Problems in classification and identification of Synuraceae (Chrysophyceae)

In the Synuraceae, the silica scales which cover the cell surface are of great taxonomic importance, although their delicate structure requires use of electron microscopy. Many species have been incompletely described by means of light microscopy, and there are serious difficulties in correlating them with species based on electron microscopy of the silica scales. The different types of variation in scale structure are described, and the variation range to be accepted within a species is discussed. However, as sexual reproduction is of rare occurrence in this family, the species concept must be highly arbitrary. It is reassuring then that many species based on scale ultrastructure also exhibit morphological and ecological characteristics. The advantages of scanning and transmission electron microscopy are emphasized for species identification and for detection of small forms with especially delicate scales.     

The composition of settling particles in Lake Zürich

Settling particles in the Lake Zürich were collected at different depths. Water samples and particles have been analyzed for heavy metals and for organic matter elements. Samples were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive X ray and X ray. The elemental composition of the settling particles was found to be almost constant. Special remarks are made on iron and phosphate and on manganese. Manganese oxidizing microorganisms were found near the bottom of the lake.     

Dynamics and genesis of calcic accumulations in soils and sediments of the Argentinean Pampa

Micromorphology of calcic accumulations(calcite,whewellite and gypsum) and geochemical indices were considered as indicators of genesis and evolution of pedogenic accumulations in soils and paleosediments of the Argentinean Pampa.Two groups of separate and independent calcic accumulations were studied using scanning electron microscopy:(i) in situ Argiudolls,reflecting the current soil formation;(ii) in the layers of calcrete(locally named tosca).reflecting the past environments and conditions of these layers sedimentation.New pedogenic gypsum accumulations in Argiudolls were described and possible ways of their formation were suggested.Combined analyses of morphology of carbonate accumulations and geochemical indices in different horizons of Argiudolls and layers of tosca showed that the tosca is paleopedocomplex with complicated formation history.Influence of current environment on tosca morphology is absent,so it is possible to use these pedofeatures for paleoreconstructions in further studying.     

A note on the role of the lichen collema auriforma in solution basin development on a carboniferous limestone substrate

A study carried out on Carboniferous limestone in the north and west of Ireland supports the idea that rock substrate is removed by the direct mechanical action of lichens. An experiment in which the lichen Collema auriforma was subjected to a number of wetting-drying cycles, showed, using scanning electron microscopy, that contraction of the lichen thallus during the drying phase plucked rock fragments from the substrate surface. This process could contribute to the formation of karstic features including solution basins.     

甘肃永登湿陷性新近堆积黄土的微观结构分析

甘肃永登县树屏村某工程场地土为第四纪新近堆积黄土,其工程性质较为特殊,具有较大的湿陷性,但在天然湿度下震陷性却很小。本文利用扫描显微镜对其微结构图象进行分析,同时结合土工试验结果,揭示了导致其特殊工程性质的微观机理。最后提出了在工程施工中应注意的问题。     

海原地区黄土的微观结构及地脉动特征分析

1920年8.5级地震诱发了大量的黄土滑坡,对研究黄土地区的滑坡灾害、土层地脉动特征分析具有重要意义。基于高精度电子扫描显微镜（SEM）分析发现海原地震现场表层黄土为架空孔隙弱胶结微观结构,且该黄土是以粉粒为主的低黏性粉土,有震陷和地震滑坡的高风险。基于地脉动测试得到滑坡场地15个地脉动数据,采用傅里叶变换法对苏堡村滑坡土层的脉动特征进行分析,获得地脉动频谱特征曲线。研究表明场地卓越周期建议值为0.126 s,将其划分为坚硬场地,可为该滑坡场地类别划分作为参考,同时发现滑坡体与未滑体的地脉动特征有较大差异,可为海原地震滑坡的脉动特性分析提供依据。     

A preliminary scanning electron microscope study of honeycomb weathering of sandstone in a coastal environment

Honeycomb weathering has been observed in a Carboniferous sandstone at a coastal location near Ballycastle on the north coast of Northern Ireland. Specimens of this sandstone have been analysed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Results reveal that calcium sulphate (gypsum) is the only salt present and is found only at and immediately below the rock surface. SEM observations suggest that crystallization of salts in pores could easily dislodge quartz grains to promote granular disintegration, whilst etching of quartz grain surfaces attests to chemical weathering activity within the rock However, the reason for the development of the honeycomb pattern is not known.     

Shock metamorphism of plagioclase and amphibole (Experimental data)

The shock metamorphism of plagioclase and amphibole of various chemical compositions from amphibolite and granulite facies schists was studied in experiments with shock wave loading of samples in steel recovery ampoules of plane geometry. A maximum shock pressure was reached after a few circulations of waves in the sample (stepwise shock wave compression) and varied within 26–52 GPa. The recovered samples were examined by the methods of scanning electron microscopy and microprobe and X-ray phase analysis. It is established that an increase in the F, Ti, and K concentrations in amphibole and a decrease in the Ca concentration in plagioclase make these minerals more stable with respect to shock waves. It is shown that the migration of some chemical elements, starting already at the solid phase stage of transformation in plagioclase and amphibole, is intensified at the stage of melting. It is established that isotropization of plagioclase occurs through two different mechanisms. At relatively low pressures, it is caused by the fragmentation of substance at the microlevel and is accompanied by the formation of maskelynite, a typical mineral of meteorites and astrobleme rocks. At higher pressures, isotropization is associated with melting-induced amorphization.     

Transformation relationship among different magnetic minerals within loess-paleosol sediments of the Chinese Loess Plateau

The dominant magnetic minerals and carriers of magnetic signals within the Chinese Loess Plateau are magnetite, maghemite, hematite, and goethite. In this study, we investigated the provenance and evolution of magnetic minerals during loess pedogenesis, using X-ray diffraction (XRD) and optical and electron microscopy, including field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). Our results reveal that single- and multiphase mineral assemblages among magnetic minerals in the loess-paleosol sequence have been formed. Partial oxidation of coarse eolian magnetite has occurred in the desert source area and the oxidation degree is enhanced after deposition of the dust upon the Chinese Loess Plateau. This mode of origin resulted in a microtexture consisting of an inner magnetite core surrounded by a hematite rim, and strongly affected the magnetic characteristics of the loess. Goethite coexists with hematite in the loess and paleosol, and nanometer-scale hematite is formed upon goethite rims via dehydration. Our study provides direct mineralogical evidence of the magnetic record and paleoclimatic implications of the loess-paleosol sequence of the Chinese Loess Plateau. Supported by National Natural Science Foundation of China (Grant Nos. 40772032 and 40573054) and National Basic Research Program (Grant No. 2007CB815603)     

Identification of magnetic minerals by scanning electron microscope and application of ferrofluid

Magnetic minerals are mostly identified by a combination of rock magnetic and microscopic techniques and the ferrofluid method in combination with an optical microscope was applied during the last decades. But today, scanning electron microscopy (SEM) is preferred for the observation of mineral phases because its depth of focus and resolving capability at the same magnification. In this study, we report on a method, which allows ferrofluid application under the SEM. We coated a polished basalt sample containing titanomagnetite grains with high demagnetizing fields, with a colloidal suspension containing magnetite particles (ferrofluid) ranging in size between 11 and 20 nm. Due to large gradients of multidomain grains the ferrofluid particles adhered to their surfaces. Other grains of similar composition present (ilmenohematite) but with low demagnetizing fields do not generate large magnetic gradients and therefore do not attract the colloidal particles. Upon evaporation of the ferrofluid and covering the sample with conducting material the magnetic grains with high demagnetizing field are easily identifiable under the scanning electron microscope. The different mineralogy observed by this method is confirmed by temperature dependent variation of magnetic susceptibility, revealing titanomagnetite and ilmenohematite as magnetic carriers in the basaltic samples.     

卵巢肿瘤之分类及CT诊断的价值

本文分析了５０例经病理证实的卵巢肿瘤。结果表明ＣＴ扫描在发现卵巢肿瘤方面是一种有效的手段，而且根据主要ＣＴ表现鉴别良恶性质是可能的．另一方面由于具有很高的密度分辨率，ＣＴ扫描在某种程度上低于传统的检查手段。     

First record of Ostreopsis cfr. ovata on macroalgae in the Northern Adriatic Sea

Ostreopsis ovata is an epiphytic potentially toxic dinoflagellate. It has a world-wide distribution, normally associated with other epiphytic or benthic dinoflagellates. In tropical seas O. ovata is often associated with the genera Gambierdiscus, Coolia and Prorocentrum, causing cinguatera fish poisoning. Recently, Ostreopsis spp. blooms in the Tyrrhenian and southern Adriatic Sea have been related to human health problems, such as breathing and skin irritation. Here we report the first record of Ostreopsis cfr. ovata in the Northern Adriatic Sea. O. cfr. ovata was isolated from macroalgae in two areas, the Gulf of Trieste (Italy) and close to Rovinj (Croatia). The microalga was identified by scanning electron microscopy and by fluorescence light microscopy. Size range and thecal pore structure were similar to those described for O. cfr. ovata in previous studies. Ostreopsis cfr. ovata was present on all the macroalgae collected, particularly browns and reds. The microalgal association on macroalgae was mostly composed of Ostreopsis sp., Coolia monotis and Coscinodiscus sp.     

内蒙古东部扎兰屯地区的b值时空变化特征

内蒙古东部的扎兰屯地区位于大兴安岭地震带北段,区域地质构造复杂,历史及现代中强地震较为活跃。本文以该地区地震活动作为研究对象,在区域地震序列完整性分析基础上,用最小二乘法进行b值时间扫描计算,用最大似然法进行b值空间扫描计算。时间扫描中的b值为每个扫描窗口内研究区的平均b值,因此其变化幅度不大,b值变化范围基本维系在0.78～1.13,误差范围为0.04～0.065。空间扫描结果显示,扎兰屯地区b值空间分布范围基本维系在0.4～1.8,误差范围为0.045～0.085;低b值区域为阿伦河断裂中北段,b值大致分布在0.5～0.7,表明该区域地壳介质处于高水平应力积累状态,可能是未来发生中强以上地震的危险区域。     

颅脑外伤CT扫描护理技术分析

目的：本文分析总结颅脑外伤病人CT扫描的护理及扫描技术要点，材料与方法：对9600例颅脑外伤病人在做CT检查前的护理技术及扫描技术进行了回顾性分析总结，了解伤后脑内改变对诊断和治疗有着和重要作用。总结了颅脑外伤CT扫描的护理技术的9项要点，结论：CT是诊断颅脑外伤的首选方法，它不仅能够明确颅外伤的范围，也是判断可进行外科手术的重要指证，CT检查的护理技术及扫描技术是确保外伤患者CT检查顺利的关键。     

Anhysteretic remanent magnetization: model of grain size distribution of spherical magnetite grains

A phenomenological model based on a linear relationship between the magnetic coercivity field and the reciprocal of the grain diameter is applied to explain the anhysteretic remanent magnetization (ARM) imparted to artificial samples with different concentrations of a very well characterized magnetite powder. By analyses of scanning electron microscopy images, the spherically shaped single domain synthetic magnetite is found to follow a lognormal grain size distribution with ~86 nm of mean diameter. The proposed model, fitted to ARM measurements up to a peak alternating field of 100 mT, yields a very good agreement. The coercivity behaviour predicted by micromagnetism theory disagrees with the experimental results of this work. A likely explanation for the discrepancy is that the magnetite particles, which consist of a mixture of grains in coherent rotation and curling modes, produce similar observations as domain processes.     

CT扫描参数优选对辐射防护的贡献

作者参照国际放射防护委员会(ICRP)1991年60号出版物规定的实践中放射防护原则,设计CT扫描中患者及公众放射防护方策,通过优选予置扫描参数和适时扫描参数,降低CT 受检者的辐射剂量,并业已经过辐射测量实验结果的证实。对此,做一介绍。     

3D Mapping of calcite and a demonstration of its relevance to permeability evolution in reactive fractures

There is a need to better understand reaction-induced changes in fluid transport in fractured shales, caprocks and reservoirs, especially in the context of emerging energy technologies, including geologic carbon sequestration, unconventional natural gas, and enhanced geothermal systems. We developed a method for 3D calcite mapping in rock specimens. Such information is critical in reactive transport modeling, which relies on information about the locations and accessible surface area of reactive minerals. We focused on calcite because it is a mineral whose dissolution could lead to substantial pathway alteration because of its high solubility, fast reactivity, and abundance in sedimentary rocks. Our approach combines X-ray computed tomography (XCT) and scanning electron microscopy. The method was developed and demonstrated for a fractured limestone core containing about 50% calcite, which was 2.5 cm in diameter and 3.5 cm in length and had been scanned using XCT. The core was subsequently sectioned and energy dispersive X-ray spectroscopy was used to determine elemental signatures for mineral identification and mapping. Back-scattered electron microscopy was used to identify features for co-location. Finally, image analysis resulted in characteristic grayscale intensities of X-ray attenuation that identify calcite. This attenuation mapping ultimately produced a binary segmented 3D image of the spatial distribution of calcite in the entire core. To demonstrate the value of this information, permeability changes were investigated for hypothetical fractures created by eroding calcite from 2D rock surfaces. Fluid flow was simulated using a 2D steady state model. The resulting increases in permeability were profoundly influenced by the degree to which calcite is contiguous along the flow path. If there are bands of less reactive minerals perpendicular to the direction of flow, fracture permeability may be an order of magnitude smaller than when calcite is contiguous. These results emphasize the importance of characterizing spatial distribution of calcite in heterogeneous rocks that also contain a similar abundance of less reactive minerals.     

Characterisation of sediments polluted by acid mine drainage in the northeast of Algeria

The present study investigates the composition and the mineralogy of sediments in the Essouk River, located in the Northeast of Algeria in Sidi Kamber mining zone at approximately 2km upstream Guenitra Reservoir.The mine is abandoned since 1976,but acidic drainage water is still a source of river contamination.Powder X-Ray diffraction(XRD),scanning electron microscopy(SEM) with energy dispersive analyses(EDX),X -Fluorescence analyses and infrared spectroscopy analyses were used to characterize surface sediments sampled at various sites in the area near the mining effluents. The obtained results show that the composition of the sediments is mainly dominated by iron and sulphur.In the vicinity of the mine,jarosite and schwertmannite are the essential precipitates. Downstream,sediments are formed by various phases of iron oxyhydroxydes with the presence of adsorbed sulphate.     

Statistical analysis of textural data from complex pyroclastic sequences: implications for fragmentation processes of the Agnano-Monte Spina Tephra (4.1 ka), Phlegraean Fields, southern Italy

The Agnano-Monte Spina eruption (4.1 ka) generated pyroclastic deposits with complex internal stratigraphy that reflects variations in eruptive style. To obtain constraints on the fragmentation processes, we analysed grain-size and scanning electron microscopy (SEM) data by means of multivariate statistical techniques of the cluster and factor analysis types. The results allow the identification of end-member deposits related to either pure magmatic activity, or pure phreatomagmatic activity. In addition, some deposits show evidence of the contemporaneous operation of both end-member fragmentation modes. The presence of the two contrasting fragmentation processes during the various phases of explosive activity is tentatively interpreted to be a function in inhomogeneities in gas exsolution processes within the magma column that feeds the eruption.     

Geostatistical modeling of clay spatial distribution in siliciclastic rock samples using the plurigaussian simulation method

In order to implement secondary and enhanced oil recovery processes in complex terrigenous formations as is usual in turbidite deposits, a precise knowledge of the spatial distribution of shale grains is a crucial element for the fluid flow prediction. The reason of this is that the interaction of water with shale grains can significantly modify their size and/or shape, which in turn would cause porous space sealing with the subsequent impact in the flow. In this work, a methodology for stochastic simulations of spatial grains distributions obtained from scanning electron microscopy images of siliciclastic rock samples is proposed. The aim of the methodology is to obtain stochastic models would let us investigate the shale grain behavior under various physico-chemical interactions and flux regimes, which in turn, will help us get effective petrophysical properties (porosity and permeability) at core scale. For stochastic spatial grains simulations a plurigaussian method is applied, which is based on the truncation of several standard Gaussian random functions. This approach is very flexible, since it allows to simultaneously manage the proportions of each grain category in a very general manner and to rigorously handle their spatial dependency relationships in the case of two or more grain categories. The obtained results show that the stochastically simulated porous media using the plurigaussian method adequately reproduces the proportions, basic statistics and sizes of the pore structures present in the studied reference images.