Search Results (2,487)

Ion-conductive-hydrogel strain sensors demonstrate broad application prospects in the fields of flexible sensing and bioelectric signal monitoring due to their excellent skin conformability and efficient signal transmission characteristics. However, traditional preparation methods face significant challenges in enhancing adhesion strength, conductivity, and mechanical stability. To address this issue, this study employed a freeze–thaw cycling method, using polyvinyl alcohol (PVA) as the matrix material, tannic acid (TA) as the adhesion reinforcement material, and lithium chloride (LiCl) as the conductive medium, successfully developing an ion-conductive hydrogel with superior comprehensive performance. Experimental data confirm that the PVA-TA-0.5/LiCl-1 hydrogel achieves optimal levels of adhesion strength (2.32 kPa on pigskin) and conductivity (0.64 S/m), while also exhibiting good tensile strength (0.1 MPa). Therefore, this hydrogel shows great potential for use in strain sensors, demonstrating excellent sensitivity (GF = 1.15), reliable operational stability, as the ΔR/R₀ signal remains virtually unchanged after 2500 cycles of stretching, and outstanding strain sensing and electromyographic signal acquisition capabilities, fully highlighting its practical value in the fields of flexible sensing and bioelectric monitoring. Full article

Gradual climate warming is favoring viticulture in Poland. At the same time, there is a lack of information about the suitability of grape varieties grown in Poland for processing. The primary aim of the study was to determine the effect of pre-treatment on the pressing yield of grape juice and its qualitative assessment. The study applied pre-treatment of raw material, involving either enzymatic liquefaction of the pulp in the first case or freezing and thawing of the pulp prior to pressing in the second case. There was considerable variation among the grape varieties studied in terms of the characteristics under analysis. The varietal characteristics had a significant effect on the pressing yield and the quality of the juice obtained. Pre-treatment had different effects on the pressing yield of the individual grape varieties and the quality of the obtained juices. The research carried out may improve the efficiency and quality of agricultural production with the rational use of locally grown grape hybrids. Full article

The Complementary Relationship (CR) principle of evapotranspiration provides an efficient approach for estimating actual evapotranspiration (ET_a), owing to its simplified computation and effectiveness in utilizing meteorological factors. Accurate estimation of actual evapotranspiration (ET_a) is crucial for understanding surface energy and water cycles, especially in permafrost regions. This study aims to evaluate the applicability of two Complementary Relationship (CR)-based methods—Bouchet’s in 1963 and Brutsaert’s in 2015—for estimating ETa on the Qinghai–Tibetan Plateau (QTP), using observations from Eddy Covariance (EC) systems. The potential evapotranspiration (ET_p) was calculated using the Penman equation with two wind functions: the Rome wind function and the Monin–Obukhov Similarity Theory (MOST). The comparison revealed that Bouchet’s method underestimated ET_a during frozen soil periods and overestimated it during thawed periods. In contrast, Brutsaert’s method combined with the MOST yielded the lowest RMSE values (0.67–0.70 mm/day) and the highest correlation coefficients (r > 0.85), indicating superior performance. Sensitivity analysis showed that net radiation (Rn) had the strongest influence on ET_a, with a daily sensitivity coefficient of up to 1.35. This study highlights the improved accuracy and reliability of Brutsaert’s CR method in cold alpine environments, underscoring the importance of considering freeze–thaw dynamics in ET modeling. Future research should incorporate seasonal calibration of key parameters (e.g., ε) to further reduce uncertainty. Full article

Kefiran, the extracellular polysaccharide produced from the Generally Recognized as Safe (GRAS) bacteria in kefir grains, with its well-documented functional and health-promoting properties, constitutes a promising biopolymer with a variety of possible uses. Its compatibility with other biopolymers, such as milk proteins, and its ability to form standalone cryogels allow it to be utilized for the fabrication of films with improved properties for applications in the food and biomedical–pharmaceutical industries. In the present work, the properties of kefiran films were investigated in the presence of milk proteins (sodium caseinate, native and heat-treated whey proteins, and their mixtures), alongside glycerol (as a plasticizer) and cryo-treatment of the film-forming solution prior to drying. A total of 24 kefiran films were fabricated and studied for their physical (thickness, moisture content, water solubility, color parameters and vapor adsorption), mechanical (tensile strength and elongation at break), and optical properties. Milk proteins increased film thickness, solubility and tensile strength and reduced water vapor adsorption. The hygroscopic effect of glycerol was mitigated in the presence of milk proteins and/or the application of cryo-treatment. Glycerol was the most effective at reducing the films’ opacity. Heat treatment of whey proteins proved to be the most effective in increasing film tensile strength, reducing, at the same time, the elongation at break, while sodium caseinates in combination with cryo-treatment resulted in films with high tensile strength and the highest elongation at break. Cryo-treatment, carried out in the present study through freezing followed by gradual thawing of the film-forming solution, proved to be the most effective factor in decreasing film roughness. Based on our results, proper selection of the film-forming solution composition and its treatment prior to drying can result in kefiran–glycerol films with favorable properties for particular applications. Full article

Hydrogels, especially Polyvinyl alcohols, have received extensive attention as alternative materials for articular cartilage. Aiming at the problems such as low strength and poor toughness of polyvinyl alcohol hydrogels in practical applications, an enhancement and modification strategy is proposed. Sodium alginate fibers were introduced into polyvinyl alcohol hydrogel network through physical blending and freezing/thawing methods. The prepared composite hydrogels exhibited a three-dimensional porous network structure similar to that of human articular cartilage. The mechanical and tribological properties of hydrogels have been significantly improved, due to the multiple hydrogen bonding interaction between sodium alginate fibers and polyvinyl alcohol. Most importantly, under a load of 2 N, the friction coefficient of the PVA/0.4SA hydrogel can remain stable at 0.02 when lubricated in PBS buffer for 1 h. This work provides a novel design strategy for the development of high-performance polyvinyl alcohol hydrogels. Full article

To address the freezing damage to tunnel lining caused by frost heaving of the surrounding rock in water-rich tunnels in cold regions, a numerical thermo-mechanical coupling model for tunnel-surrounding rock that considers the anisotropy of frost heave deformation was established by examining overall frost heaves in a freeze–thaw cycle. Using a COMSOL Multiphysics 6.0 platform and the sequential coupling method, the temperature field evolution of tunnel-surrounding rock, freezing cycle development, and distribution characteristics of the frost heaving force of a tunnel lining under different minimum temperatures, numbers of negative temperature days, frost heave ratios, and anisotropy coefficients of frost heave deformation were systematically simulated. The results revealed that the response of the temperature field of tunnel-surrounding rock to the external temperature varies spatially with time lags, the shallow surface temperatures and the area around the lining fluctuate with the climate, and the temperature of the deep surrounding rock is dominated by the geothermal gradient. The extent of the freezing cycle and the frost heaving force increase significantly when lowering the minimum temperature. The maximum frost heaving force usually occurs in the region of the side wall and the spring line, and tensile stress is prone to be generated at the spring line; the influence of slight fluctuations in the minimum temperature or the short shift in the coldest day on the frost heaving force is limited. A substantial increase in frost heaving force is observed with higher frost heave ratios; for example, an increase from 0.25% to 2.0% results in a 116% rise at the sidewall. Although the increase in the anisotropy coefficient of frost heave deformation does not change the overall distribution pattern of frost heaving force, it can exacerbate the directional concentration of frost heave strain, which can increase the frost heaving force at the periphery of the top arch of the lining. This study revealed the distribution pattern and key influencing factors of the freezing cycle and frost heaving force for tunnels, providing a theoretical basis and data reference for the frost resistance design of tunnels in cold regions. Full article

Poor solubility and bioavailability have limited the application of fucoxanthin in drug and functional food processing. In order to encapsulate fucoxanthin in delivery systems, in this study, cellulose was isolated from industrial brown algae residues and high-pressure homogenized into cellulose nanofibrils (CNFs). Then, fucoxanthin was encapsulated into the Pickering emulsion stabilized by the CNFs. The effect of high-pressure homogenization on the characteristics of cellulose and the stability of fucoxanthin emulsion was evaluated. The results indicated that CNFs prepared at 105 MPa had a diameter of 87 nm and exhibited high zeta potential and thermal stability. Encapsulation efficiency peaked at 70.8% with 1.0 mg/mL fucoxanthin, and after three freeze–thaw cycles the encapsulation efficiency was higher than 60%. The DPPH scavenging activity after 12 days’ storage at 4 °C was still 42%. Furthermore, the Pickering emulsion with 1.0 mg/mL fucoxanthin showed high stability and antioxidant activity under different pH values, salinity, temperature, and UV light exposure duration. The CNFs effectively protected fucoxanthin from degradation, offering a novel delivery system for marine bioactive compounds. To the best of our knowledge, this is the first study on the fucoxanthin delivery system of Pickering emulsion stabilized by the CNFs. Such emulsion might benefit the encapsulation and release of bioactive components in marine drugs. Full article

Zwitterionic hydrogels have emerged as eco-friendly anti-fouling materials owing to their superior hydration-mediated resistance to biofouling. Nevertheless, their practical utility remains constrained by intrinsically poor mechanical robustness. Herein, this study proposes a novel strategy to develop novel tough zwitterionic hydrogels by freezing the gels’ polymer network. As a proof of concept, a zwitterionic hydrogel was synthesized via copolymerization of hydrophobic monomer phenyl methacrylate (PMA) and hydrophilic cationic monomer N-(3-dimethylaminopropyl) methacrylamide (DMAPMA), followed by post-oxidation to yield a zwitterionic structure. At service temperature, the rigid and hydrophobic PMA segments remain frozen, while the hydrophilic zwitterionic units maintain substantial water content by osmotic pressure. Synergistically, the zwitterionic hydrogel achieves robust toughness and adhesiveness, with high rigidity (66 MPa), strength (4.78 MPa), and toughness (2.53 MJ/m³). Moreover, the hydrogel exhibits a distinct temperature-dependent behavior by manifesting softer and more stretchable behavior after heating, since the thawing of the gel network at high temperatures increases segmental mobility. Therefore, it achieved satisfactory adhesiveness to substrates (80 kPa). Additionally, the hydrogel demonstrated remarkable anti-fouling performance, effectively suppressing biofilm formation and larval attachment. In summary, this work opens up promising prospects for the development of zwitterionic hydrogels with high application potential. Full article

This study systematically investigated the corrosion evolution and protective mechanisms of X80 pipeline steel in Xinjiang’s saline soil environments under freeze–thaw cycling conditions. Combining regional soil characterization with laboratory-constructed corrosion systems, we employed electrochemical impedance spectroscopy, potentiodynamic polarization, and surface analytical techniques to quantify temporal–spatial corrosion behavior across 30 freeze–thaw cycles. Experimental results revealed a distinctive corrosion resistance pattern: initial improvement (cycles 1–10) attributed to protective oxide layer formation, followed by accelerated degradation (cycles 10–30) due to microcrack propagation and chloride accumulation. Synchrotron X-ray diffraction analyses identified sulfate–chloride ion synergism as the primary driver of localized corrosion disparities in heterogeneous soil matrices. A comparative evaluation of asphalt-coated specimens demonstrated a 62%–89% corrosion rate reduction, with effectiveness directly correlating with coating integrity and thickness (200–500 μm range). Molecular dynamics simulations using Materials Studio revealed atomic-scale ion transport dynamics at coating–substrate interfaces, showing preferential Cl⁻ permeation through coating defects. These multiscale findings establish quantitative relationships between environmental stressors, coating parameters, and corrosion kinetics, providing a mechanistic framework for optimizing protective coatings in cold-region pipeline applications. Full article

Semen cryopreservation is associated with sperm vulnerability to oxidative stress and ice crystal-induced damage, adversely affecting in vitro fertilization (IVF) success. This study aimed to investigate the effects of freezing diluent supplemented with antioxidant limonin (Lim), myo-inositol (MYO), and the ice crystal formation inhibitor L-proline (LP) through sperm motility, morphological integrity, and antioxidant capacity. The Lim (150 mM), MYO (90 mM), and LP (100 mM) significantly ameliorated the quality of post-thaw sperm in Debao boar, and combined treatment of these agents significantly enhanced sperm motility, structural integrity, and antioxidant capacity compared with individual agents (p < 0.05). Notably, the combined use of these agents reduced glycerol concentration in the freezing diluent from 3% to 2%. Meanwhile, the integrity of the sperm plasma membrane, acrosome membrane, and mitochondrial membrane potential was significantly improved (p < 0.05), and the result of IVF revealed the total cell count of the blastocysts was also greater in the 2% glycerol group (p < 0.05). In conclusion, the newly developed freezing diluent for semen, by adding Lim (150 mM), MYO (90 mM), and LP (100 mM), can enhance the quality of frozen–thawed Debao boar sperm and reduce the concentration of glycerol from 3% to 2% as high concentrations of glycerol can impair the quality of thawed sperm and affect in vitro fertilization outcomes. In conclusion, the improved dilution solution formulated demonstrated efficacy in enhancing the quality of porcine spermatozoa following cryopreservation and subsequent thawing. Full article

In shallow groundwater areas, the freeze–thaw process can easily exacerbate soil salinization. The variations and migrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, and HCO₃⁻ at the depth of 0–100 cm under shallow groundwater depth (2.63–2.87 m) during the freeze–thaw period were analyzed. And a multi-index comprehensive evaluation method based on factor analysis was employed to investigate the soil salinization degree. The results show that K⁺, Mg²⁺, and HCO₃⁻ exhibited surface enrichment during the freeze–thaw period, while Na⁺, Cl⁻, and SO₄²⁻ accumulated in the frozen layer during the freezing stage. However, there is no surface enrichment of Ca²⁺. During the freezing stage, Mg²⁺ and Cl⁻ exhibited the strongest migration capabilities among cations and anions, respectively. During the thawing stage, K⁺ and HCO₃⁻ were the cation and anion with the highest ionic migration capabilities, respectively. Total salinity (TS), Cl⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Mg²⁺, and residual sodium carbonate (RSC) were identified as the dominant factors influencing the salinization degree during the freeze–thaw period. During the freezing stage, soil salt ions predominantly migrated from the unfrozen to the frozen layer, and the salinization degree in the frozen layer increased with the development of the frozen layer. In the thawing stage, soil salt ions migrated upward from the thawing front, and the salinization degree at the depth of 0–30 cm increased. This study provides insights for the prevention and control of soil salinization in arid regions. Full article

This study looked at the performance requirements of repair materials for concrete structures in cold regions, systematically analyzing the effects of steel fiber dosage (0.7–2.1%), early-strength agent PRIORITY dosage (6–10%), and their coupling effects on the workability, interfacial bond strength, and freeze–thaw resistance of rapid-hardening ultra-high-performance concrete (UHPC). Through fluidity testing, bond interface failure analysis, freeze–thaw cycle testing, and pore analysis, the mechanism of steel fibers and early-strength agent on the multi-dimensional performance of fast-hardening UHPC was revealed. The results showed that when the steel fiber dosage exceeded 1.4%, the flowability was significantly reduced, while a PRIORITY dosage of 8% improved the flowability by 20.5% by enhancing the paste lubricity. Single addition of steel fibers decreased the interfacial bond strength, but compound addition of 8% PRIORITY offset the negative impact by optimizing the filling effect of hydration products. Under freeze–thaw cycles, excessive steel fibers (2.1%) exacerbated the mass loss (1.67%), whereas a PRIORITY dosage of 8% increased the retention rate of relative dynamic elastic modulus by 10–15%. Pore analysis shows that the synergistic effect of 1.4% steel fiber and 8% PRIORITY can reduce the number of pores, optimize the pore distribution, and make the structure denser. The study determined that the optimal compound mixing ratio was 1.4% steel fibers and 8% PRIORITY. This combination ensures construction fluidity while significantly improving the interfacial bond durability and freeze–thaw resistance, providing a theoretical basis for the design of concrete repair materials in cold regions. Full article

Interfacial solar evaporation has emerged as a promising strategy for freshwater production, where 3D evaporators offer distinct advantages in heat management and salt rejection. Freeze–thaw cycling is a widely adopted fabrication method for 3D hydrogel evaporators, yet the impact of preparation conditions (e.g., freezing temperature) on their evaporation performance remains poorly understood, hindering rational optimization of fabrication protocols. Herein, we report the fabrication of chitosan-based hydrogel evaporators via freeze–thaw cycles at different freezing temperatures (−20 °C, −40 °C, and −80 °C), leveraging its low cost and environmental friendliness. Characterizations of crosslinking density and microstructure reveal a direct correlation between freezing temperature and network porosity, which significantly influences evaporation rate, photothermal conversion efficiency, and anti-salt performance. It is noteworthy that the chitosan hydrogel prepared at −80 °C demonstrates an excellent evaporation rate in high-salinity environments and exhibits superior salt resistance during continuous evaporation testing. Long-term cyclic experiments indicate that there was an average evaporation rate of 3.76 kg m⁻² h⁻¹ over 10 cycles, with only a 2.5% decrease observed in the 10th cycle. This work not only elucidates the structure–property relationship of freeze–thaw fabricated hydrogels but also provides a strategic guideline for tailoring evaporator architectures to different salinity conditions, bridging the gap between material design and practical seawater desalination. Full article

In order to investigate the influence of graphene/rubber powder compound modified asphalt on the low-temperature cracking resistance of drainage asphalt mixtures, graphene/rubber powder compound modified asphalt mixtures were prepared using graphene/rubber powder compound modified asphalt for drainage asphalt mixtures, and compared with SBS-modified asphalt and rubber powder-modified asphalt, and the low-temperature cracking resistance of graphene/rubber powder compound modification asphalt mixtures was investigated through the Marshall Stability Test, Semi-circular Bending Test (SCB), and Freeze–Thaw Split Test. Research was carried out. At the same time, a scanning electric microscope (SEM) was adopted to analyze the micro-mechanism of the graphene/rubber powder compound modified asphalt mixtures under the microscopic condition. The findings showed that graphene dispersed the aggregation of rubber powder effectively in the microscopic state and improved the stability of the composite modified asphalt. The addition of graphene improved the fracture energy of rubber powder composite modified asphalt by 15.68% under the condition of −15 °C to 0 °C, which effectively slowed down the decrease of fracture energy; at −15 °C and −10 °C, the largest stresses were improved by 7.50% and 26.71%, respectively, compared to the drainage asphalt mixtures prepared as rubber powder-modified asphalt and SBS-modified asphalt. After a freeze–thaw cycle, the maximum stress decrease of graphene/rubber powder compound modified asphalt was 21.51% and 10.37% at −15 °C and 0 °C, respectively. When compared to rubber powder-modified asphalt, graphene/rubber powder compound modified asphalt significantly improved the low-intensity cracking resistance of drainage asphalt mixtures at low temperatures, slowed down the decrease of the maximum stress, and its low-temperature cracking resistance was more stable. Full article

In order to explore the influence of the temperature gradient on rock failure degree during freezing and thawing, freeze–thaw-cycle tests were carried out on saturated red sandstone under the conditions of all-directional freeze–thaw and unidirectional freeze–thaw. The results show that the deformation behavior of saturated red sandstone during freeze–thaw cycles is significantly affected by freeze–thaw direction, and the redistribution of water during freeze–thaw cycles leads to significant strain variations. Macro-cracks caused by all-directional freeze–thaw are located in the center of the sample and crack from the inside out, while macro-cracks caused by unidirectional freeze–thaw are perpendicular to the temperature gradient direction and located in the lower part of the sample. Unidirectional freeze–thaw cycles cause the vertical inhomogeneity of the sample to be more obvious, and the uniaxial compressive strength of the sample decreases more significantly in the early stage. After 30 freeze–thaw cycles, the uniaxial strength of all-directional freeze–thaw and unidirectional freeze–thaw samples tends to be stable and virtually identical. The freeze–thaw cycles have seriously damaged the micro-structure of the sample, but the extent of damage to the cementing agents between particles is weaker than that caused by the all-directional freeze–thaw, owing to the seepage path formed in the pore water under unidirectional freeze–thaw conditions. Full article