Tetrandrine, a bisbenzylisoquinoline alkaloid, is known to inhibit tumor cell proliferation and induce apoptosis in cancer models in vitro and in vivo. In the present study, tetrandrine significantly inhibited the proliferation of mouse endothelial cells (EOMA cell) and induced G1/S arrest in EOMA cells, in which the expressions of cyclin D and cyclin E and CDKs were downregulated. Tetrandrine treatment also caused intracellular accumulation of reactive oxygen species (ROS). Pretreatment with NAC, which is a ROS inhibitor, blocked G1/S cell arrest and cyclin regulation induced by tetrandrine, implying that ROS generation plays an important role in tetrandrine-induced cell cycle arrest. Furthermore, a decreased phospho-Akt protein level after tetrandrine treatment was reversible with the removal of the intracellular ROS by NAC. Notably, overexpression of Akt decreased tetrandrineinduced G1/S arrest. Finally, we verified the antiangiogenic effects of tetrandrine in vivo in a liver cancer xenograft model in nude mice. In conclusion, tetrandrine inhibits EOMA cell growth through the ROS/Akt pathway, and it could be a promising compound for cancer therapy as an inhibitor of tumor vascular growth.
In recent years, it has been found that the service life of cemented carbide shield machine tools used in uneven soft and hard strata is substantially reduced in engineering practice. The study found that thermal stress is the main reason for the failure of cemented carbide shield tunneling tools when shield tunneling is carried out in uneven soft and hard soil. To maintain the hardness of cemented carbide, improving the thermal conductivity of the shield machine tool is of great importance for prolonging its service life and reducing engineering costs. In this study, graphene and carbon nanotubes were mixed with WC–Co powder and sintered by spark plasma sintering (SPS). The morphology was observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The Rockwell hardness, bending strength, and thermal conductivity of the samples were tested. The results show that adding a small amount of graphene or carbon nanotubes could increase the bending strength of the cemented carbide by approximately 50%, while keeping the hardness of the cemented carbide constant. The thermal conductivity of the cemented carbide could be increased by 10% with the addition of 0.12 wt % graphene alone.
Carbon Nanotubes (CNTs) and Graphene Nano Platelets (GNPs) had been used to enhance the thermal conductivity of the epoxy composites and show a synergistic effect. Complex service conditions also put forward the requirements for the structural design of the composites to get better performance. Researches should be done to further understand the mechanism of enhancement in composites and find ways to assist the design and optimization of the structure. In this research, epoxy composites with CNTs, GNPs and hybrid CNTs-GNPs (5:2) were prepared, whose total content of fillers was kept constant at 0.4 vol%. Test of specific surface area shew the hybrid fillers had less aggregation and the composites with hybrid fillers had the highest thermal conductivity. Observing the microstructure of the composites, CNTs were absorbed on the surface of GNPs, forming a crossnetwork which could improve aggregation and provide channels for the heat. A series of finite element models were established using scripts to find the factors that affect the forming of network and heat flow. A parameter was created to reflect the distribution of the fillers: distance of non-network(DNN). Positions, orientations, ratios, shapes, and sizes are all factors. The effect of angles depends on the relative positions of the fillers. A proper bending degree of CNTs would have better enhancement. The vertical-structure network was created manually and heat flux on the network was shown: GNPs expanded the area of network for the acceptance and release of heat. CNTs provide efficient channels for the multidirectional heat flow. The combination of the geometry expanded the influence region of the network.
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