Correlations between the mechanical properties and surface scratch resistance of polylactic acid (PLA) are investigated via tensile and scratch tests on samples after degradation in soil for various times. The results show that the tensile yield strength of PLA is inversely proportional to the natural logarithm of the degradation time, and the scratch resistance and fracture toughness of PLA and the temperature rise near the indenter all increase and then decrease. The surface crystallinity of PLA also increases and then decreases, indicating that it and the scratch resistance are closely related. These findings provide useful information about how PLA behaves under degradation conditions. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).

Understanding the mechanical behaviour of water ice-bearing lunar soil is essential for future lunar exploration and construction. This study employs discrete element method (DEM) simulations, incorporating realistic particle shapes and a flexible membrane, to investigate the effects of ice content, initial packing density, and gravitational conditions on lunar soil behaviour. Initially, we calibrated DEM model parameters by comparing triaxial tests on lunar soil without ice to physical experiments and the angle of repose simulations, validating the accuracy of our approach. Building on this, we conducted simulations on water ice-bearing lunar soil, examining stress-strain responses, shear strain, bond breakage, deviatoric fabric, and N-ring structures. DEM simulations demonstrate that increasing ice content from 0 % to 10 % elevates peak strength from 85 kPa to 240 kPa in loose samples and from 0.2 MPa to 1.62 MPa in dense samples. This strengthening aligns with microstructural stabilization evidenced by 5-ring configurations and narrowed branch vector distributions. Strain field analysis reveals greater deformation magnitudes in icy regolith, suggesting a trade-off between enhanced load-bearing capacity and reduced ductility. These quantified mechanical responses, including strength gain, structural stabilization, and strain localization, reveal the dual engineering implications of water ice in lunar soil.

The discrete element method (DEM) has demonstrated significant advantages in simulating soil-tool interaction and an appropriate contact model notable affected the simulation accuracy. The accuracy of numerical simulation is compromised due to the variations in soil properties when tillage implements are employed in clay-moist soil conditions. This study aims to establish a discrete element model of clay-moist soil based on the Edinburgh Elasto-Plastic Adhesion (EEPA) contact model. Calibration tests using a combination of direct shear tests and cone penetration tests were conducted to identify sensitive parameters that need to be calibrated in the model and analyze the effects of each parameter. The results indicated that contact plasticity ratio and surface energy had significant influence on representing the mechanical properties of clay-moist soil. Then, by utilizing scanning technology to acquire furrow shape data, soil bin test was conducted to validate the reliability of the calibration parameters. Using sensitive parameters as variables, the actual value of clay-moist soil with a moisture content of 33 % as the target value obtained from experimental tests. The optimal combination was: the coefficient of static friction of 0.45, the coefficient of rolling friction of 0.18, and the surface energy of 27.95 J.m-2, the contact plasticity ratio of 0.59. The relative error between the simulated draft force value and the actual measured value was 7.98 %, and the relative errors in the furrow type parameters did not exceed 5 %. The accuracy of the calibration results was verified through comparative analysis of simulation and empirical results. This study provides a scientific approach for employing DEM in modeling clay-moist soil-tool interaction.

Microbial Induced Calcium Carbonate Precipitation (MICP), recognized as a low-carbon and environmentally sustainable consolidation technique, faces challenges related to inhomogeneous consolidation. To mitigate this issue, this study introduces activated carbon into uranium tailings. The porous structure and adsorption capacity of activated carbon enhance bacterial retention time, increase the solidification rate, and promote the growth and distribution of calcium carbonate, resulting in more uniform consolidation and improved mechanical properties of the tailings. Additionally, a novel independently developed grouting method significantly enhances the mechanical strength of the tailing sand samples. To perform a micro-scale analysis of the samples, distinct activated carbon-tailings DEM models are constructed based on varying activated carbon dosages. Physical experiments and parameter calibration are employed to investigate the micro-mechanical properties, such as velocity field and force chain distribution. Experimental and simulation results demonstrate that incorporating activated carbon increases the calcium carbonate production during the MICP process. As the activated carbon content increases, the peak stress of the tailings initially rises and then declines, reaching its maximum at 1.5 % activated carbon content. At 100 kPa confining pressure, the peak stress is 2976.91 kPa, 1.23-1.59 times that of samples without activated carbon and 6.08-7.86 times that of unconsolidated samples. Micro-scale motion analysis reveals that particle movement is predominantly axial at the ends and radial near the central axis. The initial direction of the primary force chains aligns with the loading direction. Following failure, some primary force chains dissipate, while new chains form, predominantly along the axial direction and secondarily in the horizontal direction. Compared with samples without activated carbon, those containing activated carbon exhibit more uniform force chain distribution, higher stress levels, and greater peak stress. This study offers a novel approach to enhance the stabilization and solidification efficiency of MICP and establishes a DEM model that provides valuable insights into the structural deformation and micro-mechanical characteristics of MICPcemented materials.

Cadmium (Cd) contamination in soil threatens global food production and human health. This study investigated zinc (Zn) addition as a potential strategy to mitigate Cd stress using two barley genotypes, Dong-17 (Cd-sensitive) and WSBZ (Cd-tolerant). Hydroponically grown seedlings were treated with different Cd (0, 1.0, 10 mu M) and Zn (0, 5, 50 mu M) levels. Results showed that Zn addition effectively alleviated Cd induced growth inhibition, improving SPAD values, photosynthetic parameters, fluorescence efficiency (Fv/Fm), and biomass. Zn reduced Cd contents in roots and shoots, inhibited Cd translocation, and ameliorated Cd induced ultrastructural damage to organelles. Transcriptomic analysis revealed distinct gene expression patterns between genotypes, with WSBZ showing enhanced expression of metal transporters, antioxidant defense, and stress signaling genes. Significantly, cell wall related pathways were upregulated in WSBZ, particularly lignin biosynthesis genes (PAL, C4H, 4CL, COMT, CAD/SAD), suggesting cell wall reinforcement as a key Cd tolerance mechanism. Zn induced upregulation of ZIP family transporters and downregulation of Cd transporters (HvHMA) aligned with reduced Cd accumulation. These findings provide comprehensive insights into molecular mechanisms of Zn mediated alleviation of Cd toxicity in barley, supporting improved agronomic practices for Cd contaminated soils.

This study presents a hierarchical multiscale approach that combines the finite-element method (FEM) and the discrete-element method (DEM) to investigate tunneling-induced ground responses in coarse-grained soils. The approach considers both particle-scale physical characteristics and engineering-scale boundary value problems (BVPs) simultaneously, accurately reproducing typical tunneling-induced mechanical responses in coarsegrained soils, including soil arching and ground movement characteristics observed in laboratory tests and engineering practice. The study also unveils particle-scale mechanisms responsible for the evolution of soil arching through the underlying DEM-based RVEs. The results show that the rearrangement of microstructures and the deflection of strong contact force chains drive the rotation of macroscopic principal stress and the formation of soil arch. The microscopic fabric anisotropy direction can serve as a quantitative indicator for characterizing soil arching zones. Moreover, the effects of particle size distributions (PSD) and soil densities on ground deformation patterns are interpreted based on the stress-strain responses and contact network characteristics of DEM RVEs. These multiscale insights enrich the knowledge of tunneling-induced ground responses and the same approach can be applied to other geotechnical engineering analyses in coarse-grained soils.

In cold regions, the strength and deformation characteristics of frozen soil change over time, displaying different mechanical properties than those of conventional soils. This often results in issues such as ground settlement and deformation. To analyze the rheological characteristics of frozen soil in cold regions, this study conducted triaxial creep tests under various creep deviatoric stresses and established a corresponding Discrete Element Method (DEM) model to examine the micromechanical properties during the creep process of frozen clay. Additionally, the Burgers creep constitutive model was used to theoretically validate the creep deformation test curves. The research findings indicated that frozen clay primarily exhibited attenuated creep behavior. Under low confining pressure and relatively high creep deviatoric stress, non-attenuated creep was more likely to occur. The theoretical model demonstrated good fitting performance, indicating that the Burgers model could effectively describe and predict the creep deformation characteristics of frozen clay. Through discrete element numerical simulations, it was observed that with the increase in axial displacement, particle displacement mainly occurs at both ends of the specimen. Additionally, with the increase in creep deviatoric stress, the specimen exhibits different deformation characteristics, transitioning from volumetric contraction to expansion. At the same time, the vertical contact force chains gradually increase, the trend of particle sliding becomes more pronounced, and internal damage in the specimen progresses from the ends toward the middle.

Cadmium (Cd) pollution leads to reduced crop yields and poses a threat to human health, making it an important environmental and agricultural safety issue. Selenium [Se(V)] has been shown to alleviate Cd stress in plants; however, the mechanisms underlying Se-mediated protection against Cd toxicity remain largely unclear. In this study, we investigated the physiological and molecular mechanisms of Se(W)-alleviated Cd toxicity in strawberry plants through physio-biochemical and transcriptomic analyses. Our results showed that foliar spraying with Se (IV) increased photosynthetic efficiency, reduced Cd-induced oxidative damage by enhancing antioxidant enzyme activities and soluble sugar contents, thereby improving Cd stress tolerance. Transcriptomic profiling revealed 477 common differentially accumulated transcripts (DATs), predominantly enriched in transporter activity, oxidoreductase function, and antioxidant-related processes. Notably, seven key genes involved in Cd efflux, chelation, secondary metabolite transport and nutrient uptake (FvPCR9-like, FvCBP-like, FvWATI-like, FvMOT1, FvY1476gO214O, FvNR12.1 and FvZIP8) exhibited opposite expression patterns under Se(W) and Cd treatments. Supplementation with Se(IV) also modulated phytohormone signaling, nitrogen metabolism and carbon metabolism pathways, providing a multi-dimensional approach to mitigating Cd-induced physiological disruptions. This study provides novel insights into Se(IV)-mediated Cd stress adaptation, and offers promising strategies for developing low-Cd-accumulating crops, addressing critical environmental and agricultural challenges associated with heavy metal contamination.

Permafrost thaw represents one of Earth's largest climate feedback risks, potentially releasing vast carbon (C) stores as greenhouse gases (GHG). However, our ability to predict emissions remains limited by poor understanding of how changing organic matter (OM) composition affects microbial carbon processing. We test a metabolism-centered redox framework, which views microbial processes as coupled oxidative-reductive reactions, to mechanistically explain how organic matter metabolite quality controls greenhouse gas production in permafrost-affected peatland ecosystems. Rather than relying solely on geochemical redox measurements, our approach examines how microbes balance electron flow through metabolic pathways. Using active layer peat (9-19 cm) from contrasting environments (bog and fen), we employed multi-omics approaches, including metabolomics, metagenomics, and metatranscriptomics, to link OM chemistry to microbial function. Our results reveal distinct dissolved organic matter metabolite composition, with fen systems enriched in compounds with higher substrate quality (low molecular weight (MW) sugars with high H:C ratios and low aromaticity) and bog systems dominated by compounds with lower substrate quality (high MW phenols with lower H:C ratios and higher aromaticity). In fen samples, these sugar-like compounds correlated with higher oxidative metabolism and methanogenesis, supported by increased glycolysis gene expression. Initially, electrons from increased oxidative metabolism were balanced through nitrate and sulfate reduction, but as these electron acceptors were depleted, methanogenesis increased to maintain redox balance. Fen samples showed rapid degradation of both high- and low-substrate-quality compounds, suggesting sufficient energy for efficient C cycling. Conversely, bog samples exhibited more polyphenolic compounds, lower glycolysis activity, and higher stress-related gene expression, suggesting energy was diverted towards cell maintenance under acidic conditions rather than C processing. This approach suggests that predicting greenhouse gas emissions requires an understanding of how organic matter quality shapes microbial energy allocation strategies, providing a mechanistic framework for improving emission predictions from permafrost-affected peatlands and similar ecosystems.

The stress state and density of soil have been considered as the key factors to determine the liquefaction resistance. However, the results of seismic liquefaction case histories, laboratory tests and centrifuge model tests show that the fabric characteristics also influence liquefaction resistance, even more significantly than the contributions of stress state and density. In this study, anisotropic specimens with different consolidation histories were prepared using the 3D Discrete Element Method (DEM) to investigate the influence of fabric characteristics on the mechanical behavior of granular materials and the underlying mechanisms. The simulations revealed that under monotonic shear conditions, horizontally anisotropic specimens exhibited strain hardening and dilatancy characteristics, as well as higher peak strength. Under cyclic shear condition, the normalized liquefaction resistance of the specimens showed a strong linear relationship with the degree of anisotropy, independent of confining pressures and density. Microscopic results indicate that the fabric arrangement aligned with the loading direction leads to the evolution of the mechanical coordination number and average contact force in a manner favorable to resisting loads, which is the underlying mechanism influencing macroscopic mechanical properties. Additionally, the evolution patterns of contact normal magnitude and angle in anisotropic granular materials under cyclic loading conditions were also analyzed. The results of this study provided a new perspective on the macroscopic mechanical properties and the evolution of the microstructure of granular soils under anisotropic conditions.