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Photoacoustic Tomography Image Reconstruction Using Deep Learning
Get PDFIn photoacoustic tomography, sparse sensing and limited view configurationhave been commonly applied to biomedical imaging due to the spatial constraint of the imaging source. In addition, using a large number of sensors requires sophisticated designs of imaging instruments and expensive computations to process multi-channel data, limiting the use of image reconstruction algorithms for real-time applications. In these scenarios, conventional methods fail to reconstruct high-quality images and result in the reconstructed images being contaminated by severe artifacts stemming from limited view and sparse sampling of the signals acquired by transducers. To overcome these challenges, deep learning methods are introduced. The following manuscripts are organizedxvii into three sections: (1) a comprehensive study of deep learning approaches in photoacoustic tomography (2) Fourier neural operator for solving photoacoustic wave equations (3) incorporating learned physical model into learned iterative reconstruction to speed up the photoacoustic tomography reconstruction. The rationale of the manuscripts is based on our findings. In (1), the results demonstrated that model-based learned iterative reconstruction methods perform the best in photoacoustic image reconstruction compared to the pure data-driven deep learning methods. However, superior reconstruction performance comes at the expense of computational speed due to repeatedly running simulations of physical models in the model-based learned iterative reconstruction pipeline. Therefore, in (2), deep learning-based alternatives to the conventional solver for physical models were explored. Based on the findings in (2), learned physical models were incorporated into the learned iterative reconstruction pipeline in (3) which reduced the computation time originally required by conventional methods. Consequently, the proposed approaches maintained a comparable reconstruction performance to the model-based learned iterative methods and had a 9X reduction in computational speed
On Evaluating Cyber Defense by Humans and Reinforcement Learning Agents
Get PDFA significant factor that drives the investment in/integration of a cyber defense technique is its proven effectiveness, in terms of performance, usability, and security, against an intended adversary. Measuring the effectiveness of security defenses is complex, mainly because evaluation is a never-ending process, a natural outcome of evolving technologiesand adversarial capabilities. To facilitate cyber defense evaluation, it is, thus, imperative to examine novel methods through which researchers could gain a deeper understanding of adversarial behavior from both technical and cognitive perspectives. To this purpose, the first part of this dissertation investigated the applicability of using two popular paid crowdsourcing platforms to run hacking experiments (i.e., Capture-the-Flag challenges). Paid crowdsourcing platforms can potentially facilitate studies in the Oppositional Human Factors (OHF), a field that considers attackers’ cognitive biases when examining the effectiveness of defensive techniques. Such platforms are unique in that they offer schemes eliciting real-world adversarial behaviors (e.g., maliciousness) while minimizing the constraints imposed by typical recruitment methods. Findings showed that the platforms vary significantly in data quality and workers’ technical skills. As a result, I examined the possibility of using Prolific to conduct a randomized study to analyze attackers’ cognitive biases and limitations when they encounter deception under an incentive-compatible scheme (i.e., monetary) and a design different from prior studies. Findings showed consistent behavioral patterns between the populations under consideration but revealed some shortcomings of online cybersecurity experimentation. As online experimentation with qualified human participants remains challenging, the third part of this research examined another alternative in which datasets from experimental psychology studies designed to analyze deficits in decision-making processes (e.g., gambling tasks) are used to guide the design of human-like cyber agents. More specifically, I investigated the role memory systems and settings play in predicting the behavior of healthy and unhealthy populations. The motivation behind this work came from the realization that healthy individuals and individuals with pathological tendencies—the latter are more inclined to commit cyber crimes [5]—exhibit different risk attitudes that could be partially attributed to how memories are processed and used to guide future decisions. The results demonstrated differences in the role memory systems and settings play in predicting actions taken by the populations under consideration. Having examined the role of memory in predicting real-world behavior, I augmented reinforcement learning agents with similar settings, analyzed the agents’ behavior in simulated network environments, and observed interactions between the type of memory systems used to guide the agents’ learning process, the type of experiences used in the learning process, the underlying learning strategy, and the observation spaces. The results highlighted the importance of analyzing the aforementioned factors when designing predictive models for adversarial decision-making
Large v Small Organization Software Development: Are Software Development Best Practices One-Size Fits All?
Get PDFThis research examines the differences in the way large and small organizations approach software development to better understanding if small organizations should attempt to model large organizations' practices. Practices examined include software development methodology, development tooling, how organizations deal with legacy software, documentation practices, testing practices, and how organizations differ in their code and development practice quality metrics. Mixed method research was applied starting with a qualitative semi-structured survey of 11 participants followed by a broader quantitative survey. Our analysis showed differences that could be statistically tracked to organization size in 4 of the 6 practices researched. Semi-structured interview responses did not always match results from the survey, indicating there may be common misconceptions that do not match reality when it comes to how large and small organizations operate. In one significant finding, a statistical correlation was discovered between large organization size, worker specialization, and the use of formal test plans on a low change failure rate
"A Great Uneasiness in Our County": Slavery and Its Influence on Family and Community Stability in Northern Virginia, 1782-1860
Get PDFAdopting a comparative approach, this dissertation examines the dynamics of control, resistance, and adaptation to enslavement along the borderlands of the enslaved South in northern Virginia from 1782 to 1860. The focus on three contiguous counties, Fauquier, Loudoun, and Prince William shows that despite similar political and cultural influences and location, each county developed subtle, yet distinct differences in patterns of slave ownership, flexibility towards emancipation, periods of enslaved resistance, and methods of enforcing racial control. This study investigates these local differences, their effect on the stability of enslaved families and how perceived threats to masterly control shaped community reactions. Because of its position upon the fringes of the slave South and in proximity to avenues of escape, northern Virginia presents a compelling location for study of the role of enslaved families and communities on slave societies. This dissertation exposes sources of tension through a close reading of county records such as deeds, wills, patrol accounts, tax records, and criminal case files combined with state documents, legislative petitions, church minutes, private correspondence, Freedmen's Bureau records, newspaper accounts and runaway advertisements. Major questions reveal the particular dynamics of each county's slave society through three main themes of identity, resistance, and perceptions of control. First, how did each county maintain an identity as a slave society in proximity to free states and anti-slavery rhetoric and amidst demographic changes and economic stresses? Second, how did these changes and stresses affect enslaved family stability and lead to acts of resistance? Third, how did communities, churches, and local courts support the rights of masters to hold slaves and how did enslaved persons manipulate these local powers to assert limited control over their lives and paths to freedom? A confluence of factors created distinct periods of unrest in each county: These arose when enslaved resistance challenged visions of masterly control; when the number of runaways and escape strategies changed; when slave values rose and fell; when options for emancipation crested and diminished; when abolitionist influences seemed to threaten community solidarity; and when public fears that enslaved resistance represented a wide-spread movement against slaveholders rather than singular transgressions. Even within a relatively small geographic space of the slave South, the particular location and community composition diversely affected the nature of enslavement. County-wide differences in the level of tolerance shown for manumissions and towards manumitted slaves threatened enslaved family stability. Similarly the decisions of some slaveholders to limit their slaveholdings through slave sales or to seek better opportunities through western migration dismembered enslaved families. Acts of resistance often coincided with these periods of intense enslaved family disruptions or preceded such anticipated crises such as a master's death. Runaways coordinated escapes with work schedules or seasonal (and predictable) movements of people that varied by and within each county. When enslaved families felt most threatened and options for freedom seemed most limited, violent resistance erupted in slaveholding communities. These acts of resistance combined with fears of abolitionist influences threatened the security of slaveholders; local communities then ordered out patrols or created extralegal groups for policing. Tolerance for manumission, frequency of runaways, fluctuating values of enslaved bodies, and acts of violent resistance not only altered the way that slaveholders perceived the importance of enslaved chattel to personal wealth and community control but also determined how enslaved families recognized and responded to threats to stability and actively resisted forced separation. By tracking these changes over time a more complete picture develops of when, why, and how enslaved persons challenged their subordinate status and when the public perception of these acts of resistance shifted from uneasy fears to wide-spread threats that seemed to require community action. Discerning the ability of enslaved persons to make even small improvements in their lives in slavery rests firmly at the core of this study through understanding how they cultivated beneficial networks of support and influence, sought out resources to mitigate the deprivations of enslavement, and forged alliances that generated income and local support for self-purchase. Considering these acts of self-affirmation not only in relation to broader changes across the slave South, but more importantly within their context as a borderlands underlines the importance of place in creating subtle, yet telling differences in the stability of a slave society and thus challenges sectional, regional, or even state-wide generalizations of such societies' uniform identity
Living with Disaster: Risk, Housing Instability, and Post-Disaster Migration
Get PDFThis thesis examines the 2021 Caldor Fire and the experiences of survivors with insurance and housing. The purpose is to show that the effects of disasters extend beyond what is typically considered the "disaster zone." The thesis relies on 16 interviews conducted at the beginning of 2022 and supplementary data from 30 GoFundMe campaigns. An analysis of the data finds that survivors could not acquire insurance before the fire because insurers had dropped policies due to an increased perceived risk established by previous fires. Survivors also could not receive federal assistance because methods used by FEMA overestimated how many were insured in the affected area. Ultimately, the Caldor Fire forced survivors into a competitive housing market, exacerbating the state's housing crisis. The results show that smaller-scale disasters impact surrounding communities, counties, and states in a way that is currently not being monitored or discussed. The thesis also finds that public sociologists have a role in sharing survivors' experiences with larger publics
Cinema Road
No full textThis thesis has been embargoed for 10 years. It will not be available until July 2031 at the earliest.Bobo, the narrator and main character, lives with his younger sister (Titi) and grandmother in Sagamu, a town in southwest Nigeria. His mother is dead, his father is in political exile, and his hometown - under the threat of government assault - is run by a "vigilante" group headed by his uncle, Kokonsari and his boss, whom everyone calls MC Hammer. Bobo’s preoccupations at the beginning of the story are helping his father return home, and protecting his sister and grandmother in the unstable situation they live in. He thinks he is prepared to do anything to make those possible, but soon realizes, however, that not only would he have to make some major tradeoffs to help the people he loves, but that even his best efforts would fall short often. He is, after all, only eleven years old.2031-07-3
Correlations Between Cranial and Inner Ear Morphologies of Odontocetes
Get PDFThe odontocete skull shows features that indicate specialized behaviors implemented during the animal's life such as echolocation and feeding preference. Echolocation is a highly specialized adaptation for feeding and navigation that involves the production of high frequency sound and the reception of its echo. Previous studies show that measurements of bony labyrinths of the inner ear show interspecific differences in hearing frequency ranges of odontocetes. We can use CT scanning technology to take detailed measurements of these features. Features of the inner ear that correlate with high frequency hearing include a low basal ratio, greater inter-turn distance, and lower number of turns of the cochlea. Cranial features such as asymmetry and telescoping may be involved in high frequency sound production. Odontocetes use echolocation to assist in a variety of methods to capture prey such as suction and raptorial feeding. These feeding strategies may be determined by cranial morphological features such as longirostry (long rostrum) and brevirostry (short rostrum). Finding adaptive and functional relationships between these features is an important part of understanding the evolution of odontocetes and how they behave today. To determine if there are any evolutionary correlations between cranial features for feeding, sound production, and sound reception, I collected existing measurement data of inner ear and cranial features ("characters") from a total of 65 extinct and extant odontocete species. These data incorporate all the major extinct and extant odontocete families. I mapped the characters onto phylogenetic trees. Phylogenetic generalized least squares statistical analysis was used on the phylogenetic trees to assess correlations between characters. The results provide evidence that cranial asymmetry is correlated with echolocation. There is no evidence that cranial telescoping is correlated with echolocation. The findings in this study also indicate that brevirostrine odontocetes emit higher frequencies than longirostrine odontocetes. Lastly, this study finds a positive correlation between most inner ear features, except for comparisons involving number of cochlear turns and basal ratio. This reflects how size dimensions of the cochlea are directly proportional to one another. This work highlights and clarifies relationships among cranial features for echolocation and feeding within odontocetes
Belonging from the Perspective of One School-Aged Child with an Intellectual and Developmental Disability
Get PDFThe purpose of this study was to explore the phenomenon of belonging from the perspective of Cora, a school-aged child with an intellectual disability and significant support needs. Multiple data sources, including interviews, observations, field notes, and visual aids were coded and analyzed. Findings from the study illuminated how Cora’s microsystem influenced her sense of belonging in the school, her neighborhood, and her community
Comparison of Forensically Significant Carrion Insects at Buried vs. Surface Remains in Northern Virginia
Get PDFSeveral factors complicate using necrophagous and other forensically important insects to determine a post-mortem interval in death investigations. First, insects demonstrate wide temporal ranges and spatial diversity, making it difficult to predict which species will be present. Secondly, carrion insects have consistent patterns in carcass size preference, and such patterns may indicate that dismembered remains, which represent smaller food sources, have different patterns of succession than those documented for whole cadavers. Although carrion insect succession has been well documented on whole human and porcine remains, there is limited documentation of insect succession for sectioned, or dismembered, remains. This study compares data collected from dismembered porcine remains in Central Virginia to published data for whole cadavers. Additionally, data was collected from surface-deposited dismembered and from buried remains to address differences between whole and dismembered remains under both types of conditions. Results of my study suggest that while fauna on surface dismembered remains followed a consistent successional pattern, the insects present were typical of later stages of decomposition on whole bodies. Surface dismembered remains also showed higher abundances of different Diptera taxa, such as Heleomyzidae, Sepsidae, and Phoridae, compared to the most common families – Calliphoridae, Muscidae, and Sarcophagidae – traditionally reported for whole remains. Additionally, the final amounts of tissue remaining were similar for both surface-deposited and buried dismembered remains, suggesting that smaller body parts may decompose equally rapidly regardless of the level of activity of insects or the diversity of arthropod fauna. Finally, fauna on buried remains consisted of understudied taxa that recent studies show have species-specific food preferences, and therefore, that might be of forensic significance, such as Collembola, Mycetophilidae, and Acariformes mites
DEVELOPMENT OF PROGRAMMED CELL DEATH LIGAND DERIVED PEPTIDES FOR THE TREATMENT OF AUTOIMMUNE DISEASES
Get PDFProgrammed cell death protein 1 (PD-1) is a surface protein that is involved in regulating immune responses by suppressing T cell activity. While in some cases, suppression of the immune system is beneficial, it is harmful during cancer where immune cell evasion occurs. On the other hand, it is also harmful when the immune system runs unchecked and highly activated immune cells remain in circulation. As a result, the focus of immunotherapy research has broadened to include inhibitors that target PD-1 and other regulatory checkpoints in the immune system. Here, we will focus evaluating peptides, or short sequences of amino acids, based on the original protein structure of the ligand (PD-L1) in complex with PD-1. In T cell activation assays involving reporter cell lines as well as primary human peripheral blood mononuclear cells, peptides exhibited inhibitory effects on activation including inhibiting cytokine secretion and expression of cellular activation markers. By associating a costimulatory protein, inducible T cell costimulator (ICOS) in a combinatorial peptide, a lead candidate retained inhibitory activity in an in vivo sepsis model where mice were challenged with bacterial lipopolysaccharide. Peptides were also evaluated in two autoimmune disease models: inflammatory bowel disease and cytokine release syndrome. By exhibiting immunosuppressive activity in in vitro and in vivo models, PD-L1 derived peptides show potential for therapeutics for autoimmune diseases