Number Of Bonds Research Articles

Electron beam irradiation coupled ultrasound-assisted natural deep eutectic solvents extraction: A green and efficient extraction strategy for proanthocyanidin from walnut green husk

Proanthocyanidin (PAC) is recognized as a potent natural antioxidant that prevents various diseases. As societal awareness increases, eco-friendly and efficient natural product extraction technologies are gaining more attention. In this study, an electron beam irradiation (EBI) coupled with ultrasound-assisted natural deep eutectic solvents (NADES) extraction method was developed to enable the green and highly efficient extraction of PAC from walnut green husk (WGH). NADES, prepared with choline chloride and ethylene glycol, demonstrated excellent extraction capacity and storage stability for PAC. Molecular dynamics simulations elucidated the high compatibility between NADES and PAC, attributed mainly to a higher SASA value (207.85 nm2), a greater number of hydrogen bonds (330.99), an extended hydrogen bonding lifetime (4.54 ps), and lower inter-molecular interaction energy. Based on these findings, the optimal conditions (13 kGy EBI, 42 mL/g liquid-solid ratio, 38 °C extraction temperature, 70 min extraction time) resulted in a maximum PAC extraction yield of 56.34 mg/g. Notably, this yield was 32.93 % higher than that observed in samples not treated with EBI and ultrasound-assisted extraction (UAE). Analysis of tissue morphology, extract functional groups and thermal behavior suggested a possible mechanism for the synergistically enhanced PAC extraction by the EBI-NADES-UAE method. Additionally, the PAC extracted using the NADES by the EBI coupled with ultrasound-assisted method exhibited outstanding antioxidant activity (comparable to Vc), digestive enzyme inhibition (IC50: 17–0.61 mg/mL), and anti-glycation capacity (IC50: 86.49 μg/mL). Overall, this work provided a green and efficient strategy for PAC extraction from WGH, elucidated the extraction mechanism and bioactivities, and offered valuable insights for potential industrial applications.

Investigation into geometric configurations and electronic properties of CeO2-supported gold clusters

A detailed understanding of the geometric structure and electronic properties of gold nanoparticles on the ceria surface is crucial for comprehending their unique catalytic activity. Using the first-principles method based on density functional theory, the adsorption of Aux (x = 1–4) clusters on the CeO2(111) surface was studied. It was discovered that the standing configurations of Au2 and Au3, as well as the tetrahedral structure of Au4, are the most stable adsorption structures. The stability of these configurations is jointly determined by the number and strength of Au-Au bonds, the Au-O bonding energy, and the interaction dynamics between the clusters and the substrate. The analysis of Bader charge, difference charge density and density of states suggested that lattice relaxation and electronic localization occur in the reduced Ce3+. The reduced amount and location of Ce3+ are significantly influenced by the position and charge transfer amount of Aux cluster. The adsorption of CO on Au4/CeO2(111) indicated that stronger Au-C bonding energy due to the hybridization of Au-5d and C-2p, thereby enhancing the catalytic activity for CO oxidation reactions.

DEM investigation into the small-strain stiffness of bio-cemented soils

AbstractBio-mediated methods, such as microbially induced carbonate precipitation, are promising techniques for soil stabilisation. However, uncertainty about the spatial distribution of the minerals formed and the mechanical improvements impedes bio-mediated methods from being translated widely into practice. To bolster confidence in bio-treatment, non-destructive characterisation is desired. Seismic methods offer the possibility to monitor the effectiveness and mechanical efficiency of bio-treatment both in the laboratory and in the field. To aid the interpretation of shear wave velocity measurements, this study uses the discrete element method to examine the small-strain stiffness of bio-cemented sands. Bio-cemented specimens with different characteristics, including properties of the host sand (void ratio, uniformity of particle size distribution) and properties of the precipitated minerals (distribution pattern, content, Young’s modulus), are modelled and subjected to static probing. The mechanisms affecting the small-strain properties of cemented soils are investigated from microscopic observations. The results identify two mechanisms controlling the mechanical reinforcement associated with bio-cementation, namely the number of effective bonds and the ability of a single bond to improve stiffness. The results show that the dominant mechanism varies with the properties of the host sand. These results support the use of seismic measurements to assess the mechanical efficiency and effectiveness of bio-mediated treatment.

Structural and network analysis of ADAM9 and ADAM10 and its transcript expression in the male reproductive tract of Bos Taurus

A disintegrin and metalloproteinases (ADAMs) are a family of proteins expressed as transmembrane and secreted proteins in tissues. This study investigated the expression of glycoproteins and transcripts of ADAM9 and ADAM10 in different regions of the bovine male reproductive tract (MRT). Fresh bovine samples were collected from the testis, epididymis, and vas deferens of MRT for this study. Special stains were utilized for identifying glycoproteins depending on the type of mucopolysaccharides in the seminiferous tubules of the testis and epithelial cells of the epididymis and vas deferens. Quantitative real-time PCR (qPCR) was used to assess the mRNA concentrations of ADAMs9 and 10. Additionally, structural and network analysis was performed to investigate the similarity between human and bovine ADAM9 and ADAM10. Variable glycoprotein (acidic and neutral mucopolysaccharides) expression was observed in the seminiferous tubules of the testis and epithelial cells of the epididymis and vas deferens. ADAM9 and 10 mRNA were detected in the testis epididymis and vas deferens, with ADAM9 expression being significantly higher than ADAM10 mRNA expression in the testis and tail of epididymis. Significant similarity between the protein sequence of human and bovine ADAM9 (85.75%) and ADAM10 (96.66%) was observed, while the similarity between protein sequence of ADAM 9 and ADAM10 in humans and bovine was <26%. Bovine ADAM9 showed 4 binding sites, while bovine ADAM10, human ADAM9, and human ADAM10 showed 7 binding pockets, each with considerable variations in the affinity of specific antibody sequences to these binding pockets. Network analysis confirmed that ADAM9 and ADAM10 have critical roles in physiological processes involving cell migration, protease activity, and secretase-related functions. In addition, they have large numbers of hydrogen bonds to most other members of the ADAM family. Our study reports similarities in the expression of glycoproteins and ADAM9 and ADAM10 mRNA in the MRT of Bos Taurus. Structural and network analysis of ADAM9 and ADAM10 suggested functional similarities in these proteins, which are likely to be in facilitating spermatogenesis, transcervical sperm migration, egg-sperm fusion, and fertilization. Further, the similarity between human and bovine ADAM9 and ADAM10 proteins suggests that bovine sperms can be considered as a model system for comparative medicine studies.

Effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane on the micellization thermodynamics and physicochemical properties of HS 15 and TW 80 micelles based on differences in functional groups

Herein, we investigated the effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane, each possessing varying functional groups, on polyoxyl 15 hydroxystearate (HS 15) and polysorbate 80 (TW 80) micelles. Initially, the critical micelle concentration (CMC) for both systems was determined. Subsequent measurements included the particle size, zeta potential, cloud point, micropolarity, number of aggregates, and fluorophore release profile. Finally, the number of hydrogen bonds was confirmed through molecular docking technology. Results showed distinct effects of different functional groups on TW 80 and HS 15 micelles, exhibiting a decreasing trend of CMC, Amin, Gmin, particle size, and polydispersity index (PDI) with increased functional group polarity, alongside increased zeta potential, decreased cloud point, enlarged hydrophobic region, and rapid fluorophore quenching. In particular, acids with carboxyl groups exhibited enhanced stability with HS 15 and TW 80 micelles owing to differences in polarity, solubilization sites, and intermolecular forces. Using tanshinone extract as a model drug, the study explored HS 15 and TW 80 micelles as drug carriers, and results indicated that 2-ethylbutyric acid micelles exhibited better bacterial inhibition against Staphylococcus aureus. Considering that the surface of bacteria was negatively charged, the positively charged nanoparticles exhibited strong electrostatic interactions with the bacteria, which exerted a superior antibacterial effect. In summary, 2-ethylbutyric acid micelles displayed the smallest CMC, Amin, Gmin, particle size, and PDI, along with a positive charge, highlighting the potential application of 2-ethylbutyric acid.

Exploring hydrophobicity or hydrophilicity of borophene surface via reactive molecular dynamics simulation

Borophene, a novel two-dimensional material unveiled in 1998, has garnered significant interest among researchers due to its distinct mechanical and electrical characteristics. Efforts to experimentally synthesize borophene continue to captivate researchers’ interest in recent years. Given the current lack of experimental studies on the interaction between water and the borophene surface, molecular dynamics simulation offers a valuable approach for predicting the substance’s reactivity with water. Additionally, such simulations can assess the hydrophilicity and hydrophobicity of borophene, providing valuable insights into its properties. In our current research, we utilized reactive molecular dynamics simulation to investigate the wetting behavior of borophene. Our findings reveal that the borophene surface exhibits hydrophobic characteristics, demonstrating anisotropic wettability. Specifically, the water contact angle was calculated to be 149.11° along the zigzag direction and 148.4° along the armchair direction. The contour map of the interaction energy between a water molecule and the borophene surface revealed a notable energy barrier in the zigzag direction. This barrier contributes to the asymmetric spreading of the water droplet on the surface. Density profiles and radial pair distribution function (RDF) diagrams of the water droplet on the borophene surface further corroborated the hydrophobic nature of borophene by indicating a significant distance between the water droplet and the surface. Moreover, analysis of the number of hydrogen bonds demonstrated that borophene efficiently utilizes nearly all its capacity to form hydrogen bonds. Additionally, we compared the wettability of borophene with that of other two-dimensional materials, such as various graphene allotropes and phosphorene, which have been subjects of recent investigation.

Analysis of the sweetening effects of lactone and ketone compounds in a cheddar cheese matrix using sensory analysis and molecular simulation

This study evaluated the effects of lactone and ketone compounds on sweetness perception in a Cheddar cheese matrix. According to the static sensory evaluation, a ternary mixture of γ-decanolactone/δ-decanolactone/acetoin at middle and high concentrations exhibited a significant sweetening effect closely related to olfactory input. Dynamic sensory evaluation showed that a γ-decanolactone/δ-decanolactone/acetoin ternary mixture at middle and high concentrations could enhance the sweetness perception of a Cheddar cheese matrix at different sucrose concentrations during oral processing. Molecular docking showed that the ternary mixture of γ-decanolactone/δ-decanolactone/acetoin with sucrose-T1R2 increased the number of hydrogen bond binding sites and increased the number of hydrophobic interaction sites. Molecular dynamics suggested that the molecular conformation of sucrose and T1R2 was more compact and stable in the ternary mixture. Additionally, in the presence of the ternary system, the binding free energy of the re-docking of sucrose and T1R2 was −7.28 kcal/mol, indicating that the docking structure is stable. This stability is maintained by the hydrogen bonding and hydrophobic interaction between the T1R2-sucrose complex and aroma mixtures. These findings provide a theoretical basis for using cross-modal perception to sweeten Cheddar cheese to cater to consumers’ pursuit of sweetness.

Microscopic mechanism investigation of extraction of lignin by benzyltriethylammonium chloride-based deep eutectic solvents

Benzyltriethylammonium chloride (BTEAC)-based deep eutectic solvent (DES) has a high delignification rate in the pretreatment of lignocellulose, and the lignin obtained from the removal has the advantages of high purity and low molecular weight. The interaction mechanism between BTEAC-based DES and lignin at molecular level was investigated by multiscale simulation analytical approach. By analyzing the types of weak interaction, charge distribution, number of hydrogen bonds, energy distribution and density distribution in different systems, the influence of six hydrogen bond donor (HBD) structures on the extraction process was clarified. The interaction between Cl- and lignin is mainly electrostatic interaction, and the interaction between BTEA+ and lignin is mainly van der Waals (vdW) interaction. The original π-π stacking of lignin is replaced by the new π-π stacking between BTEA+ and lignin. The effects of different functional groups and length of carbon chain on the interaction were researched. The acidic HBD with short carbon chain has a larger interaction and can affect the ether bond on the lignin. Among them, due to the smaller volume of formic acid (FA), it provides more space for BTEA+ to contact with lignin, resulting in stronger interaction. The molecular-level theoretical foundation underpinning the efficacy of BTEAC-FA in lignin removal during the pretreatment process is provided.

A Molecular Dynamics Study of the Influence of Low-Dosage Methanol on Hydrate Formation in Seawater and Pure Water Metastable Solutions of Methane

The behavior of low concentrations of methanol (0.5 and 1.0 wt% of water) as a promoter for hydrate formation in seawater or pure water metastable solutions of methane was investigated using the classical molecular dynamics method at moderate temperature and pressure. The influence of methanol on the dynamics of the re-arrangement of the hydrogen bond network in seawater and pure water solutions of methane was studied by calculating order parameters of the tetrahedral environment and intermolecular torsion angles for water molecules, as well as by calculating the number of hydrogen bonds, hydrate, and hydrate-like cavities. It was found that hydrate nucleation can be considered a collective process in which the rate of hydrate growth is faster in systems with low concentrations of methanol, and confident hydrate growth begins earlier in a metastable solution without sea salt with a small amount of methanol than in systems without methanol.

Comparative genomic analysis of thermophilic fungi reveals convergent evolutionary adaptations and gene losses

Thermophily is a trait scattered across the fungal tree of life, with its highest prevalence within three fungal families (Chaetomiaceae, Thermoascaceae, and Trichocomaceae), as well as some members of the phylum Mucoromycota. We examined 37 thermophilic and thermotolerant species and 42 mesophilic species for this study and identified thermophily as the ancestral state of all three prominent families of thermophilic fungi. Thermophilic fungal genomes were found to encode various thermostable enzymes, including carbohydrate-active enzymes such as endoxylanases, which are useful for many industrial applications. At the same time, the overall gene counts, especially in gene families responsible for microbial defense such as secondary metabolism, are reduced in thermophiles compared to mesophiles. We also found a reduction in the core genome size of thermophiles in both the Chaetomiaceae family and the Eurotiomycetes class. The Gene Ontology terms lost in thermophilic fungi include primary metabolism, transporters, UV response, and O-methyltransferases. Comparative genomics analysis also revealed higher GC content in the third base of codons (GC3) and a lower effective number of codons in fungal thermophiles than in both thermotolerant and mesophilic fungi. Furthermore, using the Support Vector Machine classifier, we identified several Pfam domains capable of discriminating between genomes of thermophiles and mesophiles with 94% accuracy. Using AlphaFold2 to predict protein structures of endoxylanases (GH10), we built a similarity network based on the structures. We found that the number of disulfide bonds appears important for protein structure, and the network clusters based on protein structures correlate with the optimal activity temperature. Thus, comparative genomics offers new insights into the biology, adaptation, and evolutionary history of thermophilic fungi while providing a parts list for bioengineering applications.

Influence of imidazole-based ionic liquid surfactants on the wetting effect of long-flame coals

In order to study the wetting effect of C12MImBF4, C12MImBr and C12MImCl on long-flame coal, and their mechanism of action on coal-water bonding, physical experiments, molecular dynamics simulation and DFT theoretical calculation were combined in this work. It is confirmed that the imidazole ionic liquid surfactant optimizes the wetting effect by forming hydrogen bonds, reducing the surface tension of water, and increasing the number of free hydroxyl groups in coal. After the wettability test, the concentration of 4 g/L of the three ionic liquid surfactants had the best wetting effect on long-flame coal, and the contact angle at this concentration was reduced by more than 40 % compared with water within 0.2 s after dripping on the coal. Due to the difference in the anionic head group of the three surfactants, there are differences in the number and strength of hydrogen bonds formed between the three surfactants and water molecules, the results of wettability C12MImBF4 > C12MImCl > C12MImBr were presented. Combined with these characteristics of imidazole ionic liquids on long-flame coal, the reasonable application in the wet dust removal process of actual coal mine production can optimize the efficiency of droplet capture of coal particles, so as to effectively improve the dust removal capacity.

Numerical and experimental investigation of the effect of interstitial liquid viscosity on the collapse of wet granular columns

The collapse of wet granular columns with high- and low-viscosity interstitial liquid is investigated through experiments and numerical simulations. By incorporating both capillary and viscous force models of interstitial liquid in the Discrete Element Method (DEM), simulations have been conducted and reproduced consistent collapse processes with the experiment. The influence of water content, contact angle, particle diameter, liquid surface tension, and viscosity is explored over a large parameter space using DEM. For wet granular columns with low-viscosity interstitial liquid of water, the final profile of the collapsed column can be predicted by Bond number (Bo), a ratio of particle gravity to capillary force. For wet granular columns where the inertial effect dominates and both capillary and viscous forces are significant, dimensional analysis is employed to characterize the collapse, indicating that the collapsed profile can be predicted by Bo and Galileo number (Ga). Using water and silicone oils with different viscosities as interstitial liquids, simulations show that the collapsed profile depends on Bo with a low capillary number (Ca ∼ 10−3), Bo and Ga when Ca is intermediate (Ca ∼ 10−1). When Ca is high (Ca > 100), the final profile is solely controlled by Bo and a rolling-collapsed regime is observed.

Effect of lubricant loading in slippery liquid-infused surface for persistent anti-icing performance

Due to the vast applications in biomedical materials and aerospace industry, smart slippery liquid-infused porous surfaces (SLIPSs) have attracted remarkable attention. However, there are still challenges in the fabrication of durable SLIPS. In this work, based on linear polyurea and silicone oil, a series of durable anti-icing surface were fabricated. Based on the long-lasting secretion of lubricant, the ice adhesion strength of 60-PUa was 2.7 ± 0.5 kPa and could remain below 10 kPa even after 30 icing-deicing cycles. And the icing delay time of 60-PUa could be extended up to 870 s at a temperature of −15 °C. The introduction of large numbers of reversible hydrogen bonds in the system and silicone oil made it possible to achieve high self-healing efficiency under natural conditions. The coating system not only improved the ice removal ability, but also had excellent water-sliding properties, the droplet could slide under its own weight on 60-PUa at a tilt angle of 4.7°. This work provides an easy way to fabricate multi-functional SLIPS with durability.

Diastereomer Characterization of PS-Modified Synthetic Oligonucleotides Using Cyclic IMS-MS.

Synthetic oligonucleotides have emerged as effective therapeutics that regulate gene expression to treat and prevent diseases. Oligonucleotide therapeutics are often modified with a substitution of a phosphorothioate (PS) linkage along the phosphodiester backbone to improve the drug performance and stability. The PS modification creates a mixture of diastereomer structures, increasing by a factor of 2n where n is the number of PS linkages. Despite recent draft guidances highlighting the importance of their characterization, analytical methods to measure the resulting diastereomers are currently lacking. Here, we present a method combining tandem mass spectrometry (MS) and tandem ion mobility spectrometry (IMS) using a cyclic IMS-MS instrument to study diastereomers in PS-modified oligonucleotides. This approach requires no enzymatic digestion as the intact oligonucleotides are directly injected into the MS instrument. Analogous to top-down proteomics, MS fragmentation of the intact oligonucleotide results in 3' and 5' fragment ends that have fewer diastereomers than their intact counterpart. Tandem IMS allows for mobility resolution of the diastereomers at the terminal ends. We tested four model oligonucleotides that differ in either the number of PS bonds or sequence to demonstrate the capability of this method to elucidate diastereomer structures on modified oligonucleotides.

Computational and Experimental Comparison of Molecularly Imprinted Polymers Prepared by Different Functional Monomers-Quantitative Parameters Defined Based on Molecular Dynamics Simulation.

In recent years, the advancement of computational chemistry has offered new insights into the rational design of molecularly imprinted polymers (MIPs). From this aspect, our study tried to give quantitative parameters for evaluating imprinting efficiency and exploring the formation mechanism of MIPs by combining simulation and experiments. The pre-polymerization system of sulfadimethoxine (SDM) was investigated using a combination of quantum chemical (QC) calculations and molecular dynamics (MD) simulations. MIPs were prepared on the surface of silica gel by a surface-initiated supplemental activator and reducing agent atom transfer radical polymerization (SI-SARA ATRP). The results of the QC calculations showed that carboxylic monomers exhibited higher bonding energies with template molecules than carboxylic ester monomers. MD simulations confirmed the hydrogen bonding sites predicted by QC calculations. Furthermore, it was observed that only two molecules of monomers could bind up to one molecule of SDM, even when the functional monomer ratio was up to 10. Two quantitative parameters, namely, the effective binding number (EBN) and the maximum hydrogen bond number (HBNMax), were defined. Higher values of EBN and HBNMax indicated a higher effective binding efficiency. Hydrogen bond occupancies and RDF analysis were performed to analyze the hydrogen bond formation between the template and the monomer from different perspectives. Furthermore, under the influence of the EBN and collision probability of the template and the monomers, the experimental results show that the optimal molar ratio of template to monomer is 1:3. The method of monomer screening presented in this study can be extended to future investigations of pre-polymerization systems involving different templates and monomers.

Effect of Hydrolyzed Polyacrylamide on the Emulsion Stability by Multiple Light Scattering and Molecular Dynamics Simulation

AbstractPolymer flooding, using hydrolyzed polyacrylamide (HPAM), is crucial in enhanced oil recovery technology. The effect of the HPAM and NaCl concentration on the stability of the simulated emulsions was assessed through multiple light scattering experiments. The results demonstrated that HPAM significantly enhanced the stability of both oil‐in‐water (O/W) and water‐in‐oil (W/O) emulsions. The HPAM concentration escalated from 200 mg L−1 to 1000 mg L−1, increasing from 1.24% to 1.31% at 60 minute in the average backscattering of W/O emulsions. The average transmittance of O/W emulsions exhibited a significant decline from 2.54% to 0.12%. The NaCl concentration had a small effect on the stability of the emulsions. Molecular dynamics simulations revealed that HPAM adsorbed at the oil water interface by the point‐like nature, with stronger interaction between its amide group and the oil molecule than its carboxyl group. The hydrogen bond number and the hydrogen bond lifetime of HPAM‐H2O and HPAM‐HPAM increase with increasing the number of HPAM molecules at the oil‐water interface, slowing diffusion coefficient of water molecules and increasing the interface thickness. Increasing salinity can weaken the HPAM‐water interaction, reducing the emulsification stability. This work provides insights into the emulsification characteristics and mechanisms of HPAM.

Optimized interfacial tension and contact angle for spontaneous imbibition in low-permeable and oil-wet sandstone cores with light crude oil

Spontaneous imbibition is an important phenomenon of fluid transports in porous media, particularly in liquid environment with a certain range of interfacial tension and wettability. Meanwhile, the spontaneous imbibition could be enhanced with the additions of surfactants, through modifying the oil–water interfacial tension (IFT) and wettability. However, ultra-low IFT impairs the capillary pressure. Hence, appropriate ranges of the IFT and contact angle (CA), though lacking adequate investigations, are key to optimizing spontaneous imbibition. Here, a series of physical experiments were conducted to evaluate the spontaneous imbibition efficiency of surfactant solutions with wide-range IFTs (10−3–101 mN/m) in the porous media of permeability 11 mD, through designed interfacial property measurements with different surfactant concentrations. Besides, the inverse Bond number was employed to determine the optimized interfacial properties during the imbibition. Overall, the best imbibition-induced hydrocarbon recovery is reached at oil viscosity of 25.26 mPa·s, an IFT of 0.1–0.2 mN/m and a CA of 70–80°.

Fluid Dynamics Studies on Bottom Liquid Detachment from a Rising Bubble Crossing a Liquid–Liquid Interface

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.

Fugacity model covering abiotic and biotic matrices to investigate the transfer and fate of perfluoroalkyl acids in a large shallow lake of eastern China

Solving the challenges faced during the measurement of the cross-interface transfer of perfluoroalkyl acids (PFAAs) in lakes is crucial for clarifying environmental behaviours of these chemicals and their efficient governance. This study developed a multimedia fugacity model based on the quantitative water–air–sediment interaction (QWASI) covering abiotic/biotic matrices to investigate the cross-interface transfer and fate of PFAAs in Luoma Lake, a typical PFAA-contaminated shallow lake in eastern China. The accuracy and reliability of the established model were confirmed using Percent bias and Monte Carlo simulation, respectively. Using the QWASI model, the multimedia transfer of the PFAAs and their accumulation and persistence in different sub-compartments were described and measured, and the differences among individual PFAAs were explored. The simulation results showed that the sedimentation and resuspension of PFAAs were the most intense cross-interfacial transfers, and the sediments served as a chemical sink in the long term. A significant negative correlation of NC-F (the number of CF bonds) with the relative outflow flux (TW·out-ct) but a positive correlation with the relative net transfer across the interface between water and aquatic plants (Tp-ct) was detected, indicating that the PFAA migration capacity decreased but the bioaccumulation potential increased with the CF bond number. The persistence in water (Pw) of individual PFAAs ranged from 19.65d (PFOA) to 32.22d (PFOS), with an average of 26.15d; their persistence in sediment (Ps) ranged from 432d (PFBA) to 3216d (PFOS), with an average of 1524d, increasing linearly with an increase in NC-F. The water advection flows into and out of the lake (QW·in and QW·out), the PFAA concentration of water inflow (CW·in), and bioconcentration factor of aquatic plants (BCFp) were the primary parameters sensitive to PFAAs in all sub-compartments, which are essential indexes for exploring promising remediation pathways for lacustrine PFAA contamination based on the fugacity model simulation.

Directional self-migration of droplets on an inclined surface driven by wettability gradient

In the current study, the anti-gravity directional self-migration of droplets on an inclined surface driven by wettability gradient (ω) was investigated using a front-tracking method. A unified mechanical model of droplet motion on an inclined wettability gradient wall was derived, considering the driving force generated by ω (Fd), gravity (G), and flow resistance (Ff). The model demonstrates that ω, G, and inclination angle (α) are key parameters affecting droplet motion. By varying ω, Bond number (Bo), and α, the droplet dynamic characteristics were analyzed, and a real-time Capillary number (Ca) was introduced to measure the droplet migration speed. The results indicate that a larger ω generates a greater Fd, leading to faster migration and more pronounced spreading. When the ratio of the channel width to the droplet diameter is 0.7, the droplet can cross three regions, obtaining double Fd, and Ca curve exhibits a bimodal structure. When the ratio of the channel width to the droplet diameter is 1.2, the droplet slides and spreads in the middle region without ω, resulting in a trimodal Ca curve. A larger Bo implies a stronger gravity effect, reducing the net driving force for upward migration and slowing the migration speed. At α=30° and ω=0.54, Bo reaches its critical value at 0.5, where G exceeds Fd, causing the droplet to slide downward along the wall. α affects droplet motion by controlling the gravitational component along the wall (Gx). A larger α results in a smaller net driving force for upward migration, reducing the migration speed.