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The production and consumption of pork are substantial worldwide, with frozen pork being the primary form for storage and transportation. To evaluate the efficiency and quality of different thawing methods, we conducted experiments using 2 kg pork samples, comparing natural air thawing (NAT), vacuum steam thawing (VST), and a novel vacuum sublimation–rehydration thawing (VSRT). This study focused on evaluating the thawing efficiency, particularly energy consumption and thawing effectiveness, by analyzing key parameters such as the thawing time, thawing loss rate, and quality attributes. The results showed that VSRT achieved the shortest thawing time (54.60 min), with reductions of 55.37% and 34.61% compared to NAT and VST, respectively. VSRT also significantly reduced the thawing loss rate (by 85.66% and 79.27%) and total color difference (by 87.04% and 82.76%) compared to NAT and VST. The color and texture parameters of VSRT-thawed pork were closer to those of fresh meat (p > 0.05), while its specific energy consumption was 40.67% lower than that of VST. These findings highlight the potential of VSRT to preserve pork quality more effectively while offering faster thawing rates and lower energy consumption, making it a promising candidate for industrial-scale applications.

Clinical trials using adult stem cells to regenerate damaged heart tissue continue to this day 1 , 2 , despite ongoing questions of efficacy and a lack of mechanistic understanding of the underlying biological effect 3 . The rationale for these cell therapy trials is derived from animal studies that show a modest but reproducible improvement in cardiac function in models of cardiac ischaemic injury 4 , 5 . Here we examine the mechanistic basis for cell therapy in mice after ischaemia–reperfusion injury, and find that—although heart function is enhanced—it is not associated with the production of new cardiomyocytes. Cell therapy improved heart function through an acute sterile immune response characterized by the temporal and regional induction of CCR2 + and CX3CR1 + macrophages. Intracardiac injection of two distinct types of adult stem cells, cells killed by freezing and thawing or a chemical inducer of the innate immune response all induced a similar regional accumulation of CCR2 + and CX3CR1 + macrophages, and provided functional rejuvenation to the heart after ischaemia–reperfusion injury. This selective macrophage response altered the activity of cardiac fibroblasts, reduced the extracellular matrix content in the border zone and enhanced the mechanical properties of the injured area. The functional benefit of cardiac cell therapy is thus due to an acute inflammatory-based wound-healing response that rejuvenates the infarcted area of the heart. Cardiac stem cell therapy in mouse models of ischaemia–reperfusion injury demonstrates that improvement in heart function is linked to an immune response characterized by the induction of CCR2 + and CX3CR1 + macrophages.

The light steel-foamed concrete composite structure is mainly used in residential building walls and light industrial plant enclosures. In order to investigate the interfacial bond between foamed concrete and cold-formed thin-walled galvanized steel bars exposed to freezing and thawing environments, this paper presents micro-scanning and push-out tests on 23 specimens of neat-cement cellular concrete that does not contain any aggregates. The effects of the number of freeze-thaw cycles, the porosity of the foamed concrete, and the frozen state of the foamed concrete at the time of push-out on the bond-slip properties of the composite structure were analyzed. Surface and internal deterioration of foamed concrete before and after freezing and thawing were also observed. The results indicate that, at the same number of freeze-thaw cycles, higher density leads to increased initial bond stress, peak bond stress, and residual bond stress at the interface of the composite structure. These values increased by 118%~178%, 62%~69%, and 53%~77%, respectively. As the number of freeze-thaw cycles increased, the combined structures of the same density peak bond stress and residual bond stress decreased by less than 14% and 31%. For the same number of freeze-thaw cycles, peak bond stress in the frozen state is 5-8% higher than in the thawed state. It was also found that the higher the density of the foamed concrete, the lower the initial porosity and the greater the resistance to freeze-thaw cycles. A three-stage bond-slip model was developed to account for porosity changes in an ambient environment, and a prediction model for relative bond strength and slip based on freeze-thaw damage was proposed.

Hemorrhage is the major hindrance over the wound healing, which triggers microbial infections and might provoke traumatic death. Herein, new hemostatic and antibacterial PVA/Kaolin composite sponges were crosslinked using a freeze-thawing approach and boosted by penicillin–streptomycin (Pen-Strep). Physicochemical characteristics of developed membranes were analyzed adopting Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), a thermal gravimetric analyzer (TGA), and differential scanning calorimetry (DSC). Furthermore, the impacts of kaolin concentrations on porosity, swelling behavior, gel fraction, and degradation of the membranes were investigated. SEM analyses revealed a spongy-like structure of hydrogels associated with high dispersion of kaolin inside PVA matrix. The thermal characteristics of PVA/Kaolin were significantly ameliorated compared to the prime PVA. Moreover, the results exhibited significant variations of swelling performance, surface roughness and pore capacity due to the alterations of kaolin contents. Besides, the adhesive strength ability was manifestly enhanced for PVA-K0.1 sponge. Biomedical evaluations including antibacterial activity, blood clotting index and thrombogenicity of the membranes were studied. The contact of PVA/Kaolin to blood revealed notable augmentation in blood clotting. Furthermore, the incorporation of kaolin into PVA presented mild diminution in antibacterial activities. Moreover, PVA/Kaolin composites illustrated no cellular toxicity towards fibroblast cells. These remarkable features substantiate that the PVA-K0.1 sponge could be applied as a multifunctional wound dressing.

In the present study, a hybrid microsphere/hydrogel system, consisting of polyvinyl alcohol (PVA)/sodium alginate (SA) hydrogel incorporating PCL microspheres is introduced as a skin scaffold to accelerate wound healing. The hydrogel substrate was developed using the freeze-thawing method, and the proportion of the involved polymers in its structure was optimized based on the in-vitro assessments. The bFGF-encapsulated PCL microspheres were also fabricated utilizing the double-emulsion solvent evaporation technique. The achieved freeze-dried hybrid system was then characterized by in-vitro and in-vivo experiments. The results obtained from the optimization of the hydrogel showed that increasing the concentration of SA resulted in a more porous structure, and higher swelling ability, elasticity and degradation rate, but decreased the maximum strength and elongation at break. The embedding of PCL microspheres into the optimized hydrogel structure provided sustained and burst-free release kinetics of bFGF. Besides, the addition of drug-loaded microspheres led to no significant change in the degradation mechanism of the hydrogel substrate; however, it reduced its mechanical strength. Furthermore, the MTT assay represented no cytotoxic effect for the hybrid system. The in-vivo studies on a burn-wound rat model, including the evaluation of the wound closure mechanism, and histological analyses indicated that the fabricated scaffold efficiently contributed to promoting cell-induced tissue regeneration and burn-wound healing.

Some biological particles and macromolecules are particularly efficient ice nuclei (IN), triggering ice formation at temperatures close to 0 ∘C. The impact of biological particles on cloud glaciation and the formation of precipitation is still poorly understood and constitutes a large gap in the scientific understanding of the interactions and coevolution of life and climate. Ice nucleation activity in fungi was first discovered in the cosmopolitan genus Fusarium, which is widespread in soil and plants, has been found in atmospheric aerosol and cloud water samples, and can be regarded as the best studied ice-nucleation-active (IN-active) fungus. The frequency and distribution of ice nucleation activity within Fusarium, however, remains elusive. Here, we tested more than 100 strains from 65 different Fusarium species for ice nucleation activity. In total, ∼11 % of all tested species included IN-active strains, and ∼16 % of all tested strains showed ice nucleation activity above −12 ∘C. Besides Fusarium species with known ice nucleation activity, F. armeniacum, F. begoniae, F. concentricum, and F. langsethiae were newly identified as IN-active. The cumulative number of IN per gram of mycelium for all tested Fusarium species was comparable to other biological IN like Sarocladium implicatum, Mortierella alpina, and Snomax®. Filtration experiments indicate that cell-free ice-nucleating macromolecules (INMs) from Fusarium are smaller than 100 kDa and that molecular aggregates can be formed in solution. Long-term storage and freeze–thaw cycle experiments revealed that the fungal IN in aqueous solution remain active over several months and in the course of repeated freezing and thawing. Exposure to ozone and nitrogen dioxide at atmospherically relevant concentration levels also did not affect the ice nucleation activity. Heat treatments at 40 to 98 ∘C, however, strongly reduced the observed IN concentrations, confirming earlier hypotheses that the INM in Fusarium largely consists of a proteinaceous compound. The frequency and the wide distribution of ice nucleation activity within the genus Fusarium, combined with the stability of the IN under atmospherically relevant conditions, suggest a larger implication of fungal IN on Earth’s water cycle and climate than previously assumed.

The stability and performance of loess infrastructure in cold regions are often challenged by seasonal freezing–thawing action. The action of the foundation loess is a complex thermo-hydro-mechanical coupling process, and it is crucial to understand this process for the loess infrastructure in cold regions. A series of controlled tests were conducted to observe the changes in temperature, moisture, and frost heave variations within loess samples under freezing–thawing, and the influences of cycle period, freezing–thawing amplitude, and cycle number on the thermo-hydro-mechanical behavior of loess were investigated. The results reveal that freeze–thaw cycles significantly affect the heat transfer, water migration, and deformation of the loess. The temperatures of sample at different heights periodically vary under freezing–thawing. Water is absorbed to the samples, which undergoes a rapid water intake stage, a water drained stage, and a slow water intake stage under freezing–thawing, resulting in moisture redistribution in loess. Loess undergoes frost heave, thaw settlement, and consolidation processes during freezing–thawing, and a slight wetting collapse may occur after several freezing–thawing cycles. Within the same cycle, frost heave is the largest while consolidation deformation is the smallest. Frost heave and consolidation deformation reach their maximum values at the second cycle, whereas thaw settlement reaches its maximum value during the second or third cycle. Each stage deformation increases with an extended cycle period and almost decreases as the freezing–thawing amplitude increases. Freeze–thaw cycles can induce wetting collapse of loess, resulting in negative residual deformation. Furthermore, the thermo-hydro-mechanical coupling process and the deformation mechanism of loess have been elucidated. These insights contribute to a more comprehensive understanding of the failure mechanisms in loess engineering in cold regions.

Water-bearing joints within rock engineering in cold areas are often subjected to frost heaving force in cold season due to water–ice phase transition. To evaluate the damage and stability of rock mass in cold regions, a 3D model that considers moisture migration loss during freezing and thawing was established to study the characteristics of frost heaving force within joints. Then, the numerical simulation of cyclic freeze-thawing of water-bearing joints was carried out through equivalent expansion coefficient and particle flow calculation methods. The distribution of frost heaving force in and around the joints was obtained. According to the results of the numerical tests and theoretical calculations, the frost heaving force in joints is basically stable, the tensile stress concentration area appears at the joint tip, and the frost heaving force decreases gradually away from the jointed rock mass area. The frost heaving force decreases considerably with increasing cycle number and moisture migration loss but it increases with increasing mechanical strength and joint geometric size of rock and ice. The comparison between the numerical solution of the equivalent expansion coefficient method and the theoretical solution shows that the force size and distribution law of frost heaving for the two methods are consistent.

The Bayan Obo mining areas of northern China’s arid regions is prone to wind erosion and strong freeze-thaw effects. Freezing-thawing leads to the degradation of soil structure and diminishes its resistance to wind erosion. Cyanobacteria crusts can inhibit wind erosion, but their biomass decreases under freeze-thaw conditions. There is limited research on whether combining biochar with cyanobacteria crusts can alleviate the impact of freeze-thaw on their wind erosion resistance. Therefore, the indoor simulated freeze-thaw and wind tunnel tests were used to systematically investigate the impact of cyanobacteria crust and biochar combination on soil wind erosion under freeze-thaw action. Results showed that freeze-thaw cycles altered crust layer soil physicochemical properties. The Pearson correlation coefficient revealed that the freeze-thaw frequency exhibited a significant negative correlation with pH ( p  < 0.01), bulk density ( p  < 0.01), clay percentage ( p  < 0.01), and > 0.25 mm aggregate content ( p  < 0.05). The sensitivity of freeze-thaw cycles to clay percentage was the highest, with a coefficient of variation of 27%. The wind tunnel test showed that the combined use of biochar and cyanobacteria exhibited the most efficient erosion reduction, the erosion reduction rate peaked at a wind speed of 15 m/s, reaching an impressive 64.73%. This was primarily attributed to the high aggregate stability and clay percentage. The above results indicate the biochar and cyanobacteria crust incorporation has great potential as a wind erosion control strategy in seasonal freeze-thaw zones.

The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the permafrost distribution on the TP. We generated a new permafrost map based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated this map using various ground-based data sets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and soil properties (moisture content and bulk density). The temperature at the top of permafrost (TTOP) model was applied to simulate the permafrost distribution. Permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06  ×  106 km2 (0.97–1.15  ×  106 km2, 90 % confidence interval) (40 %), 1.46  ×  106 (56 %), and 0.03  ×  106 km2 (1 %), respectively, excluding glaciers and lakes. Ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) were used to validate the model. Validation results showed that the kappa coefficient varied from 0.38 to 0.78 with a mean of 0.57 for the five IRs and 0.62 to 0.74 with a mean of 0.68 within the three transects. Compared with earlier studies, the TTOP modelling results show greater accuracy. The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.