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Title: RUNTIME FOR PERFORMING EXACT TESTS ON THE PI STATISTICAL MODEL FOR RANDOM GRAPHS
Creator: Dillon, Martin
Date: 2016, 2016-05
Description: In statistics, we ask whether some statistical model ts observed data. We use a Markov chain proposed by Gross, Petrovi c, and Stasi to...
Show moreIn statistics, we ask whether some statistical model ts observed data. We use a Markov chain proposed by Gross, Petrovi c, and Stasi to perform exact testing for the p1 random graph model. By comparing it to the simple switch Markov chain, we prove that it mixes rapidly on many classes of degree sequences, and we discuss why it is sometimes better suited than the simple switch chain, and try to easily introduce the concepts from the general theory along the way.
M.S. in Applied Mathematics, May 2016
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Title: Fate of Listeria Monocytogenes on Hard-cooked Eggs Treated With Citric Acid
Creator: Zeng, Hui
Date: 2021
Description: Commercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with...
Show moreCommercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with Listeria monocytogenes during or after the cooking and peeling steps is of concern since this pathogen can proliferate at refrigeration temperatures. Citric acid is a common preservative used in the food industry to treat hard-boiled eggs (HBEs). The purpose of this project was to evaluate the efficacy of citric acid treatment of HBEs to reduce the population levels of L. monocytogenes during 24 h (treatment trials) and 28 d storage (storage trials) at 5 or 25°C. Fresh eggs were boiled for 12 min, cooled to 4°C, peeled, and stored at 5°C for 24 h prior to experiments. In treatment trials, HBEs were dip inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes resulting in either 4 (low) or 7 (high) log CFU/egg. Eggs were air-dried 10 min, followed by treatment with pH 2.5 citric acid (PHCA) or 0.2 M citric acid (calculated as the molarity resulting in pH 2.5: MCA) at 5 or 25°C for 24 h. In treatment-storage trials, citric acid treatment of HBEs occurred before or after inoculation, followed by 28-d storage at 5 or 25°C. L. monocytogenes populations were enumerated by homogenization of eggs with BLEB and cultivation on BHI/rifampicin agar. Enrichment in BLEB was conducted if the pathogen was below the level of enumeration. Significant differences in the populations of L. monocytogenes due to temperature of the acid treatment (5 or 25°C) or the two citric acids (MCA and PHCA) were determined using Student’s T-test and ANOVA with Tukey’s post-test, p ≤ 0.05. Overall, the largest L. monocytogenes reduction occurred after 6 h treatment of HBEs with PHCA at 25°C (1.59 ± 0.00 log CFU/egg) and after 24 h with MCA at 5°C (1.23 ± 0.54 log CFU/egg) when the pathogen was inoculated at the low and high levels, respectively. In treatment-storage trials, citric acid treatment after HBE contamination resulted in a fewer number of samples where the pathogen was detected compared to when treatment occurred before contamination. Citric acid treatment for 24 h also resulted in a greater number of samples where L. monocytogenes was not detected than the 1 h treatment. The results of this study determined that L. monocytogenes could survive on HBEs treated with citric acid, regardless of treatment or storage temperature and acid concentration (PHCA or MCA).
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Title: Using population-level data to examine between-group health differences among transgender and cisgender United States military veterans
Creator: Woodward, Honor
Date: 2021
Description: Some subgroups of military veterans, including those with marginalized identities, may be especially vulnerable to poor health. This...
Show moreSome subgroups of military veterans, including those with marginalized identities, may be especially vulnerable to poor health. This hypothesis is supported by the Minority Stress Theory framework, which posits that disparities in health can be attributed to the stress that minority individuals experience as a result of discrimination, prejudice, and oppression (Meyer, 1995; Meyer, 2003). A specific, potentially marginalized group of veterans that is under-explored regarding health is transgender veterans. Using data from the 2019 U.S. Behavioral Risk Factor Surveillance System (BRFSS), the current study hypothesized that transgender U.S. military veterans will report worse health than cisgender U.S. military veterans. Using case control matching, groups of transgender veterans (n = 124) and cisgender veterans (n = 104) were compared on several population-relevant health outcome measures. Chi-square tests of independence were conducted to test for significant differences between transgender and cisgender military veterans on the likelihood of experiencing certain health conditions, engaging in certain health behaviors, and utilizing health care services. Independent samples t-tests were used to test continuous health outcomes, such as self-reported mental health, physical health, and access to health care services. Gender identity was significantly associated with only one health outcome variable, with transgender veterans being more likely than cisgender veterans to have received a formal depression diagnosis (p = .01, phi = .17). No significant differences emerged between transgender and cisgender veterans on continuous health outcome variables. This suggests that previous literature on health disparities between transgender and cisgender individuals may not be generalizable to transgender veterans.
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Title: Frictional behavior of bronze-graphite composite as sliding element in the base isolation system
Creator: You, Da
Date: 2021
Description: There are many calamities around the world, one of the most dangerous disasters is earthquake which threatens the safety of people and the...
Show moreThere are many calamities around the world, one of the most dangerous disasters is earthquake which threatens the safety of people and the structures. Almost every year, there are a lot of property losses and casualties caused by earthquakes. To mitigate the bad effect of the earthquake, the base isolation system was proposed by previous researchers. With the contribution of many researchers, several seismic isolations have been developed. Until now, many structures have installed seismic isolations to resist seismic energy and vibration. The seismic isolation system works well during the earthquake period, and it does help reduce the casualty and property loss induced by earthquakes. There are two main types of bearings used in the seismic isolation system. One is the elastomeric bearings and the other is the sliding bearings. The mechanics of the seismic isolation system preventing the influence of the earthquake and reducing the horizontal acceleration of the structure is to elongate the natural frequency of structure. As for the sliding bearings, the simplest way to increase the period is to reduce the friction coefficient of the two sliding elements. In conventional, two stainless steel plates are commonly used in the pure flat sliding bearing. This study tries to use bronze-graphite composite in the sliding bearing to decrease the friction coefficient.Consequently, the testing results suggest that the bronze-graphite composite has a lower friction coefficient, especially the graphite acting as a lubricant. The friction coefficient of the bronze-graphite plate is in the range of 0.12 to 0.23 under the load of 160 kg - 800kg. With a higher ratio of graphite to bronze at the sliding surface, the effect of reducing the friction coefficient more obviously. And the friction coefficient changes during the increasing loads period. It decreases at the beginning, and starts to increase at a certain load applied on it. Finally, it is reasonable to bronze-graphite composite in a low rise structure which has a relatively low weight. Because the load applied in the test is not high enough, the consequence may not work for high or heavy structure. Taken together, the use of new material with similar properties in the seismic isolation system can help improve the performance of resisting the earthquake. It should be accounted for further research in this field.
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Title: EXPERIMENTAL AND STRUCTURAL STUDIES OF FDA APPROVED EXON SKIPPING TREATMENT DRUGS
Creator: Zhang, Jingwen
Date: 2021
Description: DMD is an X-chromosome related genetic disease caused by loss of dystrophin protein expression, and which impacts 1 in 5000 boys born in the...
Show moreDMD is an X-chromosome related genetic disease caused by loss of dystrophin protein expression, and which impacts 1 in 5000 boys born in the world. The usual cause of this at the genetic level is a frame shift due to internal deletions of one or more exons that results in a change of the reading frame. This results in loss of expression of the protein encoded by this gene, dystrophin, which in turn leads to the disease phenotype. Exon skipping is a therapy for DMD which restores dystrophin pre-mRNA reading frame to produce a modified dystrophin. This is done by antisense oligonucleotides, AONs, which disturb the process of exon splicing and exclude targeted exons near the patient’s defect which restore the correct reading frame in the pre-mRNA transcript. In 2016, the first AON was approved for clinical use targeting exon 51, called eteplirsen. This provided the first disease modifying therapy for DMD, but it was only relevant to ~6% of patients who had defects that were correctable by skipping this specific exon. In 2020 two more AONs targeting exon 53 were developed, viltolarsen and golodirsen, providing benefit to an additional 5% of patients, and in 2021 casimersen targeting exon 45 was approved.However, this raises an interesting issue, in that for some patients, with an exon 52 deletion, skipping exon 51 or skipping exon 53 could both restore the reading frame. Which approved exon skipping treatment is better and the differences between them are still unknown. This is the aim of this study: to help patients figure out which AON can have a consequence of less long-term health problems like cardiomyopathy and longer life and get more precise treatment. We selected three exon skipped edits – two that represent exon 53 skipping repair of an underlying Δe52 defect and one targeting exon 51 skipping repair of a Δe52 defect. We then used a panel of biophysical and biochemical including dynamic light scattering, circular dichroism Spectroscopy, thermal denaturation, and protease K challenge to investigate the biophysical characteristics of these different exon skipped edits. From our results we found that Δe51-52 has the more structure (i.e., is less perturbed), compared to e52-53, as assessed by CD or by proteinase K challenge, but it also has lower thermal stability, with a low Tm=48C transition that begins to unfold at the physiological relevant temperature of 37C. On the other hand, e52-53 has less helical structure, but what structure did form had unfolding transitions in the normal range for wild type STRs, Tm> 60C; but this edit also had more non-helical structure. So, the total experimental results of these three edits are very complex, which may be due to the fact that these edits span the normally unfolded H3 region.
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Title: HIGH-THROUGHPUT FIRST-PRINCIPLES STUDY ON HIGH-ENTROPY ALLOYS
Creator: Zhang, Jie
Date: 2021
Description: This research thesis discusses the current ecosystem surrounding a new type of alloy: high entropy alloys (HEA) or multi-element crystalline...
Show moreThis research thesis discusses the current ecosystem surrounding a new type of alloy: high entropy alloys (HEA) or multi-element crystalline materials and lays out the high-throughput first-principles calculation as a valuable approach to study these materials. The density function theory (DFT) from computational material science prospect was implemented to investigate the HEAs. Using EMTO-CPA algorithm, high-throughput DFT calculations were conducted. A total of 1958 HEA systems including equimolar and non-equimolar systems were studied with respect to the varies properties, including lattice parameters, bulk moduli, elastic constants, and elastic anisotropy. The first-principles HEA dataset was employed as the training set for the DeepSets a machine learning model. DeepSets, in combination with EMTO-CPA high-throughput calculation, successfully predicted the mechanical properties of specific HEA composition. This paves a promising new path of designing, investigating, and validating the HEA system compared to the time-consuming conventional HEA design method. The doping effect of Vanadium (V) and Titanium (Ti) to NbMoTaW HEA, as well as V or Ti as the fifth element with different molar fraction to the NbMoTaW HEA system, were studied. The phase stability of the new systems was discussed and concluded that all proposed systems tend to form single-phase solid solution. Though the addiction of V only slightly enhances the system’s ductility, the addition of Ti not only enhances the quinary system NbMoTaWTiX (X =0.25, 0.5,0.75, 1.0) ductility, but enables the system to be closer to fully isotropic.
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Title: Sex Differences in a Network Model of Depressive Symptoms
Creator: Ginger, Emily J
Date: 2021
Description: Major Depressive Disorder (MDD) is one of the most prevalent mental health disorders, with a lifetime prevalence rate of 13-16% and 12-month...
Show moreMajor Depressive Disorder (MDD) is one of the most prevalent mental health disorders, with a lifetime prevalence rate of 13-16% and 12-month prevalence rates of 5-7%. It has long been established that the rates of MDD in females is two to three times that of males. Previous research has examined sex differences in the occurrence and severity of MDD symptoms, primarily indicating greater severity of appetite increase and weight gain in females compared to males. The majority of previous research has been conducted assuming the latent factor model that MDD accounts for the symptoms of depression, and sex operates as a mediator or moderator between the latent variable and MDD, or between MDD and its symptoms. The present study used network analysis to examine whether there are sex differences in the relations between symptoms of depression, which might be an important factor for understanding sex differences in prevalence rates of MDD. The present study compared networks of DSM MDD symptoms between currently depressed females and males, and separate networks that also included other symptoms commonly associated with depression (e.g., anxiety, anger). Sex differences were examined using jointly estimated networks, and a Network Comparison Test (NCT) for the independently estimated networks. Results indicated no sex differences in depression symptom networks. These results indicate that depressive symptom networks, or the relations between symptoms are not an important factor for understanding the disparity in sex differences in MDD prevalence rates. Interestingly, non-DSM symptoms were among the strongest and most important symptoms within the network, suggesting future research and diagnostic criteria should consider inclusion of non-DSM symptoms associated with MDD.
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Title: Child Temperament, Attachment, and Loneliness: The Mediating Effects of Social Competence
Creator: Evans, Lindsey M
Date: 2021
Description: Chronic loneliness is a risk factor associated with adverse psychological, physical, and academic outcomes. Converging evidence suggests that...
Show moreChronic loneliness is a risk factor associated with adverse psychological, physical, and academic outcomes. Converging evidence suggests that young children experience and can reliably report on their own loneliness. Due to the significant negative sequalae associated with childhood loneliness, it is critically important to examine risk factors for child loneliness. The aims of this study were two-fold: (a) to examine if temperament (i.e., negative affect, effortful control, and inhibitory control) and attachment security assessed at 4 years of age predict loneliness at age 6; and (b) to determine if social competence at age 5 mediates the relation between temperament and attachment security at age 4 and loneliness at age 6. Participants included a diverse sample of 796 4-year old children, about half of whom were male. At age 4, temperament was assessed with the Rothbart Child Behavior Questionnaire and three inhibitory control tasks, and attachment security was assessed with the Attachment Q-Sort. At age 5, the Social Skills Rating Scale was used to assess social competence, and, at age 6, loneliness was assessed with the Loneliness and Social Dissatisfaction Questionnaire. Results of hierarchical regression analyses indicated that lower levels of effortful control and inhibitory control at age 4 significantly predicted higher levels of loneliness at age 6. Also, lower levels of negative affect and higher levels of effortful control and attachment security at age 4 significantly predicted higher levels of social competence at age 5. However, social competence at age 5 did not predict loneliness at age 6. There was no evidence that social competence at age 5 mediated the relation between age 4 temperament, attachment security and age 6 loneliness. These findings reveal that early self-regulation is associated with later child-reported loneliness and that intervention for children who struggle with cognitive regulation may be effective in decreasing risk for later loneliness.
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Title: Inviscid Shock Propagation within a Variable-Geometry Scramjet Inlet
Creator: Grybko, Maciej
Date: 2021
Description: The study concerns the propagation of shockwaves within an inlet of a scramjet engine and effect of inlet geometry variation on performance. A...
Show moreThe study concerns the propagation of shockwaves within an inlet of a scramjet engine and effect of inlet geometry variation on performance. A Python code was developed to simulate and visualize a flowfield within a scramjet inlet, based on inviscid oblique shock theory. The program was validated against NASA Shock software, and the results differed only by round-off error (0.05%). Subsequently a geometric sensitivity study was conducted, showing that throughout acceleration from Mach 5 to Mach 20 parameters like inlet height could be varied to ensure constant number of shocks within an inlet (preventing discontinuous changes of flowfield), whereas lower wedge angle could control compression required for optimal combustion. Correspondingly, a trajectory was determined with a constraint on static pressure entering combustion chamber (100 kPa). For an arbitrary baseline inlet geometry, it was established that beyond Mach 10 the scramjet would exceed structural load limit, despite delivering sufficient conditions for rapid combustion. Nevertheless, below Mach 10 it would operate efficiently, proving that hydrocarbon-fueled scramjets can have a fixed geometry. For higher speeds, a variable geometry is a necessity.
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Title: ARE SUPPORTIVE FOSTER CAREGIVERS ASSOCIATED WITH IMPROVED FOSTER CARE ALUMNI OUTCOMES? A LONGITUDINAL EXAMINATION OF THE EFFECT OF SUPPORTIVE FOSTER CAREGIVERS ON MENTAL HEALTH OUTCOMES IN A NATIONALLY REPRESENTATIVE SAMPLE
Creator: Dunn, Megan Reeves
Date: 2021
Description: Foster youth are a vulnerable population associated with poor health outcomes, but relatively little research has identified factors that may...
Show moreFoster youth are a vulnerable population associated with poor health outcomes, but relatively little research has identified factors that may mitigate adverse outcomes for these youth. The present study augments previous research by utilizing a nationally representative, longitudinal study (The National Longitudinal Study of Adolescent to Adult Health or Add Health) to investigate whether foster youth in the United States face significantly different mental and behavioral health outcomes compared with same-age peers, and second, whether presence of a supportive foster caregiver may predict better mental and behavioral health outcomes in the foster youth subsample. Using data from Waves III and IV of the Add Health study (N = 12,288 participants, of which n = 282 were foster youth), analyses examined whether foster status and higher caregiver support was related to rates of depression symptoms, suicidal ideation, marijuana use, and alcohol use. Surprisingly, there were few differences between those with and without a foster history; higher frequency of marijuana use among foster youth was the only significant difference. However, analyses in the foster youth subsample indicated that the presence of a supportive caregiver was associated with lower rates of depression symptoms and lower endorsement of suicidal ideation, demonstrating caregiver support as a possible protective factor for foster youth. Future research must continue to explore potential benefits of caregiver support, as it may inform policy that can improve long-term outcomes for foster youth.
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Title: THE EFFECTS OF MODIFIED SURFACES ON INSULIN CRYSTALLIZATION
Creator: Hammadi, Okba Tahar
Date: 2021
Description: Engineered nucleation features (ENFs) were designed with the hope to improve the efficiency of protein crystallization and increase...
Show moreEngineered nucleation features (ENFs) were designed with the hope to improve the efficiency of protein crystallization and increase reproducibility both in quality and quantity. These ENFs were tested with human insulin as the protein of choice since it has flexible parameters, only one cofactor, and a large amount of commercially available crystal ready protein. Insulin crystallization on the ENFs will produce more crystals while also having a reduced crystallization on-set time compared to the control glass surface. The ENFs were compared to control surfaces under similar conditions and observed over time to record both onset-times and end times. The ENFs performed markedly better in on-set times, having an overall 87%-time reduction when compared to the control drops. The drops placed on the ENF produced more than 2.5x the number of crystals in the control drops.
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Title: Growth Kinetics of Listeria monocytogenes and Salmonella enterica on Rehydrated Enoki and Wood Ear Mushrooms during Storage
Creator: George, Josephina
Date: 2023
Description: Plant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent...
Show morePlant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent listeriosis and salmonellosis outbreaks in the U.S. have been associated with imported specialty mushrooms. These mushrooms are commonly sold fresh or dehydrated. This study evaluated the survival and growth of two foodborne pathogens Listeria. monocytogenes and Salmonella. enterica on dehydrated mushrooms during both rehydration at 25 or 5℃ and storage at 5, 10, or 25℃. Fresh enoki and wood ear mushrooms were dehydrated for 24 h at 60°C. Dehydrated mushrooms were inoculated with a four-strain cocktail of S. enterica or L. monocytogenes at 4 log CFU/g. Mushrooms were dried for 1 h, followed by rehydration for 2 h with 5 or 25°C (water and air temperature). Rehydrated mushrooms were stored at 5, 10, or 25°C for up to 14 d. The pathogens were enumerated at 0, 1, 3, 6, 9 and 14 d. Three independent trials with triplicate samples at each time point were completed. Population differences were evaluated via Student’s t-test; p<0.05 was considered significant. The growth rates were determined by DMFit in Excel. Overall, the growth rates of L. monocytogenes and S. enterica on enoki mushrooms were significantly higher when the mushrooms were rehydrated at 25℃ and stored at 25℃ (P<0.05). The growth rates were 2.69 log CFU/g per day and 3.56 log CFU/g per day, for L. monocytogenes and S. enterica respectively. Since the growth of pathogens on wood ear mushrooms during rehydration and storage was considerably less and below the level of enumeration, enrichment of the pathogens was conducted. The pathogens could be suppressed during rehydration due to less nutrient contents and antimicrobial properties of wood ear. The result of this study outlines the importance of refrigerated storage temperature and time combination for safety during rehydration and subsequent storage of the mushrooms.
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Title: Characterization and Migration of Silver Nanoparticles from Electron-Beam Irradiated Low-Density Polyethylene
Creator: Donovan, Dylan
Date: 2023
Description: Polymer nanocomposites (PNCs) and engineered nanomaterials (ENMs) may find use in a wide range of commercial applications, including food and...
Show morePolymer nanocomposites (PNCs) and engineered nanomaterials (ENMs) may find use in a wide range of commercial applications, including food and medical product packaging. Migration of nanofillers from polymer nanocomposites into food matrices could be a source of human dietary exposure to ENMs. Electron beam (e-beam) irradiation is a processing method used for microbial inactivation as well as for modifying properties of polymer films, such as stretch resistance and shrink tension. Process treatment of nanotechnology-based packaging materials either for sterilization or for strengthening of the polymer films may have a significant effect on the migration of ENMs into food matrices. The primary objective of this study is to investigate the effect of e-beam irradiation treatments of LDPE containing silver nanoparticles (AgNPs) and the subsequent migration of AgNPs into a food simulant under intended use conditions. The study observes a correlation between e-beam irradiation dose quantity and the release of AgNPs into a food simulant.
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Title: Transdiagnostic Emotional Factors as Mediators of the Relation between Obsessive-Compulsive Symptoms and Tobacco Use and Dependence in a Large Community Sample of Adolescents
Creator: Chang, Weilynn Christine
Date: 2023
Description: This study investigated the associations between obsessive compulsive disorder symptoms (OCS) and tobacco use and tobacco dependence in a...
Show moreThis study investigated the associations between obsessive compulsive disorder symptoms (OCS) and tobacco use and tobacco dependence in a large community sample of adolescents. Specifically, transdiagnostic emotional vulnerability factors (i.e., anhedonia, distress tolerance and anxiety sensitivity) were explored as potential mediators of the relation between OCS and tobacco use/dependence. Weighted logistic regression models found that OCS was significantly positively associated with likelihood of tobacco use in the past six months (when suppressor variables were excluded). Similarly, zero-inflated negative binomial regression models found a significant positive relation between OCS and tobacco dependence (when suppressor variables were excluded). There was no significant weighted indirect effect via anhedonia for the OCS-Tobacco Use association, which suggests that anhedonia was not a significant mediator in this case. However, the indirect effect via anhedonia for the OCS-Tobacco Dependence association was significant at the p < .05 level, but not the adjusted p < .001 threshold (when suppressor variables were removed). The weighted indirect effect via distress tolerance for the OCS-Tobacco Use association was significant at the p < .05 level, but not the p < .001 threshold (when suppressor variables were removed). There was no significant indirect effect via distress tolerance for the OCS-Tobacco Dependence association. There was a significant weighted indirect effect via anxiety sensitivity for the OCS-Tobacco Use association (when suppressor variables were removed). There were no significant indirect effects via anxiety sensitivity for the OCS-Tobacco Dependence association. When overlapping variance was accounted for by including all three mediators simultaneously, anhedonia was still not a significant mediator of the OCS-Tobacco Use association; there were still significant indirect effects via distress tolerance and anxiety sensitivity, under specific model parameters. Our results also revealed that while Asian adolescents demonstrated lower likelihood of tobacco use compared to those who were Hispanic/Latinae, Asian youth demonstrated more severe tobacco dependence symptoms.
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Title: The Peter Principle and Career Development in Construction Management
Creator: Bolisetty, Lakshmi Satya Bavya
Date: 2023
Description: The construction industry, like any other industry, may benefit from updating its working environment by adopting advances in technology,...
Show moreThe construction industry, like any other industry, may benefit from updating its working environment by adopting advances in technology, updating the qualifications of its workforce, and ensuring that the right professionals are employed at each level. Having effective career development programs, filling project management roles with competent professionals, and promoting competent professionals ensures a successful project delivery. Promotion typically ensures candidates are rewarded for their performance and motivates them towards achieving higher success. Promoting the wrong person or having an incompetent person at any management level has detrimental effects to the project’s success. However, according to the “Peter Principle” (Peter, 1969), incumbents in a hierarchy tend to rise to “a level of respective incompetence”. That is, they are promoted based on their success in their current role, rather than their ability to perform in the new one. Through a review of the literature and a critical analysis of the existing research, this study examines the strengths and weaknesses of the Peter Principle and its relevance to professionals employed by construction companies and construction management firms in contemporary management practice. It also explores the reasons why an incumbent is stuck in a position for a long time. The findings of this research suggest that while the Peter Principle may have some limitations, it remains an important concept for managers to consider when making decisions about employee promotion and development. It concludes that while the Peter Principle may have a significant effect in promotion decisions, there are also external circumstances unique to each individual that may affect their performance.
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Title: Organo-Functionalized Polyoxometalates
Creator: Alsaleh, Musaed Riyadh A
Date: 2023
Description: Polyoxometalates (POM) or transition metal oxide clusters are a sub-class of metal oxide-based materials of contemporary interest. POMs are...
Show morePolyoxometalates (POM) or transition metal oxide clusters are a sub-class of metal oxide-based materials of contemporary interest. POMs are molecular systems which contain highly symmetrical structures and are characteristics of group 5 and 6 metals, especially V, Mo, and W. Typical POM clusters have nuclearities ranging from 6 to 18 metal centers and are purely inorganic in their compositions. POMs can act as multielectron redox systems, while retaining their robust oxometallic framework structure. POMs have been receiving increasing attention, in part due to their potential as redox active materials for applications in various areas and their suitability as attractive molecular building units for making new functional materials of desirable properties and functions.In recent years, there has been a growing interest in the functionalization of polyoxometalates with organic moieties to synthesize organo-functionalized POMs. During the course of the work described in this thesis, we explored the synthesis of organo-functionalized polyoxometalates with special interest in polyoxovanadates incorporating heterometal center(s) in addition to vanadium in the structure. The focus of the work was on low nuclearity POMs. The thesis describes the synthesis and full characterization of a new organo-functionalized polyoxovanadate cluster - [(n-C4H9)4N]2[V6O13{(OCH2)3C (CH2CH3)}2]. The cluster compound has been characterized by a series of analytical techniques- FT-IR, Thermo Gravimetric Analysis, Bond Valence Sum calculations and complete single X-ray diffraction structure analysis. The hexavanadate cluster features {V6O19} oxometallate core composed of six edge sharing {VO6} octahedra defined by five bridging oxygen atoms and a terminal {V=Ot} oxo group. The {V6O19} oxometallic core of the cluster adopts the Lindqvist structure incorporating two 1,1,1-tris(hydroxymethyl)propane organic ligands. Six of the oxygens in the {V6O19} core come from the three alkoxy groups from two organic ligands. To the best of our knowledge, this organo-functionalized POM cluster has not been reported in the literature previously.
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Title: Efficacy of Power Ultrasound Technology on the Reduction of Listeria monocytogenes and Salmonella enterica on Produce Matrices
Creator: Biswas, Priya
Date: 2023
Description: Fresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh...
Show moreFresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh produce recalls are frequently linked with pathogenic bacteria like Salmonella enterica and Listeria monocytogenes because of minimal processing. This study evaluated the use of power ultrasound coupled with organic acids like citric, acetic, and lactic acid which are generally recognized as safe and often helps to maintain the quality and prolong the shelf life of fresh RTE fruits and vegetables.All the produce matrices which include cucumbers, romaine lettuce, tomatoes, and strawberry were inoculated with four-strain cocktails of rifampicin-resistant S. enterica or L. monocytogenes at approximately 8 log CFU/ matrix. The produce matrices were dried for 1 h and treated for 2 minutes using 2 % or 5 % citric, lactic, or malic acid. This treatment was conducted with or without power ultrasound treatment at 40 kHz. Samples were taken in sets of three and placed into a stomacher bags. The bag contained 225 ml of water or acid. Following a 2 min treatment period, the samples were placed in separate stomacher bags, each containing 225ml of BPB or BLEB, for S. enterica or L. monocytogenes respectively. Followed serial dilutions, samples were then plated on BHIARif plates. For each condition, triplicate samples were taken, and three separate trials were conducted. The use of Student's t-test allowed for the evaluation of population differences, with a significance level of p<0.05 being deemed significant. Cucumber, romaine lettuce, tomatoes, and strawberries treated with 5 % concentration of citric, lactic, and malic acids, with addition of ultrasound showed a greater result in reductions of S. enterica to populations of 5.54 ± 0.47, 4.54 ± 0.83, and 4.69 ± x 0.36, log CFU/cucumber, 6.66 ± 0.51, 4.12 ± 0.32, and 5.51 ± 0.68, log CFU/ lettuce, 4.38 ± 0. 47, 3.12, and 5.04 ± 0.37 log CFU/ tomato, 4.66 ± 0.49, 4.69 ± 0.06, and 6.22 ± 0.39, log CFU/ strawberries, respectively. For L. monocytogenes, 5 % concentration of acids with the addition of ultrasound resulted in populations of 7.69 ± 0.35, 6.04 ± 0.24, and 6.96 ± 0.41, log CFU/ cucumbers, 7.57 ± 0.12, 5.49 ± 0.55, and 5.78 ± 0.73 log CFU/ lettuce, 6.44 ± 0.13, 5.08 ± 0.12, and 6.04 ± 0.22 log CFU/ tomato, 6.16 ± 0.37, 5.18 ± 0.22, and 5.64 ± 0.50, log CFU/ strawberries, respectively. The most effective acid was lactic when compared with citric and malic acids. The objective of this study is to investigate the effectiveness of power ultrasound as a novel non-thermal processing technology, in order to contribute to the existing knowledge base on this topic.
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Title: Critical Understanding of Multi-Mode Luminescence Properties of Eu3+ Doped LaAlO3
Creator: Alolayan, Abdulelah Abdulaziz H
Date: 2023
Description: Fluorescent anti-counterfeit materials with multi-luminescent modes under different external excitation sources are always advantageous over...
Show moreFluorescent anti-counterfeit materials with multi-luminescent modes under different external excitation sources are always advantageous over the conventional anti-counterfeit techniques. In the present thesis, our aim is to develop efficient Eu3+ doped LaAlO3 phosphor materials with different modes of luminescence properties such as down conversion-luminescence (DCL), persistent-luminescence (PersL), and optically stimulated luminescence (OSL), Thermo-luminescence (TL), radioluminescence (RL) Although, there are many reports on persistent-luminescence and optically stimulated luminescence based on Eu3+ doped matrices but the red persistent luminescence of Eu3+ ion on those matrices is not very long and the OSL intensities are also low. Herein, we report a long red persistent luminescence which lasted for 17 hrs. and the OSL intensity is very high. Furthermore, we have observed that the OSL property can be achieved even after 35 days of UV excitation and indicating its potential application for optical storage phosphor. From carrying out TSL studies we have found that three different types of traps namely Trap 1, Trap 2 and Trap 3 with trap depth 0.63 eV, 0.82 eV, 1.02 eV respectively are responsible for the persistent and OSL properties. It has been concluded that Trap 1 is mostly responsible for the persistent luminescence in short term while Trap 2 and Trap 3 are responsible for intermediate and long persistent luminescence. Further, Trap 2 and Trap 3 were also found to be present even after 35 days and responsible for the OSL properties. Anti-counterfeiting PersL composite has been developed in which AC real-life application is demonstrated.
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Title: Neuropsychological Pattern of Verbal and Nonverbal Processing Speed Discrepancy in Veterans with Co-Occurring mTBI and PTSD
Creator: VanLandingham, Hannah B.
Date: 2023
Description: Rates of traumatic brain injury (TBI) exposure have increased over time (CDC, 2022). This pattern of increased TBI risk is additionally...
Show moreRates of traumatic brain injury (TBI) exposure have increased over time (CDC, 2022). This pattern of increased TBI risk is additionally associated with risk for development of posttraumatic stress disorder (PTSD; APA, 2013). Ongoing PTSD symptomology can lead to neuropsychological profiles in which deficits are more pronounced for verbally constrained performances when compared to nonverbal performances. However, less is known about this performance discrepancy in patients with a history of head injury with comorbid PTSD. Moreover, the little existing research focuses on the domains of executive functioning, learning, and memory, with little to no research on processing speed discrepancies. These findings could have significant implications for healthcare and cognitive intervention pre- and post-mTBI and/or trauma exposure because this discrepancy may impact clinical assessment and subsequent diagnosis. The analysis will include 1) determination of statistically and clinically significant differences for those with co-occurring PTSD and mTBI, and 2) examine within-subjects differences with and without the inclusion of covariates. The present research found that there are no differences between those with co-occurring PTSD and head injury compared to individuals without a co-occurring diagnosis, in addition to no significant discrepancies notes within the PTSD and mTBI group alone
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Title: Modeling and Optimization of Power Plant Cooling Tower Systems Using Physics-Based and Neural-Network-Based Models
Creator: Salomon, Basile Clément Paul
Date: 2023
Description: Condensers and cooling towers are commonly used in steam power plants to condense the steam exiting the turbine and to recycle the condensed...
Show moreCondensers and cooling towers are commonly used in steam power plants to condense the steam exiting the turbine and to recycle the condensed-water into the boiler in a closed-loop system. These condensers typically use cooling water drawn from a water body (lake, river etc) to condense the steam. Cooling towers are used to lower the temperature of the warm water exiting the condenser. Since the steam condensation temperature plays an important role in the power plant efficiency, cool- ing tower performance which is limited by the wet-bulb temperature of the ambient air has been extensively studied. This work investigates the modeling of an enhanced cooling tower technology using a new pre-cooling and dehumidifying system (PDHS). This new system, based on a reversed Brayton cycle, is made out of a compressor, an air-cooled heat exchanger (HX), a heat and mass exchanger (HMX) and an expander. The goal of this PDHS concept is to pre-cool the air entering the cooling tower in order to improve its performance. In this work, a systems model has been developed. Thermodynamic models have been used for the compressor, the air-cooled heat exchanger and the expander. For the remaining components, i.e. the heat and mass exchanger, the cooling tower and the condenser, physics-based models have been developed and tested. Once tested and validated, each model can be integrated into the integrated PDHS-cooling tower-condenser system. Two different configurations of the PDHS have been considered in this thesis. In the open water loop configuration, the water in the HMX is obtained from the municipal water supply (or an alternate water source) and is released back to the source after exiting the HMX. In the closed water loop configuration, the water used to cool down the air in the HMX is being recirculated and cooled in the power plant cooling tower. The physics-based model of the PDHS developed in this work has been validated using results from an empirical model of the PDHS by GTI Energy. This first case study also shows how the PDHS can be used to save water in the cooling tower (CT). Indeed, when using the PDHS, a 37% reduction in the cooling tower evaporation rate can be observed when comparing to the baseline. This decrease in the CT evaporation rate is the main source of make-up water savings. Moreover, the water harvested by condensation in the PDHS can be redirected towards the CT, bringing another source of water savings. These two combined lead to an overall 46% decrease of the make-up water usage in the cooling tower. Another case study has been conducted on a 500 MW condenser unit. It shows that, under summer ambient conditions i.e. Ta,db = 35°C and φ = 47%, the PDHS can help the condenser restore its designed cooling load of 453 MW. Finally, using the physics-based model to create a dataset, an artificial neural network model of the PDHS has been developed to constitute a black box for the PDHS that would be able to predict with sufficient accuracy the condenser and HMX loads, the air conditions at the inlet of the CT and water temperature at both ends of the condenser and CT given the ambient air condition, the compressor pressure ratio and the water split between the condenser and the heat and mass exchanger.
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