189 research outputs found
Uniaxial Strain-Controlled Ferroelastic Domain Evolution in BiFeO<sub>3</sub>
No full textWe investigate the effect of variable uniaxial tensile strain on the evolution of 71 degrees ferroelastic domains in (001)-oriented epitaxial BiFeO3 (BFO) thin films using piezoresponse force microscopy (PFM). For this purpose, a newly designed bending stage has been employed, which allows tensile bending as wells as in situ PFM characterization. In situ PFM imaging reveals polarization strain correlations at the nanoscale. Specifically, ferroelastic domains with in-plane polarization along the direction of applied tensile strain expand, whereas the adjoining domains with orthogonal in-plane polarization contract. The switching is mediated by significant domain wall roughening and opposite displacement of the successive walls. Further, the domains with long-range order are more susceptible to an applied external mechanical stimulus compared to the domains, which exhibit short-range periodicity. In addition, the imprint state of film reverses direction under applied tensile strain. Finally, the strain-induced changes in the domain structure and wall motion are fully reversible and revert to their as-grown state upon release of the applied stress. The strain-inducednon-180 degrees polarization rotation constitutes a route to control connected functionalities, such as magnetism, via coupled in-plane multiferroic BFO thin films.
The Predictive Factors of Acne Scarring and Post-Inflammatory Hyperpigmentation: A Retrospective Cohort Study
No full textAwadh Alamri,1– 3 Dhaii Alzahrani,1,2 Ghadi Alharbi,1,2 Rami Jan,1,2 Lulu Abdullah Alsubaie,1,2 Amjad Alghamdi,1,2 Amal H Abualola,1,2 Abdulhadi Jfri1– 3 1College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Jeddah, Saudi Arabia; 2King Abdullah International Medical Research Center, Jeddah, Saudi Arabia; 3Department of Dermatology, King Abdulaziz Medical City, Jeddah, Saudi ArabiaCorrespondence: Rami Jan, College of Medicine – Jeddah, King Saud bin Abdulaziz University for Health Sciences, P.O.Box.9515, Jeddah, 21423, Saudi Arabia, Email [email protected]: Acne vulgaris, a prevalent dermatological condition, often results in long-term complications such as scarring and hyperpigmentation. While extensive research has focused on treatment modalities, there is a notable gap in understanding the factors contributing to the development of acne scarring and post-inflammatory hyperpigmentation (PIH).Purpose: This study was conducted to identify the factors contributing to the development of acne scarring and post-inflammatory hyperpigmentation (PIH).Patients and Methods: This retrospective cohort study, conducted at King Abdulaziz Medical City, Jeddah, Saudi Arabia, analyzed data from patients with acne vulgaris between 2016 and 2023 using the hospital’s health information system, BESTCare. Statistical analysis was performed using RStudio (R version 4.3.1). We constructed a multivariable, multinomial logistic regression model to assess the independent predictors of four acne complication groups; no scarring/PIH, scarring alone, PIH alone, and acne scarring with PIH.Results: Among 417 analyzed participants, 95 participants had acne scarring (22.8%), 93 participants had PIH alone (22.3%), and 151 participants had both acne scarring with PIH (36.2%), and only 78 participants did not develop scarring or PIH (18.7%). Isotretinoin use and papules acne were associated with increased risk of acne complications. While adapalene gel was protective against acne scarring only.Conclusion: This retrospective study sheds light on factors influencing acne scarring and PIH among Acne Vulgaris patients. Our findings provide valuable insights for tailoring interventions and advancing our understanding of acne vulgaris complications in the future.Keywords: acne vulgaris, acne scarring, post-inflammatory hyperpigmentation, predictive factors, retrospective cohort stud
Polybenzimidazole-1D interconnected carbon framework decorated with nickel manganese oxide nanoparticles for hybrid supercapacitors
No full textThis study explores the synthesis and characterization of a ternary nanocomposite made up of nickel manganese oxide (NMO), polybenzimidazole (pBIM), and multiwalled carbon nanotubes (MWCNTs) for supercapacitor applications. Material characterizations confirm the structural integrity and uniformity of the synthesized components, which highlight their potential for stable performance. Through comprehensive electrochemical evaluations using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS), the NMO-pBIM-MWCNT ternary nanocomposite shows exceptional specific capacitance, energy density, and power density due to the synergistic effects among its components. The hybrid electrode achieves a maximum specific capacitance of 1766 Fg−1 and an energy density of 62 Wh kg−1. The fabricated symmetric supercapacitor device demonstrates a specific capacitance of 378.9 F g−1, an energy density of 36.4 Wh kg−1, and a power density of 171.5 W kg−1 at a current density of 0.1 Ag−1. We also investigate practical applications of the flexible supercapacitor device, showcasing its potential to power various loads with LED arrays. This study advances supercapacitor technology and highlights the versatility of ternary nanocomposites in meeting the evolving demands for energy storage
Essays on Momentum, Autoregressive Returns, and Conditional Volatility: Evidence From the Saudi Stock Market
No full textThe objective of this dissertation is to examine different aspects of return behavior and provide an out of sample evidence from the Saudi stock market (SSM). It consists of three essays. The first essay is organized into two parts. In the first part, I investigate the relationship between momentum profitability and trading volume in the SSM. The objective of this part is to find out whether momentum strategies exist in the SSM and whether trading volume affects momentum profitability. In the second part, I investigate whether a 52-week high price momentum profitability exists in the SSM. The empirical results document the existence of price momentum strategy in the SSM. In addition, the momentum strategy is more profitable when it is conditioned on high volume stocks than when it is conditioned on low volume stocks. High volume winner portfolio drives the momentum profit in the SSM. However, the results on the 52 week-high price indicate a reversal in portfolio returns which contradicts the results of earlier study conducted in the U.S and Australian markets.
The second essay examines the relationship between abnormal changes in trading volume of both firms and portfolio levels, and the short-term price autoregressive behavior in the SSM. The objective is to investigate the informational role that trading volume plays in predicting the direction of short-term returns. I evaluate whether the abnormal change in lagged, contemporaneous, and lead turnover affects serial correlation in returns. Consistent with the prediction of Campbell, Grossman, and Wang (1993) model, the result of this essay indicates that lagged abnormal change in trading volume lead to reversal in consecutive weekly returns. Contemporaneous and lead changes in volume provide mixing results.
The third essay tests the effect of trading volume on the persistence of the time varying conditional volatility in the SSM. I utilize GARCH models to test the persistence of return volatility without volume, with contemporaneous volume, with lagged volume, and with two other alternative proxies of volume. This approach is applied to the market index, five industry indices, and 15 individual companies. In addition, this essay investigates the volatility spillover between size-based portfolios in the SSM using a two-stage GARCH approach. The results indicate that the SSM exhibit strong volatility persistence; however, when I include contemporaneous volume, the persistence vanishes, indicating that the rate of information arrival measured by the volume series can be a significant source of the conditional heteroskedasticity in SSM. The results show that the spillover effect is larger and statistically significant from large to small firm portfolios
Implementation of Power-to-Gas to Reduce Carbon Intensity and Increase Renewable Content in Liquid Petroleum Fuels
No full textPower-to-gas (PtG) is an emerging energy storage concept, which can transfer the surplus and intermittent renewable generated power into a marketable hydrogen, as well as providing other ancillary services for the electrical grid. In the case of Ontario, excess power is encountered during periods of low electricity demand as a result of substantial generation from baseload nuclear and increasing integration of intermittent renewable sources powering the electrical grid.
This thesis develops various simulation and analysis of Ontario’s energy system to illustrate the use of PtG when its electrolytic hydrogen is employed in the gasoline production cycle to reduce the carbon intensity of the production process, and increase the renewable content of this traditional transportation fuel. The work includes a case study for a simulated refinery to evaluate the production cost and life cycle emission for different production scenarios, related to the deployment of polymer electrolyte membrane (PEM) electrolyzers to meet the refinery demand of hydrogen. Moreover, the study involves examining the use of the province surplus baseload generation (SBG) for which currently results in net exports to neighboring jurisdictions, and curtailed power generation capacity from wind and nuclear to meet the overall demand of the refining industry. Furthermore, a comparative assessment is conducted of blending 10% corn-ethanol and using electrolytic hydrogen supply via PtG on the ‘well to wheel’ (WTW) impacts of gasoline fuel, according to the metrics of total energy use, greenhouse gas emissions, and criteria air pollutants.
According to the study, it is found that steam methane reforming (SMR) provides a lower cost hydrogen as a result of the current low natural gas prices, even with stringent carbon-pricing policy. However, the electrolytic hydrogen production shows a potential to curb significant carbon emissions as a substitute for SMR hydrogen. At a single refinery level, the use of electrolytic hydrogen can be compared to eliminating as many as 35,000 gasoline passenger vehicles from the road when there is an installation of 130 PEM electrolyzer units (1 MW nameplate capacity per unit). Also, the analysis shows that PtG has the potential to supply the refineries within the province with the entire hydrogen demand with a fraction of the surplus power, particularly when making use of available seasonal storage at least for the next four years. Moreover, PtG is found to decrease 4.6% of the natural gas consumption on the gasoline cycle, and increase the renewable content of gasoline by extending the utilization of wind and hydro power. Furthermore, the deployment of electrolytic hydrogen results in minimizing gasoline carbon intensity by 0.5 gCO2e per MJ of the fuel. When associated with the annual gasoline sales in Ontario, it can offer the reduction of 0.26 Megaton of greenhouse gas (GHG) emissions yearly. Moreover, PtG may contribute to lowering VOCs, NOx, PM10 and PM2.5 criteria air pollutants from gasoline cycle, which cannot be achieved with blending corn based ethanol.
Accordingly, the results of this thesis outline the benefits of using power-to-gas to mitigate the existing issue of surplus power generation. Utilizing the excess electricity to produce hydrogen for refinery end user also increases the utilization of CO2 free energy and renewable content of gasoline within its life cycle production scheme
Strain engineering and control of complex oxide materials
No full textThe mechanical properties of BiFeO3 (BFO) thin films grown on SrTiO3 (001) substrates that are manually bent are studied using a specially designed uniaxial bending stage. X-ray measurements under variable uniaxial strain show that excessive strains up to ̴ 2% could be applied along the [100] direction with little cross talk between [100] and [010] directions. X-ray reciprocal space maps are acquired to investigate the evolution of -a and c-axis lattice constants under variable strain and Poisson’s ratio of BFO thin films vzx is determined to be 0.30 ± 0.01.
The effect of variable uniaxial tensile strain on the evolution of 71° ferroelastic domains in (001)-oriented epitaxial BiFeO3 (BFO) thin films using piezoresponse force microscopy (PFM) are investigated. For this purpose, a newly designed bending stage has been employed which allows for tensile bending as wells as in-situ PFM characterization. In-situ PFM imaging reveals polarization-strain correlations at the nanoscale. Specifically, ferroelastic domains with in-plane polarization along the direction of applied tensile strain expand, while the adjoining domains with orthogonal in-plane polarization contract. The switching is mediated by significant domain wall roughening and opposite displacement of the successive walls. Further, the domains with long-range order are more susceptible to an applied external mechanical stimulus compared to the domains, which exhibits short-range periodicity. In addition, the imprint state of film reverses direction under applied tensile strain. Finally, the strain-induced changes in the domain structure and wall motion are fully reversible and revert to their as-grown state upon release of the applied stress. The strain-induced non-180° polarization rotation constitutes a route to control connected functionalities such as magnetism via coupled in-plane rotation of the magnetic plane in multiferroic BFO thin films.
Ferroelectric domain structure and piezoelectric response under variable mechanical compressive stress in Pb(Zr0.2TiO0.8)O3 (PZT) thin films using high-resolution piezoresponse force microscopy (PFM) and an in-situ sample bending stage are studied. Measurements reveal a drastic change in the ferroelectric domain structure which is presented along with details of the mediating switching process involving domain wall motion, nucleation, and domain wall roughening under an applied external mechanical stimulus. Furthermore, local PFM hysteresis loops reveal significant changes in the observed coercive biases under applied stress. The PFM hysteresis loops become strongly imprinted under increasing applied compressive stress
Improving critical infrastructure resilience with application to power distribution networks
No full textOur modern societies are dependent on the functioning of infrastructure systems that support economic prosperity and quality of life. These infrastructure systems face an increasingly set of threats, natural or man-made disasters, that can cause significant physical, economic, and social disruptions. Recent extreme events have shown that total protection can not be accomplished. Therefore, Critical Infrastructure Protection strategies should focus not only on the prevention of these events but also on the response and recovery following them. This shift is realized by the concept of infrastructure resilience. In this thesis, we address the problem of assessing and improving infrastructure resilience. The contributions of this thesis focus on modelling, simulation, and optimization of infrastructure systems with respect to their resilience to extreme events. We first develop a resilience assessment framework for interdependent infrastructure systems. The developed framework provides a quantitative means to assess infrastructure resilience by introducing a generalized resilience index. To account for the inherent complexity due to infrastructure interdependencies, we use the i2Sim framework for modelling and simulating the studied infrastructure. The resilience improvement problem is formulated using the proposed resilience index as a resources allocation optimization problem. The problem aims at finding the best allocation of available resources such as power and water to mitigate the consequences of a disaster. Two solutions algorithm are proposed to solve the problem: the first one uses a simulation-optimization approach based on the Ordinal Optimization theory, and the second one uses a Linear Programming formulation. Results of both algorithms show that infrastructure resilience can be greatly improved by efficient allocations of available resources. In addition, a prioritization methodology is developed to assess decision makers to direct resilience investment to the most important components in the infrastructure. Finally, an optimal power distribution network reconfiguration algorithm is developed to complement the two resources allocation algorithms by solving the technical feasibility problem of the power distribution network. A heuristic computationally inexpensive optimization algorithm is developed based on Graph theory for solving this problem. The proposed algorithms are tested using different test cases and promising results are achieved.Applied Science, Faculty ofGraduat
Treatment Adherence and Related Factors Among Children with Attention-Deficit/Hyperactivity Disorder in Saudi Arabia
No full textMaha Ali Alsubaie,1 Zainah Yahya Alshehri,1 Ibtihaj Abdullah Alawadh,1 Razan Yasser Abulreesh,1 Hussain Mohammed Altaweel,2 Deemah Ateeq Alateeq1 1Internal Medicine Department, College of Medicine, Princess Nourah Bint Abdulrahman University, Riyadh, 16711 Saudi Arabia; 2Psychiatry Department, Prince Sultan Military Medical City, Riyadh, Saudi ArabiaCorrespondence: Deemah Ateeq Alateeq, Internal Medicine Department, College of Medicine, Princess Nourah Bint Abdulrahman University, P.O. Box 84428, Riyadh, 16711, Saudi Arabia, Email [email protected]: Attention-deficit/hyperactivity disorder (ADHD) is a common childhood psychiatric disorder. It frequently persists into adulthood and is a risk factor for other mental disorders and adverse outcomes, mainly if not managed optimally. This study aimed to assess ADHD treatment adherence and explore the underlying causes of non-adherence in ADHD children in Saudi Arabia.Methods: A cross-sectional study of a convenience sample of 221 participants. The survey included demographic characteristics of the child and parents, the child’s medical history, quality of services evaluation, as well as medication adherence assessment by Medication Adherence Report Scale (MARS), the general beliefs about medicines questionnaire (General-BMQ), in addition to assessing the parents’ beliefs about ADHD and provided/recommended treatment.Results: The sample was primarily 6 to 8-year-old children (32.81%) and males (78.52%). Most subjects were prescribed extended-release agents (45.7%), and overall, high-quality services were provided to the patients. The adherence rate of ADHD patients to their medication was 89.77%. The mother’s education correlated significantly with patient adherence (p=0.029), and the mother’s age correlated significantly with their beliefs (p=0.021), in addition to the family income (0.033). Children on Methylphenidate Immediate Release had good compliance with the medication (p=0.008). Moreover, Methylphenidate Extended Release has shown continuity results, increasing the adherence rates (p=0.035).Conclusion: ADHD medication adherence was high and associated with older age, educational status, and type of medication used. Physicians should consider these factors to improve adherence in their patients.Keywords: attention-deficit/hyperactivity disorder, children, parents, treatment adherenc
Assessing the Impact of Cyber Attacks on Wireless Sensor Nodes That Monitor Interdependent Physical Systems
No full textThis paper describes a next-generation security information and event management (SIEM) platform that performs real-time impact assessment of cyber attacks that target monitoring and control systems in interdependent critical infrastructures. To assess the effects of cyber attacks on the services provided by critical infrastructures, the platform combines security analysis with simulations produced by the Infrastructure Interdependencies Simulator (i2Sim). The approach is based on the mixed holistic reductionist (MHR) methodology that models the relationships between functional components of critical infrastructures and the provided services. The effectiveness of the approach is demonstrated using a scenario involving a dam that feeds a hydroelectric power plant. The scenario considers an attack on a legacy SCADA system and wireless sensor network that reduces electricity production and degrades the services provided by the interdependent systems. The results demonstrate that the attack is detected in a timely manner, risk assessment is performed effectively and service level variations can be predicted. The paper also shows how the impact of attacks on services can be estimated when limits are imposed on information sharing
Trading volume, time-varying conditional volatility, and asymmetric volatility spillover in the Saudi stock market
No full textDespite the well known importance of volatility-volume relationship, there is a paucity of research on this topic in emerging markets. We attempt to partially fill this gap by investigating volatility-volume relationship in the most important exchange market in the Middle East. We test the effect of trading volume on the persistence of the time-varying conditional volatility of returns in the Saudi stock market. Overall our results support the mixture of distribution hypothesis at the firm level. We also use two different proxies for information arrival, intra-day volatility, and overnight indicators. We find that these are good proxies for information and are important as contemporaneous volume in explaining conditional volatility. We also test for the volatility spillover direction between large- and small-cap portfolios. Our results show that the spillover effect is larger and statistically significant from large to small companies.Saudi stock market Trading volume Time-varying conditional volatility Mixture of distribution hypothesis
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