Strontium in rivers of the Baltic Basin     

Runo Löfvendahl  Göran Åberg  P. Joseph Hamilton 《Aquatic Sciences - Research Across Boundaries》1990,52(4):315-329

The rivers in the Baltic Basin drain a mixture of bedrocks ranging from Mesozoic-Paleozoic sediments in the south to Proterozoic-Archean intrusives in the north. The rivers in the sedimentary basin in the south have high concentrations of Sr, in the interval 100–500 µg l^–1 while the⁸⁷Sr/⁸⁶Sr ratio is close to that of seawater, i.e. 0.71. The northern rivers in the Precambrian shield area on the other hand have low Sr concentrations of 15–50 µg l^–1 with high⁸⁷Sr/⁸⁶Sr ratios of about to 0.73 (0.721–0.745). The riverine input of dissolved Sr to the brackish Baltic Sea approaches 60 tons year^–1, with a weighted mean concentration approaching 130 µg l^–1 and a weighted mean⁸⁷Sr/⁸⁶Sr ratio close to 0.712. Although the sedimentary area in the south supplies only about 43% of the total river discharge, it gives about 88% of the total Sr input. Because of this and the strong regional riverine variation in⁸⁷Sr/⁸⁶Sr ratio, Sr and its isotopes seem to be a convenient tool to unveil mixing relations of water masses in the northern Baltic Sea, provided high resolution analyses are applied. For an overall characterization of water mixing in the Baltic Sea, the Nd system will be superior to that of Sr.  相似文献   

Macromolecular Transport of Hydrophobic Contaminants in Aqueous Environments.   总被引：1，自引：0，他引：1  

Carl G. Enfield  Göran Bengtssona 《Ground water》1988,26(1):64-70

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Length scales, patterns and origin of azimuthal seismic anisotropy in the upper mantle as mapped by Rayleigh waves     

Thorsten W. Becker  Göran Ekström  Lapo Boschi  John H. Woodhouse 《Geophysical Journal International》2007,171(1):451-462

We measure the degree of consistency between published models of azimuthal seismic anisotropy from surface waves, focusing on Rayleigh wave phase-velocity models. Some models agree up to wavelengths of ∼2000 km, albeit at small values of linear correlation coefficients. Others are, however, not well correlated at all, also with regard to isotropic structure. This points to differences in the underlying data sets and inversion strategies, particularly the relative 'damping' of mapped isotropic versus anisotropic anomalies. Yet, there is more agreement between published models than commonly held, encouraging further analysis. Employing a generalized spherical harmonic representation, we analyse power spectra of orientational (2Ψ) anisotropic heterogeneity from seismology. We find that the anisotropic component of some models is characterized by stronger short-wavelength power than the associated isotropic structure. This spectral signal is consistent with predictions from new geodynamic models, based on olivine texturing in mantle flow. The flow models are also successful in predicting some of the seismologically mapped patterns. We substantiate earlier findings that flow computations significantly outperform models of fast azimuths based on absolute plate velocities. Moreover, further evidence for the importance of active upwellings and downwellings as inferred from seismic tomography is presented. Deterministic estimates of expected anisotropic structure based on mantle flow computations such as ours can help guide future seismologic inversions, particularly in oceanic plate regions. We propose to consider such a priori information when addressing open questions about the averaging properties and resolution of surface and body wave based estimates of anisotropy.  相似文献   

地理信息系统在环境与安全领域的应用研究     

宋文华袁斌  陈化然 《东北测绘》2007,30(6):4-8

以地理信息系统为平台，综合采用GPS技术、GSM技术、GPRS技术、网络技术建立工业部门监管监控系统对实现工业部门事故及时处理，分析事故成因有效预防事故，实现高效管理有重大意义；以该平台建立的城市应急救援指挥系统在对城市进行可视化与数字化的基础上，能够实现城市灾害信息的科学管理，各种灾害分析模拟，公共安全规划以及应急决策支持，从而有效提高突发性城市公共安全应急的效率和响应速度，为城市公共安全的应急工作提供有效的辅助手段。  相似文献   

A simple method of representing azimuthal anisotropy on a sphere     

Göran Ekström 《Geophysical Journal International》2006,165(2):668-671

We describe a method of expressing azimuthally anisotropic surface wave velocities on the Earth using a local and smooth spherical-spline parametrization. Anisotropy in the Earth leads to azimuthally varying Love and Rayleigh wave velocities that can be expressed as (cos 2ζ, sin 2ζ) and (cos 4ζ, sin 4ζ) perturbations to the isotropic velocities, where ζ is the direction of surface-wave propagation. The strength of the perturbations varies laterally, and a current goal of seismic tomography is the detailed global mapping of these variations. Several parametrizations have previously been used to describe azimuthally varying velocities. The representation proposed here uses spherical splines and is designed to describe smooth variations in both the strength and geometry of azimuthal anisotropy. The method builds on a simple geometrical approximation for the local azimuth of propagation expressed at the defining spline knot points. It avoids the singularities at the poles that result when azimuthal variations are parametrized using traditional scalar spherical harmonics. Compared with a generalized spherical-harmonic expansion of the tensor fields that represent 2ζ and 4ζ azimuthal variations smoothly on a sphere, the new method offers the advantages of local geographical support and simplicity of implementation.  相似文献   

Magnetograph observations with the Swedish solar telescope on La Palma     

Henrik Lundstedt  Anders Johannesson  Göran Scharmer  Jan Olof Stenflo  Ulf Kusoffsky  Birgitta Larsson 《Solar physics》1991,132(2):233-245

A high-resolution videomagnetograph that records the images of opposite circular polarization simultaneously has been constructed for the Swedish vacuum solar telescope at La Palma. Magnetograms are obtained by off-line integration of bursts consisting of typically 50 frames of 20 ms exposures, with bad frames rejected, and the frame-to-frame image motion of the remaining frames compensated for by cross-correlation techniques. The short exposures combined with frame selection and elimination of image motion optimizes the resolution and thereby also the S/N, allowing good magnetograms to be obtained with an effective exposure time of less than 1 s at an image scale of 0.1 pixel^–1. The advantages and limitations of the system are discussed and compared with other techniques of making filter magnetograms are discussed.  相似文献   

明代中篇文言小说与“才子佳人”的婚爱模式     

王冉冉 《广东海洋大学学报》2003,23(5):52-58

与唐宋传奇相比 ,明代中篇文言小说虽然从质量上来讲有不少都是粗制滥造之作 ,但它们却以其系列化制作形成了“才子佳人”之婚爱模式 ,折射出某些文化观念 ,对后世的情爱小说产生了一定的影响。  相似文献   

Introduction     

Renata Dmowska  Göran Ekström 《Pure and Applied Geophysics》1994,142(1):1-2

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Introduction     

Renata Dmowska  Göran Ekström 《Pure and Applied Geophysics》1993,140(2):179-181

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The pointing system of the Herschel space observatory     

Miguel Sánchez-Portal  Anthony Marston  Bruno Altieri  Hervé Aussel  Helmut Feuchtgruber  Ulrich Klaas  Hendrik Linz  Dieter Lutz  Bruno Merín  Thomas Müller  Markus Nielbock  Marc Oort  Göran Pilbratt  Micha Schmidt  Craig Stephenson  Mark Tuttlebee 《Experimental Astronomy》2014,37(2):453-479

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