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Vegetation Shifts from Forests to Shrublands or Grasslands in the Western U.S. due to Warming, Droughts, and Fire
No full textAnthropogenic greenhouse gas emissions have caused significant climate changes, leading to increased drought and warming, which have resulted in more frequent and severe wildfires in the western United States. This study uses a biogeochemical and biogeography model to predict change in PFT dominance, that will occur in response to increasing temperatures, droughts, and fire intensity. Climate model projections indicate that these changes will continue throughout the 21st century, with the western U.S. expected to experience significant impacts. Specifically, I focused on the changes that will result in the dominant plant functional types (PFTs) shifting from forests to grasslands or shrublands in the Western U.S. forested grids by the end of the century (2070 – 2100). Based on the BIOME4 approach, my biogeography model uses bioclimatic thresholds to determine the PFTs that can exist in each grid cell and then optimization of Net Primary Productivity (NPP) to determine the resultant dominant PFT (NPP bake-off). However, forests will not decline unless conditions allow for a replacement fire, so fire occurrences are based on biomass thresholds, soil moisture, and relative humidity. My results indicate that 54% of the originally forested grids will convert to either shrubland (29%) or grassland (25%) by the end of the century, with most of the shifts occurring in grids with the highest temperature increases and reduced soil moisture. However, the remaining forests are more productive (increased NPP) compared to historical ones due to warming, CO2 fertilization, and increased precipitation in these grids. The overall change in carbon storage as a result of the changes in dominant PFTs is a net loss of carbon equal to 9.6 PgC. These findings have important implications for managing forested ecosystems in the western U.S. and highlight the need for proactive measures to mitigate the impact of climate change on forested and grassland and shrubland ecosystems
Parent Engagement in Intervention for Adolescents with ADHD: A Person-Centered Approach
No full textAttention-deficit/hyperactivity disorder (ADHD) is a highly prevalent, life-course persistent neurodevelopmental disorder. Treatment for ADHD has been examined in multiple contexts, including medication, behavioral parent training (BPT), and multicomponent school-based interventions. Most often, intervention for both children and adolescents has involved a parent component. Notably, the understanding of parent engagement within the context of intervention has primarily been studied in BPT and interventions with younger children. Additionally, previous studies have primarily used variable-centered approaches to statistical analyses. The present study aimed to better understand parent engagement in a multicomponent intervention for high school students with ADHD, using a person-centered statistical approach. The sample included 91 participants (80.2% assigned male sex at birth; Mage = 15.2 years; 76.9% White). Data imputation was used to account for missing data after they were determined to be missing completely at random (MCAR). Latent profile analysis was used to determine profiles of parents enrolled in the studies. Results indicate that three parent profiles emerged ("no psychopathology", "moderate ADHD symptoms", and "high psychopathology"), parent stress was average across all profiles. Lower parent educational attainment was associated with greater risk of belonging to the "high psychopathology" profile, family income was not related to profile membership. Additional results indicated that parent profile and treatment content fidelity did not predict parent engagement in intervention, nor did treatment content fidelity moderate the relationship between parent profile and parent engagement in intervention. Limitations, implications for practice, and future directions were discussed
Cholinergic Modulation in the Developing Mammalian Superior Olivary Complex
No full textThe superior olivary complex (SOC) is a collection of nuclei that extract timing cues from auditory signals for initial coding. These timing cues are critical for identifying the location of sounds in the azimuth and are also important for speech perception. There are three main nuclei in the SOC that each play unique roles in signal computation: the medial superior olive (MSO), the lateral superior olive (LSO) and the medial nucleus of the trapezoid body (MNTB). The MSO uses interaural time disparity (ITD) as a cue to locate low frequency sounds while the LSO uses interaural intensity difference (IID) for high frequency sounds. The MNTB is the main source of inhibition in the SOC conveying greater accuracy to its targets and is home to the famous calyx of Held synapse. The calyx of Held synapse has been well studied since the late nineteenth century and this was made possible in part due to its massive size.Neuromodulators that regulate both the mature function and development of the SOC nuclei. The cholinergic neurotransmitter system was the first discovered yet has only recently been ascertained to play a role in modulating these auditory brainstem nuclei. The cholinergic system is driven by acetylcholine (ACh), the neurotransmitter, and two main receptor classes: nicotinic acetylcholine receptors (nAChRs) and muscarinic (mAChRs). These receptor species can play numerous roles depending on their spatial and temporal location as well as subunit composition. It has been shown that nAChRs are expressed in the rat SOC with peak expression just prior to hearing onset (Happe and Morley 2004). This peak in expression coincides with a developmentally consequential stage during which there is synaptic and dendritic refinement (Sanes and Takacs 1993; Kim and Kandler 2003) suggesting a potential developmental role. It has also been recently demonstrated that nAChRs play a role in regulating the mature MNTB (Zhang et al., 2021). Despite the intense study on SOC nuclei and a body of knowledge about cholinergic signaling elsewhere, very little is known about the nature of cholinergic modulation in the SOC or the cellular mechanisms that drive its outcomes. This body of work examines the nature of cholinergic signaling in the SOC by first characterizing important molecules that regulate cholinergic synaptic activity. Knowledge about important synaptic markers informs our understanding of the nature of cholinergic signaling and any developmental trends. This study reveales the expression of pre and postsynaptic cholinergic markers in the SOC revealing both classical synapses and developmental trends coinciding with the developmentally consequential critical period. Next, using in vitro whole cell patch clamp we demonstrate that both pre and postsynaptic nAChRs are functional and mediate cellular responses including synaptic plasticity. Lastly, we characterize mAChR function in the MNTB and demonstrate that it serves to increase cell excitability through a downstream potassium channel prior to the onset of hearing. Together these results reveal the expression patterns of important hallmarks of cholinergic signaling, demonstrate functional receptors and sheds light on a novel neurmodulatory role for ACh in the SOC
Comparing net-proton distribution µr based values in Au+Au collisions at √ssNN =14.6 GeV using mid-n and forward(backward)-n determined centrality
No full textThe strong nuclear force, as modeled by Quantum Chromodynamics (QCD), has been extensively studied in recent years in order to learn its thermodynamic properties. Modern collider experiments have been able to access the thermodynamic regime where QCD matter transitions from ordinary (hadronic) matter to a Quark-Gluon Plasma (QGP), which is characterised by colour parton degrees of freedom. This change in phase suggests a phase diagram; as such, many experiments have been aimed at finding the Critical Point (CP) in this phase diagram at the terminus of the 1st order phase transition line between hadronic matter and QGP. Among the observables theorised to be sensitive to the QCD CP are thenet-proton distribution moment (?r) based cumulant ratios, C3/C2 and C4/C2 (S? and ??2, respectively), which are believed to vary monotonically with centre-of-momentum collision energy (?sNN ) in the absence of critical phenomena, but which are also correlated to the correlation/interaction length (?) and thus may show non-monotonic correlation with ?sNN near the CP as ? diverges at the CP.The sensitivity of S? and ??2 to volume fluctuations implies they are sensitive to centrality fluctuations (CF); thus the method of centrality selection and determination is highly important to ?r based analyses. In current analyses of the Beam Energy Scan (BES) program at the Solenoidal Tracker at RHIC (STAR), both ?r analysis and centrality determination are carried out using the Time Projection Chamber (TPC); a mid-rapidity detector with a pseudorapidity (?) acceptance range of?? 1. Using the same ? range to determine both net-proton ?r based values and centrality introduces the potential for autocorrelation errors (ACE). The acceptance range of the STAR Event Plane Detector (EPD) is 2.1 ?? 5.1, thus using the EPD to determine centrality while using the TPC for particle identification would avoid the potential for ACE.This thesis analyses net-proton distribution ?2/? and S? values at ?sNN = 14.6 GeV using both mid and forward(backward) ? determined centrality. Mid-? centrality (XRM 3) is determined with the STAR TPC, which is also a main detector used in particle identification by which net-proton distribution (?Np) arrays are generated, and forward(backward)-? centrality (XEP D) is determined with the STAR EPD. In simulation, it is found that ?Np ?2/? values differ between distribution cuts made using XRM 3 and XEP D, but that both are in range of ?2/? values found usingcentrality determined via the impact parameter (b) in the most central bin (0-5%). In experiment, the ?2/? and S? values determined using XRM 3 and XEP D based centrality selection differ as the simulation values, with the ?2/? values being within error of the simulation values. For both ?2/? and S?, values found using XEP D as the centrality determination observable are higher across the centrality range than those found using XRM 3 as a centrality selector. This finding is congruent with XRM 3 centrality selection based analyses of ?Np ?r based observables suffering from ACE at ?sNN = 14.6 GeV in the STAR experiment.This work will aid in vetting the results of any ?Np ?r based analyses in the STAR Collaboration, particularly net-proton kurtosis (??2) studies. The techniques evaluated herein can be readily applied to other BES collision energies, making this a valuable addition to current analyses across the STAR BES range without adding much in the way of additional work for researchers searching for the QCD CP
On Being a Mother Teacher: A Mixed-Methods Analysis Examining Experiences of Mother Teachers during the COVID-19 Pandemic
No full textThe COVID-19 pandemic changed the ways in which people engage in their personal and professional lives. The emerging literature demonstrates that teachers are experiencing stress (Kim & Asbury, 2020a, 2020b), but little is known about how teachers are coping with stress. Women teachers\u27 reports of stress are often higher than men teachers (Antoniou et al., 2006; Chaplain, 2008; Klapproth et al., 2020; Ozamiz-Etxebarria et al., 2020), and little is known about the experience of women teachers during the COVID-19 pandemic. In addition, in comparison to fathers, mothers are taking on childcare and other responsibilities that increase their stress levels (Collins et al., 2020; LeanIn, 2020; Power, 2020). These experiences may be influencing the stress of teacher mothers and the ways in which they are coping. To develop a better understanding of the stress and coping strategies of secondary school teacher mothers, a mixed-methods design was used to 1) explore participants� experiences of stress and coping during the COVID-19 pandemic, and how their roles as teacher mothers influenced their experiences, and 2) explore the specific coping strategies used by teacher mothers. In this study, a grounded theory approach was used to capture the unique experiences of teacher mothers (Charmaz, 2006; Glaser & Strauss, 1967).A sample of 20 teacher mothers participated in video interviews about their experiences during the COVID-19 pandemic. Each interview was transcribed by the principal investigator and participants were invited to review their transcribed interviews, of which six opted to review. A team made up of three counseling psychology doctoral students and one master�s level clinician coded the transcribed interviews. Throughout each process of the qualitative data analysis, steps were taken to ensure trustworthiness of the data including self-reflexivity, triangulation, member check-in and reflections. In addition, the coding team engaged in ongoing dialogue on assumptions, biases and personalities related to the topic of the study. Results yielded three themes: the collective event, the process and the aftermath. From the three themes and the subthemes, a model emerged: �Role Complexities: On Being a Mother and a Teacher During a Collective Trauma.� This is the first model that addresses the experiences of teacher mothers in the context of a global pandemic, particularly as it relates to their mental health, coping and healing, and intersectional identities. Results from the present study will be useful in developing practices and policies that are aimed at supporting teacher mothers in and outside of the school systems that they are a part of. Suggestions are provided on how to address the experiences of teacher mothers in practice, research and school systems
Examining Patterns of Early Literacy Skills Among Preschoolers Using Latent Class Growth Analysis
No full textGiven the importance of early literacy skills in predicting later outcomes and the malleability of these skills, there have been significant efforts to develop assessments for screening and progress monitoring. Research has focused on investigating general growth and development of early literacy skills over time by examining mean patterns of growth. In addition to examining overall growth over time, the current study seeks to consider heterogeneity in literacy skills among preschool aged children by determining whether multiple growth trajectories in performance exist using the Progress Monitoring Individual Growth and Development Indicators. Participants included 276 children enrolled in early childhood programs in urban, suburban, and rural districts across the Pacific Northwest, Midwest and Northeast. Findings revealed differences in children�s initial performance and growth over time across measures. Results indicated that a 4-class model had the best fit across measures (i.e., Picture Naming, First Sounds, Sound Identification, Rhyming) except for Which One Doesn�t Belong where a 3-class model was superior.Keywords: early literacy, assessment, growth trajectorie
Numerical Modeling and Performance Evaluation of Solar Concentrator Systems with Integrated Latent Heat Energy Storage for Desalination Applications
No full textThis study investigates the integration of solar concentrators, latent heat thermal energy storage (LHTES) units, and heat exchangers for membrane desalination applications in a closed-loop system. Optical and numerical analyses assess system performance and optimize its design. It is demonstrated that the 45o conical receiver at 0.12m above the focal point is the most efficient choice, with an optical efficiency of approximately 82%. Furthermore, the numerical analysis evaluates the outlet temperature of the heat transfer fluid (HTF) in the optimal receiver configuration. Turbulent flow with a Reynolds number of 19,167 achieves the desired temperature range for membrane desalination applications with LHTES. Comparative studies of different LHTES heat exchanger designs reveal that the fin-based heat exchanger (FHE) outperforms the helical coil-based heat exchanger (HCHE) in terms of faster-melting rates when HTF is in the turbulent region, demonstrating improved heat transfer and more stable charging and discharging energy rates. The study also explores the impact of packing fractions on shell and tube LHTES heat exchangers. The higher packing fractions lead to increased melting rates and energy storage.An integrated closed-loop system is developed, incorporating a solar concentrator unit, helical coil solar receiver, LHTES unit, and heat exchanger. Evaluations through optical and numerical simulations encompass closed-loop, open-loop, varying Reynolds numbers, and varying solar radiation intensities. The results reveal significant distinctions between closed-loop and open-loop systems, with closed-loop operating temperatures being higher and influenced by HTF flow rates and solar intensity. However, the heat exchanger surface temperature is inadequate for membrane desalination applications, prompting design adjustments. The study concludes that closed-loop systems exhibit unique characteristics compared to open-loop units, which have been the primary focus of previous numerical studies by other researchers. The present study provides valuable insights into the numerical analysis of closed-loop systems, focusing on energy storage and utilization in desalination and other applications. Future research should prioritize optimizing closed-loop system design to improve heat exchanger performance, study discharging cycles, and explore the effects of varying parameters like solar radiation during the charging cycle
Disinformation and the Threat to Democratic Institutions
No full textThe College of Arts and Sciences is pleased to present the 2023 Kenner Lecture with Anne Applebaum. She will speak on "Disinformation and the Threat to Democratic Institutions." Pulitzer Prize winning historian, journalist, commentator on geo-politics and keynote speaker, Anne Applebaum examines the challenges and opportunities of global political and economic change through the lenses of world history and the contemporary political landscape. The Kenner Lecture on Cultural Understanding is an endowed lecture series of the College of Arts and Sciences at Lehigh University, established in 1997 by Jeffrey L. Kenner �65 �66
Investigating the shift in proactive and reactive control across time with a low and high working memory load
No full textCognitive control is one\u27s ability to maintain and flexibly regulate their behavior to achieve a goal. One prominent cognitive control theory is the Dual Mechanisms of Control (DMC) which posits two modes of control: proactive and reactive control. Previous research has identified multiple factors that affect the balance between proactive and reactive control such as working memory capacity, expectations, incentives, and penalties. Additionally, manipulations of these factors have highlighted two types of relationship between proactive and reactive control: independent and dependent. A popular cognitive control paradigm, the AX-Continuous Performance Task (AX-CPT), captures proactive and reactive control through performance measures on different trial types specifically designed to result in errors driven by proactive or reactive control. To examine changes across position, the cue-probe design of the AX-CPT was changed to a multiple probes AX-CPT design, where a single cue is followed by a sequence of probes. I aimed to explore the role working memory (WM) plays in maintaining or strengthening proactive control across time. To investigate WM\u27s involvement in maintaining the cue context across time, a high and low working memory load (WML) manipulation was presented prior to the cue in a multiple probe AX-CPT trial either blocked (Experiment 1) and randomly intermixed (Experiment 2). In Experiment 1, the effect of position was only significant for AY trials with a low WML condition, suggesting that proactive control strengthens task preparation across time only when WM is available. In Experiment 2, there were no effects of WML and no increase in AY errors across the Early, Middle, and Late positions, suggesting that when WM could be used to strengthen the cue context across a probe sequence in a low WML trial, they are not when the WML manipulation is intermixed. This study supports an independent relationship between proactive and reactive control
Zeros of the Goss zeta function
No full textLet be a smooth proper curve over a finite field and let
be a closed point. Let be the ring of functions on . The Goss
zeta function of is an equicharacteristic analogue of the Riemann
zeta function. In this article we study the zeros of under the
generic condition that is ordinary. We prove an analogue of the Riemann
hypothesis, which verifies a corrected version of a conjecture of Goss. We also
show that the zeros of at negative even integers are `simple\u27 and
that is nonzero at negative odd integers. This answers questions
posed by Goss and Thakur. Both of these results were previously only known
under the restrictive hypothesis that has class number one. Finally, we
prove versions of these results for -adic interpolations of the Goss zeta
function