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Exploring The Bidirectional Relations of Depressive Symptoms with Global Self-Esteem and Domain-Specific Self-Competence from Late Childhood to Early Adulthood
No full text{"value":"Longitudinal bidirectional relations between depressive symptoms and self-worth across the lifespan have been well-established. However, most work has focused on their relations at succinct developmental time periods, rather than how these relations evolve across development. In addition, most research has focused on the association between depressive symptoms and global self-esteem, rather than domain specific self-competence. The relative salience of each domain of self-competence varies by age and gender, which supports the necessity of examining these relations across different domains of self-competence and across developmental periods assessing for any differences between boys and girls. The current study uses cross-lagged structural equation models to investigate bidirectional relations among depressive symptoms, global self-esteem, and seven domains of self-competence (behavioral, physical appearance, intellectual, athletic, social, close friend, and romantic self-competence) measured at ages 10, 14, 18, and 23 years. The sample consisted of 337 European Americans who self-reported on depressive symptoms, global self-esteem, and specific self-competence at all time points.
We estimated structural equation models of the bidirectional relations between depressive symptoms global self-esteem and each domain of self-competence. Overall, our findings indicated differences in the associations between depressive symptoms and global self-esteem across development, with depressive symptoms at age 10 significantly associated with global self-esteem at age 14, and global self-esteem at age 18 associated with depressive symptoms at age 23. Our findings also indicated that the relation between depressive symptoms and domain specific self-competence varied both by the domain of interest, and developmental period. Future interventions for depression should target the age- and domain-specific processes.
","attr0":"abstract"
Electrical synapses and sensory attention at the Thalamic Reticular Nucleus
No full textSensory information from the environment is relayed to the cortex by thalamocortical (TC) relay neurons in specific pathways dedicated by sense. Axons from TC cells also collateralize upon cells of the thalamic reticular nucleus (TRN) en route to the cortex. The TRN is thought to be a strategic site for exerting attentional control over sensory input before information reaches cortex. Yet the circuitry bases for TRN’s control of thalamocortical relay are not well described. Importantly, how the electrical coupling between TRN cells might underlie modulation of sensory information is still unclear. This gap was addressed at three levels, one for each of the following chapters. First, how do the properties of a single electrical synapse between TRN neurons alter the spike responses, and thus the inhibition they impart upon thalamic cells? Second, how do the distinct cell types of the TRN, and the precise feedback circuitry with thalamic cells affect sensory relay? Lastly, how far can the electrical coupling within networks of TRN cells produce considerable changes on spiking activity of cells and the information relayed and received by a cortical integrator? Here I show that for a single electrical synapse between TRN dendrites, the directionality of that synapse strongly influences excitability and rhythmic synchrony between cells. Also, when including the cell types of TRN, sensory transmission is modified bidirectionally as determined by the exact synaptic configurations that exist between both TRN cell types and their thalamic target regions. Lastly, a network of several electrically coupled TRN cells receiving closely timed inputs can modulate firing responses up to several synapses away, and electrical synapse strength substantially changes input correlation of thalamic relay and reduces cortical input integration. Together, this investigation highlights three levels at which thalamocortical transmission could be influenced by TRN electrical synapses, and provide insights into mechanisms of sensory attention within the TRN. In particular, how synaptic properties such as electrical synapses might produce the hypothesized spotlight of attention produced by TRN is a significant question that this work has begun to elucidate. </p
Disciplinary Ecotones: Defining the borderlands between sustainability studies and environmental studies in U.S. higher education
No full textThis dissertation explores the institutionalization of sustainability studies within undergraduate programs in the United States, investigating its implications for interdisciplinary structure, faculty expertise, and curriculum focus. It specifically examines how sustainability studies differentiates itself from the established field of environmental studies. Employing a combination of social network analysis and bibliometric techniques, this study compares the disciplinary orientations of faculty across 60 institutions, revealing significant distinctions in academic culture. Additionally, quantitative analysis of coursework requirements for sustainability studies students highlights a broader integration of social sciences, business, and arts and humanities within the curriculum. The findings underscore the evolution of sustainability studies as a distinct academic discipline, characterized by a unique interdisciplinary approach that enhances its relevance in addressing complex environmental, social, and economic challenges.</p
A Comparison of Traditional and Bayesian Methods for Estimating Rates of Change on Direct Behavior Rating-Single Item Scales
No full textDirect behavior ratings (DBR) are a series of assessments that measure behavior change using a combination of systematic direct observation and behavior ratings. To assess student responsiveness to behavioral interventions, educators might consider estimating rates of change on DBR within specified time periods. The primary purpose of this study was to compare the performance of three estimators of DBR score change (ordinary least squares regression [OLSR]; uninformed Bayesian regression [UBR]; informed Bayesian regression [IBR]) in academic engagement and disruptive behavior. Of substantive interest was the extent to which specifying prior knowledge (e.g., trend magnitude and observation variability) affected the precision of rates of change estimated for hypothetical progress monitoring cases at different intervals of data collection (e.g., with four weeks of data, with eight weeks of data, etc.). Priors informed by descriptive analyses improved the precision of slope estimates in both progress monitoring domains. The effects of incorporating informed priors appeared most significant at short durations (e.g., with four weeks of data) and among cases exhibiting relatively high observation variability. The reliability of all estimates improved primarily as a function of duration and magnitude of the simulated true trend rather than estimation method. OLSR and UBR estimates were relatively unbiased. However, minor bias that was initially attributable to IBR decreased as duration increased. Results lend preliminary evidence for developing weakly-to-moderately informative prior distributions before estimating rates of change on DBR in a Bayesian framework. Researchers and practitioners might consider the potential effects of data availability and stability before estimating and interpreting OLSR-derived rates of change in academic engagement and disruptive behavior. The advantages and limitations of each estimator for evaluating intervention effects in prevention-intervention frameworks are discussed.</p
Interface Characterization and High-Temperature Tribological Properties of AM-Clad H13 for Hot Forging Tool Repair
No full text{"value":"Hot forging is a well-established manufacturing process used in theproduction of various goods, but at elevated temperatures tooling can fail due to
localized deformation and wear. Techniques exist to extend tool life, including
selective hardening, case hardening, thin-film coatings, and weld overlay
claddings. While each technique has use cases to which they are well suited, a
new technology, Additive Manufacturing (AM), can produce weld overlay
claddings with benefits over traditional techniques. These include automation via
the hybrid manufacturing process (by which a damaged tool is repaired through
an automated combination of metrology, machining, and AM) and the ability to
rebuild tools with alternate alloys to alter their surface properties. In this work, a
model H13 hot forging punch is clad with 316L stainless steel, Alloy 625 (a
nickel-base superalloy), and Haynes 188 (a cobalt-base superalloy) to improve
the high-temperature hardness and wear performance of the hot forging tool.
In the first part of this research, characterization of the dissimilar metal
interface produced by the AM claddings on H13 was undertaken. These
claddings were produced by two processes, Powder Bed Fusion (PBF) and
Direct Energy Deposition (DED) on annealed H13 and then analyzed in both the
as-printed condition and after heat treatment to bring the H13 to a quench and
temper condition. The interfaces were observed via light optical microscopy,
SEM backscatter, and SEM EDS mapping to characterize the interface and its
evolution through heat treatment. Microhardness and EDS line traces were
utilized to further assess the interfaces. From this, incomplete mixing was seen in
the as-printed interfaces of PBF samples, but not DED. Backscatter and EDS
mapping revealed Cr-rich precipitates at the interface in all samples. This
corresponds with elevated hardness found in all as-printed samples at the
interface. Heat treatment eliminates this interface hardness spike, allows for
complete interfacial mixing, and lengthens the chemical gradient at the interface,
but does not eliminate the precipitates. This characterization is consistent with
dissimilar metal weld theory which can be utilized to evaluate these interfaces.
The second part of this research assesses the high-temperature hardness
and wear properties of AM claddings. Claddings were produced identically to the
interface characterization and experiments were conducted at temperatures of
25, 300, 500, 600, 700, and 800 °C for both hot hardness and hot wear. Hot wear
testing was conducted using a pin-on-disk experiment with the cladding as the
disk and a sapphire sphere as the pin. Results indicate Alloy 625 and Haynes
188 have a lower hardness than H13 below 600 °C with only small decreases as
temperatures increase, whereas unclad H13 loses significant hardness between
600 and 700 °C. No cladding demonstrated a lower wear rate than unclad H13,
except for Haynes 188 at 800 °C. No difference was identified between PBF and
DED in hot wear, but PBF did demonstrate higher hot hardness than DED, which
may be due to greater macroscale porosity in the DED samples. Future work is
required to improve high temperature performance of the cladding alloys and to
evaluate the mechanical performance of the interface, but this research
successfully demonstrates the viability of AM as a cladding process for the repair
of H13 hot forging tools.","attr0":"abstract"
Simulation of 3-D Crack Growth in Welded Structures based on Residual Stresses Obtained from Detailed Welding Process Models
No full textResidual stresses are one of the major contributors to structural failure. For instance, the residual stresses induced by straightening processes in railway tracks can lead to vertical cracks that compromise structural integrity. Welding, as a widely used manufacturing technique, introduces significant residual stresses, which are particularly problematic in large structures where post-weld heat treatment is not feasible. Among the adverse effects of welding residual stress, its impact on fatigue crack growth is a critical concern, as it can increase the stress intensity factor (SIF) at the crack tip, thereby reducing fatigue life, and alter crack propagation trajectories, making them difficult to predict. Extensive research has been conducted on finite element (FE) simulations of welding processes and fracture mechanics; however, studies that integrate detailed welding process models with fatigue crack growth models remain scarce. Most existing works focus only on computing SIFs under residual stress conditions without incorporating comprehensive fatigue crack propagation simulations. To address this gap, this study employs a finite element method to integrate detailed welding models with fatigue fracture mechanics models for fatigue crack growth simulations in residual stress environments. The welding finite element simulations include hot cracking tests and multiple welding techniques, while the fatigue crack growth simulations are conducted using the Paris law, the maximum stress criterion, and the Walker equation. The results encompass residual stress distributions for different welding techniques, quantification of welding hot cracking tests, automated optimization and computation using APDL scripting, as well as SIF calculations and crack trajectory predictions under residual stress conditions. This research integrates detailed welding residual stress fields with the Walker equation in fracture mechanics to improve the accuracy of crack growth simulations, providing a more reliable method for fatigue life assessment in welded structures.</p
Enabling Cross-Network Consensus: A Hierarchical Framework for Independent Blockchain Systems
No full textSince the beginning of financial digitization, the management of cross-border payments between independent regions needed to be addressed. This thesis discusses a new decentralized method for international financial transactions based on a hierarchical consensus framework for independent block-chain regions that accomplishes the same goal as current centralized solutions, such as Swift, Stellar Anchors, and Ripple. Instead of instructing institutions to trust a system, they each have the autonomy to make decisions that align with their region\u27s policies and regulations in this framework. The primary issues that need to be solved when implementing a decentralized global transaction system are determining how consensus is reached, how nodes are selected and verified to be involved in consensus at a higher level of the hierarchy, and how transactions that span regions are consistent. The hierarchical consensus model enables the integration of different solutions into each region. However, this thesis discuses utilizing the Stellar Consensus Protocol as the consensus mechanism, digital identities and verifiable credentials to manage identity, verifiable random functions to select and prove representative nodes, and compensating transactions to maintain semantic correctness in transactions spanning regions. Overall, this framework provides regions more flexibility and involvement in cross-border financial transactions.</p
Understanding Electrochemical Doping in Carboxylated Mixed Ionic-Electronic Conductors: From Ion Uptake to Functional Performance
No full textOrganic mixed ionic-electronic conductors (OMIECs) are emerging as key materials for energy storage, bioelectronics, and sensing due to their dual ionic and electronic conductivity. However, the complex interplay between chemical structure, environment, and ion dynamics remains poorly understood. This thesis advances the understanding of electrochemical doping mechanisms in carboxylated polythiophenes by probing ion uptake, transport, and swelling behavior in real time. Chapter 2 investigates the influence of COOH functionality and alkyl spacer length on polymer performance, revealing materials that exhibit low swelling, high aqueous processability, and strong ionic-electronic coupling. Benchmarking studies demonstrated record-setting OECT performance, supported by in situ spectroelectrochemical analysis. Chapter 3 explores the impact of side-chain chemistry by comparing carboxylic acid and ester-functionalized analogs. Operando characterization showed that COOH groups facilitate cation expulsion and deswelling during doping, while ester groups enable cation-free, anion-driven swelling—underscoring the critical role of side-chain polarity in ion transport dynamics. Chapter 4 focuses on pH-regulated doping behavior. The degree of COOH dissociation, governed by its pKa, was shown to modulate both ion uptake and swelling: neutral pH promotes deswelling through stronger cation-polymer interactions, while acidic pH limits dissociation and leads to increased swelling. This work introduces the concept of an electrochemical dissociative balance, where ion flux and volume changes can be tuned without requiring swelling. Collectively, these findings establish key design principles for carboxylated OMIECs with enhanced performance, long-term stability, and minimized swelling across diverse electrochemical environments.</p
Finite Element Simulation of Large Deformation and Heat Transfer in Friction Welding of Ti-6Al-4V
No full text{"value":"Friction welding (FW) stands as a premier solid-state joining process renowned for its ability to produce welds of exceptional structural integrity, making it a staple in aerospace
and automotive industries for both metals and thermoplastics. However, the intrinsic
complexity arises from the generation of frictional heat through the relative movement of
components under a normal force during the joining process, leading to significant
deformations and heat transfer at the interface. Consequently, comprehending these
intricate thermal and displacement dynamics becomes imperative for advancing friction
welding technologies.
This dissertation endeavors to delve into the behavior of Titanium alloy in friction welding,
a material widely utilized in this process. It aims to explore various facets including
mechanical properties, thermal performance, and displacement mechanisms, elucidating
their correlations with different friction welding methodologies and input parameters.
Employing finite element method (FEM) simulation, a parametric study will be undertaken
to scrutinize the entirety of the friction welding process.
The main efforts will be utilizing the finite element modeling to understand different types
of the friction welding by simulate the large deformation and heat transfer, and filling the
gap in the literature by characterizing the specific orbital friction welding. Ultimately, the
research presented in this dissertation will contribute to the ongoing efforts to enhance the
integrity and reliability of orbital friction welding.
","attr0":"abstract"
Quantifying the Pleistocene Incision and Integration History of the Middle Allegheny River, a Glacial Margin Continental Drainage, in Northwestern Pennsylvania, USA
No full textA new 10Be terrestrial cosmogenic nuclide (TCN) and optically-stimulated luminescence (OSL)-based age model for eight fluvial terraces in the middle Allegheny River and upstream correlative glacial deposits has been constructed from a USGS EDMAP-funded surficial geologic map of the Parker and Emlenton 7.5 min quadrangles. The map, age model, and existing data for Glacial Lake Monongahela (GLM) test long-held views for when and where low divides were breached in the assembly of the modern Allegheny River and the respective roles of upstream glacial margin or downstream base level change in driving post-glacial river incision. The age model is anchored by a ~20 m thick paired fill terrace containing abundant rock-types exotic to the Allegheny watershed (Qt3), with a strath ~60 m above the modern channel (AMC). A TCN burial age in Qt3 of 1.1+0.4/-0.3 Ma indicates a south-flowing Allegheny River connected to the glacial margin in the early Pleistocene, and a long-term rate of incision of ~45 m/Ma. In contrast, above Qt3 are few, scattered strath terraces (Qt1 and Qt2) that lack exotic clasts, and have opposing north and south gradients astride a now breached low divide upstream of the Clarion-Allegheny rivers confluence. Inset 5 m below Qt3 lies an extensive, paired, low-relief strath terrace (Qt4-the Parker Strath), followed by scattered, unpaired, and poorly preserved strath terraces (Qt5) that decorate the steep bedrock valley walls and extend down to within ~ 20 m AMC. At least three thick, paired fill terraces containing abundant exotic material (Qt6, Qt7, and Qt8), the bases of which are not exposed, are inset into the inner Allegheny valley. The tread of Qt6 lies ~15 m AMC; the underlying alluvium has a TCN burial age of 0.513+0.15/-0.17 Ma, and it is subsequently capped by thick colluvial deposits with a TCN burial age of 0.24+0.071/-0.06 Ma. Qt7 is a late Pleistocene terrace with an OSL age of 0.017+/-0.002 Ma. These middle and late Pleistocene terraces and colluvia have similar ages to two tills exposed ~45 km to the north at Franklin, PA dated to 0.4+0.31/-0.18 Ma and 0.14+/-0.19 Ma using burial TCN and OSL respectively. Some preliminary geochemical data for the soils capping the Qt3 and Mapledale units is presented. A key finding is that the Allegheny River has experienced an average incision rate of ~40-45 m/Ma over the past half-million years or more, but this may have been as low as 25m/Ma earlier in the Pleistocene, approaching the unglaciated basin-scale erosion rate of ~30 m/Ma. The location of an early Pleistocene integration reach near modern Foxburg PA is argued. Collectively, these data suggest reversal and assembly of the Allegheny River during a very early glacial advance, perhaps the same one that was responsible for the formation of the Ohio River via spillover of GLM >> 1 Ma. </p