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Influence of Aging on Microstructural Evolution, Mechanical Properties, and Liquation Susceptibility of High Carbon Austenitic Stainless Steels
No full textHigh-temperature High Performance Nb-modified (HP-Nb) alloys are commonly used in the petrochemical industry as reformer tubes. These alloys must exhibit good creep and corrosion resistance when in service at temperatures reaching 1000°C. To reduce cost, damaged sections of reformer tubes are replaced with new as-cast sections that must be welded. However, cracking has been observed during welding due to microstructural evolutions while in service at elevated temperatures, often leading to the need for total replacement of the reformer tube. The cracking appears to be associated with a brittle "G-phase" intermetallic that forms from NbC during high temperature service. The G-phase could cause cracking by either liquation in the heat affected zone (HAZ) or a reduction in tensile ductility that produces cracking under the high welding residual stress. While cracking and intermetallic phase formation are both independently understood, the effects of nominal composition on the phase transformations during service and resulting weldability of HP-Nb alloys are not as well known. This research investigates the compositional effects on intermetallic phase formation during aging and the associated influence on tensile properties and liquation. This was done through scanning electron microscopy, electron microprobe analysis, differential scanning calorimetry, phase fraction analysis, tensile testing, and nil-strength testing of aged samples with varying compositions. It was observed that silicon concentration had the greatest influence on intermetallic G-phase formation in alloys with a niobium concentration of 0.38 to 1.34 wt.%. The intermetallic phase increased yield strength and decreased the elongation at failure in tensile samples. No correlation between the intermetallic G-phase and liquation was observed
Multidirectional Experimental Performance of a Seismically Resilient Self-Centering Cross-Laminated Timber Shear Wall System
No full textDriven by demand for sustainable buildings, mass timber, specifically cross-laminated timber (CLT), is being widely considered for mid-rise buildings in the US. A post-tensioned self-centering (SC) controlled-rocking CLT shear wall (SC-CLT wall) has potential to be a low-damage lateral-load resisting system for seismically resilient buildings. However, to achieve seismically resilient buildings, improved knowledge of the lateral-load response and damage of the SC-CLT walls under multidirectional loading and the capability of various building structural components, i.e., the floor diaphragm, collector beams, and gravity load system components, to accommodate the multidirectional building seismic response including the controlled-rocking response of the SC-CLT walls, is needed. The overall goal of this research is to design, construct and test a low-damage, resilient three-dimensional CLT building sub-assembly, with an SC-CLT wall, a CLT floor diaphragm, glulam collector beams, and glulam gravity load system.A series of 0.625-scale lateral-load tests was conducted at the NHERI Lehigh Large-Scale Multi-Directional Hybrid Simulation Experimental Facility to investigate the lateral-load response of SC-CLT walls and their interaction with the adjacent building structural components, i.e., the floor diaphragm, collector beams, and gravity load system under multidirectional lateral loading. First, the conceptual design of the test sub-assembly main components and connection details to accommodate the kinematic conditions imposed by building lateral drift response and the controlled-rocking response of the SC-CLT wall under multidirectional loading is presented. The multidirectional displacement control scheme and the associated control algorithm for three-dimensional large-scale lateral-load testing is presented. A series of structural limit and damage states are introduced to characterize the lateral-load response of SC-CLT walls. Fragility functions are developed for assessing the potential damage to SC-CLT walls under unidirectional and multidirectional loading. The lateral-load response of a proposed steel-plate reinforced SC-CLT wall as a repair approach to restore the lateral-load response of a damaged SC-CLT wall and/or as an alternative low-damage lateral-load resisting system is investigated. Finally, the behavior of the CLT floor diaphragm, the SC-CLT wall connections, and the gravity load system connections under multidirectional cyclic lateral loading within a 0.625-scale timber test sub-assembly is investigated. The experimental results are valuable for calibrating numerical models for seismic performance prediction of SC-CLT wall buildings
Computer Modeling and Dynamic Control of Post Combustion Carbon Capture Process Associated with Solar Power System
No full textCO2 emissions have become a serious issue in industry because CO2 endangers the planet and is one of the primary causes of climate change. The objective of this thesis is to conduct a dynamic control for the post-combustion carbon capture process, which is combined with a solar power system (parabolic trough solar collectors). The dynamic simulation was performed using Aspen Plus Dynamic software. Besides that, a rigorous design was initially performed using Aspen Plus software. This thesis investigated two cases: the low-pressure steam-based case and the PTC (Parabolic Trough Collector) combination case. At steady state design, the CO2 capture process is capable of removing up to 89.4 w% of CO2 with a specific reboiler energy of 4.64 GJ/tonnes CO2. More importantly, the control structure was designed to use DNI (Direct Normal Irradiance) data during the day to cover the duty of the reboiler in combination with the low-pressure steam energy. The economical comparative analysis shows a reduction in the operating cost in the PTC combination case. In contrast, the capital cost showed an increase when using PTC. Moreover, a life-cycle assessment that measures the environmental impacts in both scenarios was conducted using SimaPro software. PTC combination case showed a preferable environmental impact in all the measured categories compared to steam-based case
Maintaining synaptic integrity in aging and neuromuscular diseases
No full textMaintaining synaptic structure and function overtime is vital for overall nervous system function and survival. Recent evidence has implicated synaptic defects in aging and neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS). These synaptic defects occur long before neuronal death before the onset of clinical symptoms. Although synapse development is well understood, the mechanisms responsible for maintaining synapse structure and function is poorly understood. Thus, identifying the mechanisms responsible for synaptic maintenance are crucial for understanding the basis of early neuronal defects in aging and neurodegenerative diseases. At present, a major challenge in the field has been the lack of a genetically tractable model in which to assess how synapse maintenance fails in aging and neurodegenerative diseases in vivo. This dissertation work characterized how synapses are maintained with age, identified novel regulators of synaptic maintenance, and characterized how synapses dysfunction in ALS. I used Drosophila melanogaster as my model to study adult neuromuscular junctions (NMJs) and took advantage of the flight ability to assay synaptic structure and function. I first characterized a novel gene, mayday, that I found to have a role is sustaining trans-synaptic Glass bottom boat (Gbb) signaling in adult synapses which are requirement in both muscles and presynaptic motor neurons, to maintain synaptic integrity with age. This works provides a mechanism to sustain adult synapses that has been previously thought to be needed just in synaptic development. Upon characterizing mayday, I performed an unbiased forward genetic screen to identify SNPs in candidate genes associated with the progressive loss of flight ability. The screen provided us with a list of candidate genes that were functionally validated through testing genomic mutants and tissue specific RNAi in muscle tissue, motor neurons, and glia. The results of the screen support the role for these genes as novel regulators of synaptic maintenance in adult synapses. This has deepened our understanding of how synapses are sustained in aging. The final chapter in my work characterizes a Fused in Sarcoma (FUS) model of ALS to elucidate the mechanism of synaptic dysfunction through functional and structural analysis. This study provides insight into the nature and the timing of these synaptic deficits. Thus, my work contributes to the field of aging and synaptic deficits in neurodegenerative disease and begins to fill these gaps
"Physicians of the Soul:" The Interdisciplinarity of the Puritan New England Minister\u27s Calling in Spiritual and Physical Wellbeing, 1660 to 1730
No full textTraditional narratives of late-seventeenth and early-eighteenth century colonial New England often focus on religious decline, the professionalization of medicine, or the secularization of colonial laws. Scholars have yet to fully grapple with how the expansion of ministers\u27 knowledge in medicine strengthened their divine authority and their religious dialogues on the body-soul connection. An examination of sermons, religious writings, European medical texts, and legal archives reveals the vital place medical discourses had in ministers\u27 interpretations of bodily and spiritual health from 1660 to 1730. Ministers embraced studies outside their long-established spiritual roles to underscore the repercussions of sinful behavior and impenitence on a person\u27s overall wellbeing. As they interwove religious beliefs and medical ideas in their writings, ministers were able to broaden their unique positions in society as "physicians of the soul." With their connections to medicine, ministers integrated thoughts, theories, and actions beyond their own professions to argue that not only smaller immoral wrongdoings could be physically healed to find salvation, but transgressors convicted of death penalty crimes also could be cured prior to death through confession and contrition. A broader view of the minister\u27s calling highlights how they reinforced their standing as religious leaders as they backed the physicians\u27 expertise in causes and cures of disease and expressed reverence for the judges\u27 punishments. The recognition that late seventeenth- and early eighteenth-century Puritan New England ministers engaged with a larger transatlantic intellectual world demonstrates how they cultivated a fundamental interdisciplinary vocation that ensured the health of bodies and souls in redemption
Towards the Creation of Tunable Single-Pixel GaN:Eu LEDs
No full textIn pursuit of fully color-tunable, single-pixel LED technology, doping rare-earth ions in the active layers of GaN-based materials has been useful for achieving precise emission colors. In particular, Eu3+ can be excited electrically and emits red (~620nm) from its 5D0 state, as well as green, yellow and orange from its 5D1 state. This has been shown to be caused by a carrier-mediated re-excitation and energy shuffling between a local defect and the Eu ion. The fact that red and green emission are both accessible due to transitions from different states has allowed for controllable color tunability. This has been done in proof-of-concept LEDs where, by adjusting excitation conditions in the form of varied current injection or laser pulses, the population ratio between the two states can be controlled resulting in smooth color tunability from red to yellow.In this work, a new model is developed to predict color tunability. This is done with rate equation simulations that consider the defect-ion complex after creation or injection of electron-hole pairs. By taking the local defect into account, where the carriers are captured, recombine, and transfer energy to the Eu3+, the mitigator of energy transfer is being considered. Multiple excitations of the same defect complex before the Eu ion can relax causes the 5DJ states\u27 populations to redistribute. The results of the simulations give relative populations of these states, which can be used to predict color. Furthermore, by considering the local defect as a blue emitter, our model can predict tunability parameters within a larger color space due to the mixing of the primary colors: red, green, and blue.As color tuning from the Eu ion is a result of carrier-mediated re-excitation, multiple layer structure samples were studied in order to probe carrier confinement and consider how other rare-Earths without Eu3+\u27s specific pathways could be grown in heterostructures and designed to confine carriers in a way useful for the greater semiconductor community. To understand this system and look for future utility, other ventures include work towards utilizing nanostructures and other co-dopants. The former can enhance specific emission wavelengths and reduce the lifetime of transitions in order to increase the control and range of tunability. The latter hopes to improve color tunability by accessing emission from other transitions
A Unifying Model for Cohesinopathies and Thalidomide Teratogenicity
No full textRoberts Syndrome (RBS) and Cornelia de Lange Syndrome (CdLS) are developmental conditions in humans collectively termed cohesinopathies. RBS and CdLS result in limb malformation, craniofacial abnormalities, cognitive disabilities, and defects in numerous internal organs, such as the GI tract and cardiac systems. Cohesinopathies arise due to improper cohesin function. Cohesin is a complex that plays a role in DNA tethering both in cis (along the same strand of DNA) and trans (between sister chromatids) mechanisms. DNA tethering is crucial for sister chromatid cohesin, DNA condensation, DNA repair, and transcriptional regulation. While the gene mutations resulting in cohesinopathies are well established, the downstream impacts of such mutations are largely unknown. Interestingly, the developmental defects arising from RBS and CdLS are highly similar to those due to thalidomide exposure during pregnancy. Thalidomide was a popular drug used to treat morning sickness in the late 1950s. Thalidomide exposure led to approximately 10,000 babies being born with severe developmental abnormalities. In this case, thalidomide blocks Cullin4 Ring Ligase (CRL4), a ubiquitin ligase that clears embryos of factors that adversely impact development. The downstream targets of CRL4 that lead to organ malformations are still elusive. Yet, thalidomide is an immunomodulatory (IMiD) drug that has proven effective in treatments of Hansen\u27s Disease, leprosy, and myeloma. Thus, understanding the molecular mechanisms through which thalidomide acts is essential for drug discovery and new therapies. Here, we investigate the role of cohesin in regulating the thalidomide target, CRL4. First, we report findings that the cohesin pathway impacts gene regulation of an essential CRL4 component. Second, we identify downstream targets of the cohesin/CRL4 axis that lead to organ malformation. These findings provide a unified molecular mechanism shared by thalidomide poisoning, and genetic outcomes that produce RBS and CdLS. This study provides a model to study multi-spectrum syndromes previously believed to be unrelated to each other. This research can help advance treatment options for rare diseases, as they may not be so rare after all
Elucidating mechanisms of mycobacteriophage Butters prophage-mediated defenses
No full textMany bacterial genomes contain prophages that may act to modulate host physiology. Prophages that bolster host immunity against viral infection could challenge the effectiveness of phage therapy against pathogenic bacteria. Prophage-encoded antiphage systems are pervasive within mycobacteriophages. In this project, I have characterized two distinct antiphage systems expressed by the prophage of mycobacteriophage Butters (cluster N) in the host, Mycobacterium smegmatis. The gp30-31 antiphage system is membrane localized and inhibits several heterotypic phages including PurpleHaze (subcluster A3), Perplexer (subcluster A4), Bud and Munch (both subcluster A11). Through analysis of PurpleHaze defense escape mutants (DEMs) that overcome gp30-31 defense and adsorption assays, it is proposed that gp30-31 targets the tape measure protein (gp27) and a minor tail protein (gp33) of PurpleHaze, leading to impairment of adsorption. The gp57r antiphage system defends against several phages including PurpleHaze (subcluster A3), Island3 and Brujita (both subcluster I1), Perplexer (subcluster A4) and Bud (subcluster A11) and is proposed to act downstream of the DNA injection process. Gp57r has a HEPN domain found within many proteins involved in inter-genomic conflicts, suggesting that inhibition of heterotypic phage infection may occur via this domain. Upon Island3 infection, gp57r antagonism interferes with Island3 transcription and impairs Island3 DNA amplification. Both antiphage systems are widespread in clinical isolates of pathogen Mycobacteria abscessus and potentially pose a threat to efficient utilization of phage therapy. While Island3 DEMs that escape gp57r defense have not yet been recovered from Island3 infection of a Butters lysogen, novel recombinant phages called BIBs have been isolated that represent recombination between the Island3 genome and the Butters prophage. Recombinant BIBs overcome antiphage defense and silencing of the lytic cycle. Further characterization of recombinants formed between Island3 and the cluster N prophages of Kevin1 and Phrann shows the pervasiveness of homologous recombination between temperate mycobacteriophages. Elucidation of antiphage system mechanisms and characterization of DEMs will inform efforts to engineer therapeutic phages that circumvent antiphage systems. Discovery of naturally occurring mycobacteriophages that recombine to yield mosaic recombinant phages will allow interrogation of molecular mechanisms underpinning this phenomenon
Beyond birds and bees: Using the confluence model to assess comprehensive sexuality education as primary prevention for sexual violence outcomes
No full textFew extant sexual violence prevention programs have demonstrated significant, long-lasting reductions in sexual violence perpetration (DeGue et al., 2014). One promising solution appears to be integration of sexual violence prevention programming within school-based comprehensive sexuality education (CSE). This can happen by bringing both into alignment with prevention best practices and simultaneously addressing prominent risk factors identified through the Confluence Model of sexual aggression (Malamuth et al., 2021; Schneider & Hirsch, 2018). To build on this theoretical work, the current study examines whether there is an empirical relationship between CSE quality, relevant sexual violence risk factors (i.e., sexual violence-supportive ideology and childhood sexual abuse victimization), and sexual violence perpetration. A sample of 201 emerging adult cisgender men were recruited via Amazon MTurk and completed a series of measures assessing their perceptions of the quality of their sexuality education experiences, history of childhood sexual abuse victimization, level of endorsement of sexual violence-supportive ideology (including their rape myth acceptance, hostility toward women, gender-role traditionality, hypermasculinity, and rape proclivity), and reported perpetration of sexually violent and coercive behaviors. Two structural equation models hypothesizing the relationships among these variables were examined, and of these, better fit was found for the alternative model. This model demonstrated good fit to the data (?2(201) = 230.20, p < .001; CFI = .93; TLI = .91; SRMR = .12; RMSEA = .08). In this model, hypotheses associated with the relationship between sexual violence risk factors and sexual violence perpetration were supported, such that increased sexual violence-supportive ideology was associated with increased sexual violence proclivity, and both sexual violence proclivity and childhood sexual abuse victimization were associated with increased perpetration. However, when considering perceived CSE quality�s relationship with study variables, findings differed from hypotheses: Perceived CSE quality and childhood sexual abuse victimization were not significantly related in this model. Further, perceived CSE quality was significantly related to increased sexual violence-supportive ideology and perpetration. Overall, findings suggest continued focus on prevention efforts that target known risk factors of sexual violence. Additionally, it is suspected that men�s perceptions of their CSE experiences, when compared with extant knowledge regarding the generally poor quality of CSE within the United States, may not accurately represent the quality of the programming they received. These findings suggest that low quality CSE programming may not only be ineffectual at preventing sexually violent behavior, but potentially harmful. As such, considerable reform to improve the quality of existent CSE programming is warranted, and specific implications for further prevention programming development are explored
A Sociocultural Perspective of Interracial Contact: Examining the Efficacy of Sociocultural Contact on Black and White Interracial Experiences
No full textThis research investigates the relationship between sociocultural interracial contact (individuals� engagement with or sharing aspects related to outgroup members� or their own racial background, respectively) and intrapsychic (e.g., prejudice), interpersonal (e.g., future interactions), and systemic (e.g., collective action) race-related outcomes. Integrating research on interracial interaction, intergroup contact, and cultural psychology insights on the sociocultural self, three pilots and three studies extend the selves-in-contact framework proposed by Brannon, Taylor, and colleagues (2017) to evaluate how engaging with another�s sociocultural background during interracial contact benefits interracial attitudes. Further, it tests the role of intergroup anxiety, meta-stereotypes, (meta-)empathy, and (meta-)knowledge in explaining race-related outcomes. Pilot 1 and Study 1 find that, among Black Americans, high-quality sociocultural interracial contact is associated with positive feelings toward White Americans, intentions to engage in interracial contact, and collective action. Pilots 2-3 and Study 2 show that, among White Americans, high-quality sociocultural interracial contact is related to positive feelings towards Black Americans, intentions to engage in interracial contact, and collective action. Study 3 examines the causal relationship between imagined sociocultural interracial contact and race-related outcomes among Black Americans. While imagined sociocultural contact does not produce the same outcomes as Studies 1-2, imagining interacting with a White partner produces negative affective and meta-cognitive outcomes. These studies demonstrate that naturally occurring and greater quality sociocultural contact is associated with improved interracial outcomes for both Black and White individuals. Nevertheless, future work is needed to understand the causal impact of sociocultural interracial contact on Black Americans