My dissertation investigates the reasons behind the persistence of income among individuals and US counties. I look at the role of initial conditions in explaining current level of income. In my first essay, I look at how childhood neighborhood conditions affect income of a person. To study persistence, I model income as an autoregressive process where the coefficient on the lagged dependent variable heterogeneous across individuals. In my second essay, I derive a new way to measure chronic poverty, or long term poverty. Current measures of chronic poverty cannot be used to compare improvements of poverty rates over time. Using my measure, one can compare to see if chronic poverty rates changed over time. My third essay looks at the historical reasons behind differences in income between rich and poor counties in the US. There are about 250 counties in the US where poverty rates have been above 20 percent for the last 40 years. I look at whether current and past factors, or differences in technologies is the main reason behind persistence of high rates of poverty in these counties. Overall, I find that childhood neighborhood conditions have a big effect in determining the coefficient on the lagged dependent variable, that is, childhood neighborhood conditions affect persistence of income. I find that improving neighborhood poverty rates by one percentage point and father’s education by one year bring the greatest improvement of social welfare. In my second essay, I show the importance of measuring chronic poverty separately from total poverty; for example, between 2000 and 2005, total poverty declined, but chronic poverty rates actually increased, which shows that the long-term poor got worse off during that time period. In my last essay, I find that some US counties remained poor mainly because of differences in factor endowment, and past and present levels of human capital explain most of the differences in current level of income between poor and non-poor counties. Differences in factor endowments explained 80 percent of income between poor and non-poor counties, while technology accounted for only 20 percent of the difference.

This study made a comparative analysis of certain selected characteristics of a group of academically able male youth who persisted and those who did not persist in a five-year academic sequence in mathematics and science. Two major questions were dealt with in this study: 1. Can the persisting youth as a group be distinguished from those youth who did not persist in this academic sequence on the basis of their functioning in certain nonintellective areas? 2. Are the performances of the persisting youth on certain dimensions elevated in the same directions as are the performances of mature creatives who have been intensively studied on the same dimensions?

This study was designed to develop a procedure for the identification of freshman students at risk in the academic and social integration process at Texas Christian University. The data for the study were collected from the Student Information Form (SIF) and student records system at Texas Christian University. The data included demographic, attitudinal, educational background and one-year persistence indicators (retain and drop) as well as one-year cumulative grade point averages for the fall 1990 entering freshman class.

Purpose: The purpose of this study was to determine if traditional indicators of college readiness were better predictors of students’ first semester college GPA and persistence to the second year of coursework compared to non-traditional indicators of college readiness. Specifically, this study analyzed the predictive validity of high school class rank and ACT/SAT scores compared to that of the psychosocial skills measured by the ACT Engage on students’ first semester college GPA and their likelihood of enrollment in the second year of college coursework. Methodology: Linear and logistic regression models were used to examine the effect of gender, age, ethnicity, socioeconomic status, high school rank, Texas Success Initiative college readiness scores, SAT or ACT scores, and the ten themes of the ACT Engage Inventory (dependent variables), on students’ first semester college GPA and rate of persistence to the second year (independent variables). A sample of 4,379 first semester college freshmen participated in this study. Findings: Results indicated that high school rank, ACT/SAT scores and psychosocial skills measured by the ACT Engage theme academic discipline were accurate predictors of college performance. Results regarding the predictive power of traditional academic and non-traditional psychosocial predictors of persistence were less definitive. Students qualifying for federal financial assistance and female students showed the greatest likelihood of not returning for the second year of college. Research Limitations: One limitation of this study occurred because separate ethnicities were not evaluated as independent variables. Additionally, further research should occur regarding the relationship between the independent variables of gender and socioeconomic status and the dependent variable persistence. Practical Implications: Due to the predictive power of high school class rank, college entrance exam scores, and the psychosocial skill of academic discipline, educators and policy makers should design targeted preparation and support initiatives around improving students’ skills in these areas. Recommendations for such initiatives were provided. Value of Paper: This paper is valuable to educators at the secondary school and university levels because results can be used to design preparation and support programs in order to improve students’ performance and persistence at the college level.

The Chlamydiaceae are a bacterial family that contains a single genus: Chlamydia. The genus Chlamydia consists of 9 species that are obligate, intracellular pathogens. Untreated C. trachomatis infections can lead to serious health ramifications, such as ectopic pregnancy, tubal factor infertility, pelvic inflammatory disease, and long-term pelvic pain. In this study, it was found that a primary antibody dilution of 1:400 using methanol fixed HeLA cells, as derived from Carrasco, et al. protocol, was only optimal for PMP-C staining. Pmp-A, Pmp-B, and Pmp-F were found to stain brighter with formaldehyde fixed, infected HeLa cells and using different primary antibody dilutions. The manuscript by Carrasco, et al., demonstrated that chlamydial persistence caused by penicillin-stressed conditions showed a decrease in Pmp-B and Pmp-C protein expression between 24-48 hpi, while Pmp-A and Pmp-F expression stayed the same under the stressful conditions. We hypothesized that under HSV- induced persistence the same results would occur. However, our data indicates that the chlamydial response to stressful conditions is not the same among persistence-inducers and implies that various inducers of persistence may affect PMP expression differently. Initially, we also hypothesized that PMP expression could be utilized as an indicator to determine whether an infected individual has a productive or persistent chlamydial infection. Due to the experiments’ results, PMP expression is most likely not a good marker to identify the type of chlamydial infection (ie. productive or persistent) in the host.

La transmission des virus grippaux de type A s’effectue via l’eau, l’air ou les surfaces. Elle implique donc toujours une étape dans l’environnement, durant laquelle les virus sont inactivés plus ou moins rapidement en fonction du sous-type ou de la souche virale analysés. Cependant, à ce jour, les facteurs moléculaires déterminant la stabilité des particules virales en dehors de l’hôte restent largement méconnus. Dans le but d’identifier ces déterminants, nous avons généré différentes combinaisons de réassortiments entre deux virus grippaux de sous-types H1N1 possédant un phénotype de stabilité différent. Les stabilités respectives de ces virus réassortants ont été évaluées dans un environnement-modèle, puis comparées entre elles. Pour cela, nous avons utilisé un système d’analyse en temps réel des cultures cellulaires, permettant de calculer, pour chacun des virus testés, une pente d’inactivation moyenne et, in fine, de mesurer l’influence respective de chacun des segments viraux sur le phénotype de stabilité des virus. D’après nos résultats, le phénotype de stabilité des virus grippaux est majoritairement déterminé par l’hémagglutinine (HA) et la neuraminidase (NA), qui sont les principales glycoprotéines de surface de ces virus. De plus, nous avons identifié des changements d’acides aminés dans la HA et dans la NA, qui ont pour effet une diminution ou une augmentation de la stabilité des particules virales dans l’environnement. Nous avons également montré qu’un virus avec un gène de la HA codons-optimisés, et donc porteur de mutations synonymes, suffit pour augmenter significativement la stabilité des particules virales dans l’environnement. La stabilité de la HA à pH acide, le taux d’expression de la HA dans les cellules infectées, et le nombre de sites de fixation aux ions calcium dans la NA sont modifiés par les mutations décrites dans cette étude, et sont donc des facteurs de stabilité des particules virales. De plus, une analyse en microscopie a permis de montrer que les virus inactivés dans l’environnement peuvent fixer leurs récepteurs cellulaires, mais sont incompétents pour induire l’étape de fusion dans l’endosome nécessaire à l’entrée des virus dans la cellule. Ces deux étapes du cycle viral sont dépendantes de la HA. Dans l’ensemble, nos résultats montrent l’importance de la HA et de la NA des virus grippaux dans la détermination du phénotype de stabilité des virus grippaux dans l’environnement. Par conséquent, la diversité connue des HA et NA dans la nature laisse supposer des variations fréquentes du phénotype de stabilité de ces virus. Leur étude pourrait permettre de mieux décrire l’écologie et l’épidémiologie de ces virus. L’analyse des données épidémiologiques et climatiques des épidémies de grippe saisonnière, sur 5 ans et dans 13 pays, a ainsi révélé une différence de distribution des virus H1N1 et H3N2, en fonction de la température hebdomadaire dans ces pays. La comparaison de la stabilité de ces virus sur des surfaces, à 4 °C et à 20 °C, suggère que la distribution des sous-types viraux au début des épidémies est en partie régulée par leur stabilité en fonction de la température / The transmission of Influenza A viruses (IAV), either airborne in mammals or oro-faecal in aquatic birds, submits viral particle to a wide range of environmental conditions. These environmental conditions modulate IAV survival outside the host, which is also dependent on the viral subtype or strains. To date, the molecular drivers of IAV environmental persistence remain to be identified. In order to identify IAV molecular drivers of the environmental persistence, we generated different reassortant viruses between two H1N1 viruses that do not have the same stability outside the host. To this purpose, we performed survival kinetic and compared the inactivation slope of generated reassortant viruses in our controlledenvironment, using a real time cell analysis system. Our results demonstrate that the hemagglutinin (HA) and the neuraminidase (NA) are the main viral segments driving IAV environmental persistence. In addition, mutations driving viral stability in the environment were identified in the HA and NA amino-acid sequences. We also demonstrated that synonymous mutations introduced in the HA, using a codon-optimization strategy, drive the environmental persistence of IAV. The HA stability at low pH, HA surface expression levels in infected cells and the number of calcium binding sites of the NA were alternately changed by the mutations described in our study, indicating that these are stability determinants of IAV survival outside the host. Then, the sequential events of viral entry were analysed with fluorescence microscopy assays, showing that viral particles being exposed for a long period in saline water at 35°C are still able to bind their cellular receptor whereas the HA-mediated fusion within the endosome is not possible anymore. These two steps of the viral cycle are mainly mediated by the HA protein. Altogether, these result highlight the importance of the HA and the NA proteins, driving the environmental persistence of IAV. Given the known diversity of these two proteins in nature, this arouses interest in studying IAV environmental persistence at a more global scale. Such study could improve our knowledge on IAV ecology and epidemiology. Epidemiologic and climatic data analyse of human seasonal influenza viruses during 5 years and from 13 countries revealed that H1N1 virus and H3N2 virus distribution differs according to the mean weekly temperature in these countries. We then compared the H1N1 virus and H3N2 virus persistence on stainless steel surface at 4 °C and 20 °C, and the preliminary results suggest that IAV seasonal subtypes distribution might be partly regulated by their stability according to the temperature

<p>In this thesis we explore and extend the theory of persistent homology, which captures topological features of a function by pairing its critical values. The result is represented by a collection of points in the extended plane called persistence diagram.</p><p>We start with the question of ridding the function of topological noise as suggested by its persistence diagram. We give an algorithm for hierarchically finding such epsilon-simplifications on 2-manifolds as well as answer the question of when it is impossible to simplify a function in higher dimensions.</p><p>We continue by examining time-varying functions. The original algorithm computes the persistence pairing from an ordering of the simplices in a triangulation and takes worst-case time cubic in the number of simplices. We describe how to maintain the pairing in linear time per transposition of consecutive simplices. A side effect of the update algorithm is an elementary proof of the stability of persistence diagrams. We introduce a parametrized family of persistence diagrams called persistence vineyards and illustrate the concept with a vineyard describing a folding of a small peptide. We also base a simple algorithm to compute the rank invariant of a collection of functions on the update procedure.</p><p>Guided by the desire to reconstruct stratified spaces from noisy samples, we use the vineyard of the distance function restricted to a 1-parameter family of neighborhoods of a point to assess the local homology of a sampled stratified space at that point. We prove the correctness of this assessment under the assumption of a sufficiently dense sample. We also give an algorithm that constructs the vineyard and makes the local assessment in time at most cubic in the size of the Delaunay triangulation of the point sample.</p><p>Finally, to refine the measurement of local homology the thesis extends the notion of persistent homology to sequences of kernels, images, and cokernels of maps induced by inclusions in a filtration of pairs of spaces. Specifically, we note that persistence in this context is well defined, we prove that the persistence diagrams are stable, and we explain how to compute them. Additionally, we use image persistence to cope with functions on noisy domains.</p> / Dissertation

In recent years, engineering education has witnessed a sharp increase in research aimed at the outcomes of academic success and persistence within engineering programs. However, research surrounding the key forces shaping student persistence remains unknown. This study explores enhancements and broader perspectives of learning; the relationship among dimensions of resilience theory and learning styles in engineering students to identify elements of both that contribute towards academic persistence and to determine which components of both contribute towards strengthening students’ academic persistence in engineering. The study was conducted using two quantitative self-reporting instruments to measure resilience and learning style preference, the Personal Resilience Questionnaire (PQR) and the Index of Learning Styles (ILS). Retention was measured as the continuous enrollment of a student into the second semester of the first-year engineering program. Results indicate that the following have a statistically significant effect on student persistence in engineering programs at Texas A&M University: learning style construct sequential; resilience constructs positive (self) and focus; with both tools combined, positive (self), organized, positive (world), flexibility (self) and focus; and a newly combined construct, Walton’s self-efficacy.

This thesis presents three chapters on the subject of unemployment persistence. Two of the chapters are empirically focussed and the other is a purely theoretic work. Unemployment persistence is defined as the existence of serial correlation in individual employment outcomes. The first chapter finds evidence for unemployment persistence among men and women in the Australian youth labour market. Individual labour market dynamics are analysed using the Australian Longitudinal Survey. The analytic framework used is a Random Effects Probit model, incorporating lagged employment status as an explanatory variable status. Results support a “scarring” effect of unemployment upon individuals’ future employment prospects. The second chapter provides decision-theoretic foundations for unemployment persistence, based upon heterogeneous intrinsic productivity among workers. A representative firm is assumed to receive an imperfectly precise signal of worker ability every period, and re-forms its beliefs every period using a Bayesian updating method. A model of the dynamic behaviour of optimal employment decisions by the firm is constructed. It is shown that under certain circumstances workers of all productivities may be “scarred” in the eyes of the firm by past unemployment, due to the firm’s being unwilling to hire from an unemployment pool of dubious quality. The third chapter presents a detailed investigation into how to measure unemployment persistence within the UK. The chapter presents several modelling strategies capable of being used to analyse panel data of a binary nature, and discusses how to decide which methods are most appropriate in particular environments. Panel data on men from the British Household Panel Survey are used to estimate a structural state dependence equation in employment status, where lagged employment status is used as an explanatory variable. Particular attention is given to controlling for unobserved heterogeneity between individuals. The empirical results indicate strong evidence of unemployment persistence.

In this thesis we directly consider an object tracking problem for wireless sensor networks (WSNs), called track persistence. Track persistence temporally extends the problem of object tracking by seeking to store and retrieve the entire history of an object. To provide an initial solution to track persistence, we develop two distinct algorithms. The first algorithm, update to sink, translates track persistence into a centralized problem. The second algorithm, a linked list-like algorithm, builds a dynamic data structure as the object traverses the network, and rebuilds the object history distributively upon demand. We conduct worst case analysis upon both of these algorithms. Finally, we implement a simulation environment and run a number of tests upon both algorithms. Track persistence is a very challenging problem, and this thesis contributes a pair of solutions which stand as a basis for future research. / Thesis (Master, Computing) -- Queen's University, 2010-09-09 12:56:50.921