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961.
The oxidation of pyrite results in sulphate concentrations from 1,300 to 2,000 mg/l in the dump water of the open cast mine
Inden, which is located in Germany. Under near-neutral pH and reduced redox conditions, precipitation of siderite (FeCO3) retains up to 85% of the pre-liberated ferrous iron, so that iron concentrations in the dump water are relatively low as
compared to the concentrations of sulphate. The highly mineralised dump water will enter the aquifer system northwards of
Inden during the next centuries. This area is used intensely for water extraction. Model calculations show that there will
be no problem of acidification in the adjacent aquifer system and, therefore, no problem of high heavy metal concentrations
during the next centuries. The most important problem will be high sulphate concentrations in the groundwater. Besides dispersion
and diffusion, there are no chemical mechanisms that lower the sulphate concentrations downstream. On the basis of the simulations,
sulphate plumes of about 1–2 km in width and up to 15 km in length are expected. Within the core of these plumes, sulphate
concentrations will be above the drinking water limits. 相似文献
962.
江汉平原长湖近代沉积物磁性测量及其气候意义 总被引:5,自引:0,他引:5
根据1992年长湖所取代表性92-5 面沉积物磁性测量结果并结合化学分析和孢粉分析,研究长湖近代沉积物磁性参数变化与气候变化的关系,指出该地区最近400a来气候变化总趋势是一个由冷变暖的过程。 相似文献
963.
Sources of recent tectonic stress in the Pannonian region:inferences from finite element modelling 总被引:3,自引:0,他引:3
Gábor Bada Sierd Cloetingh Péter Gerner & Frank Horváth 《Geophysical Journal International》1998,134(1):87-101
We present the results of finite element modelling of the recent stress field in the Pannonian basin and surrounding Alpine orogenic belt. Our results show that the recent, predominantly compressive, stress regime in the Alpine–Pannonian–Carpathian–Dinaric system is governed by distinct tectonic factors. Of great importance is the deformation of crustal blocks with different geometries and rigidities in an overall convergent setting associated with the Africa–Europe collision. The most important stress source appears to be the counterclockwise rotation of the Adriatic microplate at the southwest boundary of the Pannonian basin. This plate tectonic unit has been interpreted as moving independently of both the European plate and the African plate. Additional boundary conditions—active shortening and compression in the Vrancea zone and the Bohemian Massif, and the effect of the immobile Moesian Platform—also significantly influence the modelling results. The incorporation of additional stress sources such as crustal thickness variation and the presence of two main fault zones separating the primary tectonic units in the study area have only locally important effects but improve the fit between the calculated results and the observed stress pattern. 相似文献
964.
Frank Bradshaw Wood 《Astrophysics and Space Science》1985,110(1):137-141
Triple star systems, especially those in which one star has very small mass may be more common than has been generally considered. Here is summarized some of the recent evidence supporting this possibility.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846) 相似文献
965.
Andrew Cunningham Adam Frank Peggy Varnière Alexei Poludnenko Sorin Mitran Lee Hartmann 《Astrophysics and Space Science》2005,298(1-2):317-322
We present two dimensional cylindrically symmetric hydrodynamic simulations and synthetic emission maps of a stellar wind
propagating into an infalling, rotating environment. The resulting outflow morphology, collimation and stability observed
in these simulations have relevance to the study of young stellar objects, Herbig-Haro jets and molecular outflows. Our code
follows hydrogen gas with molecular, atomic and ionic components tracking the associated time dependent molecular chemistry
and ionization dynamics with radiative cooling appropriate for a dense molecular gas. We present tests of the code as well
as new simulations which indicate the presence of instabilities in the wind-blown bubble’s swept-up shell. 相似文献
966.
A. Frank E. G. Blackman A. Cunningham S. V. Lebedev D. Ampleford A. Ciardi S. N. Bland J. P. Chittenden M. G. Haines 《Astrophysics and Space Science》2005,298(1-2):107-114
We present new data from High-Energy Density (HED) laboratory experiments designed to explore the interaction of a heavy hypersonic
radiative jet with a cross wind. The jets are generated with the MAGPIE pulsed power machine where converging conical plasma
flows are produced from a cylindrically symmetric array of inclined wires. Radiative hypersonic jets emerge from the convergence
point. The cross wind is generated by ablation of a plastic foil via soft-X-rays from the plasma convergence region. Our experiments
show that the jets are deflected by the action of the cross wind with the angle of deflection dependent on the proximity of
the foil. Shocks within the jet beam are apparent in the data. Analysis of the data shows that the interaction of the jet
and cross wind is collisional and therefore in the hydrodynamic regime. We consider the astrophysical relevance of these experiments
applying published models of jet deflection developed for AGN and YSOs. We also present results of 3-D numerical simulations
of jet deflection using a new astrophysical Adaptive Mesh Refinement code. These simulations show highly structured shocks
occurring within the beam similar to what was observed in the experiments. 相似文献
967.
Philip A. Bland Frank J. Stadermann Christine Floss Detlef Rost Edward P. Vicenzi Anton T. Kearsley Gretchen K. Benedix 《Meteoritics & planetary science》2007,42(7-8):1417-1427
Abstract— We have used a variety of complementary microanalytical techniques to constrain the mineralogy, trace‐element distributions, and oxygen‐isotopic compositions in a 50 × 50 μm area of Acfer 094 matrix. The results reveal the exceptional mineralogical and compositional heterogeneity of this material at the sub‐μm level. We observe μm‐scale and sub‐μm grains with elemental associations suggesting feldspar, metal with widely varying Ni contents, and a Cr‐Fe alloy (in addition to forsterite, pyroxene, sulfide, ferrihydrite, and amorphous groundmass previously described). A new class of μm‐scale CAI (μCAI) is also observed, which show sub‐μm compositional zoning, and a range of oxygen isotopic compositions. Unlike the larger CAIs in Acfer 094, which are uniformly 16O‐enriched, two of the three μCAIs we analyzed are isotopically normal. We also observed a Li‐rich hotspot that detailed analysis by ToF‐SIMS suggests may be a LiCr‐oxide grain. Within the resolution of the NanoSIMS, this grain has isotopically normal Li. Finally, in our 50 × 50 μm area, we positively identified a presolar grain that is the most 18O‐rich silicate found so far in meteorites. The grain may originate from an asymptotic giant branch (AGB) star, or more likely, a supernova. In line with previous TEM studies (Greshake 1997), we find no evidence for clastic material (e.g., fragmental chondrules) in the matrix of Acfer 094: although the matrix is volatile‐depleted, this depletion does not appear to result from dilution of a primordial starting material with (depleted) chondrule fragments. Assuming that matrix experienced the depletion event, our data on the detailed mineralogy of Acfer 094 are currently equivocal in constraining the nature of that event. We observe carrier phases for several elements consistent with conditions approaching equilibrium condensation; however, the presence of an amorphous groundmass is suggestive of more rapid cooling. 相似文献
968.
Frank Verheest 《Astrophysics and Space Science》2012,339(2):203-205
In a recent paper “Head-on collision of electron acoustic solitary waves in a plasma with nonextensive hot electrons” (Astrophys.
Space Sci. 338:271–278, 2012) Eslami, Mottaghizadeh and Pakzad deal with the problem of the head-on collisions between two weakly nonlinear electron-acoustic
solitary waves. Unfortunately, their treatment is deficient and leads to erroneous conclusions. 相似文献
969.
A. Frank 《Astrophysics and Space Science》2007,307(1-3):35-39
The expected lifetimes for molecular clouds has become a topic of considerable debate as numerical simulations have shown
that MHD turbulence, the nominal means of support for clouds against self-gravity, will decay on short timescales. Thus it
appears that either molecular clouds are transient features or they are resupplied with turbulent energy through some means.
Jets and molecular outflows are recognized as a ubiquitous phenomena associated with star formation. Stars however form not
isolation but in clusters of different density and composion. The ubiquity and high density of outflows from young stars in
clusters make them an intriguing candidate for the source of turbulence energy in molecular clouds. In this contribution we
present new studies, both observational and theoretical, which address the issue of jet/outflow interactions and their abilityto
drive turbulent flows in molecular clouds. Our studies focus on scales associated with young star forming clusters. In particular
we first show that direct collisions between active outflows are not effective at stirring the ambient medium. We then show
that fossil cavities from “extinct” outflows may provide the missing link in terms of transferring momentum and energy to
the cloud. 相似文献
970.
Ryan C. OGLIORE Christine FLOSS Frank J. STADERMANN A. T. KEARSLEY Jan LEITNER Rhonda M. STROUD Andrew J. WESTPHAL 《Meteoritics & planetary science》2012,47(4):729-736
Abstract– The Al foils lining the aerogel tiles of the Stardust interstellar tray represent approximately 13% of the total collecting area, about 15,300 mm2. Although the flux is poorly constrained, fewer than 100 impacts are expected in all the Al foils on the collector, and most of these are likely to be less than 1 μm in diameter. Secondary electron (SE) images of the foils at a resolution of approximately 50 nm per pixel are being collected during the Stardust Interstellar Preliminary Examination, resulting in more than two million images that will eventually need to be searched for impact craters. The unknown and complicated nature of 3‐dimensional interstellar tracks in aerogel necessitated the use of a massively distributed human search to locate only a few interstellar tracks. The 2‐dimensional nature of the SE images makes the problem of searching for craters tractable for algorithmic approaches. Using templates of craters from cometary impacts into Stardust foils, we present a computer algorithm for the identification of impact craters in the Stardust interstellar foils using normalized cross‐correlation and template matching. We address the speed, sensitivity, and false‐positive rate of the algorithm. The search algorithm can be adapted for use in other applications. The program is freely available for download at http://jake.ssl.berkeley.edu:8000/groups/westphalgroup/wiki/14e52/ISPE_SEM_Crater_Search.html . 相似文献