Assessing Mechanical Properties and Response of Expansive Soft Rock in Tunnel Excavation: A Numerical Simulation Study.

This study investigates the dynamics of moisture absorption and swelling in soft rock during tunnel excavation, emphasizing the response to support resistance. Utilizing COMSOL numerical simulations, we conduct a comparative analysis of various strength criteria and non-associated flow rules. The results demonstrate that the Mohr-Coulomb criterion combined with the Drucker-Prager model under compressive loads imposes stricter limitations on water absorption and expansion than when paired with the Drucker-Prager model under tensile loads. Restricted rock expansion leads to decreased horizontal displacement and ground uplift, increased displacement in the tunnel's bottom arch, and significantly reduced displacement in the top arch. The study also considers the effects of shear dilation, burial depth, and support resistance on the stress and displacement of the surrounding rock. Increased shear dilation angles correlate with greater rock expansion, resulting in increased horizontal displacement and ground uplift. The research study concludes that support resistance is critical in limiting the movement of the tunnel's bottom arch and impacting the stability of the surrounding rock. Additionally, the extent of rock damage during the excavation of expansive soft rock tunnels is found to be minimal. Overall, this study provides valuable insights into the processes of soft rock tunnel excavation and contributes to the development of more efficient support systems.

Dynamic changes in postmortem quality of mirror carp (Cyprinus carpio L.): Based on oxidation reaction and mitochondrial function properties.

The dynamic changes in the postmortem quality of mirror carp (Cyprinus carpio L.) were investigated. With extended postmortem time, conductivity, redness, lipid oxidation, and protein oxidation all increased, while lightness, whiteness, and freshness decreased. At 4 h postmortem, the pH value reached a minimum (6.58), while the centrifugal loss and hardness reached a maximum (17.13% and 2539 g). Additionally, variations in mitochondria-related parameters during apoptosis were studied. Within 72 h postmortem, the content of reactive oxygen species initially decreased and subsequently increased; furthermore, there was a significant increase in the mitochondrial membrane permeability transition pore, membrane fluidity, and swelling (P < 0.05). Meanwhile, the cytosolic cytochrome c level decreased from 0.71 to 0.23, which indicated potential mitochondrial damage. Thus, mitochondrial dysfunction during postmortem aging can give rise to oxidation and the production of ammonia and amine compounds, which leads to flesh quality deterioration.

Inhibition of Chitosan Ice Coating on the Quality Deterioration of Quick-Frozen Fish Balls during Repeated Freeze-Thaw Cycles.

Chitosan ice coating's properties and its inhibitory effect on the quality deterioration of quick-frozen fish balls during repeated freeze-thaw cycles were investigated. When the chitosan (CH) coating concentration increased, the viscosity and ice coating rate increased, while water vapor permeability (WVP), water solubility, and transmittance decreased, and 1.5% CH was regarded as the excellent coating to apply to freeze-thaw quick-frozen fish balls. As the freeze-thaw cycles increased, the frost production, total volatile base nitrogen (TVB-N) values, and free water content of all of the samples increased significantly (p < 0.05), and the whiteness values, textural properties, and water-holding capacity (WHC) decreased. Freeze-thaw cycles expanded the aperture between the muscle fibers and the occurrence of crystallization and recrystallization between cells increased, damaging the original intact tissue structure, which were confirmed by SEM and optical microscopy. Compared with the untreated ones, the frost production, free water, and TVB-N of the samples with 1.5% CH decreased during 1, 3, 5, and 7 cycles, and were reduced by 23.80%, 32.21%, 30.33%, and 52.10% by the 7th cycle. The WHC and texture properties showed an increasing trend during the freeze-thaw cycles. Therefore, the chitosan ice coating effectively inhibited the quality deterioration by reducing water loss, the occurrence of ice crystallization and recrystallization, and the pores of the samples.

Loading Cu-doped magnesium oxide onto surface of magnetic nanoparticles to prepare magnetic disinfectant with enhanced antibacterial activity.

In this article, Cu-doped magnesium oxide was loaded onto the surface of Fe3O4 magnetic nanoparticles via a hydrophilic carbon intermediate layer to synthesize Fe3O4@C@MgO-Cu magnetic composite. The potential application as disinfectant in water purification was investigated by examining the antibacterial activity of the Fe3O4@C@MgO-Cu composite toward Gram negative Escherichia coli and Gram positive Staphylococcus aureus. The practical bactericidal efficiency in inactivation experiment was also studied and the copper doping amount was optimized. The results show that the as-obtained magnetic composite, with good dispersion and typical multilayer structure, exhibited high antibacterial activity to both strains and the Cu-doping improved the antibacterial performance significantly. Moreover, an increasing bactericidal ability of the nanocomposite was observed with the increasing Cu-doping amount and 312.5mgL-1 of Fe3O4@C@MgO-Cu disinfectant with a 1.5% Cu-doping amount (wt% of MgO) could inactivate 99% of the tested bacteria in normal saline solution within 60minutes. The Fe3O4@C@MgO-Cu composite, with a high magnetic saturation value of 29.07emug-1, can be readily recovered from matrix solution for reuse with an external magnet, which simplified the disinfection operation greatly and avoided the waste of disinfectant.