VictorJuiz/thesis huggingface dataset:
Analog signal processing circuits in organic transistor technology [electronic resource]
Keywords: Electrical Engineering

Low-voltage organic thin-film transistors offer potential for many novel applications. Because organic transistors can be fabricated near room temperature, they allow integrated circuits to be made on flexible plastic substrates. This physical flexibility allows organic transistors to integrate with bendable organic displays, polymeric muscles, and conformal sensors. Additionally, organic semiconductors are inherently sensitive to specific molecules, making organic transistors naturally suited for chemical and biological sensors. In all these applications, data converters are the essential link between the digital processors and the analog media. However, because of the inherent non-uniformities in organic processing, organic analog circuits suffer from large variations that lead to inaccurate and unreliable data conversion. Dielectric leakage and large parasitic capacitances further limit the available design space. This dissertation describes the sources of these process handicaps and offers design techniques to counter them. By applying these techniques, this research demonstrated the world's first organic-transistor digital-to-analog converter and the first organic-transistor analog-to-digital converter. Both data converters operate at 3 V, 100 Hz and resolve 6 bits. Similar design methodology can be utilized in designing other organic-transistor based analog signal processing circuits.
Analysis of national strategies for combating the proliferation of nuclear weapons [electronic resource]
Keywords: Management Science and Engineering

Analysis of strategies for stemming the proliferation of nuclear weapons is often considered too difficult for quantitative rigor. Qualitative arguments abound for how to best influence potential proliferators, but these often arise as reactionary statements to immediate events without explicitly accounting for future uncertainties. Further, without detailed analysis of the costs and benefits resulting from the recommended actions it is unclear how to best compare the proposed actions. The goal of this research is to provide national decision makers with a framework for evaluating different counter-proliferation strategies and to help identify courses of action that optimally trade-off the potential ramifications of a country's acquisition of nuclear weapons against the U.S. cost for interdiction. A framework was developed to analyze the effectiveness of national strategies for interdicting a targeted country's nuclear weapons program. This framework models both the intent and capabilities of the potential proliferant using a combination of Bayesian networks and semi-Markov decision processes. Interdiction strategies are then evaluated based on their expected costs and the resulting level of militarized conflict. Historical and current/future case studies are provided to demonstrate framework validity and for illustrating potential insights from the proposed methodology. The contrasting cases of South Africa and Pakistan were modeled in their historical context. The results demonstrate the framework's ability to accurately represent different nuclear weapons scenarios. Sensitivity analyses on these cases depict plausible futures and are used as examples of insights attributable to the described approach. Modern day Iran was modeled to depict a current/future analysis using the developed framework. An optimal U.S. strategy was identified leveraging military, diplomatic, and economic interdiction options. Sensitivity analysis on the probability of Iran's leadership and on the probability of an attack against the U.S. or allies highlights the flexibility of the proposed approach for modeling a variety of possible situations and the ability to identify plausible interdiction strategies.
Approximate message passing algorithms for compressed sensing [electronic resource]
Keywords: Electrical Engineering

Compressed sensing refers to a growing body of techniques that `undersample' high-dimensional signals and yet recover them accurately. Such techniques make fewer measurements than traditional sampling theory demands: rather than sampling proportional to frequency bandwidth, they make only as many measurements as the underlying `information content' of those signals. However, as compared with traditional sampling theory, which can recover signals by applying simple linear reconstruction formulas, the task of signal recovery from reduced measurements requires nonlinear, and so far, relatively expensive reconstruction schemes. One popular class of reconstruction schemes uses linear programming (LP) methods; there is an elegant theory for such schemes promising large improvements over ordinary sampling rules in recovering sparse signals. However, solving the required LPs is substantially more expensive in applications than the linear reconstruction schemes that are now standard. In certain imaging problems, the signal to be acquired may be an image with
Array architecture for a nonvolatile 3-dimensional cross-point memory [electronic resource]
Keywords: Electrical Engineering

This work explores the design and capabilities of a three-dimensional cross-point array structure suitable for use with resistance-change non-volatile memory. The resistance-change cell serves as both the access element and the memory element, eliminating the need for individual selection transistors or diodes. This enables the memory to be fabricated in arrays with a line spacing of F, the minimum feature size for a given process technology. By stacking the cross-point arrays in n layers, we achieve an effective cell size of 4F^2/n. Previous works describing transistor-free memory arrays have been limited by excessive leakage current across unselected bitlines and wordlines during memory access. This work presents novel architecture and circuit techniques that minimize leakage current effects while maintaining a high effective bit density. A test chip fabricated in 0.18 um CMOS technology allows us to verify the architecture and circuit functionality. The performance of a 8 Gb memory chip build in 65 nm technology has been simulated. A random access time of 104 ns is achieved with a power dissipation of 61.2 uW. This makes the 3-D cross-point memory competitive with NOR flash in terms of read time, and competitive with NAND flash in terms of area efficiency.
The assembly and interactions of MreB in the maintenance of cell shape in Caulobacter crescentus [electronic resource]
Keywords: Biochemistry

This work focuses on the mechanism by which MreB contributes to the maintenance of cell shape in the gram-negative alpha-proteobacterium Caulobacter crescentus. The gene mreB encodes a protein that resembles actin, a eukaryotic cytoskeletal protein. Previously, it was shown that mreB is required to maintain a rod-like shape and localizes to a helical pattern near the cytoplasmic membrane. Here, we show that MreB is associated with regions of active growth in Caulobacter, as mutant strains that mislocalize MreB to the cell poles direct new growth at or near the poles. We present evidence to suggest that MreB contributes to the determination of proper length, width, and curvature through partially distinct mechanisms. The determination of proper width involves the essential proteins MreC and Pbp2, which are encoded in the mreB operon. While MreB and MreC are both required to position the cell wall transpeptidase Pbp2 along the lateral sidewalls and away from midcell, the two do not colocalize and each can maintain its localization in the absence of the other. When MreB is mislocalized to the poles, MreC and Pbp2 do not follow. These data argue against the idea that MreB provides a scaffold-like structure to localize enzymes that directly modify the cell wall. The determination of proper curvature, involves the intermediate filament-like protein, Crescentin. We identify a putative binding site on MreB for Crescentin or other curvature-mediating factors. We also show that the extent to which the subcellular localization of MreB changes over the cell cycle is correlated with cell size, indicating that MreB is involved in the coordination between elongation and division. In addition, we show that in vitro purified MreB spontaneously forms very stable polymers in the presence or absence of nucleotide. These polymers are globular or amorphous and only filamentous when placed on a highly positively charged surface of Poly-L-lysine. These in vitro data suggest that MreB is likely to be regulated at the disassembly step in the cell and that the cellular environment may influence the structure of MreB polymers. Lastly, we present biochemical evidence to support the existence of a disassembly factor in cytoplasmic Caulobacter extract. Together our data suggest that the maintenance of the crescent-rod cell shape in Caulobacter is the result of a complicated balance between MreB's dynamic subcellular localization, polymeric structure, and communication with cellular components.
Astrophysics of the intracluster medium in X-ray bright galaxy clusters [electronic resource]
Keywords: Physics

Clusters of galaxies are the most massive, gravitationally-bound structures in the universe. Detailed studies of their properties are applicable to a wide variety of astrophysical problems. These include, but are not limited to galaxy formation, large-scale structure formation, and cosmology. A cornerstone of such studies is the use of X-ray satellite observations to study the X-ray radiation from the diffuse, hot intracluster gas, which dominates the baryonic matter content. This thesis records the analysis and results of some of the deepest observations of X-ray bright galaxy clusters ever made with the Chandra X-ray Observatory, NASA's flagship X-ray observatory. The studies presented focus upon the detailed physics of the intracluster medium (ICM) including the ram-pressure stripping and the possible destruction of cool cores within clusters; the interaction between the central active galactic nucleus with the intracluster gas in cool cores; and searches for non-thermal X-ray emission components. With deep observations of the nearest and brightest galaxy clusters, the astrophysics can be probed in exquisite detail. However, the conclusions drawn are expected to be applicable to the general cluster population, with implications for statistical cluster studies and cosmology.
Background calibration of timing skew in time-interleaved A/D converters [electronic resource]
Keywords: Electrical Engineering

The increasing data rate of wireline communication systems leads to more inter-symbol interference, due to the dispersive properties of the communication channel. This requires more complex equalization blocks to meet the required bit-error rate. One solution is to use an Analog-to-Digital Converter (ADC) in the front-end, thus enabling a digitally-equalized serial link. To achieve the high-data rates of these communication systems, a time-interleaved ADC is typically used. However, this type of ADC suffers from several time-varying errors, the most prominent of which is timing skew. This thesis introduces a statistics-based background calibration algorithm that compensates for the effect of timing skew. To demonstrate the background calibration algorithm, a proof-of-concept 5 bit 12 GS/s flash ADC has been fabricated in a 65 nm CMOS process. The design of this ADC takes into consideration the tight power bounds imposed on serial links by optimizing both the time-interleaved and the sub-ADC architecture. Power consumption is further reduced by using calibration circuits to correct the offset of the flash ADC's comparators. In the measured results, the timing skew correction improves the dynamic performance of the time-interleaved ADC by 12 dB, and the proof-of-concept ADC has the lowest published power consumption for ADCs with sample rates higher than 10 GS/s.
Barriers and Facilitators to Adoption of Personal Health Records: A Study of Families with Children with Special Health Care Needs
Keywords: Medical records
Personal information management
Medical informatics
Electronic health records
Thesis

This project explores the barriers and facilitators to adoption of electronic Personal Health Records (PHRs) in low income families/caregivers of children with special healthcare needs (CSHCN). Focus groups at two community support organizations were conducted in English, Spanish, and Cantonese. Usability studies of Google Health, a personal health record that is partnering with Lucile Packard Children’s Hospital, were also conducted in English with parents. These studies will help explain: 1) the current methods by which parents manage healthcare information, 2) the knowledge, needs, and concerns of caregivers about PHRs, and 3) design goals for improving PHR accessibility.
Focus groups and interviews following the usability studies consistently showed that parents rely on paper-based methods even though healthcare providers may not always give full copies of records. This incomplete record frustrates parents and impedes information flow between the multiple healthcare providers of special needs children. The PHR was met with excitement by families, but few families were aware of the PHR’s availability before participating in the study. However, the majority of parents expressed a desire to learn and begin using a PHR to complement their information management needs. Although privacy concerns, technology literacy, and health literacy remain as foreseeable barriers to PHR adoption, families
with CSHCN can derive immediate benefit if they are informed and educated about the availability of the PHR to manage healthcare information. Developers of PHRs can support this goal by ensuring that sound usability is a priority, thereby presenting a compelling option for parents.
A Bayesian method for construction of Markov models to describe dynamics on various time scales [electronic resource]
Keywords: Chemistry

The dynamics of many biological processes of interest, such as the folding of a protein, are slow and complicated enough that a single molecular dynamics simulation trajectory of the entire process is difficult to obtain in any reasonable amount of time. Moreover, one such simulation may not be sufficient to develop an understanding of the mechanism of the process, and multiple simulations may be necessary. One approach to circumvent this computational barrier is the use of Markov state models. These models are useful because they can be constructed using data from a large number of shorter simulations instead of a single long simulation. This thesis presents a new Bayesian method for the construction of Markov models from simulation data. A Markov model is specified by (t, P, T), where t is the mesoscopic time step, P is a partition of configuration space into mesostates, and T is an N x N transition rate matrix for transitions between the mesostates in one mesoscopic time step, where N is the number of mesostates in P. The method presented here is different from previous Bayesian methods in several ways. 1. The method uses Bayesian analysis to determine the partition as well as the transition probabilities. 2. The method allows the construction of a Markov model for any chosen mesoscopic time scale t. 3. It constructs Markov models for which the diagonal elements of T are all equal to or greater than 0.5. Such a model will be called a 'consistent mesoscopic Markov model' (or CMMM). Such models have important advantages for providing an understanding of the dynamics on a mesoscopic time scale. The Bayesian method uses simulation data to find a posterior probability distribution for (P, T) for any chosen t. This distribution can be regarded as the Bayesian probability that the kinetics observed in the atomistic simulation data on the mesoscopic time scale t was generated by the CMMM specified by (P, T). An optimization algorithm is used to find the most probable CMMM for the chosen mesoscopic time step. We applied this method of Markov model construction to several toy systems (random walks in one and two dimensions) as well as the dynamics of alanine dipeptide in water and of trpzip2 in water. The resulting Markov state models were indeed successful in capturing the dynamics of our test systems on a variety of mesoscopic time scales.
Beyond "Spanglish" [electronic resource] : ideologies of language and identity in bilingual Chicana/o cultural production
Keywords: Iberian and Latin American Cultures.

Prompted by the following research question: How is the relationship between language and identity conceptualized, articulated, and represented in cultural productions by, for, and about Chicana/os?, this dissertation interrogates linguistic assumptions and expectations of Chicana/o identities. By foregrounding the study of bilingualism in analyses of coming-of-age novels, autobiographical narratives, and feminist writing, it argues for the identification of language ideologies in Chicana/o cultural production. Doing so allows for the necessary examination of social constructions of language and the systems of power they reproduce within Chicana/o cultural studies, as well as the recalibration of limiting linguistic expectations of Chicana/o identity. The first chapter presents a conceptual framework based on the study of bilingualism, identity work, language ideologies, and Chicana/o cultural studies as a critical entry into the analysis of representations of bilingualism and/or bilingual representations. The second chapter compares the proto-Chicano development of bilingualism and Mexican American identity in the protagonists and texts of José Antonio Villareal's Pocho and Américo Paredes's George Washington Gómez. The third chapter elucidates the intricate identity work required to choose and maintain a bilingual Chicana/o identity in Ernesto Galarza's Barrio Boy, Arturo Islas's The Rain God, and Sandra Cisneros's Caramelo. The fourth chapter examines the conflictive relationship to Spanish as a heritage language in writings by Michele Serros, Gloria Anzaldúa, Cherríe Moraga, and Vida Mía García that scrutinize the negation of bilingual Chicana/o identities.
Biodegradable poly (hydroxyalkanoates) [electronic resource] : melt, solid, and foam
Keywords: Chemical Engineering

Plastic materials have a huge impact to the environment. EPA statistics shows that less than 7% of the plastic products are being recycled, and many of the rest are sent to landfills or, in worse scenarios, end up in our natural environment. Poly(hydroxyalkanoates) (PHAs), a family of biodegradable polyesters that can be produced by microbes fed on renewable carbon substrates, can be used as a "green" substitute to conventional plastics and help solve this environmental problem. However, difficulties remain for using PHAs at a sizable scale. Besides the high production cost, weaknesses in material properties, including narrow thermal processing window and insufficient melt elasticity, are also limiting the application of PHAs. Recent progress in PHA syntheses has resulted in new copolymers in the PHA family which are expected to possess improved properties. In this thesis, the melt properties of a series of one such copolymer, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB-co-3HHx), with varying 3HHx content, were investigated. Results suggested that the presence of the propyl side groups on 3HHx increases the steric hindrance of the P3HB-co-3HHx chains, thus resulting in increased entanglement density, and subsequently, the melt elasticity. Solid-state properties of P3HB-co-3HHx were also studied, and the effects on biodegradability of thin films of P3HB-co-3HHx were investigated. Results show that varying copolymer composition in combination with modifying the crystalline morphology through heat treatment may enable control over biodegradation rates for PHAs materials. In addition, biodegradable cellular foams made of PHAs were synthesized through extrusion foaming, a standard melt processing for thermoplastics. A commercial PHA copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-3HV), was used and evaluated for its foamability. Another naturally-derived polymer, cellulose acetate butyrate (CAB), was chosen to blend with P3HB-co-3HV to enhance its melt properties and processability. It was found that blending significantly improved the thermal processing window and enhanced melt elasticity. Results showed that selectively combining two types of bio-based renewable polymer could be an effective way to tune the melt properties and crystallinity and thus the processability.
Biomechanical guidelines for the treatment of crouch gait in children with cerebral palsy [electronic resource]
Keywords: Mechanical Engineering

Many children with cerebral palsy walk with excessive knee flexion, an inefficient locomotion pattern known as crouch gait that progressively worsens over time without intervention. Patients often receive surgeries to lengthen tight or spastic muscles or to correct bone malalignments, but outcomes are variable and unpredictable. The goals of this dissertation were, first, to objectively identify biomechanical factors that cause a patient to walk with excess knee flexion and, second, to use these factors to predict whether a patient's crouch gait will improve after receiving treatment. We first determined the influence of abnormal bone geometry and crouched gait postures on the function of muscles during walking using a three-dimensional model of the musculoskeletal system. Our analysis revealed that a tibial torsion deformity, a common bone malalignment, reduces the capacity of lower limb muscles to generate extension of the knee and hip joints. Excess tibial torsion may thus be a significant contributor to crouch gait and warrant surgical correction. In addition, our analysis showed that a crouched gait posture markedly reduces the capacity of most lower limb muscles to extend the knee and hip joints. These findings help explain the altered muscle activations, increased energy requirements, and increased joint loading associated with walking in a crouch gait. We also developed a multi-variable linear regression model to estimate how much subjects' crouch gait would change between hospital visits by retrospectively analyzing patients' gait kinematics over time and surgical histories. The regression model was able to explain 49% of the variance in the change in knee flexion between gait visits for the 353 subject-limbs that we analyzed. Further, the regression model classified subject-limbs as 'Improved' or 'Unimproved' with approximately 70% accuracy, which contrasts with the observed improvement rate of 48% among subject-limbs in the study. We further demonstrated that more improvement in crouch gait was expected when subjects had i) adequate hamstrings lengths and velocities, ii) normal tibial torsion, and iii) greater extensor muscle strength, three variables drawn from our knowledge about the biomechanics of crouch gait. This work establishes a new framework--combining biomechanical modeling and statistical analysis--for understanding gait pathology and objectively planning treatment.