A method to estimate hydraulic conductivity from bulk geochemical compositions

A new method has been developed to estimate the hydraulic conductivity in unconsolidated aquifers. The method uses bulk geochemical compositions correlated with hydraulic conductivities measured by pumping tests. The concept is based on a general rule that hydraulic conductivity is principally controlled by grain-size distribution and particle shape,both of which relate to mineralogical composition. Using a MINLITH algorithm, normative mineralogical compositions can be derived from bulk geochemical compositions economically and expediently, and then correlated to the hydraulic conductivity determined by pumping tests in the field. In this study, 202 sediment samples from nine unconsolidated aquifers were analyzed by X-ray fluorescence. Although hydraulic conductivity does not show a definite relationship with geochemical compositions, it does demonstrate a linear logarithmic equation to the content of normative earthy minerals. However, linear regressed equations should not be applied to aquifers composed of medium to coarse sand and gravel sizes due to interference from lithic fragments. In addition, this equation tends to overestimate hydraulic conductivity possibly because the effect of compaction is ignored in this study.     

Three-dimensional petrographical investigations on borehole rock samples: a comparison between X-ray computed- and neutron tomography

Technical difficulties associated with excavation works in tectonized geological settings are frequent. They comprise instantaneous and/or delayed convergence, sudden collapse of gallery roof and/or walls, outpouring of fault-filling materials and water inflows. These phenomena have a negative impact on construction sites and their safety. In order to optimize project success, preliminary studies on the reliability of rock material found on site are needed. This implies in situ investigations (surface mapping, prospective drilling, waterflow survey, etc.) as well as laboratory investigations on rock samples (permeability determination, moisture and water content, mineralogy, petrography, geochemistry, mechanical deformation tests, etc.). A set of multiple parameters are then recorded which permit better insight on site conditions and probable behavior during excavation. Because rock formations are by nature heterogeneous, many uncertainties remain when extrapolating large-scale behavior of the rock mass from analyses of samples order of magnitudes smaller. Indirect large-scale field investigations (e.g. geophysical prospecting) could help to better constrain the relationships between lithologies at depth. At a much smaller scale, indirect analytical methods are becoming more widely used for material investigations. We discuss in this paper X-ray computed tomography (XRCT) and neutron tomography (NT), showing promising results for 3D petrographical investigations of the internal structure of opaque materials. Both techniques record contrasts inside a sample, which can be interpreted and quantified in terms of heterogeneity. This approach has the advantage of combining genetic parameters (physico-chemical rock composition) with geometric parameters resulting from alteration or deformation processes (texture and structure). A critical analysis of such 3D analyses together with the results of mechanical tests could improve predictions of short- and long-term behavior of a rock unit. Indirect methods have the advantage of being non-destructive. However, as it is the case with large-scale geophysical surveying, XRCT and NT are affected by several error factors inherent to the interaction of a radiation modality (X-ray or neutron beam) with the atomic structure of the investigated materials. Recorded signals are therefore in particular cases not artifact-free and need to be corrected in a subsequent stage of data processing.     

Investigation of NaCl deliquescence in porous substrates using RH-XRD

We report on the use of X-ray diffractometry under controlled conditions of temperature and relative humidity (RH-XRD) for the investigation of NaCl deliquescence in the pore space of glass filter frits, which were used as model substrates. The study confirms that RH-XRD is an appropriate experimental technique for the in situ observation of phase transformation in porous materials. It is used for an investigation of both the deliquescence kinetics and the deliquescence humidity within pores of different median pore diameter. Several major influences affecting deliquescence rates in the pore space close to the surface of a porous material are discussed. It appears that quite short-term variation of ambient relative humidity, e.g., typical daily fluctuations, might induce damaging deliquescence–crystallization cycles within the pore space of building materials. In agreement with theoretical considerations it was found that confinement of NaCl crystals in pores with median diameters in the range 1.4–70 μm does not affect the deliquescence humidity of the salt.     

X-ray imagery and physical core logging as a proxy of the content of sediment cores in cold-water coral mound provinces: a case study from Porcupine Seabight,SW of Ireland

Three provinces, characterized by the presence of carbonate mounds interpreted as cold-water coral banks have been reported in Porcupine Seabight, SW of Ireland and were recently subjected to many detailed studies. This contribution discusses the use of X-ray imagery and physical properties in deciphering palaeoceanographic, sedimentological and biological processes. Physical property core logging and X-ray imagery are used to identify and describe sedimentation regimes and so their respective palaeoceanographic and palaeoclimatological settings in two mound provinces, respectively the Belgica mound province and the Magellan mound province. Both provinces show at present time clear differences in the hydrodynamic environment. This study confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly. Impacts of glacial–interglacial variations and locally derived ice rafting events (IRE), comparable with the North Atlantic Heinrich events (HE) have been recognized in both provinces. Moreover, the combination of X-ray imagery, magnetic susceptibility, gamma density and P-wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized on top of carbonate mounds. A comparison between on-mound and off-mound cores in both provinces allowed revealing some mechanisms of mound evolution and coral growth versus time.     

X-ray diffraction investigation of native Si-Fe alloy minerals from Luobusha, Tibet

The origin of native Si-Fe alloy mineral is thought to be related with mantle and aerolite. The native Si-Fe alloy minerals from podiform chromites of the Luobusha ophiolite in the Yarlong Zangbo suture zone were examined by a new method for powder-like diffractograms of small single crystals, using an SMART APEX-CCD area-detector X-ray diffractometer. The powder diffraction pattern shows that the minerals are composed of FeSi, FeSi₂, β-FeSi₂ and native silicon. The association of these minerals suggests that the crystallization order of the mineral may be from early to late FeSi→FeSi₂→native silicon, accompanied by gradually increasing deoxidization. Translated from Acta Petrologica et Mineralogica, 2005, 24(5): 453–456 [译自: 岩石矿物学杂志]     

Comparison of resection–intersection algorithms and projection geometries in radiostereometry

Three resection–intersection algorithms were applied to simulated projections and clinical data from radiostereometric patients. On simulated data, the more advanced bundle-adjustment-based algorithms outperformed the classical Selvik algorithm, even if the error reductions were small for some parameters. On clinical data, the results were inconclusive.The two different projection geometries had a much larger influence on the error size and distribution. For the biplanar configuration, the position and motion errors were small and almost isotropic. For the uniplanar configuration, the position errors were comparably high and anisotropic, but still resulted in a high accuracy for some motion parameters at the expense of others.The simplified resection–intersection algorithm by Selvik may still be considered a good and robust algorithm for radiostereometry. More studies will have to be performed to find out how the theoretical advantages of the bundle methods can be utilized in clinical radiostereometry.     

痰菌阴性空洞型肺结核的临床CT影像学分析

目的旨在提高肺结核开放－菌阴综合征的诊断和鉴别诊断，材料和方法用回顾性分析经病原学或临床确诊的开放型肺结核，而痰菌阴性的42例病人的CT影像表现。结果得到42例均见斑片状高密度灶影，其中41例不规则空洞影，4例与支气管相通；28例卫星灶影，8例纤维索条影，1例仅见小斑片状影伴卫星灶影，10例见斑点状钙化影，2例淋巴结肿大等。结论是CT对肺结核开放－菌阴综合征的诊断和鉴别诊断有较高的价值，特别是对估价空洞的形态结构，心后区，脊柱旁，后肋隔区，与肺门阴影重叠的病及少量胸腔积液等方面更有价值，对诊断和疗效的观察较可靠。     

ARL 8680型X荧光光谱仪的非自动高压校正

通过实验，介绍如何设计X荧光光谱仪中测角仪检测器的非自动高压校正的方法。     

Preliminary Study on the Chemical Mapping of Individual Fluid Inclusion by Synchrotron X-ray Fluorescence Microprobe

Abstract: Synchrotron X-ray fluorescence analyses on individual hypersaline fluid inclusions were tested to using synchrotron source at Tsukuba (KEK), Japan. The XRF instrumentation at KEK meets the purpose of fluid inclusion analysis, nondestructive, multi–element, ppm detection limits, with micro spatial resolution. In practice, however, the quantitative chemical analysis of fluid inclusion requires further considerable data accumulation. Semi-quantitative distribution of elements (mass number > 25) in single fluid inclusion was obtained.