Ice core provides a valuable vertical timeline of past climates and anthropogenic activities.Environmental proxies have been widely used in these studies,but there are few biological indicators available.To address th...Ice core provides a valuable vertical timeline of past climates and anthropogenic activities.Environmental proxies have been widely used in these studies,but there are few biological indicators available.To address this gap,we investigated the bacterial community from a 74 m ice core of Muztag ata glacier on the Tibetan Plateau to link biological indicators with past climate and anthropogenic activities.By analyzing the portion of the ice core with environmental proxies available(corresponding to 1907 to 1991),we observed an increase in bacterial richness throughout the ice core,which was associated with higher NH_(4)^(+),an indicator of agricultural development.The bacterial community was jointly determined by human activity,natural input,and air temperature,with a strong human influence after the 1950s.Furthermore,the relative abundance of animal gut-associated bacteria,including Aerococcaceae,Nocardiaceae,Muribaculaceae,and Lachnospiraceae,was associated with livestock number changes in the Central Asian region.Together with other bacterial lineages,they jointly explained 59.8%of the livestock number changes.This study provides quantitative evidence of the associations between bacterial indicators and past climate and human activities,highlighting the potential of using bacterial proxies for ice core studies.展开更多
为了研制满足光纤通讯需求的高性能半导体激光器,对压应变In Ga As Sb/Ga As Sb量子阱激光器有源区进行了研究。根据应变量子阱能带理论、固体模型理论和克龙尼克-潘纳模型,确定了激射波长与量子阱材料组分及阱宽的关系。基于Lastip软...为了研制满足光纤通讯需求的高性能半导体激光器,对压应变In Ga As Sb/Ga As Sb量子阱激光器有源区进行了研究。根据应变量子阱能带理论、固体模型理论和克龙尼克-潘纳模型,确定了激射波长与量子阱材料组分及阱宽的关系。基于Lastip软件建立了条宽为50μm、腔长为800μm的半导体激光器仿真模型,模拟器件的输出特性,讨论了量子阱个数对器件光电特性的影响。结果表明:当量子阱组分为In0.44Ga0.56As0.92Sb0.08/Ga As0.92Sb0.08、阱宽为9 nm、量子阱个数为2时,器件的性能达到最佳,阈值电流为48 m A,斜率效率为0.76 W/A。展开更多
利用LASTIP软件理论分析了有源区量子阱数目对不同组分的In Ga As Sb/Al Ga As Sb 2μm半导体激光器能带、电子与空穴浓度分布以及辐射复合率等性能参数的影响。研究表明：量子阱的个数是影响激光器件性能的关键参数,需要综合分析和优...利用LASTIP软件理论分析了有源区量子阱数目对不同组分的In Ga As Sb/Al Ga As Sb 2μm半导体激光器能带、电子与空穴浓度分布以及辐射复合率等性能参数的影响。研究表明：量子阱的个数是影响激光器件性能的关键参数,需要综合分析和优化。量子阱数太少时,量子阱对电子束缚能力弱,电子在p层中泄漏明显,辐射复合率低。量子阱数过多时,载流子在阱内分配不均匀,p型层中电子浓度升高,器件内损耗加大,辐射复合率下降。结合对外延材料质量的分析,In Ga As Sb/Al Ga As Sb半导体激光器有源区最优量子阱数目为2~3。该研究结果可合理地解释已有实验报道,并为2μm半导体激光器结构设计提供理论依据。展开更多
基金supported by the National Key Research and Development Plans(Grant No.2021YFC2300904)the National Natural Science Foundation of China(Grant Nos.U21A20176 and 42330410)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0503)。
文摘Ice core provides a valuable vertical timeline of past climates and anthropogenic activities.Environmental proxies have been widely used in these studies,but there are few biological indicators available.To address this gap,we investigated the bacterial community from a 74 m ice core of Muztag ata glacier on the Tibetan Plateau to link biological indicators with past climate and anthropogenic activities.By analyzing the portion of the ice core with environmental proxies available(corresponding to 1907 to 1991),we observed an increase in bacterial richness throughout the ice core,which was associated with higher NH_(4)^(+),an indicator of agricultural development.The bacterial community was jointly determined by human activity,natural input,and air temperature,with a strong human influence after the 1950s.Furthermore,the relative abundance of animal gut-associated bacteria,including Aerococcaceae,Nocardiaceae,Muribaculaceae,and Lachnospiraceae,was associated with livestock number changes in the Central Asian region.Together with other bacterial lineages,they jointly explained 59.8%of the livestock number changes.This study provides quantitative evidence of the associations between bacterial indicators and past climate and human activities,highlighting the potential of using bacterial proxies for ice core studies.
文摘为了研制满足光纤通讯需求的高性能半导体激光器,对压应变In Ga As Sb/Ga As Sb量子阱激光器有源区进行了研究。根据应变量子阱能带理论、固体模型理论和克龙尼克-潘纳模型,确定了激射波长与量子阱材料组分及阱宽的关系。基于Lastip软件建立了条宽为50μm、腔长为800μm的半导体激光器仿真模型,模拟器件的输出特性,讨论了量子阱个数对器件光电特性的影响。结果表明:当量子阱组分为In0.44Ga0.56As0.92Sb0.08/Ga As0.92Sb0.08、阱宽为9 nm、量子阱个数为2时,器件的性能达到最佳,阈值电流为48 m A,斜率效率为0.76 W/A。
文摘利用LASTIP软件理论分析了有源区量子阱数目对不同组分的In Ga As Sb/Al Ga As Sb 2μm半导体激光器能带、电子与空穴浓度分布以及辐射复合率等性能参数的影响。研究表明：量子阱的个数是影响激光器件性能的关键参数,需要综合分析和优化。量子阱数太少时,量子阱对电子束缚能力弱,电子在p层中泄漏明显,辐射复合率低。量子阱数过多时,载流子在阱内分配不均匀,p型层中电子浓度升高,器件内损耗加大,辐射复合率下降。结合对外延材料质量的分析,In Ga As Sb/Al Ga As Sb半导体激光器有源区最优量子阱数目为2~3。该研究结果可合理地解释已有实验报道,并为2μm半导体激光器结构设计提供理论依据。
