Electronic Thesis or Dissertation

Dosimetric uncertainty in very small (< 2 x 2 cm2) photon fields is notably higher that has created research questions when using small-field virtual cone with variable multileaf collimator (MLC) fields. We evaluate the efficacy of the virtual cone with a fixed MLC field for stereotactic radiosurgery (SRS) of small targets such as trigeminal neuralgia.
We employed a virtual cone technique with a fixed field geometry, called fixed virtual cone (fVC), for small target radiosurgery using the EDGE (Varian Medical Systems, Palo Alto, CA) linac. The fVC is characterized by 0.5 cm x 0.5 cm high-definition MLC field of 10 MV flattening filter-free (FFF) beam defined at 100 cm SAD, while jaws are positioned at 1.5 cm x 1.5 cm. A spherical dose distribution equivalent to 5 mm cone was generated by using 10–14 non-coplanar partial arcs. The dosimetric accuracy of this technique was validated using the SRS MapCHECK (Sun Nuclear Corporation, FL) and the EBT3 (Ashland Inc., NJ) film based on absolute dose measurements. For the quality assurance (QA), 10 treatment plans for trigeminal neuralgia consisting of various arc fields at different collimator angles were analyzed retrospectively using 6 MV and 10 MV FFF beams, including the field-by-field study (n = 130 fields). Dose outputs were compared between the SRS MapCHECK measurements and Eclipse treatment planning system (TPS) with Acuros XB algorithm (version 16.1). In addition, important clinical parameters of 15 cases treated for trigeminal neuralgia were evaluated for the clinical performance. Moreover, dosimetric (field output factors, dose/MU) uncertainties considering a minute (± 0.5–1.0 mm) leaf shift in the field defining fVC, were examined from the TPS, SRS diode (PTW 60018) measurements, and Monte Carlo (MC) simulations.

This dissertation is a study about applied dynamical systems on two concentrations. First, on the basis of the growing association between opioid addiction and HIV infection, a compartmental model is developed to study dynamics and optimal control of two epidemics; opioid addiction and HIV infection. We show that the disease-free-equilibrium is locally asymptotically stable when the basic reproduction number R0 = max(Ru0; Rv0) < 1; here Rv0 is the reproduction number of the HIV infection, and Ru0 is the reproduction number of the opioid addiction. The addiction-only boundary equilibrium exists when Ru0 > 1 and it is locally asymptotically stable when the invasion number of the opioid addiction is Ruinv < 1: Similarly, HIV-only boundary equilibrium exists when Rv0 > 1 and it is locally asymptotically stable when the invasion number of the HIV infection is Rvinv < 1. We study structural identifiability of the parameters, estimate parameters employing yearly reported data from Central for Disease Control and Prevention (CDC), and study practical identifiability of estimated parameters. We observe the basic reproduction number R0 using the parameters. Next, we introduce four distinct controls in the model for the sake of control approach, including treatment for addictions, health care education about not sharing syringes, highly active anti-retroviral therapy (HAART), and rehab treatment for opiate addicts who are HIV infected. US population using CDC data, first applying a single control in the model and observing the results, we better understand the influence of individual control. After completing each of the four applications, we apply them together at the same time in the model and compare the outcomes using different control bounds and state variable weights. We conclude the results by presenting several graphs.

Mixed conifer forests in the Sierra Nevada, California, face threats from frequent highseverity fire associated with climate change and fuel accumulation leading to vegetation shifts at local and landscape scales. Under rapid climate change, a clear understanding of how vegetation responds to single and/or repeated wildfires is still lacking and needs to be investigated. Using field and satellite data, the effects of wildfire on vegetation dynamics were explored at the plot and landscape levels in this dissertation project. Results from the field data suggest that management activities may be required in high-severity burned areas to restore dominance of mixed conifer forests and regain historical species composition in areas where live trees persist. Results from satellite data suggested that large shrub patches, created after mixed severity fire, fragment the homogenous mixed conifer dominated forest of the Sierra Nevada to create a more heterogeneous landscape, however the extent of diversity and fragmentation were dependent on fire severity and scales. Natural wildfires may restore landscape heterogeneity to conditions equivalent to the pre-Columbian era, but effects under the projected climate change scenario for 21st century remain uncertain. Mixed conifer dominated forests are predicted to be the dominant component of the Sierra Nevada landscape under historical fire probabilities and excluding higher probability of high-severity fire over the next 100 years.

A review of the literature revealed the need to further explore continuing-generation college students attending community colleges. This case study sought to understand the choice process of continuing-generation, direct-entry college students who enrolled in Miami Dade College (MDC), a baccalaureate community college. This research was planned prior to the COVID-19 pandemic, yet was conducted during the pandemic, creating a unique context for the study. A total of 25 participants were interviewed, including continuing-generation students, parents/family members, and high school personnel. This study used Hossler and Gallagher’s (1987) choice model as the conceptual framework to address how and why continuing-generation college students decided to pursue higher education in a community college rather than a traditional four-year college or university.
The study derived five findings: financial considerations, addressing affordability and cost in the choice process; family influence and support, describing the role family play in the college selection process; proximity and accessibility, addressing how MDC is a good choice for being “close to home” and being accessible to students who may not have otherwise accessed higher education; institutional reputation, and its importance in the selection process as related to students’ knowledge of MDC, transferability options, faculty and opportunities; and college preparedness, addressing the choice process in terms of student exposure, academic readiness, and college transfer preparedness.

Due to the phenomenon of gravitational lensing, light from distant sources may appear as several images. The “image counting problem from gravitational lensing" refers to the question of how many images might occur, given a particular distribution of lensing masses. A common model treats the lensing masses as a finite collection of points situated in a finite collection of planes. The position of the apparent images correspond to the critical points of a real-valued function and also as solutions to a system of complex rational equations. Herein, we give upper bounds for the number of images in a point mass multiplane ensemble with an arbitrary number of masses in an arbitrary number of planes. We give lower bounds on the number of solutions in a closely related problem concerning gravitational equilibria. We use persistence homology to investigate two different stochastic ensembles. Finally we produce a multiplane ensemble, related to the maximal one plane ensemble, that produces a large number of images.

“Psychoanalysis and Dreams in Toni Morrison’s Beloved: Exploring Continuities and Ruptures of Trauma Cycles,” explores the function of dreams as they relate to trauma and memory. This thesis argues that a character’s engagement with their dreams leads to a healing discontinuity of traumatic cycles, while dreams left untouched likely result in historical and transgenerational cycles and the continuation of personal trauma and its symptoms. This thesis compares the dreams of the characters Beloved and Denver. In part because Morrison notes her influence from both African and Western traditions, this paper argues that a sufficient understanding of dreams in her work requires a multiplicity of approaches. This thesis draws on a plurality of ideas from African and Western perspectives of dreams, the intersections of race and psychoanalysis, and trauma theory. The focus on dreams extends the arguments of critics who analyze trauma in Beloved more generally.

The aim of this thesis is to examine biracial family-building and the reimagination of the ideal home in post-WWII English literature using Hanif Kureishi’s The Buddha of Suburbia and Zadie Smith’s White Teeth. Focusing on biracial children of both the Caribbean and South Asian diasporas, this thesis explores the nuances with which black self-identification is curated and how blackness as both a racial and social category in the UK is prescribed and performed depending on the Black and Brown biracial characters’ social location to white characters and family units. Mark Christian’s Mulitracial Identity: An International Perspective and Zygmunt Bauman’s Modernity and Ambivalence operate as lenses to better understand the social classification of mixed-families individuals as strangers in England and how biracial individuals are strangers to their families and respective homelands. This thesis will also argue that Black biracial women’s identity-building is oftentimes more stifled in England than their South Asian male counterparts as it is dependent on a reconciliation with their family’s erased past.

Quantum Gravity attempts to unify general relativity (GR) and quantum theory, and is one of the challenging research areas in theoretical physics. LQG is a background-independent and non-perturbative approach towards the theory of quantum gravity. The spinfoam formulation gives the covariant path integral formulation of LQG.
The spinfoam amplitude plays a crucial role in the spinfoam formulation by defining the transition amplitude of covariant LQG. It is particularly interesting for testing the semiclassical consistency of LQG, because of the connection between the semiclassical approximation of path integral and the stationary phase approximation. The recent semiclassical analysis reveals the interesting relation between spinfoam amplitudes and the Regge calculus, which discretizes GR on triangulations. This relation makes the semiclassical consistency of covariant LQG promising. The spinfoam formulation also provides ways to study the n-point functions of quantum-geometry operators in LQG.
Despite the novel and crucial analytic results in the spinfoam formulation, the computational complexity has been obstructed further explorations in spinfoam models. Nevertheless, numerical approaches to spinfoams open new windows to circumvent this obstruction. There has been enlightening progress on numerical computation of the spinfoam amplitudes and the two-point function. The numerical technology should expand the toolbox to investigate LQG.

Coastal landscape plays a vital role in reflecting various natural processes. Vegetation resource management improves the quality of life above the surface of the earth. Due to factors such as climatic change, urban development, and global warming, monitoring the coastal region as well as its vegetation has indeed become a challenge to mankind. The purpose of the study is to propose an effective low-cost methodology to monitor the 120- acre Jupiter Inlet Lighthouse Outstanding Natural Area (ONA) located in Jupiter, Florida (USA) using Unmanned Aerial Systems (UAS) Imagery deployed with RedEdge Micasense Multispectral sensor having five bands. Since, UAS provides high resolution imagery at lower altitudes, it has a lot of potential for variety of applications. This research aims to (1) Automate the extraction of shoreline and coastline through Modified Normalized Difference Index (MNDI), thereby comparing it with the manually digitized shoreline using transect-based analysis (2) Automate the volume change computation, as the area has been affected due to various natural and anthropogenic factors in the past few decades. (3) Perform shoreline change detection for the time period 1953 to 2021 (4) Develop an algorithm to differentiate ground and non-ground points along the shore region and generate Digital Terrain Model (DTM) (5) Land use and Land cover (LULC) mapping using different band combinations and compare its result using deep learning approach.

A set of informal street codes that govern inner city environments in the U.S. have been identified by scholar Elijah Anderson. Anderson’s street code has been analyzed in a variety of ways, including via rap lyrics. This analysis documented how reflective culture and the street code is within a nontraditional source - music. By researching a Mexican sub-genre of music known as narco corridos, I extend this work with a qualitative lyrical content analysis. Using a sample size of 100 narco corridos sourced via the music application Spotify, Anderson’s framework was used as a starting point to uncover themes of violence, poverty, and respect. Findings support the existence of the street code in a violent Mexican subculture. To conclude, using music as a nontraditional academic source can be a powerful way to analyze and comprehend crime and culture in other areas of the world.