Search Results (307)

In the saline, cold, and arid regions of Western China, the adhesive performance at the carbon fiber-reinforced polymer (CFRP)–concrete interface critically affects the long-term reliability of CFRP-strengthened structures. Replacing the organic epoxy resin (EP) with inorganic magnesium phosphate cement (MPC) has been proposed as an alternative. However, comparative studies on the deterioration of MPC- and EP-bonded CFRP–concrete under sulfate freeze–thaw cycles are limited. This study employed double-shear tests to systematically compare the failure modes, ductility, and bond performance of the CFRP–concrete interface bonded with MPC and EP after 25, 50, and 75 sulfate freeze–thaw cycles. The results indicate that, as the number of cycles increased, MPC-bonded specimens exhibited progressive interfacial peeling, whereas EP-bonded specimens underwent abrupt brittle fracture. At 0, 25, 50, and 75 cycles, the peak strains of MPC specimens exceeded those of EP specimens by 9.28%, 10.13%, 5.99%, and 0.86%, respectively, indicating greater ductility. Bond performance declined markedly for both groups as cycles increased, with MPC specimens showing greater deterioration. After 75 cycles, compared with EP-bonded specimens, MPC-bonded specimens showed a 16.56% lower interfacial load capacity, a 21.53% reduction in peak bond stress, and a 6.03% shorter effective bond length. This systematic comparison of MPC- and EP-bonded CFRP–concrete under sulfate freeze–thaw exposure provides guidance for adhesive selection and strengthening practices in saline, cold, and arid regions. Full article

Ultra-high-performance concrete (UHPC) has been widely utilised in strengthening and rehabilitating conventional normal concrete (NC) structures due to its exceptional mechanical properties and durability. However, in cold climates, the interfacial bond between UHPC and NC is susceptible to degradation under freeze–thaw cycles, potentially compromising the composite action and long-term performance of strengthened structures. This study systematically investigated the shear behaviour of a UHPC-NC interface with planted reinforcement subjected to various freeze–thaw conditions. The experiments were conducted considering different numbers of freeze–thaw cycles (0, 20, 40, 60, 80, and 100) and salt solution concentrations (0%, 3.5%, and 5%). Direct shear tests were performed to evaluate interfacial failure modes, mass loss, and shear strength degradation. Results identified three characteristic failure modes: adhesive debonding at the interface, mixed failure involving both the interface and the NC substrate, and crushing failure within the NC substrate. Specimens exposed to 3.5% salt solution experienced the most significant deterioration, exhibiting a 35% reduction in shear strength after 100 freeze–thaw cycles. Normally, lower salt concentrations were found to induce greater interfacial damage compared to higher concentrations. The study underscores the importance of increasing the embedment depth of the planted reinforcement to alleviate stress concentration and enhance interfacial durability in freeze–thaw environments. Full article

Sperm cryopreservation is a key technique in assisted reproductive technologies (ART), livestock breeding, fertility preservation, and wildlife conservation. However, the freeze–thaw process induces significant oxidative stress through the production of reactive oxygen species (ROS) by mitochondria, which can lead to impaired sperm motility, membrane damage, DNA fragmentation, and reduced fertilization potential. MitoQ is a mitochondria-targeted antioxidant consisting of a ubiquinone moiety conjugated to triphenylphosphonium (TPP⁺). MitoQ selectively accumulates in the mitochondrial matrix, where it efficiently scavenges reactive oxygen species (ROS) at their point of origin. This targeted action helps preserve mitochondrial function, sustain ATP production, and inhibit apoptotic signaling. Extensive experimental evidence across diverse species, including bulls, rams, boars, humans, dogs, and goats, shows that MitoQ supplementation during cryopreservation enhances post-thaw sperm viability, motility, membrane integrity, and DNA stability. Optimal dosing between 50 and 150 nM achieves these benefits without cytotoxicity, although higher doses may paradoxically increase oxidative damage. Compared to conventional antioxidants, MitoQ offers superior mitochondrial protection and enhanced preservation of sperm bioenergetics. Future directions involve exploring synergistic combinations with other cryoprotectants, advanced delivery systems such as nanoparticles and hydrogels, and detailed mechanistic studies on long-term effects. Overall, MitoQ represents a promising adjunct for improving sperm cryopreservation outcomes across clinical, agricultural, and conservation settings. Full article

Replacing natural aggregates in cement-stabilized macadam (CSM) with waste rubber particles reduces mineral resource consumption, manages solid waste, and enhances the long-term performance of cementitious materials, addressing environmental challenges. An optimized gradation of rubber particles was proposed based on different combinations of particle sizes. Five rubber particle combinations with different gradations were incorporated into CSM to create a rubberized cement-stabilized macadam (RCSM). The strength of RCSM was verified through compressive and flexural tensile tests. The toughness of RCSM was evaluated using the flexural ultimate failure strain and flexural tensile resilient modulus. Crack resistance was evaluated through freeze–thaw, fatigue, and shrinkage tests. The results indicate that the compressive and flexural strengths of RCSM with 1.18–4.75 mm rubber particles are closest to those of CSM. The ultimate strain of CSM increased by up to 1.83 times with optimized rubber gradation, while its modulus decreased by more than half. Furthermore, RCSM with 1.18–4.75 mm rubber particles exhibited the best performance in fatigue life under high stress ratio, frost resistance, and shrinkage behavior. Comprehensive test results showed that rubber particles ranging from 1.18 to 2.36 mm were most effective in improving the road performance of RCSM. Full article

Three-dimensional-printed concrete (3DPC) is an additive manufacturing technology that forms 3D solids via layer-by-layer printing based on 3D model data, but it consumes large amounts of river sand (RS) and has poor frost resistance. To address these issues, this study used industrial waste electric arc furnace slag (EAFS) as an aggregate at 0–100% replacement ratios to test the workability, mechanical properties, frost resistance, and microstructures of 3DPC specimens. The results show that EAFS improves mortar flowability and extends the printing window, but full replacement increases slump and reduces constructability. The stress dispersion and dense packing effects of EAFS ensure excellent mechanical properties of specimens before and after freeze–thaw cycles. At an 80% EAFS replacement ratio, compressive and flexural strengths increase by 2.52%/13.8% and 10.6%/18.2%, respectively; after freeze–thaw cycles, the specimens exhibit the best frost resistance. The interfacial transition zone between EAFS and cement matrix is only 2 μm, with 1.8% lower porosity and 20.14% fewer harmful pores than the 100% RS specimen after freeze–thaw cycles. In conclusion, 80% EAFS replacement balances 3DPC performance and solid waste utilization, providing important references for EAFS’s safe application in 3DPC and its performance improvement mechanism. Full article

Fiber-reinforced polymer (FRP)–concrete bonding is widely adopted for structural strengthening, yet its durability is highly vulnerable to freeze–thaw (FT) degradation. This study combines experimental testing with interpretable machine learning (ML) to reveal the degradation mechanism and predict the interfacial behavior of FRP–concrete systems under FT exposure. Single-lap shear tests showed that all specimens failed through interfacial debonding accompanied by partial concrete peeling. The ultimate bond strength decreased by 6.0–18.5%, and the peak shear stress dropped by 53–80%, indicating a pronounced loss of ductility and adhesion. To extend the analysis, experimental data were integrated with literature datasets, and three ensemble ML algorithms—AdaBoost, Random Forest (RF), and Extreme Gradient Boosting (XGBoost)—were employed to predict key bond–slip parameters including ultimate bond strength, local maximum bond stress, slip values, and interfacial fracture energy. Among them, XGBoost achieved the highest predictive accuracy, with R² values exceeding 0.94 for most output parameters and consistently low RMSE values. Shapley Additive exPlanations (SHAP) and Partial Dependence Plots (PDPs) further identified adhesive tensile strength, fiber modulus, FRP thickness, and concrete strength as dominant factors and defined their optimal ranges. The findings offer a scientific foundation for evaluating and predicting the long-term bond durability of FRP–concrete systems and support the development of reliable reinforcement strategies for infrastructure in cold and severe environments. Full article

Cold-adapted species display remarkable genomic resilience under prolonged freezing and thawing cycles that would be lethal to most organisms. This review synthesizes current knowledge on the molecular mechanisms of DNA damage response (DDR) and epigenetic regulation that collectively safeguard genome integrity in these organisms. We highlight key DNA repair pathways, including base excision repair (BER), nucleotide excision repair (NER), homologous recombination (HR), and non-homologous end joining (NHEJ), that are activated during freeze–thaw stress to repair oxidative and strand break damage. Epigenetic regulators such as DNA methyltransferases (DNMTs), histone methyltransferases, and histone deacetylases (HDACs) dynamically remodel chromatin and modulate DDR signaling, facilitating efficient repair and transcriptional reprogramming during recovery. Comparative evidence from freeze-tolerant vertebrates, hibernating mammals, and polar fish underscores the conservation of these adaptive pathways across taxa. Integrating these insights provides a molecular network perspective (MNP) linking DDR and epigenetic mechanisms to environmental resilience, with potential applications in crop improvement and biotechnological adaptation strategies for extreme environments. Full article

Concrete structures in western China often endure severe freeze–thaw cycles under sustained loading. However, the combined effects of desert sand admixtures and long-term stress on freeze–thaw durability are insufficiently investigated. The existing research has focused on the material modification of desert sand concrete (DSC) or on the mechanical-environment coupling of ordinary concrete. This leaves a knowledge gap about how sustained compressive stress influences the macro- and mesoscale freeze–thaw behaviour of DSC. This study systematically investigated the freeze–thaw resistance of DSC under varying sustained compressive stresses. Testing methods and conditions were tailored to the climatic characteristics of China’s high-altitude cold regions. Freeze–thaw degradation was assessed using mass loss, relative dynamic modulus of elasticity, and compressive strength. Controlled loading effectively mitigated freeze damage. After cyclic freeze–thaw, the 0.3 and 0.5 stress groups retained 89.36% and 77.92% of their original compressive strength, respectively. Scanning electron microscopy, mercury porosimetry, and CT scanning revealed mesoscale damage mechanisms. Sustained loading optimized pore structure and enhanced compactness. A two-parameter Weibull probability model was then established to describe damage evolution patterns and assess the service life of desert sand concrete under regional climatic conditions. Full article

Biochar shows potential for regulating nitrogen cycling in cold-region soils, but the roles of its different fractions during freeze-thaw cycles (FTCs) remain unclear. To elucidate the regulation of cold-region soil environments by biochar at the fraction scale, we examined the effects of biochar and its fractions (dissolved and undissolved) on soil nitrogen forms and microbial communities under simulated FTCs. The experiment included a constant-temperature control, a freeze–thaw control, and three biochar treatments with pristine biochar (PBC), dissolved biochar fraction (DBC), and undissolved biochar fraction (UBC), respectively, maintained in triplicate at five FTC frequencies (0, 1, 5, 10, and 20). Changes in soil physicochemical properties and nitrogen forms were measured at five FTC frequencies, and microbial community composition was analyzed by high-throughput sequencing after the 20th cycle. Both biochar fractions reduced inorganic nitrogen, with ammonium nitrogen decline resulting from joint action and nitrate nitrogen (NO₃⁻-N) reduction dominated by UBC. PBC alleviated microbial biomass nitrogen stress by relying primarily on its undissolved fraction to enhance soil water retention, organic carbon, and total nitrogen. Redundancy analysis indicated that total nitrogen and NO₃⁻-N were the key factors affecting microbial community composition. Partial least squares structural equation modeling results suggested that soil physicochemical properties influenced microbial community structure characteristics more strongly than nutrient properties. These findings provide a new perspective on the regulatory mechanism of biochar on the agricultural soil environment in cold regions. Full article

Semen cryopreservation is a crucial technology for enhancing reproductive efficiency in livestock production; however, oxidative stress-induced sperm damage during the freeze–thaw process remains a significant challenge. In this study, metabolomics was used to analyze the differences in metabolites in semen from Qinchuan cattle with different freezing tolerance, and to screen out the candidate markers of sperm freezing tolerance. The metabolomics results indicate that a total of 264 differential metabolites were identified, and KEGG pathway annotation revealed that amino acid metabolism (15.07%) were prominently represented, and L-glutamine (L-Gln) showed a particularly high abundance in high freezability group (HFG) compared to the low freezability group (LFG). Further experiments demonstrated that L-glutamine supplementation significantly improved post-thaw sperm motility, plasma membrane integrity, and acrosomal integrity (p < 0.05). It also enhanced sperm antioxidant capacity by increasing the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), while reducing malondialdehyde (MDA) content (p < 0.05). Additionally, L-Gln maintained mitochondrial function and energy homeostasis by elevating mitochondrial membrane potential (MMP) and promoting AMPK phosphorylation (p < 0.05). These results indicate that L-glutamine alleviates oxidative damage during cryopreservation and enhances semen freeze tolerance. Full article

Soil organic matter (SOM) is a key component of nutrient cycling and soil fertility in terrestrial ecosystems. SOM is of great significance to the stability of terrestrial ecosystems and the improvement of soil productivity; to further exert its role, it is first necessary to clarify its actual distribution and occurrence status in specific regions. Under the combined impacts of intensive agriculture, unreasonable farming practices, and climate change, the SOM content in the Songnen Plain is showing a degradation trend, posing multiple stresses on its soil ecosystem functions. This study aims to systematically track the dynamic changes of SOM in the Songnen Plain, assess its spatiotemporal evolution characteristics, and reveal its driving mechanisms. A total of 113 representative soil profiles were selected in 2023; standardized excavation and sampling procedures were employed in the Songnen Plain. Soil pH, SOM, total nitrogen (TN), total phosphorus (TP), total potassium (TK), particle size (PSD), texture, and Munsell soil colors of samples were determined. Temporal variation characteristics, as well as horizontal and vertical spatial distribution patterns, in SOM content in the Songnen Plain were assayed. Structural equation modeling (SEM), together with freeze–thaw of soil and soil color mechanism analyses, was applied to reveal the spatiotemporal dynamics and driving mechanisms of SOM. The result indicated that the distribution pattern of SOM content in horizontal space shows higher levels in the northeastern region and lower levels in the southwestern region, and decreased with increasing soil depth. SEM analysis indicated that TN and PSD were the main positive factors, whereas bulk density exerted a dominant negative effect. The ranking of contribution rates is TN > TK > TP > PSD > annual average temperature > annual precipitation > bulk density. Mechanistic analysis revealed a significant negative correlation between SOM content and R, G, B values, with soil color intensity serving as a visual indicator of SOM content. Freeze–thaw thickness of soil was positively correlated with SOM content. These findings provide a scientific basis for soil fertility management and ecological conservation in cold regions. Full article

Against the backdrop of global climate change intensifying seasonal freeze–thaw cycles, deteriorating soil conditions in farmland within seasonal frost zones constrain agricultural sustainability. This study employed an in situ field experiment during seasonal freeze–thaw periods in the black soil zone of Northeast China to investigate the joint regulatory effects of seasonal freeze–thaw processes and tillage practices on multidimensional features of soil bacterial communities. Key results demonstrate that soil bacterial communities possess self-reorganization capacity. α-diversity exhibited cyclical fluctuations: an initial decline followed by a rebound, ultimately approaching pre-freeze–thaw levels. Significant compositional shifts occurred throughout this process, with the frozen period (FP) representing the phase of maximal differentiation. Actinomycetota and Acidobacteriota consistently dominated as the predominant phyla, collectively accounting for 33.4–49% of relative abundance. Bacterial co-occurrence networks underwent dynamic topological restructuring in response to freeze–thaw stress. Period-specific response patterns supported sustained soil ecological functionality. Furthermore, NCM and NST analyses revealed that stochastic processes dominated community assembly during freeze–thaw (NCM R² > 0.75). Tillage practices modulated this stochastic–deterministic balance: no-tillage with straw mulching (NTS) shifted toward determinism (NST = 0.608 ± 0.224) during the thawed period (TP). Across the seasonal freeze–thaw process, soil temperature emerged as the primary driver of temporal community variations, while soil water content governed treatment-specific differences. This work provides a theoretical framework for exploring agricultural soil ecological evolution in seasonal frost zones. Full article

Buried pipelines in permafrost areas are affected by harsh environments, especially those with defects and damages, which are prone to failure or even leakage accidents. However, current research is limited to single-factor analysis and fails to comprehensively consider the interaction relationships among temperature fields, moisture fields, and stress fields. Therefore, based on the thermodynamic equilibrium equation and the ice–water phase transition theory, this paper constructs the temperature field equation including the latent heat of phase transition, the water field equation considering the migration of unfrozen water, and the elastoplastic stress field equation. A numerical model of the heat–water–force three-field coupling is established to systematically study the influence laws of key parameters such as burial depth, water content, pipe diameter, and wall thickness on the strain distribution of pipelines with defects. The numerical simulation results show that the moisture content has the most significant influence on the stress of pipelines. Pipelines with defects are more prone to damage under the action of freeze–thaw cycles. Based on data analysis, the safety criteria for pipelines were designed, the strain response surface function of pipelines was constructed, and the simulation was verified through experiments. It was concluded that the response surface function has good predictability, with a prediction accuracy of over 90%. Full article

This study addresses the issues of the reduced strength and increased brittleness of non-autoclaved aerated concrete by introducing an ionic modifying additive (MIA) derived from lignin-rich softwood sawdust. The additive is intended to reduce internal stresses during hydration and enhance the stability of the pore structure. Concrete samples containing 10%, 20%, and 30% additive are tested for compressive strength, wear resistance, water absorption, frost resistance, thermal conductivity, and mineral composition. Optimising the MIA content to 20% increases compressive strength by 19%, improves wear resistance by 15%, reduces water absorption by 22%, and achieves a frost resistance class of F50 versus F30 for the control sample. An X-ray diffraction analysis shows a reduction in the portlandite content from 52% to 31%, as well as increased calcite and hatrurite formation. These results confirm that the MIA optimises hydration, enhances microstructural homogeneity, and significantly extends the service life of non-autoclaved aerated concrete under cyclic freeze–thaw conditions. Full article

The cryopreservation of Chengde polled goat semen plays a critical role in conserving genetic resources, enhancing the utilization efficiency of superior breeding bucks, and advancing artificial insemination techniques. However, spermatozoa are vulnerable to oxidative stress during the freezing process, which can significantly compromise sperm motility. In this study, pooled ejaculates from multiple bucks were divided into six groups, including a control group cryopreserved with conventional extender and five treatment groups supplemented with sericin at concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (w/v). The results demonstrated that supplementation of the semen cryoprotectant with 0.6% sericin significantly improved post-thaw sperm viability to 65.25% in Chengde hornless goats, while concurrently reducing both the sperm abnormality rate (p < 0.05) and intracellular ROS levels (p < 0.05). Integrated TMT proteomics and LC/MS metabolomics further compared the 0.6% sericin group with the frozen control group and identified 162 differentially expressed proteins and 109 differential metabolites between the sericin supplementation and frozen control groups. Functional analysis revealed the significant enrichment of differential metabolites, such as glutamine, in the alanine, aspartate, and glutamate metabolism pathway, concomitant with the marked upregulation of antioxidant proteins including LRP8, GSTM3, and SIRT2. Thus, 0.6% sericin enhances cryotolerance primarily by improving sperm viability, reducing oxidative damage, and sustaining energy metabolism. These findings indicate that sericin enhances cryotolerance by reducing oxidative damage and supporting metabolic function, providing preliminary molecular insights for improving goat semen cryopreservation. Full article