On the basis of recently published astrophysical parameters of the open clusters, we have selected 301 clusters with measurements of their kinematical parameters to trace the local structure and kinematics of the Gala...On the basis of recently published astrophysical parameters of the open clusters, we have selected 301 clusters with measurements of their kinematical parameters to trace the local structure and kinematics of the Galactic disk. The present sample covers a range of over 3.0 kpc from the Sun and gives significant estimates of the disk structure and kinematical parameters of the Galaxy. We derive the disk scale height, vertical displacement of the Sun to the Galactic plane, solar motion with respect to the local standard of rest, circular speed of the Galactic rotation, Galactocentric distance from the Sun, etc. We found that the average scale height of the disk defined by the open clusters is Zh = 58 ± 4pc, with a vertical displacement of the Sun below the Galactic plane of z0 -= - 16±4 pc. Clusters with ages older than 50 Myr are less concentrated in the average plane （Zh=67 ±6pc） than the younger clusters （Zh = 51±5pc）. Using the approximation of axisymmetric circular rotation, we have derived the distance to the Galactic center from the Sun R0 = 8.03 ±0.70 kpc, which is in excellent agreement with the best estimate of the Galactocentric distance. From a kinematical analysis, we found an agedependent rotation of the Galaxy. The older clusters exhibit a lower velocity of vorticity, but have the same shear as the younger clusters. The mean rotation velocity of the Galaxy was obtained as 235 ± 10 km s-1.展开更多
Fruitful efforts have been made for the assembly of nanosized silver clusters,and the majority of which are protected by thiolates and alkynyl ligands.By comparison,the reported silver clusters or silvercluster-based ...Fruitful efforts have been made for the assembly of nanosized silver clusters,and the majority of which are protected by thiolates and alkynyl ligands.By comparison,the reported silver clusters or silvercluster-based supramolecular networks protected by N-donor ligands are very rare because of the hard basicity of N-donor ligands with respect to the soft acid Ag(Ⅰ).Here,by using an N-donor ligand,a 2D Cl@Ag_(11)N_(24)-based supramolecular network[Cl@Ag_(11)(L)_(8)X_(2)]_(n)(X=CF_(3)COO^(-)for 1,NO_(3)^(-)for 2 and CF_(3)SO_(3)^(-)for 3)has been constructed with a Ag-O bond as the linker.This high-nuclearity silver cluster Cl@Ag_(11)N_(24) has an open dendritic structure with a high coordination ratio of the N atom,which is different from the well-established macrocycle,spheroidal cage and core-shell architectures based on silver-thiolate/alkynyl/phosphine clusters.The stability and assembly process of the 2D network has been studied by high-resolution electrospray mass spectrometry(HR-ESI-MS).Notably,1 shows an intriguing dual-emission feature that is strongly influenced by different excitation wavelengths and temperatures.Significantly,this work sheds new light on the construction of novel silver clusters and supramolecular networks based on them and provides a kind of luminescent material.展开更多
基金funded by the National Natural Science Foundation of China (NSFC) (Grant No.10673005)
文摘On the basis of recently published astrophysical parameters of the open clusters, we have selected 301 clusters with measurements of their kinematical parameters to trace the local structure and kinematics of the Galactic disk. The present sample covers a range of over 3.0 kpc from the Sun and gives significant estimates of the disk structure and kinematical parameters of the Galaxy. We derive the disk scale height, vertical displacement of the Sun to the Galactic plane, solar motion with respect to the local standard of rest, circular speed of the Galactic rotation, Galactocentric distance from the Sun, etc. We found that the average scale height of the disk defined by the open clusters is Zh = 58 ± 4pc, with a vertical displacement of the Sun below the Galactic plane of z0 -= - 16±4 pc. Clusters with ages older than 50 Myr are less concentrated in the average plane （Zh=67 ±6pc） than the younger clusters （Zh = 51±5pc）. Using the approximation of axisymmetric circular rotation, we have derived the distance to the Galactic center from the Sun R0 = 8.03 ±0.70 kpc, which is in excellent agreement with the best estimate of the Galactocentric distance. From a kinematical analysis, we found an agedependent rotation of the Galaxy. The older clusters exhibit a lower velocity of vorticity, but have the same shear as the younger clusters. The mean rotation velocity of the Galaxy was obtained as 235 ± 10 km s-1.
基金supported by the NSFC(21771113,21531005,and 21421001)the Nature Science Fund of Tianjin,China(16JCZDJC36900).
文摘Fruitful efforts have been made for the assembly of nanosized silver clusters,and the majority of which are protected by thiolates and alkynyl ligands.By comparison,the reported silver clusters or silvercluster-based supramolecular networks protected by N-donor ligands are very rare because of the hard basicity of N-donor ligands with respect to the soft acid Ag(Ⅰ).Here,by using an N-donor ligand,a 2D Cl@Ag_(11)N_(24)-based supramolecular network[Cl@Ag_(11)(L)_(8)X_(2)]_(n)(X=CF_(3)COO^(-)for 1,NO_(3)^(-)for 2 and CF_(3)SO_(3)^(-)for 3)has been constructed with a Ag-O bond as the linker.This high-nuclearity silver cluster Cl@Ag_(11)N_(24) has an open dendritic structure with a high coordination ratio of the N atom,which is different from the well-established macrocycle,spheroidal cage and core-shell architectures based on silver-thiolate/alkynyl/phosphine clusters.The stability and assembly process of the 2D network has been studied by high-resolution electrospray mass spectrometry(HR-ESI-MS).Notably,1 shows an intriguing dual-emission feature that is strongly influenced by different excitation wavelengths and temperatures.Significantly,this work sheds new light on the construction of novel silver clusters and supramolecular networks based on them and provides a kind of luminescent material.
