VictorJuiz/thesis huggingface dataset:
A Direct Measure of Technical Change and Its Economic Implications

Movements in total factor productivity (TFP) have strong economic implications. For example, improvements in TFP are conducive to long-run economic growth. Also, variations in TFP explain cross-country income differences and, to many real business cycle economists,/nTFP shocks account for a large fraction of aggregate fluctuations./nDespite being important, TFP is a black-box, or some sort of measure of our ignorance about the causes of economic growth (Abramotitz 1956, 11). Most economists agree, however, that technological change/nis a major component of TFP./nTo evaluate the effects of technological change on TFP, there is a need for a good indicator of technical change because conventional indicators, whether presented as indirect or direct measures of technology, have shortcomings. The most important of these shortcomings is/ntheir inability to measure true technical change./nIn the essays that follow, I present a new and direct measure of technical change and evaluate its economic implications. The direct measure is derived from actual inventions, in information and communication technology (ICT), identified by engineers that are expert in the field of technology. The exact timing of when the inventions are widely adopted is/ndetermined using contemporaneous and ex-post narrative coverage of the identified innovations. This new indicator of technical change has one key advantage over existing indicators in that it consists of actual inventions chosen by technology experts./nUsing the new indicator, I find that technological innovations have/nsignificant impacts on TFP, output, hours, investment and consumption. In addition, and using variation in ICT capital intensity at the sectoral level, I present evidence that industries that use ICT capital more intensively gain more, in terms of productivity, from technological innovations./nThis sectoral finding provides new evidence that advances in information technology are not limited to industries that produce information technology, contrary to the neoclassical prediction. Furthermore, narrative evidence suggests that the introduction of major inventions leads/nmarket participants to react positively in anticipation of future improvements in productivity./nA formal test of whether the aggregate S&P 500 significantly responds to technology shocks shows that stock prices fall following technology shocks, a result consistent with the study by Jovanovic and Hobijn (2001).

Advisor: Romer, David H
Implementing a Dialogic Reading Intervention: The Experiences of Teachers of Deaf and Hard of Hearing Students

Deaf and hard of hearing children (hereafter DHH) frequently have delayed language and little experience with books because they do not share a common language with their hearing parents. However, there is little research concerning language and literacy development in the DHH classroom and equally little discussion of teacher responsibilities to address these issues. This study investigated the implementation of dialogic reading, which aims to engage students in active discussion and retellings of stories, using American Sign Language, called story signings. Because dialogic reading research with language delayed, hearing preschool students resulted in significant improvement of language skill (Whitehurst, Arnold, et al., 1994; Whitehurst, et al., 1999), it was a logical candidate for implementation with DHH students./nA hybrid of case study and design-based research methods was used to investigate the implementation of dialogic reading with four elementary teachers of DHH students. This study was undertaken collaboratively with teachers in order to overcome obstacles that might interfere with implementation and sustainability, to make adjustments to alleviate such problems as they arose during implementation, and to identify necessary adaptations for their student population. The teachers taught grades one through five. Two taught in a school for DHH children, and the other two taught in special day classes for DHH students located within elementary schools. Data sources included videotapes of story signings and reading instruction and audiotapes of meetings with teachers./nFindings indicate that the teachers were hindered first by a lack of knowledge and then subsequently by the difficulties of implementation. These difficulties included those identified in previous research: teacher time for small groups, a difference in philosophy of teaching and learning, and teacher effort (Lonigan & Whitehurst, 1998). Specifically, teachers were not regularly engaged in reading to students, admitted they did not know how to address language delays within the classroom, and felt additional adaptations for their students competed with their professional commitment to other curricular areas. Future research needs to investigate implementation issues for the purposes of sustainability, and teacher education programs — for pre-and in-service teachers — need to prepare teachers for the multifaceted, complex nature of instruction.

Advisor: Pearson, P. David
Prinz, Philip M.
A Theoretical Analysis of Singularity-induced Micro-electroporation and its Applications

Electroporation - the permeabilization of the cell membrane lipid bilayer due to a pulsed electric field - has important implications in the biotechnology, medicine, and food industries. Although the physical mechanism that causes electroporation is not entirely understood, it is believed that pulsed electric fields significantly increase the potential difference across the cell membrane, resulting in the formation of pores. Depending on the magnitude and duration of a pulsed electric field, membrane permeabilization is either reversible or irreversible. Reversible electroporation is commonly used to transfer macromolecules such as proteins, DNA, or drugs into cells, and the destructive nature of irreversible electroporation makes it suitable for cell ablation and sterilization./nMost electroporation devices have facing electrodes that generate uniform electric fields. Consequently, the magnitudes of these electric fields are inversely proportional to the distance between the electrodes. Since reversible and irreversible electroporation require electric field magnitudes on the order of 1 and 10 kV/cm, respectively, large potential differences are required to induce electroporation. Reducing the potential difference required to perform electroporation eliminates the need for a power supply, making electroporation cheaper and more accessible./nSingularity-induced micro-electroporation - an electroporation configuration composed of two adjacent electrodes separated by a nanoscale insulator - aims to reduce the potential difference required to perform electroporation. Application of a small potential difference between the electrodes creates a radially varying electric field emanating from the insulator. Secondary current distribution models of singularity-induced micro-electroporation show that applying a potential difference as low as 2.9 V creates an electric field that is capable of inducing reversible and irreversible electroporation. To date, the lowest potential difference used to perform irreversible electroporation is ~20 V. More impressively, these models demonstrate that the ohmic drops in galvanic electrochemical cells can generate electroporation-inducing electric fields, enabling the creation of a self-powered micro-electroporation device.

Advisor: Rubinsky, Boris
Invariance in Human Visual Perception

This dissertation explores invariance in human visual perception via three unique studies. In the first two studies we probe the visual system to see how robust it is to impoverished stimuli. These investigations not only offer limits on perceptual abilities, but also offer key insights into the mechanisms underlying vision./nThe first study explores rapid category detection, as discovered by Thorpe, Fize, and Marlot (1996). This study demonstrated that the human visual system can detect object categories in natural images in as little as 150 ms. To gain insight into this phenomenon and to determine its relevance to naturally occurring conditions, we degrade the stimulus set along a wide variety of image dimensions and investigate the effects on perception. We discover that rapid category detection in humans is quite robust to naturally occurring degradations and is mediated by a non-linear interaction of visual features./nThis investigation into degradation is followed by our second study where we explore the limits of 3D shape perception. The shape-from-texture and shape-from-shading perspectives would motivate that 3-D perception vanishes once low-level cues are disrupted. Is this the case in human vision? Or can top-down influences salvage the percept? In this study, we explore this question by employing a gauge-figure paradigm similar to that used by Koenderink et al (1992). Subjects were presented degraded natural images and instructed to make local assessments of slant and tilt at various locations thereby quantifying their internal 3-D percept. Analysis of subjects' responses reveals recognition to be a significant influence thereby allowing subjects to perceive 3-D shape at high levels of degradation. Specifically, we identify the medium-blur condition, images approximately 32 pixels on a side, to be the limit for accurate 3-D shape perception. In addition, we find that degradation affects the perceived slant of point-estimates making images look flatter as degradation increases./nThese 2 studies, in conjunction with previous work, point to 32-pixel color images as a rough threshold for a rich perceptual experience. The first study demonstrates that rapid recognition breaks down at around this point, and the second shows that it is also the limit to reliably perceive 3-D shape. Presumably many perceptual abilities are tied together at this level - shape, recognition, etc, so that when one percept is lost, other percepts break as well./nIn the third study, we explore how invariant properties of the natural world drive perceptual coding mechanisms in the brain. Specifically, we explore how the statistics of object regions in natural images motivate a sensitivity to hue by the perceptual system. To investigate this question, we compute the coding advantage of using hue angle to encode color inside real-world object regions. For this analysis, we use natural image datasets which provide pre-segmented object regions and surfaces.

Advisor: Malik, Jitendra
Ablation on Taylor Glacier, Antarctica

Taylor Glacier, an outlet of the East Antarctic Ice Sheet, flows through the Transantarctic Mountains and terminates in the Dry Valleys. Understanding how this glacier fluctuates is important for studies of glacial geology, paleoclimate, ice dynamics, and ecology. Sublimation is the primary mass-loss process for most of the glacier. Four years of specific balance measurements from the ablation zone show sublimation rates up to 40 cm per year. We used data from an array of weather stations as inputs to a model for latent heat flux and hence sublimation rate. Calculated and measured ablation rates agree to within uncertainties, indicating that wind speed and vapor pressure gradient (a function of temperature and humidity) are the governing variables, as expected from theory. Measurements and model results together allowed us to examine the spatial and temporal variations of sublimation on the glacier. On average, sublimation is about two times faster in summer than winter. Rapid sublimation occurs during storms and katabatic wind events, but such periods contribute less to the annual total than do slow, persistent losses. Spatially, sublimation reaches a maximum midway along the glacier, where descending surface air currents are focused by the topography of the aptly-named tributary, Windy Gully.

Advisor: Cuffey, Kurt M.
The role of individual or neighborhood factors: HIV acquisition risk among high-risk populations in San Francisco

The majority of new HIV infections occur among high-risk groups such as men who have sex with men (MSM) and transfemales. Segments of these populations are also more likely to be economically disadvantaged. Economic disadvantage or low socioeconomic status has been linked to disease acquisition, morbidities and mortality. Interventions have been proposed to address these health issues through the reduction of poverty. However, this approach to intervention does not address underlying structural factors such as high HIV prevalence in impoverished neighborhoods and thus in social and sexual networks./nThe present analysis examines low individual socioeconomic status and /or social and sexual network factors and their relationship to HIV acquisition risk among three populations at high-risk for HIV infection. Geographic analysis examined residential patterns and neighborhood patterns of HIV prevalence in San Francisco. Data collected in San Francisco from White MSM, Black MSM and transfemales were analyzed using Poisson regression to determine the factors associated with engaging in more episodes of potentially serodiscordant unprotected receptive anal intercourse./nAs expected, transfemales and Black MSM were more likely to live in areas of higher HIV prevalence and lower income compared to White MSM. Interestingly the areas of higher HIV prevalence and lower income were also the areas with greater numbers of HIV prevention and care services. Black MSM and transfemales had lower socioeconomic status (SES) scores compared to White MSM. Black MSM were more likely to report serodiscordant partnerships and higher numbers of potentially serodiscordant unprotected sex acts. Decreasing SES and increasing neighborhood HIV/AIDS case density did not predict serodiscordant partnerships in any group. Increasing neighborhood HIV prevalence predicted an increase in the number of potentially serodiscordant unprotected sex acts among transfemales and Black MSM but only significantly so for transfemales./nHIV prevention interventions must also consider neighborhood factors such as neighborhood HIV prevalence in addition to considering individual level behavior change

Advisor: Syme, S Leonard
The Influence of Cognitive Autonomy and Learning Environments on Student Academic Performance: An investigation of the relationships between levels of cognitive autonomy, aspects of school learning environments and academic performance at the ninth-grade level

Students transitioning from middle school to high school often experience academic difficulty in the ninth grade. The discontinuance between the two systems gives rise to the need for students to adapt to new academic environments. Academic failure or success is a predictor of high school graduation. Research reveals the personal characteristics of students influence successful adaptation to this transition and that the academic achievement of students depends upon the design of the learning environment./nThis goal of this study was to examine whether the student characteristic of cognitive autonomy showed correlation to academic achievement during the ninth grade. This study also examined the relationships of non-cognitive characteristics of students to academic achievement. A sample of 458 ninth-grade students in a suburban high school participated in this study. The student participants were representative of a diverse community, allowing for the personal non-cognitive measures of students to include ethnicity, language proficiency, and gender./nMethodology included administration of a survey to the ninth-grade student population at the selected school. We entered the resulting survey data and demographic information into a statistical program, and academic information for each student was obtained from the school's student information database. Using a variety of statistical analyses, we disaggregated the data and examined for patterns giving indications of the relevance of student characteristics to their academic achievement. Specifically outlined in this study are the mean values of disaggregated data and correlations between cognitive characteristics, non-cognitive characteristics, the learning environment, and student academic achievement./nThe results of the study indicated the characteristic of cognitive autonomy to have minimal influence on student academic achievement while non-cognitive characteristics of students showed stronger correlation to academic performance. The resulting implications from this study centered on improving teacher understanding of student characteristics and the resulting need to alter instructional practices. Further implications arise for district and site leaders and center on school structure, staff development, and budget considerations. While centered on the ninth-grade transition point, the implications from this study can be scaled to include further aspects of the high school system.

Advisor: Gifford, Bernard R.
Enclosed Microfluidic Platform Realizing Enhanced Stem-cell Survival

Here we present a microfluidic culture platform for enhancing single stem cell survival. Traditional plate culture is inadequate for large scale single cell studies because of (1) less than 40% single stem cell survival leading to (2) possible inaccuracies in the biostatistics in single cell studies from lack of sufficient data. This platform mitigates these issues by doubling overall survival rates as well as increasing the available data points by two orders of magnitude, both factors which improve statistical certainty. The platform is fabricated using widely accepted biocompatible polymers and incorporates the novel integration of an enclosed microwell array with an upstream linear gradient generator. The device can selectively trap single cells, tightly control intercell spacing, and change the chemical microenvironment around the stem cells in real-time. In this dissertation, we first characterize the performance of the platform in improving single cell survivability. Subsequently, the system was tested using two difference stem cell types: mouse embryonic stem cells (mES) and induced pluripotent stem cells (iPS). Using this platform we are able to highlight the thresholds of leukemia inhibitory factor concentrations which lead to metastable gene expression of Nanog, a key stem cell pluripotency regulator in mES cells. The enhanced survival of single cells has also enabled the statistically significant observation of Nanog+, non-proliferative, single mES cells which are previously unreported in literature.

Advisor: Tirrell, Matthew V
"She Talked Me Down Off the Ledge:" Listening to New Principals and Their Experience of Being Coached

With increased accountability and newly introduced alternative paths to administrative licensure, stakeholders are compelled to re-conceptualize the preparation of principals from a front-loaded process during the pre-service phase to a well-distributed plan across a principal's career. In a recent review of state policy, states have shifted their focus from university-based leadership development programs to a system of continuous professional development, specifying a shared responsibility for such development (Roach, Smith and Boutin, 2011). Such regulatory shifts force employing schools and districts to reflect upon and accept their role in supporting the successful entry of new principals, that is, to formally and informally induct new school leaders into their organization as well as the profession./nThe purpose of the study is to contribute to the research base on the induction of principals by focusing on an increasingly popular induction support strategy, that is, the coaching of new principals. This study sought to thoroughly explore new principals' experiences with coaching, allowing for a more nuanced understanding of the effects of coaching to emerge from the principal's perspective. This study utilized a mixed method, cross-case study design that began with the traditional satisfaction survey, moved to follow-up telephone interviews and then examined new principal conceptions of the coaching experience through in-depth interviewing. Rather than start with a priori definitions and codes of points of investigation, new principals emergent descriptions reveal their deeper understanding of satisfaction with an individualized induction support.

Advisor: Hollingsworth, Sandra
Switched Capacitor DC-DC Converter: Superior where the Buck Converter has Dominated

The traditional inductor-based buck converter has been the default design for switched-mode voltage regulators for decades. Switched capacitor (SC) dc-dc converters, on the other hand, have traditionally been used in low power (<10mW) and low conversion ratio (<4:1) applications where neither regulation nor efficiency is critical. This work encompasses the complete successful design, fabrication, and test of a CMOS based switched capacitor dc-dc converter, addressing the ubiquitous 12 V to 1.5 V board-mounted point-of-load application, which the buck converter has dominated. In particular, the circuit developed in this work attains higher efficiency (92% peak, and >80% over a load range of 5 mA to 1 A) than surveyed competitive buck converters, while requiring less board area and less costly passive components. The topology and controller enable a wide input range of 7.5 V to 13.5 V. Controls based on feedback and feedforward provide tight regulation under worst case line and load step conditions. This work shows that the SC converter can outperform the buck converter, and thus the scope of SC converter application can and should be expanded.

Advisor: Sanders, Seth R
Motor Neurons Controlling Fluid Ingestion in Drosophila melanogaster

How environmental stimuli are detected and processed by the brain to produce a behavioral output remains a central question in neurobiology. The gustatory system in Drosophila is an excellent model for studying this problem as flies possess strong innate behaviors to many taste stimuli and can be studied using a variety of molecular and genetic tools. Because of these advantages, it should be possible to assemble a complete anatomical and functional map of the neurons mediating taste perception and behavior./nIn Drosophila , taste compounds are detected by sensory neurons that send axons into the brain. Second- and higher-order neurons in the gustatory circuit have not yet been identified. In the first part of my thesis, I describe the results of an inducible activation screen to identify neuronal populations whose activity is sufficient to elicit proboscis extension. This screen led to the identification of motor neurons that control pumping behavior./nIn the second part of my thesis, I describe my work studying motor neurons that innervate the proboscis musculature of Drosophila. These neurons drive a pump that draws fluid into the esophagus during feeding. My results show that these motor neurons are necessary for normal pumping and ingestion to occur, and that their activity is sufficient to elicit pumping. Furthermore, my data suggests that these neurons are not just passive effectors of a pumping circuit but play a role in generating the pumping rhythm./nIn the third part of my thesis, I describe a population of neurons whose morphology suggests they may receive input from sensory taste neurons. They project from the taste region of the fly brain to higher order regions that have not been well-described. The results of my experiments showed that these neurons do contact sensory taste neurons, but are not required for normal gustatory learning. Future experiments will help determine if they play a role in the processing of gustatory information.

Advisor: Scott, Kristin