Abstract Aflatoxin B1 (AFB1), a widespread mycotoxin found in food, poses a significant threat to the food industry and production. The primary target of AFB1 is the liver. Probiotic-mediated antitoxicity has been proposed to overcome aflatoxin toxicity. In the present study, to investigate the protective effects and molecular mechanisms of Lactobacillus plantarum SCS2 (L. plantarum SCS2) against HepG2 cells oxidative stress induced by AFB1. HepG2 cells were cultured and treated with different concentrations of AFB1 (0-10 μmol/L) to induce oxidative stress and L. plantarum SCS2 (total protein, 0.4 mg/mL) was pretreated HepG2 for 2 h and then supplemented with AFB1 (10 μmol/L) for 22 h to observe cellular oxidative stress. The cytotoxicity, reactive oxygen species, malondialdehyde, activities and mRNA expressions of antioxidant enzymes and activation of the Nrf2 signaling pathway were measured. The results showed that AFB1 exposure caused oxidative stress in HepG2. Supplementation of L. plantarum SCS2 prevented AFB1-induced HepG2 cells activity decreased and activated antioxidant enzymes activity by inhibiting Nrf2 over expression. The results of in vitro experiments revealed that L. plantarum SCS2 evidently protected against AFB1-induced oxidative stress.

Dynamic compressive and tensile properties of mortar under impact loading were investigated experimentally by using a split Hopkinson pressure bar (SHPB) apparatus with pulse shaping technique. Firstly, the basic principle, experimental limitations and some feasible improvements/modifications of SHPB technique used for dynamic tests on concrete-like materials were summarized briefly. And then the dynamic compressive strength, stress versus strain response, and failure modes of mortar were discussed and analyzed. Finally, a dynamic Brazilian disc test was conducted to obtain the splitting tensile property of mortar, and some typical experimental results were presented. Both compressive and splitting tensile results show that mortar is a strain-rate sensitive material. Either compressive or tensile strength enhances with the increase of strain rate, especially when the strain rate is greater than the transition strain rate, which is around 20 s-1 for the dynamic compression and 2.0 s-1 for the splitting tension, respectively. These findings are helpful to guide the design and application of concrete structures.

The dynamic response of cylindrical sandwich shells with aluminum foam cores subjected to air blast loading was investigated numerically in this paper. According to KNR theory, the nonlinear compressibility of the air and finite shock conditions were taken into account in the finite element model. Numerical simulation results show that the compression strain, which plays a key role on energy absorption, increases approximately linearly with normalized impulse, and reduces with increasing relative density or the ratio of face-sheet thickness and core thickness. An increase of the impulse will delay the equalization of top and bottom face-sheet velocities of sandwich shell, but there is a maximum value in the studied bound. A limited study of weight optimization was carried out for sandwich shells with respect to the respective geometric parameters, including face-sheet thickness, core thickness and core relative density. These numerical results are of worth to theoretical prediction and engineering application of cellular metal sandwich structures.

The dynamic response of the clamped sandwich beams was investigated by impacting the beams at mid-span with metal foam projectiles. Efects of applied impulse, face-sheet thickness and core thickness on the impact resistance of sandwich beams are discussed. Using strain gauge measurement technique, the deformation mechanism of sandwich beams was analyzed in the paper. The results indicate that the structural response is sensitive to the configuration of sandwich structures. Based on the experiments, corresponding finite element simulations have been undertaken using the LS-DYNA software. A good agreement has been obtained between the numerical and experimental results. The deformation and failure modes of sandwich beams under impact loading are presented, i.e. large inelastic deformation, core compression and core shear with interfacial failure. Numerical results also show that the velocity-time histories of the mid-span of the front and back sheet of sandwich beams are related to not only core strength but also core thickness. The research results are of worth to the theoretical prediction of the dynamic response of metallic sandwich beam.