VictorJuiz/thesis huggingface dataset:
Understanding and manipulating charges surrounding carbon nanotubes : a step towards high-performance computing with carbone nanotube transistors
Keywords: Electrical Engineering.

The biggest obstacle in introducing new nanomaterials is that innovative techniques and solutions are required to overcome the various challenges. In particular, conventional understandings based on bulk channel materials (i.e. Si) are often not applicable to carbon nanotubes (CNTs) due to their ultrathin (1~2 nm) one-dimensional structure. Additionally, the large surface-to-volume ratio from the one-dimensional structure makes CNTs greatly susceptible to nearby charges. In this dissertation, I will document the new knowledge obtained for understanding the physics behind -- and even utilize -- the charges surrounding the CNT with a view toward high-performance computing using carbon nanotube field effect transistors (CNFETs). In particular, this thesis presents a study on the following topics in CNFETs: Hysteresis -- A pulse-based measurement technique combined with a physics-based model is developed to characterize traps which affect hysteresis in CNFETs. With the insight gained from this work, hysteresis-free CNFETs are fabricated by minimizing the effect of traps onto the CNTs. Subthreshold Swing -- Hysteresis-free curves are an important, but often neglected, prerequisite to measuring the subthreshold swing (SS). By continuing our studies using hysteresis-free CNFETs, the source of large SS is identified. Doping -- Through a charge transfer doping mechanism, molybdenum oxide (MoOx) heavily dopes the CNTs, but the effect is unstable over time. The gradual change in material properties of MoOx and a method to stabilize the doping strength are investigated
Understanding inhibitor-based area selective atomic layer deposition for dielectric-on-dielectric growth
Keywords: Chemical Engineering.

Electronic device fabrication today is based on 'top-down' processes with multiple lithography and etching steps. As semiconductor dimensions shrink and adopt more complex architectures, these processes are reaching their limits. One promising solution is area-selective atomic layer deposition (AS-ALD), which combines a surface modification technique and atomic layer deposition (ALD) in a 'bottom-up' approach to nanopatterning. A common approach for achieving AS-ALD involves the use of densely-packed self-assembled monolayers (SAMs) as inhibiting layers against undesired ALD growth. Incorporating this technique into fabrication schemes requires an understanding of how SAMs interact with different surfaces and how this in turn affects the ability of the SAM to act as an effective inhibitor against ALD reactions. In the first part of this thesis, a comparative study of octadecylphosphonic acid (ODPA) SAM formation on four technologically relevant metals— Cu, Co, W and Ru—was carried out. Following SAM deposition, zinc oxide (ZnO) and aluminum oxide (Al2O3) model ALD processes were performed to assess the blocking ability of the SAM layer formed on each substrate. Surface characterization of these samples revealed that ODPA-treated Cu, Co and W inhibited the growth of ZnO and Al2O3 ALD to varying degrees, while no inhibition was observed on ODPA-treated Ru. Specifically, the ODPA-treated W prevented the growth of at least 17 nm of ZnO, compared to less than half this amount on Co and Cu. Similarly, 3-4 times more Al2O3 ALD was blocked using ODPA on W versus Cu and Co. The reaction mechanism of ODPA SAM formation and how surface properties, such as the roughness and the Lewis acid nature of the substrate, could impact that SAM's formation and in turn ALD inhibition is discussed. In the second part, a series of spectroscopic analyses were performed which provide details about the structure and coverage of the ODPA layer formed on each substrate. It was determined that the average tilt angle of the ODPA chains formed on Co, Cu and W are ~66° from the surface plane of the substrate, indicating that (on average) the molecules are oriented upright. Conversely, ODPA chains on the Ru substrate were found to be disordered. Further, it was determined that ODPA on Co and Cu formed a densely packed 'crystal-like' structure while on W and Ru, the ODPA molecules appeared to exhibit a more 'liquid-like' structure. The data indicate that although ODPA forms an incomplete layer on W, it still provides the best blocking against ZnO and Al2O3. The results highlight the importance of the chemical nature of the substrate surface in achieving SAM-based AS-ALD. Finally, since the overarching goal of this research is to achieve AS-ALD on metal/dielectric patterns (which mimic interconnect devices), the selective growth of ZnO and Al2O3 was demonstrated on Cu/SiO2 and Co/SiO2 2D-patterned substrates. Challenges in achieving SAM-assisted selective ALD and methods to improve the process on smaller feature sizes are also discussed
Understanding the limits of hybrid optoelectronic semiconductors : photothermal techniques and beyond
Keywords: Chemistry.

Some of our earliest artisans were pioneers of nanoengineering, building the stained-glass windows of Notre-Dame before anyone knew to define the length scale. But, today, there are fewer nano-artisans than scientists studying life at the sub 10nm scale. In this dissertation, we leverage and develop sensitive characterization techniques to further push the limits of functional devices at the nanoscale and hopefully walk away with new and exciting materials. We begin with the history and fundamental chemical developments of nanoscience, from the early days of extracting metal and semiconductive crystals from sintered glass. Followed by the vital Brus equation for quantum confinement and its optical properties. We then explore the kinetics and surface chemistry that makes up 20 yrs of scientific advancement in semiconductive nanocrystals chemistry. There is an overview of some of the standard techniques used in this work to characterize and study nanocrystals. We introduce transverse photothermal deflection spectroscopy, a very sensitive photothermal absorption spectrometer, invented by Warren Jackson at LBNL in the 1980's to study thin film single crystals, polycrystals and amorphous glasses. Photothermal deflection spectroscopy measures the photothermal heat-wave propagating into a deflection fluid and can indirectly measure optical absorptivities over the range of (0.1 -10000.0 1/cm). We review the fundamental principles and limitations of a modern-day photothermal deflection spectrometer, and how to use one of the world's most sensitive optical thermometers. Then we look at how photothermal deflection spectroscopy (PDS) can be used to study modern-day thin films and solution process materials. We show new ways to apply ultra-sensitive absorption techniques towards making better optoelectronic materials. In doing so, we introduce our first look at semiconductive nanocrystals in the form of lead sulfide. I aim to use PDS as a new tool to overcome some of the fundamental limitations still hindering the development of better near-IR materials for solar-cell and transistors. Finally, we take what we learned about studying photothermal absorption and lensing at the nanoscale to push the fundamental limits of solid-state luminescence in core-shell nanocrystals. We run into the significant challenges associated with the upper limit of the uncertainty in absolute integrating sphere techniques, based on Richard Friend's photons in and photons out approach. By borrowing inspiration from the solid-state optical refrigeration community, we develop a new calorimetric quantum yield technique that uses a heat out/ light out increasing accuracy 100x when measuring highly luminescent systems. Finally, we take advantage of this increased accuracy to synthetically build and benchmark the world's brightest quantum dot emitters. All of this builds on the hope of pushing for better and more advanced nanomachines through chemistry and spectroscopy
UNESCO and the global responsibility for heritage preservation
Keywords: Anthropology.

Under the aegis of the 1972 UNESCO World Heritage Convention, heritage preservation has gained considerable public visibility, but it has also become gridlocked in multilateral diplomacy. This thesis examines the history and challenges, of implementing, within UNESCO, the ideal of international fiscal responsibility for the preservation of the world's heritage. With the popular success of the World Heritage List and a growing global economy of international tourism, the original aims of the Convention have been misplaced. Conceived as a program of international collaboration for the protection of heritage of significance to humanity, World Heritage has been transformed into an international certification scheme, subject to the selfish ambitions of UNESCO's Member States. I expose the divide between the goals of the Convention and the national politics that rule the decisions of its governing body, the World Heritage Committee. My archival and ethnographic analysis goes beyond snapshots of the current political and financial challenges confronting World Heritage, instead tracing their development over time. Adopting a diachronic view and following the money, I deconstruct the idea of sudden crisis and show how that theme is a tactic used to mask recurring missed opportunities and repetitive patterns. My work shows the gradual unfolding of bureaucratic decisions, buried in documents, that pretend to take action but result in maintenance of the status quo. I reveal how inertia, more than natural disasters or conflicts, threatens the lofty ideals of the World Heritage Convention. The current political and financial difficulties within UNESCO also indicate the faltering of post-WWII ideals, integral to the UN and its specialized agencies, of an intergovernmental responsibility for rebuilding and rehabilitation . The events described in my study may serve as an object lesson for the multilateral agencies seeking to enforce collective responsibility for issues of global significance
Unintended Consequences: The Impact of the CVRA Upon Superintendent Turnover
Keywords:  Public Policy Program
Stanford University
Humanities and Sciences
Public Policy Program
superintendent
district governance
CVRA
superintendent turnover
at-large elections
by-trustee area elections
school boards
California Voting Rights Act
Thesis

Since 2001, in its efforts to increase minority representation in elected bodies and boards, the California Voting Rights Act has largely catalyzed the switch from at-large to by-trustee area elections across the state. Up to this point, myriad studies have focused on determining the efficacy of the CVRA in achieving its more explicit endeavors. However, less attention has been paid to potential peripheral impacts of the policy. My analysis thus focuses not on whether the CVRA has accomplished its intended purpose; rather, my research endeavors to understand if, and to what extent, the CVRA’s change in election methodology from at-large to by-trustee area elections has affected superintendent turnover. While it’s clear that turnover is higher in the CVRA treated group as compared to the comparison group, the CVRA also seems to be slowing down this trend with statistical significance in terms of retention by about .11, to .13, and finally, to .25 superintendents – after 3, 4, and 5 years, respectively. If this is the case, then the CVRA might be smothering the flames of superintendent turnover, as opposed to fanning these flames – as it appears to do at first glance.
Unmasking Identities and Healing in the Classroom: The Impact of Ethnic Studies on the Psychosocial Well-Being of First-Generation Latinx College Students
Keywords: Graduate School of Education
Stanford University
first-generation college students
Latinx students
Ethnic Studies
psychosocial well-being
belonging
loneliness
self-esteem
ethnic identity affirmation
higher education
elite institutions
Thesis

This study explores the loneliness, self-esteem, and belonging that first-generation Latinx college students at a private elite university experience both within and outside of the Ethnic Studies classroom. More specifically, this study aims to 1) uncover the psychosocial effects (e.g., levels of loneliness, self-esteem, and sense of school membership) of engaging with culturally relevant Ethnic Studies courses and 2) understand the mechanisms by which Ethnic Studies impacts the psychosocial well-being of first-generation Latinx college students traversing a highly selective, exclusionary space within Higher Education. The sample population is comprised of 61 Stanford University students who self-identify as both first-generation college students and Latinx individuals. Group 1 is formed by 29 students who have taken two or more Ethnic Studies courses and Group 2 is formed by 32 students who have not taken two or more of these courses. Applying a mixed-methods approach, data were collected through an anonymous virtual survey and semi-structured exploratory interviews about the well-being and experience of participants in Ethnic Studies courses. Drawing upon the UCLA Loneliness Scale (Version 3), Rosenberg Self-Esteem Scale, and an adapted version of the Psychological Sense of School Membership Scale within the online survey, t-test results revealed a significant difference between Group 1 and Group 2 solely for the school belonging scale. Group 2 students who had not taken two or more Ethnic Studies courses demonstrated higher levels of school belonging overall, yet 86.2% of Group 1 students reported that Ethnic Studies helped cultivate their belonging on campus. Future studies and interventions should explore ways to mitigate the alienation first-generation Latinx students feel within the wider school community, a magnified contrast to the belonging they experience specifically in their culturally affirming, identity safe classrooms through community match and validation. Additionally, neither group scored exceptionally high in self-esteem or low in loneliness, illuminating the need for universities to acquire a whole student approach that centers well-being and culture in all classrooms as a means to promote educational equity and bolster the psychosocial well-being of underrepresented racially minoritized students.
User community innovation : implications for firm strategy, organizing and performance
Keywords: Management Science and Engineering.

Community-based innovation has recently emerged as a focal point of research on strategy and innovation. Scholars have argued that communities have several advantages over firms, such that managers must increasingly consider how to best compete and collaborate with this unique organizational form. Extant empirical work provides significant insight. However, it remains unclear how and when firms benefit from user community-based innovation. Across three tightly-linked papers, this dissertation addresses this gap. The first is a comprehensive review of prior work that studies user communities as they relate to firm strategy and performance. The second paper is a comparative case study of innovation by two civilian drone ventures—one that organized as a community, the other that organized as a firm. Finally, using a novel panel dataset of 2,586 video game development projects, the third paper develops and tests theory on whether firms can improve performance via learning from communities. Together, these papers contribute several interrelated findings to literature on firm strategy, organization theory and user community innovation, as well as several insights for management practice
Using AI and Deep Learning to Predict IQ and Reading Skills in Humans through Analysis of Human Brain White Matter Fascicles
Keywords: iq
plasticity
connectome
tensor
education
white matter
human brain
biomarker
tractography
oligodendrocytes
Thesis

This study uses Artificial Intelligence techniques and white matter data in the human brain, to analyze potential pathways to transhumanism: enhancing human cognitive abilities, and eventually creating a brain-computer interface that could result in brains enhanced by artificial intelligence. For example, using machine learning technologies, we could predict the particular development curves for some brain regions or tracts, and teach particular skills at the right time, when that area’s development is taking place. Moreover, by imaging the brain, we could identify specific brain substrates to stimulate while learning new skills, as performed by some existing researchers and companies,.
Deep Machine Learning models could be used to personalize content for different subjects based on their specific brain psychology, which can be applied in multiple fields, from education to entertainment, marketing, business and sales..
In this research, we have used brain magnetic resonance imaging techniques to identify brain white matter structure (brain tracts in particular) to train deep learning and other shallow artificial intelligence models which predict reading abilities and cognitive skills' scores.
The fractional anisotropy, a measure of how water diffuses within a brain location can be measured along the length of a tract (the FA profile). These profiles correlate with reading proficiency. We use these profiles to analyze the relationship between white matter in the human brain and reading and cognitive abilities. We examine multiple machine learning models that could help predict cognitive skills measures such as IQ and reading proficiency in subjects based on their fractional anisotropy profiles.
Using chromatin dynamics to understand transcriptional regulation and genetic variance
Keywords: Stem Cell Biology and Regenerative Medicine.

The genome is the same in every cell of an organism, but complex organisms have multiple cell types. This is due to the epigenome specifying a cell's transcriptional state resulting in distinct cell identities. Despite 98.5% of the human genome is non-coding and the site of epigenomic activity, which specifies instructions for regulating transcription of the coding region, relatively little is known about its function. A major hurdle with studying non-coding regulatory elements is identifying their distal gene and regulatory targets. Here, I solve this issue by using the three-dimensional chromatin conformation to identify targets that are in close physical proximity of the regulatory element. By integrating data on the three-dimensional chromatin state with other epigenomic measures including the open chromatin regions, transcription factor binding sites, and histone modifications I provide genome-wide insight into how the epigenome establishes the transcriptional state of the cell. In addition, I have developed a new method for prioritizing non-coding genetic variants in complex phenotypes. I validated this method in the context of Type 1 Diabetes and craniofacial disorders. In this dissertation, I demonstrate how data integration of multiple measurements of the epigenome and transcriptome provides insight into methods of transcriptional regulation and how this regulation is influenced by genetic variance
Using Complex Geometry to Rederive the BPS Spectrum of Seiberg-Witten Theory
Keywords:  Department of Physics
Complex Geometry
Seiberg
Witten
Supersymmetry
Compactification
Wall-Crossing
Thesis

This thesis reports on a novel procedure to derive the BPS spectrum of supersymmetric quantum field theories using the geometric properties of their vacuum moduli spaces. This procedure is demonstrated with a 4D, N=2 supersymmetric field theory, Seiberg-Witten theory. We examine the Coulomb branch of the vacuum moduli space of Seiberg-Witten theory compactified from 4D to 3D. It is known that the compactified metric is hyper-Kähler and therefore Ricci flat (Seiberg and Witten, 1996). Through using the wall-crossing formulae outlined by Gaiotto, Moore and Neitzke (Gaiotto, Moore, and A. Neitzke, 2010) and by imposing Ricci flatness on the compactified metric, it should be possible to extract the counts of BPS particles. This thesis reports on a method a validating this hypothesis using Seiberg-Witten theory, where the exact counts of BPS particles are known. In particular, I look at the strong coupling region of Seiberg-Witten theory and find that the integer count of the magnetic monopole can be derived through this approach. Through investigating the Ricci scalar at certain points in the Coulomb branch, the integer count of the monopole minimises the Ricci scalar numerically. This project was undertaken with Lark Wang, another undergraduate student
Using Poison Frogs to model sex differences in spatial navigation
Keywords:  Department of Biology
Stanford Department of Biology
O'Connell Lab
Poison Frogs
Ranitomeya imitator
Oophaga Sylvatica
Dendrobates Tinctorius
Open Field test
Exploratory behaviors
Thesis

The ability to navigate one’s environment is a key aspect of individual survival and overall fitness in many species. For example, spatial navigation is important for foraging, finding potential mates, or returning home. A critical part of spatial navigation is exploration behavior, or how an individual behaves in a novel environment. Exploration is also an important step in building a cognitive map of a new environment. Interestingly, the propensity to explore a new environment can differ between males and females in many species. In mammals, females often have decreased exploratory behavior compared to males and some have suggested this difference is linked to reproductive strategy where females must stay close to home to care for offspring. However, little work has been performed on exploratory behavior in animals with contrasting reproductive strategies. To better understand how sex differences in exploratory behavior is linked to reproductive strategies, I quantified exploratory behavior in an open field assay with several species of South American poison frogs (Family Dendrobatidae) that vary in parental care strategies, including male- and female-uniparental and biparental care. I found no significant sex differences in exploration rate or average speed between sexes for any of the species, though there were significant differences among species, with the male uniparental species exhibiting higher exploratory behaviors than female uniparental and biparental species. Overall, this work shows exploratory behavior in dendrobatid poison frogs differs across species, but not sex, which may be linked to general life-history differences rather than parental care strategies.