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Data on the diffusion and migration characteristics of rare earth metal ions in fluoride molten salt systems are crucial for optimizing the electrolytic preparation of rare earth metals and alloys. This study investigated the solubility, conductivity, and density of the (LiF-CaF2)eut. system saturated with Nd₂O₃ using the isothermal saturation method, conductivity cell constant variation, and the Archimedes method, respectively. Employing the Hittorf method's principles, a three-compartment electrolyzer was designed to determine the mobility number of dissolved Nd* (III) ions in the saturated (LiF-CaF2)eut.-Nd2O3 system. The radial distribution function was computed via ab initio molecular dynamics, and the self-diffusion coefficient of ions in the system was analyzed. Utilizing the Nernst–Einstein equation, the diffusion coefficient of Nd* (III) ions was calculated. The solubility, conductivity, and density of the saturated (LiF-CaF2)eut.-Nd2O3 system exhibit linear variation within 1173–1473 K. The mobility number of solvated Nd* (III) ions increases linearly with temperature, displaying nonlinear variation with potential within 3.5–4.5 V, and gradually decreases after reaching a maximum of 4.0–4.25 V. The radial distribution function reveals the highest diffusion and mobility barriers for Nd* (III) ions, with solvated O* (II) ions presenting the most significant hindrance. The Nd* (III) ion diffusion coefficients linearly increase with temperature (1123–1373 K) under specific potential conditions (3.5–4.5 V) but exhibit nonlinear changes with potential (3.5–4.5 V) under fixed temperature conditions (1123–1373 K), then decrease after peaking within 4.0–4.5 V. The diffusion coefficients of Nd* (III) ions are sensitive to potential changes. [ABSTRACT FROM AUTHOR]

Hydrogen is currently used as an energy source, and there are already vehicles (cars and buses) that run on hydrogen in our public spaces. Additionally, in the chemical, petrochemical and nuclear industries, many devices come into contact with hydrogen. This short review covers a broad range of topics related to HE, i.e., the main hydrogen charging methods, aspects related to hydrogen diffusion in metallic materials, and the main models of hydrogen-induced material degradation and their assumptions, and discusses the influence of hydrogen on the properties and degradation of different metallic materials used in the industry based on the latest research results. This review focuses on the four primary groups of materials used in hydrogen devices, i.e., steels, aluminium alloys, nickel alloys and titanium alloys. The basic information on the influence of hydrogen on the structure and properties, mainly elongation, hardness and tensile strength, of these metallic material groups are presented. The influence of the method of hydrogen charging and the time of hydrogen saturation, as well as the effect of structure, on the content of hydrogen in the material, as well as on such material properties as hardness, tensile strength, and fatigue strength, is shown. [ABSTRACT FROM AUTHOR]

A reaction–diffusion susceptible–infectious–susceptible disease model with advection, vital dynamics (birth–death effects), and a standard incidence infection mechanism is carefully analyzed. Two distinct diffusion coefficients for the susceptible and infected populations are considered. The Lie symmetries and closed-form solutions for the RDA–SIS disease model are established. The derived solution allows to study dynamics of disease transmission. Our simulation clearly illustrates the evolution dynamics of the model by using the values of parameters from academic sources. A sensitivity analysis is performed, offering valuable perspectives that could inform future disease management policies. [ABSTRACT FROM AUTHOR]

Crystallization-induced blockages in tunnel drainage systems pose significant challenges to their functionality and longevity. To address this issue, this study proposes a novel adaptive drainage pipe designed to prevent crystallization. By constructing an indoor experimental model for anti-crystallization tests, combined with scanning electron microscopy (SEM) and molecular dynamics simulations, this study investigates the mechanism and effectiveness of the proposed system. The findings reveal that flexible PVC pipes in dynamic flow and expansion states significantly reduce crystallization compared to conventional PVC pipes. Among tested materials, EVA and TPU demonstrate superior crystallization resistance, with EVA exhibiting the lowest crystallization accumulation (7.13 g/m). Molecular dynamics simulations further elucidated the influence of material properties on the diffusion coefficient and binding energy of calcium carbonate crystals, with EVA showing the lowest binding energy with calcium carbonate at 135.11 kcal/mol, ultimately confirming EVA as the optimal material for crystallization prevention. These results offer new strategies and valuable references for managing crystallization in tunnel drainage systems. [ABSTRACT FROM AUTHOR]

When heterogeneous joints are created, problems with the formation of intermetallic phases arise. There are various ways to reduce the formation of intermetallics. One of the ways that is discussed in this article is to use a suitable interlayer of appropriate thickness when forming the joint. A too-thin interlayer does not protect against the formation of brittle intermetallic phases. On the other hand, a too-thick interlayer increases the heterogeneity of the joint and, thus, decreases its useful properties. Within this paper, the formation of diffusion joints between the base material (AISI 304 steel, duplex steel, AISI 316L steel, or titanium grade 2) and the 0.2 mm thick intermediate layer (nickel or vanadium) was studied. Initial diffusion joints were prepared in a Gleeble 3500 machine, and samples for the study of diffusion kinetics were subsequently heat-treated in a vacuum furnace. The result of the research was the determination of specific diffusion parameters of nickel and vanadium into all four tested base materials. The initial diffusion depth (simple heating to the target temperature without holding at this temperature) of nickel was 4.46 µm into duplex steel and 5.48 µm into Ti Gr. 2 at 950 °C. At the same temperature, the initial diffusion depth of vanadium was 14.54 µm into duplex steel and 14.32 µm into Ti Gr. 2. In addition, general equations for the calculation of diffusion coefficients for the mentioned materials in the temperature range of 850 to 1150 °C were established. [ABSTRACT FROM AUTHOR]

This study proposes to analyze the chemical composition and the hydration kinetics of soryz (Sorghum Oryzoidum) grains in water at different temperatures (20, 30, 40, 45, 50, and 60 °C). The analyzed soryz variety presented a starch content of over 70%, and protein of about 10%, with an important supply of amino acids and a good source of K, Mg, and Ca. The efficiency of the hydration process was studied by applying Peleg's model, which predicted water absorption by soryz under the experimental conditions. With increasing temperature, the Peleg's rate constant, K1, and capacity constant, K2, decreased from 251 to 239 min/% and 2.52 to 2.49%−1, respectively. Fick's second law was used to calculate the diffusion coefficient values. These values increased linearly with the temperature increase from 20 to 50 °C, ranging from 0.65 × 10−11 to 1.54 × 10−11 m2/s. They decreased with the subsequent rise in the environmental temperature up to 60 °C, 1.49 × 10−11 m2/s. The activation energy of soryz grains was 23.86 kJ/mol. The Arrhenius equation satisfactorily described the temperature dependence of the diffusivity coefficient. The results regarding the hydration kinetics of the soryz grains obtained are decisive in preparing this cereal for further use in meat analog manufacture. [ABSTRACT FROM AUTHOR]

In this work, we propose a comprehensive experimental study of the diffusion of isoniazid, one of the first-line anti-tuberculosis drugs, in combination with another drug (ethambutol dihydrochloride) and with different cyclodextrins as carrier molecules, for facilitated transport and enhanced solubility. For that, ternary mutual diffusion coefficients measured by the Taylor dispersion method (D11, D22, D12, and D21) are determined for aqueous solutions containing isoniazid and different cyclodextrins (that is, α–CD, β–CD, and γ–CD) at 298.15 K. From the significant effect of the presence of these carbohydrates on the diffusion of this drug, interactions between these components are suggested. Support for this arose from models, which shows that these effects may be due to the formation of 1:1 (CDs:isoniazid) complexes. [ABSTRACT FROM AUTHOR]

CO2 flooding plays a significant part in enhancing oil recovery and is essential to achieving CCUS (Carbon Capture, Utilization, and Storage). This study aims to understand the fundamental theory of CO2 dissolving and diffusing into crude oil and how these processes vary under reasonable reservoir conditions. In this paper, we primarily use molecular dynamics simulation to construct a multi-component crude oil model with 17 hydrocarbons, which is on the basis of a component analysis of oil samples through laboratory experiments. Then, the CO2 dissolving capacity of the multi-component crude was quantitatively characterized and the impacts of external conditions—including temperature and pressure—on the motion of the CO2 dissolution and diffusion coefficients were systematically investigated. Finally, the swelling behavior of mixed CO2–crude oil was analyzed and the diffusion coefficients were predicted; furthermore, the levels of CO2 impacting the oil's mobility were analyzed. Results showed that temperature stimulation intensified molecular thermal motion and increased the voids between the alkane molecules, promoting the rapid dissolution and diffusion of CO2. This caused the crude oil to swell and reduced its viscosity, further improving the mobility of the crude oil. As the pressure increased, the voids between the internal and external potential energy of the crude oil models became wider, facilitating the dissolution of CO2. However, when subjected to external compression, the CO2 molecules' diffusing progress within the oil samples was significantly limited, even diverging to zero, which inhabited the improvement in oil mobility. This study provides some meaningful insights into the effect of CO2 on improving molecular-scale mobility, providing theoretical guidance for subsequent investigations into CO2–crude oil mixtures' complicated and detailed behavior. [ABSTRACT FROM AUTHOR]

In lithium–polymer batteries, the electrolyte is an essential component that plays a crucial role in ion transport and has a substantial impact on the battery's overall performance, stability, and efficiency. This article presents a detailed study on developing nanostructured composite polymer electrolytes (NCPEs), prepared using the solvent casting technique. The materials selected for this investigation include poly(vinyl chloride) (PVC) as the host polymer, lithium bromide (LiBr) as the salt, and silica (SiO2) as the nanofiller. The addition of nano-SiO2 dramatically enhanced the ionic conductivity of the electrolytes, with the highest value of 6.2 × 10−5 Scm−1 observed for the sample containing 7.5 wt% nano-SiO2. This improvement is attributed to an increased amorphicity resulting from the interactions between the polymer, salt, and filler components. A structural analysis of the prepared NCPEs using X-ray diffraction revealed the presence of both crystalline and amorphous phases, further validating the enhanced ionic transport. Additionally, the thermal stability of the NCPEs was found to be excellent, withstanding temperatures up to 334 °C, thereby reinforcing their potential application in lithium–polymer batteries. This work explores the electrochemical performance of a fabricated lithium-ion-conducting primary electrochemical cell (Zn + ZnSO4·7H2O|PVC: LiBr: SiO2|PbO2 + V2O5), which demonstrated an open circuit voltage of 2.15 V. The discharge characteristics of the fabricated cell were thoroughly studied, showcasing the promising potential of these NCPEs. With the support of superior morphological and electrical properties, as-prepared electrolytes offer an effective pathway for future advancements in lithium–polymer battery technology, making them a highly viable candidate for enhanced energy storage solutions. [ABSTRACT FROM AUTHOR]

Climate change poses a significant threat to the durability of reinforced concrete (RC) bridges, which are particularly vulnerable to chloride-induced corrosion of steel reinforcements. The main problem for the current research is the increase in the projected maximum temperature values, especially for the high emission scenario in the future because of climate change, applied to the upper part of the RC bridge deck made of geopolymer concrete (GPC) composed of 50% fly ash and 50% slag. This will reduce the corrosion initiation time and the safety and durability of the RC bridge deck structure. Despite extensive research on chloride-induced corrosion, there is a scientific gap in understanding how future climate variations will influence the rate of corrosion in RC bridges. Specifically, comprehensive studies assessing the effect of maximum temperature on the probability of the corrosion initiation process in RC bridge decks made of GPC exposed to chloride environments are lacking. This study used the Monte Carlo simulation method to assess the probability of corrosion initiation (PCI) under various future climate scenarios for Toronto City, Canada. This research examines the impact of the maximum temperature and relative humidity on the diffusion coefficient of chloride ions in concrete. It assesses the PCI for different concrete cover thicknesses in RC decks made of geopolymer concrete composed of 50% fly ash and 50% slag over specified periods, dealing with the sensitivity analysis for this parameter among different parameters defined in the performance function. The results indicate a substantial increase in the PCI for a 40 mm concrete cover compared with a 50 mm cover in various years. Furthermore, maximum temperatures ranging from 40 °C to 45 °C significantly increase the PCI compared with temperatures between 25 °C and 35 °C for a 50 mm concrete cover. Finally, polynomial functions have been deduced to investigate the reliability index and PCI as a function of various coefficients of variations for mean concrete covers made of GPC at various maximum temperature values in different years. These findings provide important information for the design and maintenance of RC structures, ensuring their longevity in the face of climate change. [ABSTRACT FROM AUTHOR]

The self-diffusion coefficients of carbonaceous fuels in a supercritical CO2 environment provide transport information that can help us understand the Allam Cycle mechanism at a high pressure of 300 atm. The diffusion coefficients of pure CO2 and binary CO2/CH4 and CO2/C2H6 at high temperatures (500 K~2000 K) and high pressures (100 atm~1000 atm) are determined by molecular dynamics simulations in this study. Increasing the temperature leads to an increase in the diffusion coefficient, and increasing the pressure leads to a decrease in the diffusion coefficients for both methane and ethane. The diffusion coefficient of methane at 300 atm is approximately 0.012 cm2/s at 1000 K and 0.032 cm2/s at 1500 K. The diffusion coefficient of ethane at 300 atm is approximately 0.016 cm2/s at 1000 K and 0.045 cm2/s at 1500 K. The understanding of diffusion coefficients potentially leads to the reduction in fuel consumption and minimization of greenhouse gas emissions in the Allam Cycle. [ABSTRACT FROM AUTHOR]

Dependency on fossil fuels for global energy demand has led to an increase in the concentration of CO2 in the atmosphere, thereby contributing to environmental challenges such as climate change, rise in atmospheric temperature, etc. Since the major contributions of CO2 emissions are from industries, capturing CO2 from post-combustion flue gas has become the focus of many research communities. As such, membrane-based carbon capture and storage (CCS) is an important pathway for controlling CO2 emissions. However, performance validation for membrane separation is required to find the best composite material with a high diffusion rate. Hence, the objectives of this research included determining the performance of the nanocomposite membranes comprising polyether-block-amide (PEBAX) as a matrix and carbon nanotube (CNT) and armchair graphene as reinforcements as well as obtaining the flue gas diffusion rate using molecular dynamic (MD) analysis. Two different composition ratios of the flue gas with an equal ratio (1:1) and an actual post-combustion ratio were developed. The molecular dynamic simulation results obtained from LAMMPS and OVITO determined that graphene-based nanocomposites were better suited for the diffusion of the CO2/N2 and CO2/N2/O2 flue gas compositions, and CNT-reinforced nanocomposite membranes performed better for the CO2/O2 flue gas blend. [ABSTRACT FROM AUTHOR]

The electroanalytical behavior of SnSx (x = 1, 2) encapsulated into a carbon phase was studied using the galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). These techniques are widely utilized in battery systems to investigate the diffusion of alkali metal cations in anode and cathode materials depending on the concentration of ions in the host material. Here, we report different calculation methods showing how the applied model affects the derived diffusion coefficient. The calculated value of the apparent chemical diffusion coefficient of sodium ions ( D N a + ) is in the range of 1 × 10−10 to 1 × 10−15 cm2/s depending on the technique, mathematical protocol, geometry of the electrode material, and applied potential. [ABSTRACT FROM AUTHOR]

Reinforced concrete structures are prone to the corrosion of steel bars when exposed to chloride-rich environments, which can severely impact their durability. To address this issue, a comprehensive understanding of the factors influencing chloride ion diffusion in concrete is essential. This paper provides a summary of recent domestic and foreign research on chloride ion transport in concrete, focusing on six key factors: water–binder ratio, additive content, crack width, ambient temperature, relative humidity, and dry–wet cycles. The findings show that the diffusion coefficient of chloride ions in concrete increases with a higher water–binder ratio and decreases with increased additive content. Additionally, wider cracks result in a greater diffusion of chloride ions. The permeability resistance of concrete to chloride ions decreases with rising temperature and humidity, and dry–wet cycles further accelerate the diffusion of chloride ions. The article concludes by discussing various anti-corrosion measures, such as the use of corrosion inhibitors, surface coatings, and electrochemical treatments, to ensure the longevity of the structure. Finally, directions for future research are proposed. [ABSTRACT FROM AUTHOR]

Simple Summary: The human brain is still an enigma, and the relation between its physiology and function is still poorly understood. Advancements in quantum computations led to the hypothesis that neurons can also exercise quantum coherence, and a model for neuronal activity with quantum correlations appearing from the nuclei entanglement was proposed. However, whether such correlations can survive in a high-temperature biological environment to propagate through a neural network is still an open question. In this work, we examine one of the first steps in this process, the diffusion of neurotransmitters through the synaptic cleft, and show that, at least at this step, the correlations are persistent. Our results do not confirm the "quantum brain" hypothesis, but at least, they do not disprove it either, with studies on further steps needed. The "quantum brain" proposal can revolutionize our understanding of cognition if proven valid. The core of the most common "quantum brain" mechanism is the appearance of correlated neuron triggering induced by quantum correlations between ions. In this work, we examine the preservation of the correlations created in the pre-synaptic neurons through the transfer of neurotransmitters across the synaptic cleft, a critical ingredient for the validity of the "quantum brain" hypothesis. We simulated the transport of two neurotransmitters at two different clefts, with the only assumption that they start simultaneously, and determined the difference in their first passage times. We show that in physiological conditions, the correlations are persistent even if the parameters of the two neurons are different. [ABSTRACT FROM AUTHOR]

The influence of grain size on the corrosion behavior of pure aluminum and the defect density and diffusion coefficient of surface passive films were investigated using electron backscatter diffraction (EBSD) and electrochemical testing techniques, based on the point defect model (PDM). Samples with three different grain sizes (23 ± 11, 134 ± 52, and 462 ± 203 μm) were obtained by annealing at different temperatures and times. The polarization curves and electrochemical impedance spectroscopy results for the pure aluminum in the 3.5% NaCl solution showed that with decreasing grain size, the corrosion current (icorr) decreased monotonously, giving rise to a noble corrosion potential and a large polarization resistance. The Motte–Schottky results showed that the passive films that formed on pure aluminum with fine grains of 23 ± 11 μm had a low density (3.82 × 1020 cm−3) of point defects, such as oxygen vacancies and/or metal interstitials, and a small diffusion coefficient (1.94 × 10−17 cm2/s). The influence of grain size on corrosion resistance was discussed. This work demonstrated that grain refinement could be an effective approach to achieving high corrosion resistance of passive metals. [ABSTRACT FROM AUTHOR]

Diffusion processes in operations involving polymeric materials are of significant interest. Determining experimental values for diffusion coefficients is often challenging. Estimating these coefficients in concentrated polymer solution, polymer films, and membranes relies on experimental tests where the polymer is brought into contact with certain components/solvents. The diffusion coefficient values depend on the diffusion type, which is affected mainly by the nature of the polymer, concentration, and temperature. The literature presents an extensive amount of information regarding the diffusion phenomenon. This paper makes a particular contribution by showing how experimental data obtained from different applications can be processed to determine diffusion coefficients. The manuscript addresses some aspects regarding solvent diffusion in polymers, and illustrates how to determine the diffusion coefficients from experimental data. For specific cases of diffusion, several models for the predictive estimation of diffusion coefficients are also presented. Polymer–solvent systems such as polyvinyl alcohol (PVA)–water, cellulose acetate (CA)–tetrahydrofuran (THF) and cellulose triacetate (CTA)–dichloromethane (DCM) are investigated, with their diffusion mechanisms influenced by changes in structure caused by variations in concentration and temperature. The experimental data obtained through a gravitational technique allow for the highlighting of the diffusion mechanism and the selection of an appropriate mathematical model. A change in the structure of the polymer during the experiment leads to diffusion anomalies. Modeling the experimental data yielded diffusion coefficient values that vary based on the type of system investigated, composition and temperature. Thus, in the case of the CTA-DCM system, the diffusion coefficient at 303 K, at various concentration values, is in the range of 4.5 and 8·10−11 m2/s; for the PVA-H2O system, D = 4.1·10−12 m2/s at 303 K, and D = 6.5·10−12 m2/s at 333 K; while for the CA-THF system, the solvent–polymer diffusion coefficient has a value of 2.5∙10−12 m2/s at 303 K, and D = 1.75∙10−11 m2/s at 323 K. Mathematical models can be useful in studies regarding the drying of polymer films with complex structures, providing knowledge for designing or selecting suitable equipment. [ABSTRACT FROM AUTHOR]

CO2-enhanced coalbed methane recovery (CO2-ECBM) has been demonstrated as an effective enhanced oil recovery (EOR) technique that enhances the production of coalbed methane (CBM) while achieving the goal of CO2 sequestration. In this paper, the grand canonical Monte Carlo simulation is used to investigate the dynamic mechanism of CO2-ECBM in anthracite pores. First, an anthracite pore containing both organic and inorganic matter was constructed, and the adsorption and diffusion characteristics of CO2 and CH4 in the coal pores under different temperature and pressure conditions were studied by molecular dynamics (MD) simulations. The results indicate that the interaction energy of coal molecules with CO2 and CH4 is positively associated with pressure but negatively associated with temperature. At 307.15 K and 101.35 kPa, the interaction energies of coal adsorption of single-component CO2 and CH4 are −1273.92 kJ·mol−1 and −761.53 kJ·mol−1, respectively. The interaction energy between anthracite molecules and CO2 is significantly higher compared to CH4, indicating that coal has a greater adsorption capacity for CO2 than for CH4. Furthermore, the distribution characteristics of gas in the pores before and after injection indicate that CO2 mainly adsorbs and displaces CH4 by occupying adsorption sites. Under identical conditions, the diffusion coefficient of CH4 surpasses that of CO2. Additionally, the growth rate of the CH4 diffusion coefficient as the temperature increases is higher than that of CO2, which indicates that CO2-ECBM is applicable to high-temperature coal seams. The presence of oxygen functional groups in anthracite molecules greatly influences the distribution of gas molecules within the pores of coal. The hydroxyl group significantly influences the adsorption of both CH4 and CO2, while the ether group has a propensity to impact CH4 adsorption, and the carbonyl group is inclined to influence CO2 adsorption. The research findings are expected to provide technical support for the effective promotion of CO2-ECBM technology. [ABSTRACT FROM AUTHOR]

A squaramide-based organocatalyst for asymmetric Michael reactions has been tested as a chiral solvating agent (CSA) for 26 carboxylic acids and camphorsulfonic acid, encompassing amino acid derivatives, mandelic acid, as well as some of its analogs, propionic acids like profens (ketoprofen and ibuprofen), butanoic acids and others. In many cases remarkably high enantiodifferentiations at 1H, 13C and 19F nuclei were observed. The interaction likely involves a proton transfer from the acidic substrates to the tertiary amine sites of the organocatalyst, thus allowing for pre-solubilization of the organocatalyst (when a chloroform solution of the substrate is employed) or the simultaneous solubilization of both the catalyst and the substrate. DOSY experiments were employed to evaluate whether the catalyst–substrate ionic adduct was a tight one or not. ROESY experiments were employed to investigate the role of the squaramide unit in the adduct formation. A mechanism of interaction was proposed in accordance with the literature data. [ABSTRACT FROM AUTHOR]

In this research, the diffusion behaviors within the Ti-Fe-Cr ternary system were examined at the temperatures of 1273 K and 1373 K through the diffusion couple technique. This study led to the determination of both ternary inter-diffusion and impurity diffusion coefficients in the body-centered cubic (bcc) phase for the Ti-Fe-Cr alloy, utilizing the Whittle–Green and Hall methods. The statistics show that the average diffusion coefficients D ˜ F e F e T i and D ˜ C r C r T i measured at 1273 K were 1.34 × 10−12 and 3.66 × 10−13, respectively. At 1373 K, the average values of D ˜ F e F e T i and D ˜ C r C r T i were 4.89 × 10−12 and 1.43 × 10−12. By adopting the CALPHAD method, a self-consistent database for atomic mobility in the bcc phase of the Ti-Fe-Cr system was established. This database underwent refinement by comparing the newly acquired diffusion coefficients with data from the existing literature. Diffusion simulations for the diffusion couples were performed, drawing on the established database. The error between the simulated diffusion coefficient and the experimental measurement data is within 15%, and the simulated data of the component distance distribution and diffusion path are in good agreement with the experimental data. The simulations generated results that aligned well with the observed experimental diffusion characteristics, thereby affirming the reliability and accuracy of the database. [ABSTRACT FROM AUTHOR]

Comprehending the water absorption process inherent to coal, including the associated spatial distribution patterns of water, proves indispensable in the design and evaluation of coal pillar dams in underground water reservoirs. To better understand this process, a series of NMR (nuclear magnetic resonance) tests were carried out on cylindrically shaped coal samples immersed in water for varying durations, with the upper and lower surfaces of the samples sealed. A method involving image digital processing and finite element simulation was used to quantitatively characterise the water absorption process, as well as the spatial distribution of water in the samples. The results showed that NMR imaging colour brightness differences were positively correlated with water content and that the wetted ring gradually increased in width as the water immersion time increased. The expectation and sum of squared deviations of the pixel greyscale values of the NMR images, which were used to characterise the water saturation and spatial distribution of the coal samples, represented positive and negative exponential functions of the water immersion time, respectively. This indicated that the water saturation gradually increased and became more uniformly distributed. Furthermore, based on the set threshold value of the target variable rate of change, the limiting expectation of the pixel greyscale values was obtained, and the limiting water absorption time of the coal sample was predicted. The water diffusion equation was then used to characterise the water absorption process of the coal samples, and a water diffusion model was developed to accurately obtain the wet ring boundary data. A reasonable value of the diffusion coefficient was determined by comparing and correcting the results of the numerical simulation and physical experiments with full consideration of the non-homogeneity of the numerical model. This water diffusion model can better characterise the water transport phenomena in the macroscopic barrier zone of coal pillar dams. Finally, the application prospects in terms of practical engineering were investigated. [ABSTRACT FROM AUTHOR]

Understanding electrochemical reactions at the surface of electrodes requires the accurate calculation of key parameters—the transfer coefficient (α), diffusion coefficient (D0), and heterogeneous electron transfer rate constant (k0). The choice of method to calculate these parameters requires careful consideration based on the nature of the electrochemical reaction. In this study, we conducted the cyclic voltammetry of paracetamol to calculate the values of these parameters using different methods and present a comparative analysis. Our results demonstrate that the Ep − Ep/2 equation for α and the modified Randles–Ševčík equation for D0 is particularly effective for the calculations of these two parameters. The Kochi and Gileadi methods are reliable alternatives for the calculation of k0. Nicholson and Shain's method using the equation k0 = Ψ(πnD0Fν/RT)1/2 gives the overestimated values of k0. However, the value of k0 calculated using the plot of ν−1/2 versus Ψ (from the Nicholson and Shain equation, where ν is scan rate) agrees well with the values calculated from the Kochi and Gilaedi methods. This study not only identifies optimal methodologies for quasi-reversible reactions but also contributes to a deeper understanding of electrochemical reactions involving complex electron transfer and coupled chemical reactions, which can be broadly applicable in various electrochemical studies. [ABSTRACT FROM AUTHOR]

Chloride transport within concrete is critical for the durability of reinforced concrete structures; however, its diffusion under the coupling action of temperature and humidity has not been fully comprehended. Therefore, in this work, the coupling effects of temperature, relative humidity, and mineral admixtures on chloride transport in concrete were investigated through experimental and numerical simulation work. The results show that the chloride diffusion coefficient decreases with the decreased temperature and growth of relative humidity; however, the chloride concentration on the concrete surface is increased with the growth of temperature and relative humidity. Moreover, compounding about 15% fly ash (FA) and 30% granulated ground blast furnace slag (GGBS) to replace the cement is the most beneficial for improving the antichloride capacity of concrete, considering also the strength. In addition, the numerical simulation considering the coupled effect of temperature and relative humidity of chloride transport in concrete has good agreement with that of experimental results. [ABSTRACT FROM AUTHOR]

To understand the cause of the high content of phosphorus in the North Chaohu Lake Catchment of China, the distribution of the total phosphorus in groundwater and the dissolution of rock phosphorus near Chaohu Lake were investigated, and a few interesting findings have been revealed. Firstly, four main processes affecting the groundwater quality in North Chaohu Lake Catchment were identified with the results of factor analysis, including anthropogenic activities and the dissolution of carbonate rocks, phosphorus, and fluorine-bearing minerals. Secondly, the dissolution of rock phosphorus can be well described using the one-dimensional diffusion equation, with a semi-infinite boundary condition, and the Langmuir kinetic equation. A relatively low ambient temperature (less than 25 °C) was probably responsible for the small diffusion coefficient compared to that of the previous studies. Thirdly, the high-potential maximum dissolution of rock phosphorus (Cmax) indicated that the dissolution of rock phosphorus could pose a risk to the ambient water body, and Cmax was found to be independent of the total rock phosphorus content. [ABSTRACT FROM AUTHOR]

Detailed knowledge of the flow characteristics, bubble movement, and mass transfer is a prerequisite for the proper design of multiphase bioreactors. Often, mechanistic spatiotemporal models and computational fluid dynamics, which intrinsically require computationally demanding analysis of local interfacial forces, are applied. Typically, such approaches use volumetric mass-transfer coefficient (kLa) models, which have demonstrated their predictive power in water systems. However, are the related results transferrable to multiphase fermentations with different physicochemical properties? This is crucial for the proper design of biotechnological processes. Accordingly, this study investigated a given set of mass transfer data to characterize the fermentation conditions. To prevent time-consuming simulations, computational efforts were reduced using a force balance stationary 0-dimension model. Therefore, a competing set of drag models covering different mechanistic assumptions could be evaluated. The simplified approach of disregarding fluid movement provided reliable results and outlined the need to identify the liquid diffusion coefficients in fermentation media. To predict the rising bubble velocities uB, the models considering the Morton number (Mo) showed superiority. The mass transfer coefficient kL was best described using the well-known Higbie approach. Taken together, the gas hold-up, specific surface area, and integral mass transfer could be accurately predicted. [ABSTRACT FROM AUTHOR]

The present work aims to analyse the influence of present-day burial depths of coal seams on the sorption properties towards CH4 and CO2, respectively. For medium-rank coals located in the southwestern area of the Upper Silesian Coal Basin (USCB), the gravimetric sorption measurements were carried out with pure gases at a temperature of 30 °C. The variability of CO2/CH4 exchange sorption and diffusivity ratios was determined. It was revealed that in coal seams located at a depth above 700 m, for which the sorption exchange ratio was the greatest, the process of CO2 injection for permanent storage was more beneficial. In the coal seams lying deeper than 700 m with a lower CO2/CH4 sorption ratio, the CH4 displacement induced by the injection of CO2 (CO2-ECBM recovery) became more favourable. [ABSTRACT FROM AUTHOR]

Lithium–titanium–sulfur cathodes have gained attention because of their unique properties and have been studied for their application in lithium-ion batteries. They offer different advantages such as lower cost, higher safety, and higher energy density with respect to commonly adopted transition metal oxides. Moreover, this family of compounds is free from critical raw materials such as cobalt and nickel. For cathode materials, a crucial aspect is evaluating the evolution and behavior of the structure and properties during the cycling process, which means simulating the system under lithium extraction and insertion. Structural optimization, electronic band structures, density of states, and Raman spectra were simulated, looking for fingerprints and peculiar aspects related to the delithiation and overlithiation process. Lithium transport properties were also investigated through the nudged elastic band methodology. This allowed us to evaluate the diffusion coefficient of lithium, which is a crucial parameter for cathode performance evaluation. [ABSTRACT FROM AUTHOR]

On average, one hundred people die each year under avalanche snow. Despite extensive global research on gas exchange in buried avalanche victims, it remains unclear how the diffusion of respiratory gases affects survival under avalanche snow. This study aims to determine how oxygen and carbon dioxide diffuse through snow, as well as through wet and dry perlite, which may serve as a surrogate for avalanche snow. A custom-made apparatus to study the diffusion of respiratory gases consisted of a plastic cylinder (1200 mm long, ID 300 mm) with 13 gas sampling needles evenly spaced along the axis of the cylinder filled with the tested material. Following 60 min of free diffusion, gas samples were analyzed using a vital signs monitor with a module for respiratory gas analysis (E-CAiOVX, Datex-Ohmeda, GE Healthcare, Chicago, IL, USA). A combination of 16% oxygen, 5% carbon dioxide, and 79% nitrogen was used. The rates of diffusion for both respiratory gases were comparable in snow and both forms of perlite. Oxygen propagated faster than carbon dioxide. Due to similar diffusion characteristics to snow, perlite possesses the potential to stand in as an effective substitute for soft snow for the study of respiratory dynamics, for conducting breathing experiments, and for testing avalanche safety equipment. [ABSTRACT FROM AUTHOR]

As a clean energy source, coalbed methane (CBM) produces almost no exhaust gas after combustion, and its extraction and efficient utilization play a key role in supporting sustainable development. Therefore, molecular dynamics simulations were used to research the diffusion of CH4 in coal after injecting CO2/N2 in different sequences and to clarify the efficiency of CBM extraction under different injection sequences, so as to contribute to sustainable development. The results show that the adsorption amounts of CO2 and N2 in different injection sequences are obviously different. To narrow the gap between the two injection amounts, the injection pressure of N2 can be appropriately increased and that of CO2 can be reduced, or N2 can be injected preferentially instead of CO2. When CO2 is injected first, the interaction energy between CH4 and coal is stronger and increases slightly with displacement time as a whole. The interaction energy curve of the N2 injection decreases, and the displacement effect becomes worse and worse. From the diffusion and relative concentration distribution of CH4, it can be seen that the diffusion of CH4 molecules outside the grain cell is more obvious when N2 is injected first. In terms of the number of CH4 molecules diffusing outside the crystal cell, it is less when CO2 is injected first than when N2 is injected first. The average value of the velocity distribution of CH4 increases slightly when CO2 is injected first and decreases significantly when N2 is injected first, but the average value is overall higher for N2 injection first. From the difference in diffusion coefficients before and after the gas injection, it can be seen that the decrease in permeability due to the expansion of the coal matrix by CO2 is more obvious than the increase in permeability due to the contraction of the coal matrix by N2. [ABSTRACT FROM AUTHOR]

The diffusion coefficient of heavy quarks in a deconfined medium is examined in this research using a deep convolutional neural network (CNN) that is trained with data from relativistic heavy ion collisions involving heavy flavor hadrons. The CNN is trained using observables such as the nuclear modification factor  R A A  and the elliptic flow  v 2  of non-prompt  J / ψ  from the B-hadron decay in different centralities, where B meson evolutions are calculated using the Langevin equation and the instantaneous coalescence model. The CNN outputs the parameters, thereby characterizing the temperature and momentum dependence of the heavy quark diffusion coefficient. By inputting the experimental data of the non-prompt  J / ψ (R A A , v 2)  from various collision centralities into multiple channels of a well-trained network, we derive the values of the diffusion coefficient parameters. Additionally, we evaluate the uncertainty in determining the diffusion coefficient by taking into account the uncertainties present in the experimental data  (R A A , v 2) , which serve as inputs to the deep neural network. [ABSTRACT FROM AUTHOR]

In this study, we investigated the relationship between the decarburization effect of the solid-state decarburization method for preparing silicon steel and the atomic diffusion behavior in the matrix, focusing on 1 mm thick Fe-0.18 wt% C-Si (1.5, 3.5 wt%) alloy strips as the research object. Solid-state decarburization experiments were carried out in an Ar-H2O-H2 atmosphere, and the self-diffusion behavior of C and Si in Fe-C-Si alloy system was simulated by molecular dynamics. The results show that the molecular dynamics simulation results are consistent with the decarburization experimental results. When the temperature is lower than 800 °C, the atoms maintain a compact bcc structure, so the migration rate of carbon is low. When the temperature rises, the atoms move violently, resulting in the destruction of the crystal structure. Because the atomic arrangement tends towards a disordered structure, the migration rate of C is high and the diffusion coefficient increases. The experimental results showed that the decarburization rate was accelerated. At the same temperature, the diffusion activation energy Q = 48.7 kJ·mol−1 of carbon in an Fe-3.5 wt% Si-C alloy matrix can be calculated. The diffusion activation energy of carbon Q = 47.3 kJ·mol−1 was calculated using a molecular dynamics simulation. When the content of Si is 3.5 wt% and 1.5 wt%, the diffusion series of Si can be expressed as D3.5Si, Si = 8.54 × 10−10 exp(−33,089.7/RT) m2/s and D1.5Si, Si = 2.06 × 10−9 exp(−46,641.5/RT) m2/s, respectively. When the Si content is 3.5 wt%, the diffusion coefficient of Si is larger. After diffusion to the near surface, it combines with the remaining O to form a continuous strip of SiO2. When the Si content is 1.5 wt%, the diffusion coefficient of Si is small. The remaining O diffuses in the matrix and will oxidize when encountering Si; it cannot aggregate in a highly-dispersed distribution. The lattice transition from face centered cubic lattice austenite to body centered cubic lattice ferrite occurred in the matrix of the thin strip. The diffusion coefficient of C in ferrite is much larger than that in austenite. Therefore, the decarburization rate suddenly increases before decarburization stagnation. With the increase in Si content, the diffusion activation energy of C decreases, which promotes the decarburization effect. [ABSTRACT FROM AUTHOR]

Methacrylate-based polyhedral oligomeric silsesquioxane (POSS) is one of the new composites used as a dental resin. Both monofunctional methacryl isobutyl POSS (MIPOSS) and multifunctional methacryl POSS (MAPOSS) are reported to be possible resins that possess the desired properties for using them as dental resins. Our group's previous comparative study on these two resins showed that the MAPOSS composite has superior mechanical properties compared with the MIPOSS composite. In this article, molecular dynamic simulations (MD simulations) are performed to study the water sorption in these two composites. Water sorption in dental composites can have several effects on the material properties, performance, and longevity of dental restorations. Water sorption in MAPOSS and MIPOSS composites is analyzed by studying the hydrogen bonding, cluster analysis, density projection calculations, and diffusion coefficient calculation of water molecules within the resin matrix. MD simulations results are further used to understand the interaction of water molecules with the resin matrix comprehensively, which governs the composite's mechanical properties. The water sorption study showed that the MAPOSS composite has less water sorption capacity than the MIPOSS composite. The practical significance of this study is to find properties that affect dental restoration and longevity, which can help in the design of better materials for dental applications. [ABSTRACT FROM AUTHOR]

Diffusion bonding has many advantages, but it also has its specifics. When creating heterogeneous joints, problems arise with the creation of intermetallic phases. For this reason, an interlayer is needed to prevent the creation of these unfavorable phases. It is important to ensure that the interlayer is of sufficient thickness to prevent the elements from diffusing through the entire interlayer and the intermetallic phases from being formed again. Conversely, too thick an interlayer causes an increase in the heterogeneity of the bond properties. The creation of the initial diffusion bonds in a heterogeneous diffusion joint of AISI 304 and AISI 316L steel with a 0.2 mm thick nickel interlayer was made in a Gleeble 3500. The experiments to determine the diffusion kinetics were carried out in a vacuum furnace, with subsequent evaluation by EDX (Energy Dispersive X-ray Spectroscopy) analysis. Subsequently, the diffusion coefficients of nickel into both steels were determined, and generalized equations were formulated to calculate the diffusion coefficients for temperatures in the range of 950 to 1150 °C and holding times in the range of 3600 to 18,000 s. Equations are also given to determine the width of the diffused zone between each steel and the Ni interlayer. [ABSTRACT FROM AUTHOR]

To investigate the influence of alloying elements (Zn, Mg, and Cu) on the structural and dynamical properties of liquid Al−9Si alloy, we conducted ab initio molecular dynamics (AIMD) simulations. Our results indicate that the structure of Al−Si−M ternary alloys is determined with a combination of atomic radii and mixing enthalpy, while the dynamic properties are primarily influenced by electronic structure of the alloying elements. Specifically, the addition of Cu promotes the formation of Al−Cu short-range order (SRO), while Zn has a higher propensity for Zn−Zn SRO. The Al−Cu SRO in liquid alloy may serve as the precursor for the Al2Cu reinforcing phase in Al−Si−Cu alloys. Upon the addition of Mg, a greater number of relatively stable perfect and distorted icosahedral structures, as well as hcp and bcc ordered structures with lower energies, are observed. Additionally, the presence of Mg leads to a reduction in the atomic diffusion rates of Al and Si, while Cu and Zn exhibit complex diffusion behavior influenced by the presence of Si atoms. [ABSTRACT FROM AUTHOR]

Hydrogen's wide availability and versatile production methods establish it as a primary green energy source, driving substantial interest among the public, industry, and governments due to its future fuel potential. Notable investment is directed toward hydrogen research and material innovation for transmission, storage, fuel cells, and sensors. Ensuring safe and dependable hydrogen facilities is paramount, given the challenges in accident control. Addressing material compatibility issues within hydrogen systems remains a critical focus. Challenges, roadmaps, and scenarios steer long-term planning and technology outlooks. Strategic visions align actions and policies, encompassing societal and ecological dimensions. The confluence of hydrogen's promise with material progress holds the prospect of reshaping our energy landscape sustainably. Forming collective future perspectives to foresee this emerging technology's potential benefits is valuable. Our review article comprehensively explores the forthcoming challenges in hydrogen technology. We extensively examine the challenges and opportunities associated with hydrogen production, incorporating CO2 capture technology. Furthermore, the interaction of materials and composites with hydrogen, particularly in the context of hydrogen transmission, pipeline, and infrastructure, are discussed to understand the interplay between materials and hydrogen dynamics. Additionally, the exploration extends to the embrittlement phenomena during storage and transmission, coupled with a comprehensive examination of the advancements and hurdles intrinsic to hydrogen fuel cells. Finally, our exploration encompasses addressing hydrogen safety from an industrial perspective. By illuminating these dimensions, our article provides a panoramic view of the evolving hydrogen landscape. [ABSTRACT FROM AUTHOR]

Transient uptake curves for propane gas in a bed of HZSM-5 using a volumetric frequency response setup (batch system) were obtained. Thereby, a perturbation, such as a change in volume, was applied to the solid/gas system, and the resulting change in pressure was detected. Two cases of mass transfer limitations (bed diffusion control and micropore diffusion control) were compared, and it was concluded that, in the presented case, micropore diffusion is the rate-determining process. The obtained micropore diffusion coefficient for propane in HZSM-5 was, on average, about 1.2 × 10−10 m2 g−1, which is in good agreement with other frequency response studies shown by literature data. The homemade setup and the modeling presented in this work serve as the basis for ongoing numerical simulations. [ABSTRACT FROM AUTHOR]

One of the major challenges in recycling plastics is the removal of undesired volatile components from the polymeric phase, which may reduce process efficiency and negatively affect product quality. Accordingly, the recycling industry employs a broad range of degassing techniques, the efficiency of which often depends on the diffusion coefficient—a measure of the mass transport of volatile components in polymeric phases. The aim of this study was to develop a practically feasible experimental approach using thermogravimetric analysis (TGA) to determine the average diffusion coefficient of volatile components in polymer waste materials. First, the TGA method was validated with a pressure decay apparatus (PDA) using predefined binary material mixtures: Thin sheets were pressed from virgin high-density polyethylene (HDPE) and polypropylene (PP) and deliberately saturated with toluene in a sorption experiment. These saturated samples were then used in TGA and PDA desorption experiments at 60 °C, 80 °C and 100 °C, which yielded similar results with an average difference of 7.4% for the HDPE-toluene system and 14.7% for the PP-toluene system. When validated, TGA was employed to determine the diffusion coefficient of volatile components in post-industrial plastic waste melt at a temperature of 220 °C. The proposed method contributes to the understanding of diffusion-based mass transport in polymer waste materials and provides a key parameter for model-based process control and optimization. In practice, the diffusion coefficient results can be used to predict the degassing performance of an extrusion process in the mechanical recycling of plastic waste. [ABSTRACT FROM AUTHOR]

The diffusion coefficient (D) is a key parameter that characterizes the gas transport occurring in coal seams. Typically, D is calculated using the desorption curve of particle coal. However, this method cannot accurately reflect the diffusion characteristics under the stress constraint conditions of in situ coal seams. In this study, different metamorphic deformed coals of medium and high coal rank were considered based on Fick's law of counter diffusion. The change laws of D under different confining pressures, gas pressures, and temperature conditions were tested and analyzed, and the influencing mechanisms on D are discussed. The results showed that D of different metamorphic deformed coals exponentially decreased with an increase in confining pressures, and exponentially increased with increases in gas pressures and temperature. There is a limit diffusion coefficient. The influence of the confining pressure on D can essentially be determined by changes in the effective stress, and D negatively affects the effective stress, similar to permeability. The effect of gas pressure on D involves two mechanisms: mechanical and adsorption effects, which are jointly restricted by the effective stress and the shrinkage and expansion deformation of coal particles. Temperature mainly affects D by changing the root-mean-square speed and average free path of the gas molecules. Under the same temperature and pressure conditions, D first increased and then decreased with an increase in the degree of deformation. D of the fragmented coal was the largest. Under similar deformation conditions, D of the high-rank anthracite was larger than that of the medium-rank fat coal. Porosity is a key factor affecting the change in D in different metamorphic deformed coals. [ABSTRACT FROM AUTHOR]

In this study, we review some aspects of the application of free randomly moving (RM) electron density and its probability density function distribution to the main free electron transport characteristics of elemental metals. It is shown that metal atom thermal vibrations not only produce free RM electrons, but also produce the same number of electronic defects (weakly shielded ions). The general expressions for the drift mobility, diffusion coefficient, and mean free path of randomly moving electrons are presented. It is shown that the scattering of free RM electrons is mainly due to electronic defects, which cause the distortion of the periodic potential (or the charge density) distribution in the periodic lattice. The resistivity of the elemental metal is caused by electronic defect scattering, taking into account the exchange in the thermal energies between phonons and free RM electrons. Special attention is paid to the analysis of the Hall effect measurement data: the Hall coefficient is presented for two types of RM electrons and holes, taking into account electron-like and hole-like densities of states. The paramagnetism and diamagnetism of the free RM electrons are simply explained using the definition of free RM electron density. [ABSTRACT FROM AUTHOR]

The precipitates and the intergranular corrosion behavior of a UNS N08028 nickel–iron–chromium alloy sensitized at different temperatures were studied by employing transmission electron microscopy, Kelvin probe force microscopy and other methods. It was found that sigma precipitates appeared at the grain boundaries of the alloy being sensitized. There was a Cr-depleted zone and a low-potential zone around these precipitates. The potential difference between the sigma precipitates and the low-potential zone was 102 mV, and this increased with the growth of the sigma precipitates. At this potential difference, the migration of the vacancies in the passive film accelerated significantly, and then the protectiveness of the passive film decreased. The intergranular corrosion mechanism of the steel has also be discussed. [ABSTRACT FROM AUTHOR]

This paper presents an innovative and efficient methodology for the determination of the solid-state diffusion coefficient in electrode materials with phase transitions for which the assumption of applying the well-known formula from the work of Weppner et al. is not satisfied. This methodology includes a k-means machine learning screening of Galvanostatic Intermittent Titration Technique (GITT) steps, whose outcomes feed a physics-informed algorithm, the latter involving a pseudo-two-dimensional (P2D) electrochemical model for carrying out the numerical simulations. This methodology enables determining, for all of the 47 steps of the GITT characterization, the dependency of the Na+ diffusion coefficient as well as the reaction rate constant during the sodiation of an NVPF electrode to vary between 9 × 10 − 18 and 6.8 × 10 − 16 m2·s−1 and between 2.7 × 10 − 14 and 1.5 × 10 − 12 m2.5·mol−0.5·s−1, respectively. This methodology, also validated in this paper, is (a) innovative since it presents for the first time the successful application of unsupervised machine learning via k-means clustering for the categorization of GITT steps according to their characteristics in terms of voltage; (b) efficient given the considerable reduction in the number of iterations required with an average number of iterations equal to 8, and given the fact the entire experimental duration of each step should not be simulated anymore and hence can be simply restricted to the part with current and a small part of the rest period; (c) generically applicable since the methodology and its physics-informed algorithm only rely on "if" and "else" statements, i.e., no particular module/toolbox is required, which enables its replication and implementation for electrochemical models written in any programming language. [ABSTRACT FROM AUTHOR]

In this paper, we propose an alternative road to calculate the transport coefficients of fluids and the slip length inside nano-conduits in a Poiseuille-like geometry. These are all computationally demanding properties that depend on dynamic, thermal, and geometrical characteristics of the implied fluid and the wall material. By introducing the genetic programming-based method of symbolic regression, we are able to derive interpretable data-based mathematical expressions based on previous molecular dynamics simulation data. Emphasis is placed on the physical interpretability of the symbolic expressions. The outcome is a set of mathematical equations, with reduced complexity and increased accuracy, that adhere to existing domain knowledge and can be exploited in fluid property interpolation and extrapolation, bypassing timely simulations when possible. [ABSTRACT FROM AUTHOR]

The consequences of the loss of the load-bearing capacity due to the corrosion of prestressing steel can be much more dangerous than in the case of reinforced concrete structures, since failure can occur quite rapidly and without warning. A very important issue, therefore, is to determine the factors affecting the durability of prestressed structures exposed to aggressive agents, especially chloride ions. The aim of this study was to verify the protective properties of concrete of prefabricated HC-type prestressed concrete slabs in order to evaluate the possibility of their application in the ceilings of multilevel garages. In this paper, the corrosion rate of rebar steel in HC-550 floor slabs at a width of 1200 mm was estimated with nondestructive electrochemical methods: linear polarization and impedance spectroscopy. The general and mechanical properties of concrete prepared according to a formula in a laboratory and analogous concrete cut directly from the analyzed floor slabs were also studied. The porosity of concrete from these slabs was determined using X-ray-computed tomography for pore-related characterization. The values of the diffusion coefficient of chloride ions determined in previous works and the previously proposed model for the overexposure of the durability of floor slabs in chloride-containing environments were used to determine the durability of these slabs. Based on the empirical correlations adopted from the literature presenting the relationship of durability/adhesion over time and the corrosion parameters studied, a safe service life was determined at the nominal class of concrete equal to Δtcor.red = 30.48 years. In addition, in the case of discontinuities in the concrete structure, there may be a dangerous reduction in the time of corrosion initiation and a subsequent reduction in service life due to the loss of the adhesion of strut strands for up to 10.68 years of service life. [ABSTRACT FROM AUTHOR]

Plenty of research has verified that nano-ZnO particles could improve the properties of asphalt, but studies on nano-ZnO-modified asphalt haven't been conducted at the molecular level. Therefore, to investigate the effect of ZnO particles on the properties, structure and morphology of asphalt, the molecular dynamics (MD) methods were carried out. In this study, the models of asphalt, ZnO cluster and ZnO/asphalt blending systems with different particle sizes were built using Materials Studio software. Then, the interaction energies of ZnO/asphalt blending systems under different temperatures were calculated, and the effect of ZnO particles on the modulus and glass transition temperature of matrix asphalt was simulated. The results indicated that the bulk modulus of asphalt increased by ZnO with particle size at 4 Å, 6 Å, 8 Å and 10 Å increased by 15.09%, 12.46%, 10.06% and 8.51%, respectively, which can illustrate that the shear resistance ability and low-temperature properties of asphalt were enhanced. Compared with matrix asphalt, the glass transition temperature of the ZnO/asphalt system decreased by less than 0.1 K, indicating that ZnO's effect on the low temperature of asphalt was not apparent. With the increase of ZnO particle size, the diffusion coefficient decreased sharply. Compared to matrix asphalt, when the particle size increased to 8 Å and 10 Å, the diffusion coefficient decreased by 13% and 22%, respectively. So, in practice projects, to achieve better dispersion of particle materials in base bitumen, a smaller particle size would be recommended. The results of the radial distribution function (RDF) and AFM simulation indicated that ZnO particles changed the micro-structure of asphalt and increased the roughness of the asphalt surface. As a result, ZnO particles bring matrix asphalt better physical properties. [ABSTRACT FROM AUTHOR]

The equivalent characteristics of the materials' interfaces are known to impact the overall mechanical properties of ceramic–metal composites significantly. One technological method that has been suggested is raising the temperature of the liquid metal to improve the weak wettability of ceramic particles with liquid metals. Therefore, as the first step, it is necessary to produce the diffusion zone at the interface by heating the system and maintaining it at a preset temperature to develop the cohesive zone model of the interface using mode I and mode II fracture tests. This study uses the molecular dynamics method to study the interdiffusion at the interface of α-Al2O3/AlSi12. The hexagonal crystal structure of aluminum oxide with the Al- and O-terminated interfaces with AlSi12 are considered. A single diffusion couple is used for each system to determine the average main and cross ternary interdiffusion coefficients. In addition, the effect of temperature and the termination type on the interdiffusion coefficients is examined. The results demonstrate that the thickness of the interdiffusion zone is proportional to the annealing temperature and time, and Al- and O-terminated interfaces exhibit similar interdiffusion properties. [ABSTRACT FROM AUTHOR]

The influence of oligosaccharides (α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin), and a polysaccharide, sodium hyaluronate (NaHy), on the diffusion of aqueous solutions of cobalt and chromium chlorides has been investigated. Cobalt and chromium are constituents of metal alloys for biomedical use, including dental prostheses. Thus, the release of these ions in the human body can lead to harmful biological effects. The interaction of metal ions with saccharides might have information on the role of mouthwashes in preventing these effects. This interaction has been assessed by measuring multicomponent intermolecular diffusion coefficients at 298.15 K. It has been found that β-cyclodextrin has the highest interaction towards cobalt and chromium ions. This work will contribute to unveiling the mechanisms responsible for transport by diffusion in aqueous solutions, and, therefore, mitigating the potential toxicity inherent to those metal ions. [ABSTRACT FROM AUTHOR]

Nematic liquid crystals (LCs) are known to undergo a phase transition to chiral nematic LCs possessing helices upon doping with enantiomeric molecules known as chiral dopants. The relationship between the helical pitch (p), the molar fraction (x), and the power of the chiral dopant to induce a helix in a nematic solvent ( β M ) is expressed as p = 1 / (x · β M). The helical pitch is easily controlled by the concentration of the chiral dopant when the dopant molecule is miscible with the host nematic LC. However, it has not yet been clarified what the miscibility of the chiral dopant molecules with the nematic LCs depends. Therefore, we performed all-atom molecular dynamics (MD) simulations for the system composed of both Δ and Λ isomers of a chiral dopant molecule dispersed in a nematic LC and investigated the relationship between the microdynamics of the chiral molecules and their miscibility with the nematic solvent. The miscibility of the chiral dopant molecules with the LC solvent was found to correlate with the diffusion coefficient of the LC solvent. In the system where the chiral dopant molecules with high miscibility were added, the diffusion coefficient of the LC solvents was comparable to that of the system in which the chiral molecule was not doped. Furthermore, it was confirmed that more elongated chiral dopants were more miscible with the nematic solvent consisting of calamitic molecules, and that these dopant molecules did not have a significant effect on the diffusion behavior of the LC molecules. [ABSTRACT FROM AUTHOR]

Actin polymerization drives cell movement and provides cells with structural integrity. Intracellular environments contain high concentrations of solutes, including organic compounds, macromolecules, and proteins. Macromolecular crowding has been shown to affect actin filament stability and bulk polymerization kinetics. However, the molecular mechanisms behind how crowding influences individual actin filament assembly are not well understood. In this study, we investigated how crowding modulates filament assembly kinetics using total internal reflection fluorescence (TIRF) microscopy imaging and pyrene fluorescence assays. The elongation rates of individual actin filaments analyzed from TIRF imaging depended on the type of crowding agent (polyethylene glycol, bovine serum albumin, and sucrose) as well as their concentrations. Further, we utilized all-atom molecular dynamics (MD) simulations to evaluate the effects of crowding molecules on the diffusion of actin monomers during filament assembly. Taken together, our data suggest that solution crowding can regulate actin assembly kinetics at the molecular level. [ABSTRACT FROM AUTHOR]

One of the key problems that affect the durability of reinforced concrete structures is the corrosion of rebar induced by chloride. Despite the complicated transport mechanism of chloride ions in cementitious materials, diffusion is still the key mechanism of chloride ingress. The determination of the chloride diffusion coefficient will help to predict the chloride profile inside the cementitious materials and estimate the service life with regard to chloride-induced corrosion. However, this paper shows that the chloride diffusion coefficient in the literature is sometimes misunderstood. Such a misunderstanding results in the overestimation of the chloride resistance of cementitious materials. To clarify the chloride diffusion coefficient, this paper first presents the steady- and non-steady-state diffusion equations in cementitious materials. The factors that influence the diffusive flux are identified. The effective and apparent diffusion coefficients are then clearly explained and properly defined. We also point out the obscure definitions of the effective diffusion coefficient in the literature. The varied definitions of the effective diffusion coefficient are the result of the consideration of different factors affecting the diffusion process. Subsequently, this paper discusses two natural diffusion test methods that are frequently employed in cementitious materials to measure the chloride diffusion coefficient. The influencing factors considered by the measured diffusion coefficients are analyzed in detail. Then, the diffusion coefficients determined in some of the studies are reviewed. It is shown that three typical errors could occur when numerically determining the diffusion coefficients. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations employing the all-atom optimized potential for liquid simulations (OPLS-AA) force field were performed for determining self-diffusion coefficients ( D 11 ) of ethanol and tracer diffusion coefficients ( D 12 ) of solutes in ethanol at several temperature and pressure conditions. For simulations employing the original OPLS-AA diameter of ethanol's oxygen atom ( σ OH ), calculated and experimental diffusivities of protic solutes differed by more than 25%. To correct this behavior, the σ OH was reoptimized using the experimental D 12 of quercetin and of gallic acid in liquid ethanol as benchmarks. A substantial improvement of the calculated diffusivities was found by changing σ OH from its original value (0.312 nm) to 0.306 nm, with average absolute relative deviations (AARD) of 3.71% and 4.59% for quercetin and gallic acid, respectively. The new σ OH value was further tested by computing D 12 of ibuprofen and butan-1-ol in liquid ethanol with AARDs of 1.55% and 4.81%, respectively. A significant improvement was also obtained for the D 11 of ethanol with AARD = 3.51%. It was also demonstrated that in the case of diffusion coefficients of non-polar solutes in ethanol, the original σ OH = 0.312 nm should be used for better agreement with experiment. If equilibrium properties such as enthalpy of vaporization and density are estimated, the original diameter should be once again adopted. [ABSTRACT FROM AUTHOR]