bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Molecular Simulation of Polyethylene/Organoclay Nanocomposites for Their Physical Properties and Foam Morphology
Authors: Sharudin Rahida Wati , Md Azmi Nik Salwani , Hanizan Anuaruddin , Akhbar Suffiyana , Ahmad Zakiah , Ohshima Masahiro
Published: April 2023

Polyethylene materials are of great interest to be used in many applications due to their many advantageous characteristics. It is light, highly chemical resistant, easy to process, low in cost and has good mechanical properties. Polyethylene is widely used as a cable-insulating material. However, research is still needed to further improve its insulation quality and properties. In this study, an experimental and alternative approach through a dynamic modeling method was conducted. The main objective was to investigate the effect of modified organoclay concentration on the properties of polyethylene/organoclay nanocomposites by observing their characterization and optical and mechanical properties. The thermogram curve reveals that 2 wt% organoclay used has the highest crystallinity (46.7%) while the highest amount of organoclay used produced the lowest crystallinity (31.2%). The presence of cracks was also observed mostly in the nanocomposite with higher content of organoclay, usually where 2.0 wt% and above of organoclay was used. Morphological observation from simulation results supports the experimental work. Only small pores were observed to form in lower concentrations, and as the concentration was increased to 2.0 wt% and above, the pores present became larger in size. Increasing the concentration of organoclay up to 2.0 wt% reduced the interfacial tension while increasing the concentration above 2.0 wt% did not bring any changes to the interfacial tension value. Different formulations produced different behavior of nanocomposite. Hence the control of the formulation was important to control the final result of the products for appropriate application in different sectors of industry.
Wet–Dry Cycles and Microstructural Characteristics of Expansive Subgrade Treated with Sustainable Cementitious Waste Materials
Authors: Abbey Samuel J. , Amakye Samuel Y. O. , Eyo Eyo U. , Booth Colin A. , Jeremiah Jeremiah J.
Published: April 2023

This work presents an experimental study on the physico-mechanical and microstructural characteristics of stabilised soils and the effect of wetting and drying cycles on their durability as road subgrade materials. The durability of expansive road subgrade with a high plasticity index treated with different ratios of ground granulated blast furnace slag (GGBS) and brick dust waste (BDW) was investigated. Treated and cured samples of the expansive subgrade were subjected to wetting–drying cycles, California bearing ratio (CBR) tests, and microstructural analysis. The results show a gradual reduction in the California bearing ratio (CBR), mass, and the resilient modulus of samples for all subgrade types as the number of cycles increases. The treated subgrades containing 23.5% GGBS recorded the highest CBR value of 230% under dry conditions while the lowest CBR value of 15% (wetting cycle) was recorded for the subgrade treated with 11.75% GGBS and 11.75% BDW at the end of the wetting–drying cycles, both of which find useful application in road pavement construction as calcium silicate hydrate (CSH) gel was formed in all stabilised subgrade materials. However, the increase in alumina and silica content upon the inclusion of BDW initiated the formation of more cementitious products due to the increased availability of Si and Al species as indicated by EDX analysis. This study concluded that subgrade materials treated with a combination of GGBS and BDW are durable, sustainable and suitable for use in road construction.
Experimental Research on Dynamic Behavior of Stiffened Plates under Drop-Weight Impacts of a Wedge Impactor
Authors: Yu Rong , Luo Wei , Chen Hao , Liu Jingxi
Published: April 2023

Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20–26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures.
Increasing Electrical Resistivity of P-Type BiFeO3 Ceramics by Hydrogen Peroxide-Assisted Hydrothermal Synthesis
Authors: Casut Cristian , Bucur Raul , Ursu Daniel , Malaescu Iosif , Miclau Marinela
Published: April 2023

Bismuth ferrite (BiFeO3, BFO) is still widely investigated both because of the great diversity of its possible applications and from the perspective of intrinsic defect engineering in the perovskite structure. Defect control in BiFeO3 semiconductors could provide a key technology for overcoming undesirable limitations, namely, a strong leakage current, which is attributed to the presence of oxygen vacancies (VO) and Bi vacancies (VBi). Our study proposes a hydrothermal method for the reduction of the concentration of VBi during the ceramic synthesis of BiFeO3.Using hydrogen peroxide (H2O2) as part of the medium, p-type BiFeO3 ceramics characterized by their low conductivity were obtained. Hydrogen peroxide acted as the electron donor in the perovskite structure, controlling VBi in the BiFeO3 semiconductor, which caused the dielectric constant and loss to decrease along with the electrical resistivity. The reduction of Bi vacancies highlighted by a FT-IR and Mott—Schottky analysis has an expected contribution to the dielectric characteristic. A decrease in the dielectric constant (with approximately 40%) and loss (3 times) and an increase of the electrical resistivity (by 3 times) was achieved by the hydrogen peroxide-assisted hydrothermal synthesized BFO ceramics, as compared with the hydrothermal synthesized BFOs.
Effective Combination of the Metal Centers in MOF-Based Materials toward Sustainable Oxidation Catalysts
Authors: Viana Alexandre M. , Leonardes Francisca , Corvo Marta C. , Balula Salete S. , Cunha-Silva Luís
Published: April 2023

A successful encapsulation of Keggin-type polyoxomolybdate (H3[PMo12O40], PMo12) into metal-organic framework (MOF) materials with an identical framework but distinct metal centers (ZIF-8 with Zn2+ and ZIF-67 with Co2+) was accomplished by a straightforward room-temperature procedure. The presence of Zn2+ in the composite material PMo12@ZIF-8 instead of Co2+ in PMo12@ZIF-67 caused a remarkable increase in the catalytic activity that achieved a total oxidative desulfurization of a multicomponent model diesel under moderate and friendly conditions (oxidant: H2O2 and solvent: ionic liquid, IL). Interestingly, the parent ZIF-8-based composite with the Keggin-type polyoxotungstate (H3[PW12O40], PW12), PW12@ZIF-8, did not show the relevant catalytic activity. The ZIF-type supports present an appropriate framework to accommodate active polyoxometalates (POMs) into their cavities without leaching, but the nature of the metallic center from the POM and the metal present in the ZIF framework were vital for the catalytic performance of the composite materials.
Highly Transparent and Zirconia-Enhanced Sol-Gel Hybrid Coating on Polycarbonate Substrates for Self-Cleaning Applications
Authors: Zhang Bing , Xia Ruohan , Yan Yao , Liu Jia , Guan Zisheng
Published: April 2023

To improve the efficacy of polymer-based substrate hybrid coatings, it is essential to simultaneously optimize mechanical strength and preserve the optical properties. In this study, a mixture of zirconium oxide (ZrO2) sol and methyltriethoxysilane modified silica (SiO2) sol-gel was dip-coated onto polycarbonate (PC) substrates to form zirconia-enhanced SiO2 hybrid coatings. Additionally, a solution containing 1H, 1H, 2H, and 2H-perfluorooctyl trichlorosilane (PFTS) was employed for surface modification. The results show that the ZrO2-SiO2 hybrid coating enhanced the mechanical strength and transmittance. The average transmittance of the coated PC reached up to 93.9% (400–800 nm), while the peak transmittance reached up to 95.1% at 700 nm. SEM images and AFM morphologies demonstrate that the ZrO2 and SiO2 nanoparticles were evenly distributed, and a flat coating was observed on the PC substrate. The PFTS-modified ZrO2-SiO2 hybrid coating also exhibited good hydrophobicity (WCA, 113°). As an antireflective coating on PC, with self-cleaning capability, the proposed coating has application prospects in optical lenses and automotive windows.
Complex Formation of Rare-Earth Elements in Carbonate–Alkaline Media
Authors: Litvinova Tatiana , Kashurin Ruslan , Lutskiy Denis
Published: April 2023

Rare earth metals are critical components for many industries. The extraction of rare earth metals from mineral raw materials presents many problems, both of a technological and theoretical nature. The use of man-made sources imposes strict requirements on the process. Thermodynamic and kinetic data that could describe the most detailed technological water–salt leaching and precipitation systems are insufficient. The study addresses the problem of a small amount of data on the formation and equilibrium of carbonate–alkali systems of rare earth metals. Isotherms of solubility of sparingly soluble carbonates with the formation of carbonate complexes are presented to evaluate equilibrium constants logK at zero ionic strength for Nd −11.3, Sm −8.6, Gd −8.0, and Ho −7.3. To accurately predict the system under consideration, a mathematical model was developed, which allows to calculate the water–salt composition. The initial data for calculation are concentration constants of stability of lanthanide complexes. This work will contribute to deepening knowledge about rare earth elements extraction problems and will serve as a reference for studying the thermodynamics of water–salt systems.
Effects of Sodium Tripolyphosphate Addition on the Dispersion and Hydration of Pure Calcium Aluminate Cement
Authors: Cheng Benjun , Feng Hao , Armia Erbolat , Guo Hongli , Zhang Shaowei , Zhang Haijun
Published: April 2023

In this paper, the effect of a sodium tripolyphosphate (STPP) addition on the dispersion and hydration of pure calcium aluminate cement (PCAC) was investigated, and the corresponding mechanism of effect was studied. The effects of STPP on the dispersion, rheology, and hydration processes of PCAC and its adsorption capacity on the surface of cement particles were analysed by measuring the 𝜁-potential on the surface of cement particles, the changes in the concentrations of elemental P and Ca2+ ions in a solution at different STPP additions. The experimental results show that STPP easily complexes with Ca2+ ions to produce the complex [CaP3O10]3− adsorbed on the surface of cement particles, which changes the potential on the surface of cement particles and increases the electrostatic repulsive force between cement particles, thus improving the dispersion and rheology of cement. At the same time, the contact area between cement particles and water is reduced, which hinders the hydration process and makes the time of hydration process longer. A comprehensive analysis shows that the best effect of STPP on pure calcium aluminate cements is achieved when the addition of STPP is 0.2%. This study can provide a reference for the addition of water-reducing agents in refractory castables as well as improving the quality of refractory materials.
Some Critical Reflections on the SEM-EDS Microanalysis of the Hydrotalcite-like Phase in Slag Cement Paste
Authors: Zhang Yu , Saravanakumar Karthikeyan , Çopuroğlu Oğuzhan
Published: April 2023

For a better understanding of the hydrotalcite-like phase with SEM-EDS microanalysis, the present research paid special attention to the data acquisition and interpretation of this technique. A lower Mg/Al ratio was obtained when using a higher accelerating voltage, and a beam energy of 10 kV was more appropriate than 15 kV for investigation when the slag rim was thin, to compromise to meet the requirements of obtaining an adequate overvoltage ratio and minimizing the interference. Additionally, it was noted that the Mg/Al ratio decreased from zones rich in hydrotalcite-like phase to zones rich in the C−S−H gel phase, and indiscriminately fitting scatter points selected from the slag rim would bias the Mg/Al ratio of the hydrotalcite-like phase. According to the standard-based microanalysis, it was concluded that the analysis total of the hydrates within the slag rim was in the range of 30–40%, lower than that located in the cement matrix. Besides the water chemically bound in the C−S−H gel phase, the hydrotalcite-like phase also contained a certain amount of hydroxide ions and chemically bound water.
Titanium Dioxide Thin Films Produced on FTO Substrate Using the Sol–Gel Process: The Effect of the Dispersant on Optical, Surface and Electrochemical Features
Authors: Mîndroiu Vasilica Mihaela , Stoian Andrei Bogdan , Irodia Roberta , Trușcă Roxana , Vasile Eugeniu
Published: April 2023

In this study, TiO2 thin films formed by dip-coating on an FTO substrate were obtained and characterized using surface, optical and electrochemical techniques. The impact of the dispersant (polyethylene glycol-PEG) on the surface (morphology, wettability, surface energy), optical (band gap and Urbach energy) and electrochemical (charge-transfer resistance, flat band potential) properties were investigated. When PEG was added to the sol–gel solution, the optical gap energy of the resultant films was reduced from 3.25 to 3.12 eV, and the Urbach energy increased from 646 to 709 meV. The dispersant addition in the sol–gel process influences surface features, as evidenced by lower contact-angle values and higher surface energy achieved for a compact film with a homogenous nanoparticle structure and larger crystallinity size. Electrochemical measurements (cycle voltammetry, electrochemical impedance spectroscopy and the Mott–Schottky technique) revealed improved catalytic properties of the TiO2 film, due to a higher insertion/extraction rate of protons into the TiO2 nanostructure, as well as a decrease in charge-transfer resistance from 418 k to 23.4 k and a decrease in flat band potential from 0.055 eV to −0.019 eV. The obtained TiO2 films are a promising alternative for technological applications, due to their advantageous surface, optical and electrochemical features.
Effect of Rice Husk Ash on the Properties of Alkali-Activated Slag Pastes: Shrinkage, Hydration and Mechanical Property
Authors: Tian Bo , Li Xiangguo , Lv Yang , Xu Jinsheng , Ma Weinan , He Chenhao , Chen Yang , Jian Shouwei , Wang Weizhen , Zhang Cheng , Wu Kai
Published: April 2023

In this paper, rice husk ash (RHA) with different average pore diameters and specific surface areas was used to replace 10% slag in the preparation of alkali-activated slag (AAS) pastes. The effect of RHA addition on the shrinkage, hydration, and strength of AAS pastes was studied. The results show that RHA with a porous structure will pre-absorb part of the mixing water during paste preparation, resulting in a decrease in the fluidity of AAS pastes by 5–20 mm. RHA has a significant inhibitory effect on the shrinkage of AAS pastes. The autogenous shrinkage of AAS pastes decreases by 18–55% at 7 days, and the drying shrinkage decreases by 7–18% at 28 days. This shrinkage reduction effect weakens with the decrease in RHA particle size. RHA has no obvious effect on the type of hydration products of AAS pastes, whereas RHA after proper grinding treatment can significantly improve the hydration degree. Therefore, more hydration products are generated and fills the internal pores of the pastes, which significantly improves the mechanical properties of the AAS pastes. The 28 day compressive strength of sample R10M30 (the content of RHA is 10%, RHA milling time is 30 min) is 13 MPa higher than that of blank sample.
Multi-Scale Topology Optimization of Femoral Stem Structure Subject to Stress Shielding Reduce
Authors: Xiao Zhongmin , Wu Longfei , Wu Wenqiang , Tang Ruizhi , Dai Jietao , Zhu Dachang
Published: April 2023

Hip replacement femoral implants are made of substantial materials that all have stiffness considerably higher than that of bone, which can cause significant bone resorption secondary to stress shielding and lead to severe complications. The topology optimization design method based on the uniform distribution of material micro-structure density can form a continuous mechanical transmission route, which can better solve the problem of reducing the stress shielding effect. A multi-scale parallel topology optimization method is proposed in this paper and a topological structure of type B femoral stem is derived. Using the traditional topology optimization method (Solid Isotropic Material with Penalization, SIMP), a topological structure of type A femoral stem is also derived. The sensitivity of the two kinds of femoral stems to the change of load direction is compared with the variation amplitude of the structural flexibility of the femoral stem. Furthermore, the finite element method is used to analyze the stress of type A and type B femoral stem under multiple conditions. Simulation and experimental results show that the average stress of type A and type B femoral stem on the femur are 14.80 MPa, 23.55 MPa, 16.94 MPa and 10.89 MPa, 20.92 MPa, 16.50 MPa, respectively. For type B femoral stem, the average error of strain is −1682με and the average relative error is 20.3% at the test points on the medial side and the mean error of strain is 1281με and the mean relative error is 19.5% at the test points on the outside.
Structure and Physical Properties of Conductive Bamboo Fiber Bundle Fabricated by Magnetron Sputtering
Authors: Wang Wenqing , Li Jiayao , Shi Jiangtao , Jiao Yue , Wang Xinzhou , Xia Changlei
Published: April 2023

The variety of conductive fibers has been constantly enriched in recent years, and it has made rapid development in the fields of electronic textiles, intelligent wearable, and medical care. However, the environmental damage caused by the use of large quantities of synthetic fibers cannot be ignored, and there is little research on conductive fibers in the field of bamboo, a green and sustainable material. In this work, we used the alkaline sodium sulfite method to remove lignin from bamboo, prepared a conductive bamboo fiber bundle by coating a copper film on single bamboo fiber bundles using DC magnetron sputtering, and analyzed its structure and physical properties under different process parameters, finding the most suitable preparation condition that combines cost and performance. The results of the scanning electron microscope show that the coverage of copper film can be improved by increasing the sputtering power and prolonging the sputtering time. The resistivity of the conductive bamboo fiber bundle decreased with the increase of the sputtering power and sputtering time, up to 0.22 Ω·mm; at the same time, the tensile strength of the conductive bamboo fiber bundle continuously decreased to 375.6 MPa. According to the X-ray diffraction results, Cu in the copper film on the surface of the conductive bamboo fiber bundle shows the preferred orientation of (111) the crystal plane, indicating that the prepared Cu film has high crystallinity and good film quality. X-ray photoelectron spectroscopy results show that Cu in the copper film exists in the form of Cu0 and Cu2+, and most are Cu0. Overall, the development of the conductive bamboo fiber bundle provides a research basis for the development of conductive fibers in a natural renewable direction.
Effect of the Chemical and Mechanical Recycling of PET on the Thermal and Mechanical Response of Mortars and Premixed Screeds
Authors: Lerna Michela , Foti Dora , Petrella Andrea , Sabbà Maria Francesca , Mansour Sulyman
Published: April 2023

In this paper, recycled polyethylene terephthalate (PET) was used to produce eco-innovative engineering materials with optimized performance, minimizing the environmental impact deriving from plastic consumption activity and limiting the continuous consumption of raw materials. The recycled PET obtained from waste bottles, commonly used to improve the ductility of concrete, has been used with a different weight percentage as plastic aggregate in the replacement of sand in cement mortars and as fibers added to premixed screeds. In detail, the effect of PET treatment (chemical or mechanical) on the thermal performance was evaluated. Non-destructive physical tests were conducted to determine the thermal conductivity of the investigated building materials. The performed tests showed that chemically depolymerized PET aggregate and recycled PET fibers derived from plastic wastes can reduce the heat conduction capacity of the cementitious materials with limited reduction in compressive strength. The results of the experimental campaign have made it possible to evaluate the influence of the recycled material on the physical and mechanical properties and its feasibility in non-structural applications.
Stress Relaxation Behaviour Modeling in Rigid Polyurethane (PU) Elastomeric Materials
Authors: Zielonka Paweł , Junik Krzysztof , Duda Szymon , Socha Tomasz , Kula Krzysztof , Denisiewicz Arkadiusz , Olaleye Kayode , Macek Wojciech , Lesiuk Grzegorz , Błażejewski Wojciech
Published: April 2023

Polyurethane (PU) has been used in a variety of industries during the past few years due to its exceptional qualities, including strong mechanical strength, good abrasion resistance, toughness, low-temperature flexibility, etc. More specifically, PU is easily “tailored” to satisfy particular requirements. There is a lot of potential for its use in broader applications due to this structure–property link. Ordinary polyurethane items cannot satisfy people’s increased demands for comfort, quality, and novelty as living standards rise. The development of functional polyurethane has recently received tremendous commercial and academic attention as a result. In this study, the rheological behavior of a polyurethane elastomer of the PUR (rigid polyurethane) type was examined. The study’s specific goal was to examine stress relaxation for various bands of specified strains. We also suggested the use of a modified Kelvin–Voigt model to describe the stress relaxation process from the perspective of the author. For the purpose of verification, materials with two different Shore hardness ratings—80 and 90 ShA, respectively—were chosen. The outcomes made it possible to positively validate the suggested description in a variety of deformations ranging from 50% to 100%.
The Optimization of Radiation Synthesis Modes for YAG:Ce Ceramics
Authors: Lisitsyn Victor , Mussakhanov Dossymkhan , Tulegenova Aida , Kaneva Ekaterina , Lisitsyna Liudmila , Golkovski Mikhail , Zhunusbekov Amangeldy
Published: April 2023

Synthesis in the radiation field is a promising direction for the development of materials transformation processes, especially those differing in melting temperature. It has been established that the synthesis of yttrium–aluminum ceramics from yttrium oxides and aluminum metals in the region of a powerful high-energy electron flux is realized in 1 s, without any manifestations that facilitate synthesis, with high productivity. It is assumed that the high rate and efficiency of synthesis are due to processes that are realized with the formation of radicals, short-lived defects formed during the decay of electronic excitations. This article presents descriptions of the energy-transferring processes of an electron stream with energies of 1.4, 2.0, and 2.5 MeV to the initial radiation (mixture) for the production of YAG:Ce ceramics. YAG:Ce (Y3Al5O12:Ce) ceramics samples in the field of electron flux of different energies and power densities were synthesized. The results of a study of the dependence of the morphology, crystal structure, and luminescence properties of the resulting ceramics on the synthesis modes, electron energy, and electron flux power are presented.
Echo State Network-Based Adaptive Event-Triggered Control for Stochastic Nonaffine Systems with Actuator Hysteresis
Authors: Lun Shuxian , Qin Zhenkai , Lu Xiaodong , Li Ming , Tao Tianping
Published: April 2023

This paper studies the problem of the event-triggered control of nonaffine stochastic nonlinear systems with actuator hysteresis. The echo state network (ESN) is introduced to approximate an unknown nonlinear function. The command filtering technology is used to avoid the derivation of the virtual controller in the controller design process and tries to solve the problem of complexity explosion in the traditional method. Based on Lyapunov’s finite-time stability theory, the proposed method verifies the stability of non-affine stochastic nonlinear systems. It is proved that the proposed controller method can guarantee that all of the signals in the closed-loop system are bounded, and the tracking error can converge to a minimal neighborhood of zero even if there exists an actuator hysteresis. The effectiveness of the proposed method is demonstrated by the simulation example. The simulation results show that the proposed method is effective.
Blockchain-Assisted Hybrid Harris Hawks Optimization Based Deep DDoS Attack Detection in the IoT Environment
Authors: Katib Iyad , Ragab Mahmoud
Published: April 2023

The Internet of Things (IoT) is developing as a novel phenomenon that is applied in the growth of several crucial applications. However, these applications continue to function on a centralized storage structure, which leads to several major problems, such as security, privacy, and a single point of failure. In recent years, blockchain (BC) technology has become a pillar for the progression of IoT-based applications. The BC technique is utilized to resolve the security, privacy, and single point of failure (third-part dependency) issues encountered in IoT applications. Conversely, the distributed denial of service (DDoS) attacks on mining pools revealed the existence of vital fault lines amongst the BC-assisted IoT networks. Therefore, the current study designs a hybrid Harris Hawks with sine cosine and a deep learning-based intrusion detection system (H3SC-DLIDS) for a BC-supported IoT environment. The aim of the presented H3SC-DLIDS approach is to recognize the presence of DDoS attacks in the BC-assisted IoT environment. To enable secure communication in the IoT networks, BC technology is used. The proposed H3SC-DLIDS technique designs a H3SC technique by integrating the concepts of Harris Hawks optimization (HHO) and sine cosine algorithm (SCA) for feature selection. For the intrusion detection process, a long short-term memory auto-encoder (LSTM-AE) model is utilized in this study. Finally, the arithmetic optimization algorithm (AOA) is implemented for hyperparameter tuning of the LSTM-AE technique. The proposed H3SC-DLIDS method was experimentally validated using the BoT-IoT database, and the results indicate the superior performance of the proposed H3SC-DLIDS technique over other existing methods, with a maximum accuracy of 99.05%.
Convective Heat Transfer and Entropy Generation for Nano-Jet Impingement Cooling of a Moving Hot Surface under the Effects of Multiple Rotating Cylinders and Magnetic Field
Authors: Kolsi Lioua , Selimefendigil Fatih , Larguech Samia , Ghachem Kaouther , Albalawi Hind , Alshammari Badr M. , Labidi Taher
Published: April 2023

In this study, confined slot nano-jet impingement cooling of a hot moving surface is investigated under the combined utilization multiple rotating cylinders and magnetic field. Both convective heat transfer and entropy generation analysis are conducted using a finite element method. Parametric variation of the rotational Reynolds number (Rew between −500 and 500), velocity ratio (VR between 0 and 0.25), Hartmann number (Ha between 0 and 20) and the horizontal location of cylinders (Mx between −8 and 8) are considered. Rotation of the cylinders generally resulted in the degradation of cooling performance while increasing the wall velocity, and the horizontal location of the cylinder was found to positively contribute to this. Heat transfer rate reductions of 20% and 12.5% are obtained using rotations at the highest Rew for the case of stationary (VR = 0) and moving wall (VR = 0.25). When magnetic field at the highest strength is imposed in the rotating cylinder case, the cooling performance is increased by about 18.6%, while it is reduced by about 28% for the non-rotating cylinder case. The hot wall movement contributes, by about 14%, to the overall cooling performance enhancement. Away from the inlet location of the rotating cylinders, thermal performance improvement of 12% is obtained. The entropy generation rises with higher hot wall velocity and higher horizontal distances of the rotating cylinders, while it is reduced with a higher magnetic field for non-rotating cylinders. The best configurations in terms of cooling performance provide 8.7% and 34.2% enhancements for non-rotating and rotating cylinders compared with the reference case of (Rew, VR, Ha, Mx) = (0, 0, 0, 0), while entropy generation becomes 1% and 15% higher.
Three-Dimensional Unsteady Mixed Convection Flow of Non-Newtonian Nanofluid with Consideration of Retardation Time Effects
Authors: Ayadi Badreddine , Ghachem Kaouther , Al-Khaled Kamel , Khan Sami Ullah , Kriaa Karim , Maatki Chemseddine , Zahi Nesrine , Kolsi Lioua
Published: April 2023

The advances in nanotechnology led to the development of new kinds of engineered fluids called nanofluids. Nanofluids have several industrial and engineering applications, such as solar energy systems, heat conduction processes, nuclear systems, chemical processes, etc. The motivation of the present work is to analyze and explore the thermal and dynamic behaviors of a non-Newtonian fluid flow under time retardation effects. The flow is unsteady and caused by a bidirectional, periodically moving surface. In addition to the convective heat transfer and fluid flow, the radiation and chemical reactions have also been considered. The governing equations are established based on the modified Cattaneo–Christov heat flux formulation. It was found that the bidirectional velocities oscillate periodically, and that the magnitude of the oscillation increases with the retardation time. Higher temperatures occur when the porosity parameter is increased, and lower concentrations are encountered for higher values of the concentration relaxation parameter. The current results can be applied in thermal systems, heat transfer enhancement, chemical synthesis, solar systems, power generation, medical applications, the automotive industry, process industries, refrigeration, etc.
Optimal Multi-Level Fault-Tolerant Resolving Sets of Circulant Graph C(n : 1, 2)
Authors: Saha Laxman , Das Bapan , Tiwary Kalishankar , Das Kinkar Chandra , Shang Yilun
Published: April 2023

Let G=(V(G),E(G)) be a simple connected unweighted graph. A set R⊂V(G) is called a fault-tolerant resolving set with the tolerance level k if the cardinality of the set Sx,y={w∈R:d(w,x)≠d(w,y)} is at least k for every pair of distinct vertices x,y of G. A k-level metric dimension refers to the minimum size of a fault-tolerant resolving set with the tolerance level k. In this article, we calculate and determine the k-level metric dimension for the circulant graph C(n:1,2) for all possible values of k and n. The optimal fault-tolerant resolving sets with k tolerance are also delineated.
Thiolactones and Δ8,9-Pregnene Steroids from the Marine-Derived Fungus Meira sp. 1210CH-42 and Their α-Glucosidase Inhibitory Activity
Authors: Shin Hee Jae , Lee Min Ah , Lee Hwa-Sun , Heo Chang-Su
Published: April 2023

The fungal genus Meira was first reported in 2003 and has mostly been found on land. This is the first report of second metabolites from the marine-derived yeast-like fungus Meira sp. One new thiolactone (1), along with one revised thiolactone (2), two new Δ8,9-steroids (4, 5), and one known Δ8,9-steroid (3), were isolated from the Meira sp. 1210CH-42. Their structures were elucidated based on the comprehensive spectroscopic data analysis of 1D, 2D NMR, HR-ESIMS, ECD calculations, and the pyridine-induced deshielding effect. The structure of 5 was confirmed by oxidation of 4 to semisynthetic 5. In the α-glucosidase inhibition assay, compounds 2–4 showed potent in vitro inhibitory activity with IC50 values of 148.4, 279.7, and 86.0 μM, respectively. Compounds 2–4 exhibited superior activity as compared to acarbose (IC50 = 418.9 μM).
Epidural Abscesses as a Complication of Interleukin-6 Inhibitor and Dexamethasone Treatment in a Patient with COVID-19 Pneumonia: A Case Report
Authors: Ģībietis Valdis
Published: April 2023

A 66-year-old female patient was hospitalized with severe COVID-19 pneumonia, which led to hypoxia requiring oxygen support with high-flow nasal cannulae. She received anti-inflammatory treatment with a 10-day dexamethasone 6 mg PO course and a single infusion of IL-6 monoclonal antibody tocilizumab 640 mg IV. Treatment led to gradual reduction of oxygen support. However, on Day 10, she was found to have Staphylococcus aureus bacteremia with epidural, psoas, and paravertebral abscesses as the source. Targeted history taking revealed a dental procedure for periodontitis 4 weeks prior to hospitalization as the probable source. She received an 11-week antibiotic treatment, which led to resolution of the abscesses. This case report highlights the importance of individual infection risk assessment before the initiation of immunosuppressive treatment for COVID-19 pneumonia.
Valgus Arthritic Knee Responds Better to Conservative Treatment than the Varus Arthritic Knee
Authors: Lee SeungHoon , Choi YunSeong , Lee JaeHyuk , Lee HeeDong , Yoon JungRo , Chang ChongBum
Published: April 2023

Background and Objectives: Clinically, it is beneficial to determine the knee osteoarthritis (OA) subtype that responds well to conservative treatments. Therefore, this study aimed to determine the differences between varus and valgus arthritic knees in the response to conservative treatment. We hypothesized that valgus arthritic knees would respond better to conservative treatment than varus arthritic knees. Materials and Methods: Medical records of 834 patients who received knee OA treatment were retrospectively reviewed. Patients with Kellgren–Lawrence grades III and IV were divided into two groups according to knee alignment (varus arthritic knee, hip-knee-ankle angle [HKA] > 0° or valgus arthritic knee, HKA < 0°). The Kaplan–Meier curve with total knee arthroplasty (TKA) as an endpoint was used to compare the survival probability between varus and valgus arthritic knees at one, two, three, four, and five years after the first visit. A receiver operating characteristic (ROC) curve was used to compare the HKA thresholds for TKA between varus and valgus arthritic knees. Results: Valgus arthritic knees responded better to conservative treatment than varus arthritic knees. With TKA as an endpoint, the survival probabilities for varus and valgus arthritic knees were 24.2% and 61.4%, respectively, at the 5-year follow-up (p < 0.001). The thresholds of HKA for varus and valgus arthritic knees for TKA were 4.9° and −8.1°, respectively (varus: area under the ROC curve [AUC] = 0.704, 95% confidence interval [CI] 0.666–0.741, p < 0.001, sensitivity = 0.870, specificity = 0.524; valgus: AUC = 0.753, 95% CI 0.693–0.807, p < 0.001, sensitivity = 0.753, specificity = 0.786). Conclusions: Conservative treatment is more effective for valgus than for varus arthritic knees. This should be considered when explaining the prognosis of conservative treatment for knees with varus and valgus arthritis.
Strategies for Avoiding Typical Drug–Drug Interactions and Drug-Related Problems in Patients with Vascular Diseases
Authors: Schmelzer Klaus Peter , Liebetrau Dominik , Kämmerer Wolfgang , Meisinger Christine , Hyhlik-Dürr Alexander
Published: April 2023

Background and objectives: Drug–drug interactions and drug-related problems in patients with vascular diseases are common. To date, very few studies have focused on these important problems. The aim of the present study is to investigate the most common drug–drug interactions and DRPs in patients with vascular diseases. Materials and Methods: The medications of 1322 patients were reviewed manually in the time period from 11/2017 to 11/2018; the medications of 96 patients were entered into a clinical decision support system. Potential drug problems were identified, and a read-through consensus was reached between a clinical pharmacist and a vascular surgeon during the clinical curve visits; possible modifications were implemented. The focus was on additional dose adjustment and drug antagonization on drug interactions. Interactions were classified as contraindicated/high-risk combination (drugs must not be combined), clinically serious (interaction can be potentially life-threatening or have serious, possibly irreversible consequences), or potentially clinically relevant and moderate (interaction can lead to therapeutically relevant consequences). Results: A total of 111 interactions were observed. Of these, 6 contraindicated/high-risk combinations, 81 clinically serious interactions, and 24 potentially clinically relevant and moderate interactions were identified. Furthermore, 114 interventions were recorded and categorized. Discontinued use of the drug (36.0%) and drug dose adjustment (35.1%) were the most common interventions. Mostly, antibiotic therapy was continued unnecessarily (10/96; 10.4%), and the adjustment of the dosage to kidney function was overlooked in 40/96; 41.7% of the cases. In the most common cases, a dose reduction was not considered necessary. Here, unadjusted doses of antibiotics were found in 9/96, 9.3% of the cases. Notes for medical professionals summarized information that did not require direct intervention but rather increased attention on the part of the ward doctor. It was usually necessary to monitor laboratory parameters (49/96, 51.0%) or the patients for side effects (17/96, 17.7%), which were expected with the combinations used. Conclusions: This study could help identify problematic drug groups and develop prevention strategies for drug-related problems in patients with vascular diseases. A multidisciplinary collaboration between the different professional groups (clinical pharmacists and surgeons) might optimize the medication process. Collaborative care could have a positive impact on therapeutic outcomes and make drug therapy safer for patients with vascular diseases.
Interaction of Hyaluronan Acid with Some Proteins in Aqueous Solution as Studied by NMR
Authors: Melnikova Daria , Khisravashirova Catherine , Smotrina Tatiana , Skirda Vladimir
Published: April 2023

According to actual literature data, hyaluronic acid (HA) that is presented in the extracellular matrix can interact with proteins and thereby affect several important functions of the cell membrane. The purpose of this work was to reveal the features of the interaction of HA with proteins using the PFG NMR method by sampling two systems: aqueous solutions of HA with bovine serum albumin (BSA) and aqueous solutions of HA with hen egg-white lysozyme (HEWL). It was found that the presence of BSA in the HA aqueous solution initiates a certain additional mechanism; as a result, the population of HA molecules in the gel structure increases to almost 100%. At the same time, for an aqueous solution of HA/HEWL, even in the range of low (0.01–0.2%) HEWL contents, strong signs of degradation (depolymerization) of some HA macromolecules were observed such that they lost the ability to form a gel. Moreover, lysozyme molecules form a strong complex with degraded HA molecules and lose their enzymatic function. Thus, the presence of HA molecules in the intercellular matrix, as well as in the state associated with the surface of the cell membrane, can, in addition to the known ones, perform one more important function: the function of protecting the cell membrane from the destructive action of lysozymes. The obtained results are important for understanding the mechanism and features of the interaction of extracellular matrix glycosaminoglycan with cell membrane proteins.
Aliquots of MIL-140 and Graphene in Smart PNIPAM Mixed Hydrogels: A Nanoenvironment for a More Eco-Friendly Treatment of NaCl and Humic Acid Mixtures by Membrane Distillation
Authors: Di Luca Giuseppe , Chen Guining , Jin Wanqin , Gugliuzza Annarosa
Published: April 2023

The problem of water scarcity is already serious and risks becoming dramatic in terms of human health as well as environmental safety. Recovery of freshwater by means of eco-friendly technologies is an urgent matter. Membrane distillation (MD) is an accredited green operation for water purification, but a viable and sustainable solution to the problem needs to be concerned with every step of the process, including managed amounts of materials, membrane fabrication procedures, and cleaning practices. Once it is established that MD technology is sustainable, a good strategy would also be concerned with the choice of managing low amounts of functional materials for membrane manufacturing. These materials are to be rearranged in interfaces so as to generate nanoenvironments wherein local events, conceived to be crucial for the success and sustainability of the separation, can take place without endangering the ecosystem. In this work, discrete and random supramolecular complexes based on smart poly(N-isopropyl acrylamide) (PNIPAM) mixed hydrogels with aliquots of ZrO(O2C-C10H6-CO2) (MIL-140) and graphene have been produced on a polyvinylidene fluoride (PVDF) sublayer and have been proven to enhance the performance of PVDF membranes for MD operations. Two-dimensional materials have been adhered to the membrane surface through combined wet solvent (WS) and layer-by-layer (LbL) spray deposition without requiring further subnanometer-scale size adjustment. The creation of a dual responsive nanoenvironment has enabled the cooperative events needed for water purification. According to the MD’s rules, a permanent hydrophobic state of the hydrogels together with a great ability of 2D materials to assist water vapor diffusion through the membranes has been targeted. The chance to switch the density of charge at the membrane–aqueous solution interface has further allowed for the choice of greener and more efficient self-cleaning procedures with a full recovery of the permeation properties of the engineered membranes. The experimental evidence of this work confirms the suitability of the proposed approach to obtain distinct effects on a future production of reusable water from hypersaline streams under somewhat soft working conditions and in full respect to environmental sustainability.
Mechanism of Extracting Germanium from Ge-Containing Solution with Tannins
Authors: Hong Yan , Di Haokai , Li Shiwei , Yang Kun , Zhang Libo
Published: April 2023

The process of germanium–tannin complex is the oldest form of technology for extracting germanium from Ge-containing solutions. This reaction mechanism is relatively controversial as it imposes restrictions on ideas and methods for reducing the amount of tannin. In this paper, using SEM, TEM, FT-IR, XPS, NMR, TOF-SIMS and UV diffuse reflectance spectroscopy for a deep analysis of germanium–tannin complex, the mechanism of extracting germanium from Ge-containing solutions with tannins is investigated. The results show that the theoretical tannin complex mass is 30 times that of tannin mass, and the complex rate reaches 98.84%. The changes of -OH stretching band in FT-IR spectra, the emergence of C3H3GeO7, C2H3GeO6, and C8H7GeO7 in TOF-SIMS images, and the shift of Ge and O banding energy in XPS detail spectra provided definitive evidence for the germanium–tannin complex process, highlighting that the formed complexes of tannins with germanium involve six coordinate Ge-O bonds, which are obtained through orthophenol hydroxyl groups in tannins reacting with Ge4+. Furthermore, the complex mode of germanium–tannins is layer polymerization, which finally forms an agglomeration of complex flocs. The findings of this research is innovative, and can have a profound impact on the future introduction of various methods to reduce the mass of tannins.
The Corrosion Behavior in Different Environments of Austenitic Stainless Steels Subjected to Thermochemical Surface Treatments at Low Temperatures: An Overview
Authors: Borgioli Francesca
Published: April 2023

Low-temperature thermochemical treatments are particularly suitable for use in the surface hardening of austenitic stainless steels without impairing their corrosion resistance. In fact, when using treatment media rich in nitrogen and/or carbon at relatively low temperatures (<450 °C for nitriding, <550 °C for carburizing), it is possible to inhibit the formation of chromium compounds and obtain modified surface layers that consist mainly of a supersaturated solid solution, known as expanded austenite or S-phase. It has been observed that this hard phase allows the enhancement of corrosion resistance in chloride-ion-containing solutions, while the results were contradictory for chloride-free acidic solutions. This overview aims to discuss the corrosion behavior of low-temperature-treated austenitic stainless steels, taking into account the different microstructures and phase compositions of the modified layers, as well as the different test environments and conditions. In particular, the corrosion behavior in both chloride-ion-containing solutions and chloride-free solutions (sulfuric acid, sulfate and borate solutions) is discussed. The analysis of the international literature presents evidence that the microstructure and phase composition of the modified layers have key roles in corrosion resistance, especially in sulfuric acid solutions.
Effects of Alloying Elements on the Solution and Diffusion of Oxygen at Iron Grain Boundary Investigated by First-Principles Study
Authors: Zhang Jingdan , Li Xiaolin , Lei Yawei , Zhang Yange , Li Xiangyan , Xu Yichun , Wu Xuebang , Yang Junfeng , Li Bingsheng , Liu Changsong
Published: April 2023

The effects of alloying elements (Si, Cr, Mo) on the solution and diffusion of oxygen (O) atoms at the grain boundary of iron (Fe) Σ5(310)/[001] are investigated by the simulations of ab initio density functional theory (DFT). It is found that Si, Mo and Cr prefer to segregate to the grain boundary, and further affect the solution and diffusion of O atoms at Fe grain boundaries. The segregated Cr promotes the solution of O, while Si and Mo inhibit the solution of O at the grain boundary. Meanwhile, Cr and Si accelerate the diffusion of O, and Mo retards the diffusion of O in the grain boundary. Further analysis indicates that the effects are closely related to the interactions between the alloying elements and O atoms, which are determined by the competition between the distortion of local structure and the charge transfer between local atoms. Finally, the effects of alloying elements on the O concentration distribution near the grain boundary are explored by employing the Langmuir–McLean models. This work not only provides insights into the effects of alloying elements on the solution and diffusion of O at grain boundaries, but also provides parameters of the atomic interactions for the initial oxidation simulation on a large scale, which relates to the growth of oxide in polycrystalline systems with various grain sizes at experimental temperatures.