Low-frequency damping behavior of closed-cell Mg alloy foams reinforced with SiC particles

The damping properties of an Mg alloy foam and its composite foams were investigated using a dynamic mechanical thermal analyzer. The results show that the loss factors of both the Mg alloy and its composite foams are insensitive to temperature and loading frequency when the temperature is less than a critical temperature Tcrit. However, it increases when the temperature exceeds the Tcrit values, which are 200 and 250°C for the Mg alloy foam and the Mg alloy/SiCp composite foams, respectively. The Mg alloy/SiCp composite foams exhibit a higher damping capacity than the Mg alloy foam when the temperature is below 200°C. By contrast, the Mg alloy foam exhibits a better damping capacity when the temperature exceeds 250°C. The variation in the damping capacity is attributed to differences in the internal friction sources, such as the characteristics of the matrix material, abundant interfaces, and interfacial slipping caused by SiC particles, as well as to macrodefects in the Mg alloy and its composite foams.

Fasudil prevents liver fibrosis via activating natural killer cells and suppressing hepatic stellate cells

BACKGROUND Fasudil,as a Ras homology family member A(RhoA)kinase inhibitor,is used to improve brain microcirculation and promote nerve regeneration clinically.Increasing evidence shows that Rho-kinase inhibition could improve liver fibrosis.AIM To evaluate the anti-fibrotic effects of Fasudil in a mouse model of liver fibrosis induced by thioacetamide(TAA).METHODS C57BL/6 mice were administered TAA once every 3 d for 12 times.At 1 wk after induction with TAA,Fasudil was intraperitoneally injected once a day for 3 wk,followed by hematoxylin and eosin staining,sirius red staining,western blotting,and quantitative polymerase chain reaction(qPCR),and immune cell activation was assayed by fluorescence-activated cell sorting.Furthermore,the effects of Fasudil on hepatic stellate cells and natural killer(NK)cells were assayed in vitro.RESULTS First,we found that TAA-induced liver injury was protected,and the positive area of sirius red staining and type I collagen deposition were significantly decreased by Fasudil treatment.Furthermore,western blot and qPCR assays showed that the levels of alpha smooth muscle actin(α-SMA),matrix metalloproteinase 2(MMP-2),MMP-9,and transforming growth factor beta 1(TGF-β1)were inhibited by Fasudil.Moreover,flow cytometry analysis revealed that NK cells were activated by Fasudil treatment in vivo and in vitro.Furthermore,Fasudil directly promoted the apoptosis and inhibited the proliferation of hepatic stellate cells by decreasingα-SMA and TGF-β1.CONCLUSION Fasudil inhibits liver fibrosis by activating NK cells and blocking hepatic stellate cell activation,thereby providing a feasible solution for the clinical treatment of liver fibrosis.

Dynamic Compressive Property of Closed-Cell Mg Alloy Composite Foams Reinforced with SiC Particles

The high-strain-rate mechanical response of Mg alloy/SiC_p composite foams has received increased attention in recent years due to their light weight and potential to absorb large amounts of energy during deformation. Dynamic compressive properties of closed-cell Mg alloy/SiC_p composite foams with diff erent relative densities(0.162, 0.227 and 0.351) and diff erent SiC_p additions(0, 4 and 8 wt%) have been investigated using Split-Hopkinson pressure bar. It is shown that peak stress and energy absorption capacity signifi cantly increase as the relative density increases at the range of testing strain rates. Peak stress and energy absorption display strain rate dependence. The peak stress of specimens with 0 wt% and 4 wt% SiC particles additions grows with increasing strain rate. Meanwhile, the increment in the peak stress of specimens with 8 wt% addition is not signifi cant with strain rate increasing. The increase in strain rate increases the energy absorption capacity. The suitable amount of SiC particles addition has great advantages over increasing the peak stress and energy absorption capacity at the high strain rate. The strain-rate-sensitive matrix, cell morphology, morphological defects and gas pressure have an impact on the strain-rate sensitivity of Mg alloy/SiC_p composite foams.