A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio ¹¹⁴Cd/¹¹⁰Cd for NIST SRM 3108 lies within ～ 10 ppm Da^?1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.     

一次降雹过程的数字化雷达回波分析

利用东营市７１３数字化雷达和卫星云图资料，分析了１９９５年６月２４日发生在黄河三角洲地区的暴雹天气过程，对冰雹云的雷达回波特征及卫星云图特征进行了分析。     

Simulationsof Aerosol Optical Properties to Top of Atmospheric Reflected Sunlight in the Near Infrared CO2 Weak Absorption Band

Over the Asian continent,high aerosol loading is critical to ensure the high accuracy of CO₂ retrieval in the near infrared absorption band.Simulations were performed to explore the effect of light path modification by aerosol son the atmospheric CO₂ near infrared band(6140-6270 cm^-1).The Vector LInearized Discrete Ordinate Radiative Transfer（VLIDORT） model and the Line-By-Line Radiative Transfer Model（LBLRTM） were used for forward calculations.The U.S.standard atmosphere was used for atmospheric profiles.The results indicate that the aerosols caused similar effects to increases in CO₂ in the planetary boundary layer and became more significant with aerosol layer rising while aerosol optical depth was 0.1.This effect will cause an over estimation of the CO₂ mixing ratio in the retrieval process and an under estimation in the aerosol layer.The results also indicate that the effect of urban and industrial aerosols is smaller than that of non-absorbing and dust aerosols because of the nearly constant absorption properties in the near infrared band.     

Annual dissolved fluxes from Central Nepal rivers: budget of chemical erosion in the Himalayas

Annual dissolved element fluxes of Himalayan rivers from Central Nepal are calculated using published river discharge and a new set chemical data of rivers, including monsoon sampling. These are used to study the control on chemical erosion of carbonate and silicate over the whole basin. Chemical erosion of carbonate is mainly controlled by the river runoff but it can be limited by the availability of carbonate in limestone-free basin. Chemical erosion of silicate is well correlated to the runoff. However differences between High Himalayan and Lesser Himalayan basins suggest that physical erosion may also play an important control on silicate weathering. To cite this article: C. France-Lanord et al., C. R. Geoscience 335 (2003).     

The imprinting of aridity upon a lateritic landscape: an illustration from southwestern Australia

The southwestern region of Australia contains the Yilgarn Craton that has been exposed to subaerial weathering since mid-Proterozoic. The gently undulating landscape experienced lateritic weathering so that today variably dissected, deep in situ isovolumetrically weathered regolith is widespread. Imposition of a more arid climate since the Miocene with the cessation of effective external drainage has resulted in substantial geochemical modification of the highly porous regolith. This vast pore volume acts as a reservoir for complex solutions that may be highly saline, extremely acid to alkaline and reducing. Diverse precipitates have formed in the regolith including widespread occurrence of silcrete, calcrete, dolocrete, ferricrete and gypcrete together with localised occurrences of pyrite, alunite, jarosite, barite, halite and other salts. Clearing of bush land for agriculture in the 20th century increased recharge so that rising chemically active groundwaters are damaging farmland and infrastructure throughout the region. To cite this article: B. Gilkes et al., C. R. Geoscience 335 (2003).     

Ground penetrating radar inversion in 1-D: an approach for the estimation of electrical conductivity, dielectric permittivity and magnetic permeability

This paper presents a method for inverting ground penetrating radargrams in terms of one-dimensional profiles. We resort to a special type of linearization of the damped E-field wave equation to solve the inverse problem. The numerical algorithm for the inversion is iterative and requires the solution of several forward problems, which we evaluate using the matrix propagation approach. Analytical expressions for the derivatives with respect to physical properties are obtained using the self-adjoint Green's function method. We consider three physical properties of materials; namely dielectrical permittivity, magnetic permeability and electrical conductivity. The inverse problem is solved minimizing the quadratic norm of the residuals using quadratic programming optimization. In the iterative process to speed up convergence we use the Levenberg–Mardquardt method. The special type of linearization is based on an integral equation that involves derivatives of the electric field with respect to magnetic permeability, electrical conductivity and dielectric permittivity; this equation is the result of analyzing the implication of the scaling properties of the electromagnetic field. The ground is modeled using thin horizontal layers to approximate general variations of the physical properties. We show that standard synthetic radargrams due to dielectric permittivity contrasts can be matched using electrical conductivity or magnetic permeability variations. The results indicate that it is impossible to differentiate one property from the other using GPR data.     

Advances, Problems and Prospects of Modern Geodesy Applied in Tibetan Geodynamic Changes

Modern geodetic techniques have developed rapidly in recent years, providing reliable observation data and new effective approaches, and greatly enhancing studies of the Tibetan geodynamics. For instance, the well-known GPS technique has been employed to measure seismic slips for many faults in the Tibetan Plateau. GPS data agree well with the hypothesis of a thickening crust and eastward mass flow. Moreover, absolute gravimetric data have been applied to interpret geophysical phenomena such as crust movement, co-seismic gravity change, GIA, and ground water change. The satellite gravity mission GRACE launched in 2002 provided global gravity models with unprecedentedly high precision and high spatial resolution. It has been used in implementing temporal gravity changes and improving our knowledge of the Earth’s interior, including lithosphere dynamics, mantle viscosity and rheology, plateau uplift, and subduction processing. It is noteworthy that gravity presents unique advantages for the study of Tibetan geodynamics because of its sensitivity to mass migration and dynamic redistribution. To date, great advances have been made in applying modern geodetic data in studying dynamic changes of Tibetan plateau. For instance, the horizontal displacement field from GPS data revealed dynamical characteristics of the present-day Tibetan plateau. The combination of gravity anomalies and topographic data describe the tectonic characteristics of Tibetan plateau. The combination of gravity data and GPS data show present properties of the Tibetan plateau such as crust thickening, Moho’s subsidence, and plateau uplift. GRACE data were used to estimate the distribution of ice/snow melting.     

SMALL STATES AND CYBERBOOSTERISM

ABSTRACT. The introduction and rapid diffusion of the World Wide Web for commercial purposes provides states with opportunities to present themselves to millions of other governmental, business, and individual consumers. In the world of expanding electronic commerce, images and symbols are key elements in the messages that states use to promote themselves and to seek a competitive advantage. Content analyses of the official Web homepages of four small states—Singapore, Slovenia, Western Samoa, and Costa Rica—attest to the colorful, playful, and creative images designed to attract investors and tourists.     

阜新市海州露天矿区开采对空气质量的影响

利用遥感技术可快速、准确、大范围地监测矿山开发状况和了解矿区生态环境现状。以Landsat TM和CBERS卫星影像为主要数据来源,采用栅格数据、遥感数据与统计数据相结合的内业处理与外业调查相结合的技术路线,通过目视解译、人机交互解译、计算机自动识别等遥感信息提取技术和遥感影像处理,分析近20 a阜新市海州露天矿矿区面积变化趋势及近5a来对当地空气质量的影响。结果表明:阜新市海州露天矿矿区面积逐年减小,当地空气质量逐年优化。由此可见,露天矿矿区面积的减小对于当地空气质量的改善起到了一定的推动作用。     

基于麻雀搜索算法优化的BP神经网络卫星钟差预报

使用麻雀搜索算法(sparrow search algorithm,SSA)对BP神经网络的初始权值和阈值进行优化和调整,以提高神经网络模型短期预报的精度和稳定性.采用IGS产品中的卫星钟差数据,对SSA-BP神经网络模型、PSO-BP神经网络模型、传统BP神经网络模型及传统二次多项式模型(QP模型)进行实验对比,结果...