The thickness dependence of mechanical properties of nacre in Cristaria plicata shell was studied under three-point bending tests.The results show that the mechanical behavior of nacre exhibits a strong thickness depe...The thickness dependence of mechanical properties of nacre in Cristaria plicata shell was studied under three-point bending tests.The results show that the mechanical behavior of nacre exhibits a strong thickness dependence.The bending strength firstly increases with the increase of specimen thickness and then becomes roughly constant as the thickness reaches a certain value of∼2.5mm.However,the mean value of work per unit volume increases constantly with increasing specimen thickness;meanwhile,the cracking mode changes from penetration into the platelets to deflection along the interfaces.The theoretical analyses indicate that the thickness-dependent mechanical properties of nacre are mainly caused by the variation in the number of inter-lamellar interfaces.The more the number of inter-lamellar interfaces is,the higher the strength and work of fracture of nacre under bending tests will be.However,as the number of inter-lamellar interfaces reaches a certain value(e.g.,in the present specimen with 2.5mm thickness),the strength tends to remain constant,while the work of fracture still increases.Therefore,the present research findings are expected to provide a valuable guidance for the interfacial design of nacre-like materials with high strength and toughness.展开更多
Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in D...Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in Dongting Lake, China and the human health risks of mussel consumption are largely unknown. We investigated the concentrations of 15 trace metals and metalloids in surface water, sediments, and C. plicata organs(foot, gill, mantle, and visceral mass) and quantified the bioaccumulation and human health risk of these trace metals in specimens collected from Dongting Lake. The concentrations of most metals in surface water exceeded previously published background values. In contrast, the concentrations of most metals in sediments showed a decreasing trend. Overall, the metal concentrations in the gill and visceral masses of C. plicata were higher than those in the foot and mantle, and higher bioaccumulation capacities were observed for essential metals than for nonessential metals. The mean concentrations of the trace elements Zn, Pb, Cd, As, Cu, and Cr in C. plicata foot samples were lower than the threshold values established by international and Chinese organizations. The estimated daily intake(EDI) values of the essential metal Mn in C. plicata foot was higher than the recommended tolerable daily intake(TDI) values for juveniles. Only Mn for juveniles and As for both juveniles and adults may pose noncarcinogenic health risks through foot consumption. The hazard index(HI) values for adults and juveniles were higher than 1, suggesting significant risks of noncarcinogenic effects to humans by exposure to multiple metals.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51902043)the China Postdoctoral Science Foundation(Grant No.2018M641704)+1 种基金and the Fundamental Research Funds for the Central Universities(Grant No.N180203018)This work was also partially supported by the National Natural Science Foundation of China(Grant Nos.51571058 and 51871048).
文摘The thickness dependence of mechanical properties of nacre in Cristaria plicata shell was studied under three-point bending tests.The results show that the mechanical behavior of nacre exhibits a strong thickness dependence.The bending strength firstly increases with the increase of specimen thickness and then becomes roughly constant as the thickness reaches a certain value of∼2.5mm.However,the mean value of work per unit volume increases constantly with increasing specimen thickness;meanwhile,the cracking mode changes from penetration into the platelets to deflection along the interfaces.The theoretical analyses indicate that the thickness-dependent mechanical properties of nacre are mainly caused by the variation in the number of inter-lamellar interfaces.The more the number of inter-lamellar interfaces is,the higher the strength and work of fracture of nacre under bending tests will be.However,as the number of inter-lamellar interfaces reaches a certain value(e.g.,in the present specimen with 2.5mm thickness),the strength tends to remain constant,while the work of fracture still increases.Therefore,the present research findings are expected to provide a valuable guidance for the interfacial design of nacre-like materials with high strength and toughness.
基金jointly supported by the National Natural Science Foundation of China (Nos. 51622901 , 51709225 )the Young Scientific Research Innovation Team Project of Xi'an University of Technology (No. 104/256051715 )。
文摘Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in Dongting Lake, China and the human health risks of mussel consumption are largely unknown. We investigated the concentrations of 15 trace metals and metalloids in surface water, sediments, and C. plicata organs(foot, gill, mantle, and visceral mass) and quantified the bioaccumulation and human health risk of these trace metals in specimens collected from Dongting Lake. The concentrations of most metals in surface water exceeded previously published background values. In contrast, the concentrations of most metals in sediments showed a decreasing trend. Overall, the metal concentrations in the gill and visceral masses of C. plicata were higher than those in the foot and mantle, and higher bioaccumulation capacities were observed for essential metals than for nonessential metals. The mean concentrations of the trace elements Zn, Pb, Cd, As, Cu, and Cr in C. plicata foot samples were lower than the threshold values established by international and Chinese organizations. The estimated daily intake(EDI) values of the essential metal Mn in C. plicata foot was higher than the recommended tolerable daily intake(TDI) values for juveniles. Only Mn for juveniles and As for both juveniles and adults may pose noncarcinogenic health risks through foot consumption. The hazard index(HI) values for adults and juveniles were higher than 1, suggesting significant risks of noncarcinogenic effects to humans by exposure to multiple metals.
