bluuebunny/crossref_metadata_2025 huggingface dataset:
Glass-Ceramics of the Lithium Aluminosilicate System Nucleated by TiO2: The Role of Redox Conditions of Glass Melting in Phase Transformations and Properties
Authors: Maltsev Stanislav , Dymshits Olga , Alekseeva Irina , Volokitina Anna , Tenevich Maksim , Bachina Anastasia , Bogdanov Kirill , Zapalova Svetlana , Shakhgildyan Georgiy , Zhilin Aleksandr
Published: February 2025

Lithium aluminosilicate glasses nucleated by TiO2 are usually melted in oxidizing conditions. The reducing conditions of glass melting, which allow to obtain ions of variable valence in lower oxidation states, can influence the ability of titania to provide proper phase assemblage, structure and properties of lithium aluminosilicate glass-ceramics. The aim of this study is to reveal this influence. The model glass containing TiO2 was melted with and without the addition of As2O3. Using heat treatments between 680 °C and 1300 °C, XRD, SEM and DSC data, Raman and absorption spectroscopy, transparent glass-ceramics based on nanocrystals of β-quartz solid solutions (ss) and/or γ-Al2O3 with spinel structure and opaque glass-ceramics based on nanocrystals of β-spodumene ss were obtained and characterized. Three-phase immiscibility develops during secondary heat treatments. Al2TiO5 crystallizes from aluminotitanate amorphous regions simultaneously with the appearance of β-quartz ss, while traces of anatase and then rutile appear at elevated temperatures. Phase assemblage and the sequence of phase transformations do not depend on the redox conditions of glass melting, while the rate of these transformations is significantly higher in glass melted without the addition of As2O3. Absorption in glass melted without the addition of As2O3 and the corresponding glass-ceramics originate from octahedrally coordinated Ti3+ ions and Ti3+-Ti4+ pairs in glass and nanocrystals of γ-Al2O3, Al2TiO5 and β-quartz ss. Transparent glass-ceramics with a thermal expansion coefficient of ~0.3 × 10−6 K−1 were obtained from both glasses.
A Green Electromagnetic Energy Harvester with Up-Frequency and Unidirectional Rotation for Smart Pavement
Authors: Mou Keliang , Ji Xiaoping , Li Xiaojuan , Zhou Haoyu , Wu Yunrui , Fang Yeyang
Published: February 2025

Smart pavement is composed of a monitor network, communication network, data center, and energy supply system, and it requires reliable and efficient energy sources to power sensors and devices. The mechanical energy is wasted and dissipated as heat in traditional pavement; this energy can be reused to power low-power devices and sensors for smart pavement. Mechanical energy harvesting systems typically perform through electromagnetic, piezoelectric, and triboelectric methods. Among the different methods, electromagnetic harvesters stand out for their higher output power. However, current electromagnetic harvesters face challenges such as bulky designs, low power density, and high input displacement requirements. This study proposed a green electromagnetic harvester (GEH) based on up-frequency and a unidirectional rotation mechanism to harvest mechanical energy from the pavement. A prototype was designed and prepared. The influence of different parameters on the electrical performance of the harvester was studied by using an MTS test instrument and simulation methods. The results demonstrate that increasing the frequency and optimizing the magnetic array significantly enhances electrical output. The open-circuit voltage in the N-S mode is 3.1 times higher than that in the N-N mode. At a frequency of 9 Hz and a displacement of 3.0 mm, the open-circuit voltage of the GEH is 6.73 V, the maximum power output is 171.14 mW, the peak power density is 1277.16 W/m3, and the voltage has almost no decay after 100,000 cycles. Further, the application of the GEH in charging sensors and capacitors was demonstrated, which indicates the potential of a GEH to power sensors for smart roads.
Effect of Bayer Red Mud on the Mechanical Strength of Grouting Material
Authors: Li Xiran , Han Yanna , Feng Guorui , Bai Jinwen , Ma Junbiao , Wu Guowei , Su Shengyu , Qiu Jiahui , Lv Mingzhuang
Published: February 2025

The massive stockpiles of Bayer-process red mud (BRM) severely compromise soil integrity, necessitating the urgent development of efficient large-scale utilization strategies. BRM contains large amounts of calcium, silicon, and aluminum. Theoretically, water glass and flue gas desulfurization gypsum (FGD) can increase the active substances in BRM, making it a cementitious raw material capable of replacing cement. This study pioneers a novel activation strategy utilizing water glass–FGD synergism to amplify the BRM reactivity, enabling an increased dosage in construction materials through enhanced pozzolanic activity. They were blended into the cement at different ratios to prepare a grouting material (BF-C) for fissure sealing in mine rock strata. The hydration mechanism of BF-C was analyzed from a micro perspective by XRD, FTIR, ICP-OES, and SEM-EDS, and combined with the Ca/(Si + Al) ratio to reveal its hydration synergy. The results showed that the 3 d and 28 d strength of 70% BRM-FGD reached 8.94 MPa and 13.71 MPa, respectively. At this ratio, the hydration synergy of BF-C was the strongest. The addition of water glass and FGD can directly modulate the Ca/(Si + Al) ratio of the system to an optimal value of 0.94, which promotes the formation of early hydration products. C-S-H gel, calcite, and C(N)-A-S-H are the main hydration products of BF-C. C-S-H gels are encapsulated on cancrinite, and their three-dimensional network structures are dense. Meanwhile, C(N)-A-S-H crystals are interspersed between C-S-H gels, making the structure more stable. This achievement introduces an innovative method for the large-scale utilization of Bayer red mud, providing an effective solution in grouting technology using solid waste as raw material.
Influence of a Siloxane-Modified DOPO Derivative on the Properties of Polyurethane Cationomer Coatings
Authors: Byczyński Łukasz , Szołyga Mariusz , Król Piotr
Published: February 2025

Waterborne polyurethane cationomer coatings modified with 1,3-bis(3(3-(propoxy-2-ol-)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-3-propyloxy))tetramethyldisiloxane (TMDS–AGE–DOPA) containing phosphorus and silicon atoms were obtained. Their structures were confirmed by Fourier transform infrared (FTIR) spectroscopy. The effect of TMDS–AGE–DOPA on thermal properties, flame retardancy, and surface characteristics (gloss, contact angle, surface free energy), as well as performance properties (hardness, impact resistance), was investigated. A coupled TG-FTIR technique was employed for evolved gas analysis. Thermal stability decreased with the addition of the modifier, while the glass transition temperature increased from −19 to 25 °C. The modifier improved the flame retardancy of the material by shifting the peak temperature of the heat release rate (TPHRR) to lower values. The gloss of the coatings was very high (>90 GU at all angles studied), although it decreased with increasing modifier content. The presence of phosphorus moieties from the modifier enhanced hydrophilicity, raising surface free energy (SFE) from 37.9 to 44.0 mJ/m2. The coatings are soft materials with a Persoz hardness in the range of 0.05–0.32. The modifier increased hardness but reduced impact strength. The obtained cationomers can be applied as environmentally friendly coatings on hydrophilic surfaces such as textiles, glass, or wood.
Study of the Material Removal Mechanism and Surface Damage in Laser-Assisted Milling of CF/PEEK
Authors: Wang Qijia , Wang Minghai , Fu Li , Xiao Kang , Wang Xuezhi
Published: February 2025

Carbon-fiber-reinforced polyetheretherketone (CF/PEEK) composites are being increasingly used in aerospace, biomedical, and other industries due to their superior mechanical properties. However, CF/PEEK structural components require secondary processing after curing and molding to meet connection and assembly precision requirements. This process, however, often results in defects such as burrs and pits, which significantly compromise the mechanical performance and assembly quality of the structural components. This study first employed finite element simulations to analyze the laser-assisted milling of CF/PEEK composites, investigating the material removal mechanism under thermal coupling, which was then experimentally validated. Variations in the cutting force, cutting heat, surface damage, and fiber fracture mechanisms during milling were investigated. During laser-assisted milling, the fibers fractured mainly in bending at a cutting angle of 0°, in bending shear at a cutting angle of 45°, in compression at a cutting angle of 90°, and in compression shear at a cutting angle of 135°. The experimental findings were generally consistent with the simulation results. In addition, laser-assisted milling effectively reduced the cutting forces, cutting temperatures, and surface damage compared to conventional milling; laser-assisted milling reduced the cutting forces in the 90° fiber direction by 24.8% (total cutting forces) and 16.3% (feed-cutting forces). The fiber integrity was further increased with increasing spindle speed.
Shear Energy Evolution and Fracture Behavior of Rock–Concrete Interfaces Under Different Stress-Level Conditions
Authors: Liu Taoying , Tang Min , Cao Ping , Cui Mengyuan , Dong Longjun
Published: February 2025

Indoor direct shear tests under different stress levels were conducted on sandstone–concrete samples to investigate the rock–concrete interfaces’ shear energy evolution features and fracture behaviors under different normal stresses, combined with acoustic emission (AE) and digital image correlation (DIC) techniques. The research results show that the growth of normal stress restricts the coalescence and failure of micro-cracks inside the sample and improves the bearing capacity. The shear strength of the sandstone–concrete cemented interface increases by 12.3–34.34% with increasing normal stress. The evolution behaviors of the total input energy, elastic strain energy and dissipated energy density are similar under different normal stress conditions, and the increase in normal stress raises the energy storage capacity of the sample, as well as the input external energy required for a sample’s failure, thereby enhancing the bearing capability of the sample. In addition, the AE count and b value characteristics indicate that crack propagation shows a three-stage variation trend. It can be seen from the RA (rise time/amplitude)-AF (AE count/duration time) curves that as the normal stress increases, the proportion of shear cracks in the sample progressively increases. When the final overall failure of the sample is imminent, the high-energy level fracture type changes from tensile fracture to shear fracture with increased normal stress, leading to an increasing percentage of shear fracture. Finally, the speckle results indicate that the nucleation and coalescence of tensile wing-shaped cracks are the main causes of sample failure. Under relatively high normal stress conditions, the damage degree of the serrated interface increases and the crack morphology becomes more intricate.
Structure and Properties of Strontium-Modified Zn–Al–Cu Alloys
Authors: Krupiński Mariusz , Labisz Krzysztof , Krupińska Beata
Published: February 2025

(1) In recent years, an increase in the available functionality of non-ferrous alloys has been observed based on the modification and optimization of their chemical composition. This study investigated the effect of Sr addition on the structure and properties of hypereutectic Zn–Al–Cu alloys. The objective was to determine how a modification with Al–Sr master alloy affects the crystallization kinetics, microstructure, hardness, and abrasive wear resistance and whether the modification of the phase composition reduces the corrosion resistance. (2) The total influence of strontium was determined based on the microstructure, phase composition, and derivative curve changes of the tested Zn–Al–Cu alloys with added Sr. Optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to analyze the influence of chemical and phase composition, and thermo-derivative analysis (TDA) was used to investigate the crystallization kinetics of zinc alloys with different chemical compositions. (3) Sr modification caused the formation of primary Al2Sr phases in the Zn alloy and also secondary Zn13Sr and Al4Sr phases (depending on the melting temperature of the alloy). (4) The primary and secondary intermetallic phases with strontium increased the hardness by approx. 20% and the abrasion resistance by approx. 7.5%.
Numerical Analysis of Residual Stress in Swing-Arc Narrow-Gap Gas Metal Arc Welding
Authors: Wu Yejun , Wang Jiayou , Xu Guoxiang , Jiang Yuqin
Published: February 2025

In order to gain a deeper understanding of the distribution of residual stresses in swing-arc narrow-gap GMA welding, this paper comprehensively considers the arc motion trajectory and joint geometry and establishes a three-dimensional finite element numerical analysis model for residual stresses based on elastic–plastic theory. Using the Ansys software, the welding residual stresses were calculated under swing frequencies of 4 Hz, 3 Hz, and 2 Hz, and the distribution characteristics of residual stresses were analyzed. The results indicate that the model effectively and accurately represents the movement trajectory and distribution characteristics of the swing arc. Furthermore, the calculated temperature field and residual stress outcomes align closely with the experimental findings, thereby validating the accuracy of the model. Under varying swing frequencies, the distribution patterns of residual stress along each sampling line exhibit a consistent similarity. The residual stress is predominantly concentrated in the weld zone and the adjacent heat-affected zone, while it remains relatively low in areas further away from the weld. As the swing frequency increases, the residual stress decreases. The reason for this is that an increase in swing frequency can lead to a more uniform distribution of arc heat within the weld bead, ultimately resulting in lower residual stress.
Nonlinear Ultrasonic Characterization of Processing Defects in Wire Arc Additive Manufacturing 316L Stainless Steel
Authors: Wang Pengfei , Zeng Jia , Lou Dong , Zheng Wenjian , Zheng Sanlong , Chen Bingbing , Gao Zengliang
Published: February 2025

Wire Arc Additive Manufacturing (WAAM) 316L stainless steel unavoidably introduces defects such as porosity, oxide inclusions, and lack of fusion due to the inherent characteristics of the process. These defects can significantly affect the mechanical properties and service reliability of the material. This study focused on evaluating the defects in WAAM 316L stainless steel by nonlinear ultrasonic testing based on Lamb waves. The effects of FCAW (flux cored arc welding) parameters, including shielding gases (98% Ar + 2% O2 and 100% CO2) and welding speeds (20, 30, and 40 cm/min), on the columnar grain, porosity, and defect types were systematically analyzed. The formed specimens were then subjected to nonlinear ultrasonic testing, and the results showed that the ultrasonic nonlinear parameters exhibited high sensitivity to changes in porosity. This suggests that nonlinear ultrasonic testing can effectively assess processing defects in WAAM 316L stainless steel. The findings provide valuable insights for optimizing the WAAM process and improving the reliability of additive manufacturing components.
Correction: Badea et al. New Trends in Separation Techniques of Lithium Isotopes: A Review of Chemical Separation Methods. Materials 2023, 16, 3817
Authors: Badea Silviu-Laurentiu , Niculescu Violeta-Carolina , Iordache Andreea-Maria
Published: February 2025

In the original publication [...]
Creep Failure Behavior in the Weak Areas of 12Cr1MoV Main Steam Pipe Elbow Utilized in Thermal Power Plants
Authors: Wang Shutao , Shi Renqiang , Wu Jian , Yang Chao , Liu Huan
Published: February 2025

The main steam pipe elbow is a critical metallic component in thermal power plants. Due to prolonged exposure to high temperatures and pressures, it experiences microstructural degradation and creep damage, thereby affecting its service life. Currently, there is debate regarding the location of the weakest region within the elbow, with uncertainty over whether it lies in the inner arc or neutral plane area. This study investigates the microstructure and creep properties of both the inner arc and neutral surface regions of an elbow that has been in operation for 183,088 h, aiming to identify the actual weak region and explore the underlying creep damage mechanisms. The results indicate that under identical temperature and stress conditions, samples from the neutral plane region exhibit significantly higher creep rates and shorter creep rupture times compared to those from the inner arc region. This suggests that the creep life in the vicinity of the inner surface in the neutral plane is markedly lower than that in the inner arc region. Microstructural analysis before and after creep fracture reveals that key factors influencing the creep performance of 12Cr1MoV elbows include carbide size, precipitation amount and distribution, grain size and morphology, as well as the stability and uniformity of grain orientation. Specifically, the growth of intragranular precipitates, the accumulation and non-uniform distribution of grain boundary carbides, and the non-uniform distribution of grain sizes all contribute to the rapid formation of creep cracks and premature material failure. This study concludes that the weakest region in the elbow is located at the inner surfaces of the neutral plane. Future inspections and life assessments of thermal power plant elbows should therefore focus on this area to enhance the accuracy of life evaluations and ensure the safety of thermal power plants.
Geometry of Weak Metric f-Manifolds: A Survey
Authors: Rovenski Vladimir
Published: February 2025

The interest of geometers in f-structures is motivated by the study of the dynamics of contact foliations, as well as their applications in physics. A weak f-structure on a smooth manifold, introduced by the author and R. Wolak, generalizes K. Yano’s f-structure. This generalization allows us to revisit classical theory and discover applications of Killing vector fields, totally geodesic foliations, Ricci-type solitons, and Einstein-type metrics. This article reviews the results regarding weak metric f-manifolds and their distinguished classes.
Spectral Theory and Hardy Spaces for Bessel Operators in Non-Standard Geometries
Authors: Hashemi Sababe Saeed
Published: February 2025

This paper develops novel results in the harmonic analysis of Bessel operators, extending their theory to higher-dimensional and non-Euclidean spaces. We present a refined framework for Hardy spaces associated with Bessel operators, emphasizing atomic decompositions, dual spaces, and connections to Sobolev and Besov spaces. The spectral theory of families of boundary-interpolating operators is also expanded, offering precise eigenvalue estimates and functional calculus applications. Furthermore, we explore Bessel operators under non-standard measures, such as fractal and weighted geometries, uncovering new analytical phenomena. Key implications include advanced insights into singular integrals, heat kernel behavior, and the boundedness of Riesz transforms, with potential applications in fractal geometry, constrained wave propagation, and mathematical physics.
The Constraint Function Response Shifting Scalar-Based Optimization Method for the Reliability-Based Dynamic Optimization Problem
Authors: Qiao Ping , Zhang Qi , Wu Yizhong
Published: February 2025

This work aims to improve the reliability of dynamic systems by eliminating the effect of random control variables. At first, the reliability-based dynamic optimization problem (RB-DOP) is introduced and defined to account for dynamic systems with uncertainty associated with random control variables. Whereafter, in order to solve RB-DOP efficiently, the constraint function response shift scalar (CFRSS)-based RB-DOP optimization method is proposed, in which the nested RB-DOP is decoupled into an equivalent deterministic DOP and a CFRSS search problem, and the two problems are addressed iteratively until the control law converges. Specifically, the shift scalar CFRSS is calculated by the probability density function of the constraint function response and deducted for probabilistic constraints in the constraint function response space to move the violated constraints toward the reliable region, avoiding solving large-scale optimization problems in the control variable space. Finally, two numerical examples and a low-thrust orbit transfer problem are investigated to demonstrate the feasibility of the proposed approach.
A Possible Degree-Based D–S Evidence Theory Method for Ranking New Energy Vehicles Based on Online Customer Reviews and Probabilistic Linguistic Term Sets
Authors: Zhang Yunfei , Xu Gaili
Published: February 2025

As people’s environment awareness increases and the “double carbon” policy is implemented, the new energy vehicle (NEV) becomes a popular form of transformation and more and more car manufacturers start to produce NEVs. Thus, how to choose an appropriate type of NEVs from many brands is an interesting topic for customers, which can be regarded as a multiple-attribute decision-making (MADM) problem because customers often concern several different factors such as the price, endurance mileage, appearance and so on. This paper proposes a possible degree-based D–S evidence theory method for helping customers select a proper type of NEVs in the probabilistic linguistic environment. In order to derive decision information reflecting customer demands, online customer reviews (OCRs) are crawled from multiple websites and converted into five-granularity probabilistic linguistic term sets (PLTSs). Afterwards, by maximizing deviation and minimizing the information uncertainty, a bi-objective programming model is built to determine attribute weights. Furthermore, a possible degree-based D–S evidence theory method in the PLTS environment is proposed to rank alternatives in each website. For fusing these ranking results, a 0–1 programming model is set up by maximizing the consensus between the comprehensive ranking and individual ones in each website. At length, a case study of selecting a type of NEVs is provided to show the application and validity of the proposed method.
On Ideals of Submonoids of Power Monoids
Authors: García-García Juan Ignacio , Marín-Aragón Daniel , Vigneron-Tenorio Alberto
Published: February 2025

Let S be a numerical monoid, while a Pfin(S)-monoid S is a monoid generated by a finite number of finite non-empty subsets of S. That is, S is a non-cancellative commutative monoid obtained from the sumset of finite non-negative integer sets. This work provides an algorithm for computing the ideals associated with some Pfin(S)-monoids. These are the key to studying some factorization properties of Pfin(S)-monoids and some additive properties of sumsets. This approach links computational commutative algebra with additive number theory.
A Graph-Induced Neighborhood Search Heuristic for the Capacitated Multicommodity Network Design Problem
Authors: Zhang Houshan
Published: February 2025

In this work, an efficient graph-induced neighborhood search heuristic is proposed to address the capacitated multicommodity network design problem. This problem, which commonly arises in transportation and telecommunication, is well known for its inherent complexity and is often classified as NP-hard. Our approach commences with an arbitrary feasible solution and iteratively improves it by solving a series of small-scale auxiliary mixed-integer programming problems. These small-scale problems are closely tied to the cycles inherent in the network topology, enabling us to reroute the flow more effectively. Furthermore, we have developed a novel resource-efficient facility assignment technique that departs from standard variable neighborhood search algorithms. By solving a series of small knapsack problems, this technique not only enhances the quality of solutions further but also can serve as a primary heuristic to generate initial feasible solutions. Furthermore, we theoretically guarantee that our algorithm will always produce an integer-feasible solution within polynomial time. The experimental results highlight the superior performance of our method compared to other existing approaches. Our heuristic algorithm efficiently discovers high-quality feasible solutions, substantially reducing the computation time and number of nodes in the branch-and-bound tree.
Evaluating Machine Learning Algorithms for Financial Fraud Detection: Insights from Indonesia
Authors: Lee Cheng-Wen , Fu Mao-Wen , Wang Chin-Chuan , Azis Muh. Irfandy
Published: February 2025

The study utilized Multiple Linear Regression along with advanced classification algorithms such as Logistic Regression, K-Nearest Neighbors (KNN), Support Vector Machine (SVM), Decision Tree, and Random Forest, to detect financial statement fraud. Model performance was evaluated using key metrics, including precision, recall, accuracy, and F1-Score. The analysis also identified significant indicators of fraud, such as Accounts Receivable Turnover, Days Outstanding Accounts Receivable, Days Payables Outstanding, Logarithm of Gross Profit, Gross Profit Margin, Inventory to Sales Ratio, and Total Asset Turnover. Among the models, Random Forest emerged as the most effective algorithm, consistently outperforming others on both training and testing datasets. Logistic Regression and SVM demonstrated strong reliability, whereas KNN and Decision Tree faced overfitting challenges, limiting their practical application. These findings emphasize the critical need for enhanced fraud detection frameworks, leveraging machine learning algorithms like Random Forest to identify fraud patterns effectively. The study highlights the importance of strengthening internal controls, implementing targeted fraud detection measures, and promoting regulatory improvements to enhance transparency and financial accountability.
Automatic Neural Architecture Search Based on an Estimation of Distribution Algorithm for Binary Classification of Image Databases
Authors: Franco-Gaona Erick , Avila-Garcia Maria Susana , Cruz-Aceves Ivan
Published: February 2025

Convolutional neural networks (CNNs) are widely used for image classification; however, setting the appropriate hyperparameters before training is subjective and time consuming, and the search space is not properly explored. This paper presents a novel method for the automatic neural architecture search based on an estimation of distribution algorithm (EDA) for binary classification problems. The hyperparameters were coded in binary form due to the nature of the metaheuristics used in the automatic search stage of CNN architectures which was performed using the Boltzmann Univariate Marginal Distribution algorithm (BUMDA) chosen by statistical comparison between four metaheuristics to explore the search space, whose computational complexity is O(229). Moreover, the proposed method is compared with multiple state-of-the-art methods on five databases, testing its efficiency in terms of accuracy and F1-score. In the experimental results, the proposed method achieved an F1-score of 97.2%, 98.73%, 97.23%, 98.36%, and 98.7% in its best evaluation, better results than the literature. Finally, the computational time of the proposed method for the test set was ≈0.6 s, 1 s, 0.7 s, 0.5 s, and 0.1 s, respectively.
On Ulam–Hyers–Mittag-Leffler Stability of Fractional Integral Equations Containing Multiple Variable Delays
Authors: Tunç Osman , Tunç Cemil
Published: February 2025

In recent decades, many researchers have pointed out that derivatives and integrals of the non-integer order are well suited for describing various real-world materials, for example, polymers. It has also been shown that fractional-order mathematical models are more effective than integer-order mathematical models. Thereby, given these considerations, the investigation of qualitative properties, in particular, Ulam-type stabilities of fractional differential equations, fractional integral equations, etc., has now become a highly attractive subject for mathematicians, as this represents an important field of study due to their extensive applications in various branches of aerodynamics, biology, chemistry, the electrodynamics of complex media, polymer science, physics, rheology, and so on. Meanwhile, the qualitative concepts called Ulam–Hyers–Mittag-Leffler (U-H-M-L) stability and Ulam–Hyers–Mittag-Leffler–Rassias (U-H-M-L-R) stability are well-suited for describing the characteristics of fractional Ulam-type stabilities. The Banach contraction principle is a fundamental tool in nonlinear analysis, with numerous applications in operational equations, fractal theory, optimization theory, and various other fields. In this study, we consider a nonlinear fractional Volterra integral equation (FrVIE). The nonlinear terms in the FrVIE contain multiple variable delays. We prove the U-H-M-L stability and U-H-M-L-R stability of the FrVIE on a finite interval. Throughout this article, new sufficient conditions are obtained via six new results with regard to the U-H-M-L stability or the U-H-M-L-R stability of the FrVIE. The proofs depend on Banach’s fixed-point theorem, as well as the Chebyshev and Bielecki norms. In the particular case of the FrVIE, an example is delivered to illustrate U-H-M-L stability.
Wound Healing, Antioxidant, and Antiviral Properties of Bioactive Polysaccharides of Microalgae Strains Isolated from Greek Coastal Lagoons
Authors: Vasilakis Gabriel , Marka Sofia , Ntzouvaras Alexandros , Zografaki Maria-Eleftheria , Kyriakopoulou Eirini , Kalliampakou Katerina I. , Bekiaris Georgios , Korakidis Evangelos , Papageorgiou Niki , Christofi Stefania , Vassilaki Niki , Moschopoulou Georgia , Tzovenis Ioannis , Economou-Amilli Athena , Papanikolaou Seraphim , Flemetakis Emmanouil
Published: February 2025

Microalgae have gained significant attention as sustainable sources of high value compounds, such as bioactive polysaccharides that are usually rich in sulfated groups and exhibit antioxidant properties. Here, 14 new microalgae strains of the genera Tetraselmis, Dunaliella, and Nannochloropsis, isolated from Greek coastal lagoons were analyzed to quantify and characterize their polysaccharide content. Heterogeneity was observed regarding the content of their total sugars (5.5–40.9 g/100 g dry biomass). The strains with a total sugar content above 20% were analyzed concerning the content of total, α- and β-glucans. Tetraselmis verrucosa f. rubens PLA1-2 and T. suecica T3-1 were rich in β-glucans (11%, and 8.1%, respectively). The polysaccharides of the two Tetraselmis strains were isolated and they were mainly composed of glucose and galactose. The isolated polysaccharides were fractionated using ion-exchange-chromatography. The anionic fraction from T. verrucosa f. rubens PLA1-2 was rich in sulfated polysaccharides, had antioxidant capacity, and exhibited healing properties. The anionic polysaccharides from the two Tetraselmis strains did not negatively influence the viability of human cells, while exhibiting antiviral properties against the replication of Hepatitis C Virus (HCV), with median efficient concentrations (EC50) at a range of 210–258 μg/mL.
Marmaricines A-C: Antimicrobial Brominated Pyrrole Alkaloids from the Red Sea Marine Sponge Agelas sp. aff. marmarica
Authors: Youssef Diaa T. A. , Alqarni Areej S. , Almohammadi Ameen M. , Abujamel Turki , Shaala Lamiaa A.
Published: February 2025

The Red Sea is the home of a rich diversity of sponge species with unique ecological adaptations that thrive in its saline, warm, and nutrient-poor waters. Red Sea sponges offer potential as sources of bioactive compounds and novel drugs. The organic extract of the Red Sea sponge Agelas sp. aff. marmarica was investigated for its antimicrobial constituents. Through bioassay-guided fractionation of the antimicrobial fraction of the extract on SiO2 and Sephadex LH-20, as well as HPLC purification, three bioactive compounds, marmaricines A-C (1–3), were isolated. Structural elucidation of the compounds was performed using 1D (1H and 13C) and 2D (COSY, HSQC, HMBC, and NOESY) NMR, as well as (+)-HRESIMS, leading to the identification of the compounds. The antimicrobial activities of the compounds were assessed through evaluation of their inhibition zones, MIC, MBC, and MFC, against Methicillin-Resistant Staphylococcus aureus (MRSA), Escherichia coli, and Candida albicans. Marmaricines A and B exhibited the strongest antibacterial effects against MRSA, with inhibition zones ranging from 14.00 to 15.00 mm, MIC values of 8 µg/mL, and MBC values of 16 µg/mL. In comparison, marmaracine C showed slightly weaker activity (inhibition zone: 12 mm, MIC: 16 µg/mL, MBC: 32 µg/mL). In terms of antifungal activity, marmaricines B and C demonstrated the greatest effect against C. albicans, with inhibition zones of 14–15 mm, MIC values of 8 µg/mL, and MFCs of 16 µg/mL. Interestingly, none of the compounds showed any inhibitory effect against E. coli. The results indicate that marmaricines A-C are selectively active against MRSA, and marmaricines B and C demonstrate potential against C. albicans, making them promising candidates for the development of novel antimicrobial agents targeting resistant pathogens.
The Relationship Between Thrombophilia and Modifications in First-Trimester Prenatal Screening Markers
Authors: Murvai Viorela Romina , Radu Casandra-Maria , Galiș Radu , Ghitea Timea Claudia , Tătaru-Copos Anca-Florina , Vesa Alexandra-Alina , Huniadi Anca
Published: February 2025

Background and Objective: Thrombophilia significantly increases the risk of complications like recurrent pregnancy loss, preeclampsia, IUGR, and stillbirth. Objective: This study aimed to evaluate the impact of inherited thrombophilic mutations on first-trimester screening outcomes, focusing on their relationship with maternal biomarkers and ultrasonographic parameters. Materials and Methods: A prospective observational study was conducted on 105 pregnant women during the first trimester (10–13 weeks of gestation). Genetic testing identified common thrombophilic mutations, including factor V Leiden, prothrombin G20210A, and MTHFR polymorphisms. First-trimester screening parameters, including PAPP-A, free β-hCG, and nuchal translucency (NT), were assessed. Maternal demographic and clinical characteristics, such as parity and smoking status, were recorded. Pearson correlation and risk estimates were calculated to explore associations between thrombophilic mutations, maternal factors, and screening results. Results: Lower parity (≤2) was significantly associated with a reduced risk of low PAPP-A levels (<1.0 MoM) (OR = 0.173; 95% CI: 0.044–0.676). Non-smokers showed a trend toward lower risk of low PAPP-A, although the association was not statistically significant. NT measurements <2.5 mm were consistent with normal fetal development, while maternal factors such as chronic hypertension and a history of small-for-gestational-age infants showed no significant correlations with screening markers. No significant association was observed between thrombophilic mutations and biomarker levels. Conclusions: Parity emerges as a significant factor influencing first-trimester screening outcomes, particularly PAPP-A levels, underscoring the need for tailored risk assessments in multiparous women. While smoking and thrombophilic mutations showed no definitive impact, their potential role in placental dysfunction warrants further investigation. These findings emphasize the importance of integrating maternal characteristics into screening protocols to enhance predictive accuracy and maternal–fetal outcomes.
A Pilot Study on the Effect of Added Sugar on Response Inhibition: Event-Related Potentials in a Go/NoGo Task
Authors: Jocbalyte Karolina , Stanikunas Rytis
Published: February 2025

Background and Objectives: Added sugar usage has become an important public health issue nowadays. Therefore, the interest in studying the cognitive and emotional effects associated with sugar consumption has increased. The present study aimed to investigate how the intake of added sugar affects participants’ impulsivity and cognitive functions monitored during the performance of a computerized Go/NoGo task. Materials and Methods: This study included 20 subjects (10 men and 10 women). Quantitative data for this study were collected via self-report questionnaires, including demographics, the Dietary Fat and Free Sugar—Short Questionnaire (DFS), the Yale Food Addiction Scale (YFAS 2.0), and the Barratt impulsiveness scale-11 (BIS-11). Results: Event-related potentials (ERPs) were registered throughout this study. Comparing the results of psychophysiological and neuropsychological evaluations before and after the added sugar consumption reveals differences in ERPs. Specifically, the NoGo-P3 amplitude increased after the intake of added sugar. However, there were no behavioral differences between the two experimental sessions. Conclusions: Overall, the results of our study suggest that added sugar intake was associated with stronger neuronal firing in NoGo trials. One possible explanation for this could be the need for more cognitive endeavors for participants to successfully inhibit their response impulses after added sugar consumption.
Challenges and Opportunities of Choosing a Membrane for Electrochemical CO2 Reduction
Authors: Rehberger Helene , Rezaei Mohammad , Aljabour Abdalaziz
Published: February 2025

The urgent need to reduce greenhouse gas emissions, particularly carbon dioxide (CO2), has led to intensive research into novel techniques for synthesizing valuable chemicals that address climate change. One technique that is becoming increasingly important is the electrochemical reduction of CO2 to produce carbon monoxide (CO), an important feedstock for various industrial processes. This comprehensive review examines the latest developments in CO2 electroreduction, focusing on mechanisms, catalysts, reaction pathways, and optimization strategies to enhance CO production efficiency. A particular emphasis is placed on the role of ion exchange membranes, including cation exchange membranes (CEMs), anion exchange membranes (AEMs), and bipolar membranes (BPMs). The review explores their advantages, disadvantages, and the current challenges associated with their implementation in CO2 electroreduction systems. Through careful analysis of the current literature, this report aims to provide a comprehensive understanding of state-of-the-art methods and their potential impact on sustainable CO production, with a special focus on membrane technologies.
Effects of Tool Structure and Process Parameters in Friction Stir Welding on the Temperature and Mechanical Properties of Dissimilar Copper–Aluminium Welded Joints
Authors: Zhang Yuxun , Shi Jinlong , Liao Guofang , Li Ruixiang , Peng Jianyun , Kuang Shaoqun , Shen Fanghua
Published: February 2025

Friction stir welding (FSW) is a solid-state welding method. The effects of tool structure, tool rotational speed, and welding speed in friction stir welding on the temperature, microstructure, and mechanical properties during the welding of 3 mm thick 6061-T6 aluminium alloy and T2 pure copper plates were investigated through experiments, numerical simulations, mechanical property tests, and microstructural observations, with the aim of enhancing welding strength and efficiency. The results showed that the welding heat input increased with the shoulder and pin diameters. When the shoulder diameter was in the range of 10–16 mm, proportional increases in the pin diameter resulted in an approximate increase of 30 °C in the weld centre temperature for every 2 mm increase in shoulder diameter. Compared to welding speed, rotational speed had a more significant effect on the heat input. Compared to the smooth tool, the threaded tool promoted the dispersion of copper particles within the aluminium matrix, facilitating the formation of Al2Cu phases. This increased the tensile strength of the weld joint from 183 to 236 MPa (a 28.9% improvement), along with a 57% increase in the weld centre hardness. An energy-dispersive X-ray spectroscopy analysis indicated that welding with the threaded tool resulted in the presence of significantly hard and brittle intermetallic compounds, including AlCu and Al2Cu, in the stirring zone, which substantially enhanced the weld strength.
Characterization of High-Speed Steels—Experimental Data and Their Evaluation Supported by Machine Learning Algorithms
Authors: Wiessner Manfred , Gamsjäger Ernst
Published: February 2025

X-ray diffractograms of high-speed steels are analyzed using machine learning algorithms to accurately classify various heat treatments. These differently heat-treated steel samples are also investigated by dilatometric analysis and by metallographic analysis in order to label the samples accordingly. Both agglomerative hierarchical clustering and t-distributed stochastic neighbor embedding are employed to automatically classify preprocessed X-ray datasets. The clusters obtained by this procedure agree well with the labeled data. By supervised learning via a support vector machine, hyperplanes are constructed that allow separating the clusters from each other based on the X-ray measurements. The exactness of these hyperplanes is analyzed by cross-validation. The machine learning algorithms used in this work are valuable tools to separate different microstructures based on their diffractograms. It is demonstrated that the separation of martensitic, bainitic, and pearlitic microstructures is possible based on the diffractograms only by means of machine learning algorithms, while the same problem is error-prone when looking at the diffractograms only.
Burden of Multidrug-Resistant Organisms in Oman: A Six-Year Single-Study Calling for Urgent Actions
Authors: Al Shuhoumi Mohammed Abdullah , Ghafri Suleiman Al , Hameed Fareed J. , Hinai Asma Al , Ghafri Abir Al , Mony Sathiya R. , Sawafi Bader Al , Govindaraj Gopinath , Yaqoobi Asma Al , Alawi Badryia Al , Arora Vinod , Waili Amani H. Al , Mhrooqi Abdulrahman Al
Published: February 2025

Background: Healthcare facilities worldwide are struggling to combat the increasing prevalence of multidrug-resistant organisms (MDROs). MDROs pose a serious threat to patient safety, resulting in longer hospital stays, higher healthcare expenses, and increased mortality rates. Oman aims to enhance patient safety by implementing data-driven strategies for infection control protocols. MDRO studies are limited, with only one-year data available from a tertiary hospital. No comprehensive six-year study has been released from Oman, leaving a gap in understanding the true burden of MDROs in the country. Methods: A 6-year retrospective cross-sectional analysis of MDRO files at Ibri Regional Hospital was conducted from 1 January 2017 to 31 December 2022 on clinical samples (urine, pus, eye, ear, tissue, fluid, wound, CSF, blood, ET, and sputum culture). Non-clinical and duplicate samples were excluded. Two prevalence rates were calculated: isolates and patients per 1000 admissions. Isolates were identified using the API system, VITEK-2, and MALDI-TOF MS. CLSI guidelines that are updated annually were used for antibiotic susceptibility testing. Statistical analysis was performed using SPSS to identify significant associations between pre-established variables. Ethical approval was obtained from the Centre for Studies and Research (MOH/CSR/26193). Results: MDRO prevalence in our cohort (1846 cases) was illustrated per isolate and per patient (1000 admission) and showed a growing trend; 25.60:18.70/1000 (2017), 24.40:22.40/1000 (2018), 26.80:19.40/1000 (2019), 31.20:21.70/1000 (2020), 32.50:19.00/1000 (2021), and 31.70:20.40/1000 (2022). Urinary infections were predominant, followed by surgical, respiratory, blood, and neurological infections. Respiratory infections increased during the COVID-19 era. ESBL remained the primary burden, followed by Acinetobacter MDR, MRSA, CRE, pseudomonas MDR, and VRE. VRE showed a spike in 2021 but returned to baseline in 2022. Conclusions: The study reveals a growing trend of MDROs in Oman, with species prevalence similar to that of adjacent countries. Urgent actions needed include national antibiotic policies, a local antibiogram database, public awareness campaigns on antibiotic resistance, and predicting bed occupancy for expansion/construction programs.
What We Still Don’t Know About Biofilms—Current Overview and Key Research Information
Authors: Damyanova Tsvetozara , Paunova-Krasteva Tsvetelina
Published: February 2025

The existence of biofilms as heterogeneous structures, comprising bacterial cells embedded in a self-synthesized polymeric matrix and adhered to biotic and abiotic surfaces, exhibiting high antibiotic tolerance, is a fact that, in recent years, has exerted selective pressure on healthcare systems with the emergence of numerous infections. This review provides a historical overview of the emergence of biofilms, the latest insights into their functionality and distribution, as well as data on innovative strategies to combat them. Special attention is given to significant diseases caused by biofilms, alongside current data on the molecular mechanisms underpinning their tolerance and resistance.
Designed Reactive Natural Deep Eutectic Solvents for Lipase-Catalyzed Esterification
Authors: Buzatu Alina Ramona , Todea Anamaria , Pop Raluca , Dreavă Diana Maria , Paul Cristina , Bîtcan Ioan , Motoc Marilena , Peter Francisc , Boeriu Carmen Gabriela
Published: February 2025

Natural deep eutectic solvents (NADESs) are a sustainable, green option for extraction and reaction media in biorefineries and various chemical and biotechnological applications. Particularly, enzymatic reactions profit from NADES applications, as these solvents help to maintain high substrate solubility while improving both enzyme stability and efficiency. Recent studies confirmed that NADESs can perform multiple functions simultaneously, as reaction media for biocatalytic conversions, but also as substrates and catalysts for reactions, fulfilling the role of a reactive solvent. This study reports the beneficial effect of designed reactive natural deep eutectic solvents (R-NADESs) on the esterification activity and thermal stability of free and immobilized lipases in the synthesis of polyol- and carbohydrate-based biosurfactants. We manufactured and characterized 16 binary and ternary R-NADES systems with choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and carbohydrate polyols; mono-, di-, and oligosaccharides; urea (U); N-methyl urea (MU); and water as the hydrogen bond donors (HBDs), in different combinations and molar ratios, most of which are reported for the first time in this paper. We determined their physicochemical, thermal, and molecular properties, including among others viscosity, polarizability, and the number of hydrogen bonds, and we showed that these properties are controlled by composition, molar ratio, molecular properties, temperature, and water content. Many lipases, both native and immobilized, showed high stability and remarkable catalytic performance in R-NADESs during esterification reactions.