VictorJuiz/thesis huggingface dataset:
Forming-free nitrogen-doped aluminum oxide resistive random access memory [electronic resource]
Keywords: Electrical Engineering

The persistent request for smaller, faster, cheaper, more capable electronic devices continues to drive the development of technology and to drive the exploration of unique materials to overcome the limits of conventional Si-based technology. Since many modern electronic devices become mobile and multifunctional, they need a new high-density nonvolatile memory overcoming density limitations of currently used flash memory. Bi-stable switching is reported to be observed in a variety of next-generation non-volatile memory technologies such as a resistive random access memory (RRAM), a phase-change random access memory (PRAM), a magnetoresistive random access memory (MRAM) and a ferroelectric random access memory (FeRAM). Among these nonvolatile memories, resistive random access memory (RRAM) is a promising candidate for next-generation nonvolatile memory with higher density than that of flash memory since it is based on a low-temperature grown oxide thin film with bi-stable resistance states and is compatible with three-dimensional stack structure. Among various oxide films exhibiting the resistive switching phenomenon, aluminum oxide (AlOX) is one of the most promising materials because of its simple constituents, clear switching characteristics, and moderate on/off ratio. In addition, since AlOX has a simple binary system, it has an advantage for the industrial fabrication. However, there are some challenges that need to be addressed for the AlOX based RRAM. One of the challenges is that AlOX RRAM cells have been reported to require a high voltage forming process. So, making good quality aluminum oxide film with a moderate amount of defects is a main issue for realizing AlOX RRAM devices. In this dissertation, we present a simple nitrogen-doped AlOX (N-AlOX) RRAM cell that has a moderate amount of defects. The main contribution of this dissertation is a new type of RRAM (N-AlOX RRAM) that does not require a forming process and shows small programming currents. Some switching mechanisms have been proposed to explain the resistance switching phenomenon of AlOX RRAM. However, the underlying mechanism of resistance switching behavior of N-AlOX RRAM has not been understood. So, we perform some material analyses of N-AlOX RRAM in detail to understand the switching mechanism. Next, we discuss various electrical characteristics of N-AlOX RRAM. Based on the electrical characteristics, we present a Frenkel-Poole model for the current conduction mechanism of N-AlOX RRAM. The last topic of this dissertation is titanium oxide (TiOX) based RRAM. We focus on evaluating many electrodes and understanding the impact on the switching characteristics of TiOX RRAM. As a result, we find iridium oxide (IrO2) as a viable electrode for TiOX RRAM. In addition, we successfully improve the uniformity of switching parameters by inserting two hafnium (Hf) interfacial layers. Finally, we conclude this dissertation with a summary of the main points and some suggestions for future work on this topic.
Framed [electronic resource] : bilingual education and the construction of national identities
Keywords: Anthropology

Abstract This work examines what role, if any, bilingual education has in the construction of a national identity. I explore the issue in the Autonomous Basque Community in Spain. This region provides the discussion with a well known nationalist struggle and a wide variety of academic models and experiences of bilingual education. In this environment I ask, when and how do issues of nationalism and identity enter into language education? How does policy design differ from classroom implementation and results? What is the role of parents, teacher, students or the community at large? These questions are explored using ethnographic data gathering methods, interviews, surveys, and analysis of language use across various levels of engagement with bilingual education. The analysis moves from general public opinion, to school culture and classroom ethnographies. Along the way, this research addresses politicized or toxic schools, silent resistance, and teachers whose lesson plan is co-opted and rendered as something different. The experiences of students in schools show that language education is not just one grade, one teacher and is far from being a perfectly oiled nationalist machinery. Students emerge as expert frame casters, actively analyzing the sociolinguistic environment of every classroom and tailoring their participation accordingly. Early competence in abstracting content and framing interpersonal exchanges are key to understanding how it is that, in certain schools, youth may be radicalized in spite of teachers' efforts while in other schools silenced majorities find their way through cultures in conflict to give birth to new cultural identities and political agendas.
Frequency conversion of single photons [electronic resource] : physics, devices, and applications
Keywords: Applied Physics

The ability to manipulate the carrier frequency of quantum states of light, through a process called quantum frequency conversion (QFC), has numerous applications for both technology and basic science. For example, one can upconvert a single-photon-level signal in the 1.5-micron telecommunications band (where single-photon detection has been challenging) to a visible wavelength to take advantage of well-developed single-photon detectors based on silicon avalanche photodiodes. On the more fundamental side, the manipulation of a single photon's frequency may enable the construction of networks of dissimilar quantum systems, whereby one can imagine generating many-body entangled quantum states over vast distances. Quantum frequency conversion will only be useful if it can be done both efficiently and with little added noise. We demonstrated a conversion efficiency exceeding 99.99% using reverse-proton-exchange waveguides in periodically poled lithium niobate with approximately 150 mW of pump power. Noise has been a more serious issue: the generation of noise photons, due to inelastic scattering of light from the strong pump laser used to drive the frequency conversion, has limited the utility of QFC devices in many applications. We present an analysis of the two primary noise processes in QFC devices (spontaneous Raman scattering and spontaneous parametric fluorescence), and offer solutions on how they may be either mitigated or avoided completely. We then discuss applications of QFC devices for up- and downconversion of single-photon signals. We used a long-wavelength pump to enable high-efficiency and low-noise single-photon detection for 1550-nm telecom band signals, and demonstrated a cascaded frequency conversion approach that enabled low timing jitter as well. We also demonstrated a downconversion quantum interface, in which the emission from a single semiconductor quantum dot at a wavelength of 910 nm was downconverted to 1560 nm while maintaining the single-photon character of the light. The results presented in this dissertation indicate a promising future for QFC devices as the field of quantum communications matures.
From affirmative action to diversity [electronic resource] : rationales for faculty diversification efforts in a state anti-affirmative action regulatory environment
Keywords: Education.

This dissertation examines how state bans on affirmative action affect rationales for diversity in faculty recruitment and hiring at a public university and a private university. The study is motivated by concerns regarding the ability of universities to attract a diverse professoriate, particularly within an anti-affirmative action climate. The study employs a qualitative research design and uses a framework that incorporates concepts from neoinstitutional theory. Interviews with 21 faculty and administrators from a public university and a private university coupled with a review of documents from both universities form the basis of the analysis. The two universities examined in this study navigated the state anti-affirmative action regulatory environment similarly and drew upon a nearly identical set of rationales to support faculty diversity policies and practices. Affirmative action programs were eliminated or reconstituted into programs that were legally permissible. Explicit discussions of affirmative action have been largely replaced with a broadening use of the term "diversity." Faculty accounts reveal myriad interpretations of the diversity rationale, leading to heightened confusion in faculty search deliberations. The state anti-affirmative action regulatory environment did not result in diversity no longer mattering in higher education; rather, it changed how diversity mattered. The study generates knowledge about the relationship between public policy and higher education and produces insights on whether universities acquiesce to or resist pressures to alter behavior and rationales as a result of public mandates. The study also illustrates how the interaction of internal and external pressures for and against affirmative action in faculty searches leads to how faculty recruitment and hiring policies are understood, re-interpreted, and put into practice. Ultimately, the study furthers our understanding of the regulatory factors that may contribute to the persistent underrepresentation of scholars of color.
Gene expression control by nuclear phosphoinositides and chromatin [electronic resource]
Keywords: Biology.

The physiological state of the genome is chromatin. Chromatin is a dynamic polymer composed of genomic DNA, histone proteins, and other factors. Dysregulation of chromatin homeostasis can lead to diverse human pathologies including cancer. This work focuses on chromatin-based mechanisms of gene regulation; more specifically the (1) targeting and (2) stabilization of gene-regulatory proteins on the chromatin template. In regard to chromatin targeting, not much is known about how gene-regulatory proteins selectively associate with their targets. Herein we detail the discovery of a new targeting factor, the nuclear phospholipid phosphatidylinositol-5-phosphate (PtdIns(5)P). PtdIns(5)P directly interacts with the tumor suppressor ING2 (inhibitor of growth family member 2) in the nucleus to coordinate gene expression of select ING2 targets. In regard to chromatin stabilization, lysine methylation is a principle mechanism for retaining chromatin-effector modules at discrete chromatin zones. Numerous lysine methylation events have been discovered on the major protein component of chromatin, histones, but relatively few specific modules have been characterized to sense these modifications. We screened through a library of putative methyl-lysine binding domains, which resulted in the identification of three novel chromatin binding modules. Taken together these data shed insight into the molecular modes of action of gene regulation by chromatin and phosphoinositide pathways.
Generation of extremely low frequency waves via modulated ionospheric heating for communications applications [electronic resource]
Keywords: Electrical Engineering

Extremely low frequency (ELF) electromagnetic waves (0.3—3 kHz) have many applications including communications with submerged submarines, remote sensing of the lower ionosphere, and active wave-particle interaction experiments involving energetic particles trapped in Earth's radiation belts. However, waves in this frequency range are difficult to generate due to their large wavelengths (~100—1000 km) and therefore the large antennas required for efficient radiation. One relatively new and unconventional technique for ELF generation uses modulated heating of the lower ionosphere. The modulated ionospheric heating technique utilizes a high frequency beam (HF, 3—10 MHz) amplitude modulated at ELF frequencies to create a time-varying change in the conductivity of the lower ionosphere. When performed in regions where natural, large-scale horizontal ionospheric currents exist, such as the auroral electrojet at polar latitudes, the conductivity change results in a time-varying current that radiates at the ELF modulation frequency. While sidestepping the challenges of constructing a conventional ELF antenna, the modulated heating technique introduces new difficulties. The amplitude of the ELF waves depends strongly on the strength of the electrojet and the conversion between HF power and the ELF field is highly nonlinear. The purpose of this work is to characterize the dependence on electrojet strength and mitigate or utilize the nonlinearity between HF power and ELF fields so that experimenters and communication systems operators can optimize the generation of ELF waves using modulated ionospheric heating. Higher ionospheric density results in a large increase in the electrojet current strength but only a small increase in the generated ELF amplitude while lower ionospheric density can result in a weaker electrojet but only a small decrease in ELF generation. Harmonic content can be reduced by transmitting a predistorted HF power envelope that results in a sinusoidal ELF current at a particular altitude. This technique depends on a correct model of the ionosphere, which is highly variable in practice. Other modulation envelopes explored, such as square wave modulation, create stronger harmonics but can also result in higher generated ELF power or greater efficiency. Finally, we conduct experiments using quaternary phase shift keying (QPSK) to transmit digital data and examine how the bit error rate (BER) varies with generation conditions and changes in transmitter parameters.
Genetic and chemical studies towards the mechanistic understanding of Gli activation [electronic resource]
Keywords: Chemical and Systems Biology.

The activation of the Hedgehog (Hh) pathway leading to Gli-dependent transcription plays critical roles in tissue patterning, homeostasis, and transformation. Despite the initial discovery of the pathway 30 years ago, a complete mechanistic understanding of Hh signal transduction remains elusive. By conducting a genome-scale overexpression screen using mammalian open reading frames (ORFs), I have identified the Rho GAP domain-containing protein Arhgap36, the homeodomain-interacting protein kinase Hipk4, and MED26, a subunit of the Mediator complex, as regulators of Gli function. This study represents the first report describing a functional role of Arhgap36 in any signaling process, and demonstrates Hipk4 modulates the cellular response to Hh ligand. The activity of MED26 was revealed in the context of the small molecule Hedgehog Pathway Inihibitor-1 (HPI-1), giving further insight to its mechanism of action. In addition, we describe the relevant mechanism of action of the small molecule JK184, a microtubule-disrupting agent that can have both positive and negative effects on pathway activity, depending on the nature of pathway perturbation. These findings provide new insights into how cells regulate Gli-dependent transcription and suggest strategies for the therapeutic intervention of Hh pathway-dependent disease.
The genomic basis of yeast adaptation to limiting glucose [electronic resource]
Keywords: Genetics

Adaptive evolution by natural selection is largely responsible for the variety of forms and functions observable in the natural world. Identifying the genetic changes underlying adaptive evolution of organisms to their environment is of fundamental importance in understanding the history of life, as well as predicting how organisms will evolve to novel environments in the future. Experimental evolution of microbes in the laboratory provides a precisely controlled environment for investigations into the genetic basis of adaptation, while also allowing for large population sizes and experimental replication, benefits that are often not available in natural populations. Recent technologies have enabled the identification of the genetic changes responsible for adaptive evolution genome-wide, giving us a genomic view of adaptation during evolution experiments. Here, I have added to our understanding of the genomic basis of adaptation by investigating how Saccharomyces cerevisiae adapts to limiting glucose environments during experimental evolution. Throughout this work, I utilize next- generation, whole-genome sequencing to identify the mutations responsible for adaptation. In Chapter 1, I investigate how genetic interactions define the fitness landscape, and find that very strong negative epistasis between two beneficial mutations creates a fitness valley, so each mutation effectively determines the evolutionary trajectory of adaptation. In Chapter 2, I take a step back and look more broadly at adaptation while asking the question: is there a general functional theme for the genomic basis of adaptation to limiting glucose? To facilitate answering this question in an unbiased manner, I develop a whole-population, whole-genome sequencing technique, and find that the theme of adaptation in the constant and predictable environment of the glucose-limited chemostat is for the yeast to lose function of signaling networks responsible for sensing environmental stimulus, effectively decoupling environmental sensing from response. In Chapter 3, in a collaborative project, we seek to understand the extent that genotypic convergence underlies phenotypic convergence by evolving genetically distinct yeast under different conditions. We find a single gene is recurrently mutated across most genetic backgrounds, suggesting that genotypic convergence plays a large role in adaptive evolution.
Geology and 40-argon/39-argon geochronology of the mid-miocene high rock caldera complex, northwest Nevada [electronic resource]
Keywords: Geological and Environmental Sciences.

Large igneous provinces are characterized by eruption of > 100,000 cubic km of magma over time scales of less than a few million years. Although most studies of large igneous provinces focus on flood basalt magmatism, there is increasing evidence that voluminous eruptions of silicic ignimbrites and lavas occur contemporaneous with global flood basalt magmatism. Estimated volumes of silicic magma range from 1 to 6% of the volume of coeval flood basalt lavas. Although these volumes are significant, poor preservation has resulted in relatively few detailed geologic investigations of cogenetic silicic deposits in large igneous provinces. In this dissertation, I investigate silicic caldera-forming eruptions that are contemporaneous with eruptions of the youngest and best exposed continental flood basalt province on Earth, the Columbia River flood basalt province, located in the northwestern United States. I present new 40-Argon/39-Argon ages and geologic evidence for silicic volcanism in northwest Nevada and southern Oregon at the High Rock Caldera Complex (HRCC). The HRCC consists of the products of four major overlapping calderas, 24- to 40-km in diameter, which collapsed between 16.4 and 15.7 Ma, shortly after initiation of flood basalt eruptions at Steens Mountain at ca. 16.7 Ma. Regionally, silicic volcanism that was contemporaneous with the peak flood basalt eruption interval between 16.7 and 15.0 Ma was more voluminous and occurred over a wider area than previously recognized. The most voluminous silicic eruptions were early and peralkaline, occurring at HRCC and McDermitt Caldera. The largest calderas are located along a narrow NNE trend near the transition between continental and accreted oceanic crust, and occur peripheral to zones of intense basaltic diking. I present a new model in which flood basalt magmas that intruded along the edge of the western margin of continental North American craton controlled the timing, location, and composition of 16.6 to 15.0 Ma silicic calderas at the HRCC and McDermitt Caldera. I also present evidence for the Steens basalt being the source for peralkaline rhyolite magmatism at the HRCC. These new findings are important because they agree with observations from other large igneous provinces that these massive eruptive events are predominantly bimodal. These observations require modification of models for the initiation of the Snake River Plain-related silicic magmatism.
Geomechanical analysis of intraplate earthquakes and earthquakes induced during stimulation of low permeability gas reservoirs [electronic resource]
Keywords: Geophysics

This thesis applies the principals of geomechanics to address a breadth of fundamental scientific questions regarding rock properties near major active faults, physical mechanisms driving intraplate earthquake activity, and how induced earthquakes in low-permeability natural gas reservoirs provide insight into reservoir deformation during hydraulic fracture stimulations. The first part of this thesis applies a shear-wave splitting analysis to examine physical controls on crustal anisotropy mechanisms on and near the North Anatolian Fault in northwest Turkey. The analysis indicates that stress-controlled mechanisms appear to prevail at distances greater than 1 km from the main fault trace while structure-controlled mechanisms are observed within 1 km of the main fault trace, suggesting the existence of heterogeneous physical properties between the main fault zone and surrounding crust. The second part of this thesis applies fundamental geomechanical principals to examine the compatibility of shear slip on intraplate faults in the central and eastern United States and southeastern Canada with frictional faulting theory in the context of the regional tectonic stress field. The application demonstrates that maximum horizontal stress orientations consistently trend NE-SW across the study area, horizontal principal stress magnitudes become increasingly compressive with respect to the vertical stress moving from the central U.S. toward the northeastern U.S. and southeastern Canada, and shear slip on the vast majority of intraplate fault planes is well described by the Mohr-Coulomb failure criterion in the current stress field assuming hydrostatic pore pressure in the upper crust and laboratory-determined coefficients of fault friction. The final part of this thesis applies an integrated, geomechanical and seismological analysis to evaluate the response of low permeability natural gas reservoirs to hydraulic fracturing stimulations in two case studies in western Canada. Geomechanical, waveform similarity, and microseismic event magnitude scaling analyses indicate that the reservoir response to hydraulic fracturing is generally characterized by shear deformation occurring on small faults reactivated during hydraulic fracturing stimulations. The advanced double-difference earthquake relocation technique is applied to improve microseismic event hypocenter locations. While the technique reduces scatter in microseismic event hypocenter locations, it is susceptible to producing hypocenter location artifacts in limited (single or double) monitoring array configurations. However, synthetic test show the double-difference technique could be a viable tool in accurately relocating microseismic events provided a suitable monitoring array configuration (three arrays or more) exists.