Browsing by Subject "Selection"
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Item Discovery and design of an optimal microRNA loop substrate(2013-05) Hwang, Tony Weiyang; Ellington, Andrew D.RNA interference, or RNAi, is a cellular mechanism that describes the sequence-specific post transcriptional gene silencing observed in plants, fungi, and metazoans, facilitated by short double-stranded RNAs and microRNAs (miRNAs) with sequence complementarity to target mRNAs. Many of the regulatory mechanisms of the RNAi pathway by which these small miRNAs are first processed, from primary transcripts to precursor miRNA stemloops and then to mature miRNAs, by the multiprotein complexes Drosha and Dicer, respectively, still remain unknown. Within the miRNA biogenesis pathway, there is strong evidence pointing to the terminal loop region as an important regulatory determinant of miRNA maturation. To further elucidate the terminal loop's exerted control over miRNA processing, we propose a combined in vitro / in vivo selection experiment of a randomized pri-miRNA terminal loop library in search of an optimally processed pre-miRNA substrate. Here, we report the isolation of a premiRNA terminal loop sequence that is favorably processed by Drosha in vivo but also functions as an effective cis-inhibitor of further pre-miRNA processing by downstream Dicer. This terminal loop also demonstrated modular properties of Dicer inhibition in two different miRNAs, and should prove useful in further elucidating the mechanisms of miRNA processing in context of a newly proposed Dicer cleavage model (Gu et al. 2012). In combination, these findings may have important implications in both Drosha and Dicer's direct role in gene expression and miRNA biogenesis, the regulatory proteins that modulate their respective functions, as well as the potential development of new design rules for the more efficient processing and targeting of miRNA-based technology and RNAi therapeutics.Item The effect of range restriction on personnel selection(2010-05) Steindl, James Richard; Pituch, Keenan A.; Emmer, EdmundIn 1903 Karl Pearson identified the effects of censorship, or range restriction, on the correlation coefficient. The current report reviews the history and literature examining those effects, corrections for range restriction, and the limitations of previous research. A rationale for further research of the effect of range restriction on logistic regression parameter estimates is presented.Item Eksen : regression test selection for VHDL(2018-01-26) Loyola, Jose Luis; Khurshid, Sarfraz; Gligoric, MilosRegression testing - running tests after a change - has become a critical component of software development, but as projects grow bigger it becomes a time consuming task. For this reason Regression Test Selection (RTS) techniques have become very important. RTS consists of analyzing the changes to a code base and selecting a subset of tests to be run based on these changes. In the context of regression testing, VHDL development is not so different from any other programming language. Modules have unit tests and integration tests. Similarly, the larger the project, the longer it takes to run the test suite. We propose Eksen, a tool for VHDL test selection inspired by the Ekstazi tool for Java. Eksen keeps track of which files have changed including its dependencies and uses this information to select which tests must be run. Eksen statically analyzes the VHDL file dependency tree, it determines which files are affected by the change and only run the tests from that dependency branch. By targeting only the tests on the dependency branch, Eksen can significantly reduce the test suite execution time. For evaluation purposes, we implemented two versions of Eksen: one using VUnit (an open-source VHDL testing framework). The second using a proprietary enterprise VHDL compiler. This allowed us to verify the time savings on a real industrial projects. Eksen was able to cut test time in half on some of these projects. The results of this experiment are presented in the evaluation section.Item Explaining the success of Roman freedmen : a pseudo-Darwinian approach(2014-08) Sibley, Matthew John; Galinsky, Karl, 1942-In Roman society, freed slaves were elevated to a citizen-like status, yet they never had the full rights of their free-born counterparts. Despite the inequality of the system, many freedmen appear to have found great success in the realm of business. This report endeavors to reveal why it was that this group prospered within the Roman economy using a pseudo-Darwinian perspective. Scholarship has, for the most part, tended to avoid Darwinian lines of thought in sociological studies but this report shows the power of this type of thinking. The first chapter clarifies the nature of slavery in the Roman world and the wide variety of experiences that slaves could have. Chapter two considers the different ways that slaves could be manumitted and how a freedman’s status could differ depending on the formality of his release from servitude. The third chapter examines the literary representations of freedmen in the genre of comedy and Petronius’ Satyricon. Chapter four turns to the archaeological evidence and provides a sense of how freedmen represented themselves to the wider community. Lastly, the fifth chapter, using a pseudo-Darwinian model, will show that the image of the successful freedman is not an anomaly of the archaeological record or a trope of Latin literature but an inevitable outcome of the intense selection that slaves underwent.Item Materials selection for concrete overlays(2011-08) Kim, Dong Hyun, 1984-; Ferron, Raissa; Fowler, David W.Concrete overlays have been a rehabilitation method for many years. It has been extensively utilized and studied in other states, but Texas is still at an initial stage of fully implementing the method. The large volume of concrete highways in Texas makes bonded concrete overlays, unbonded concrete overlays, and whitetoppings very viable options. However, there is a lack of educational guidelines for pavement engineers for concrete overlay construction. This research presents the information gathered from literature review, condition survey, and evaluation of existing concrete overlays in Texas. Also, a laboratory research was performed for recommendations for materials selection and construction for concrete overlays. From these, guidelines for materials selection and construction method developed that will assist in future concrete overlays in Texas are presented.Item Risk and innovation in project delivery method selection for complex highway projects(2023-08-01) Demetracopoulou, Vassiliki A.; O'Brien, William J.; Faust, Kasey; Machemehl, Randy; Bickel, Eric; El Asmar, MounirThe selection of a project delivery method (PDM) is a crucial decision that state highway agencies (SHAs) must make during the pre-procurement stage of infrastructure projects. The chosen PDM will determine the project's stakeholders, contract structure, final design, and construction. However, the PDM selection process remains challenging due to uncertainties stemming from low project scope definition during evaluation and the evolution of PDMs over the last 20 years. When first implemented, design-build (DB) was seen as a way to transfer risk to contractors and improve cost and schedule performance through early integration and overlap of design and construction. However, recent studies have questioned the effectiveness of DB contracts in terms of cost performance and unnecessary risk transfer. As such, SHAs must adjust their PDM selection processes to account for these factors. This dissertation aims to provide comprehensive guidance for efficient PDM selection for complex highway projects, with input from the private sector (Industry), the Texas Department of Transportation (TxDOT), and the Federal Highway Administration (FHWA). The first chapter addresses the gap in defining innovation and complexity for PDM selection, outlining six dimensions grouped by inherent project complexity and exogenous innovation opportunities. The second chapter presents empirical impact assessments for selection criteria to achieve cost- and schedule-related goals, emphasizing the tradeoff between DB and DBB selection and the importance of risk management and mitigation. The third chapter identifies factors that impact risk assessment and allocation in DB contracts. Building on these results, the dissertation’s final chapter outlines a deterministic and probabilistic PDM selection framework developed for TxDOT as an implementation case study. Overall, this dissertation contributes to PDM selection literature by providing a novel approach that defines innovation, incorporates uncertainty and risk management strategies, and is independent of project cost estimates. By providing comprehensive guidance for efficient PDM selection, this work can help SHAs make informed decisions to optimize project outcomes.Item Scheduling observers and agents over a shared medium with hard delivery deadlines(2019-09-25) Al Jurdi, Rebal; Andrews, Jeffrey G.; Heath, Robert W., Jr., 1973-; de Veciana, Gustavo; Vikalo, Haris; Viswanathan, HarishApplications that require ultra low latency and high reliability--such as intelligent transportation, telemedicine, and industrial automation--often involve a significant element of control and decision making. In particular, such systems involve three logical components: observers (e.g. sensors) measuring the state of an environment or dynamical system, a centralized executive (e.g. controller) deciding on the state, and agents (e.g. actuators) that implement the executive's decisions. The executive harvests the observers' measurements and decides on the short-term trajectory of the system by instructing its agents to take appropriate actions. All observation packets (typically uplink) and action packets (typically downlink) must be delivered by hard deadlines to ensure the proper functioning of the controlled system. This is very challenging in a wireless system due to inherent uncertainties in wireless channels due to phenomena such as fading and unpredictable interference, and for this reason applications with hard deadlines historically have typically used wired communication connections. This dissertation studies three main aspects involving communication systems with hard deadlines. First, we develop a probabilistic framework to study the outage of a controlled system. We model a communication method that uses periodic transmission frames, link adaptation, and controlled channel access. We obtain simple, closed-form expressions and upper and lower bounds on the probability of outage due to packet decoding errors and deadline violations. We perform detailed system-level simulations to identify design guidelines such as the optimal amount of training time, as well as benchmarking the proposed system design versus non-cooperative cellular, cooperative fixed-rate, and cooperative relaying systems. Second, we develop a novel framework that abstracts the context around different control and decision processes by using a common mathematical model to formulate and solve the observer selection problem (OSP). The executive solves this problem to select a feasible, schedulable sequence of observations that maximize its knowledge about the state of the system. To solve this constrained selection problem, we devise a branch-and-bound algorithm that efficiently prunes the search space. This work is fundamentally different from existing work on real-time communications in that communication reliability is not conveyed by packet loss or error rate, but rather by the extent of the executive's knowledge about the state of the system it controls. Third, we derive conditions that reduce the OSP constraint to 1) a sum (sum-of-weights) constraint and 2) an extremal (max-weight) constraint. We prove an optimal substructure of OSP which shows that if an observation sequence is optimal, then all of its subsequences are suboptimal. We propose a dynamic programming algorithm to optimally solve OSP with a sum constraint, and a reverse linear search to solve OSP with an extremal constraintItem Self-regulation strategies in managing multi-morbidities among community-dwelling people aging with arthritis(2019-05) Zhang, Wenhui, Ph. D.; Radhakrishnan, Kavita; Becker, Heather; Acton, Gayle J; Holahan, Carole K.Complexities in managing arthritis and multiple chronic conditions (MCCs) by an individual can explain the poor outcomes in arthritis self-management, higher healthcare utilizations, and poor quality of life (QoL). Evidence supported the aging theory of self-regulation strategies of Selection, Optimization, and Compensation (SR-SOC), as used by people aging with single and MCCs to adapt to chronic disabling symptoms and live well. Based on this theoretical framework, this research investigated the SR-SOC strategies by community-dwelling people aging with arthritis and MCCs. One hundred and forty individuals over age 50 were recruited from community settings and via social media. Each participant completed the demographic questionnaire, Functional Comorbidity Index (FCI), Brief Health Literacy Screening Tool, Lubben Social Network Scale, Patient-Healthcare Provider Communication Scale, Health Insurance Check-list, PROMIS Adult Self-Reported Health Measures, SOC Questionnaire, Arthritis Self-Efficacy Scale, Healthcare Service Utilization Questionnaire, and a visual analogue QoL scale. Correlations analyzed the relationships among the sample characteristics, SR-SOC strategies, and health outcomes. Guided by the theoretical framework, this research used multivariate hierarchical stepwise regressions to predict SR-SOC Strategies, arthritis self-efficacy, healthcare utilizations, and QoL among people aging with arthritis and co-morbidities. The majority of the sample were female (70%), aged 65 to 85 (66%), with less than Bachelor’s degree education (56%), White (34%) or African American (33%), living with others (64%), with personal annual income less than $25,000 (52%). Osteoarthritis (51%) and rheumatoid arthritis (28%) were the two most common types of arthritis. FCI ranged from 2 to 14 with mean of 3.8. The top four comorbidities were obesity, diabetes, visual impairment, and degenerative disc disease. QoL ranged from 0.5 to 10.0 (Mean = 7.2, SD = 2.2). SR-SOC strategy use was predicted significantly by physical symptoms, healthcare provider communication quality, and age (p < .05). Physical symptoms, SR-SOC strategies, especially optimization, and income adequacy significantly predicted arthritis self-efficacy. SR-SOC was significantly associated with QoL only in bivariate correlations but was not a significant predictor in multivariate regressions. Arthritis self-efficacy, mental, and physical symptoms, significantly predicted QoL. SR-SOC was also not a significant predictor of healthcare utilization, instead FCI significantly (p < .05) predicted healthcare utilization. The findings added evidence on the self-regulation strategies for managing arthritis and MCCsItem The antecedents and outcomes of preschool programs for children in America(2016-05) Ansari, Arya; Gershoff, Elizabeth T.; Crosnoe, Robert; Benner, Aprile; Kim, Su Yeong; Callahan, RebeccaThere has been an increased interest in the early childhood years as a point of intervention and, specifically, on preschool programs, which hold great promise in preparing children for school. Despite the extensive body of literature on preschool education, there remain a number of key issues that need to be addressed to move the early childhood field forward. This dissertation addresses three of these areas that require continued attention. First, we need to know why Latino children from U.S.- and foreign-born households are under-enrolled in preschool education (Aim 1). The second area that we need to know more about is the potential long-term benefits of large-scale preschool programs (Aim 2). Finally, the third area where more information is needed is on the different sources of heterogeneity in the benefits of preschool for children (Aim 3). Thus, the aims of this dissertation were to address these gaps in the knowledge-base by using data from the Early Childhood Longitudinal Study Birth (ECLS-B) and Kindergarten (ECLS-K 1998) Cohorts. The first set of findings reveals that there are important differences that exist within the Latino population (culture, household resources, parents’ beliefs about school readiness, and child elicitation) with respect to preschool selection. These differences indicate that, in order to boost the preschool enrollment of Latino children from U.S.- and foreign-born households, policymakers may need to focus on targeting a specific set of barriers. Findings from Aim 2 underscore the potential long-term benefits of preschool education. Specifically, despite evidence for partial convergence of test scores, children who attended preschool at age four consistently outperformed their classmates who attended informal care in areas of academic achievement through the end of middle school. Although all children benefited from preschool participation, analyses from Aim 3 of this dissertation revealed that there was evidence for systematic heterogeneity, with findings supporting developmental theories on cumulative advantage and diverging destinies. Taken together, the results from this dissertation add to the existing evidence base on preschool education by highlighting new means of engaging families in the preschool market and underscoring both how and why preschool programs have long-term benefits for children.Item The effect of dispersal behavior on stability in populations, communities, and ecosystems(2019-08-01) Deans, Robert Andrew; Gilbert, Lawrence E.; Leibold, Mathew A.; Jha, Shalene; Resetarits, William; Keitt, TimothyHabitat choice, when organisms move among habitat patches in a directed fashion based on environmental cues, is an underappreciated force in Ecology. Theoretical work suggests that such choice behavior might be a potent source of stability in populations, communities, and ecosystems. I tested the effects of dispersal behavior on stability with a series of mesocosm experiments at each of these scales. In populations of snails with stochastic disturbance, I found that movement among patches was density-dependent: snails tended to move away from high density and toward low density. These movements had dampening effect on oscillations in abundance, and they contributed to longer population persistence times relative to populations that were not connected by dispersal. A second experiment manipulated the colonization behavior of aquatic insects in order to see how this dispersal behavior affects the community response to a pulse of fish predation on the insect communities. While choice behavior exacerbated the effects of fish predation, reducing species richness beyond what was observed in communities with randomized colonization, choice resulted in faster recovery of communities relative to random colonization. A third experiment explored the effects of pulses of nutrient additions in mesocosms with developing aquatic insect communities. Presence of sediment had weak effects on stability, with small pulses of nutrients supporting more stable abundance values than ecosystems with no sediment. This stabilization effect was likely driven by habitat choice behavior, since the sediment input treatments affected organisms with active dispersal more than those with passive dispersal. Collectively, these experiments show that dispersal behavior is an important factor to consider when attempting to explain the spatial and temporal variation in ecosystems. Habitat choice behavior can have particularly significant effects on stability. Predicting how species respond to environmental change therefore requires knowledge of how they move.