Search Results (316)

To clarify the effect of sand ratio on the freeze–thaw performance of full solid waste geopolymer concrete (FSWGC) and establish a constitutive model for its post-freeze–thaw mechanical behavior, FSWGC was prepared via alkali activation—using fly ash, slag, silica fume as cementitious materials, and cold-bonded geopolymer lightweight aggregates (CBGLAs) and recycled sand as aggregates. With sand ratios (0.45, 0.55, 0.65) as the core variable, rapid freeze–thaw tests were conducted to measure mass loss, relative dynamic elastic modulus, mechanical properties, and axial compressive stress–strain characteristics of FSWGC. Results show that higher sand ratios significantly aggravate freeze–thaw damage: after 100 cycles, the 0.65 sand ratio specimen has a mass loss rate of 4.61% and a relative dynamic elastic modulus retaining only 34.4% of its initial value, with accelerated strength degradation. This is due to yjr weakened wrapping of recycled sand by cementitious materials, forming a weak interfacial transition zone. The modified Guo constitutive model for FSWGC, and the further established model considering freeze–thaw cycles, accurately describe the stress–strain curve of FSWGC before and after freeze–thaw. This study provides theoretical and experimental support for FSWGC mix optimization, durability design, and mechanical response calculation in cold regions. Full article

Background: Inactivated enterovirus 71 (EV71) vaccines play a vital role in preventing severe cases of hand, foot, and mouth disease, with their quality and stability determined by the degree of viral particle aggregation. Objective: This study aimed to use dynamic light scattering (DLS) for monitoring EV71 particle size, comprehensively evaluate the effects of environmental stresses on viral aggregation, and identify suitable stabilizing agents. Methods: The DLS technique was validated. Using this method, the effects of pH, ionic strength, freeze–thaw cycles, temperature, and mechanical stresses on viral particle size were assessed. Additionally, the ability of different buffer salts and stabilizers to inhibit stress-induced aggregation was systematically evaluated. Results: The DLS method exhibited robust performance. EV71 particles were stable at pH 7.0–7.5. Exposure to 47 °C and magnetic stirring promoted viral aggregation. Phosphate buffer and citrate buffer exhibited the highest inhibitory effects on heat-induced aggregation and stirring-induced aggregation, respectively. M199 and Tween 80 efficiently mitigated heat-induced particle aggregation and shear stress-induced particle aggregation, respectively. Conclusions: This study demonstrated the performance of DLS in viral aggregation monitoring. Additionally, this study revealed tailored stabilization strategies, providing key insights for vaccine formulation and quality control. Full article

This review examines scientific and engineering strategies for adapting bituminous and asphalt concrete materials to the highly diverse climates of Central Asia. The region’s sharp gradients—from arid lowlands to cold mountainous zones—expose pavements to thermal fatigue, photo-oxidative aging, freeze–thaw cycles, and wind abrasion. Existing climatic classifications and principles for designing thermally and radiatively resilient pavements are summarized. Special emphasis is placed on linking binder morphology, rheology, and climate-induced transformations in composite bituminous systems. Advanced characterization methods—including dynamic shear rheometry (DSR), multiple stress creep recovery (MSCR), bending beam rheometry (BBR), and linear amplitude sweep (LAS), supported by FTIR, SEM, and AFM—enable quantitative correlations between phase composition, oxidative chemistry, and mechanical performance. The influence of polymeric, nanostructured, and biopolymeric modifiers on stability and durability is critically assessed. The review promotes region-specific material design and the use of integrated accelerated aging protocols (RTFOT, PAV, UV, freeze–thaw) that replicate local climatic stresses. A climatic rheological profile is proposed as a unified framework combining climate mapping with microstructural and rheological data to guide the development of sustainable and durable pavements for Central Asia. Key rheological indicators—complex modulus (G*), non-recoverable creep compliance (Jnr), and the BBR m-value—are incorporated into this profile. Full article

Cryopreservation is a crucial technique for the long-term preservation of swine genetic resources. However, its efficiency remains limited by cryo-induced oxidative stress, which compromises sperm membrane integrity, mitochondrial function, and fertilizing capacity. Methyl gallate (MG), a naturally occurring polyphenolic antioxidant, has demonstrated strong free radical scavenging and lipid peroxidation inhibitory properties. This study aimed to evaluate the effects of MG supplementation on sperm quality and fertilization capacity during boar semen cryopreservation. Semen samples were cryopreserved in extenders containing different concentrations of MG (0, 10, 20, 30, and 50 µM). Post-thaw sperm quality, oxidative status, mitochondrial activity, apoptosis-related markers, and in vitro fertilization (IVF) outcomes were comprehensively assessed. The results showed that supplementation with 20 µM MG significantly improved post-thaw motility, viability, membrane and acrosome integrity, mitochondrial membrane potential, ATP content, and antioxidant capacity, while decreasing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and reducing apoptosis (p < 0.05). Moreover, the expression of the anti-apoptotic protein BCL-2 was upregulated, whereas that of the pro-apoptotic protein BAX was downregulated. Sperm cryopreserved with 20 µM MG also exhibited a significantly higher IVF cleavage rate compared with the control group (p < 0.05). In conclusion, MG supplementation effectively enhanced boar sperm cryosurvival by maintaining membrane stability, improving mitochondrial function, and mitigating oxidative stress during freezing and thawing. These findings suggest that MG is a promising antioxidant additive for improving the efficiency of boar semen cryopreservation systems. Full article

Partially frozen soil (PFS) is comprises of coexisting unfrozen water and ice within its pores at subzero temperatures. The review paper examines how unfrozen water content (UWC) and pore ice content interact during phase changes under near-freezing conditions, governed by microscopic thermodynamic equilibrium. Key theories describing why UWC persists (premelting, disjoining pressure) and the soil freezing characteristic curve (SFCC), along with measurement techniques, including the gravimetric approach to advanced nuclear magnetic resonance for characterization of water content. The influence of the water–ice phase composition on mechanical behavior is discussed, signifying pore pressure and effective stress. Various modelling approaches categorized into empirical SFCC, physio-empirical estimations, and emerging machine learning and molecular simulations are evaluated for capturing predictions in PFS behavior. The relevance of PFS to infrastructure foundation, tailings dams, permafrost slope stability, and climate change impacts on cold regions’ environmental geotechnics is also highlighted as a challenges in practical application. Hence, understanding pore pressure dynamics and effective stress in PFS is critical when assessing frost heave, thaw weakening, and the overall performance of geotechnical structures in cold regions. By combining micro-scale phase interaction mechanisms and macro-scale engineering observations, this review paper provides a theoretical understanding of the underlying concepts vital for future research and practical engineering in cold regions. Full article

Nanogels provide unique opportunities for stabilizing fragile enzymes through soft, hydrated polymer networks. Here, we report the development of a glutathione peroxidase (GPx)-loaded nanogel (GPxNG) engineered via a mild “grafting-to” epoxy–amine coupling strategy to enhance enzyme stability and antioxidant function. An amphiphilic copolymer composed of methacrylated 2,2,6,6-tetramethyl-4-piperidyl (PMA) and glycidyl methacrylate (GMA) was synthesized by controlled reversible addition–fragmentation chain-transfer (RAFT) polymerization using a poly(ethylene glycol) (PEG) macro-chain transfer agent (macro-CTA), yielding well-defined polymer chains with reactive epoxy groups. Covalent conjugation between polymer epoxides and GPx enzyme surface amines generated soft, PEGylated nanogels with high coupling efficiency, uniform particle sizes, and excellent colloidal stability. The engineered nanogels exhibited shear-thinning injectability, robust storage stability, and non-cytotoxic behavior in RAW 264.7 macrophages. Compared with native GPx enzyme, GPxNGs demonstrated significantly enhanced reactive oxygen species (ROS) scavenging activity, including strong inhibition of lipid peroxidation and copper-induced low-density lipoprotein (LDL) oxidation. Importantly, the nanogels preserved GPx enzyme activity after extended storage, freeze–thaw cycles, and repeated catalytic use, whereas the free enzyme rapidly lost function. This protective effect arises from the nanoscale confinement of the GPx enzyme within the flexible PEG-based network, which limits unfolding and aggregation. Overall, this work introduces a simple and biocompatible “grafting-to” nanogel platform capable of stabilizing redox-active enzymes without harsh conditions. The GPx nanogels combine high enzymatic preservation, potent antioxidant activity, and excellent handling properties, highlighting their potential as a therapeutic nanoplatform for mitigating oxidative stress-associated disorders such as atherosclerosis. Full article

The paper explored the impact of sodium caseinate (CAS) emulsion on the freeze–thaw stability of konjac glucomannan (KGM)/κ-carrageenan (KC) composite gels. It found that the emulsion and KGM both increased the viscoelasticity of the composite gel, giving it a greater elastic stress. Emulsion addition enhanced the water-holding capacity (WHC) of the KC gel from 72.36% to 89.34%. KGM addition further improved WHC to 97.54%. The hardness of the emulsion KGM/KC gel reached 9.35 N, while the values were essentially not affected by freeze–thaw. This study shows that CAS emulsion, especially under the regulation of KGM and KC, can improve the freeze–thaw stability of the gel system. The results show that emulsion has great potential in regulating the physical and textural properties of multiphase gels. The emulsion coupling method could effectively enhance the freeze–thaw stability of gels, which may provide a new strategy for the development of frozen multiphase gel foods. Full article

Sulfiting agents are common preservatives in the food and beverage industry to inhibit spoilage microorganisms. Sulfite produced by the dissolution of sulfur dioxide (SO₂) in water is used as a microbial inhibitor and antioxidant during winemaking. Thus, sulfite resistance is a desirable trait for wine yeasts. However, consumer health concerns regarding SO₂ exposure require a better understanding of the molecular basis of sulfite resistance/response. In this study, we have developed a highly SO₂-stress-resistant Saccharomyces cerevisiae strain (F3) using evolutionary engineering by repeated batch selection at gradually increased potassium metabisulfite (K₂S₂O₅) levels. F3 was resistant to 1.1 mM K₂S₂O₅ stress, which was strongly inhibitory to the reference strain, and cross-resistant to oxidative, heat, and freeze–thaw stresses. F3 also had enhanced cell wall integrity and altered carbon metabolism, indicating its potential for industrial applications, including winemaking. Comparative whole genome sequencing revealed point mutations in SSU1 and FZF1 that are related to SO₂ transport; ATG14, related to autophagy; and other genes involved in vacuolar protein sorting. Comparative transcriptomic analysis showed significant upregulation of SSU1 and differential expression of genes related to transport and carbohydrate metabolism. These findings may shed light on the molecular mechanisms contributing to SO₂ resistance and industrial robustness in S. cerevisiae. Full article

This study investigated the physicochemical properties and nutrient dynamics on the Romanian shelf of the northwestern Black Sea in July 2024, collecting data across 36 stations (13–1116 m depth) heavily influenced by Danube discharges. Vertical CTD profiling revealed a pronounced seasonal thermocline and a deep-lying permanent halocline. The Cold Intermediate Layer (CIL) boundary, defined by the 8 °C isotherm, was absent, indicating warmer subsurface waters. Surface nutrient concentrations, particularly for nitrate (NO₃) and phosphate (PO₄), were considerably lower than peak eutrophication periods, approaching pre-1970s values, suggesting a positive trend due to reduced anthropogenic loading. They are also comparable to or lower than other coastal regions in the Black Sea. Vertical nutrient profiles confirmed the typical anoxic Black Sea structure, but with regional specifics: the PO₄ maximum was slightly deeper, and the NO₃ maximum position and concentration mirrored the pre-eutrophication period, further supporting reduced anthropogenic nitrogen input. Silicate (SiO₄) concentrations were consistently low throughout the water column, suggesting the northwest shelf functions as a SiO₄ sink compared to the southeastern Black Sea. Overall results indicate a shift towards a less eutrophic state on the Romanian shelf while highlighting the continued dominance of Danube-driven hydrodynamics. In addition to those investigations, this study assessed nutrient preservation techniques, finding that pasteurization was significantly superior to freezing for maintaining the stability of PO₄ and NOx (losses up to 20% and 47% for frozen samples, respectively) over six months. Though SiO₄ was stable under both methods, the freezing produced lower concentrations, possibly from incomplete depolymerization during thawing. These findings stress that pasteurization could be taken into consideration as a reliable preservation technique for long-term storage of nutrient samples. Full article

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