8 research outputs found
Three essays in labor economics
No full textThis dissertation has three chapters that discuss issues regarding the U.S. labor market. The first chapter investigates how establishments adjust their production on various margins when wage rates rise. Exploiting state-by-year variation in minimum wage laws, I analyze U.S. manufacturing plants’ responses over a 23-year period using restricted-access Census Microdata. A one-percent increase in production workers’ hourly wages reduces total production worker hours by 0.7 percent and increases capital investment on machines by 2.7 percent. Manufacturing plants reduce average hours per production worker more than number of production workers. The elasticity of substitution between capital and labor is 0.85. In addition, when wage rates increase, manufacturing plants are also more likely to exit. Finally, suggestive evidence shows that when minimum wage laws increase wages paid by some of the establishments in a firm, the firm also increases the wages paid at its other establishments.
The second chapter studies idleness---time spent out of work and school---among young men in the first 10 years after graduating from high school in the United States. We begin by documenting new facts regarding the distribution of idleness spells and cumulative exposure to idleness.These facts motivate a dynamic model of the school-to-work transition that allows for movement between work, idleness, and two levels of schooling. We find evidence of an idleness trap, a causal effect of idleness on future idleness. Our estimates also reveal that low-commitment school options, such as community college, provide a meaningful stepping stone to further schooling but not to work. We then use the model's characterization of individual heterogeneity to identify the effects of youth idleness on employment and earnings when young men are in their early thirties. We find that idleness reduces employment and earnings for such men in their early 30's. We estimate that an additional six-month period in idleness lowers the share of time employed by 1.6 percent and earnings by 5.4 percent.
The third chapter builds two analytical general equilibrium (GE) models of the U.S. economy to evaluate efficiency impacts and other effects of the minimum wage on labor. First, we couple the GE framework with a search model and competitive markets to highlight a potential but underappreciated source of inefficiency: a higher minimum wage can increase unproductive search time of unemployed workers. In a second model, we assume a monopsony labor market. The analytical models allow us to solve explicit equations for outcomes in GE and to derive testable hypotheses. We compare the testable hypotheses from the two models and use them to guide our empirical work.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-08-01The student, Yuci Chen, accepted the attached license on 2020-07-13 at 09:42.The student, Yuci Chen, submitted this Dissertation for approval on 2020-07-13 at 10:01.This Dissertation was approved for publication on 2020-07-15 at 14:37.DSpace SAF Submission Ingestion Package generated from Vireo submission #15584 on 2020-10-02 at 15:50:32Made available in DSpace on 2020-10-07T22:49:57Z (GMT). No. of bitstreams: 2
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Previous issue date: 2020-07-15Embargo set by: Seth Robbins for item 116326
Lift date: 2022-10-07T22:50:13Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimite
Youth Disconnection During the COVID-19 Pandemic
No full textThis paper studies the impact of the COVID-19 pandemic on youth disconnection—i.e., the share of young people who were neither in school nor at work. Youth disconnection offers important advantages, relative to unemployment or participation rates, as a measure of the labor market for the most marginal and disadvantaged youth. Before the pandemic, approximately one out of eight young people between the ages of 18 and 24 were disconnected. The disconnection rate increased dramatically in April 2020 because of the pandemic; however, it has decreased quickly since that time. The increase in the disconnection rate at the beginning of the pandemic was mostly driven by a reduction in full-time work, but toward the end of 2020, the school enrollment rate also fell. Within-individual transition analysis reveals that the pandemic drove some individuals to disconnection, regardless of whether those persons were in school, at work, or already disconnected. Full-time workers saw the largest increase in transition to disconnection. Compared to the 2007 recession, the full-time-work to full-time-work transition decreased more and the full-time-work to disconnection transition increased more during this pandemic
High Protein Yangyu jiaotuan (洋芋搅团): In Vitro Oral-Gastro-Small Intestinal Starch Digestion and Some Physico-Chemical, Textural, Microstructural, and Rheological Properties
No full textBiomimetic foods are expected to have potential health benefits for the management and prevention of chronic diseases, such as diabetes and cardiovascular disease. In the current research, two commercially available and affordable plant proteins (soy protein isolate—SPI and pea protein isolate—PPI) at two levels (5%, 10%) were added to the Yangyu jiaotuan with the objective of developing a product with reduced glycaemic properties and high protein content while maintaining its original taste and texture. The results showed that several important textural properties such as hardness and chewiness did not change significantly during the refrigerated storage. The storage modulus G′ increased with refrigerated storage time for different samples, but there were significant differences among the five samples (with and without protein addition) with respect to frequency dependence during rheological measurements. The in vitro starch digestion experiments showed that the starch hydrolysis of Yangyu jiaotuan decreased considerably (by up to 42.08%) with the increase in PPI content and during refrigerated storage due to starch retrogradation. Protein has protected the microstructure and there was less damage when compared to samples without protein. The bimodal peaks of the particle size distribution curves showed that the newly developed Yangyu jiaotuan contains two different sizes of particles; the smaller particles (~30 μm) corresponded to PPI and starch granules, while the larger particles corresponded to the fragments of the gel network of the starch matrix. Based on the above results, Yangyu jiaotuan mixed with pea protein is a convenient potato staple food product, which complies with the biomimetic potato food very well
Abundant mRNA m1A modification in dinoflagellates: a new layer of gene regulation
No full textAbstract Dinoflagellates, a class of unicellular eukaryotic phytoplankton, exhibit minimal transcriptional regulation, representing a unique model for exploring gene expression. The biosynthesis, distribution, regulation, and function of mRNA N1-methyladenosine (m1A) remain controversial due to its limited presence in typical eukaryotic mRNA. This study provides a comprehensive map of m1A in dinoflagellate mRNA and shows that m1A, rather than N6-methyladenosine (m6A), is the most prevalent internal mRNA modification in various dinoflagellate species, with an asymmetric distribution along mature transcripts. In Amphidinium carterae, we identify 6549 m1A sites characterized by a non-tRNA T-loop-like sequence motif within the transcripts of 3196 genes, many of which are involved in regulating carbon and nitrogen metabolism. Enriched within 3′UTRs, dinoflagellate mRNA m1A levels negatively correlate with translation efficiency. Nitrogen depletion further decreases mRNA m1A levels. Our data suggest that distinctive patterns of m1A modification might influence the expression of metabolism-related genes through translational control
Primate‐Specific DAZ Regulates Translation of Cell Proliferation‐Related mRNAs and is Essential for Maintenance of Spermatogonia
No full textAbstract Primate‐specific DAZ (deleted in azoospermia) has evolved in the azoospermia factor c (AZFc) locus on the Y chromosome. Loss of DAZ is associated with azoospermia in patients with deletion of the AZFc region (AZFc_del). However, the molecular mechanisms of DAZ in spermatogenesis remain uncertain. In this study, the molecular mechanism of DAZ is identified, which is unknown since it is identified 40 years ago because of the lack of a suitable model. Using clinical samples and cell models, it is shown that DAZ plays an important role in spermatogenesis and that loss of DAZ is associated with defective proliferation of c‐KIT‐positive spermatogonia in patients with AZFc_del. Mechanistically, it is shown that knockdown of DAZ significantly downregulated global translation and subsequently decreased cell proliferation. Furthermore, DAZ interacted with PABPC1 via the DAZ repeat domain to regulate global translation. DAZ targeted mRNAs that are involved in cell proliferation and cell cycle phase transition. These findings indicate that DAZ is a master translational regulator and essential for the maintenance of spermatogonia. Loss of DAZ may result in defective proliferation of c‐KIT‐positive spermatogonia and spermatogenic failure
Fecal contamination of drinking-water in low- and middle-income countries: a systematic review and meta-analysis
No full textBackground: access to safe drinking-water is a fundamental requirement for good health and is also a human right. Global access to safe drinking-water is monitored by WHO and UNICEF using as an indicator “use of an improved source,” which does not account for water quality measurements. Our objectives were to determine whether water from “improved” sources is less likely to contain fecal contamination than “unimproved” sources and to assess the extent to which contamination varies by source type and setting.Methods and findings: studies in Chinese, English, French, Portuguese, and Spanish were identified from online databases, including PubMed and Web of Science, and grey literature. Studies in low- and middle-income countries published between 1990 and August 2013 that assessed drinking-water for the presence of Escherichia coli or thermotolerant coliforms (TTC) were included provided they associated results with a particular source type. In total 319 studies were included, reporting on 96,737 water samples. The odds of contamination within a given study were considerably lower for “improved” sources than “unimproved” sources (odds ratio [OR] = 0.15 [0.10–0.21], I2 = 80.3% [72.9–85.6]). However over a quarter of samples from improved sources contained fecal contamination in 38% of 191 studies. Water sources in low-income countries (OR = 2.37 [1.52–3.71]; p<0.001) and rural areas (OR = 2.37 [1.47–3.81] p<0.001) were more likely to be contaminated. Studies rarely reported stored water quality or sanitary risks and few achieved robust random selection. Safety may be overestimated due to infrequent water sampling and deterioration in quality prior to consumption.Conclusion: access to an “improved source” provides a measure of sanitary protection but does not ensure water is free of fecal contamination nor is it consistent between source types or settings. International estimates therefore greatly overstate use of safe drinking-water and do not fully reflect disparities in access. An enhanced monitoring strategy would combine indicators of sanitary protection with measures of water qualit
Microbiome preterm birth DREAM challenge: crowdsourcing machine learning approaches to advance preterm birth research
No full textEvery year, 11% of infants are born preterm with significant health consequences, with the vaginal microbiome a risk factor for preterm birth. We crowdsource models to predict (1) preterm birth (PTB; <37 weeks) or (2) early preterm birth (ePTB; <32 weeks) from 9 vaginal microbiome studies representing 3,578 samples from 1,268 pregnant individuals, aggregated from public raw data via phylogenetic harmonization. The predictive models are validated on two independent unpublished datasets representing 331 samples from 148 pregnant individuals. The top-performing models (among 148 and 121 submissions from 318 teams) achieve area under the receiver operator characteristic (AUROC) curve scores of 0.69 and 0.87 predicting PTB and ePTB, respectively. Alpha diversity, VALENCIA community state types, and composition are important features in the top-performing models, most of which are tree-based methods. This work is a model for translation of microbiome data into clinically relevant predictive models and to better understand preterm birth
