The kinematical parameters,spatial shape and structure of the open cluster IC 2391 and the associated stellar stream are studied here using Gaia Data Release 2(GDR2) astrometry data.The apex positions are determined f...The kinematical parameters,spatial shape and structure of the open cluster IC 2391 and the associated stellar stream are studied here using Gaia Data Release 2(GDR2) astrometry data.The apex positions are determined for the open cluster IC 2391(data taken from Cantat-Gaudin et al.) and for the kinematical stream’s stars mentioned in Montes et al.employing both convergent point and AD-diagram methods.The values of apex coordinates are:(A,D)CP=(6.~h17 ± 0.~h004,-6.°88 ± 0.°381;for cluster) and(6.~h07 ± 0.~h007,-5.°00 ± 0.°447;stream),and(A0,D0) =(6.~h12 ± 0.~h004,-3.°4 ± 0.°3;cluster) and(6.~h21 ±0.~h007,-11.°895 ± 0.°290;stream).The results are in good agreement with the previously calculated values.The positions of the stars in the disk and the spatial dispersion velocities are determined.The paths of cluster and associated stream are traced in the disk by orbit calculation back in time to their places of formation.A possible genetic relationship between the cluster and stream has been detected.The approximation of the spatial and kinematical shape of the stream and the cluster is made.According to this study,even though currently the cluster and stream seem to have a spatial difference in their locations,they appear to have formed in the same region of the Galactic disk.展开更多
The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin incl...The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and waterfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km<sup>2</sup> in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.展开更多
深入研究硫沉降对森林土壤有机碳库影响,可以为正确评估森林生态系统碳循环过程及其对全球气候变化的响应提供依据。在山西太岳山34年生华北落叶松人工林设置人工模拟硫沉降实验,采用物理分组的方法,研究施硫水平(0、50、100、150 kg S&...深入研究硫沉降对森林土壤有机碳库影响,可以为正确评估森林生态系统碳循环过程及其对全球气候变化的响应提供依据。在山西太岳山34年生华北落叶松人工林设置人工模拟硫沉降实验,采用物理分组的方法,研究施硫水平(0、50、100、150 kg S·hm-2·a-1)对土壤粗颗粒有机碳(CPOC,>250μm)、细颗粒有机碳(FPOC,53~250μm)和矿质结合态有机碳(MOC,<53μm)含量的影响,并运用通径分析探讨了土壤有机碳组分与土壤环境因子的关系。结果表明:华北落叶松人工林土壤表层(0~10 cm)POC、MOC和POC/MOC值均高于亚表层(10~20 cm);土壤POC和MOC随月份变化显著,8月土壤POC和MOC均显著低于6月和10月;对照处理6月表层土壤的POC/MOC值低于8月和10月,亚表层则相反;施硫显著改变了土壤MOC,但并未显著改变土壤POC;低硫和中硫水平表层土壤MOC较对照处理显著减少,高硫水平亚表层土壤MOC较对照处理显著增加(P<0.01);土壤CPOC、FPOC和MOC与土壤温度、湿度、p H值有极显著负相关关系。通径分析表明,温度对3种土壤有机碳含量直接作用最大,而湿度对土壤POC并没有直接作用。试验结果表明,短期施硫降低了华北落叶松人工林土壤有机碳稳定性,后期在对硫沉降影响研究中应多加考虑温度这一重要因子的作用。展开更多
基金supported by grants from the Ministry of Science and Technology(MOST),Taiwan(MOST 105-2811-M-007-038,MOST 105-2119-M-007-029-MY3,MOST 106-2112-M-007-006-MY3 and MOST 106-2811-M-007-051)
文摘The kinematical parameters,spatial shape and structure of the open cluster IC 2391 and the associated stellar stream are studied here using Gaia Data Release 2(GDR2) astrometry data.The apex positions are determined for the open cluster IC 2391(data taken from Cantat-Gaudin et al.) and for the kinematical stream’s stars mentioned in Montes et al.employing both convergent point and AD-diagram methods.The values of apex coordinates are:(A,D)CP=(6.~h17 ± 0.~h004,-6.°88 ± 0.°381;for cluster) and(6.~h07 ± 0.~h007,-5.°00 ± 0.°447;stream),and(A0,D0) =(6.~h12 ± 0.~h004,-3.°4 ± 0.°3;cluster) and(6.~h21 ±0.~h007,-11.°895 ± 0.°290;stream).The results are in good agreement with the previously calculated values.The positions of the stars in the disk and the spatial dispersion velocities are determined.The paths of cluster and associated stream are traced in the disk by orbit calculation back in time to their places of formation.A possible genetic relationship between the cluster and stream has been detected.The approximation of the spatial and kinematical shape of the stream and the cluster is made.According to this study,even though currently the cluster and stream seem to have a spatial difference in their locations,they appear to have formed in the same region of the Galactic disk.
文摘The Snake River in northwestern United States is 1735 km long, the largest tributary of the Columbia River and is the 13<sup>th</sup> longest river in the United States. The Snake River drainage basin includes parts of six U.S. states. The Snake River Plain was created by a volcanic hotspot that lies beneath Yellow-stone National Park. The previous Ice Age carved out canyons, cliffs and waterfalls along the middle and lower Snake River. The Missoula Flood was to the north and Bonneville Flood to the south altered the Snake River and surrounding landscape. The Snake River has a drainage basin of 282,000 km<sup>2</sup> in the states of Oregon, Washington, Utah, Nevada and Idaho. The Snake River drops from mountain elevations of 3000 m to its confluence with the Columbia River. The river is one of the most biologically diverse freshwater systems in the United States with trails designed to promote recreational tourism, increase use of the Snake River and create generations of people who care about the river and are willing to protect and provide environmental stewardship of the river watershed resources.
