Stromatolites Discovered in Nihewan Formation and Their Paleoenvironment

Columnar stromatolites have been discovered in two beds of the upper part of the Nihewan Formation, a series of lacustrine deposits. The structure of the stromatolites is characterized by alternation of light, intergranular pore-rich laminae and dark, organic substance-rich laminae. Abundant filamentous algal remains have been discovered in stromatolite laminae, some of them are similar to the species present on the shore of the Caribbean Sea that are living in warmer climate than in the Nihewan area now. With the ESR and U-series age methods, it has been determined that the ages of the lower and upper stromatolite beds are about 130,000 and 93,000 a B. P. , respectively. Compared with many other geologic events taking place during the period in Northern China, we conclude that the two stromatolite beds were formed during the two warmer stages of the Last Interglacial.     

泥河湾层中叠层石的发现及其古环境意义

本文描述了泥河湾层中发现的二层叠层石,指出它们是蓝藻(蓝菌)活动造成的生物沉积结构,分别形成于距今13万年和9万年左右,是末次间冰期温暖气候的产物。     

磁纳米粒子介导的靶向剪切波弹性成像

组织力学特性与其生理病理变化过程密切相关.因此,对组织力学特性的分析有望为疾病诊断提供重要依据.超声弹性成像可以定量分析组织的剪切模量,但在检测的特异性和灵敏度等方面仍存在局限性.针对这一问题,该文发展一种磁纳米粒子介导的靶向剪切波弹性成像新方法.该方法是基于磁纳米粒子在脉冲磁场作用下产生磁致振动,从而导致周围组织的剪...     

磁纳米粒子介导的磁致振动超声成像研究现状及展望

超声成像作为临床上常用的影像检测方法,在疾病诊断、术中导航和术后评估等方面发挥重要作用.随着纳米技术的快速发展,不同的微纳米材料或成像探针的构建,为超声成像提供新的发展动力.其中,磁纳米粒子介导的磁致振动超声成像是近年来发展的一种新兴的成像技术.其主要原理是基于磁纳米粒子在变化磁场作用下产生磁致振动,利用超声波探测粒子...