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Title: OCCUPATIONAL STRESS AMONG EMPLOYEES IN CRIMINAL-LEGAL SYSTEMS : A META-ANALYSIS
Creator: Lawson, Spencer Grant
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Occupational stress is all too common, especially for employees in the criminal-legal system. Many sources of stress (i.e., stressors) have been shown to be associated with perceived occupational stress in the literature; yet, methodological variations and inconsistent findings across research articles obscure the empirical status of the effect of stressors on occupational stress among criminal-legal employees. To synthesize the research on this stressor-stress link, a meta-analysis was...
Show moreOccupational stress is all too common, especially for employees in the criminal-legal system. Many sources of stress (i.e., stressors) have been shown to be associated with perceived occupational stress in the literature; yet, methodological variations and inconsistent findings across research articles obscure the empirical status of the effect of stressors on occupational stress among criminal-legal employees. To synthesize the research on this stressor-stress link, a meta-analysis was conducted. Based on 80 peer-reviewed articles representing 57 unique data sets that contained 1,993 effect size estimates, random-effects analyses using multilevel modeling techniques were used to establish the grand mean effect of stressors on occupational stress. Results showed a modest effect of stressors on occupational stress (Mz = 0.15, 95% CI = [0.13, 0.18]). Importantly, the findings indicate that the strength of the effect size differed by the type of stressor. Specifically, larger effect sizes were yielded if the type of stressor was operational, followed by organizational stressors. The predicted effect size was smaller if the stressor was an individual demographic. Also, certain methodological decisions and study quality indicators moderate this effect. Overall, researchers must continue to explore the dimensions of these stressors to better understand their impact on occupational stress in criminal-legal systems. Theoretical, methodological, and practical implications of the meta-analytic findings are discussed and several directions for future research are identified in an effort to bring synergy to a disjointed evidence base.
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Title: DEVELOPMENT OF GENOMIC RESOURCES TO FACILITATE PLANT BREEDING
Creator: Bornowski, Nolan
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Recent advances in sequencing and computation power have greatly contributed to our knowledge of plant genomics, and the development and use of plant genomic resources will be critical as plant researchers and breeders address future food security in light of the increasing world population, decreasing arable land, and variable effects of climate change. Plants belonging to the mint family provide culinary, medicinal, and cultural value due to their production of secondary metabolites. Genome...
Show moreRecent advances in sequencing and computation power have greatly contributed to our knowledge of plant genomics, and the development and use of plant genomic resources will be critical as plant researchers and breeders address future food security in light of the increasing world population, decreasing arable land, and variable effects of climate change. Plants belonging to the mint family provide culinary, medicinal, and cultural value due to their production of secondary metabolites. Genome assemblies and annotations for four important culinary herbs were generated to highlight genes involved in terpenoid biosynthetic pathways. Maize (Zea mays L.) is the most produced crop worldwide due in part to extensive commercial breeding programs. Genome assemblies and annotations for five commercially relevant maize inbred lines belonging to the stiff-stalk heterotic group were generated to characterize the pan-stiff-stalk gene repertoire and genomic regions associated with these founder lines. Tepary bean (Phaseolus acutifolius A. Gray), a close relative of the common bean (Phaseolus vulgaris L.), is indigenous to the arid climates of northern Mexico and produces high seed yields under drought stress. A diverse panel of tepary bean accessions was assembled, genotyped, and phenotyped to identify genomic regions associated with key agronomic traits that can be harnessed for tepary bean improvement.
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Title: DEVELOPMENT OF A NEWS SUBSCRIPTION MOTIVATION SCALE
Creator: Chen, Weiyue
Date: 2022
Collection: Electronic Theses & Dissertations
Description: As news organizations face accelerated loss in advertising revenue, increasing importance is placed on strategies to increase subscription sales. Although previous studies have found several predictors of paywall, willingness to pay, and paying for news research, these factors did not fit into one clear conceptual framework that links them together. In this dissertation, I aim to introduce a new construct, News Subscription Motivation, that provides theoretical linkages between different...
Show moreAs news organizations face accelerated loss in advertising revenue, increasing importance is placed on strategies to increase subscription sales. Although previous studies have found several predictors of paywall, willingness to pay, and paying for news research, these factors did not fit into one clear conceptual framework that links them together. In this dissertation, I aim to introduce a new construct, News Subscription Motivation, that provides theoretical linkages between different predictors of paying for news. Mixed method research was employed to conceptualize and operationalize this new construct. In Chapter 1, I discuss my thought process developing this study, the purpose of the study, and why this topic matters in the context of digital economy. Chapter 2 includes a review of previous research on what drives people to pay for news, and the literature on consumer decision-making processes, consumer decision-making styles, and consumer motivation in general. The need to develop a new construct and measurement tools that are specially designed for news consumption was also addressed. In Chapter 3, I conducted 22 in-depth interviews to generate possible dimensions of the construct, analyzed the qualitative data to propose a conceptual framework and definition. Study 1 results suggested nine possible dimensions: content utility, journalism quality, price, convenience, hitting the paywall, surveillance, being a good citizen, brand reputation, and journalism. Conceptual definitions of each dimension were also elaborated. Chapter 4 focuses on the operationalization of News Subscription Motivation. An initial items pool was generated based on Study 1. After the pilot test, I recruited two independent samples, and they were respectively subjected to Exploratory Factor Analysis and Confirmatory Factor Analysis. The final scale included six dimensions with 19 items, and this scale demonstrated robust model fit and adequate convergent and discriminant validity. Six dimensions of News Subscription Motivation were identified: supporting journalism, journalism quality, triggered by the paywall, community attachment, price, and content utility. In Chapter 5, I aim to establish the nomological validity of News Subscription Motivation. Factors extracted from Chapter 4 demonstrated statistically significant relationships with numbers of news subscription people report paying for, types of subscriptions people get, and individuals’ intention to maintain their primary subscriptions in the next 3 months, 6 months, and 12 months. Finally, I discuss the theoretical and practical implications of the scale of News Subscription Motivation in Chapter 6.
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Title: The efficacy of implementing a technology-mediated dialogic pedagogy to support reading comprehension in virtual and co-located settings
Creator: Working, Christopher Scott
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Text-based discussion within a technology-mediated dialogic discussion (T+DLD) has the potential to engage students in higher-level reading comprehension with upper elementary students. While supported empirically, this approach is still not commonplace, and little is known about its efficacy within a remote setting. The primary aim of this project was to synthesize what is currently known about T+DLD and to explore changes in discussion within a remote setting to support practitioners...
Show moreText-based discussion within a technology-mediated dialogic discussion (T+DLD) has the potential to engage students in higher-level reading comprehension with upper elementary students. While supported empirically, this approach is still not commonplace, and little is known about its efficacy within a remote setting. The primary aim of this project was to synthesize what is currently known about T+DLD and to explore changes in discussion within a remote setting to support practitioners enacting the approach. This was achieved through a systematic review of the literature on T+DP that analyzed 18 included studies for study quality as well as patterns around study features (i.e., instructional design, environmental factors, task, methodology). Text-based discussion via web-based teleconferencing was studied using a comparative case study using sociocultural discourse analysis to study student discussion in three different training conditions: dialogic only, technology only, and a T+DLD training. A pathway of implementation was then developed to translate research into practice to support teachers in adopting T+DLD. A key finding within this project was that T+DLD builds on the key elements of ground rules for talk, an open task, and student reflection for talk. Additionally, the pedagogical approach of the teacher influences the way technology is used by students. Finally, technology can successfully support T+DLD in both co-located and remote settings. This dissertation provides recommendations for future research that compares methods of implementation and evaluates the direct impact on reading comprehension.
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Title: Data-Driven Multi-Scale Modeling, Analysis and Simulation of Material Failure
Creator: Barros de Moraes, Eduardo Augusto
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Material failure processes are inherently stochastic and anomalous, occurring across a wide span of length and time scales, from dislocation motion at the micro-scale, to formation of micro-cracks, up to crack propagation and aging mechanisms at the macro-scale and cascading failure at the system-level. Anomalies such as intermittent signals in Acoustic Energy experiments, power-law distribution of the energy spectrum, crackling noise, dislocation avalanches, among other indicators, occur...
Show moreMaterial failure processes are inherently stochastic and anomalous, occurring across a wide span of length and time scales, from dislocation motion at the micro-scale, to formation of micro-cracks, up to crack propagation and aging mechanisms at the macro-scale and cascading failure at the system-level. Anomalies such as intermittent signals in Acoustic Energy experiments, power-law distribution of the energy spectrum, crackling noise, dislocation avalanches, among other indicators, occur even in standard, ordered, crystalline materials. Modeling and simulation of failure must take into account parametric and model-form uncertainties that propagate across the scales, when seemingly unimportant material properties or loading conditions could cause catastrophic failure at the component level. The pursuit of a unified framework for quantitative and qualitative failure prediction that can bridge the multiple scales while still incorporating the material’s underlying stochastic processes is still a challenge, which requires a new modeling paradigm that incorporates such features with both robustness and simplicity.In this work, we propose a data-driven methodology for multi-scale, statistically consistent modeling of anomalous failure processes. At the micro-scale, the goal is to study the dynamics of dislocations, which play a vital role in plasticity and crack nucleation mechanisms, and shows anomalous features across different time and length-scales. We start by investigating the dislocation mobility properties at the nano-scale and propose a surrogate model for dislocation motion based on a Kinetic Monte Carlo method, where the dislocation motion is emulated as a random-walk on a network following a Poisson process. The surrogate learns the rates of the corresponding Poisson process directly from high-fidelity, Molecular Dynamics (MD) simulations. The surrogate is capable of efficiently obtaining uncertainty measures for the mobility parameter, which can be then propagated to more complex simulations in upper scales. At the meso-scale, the collective behavior of dislocation dynamics leads to avalanche, strain bursts, intermittent energy spikes, and nonlocal interactions. We develop a probabilistic model for dislocation motion constructed directly from trajectory data from Discrete Dislocation Dynamics (DDD). We obtain the corresponding Probability Density Function for the dislocation position, and propose a nonlocal transport model for the PDF. We use a bi-level Machine Learning framework to learn the parameters of the nonlocal operator and the coefficients of the PDF evolution equation, facilitating a continuum representation of the anomalous phenomena.At the macro-scale, parametric material uncertainties substantially affect the predictability of failure at the component level. We develop an Uncertainty Quantification (UQ) and Sensitivity Analysis (SA) framework for propagation of parametric uncertainties in a stochastic phase-field model of damage and fatigue, and we use the Probabilistic Collocation Method (PCM) as a building block. A Global SA indicates the most influential parameters in solution uncertainty and shows that damage initiation is sensitive to parameters associated with classical free-energy potential definitions, providing another motivation to incorporate the heavy-tail processes as observed in the meso-scale. We extend the framework and develop a Machine Learning (ML) framework for failure prediction phase-field models for brittle materials. We combine a classification algorithm with a pattern recognition scheme using virtual nodes from the phase-field damage model to generate patterns of material softening at each time-step. The framework identifies the presence and location of cracks and is robust even under noisy data, whether from model, parametric, or experimental uncertainties.
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Title: HELLGATE TO HIGHWAY : ISLAND MAKING, DREDGING, AND INFRASTRUCTURE IN THE DETROIT RIVER, 1874-1938
Creator: Swayamprakash, Ramya
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation exposes the tensions, trials, and tribulations along the U.S.-Canada border in the Detroit River between 1874 and 1938. I study how dredging—a seemingly inert process of removing river bottom sediment and depositing it elsewhere—helped create landforms across and along the political border, in turn, revealing the myriad social and political tensions that undergird it. By exposing how infrastructure revealed border tensions, especially those related to resource extraction,...
Show moreThis dissertation exposes the tensions, trials, and tribulations along the U.S.-Canada border in the Detroit River between 1874 and 1938. I study how dredging—a seemingly inert process of removing river bottom sediment and depositing it elsewhere—helped create landforms across and along the political border, in turn, revealing the myriad social and political tensions that undergird it. By exposing how infrastructure revealed border tensions, especially those related to resource extraction, scarcity, and national security—on both sides of the Canada-U.S. border—this dissertation offers a new way to link environmental and border history as well as environmental diplomacy.The lower Detroit River forms the ideal study site for two interrelated reasons. One, its narrow and rocky riverbed along the shipping channel was a dangerous bottleneck, slowing traffic on one of the busiest waterways in the world. Two, dredging the lower part of the river kept this busy waterway running efficiently. The Livingstone Channel fundamentally reordered the Detroit River when it was carved out of the riverbed where hitherto there existed fish spawning grounds and shallow water. Concentrating on the lower Detroit River in general and the Livingstone Channel in particular, this dissertation will show how conflict and cooperation overlapped when it came to international diplomacy in the Great Lakes. Cultural and social historians have analyzed Great Lakes borderlands. Environmental historians though have yet to fully analyze these lakes. The political border between the United States and Canada has often been portrayed as being benign and uncontested. Yet, as this dissertation shows, border infrastructure, such as shipping channels, was seldom uncontested. By focusing on the political border, this dissertation aims to bring attention to the border as a site rather than a liminal space or an end zone of state sovereignty. The border in this reading is the origin of state sovereignty. Studies of the Canada-U.S. borderlands have often explored the role of international environmental diplomacy, especially in the joint management and conservation of binational water bodies like the Great Lakes through policy mechanisms such as the Boundary Waters Treaty (BWT) of 1908 and the International Joint Commission. As my dissertation shows, however, the BWT was an important staging point on which the different intercultural and international misunderstandings were exposed. The Great Lakes have often been cast as being abundant, yet there is little or no work on how that plentitude was not just manufactured in thought, but also embodied in infrastructures. As a transformative process, dredging does not seem monumental. Yet, dredging in the Detroit River has permanently lowered the levels of Lakes Huron and Michigan by at least 25 cm. Dredging thus reveals how environmental transformation lies at the heart of Great Lakes geography as we know it. By exposing dredging in a connecting channel, this dissertation shows that infrastructural creation and imagination undergirds the Great Lakes environment. Infrastructure, as I show, is an important and unseen filter to understand intercultural and international relationships. This is especially true of countries such as the U.S. and Canada which pride themselves in intercultural similarities more than differences. Studying conflict and contestation offers a novel way to understand the cooperative mechanism that drives current borderlands diplomacy. Studying dredging along the lower Detroit River in the nineteenth and twentieth centuries reveals ideas about nature as well as historical challenges and contestations to them.
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Title: IMPROVING QT CORRECTION METHODS THROUGH THE ANALYSIS OF PRECLINICAL SAFETY PHARMACOLOGY DATA
Creator: Ether, Nicholas David
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Torsade de pointes is a polymorphic ventricular tachycardia that has been linked to sudden cardiac death. While typically rare and fleeting, increased risk for occurrence of and problematic outcomes from this arrhythmia has been attributed to prolonged QT intervals. These interval measurements of electrocardiogram waveforms represent the time between depolarization and repolarization of the ventricles. Prolongation of this period increases the likelihood of disruptions in ventricular...
Show moreTorsade de pointes is a polymorphic ventricular tachycardia that has been linked to sudden cardiac death. While typically rare and fleeting, increased risk for occurrence of and problematic outcomes from this arrhythmia has been attributed to prolonged QT intervals. These interval measurements of electrocardiogram waveforms represent the time between depolarization and repolarization of the ventricles. Prolongation of this period increases the likelihood of disruptions in ventricular cardiomyocyte conduction, which can lead to torsade de pointes events. Due to the potentially fatal outcomes associated with QT prolongation, it was not long until drugs found to induce this prolongation began to be removed from the market. These concerns led to the creation of safety pharmacology guidelines S7B and E14 that outlined suggested QT prolongation risk assessments to be performed during the preclinical and clinical stages of drug development, respectively. Studies based on these guidelines are intended to identify drug-induced changes to the QT interval, but must first control for the effect heart rate has on QT. To isolate drug effect QT correction methods are used to estimate corrected QT values as if the data was collected at a fixed heart rate. Using these values as a biomarker has led to highly sensitive assessments that have prevented any new drugs from reaching the market with unacceptable QT prolongation risk. However, these assessments are still in need of improvement as the pharmaceutical industry must deal with costly and time-consuming clinical safety studies despite the high sensitivity of preclinical assessments, leading to calls for the integration of preclinical and clinical guidelines. To achieve this, the translatability of preclinical results must be improved.This dissertation aims to increase the reliability of preclinical results and improve their translatability by optimizing the QT correction methods they rely on. To do this, I analyzed large ECG datasets from preclinical safety pharmacology studies obtained through Eli Lilly and Company (Indianapolis, IN). The central hypothesis of this dissertation is that through statistical analysis of these data, the collective understanding of QT correction methods will be expanded, and an improved method can be developed. In pursuit of this goal, the effectiveness of various preclinical QT correction methods was evaluated in simulated drug treatment scenarios, against 130,000+ bootstrap resampled ECG recordings of vehicle control treatments, and with study data from non-human primates treated with known QT prolonging drugs. The results of these evaluations provided evidence of how assumptions inherent to these methods affect the result of correction. Examples of such assumptions include what heart rate is relevant for the species, that a predetermined population-based estimate of the QT-rate relationship is appropriate for individuals, that this relationship will not change over time or between treatments, and that assuming this relationship before correction is appropriate in the first place. All of this led to the development of the novel Ratio QT correction method designed to be applicable to any scenario by dynamically responding to moment-to-moment changes in the relationship between timepoints. This novel method combines the simplicity and ease-of-use of population-based methods with the effectiveness of individual methods. Taken together, this research has increased the collective understanding of QT correction methods and resulted in a novel method that is as effective as it is simple to use. The investigations presented in this dissertation have explored aspects of QT correction methods that have been in question for years. Optimizing these methods is now easier thanks to the information gained through these analyses of large preclinical ECG datasets. An integral step has been made towards the creation of a new industry standard of QT correction capable of bridging the gap between preclinical and clinical safety pharmacology studies. Such improvements can be used to help reduce the number of research subjects necessary for preclinical and clinical QT prolongation assessments.
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Title: THREE ESSAYS ON THE CHOICE OF COLLEGE MAJOR AND TRADE EXPOSURE
Creator: Wu, Yu-Siang
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation is composed of three chapters on the effects of import exposure. For my dissertation I mainly use the variation of import competition across local labor markets to explore its impact on labor market outcomes (e.g., wages and employment status), human capital investment decisions (choice of college major), and education-job mismatch.Chapter one explores the relationship between increasingly intense Chinese import competition and American college students’ choice of major in...
Show moreThis dissertation is composed of three chapters on the effects of import exposure. For my dissertation I mainly use the variation of import competition across local labor markets to explore its impact on labor market outcomes (e.g., wages and employment status), human capital investment decisions (choice of college major), and education-job mismatch.Chapter one explores the relationship between increasingly intense Chinese import competition and American college students’ choice of major in the 2000s. By employing a modified version of the measure for Chinese import competition from Autor, Dorn, and G. Hanson (2013) and analyzing the relationship between industries and college majors, I find that rising Chinese trade exposure of nineteen industries in the 2000s has a negative effect on American students’ choice ofsix engineering majors. The magnitudes of the effects range from 0.62 to 0.69 percentage point decreases in the probability of choosing those six engineering majors. I also find that males are more negatively affected by Chinese import competition in terms of the choice of the six engineering majors, whereas no significant results exist if I restrict my sample to females.Chapter two analyzes how increased trade exposure affects students’ choice of STEM major. I first present a simple model to illustrate how trade exposure impacts students’ utility functions through their self-beliefs about labor market outcomes and then use assorted data to show that import competition positively affects the choice of STEM major. I find that increased import exposure in the 2000s leads to 1.05 and 0.72 percentage point increases in the probability of choosing STEM majors for college underclassmen and upperclassmen, respectively. As for labor market outcomes, my results suggest that a rise in import competition leads to a pronounced negative effect on weekly wages, employment status, and full-time employment across STEM and non-STEM occupations from the late 1990s through the 2000s. STEM occupations, however, are less negatively impacted by import competition, which helps explain why a rise in import exposure increases the probability of students choosing STEM majors.Chapter three investigates the impact of import exposure on education-occupation mismatch. I first use the concept of a matching function to explain the connection between mismatch and the supply of and demand for college graduates. Next, I use an input-output table to construct a measure of import exposure that accounts for both direct and indirect trade shocks. Findings show that increased import exposure leads to a rise in education-occupation mismatch from 2011 through 2019. Moreover, for the supply side I present that a rise in import exposure significantly increases the number of bachelor’s degrees awarded in 4-year colleges and in most degree fields. However, for the demand side, I do not observe corresponding increases in occupational employment for most fields of education. The unbalanced demand for and supply of college graduates might potentially explain the rise in education-occupation mismatch.
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Title: Iris Recognition : Enhancing Security and Improving Performance
Creator: Sharma, Renu
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Biometric systems recognize individuals based on their physical or behavioral traits, viz., face, iris, and voice. Iris (the colored annular region around the pupil) is one of the most popular biometric traits due to its uniqueness, accuracy, and stability. However, its widespread usage raises security concerns against various adversarial attacks. Another challenge is to match iris images with other compatible biometric modalities (i.e., face) to increase the scope of human identification....
Show moreBiometric systems recognize individuals based on their physical or behavioral traits, viz., face, iris, and voice. Iris (the colored annular region around the pupil) is one of the most popular biometric traits due to its uniqueness, accuracy, and stability. However, its widespread usage raises security concerns against various adversarial attacks. Another challenge is to match iris images with other compatible biometric modalities (i.e., face) to increase the scope of human identification. Therefore, the focus of this thesis is two-fold: firstly, enhance the security of the iris recognition system by detecting adversarial attacks, and secondly, accentuate its performance in iris-face matching.To enhance the security of the iris biometric system, we work over two types of adversarial attacks - presentation and morph attacks. A presentation attack (PA) occurs when an adversary presents a fake or altered biometric sample (plastic eye, cosmetic contact lens, etc.) to a biometric system to obfuscate their own identity or impersonate another identity. We propose three deep learning-based iris PA detection frameworks corresponding to three different imaging modalities, namely NIR spectrum, visible spectrum, and Optical Coherence Tomography (OCT) imaging inputting a NIR image, visible-spectrum video, and cross-sectional OCT image, respectively. The techniques perform effectively to detect known iris PAs as well as generalize well across unseen attacks, unseen sensors, and multiple datasets. We also presented the explainability and interpretability of the results from the techniques. Our other focuses are robustness analysis and continuous update (retraining) of the trained iris PA detection models. Another burgeoning security threat to biometric systems is morph attacks. A morph attack entails the generation of an image (morphed image) that embodies multiple different identities. Typically, a biometric image is associated with a single identity. In this work, we first demonstrate the vulnerability of iris recognition techniques to morph attacks and then develop techniques to detect the morphed iris images.The second focus of the thesis is to improve the performance of a cross-modal system where iris images are matched against face images. Cross-modality matching involves various challenges, such as cross-spectral, cross-resolution, cross-pose, and cross-temporal. To address these challenges, we extract common features present in both images using a multi-channel convolutional network and also generate synthetic data to augment insufficient training data using a dual-variational autoencoder framework. The two focus areas of this thesis improve the acceptance and widespread usage of the iris biometric system.
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Title: Differential Effects in Exposure to ACEs and Problematic Drinking : An Examination of Protective Factors
Creator: Welch, Timothy Sean
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Exposure to Adverse Childhood Experiences (ACEs) has been associated with numerous negative developmental outcomes across the lifespan, including problematic drinking. However, not all individuals exposed to ACEs go on to drink problematically. This difference in the effect of exposure to ACEs on drinking use is an example of heterogeneity and is called a differential effect. Relatively little research has examined what factors predict resilience to the harmful effects of ACEs. Most existing...
Show moreExposure to Adverse Childhood Experiences (ACEs) has been associated with numerous negative developmental outcomes across the lifespan, including problematic drinking. However, not all individuals exposed to ACEs go on to drink problematically. This difference in the effect of exposure to ACEs on drinking use is an example of heterogeneity and is called a differential effect. Relatively little research has examined what factors predict resilience to the harmful effects of ACEs. Most existing research has examined either a single protective factor or examined the total number of protective factors in a cumulative scale. No study has yet to specifically examine differential effects in the context of ACEs and alcohol use. The aim of this study was to examine differential effects in exposure to ACEs and alcohol use to empirically identify a resilient group of individuals. Two research questions drove this study 1) How can heterogeneity in the association between ACEs and alcohol use be characterized? and 2) What factors predict group membership? Using data from the National Longitudinal Study of Adolescent to Adult Health (Add health), two complimentary analytic tools were used to achieve these aims: Regression Mixture Modeling (RMM) and Structural Equation Model Trees (SEM trees). Results from the RMM found evidence of two groups: a resilient group consisting of 72.6% percent of the sample and a harmful effects group consisting of 27.4% percent of the sample. Two factors were positively associated with belonging to the resilient group, school bonding and self-control. One factor, having a mentor, was associated with a lower likelihood of being in the resilient group. Results from the SEM-tree divided the data into three groups based on two variables: self-esteem and having a mentor. In this analysis, higher self-esteem and having a mentor during adolescence were both associated with problematic drinking. Findings from this study provide empirical evidence of a resilient group of individuals for whom there is not an association between exposure to ACEs and alcohol use. Despite testing multiple theoretically based protective factors, only school bonding and problem solving were associated with resilience. This suggests future research should consider additional alternative protective factors. The results suggest therapists and clinicians working with youths exposed to ACEs should work to foster increased levels of school bonding during adolescence and should assess levels of self-control and focus on helping youths develop greater self-control.
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Title: SLEEP MANAGEMENT AS A COLLABORATIVE WORK FOR THE FAMILY : DESIGNING SLEEP MANAGEMENT SYSTEMS TO IMPROVE BEDTIME ROUTINE
Creator: Shin, Ji Youn
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Sleep is a vital health issue. In families with young children, sleep problems can influence the physical, emotional, and behavioral health of all family members. Previous studies have investigated sleep as an individual activity, rarely considering the interconnected aspects of sleep among family members. To understand the social aspects of family sleep, this dissertation consists of two studies which can help researchers and designers understand the core issues of family sleep and address...
Show moreSleep is a vital health issue. In families with young children, sleep problems can influence the physical, emotional, and behavioral health of all family members. Previous studies have investigated sleep as an individual activity, rarely considering the interconnected aspects of sleep among family members. To understand the social aspects of family sleep, this dissertation consists of two studies which can help researchers and designers understand the core issues of family sleep and address them through the design of sleep-support technology. In the first study, I identified sleep as a complex experience entangled with the social dynamics between family members. For example, children's sleep means time not just for children to rest, but for a parent to have self-care. The results suggested how the boundaries that define sleep in terms of time (at night), space (in bedrooms), and unit of analysis (individual-focused) limit designers' opportunities to tackle the deeper sleep issues of families. I also suggest "division of labor" as an important but rarely discussed design concept to enhance family sleep, and as a promising design theme for home technologies that address issues emerging from social dynamics between household members. In the second study, by incorporating the identified themes from the first stage, I designed and tested two types of family-based sleep management prototypes. These prototypes redistributed the sleep-relevant tasks among family members and provided them with chances to reflect on the difficulties and values involved in the tasks. Through the in-the-wild study deploying two design prototypes in home settings, this study empirically revealed the importance of considering social dynamics as a design factor for family sleep management technologies. Implications of future design are discussed.
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Title: Assessing Theoretical Mediators of Campaign-Induced Communication in the Context of Social Norms Campaigns
Creator: Park, Sunyoung
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The present paper examines the role of campaign-induced communication on the effects of a social norms campaign by focusing on cognitive elaboration, perceived injunctive norms, and message recall as mediating variables. Participants (n = 252) read an injunctive norms campaign message about choosing not to drink at parties or when socializing and were randomly assigned to one of three conditions (control: received no prompts, prompt only; received prompts to engage in interpersonal...
Show moreThe present paper examines the role of campaign-induced communication on the effects of a social norms campaign by focusing on cognitive elaboration, perceived injunctive norms, and message recall as mediating variables. Participants (n = 252) read an injunctive norms campaign message about choosing not to drink at parties or when socializing and were randomly assigned to one of three conditions (control: received no prompts, prompt only; received prompts to engage in interpersonal communication about the campaign message with close others during the following week; prompt & plan: received prompts to engage in interpersonal communication with close others during the following week and to write a plan for the communication). The results revealed that the prompt (either alone or with the plan) significantly motivated participants to engage in positive conversations about the campaign message during the next week. Similar to past findings (Morgan et al., 2018), a higher frequency of positive conversations about the campaign message indirectly predicted better behavioral outcomes via higher cognitive elaboration. The findings suggest that social norms campaign developers should be encouraged to design social norms messages with a brief prompt to motivate the target audience to engage in interpersonal communication and need to account for such interpersonal communication and its indirect effects in evaluating campaign messages.
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Title: STUDYING MENTORS AND MENTORING FROM A LEARNER-CENTERED PERSPECTIVE
Creator: Croel-Perrien, Amy
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Teacher candidates, while completing their student teaching internship, are part of an important teaching-and-learning triad. The other members of the triad, mentor teachers and university field instructors, provide essential support to teacher candidates throughout the student teaching internship experience (Yee, 1968). Recent research has examined the roles of mentor teachers and university field instructors. Not as much is understood, however, about the moments or experiences teacher...
Show moreTeacher candidates, while completing their student teaching internship, are part of an important teaching-and-learning triad. The other members of the triad, mentor teachers and university field instructors, provide essential support to teacher candidates throughout the student teaching internship experience (Yee, 1968). Recent research has examined the roles of mentor teachers and university field instructors. Not as much is understood, however, about the moments or experiences teacher candidates recognize as when they learned the most about teaching. With retirements increasing and as much as 50% leaving the field within the first five years of teaching (Shwartz & Dori, 2016), there is an urgency in studying, and hopefully improving, novice teacher support systems.In this dissertation, I explore the moments or experiences teacher candidates recognize as insightful and valuable from their student teaching experience, from the perspective of four recent student teachers. Using phenomenology as a method of inquiry (Giorgi, 1985), data were collected through phenomenological interviews of four teacher candidates after they completed a year-long student teaching internship. These interviews tell the story of teacher candidates becoming through learning (Hodkinson et al., 2008). Findings indicate that framing problems of practice within practical situations, situations that likely occur in an elementary classroom, positively influence teacher candidates’ learning. The practice of adaptative mentoring (van Ginkel et al., 2015) provides opportunities for mentor teachers to support teacher candidates as they learn about teaching practice, while also helping them with emotional and practical concerns. Ultimately, I argue that grounding mentoring in both the how and why of teaching, along with adapting to the individual needs of teacher candidates, provides supportive opportunities for teacher candidates’ learning.
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Title: UNDERSTANDING THE PARASITIC VARIABILITY OF THE NORTHERN ROOT KNOT NEMATODE (MELOIDOGYNE HAPLA) THROUGH MULTIDISCIPLINARY APPROACHES OF SOIL BIOME AND ENVIRONMENT
Creator: Lartey, Isaac
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Managing Meloidogyne hapla remains challenging due to the ban of broad-spectrumnematicides, lack of resistant crops and its broad host range. It also has parasitic variability (PV) where populations (pop) are morphologically and genetically similar but vary in pathogenicity and reproductive potential. Although PV in M. hapla appears to have some relationship to soil types, what soil conditions favor its PV and/or its distribution are unknown. The goal of my research was to understand the soil...
Show moreManaging Meloidogyne hapla remains challenging due to the ban of broad-spectrumnematicides, lack of resistant crops and its broad host range. It also has parasitic variability (PV) where populations (pop) are morphologically and genetically similar but vary in pathogenicity and reproductive potential. Although PV in M. hapla appears to have some relationship to soil types, what soil conditions favor its PV and/or its distribution are unknown. The goal of my research was to understand the soil conditions where M. hapla PV exist by quantifying the biophysicochemical (BPC) conditions from the ecosystem down to microbiome level. I designed observational and experimental approaches and tested four objectives. First, was to evaluate the association between soil conditions and M. hapla distribution at the ecosystem level. My hypothesis was that the presence of M. hapla will be associated with degraded soil conditions. I selected 15 (6 muck and 9 mineral soil) agricultural fields with adjacent natural vegetation in southwest, northwest and eastern regions of the lower peninsula of Michigan as study sites. I collected a total of 75 (5 per field) georeferenced soil samples from agricultural fields and equal number from adjacent natural vegetation soils, quantified the soil food web (SFW) conditions using the Ferris SFW model, and screened for M. hapla presence or absence. The fields were described either as disturbed, degraded (worst-case) or maturing (best-case). Meloidogyne hapla was present in 3 mineral (2, 8 and 13) and 6 muck (4, 5, 6, 10, 14 15) agricultural fields with degraded and/or disturbed soil conditions and absent from maturing soils, partially supporting the hypothesis. Degraded soils had low nitrogen content in both soil groups. The second objective was to isolate and culture the 9 M. hapla populations to test a hypothesis that PV is related to specific SFW conditions. I found three categories of reproductive potential: the highest (Pop 13), medium (Pop 8), both from degraded mineral soils, and lowest from disturbed mineral (Pop 2) and disturbed (Pops 4, 6 and 10) and degraded (Pops 5, 14 and 15) muck soils. Thus, the hypothesis was not supported. The third objective, was to determine relationships between microbial community structure and M. hapla distribution. My working hypotheses were that there is a relationship among microbiome, soil health and M. hapla occurrence. Microbial community structure in the fields was determined from sub-samples of the same samples where the nematodes were isolated. I used 16S (bacteria) and ITS (fungi) rDNA analysis and characterized the microbial composition, core- and indicator-microbes co-existing with M. hapla pop in the field soils and soil conditions relative to the Ferris SFW model description. The results showed that bacterial and fungal community abundance and composition varied by soil group, SFW conditions and/or M. hapla occurrence. I found that a core of 39 bacterial and 44 fungal sub-operational taxonomic units (OTUs) were found variably, 25 bacterial OTUs associated with presence or absence of M. hapla, and 1,065 OTUs were associated SFW conditions. All three hypotheses were supported. The final objective was to determine the relationship between PV and the microbes associated with M. hapla pop. I compared bacteria present in M. hapla pop isolated from the field and greenhouse cultures. The hypothesis was that either presence and/or absence of specific bacteria are associated with M. hapla population. Population 8 shared more bacteria with the lowest reproductive potential pop than Population 13. Presence of several bacteria was unique to Population 8 as was the absence of other bacteria to Pop 13 in either field or greenhouse nematodes. Therefore, the hypothesis was supported. My research findings provide a foundation for: a) testing the relationship between M. hapla PV and the BPC conditions and b) designing soil health-based management strategies.
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Title: THROUGH THE MAGMA MUSH : TRACING MAGMA EVOLUTION FROM THE MANTLE, THROUGH THE CRUST, AND TO THE SURFACE USING THE GEOCHEMISTRY OF ERUPTED MELTS AND MINERALS
Creator: Svoboda, Christopher
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Studies synthesizing field work, numerical simulations, petrology, geochemistry, and geophysical observations indicate that the compositional diversity of lavas results from evolution of mantle-derived basaltic magmas by mixing, assimilation, and fractional crystallization. These studies indicate this evolution occurs within dispersed complexes called transcrustal magmatic systems, rather than tank-like magma chambers. The processes within these magmatic systems have implications for...
Show moreStudies synthesizing field work, numerical simulations, petrology, geochemistry, and geophysical observations indicate that the compositional diversity of lavas results from evolution of mantle-derived basaltic magmas by mixing, assimilation, and fractional crystallization. These studies indicate this evolution occurs within dispersed complexes called transcrustal magmatic systems, rather than tank-like magma chambers. The processes within these magmatic systems have implications for understanding the evolution of continental crust, the breakup of continental landmasses, and the hazards associated with volcanism. We present three studies in various tectonic and magmatic settings, using the geochemistry of whole rocks and minerals to relate magmatic processes within transcrustal magma systems and their inputs from the mantle to large-scale plate tectonic and geodynamic questions. In a study of magnesium-rich andesites from the Taupo Volcanic Zone, I link primitive mineral compositions in Mg-depleted melts to the growth of magma accommodation zones in a rifting segment of arc crust. Mineral constraints on temperature and pressure indicate that the plumbing system first formed at mid- to lower-crustal pressures (3.5-7.0±2.8 kbar). I interpret the mafic mineralogy and presence of disequilibrium features as evidence that these andesites and their crystal cargo represent the products of a developing magmatic system in the middle to lower crust. This study addresses the question of how magmatic systems initially form and evolve. I examine lavas from the back arc of Patagonian Argentina, where volcanism is displaced from the magmatic arc due to subduction of oceanic spreading centers. I demonstrate using thermodynamic models that the source regions for melts contain volumes of pyroxenite (3-11%), and were generated at high pressures (2.6-2.7 GPa). These melting conditions have been consistent since the Eocene. I interpret these results as evidence of detachment of pyroxene-rich lithosphere that was created by magma-lithosphere interaction during the Mesozoic breakup of Gondwana. These results show a link between prior magmatic events the role of pyroxene-rich mantle lithologies in subsequent mantle melting episodes. Finally, I present a study that probes the evolution of late-stage magmas in the failed 1.1-billion-year-old Mid-Continent Rift that are analogous to packages of lava and sediment that are buried during the final stages of continental breakup. I present evidence showing magma mixing between primitive and evolved residual magma controls the magma composition in these lavas. The highly negative εHf and εNd isotopic characteristics of these magmas, supported by modeling outcomes, suggest extensive assimilation (15%) of continental crust accompanying fractional crystallization of olivine, plagioclase feldspar, and spinel at 4 kbar pressure and 1060° C. I interpret this as a renewed pulse of magma that has exploited a preexisting transcrustal magmatic system. I posit that this system had its magma supply exhausted at the end of the main stage of volcanism but remained partially molten due to residual heat from the main stage. The results of this study have implications for the persistence of these magmatic systems through time. Each individual study, while from disparate time periods and tectonic settings, demonstrates that the transcrustal magmatic system (and the transcrustal system’s link to the mantle) provides a suitable conceptual framework for modeling and describing the evolution of magmas. These systems are not static but rather change with time to respond to geodynamic forces and rates of magma delivery.
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Title: EFFICIENT AND PORTABLE SPARSE SOLVERS FOR HETEROGENEOUS HIGH PERFORMANCE COMPUTING SYSTEMS
Creator: Rabbi, Md Fazlay
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Sparse matrix computations arise in the form of the solution of systems of linear equations, matrix factorization, linear least-squares problems, and eigenvalue problems in numerous computational disciplines ranging from quantum many-body problems, computational fluid dynamics, machine learning and graph analytics. The scale of problems in these scientific applications typically necessitates execution on massively parallel architectures. Moreover, due to the irregular data access patterns and...
Show moreSparse matrix computations arise in the form of the solution of systems of linear equations, matrix factorization, linear least-squares problems, and eigenvalue problems in numerous computational disciplines ranging from quantum many-body problems, computational fluid dynamics, machine learning and graph analytics. The scale of problems in these scientific applications typically necessitates execution on massively parallel architectures. Moreover, due to the irregular data access patterns and low arithmetic intensities of sparse matrix computations, achieving high performance and scalability is very difficult. These challenges are further exacerbated by the increasingly complex deep memory hierarchies of the modern architectures as they typically integrate several layers of memory storage. Data movement is an important bottleneck against efficiency and energy consumption in large-scale sparse matrix computations. Minimizing data movement across layers of the memory and overlapping data movement with computations are keys to achieving high performance in sparse matrix computations. My thesis work contributes towards systematically identifying algorithmic challenges of the sparse solvers and providing optimized and high performing solutions for both shared memory architectures and heterogeneous architectures by minimizing data movements between different memory layers. For this purpose, we first introduce a shared memory task-parallel framework focusing on optimizing the entire solvers rather than a specific kernel. As most of the recent (or upcoming) supercomputers are equipped with Graphics Processing Unit (GPU), we decided to evaluate the efficacy of the directive-based programming models (i.e., OpenMP and OpenACC) in offloading computations on GPU to achieve performance portability. Being inspired by the promising results of this work, we port and optimize our shared memory task-parallel framework on GPU accelerated systems to execute problem sizes that exceed device memory.
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Title: HYALURONAN AS EFFECTIVE PLATFORMS FOR COMBINATORIAL CARBOHYDRATE DERIVATIVE GENERATION, AND FOR IMAGE-GUIDED SURGERY WITH SURFACE-ENHANCED RAMAN SPECTROSCOPY (SERS)
Creator: Liu, Kunli
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Hyaluronan (HA) is a polysaccharide consisting of repeating disaccharides of N-acetyl-D-glucosamine and D-glucuronic acid. HA plays important roles in a wide range of biological events. The principal endogenous receptor of HA, cluster of differentiation 44 (CD44), is overexpressed on many types of tumor cells as well as inflammatory cells in human bodies. HA-CD44 interactions are important in cell adhesion, cell migration, induction of hematopoietic differentiation, and signaling for cell...
Show moreHyaluronan (HA) is a polysaccharide consisting of repeating disaccharides of N-acetyl-D-glucosamine and D-glucuronic acid. HA plays important roles in a wide range of biological events. The principal endogenous receptor of HA, cluster of differentiation 44 (CD44), is overexpressed on many types of tumor cells as well as inflammatory cells in human bodies. HA-CD44 interactions are important in cell adhesion, cell migration, induction of hematopoietic differentiation, and signaling for cell activation. Other HA receptors include lymphatic vessel endothelial HA receptor-1 (LYVE-1), and HA receptor for endocytosis (HARE). HA is versatile for chemical modification or conjugation by exploiting the reactivity of carboxyl group, hydroxyl group, or the reducing end of the HA chain. Through chemical modification of HA, various kinds of self-assembled HA nanoparticles (HA-NPs) can be generated. There are increasing interests in utilizing HA-NPs for targeted imaging and therapy. Active targeting from HA-CD44 mediated interaction could lead to selective accumulation of HA-NPs at targeted disease sites. Chapter 1 is a review focusing on the synthesis strategies of self-assembled HA-NPs, as well as their applications in therapy and biomedical imaging. With the recognition of the importance of HA-CD44 interactions, there have been substantial efforts to develop novel compounds capable of binding with CD44 to modulate CD44 biology. Chapter 2 reports a novel approach for generating HA derivatives with enhanced CD44 binding. By modifying the carboxyl group on HA with various amine, aldehyde, and isocyanide moieties through the Ugi reaction, 36 HA like polysaccharides were generated. Two lead compounds were identified with enhanced CD44 binding from the polysaccharide library compared to unmodified HA, which was confirmed by surface plasmon resonance and cellular studies. Ski-learn as a machine learning tool was utilized to analyze the library of binding data and yield prediction with an accuracy over 80%. In conclusion, modification of HA via the Ugi reaction can be a promising approach to develop novel binders toward CD44. While HA has been frequently employed as the targeting molecule in imaging via near infrared (NIR) or magnetic resonance (MRI) imaging, the potential of HA for surface-enhanced Raman spectroscopy (SERS) imaging has not yet been explored. SERS NPs are well-known for strong multiplexing capability, since different flavors of SERS NPs can be synthesized using different SERS dyes, resonant or non-resonant dye. SERS NPs are a promising tool for tumor margin removal in image-guided surgery. However, there are several challenges associated with SERS NPs for cancer imaging: 1) reproducible synthesis of SERS NPs; 2) ligand attachment for SERS NPs. Chapter 3 addresses these two issues by: 1) developing a reproducible protocol for 50 nm SERS NPs with low-femtomolar detection sensitivity; 2) employing liposome as the bridge for HA attachment to SERS NPs. The resulting HA-liposome SERS NPs have been successfully applied in imaging guided surgical removal of breast cancer in a spontaneous mouse breast cancer model.
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Title: (de)(anti)(intra) : Queer Self-Storying as Embodied, Community, and Theory-Building Processes
Creator: de Sostoa-McCue, Tania
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This cultural rhetorics project asserts that story is theory, and surfaces self-storying as an embodied, theory-building process. I undertook phased interviews with three queer creative writers, holding space for their stories in order to witness, interact with and to learn from the ways in which queer authors discuss and approach relationships with one another through storying and composing. This desire to learn from other queer-identified community stakeholders led to the emergence of a...
Show moreThis cultural rhetorics project asserts that story is theory, and surfaces self-storying as an embodied, theory-building process. I undertook phased interviews with three queer creative writers, holding space for their stories in order to witness, interact with and to learn from the ways in which queer authors discuss and approach relationships with one another through storying and composing. This desire to learn from other queer-identified community stakeholders led to the emergence of a story-theory, through which a narrative thread of failure, survival and agency emerged. I articulate a reorientation and reframing of guiding concepts of community, composition and embodiment within queer spaces as (intra)community, (de)composition, and the (anti)body. An important impetus for this project was a desire to address the future of Queer in the academy. I utilize tools and theories from queer theory and cultural rhetorics not only to build, but to show spaces in which these conceptual frames can inform future, positive shifts. I do so to provide my own insights and to offer tools to continue the work Queer in the academy and to bridge the space between academic Queer and non-academic queer. I utilize cultural rhetorics to continue the work of what I see as one of Queer’s primary purposes: to subvert, to disrupt and to re-imagine the ways in which the queer community and Queer can thrive and effect systemic change.
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Title: Level Structures on Finite Group Schemes and Applications
Creator: Guan, Chuangtian
Date: 2022
Collection: Electronic Theses & Dissertations
Description: The notion of level structures originates from the study of the moduli of elliptic curves. In this thesis, we consider generalizing the notion of level structures and make explicit calculations on different moduli spaces. The first moduli space we consider is the moduli of finite flat (commutative) group schemes. We give a definition of $\Gamma(p)$-level structure (also called the ``full level structure") over group schemes of the form $G\times G$, where $G$ is a group scheme or rank $p$ over...
Show moreThe notion of level structures originates from the study of the moduli of elliptic curves. In this thesis, we consider generalizing the notion of level structures and make explicit calculations on different moduli spaces. The first moduli space we consider is the moduli of finite flat (commutative) group schemes. We give a definition of $\Gamma(p)$-level structure (also called the ``full level structure") over group schemes of the form $G\times G$, where $G$ is a group scheme or rank $p$ over a $\Z_p$-scheme. The full level structure over $G\times G$ is flat over the base of rank $|\GL_2(\F_p)|$. We also observe that there is no natural notion of full level structures over the stack of all finite flat commutative group schemes. The second moduli space we consider is the moduli of principally polarized abelian surfaces in characteristic $p>0$ with symplectic level-$n$ structure ($n\ge 3$), which is known as the Siegel threefold. By decomposing the Siegel threefold using the Ekedahl--Oort stratification, we analyze the $p$-torsion group scheme of the universal abelian surface over each stratum. To do this, we establish a machinery to produce group schemes from their Dieudonn\'e modules using a version of Dieudonn\'e theory due to de Jong. By using this machinery, we give explicit local equations of the Hopf algebras over the superspecial locus, the supersingular locus and ordinary locus. Using these local equations, we calculate explicit equations of the $\Gamma_1(p)$-covers over these strata using Kottwitz--Wake primitive elements. These equations can be used to prove geometric and arithmetic properties of the $\Gamma_1(p)$-cover over the Siegel threefold. In particular, we prove that the $\Gamma_1(p)$-cover over the Siegel threefold is not normal.
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Title: Essays in Labor Economics
Creator: VanderBerg, Bryce Scott
Date: 2022
Collection: Electronic Theses & Dissertations
Description: This dissertation consists of two empirical studies and one applied theoretical study in labor economics. In the first chapter, I study the extend to which an observed layoff is used by employers to infer a worker's unobserved ability early in their labor market career. In the second chapter, I develop a theoretical model of wage dynamics that extends the employer learning and statistical discrimination model of Altonji and Pierret (2001) to allow for discrete changes in observable...
Show moreThis dissertation consists of two empirical studies and one applied theoretical study in labor economics. In the first chapter, I study the extend to which an observed layoff is used by employers to infer a worker's unobserved ability early in their labor market career. In the second chapter, I develop a theoretical model of wage dynamics that extends the employer learning and statistical discrimination model of Altonji and Pierret (2001) to allow for discrete changes in observable characteristics. In the third chapter, which is joint work with Gabrielle Pepin at the W.E. Upjohn Institute, we study the contribution of occupational sorting and mismatch to child penalties in the United States. I: The Signaling Role of Early Career Job LossI examine the extent to which ability signaling explains long-term wage losses suffered by young workers who experience layoffs. Young workers are of particular interest because employers have limited information about their ability, so signaling theoretically plays a larger role in determining wages. In addition, young workers are unlikely to experience wage losses due to loss of industry-specific human capital or separation from high-quality job matches, which may explain long-term wage decreases among older workers. Using data from the National Longitudinal Survey of Youth 1997, I show that young workers of all ability levels initially experience similar wage losses following layoffs, but high-relative ability workers fully recover within five years while low-relative ability workers experience persistent wage losses. Consistent with traditional learning models, relative, not actual, ability affects wage trajectories. I illustrate a conceptual model of layoff signaling that varies by pre-layoff experience and can explain divergent wage trajectories across high- and low-relative ability workers. I test the model empirically and find that low-relative ability workers' inability to overcome negative layoff signals explains a substantial proportion of long-term wage losses among young workers. Employer learning effects vary by race and gender.II: Employer Learning and Statistical Discrimination with Unexpected InformationThe Employer Learning and Statistical Discrimination (EL-SD) model of Altonji and Pierret (2001) assumes that employers learn about a worker's unobserved ability in a smooth, continuous manner, holding observable characteristics constant. In practice, observable characteristics, such as years of education, often change discretely over time for many workers. I extend the EL-SD model to allow for changes in observable characteristics to influence an employer's belief about a worker's ability. I show that changes in observable characteristics that are correlated with ability lead to discrete changes in employers' beliefs about the worker's ability, interrupting the smooth, continuous employer learning processes described in the EL-SD model. I further show that this discrete change in employer learning is larger for workers early in their labor market career, with the effect diminishing as labor market experience increases. I then use data from the NLSY97 to empirically test these predictions in the context of the signaling role of returning to school. I find suggestive evidence that returning to school to receive a GED or graduate degree sends a positive ability signal to the labor market, while returning to school to receive an associate or bachelor's degree does not.III: Occupational Sorting, Multidimensional Skill Mismatch, and the Child Penalty among Working MothersWe study the extent to which occupational sorting explains child penalties---gender gaps in labor market outcomes due to children---among working parents. Using an event-study approach and data from the National Longitudinal Surveys of Youth (NLSY) 1979 and 1997, we estimate that children generate long-run earnings gaps of over \$200 per week among working parents. In the NLSY79, we find that children lead mothers to sort into lower-paying occupations in which employees tend to work fewer hours. We estimate that children increase multidimensional occupation-skill mismatch among working mothers by 0.3 standard deviations, relative both to their own levels of mismatch from before birth and to those of fathers. In the NLSY97, results suggest that improvements in labor market outcomes among fathers in response to children, rather than a worsening of labor market outcomes among mothers, seem to drive child penalties.
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