MDPI Collection
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12588/185
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Item On the Boundary Value Problems of Hadamard Fractional Differential Equations of Variable Order via Kuratowski MNC Technique(2021-05-17) Refice, Ahmed; Souid, Mohammed Said; Stamova, IvankaIn this manuscript, we examine both the existence and the stability of solutions of the boundary value problems of Hadamard-type fractional differential equations of variable order. New outcomes are obtained in this paper based on the Darbo’s fixed point theorem (DFPT) combined with Kuratowski measure of noncompactness (KMNC). We construct an example to illustrate the validity of the observed results.Item Inactivating Host Bacteria for Characterization and Use of Phages(2023-09-27) Chambers, James P.; Wright, Elena T.; Hunter, Barbara; Serwer, PhilipPhage characterization for research and therapy can involve newly isolated phages propagated in pathogenic bacteria. If so, characterization requires safety-managing the bacteria. In the current study, we adapt a common and inexpensive reagent, PrimeStore (Longhorn Vaccines and Diagnostics, San Antonio, TX, USA), to safety-manage bacteria in 20 min by selectively inactivating the bacteria. No bacterial survivors are observed among >109 bacteria per ml for a representative of both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Bacillus thuringiensis). This procedure causes no detected inactivation of podophage T3, myophage T4 and siphophage 0105phi7-2. Margins of safety for PrimeStore concentration exist for bacterial inactivation and phage non-inactivation. Thus, general applicability is expected. Subsequent dialysis is used to block long-term effects on phages. Nonetheless, comparable tests should be performed for each pathogenic bacterial strain/phage. Electron microscopy of thin sections reveals inactivation-altered bacterial cytoplasm and a non-disintegrated bacterial envelope (ghosts). Ghosting of E. coli includes re-arrangement of the cytoplasm and the release of endotoxin. The activity of the released endotoxin is >99% reduced after subsequent dialysis, which also removes PrimeStore components. Ghosting of B. thuringiensis includes apparent phase separation within the cytoplasm. The primary application envisaged is biophysical and other screening of phages for therapy of infectious disease.Item A General Procedure to Formulate 3D Elements for Finite Element Applications(2023-10-03) Shahriar, Adnan; Majlesi, Arsalan; Montoya, ArturoThis paper presents a general procedure to formulate and implement 3D elements of arbitrary order in meshes with multiple element types. This procedure includes obtaining shape functions and integration quadrature and establishing an approach for checking the generated element’s compatibility with adjacent elements’ surfaces. This procedure was implemented in Matlab, using its symbolic and graphics toolbox, and complied as a GUI interface named ShapeGen3D to provide finite element users with a tool to tailor elements according to their analysis needs. ShapeGen3D also outputs files with the element formulation needed to enable users to implement the generated elements in other programming languages or through user elements in commercial finite element software. Currently, finite element (FE) users are limited to employing element formulation available in the literature, commercial software, or existing element libraries. Thus, the developed procedure implemented in ShapeGen3D offers FEM users the possibility to employ elements beyond those readily available. The procedure was tested by generating the formulation for a brick element, a brick transition element, and higher-order hexahedron and tetrahedron elements that can be used in a spectral finite element analysis. The formulation obtained for the 20-node element was in perfect agreement with the formulation available in the literature. In addition, the results showed that the interpolation condition was met for all the generated elements, which provides confidence in the implementation of the process. Researchers and educators can use this procedure to efficiently develop and illustrate three-dimensional elements.Item Centralized versus Decentralized Cleanup of River Water Pollution: An Application to the Ganges(2023-10-07) Batabyal, Amitrajeet A.; Beladi, HamidWe exploit the public good attributes of Ganges water pollution cleanup and theoretically analyze an aggregate economy of two cities—Kanpur and Varanasi—through which the Ganges flows. Our specific objective is to study whether water pollution cleanup in these two cities ought to be provided in a centralized or in a decentralized manner. We first determine the efficient cleanup amounts that maximize the aggregate surplus from making the Ganges cleaner in the two cities. Second, we compute the optimal amount of water pollution cleanup in the two cities in a decentralized regime in which spending on cleanup is financed by a uniform tax on the city residents. Third, we ascertain the optimal amount of water pollution cleanup in the two cities in a centralized regime subject to equal provision of cleanup and cost sharing. Fourth, we show that if the two cities have the same preference for pollution cleanup, then centralization is preferable to decentralization as long as there is a spillover from pollution cleanup. Finally, we show that if the two cities have dissimilar preferences for pollution cleanup, then centralization is preferable to decentralization as long as the spillover exceeds a certain threshold.Item Global Asymptotic Stability and Synchronization of Fractional-Order Reaction–Diffusion Fuzzy BAM Neural Networks with Distributed Delays via Hybrid Feedback Controllers(2023-10-11) Syed Ali, M.; Stamov, Gani; Stamova, Ivanka; Ibrahim, Tarek F.; Dawood, Arafa A.; Osman Birkea, Fathea M.In this paper, the global asymptotic stability and global Mittag–Leffler stability of a class of fractional-order fuzzy bidirectional associative memory (BAM) neural networks with distributed delays is investigated. Necessary conditions are obtained by means of the Lyapunov functional method and inequality techniques. The hybrid feedback controllers are then developed to ensure the global asymptotic synchronization of these neural networks, resulting in two additional synchronization criteria. The derived conditions are applied to check the fractional-order fuzzy BAM neural network’s Mittag–Leffler stability and synchronization. Three examples are given to demonstrate the effectiveness of the achieved results.Item Post-Secondary Education Outcomes for Individuals with Intellectual and Developmental Disabilities: Self-Determination, Independent Living, Employment, and the Impact of COVID-19(2023-10-11) Zhang, Dalun; Roberts, Eric; Maddalozzo, Robert; Li, Yi-Fan; Orsag, Meagan; Glass, TracyPost-secondary education (PSE) plays an important role in preparing individuals with an intellectual and developmental disability (IDD) to gain employment and independent living. Despite the recent increase in PSE programs, however, there is a lack of research examining outcomes of individuals with IDD who have attended a PSE program. This study examined three years of data from students who participated in one PSE program that focuses on the acquisition of skills regarding self-determination, employment, and independent living. We analyzed the outcome data of program graduates regarding their acquisition of skills in employment and self-determination, as well as follow-up data on employment. It was found that participation in the program increased self-determination and post-secondary readiness. Our findings also indicated that the COVID-19 pandemic impacted the self-determination scores of participants and their employment outcomes.Item Fast-Responding Pressure-Sensitive Paint Measurements of the IC3X at Mach 7.2(2023-10-18) Delgado Elizondo, Valeria; Dhanagopal, Abinayaa; Combs, Christopher S.Global surface pressure measurements of a 5.7% scale AFRL Initial Concept 3.X vehicle (IC3X) were obtained using a fast-responding ruthenium-based pressure-sensitive paint (PSP) at the UTSA Mach 7 Ludwieg Tube Wind Tunnel at two different angles of attack, 0° and 2.5°. Static calibration of the paint was performed over a range of 0.386 kPa to 82.7 kPa to relate luminescent intensity to pressure. Details on the facility, paint preparation, application, calibration, and image processing techniques are provided in the manuscript. The results from statistical, spectral, and proper orthogonal decomposition (POD) analyses are presented to characterize the pressure field observed on the model. The experimental results qualitatively follow the expected trends and correspond to the occurrence of shock waves and expansion fans, which were visualized via Schlieren imaging. The theoretical pressure range obtained from conical shock analysis for 0° agrees with the experimentally derived pressure range for the model, and the outliers are attributed to errors in image registration. This study presents preliminary pressure measurements that pave the way for obtaining time-resolved global PSP measurements to train and validate aerothermodynamic machine learning models.Item ¡Miranos! An 8-Month Comprehensive Preschool Obesity Prevention Program in Low-Income Latino Children: Effects on Children’s Gross Motor Development(2023-10-25) Errisuriz, Vanessa L.; Parra-Medina, Deborah; Liang, Yuanyuan; Howard, Jeffrey T.; Li, Shiyu; Sosa, Erica; Ullevig, Sarah L.; Estrada-Coats, Vanessa M.; Yin, ZenongOrganized childcare is an ideal setting to promote gross motor development in young children from low-income minority families. A three-group clustered randomized controlled trial was conducted in Head Start centers serving low-income Latino children to evaluate the impact of an 8-month comprehensive obesity-prevention intervention on children’s percentile scores for locomotive skills (LS pctl) and ball skills (BS pctl), and general motor quotient (GMQ). Trained Head Start staff delivered the center-based intervention (CBI) to modify center physical activity and nutrition policies, staff practices, and child behaviors, while the home-based intervention (HBI) offered training and support to parents for obesity prevention at home. Participants were 3-year-old children (n = 310; 87% Latino; 58% female) enrolled in Head Start centers in South Texas. Twelve centers were randomized (1:1:1 ratio) to receive CBI, CBI and HBI (CBI + HBI), or control treatment. Posttest data were collected from 79.1% of participants. All gross motor development measures improved significantly for children in CBI compared to the control, while children in CBI + HBI only showed improvement for GMQ (p = 0.09) and LS pctl (p < 0.001) compared to the control. A comprehensive and culturally competent intervention targeting childcare centers and children’s homes was effective at improving children’s gross motor development and reducing disparities in child development.Item Multi-Agent Reinforcement Learning for Online Food Delivery with Location Privacy Preservation(2023-11-03) Abahussein, Suleiman; Ye, Dayong; Zhu, Congcong; Cheng, Zishuo; Siddique, Umer; Shen, ShengOnline food delivery services today are considered an essential service that gets significant attention worldwide. Many companies and individuals are involved in this field as it offers good income and numerous jobs to the community. In this research, we consider the problem of online food delivery services and how we can increase the number of received orders by couriers and thereby increase their income. Multi-agent reinforcement learning (MARL) is employed to guide the couriers to areas with high demand for food delivery requests. A map of the city is divided into small grids, and each grid represents a small area of the city that has different demand for online food delivery orders. The MARL agent trains and learns which grid has the highest demand and then selects it. Thus, couriers can get more food delivery orders and thereby increase long-term income. While increasing the number of received orders is important, protecting customer location is also essential. Therefore, the Protect User Location Method (PULM) is proposed in this research in order to protect customer location information. The PULM injects differential privacy (DP) Laplace noise based on two parameters: city area size and customer frequency of online food delivery orders. We use two datasets—Shenzhen, China, and Iowa, USA—to demonstrate the results of our experiments. The results show an increase in the number of received orders in the Shenzhen and Iowa City datasets. We also show the similarity and data utility of courier trajectories after we use our obfuscation (PULM) method.Item Green Infrastructure and Urban Vacancies: Land Cover and Natural Environment as Predictors of Vacant Land in Austin, Texas(2023-11-08) Kim, Young-Jae; Lee, Ryun Jung; Lee, Taehwa; Shin, YongchulUrban vacancies have been a concern for neighborhood distress and economic decline and have gained more recent attention as potential green infrastructure is known to benefit communities in diverse ways. To investigate this, this study looked into the relationship between land cover, natural environment, and urban vacancies in Austin, Texas. Additionally, we investigated the spatial patterns of green infrastructure and urban vacancies by different income groups to see if low income communities would potentially lack the benefits of green infrastructure. To measure green infrastructure, we used different land covers such as forests and shrublands, as well as natural environments such as tree canopies and vegetation richness, using remote sensing data. Urban vacancy information was retrieved from the USPS vacant addresses and parcel land uses. Through a series of multivariate analyses examining green infrastructure variables one by one, the study results indicate that green infrastructure interacts with residential and business vacancies differently. Additionally, low-income communities lack green infrastructure compared with the rest of the city and are exposed to more urban vacancies in their neighborhoods. Further study is required to understand the dynamics of vacancies in underserved communities and examine how existing vacant land can benefit the communities as ecological resources.Item An Autochthonous Susceptible Candida auris Clade I Otomycosis Case in Iran(2023-11-11) Ahmadi, Bahram; Naeimi, Behrouz; Ahmadipour, Mohammad Javad; Morovati, Hamid; de Groot, Theun; Spruijtenburg, Bram; Badali, Hamid; Meis, Jacques F.Candida auris is a newly emerging multidrug-resistant fungal pathogen considered to be a serious global health threat. Due to diagnostic challenges, there is no precise estimate for the prevalence rate of this pathogen in Iran. Since 2019, only six culture-proven C. auris cases have been reported from Iran, of which, five belonged to clade V and one to clade I. Herein, we report a case of otomycosis due to C. auris from 2017 in a 78-year-old man with diabetes mellitus type II without an epidemiological link to other cases or travel history. Short tandem repeat genotyping and whole genome sequencing (WGS) analysis revealed that this isolate belonged to clade I of C. auris (South Asian Clade). The WGS single nucleotide polymorphism calling demonstrated that the C. auris isolate from 2017 is not related to a previously reported clade I isolate from Iran. The presence of this retrospectively recognized clade I isolate also suggests an early introduction from other regions or an autochthonous presence. Although the majority of reported C. auris isolates worldwide are resistant to fluconazole and, to a lesser extent, to echinocandins and amphotericin B, the reported clade I isolate from Iran was susceptible to all antifungal drugs.Item A Review of AI-Based Cyber-Attack Detection and Mitigation in Microgrids(2023-11-18) Beg, Omar A.; Khan, Asad Ali; Rehman, Waqas Ur; Hassan, AliIn this paper, the application and future vision of Artificial Intelligence (AI)-based techniques in microgrids are presented from a cyber-security perspective of physical devices and communication networks. The vulnerabilities of microgrids are investigated under a variety of cyber-attacks targeting sensor measurements, control signals, and information sharing. With the inclusion of communication networks and smart metering devices, the attack surface has increased in microgrids, making them vulnerable to various cyber-attacks. The negative impact of such attacks may render the microgrids out-of-service, and the attacks may propagate throughout the network due to the absence of efficient mitigation approaches. AI-based techniques are being employed to tackle such data-driven cyber-attacks due to their exceptional pattern recognition and learning capabilities. AI-based methods for cyber-attack detection and mitigation that address the cyber-attacks in microgrids are summarized. A case study is presented showing the performance of AI-based cyber-attack mitigation in a distributed cooperative control-based AC microgrid. Finally, future potential research directions are provided that include the application of transfer learning and explainable AI techniques to increase the trust of AI-based models in the microgrid domain.Item Tetrahydrocurcumin Derivatives Enhanced the Anti-Inflammatory Activity of Curcumin: Synthesis, Biological Evaluation, and Structure–Activity Relationship Analysis(2023-11-26) González, Yisett; Mojica-Flores, Randy; Moreno-Labrador, Dilan; Pecchio, Marisín; Rao, K. S. Jagannatha; Ahumedo-Monterrosa, Maicol; Fernández, Patricia L.; Larionov, Oleg V.; Lakey-Beitia, JohantTetrahydrocurcumin, the most abundant curcumin transformation product in biological systems, can potentially be a new alternative therapeutic agent with improved anti-inflammatory activity and higher bioavailability than curcumin. In this article, we describe the synthesis and evaluation of the anti-inflammatory activities of tetrahydrocurcumin derivatives. Eleven tetrahydrocurcumin derivatives were synthesized via Steglich esterification on both sides of the phenolic rings of tetrahydrocurcumin with the aim of improving the anti-inflammatory activity of this compound. We showed that tetrahydrocurcumin (2) inhibited TNF-α and IL-6 production but not PGE2 production. Three tetrahydrocurcumin derivatives inhibited TNF-α production, five inhibited IL-6 production, and three inhibited PGE2 production. The structure–activity relationship analysis suggested that two factors could contribute to the biological activities of these compounds: the presence or absence of planarity and their structural differences. Among the tetrahydrocurcumin derivatives, cyclic compound 13 was the most active in terms of TNF-α production, showing even better activity than tetrahydrocurcumin. Acyclic compound 11 was the most effective in terms of IL-6 production and retained the same effect as tetrahydrocurcumin. Moreover, acyclic compound 12 was the most active in terms of PGE2 production, displaying better inhibition than tetrahydrocurcumin. A 3D-QSAR analysis suggested that the anti-inflammatory activities of tetrahydrocurcumin derivatives could be increased by adding bulky groups at the ends of compounds 2, 11, and 12.Item Impulsive Controllers Design for the Practical Stability Analysis of Gene Regulatory Networks with Distributed Delays(2023-11-29) Cao, Jinde; Stamov, Trayan; Stamov, Gani; Stamova, IvankaThis paper studies gene regulatory networks (GRNs) with distributed delays. The essential concept of practical stability of the genes is introduced. We investigate the problems of practical stability and global practical exponential stability of the GRN model under an impulsive control. New practical stability criteria are proposed by designing appropriate impulsive controllers via the Lyapunov functions approach. In the design of the impulsive controller, we consider the effect of impulsive perturbations at fixed times and distributed delays on the stability of the considered GRNs. Several numerical examples are also presented to justify the proposed criteria.Item Irradiation of ZnPPIX Complexed with Bovine β-Lactoglobulin Causes Chemical Modifications and Conformational Changes of the Protein(2023-11-29) Albalawi, Abdullah; Castillo, Omar; Denton, Michael L.; Rickman, John Michael; Noojin, Gary D.; Brancaleon, LorenzoPhotosensitization of proteins mediated by chromophores is a mechanism commonly employed by nature and mimicked in a broad array of laboratory research and applications. Nature has evolved specialized complexes of proteins and photosensitizers (PS) that assemble to form photoreceptor proteins (PRP). These are used by many organisms in diverse processes, such as energy conversion, protection against photodamage, etc. The same concept has been used in laboratory settings for many applications, such as the stimulation of neurons or the selective depletion of proteins in a signaling pathway. A key issue in laboratory settings has been the relationship between the photooxidation of proteins and conformational changes in host proteins. For several years, we have been interested in creating non-native PRP using porphyrin PS. In this study, we investigated the self-assembled complex between zinc protoporphyrin IX (ZnPPIX) and bovine β-lactoglobulin (BLG) as a model of non-native PRP. Since BLG undergoes a significant conformational transition near physiological pH, the study was carried out at acidic (pH 5) and alkaline (pH 9) conditions where the two conformations are respectively prevalent. We employed a series of steady-state and time-resolved optical spectroscopies as well as gel electrophoresis to experimentally characterize the photosensitization mechanisms and their effect on the host protein. Our results show that ZnPPIX prompts light-dependent modifications of BLG, which appear to be much more significant at alkaline pH. The modifications seem to be driven by photooxidation of amino acid residues that do not lead to the formation of cross-links or protein fragmentation.Item Advances in Fractional-Order Neural Networks, Volume II(2023-11-29) Stamova, Ivanka; Stamov, Gani; Li, XiaodiFractional-order neural network models have become an active research subject and have attracted increasing attention in many fields [...]Item Introduction to the Special Issue Social Meanings of Language Variation in Spanish(2023-12-06) Barnes, Sonia; Chappell, WhitneyCentering stances, positionalities, and style, the third wave of sociolinguistic study positions individuals at the heart of its analysis [...]Item A p-Refinement Method Based on a Library of Transition Elements for 3D Finite Element Applications(2023-12-14) Shahriar, Adnan; Mostafa, Ahmed JenanWave propagation or acoustic emission waves caused by impact load can be simulated using the finite element (FE) method with a refined high-fidelity mesh near the impact location. This paper presents a method to refine a 3D finite element mesh by increasing the polynomial order near the impact location. Transition elements are required for such a refinement operation. Three protocols are defined to implement the transition elements within the low-order FE mesh. Due to the difficulty of formulating shape functions and verification, there are no transition elements beyond order two in the current literature for 3D elements. This paper develops a complete set of transition elements that facilitate the transition from first- to fourth-order Lagrangian elements, which facilitates mesh refinement following the protocols. The shape functions are computed and verified, and the interelement compatibility conditions are checked for each element case. The integration quadratures and shape function derivative matrices are also computed and made readily available for FE users. Finally, two examples are presented to illustrate the applicability of this method.Item Development of Intensity–Duration–Frequency (IDF) Curves over the United Arab Emirates (UAE) Using CHIRPS Satellite-Based Precipitation Products(2023-12-20) Alsumaiti, Tareefa S.; Hussein, Khalid A.; Ghebreyesus, Dawit T.; Petchprayoon, Pakorn; Sharif, Hatim O.; Abdalati, WaleedThe recent flooding events in the UAE have emphasized the need for a reassessment of flood frequencies to mitigate risks. The exponential urbanization and climatic changes in the UAE require a reform for developing and updating intensity–duration–frequency (IDF) curves. This study introduces a methodology to develop and update IDF curves for the UAE at a high spatial resolution using CHIRPS (Climate Hazards Group InfraRed Precipitation with Station) data. A bias correction was applied to the CHIRPS data, resulting in an improved capture of extreme events across the country. The Gumbel distribution was the most suitable theoretical distribution for the UAE, exhibiting a strong fit to the observed data. The study also revealed that the CHIRPS-derived IDF curves matched the shape of IDF curves generated using rain gauges. Due to orographic rainfall in the northeastern region, the IDF intensities were at their highest there, while the aridity of inland regions resulted in the lowest intensities. These findings enhance our understanding of rainfall patterns in the UAE and support effective water resource management and infrastructure planning. This study demonstrates the potential of the CHIRPS dataset for IDF curve development, emphasizes the importance of performing bias corrections, and recommends tailoring adjustments to the intended application.Item A Spectral/hp-Based Stabilized Solver with Emphasis on the Euler Equations(2024-01-08) Ranjan, Rakesh; Catabriga, Lucia; Araya, GuillermoThe solution of compressible flow equations is of interest with many aerospace engineering applications. Past literature has focused primarily on the solution of Computational Fluid Dynamics (CFD) problems with low-order finite element and finite volume methods. High-order methods are more the norm nowadays, in both a finite element and a finite volume setting. In this paper, inviscid compressible flow of an ideal gas is solved with high-order spectral/hp stabilized formulations using uniform high-order spectral element methods. The Euler equations are solved with high-order spectral element methods. Traditional definitions of stabilization parameters used in conjunction with traditional low-order bilinear Lagrange-based polynomials provide diffused results when applied to the high-order context. Thus, a revision of the definitions of the stabilization parameters was needed in a high-order spectral/hp framework. We introduce revised stabilization parameters, τsupg, with low-order finite element solutions. We also reexamine two standard definitions of the shock-capturing parameter, δ: the first is described with entropy variables, and the other is the YZβ parameter. We focus on applications with the above introduced stabilization parameters and analyze an array of problems in the high-speed flow regime. We demonstrate spectral convergence for the Kovasznay flow problem in both L1 and L2 norms. We numerically validate the revised definitions of the stabilization parameter with Sod’s shock and the oblique shock problems and compare the solutions with the exact solutions available in the literature. The high-order formulation is further extended to solve shock reflection and two-dimensional explosion problems. Following, we solve flow past a two-dimensional step at a Mach number of 3.0 and numerically validate the shock standoff distance with results obtained from NASA Overflow 2.2 code. Compressible flow computations with high-order spectral methods are found to perform satisfactorily for this supersonic inflow problem configuration. We extend the formulation to solve the implosion problem. Furthermore, we test the stabilization parameters on a complex flow configuration of AS-202 capsule analyzing the flight envelope. The proposed stabilization parameters have shown robustness, providing excellent results for both simple and complex geometries.