VictorJuiz/thesis huggingface dataset:
Virtual scanning tunneling microscopy [electronic resource] : a local spectroscopic probe of two-dimensional electron systems
Keywords: Applied Physics

Two dimensional electron systems (2DESs) at semiconductor interfaces are a useful medium for studying complex physics due to their very low disorder and relative simplicity. Many interesting effects, such as the quantum Hall effect, have been discovered through transport measurements in such systems. Unfortunately, the interfacial nature of 2DESs and the related surface energy barrier means that directly accessing them from the surface is difficult. This has limited our understanding of theoretically-predicted, spatially-organized effects such Wigner-crystal microemulsions and quantum Hall stripes, which have been probed only indirectly. In this dissertation, we develop a new type of local probe that circumvents the surface barrier by tunneling into a 2DES from a second 2DES grown nearby. The interlayer tunneling happens directly below a scanned metal tip outside the sample, behaving as a virtual tip in a system we call Virtual Scanning Tunneling Microscopy (VSTM). In the first half of the dissertation, we discuss a novel mechanism for tuning tunneling locally between two 2DESs. Its premise is that raising a quantum potential well next to an adjacent barrier is energetically similar to lowering the barrier relative to a fixed well. A lower barrier leads to the quantum well wave function extending into it and to increased tunneling into a second quantum well on the opposite side. We characterize this mechanism in a GaAs-AlGaAs heterostructure as a new type of transistor. In the second half of the dissertation, results from a working VSTM system are presented, with local interlayer tunneling revealing hidden features in the interfaces below the surface.
Vision and revision [electronic resource] : cue-triggered perceptual reorganization of two-tone images in US preschoolers and adults
Keywords: Psychology

Two-tones are a class of detail-poor ambiguous images that are puzzles for the mind's eye. The images first confuse, then surprise and delight with a flash of perceptual "insight" when the puzzle is solved and the image transforms in the observer's mind into an easily recognizable figure. Such "aha!" moments are achieved without transforming the original two-tone in any way, but instead by simply providing a clue which allows the observer to "solve" the two-tone, for example by verbally labeling the image, or by showing the corresponding photo from which the two-tone was derived. More precisely, we can call this process cue-triggered perceptual reorganization. Drawing on data contrasting effortless performance in adults with striking failures in preschool-aged children and adults from a remote culture, I argue that this phenomenon may be a unique and important case study in visual enculturation. This framing is in contrast to culture-invariant processes such as high-level visual expertise and visual cortical maturation. Instead, I emphasize the core component process of representation revision, arguably a fundamental component of social cognition broadly as well as in specific material symbolic cultural pursuits such as reading. At least three component processes of representational extraction, alignment, and selection are required for successful cue-triggered perceptual reorganization. Cognitive manipulations that simplify these component processes improve preschoolers' performance, consistent with the argument that cue-triggered perceptual reorganization is a problem of representation revision, which itself may be entrained by a material symbolic culture. The data supporting the claims above are laid out in three chapters. Chapter 1 includes five studies demonstrating the robustness of children's difficulties in cue-triggered perceptual reorganization and culminates in the development of an experimental procedure and analysis method for quantifying this effect. Chapter 2 includes two experiments testing children's recognition across a continuous series of images that increase in difficulty from original full grayscale to two-tone in order to see if we can more precisely identify the point at which recognition breaks down, and instead find evidence that this recognition threshold is not absolute, but depends in part on children's mental representation of the photo cue. Chapter 3 includes four different manipulations of children's understanding of the relationship between the photo cue and two-tone image, revealing that cognitive interventions in the same age group and without stimulus simplification can improve recognition performance. Together these studies support the existence of a striking failure of cue-triggered perceptual reorganization in children that can best be understood as a failure of visual representation revision, a cognitive process already achievable by the preschool years, but not yet fully entrained by US culture.
A visual representation to characterize moment-to-moment concept generation through interpersonal interactions in engineering design teams [electronic resource]
Keywords: Mechanical Engineering

Concept generation activity, an activity in which a number of design concepts are generated for further evaluation through prototyping and testing, is an important stage in the engineering design process. In design practice and design education, concept generation activity is often conducted in teams. During this activity, designers interact with one another to generate a number of design concepts. Prior research on concept generation activity in design teams has either looked into understanding the inter-relations between concepts generated, or into identifying specific behaviors in interpersonal interaction. There is a lack of understanding of the manner through which design concepts are generated moment-to-moment from the interpersonal interactions between designers. The present work aims to provide an explanation of concept generation through moment-to-moment interpersonal interaction behaviors by developing a visual representation of the phenomenon. In order to develop this visual representation, an empirical study is conducted in which the concept generation activity of two teams is analyzed through the point of view of collective improvisation. Based on improvisation principles, a visual notation called the Interaction Dynamics Notation is developed. In order to evaluate the effectiveness of this visual notation, it is applied to concept generation activity of three teams selected from a field context of ongoing graduate engineering design projects. The resultant visual representation of the concept generation activity is successful in identifying eight patterns of interaction that characterize moment-to-moment concept generation, such as transitions between ideas and facts, the presence of periods of sustained idea expressions, the occurrence of improvisation behavior, question-asking and humor in periods of sustained idea expressions, the existence of blocking behavior which at times influenced further ideas, the presence of interruptions that were not detrimental to concept generation, and the resumption of concepts in conversation. The Interaction Dynamics Notation thus enables us to 'see' concept generation through moment-to-moment interpersonal interactions in design teams. The main contribution of this study is the development of a visual representation, the Interaction Dynamics Notation that brings together prior research on concept generation and prior research on interpersonal behaviors in a team. The notation provides a detailed explanation of concept generation activity through moment-to-moment interpersonal interactions in an intuitive visual form.
Visualization of Pore-Level Mechanisms of Alkaline Surfactant Polymer Flooding Using Micromodels
Keywords:  Department of Energy Resources Engineering
School of Earth Energy &amp; Environmental Sciences
Thesis

Primary and secondary recovery methods, such as water flooding, recover as much as 50% of the original oil in place and therefore end up leaving remaining oil that is less likely to be produced behind in the reservoir. In fractured reservoirs, the recovery efficiency is even lower as water prefers to channel leaving a considerable amount of unswept reservoir. New techniques have been introduced in order to access this unrecoverable potential; these techniques are assembled in what is called Enhanced Oil Recovery (EOR). Enhanced oil recovery processes play a major role in increasing the recovery efficiency and extracting the inaccessible oil that has been trapped in a reservoir. One type of enhanced oil recovery applicable to waterflood reservoirs is alkali surfactant polymer (ASP) flooding. Polymer flooding (PF) and alkaline/surfactant/polymer (ASP) flooding have been known and in practice for more than 20 years. These processes have shown successful results during large-scale implementations in China, for instance. ASP flooding is a form of chemical enhanced oil recovery (EOR) that allows operators to extend reservoir pool life and extract incremental reserves currently inaccessible by conventional EOR techniques such as water flooding. The combination of all three chemicals is synergetic. The surfactant is ultimately used to lower the interfacial tension between the oil and the injected water. The alkali reacts with the acidic portion of oil to produce in-situ soap (surfactant) and the polymer increases the injection water viscosity to reduce the possibility of channeling and viscous fingering during the process. The objective of this study is to grasp a better understanding of the mechanisms of ASP flooding by conducting experiments in carbonate micromodels. A micromodel is a two dimensional porous medium created by etching a pore network into silicon. Pore-level mechanisms are observed directly using a micromodel. The challenge is to understand how the combination of alkali, surfactant, and polymer allows us to best access the matrix and efficiently sweep the oil. Therefore, a screening study was conducted to evaluate diverse surfactants of concentrations ranging from 0.5 to 5.0 wt% by measuring the interfacial tensions in order to select one compatible with light crude oil (27°API). Both secondary and tertiary flooding of the ASP slug was tested at realistic flood rates of 0.1 m/day Darcy velocity. Greater flow rates were later attempted to maximize recovery, within the reasonable pressure range that the micromodel can handle. The results are presented in the form of image analysis of microscopic pictures taken at different locations to estimate the oil recovery. The ASP displacement experiments conducted yields reasonable improvement of recovery for all cases.
Water songs, spell books, and land rites; the reparations of ceremony in diaspora [electronic resource]
Keywords: Drama

Performance Studies, like English, Post-Colonial Studies, and other related Humanities fields, has issued an extensive critique on the detrimental effects of Enlightenment Rationalism (chattel slavery, colonization of land and bodies), but these fields have not yet been self-reflexive enough to critique how this normative theoretical apparatus continues to govern what constitutes knowledge, and the way we, as scholars, go about getting it. My dissertation, influenced by the burgeoning fields of Eco-Criticism, Indigenous Studies, and the radical turn in the sciences, investigates "the sacred" as a source of knowledge about the world. My project takes as its subject three playwrights and performance artists who engage with "the sacred" by utilizing pre-colonial African and Native American epistemological practices (ceremony, spell, song, performance, and prayer) in projects of social and environmental justice. Towards this end, I conduct an analysis on the work of Sharon Bridgforth (African-American playwright), Cherríe Moraga (Chicana playwright), and Celia Herrera Rodríguez (Chicana/Odami Multi-disciplinary Artist and Ceremonial Leader). Because the African-American and Chicana artists/ritualists I write on are simultaneously female, diasporic, and queer, they are triply situated to question notions of patriarchal and heteronormative cultural tradition, at the same time as maintaining ancestral and intuitive inheritance. Rejecting the always already sinfulness of their sexualities taught by an inherited colonial Christianity (from within their communities), these artists/ritualists 1) engage indigenous belief-systems which, in both colonialist and oral narratives, are considerably more accepting of a diversity of gender/sex possibilities and 2) utilize alternative epistemological strategies, like intuition, ceremony, and dance as means to re-apprehend "tradition" where the existing sources of knowledge are absent or inaccurate. The textual and embodied communal practices enacted by these women recover value systems alternative to Enlightenment Rationality, prioritizing inter-subjectivity with the environment, a balanced social and ecological system, and perhaps most importantly, another way to "know." Their works fruitfully engage with indigeneity, allowing us to perceive an innovative role for women of color in the creation, critique, and transmission of culture in diaspora.
Weighing the giants [electronic resource] : methods and measurements of accurate galaxy cluster weak-lensing masses
Keywords: Physics

Clusters of galaxies have become a cornerstone of the experimental evidence supporting the standard Lambda-CDM cosmological model, and will be a mainstay in testing the nature of dark energy with upcoming surveys. To constrain cosmological models, these surveys indirectly measure cluster masses as part of cluster counting experiments, requiring surveys to calibrate their mass proxies. In this thesis, I will present weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known. This cluster sample spans redshifts 0.15 < z < 0.7, and is well suited to calibrate mass proxies for current cluster cosmology experiments. To this end, I will discuss a new weak-lensing method that exploits all information available in the photometric redshift posterior probability distributions of individual galaxies.Using simulations based on the COSMOS-30 catalog, I will demonstrate control of systematic biases in the mean mass of the sample with this method, from photometric redshift biases and associated uncertainties, to better than 3%. The performance of this new photometric redshift-based method allows us to calibrate `color-cut` masses for all 51 clusters in the present sample to a total systematic uncertainty of ~7% on the mean mass, a level sufficient to significantly improve current cosmology constraints from galaxy clusters. Finally, I will discuss how these results bode well for future cosmological studies of clusters.
What does it mean to be a student at this school? [electronic resource] : investigating academic identity in instructional context
Keywords: Education.

Abundant educational research indicates that there is a drop off in students' attitudes about and participation in school as they transition to middle school (Anderman & Maehr, 1994; Eccles, Lord, & Midgley, 1991). This drop off may have particularly deleterious effects for low-income students of color, who are most at risk of dropping out or being pushed out of school. Although some research has examined the fit between students' developmental needs and the typical middle school environment (Eccles, Lord & Midgley, IBID), there has been very little research that examines how different instructional contexts shape young peoples' understanding of themselves as students (or academic identity) at this transition. This study aimed to fill that gap by examining how three different instructional contexts (traditional teacher/textbook centered, Montessori, and social justice oriented) afforded low-income students of color different opportunities to understand what it meant to be a student and a learner as they prepared to transition to middle school. The study used a mixed methods design to understand students' academic identity meanings with both a cross-sectional survey of third, fifth and seventh grade students in each context as well as in-depth observation of one fifth grade classroom at each site and interviews with four to six target students in each of these fifth grade classrooms. Quantitative survey analysis revealed large effects for students' developmental stage, such that, as expected, student attitudes about school did drop off between fifth and seventh grade across all sites. Quantitative differences between sites were less clear, though did indicate a generally higher value of learning and curiosity at the Montessori site, a lesser valuing of school as an institution at the social justice site, and a higher valuing of test scores and grades at the traditional site. Qualitative differences between sites were more pronounced, with students at the Montessori and social justice sites enacting more active and agentic roles in their learning than students at the traditional site. There was also evidence that students utilized the ideational resources that were made available in each classroom context as tools in their reflections about whether they were a competent student and whether they belonged in their classroom and school. In addition, across sites students consistently used certain classroom practices and factors as ideational tools in their self-reflections about academic identity. These practices and factors included: ability cues and grouping, structures around peer helping, contextual definitions of competence, opportunities for self monitoring, relationships with adults, opportunities to build on out-of-school knowledge, opportunities for choice in school work, awareness of identity threats and the cultural make up of the school and faculty.
What does it mean to be literate here? [electronic resource] : the bounded nature of teaching and learning in an urban first grade classroom
Keywords: Education.

Beginning around the turn of the 21st century, a large number of American public school classrooms were required to implement decontextualized, skills-based literacy programs. These classrooms were primarily located in impoverished communities populated by children of color. Touted as largely "teacher-proof, " the curricula shaping Language Arts instruction was generally so rigid that they included a script for the teacher as well as examples of acceptable student responses. At the same time, the educational community was becoming increasingly aware of the fact that legitimate language need not conform to the academic model and that students who are non-native speakers of academic English have distinct intellectual needs. Using the guiding question, "What does it mean to be literate here?" this study attempted to determine the type of learning and language development that resulted from the privileging of standardized language instruction in an environment that acknowledged a diversity of language forms and structures. Using teacher-research and ethnographic methods, this teacher research study took place in a first grade classroom. Three central findings emerged. The first related to the conflation of compliance and learning. It became clear that actual instructional and curricular goals were directed at behavioral rather than academic outcomes. Building on this focus on compliance, a second finding pointed to the establishment of boundaries of acceptable academic participation. While pushing boundaries often signaled engaged participation, such boundary pushing was rarely cultivated. Finally, it became apparent that the challenging of boundaries was required for innovation and was evidence of one's ownership over work.
Who can improve? A target's race dictates perceptions of potential for growth [electronic resource]
Keywords: Psychology

People regularly judge others' potential for growth in deciding who to hire, promote, admit, or parole. Yet research on racial stereotyping has focused on trait judgments in the moment and has largely ignored how race influences judgments about growth over time. Historically, Blacks have been portrayed as lacking the potential to grow, and in this paper, I test the hypothesis that they are still seen this way. In Studies 1-3, Black targets were judged to have less potential to improve compared to White targets even when they were viewed similarly in the present and even for non-stereotypical traits. In Study 4, priming with Black faces increased participants' endorsement of the view that people are fixed. Finally, Study 5 addressed implications for societal policies. Together, this research reveals a new dimension of how a target's race may affect person perception.
Word recognition prompts and student growth in reading [electronic resource]
Keywords: Education.

Word recognition prompting is a method of instruction used by many teachers during oral reading instruction. However, it is a nuanced practice that is still being described and understood. This study explored the relationship between what a teacher says during reading instruction and the word recognition ability of a reader receiving instruction. The goals of this research were three-fold: 1) to identify and describe ways teachers support beginning readers in word recognition during oral reading instruction, 2) to determine whether certain patterns of prompting are associated with word recognition growth and, ultimately, 3) add detail to the current knowledge base about the types of prompts used. Four first-grade teachers, who taught in the same district at 2 different schools with similar demographics, were recruited for this mixed methods study. I followed the word recognition and reading development of students, and changes in teachers' instructional moves over the course of one school year, to discover how teachers were prompting students and how students responded. Student growth was measured with standardized assessments of word reading and evidence of self-correcting and decreased errors during independent reading. Findings suggest that students of teachers who used a moderate percentage of most prompts with a greater emphasis on primary and grapho-phonemic prompts made the most growth in word reading over the course of the study. These teachers also used a collaborative style of instruction that encouraged a focus on processes of word-processing rather than accuracy. Finally, students who were prompted to self-monitor as they improved in ability made fewer errors and self-corrected miscues more often.
Writing love and agency [electronic resource] : narrative revisions in the academic and life texts of high school youth
Keywords: Education.

This dissertation presents the self-narratives and academic texts of four high school students who engage in the work of revision. It is also my attempt to translate between theory and practice in my high school classroom. Over the course of a literacy curriculum that builds around Toni Morrison's Song of Solomon, students write their way through a series of narratives and essays that they develop around themes of narrative truth, family relationships, defeat and agency, and personal and collective struggle. By focusing first on the topic of love, students attempt to identify their surface stories and the more internal stories that drive them, and consider how well these stories are serving them. In some cases, students are able to shift their interpretation and framing of life experience to a more agentic tone and outlook. As they consider revisions to their self-narratives, they reconsider their readings of Morrison's novel and its characters, as their academic writings reveal. The curriculum develops within the classroom social context over the two years that the students and I work together, as they increasingly grow to share their views and writing with one another. Implicit in students' ways of thinking about life challenge is their relationship with education and school. Students' evolving views of reading, writing and education that surface in their writings, interviews and class discussions, emerge throughout the dissertation.