SACM - United States of America

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    OPTIMIZING SPEED SINTERING PARAMETERS FOR YTTRIA-STABILIZED ZIRCONIA
    (University of Pennsylvania, 2024) Alshahrani, Abdulaziz; Zhang, Yu
    Sintering zirconia-based ceramics is a time-consuming process that uses slow heating and cooling rates. To fulfill the requirement of chair-side production of zirconia, speed and high-speed sintering technologies have emerged. However, the impact of these recent technologies on the thermal (transient stresses), physical, optical, and mechanical properties of yttria-stabilized zirconia (YSZ) still needs to be investigated. Therefore, a total of 750 disc-shaped specimens were pressed from zirconia powder (Zpex series, Tosoh Corp., Japan). Density was measured using the Archimedes method; the phase contents were determined by XRD; translucency was evaluated by a spectrophotometer on a black and white background; flexural strength and fatigue resistance were assessed by the biaxial flexure method; and the microstructure was examined by SEM imaging. We observed that transient thermal stresses were developed during sintering as a result of thermal gradients due to the fast heating and cooling rates adopted by speed firing. Finite element analysis (FEA) was utilized to quantify the magnitude of transient thermal stress. These significant observations highlighted the importance of pre-sintering conditions, especially if the pre-sintered zirconia blocks and discs were intended for speed sintering. Further, our findings showed that the currently recommended speed and high-speed sintering protocols of YSZ resulted in incomplete densification due to the brief dwell time of 5–16 min compared to 120 min in conventional sintering. Subsequently, the entrapped pores resulted in light scattering and reduced optical translucency. Interestingly, residual pores did not affect the flexural strength. The speed sintering protocols for 3–5 mol% YSZ were optimized by proposing higher sintering temperatures, 1550°C and 1580°C, and longer dwelling times, 40 min and 60 min. As a result, SS-1 (1550°C/40 min) for 3YSZ, SS-3 (1580°C/40 min) for 4YSZ, and SS-4 (1580°C/60 min) for 5YSZ was the optimal speed sintering conditions for those compositions, which led to significantly lower properties than the current speed and high-speed sintered YSZ and comparable to the gold standard “conventional sintering.” Finally, we demonstrated that the selected optimal speed sintering protocol for 5YSZ is more fatigue-resistant and exhibits better long-term mechanical stability.
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    ELECTROCHEMICAL NITROGEN REDUCTION TO AMMONIA USING MOLYBDENUM DISULFIDE-BASED NANOCATALYSTS
    (UA Little Rock, 2019-12) Basurrah, Assem; Zhao, Wei
    Ammonia is the basis for producing fertilizers for food production. The Haber Bosch process is the main method to produce ammonia. Because of the energy and environmental problems associated with the Haber-Bosch process, extensive research is being explored for other ammonia production methods, including electrochemical methods based on nitrogen reduction reaction (NRR). In this thesis, molybdenum disulfide (MoS2) nanocatalysts (~4 nm) on carbon fibers were synthesized by hydrothermal reactions. The resulting composites were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the composites were measured by using linear sweep voltammetry, cyclic voltammetry, and controlled potential electrolysis to evaluate their NRR performances and effectiveness in the production of ammonia. Ammonia was produced with a yield rate of 1.5810-10 mole s −1 cm−2 and Faradaic efficiency 9.39% for NRR, both of them were higher than or close to those in literatures in aqueous solutions without using co-catalysts
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    Monoclonal Antibodies Directed Against Surface Antigens of Klebsiella Pneumoniae as Potential Immunoprophylactic Treatment Against Bacterial Infection
    (George Mason University, 2024-09) Alruwaili, Intisar Turayf; Hoek, Monique van
    Antimicrobial resistance represents a significant threat to global health, contributing to millions of deaths annually. The rapid emergence of multidrug-resistant (MDR) pathogens, such as Klebsiella pneumoniae, has exacerbated the challenge, particularly in the absence of new antibiotics. K. pneumoniae is responsible for a wide range of infections, including pneumonia, bloodstream infections, and urinary tract infections, often leading to increased morbidity and mortality due to its resistance to multiple antibiotics. This critical global situation requires urgent need for alternative therapeutics, for example, immunotherapies based on highly effective monoclonal antibodies (mAbs). We hypothesize that mAbs targeting critical K. pneumoniae surface proteins, such as outer membrane proteins and siderophores, can serve as an effective prophylactic or therapeutic strategy against MDR infections. In this study, we developed murine mAbs against two key proteins of K. pneumoniae, outer membrane protein (OmpW) and the siderophore receptor (FepA), both of which are associated with bacterial virulence and survival. We expressed both proteins in E. coli and used the recombinant proteins as adjuvanted immunogens for immunization and induction of activated B cells in BALB/c mice. We generated mAbs using standard hybridoma fusion techniques with SP2/0 myeloma cells. Supernatants from positive hybrids, as determined microscopically, were screened for antibody specificity using enzyme-linked immunosorbent assay (ELISA). Hybridomas that produced high titers of antibodies were cloned by limiting dilution to achieve monoclonal antibodies. Culture supernatants from the clonal population were screened again, and the developed K. pneumoniae mAbs were characterized for their class and isotype as well as their ability to bind to the immunogen and K. pneumoniae. mAbs of each specificity were also evaluated for their ability to engage in opsonophagocytosis (OP) using murine phagocytic macrophage cell lines, which express Fc receptors crucial for antibody-mediated clearance. The OP assay, based on flow cytometry, was optimized using fixed and pHrodo Red-labeled K. pneumoniae to quantify the phagocytic uptake by macrophages. Results demonstrated that mAbs targeting OmpW-2, but not OmpW-1 significantly increased OP, as determined by the mean fluorescence intensity, compared to the control mAbs. We also evaluated the OmpW and FepA mAbs for their efficacy to prevent K. pneumoniae infection using the Galleria mellonella worm model. Measuring the survival of G. mellonella larvae for either 24 or 48 hours in the presence of mAbs, we observed that while some mAbs were quite effective (e.g., anti-OmpW-1), mAbs targeting the other specificities, OmpW-2 and FepA, were ineffective. Overall, these data suggest that targeting surface proteins of K. pneumoniae with mAbs could enhance bacterial clearance in vitro and in vivo, although further studies are needed to optimize mAbs dosage and improve synergistic effects for potential clinical applications.
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    Studying the defect-photocarrier interaction in halide perovskites
    (University of Kansas, 2024) Alkhalifah, Ghadah; Wai-Lun, Chan
    Organometal halide perovskites have emerged as exceptional materials for use in photovoltaics (PVs), light-emitting diodes, and detector devices due to their outstanding optoelectronic properties. These materials show a high absorption coefficient, a tunable band gap, and a long carrier diffusion length. Because of these outstanding properties, halide perovskite PVs have shown a rapid improvement in power conversion efficiency in recent years, with a current record exceeding 26%. However, a major obstacle to the commercialization of these perovskite PVs is their inherent instability, which makes them less reliable devices. These materials intrinsically have a high concentration of point defects that migrate and interact with electronic charges, resulting in poor photostability under various illumination conditions. In this thesis, we investigate defect-photocarrier interactions in halide perovskites. We fabricated samples by intentionally enhancing or suppressing the amount of iodide vacancies (VI). Our finding indicates that samples with more VI exhibit a large and reversible Fermi level shift (~0.7 eV) when samples are exposed to light illumination. Moreover, we observe that VI can interact with photoelectrons to form prolonged deep electron traps, which can lead to photo-induced instabilities. These observations can be attributed to the capturing of photocarriers by VI, leading to the formation of Pb-Pb dimer that shifts the energy level of the defect state. This process resembles the polaron formation at a defect site. To mitigate these polaronic interactions with point defects, we partially replaced the MA+ cation with cations of different ionic radii. We observed that light-induced deep electron traps and the associated Fermi level shifts are suppressed by replacing MA+ with the smaller cesium (Cs+) ions but are enhanced by replacing MA+ with the larger formamidinium (FA+) ions. Point defects can also migrate easily, leading to defect segregation within the perovskite film. The segregation of defects affects electron transport and results in instability in the performance of halide perovskite devices. Conventional ultrafast spectroscopies used to study electron dynamics in halide perovskites commonly illuminate the sample continuously with millions of laser pulses, resulting in unavoidable disruption of steady-state conditions, such as the steady-state concentration of photocarriers and the extent of ion segregation, in the perovskite film. Hence, it is crucial to develop an experimental technique to unveil the correlation between charged defect segregation and fast electron transport. Here, an experimental approach is developed to study how the charged defect segregation induced by light can influence the electron transport time. In this approach, we combine single-pulse femtosecond (fs) excitations with electrical measurements on a perovskite/graphene heterostructure to probe nanosecond scale electron transport times under different continuous light illumination conditions. We observed that light-induced ion segregation shortens electron and hole transport times in perovskite film. This enhancement in the transport rate can be explained by the formation of an internal p-n junction induced by the ion segregation.
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    Analytical Study of the Reformation of the Saudi Public Procurement Contract Legal Framework and Its Success in Promoting the Saudi Construction Contractor Sector
    (Wake Forest University, 2024-11) Abu Ras, Bayan Ali; Davis, Timothy
    The construction contracting sector in Saudi Arabia has long faced challenges in tendering and executing Public Procurement Contracts (PPCs) due to inherent issues within the legal framework of these contracts. These challenges have led to project delays, stoppages, and cancellations, negatively affecting national development, contractor performance, and contractor-government relationships. In response to these problems, and as part of the broader Vision 2030 initiatives, the Saudi legislature introduced a new law for PPCs. This research critically examines the reforms to PPC legal framework, focusing on the former and current Government Tenders and Procurement Law (GTPL) from the perspective of construction contractors. It evaluates whether these reforms effectively address the contractor’s systemic challenges during the tendering and execution phases of PPCs. While recognizing the significant progress achieved under the current GTPL, this study offers targeted recommendations to address persisting issues and further enhance the legal framework of PPC, ensuring better alignment with contractor needs and sustained development in the construction sector.
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    Corporate Social Responsibility in an Islamic Environment: Analysis of Ramadan and Eid Al-Fitr Advertisements for STC, Zain, and Mobily Telecom Company from the Lens of Legitimacy Theory
    (Virginia Commonwealth University, 2024) Albarakati, Entesar; Song, Baobao
    CORPORATE SOCIAL RESPONSIBILITY IN AN ISLAMIC ENVIRONMENT: ANALYSIS OF RAMADAN AND EID AL-FITR ADVERTISEMENTS FOR STC, ZAIN, AND MOBILY TELECOM COMPANY FROM THE LENS OF LEGITIMACY THEORY By Entesar Albarakati, Ph.D. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, at Virginia Commonwealth University. Virginia Commonwealth University, 2024 Major Director: Baobao Song, Assistant Professor, Richard T. Robertson School of Media and Culture The concept of corporate social responsibility (CSR) has gained popularity in recent decades as the number of corporations that engage in CSR continues to grow. In the last 20 years the breadth of CSR has expanded substantially, not only in terms of the variety, scope, and influence of business policies, but also in terms of scholarly research. Despite the expansion of the field of CSR, Islamic corporate social responsibility (ICSR) still receives less attention in academic research than traditional CSR, perhaps because of the lack of defining boundaries and basic principles of ICSR. In Islamic countries such as the Middle East, there exist notable variations in cultural, economic, political, and religious traditions. Hence, the applicability of the existing body of research on CSR in other regions cannot be readily extrapolated to the Middle East (ME). This research aims to investigate CSR messages in an Islamic environment by assessing the content of advertisements for three telecom communication companies operating in Saudi Arabia during Ramadan and Eid al-Fitr. The study used a quantitative content analysis technique guided by legitimacy theory to answer the research questions. A total of 51 advertisements issued from 2008 to 2023 were examined. The results revealed that the bulk of CSR advertisements were concentrated between 2016 and 2023; they also showed the importance of advertising during Ramadan and Eid al-Fitr, as the rate of ad views reached millions, confirming the importance of these two religious occasions. The study dealt with three primary axes that were included in CSR ads—first, legitimacy. The results demonstrated that moral legitimacy (23%) was the most common type of legitimacy included in CSR ads, followed by pragmatic legitimacy (13%), followed by practical legitimacy (5.9%). Second, religious customs and values were included in 58.8% of advertisements. Third, SDSGs—29.4% of ads included SDGs. This study and previous studies confirm that CSR in Islam still receives less attention in academic research compared to traditional corporate social responsibility. Therefore, this study recommends establishing specific limits and basic principles for corporate social responsibility in Islam. This is done by defining established standards and guidelines for measuring and evaluating CSR practices in Islam. The study recommends diversifying the method, industries, religious customs and values, and geographical and economic regions in Islamic countries,
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    REPURPOSING DRUGS FOR HYPERCOAGULABLE CONDITIONS: A PRECISION MEDICINE APPROACH TO ADVANCE THERAPEUTIC DISCOVERY
    (Virginia Commonwealth University, 2024-12) Alghubayshi, Ali; Wijesinghe, Dayanjan S
    Background: Sickle Cell Disease (SCD) and related hypercoagulable conditions, particularly those associated with elevated von Willebrand factor (vWF) levels, pose significant health challenges globally, with a notable burden in Saudi Arabia. Despite known genetic factors influencing these conditions, effective treatment options remain limited. This dissertation aims to leverage genomic data and bioinformatic techniques to identify novel therapeutic targets and drug repurposing opportunities for SCD and vWF-linked hypercoagulability. Methods: This research comprises three interconnected studies. First, a case-control Genome-Wide Association Study (GWAS) was conducted comparing Saudi SCD patients with healthy controls. The second study utilized bioinformatic pipelines to analyze the druggability of the identified genes that characterize Saudi SCD patients. The interaction of these genes with the currently approved medications was estimated. The third study extended this approach to vWF-linked hypercoagulability, utilizing publicly available GWAS data. These analyses integrated data from various sources, including databases of drug-gene interaction and protein structures, to identify potential drug repurposing candidates and novel drug targets. Results: The initial GWAS identified numerous significant genetic variants characterizing SCD cases in the Saudi population. Building on these findings, the second study revealed several approved medications showing potential for repurposing in SCD. Notably, drugs such as simvastatin, allopurinol, and specific immunomodulators have emerged as promising candidates. The analysis also identified novel drug targets with high druggability scores, in particular, the olfactory receptor gene clusters. The third study, focusing on vWF-linked hypercoagulability, identified additional potential candidates, including nebivolol, pravastatin, riociguat, candesartan, and acetylcysteine. This study also revealed several novel, highly druggable targets implicated in key processes related to blood coagulation and vascular function, such as CLEC4M and SLC44A2. Conclusion: This research provides a comprehensive framework for drug repurposing and novel drug discovery in SCD and related hypercoagulable conditions. The findings underscore the potential of leveraging genetic data to identify targeted therapies, offering a pathway to more personalized and likely effective treatments. While promising, these computational predictions require further validation through conducting clinical studies to be translated into clinical practice.
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    Advanced Autonomous Vehicles Analytics for Predicting Navigation Performance
    (University of Pittsburgh, 2024) Alharbi, Mohammed Abdullah H; Karimi, Hassan Ali
    Autonomous Vehicles (AVs) stand as a monumental leap in modern transportation technology, offering the potential to enhance road safety and optimize transportation efficiency. However, their broad adoption is hindered by uncertainties associated with their sensors that allow for perceiving, interpreting, and interacting with their surroundings. Sensor uncertainties (SUs) arise from various sources, including sensor noise, varying environmental conditions, and inherent limitations in sensor design. SUs undermine the accuracy and reliability of AV navigation, posing substantial risks to AV performance and, by extension, to passenger safety. Considering the high stakes involved, including human lives, traffic flow optimization, and the structural integrity of transportation infrastructures, it is crucial for AVs to operate with minimal SUs. As driving on roads is dynamic with unpredictable elements, like sudden weather changes, AVs must be designed to handle both planned and unforeseen changes with unwavering precision. Failure to account for such uncertainties can cause unsafe driving and culminate in catastrophic outcomes, thereby deteriorating public confidence in autonomous driving technologies. Common approaches to identifying and handling SUs in AVs involve data fusion and machine learning techniques. Despite their acceptable performance, these techniques are constrained by several critical limitations that hinder their applicability in complex real-world scenarios. For instance, conventional sensor fusion techniques often make overly simplistic assumptions, such as treating uncertainties as independent and normally distributed, which fail to capture the complex interdependencies and nonlinearities present in real sensor data. This simplification leads to suboptimal solutions, especially in challenging environments. Additionally, these techniques lack adaptive mechanisms to respond to changing environmental conditions, limiting their robustness. On the other hand, machine learning techniques, though capable of processing large volumes of data and uncovering hidden patterns, typically suffer from a lack of interpretability, often referred to as the “black-box” problem. This opacity inhibits a comprehensive understanding of the decision-making processes, complicating efforts to ensure transparency and accountability in AV operations. Furthermore, the extant literature is void in furnishing robust evaluative metrics and tools that could facilitate the systematic analysis of AV sensor performance, both before and after occurrence of incidents. This thesis addresses these critical gaps by introducing an advanced AV analytics (AVA) framework and making the following contributions. Firstly, it introduces a novel ontology that represents and formalizes major concepts related to SUs in AV navigation. This ontology serves as a conceptual foundation for automated reasoning about navigation safety. Secondly, the thesis formulates a set of tailored performance metrics that provides a more nuanced evaluation of sensor reliability and accuracy under varying operational conditions. Thirdly, the AVA framework incorporates predictive models that not only quantify AV navigation sensor performance but also identify factors contributing to SUs. These models are unique in their multidimensional scope, encompassing environmental variables, and sensor specifications, and are of two types: online and offline. Online models focus on real-time evaluation of uncertainties for immediate decision-making, while offline models, also called forensic models, allow to analyze factors behind any unexpected behaviors. Finally, the thesis introduces a global path planner that integrates AVA’s analytical outputs to optimize AV route planning. Unlike commonly used route optimization criteria, such as shortest or fastest routes, this path planner incorporates sensor performance to identify safest routes by avoiding high-risk areas or conditions that could exacerbate SUs. These contributions are thoroughly validated using simulated and real data. The outcomes of the proposed research will help develop AV navigation solutions that are reliable and safe.
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    USING AND IMPROVING THE OFFICEHOLDER ROLE IN ENHANCING THE USE OF CORPORATE AND TRUST INSOLVENCY IN THE KINGDOM OF SAUDI ARABIA
    (Case Western Reserve University, 2024-09-12) Alhenaki, Abdulrahman; Salerno, Matthew
    The Kingdom of Saudi Arabia recently released a new bankruptcy law, showing its intent to enhance the effectiveness of insolvency procedures in the country. However, insolvency remains primarily reserved and designed for corporations, leaving trusts at the mercy of traditional bankruptcy methods. With the introduction of the new bankruptcy law and related bankruptcy commission, the Kingdom of Saudi Arabia benefits from the opportunity to use the Officeholder role to standardize, promote, and enhance the use of insolvency proceedings for both corporations and trusts. This dissertation defines the main concepts of the Kingdom of Saudi Arabia’s new bankruptcy law. The dissertation aims to identify the opportunities and lapses in legal practice revolving around the Kingdom of Saudi Arabia’s new insolvency laws for trusts and corporations that must be addressed to facilitate this transformation of Saudi insolvency. In pursuit of this objective, the dissertation highlights the background cultural and ideological foundations and the historical progress of bankruptcy law reforms before highlighting the promotion of the new advanced bankruptcy law per international standards. By focusing on businesses and trusts, this dissertation will highlight and address loopholes typically used to safeguard assets at the expense of beneficiaries and creditors. A comparative approach of the Officeholder’s role in the Kingdom of Saudi Arabia to the role, power, functions, duties, and appointment of bankruptcy trustees in Western models is applied to identify and address gaps in the Kingdom of Saudi Arabia's bankruptcy practices. The approach also provides the opportunity to further improve the Kingdom of Saudi Arabia’s insolvency laws by drawing from the critical role that trustees can play in guaranteeing the effective amalgamation and implementation of insolvency laws to bridge the trust divide between Saudi businesspersons and the government. This dissertation compares the Islamic early endowment model to the bankruptcy trustee model used in other countries. The analysis provides insight into the conceptualization of the Officeholder role under the Kingdom of Saudi Arabia’s bankruptcy law. The dissertation further compares the role of the Officeholder in the Kingdom of Saudi Arabia to the role of the trustee in other countries, such as the United States of America and the United Kingdom, to determine crucial developments and gaps. Accordingly, this dissertation constructs a comprehensive comparison of issues, substantive rights, and procedures from the perspective of rescue mechanisms and principles. This dissertation's findings will be applied to advance the Kingdom of Saudi Arabia’s new bankruptcy law in line with the Kingdom of Saudi Arabia’s objectives under its Vision 2030.
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    The Impact of Adopting OER Videos as Supplementary Resources on Student Scores and Engagement
    (Claremont Graduate University, 2024) Albalawi, Awad; Chipidza, Wallace
    Open educational resources (OER) have gained immense popularity in recent years, due to their ability to offer students and educators access to high-quality, free-to-use educational materials. The widespread use of OER has also been driven by the increasing availability of digital resources and the internet, which has made it easier to create and share educational materials. The scholarly literature demonstrates the significant benefits that can be gained by incorporating technology into educational practices. This study aimed to examine the impact of adopting OER videos as supplementary resources on student scores and engagement. The study employed a quasi-experimental design complemented by a survey conducted with the treatment group at the end of the experiment. The independent t-test results on the impact of adopting OER on student scores revealed no significant difference between the control group (who did not use OER) and the treatment group (who used OER). However, descriptive statistics indicated a positive effect on student engagement, supporting the alternative hypothesis that incorporating OER videos influences student engagement in traditional mathematics courses. These results suggest that OER videos can serve as an effective tool for promoting student engagement, even if their immediate effect on academic performance is limited. The findings also underscore the importance of careful instructional design in maximizing the impact of OER resources, as cognitive load and the complexity of the material may influence their effectiveness.
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