Search Results (663)

The quality of frozen crayfish (Procambarus clarkii) is challenged by freeze–thaw (FT) cycles during storage. The effect of freezing methods on the quality of crayfish during FT cycles was investigated by comparing physicochemical properties, microstructure, and myofibrillar protein (MPs) properties. Three methods were used for crayfish freezing, including air convective freezing (AF) at −20 °C and −50 °C, as well as liquid nitrogen freezing (LNF) at −80 °C. The frozen crayfish were thawed at 4 °C after 45 d of frozen storage as 1 FT cycle. After 5 FT cycles, the water holding capacity of LNF crayfish (70.8%) was significantly (p < 0.05) higher than that of −20 °C AF crayfish (60.6%) and −50 °C AF crayfish (63.5%). The drip loss of LNF crayfish (7.83%) was significantly lower than that of AF crayfish. Moreover, LNF maintained the gel strength and the thermal stability of MPs from crayfish with higher gel storage modulus and enthalpy. These results demonstrated that LNF minimized the formation of large ice crystals, preserving the structural integrity of muscle and the properties of MPs, thereby maintaining crayfish quality. This study investigated the effect of LNF in preserving crayfish quality during FT cycles, providing valuable insights for reducing the quality degradation of aquatic products during storage and transportation. Full article

To meet the growing demand for sustainable building materials in modern construction projects, nanomaterials are widely used in concrete to improve its mechanical properties, durability, and environmental adaptability. The effects of different calcium carbonate nanoparticles (NC) and titanium carbide nanoparticles (NT) substitution rates (0%, 0.5%, 1% and 1.5%) on the mechanical and durability properties of steel fiber-reinforced concrete (SFRC) were analyzed by experimental studies. We also analyzed the evolution of the microstructure, chemical composition, and the evolution of functional groups of concrete by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The results demonstrated that NC replacement of 0.5% and NT replacement of 1% was the optimal combination for the preparation of composite concrete. Compared to SFRC with 0% substitution for both NC and NT (CG), the 28-day compressive strength of NC0.5NT1 increased by 35.5%, the flexural strength increased by 26.5%, and the splitting tensile strength increased by 16.3%. The durability performance of SFRC has been significantly improved. After 150 freeze–thaw cycles, the quality loss rate of SFRC cured for 28 days decreased by 40.6%, and the relative dynamic elastic modulus increased by 7.7%. Microscopic analysis indicates that an appropriate amount of NC and NT replacing cement improves the hydration reaction process of SFRC, increases the content of chemically more stable C-S-H gel, but does not change the types of hydration products of the cement. NC and NT have a filling effect, improving the pore structure of concrete, which helps enhance the mechanical and durability performance of concrete. The results of the study provide a theoretical basis for the application of NC and NT as reinforcing particles for cementitious materials in sustainable building materials. Full article

Background/Objectives: Differential diagnosis of sudden cardiac death (SCD) remains challenging, particularly in cases lacking evident structural abnormalities. Cardiac markers have been proposed as useful tools for this differentiation in forensic contexts. However, key issues include the influence of postmortem interval (PMI) on marker stability and the limitations of traditional approaches that focus on pericardial fluid, which requires invasive sampling compared to peripheral blood. This study aimed to evaluate the potential of cardiac markers in peripheral blood for diagnosing SCD, addressing methodological concerns related to PMI, hemolysis, and sample handling. Methods: This study analyzed 5 cardiac markers (creatine kinase-MB [CK-MB], myoglobin, troponin I [TnI], BNP, and D-dimer) in peripheral blood samples from 42 autopsied cadavers, divided into an SCD group and a control group. Marker levels were quantified using immunofluorescence, with cases meticulously selected to exclude confounding factors such as chronic diseases, pulmonary thromboembolism, and drowning. The study also accounted for potential degradation due to PMI, and evaluated the accuracy of point-of-care testing (POCT) in forensic samples. Results: The study identified statistically significant differences in myoglobin and TnI levels between the SCD group and the control group, though myoglobin’s diagnostic reliability remains limited due to its lack of specificity for myocardial injury. TnI emerged as a more robust marker for SCD. Contrary to prior concerns, PMI showed no significant correlation with marker levels in samples handled without freeze–thaw cycles. Issues related to hemolysis were addressed, and no significant effects were observed from resuscitation maneuvers. Conclusions: This study supports the potential use of cardiac markers, particularly TnI, in peripheral blood for postmortem SCD diagnosis, emphasizing the importance of rapid and systematic analysis to minimize hemolysis-related variability. While further validation is needed to confirm these findings, this approach offers a less invasive, economical, and practical method for forensic investigations. Full article

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a major concern for swine health. Isolating PRRSV is essential for identifying infectious viruses and for vaccine formulation. This study evaluated the potential of using tongue fluid (TF) from perinatal piglet mortalities for PRRSV isolation. Four collection protocols were tested: extracting TF from fresh tissues using phosphate-buffered saline (PBS group), extracting TF from fresh tissues using virus transportation medium (VTM group), extracting TF from freeze-thawed tissue (freeze-thaw group), and using tissue homogenates (homogenate group). Two cell lines (ZMAC and MARC-145) and primary alveolar macrophages (PAM) were evaluated for their effect on successful PRRSV isolation. An eligible PRRSV-positive unstable breeding herd in Midwestern USA was chosen for the study. Tongues were collected in 20 batches (~30 mortalities per batch). Within each batch, each tongue tissue was cut into four quarters, with each quarter randomly assigned to one of the four collection protocols and RT-qPCR tested. Virus isolation (VI) was attempted on 10 batches. The mean RT-qPCR cycle threshold (Ct) values for the PBS, VTM, freeze-thaw, and homogenate groups were 21.9, 21.8, 22.6, and 24.8, respectively. The VI success rate was 22.6%, 12.1%, 2.8%, and 2.8% in the PBS, VTM, freeze-thaw, and homogenate groups, respectively. The probability of successful VI was 3.1% and 21.0% in the MARC-145 and ZMAC cell lines, respectively, and 4.8% in the PAM cells. TF from perinatal mortalities is an option for PRRS VI, aiding in PRRSV monitoring and control programs. Full article

This article systematically investigated the improvement effect of polypropylene fiber (PPF) on the mechanical and freeze–thaw properties of alkali-activated fly ash slag concrete (AAFSC) with high fly ash content and cured at room temperature. Fly ash and slag were used as precursors, with fly ash accounting for 80% of the total mass. A mixed solution of sodium hydroxide and sodium silicate was used as alkali activator, and short-cut PPF was added to improve the performance of AAFSC. Firstly, the strength characteristics of AAFSC at different curing ages were studied. Then, key indicators such as morphology, residual compressive strength, weight loss, relative dynamic modulus of elasticity (RDME), and pore characteristics of AAFSC after different freeze–thaw cycles were tested and analyzed. The strength performance analysis showed that the optimal dosage of PPF was 0.90%. When the alkali equivalent of the alkali activator was increased from 4% to 6%, the frost resistance of AAFSC could be improved. Furthermore, adding 0.90% PPF could increase the freeze–thaw cycle number of AAFSC by about 50 times (measured by RDME). With the increase in freeze–thaw cycles, the porosity of AAFSC increased, the fractal dimension decreased, and the proportion of harmless and less harmful pores decreased, while the proportion of harmful and multiple harmful pores increased. The relationship model between the porosity and compressive strength of AAFSC after freeze–thaw cycles was established. Full article

Seasonal freeze–thaw cycles compromise soil structure, thereby increasing hydraulic conductivity but diminishing water retention capacity—both of which are essential for sustaining crop health and nutrient retention in agricultural soils. Prior research has suggested that biochar may alleviate these detrimental effects; however; further investigation into its influence on soil hydraulic properties through freeze–thaw cycles is essential. This study explores the impact of freeze–thaw cycles on the soil water retention and hydraulic conductivity and evaluates the potential of peanut shell biochar to mitigate these effects. Peanut shell biochar was used, and its effects on soil water retention and unsaturated hydraulic conductivity were evaluated through evaporation tests. The findings indicate that freeze–thaw cycles predominantly affect clay’s ability to retain water and control hydraulic conductivity by generating macropores and fissures; with a notable increase in conductivity at high matric potentials. The impact lessens as matric potential decreases below −30 kPa, resulting in smaller differences in conductivity. Introducing biochar helps mitigate these effects by converting large pores into smaller micro- or meso-pores, effectively increasing water retention, especially at higher content of biochar. While biochar’s impact is more pronounced at higher matric potentials, it also significantly reduces conductivity at lower potentials. The total porosity of the soil increased under low biochar application rates (0% and 1%) but declined at higher application rates (2% and 3%) as the number of freeze–thaw cycles increased. Furthermore, the characteristics of soil deformation during freeze–thaw cycles shifted from frost heaving to thaw settlement with increasing biochar application rates. Notably, an optimal biochar application rate was observed to mitigate soil deformation induced by freeze–thaw processes. These findings contribute to the scientific understanding necessary for the development and management of sustainable agricultural soil systems. Full article

Arthospira platensis is a filamentous cyanobacterium considered an important source of phycobiliproteins (PBP), a class of water-soluble pigments with a wide range of applications. Although several extraction and purification techniques of PBP have been reported, there is still a need for strategies that achieve a balance between simplicity, cost-effectiveness, and scalability. To address this need, this study systematically evaluated conventional extraction methods—homogenisation, freeze–thaw cycles, and maceration. Maceration showed the best balance between yield purity and recovery among the tested techniques, and under optimal conditions (three cycles, 2 h/cycle, 0.1 M phosphate buffer), 55.9 mg/g of biomass of phycocyanin (PC) and 24.9 mg/g of biomass of allophycocyanin (APC) with notable antioxidant capacity (Folin-Ciocalteu’s and ABTS^●+ assays) were yielded. Among the tested purification techniques, ammonium sulphate fractionation achieved a purity of 2.3 with recoveries of 92.9% and 79.9% for PC and APC, respectively, while purification with 0.5% activated carbon resulted in an extract purity of 2.5 and recoveries of 90.9% (PC) and 87.2% (APC). The suggested procedures could be considered a fast and cost-effective way to obtain cosmetic-grade PBP, thus offering an accessible solution for industries prioritising sustainable and economically viable production pipelines. Full article

Defects can be introduced into shotcrete materials after a few freeze–thaw cycles, which has a significant influence on the fracture performance of shotcrete. In this study, a series of shotcrete specimens with varying sizes, geometries, and initial crack lengths were prepared to investigate the fracture properties of notched shotcrete under freeze–thaw conditions. Considering the effects of specimen boundaries and material microstructure, a linear closed-form solution was proposed to determine the fracture toughness of frost-damaged shotcrete. The fracture toughness was found to be a reliable material constant, independent of specimen geometry variations. Results from three-point bending (3PB) tests show that freeze–thaw cycles severely weaken the fracture toughness of shotcrete, which is consistent with CT scan images of the damaged microstructure of the shotcrete specimens. Moreover, specimens with longer initial notches exhibited more severe freeze–thaw damage, which should be carefully considered in practical engineering assessments. These findings highlight the critical importance of considering freeze–thaw effects and notch length when evaluating the durability of shotcrete in cold region applications. Full article

Researchers have been investigating the physical and morphological properties of biodegradable polymer and copolymer films, blending them with other chemicals to solve challenges in medical, industrial, and eco-environmental fields. The present study introduces a novel, straightforward method for preparing biodegradable hydrogels based on polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) for medical applications. The resulting PVA/PVP-based hydrogel uniquely combines the water absorbency, biocompatibility, and biodegradability of the polymer composite. For hygiene products and medical uses, such as wound healing, hydrogen peroxide (HP) was encapsulated in the PVA/PVP hydrogels for controlled release application. Incorporating PVP into PVA significantly enhances the hydrogel water absorbency and improves the mechanical properties. However, to mitigate the disadvantage of high water absorbency which could result in undesired early dissolution, efforts were made to increase the water resistance and the mechanical characteristics of these hydrogels using freeze–thaw (F/T) cycles and chemical crosslinking PVA chains with trisodium trimetaphosphate (STMP). The resulting hydrogels serve as environmentally friendly bio-based polymer blends, broadening their applications in medical and industrial products. The structural and morphological properties of the hydrogel were characterized using Fourier transform infrared spectroscopy (FTIR), environmental scanning electron microscope analysis (E-SEM), and water-swelling tests. The HP controlled release rate was evaluated through kinetic release experiments using the ex vivo skin model. The antibacterial activity of the hydrogel films was examined on four medically relevant bacteria: Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa, with an adapted disk diffusion assay. Using this assay, we also evaluated the antibacterial effect of the hydrogel films over the course of days, demonstrating the HP controlled release from these hydrogels. These findings support further in vivo investigation into controlled HP release systems for improved wound-healing outcomes. Full article

Using silty clay as roadbed filling can lead to roadbed diseases. In this paper, silty clay was modified with lignin and BFS (GGBS). Then, the mechanical properties, freeze-thaw characteristics, and microscopic mechanisms were investigated using unconfined compression tests, California bearing ratio tests, rebound modulus tests, freeze-thaw cycling tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results showed that as the curing age increased, the unconfined compressive strength (UCS) of modified silty clay gradually increased, and the relationship between the stress and axial strain of the samples gradually transitioned from strain-softening to strain-hardening. As the lignin content decreased and the BFS content increased, the UCS, California bearing ratio (CBR), and rebound modulus of the modified silty clay first increased and then tended to stabilize. Adding lignin and BFS can effectively resist volume increase and mass loss during freeze-thaw cycles. When the ratio of lignin to BFS was 4%:8%, the growth rate of the UCS, CBR, and rebound modulus was the largest, the change rate in volume and mass and the loss rate of the UCS under the freeze-thaw cycle were the smallest, and the silty clay improvement effect was the most significant. The microscopic experimental results indicated that a large amount of hydrated calcium silicate products effectively increased the strength of interunit connections, filled soil pores, and reduced pore number and size. The research results can further improve the applicability of silty clay in roadbed engineering, protect the environment, and reduce the waste of resources. Full article

Gelatin coatings have been shown to successfully slow the oxidation of fresh foods. Furthermore, organic acids have proven effective in the inhibition of bacteria and the extension of product shelf life. The purpose of this study was to observe the effects of gelatin and lactic acid treatment combinations on fresh and previously frozen (thawed) wild-caught shrimp. The samples were separated into four treatment groups: control (C), gelatin coating (G), lactic acid followed by gelatin coating (L), and gelatin infused with lactic acid coating (LG). Half of each group was stored at refrigeration temperature (≤4 °C), while the other half was frozen (≤−18 °C) and thawed for the thawed study. Physical, chemical, and microbiological changes were observed in refrigeration storage for 8 days. Results showed that fresh and thawed shrimp exhibited darkening in color over time. Treatments with lactic acid were more blue than yellow. Treated samples developed less oxidation than the control. Psychrophilic counts for samples L and LG remained below the 7 log CFU/g threshold throughout the study. In fresh shrimp samples, the addition of just a gelatin coating was able to increase shelf life by three days, while the addition of lactic acid successfully lowered microbial counts and extended the shelf life by six days. The freeze–thaw cycle negatively affected the extension of shelf life in the G group. Full article

In cold-region mines, the dual effects of heat islands and cold islands, caused by cycling of hot and cold temperature extremes, facilitate the outward dispersion of heavy metal dust. Freeze–thaw cycles occurring in ice provide a conducive environment for the enrichment and conversion of heavy metals, allowing them to enter downstream rivers with meltwater. This process significantly impacts human activities and ecosystems in areas traversed by these rivers. This study is conducted in the typical alpine mining area in Xinjiang, China, and focuses on the impact of freeze–thaw cycles on the enrichment and conversion of heavy metals in alpine mining regions. It employs a comprehensive approach combining field measurements, environmental simulations, theoretical analysis, and laboratory experiments. The findings indicate that the environmental behavior of heavy metals is influenced not only by the freeze–thaw cycles themselves but also by factors such as temperature, pH, and redox conditions. Heavy metal elements may enter water bodies during the melting process and pose risks to downstream ecosystems and human health. Full article

Concrete, as the most widely used construction material globally, is prone to cracking under the influence of external factors such as mechanical loads, temperature fluctuations, chemical corrosion, and freeze–thaw cycles. Traditional concrete crack repair methods, such as epoxy resins and polymer mortars, often suffer from a limited permeability, poor compatibility with substrates, and insufficient long-term durability. Microbial biogrouting technology, leveraging microbial-induced calcium carbonate precipitation (MICP), has emerged as a promising alternative for crack sealing. This study aimed to explore the potential of Bacillus pasteurii for repairing concrete cracks to enhance compressive strength and permeability performance post-repair. Experiments were conducted to evaluate the bacterial growth cycle and urease activity under varying concentrations of Ca²⁺. The results indicated that the optimal time for crack repair occurred 24–36 h after bacterial cultivation. Additionally, the study revealed an inhibitory effect of high calcium ion concentrations on urease activity, with the optimal concentration identified as 1 mol/L. Compressive strength and water absorption tests were performed on repaired concrete specimens. The compressive strength of specimens with cracks of varying dimensions improved by 4.01–11.4% post-repair, with the highest improvement observed for specimens with 1 mm wide and 10 mm deep cracks, reaching an increase of 11.4%. In the water absorption tests conducted over 24 h, the average mass water absorption rate decreased by 31.36% for specimens with 0.5 mm cracks, 29.06% for 1 mm cracks, 27.9% for 2 mm cracks, and 28.2% for 3 mm cracks. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed the formation of dense calcium carbonate precipitates, with the SEM–EDS results identifying calcite and vaterite as the predominant self-healing products. This study underscores the potential of MICP-based microbial biogrouting as a sustainable and effective solution for enhancing the mechanical and durability properties of repaired concrete. Full article

This study examines the crack resistance of basalt-fiber-reinforced concrete (BFRC) materials subjected to freeze–thaw cycles (FTCs). We utilized a φ50 mm Split Hopkinson Pressure Bar (SHPB) apparatus alongside numerical simulations to carry out impact compression tests at a velocity of 5 m/s on BFRC specimens that experienced 0, 10, 20, and 30 FTCs. Additionally, we investigated the effects of basalt fiber (BF) orientation position and length on stress intensity factors. The results reveal that with an increasing number of FTCs, the dynamic crack propagation speed of BFRC with a prefabricated crack inclined at 0° rises from 311.84 m/s to 449.92 m/s, while its pure I fracture toughness decreases from 0.6266 MPa·m^0.5 to 0.4902 MPa·m^0.5. For BFRC specimens with a prefabricated crack inclination of 15°, the dynamic crack propagation speed increases from 305.81 m/s to 490.02 m/s, accompanied by a reduction in mode I fracture toughness from 0.3901 MPa·m^0.5 to 0.2867 MPa·m^0.5 and mode II fracture toughness from 0.6266 MPa·m^0.5 to 0.4902 MPa·m^0.5. In the case of a prefabricated crack inclination of 28.89°, the dynamic crack propagation speed rises from 436.10 m/s to 494.28 m/s, while its pure mode II fracture toughness decreases from 1.1427 MPa·m^0.5 to 0.7797 MPa·m^0.5. Numerical simulations indicate that fibers positioned ahead of the crack tip—especially those that are longer, located closer to the crack tip, and oriented more perpendicularly—significantly reduce the mode I stress intensity factor. However, these fibers have a minimal impact on reducing the mode II stress intensity factor. The study qualitatively and quantitatively analyzes the crack resistance of basalt-fiber-reinforced concrete in relation to freeze–thaw cycles and the fibers ahead of the crack tip, offering insights into the fiber reinforcement effects within the concrete matrix. Full article

The processing properties of resistant starch (RS) and its digestion remain unclear, despite the widespread use of autoclaving combined with debranching in its preparation. In this study, the physicochemical, rheological and digestibility properties of autoclaving modified starch (ACB), autoclaving–pullulanase modified starch (ACPB) and native black Tartary buckwheat starch (NB) were compared and investigated. The molecular weight and polydispersity index of modified starch was in the range of 0.15 × 10⁴~1.90 × 10⁴ KDa and 1.88~2.82, respectively. In addition, the SEM results showed that both modifications influenced the morphological characteristics of the NB particles, and their particles tended to be larger in size. Autoclaving and its combination with pullulanase significantly increased the short-range ordered degree, resistant starch yield and water- and oil-absorption capacities, and decreased the syneresis properties with repeated freezing/thawing cycles. Moreover, rheological analysis showed that both ACB and ACPB exhibited shear-thinning behavior and lower gel elasticity as revealed by the power law model and steady-state scan. The degradation of starch chains weakened the interaction of starch molecular chains and thus changed the gel network structure. The in vitro digestion experiments demonstrated that ACB and ACPB exhibited greater resistance to enzymatic digestion compared to the control, NB. Notably, the addition of pullulanase inhibited the hydrolysis of the ACB samples, and ACPB showed greater resistance against enzymatic hydrolysis. This study reveals the effects of autoclaving combined with debranching on the processing properties and functional characteristics of black Tartary buckwheat starch. Full article