计算贫金属星重元素丰度分布方法的比较

用目前普遍采用的各种不同的方法以及我们所提出的方法计算了贫金属星HD126238重元素丰度分布并与其丰度的观测值进行比较,结果表明我们提出的计算方法是比较合理和可靠的方法。     

基于SCUSS和SDSS数据的银河系晕金属丰度分布

基于SCUSS u波段测光数据和SDSS g、r波段测光数据,根据F/G型主序星金属丰度与u-g和g-r色指数的相关性,运用蒙特卡罗方法模拟银河系晕的金属丰度分布。筛选晕中的F/G型主序星并按柱坐标分区间Z<-10 kpc,Z<-12 kpc,和Z<-15 kpc研究。样本的[Ee/H]分布可用三峰高斯模型拟合且模型的峰值位于[Ee/H]~-0.60,-1.55,和-2.20。经对比分析,发现两个贫金属峰是内外晕的贡献,而较富的成分则对应晕中子结构的影响。     

Novel 2D CaCl crystals with metallicity,room-temperature ferromagnetism,heterojunction, piezoelectricity-like property and monovalent calcium ions

Under ambient conditions, the only known valence state of calcium ions is +2, and the corresponding crystals with calcium ions are insulating and nonferromagnetic. Here, using cryo-electron microscopy, we report direct observation of two-dimensional (2D) CaCl crystals on reduced graphene oxide (rGO) membranes, in which the calcium ions are only monovalent (i.e. +1). Remarkably, metallic rather than insulating properties are displayed by those CaCl crystals. More interestingly, room-temperature ferromagnetism, graphene–CaCl heterojunction, coexistence of piezoelectricity-like property and metallicity, as well as the distinct hydrogen storage and release capability of the CaCl crystals in rGO membranes are experimentally demonstrated. We note that such CaCl crystals are obtained by simply incubating rGO membranes in salt solutions below the saturated concentration, under ambient conditions. Theoretical studies suggest that the formation of those abnormal crystals is attributed to the strong cation-π interactions of the Ca cations with the aromatic rings in the graphene surfaces. The findings highlight the realistic potential applications of such abnormal CaCl material with unusual electronic properties in designing novel transistors and magnetic devices, hydrogen storage, catalyzers, high-performance conducting electrodes and sensors, with a size down to atomic scale.     

Hydroxylation-induced half-metallicity in graphitic ZnO sheet

The structural, electronic and magnetic properties of the hydroxylated graphitic Zinc oxide (ZnO) sheet were studied using the density functional theory. We found that the hydroxylation can induce a magnetic moment of 1.0 μB per unit cell and turn graphitic ZnO sheet from semiconductor into half metal for the three studied hydroxylated configurations with a half-metal gap up to 0.60 eV. The relative stability of each situation was also discussed and the structure for hydroxyl absorbed above the hexagonal ring of ZnO sheet was the most steady. The prominent electronic and magnetic properties may endow 2D ZnO sheet great opportunity in future spintronics.     

SCUSS测光金属丰度定标及南银冠人马座星流的金属丰度估计

基于SDSS g,SDSS r和SCUSS u测光数据,利用F/G型主序星的光谱,从u－g和g－r色指数中进行测光金属丰度定标.定标过程中,当g－r<0.4时,测光金属丰度与基于光谱的金属丰度之间的方均根误差为0.14,当g－r>0.4时为0.16.由于SCUSS u更深更精确的星等,能够将测光金属丰度估计的应用范围设置在g<21内.选择南银冠人马座星流来研究金属丰度分布,发现大约在以银心为中心的柱坐标R~19 kpc和|Z|~14 kpc处的人马座星流呈现出比背景晕星更富的金属丰度分布.