The large plastic produced by human production and life is degraded into micro-plastics in the environment. Micro-plastics are harmful to organisms and the environment. In order to determine the hazards of micro-plast...The large plastic produced by human production and life is degraded into micro-plastics in the environment. Micro-plastics are harmful to organisms and the environment. In order to determine the hazards of micro-plastic pollution, zebrafish embryos were used as the tested organism, and 0.6-1.0 μm polystyrene micro-plastic was used to carry out embryo exposure experiment. The toxic effects of polystyrene plastic particles on zebrafish embryos were investigated comprehensively, and the toxicity was evaluated. The results of this study showed that 0.6-1.0 μm polystyrene micro-plastic had certain toxicity on zebrafish embryos, and it had a lethal effect when the concentration reached 250 mg/L; 25 mg/L 0.6-1.0 μm polystyrene particles can cause cyrtosis and pericardial edema of zebrafish embryos and other non-lethal toxic effects; and 250 and 1 000 mg/L exposure concentration can slow down heart rate. A hazard evaluation index system of polystyrene particles to zebrafish embryos was established, and it is determined that the exposure to 250 mg/L or lower concentration of polystyrene particles has slight hazard.展开更多
Very high cycle fatigue behavior （107 --109 cycles） of 304L austenitic stainless steel was studied with ultra- sonic fatigue testing system （20 kHz）. The characteristics of fatigue crack initiation and propagation...Very high cycle fatigue behavior （107 --109 cycles） of 304L austenitic stainless steel was studied with ultra- sonic fatigue testing system （20 kHz）. The characteristics of fatigue crack initiation and propagation were discussed based on the observation of surface plastic deformation and heat dissipation. It was found that micro-plasticity （slip markings） could be observed on the specimen surface even at very low stress amplitudes. The persistent slip mark- ings increased clearly along with a remarkable process of heat dissipation just before the fatigue failure. By detailed investigation using a scanning electron microscope and an infrared camera, slip markings appeared at the large grains where the fatigue crack initiation site was located. The surface temperature around the fatigue crack tip and the slip markings close to the fracture surface increased prominently with the propagation of fatigue crack. Finally, the cou- pling relationship among the fatigue crack propagation, appearance of surface slip markings and heat dissipation was analyzed for a better understanding of ultrasonic fatigue damage behavior.展开更多
基金Supported by Innovation and Entrepreneurship Program Project of Students in Hainan Medical University(HYCX2016040)Program of Hainan Association for Science and Technology Plans to Youth R&D Innovation(2015013)
文摘The large plastic produced by human production and life is degraded into micro-plastics in the environment. Micro-plastics are harmful to organisms and the environment. In order to determine the hazards of micro-plastic pollution, zebrafish embryos were used as the tested organism, and 0.6-1.0 μm polystyrene micro-plastic was used to carry out embryo exposure experiment. The toxic effects of polystyrene plastic particles on zebrafish embryos were investigated comprehensively, and the toxicity was evaluated. The results of this study showed that 0.6-1.0 μm polystyrene micro-plastic had certain toxicity on zebrafish embryos, and it had a lethal effect when the concentration reached 250 mg/L; 25 mg/L 0.6-1.0 μm polystyrene particles can cause cyrtosis and pericardial edema of zebrafish embryos and other non-lethal toxic effects; and 250 and 1 000 mg/L exposure concentration can slow down heart rate. A hazard evaluation index system of polystyrene particles to zebrafish embryos was established, and it is determined that the exposure to 250 mg/L or lower concentration of polystyrene particles has slight hazard.
基金Item Sponsored by National Natural Science Foundation of China(10925211,11172188)Fundamental Research Funds from the Central Universities of China(2012SCU04A05)
文摘Very high cycle fatigue behavior （107 --109 cycles） of 304L austenitic stainless steel was studied with ultra- sonic fatigue testing system （20 kHz）. The characteristics of fatigue crack initiation and propagation were discussed based on the observation of surface plastic deformation and heat dissipation. It was found that micro-plasticity （slip markings） could be observed on the specimen surface even at very low stress amplitudes. The persistent slip mark- ings increased clearly along with a remarkable process of heat dissipation just before the fatigue failure. By detailed investigation using a scanning electron microscope and an infrared camera, slip markings appeared at the large grains where the fatigue crack initiation site was located. The surface temperature around the fatigue crack tip and the slip markings close to the fracture surface increased prominently with the propagation of fatigue crack. Finally, the cou- pling relationship among the fatigue crack propagation, appearance of surface slip markings and heat dissipation was analyzed for a better understanding of ultrasonic fatigue damage behavior.
