Substrate is an important abiotic factor for burrowing shellfish,as it not only provides them with shelter,but also impose significant effect on their physiological metabolism.However,the physiological responses of bu...Substrate is an important abiotic factor for burrowing shellfish,as it not only provides them with shelter,but also impose significant effect on their physiological metabolism.However,the physiological responses of burrowing clams within various substrates get less attention due to difficulty in carrying out physiological tests in buried conditions.Consequently,this study investigated the burrowing behavior,feeding physiology and energy budget of Paphia undulata,which is an important aquaculture bivalve species in south China.The clams were exposed to mud and sand substrates with variable physical properties in the laboratory,to determine the suitable substrate conditions for this species.The results showed that the percentage of burrowing clams,digging index,burrowing time,burrowing depth and scope for growth(SFG)were higher in mud substrates with≥40%water content.Likewise,burrowing percentage,digging index,and burrowing depths were higher in substrates with≤40%sand content.Moreover,the burrowing depth had significant effect on the feeding physiology and SFG of P.undulata as clams burrowed at 6.3±1.8 cm had higher clearance rates and SFG as compared to other buried depths.This study further revealed that low water content in the sediment inhibited physiological performances of P.undulata by impairing feeding or absorption,hence reducing the SFG.In conclusion,mud substrate with≥40%water content or with≤40%sand content is suitable for proper burrowing and growth of P.undulata.Our findings therefore provide fundamental knowledge that will be applicable in the improvement of bottom aquaculture and conservation of P.undulata.展开更多
Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elu...Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elusive. Here, the optimal room-temperature storage time,properties and micromechanisms of Al-0.43 Mg-1.2Si-0.1Sn-0.1Sc(wt%) alloy are investigated by atomic-resolution scanning transmission electron microscopy(STEM),microhardness and corrosion resistance tests. The results show that the peak-aging Al-Mg-Si-Sn-Sc alloy exhibits vastly shortened peak hardening time, increased thermal stability and corrosion resistance compared with its Sc-free counterpart after a long room-temperature storage time of 1 week. Under such a designed double-stage aging regime(1-week room-temperature storage + artificial aging at 180℃), the addition of Sc to Al-Mg-Si-Sn alloy induces a decrease in diameter but an increase in length of peakhardening β″-based precipitates. In addition, a suppressed over-aging phase transition from Sc/Sn-containing β″ to β′ is identified in the Al-Mg-Si-Sn-Sc alloy. The Sn tends to segregate to the Si site in the low-density cylinder of β″ and the central site of sub-B′ in the precipitate can be occupied by Sn/Sc. Further study reveals that Sc and Sn coexist in the precursors of β″. Both reduced width of precipitation free zones and protective corrosion product film easily formed on the material contribute to the improved corrosion resistance of Al-Mg-Si-Sn-Sc alloy.The results provide important insight into the development of high-performance Al alloys.展开更多
Metal corrosion often results in incalculable economic loss and significant safety hazards. Although numerous traditional methods have been used to mitigate the issue, such as coating and corrosion inhibitors, they ar...Metal corrosion often results in incalculable economic loss and significant safety hazards. Although numerous traditional methods have been used to mitigate the issue, such as coating and corrosion inhibitors, they are environmentally unfriendly and difficult to maintain. Therefore, in this study, an environmental approach was taken to protect steels from corrosion in a multi-species bacterial environment via synergistic biomineralization. The marine bacterium Pseudoalteromonas lipolytica mixed with Bacillus subtilis or Pseudomonas aeruginosa strains offered extraordinary corrosion protection for steel.The surface characterization and electrochemical tests showed that the biomineralized film generated by the mixed bacteria was more compact and protective than that induced by a single bacterium. Herein,we found that the synergistic mechanisms were rather different for the different bacterial groups. For Pseudoalteromonas lipolytica and Bacillus subtilis group, the related mechanisms were due to the increase of pH in the medium, secretion of carbonic anhydrase. As for Pseudoalteromonas lipolytica and Pseudomonas aeruginosa group, the synergistic mechanism was attributed to the inhibiting corrosive bacteria in biofilm by the growth advantage of Pseudoalteromonas lipolytica. Therefore, this study may introduce a new perspective for future use of biomineralization in a real marine environment.展开更多
In this study, the Al-5.10Cu-0.65 Mg alloys without and with 0.2 wt% Sc addition were prepared to unveil the effect of Sc on the precipitate behavior and properties by atomic-scale scanning transmission electron micro...In this study, the Al-5.10Cu-0.65 Mg alloys without and with 0.2 wt% Sc addition were prepared to unveil the effect of Sc on the precipitate behavior and properties by atomic-scale scanning transmission electron microscopy. The results show that addition of Sc is able to significantly suppress the formation of the peak-hardening θ’ and S precipitates but in favor of stabilizing Guinier–Preston–Bagaryatsky(GPB) zones during isothermal aging at 180 ℃. The generation of unique GPB precursors dictating the evolution of the subsequent peak-hardening GPB zones is highly correlated with the insufficient vacancies and dragging effect of Sc to Cu in the Al-Cu-Mg-Sc alloy, thereby restricting the nucleation of θ′ and S precipitates owing to the decreased available Cu solutes. In property, 0.2 wt% Sc addition can not only enhance the corrosion resistance but also the electrical conductivity of the peak-hardening alloy. In addition, the peak-hardening Al-Cu-Mg-Sc alloy is also featured with increased strength without losing the ductility compared to its solid solution state. Further analyses indicate that the improved properties are essentially attributed to the formation of densely distributed strain-free GPB zones and smaller precipitate-free zones. The obtained results could provide a potential design strategy of high-performance alloys by Sc addition.展开更多
基金Supported by the Guangxi Science and Technology Base and Talent Special Project (No.AD23026114)。
文摘Substrate is an important abiotic factor for burrowing shellfish,as it not only provides them with shelter,but also impose significant effect on their physiological metabolism.However,the physiological responses of burrowing clams within various substrates get less attention due to difficulty in carrying out physiological tests in buried conditions.Consequently,this study investigated the burrowing behavior,feeding physiology and energy budget of Paphia undulata,which is an important aquaculture bivalve species in south China.The clams were exposed to mud and sand substrates with variable physical properties in the laboratory,to determine the suitable substrate conditions for this species.The results showed that the percentage of burrowing clams,digging index,burrowing time,burrowing depth and scope for growth(SFG)were higher in mud substrates with≥40%water content.Likewise,burrowing percentage,digging index,and burrowing depths were higher in substrates with≤40%sand content.Moreover,the burrowing depth had significant effect on the feeding physiology and SFG of P.undulata as clams burrowed at 6.3±1.8 cm had higher clearance rates and SFG as compared to other buried depths.This study further revealed that low water content in the sediment inhibited physiological performances of P.undulata by impairing feeding or absorption,hence reducing the SFG.In conclusion,mud substrate with≥40%water content or with≤40%sand content is suitable for proper burrowing and growth of P.undulata.Our findings therefore provide fundamental knowledge that will be applicable in the improvement of bottom aquaculture and conservation of P.undulata.
基金financially supported by the National Natural Science Foundation of China (Nos. 52061003 and U20A20274)the Natural Science Foundation of Guangxi (No.2018GXNSFAA050012)Guangxi Science and Technology Project (Nos. AA17204036-1, AA18118030 and AA17204100)。
文摘Sn microalloying can depress the adverse effect of natural aging after quenching(i.e., room-temperature storage) of Al-Mg-Si alloys. However, the other effect of Sc micro-addition to the Al-Mg-Si-Sn alloys remains elusive. Here, the optimal room-temperature storage time,properties and micromechanisms of Al-0.43 Mg-1.2Si-0.1Sn-0.1Sc(wt%) alloy are investigated by atomic-resolution scanning transmission electron microscopy(STEM),microhardness and corrosion resistance tests. The results show that the peak-aging Al-Mg-Si-Sn-Sc alloy exhibits vastly shortened peak hardening time, increased thermal stability and corrosion resistance compared with its Sc-free counterpart after a long room-temperature storage time of 1 week. Under such a designed double-stage aging regime(1-week room-temperature storage + artificial aging at 180℃), the addition of Sc to Al-Mg-Si-Sn alloy induces a decrease in diameter but an increase in length of peakhardening β″-based precipitates. In addition, a suppressed over-aging phase transition from Sc/Sn-containing β″ to β′ is identified in the Al-Mg-Si-Sn-Sc alloy. The Sn tends to segregate to the Si site in the low-density cylinder of β″ and the central site of sub-B′ in the precipitate can be occupied by Sn/Sc. Further study reveals that Sc and Sn coexist in the precursors of β″. Both reduced width of precipitation free zones and protective corrosion product film easily formed on the material contribute to the improved corrosion resistance of Al-Mg-Si-Sn-Sc alloy.The results provide important insight into the development of high-performance Al alloys.
基金financially supported by the National Basic Research Program of China (No. 2016YFB0300700)the National Natural Science Foundation of China (Nos. 41976039, 41606179 and 51901127)+1 种基金the Shanghai Natural Science Fund (No. 19ZR1422100)the China Postdoctoral Science Foundation (No. 2018M641980)。
文摘Metal corrosion often results in incalculable economic loss and significant safety hazards. Although numerous traditional methods have been used to mitigate the issue, such as coating and corrosion inhibitors, they are environmentally unfriendly and difficult to maintain. Therefore, in this study, an environmental approach was taken to protect steels from corrosion in a multi-species bacterial environment via synergistic biomineralization. The marine bacterium Pseudoalteromonas lipolytica mixed with Bacillus subtilis or Pseudomonas aeruginosa strains offered extraordinary corrosion protection for steel.The surface characterization and electrochemical tests showed that the biomineralized film generated by the mixed bacteria was more compact and protective than that induced by a single bacterium. Herein,we found that the synergistic mechanisms were rather different for the different bacterial groups. For Pseudoalteromonas lipolytica and Bacillus subtilis group, the related mechanisms were due to the increase of pH in the medium, secretion of carbonic anhydrase. As for Pseudoalteromonas lipolytica and Pseudomonas aeruginosa group, the synergistic mechanism was attributed to the inhibiting corrosive bacteria in biofilm by the growth advantage of Pseudoalteromonas lipolytica. Therefore, this study may introduce a new perspective for future use of biomineralization in a real marine environment.
基金supported by the National Natural Science Foundation of China(Grant Nos.52061003,U20A20274)the Natural Science Foundation of Guangxi(2018GXNSFAA050012)+1 种基金the Guangxi Science and Technology Project(Nos.AA17204036-1,AA18118030,AA17204100)。
文摘In this study, the Al-5.10Cu-0.65 Mg alloys without and with 0.2 wt% Sc addition were prepared to unveil the effect of Sc on the precipitate behavior and properties by atomic-scale scanning transmission electron microscopy. The results show that addition of Sc is able to significantly suppress the formation of the peak-hardening θ’ and S precipitates but in favor of stabilizing Guinier–Preston–Bagaryatsky(GPB) zones during isothermal aging at 180 ℃. The generation of unique GPB precursors dictating the evolution of the subsequent peak-hardening GPB zones is highly correlated with the insufficient vacancies and dragging effect of Sc to Cu in the Al-Cu-Mg-Sc alloy, thereby restricting the nucleation of θ′ and S precipitates owing to the decreased available Cu solutes. In property, 0.2 wt% Sc addition can not only enhance the corrosion resistance but also the electrical conductivity of the peak-hardening alloy. In addition, the peak-hardening Al-Cu-Mg-Sc alloy is also featured with increased strength without losing the ductility compared to its solid solution state. Further analyses indicate that the improved properties are essentially attributed to the formation of densely distributed strain-free GPB zones and smaller precipitate-free zones. The obtained results could provide a potential design strategy of high-performance alloys by Sc addition.
