Macroscopic Experiments Research Articles

Experimental and molecular dynamics simulation studies on the effect of composite surfactants on the wettability of anthracite coal

In order to improve the wettability of coal bed water injection, the effects of several composite surfactants on the wettability of anthracite coal were investigated. Firstly, the wettability of different composite surfactants on anthracite was analysed by macroscopic experiments (surface tension and settling time) to determine the optimal concentration and optimal ratio of composite surfactants. Secondly, the effects of adsorption of different composite surfactants on the physicochemical properties of the coal dust surface were investigated by mesoscopic experiments (scanning electron microscopy, energy spectrometer analysis, infrared spectroscopy, X-ray electron spectroscopy and zeta potential), and the results showed that the content of hydrophilic functional groups (Si-O-Si, C-O-C, C-O and C=O) on the surface of anthracite coal after treatment with the composite surfactant increased significantly, and the surface potential value decreased significantly in absolute value, agglomerated large coal particles would be formed on the coal surface, and the cracks between coal particles were favourable for the penetration of aqueous solution. Finally, the synergistic mechanism of different composite surfactants was analysed from the perspective of microscopic molecular simulation. The results showed that the composite surfactants enhanced the interaction energy of the coal/composite surfactant/water system, improved the relative concentration distribution of the system, and increased the diffusion coefficient of water molecules. The results of the study can provide valuable guidance for the development of new composite surfactants with wetting effect, which has important application value for mine dust control.

Playing with active matter

In the past 20 years, active matter has been a very successful research field, bridging the fundamental physics of nonequilibrium thermodynamics with applications in robotics, biology, and medicine. Active particles, contrary to Brownian particles, can harness energy to generate complex motions and emerging behaviors. Most active-matter experiments are performed with microscopic particles and require advanced microfabrication and microscopy techniques. Here, we propose some macroscopic experiments with active matter employing commercially available toy robots (the Hexbugs). We show how they can be easily modified to perform regular and chiral active Brownian motion and demonstrate through experiments fundamental signatures of active systems such as how energy and momentum are harvested from an active bath, how obstacles can sort active particles by chirality, and how active fluctuations induce attraction between planar objects (a Casimir-like effect). These demonstrations enable hands-on experimentation with active matter and showcase widely used analysis methods.

Simulation and experimental verification of the orthogonal friction continuous wear of PTFE-Kevlar fabric liner

Woven fabric liners, which are customizable and maintenance-free, have extensive applications in self-lubricating spherical bearings. However, owing to the orthogonal anisotropy and non-homogeneous characteristics, their frictional and wear behaviors are complex. Currently, average performance testing is primarily based on long-term macroscopic wear experiments. However, unobservable parameters such as mesoscopic stress and pressure distribution in liners are bottlenecks in the experimental exploration of wear sources and mechanisms. Therefore, an innovative strategy for modeling orthogonal friction and continuous wear in non-homogeneous liners is presented. This approach has the potential to overcome experimental limitations and significantly expedite liner design and cost-effective validation. The initial step involves establishing a mesoscopic voxel-based planar model of the liner that maintains the topological relationship during wear processes. This is achieved by introducing a circular voxel mesh and spatial transformation methods. Based on orthogonal friction and wear assumptions, separate constitutive models for orthogonal friction and wear are developed. Using the CETR UMT-3 friction and wear testing machine, GCr15 is selected as the counterface material, the pin disc wear method is adopted to conduct sliding test on PTFE and Kevlar fibers, and the required wear constitutive parameters are fitted. Furthermore, incremental equations for the total wear are derived. An element wear fusion strategy is introduced. This approach leads to the development of a continuous wear algorithm for liners and subsequently to the establishment of a voxel-based finite element model with continuous wear capability in the form of a circular voxel grid. This method transcends experimental methods and allows for the determination of the mesoscopic contact pressure, stress distribution, and variations in the contact material composition patterns of liner. The accuracy of the average macroscopic wear prediction is validated experimentally. This method has the potential for practical applications in bearing design.

Shear-induced migration of rigid spheres in a Couette flow

Concentration inhomogeneities occur in many flows of non-Brownian suspensions. Their modeling necessitates the description of the relative motion of the particle phase and of the fluid phase, as well as the accounting for their interaction, which is the object of the suspension balance model (SBM). We systematically investigate the dynamics and the steady state of shear-induced migration in a wide-gap Couette flow for a wide range of particle volume fraction, and we test the ability of the SBM to account for the observations. We use a model suspension for which macroscopic particle stresses are known. Surprisingly, the observed magnitude of migration is much lower than that predicted by the SBM when the particle stress in the SBM is equated to the macroscopic particle stress. Another noteworthy observation is the quasi-absence of migration for semidilute suspensions. From the steady-state volume fraction profiles, we derive the local particle normal stress responsible for shear-induced migration according to the SBM. However, the observed dynamics of migration is much faster than that predicted by the SBM when using this stress in the model. More generally, we show that it is not possible to build a local friction law consistent with both the magnitude and the dynamics of migration within the standard SBM framework. This suggests that there is a missing term in the usual macroscopic constitutive law for the particle normal stress driving migration. The SBM is indeed capable of accurately predicting both the magnitude and the dynamics of migration when a tentative phenomenological term involving a concentration gradient is added to the particle normal stresses determined in macroscopic experiments.

Effects of hexagonal boron nitride nanosheets on the biostabilization of recycled sands for geotechnical fill applications

Biostabilization techniques including plant enzyme induced calcite precipitation (EICP) and microbially induced calcite precipitation (MICP) represent promising and environmentally friendly methods for improving the engineering properties of recycled geomaterials for geotechnical fill applications. In this study, hexagonal boron nitride (h-BN) nanosheets were dispersed and utilized as nano-additives in the EICP and MICP reaction processes to facilitate the precipitation of calcium carbonate polymorphs (CaCO3) in washed recycled sands (RS) derived from construction and demolition (C&D) wastes for geotechnical fill applications. The investigation comprised a systematic range of biological and chemical microscopic and macroscopic experiments intending to stabilize the RS for geotechnical fill applications. The study results suggested that using h-BN nanosheets did not have a notable impact on bacterial growth or the functioning of bacterial and plant enzyme activity. In addition, it was observed that the optimal addition of h-BN nanosheet additives substantially increased CaCO3 precipitation by up to 34 % and 28 % in the EICP and MICP reaction processes respectively, which can be postulated to be due to the nanosheets acting as nucleation sites throughout the high surface area and negatively surface charge. Furthermore, the introduction of h-BN nanosheets led to a significant enhancement in the performance of unconfined compressive strength (UCS) of the stabilized RS through nanofillers and reinforcements, with improvements of up to 20 % and 13 % in the biostabilization of RS using the EICP and MICP after 10 treatment cycles. Detailed analyses, including Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) imaging, revealed that h-BN nanosheets, with a substantial surface area and effective chemical functional groups, interconnected with the CaCO3 mineral surface. Overall, the study suggests that integrating effective additives can improve the utilization of EICP and MICP in geotechnical fill applications, namely in road embankments and pavements, whilst providing both commercial viability and enhanced performance.

Experimental and molecular dynamics simulation of the effect of surfactant concentration on the wettability of bituminous coal

Currently, studies on the mechanism of coal dust wetting have largely ignored the key factor of surfactant concentration, so it is of significant scientific value to systematically investigate the effect of concentration change on the efficacy of surfactant wetting of coal dust. In this paper, with the help of macroscopic wettability experiments and molecular dynamics simulations, the wetting characteristics of SDBS surfactant on coal at different concentrations were analyzed in depth. An increase in the concentration of the SDBS surfactant solution causes the wettability of the coal to show a crest change that increases and then decreases. Coal wettability is optimized when the solution concentration reaches a specific threshold of 7 wt%. The simulation results show that SDBS surfactant mostly forms hydrogen bonds with water molecules in the form of strong hydrogen bonds, and the hydrogen bonding ability with water molecules is stronger than that of coal. There is a positive correlation between the onset distribution of water molecules within coal and the overlap region at the coal/water interface. The dynamic properties of water molecules show the order E<F<D<C<B<A. The number of highly active sites does not continuously increase with the amount of SDBS molecules adsorbed, but begins to decrease after a critical point is reached. The results of the study contribute to a theoretical framework to guide and use different types of surfactants to improve coal dust wettability at various concentration levels.

Investigation on compressive strength and splitting tensile strength of manufactured sand concrete: Machine learning prediction and experimental verification

Due to experimental constraints, traditional strength prediction models for manufactured sand concrete (MSC) exhibit significant limitations and have a narrow range of applicability. To overcome these limitations and enhance prediction accuracy, this paper, based on the widespread application of machine learning in concrete performance research, employed four algorithms: Support Vector Regression (SVR), Random Forest Regression (RFR), Gradient Boosting (GB), and Extreme Gradient Boosting (XGB) to develop highly accurate and strongly generalizable models for predicting the compressive strength (CS) and splitting tensile strength (STS) ofMSC. The predictive performance of each model was evaluated, the influence laws of various factors were analyzed, and finally, macroscopic experiments were conducted to validate the models' prediction accuracy and generalization ability. The development of these models and the analysis of the influence laws of various factors on the strength of MSC provide a valuable reference for the mix design. The conclusions are as follows: (1) The XGB model demonstrates the highest prediction accuracy and strongest generalization ability for both the CS and STS of MSC, achieving R2 values of 0.98 and 0.94 on the testing set, respectively. (2) The CS and STS of MSC are primarily influenced by four factors: water-binder ratio (W/B), curing age (AGE), cement (C), and coarse aggregate (RI≥0.08869, RI: relative importance), showing a positive correlation with AGE and C, and a negative correlation with W/B. As the fly ash content, stone powder content, maximum particle size of coarse aggregate, and sand ratio increase, the CS and STS initially increase and then decrease. Appropriately increasing the fineness modulus of manufactured sand is beneficial to both CS and STS, while the addition of slag is beneficial to CS and harmful to STS. (3) The prediction accuracy and generalization ability of the XGB model are verified through three sets of macroscopic experiments: C30, C35, and C40. The relative errors of each set's predictions are less than 8 %. (4) A graphical user interface is constructed based on the XGB model, enhancing its practicality.

Bridging Microscopic Dynamics and Hydraulic Permeability in Mechanically-Deformed Nanoporous Materials.

In the field of nanoconfined fluids, there are striking examples of deformation/transport coupling in which mechanical solicitation of the confining solid and dynamics of the confined fluid impact each other. While this intriguing behavior can be harnessed for applications (e.g., energy storage, phase separation, catalysis), the underlying mechanisms remain to be understood. Here, using molecular simulations, we investigate fluid flow in deformable nanoporous materials subjected to external mechanical stresses. We show that the pore mechanical properties significantly affect fluid flow as they lead to significant pore deformations and different fluid organization at the solid surface. Despite such mechanical effects, we show that the fluid thermodynamic properties (i.e., adsorption) can be linked consistently to Darcy's law for the permeability by invoking a pore size definition based on the concept of Gibbs' dividing surface. In particular, regardless of the solid stiffness and applied external stress, all data can be rationalized by accounting for the fluid viscosity and slippage at the solid surface (independently of a specific pore size definition). Using such a formalism, we establish that the intimate relation─derived using the linear response theory─between collective diffusivity and hydraulic permeability remains valid. This allows linking consistently microscopic dynamics experiments and macroscopic permeability experiments on fluid flow in deformable nanoporous materials.

High N2-selectivity of nitrite reduction by palladium-laden nanocomposite with self-sufficient electron donators

Selectively reducing nitrite to gaseous nitrogen (N2) with an effective and recyclable fashion stands as an attractive alternative for treating the relevant wastewater. Herein, a Pd-based nanocomposite (Pd@EDA-CMPS) was subtly assembled by encapsulating Pd(0) nanoparticles into a porous polystyrene carrier, which was aforehand functionalized with ethylenediamine (EDA) as the endogenous electron donator. Systematical macroscopic experiments confirm that the pre-grafted EDA groups can substantially stimulate the catalytic activity of the laden Pd(0) nanoparticles with high removal efficiency and N2 selectivity of Pd@EDA-CMPS toward nitrite; specifically, high N2 selectivity (86%) was achieved by Pd@EDA-CMPS with an excellent anti-interference ability against competing anion and a broad pH-range applicability (4–11), whereas no N2 production was detected for its counterparts (CMPS, EDA-CMPS, and Pd@CMPS). Spectroscopic analyses reveal that the grafted EDA groups played a decisive role in the formation of H-loaded Pd(0) nanoparticles inside the porous substrate, which joint with the unique pH-buffering ability of EDA drove the reaction to the production of nitrogen (N2) rather than ammonia (NH3). The exhausted Pd@EDA-CMPS can be promisingly regenerated by NaOH (eluting) and NaBH4 (restoring) solution without obvious loss in treatment capacity and N2 selectivity. This work provides a feasible strategy for catalytically reducing nitrite into N2 without the provision of exogenous reductor such as hydrogen.

Effect of acid type on biomineralization of soil using crude soybean urease solution

The one-phase-low-pH method is a simple, efficient, and user-friendly biogrouting technique that can effectively improve the biomineralization of enzyme-induced carbonate precipitation (EICP) using free urease enzyme. One of the most significant advantages of this method is its capacity to effectively delay calcium carbonate (CaCO3) precipitation by reducing the pH of the solution through the addition of acid. This prevents bioclogging during the biogrouting process and improves the biomineralization effect. However, the biomineralization of the one-phase-low-pH based EICP method may be influenced by the specific acid used. To investigate the impact of acid type on the one-phase-low-pH EICP method using crude soybean urease solution (CSUS), four types of acids, including hydrochloric acid (HCl), nitric acid (HNO3), acetic acid (CH3COOH), and lactic acid (C3H6O3), were used to adjust the pH of CSUS. A series of macroscopic and microscopic experiments were conducted to evaluate the effect of acid type on the one-phase-low-pH EICP method. The results indicate that the acid has an inhibition on the urease activity (UA) of CSUS. Among the acids tested, HNO3 exhibits the most pronounced inhibitory effect on the UA of CSUS, followed by HCl, and the least pronounced inhibitory effect for CH3COOH and C3H6O3 under the same pH conditions. Meanwhile, CH3COOH and C3H6O3 could provide a longer delay duration of CaCO3 precipitation than HNO3 and HCl. Therefore, the one-phase-low-pH EICP method based on CH3COOH and C3H6O3 can significantly improve the effective biocementation depth compared to that based on HNO3 and HCl. Nevertheless, the different types of acids appear to have no obvious effect on the polymorph and crystalline of the precipitated CaCO3 crystals.

A crystal plasticity-based creep model considering the concurrent evolution of point defect, dislocation, grain boundary, and void

Creep poses a significant threat to the integrity and longevity of structural components at high-temperature. The most current understanding of creep mainly focuses on the coupled dynamics of point defects and dislocation, which may well describe the first and second stage of creep. However, the behavior of the three stages of creep is jointly controlled by point defect (vacancy) diffusion, dislocation glide, dislocation climb, grain boundary (GB) sliding, and void evolution. A critical knowledge gap still exists regarding how these different creep mechanisms are simultaneously coupled during the three stages of creep. In this work, a multi-physical mechanisms-based crystal plasticity model is proposed to consider the concurrent evolution of point defect, dislocation, GB, and void based on a unified thermodynamic framework. In-situ scanning electron microscope creep experiments and macroscopic creep experiments of Ti-6Al-4V were conducted to validate our model. The in-situ creep experiment directly revealed the GB sliding creep failure behavior of Ti-6Al-4V for the first time. The proposed model well predicts both the microscopic and macroscopic experimental behavior of creep. The contribution of different microstructure evolutions is discussed, and a phase diagram of the dominated creep mechanism is obtained. An in-depth analysis was conducted on the coupling effects and microstructure characteristics of different creep mechanisms. This work not only deepens our understanding of the micro creep mechanism but also offers valuable insights for designing materials with specific microstructures to enhance their creep resistance.

Mechanical strength and durability of GBFS geopolymer modified with metakaolin and functionalized beta-silicon carbide whiskers

Durability is crucial for materials development in construction and transportation industries. This paper investigates the mechanical strength and durability of alkali-activated granulated blast-furnace slag (GBFS) and modified geopolymer with varying contents of metakaolin (MK) and functionalized beta-silicon carbide whiskers (β-SiCw). Functionalized β-SiCw were prepared utilizing successful chemical methods. Macroscopic experiments tested mechanical strength, bulk density loss rate after exposure to severe conditions, and durability through sulfate wet-dry and freeze-thaw cycles. Microscopic experiments, including SEM-EDS, XRD, TG-DSC, and BET, revealed the microstructure mechanisms. Results showed that MK and functionalized β-SiCw improved mechanical strength by creating a more reactive phase and denser pore structures. Reduced bulk density loss rates and enhanced durability were observed, with a 71.9 % mass loss and 63.4 % compressive strength loss reduction after 50 freeze-thaw cycles, and a 12.2 % decrease in compressive strength loss after 56 days of sulfate wet-dry cycles, compared to control groups. The modified geopolymer had higher tortuosity and finer porosity due to more gel formation and nucleation sites, and functionalized β-SiCw effectively bridged micro-cracks and micro-pores.

Molecular dynamics simulation on the variations in characteristics of aqueous solution with diverse additives: Inspirations for binary ice preparation

Ice slurry, as a novel energy storage medium, possesses the superiority of high energy storage density. The freezing point inhibitors are employed to regulate the supercooling phenomenon of water, while the macroscopic experiments are complicated to elucidate the action mechanism. Consequently, this paper adopts molecular dynamic simulation method to investigate the mean square displacement, radial distribution function, hydrogen bonds types, hydrogen bonds number and length of water at various concentrations of ethanol, NaCl, and SiO2 additives. The results indicate that the average number of hydrogen bonds of the system composed with 600 pure water molecules is 1127.24, and the average length of hydrogen bonds is 2.33 Å. Moreover, the addition of alcoholics and chlorides inhibits the hydrogen bonds between water and water molecules, and promotes the generation of hydrogen bonds, thus weakening the diffusion motion of water molecules. Whereas, it is observed that the addition of nanoparticles leads to agglomeration in pure water system, resulting an increase in the viscosity and a decrease in the diffusion rate of the system. The proposed microscopic model can effectively depict the potential interaction mechanisms of additives and water, which is contributing to develop effective freezing point inhibitors and improve the energy utilization efficiency.

Experimental and molecular simulation study on the influence of chain length and anion structure of ionic liquids on the wettability of highly hydrophobic bituminous coal

The wettability of bituminous coal is critical for the coal dust suppression and can be apparently modulated by ionic liquids. However, the modulation mechanism still remains elusive. Here, a combination of macroscopic experiments, mesoscopic characterization, and microscopic simulations (quantum mechanics and molecular dynamics) are leveraged to parse the effect on the wettability of coal dust surfaces of three novel ionic liquids ([C12MIm]Br, [BMIm]Br, [BMIm]Cl) featuring the varying chain lengths and anions in the coal-water system. The results show that the selected ionic liquids exert a distinct bridging function from traditional surfactants which invoke the hydrogen bonding interaction. This ionic liquids-mediated bridging mechanism heavily depends on their chain length structure, which can firstly penetrate deeply the internal pores of coal dusts and then adsorb on the coal surfaces to rapidly strike a dynamic equilibrium. Ionic liquids interacting with coal dust can primarily reduce the energy difference between polar and nonpolar interactions within coal dust, thereby enhancing the electrostatic interactions between coal dust and water molecules and effectively improving coal dust wetting properties. These findings provide a theoretical basis for the rational design of high-performance ionic liquids for coal mine dust control.

Advancing oil-water separation: Design and efficiency of amphiphilic hyperbranched demulsifiers

Hypothesis: An innovative strategy for designing high-performance demulsifiers is proposed. It hypothesizes that integrating mesoscopic molecular simulations with macroscopic physicochemical experiments can enhance the understanding and effectiveness of demulsifiers. Specifically, it is suggested that amphiphilic hyperbranched polyethyleneimine (CHPEI) could act as an efficient demulsifier in oil–water systems, with its performance influenced by its adsorption behaviors at the oil–water interface and its ability to disrupt asphaltene-resin aggregates.Experiments: Several coarse-grained models of oil–water systems, with CHPEI, are constructed using dissipative particle dynamics (DPD) simulation. Following the insights gained from the simulations, a series of CHPEI-based demulsifiers are designed and synthesized. Demulsification experiments are conducted on both simulated and crude oil emulsions, with the process monitored using laser scanning confocal microscopy. Additionally, adsorption kinetics and small angle X-ray scattering are employed to reveal the inherent structural characteristics of CHPEI demulsifiers.Findings: CHPEI demonstrates over 96.7 % demulsification efficiency in high acid-alkali-salt systems and maintains its performance even after multiple reuse cycles. The simulations and macroscopic experiments collectively elucidate that the effectiveness of a demulsifier is largely dependent on its molecular weight and the balance of hydrophilic and hydrophobic groups. These factors are crucial in providing sufficient interfacial active functional groups while avoiding adsorption sites for other surfactants. Collaborative efforts between DPD simulation and macroscopic measurements deepen the understanding of how demulsifiers can improve oil–water separation efficiency in emulsion treatment.

Effect of hydrophilic group substituent position on adhesion at the emulsified asphalt/aggregate interface

Emulsified asphalt offers energy-saving and environmental benefits, aligning with low-carbon, high-quality development requirements. However, poor adhesion hampers the development of emulsified asphalt. The hydrophilic group substituent position significantly influences the adhesive strength at the emulsified asphalt/aggregate interface. To further elucidate this mechanism, this study employs molecular dynamics (MD) simulation techniques, focusing on the positional variations of the hydrophilic group in the sodium dodecylbenzene sulfonate molecule, particularly the SDBS2–1#, SDBS3–1#, and SDBS4–1# configurations. The objective is to enhance adhesion between these two materials. The simulation results were validated through macroscopic demulsification experiments, encompassing a comprehensive analysis of various parameters, including relative concentration distribution, diffusion coefficient, adhesion work, electron density difference, and electrostatic potential distribution. The result demonstrated a strong synergistic effect between the emulsifiers' molecular structure and the aggregates' chemical composition. The emulsifier SDBS4–1# with para-substitution enhances adhesion at the interface between the emulsified asphalt and alkaline aggregate (CaCO₃) by 50.4 %. The emulsifier SDBS2–1# with ortho-substitution enhances adhesion at the interface between the emulsified asphalt and acidic aggregate (SiO₂) by 33.3 %. Furthermore， the emulsifiers SDBS4–1# and SDBS2–1# promote the accumulation of electrons in asphalt molecules on CaCO₃ and SiO₂ surfaces, respectively. This increase in electron accumulation enhances the adhesion performance between emulsified asphalt and aggregate at their interface. Therefore, optimizing the structure of emulsifier molecules significantly increases the bonding strength between emulsified asphalt and aggregate surfaces.

Quantifying the influence of lipophilic carbon chain length on adhesion between emulsified asphalt and acidic aggregates

ABSTRACT Emulsified asphalt technology conserves resources and reduces costs while aligning with the principles of low-carbon and high-quality development. Acidic aggregates demonstrate excellent mechanical properties and are suitable alternatives to alkaline aggregates. This study develops molecular dynamics models and macroscopic experiments to quantify the influence of carbon chain length on the adhesion between emulsified asphalt and acidic aggregate interfaces from a molecular perspective. The results revealed that aromatics and saturates exhibit high sensitivity to variations in carbon chain length. Their adsorption on the SiO2 interface is directly proportional to the carbon chain length. The diffusion coefficient and adhesion parallelly show an initial increase followed by a decrease with the same factors. The van der Waals forces contributed to more than 67% of the adhesion. Water molecules establish hydrogen bonds with the hydroxyl groups on the SiO2 interface, thereby decreasing the adhesion between the emulsified asphalt and the SiO2 interface. The strong hydrogen bonds between free water and asphalt hinder the accumulation of asphalt at the SiO2 interface. In summary, regulating the emulsifier through the carbon chain length and chloride ions enhances the adhesion between the emulsified asphalt and acidic aggregate interface.

Influence of tartaric acid on the electron transfer between oxyanions and lepidocrocite

Iron oxide minerals control the environmental behavior of trace elements. However, the potential effects of electron transfer directions by iron oxides between organic acids and trace elements remain unclear. This study investigates the redox capacity of tartaric acid (TA) with chromate (Cr(Ⅵ)) or arsenate (As(V)) on lepidocrocite (Lep) from the perspective of electron transfer. The results demonstrated the configurations of TA (bidentate binuclear (BB)), As(V) (BB), and Cr(Ⅵ) (BB and protonated monodentate binuclear (HMB)) on Lep. Frontier molecular orbital calculations and X-ray photoelectron spectroscopy (XPS) binding energy shifts further indicated different electron transfer directions between TA and the oxyanions on Lep. The iron of Lep might act as electron acceptors when TA is adsorbed, whereas the iron and oxygen of Lep act as electron donors when As(V) is adsorbed. The iron of Lep might accept electrons from its oxygen and subsequently transfer these electrons to Cr(Ⅵ). Macroscopic validation experiments showed the reduction of Cr(VI), whereas no reduction of As(V). The XPS analysis showed a peak shift, with the possible formation of As–Fe–TA ternary complexes and electron transfer on Lep. These findings indicate that mineral interfacial electron transfer considerably influences the transport and transformation of oxyanions.

Mechanisms of interface electrostatic potential induced asphalt-aggregate adhesion

The electrostatic potential at the interface of the asphalt molecular and aggregate oxides is the primary factor generating the adhesion between the asphalt-aggregate contact surfaces. However, the route of electrostatic potential affecting the asphalt-aggregate adhesion is yet to be determined at the molecular level. This study proposed that the electron accumulation at the interface of the asphalt molecular and aggregate oxides generates a significant electrostatic potential hence to induce the adhesion between the asphalt and aggregate in asphalt pavement. A microscopic molecular dynamics (MD) simulation incorporated with macroscopic adhesion work experiments is conducted to analyze the interface adhesive performance between the asphalt and aggregate. The adhesion work experiment demonstrated the effect of aggregate surface oxides on asphalt adhesion at the macro level and further verified the simulation results. The result demonstrated that a notable electron accumulation can be observed by MD at the interface of asphalt molecular and multiple oxides which generates the electrostatic potential. The strong electrostatic attractions and hydrogen bonds between alkaline oxides (MgO, CaO, CaCO3) and asphalt molecules enhance the relative concentration distribution, diffusion coefficient, and adhesion of asphalt on the aggregate surface. The significant electrostatic potential difference at the interface of the asphalt molecular and the oxide enables a strong adhesion between them due to the near-surface failure potential. Besides, the negative charge accumulation on both the benzene ring structure and oxygen atoms in the asphalt molecules results in poor adhesion at the interface of asphalt molecules and multiple oxides. It was found that a high correlation exists between the MD prediction and experimental testing results. Thus, this research provides a valuable tool for guiding the pairing and selection of asphalt with various minerals for pavement design, construction, and maintenance agencies.

Design and analysis of quorum sensing language “Interpreter” ecosystem for microbial community

Microbes in diverse natural communities communicate via quorum sensing (QS) signals that act as microbial languages. QS-based communications have been reconstructed in two-strain microbiota for promising consortium-based applications. However, investigation and synthesis of multiple QS signals transmission in the QS communication network (QSCN) are less explored. In this study, QS language “interpreter” was proposed and constructed in five Escherichia coli strains to simulate the linear and circular QSCN among natural microbial communities. Specifically, by combining strain-level microscopic and bulk-level macroscopic measurements, we investigate the performances and dynamics of synthetic three-strain QS language “interpreter” ecosystems that are in response to dramatic environmental changes. Results of micro- and macroscopic experiments showed that the existence of complex QS language “interpreter” ecosystems promote the stability maintenance of microbial community. Furthermore, a comprehensive kinetic computational model was developed for the optimization of tunable directed QSCN. Finally, the perspectives of the QSCN for the effective control of microbial communities were discussed and summarized. This study revealed the dynamic control of complex microbial communications, contributing to ecosystem-based engineering and microbiome-based therapeutics.