The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochem...The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%？0.5%, the microstructure of the as-extruded Mg？Sn？Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg？1Sn？0.5Ca alloy was promising as a biodegradable orthopedic implant.展开更多
Wedelia （Sphagneticola trilobata （L.） Pruski） has become one of the most dominant invasive plant species in Fiji. However, the soil seed bank of its monospecific stand and its ability to reproduce by seed is relat...Wedelia （Sphagneticola trilobata （L.） Pruski） has become one of the most dominant invasive plant species in Fiji. However, the soil seed bank of its monospecific stand and its ability to reproduce by seed is relatively unknown. A soil seed bank study was undertaken in a monospecific stand ofS. trilobata in Sawani, Natavea and Wainivesi in south-east Viti Levu, Fiji in March 2012. The soil samples were collected from within 1.0 m2 quadrat taken at 10 spots in each of the study areas and spread thinly over a base of Yates Thrive Premium potting mix in seedling trays and placed in a glasshouse at Koronivia Research Station, Fiji. A total of 23, 26 and 33 plant species were found in the soil seed bank in Wainivesi, Sawani and Natavea respectively which may have succumbed to S. trilobata invasiability. There were ca. 3,800 （17%）, 2,100 （11%） and 2,600 （6%） germinable S. trilobata seeds-m-2 in the soil seed bank in Wainivesi, Sawani and Natavea areas respectively. This study has demonstrated that S. trilobata seeds may have a role in the spread of the invasive species in Fiji and movement of soil to S. trilobata free areas should be restricted.展开更多
Aims Sorghum halepense is a perennial invasive weed causing great harm worldwide,including some regions on Hainan island.In this study,we compared the performance between plants from outbreaking(dense stands covering ...Aims Sorghum halepense is a perennial invasive weed causing great harm worldwide,including some regions on Hainan island.In this study,we compared the performance between plants from outbreaking(dense stands covering large areas)and those from non-outbreaking(less dense stands covering smaller areas)populations.We also tested the hypothesis that plants with greater intraspecific competitive ability will have a lower stand biomass when grown under high-density conditions.Methods We grew plants of S.halepense individually,with an intraspecific competitor,with two interspecific competitors and with three or six plants from the same population per pot,and tested whether outbreaking and non-outbreaking populations differed in their performance.We also tested whether stand biomass(i.e.total biomass when three or six plants were grown together)was related to total biomass of individuals grown alone,and intra-or interspecific competitive ability.Important Findings Outbreaking and non-outbreaking populations of S.halepense differed in their biomass when individuals were grown alone,but not when grown in competition or when three or six plants from the same population were grown together.Across populations,biomass of individuals grown alone was negatively correlated with intra-and interspecific competitive ability,indicating that there is a trade-off between individual growth and competitive ability.Stand-level biomass was not related to total biomass of individuals grown alone,and intra-or interspecific competitive ability,indicating that low biomass when grown alone and high competitive ability may not reduce the performance of S.halepense when grown in dense monocultural stands.展开更多
基金Project(2013CB632200)supported by the National Basic Research Program of ChinaProjects(51474043,51531002)supported by the National Natural Science Foundation of China+1 种基金Projects(CSTC2013JCYJC60001,KJZH14101)supported by Chongqing Municipal Government,ChinaProject(2015M581350)supported by the China Postdoctoral Science Foundation
文摘The as-extruded Mg？Sn？Ca alloys were prepared and investigated for orthopedic applications via using optical microscopy, scanning electron microscopy, X-ray diffraction, as well as tensile, immersion and electrochemical tests. The results showed that, with the addition of 1% Sn and the Ca content of 0.2%？0.5%, the microstructure of the as-extruded Mg？Sn？Ca alloys became homogenous, which led to increased mechanical properties and improved corrosion resistance. Further increase of Ca content up to 1.5% improved the strength, but deteriorated the ductility and corrosion resistance. For the alloy containing 0.5% Ca, when the Sn content increased from 1% to 3%, the ultimate tensile strength increased with a decreased corrosion resistance, and the lowest yield strength and ductility appeared with the Sn content of 2%. These behaviors were determined by Sn/Ca mass ratio. The analyses showed that as-extruded Mg？1Sn？0.5Ca alloy was promising as a biodegradable orthopedic implant.
文摘Wedelia （Sphagneticola trilobata （L.） Pruski） has become one of the most dominant invasive plant species in Fiji. However, the soil seed bank of its monospecific stand and its ability to reproduce by seed is relatively unknown. A soil seed bank study was undertaken in a monospecific stand ofS. trilobata in Sawani, Natavea and Wainivesi in south-east Viti Levu, Fiji in March 2012. The soil samples were collected from within 1.0 m2 quadrat taken at 10 spots in each of the study areas and spread thinly over a base of Yates Thrive Premium potting mix in seedling trays and placed in a glasshouse at Koronivia Research Station, Fiji. A total of 23, 26 and 33 plant species were found in the soil seed bank in Wainivesi, Sawani and Natavea respectively which may have succumbed to S. trilobata invasiability. There were ca. 3,800 （17%）, 2,100 （11%） and 2,600 （6%） germinable S. trilobata seeds-m-2 in the soil seed bank in Wainivesi, Sawani and Natavea areas respectively. This study has demonstrated that S. trilobata seeds may have a role in the spread of the invasive species in Fiji and movement of soil to S. trilobata free areas should be restricted.
基金This work was funded by the Project for High-level Talents of Basic and Applied Basic Research(Natural Science)in Hainan(2019RC280)the Key Research and Development Project of Hainan(ZDYF2019055)the Central Public-interest Scientific Institution Basal Research Fund for Chinese Academy of Tropical Agricultural Sciences(630042019014 and 1630042017017).
文摘Aims Sorghum halepense is a perennial invasive weed causing great harm worldwide,including some regions on Hainan island.In this study,we compared the performance between plants from outbreaking(dense stands covering large areas)and those from non-outbreaking(less dense stands covering smaller areas)populations.We also tested the hypothesis that plants with greater intraspecific competitive ability will have a lower stand biomass when grown under high-density conditions.Methods We grew plants of S.halepense individually,with an intraspecific competitor,with two interspecific competitors and with three or six plants from the same population per pot,and tested whether outbreaking and non-outbreaking populations differed in their performance.We also tested whether stand biomass(i.e.total biomass when three or six plants were grown together)was related to total biomass of individuals grown alone,and intra-or interspecific competitive ability.Important Findings Outbreaking and non-outbreaking populations of S.halepense differed in their biomass when individuals were grown alone,but not when grown in competition or when three or six plants from the same population were grown together.Across populations,biomass of individuals grown alone was negatively correlated with intra-and interspecific competitive ability,indicating that there is a trade-off between individual growth and competitive ability.Stand-level biomass was not related to total biomass of individuals grown alone,and intra-or interspecific competitive ability,indicating that low biomass when grown alone and high competitive ability may not reduce the performance of S.halepense when grown in dense monocultural stands.
