Induced Calcite Precipitation by Cyanobacterium Synechococcus

This study investigated the role of the solution composition on calcite precipitation induced by cyanobacteria. The precipitation of calcium carbonate was induced by addition of cyanobacterium cells Synechococcus strain PCC 7942 in two artificial solutions with a different composition at similar saturation states in respect to calcite. Ion‐selective electrodes for pH, Ca²⁺, and COequation/tex2gif-stack-1.gif monitored the experiments, and the morphology of precipitated crystals was analysed by scanning electron microscopy. The calcite precipitation was observed in all experiments after the addition of the cells. The composition of solution (the ratio of dissolved inorganic carbon to dissolved calcium) strongly influenced the calcite precipitation. Based on laboratory experiment results, a possible mechanism for precipitation induced by Synechococcus is proposed linking precipitation with the conditions near to cell walls rather than with the saturation conditions in the bulk solution.     

腰椎峡部CT反向扫描技术的探讨

目的　探讨腰椎峡部CT反向扫描技术的价值。方法　CT扫描架向头侧倾斜，定位线与腰椎峡部平面平行，扫描角度与间盘层面相反。结果　反向扫描技术图像可清晰显示腰椎峡部裂隙宽度及关节错乱情况，防止漏诊。结论　反向扫描技术应在腰椎间盘扫描中常规使用。     

Thermal monitoring of Lascar Volcano, Chile, using infrared data from the along-track scanning radiometer: a 1992–1995 time series

 Lascar Volcano (22°22'S, 67°44'W) is the most active volcano of the central Andes of northern Chile. Activity since 1984 has been characterised by periods of lava dome growth and decay within the active crater, punctuated by explosive eruptions. We present herein a technique for monitoring the high-temperature activity within the active crater using frequent measurements of emitted shortwave infrared (SWIR) radiation made by the spaceborne along-track scanning radiometer (ATSR). The ATSR is an instrument of low spatial resolution (pixels 1 km across) that shares certain characteristics with the MODIS instrument, planned for use as a volcano monitoring tool in the NASA EOS Volcanology Project. We present a comprehensive time series of over 60 cloud- and plume-free nighttime ATSR observations for 1992–1995, a period during which Lascar experienced its largest historical eruption. Variations in short wavelength infrared flux relate directly to changes in high-temperature surfaces within the active crater. From these data, interpretations can be made that supplement published field reports and that can document the presence and status of the lava dome during periods where direct, ground-based, observations are lacking. Our data agree with less frequent information collected from sensors with high spatial resolution, such as the Landsat thematic mapper (Oppenheimer et al. 1993) and are consistent with field observations and models that relate subsidence of the dome to subsequent explosive eruptions (Matthews et al., 1997). Most obviously, Lascar's major April 1993 eruption follows a period in which the magnitude of emitted shortwave infrared radiation fell by 90%. At this time subsidence of the 1991–1992 lava dome was reported by field observers and this subsidence is believed to have impeded the escape of hot volatiles and ultimately triggered the eruption (Smithsonian Institution 1993a). Extrapolating beyond the period for which field observations of the summit are available, our data show that the vulcanian eruption of 20 July 1995 occurred after a period of gradual increase in short wavelength infrared flux throughout 1994 and a more rapid flux decline during 1995. We attribute this additional, otherwise undocumented, cycle of increasing and decreasing SWIR radiance as most likely representing variations in degassing through fumaroles contained within the summit crater. Alternatively, it may reflect a cycle of dome growth and decay. The explosive eruption of 17 December 1993 appears to have followed a similar, but shorter, variation in SWIR flux, and we conclude that large explosive eruptions are more likely when the 1.6-μm signal has fallen from a high to a low level. The ATSR instrument offers low-cost data at high temporal resolution. Despite the low spatial detail of the measurements, ATSR-type instruments can provide data that relate directly to the status of Lascar's lava dome and other high-temperature surfaces. We suggest that such data can therefore assist with predictions of eruptive behaviour, deduced from application of physical models of lava dome development at this and similar volcanoes. Received: 1 October 1996 / Accepted: 13 January 1997     

扫描电镜在黄土湿陷及花岗岩古风化壳成生机理研究中的应用

本文利用扫描电镜对黄土湿陷变形机理及古风化花岗岩成生环境机理进行了研究, 分析了扫描电镜在工程岩土的变形与强度问题机理研究中的重要作用。     

大比例尺地图扫描数字化软件的研制

介绍的大比例尺地形图扫描数据处理系统ＬＳＭＳＳ，是利用扫描仪将地图输入计算机，以图像处理技术，实现了从栅格数据到矢量数据格式，根据大比例尺地形图特点，利用已测坐标点，进行分块局部纠正的数字化方法，以提高数字化后图精度，并消 除地形图要素间的互位置的矛盾。     

午后极光强度与行星际磁场的相关

利用1997年和199年南极中山站多通道扫描光度计的地面观测数据和WIND卫星在弓激波上游对行星际磁场(IMF)的观测数据,对午后高纬极光强度与IMF各分量、以及时钟角之间的相关进行了定量研究. 统计表明,630nm的强度Ir随IMF Bx的增大而减小,其线性相关系数为-0.3;而557.7nm的变化趋势与此相反,其相关系数要低得多. 630nm的强度随IMF By的变化曲线为一"V"形结构,其谷底在By=-3nT附近;557.7nm的强度也有相似的变化趋势,其谷底的位置在By=-2nT附近. 极光强度随IMF Bz的变化曲线为一倒着的"Z"字形结构. 630nm的强度随IMF的模B的增大而增强,其线性相关系数达到0.9,而557.7nm与B之间的相关性要差得多. 极光强度随IMF时钟角的变化曲线为一倒"V"结构,其反转点在θ=130°附近.     

橡皮筋法在点云数据编辑中的应用

针对点云数据编辑中需要大量绘制任意多边形工作,提出用橡皮筋方法来绘制任意多边形,并用AutoLISP语言实现了该方法。实践表明,该方法提高了点云编辑的自动化程度和工作效率,在一定程度上减轻了绘图人员的劳动强度。     

我国南方持续性低温与东亚冬季风“北弱南强”模态的关系

本文研究了南方持续性低温事件的环流特征,并讨论了它与冬季风南北反相模态的关系。南方持续性低温过程与寒潮过程不同。与寒潮过程相比,南方低温事件持续时间较长,发生频率较低。寒潮过程中,中高纬度环流以波列状槽脊形势为主。而南方低温事件中,中高纬度以大型斜脊斜槽为主要影响系统。大型斜脊斜槽导致冷空气主要以西方路径为主,中纬度为平直气流所控制。东亚大槽向北收缩,日本南部地区为正高度距平控制,它对冷空气东移起了阻挡作用,使得南方地区长期处于冷空气控制,造成极端低温主要出现在黄河以南地区。同时,活跃的南支扰动也显著影响南方持续性低温的发生。东亚冬季风通常被视为一个整体。近年来的研究指出,除了南北一致变化模态,冬季风还存在南北反相变化模态。在南方持续性低温事件中,地表风场距平表现出南北变化反相的特征,即北方为偏南风距平控制,南方为偏北风距平控制。这与冬季风分布的南北反相变化的特征相一致。这种类型与北风相联系的南方降温并不是由高纬度强冷空气南下造成的。个例分析的结果也验证了上述结果。     

CBS图像重建中的数据修正

本文依据康普顿背散射扫描原理,给出了图像重建算法,讨论了有关的数据修正因子,得出了检测深度增大时误差累积传播的数据修正模型。     

泥鳅鳃表面形态结构扫描电镜研究

本文应用扫描电镜对泥鳅鳃表面形态结构进行了详细的观察和研究，结果表明：泥鳅鳃的鳃弓、鳃耙、鳃丝及鳃小片的上皮细胞表面各具不同的形态特征。鳃弓、鳃耙及鳃丝上皮细胞表面都有环形隆嵴、断续的短纹或点纹及小孔，而鳃小片的表面结构与其明显不同。这些结构特点与其鳃的功能机理是密切相关的。