A gravitationally lensed quasar with quadruple images separated by 14.62 arcseconds

Gravitational lensing is a powerful tool for the study of the distribution of dark matter in the Universe. The cold-dark-matter model of the formation of large-scale structures (that is, clusters of galaxies and even larger assemblies) predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 arcsec. Numerous searches for large-separation lensed quasars have, however, been unsuccessful. All of the roughly 70 lensed quasars known, including the first lensed quasar discovered, have smaller separations that can be explained in terms of galaxy-scale concentrations of baryonic matter. Although gravitationally lensed galaxies with large separations are known, quasars are more useful cosmological probes because of the simplicity of the resulting lens systems. Here we report the discovery of a lensed quasar, SDSS J1004 + 4112, which has a maximum separation between the components of 14.62 arcsec. Such a large separation means that the lensing object must be dominated by dark matter. Our results are fully consistent with theoretical expectations based on the cold-dark-matter model.     

面向飞机PHM的大数据分析与人工智能应用

针对新一代电子产品密集型的飞机,其系统结构和失效机理复杂、失效模式多样,传统的方法难以对其进行有效健康管理的现状,因此提出了基于海量数据挖掘的飞机PHM研究。首先从系统结构、服役环境、数据来源与存储方式等角度分析了新一代飞机对海量数据挖掘的应用需求;其次论述了基于海量数据挖掘的关键技术,包括数据的预处理、集成管理、聚类、分类、关联、预测等;最后提出了一种基于私有云的飞机PHM海量数据挖掘平台,详细阐述了该平台的总体框架和软硬件结构,该平台为飞机PHM提供了验证平台,对促进飞机PHM的集成与工程化实现具有重大的军事应用意义。     

X-ray microanalysis of animal tissues by means of the field emission-scanning electron microscope

Summary With FESEM the X-ray microanalysis of unstained ultrathin sections (600 Å) free of osmium is possible. Deposits in smooth muscle cells of arteriosclerotic aortae show high calcium-peaks already after 80 sec of measurement. No contamination spots were seen after 11 min of measurement on the same point.