Freeze-thaw Process Research Articles

Monitoring evolutionary damage of bended concrete beams subjected to freeze-thaw cycling through piezoelectric-enabled wave propagation method

Tunnels in cold regions are often subjected to freeze-thaw cycling, which poses a great challenge to a large number of tunnels in operation or to be built in these regions. Therefore, structural health monitoring (SHM) for lining concrete in cold regions is essential to ensure the safety and long-term operation of tunnels. In this study, the wave propagation method (WPM) is applied for the first time to monitor the cyclic freeze-thaw damage of lining concrete. First of all, the failure behaviors of concrete beams subjected to the coupling effect of flexural loading and freeze-thaw cycling are investigated. Particularly, the authors propose a refined numerical model to simulate the freeze-thaw cycling damage process of concrete beams considering the ice-water phase transition and concrete elastoplastic damage. Based on the numerical results, the internal damage expansion and flexural strength attenuation of concrete beams are revealed. Furthermore, the dynamic attenuation characteristics of stress waves are analyzed by using the wavelet packet decomposition and continuous wavelet transform to reveal. In addition, the WPM-based energy index is proposed to characterize the freeze-thaw damage degree of the lining concrete. A strong correlation is found between the stress wave signal and freeze-thaw damage, with a favorable correlation coefficient of 0.932, suggesting the excellent performance of the WPM in assessing the freeze-thaw damage of lining concrete. This research sufficiently manifests the applicability of the WPM method to monitoring the freeze-thaw damage within cold regional tunnel linings.

Comparative study of Tris Turmeric, Tris Turmeric Dimethyl Sulfoxide and Tris Turmeric Ethylene glycol extenders on the cryosurvivability, sperm resistance, in- vivo fertility and antioxidant status in buffalo bull semen

The freeze-thaw process leads to structural and functional damage due to excessive accumulation of reactive oxygen species (ROS). The addition of exogenous antioxidants to sperm diluents is of great importance to overcome oxidative damage during freezing. The purpose of this study was to explore the effects of three diluents Tris Turmeric, Tris Turmeric Dimethyl Sulfoxide and Tris Turmeric Ethylene glycol on the cold survival ability of buffalo sperm. Semen was collected from five local adult male buffalo breeds. A base diluent of Tris-citric acid-fructose (TCF) was prepared, adding 20% whole egg yolk (TCFY). The Tris extender without turmeric, without DMSO, and without EG was kept as a control. Other extenders are Tris containing turmeric TT (100 ml/5 ml Tris), Tris containing turmeric dimethyl sulfoxide TTD (100 ml/5 ml Tris + 1.5% DMSO) and Tris containing turmeric and ethylene glycol TTE EG (100 ml/5 ml Tris + 1.5% EG). Semen samples were added and a pure sperm concentration of 60 × 106/ml was achieved. Frozen buffalo sperm after thawing showed significant improvements in all research parameters of the three breeding samples compared to the control. Tris Turmeric Ethylene was the type that best improved sperm survival under frozen conditions, followed by Tris Turmeric and Tris Turmeric Dimethyl Sulfoxide compared to the control. A significant decrease in sperm motility after thawing was evident as usage time increased in all expanders. There was a significant increase in total antioxidant content (TAC) and insignificant change in malondialdehyde (MDA) of the diluent used compared to the control. Conception rate (CR) was higher in Tris Turmeric Ethylene glycol (65.2%), followed by Tris Turmeric (60.3%) and Tris Turmeric Dimethyl Sulfoxide (55.9%) compared to the control (36, 7%). It can be concluded that Tris Turmeric Ethylene Glycol is considered the best agent for improving cold survival and sperm fertility, followed by Tris Turmeric and Tris Turmeric Dimethyl Sulfoxide.

Investigating the effects of vitamin B12 and Myo-inositol on human sperm parameters during the freeze-thaw process

Background and aims: While sperm freezing has proven to be beneficial for addressing clinical needs, it can also have negative impacts on sperm function. However, it has been observed that additives with antioxidant properties can help alleviate the damage caused by reactive oxygen species (ROS) and cold shock. The objective of this research was to examine the effects of incorporating vitamin B12 and Myo-inositol into the freezing medium on human sperm and how they influence sperm parameters. Methods: The semen samples of 20 people with normal fertility were divided into four equal parts after preparation, including the control group, vitamin B12, Myo-inositol, and both vitamin B12 and Myo-inositol. Sperm parameters were examined after melting and washing the samples. The obtained data were analyzed with SPSS software (version 23) and analysis of variance (P<0.05). Results: The results revealed that the groups receiving antioxidants experienced a significant improvement in sperm motility, viability, morphology, and total antioxidant capacity (TAC) levels compared to the control group. Based on the obtained data, the average sperm motility in the control group was 40.65±4, which was less than that of the B12 group’s average (49.5±5.92), the Myo-inositol group (68.70±15.42), and the vitamin B12+Myo-inositol group (71.5±8.63), and this difference was significant (P<.001). Conclusion: According to the findings, the quality of sperm and the rate of recovery of sperm parameters increase with an increase in the TAC concentration and a decrease in the malondialdehyde (MDA) concentration.

Investigating soil properties and their effects on freeze-thaw processes in a thermokarst lake region of Qinghai-Tibet Plateau, China

Soil parameters form the foundation of hydrogeological research and are crucial for studying engineering construction and maintenance, climate change, and ecological environment effects in cold regions. However, the soil properties in the permafrost region of the Qinghai–Tibet Plateau (QTP) remain unclear. Hence, in this study, soil temperature (Ts), volumetric specific heat capacity (C), thermal conductivity (K), thermal diffusivity (D), soil water content (SWC), electric conductivity (EC), vertical (Kv) and horizontal (Kh) saturated hydraulic conductivity, bulk density (ρb), and soil texture near the Qinghai-Tibet Railway were measured, and their effects on the freeze-thaw process were evaluated. The results revealed a predominantly sandy loam soil texture, with Kh and Kv showing strong spatial variability, while the other parameters presented moderate spatial variability. Thermokarst lake had a limited influence on D, C, K, and ρb but significantly reduced Kh and Kv. Groundwater affected SWC, Ts, and EC. The model results showed that all parameters indicated small sensitivities to the maximum thawing depth (MTD), with MTD positively responding to all parameters except for Kv and porosity (ρp). Except for Kh and Kv, all parameters showed high sensitivities to the time from starting to complete freezing (TSCF). TSCF responded positively to C, ρp, and density (ρd) and negatively to K and Kh. This study expanded the quantification of soil properties in the QTP, which can help improve the accuracy of cryohydrogeologic models, thus guiding the construction and maintenance of infrastructure engineering.

Evaluation of the effect of lecithin and nanolecithin in repairing membrane damage, maintaining membrane integrity, and improving human sperm function in the freezing-thawing process.

Our study aimed to evaluate the effects of lecithin nanoparticles on sperm quality during cryopreservation. In phase one, sperm-freezing media were prepared with lecithin concentrations (0.5%, 1%, and 2%) and lecithin nanoparticles of various sizes (50-100, 100-200, and ≥ 200nm). Post-thaw, sperm motility, viability, mitochondrial membrane potential (MMP), lipid peroxidation (measured by malondialdehyde, MDA), and DNA fragmentation were evaluated. In phase two, the acrosomal reaction was assessed in the best and worst-performing groups from phase one. DiI labeling detected interactions between lecithin nanoparticles and the sperm membrane. Field emission scanning electron microscopy (FESEM) examined the sperm membrane's surface structure and lecithin binding sites. Atomic force microscopy (AFM) assessed height differences in the sperm surface layer in the best-performing group from phase one. The group treated with 1% lecithin nanoparticles (50-100nm) showed significantly increased viability post-thaw compared to other groups, with reduced DNA fragmentation and MDA levels. While motility significantly decreased in all groups compared to before freezing levels, lower concentrations, and smaller particle sizes yielded better results. MMP also significantly decreased across all groups with no significant differences. The acrosomal reaction significantly decreased with 1% lecithin nanoparticles (50-100nm) compared to the 2% (≥ 200nm) group. DiI-labeled nanoparticles and FESEM revealed that lecithin nanoparticles primarily bound to and infiltrated the sperm membrane, particularly in the head and postacrosomal regions. Lecithin nanoparticles effectively bind to the sperm membrane, protecting it during the freeze-thaw process and improving sperm viability.

Evaluation of a Chemiluminescent Enzyme Immunoassay for the Detection of Prostaglandin E-Major Urinary Metabolite (PGE-MUM).

We developed a fully automated quantitative immunoassay for the detection of prostaglandin E-major urinary metabolite (PGE-MUM). In this study, we evaluated the analytical performance of this assay. Sensitivity, within-run reproducibility, correlation with radioimmunoassay (RIA), cross-reactivity, dilution linearity, spike recovery performance, analyte stability, and effects of coexisting substances were evaluated. The assay was also used to measure PGE-MUM in 211 healthy people. The limit of detection and quantification were 1.0 and 1.3 ng/mL, respectively. When the assay was performed six times in a single run, the coefficient of variation ranged from 1.4% to 2.2%. The coefficient of correlation with a preceding RIA method was 0.970 with a correlation slope of 0.88. There was no cross-reactivity with PGE-MUM analogs. Linearity of dilution was confirmed at up to 16-fold dilution with assay results within 100 ± 20% of the theoretical values calculated based on the undiluted sample. Spike recovery was good and ranged from 94% to 101%. Analyte stability was tested by storing samples at 25°C for 6 days, 10°C for 1 month, and by performing up to five freeze-thaw cycles. Assay results were all within 100 ± 10%, the values measured before storage and before the freeze-thaw process. Assay results in healthy people ranged from 3.1 to 162.7 ng/mL (mean: 35.8 ng/mL). After correction for creatinine, the 95% confidence interval was 8.68-42.25 μg/g creatinine. The assay precisely detects PGE-MUM.

Study of freeze-thaw deterioration of saturated and unsaturated hydraulic concrete based on measured strain

In actual concrete water projects, areas such as the back surface, above-water surface, and even areas where the water level fluctuates are in the unsaturated freeze-thaw state. The complexity of freeze-thaw tests of unsaturated hydraulic concrete has thus far prevented a sound understanding of the mechanisms at work in freeze-thaw deterioration of unsaturated hydraulic concrete. Given this situation, this study first compares three different unsaturated hydraulic concrete freeze-thaw test processes (polyurea seal, paraffin seal, and vacuum-bag seal) and then uses the vacuum-bag seal method to implement freeze-thaw tests of unsaturated hydraulic concrete. Afterward, three test schemes (unsaturated sealed freeze-thaw, water-freeze-thaw without air-entraining agent, and water-freeze-thaw with air-entraining agents) are conducted and the mechanisms of freeze-thaw deterioration of saturated and unsaturated hydraulic concrete are evaluated based on the measured temperature and strain of the concrete specimens. The results reveal a continuous and irreversible deterioration leading to the freeze-thaw damage of unsaturated sealed freeze-thaw specimens and water-freeze-thaw specimens with and without an air-entraining agent. After 200 freeze-thaw cycles, the cumulative residual strain of the aforementioned three test schemes reach 47 με, 616 με, and 273 με, respectively. The thermal expansion coefficient of concrete remains relatively constant with increasing freeze-thaw cycles. Water-freeze-thaw specimens without air-entraining agents have a greater thermal expansion coefficient than those with air-entraining agents, and unsaturated sealed freeze-thaw specimens have the smallest thermal expansion coefficient. The frost heave coefficient increases with increasing freeze-thaw cycles, and water-freeze-thaw specimens without air-entraining agents have greater frost heave coefficients than those with air-entraining agents.

Chestnut soil organic carbon is regulated through pore morphology and micropores during the seasonal freeze–thaw process

Soil aggregates are basic structural units in soil organic carbon (SOC) protection. In alpine ecosystems, the seasonal freeze–thaw (FT) process characterizes soil formation and nutrient cycling. However, previous studies were mostly based on simulated FT experiments, which amplified the effects of natural FT processes. And, the regulations of pore structure on SOC protection/loss of aggregates during the FT processes were still not well understood. To investigate the effect of the seasonal FT process on SOC and pore structure of aggregates, as well as the interactions among them, soil samples were selected during a whole seasonal FT cycle, which can be divided into four periods: unstable freezing (UFP), stable frozen (SFP), unstable thawing (UTP), and stable thawed periods (STP). The results demonstrated that freezing increased SOC concentration as the total organic carbon (TOC) content of all aggregate fractions peaked in the SFP (17.46 g/kg on average). The TOC content of aggregates in the UFP dropped to 7.91 g/kg on average, which revealed a dramatic SOC loss after thawing began. Thawing also decreased the proportions of particulate organic carbon (POC) compared with mineral-associated organic carbon (MAOC). The highest microbial abundance was also found in the SFP. Freezing promoted the formation of pores > 80 μm while thawing increased the regularity of pore morphology. Pore structure explained 48.77 % of the SOC variance in the thawing period, but only 19.29 % of that in the freezing period. Overall, in the freezing process, soil pore structure impacted the SOC input by mediating pore morphology. In the thawing process, soil pore structure inhibited SOC loss by enhancing the formation of pores < 15 μm. These results demonstrate new perspectives on the soil aggregate microstructure–microbe–SOC interactions.

RAFT polymerization assisted P(NIPAm-co-AAc)-AEMR integrated PVA hydrogels: Dual responsive features, texture analysis, and cytotoxicity studies

Modified P(NIPAm-co-AAc) copolymers are prepared using Radical Addition Fragmentation Chain Transfer (RAFT) copolymerization by varying the concentration of castor oil sourced acrylated epoxy methyl ricinoleate (AEMR). Subsequently, hydrogels are prepared by integrating copolymers with polyvinyl alcohol (PVA) via freeze-thaw process. The employment of RAFT polymerization yielded copolymers with dispersity (D) value of 1.2–1.3 revealing the formation of structurally well controlled polymer chains. The lower critical solution temperature (LCST) of the copolymers (∼30–35 °C) are tuned to the range of physiological temperature (∼37 °C) in PVA hydrogel system. Temperature dependent viscoelastic properties indicated that the characteristics of copolymeric solutions and hydrogels are composition dependent while undergoing noncovalent interactions and the conformational changes and the samples showed extremely elastic behaviour beyond LCST. Swelling ratio of hydrogels are also found to be pH dependent, which displayed higher swelling ratio in alkaline and reduced swelling ratio in acidic medium. Cytotoxicity studies with L929 cells showed that the copolymers and hydrogels exhibited desirable biocompatibility, which gets improved with AEMR concentrations. Thus, these dual responsive PA-AEMR-PVA smart hydrogels can be used as a viable functional material for possible bio-medical applications.

Design of self-healing nanocomposite hydrogels and the application to the detection of human exercise and ascorbic acid in sweat

Hydrogel sensors have broad application prospects in human motion monitoring and sweat composition detection. However, hydrogel-based sensors are faced with challenges such as low accuracy and poor mechanical properties of analytes detection. Based on mussel-inspired chemistry, we synthesized mesoporous silica@polydopamine-Au (MPS@PDA-Au) nanomaterials and designed a self-healing nanocomposite hydrogel to monitor human movement and ascorbic acid detection in sweat. Mesoporous silica (MPS) possess orderly mesoporous structure. Dopamine (DA) polymerized on the surface of MPS to generate polydopamine (PDA), forming the composite material MPS@PDA-Au. This composite was then embedded into polyvinyl alcohol (PVA) hydrogels through a simple freeze-thaw cycle process. The hydrogels have achieved excellent deformable ability (508.6%), self-healing property (90.5%) and mechanical strength (2.9 MPa). The PVA/MPS@PDA-Au hydrogel sensors had the characteristics of fast response time (123.2 ms), wide strain sensing range (0–500%), excellent fatigue resistance and stability in human detection. The detection range of ascorbic acid (AA) in sweat was wide (8.0 μmol/L-100.0 μmol/L) and the detection limit was low (3.3 μmol/L). Therefore, these hydrogel sensors have outstanding application prospects in human motion monitoring and sweat composition detection.

Immunofluorescence and biochemical investigation of the protective effects of naringin and diosmin on the freezability of Merino ram semen

BACKGROUND: Various antioxidant substances are added to sperm extenders to protect spermatozoa against oxidative stress and cryodamage. OBJECTIVE: To investigate the effects of the flavonoid diosmin (DIO) and a flavanone glycoside naringin (NAR) on the freezability of ram semen. MATERIALS AND METHODS: In this study, six Merino rams were used during the breeding season. The ejaculates were pooled after collection from the rams. Pooled ejaculates were divided into six groups: control, NAR 1 mM, NAR 2 mM, NAR 4 mM, DIO 2 mM, and DIO 4 mM, and then diluted with a TRIS-based diluent. The pooled semen was equilibrated, placed in 0.25 mL pipettes with 10 × 107 sperm cells in each pipette, and frozen in liquid nitrogen vapor. After 24 h, the pipettes were thawed at 37°C for 25 s and analyzed in terms of spermatological parameters. RESULTS: The highest plasma membrane integrity ratio was found in the DIO 4 mM group, whereas a statistically significant difference was found between the NAR 1 mM and NAR 2 mM groups (p&lt;0.05). While the DIO 4 mM group had the highest acrosome integrity rate, a statistically significant difference was found between the other groups (p&lt;0.05). Mitochondrial activity was the highest in the NAR 4 mM, DIO 4 mM and DIO 2 mM groups (p&lt;0.05). In the analysis of the sperm membrane lipid profile, it was observed that the DIO group had the highest lipid-phospholipid ratio. In sperm membrane protein profile analysis, it was found that both additives exerted protective effects at different levels. The highest total protein content was seen in the DIO 4 mM and NAR 4 mM groups. 8-hydroxydeoxyguanosine (8-OhDG) positivity was more common in the control group than in the DIO and NAR groups. Cu-Zn superoxide dismutase (SOD) expression was lower in the control group and more intense in all other groups. Positive results were especially observed in the acrosome of the sperm cells. CONCLUSION: The addition of NAR and DIO to the ram semen extender increased the quality of sperm parameters after the freeze-thaw process.

Water budgets in an arid and alpine permafrost basin: Observations from the High Mountain Asia

Ground freeze‒thaw processes have significant impacts on infiltration, runoff and evapotranspiration. However, there are still critical knowledge gaps in understanding of hydrological processes in permafrost regions, especially of the interactions among permafrost, ecology, and hydrology. In this study, an alpine permafrost basin on the northeastern Qinghai‒Tibet Plateau was selected to conduct hydrological and meteorological observations. We analyzed the annual variations in runoff, precipitation, evapotranspiration, and changes in water storage, as well as the mechanisms for runoff generation in the basin from May 2014 to December 2015. The annual flow curve in the basin exhibited peaks both in spring and autumn floods. The high ratio of evapotranspiration to annual precipitation (>1.0) in the investigated wetland is mainly due to the considerably underestimated ‘observed’ precipitation caused by the wind-induced instrumental error and the neglect of snow sublimation. The stream flow from early May to late October probably came from the lateral discharge of subsurface flow in alpine wetlands. This study can provide data support and validation for hydrological model simulation and prediction, as well as water resource assessment, in the upper Yellow River Basin, especially for the headwater area. The results also provide case support for permafrost hydrology modeling in ungauged or poorly gauged watersheds in the High Mountain Asia.

The Application of Converter Sludge and Slag to Produce Ecological Cement Mortars.

The paper presents an analysis of the effective use of a mixture of steel sludge (S1) and slag (S2) from the converter process of steel production for the production of cement mortars. Metallurgical waste used in the research, which is currently deposited in waste landfills and heaps near plants, posing a threat to groundwater (possibility of leaching metal ions present in the waste), was used as a substitute for natural sand in the range of 0-20% by weight of cement (each). The obtained test results and their numerical analysis made it possible to determine the conditions for replacing part of the sand in cement mortars with a mixture of sludge and slag from a basic oxygen furnace (BOF) and to determine the effects of such modification. For the numerical analysis, a full quadratic Response Surface Model (RSM) was utilized for two controlled factors. This model was subsequently optimized through backward stepwise regression, ensuring the inclusion of only statistically significant components and verifying the consistency of residual distribution with the normal distribution (tested via Ryan-Joiner's test, p > 0.1). The designated material models are helpful in designing ecological cement mortars using difficult-to-recycle waste (i.e., sludge and converter slag), which is important for a circular economy. Mortars modified with a mixture of metallurgical waste (up to 20% each) are characterized by a slightly lower consistency, compressive and flexural strength, and water absorption. However, they show a lower decrease in mechanical strength after the freezing-thawing process (frost resistance) compared to control mortars. Mortars modified with metallurgical waste do not have a negative impact on the environment in terms of leaching heavy metal ions. The use of a mixture of sludge and steel slag in the amount of 40% (slag/sludge in a 20/20 ratio) allows you to save 200 kg of sand when producing 1 m3 of cement mortar (cost reduction by approx. EUR 5.1/Mg) and will also reduce the costs of the environmental fee for depositing waste.

Mechanical properties and damage modeling of hybrid fiber reinforced concrete under freeze-thaw cycles

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles, the freeze-thaw damage degree of the hybrid fiber reinforced concrete with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.

Multifunctional chitosan-based composite hydrogels engineered for sensing applications

Chitosan-based hydrogels, as natural high-molecular-weight flexible materials, are widely utilized due to their outstanding properties. In this research, we developed a one-pot method for synthesizing a novel PVA/CS@PPy-PDAx% conductive hydrogel and explored the internal bonding patterns through molecular dynamics simulations. By adding PPy-PDA nanoparticles into a hydrogel matrix, an interpenetrating conductive network established successfully. The uniform distribution of PPy-PDA nanoparticles endowed the hydrogel with good electrical conductivity (0.171 S/m), significantly enhanced mechanical properties, and strain sensing (S = 5.04), as well as near-infrared photothermal responsiveness (temperature increase of 41.9 °C within 30 s). Additionally, due to the hydrogel's significant photothermal conversion efficiency under near-infrared radiation, it exhibits rapid elimination of Escherichia coli with an antibacterial efficiency exceeding 90 %. The unique hydrogen-bonded crosslinked structure provides the hydrogel with excellent re-healing properties, allowing for restoration through a freeze-thaw process after damage. The conductivity remains nearly unchanged after re-healing, maintaining the material's integrity and functionality. The flexible sensor based on this hydrogel has a response time of 100 ms and can sensitively detect large-scale deformations (e.g., joint bending at various angles), different gravitational forces, and recognize human handwriting. These characteristics make this hydrogel a promising candidate for advancing intelligent wearable technologies and human-machine interaction systems.

Rheology, stability, and physicochemical properties of NaOH-tannic acid solvent for β-chitin dissolution

The applicability of chitin in food systems is limited by its poor solubility in ordinary solvents. This study explores a novel solvent system composed of sodium hydroxide and tannic acid (NaOH/TA) in combination with a repeated freeze-thaw process for dissolving chitin. The highest chitin solubility in 8% NaOH/0.3% TA and 10% NaOH/0.3% TA was 2.1% and 2.3% (w/v), respectively. The lower NaOH and excessive tannic acid content may lead to reduction of chitin solubility. We also observed a unique rheological property of the chitin/NaOH/TA system. A higher concentration of TA reduced the chitin solution's shear viscosity, storage modulus, loss modulus, and gelling temperature. Its shear viscosity decreases with increasing shear rate, showing a shear thinning behavior. When the chitin/NaOH/TA solution system was stored at 30oC, the crystalline degree of chitin decreased, and the diffraction peak shifted, suggesting the formation of different intermolecular forces. The TA contents show no significant effect on the crystallinity of chitin. With increased storage time, the molecular weight of chitin decreased, and the degree of deacetylation (DD) increased. These results underscore the potential applications of the chitin/NaOH/TA system in the food industry.

Multi-scale damage characterisation of semi-flexible pavements under freeze-thaw cycles

This study aims to investigate the failure mechanism of semi-flexible pavements (SFP) under freeze-thaw conditions and to provide theoretical support for optimizing the material properties. By simulating the freeze-thaw damage process of SFP in actual service scenarios and combining various experimental methods, the strength characteristics and microstructural change rules of SFP in the freeze-thaw process are systematically analyzed. The study used freeze-thaw tests to simulate the real environment, combined with indirect tensile tests (IDT) and three-point bending tests to evaluate the mechanical properties of SFP. To further investigate the failure mechanism, scanning electron microscopy (SEM) was used to observe the interfacial changes between asphalt and early-strength sulphoaluminate cement (JGM301). Additionally, CT scanning was used to capture the structural changes of SFP during freeze-thaw cycles. The results showed that freeze-thaw cycles significantly and negatively affected the split tensile strength of SFP. SEM observations revealed that cracks appeared at the asphalt-cement interface (ITZ), the cement-SBS bond weakened, and the structure of the cement itself became loose. CT revealed structural changes such as cracking at the interface of the two-phase material, creation of new voids, and linkage of old voids during freeze-thawing of the SFP. In summary, the reduction in adhesion at the cement-asphalt interface and the frost swelling of JGM301 are the main reasons for the damage of SFP in freeze-thaw cycles. This study provides an important basis for an in-depth understanding of the freeze-thaw damage mechanism of SFP and optimization of its performance.

Heat transfer deformation test and model of coal during LN2 cyclic freezing and thawing process

Exploring the temperature response and deformation characteristics of coal during the freeze–thaw process is crucial for maintaining coal seam stability under liquid nitrogen (LN2) treatment and enhancing gas extraction efficiency. This study investigates the temperature diffusion and deformation characteristics of coal during LN2 cyclic freeze–thaw processes, using saturated and dry anthracite samples. Real-time monitoring of the freeze–thaw characteristics of the anthracite samples was conducted using temperature and strain detectors to quantitatively analyze the evolution of coal temperature and strain. Additionally, a nuclear magnetic resonance (NMR) testing system was used to monitor the pore evolution characteristics of the coal before and after LN2 treatment. The results indicate: After LN2 cyclic freeze–thaw, the internal pores of the saturated samples were highly developed, and fracture connectivity was enhanced, whereas the pores in the dry samples significantly decreased, leading to a sharp reduction in overall connectivity. The cooling and heating rates of the saturated samples were higher than those of the dry samples, both exhibiting exponential trends. This variation is primarily due to the phase change of pore water and the formation and expansion of the internal fracture network within the coal. The deformation magnitude of both sample types showed an overall exponential decline, with the saturated samples exhibiting higher deformation magnitudes than the dry samples. The presence of fracture water not only accelerates coal deterioration during the freeze–thaw process but also enhances coal cementation, maintaining deformation stability. Furthermore, this paper derives a temperature-strain coupling model for coal subjected to LN2 F-T cycles, aiming to provide a reference for understanding the freeze–thaw damage mechanism of coal and the practical application of LN2 fracturing.

Polyvinyl alcohol/soybean isolate protein composite pad with enhanced antioxidant and antimicrobial properties induced by novel ternary nanoparticles for fresh pork preservation

In this study, oregano essential oil (OEO)-loaded soluble soybean polysaccharide (SSPS) -nisin nanoparticles (ONSNPs) were formulated through electrostatic attraction-driven and hydrophobic interactions utilizing SSPS, nisin, and OEO as raw materials. ONSNPs were integrated into polyvinyl alcohol (PVA) and soybean protein isolate (SPI) matrices to create composite pads (PS-ONSNPs) by physically cross-linked using a simple freeze-thaw cycling process. The effects of ONSNPs content on the structure and physicochemical properties were evaluated. The results revealed that strong intermolecular interactions between ONSNPs and the PS matrices affected the crystallinity, microstructure, and thermal stability of the pads. Upon incorporating 5 % to 15 % ONSNPs, the structure of composite pads became denser, and the mechanical properties and water resistance were enhanced. Concurrently, the PS-ONSNPs pads facilitated the protection and controlled release of OEO. Furthermore, ONSNPs significantly improved the antioxidant activity of the pads and effectively inhibited the growth of Staphylococcus aureus and Escherichia coli. The prepared PS-ONSNPs 15 % pad was applied to storage experiments of fresh pork, which could extend the shelf life of meat to 10–12 days under 4 °C storage conditions. Therefore, the composite pad devised in this research holds promise as a viable option for intelligent active packaging of fresh meat.

Effect of freeze-thaw treatment on the yield and quality of tiger nut oil

To investigate the effect of freeze-thaw (FT) process on the yield and quality of tiger nut oil, tiger nuts were subjected to 0–12 cycles of FT treatment. Results indicated that FT treatment ruptured the cell structure of tiger nut, resulting in an increase in oil yield. Acid value (2.09–2.42 mg KOH/g) and peroxide value (0.40–0.42 mmol/kg) increased with the number of FT cycles, but the increments were small. Likewise, slight differences in fatty acid composition and thermal properties between control and FT-treated samples were observed. FT treatment remarkably increased the bioactive components (e.g., vitamin E, sterols, chlorophyll and carotenoids) in the oil and extended the oxidation induction time from 1.2 to 5.57 h. FT treatment altered the volatile composition of tiger nut oil, increasing the relative content of heterocycles and pyrazines such as 2-methoxy-4-vinylphenol, trimethylpyrazine and tetramethylpyrazine. It was suggested that FT treatment prior to oil extraction was beneficial to improve the oil yield and quality.