VictorJuiz/thesis huggingface dataset:
Thermodynamic Optimization of Retinal Photocoagulation Surgery: Computational Model with Experimental Verification
Keywords: Physics
retinal photocoagulation
Thesis

Current safety considerations in retinal laser photocoagulation limit the exposure duration to a minimum of 20 ms per pulse. By numerical thermal modeling verified by in vivo experiments with 22 Dutch Belted rabbits, we demonstrate that this procedure can be rendered safe at pulse durations as short as 10 ms by spatial or temporal profile shaping of the laser beam. A combined spatio-temporal modulation may further decrease the minimal duration to 5 ms. Along with decreasing operation time, this increase of speed is expected to decrease the heat diffusion into the inner retina and choroid, therefore reducing the pain and discomfort for the patient, as well as decreasing collateral damage to the inner retina.
The thin brown line [electronic resource] : re-indigenizing inequality in aotearoa New Zealand
Keywords: Sociology.

This study critically examines inequality within New Zealand's indigenous Māori population. Specifically it asks whether strong ties to Māori identity incur higher socio-economic costs. Historical expository analysis is undertaken in concert with statistical analyses of data from the New Zealand Census of Population and Dwellings (1996, 2001, 2006), and a longitudinal study of Māori households. I find strong evidence of ethnic and socio-economic segmentation within the Māori population. In each census, individuals identified exclusively as Māori by ethnicity are the most disadvantaged across a wide range of socio-economic indicators. Those identified as Māori solely by ancestry are the least disadvantaged. Pronounced differences in Māori language ability and intra-Māori partnering are also evident, indicating that the association between Māori identification and disadvantage may be partially explained by ties to Māori identity. Regression analyses of multi-wave survey data reveal a complex set of relationships. Changing patterns of identification suggest self-designation as a Māori is best conceived as a fluid, contingent process rather than a stable, individual trait. Māori identification is generally a less salient predictor of disadvantage than specific ties to Māori identity, expressed through network ties, language, and practices. However, while some ties to Māori identity appear to incur high socio-economic costs, other ties are inconsequential, or advantageous. Taken together, the analyses contribute new insights into patterns of inequality between Māori, and highlight the need for more careful theorizing and interpretation of ethnicity variables in empirical analysis.
"The things they carried" [electronic resource] : a study of learning to teach across activity settings
Keywords: Education.

The study described here examines the practices of 7 beginning English-Language Arts teachers in two schools over the course of an academic year. The analysis of classroom observations and data on the preparation for teaching highlighted the elements of learning settings in both pre-service and in-service settings that supported appropriation of subject specific tools for teaching. The common features across settings that supported appropriation were a foundation of conceptual tools for teaching, the enactment or unpacking of practical tools through explicit modeling or collaboration, and opportunities to enact tools within and/or across learning settings. The study also highlighted the importance of the reinforcement of tools across settings for promoting not only appropriation of practices but depth of appropriation. The cases suggest that it was the features of the individual and overlapping settings for teacher learning such as the availability of models, norms around practical tools, opportunities to enact tools, and the access to these features across settings that best explain the teaching practice of these 7 teachers. The study reveals a more complicated and nuanced picture of the development of teaching practices across settings in which teachers learn to teach their subject matter. The findings suggest that in addition to considering how to better scaffold tool appropriation in their respective settings, teacher educators, professional developers, departmental leadership, and policy makers should work together to provide support for tool appropriation that spirals across settings.
Thinning and skeletonizing grayscale cubical complex images of any dimensionality [electronic resource]
Keywords: Electrical Engineering

In this thesis, we present a practical, flexible, and theoretically rigorous method of extracting a sparse skeletal representation of higher-intensity shapes in a grayscale image of any dimensionality. Our approach assumes that the input d-dimensional image belongs to the newly-defined subclass of cubical complex images (CCIs), whose superlevel sets are equivalent to a nested family of cubical complexes. Though the fraction of images that fall into this category is small, we show that every image can be easily transformed into a CCI whose linear dimensions are double those of the original, so our skeletonization scheme remains applicable to all images. The majority of this thesis is devoted to a new grayscale image thinning algorithm, applicable only to CCIs, which reduces the higher-intensity points in an image to a much smaller representative subset. We introduce the algorithm in three stages. In the first stage, we assume that the image is binary, and we use this simple case to clearly explain the underlying thinning mechanism, the unique geometric structure that generalizes to images of any dimensionality, and the many new guarantees we can make on the thinned foreground shape including thinness, centeredness, and topological equivalence to the original foreground set. In the second stage, we generalize the binary image technique into one for grayscale images. We show how the incompatible shapes represented by different gray levels of the image can be reconciled, including an elegant framework for mitigating the effects of low-contrast noise while preserving high-contrast image features. In the final stage, we consider the possibility that thinning might only be performed along a subset of the image axes. We explore the resulting thinning behavior, and we offer an optimized version of the thinning algorithm that capitalizes on the great opportunities for parallel processing that appear under these conditions. After fully developing the thinning algorithm, we study how to best select a sparse subset of points in the thinned image to serve as a representative of the underlying shape. We explore three possible approaches that balance skeletal sparsity with the preservation of image topology. Finally, we address a shortcoming of our grayscale thinning algorithm: it runs in time proportional to the number of distinct values in an input image. To improve the computation time of the thinning routine, we explore an image quantization scheme that attempts to reduce the number of distinct image values while limiting changes in image contrast which affect the behavior of our thinning algorithm.
Three barriers to more useful education research [electronic resource]
Keywords: Education.

Many conceptual barriers stand in the way of more useful educational research. This dissertation examines three such barriers. The first intellectual barrier is an unproductive distinction between "scientifically based" research and other forms of educational inquiry—a distinction that, thanks to recent federal acts, now carries the weight of law. The second barrier is a failure to draw meaningful distinctions between "basic" and "applied" educational knowledge. Neither researchers nor federal funding agencies have outlined a clear definition of educational knowledge in these domains, nor have they offered a compelling account of how research aimed at one domain produces knowledge gains in the other, though a connection is frequently implied. And a third barrier is confusion about the relationship between what might be called the "positive" (or descriptive) and the "normative" (or prescriptive) dimensions of educational inquiry. Researchers often exhibit either too much comfort openly incorporating value judgments into research or too little, and the traditional distinction offers scant guidance to researchers wanting to directly engage practical educational problems.
Three essays on teacher labor markets in Thailand [electronic resource]
Keywords: Education.

The first essay of this dissertation examines the role of teacher characteristics in schools on student outcomes using datasets from TIMSS 1999 and TIMSS 2007 international tests. Taking an advantage that students have to take both mathematics and science subjects from different teachers, I use the method of First Difference (FD) analysis in order to remove the potential biases between teacher attributes and unobserved student characteristics. The findings show some contradictory outcomes between the FD analysis and ordinary least squares (OLS) analysis. The second essay looks into the problem of recruitment of well-qualified high school and college graduates to work as primary and secondary school teachers. I compare teacher salaries and benefits vis-à-vis other mathematics and science-oriented professions namely medical professions, engineers, accountants, scientists and nurses. In addition, I compare incomes between people who graduate from teacher colleges and non-teacher colleges. Using data from Thailand Labor Force Survey from 1985 to 2005, I find that teachers are the most poorly paid of all professions, including nurses. The difference in terms of an opportunity cost between male and female teachers is also striking. Among the graduates from teacher colleges, male graduates earn more than their peers if they chose other occupations whereas female graduates earn less if they make other choices. The third essay looks at the reasons teachers choose part-time jobs, the type of jobs they choose, and the amount of income they receive from these jobs, as well as factors influencing these decisions. I find that approximately 20-25% of Thai teachers participated in moonlighting activities. The majority of them have part-time jobs including tutoring, selling food and other products, and farming. Low salaries and high level of indebtedness are the most important factors associated with the increased likelihood of having a part-time job. However, economic status does not correlate significantly with their decision to tutor as their part-time job.
Three essays on the cognitive effects of categorization processes in markets [electronic resource]
Keywords: Business.

Categorical boundaries serve to partition continuously differing social actors into groups that are perceived to be alike. The work in economic and organizational sociology often draws upon findings in cognitive psychology to understand how these categorization processes impact organizational and individual outcomes. In particular, researchers have recently focused their attention on the finding that these social mechanisms of categorization lead actors who straddle multiple categories to suffer a disadvantage. Those who span multiple categories defy clear categorization and are subsequently devalued because they are difficult to understand. In the three essays to follow, I aim to contribute to the work on understanding the cognitive aspects of categorization processes in markets. In the first essay, I use a natural experiment to provide a more solid empirical foundation as to the existence of a cognitively driven penalty for multiple-category membership. In my second essay, I theorize on whether the sequence of categorical affiliations affects how one is evaluated. I propose that those social actors who display a history of moves between less cognitively associated categories will be seen as being less credible. In my third essay, I examine how heterogeneity in audience experiences affects their ability to communicate with potential market participants. I hypothesize that audience with greater depth of expertise are able to attract more accurate offers from more focused producers, while those audience members with greater breadth of experiences attract less accurate offers from less focused producers.
The three sovereigns tradition [electronic resource] : talismans, elixirs, and meditation in early medieval China
Keywords: Religious Studies

This dissertation attempts to elucidate the origins and nature of the lost Sanhuang wen (Writ of the Three Sovereigns), and identify its surviving fragments in the Daoist Canon. Through a close examination of these fragments, this study reconstructs various stages in scripture's transmission and traces its development from a single text to a fourteen-scroll corpus replete with mantic methods, cosmological speculations, and elaborate liturgies. The present study pushes beyond conventional views of the Sanhuang by underscoring the pivotal role of alchemy and meditation alongside talismans as defining components of the tradition. It analyzes key notions, such as "true form" (zhenxing), in the sophisticated conceptual apparatus that governs Sanhuang talismanic, alchemical, and meditative practices. In so doing, this dissertation reveals the profound impact of the Sanhuang wen on the religious landscape of Six Dynasties Jiangnan, and in a larger framework, on the development of Daoism.
"Through the same lens but from a different angle" [electronic resource] : Latino ethnic identity formation in the San Francisco Bay Area, 1968-1974
Keywords: Education.

In the politically charged atmosphere of the 1960s and 1970s in the Bay Area of northern California, many Latino and Chicano youth formed multiple and fluid identities influenced by their experiences in schools and community organizations and encounters with adults in their neighborhoods. This study examines ethnic identity formation for immigrant and native-born school-age youth as well as adults and college-age students by drawing comparisons between the diverse Latino population in San Francisco and the predominantly Mexican-American population in the East Bay. This contrast highlights the complexities within the story of Latino ethnic identity formation and how this identity is often layered and situational depending on the context.
Time-changed birth processes, random thinning, and correlated default risk [electronic resource]
Keywords: Management Science and Engineering

Credit risk pervades all nancial transactions. The credit crisis has indicated the need for quantitative models for valuation, hedging, rating, risk management and regulatory monitoring of credit risk. A credit investor such as a bank granting loans to rms or an asset manager buying corporate bonds is exposed to correlated default risk. A portfolio credit derivative is a nancial security that allows the investor to transfer this risk to the credit market. In the rst part of this thesis, we study the valuation and risk analysis of portfolio derivatives. To capture the complex economic phenomena that drive the pricing of these securities, we introduce a time-changed birth process as a probabilistic model of correlated event timing. The self-exciting property of a time-changed birth process captures the feedback from events that is often observed in credit markets. The stochastic variation of arrival rates between events captures the exposure of rms to common economic risk factors. We derive a closed-form expression for the distribution of a time-changed birth process, and develop analytically tractable pricing relations for a range of portfolio derivatives valuation problems. We illustrate our results by calibrating a tranche forward and option pricer to market rates of index and tranche swaps. A loss point process model such as a time-changed birth process is speci ed without reference to the portfolio constituents. It is silent about the portfolio constituent risks, and cannot be used to address applications that are based on the relationship between portfolio and component risks, for example constituent risk hedging. The second part of this thesis develops a method that extends the reach of these models to the constituents. We use random thinning to decompose the portfolio intensity into the sum of the constituent intensities. We show that a thinning process, which allocates the portfolio intensity to constituents, uniquely exists and is a probabilistic model for the next-to-default. We derive a formula for the constituent default probability in terms of the thinning process and the portfolio intensity, and develop a semi-analytical transform approach to evaluate it. The formula leads to a calibration scheme for the thinning processes, and an estimation scheme for constituent hedge sensitivities. An empirical analysis for September 2008 shows that the constituent hedges generated by our method outperform the hedges prescribed by the Gaussian copula model, which is widely used in practice.
Topics in unsupervised learning [electronic resource] : feature selection and multi-modality
Keywords: Statistics

Often in the unsupervised setting one clusters data attempting to learn the unobserved latent class variable. Proper inference requires determining both the correct number of clusters and the subset of features dependent on the class variable. In the supervised setting one has prediction error to guide the decision making process. An analog for unsupervised data is prediction strength, Tibshirani and Walther (2005), whereby one attempts to estimate this error by measuring cluster stability. Originally proposed as a method for determining the number of clusters, we will show that prediction strength can also be used for feature selection. Additionally, one can compute the likelihood a feature depends on the latent variable when feature selection is posed as a model selection problem. As the dimensionality of the problem gets large sampling models must be approached with care, motivating a survey of various sampling methods. The second part of the thesis considers low-dimensional projections of the data via principal curves, Hastie and Stuetzle (1989), as a vehicle for determining the number of clusters. In the low-dimensional setting (often a single dimension) multi-modality investigation is simplified resulting in flexible estimation of the actual number of clusters.
Towards a precision measurement of the half life of neutrinoless double beta decay of 136Xe [electronic resource]
Keywords: Physics

Recent neutrino oscillation experiments provide proof that neutrinos are massive par- ticles, but the absolute neutrino mass scale remains unknown. Observation of neu- trinoless double beta-decay (0vBB), a hypothetical nuclear transition, would provide information on the absolute neutrino mass scale. This decay violates lepton number conservation and requires that neutrinos are massive Majorana particles. Current limits on the half-life of 0vBB are in excess of 10^25 yr. The 200 kg Enriched Xenon Observatory experiment (EXO-200) is a double beta-decay exper- iment designed to improve upon this limit. It is currently in the early stages of commissioning at the Waste Isolation Pilot Plant near Carlsbad, New Mexico. This work discusses first the use of liquid xenon as source and detector medium for double beta decay. The design and construction of EXO-200 is then presented, including a detailed prediction of detector backgrounds and sensitivity.
Towards an efficient and robust high order accurate flow solver for viscous compressible flows [electronic resource]
Keywords: Aeronautics and Astronautics

Despite the advance in CFD over the past few decades, the field of high-order methods for unstructured grids has not yet reached the level of maturity required to solve real flow problems on complicated geometries. The present thesis work makes an effort towards the realization of a flow solver that is high-order accurate but also efficient, robust and geometrically flexible at the same time. The approach to high-order spatial discretization is based on the Spectral Difference (SD) method for unstructured quadrilateral meshes. High-order (quadratic and cubic) representation is used for curved boundary surfaces. Due to their slow convergence rates with standard explicit time-stepping schemes, the use of high order schemes becomes viable only when there is some kind of convergence acceleration technique used. Towards this end, the multi-order (p-multigrid) method and Implicit time-stepping are implemented, and significant convergence acceleration is achieved for both steady and unsteady flow problems. Another significant challenge with using high-order methods is their inability to handle flow discontinuities. An artificial viscosity based approach is designed and implemented to enable computation of flows with shocks. Adaptive mesh and order refinement have great potential in reducing the computational effort required to reach a specified level of accuracy, particularly in the context of high-order formulations. The capability for adaptive mesh and order refinement is enabled using mortar elements to handle non-conforming solution approximations at the cell interfaces. The flow solver is tested, validated and applied to a variety of flow problems. The current work also demonstrates the effectiveness of computational tools such as convergence acceleration, shock-capturing and adaptive refinement, for enhancing the efficiency and robustness of high order flow computations.
Towards Multicultural Education for All: The National and International Influences on Brazilian Educational Policy
Keywords: Brazil
multicultural education
curricular policies
education policy
Stanford Graduate School of Education International Educational Administration and Policy Analysis
Thesis

Until recently, Brazil has prided itself in being a country free of discrimination and inequalities based on racial or ethnic differences. However, the Brazilian government has changed its posture and began to acknowledge the disadvantaged position of Indigenous People and the descendants of African slaves. Educational policies were among the first to incorporate this concept. Bilingual education, affirmative action and curriculum changes to include cultural diversity were implemented and a new department–Secretary of Continuous Education, Literacy and Diversity (SECAD)–was created in 2004. To explain these changes in policy, the literature on the development of multicultural education in Brazil and globally identify explanatory factors of a domestic nature but do not take the emergence of a global trend of celebration of diversity into account. The present study analyzes the curricular policies of the Brazilian government as well as recommendations from international and national organizations from 1985 to the present to comparatively examine how issues of cultural diversity and inequality are addressed in educational policies. The analysis identifies three discourses that explain (1) why multicultural education is necessary, (2) the goal of multicultural education, and (3) the content of multicultural education. In addition, the findings demonstrate that international movements and values celebrating multiculturalism have been significant factors in the Brazilian government’s surrendering its myth of racial equality, adoption of educational reforms, and embracing old national movements against racial discrimination.
Towards precision tests of general relativity using an atom interferometer [electronic resource]
Keywords: Physics

A 10-meter tall, dual-species atomic fountain gravimeter was designed and built for the purpose of testing the Equivalence Principle with freely-falling atoms. Once completed, the apparatus promises to be the most sensitive atom interferometer ever built, with a projected differential acceleration sensitivity of 10^-15 g. This phenomenal force sensitivity opens the door to exciting science applications which are reviewed, including setting new limits on the Equivalence Principle, measuring effects of General Relativity in a laboratory setting, and detecting gravitational waves.