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This interdisciplinary research centers on 21st-century queer and undocumented im/migrant cultural production and political organizing to understand questions of rights, citizenship, and belonging in the U.S. I approach citizenship and belonging from socially, physically, politically, and economically marginalized subjectivity. By analyzing cultural, visual, and literary text produced by artists who identify as women, queer, and (dis)abled, this dissertation interpellates national narratives of belonging, complicating the story of im/migrant assimilation that has dominated North American scholarship. The project centers (dis)ability as a category intrinsically linked to im/migrant subjectivity by understanding national exclusion as an expansive project grounded on colonialism that continues to shape the daily lives of people imagined as unfit citizens or those who do not belong. Through what I term the epistemology of the unsettled, I highlight the limits and possibilities of bringing together (dis)ability and im/migrant discourse. Focusing on queer and undocumented im/migrant networks of resistance reorients assimilation narratives of im/migration to emphasize the migrant relationship to (dis)ability, presents new perspectives on citizenship, and rethinks paradigms of racial liberalism and Civil Rights. Traditionally, discussions about U.S. immigration policies have focused on country-specific research and analysis, particularly on the U.S.-Mexico border or the Chinese Exclusion Act, limiting the ethnic and racial scope of conversations on im/migration. I contribute to existing scholarship by interweaving im/migrant subjects from different ethnicities, national origins, and linguistic backgrounds but living in the U.S. and responding to the weight of settler colonialism and capitalist exploitation of racialized im/migrants. I attend to the different migratory experiences alongside racial, ethnic, gender, and (dis)ability frameworks by contextualizing colonial and imperial histories to highlight the broader effects of white settler logic around race, citizenship, and borders beyond specific im/migration policies.

In many clinical trials, patients are not followed continuously. This means their vital status may not be immediately recorded. In such cases, the results from the Kaplan-Meier estimator or the log rank test, popular methods used for survival analysis, may be biased or inconsistent. Hu and Tsiatis first produced a new estimator to estimate survival distribution for right-censored data with delayed ascertainment, Van der Laan and Hubbard modified their estimator. We investigate each of these proposed estimators and their properties. Using simulations, we compare these new estimators to each other and to the Kaplan-Meier estimator using different sample sizes, different failure rates, and different maximum delay times. The public health importance of this thesis is that we can partially alleviate the problem caused by delayed ascertainment in the analysis of right-censored time to event data by choosing the most accurate and consistent estimator that accounts for the delayed ascertainment. The reduction of bias in analyses of public health data ensures that such studies are reliable so that proper inference can be made and hence, potential public health policy can be based on an accurate decision making process.

The rapid growth of the elderly population raises concerns in the United States for older people’s well-being. Effective financial management is important to the well-being of retired people since the elderly are more likely to face limited financial resources and complicated financial management tasks, such as navigating health care insurance payments and managing stocks. One way for the elderly to successfully manage their finances is to seek assistance from others. This study uses the 2000 Health and Retirement Study to examine factors affecting financial management assistance use by the elderly (individuals 65 years and older) facing difficulties managing their own finances. “Vulnerability” is suggested as a factor affecting financial management assistance use by the elderly. Vulnerability is a multidimensional concept incorporating health status, cognitive ability, and social interaction factors. The vulnerable elderly have health problems, reduced cognitive skills, and are often socially isolated due to the death of a spouse or retirement. Persons 65 years and older were found to be more vulnerable than persons younger than 65 years in terms of health status, cognitive ability, and social interaction. (n=11,492). Since vulnerability is more prevalent among the older people, the study sample was limited to persons 65 years and older. Elderly persons reporting difficulty with financial management were studied to identify factors affecting financial management assistance use by the vulnerable elderly (n=271). Logistic regression analysis revealed that age, presence of an IADL problem, depression, and computation ability affect older people’s financial management assistance use. Elderly who are older, not depressed, and have an IADL problem and computation inability are more likely to use financial management assistance. Since depressed elderly persons are less likely to use assistance even if they have difficulties managing finances, the depressed elderly may be in a vulnerable situation with respect to effective financial management. Interventions related to financial management may improve the financial well-being of the depressed elderly. The findings of this study suggest that the factors determining older people’s use of financial management assistance are physical and mental health status and cognitive ability rather than economic status.

The aim of this thesis is to investigate nonlinear dynamical systems that exist in various fields such as engineering and science. Nonlinear dynamical systems permit the understanding and development of models of simple and complex phenomena. Specifically, this thesis includes an investigation of the following systems; the logistic model, the Gompertz model, predator-prey model, and three species model. In addition, we perform a comparison between the two most popular growth models; logistic and Gompertz models from the viewpoint of variability. The main focus is on the use of Fisher information as a measure of variability/sustainability which depends on the gradient of Probability Density Function (PDF). In this work, we present two case studies for each dynamical system. The first case study describes the analysis of these systems in their deterministic conditions whereas the second one presents the investigation of these systems in their indeterministic conditions (perturbed conditions), where the model parameters involve perturbations, elucidating the effects of these perturbations on the behaviour of the system. The variation in the model parameter values is considered in order to observe the behaviour of the different dynamical systems and detect dynamical changes in the behaviour of each species. Since Fisher information is considered as a measure of an intrinsic accuracy of the dynamical systems, therefore, we obtain Fisher information for different values of parameters in order to select the optimal parameter value where a peak of Fisher information is observed, which indicates to less variability in the behaviour of the system. Thus, the existence of Fisher information peak which linked to the narrowest PDF is investigated in the frame of time trace analysis. In summary, the main contribution of this work to the field is to assess the significance of Fisher information index for nonlinear dynamical systems including perturbations in the model parameters. Applying this measure to more complicated systems and comparing the results to other widely used measures would be of interest for future work.

A nonlinear dynamical system is a mathematical model for a portion of the physical world where continuous components are interacting with each other. Such systems are complex, and it is difficult to predict how they will react towards changing the driving parameters and initial conditions. This dissertation is concerned with the numerical aspect of controlling the Lorenz system that studies the production of the magnetic field in sunspots. The study aims to do this by applying different approaches to the system.

The study of Statistical Mechanics goes back to the 1800s and the work of Boltzmann. Since that time the field has been divided into equilibrium theory and non-equilibrium theory, with the formers progression far outpacing the latter. That is until relatively recently. New insights such as the thermodynamic length, fluctuation theorems and spectral methods such as the Observable Representation have given us new tools to deal with large and complex non-equilibrium systems. In this work we will look at two specific tools in depth. The Observable Representation (OR), its irreversible extension the Non-Detailed balance Observable Representation (NOR) and the information length. The NOR allows one to take the complex and often messy calculations of a systems evolution operator and represent it with a much simpler geometric version. In this version distances correspond to relationships in the original system. We will show how these distances can be used to elucidate the underlying structure of a given system and even to control chaotic systems by forming periodic orbits from said distances. The second method to be analysed in detail is the thermodynamic length and its non-equilibrium extension the information length. This gives us a measure of distance between probability distribution the system takes in its evolution. Each distribution is represented as a point in statistical space and as the system evolves each point generates a path we can measure the distances of. This abstract space then allows us to often calculate fundamental quantities of systems under study such as the maximum available work or the dissipation as the system evolves. Both methods may seem abstract and un-necessarily far removed from the actual systems they represent. What we gain from this abstractness far outweighs its added mathematical machinery, for from abstraction we gain generality. These methods allow us to analyse huge classes of system under one umbrella, such as irreversible or chaotic systems which before were out of reach of equilibrium statistical mechanics.

Stellar rotation plays an important role in maintaining the magnetic fields inside the stellar interior through convection, and starspots are the most visible manifestation of the interplay between stellar rotation rate and magnetic fields. It is revealed through high end observations of evolution of magnetic fields and rotation rate of the Sun and other solar type stars that they exhibit a wide range of variation among their rotation rates yet there are some common ingredients such as rotational shear, turbulent transport and various nonlinear transport mechanisms which contribute towards the evolution and maintenance of the magnetic activity displayed by them. Also, these observations provide us with valuable information about the dependence of differential rotation and magnetic activity on rotation rate of stars with different ages and different rotation rates. Thus, the main challenge in dynamo theory is to explain these observations which is in fact a very strenuous problem and is challenging to do with full MHD simulations due to the various constraints such as expensive computations in terms of time and resolution. Therefore, it is useful to construct a simple parameterized model in order to understand the evolution of rotation rate and magnetic fields which can provide valuable insight into the various observations. This thesis discusses the modelling of solar dynamo and spindown of solar-type stars by using ODE and the effect of shear in kinematic dynamo in full MHD. We propose a simple parameterized model to understand the effect of nonlinear transport coefficients as well as mean/fluctuating differential rotation in the generation and destruction of magnetic fields and their capability in the working of dynamo near marginal stability. This model is then utilised to discuss detailed dynamics to understand the self-regulation of magnetic fields in solar/stellar dynamo. This work is further extended to understand the spindown of solar-type stars where the angular momentum loss is dynamically prescribed via equation of evolution of rotation rate and magnetic fields. The results obtained from this model are consistent with observations. Furthermore, regulatory behaviour of a kinematic dynamo by shear flow is investigated. Specifically, we study the induction equation by prescribing small scale velocity field to which a large scale radial/latitudinal shear is added in the direction of zonal flow. The results from numerical simulations are analysed and we conclude that the presence of large scale shear suppresses the small scale flows and results in quenching of a kinematic dynamo.