence seems to coincide with ion temperature isotropy and electron temperature anisotropy biased to the direction parallel to the magnetic field. It was further observed that solitary wave occurrence was highly negatively correlated with the position of the KHI event along the magnetospheric flank, supporting the previous hypothesis. Additional correlations to solar wind velocity and pressure were also found.
2023-08-07T00:00:00ZSensitivity Study for Low Mass Dark Matter Search at DUNE
http://hdl.handle.net/10106/31702
Sensitivity Study for Low Mass Dark Matter Search at DUNE
Many anomalies in the predictions of mass and gravity at the galactic scale have been attributed to an elusive form of matter we refer to as dark matter. The excessive rotational velocity of galaxies and gravitational lensing observed in the cosmos have not found any explanation within the standard model of physics. However, dark matter itself remains undetected as it seems to only interact with gravity. If it does interact with other forces, it has a minuscule cross section similarly to the neutrino particle. Many emerging theories hope to explain the mechanisms of production and interaction of dark matter and many future experiments hope to detect it. It is thought that the detection of dark matter will be more likely by producing boosted dark matter with the use of high energy particle accelerators, and since dark matter is also thought to interact similarly to the neutrino, the use of a neutrino detector also proves to be a good choice. These are all components of the Deep Underground Neutrino Experiment (DUNE) at Fermilab. This paper explores the possibility of detection in the low mass range of light dark matter at DUNE using electron elastic scatter events in the Near detector. We use computer simulations of dark matter and neutrinos produced in the experiment and their signals in the detector to set 90% confidence limits over the light dark matter parameter space.
CARDIAC SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) SIMULATION USING THE XCAT PHANTOM AND THE SIMIND PACKAGE
http://hdl.handle.net/10106/30926
CARDIAC SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) SIMULATION USING THE XCAT PHANTOM AND THE SIMIND PACKAGE
Clinical data indicates a prevalence of transmural perfusion defects in the apical, mid, and basal segment of the left ventricle (LV) wall in patients with coronary artery diseases (CAD). To administer therapeutic regimes on myocardial function, detection of lesions in various region of the LV wall is essential. Cardiac single photon emission computed tomography (SPECT) is one of the most prevalent diagnostic tools to detect perfusion defects. Computer simulation using digital phantoms based on real patient data obtained from National Library of Medicine (NLM) offers a cost-effective approach to generate realistic imaging data to test novel imaging hardware and software ideas in the first place. This work aims to simulate cardiac SPECT using the Monte Carlo simulation (MCS) of 4D extended cardiac-torso (XCAT) Phantoms. In the first part of this work, we used the XCAT phantom program to generate different patients and perfusion defects at different location and with different sizes and severity. The XCAT phantoms are generated using nonuniform rational B-spline (NURBS) and subdivision surfaces to fit the real patient computed tomography (CT) data to provide detailed anatomical structures, as well as flexibility of definition of patient physiological motion and perfusion defects. The generation of a population of patients will provide a database that is important to investigate the impact of advanced SPECT reconstruction and compensation strategies for different patients and perfusion defects. In the second part of this work, we used the MCS package – SIMIND – to mimic 99mTc-sestamibi SPECT perfusion imaging of the XCAT phantom. The radiotracer decay, gamma photon transportation inside the human body, and photon detection by the gamma camera can be simulated in SIMIND accurately. The projection data from SIMIND highly resembles the real data acquired by a real SPECT system. These data will be used to develop and evaluate the compensation strategies for dual cardiac-respiratory gated SPECT for cardiac perfusion imaging to significantly improve the benefit-and-risk ratio of this prevalent diagnostic tool.
2022-08-17T00:00:00ZA comparative look at atomic oxygen and carbon dioxide neutral densities on Mars using data from the MAVEN satellite mission
http://hdl.handle.net/10106/30862
A comparative look at atomic oxygen and carbon dioxide neutral densities on Mars using data from the MAVEN satellite mission
This thesis uses the level 2 limb scan data from the IUVS instrument onboard the MAVEN satellite to investigate the density distributions of atomic oxygen and carbon dioxide in the lower thermosphere of Mars. In addition to examining the density as a function of spatial position, the dependencies on SZA and local time are also inspected. The data used in the study are during the time interval between October 2014 and June 2018.
Results of this study show that the density of carbon dioxide, the major species on Mars, is predominantly driven by typical atmospheric forces related to solar irradiation absorption. An atmosphere wave 2 structure appears clearly when examining the average density variation over longitudes, and an inverse relationship between the solar zenith angle and density occurs above 50 degrees SZA. During the spring and autumn equinox, the density distribution peaks about the equatorial region, and the dependence on local time shows that the density peaks in the afternoon. However, the same studies with the atomic oxygen data show more variations at all altitudes, which lead to the conclusion that oxygen is being strongly affected by other driving forces even in the thermosphere as low as 120 km. The study of carbon dioxide and atomic oxygen will contribute to primary knowledge of the Martian thermosphere and improve understanding of the driving forces that affect these species.
2020-05-14T00:00:00Z