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The Impact of Age on Second Language Vocabulary Learning
Get PDFSecond language (L2) vocabulary learning is challenging for many would-be language learners, regardless of their cognitive abilities. The volume of to be learned vocabulary can be a roadblock to language fluency (Nation, 2006), especially for older adults who have diminished memory capabilities due to age-related memory decline, a degradation in our ability to remember information that naturally occurs as we age (Salthouse, 2009; Schaie, 1993). The process of L2 vocabulary acquisition can be separated into three components, the native language (L1) meaning of the new word (cat), the new L2 word form itself (gato) and the connection between the new word and its meaning (gato means cat; Barcroft, 2002; Kida & Barcroft, 2018). For young adults, there is little difference in their ability to encode and recall these three components, but prior research suggests older adults may struggle with forming a connection between the novel word and its meaning (Naveh-Benjamin, 2000). This dissertation is comprised of two experiments that examine younger and older adult L2 vocabulary learning. There were 4 aims: (1) compare younger and older adults on L1 item memory, L2 item memory, and L1-L2 associative memory during L2 vocabulary learning, (2) identify the relationship between episodic memory and L2 vocabulary learning, (3) identify the unique contributions of working memory to L2 vocabulary learning in older and younger adults, and (4) identify how receptive and productive retrieval practice affects long-term memory for L2 items and L1-L2 associative memory in older and younger adults. Experiment 1 addresses aims 1-3, which seek to understand L2 vocabulary acquisition and how each age group encodes the three components. Participants were first given a working memory test, followed by a learning task for L1-L2 and L1-L1 word pairs and three recognition tests (one for L1 items, one for L2 items, and one for L1-L2 word pairs). Results indicated no age-related differences in the ability to recognize L1 items, L2 items and L1-L2 items, and both age groups were better able to recognize L2 items compared to L1 items. Results also indicated working memory was related only to the L1-L2 pair recognition test with higher working memory leading to improved performance. While older adults did have poor working memory scores compared to young adults, there was no statistical difference between the age groups on L1-L2 pair recognition performance. These findings suggest that age-related cognitive decline may not have a significant impact on L2 vocabulary learning. Experiment 2 addressed aim 4 to examine how study method affected L2 vocabulary learning for both age groups. Participants were tasked with learning L1-L2 word pairs in one of three ways: repeated study, retrieval practice with a L2 target given an L1 cue, and retrieval practice with a L1 target given an L2 cue. After the learning session, participants were given the same three recognition tests as Experiment 1. Results indicated that retrieval practice and repeated study lead to equivalent performances for older adults, but young adults benefitted more from retrieval practice compared to repeated study. Additionally, for young adults retrieving the L1 word improved memory for the L1 item but retrieving the L2 item did not improve memory for the L2 item. These results suggest that retrieval practice may not be as an effective of a tool for older adults as it is for young adults for L2 vocabulary acquisition
Essays on Industrial Organization
No full textBig pharma is increasingly using acquisitions to fill their R&D pipelines and the proliferation of the biotechnology industry has created a thick market of innovative target startups. This dissertation analyzes the dynamic equilibrium effects of biotech startup acquisitions by big pharma on drug innovation and entry. Using a novel dataset on 175 acquired startups from 2000 - 2018, I document several new facts regarding the R&D outcomes of acquired drug projects and entry behavior of startups in markets where acquisitions occur. Motivated by this evidence, I build a dynamic oligopoly model of the pharmaceutical industry featuring big firms and startups that endogenizes drug development, startup acquisitions, product market competition, and entry. Firms select on unobserved project quality at each phase of R&D and into acquisition, allowing higher quality projects to reach later phases of R&D and be a more likely acquisition target. Counterfactual simulations focused on oncology markets suggest that banning startup acquisitions leads to a decline in entry among low-quality startups, who benefit most from lower R&D costs of their acquiring big firms. This and higher selection on quality during R&D among startups results in a decrease in the number of projects that reach the product market and an increase in their quality. Both of these effects are generally small in magnitude. This result directly informs recent discussions among regulators who have expressed concern about the implications of startup acquisitions for market concentration and innovation in the pharmaceutical industry
Development and Structure of Spinal Interneuron Connectivity in Larval Zebrafish
Get PDFIn vertebrates, spinal interneurons are essential for the initiation and propagation of locomotor activity with each class of interneurons serving its own unique role. Ipsilateral interneurons function to control locomotor speed; whereas, commissural interneurons aid in left – right alternation. To date, most studies have been aimed at studying the impact of each individual class of interneurons onto motor neurons. However, not much work has revolved around studying interneuron – interneuron connectivity among the various cardinal classes. Furthermore, it remains unknown how the connectivity of interneurons changes along their entire axonal reach. This thesis aims to address the developmental patterns and structure of interneuron connectivity along the spinal cord. Among the various types of interneurons, two major groups of ipsilaterally projecting interneurons emerge from the same progenitor cell yet diverge into distinct cell types due to differences in Notch signaling. V2a (NotchOFF) neurons and V2b (NotchON) neurons provide glutamatergic and GABAergic/glycinergic input onto motor neurons, respectively. Given their shared origin, it was important to evaluate their developmental connectivity because previous work showed that sisters neurons exhibit stereotypic patterns of connectivity. In mammals, sister neurons assemble into shared microcircuits, whereas in Drosophila, Notch-differentiated sister neurons integrate into distinct circuits. Using an in vivo labeling approach, we identified pairs of sister V2a/b neurons born from individual Vsx1+ progenitors in the zebrafish spinal cord. We used paired whole-cell electrophysiology and optogenetics to reveal that sister V2a/b neurons do not communicate with each other, receive input from different presynaptic sources, and connect to distinct targets. These results resemble the divergent connectivity in Drosophila and represent the first evidence of Notch-differentiated circuit integration in vertebrates. The scarcity of shared targets revealed potential differences in connectivity between V2a and V2b neurons. Prior research on the mapping of V2b postsynaptic targets revealed a connectivity preference for short range targets, but to date, there has been no systematic assessment of V2a postsynaptic targets. Direct assessment of V2a postsynaptic targets using optogenetics revealed that connections from V2a neurons are weighted to longer ranges, explaining the lack of shared targets. Not only did V2a neurons elicit more EPSCs onto target neurons at longer ranges ( \u3e 4 muscle segments away from the target neuron), the strength of the evoked EPSC events were larger than any of the observed local connections. Given the scarcity and strength of local connections, it is unlikely that V2a neurons function as the recurrent and rhythmogenic source in the unit burst generator model, but instead, the propensity to form long range connections could result from the need to ensure propagation of an excitatory wave down the spinal cord during locomotion and provide patterned input, such as directing turns
Electrochemical Phosphorus Recovery from the Anaerobically Digested Sludge: Mechanism, Performance, Application, and Solids Disposal
Get PDFPhosphorus (P) is life’s bottleneck element and an essential nutrient for food production. However, phosphate rock is a non-renewable resource and its geological distribution is highly uneven, making P recovery a crucial step for a circular economy. Approximately 55% of mined phosphorus ends up in centralized wastewater treatment plants (WWTPs), where up to 90% is captured in the sludge. This sludge, treated in anaerobic digesters to produce anaerobically digested sludge (ADS), emerges as a viable secondary source for phosphorus recovery. Recovering phosphorus from ADS typically involves leaching and separation. Leaching mobilizes phosphates from sludge solid phase into a liquid phase, often through acidification, followed by separation of the mobilized phosphate. Traditional methods for these steps are energy and chemically intensive. However, electrochemical systems present a promising alternative with their modular design, operational flexibility, and minimal chemical requirements. Despite these benefits, research into electrochemical P recovery from ADS is still in its early stages, with much to explore in process mechanisms, design optimization, recovery efficiency, product reuse, and solid waste management. This dissertation examines the efficacy of electrochemical P recovery from liquid streams and the development of three electrochemical systems for P recovery from solid stream ADS. It aims to minimize chemical inputs and enhance the quality of recovered P products. The study demonstrates the application of recovered P products in microalgae cultivation and investigates the underlying mechanisms for sludge dewaterability improvement after P recovery. To recover P from liquid streams for reuse, I developed a coupled system consisting of a microbial nutrient recovery cell (MNRC) and a photobioreactor (PBR). The MNRC-PBR system, tested on both synthetic and real food wastewater, significantly enhanced microalgal biomass density and purity compared to direct cultivation in food wastewater. Operational parameters, like the liquid exchange ratio between MNRC and PBR and the water recycling ratio in the PBR, were found to be optimal for microalgae growth at 30% and 50%, respectively. A systematic literature analysis on electrochemical sludge P recovery revealed that the most common P leaching approach for ADS is anodic leaching with a median leaching rate of 92.4 mg d-1. However, few studies report energy consumption data and there was a scarce of studies on chemical-free P recovery methods. This gap led to the development of the electrochemical nutrient recovery cell (ENRC) and the electrochemical phosphorus recovery cell (EPRC). The ENRC, achieving P leaching efficiency similar to direct acid adjustment, separated P via the selective anion exchange membrane. Catholyte acidification was found important to improve P recovery efficiency from 42% to 90%. Conversely, EPRC used electrolysis-assisted precipitation for direct P precipitation in ADS liquid phase, significantly lowering energy consumption from 229 to 83 kWh kg-1 P and reducing chemical input by over 80% as compared to ENRC. The long-term performance, maintenance strategies, and product contamination were discussed and characterized. To lower product contamination, a two-step electrochemical phosphorus recovery system (EPRS) was developed, featuring a leaching unit for P leaching and a recovery unit for its purification and concentration. The EPRS was operated over long-term to reach a steady-state PO43--P concentration of 4040 mg L-1, which can be increased to 5900 mg L-1 by adjusting the anolyte pH to 3-4 according to a mechanistic model. EPRS effectively separated P from heavy metals (Ni, Cd, Cr, Pb, Cu) but showed limited effectiveness against As. EPRS emerged as an energy-intensive process with 441 kWh kg-1 P energy input but produced struvite and magnesium phosphate with minimal impurities. The leaching unit also produced biosolids meeting USEPA Class A pathogen standards. In the dewaterability test, electrochemical P leaching significantly improved sludge dewaterability, reducing the specific resistance to filtration by over 97% for raw sludge before anaerobic digestion, ADS, and primary sludge. The acidification, cation removal, and electrooxidation showed a synergistic effect in releasing bound water. The dissertation concludes with identifying future research opportunities in integrating nutrient resource recovery with sludge pretreatment, evaluating P product reuse, improving electrochemical P recovery efficiency, and scaling up and deploying the technology
Novel Mass Spectral Data Acquisition and Data Analysis Tools for the Study of Organic Gases and Particles in Indoor and Atmospheric Environments
No full textParticulate matter (PM) has a significant impact on visibility, hydrological cycles, and climate change through direct and indirect radiative properties. PM is also ubiquitous in both indoor and outdoor air, presenting adverse effects on human health. Organic matter (OM) constitutes 20-50% of these particulate matter, known as organic aerosols (OA). The chemical composition of OA is linked to its sources and processes, making it crucial to understand its characteristics for developing aerosol-related control policies, air quality regulations, and climate models. Semi-volatile organic compounds (SVOCs) compose a substantial portion of OA, existing in both gas and particle phases. The distribution of these compounds between the two phases can change rapidly depending on conditions such as temperature, relative humidity, the chemical composition of particles, and particle concentration, increasing the chemical complexity of OA. Mass spectrometry has been frequently used to analyze the chemical composition of environmental samples, including OA, from bulk scale to the molecular level. Aerosol Mass Spectrometer (AMS) is widely used for analyzing the bulk chemical composition of fine particles. Thermal Desorption Aerosol Gas Chromatography Mass Spectrometry (TAG) enables molecular level of analysis with data acquisition in higher time resolution coupling with an automated particle sampling system. Additionally, the multi-turn Time-Of-Flight mass spectrometry (InfiTOF) has been developed for high-resolution gas analysis of environmental samples. These advancements in mass spectrometry techniques have significantly contributed to our understanding of the fate of OA in indoor and outdoor environments, with ongoing developments aiming for more precise and efficient analysis of complex environmental samples like OA. As mass spectrometry techniques continue to advance, there is a growing demand for advanced tools in data acquisition and analysis to enhance research efficiency. This demand has led to the development of various mass spectrometry tools depending on specific purposes and needs. This dissertation addresses the development of such tools. Chapter 2 presents a mass spectral database and comparison tool for Aerosol Mass Spectrometer (AMS) and Aerosol Chemical Speciation Monitor (ACSM) developed to compare users’ own mass spectral data efficiently and visually with previous studies. Chapter 3 introduces an automated approach, \u27AutoPMF,\u27 for quantifying chemical compounds in large GC-MS datasets obtained from TAG using positive matrix factorization (PMF), aimed at saving data-processing time and reducing manual inspection. Furthermore, Chapter 5 presents a guide tool for optimizing resolution in infiTOF mass spectrometer operations to enhance data acquisition efficiency. Each tool is demonstrated for its effectiveness through application with previous data, aligning with its intended purpose. Among the developed tools, AutoPMF was utilized to analyze TAG data, focusing on investigating the influence of particle type on the phase-partitioning of SVOCs in indoor environments described in Chapter 4. Specifically, the study concentrated on gas-to-particle partitioning and the desorption of SVOCs from chamber walls depending on particle type. The results demonstrate that organic particles enhance the phase partitioning of SVOCs, while inorganic particles have no significant impact
We live in an unjust system by design, schools included... : Exploring the Perceptions of Black K-12 Administrators on Social Justice in Schools
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Lysimachos and His Coinage in Context: The “Hellespont Workshop” and the “Philo” Lysimachi, c. 302 to 255 BCE
Get PDFThe Domain Specificity and Conscious Awareness of Learned Memory Biases
Get PDFThe False Positive Feedback (FPF) manipulation encourages certain recognition errors by inducing either liberal (lax) or conservative (strict) recognition memory decision biases. FPF manipulation involves trial-by-trial probabilistic positive feedback for commission or omission errors while the other stimulus class always received fully correct feedback during testing. We investigated whether these learned biases are restricted to the stimulus class triggering FPF, or whether they instead spread to an intermixed class receiving valid feedback, by selectively delivering FPF to words or pictures. A spreading bias would suggest that subjects learn to be liberal or conservative in interpreting recognition evidence in general during the testing context (general recognition bias). A restricted bias, however, would indicate a specialized form of learning tied to each class’s unique features (feature-specific bias). In Experiment 1, FPF applied to pictures yielded selective biases that did not spread to intermixed words (FPF applied to words was ineffective). In Experiment 2, FPF applied to words yielded selective biases that did not spread to pictures (FPF applied to pictures was ineffective). These results suggested that biases occurred in a feature-specific manner. Questionnaire data indicated that subjects were unaware of feedback’s purpose and stimulus selective nature, suggesting that recognition decision biases can be unintentionally acquired and yet specific to one of two classes of encountered memoranda