Crystallization pathways in the Great Artesian Basin (Australia) spring mound carbonates: Implications for life signatures on Earth and beyond

Recent studies of continental carbonates revealed that carbonates with similar fabrics can be formed either by biotic, biologically-induced, biologically-influenced or purely abiotic processes, or a combination of all. The aim of this research is to advance knowledge on the formation of carbonates precipitated (or diagenetically altered) in extreme, continental environments by studying biotic versus abiotic mechanisms of crystallization, and to contribute to the astrobiology debate around terrestrial analogues of Martian extreme environments. Both fossil (upper Pleistocene to Holocene) and active carbonate spring mounds from the Great Artesian Basin (South Australia) have been investigated. These carbonates consist of low-Mg to high-Mg calcite tufa. Four facies have been described: (i) carbonate mudstone/wackestone; (ii) phytohermal framestone/boundstone; (iii) micrite boundstone; and (iv) coarsely crystalline boundstone. The presence of filaments encrusted by micrite, rich in organic compounds, including ultraviolet-protectants, in phytohermal framestone/boundstone and micrite boundstone is clear evidence of the existence of microbial mats at the time of deposition. In contrast, peloidal micrite, despite commonly being considered a microbial precipitate, is not directly associated with filaments in the Great Artesian Basin mounds. It has probably formed from nanocrystal aggregation on colloid particulate. Thus, where biofilms have been documented, it is likely that bacteria catalyzed the development of fabrics. It is less certain that microbes induced calcium carbonate precipitation elsewhere. Trace elements, including rare earth element distribution from laminated facies, highlight strongly evaporative settings (for example, high Li contents). Carbon dioxide degassing and evaporation are two of the main drivers for an increase in fluid alkalinity, resulting in precipitation of carbonates. Hence, although the growth of certain fabrics is fostered by the presence of microbial mats, the formation of carbonate crystals might be independent from it and mainly driven by extrinsic factors. More generally, biological processes may be responsible for fabric and facies development in micritic boundstone whilst micrite nucleation and growth are driven by abiotic factors. Non-classical crystallization pathways (aggregation and fusion of nanoparticles from nucleation clusters) may be more common than previously thought in spring carbonate and this should be carefully considered to avoid misinterpretation of certain fabrics as by-products of life. It is proposed here that the term ‘organic-compound catalyzed mineralization’ should be used for crystal growth in the presence of organic compounds when dealing with astrobiological problems. This term would account for the possibility of multiple crystallization pathways (including non-classical crystallization) that occurred directly from an aqueous solution without the direct influence of microbial mats.     

胶州湾夜光藻种群动态及其大量繁殖的生态机制

为研究胶州湾夜光藻大量繁殖的生态机制,于2015年逐月对胶州湾12个站位进行了多学科综合调查,获取了温度、盐度、营养盐等环境因子的周年数据,分析了夜光藻种群丰度和结构的时空分布特征,探讨了环境因子对夜光藻种群动态的影响,以及夜光藻种群增长与其繁殖方式的相关关系。结果发现:全年各站位夜光藻丰度范围为0—31.17×10~3ind./m~3,月平均丰度呈现双峰分布;二分裂个体比例介于0—31.25‰,有性繁殖个体比例介于0—29.41‰,两种繁殖方式均呈现出季节差异及空间差异。相关性分析表明,影响夜光藻种群动态的主要因子包括水温、叶绿素a、硝氮及亚硝氮。夜光藻是冷水种,水温与夜光藻种群丰度、两种繁殖个体比例均呈显著负相关;叶绿素a反映夜光藻食物的丰富程度,与夜光藻丰度、两种繁殖个体比例呈显著正相关;亚硝氮和硝氮可能对夜光藻代谢繁殖起调控作用,与夜光藻丰度及有性繁殖个体比例呈负相关。     

半参数模型在GPS季节性信号分离中的应用

根据噪声序列的Hurst指数特性,提出一种新的确定半参数模型平滑因子的方法--基于Hurst指数的二分搜索法,并将该方法应用于分离时变GPS季节性信号。通过对模拟数据及实测GPS坐标序列的分析,验证了该方法是一种有效的确定平滑因子的方法。将计算得到的平滑因子代入半参数模型,能够将GPS坐标序列中的季节性信号充分地分离出来。     

汶川地震断裂带科学深钻井孔附近微震观测问题及微震数据转换

为了配合汶川地震科学深钻,弄清楚钻孔附近浅层的断层面结构,中国地震局地球物理研究所分别在四川省绵竹市天池乡和四川省绵阳市南坝镇布设15套南非矿山地震研究所(IMS)生产的矿山地震仪.分析矿山地震仪天然微震监测中仪器布设、数据采集和数据处理等方面遇到的问题,介绍与该仪器对应的数据的文件格式,并实现该数据与通用地震数据格式SAC二进制格式的转换.     

二维空间关系定性表达模型的研究

通过对几种典型的定性表达模型的分析及比较,论述了单一模型实现空间查询所存在的局限,提出利用组合模型来表达空间关系的方法。最后结合空间查询中的实例,通过介绍如何同时运用二值拓扑关系模型和符号空间索引模型来实现同时包含拓扑关系和方向关系的复杂空间查询来说明这种方法。     

HIGH PRECISION CCD CALIBRATION AND ITS APPLICATIONS

ABSTRACT

With the help of CCD images, the realization of high precision positioning and measurement has become the basic standard for machine vision and real time photogrammetry systems. However, deformation and other sorts of degradation occurring during transmission are major limiting factors of the precision attainable with most current CCD cameras and frame grabbers. So a precise radiometric and geometric transmission of images from CCD sensor to memory is a fundamental aspect of CCD camera calibration. The geometric calibration system, which uses some image processing algorithms of the CCD camera based on the researched and developed system is discussed. The reliability and validity are also discussed. The experimental results for the calibration of the CCD array will be taken as an important quality index for CCD evaluation.     

ArcSDE压缩二进制存储格式的研究与改进

ArcSDE压缩二进制是ArcSDE在关系型数据库(RDBMS)中保存地理信息中二进制几何图形的存储格式,这种格式采用将浮点几何数据整形化的方法进行数据压缩,减少了数据存储空间,同时也加快了数据在网络上传输的速度。本文通过对ArcSDE压缩二进制存储格式的研究与分析,指出了这种格式在存取和处理效率上的不足之处,并提出了更为高效的改进方法。     

基于立方体元的Shear - warp体绘制加速算法

大规模三维地震数据的直接体绘制,是一个计算和数据双重密集型问题.为了提高三维图像的重建效率,提出了一种基于立方体元的Shear- warp地震数据体绘制算法.该算法通过构建立方体元在相邻的体素点之间建立联系;然后根据地震数据的特征对体元进行分类,在绘制过程中通过二叉树索引,快速定位分类结果.通过索引结果,避免了对等值体...     

Matlab对基于二进制-XML混合格式的SMOS盐度数据的提取方法与实现

基于二进制-XML混合文件格式的SMOS盐度数据的处理和延伸应用仍处于初级阶段,其前提是对SMOS数据的提取.本文详细介绍了SMOS的文件格式和利用Matlab对SMOS文件进行读写操作的方法,在此基础上给出了提取SMOS数据的流程图和实例,为SMOS数据产品的开发等下了基础.     

跨国零售企业在华区位研究——以沃尔玛和家乐福为例

与制造业外资高度集聚在沿海地区不同,服务业外资则沿着中国城市体系布局,消费者外资服务业在渗透大城市市场的同时,以等级式扩散方式向内陆地区城市扩张,以蔓延式扩散方式在都市圈内扩张。本文以沃尔玛和家乐福为例,研究跨国零售企业在中国的空间扩张。截止到2009年,沃尔玛超市已经渗透到许多中等城市,主要以等级式扩散方式进行空间扩张。家乐福超市则主要集中在珠三角、长三角和京津冀都市圈,在各都市圈内部蔓延式扩张。二项式逻辑模型分析表明,家乐福更重视本地化零售业市场规模与潜力,偏好零售业开放时间较长的城市,同时也关注竞争对手沃尔玛新开门店的城市选择。沃尔玛则重视利用零售业集聚经济和规模经济以及家乐福门店城市选择策略,但不在意本地零售业市场规模及其开放政策制度的影响。综合其空间扩散模式、物流配送以及区位选择行为,本文认为两个企业在中国采取了全球化与本土化兼顾的战略,从而得以在中国实现快速扩张。