Autoplot: a browser for scientific data on the web     

Jeremy B. Faden  Robert S. Weigel  Jan Merka  Reiner H. W. Friedel 《Earth Science Informatics》2010,3(1-2):41-49

Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web, usually in the form of a directory containing data files with multiple parameters contained in each file. Data from a data source is abstracted into a common internal data model called QDataSet. Autoplot is built from individually useful components, and can be extended and reused to create specialized data handling and analysis applications and is being used in a variety of science visualization and analysis applications. Although originally developed for viewing heliophysics-related time series and spectrograms, its flexible and generic data representation model makes it potentially useful for the Earth sciences.  相似文献   

Bosumtwi impact structure,Ghana: Geochemistry of impactites and target rocks,and search for a meteoritic component     

Xiongxin Dai  Daniel Boamah  Christian Koeberl  Wolf Uwe Reimold  Gordon Irvine  Iain McDonald 《Meteoritics & planetary science》2005,40(9-10):1493-1511

Abstract— Major and trace element data, including platinum group element abundances, of representative impactites and target rocks from the crater rim and environs of the Bosumtwi impact structure, Ghana, have been investigated for the possible presence of a meteoritic component in impact‐related rocks. A comparison of chemical data for Bosumtwi target rocks and impactites with those for Ivory Coast tektites and microtektites supports the interpretation that the Bosumtwi structure and Ivory Coast tektites formed during the same impact event. High siderophile element contents (compared to average upper crustal abundances) were determined for target rocks as well as for impactites. Chondrite‐normalized (and iron meteorite‐normalized) abundances for target rocks and impactites are similar. They do not, however, allow the unambiguous detection of the presence, or identification of the type, of a meteoritic component in the impactites. The indigenous siderophile element contents are high and possibly related to regional gold mineralization, although mineralized samples from the general region show somewhat different platinum‐group element abundance patterns compared to the rocks at Bosumtwi. The present data underline the necessity of extensive target rock analyses at Bosumtwi, and at impact structures in general, before making any conclusions regarding the presence of a meteoritic component in impactites.  相似文献   

Improved representation of topographic effects by a vertical adaptive grid in Vector-Ocean-Model (VOM). Part II: Simulations in unstructured adaptive grids     

Jan O. Backhaus  Ingo Harms  Udo Hübner 《Ocean Modelling》2008,22(3-4):128-145

A static adaptive grid approximates the topography and defines the vertical resolution in Vector-Ocean-Model (VOM). The adaptation to topography creates unstructured grids, which are organised in a one-dimensional vector by column-wise storage of only wet cells. The model’s name reflects this data structure. The intention of VOM is better resolving flow and stratification near topographic boundaries in Z-coordinates. This is the second part of a publication that describes the generation of adaptive grids (part I), and simulations with VOM in unstructured grids (this part). Adaptive grids generated for a synthetic topography in part I include shelf, continental slope, and ocean. Three of those grids are here utilised in upwelling simulations. Under the same forcing increased vertical resolution at seabed and slopes yields a significant increase in flow energy as compared to coarser grids. Results allow explaining the surface intensification of a continental slope jet by vertical displacements of water masses in the seabed Ekman layer. Results in unstructured grids are almost identical to reference simulations in equidistant grids where the respective smallest grid size of unstructured grids was used. Negative effects of grids on predicted flow and stratification are absent also over particularly rough topography, as demonstrated by using vertical velocity as most sensitive indicator. In a further simulation an overflow governed by the advection of water mass properties is presented to demonstrate the conservation properties of the model. After 5 months of simulation the predicted domain average temperature deviated by 10⁻⁸ from the initial temperature field. Compared to equidistant grids the advection/diffusion scheme looses about one order of magnitude in accuracy when used in an unstructured grid. The results of VOM, being defined in Z-coordinates, are void of coordinate transformation errors. In an arbitrary topography unforced zero-flow remains quiescent in a stratification that only varies in the vertical. VOM due to its depth-independent vertical resolution appears particularly suitable for simulations of ocean-shelf exchange.  相似文献   

Cadmium and phosphate in coastal Antarctic seawater: Implications for Southern Ocean nutrient cycling     

Katharine R. Hendry  Rosalind E.M. Rickaby  Jan C.M. de Hoog  Keith Weston  Mark Rehkmper 《Marine Chemistry》2008,112(3-4):149-157

Cadmium is a biologically important trace metal that co-varies with phosphate (PO₄³⁻ or Dissolved Inorganic Phosphate, DIP) in seawater. However, the exact nature of Cd uptake mechanisms and the relationship with phosphate and other nutrients in global oceans remain elusive. Here, we present a time series study of Cd and PO₄³⁻ from coastal Antarctic seawater, showing that Cd co-varies with macronutrients during times of high biological activity even under nutrient and trace metal replete conditions. Our data imply that Cd/PO₄³⁻ in coastal surface Antarctic seawater is higher than open ocean areas. Furthermore, the sinking of some proportion of this high Cd/PO₄³⁻ water into Antarctic Bottom Water, followed by mixing into Circumpolar Deep Water, impacts Southern Ocean preformed nutrient and trace metal composition. A simple model of endmember water mass mixing with a particle fractionation of Cd/P (α_Cd–P) determined by the local environment can be used to account for the Cd/PO₄³⁻ relationship in different parts of the ocean. The high Cd/PO₄³⁻ of the coastal water is a consequence of two factors: the high input from terrestrial and continental shelf sediments and changes in biological fractionation with respect to P during uptake of Cd in regions of high Fe and Zn. This implies that the Cd/PO₄³⁻ ratio of the Southern Ocean will vary on glacial–interglacial timescales as the proportion of deep water originating on the continental shelves of the Weddell Sea is reduced during glaciations because the ice shelf is pinned at the edge of the continental shelf. There could also be variations in biological fractionation of Cd/P in the surface waters of the Southern Ocean on these timescales as a result of changes in atmospheric inputs of trace metals. Further variations in the relationship between Cd and PO₄³⁻ in seawater arise from changes in population structure and community requirements for macro- and micronutrients.  相似文献   

Comment on `Tectono‐sedimentary evolution of lower to middle Miocene halfgraben basins related to an extensional detachment fault (western Crete,Greece)' by M. Seidel,E. Seidel and B. Stöckhert     

Douwe J. J. Van Hinsbergen  Willem‐Jan Zachariasse  Anne R. Fortuin 《地学学报》2008,20(5):414-416

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The case and fate of HD 75767 – neutron star or supernova?     

Klaus Fuhrmann  Eike Guenther  Brigitte König  Jan Bernkopf 《Monthly notices of the Royal Astronomical Society》2005,361(3):803-808

We report the discovery of the nearby  ( d = 24 pc)  HD 75767 as an eight billion year old quadruple system consisting of a distant M dwarf pair, HD 75767 C–D, in orbit around the known short-period   P = 10.25 d  single-lined binary HD 75767 A–B, the primary of which is a solar-like G star. On the reasonable assumption of synchronous orbital rotation as well as rotational and orbital coplanarity for the inner pair, we get   M _B= 0.96 M_⊙  for the unseen HD 75767 B, that is, the case of a massive white dwarf. Upon future evolution, mass transfer towards HD 75767 B will render the   M _A= 0.96 M_⊙  G-type primary, now a turnoff star, to become a helium white dwarf of   M _A∼ 0.33 M_⊙  . Depending on the mass accretion rate, accretion efficiency and composition of the massive white dwarf, this in turn may result in a collapse of HD 75767 B with the formation of a millisecond pulsar, i.e. the creation of a low-mass binary pulsar (LMBP), or, instead, a Type Ia supernova explosion and the complete disruption of HD 75767 B. Irrespective of which scenario applies, we point to the importance of the distant M dwarfs as the likely agents for the formation of the inner, short-period HD 75767 A–B pair, and hence a path that particularly avoids preceding phases of common envelope evolution.  相似文献   

Physical effects on the Lyα forest flux power spectrum: damping wings, ionizing radiation fluctuations and galactic winds     

Patrick McDonald  Uro&#; Seljak  Renyue Cen  Paul Bode  Jeremiah P. Ostriker 《Monthly notices of the Royal Astronomical Society》2005,360(4):1471-1482

We explore several physical effects on the power spectrum of the Lyα forest transmitted flux. The effects we investigate here are not usually part of hydrodynamic simulations and so need to be estimated separately. The most important effect is that of high column density absorbers with damping wings, which add power on large scales. We compute their effect using the observational constraints on their abundance as a function of column density. Ignoring their effect leads to an underestimation of the slope of the linear theory power spectrum. The second effect we investigate is that of fluctuations in the ionizing radiation field. For this purpose we use a very large high-resolution N -body simulation, which allows us to simulate both the fluctuations in the ionizing radiation and the small-scale Lyα forest within the same simulation. We find an enhancement of power on large scales for quasars and a suppression for galaxies. The strength of the effect rapidly increases with increasing redshift, allowing it to be uniquely identified in cases where it is significant. We develop templates that can be used to search for this effect as a function of quasar lifetime, quasar luminosity function and attenuation length. Finally, we explore the effects of galactic winds using hydrodynamic simulations. We find the wind effects on the Lyα forest power spectrum to be degenerate with parameters related to the temperature of the gas that are already marginalized over in cosmological fits. While more work is needed to conclusively exclude all possible systematic errors, our results suggest that, in the context of data analysis procedures, where parameters of the Lyα forest model are properly marginalized over, the flux power spectrum is a reliable tracer of cosmological information.  相似文献   

    

Jan Pícha 《Studia Geophysica et Geodaetica》1973,17(1):72

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Hydrology of cave drip waters at varying bedrock depths from a karst system in southeastern Australia     

Janece McDonald  Russell Drysdale 《水文研究》2007,21(13):1737-1748

The study of how cave drip‐water discharge responds to recharge events is fundamental to evaluating the potential of actively forming speleothems as high‐resolution climate archives. Most previous research has focused on caves of the Northern Hemisphere middle latitudes, where recharge is strongly seasonal. Few studies have explored drip‐water behaviour from regions where the expected seasonal rainfall pattern is significantly perturbed on an irregular basis by changing regional atmospheric circulation patterns. Here, we report the results of a 4‐year study of cave drip‐water–climate relationships from two caves in eastern Australia. The discharge of 10 drip sites located beneath bedrock thicknesses of 12, 22 and 45 m was monitored either continuously (using automated infrared sensors) or at discrete approximately monthly intervals and compared with local rainfall and water balance data. The study period traversed two major droughts, including the severe 2002–2003 El Niño. Drips at 12 and 22 m depths responded almost simultaneously to individual recharge events, although the time lag between individual events varied according to the volume of recharge and pre‐event storage. Overall, a steady decline in discharge is evident through the moisture‐deficit period, with increased flows through phases of positive water balance. Speleothems growing at these and similar shallow‐chamber sites have potential for reconstructing palaeo‐rainfall trends at high‐resolution, although the highly variable nature of year‐to‐year recharge would make it difficult to obtain data on a calendrical time‐scale. Drips at 45 m depth did not respond consistently to individual recharge events and displayed hydrological behaviour markedly dissimilar to one another and to the near‐surface drip sites, indicating great complexity in karst architecture and the absence of fissure flow. Although speleothems at this depth may well preserve information on longer‐term rainfall trends, their potential to encode a palaeo‐rainfall variability signal at interannual resolution is poor. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Multichannel Blind Deconvolution As A Tool For Solar Image Restoration     

Stanislava Šimberová  Jan Flusser 《Solar physics》2005,228(1-2):165-175

A principle of restoration methods based on multichannel blind deconvolution (MBD) is introduced. The methods assume that for every un-degraded unobservable image several degraded observed images are available. It is better conditioned than classical single channel approach. The first algorithm represents a generalization of iterative deconvolution scheme introduced for single images. The second MBD algorithm is based on so-called subspace technique. The subspace method is not iterative and this possibly implies an implementation that can be computationally more efficient. Both methods are presented in applications to artificial image data (computer-generated multichannel degraded data) with known ideal image to get a comparison with restored one. Performance in a real situation on solar photosphere images is shown.  相似文献