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131.
132.
The paper deals with the modeling of some aspects, such as the formulation of constitutive equations for sediment material or finite element approach for basin analysis, related to mechanical compaction in sedimentary basins. In addition to compaction due to gravity forces and pore‐pressure dissipation, particular emphasis is given to the study of deformation induced by tectonic sequences. The numerical model relies upon the implementation of a comprehensive constitutive model for the sediment material formulated within the framework of finite poroplasticity. The theoretical model accounts for both hydromechanical and elasticity–plasticity coupling due to the effects of irreversible large strains. From the numerical viewpoint, a finite element procedure specifically devised for dealing with sedimentary basins as open systems allows to simulate within a two‐dimensional setting the process of sediment accretion or erosion. Several basin simulations are presented. The main objective is to analyze the behavior of a sedimentary basin during the different phases of its life cycle: accretion phase, pore‐pressure dissipation phase and compressive/extensional tectonic motions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
133.
M. Hoeft S. E. Nuza S. Gottlöber R. J. van Weeren H. J. A. Röttgering M. Brüggen 《Journal of Astrophysics and Astronomy》2011,32(4):509-517
Radio relics have been discovered in many galaxy clusters. They are believed to trace shock fronts induced by cluster mergers.
Cosmological simulations allow us to study merger shocks in detail since the intra-cluster medium is heated by shock dissipation.
Using high resolution cosmological simulations, identifying shock fronts and applying a parametric model for the radio emission
allows us to simulate the formation of radio relics. We analyze a simulated shock front in detail. We find a rather broad
Mach number distribution. The Mach number affects strongly the number density of relativistic electrons in the downstream
area, hence, the radio luminosity varies significantly across the shock surface. The abundance of radio relics can be modeled
with the help of the radio power probability distribution which aims at predicting radio relic number counts. Since the actual electron acceleration efficiency is not known, predictions
for the number counts need to be normalized by the observed number of radio relics. For the characteristics of upcoming low
frequency surveys we find that about thousand relics are awaiting discovery. 相似文献
134.
Harry Enke Matthias Steinmetz Hans-Martin Adorf Alexander Beck-Ratzka Frank Breitling Thomas Brüsemeister Arthur Carlson Torsten Ensslin Mikael Högqvist Iliya Nickelt Thomas Radke Alexander Reinefeld Angelika Reiser Tobias Scholl Rainer Spurzem Jürgen Steinacker Wolfgang Voges Joachim Wambsganß Steve White 《New Astronomy》2011,16(2):79-93
We present status and results of AstroGrid-D, a joint effort of astrophysicists and computer scientists to employ grid technology for scientific applications. AstroGrid-D provides access to a network of distributed machines with a set of commands as well as software interfaces. It allows simple use of computer and storage facilities and to schedule or monitor compute tasks and data management. It is based on the Globus Toolkit middleware (GT4).Chapter 1 describes the context which led to the demand for advanced software solutions in Astrophysics, and we state the goals of the project.We then present characteristic astrophysical applications that have been implemented on AstroGrid-D in chapter 2. We describe simulations of different complexity, compute-intensive calculations running on multiple sites (Section 2.1), and advanced applications for specific scientific purposes (Section 2.2), such as a connection to robotic telescopes (Section 2.2.3). We can show from these examples how grid execution improves e.g. the scientific workflow.Chapter 3 explains the software tools and services that we adapted or newly developed. Section 3.1 is focused on the administrative aspects of the infrastructure, to manage users and monitor activity. Section 3.2 characterises the central components of our architecture: The AstroGrid-D information service to collect and store metadata, a file management system, the data management system, and a job manager for automatic submission of compute tasks.We summarise the successfully established infrastructure in chapter 4, concluding with our future plans to establish AstroGrid-D as a platform of modern e-Astronomy. 相似文献
135.
Trace-element characteristics of different pyrite types in Mesoarchaean to Palaeoproterozoic placer deposits 总被引:7,自引:0,他引:7
Nikola Koglin Hartwig E. Frimmel W. E. Lawrie Minter Helene Brätz 《Mineralium Deposita》2010,45(3):259-280
A comparative in situ LA-ICP MS trace-element study on pyrite from three different, variably auriferous, Archaean to Palaeoproterozoic
palaeoplacer deposits in the Ouro Fino Syncline (Quadrilátero Ferrífero; Brazil), the Elliot Lake area north of Lake Huron
(SE Canada) and several deposits within the Witwatersrand Basin (South Africa) revealed systematic differences between morphologically
different pyrite types and between the various palaeoplacer deposits. Especially the Ni and Au concentrations as well as Co/Ni
and Mo/Ni ratios were found to be systematically different in detrital compact, detrital porous and post-sedimentary/hydrothermal
pyrite grains from different source areas. High Co/Ni ratios and low Au concentrations are typical of post-sedimentary pyrite,
which is hydrothermal in origin. In contrast, relatively low Co/Ni ratios and high Au contents characterise detrital porous
banded and concentric pyrite grains (Au > 1 ppm), which are syn-sedimentary in origin. In the Elliot Lake area and the Witwatersrand
Basin, detrital compact rounded pyrite is characterised by high Co/Ni ratios, which is in agreement with derivation from a
hydrothermal source. Low Au concentrations in this pyrite type support the contention of the gold and the pyrite in these
deposits coming from different source rocks. In contrast, derivation from an originally diagenetic pyrite is suggested for
the detrital compact pyrite in the Ouro Fino Syncline because of low to intermediate Co/Ni ratios. High Au contents may indicate
a genetic relationship between pyrite and gold there. Systematic differences exist between the three areas with respect to
Au, Ni, Co, Mo and Cu distributions in detrital pyrite, which reflects differences in the provenance. A predominantly mafic/ultramafic
source is indicated for the Ouro Fino, a felsic source for the Elliot Lake, and a mixed felsic–mafic provenance for the Witwatersrand
pyrite populations. Independently of pyrite type, the higher Au endowment of the studied Witwatersrand and Ouro Fino conglomerates
are also reflected by an overall higher Au concentration in the respective pyrite grains compared to the relatively Au-poor
samples from Elliot Lake. In general, a strong positive correlation between Au and Pb levels in the various pyrite grains
is noted. Analogous to Pb, which is well known for not being easily accommodated in the pyrite crystal lattice but occurring
as discrete PbS phases, Au is considered to be present mainly in the form of discrete Au phases in minute pores and interstices
of the pyrite grains rather than within the pyrite lattice. 相似文献
136.
Multiple origins of zircons in jadeitite 总被引:1,自引:1,他引:0
Bin Fu John W. Valley Noriko T. Kita Michael J. Spicuzza Chad Paton Tatsuki Tsujimori Michael Bröcker George E. Harlow 《Contributions to Mineralogy and Petrology》2010,159(6):769-780
Jadeitites form from hydrothermal fluids during high pressure metamorphism in subduction environments; however, the origin
of zircons in jadeitite is uncertain. We report ion microprobe analyses of δ18O and Ti in zircons, and bulk δ18O data for the jadeitite whole-rock from four terranes: Osayama serpentinite mélange, Japan; Syros mélange, Greece; the Motagua
Fault zone, Guatemala; and the Franciscan Complex, California. In the Osayama jadeitite, two texturally contrasting groups
of zircons are identified by cathodoluminescence and are distinct in δ18O: featureless or weakly zoned zircons with δ18O = 3.8 ± 0.6‰ (2 SD, VSMOW), and zircons with oscillatory or patchy zoning with higher δ18O = 5.0 ± 0.4‰. Zircons in phengite jadeitite from Guatemala and a jadeitite block from Syros have similar δ18O values to the latter from Osayama: Guatemala zircons are 4.8 ± 0.7‰, and the Syros zircons are 5.2 ± 0.5‰ in jadeitite and
5.2 ± 0.4‰ in associated omphacitite, glaucophanite and chlorite-actinolite rinds. The δ18O values for most zircons above fall within the range measured by ion microprobe in igneous zircons from oxide gabbros and
plagiogranites in modern ocean crust (5.3 ± 0.8‰) and measured in bulk by laser fluorination of zircons in equilibrium with
primitive magma compositions or the mantle (5.3 ± 0.6‰). Titanium concentrations in these zircons vary between 1 and 19 ppm,
within the range for igneous zircons worldwide. Values of δ18O (whole-rock) ≅ δ18O (jadeite) and vary from 6.3 to 10.1‰ in jadeitites in all four areas. 相似文献
137.
On the extension of the wind profile over homogeneous terrain beyond the surface boundary layer 总被引:7,自引:5,他引:2
Sven-Erik Gryning Ekaterina Batchvarova Burghard Brümmer Hans Jørgensen Søren Larsen 《Boundary-Layer Meteorology》2007,124(2):251-268
Analysis of profiles of meteorological measurements from a 160 m high mast at the National Test Site for wind turbines at Høvsøre (Denmark) and at a 250 m high TV tower at Hamburg (Germany) shows that the wind profile based on surface-layer theory and Monin-Obukhov scaling is valid up to a height of 50–80 m. At higher levels deviations from the measurements progressively occur. For applied use an extension to the wind profile in the surface layer is formulated for the entire boundary layer, with emphasis on the lowest 200–300 m and considering only wind speeds above 3 m s?1 at 10 m height. The friction velocity is taken to decrease linearly through the boundary layer. The wind profile length scale is composed of three component length scales. In the surface layer the first length scale is taken to increase linearly with height with a stability correction following Monin-Obukhov similarity. Above the surface layer the second length scale (L MBL ) becomes independent of height but not of stability, and at the top of the boundary layer the third length scale is assumed to be negligible. A simple model for the combined length scale that controls the wind profile and its stability dependence is formulated by inverse summation. Based on these assumptions the wind profile for the entire boundary layer is derived. A parameterization of L MBL is formulated using the geostrophic drag law, which relates friction velocity and geostrophic wind. The empirical parameterization of the resistance law functions A and B in the geostrophic drag law is uncertain, making it impractical. Therefore an expression for the length scale, L MBL , for applied use is suggested, based on measurements from the two sites. 相似文献
138.
Ewald Brückl Johanna Brückl Werner Chwatal Christian Ullrich 《Swiss Journal of Geoscience》2010,103(3):329-344
Results from geophysical explorations of three deep valleys, selected from different tectonic regimes in the Eastern Alps (Ötz-, Oichten-, and Drau Valley), are presented and discussed. Ongoing tectonic deformation may use tectonic structures related to these valleys. However, seismic activity is low there. During the Würm ice age, the thickness of the ice cover ranged between 300 and 1,500 m above present ground elevation. The geophysical investigations comprised reflection seismology, gravity- and resistivity surveys. The maximum depth down to the erosional base of the valleys varies from ~340 to 700 m. Distinct layer packages of the valley-infill at depths greater than 250 m were termed “old valley-fill”. Geophysical parameters and a comparison with the reflection seismic image of an intermediate layer at the recent Pasterze glacier suggest that the top of the “old valley-fill” represents the glacier bed during the decay of the Würm glaciation. Deep erosion is not related to high basal shear stress. The confluence of tributary glaciers is apparently not a significant factor for deep erosion in our examples of deep alpine valleys. We conclude that deep erosion may be related to high water pressure at the glacier bed, supported by specific processes of tectonic weakening. 相似文献
139.
Ulf B��ntgen Rudolf Br��zdil Petr Dobrovolny Mirek Trnka Tom��? Kyncl 《Theoretical and Applied Climatology》2011,105(1-2):167-180
Past, present, and projected fluctuations of the hydrological cycle, associated to anthropogenic climate change, describe a pending challenge for natural ecosystems and human civilizations. Here, we compile and analyze long meteorological records from Brno, Czech Republic and nearby tree-ring measurements of living and historic firs from Southern Moravia. This unique paleoclimatic compilation together with innovative reconstruction methods and error estimates allows regional-scale May?CJune drought variability to be estimated back to ad 1500. Driest and wettest conditions occurred in 1653 and 1713, respectively. The ten wettest decades are evenly distributed throughout time, whereas the driest episodes occurred in the seventeenth century and from the 1840s onward. Discussion emphasizes agreement between the new reconstruction and documentary evidence, and stresses possible sources of reconstruction uncertainty including station inhomogeneity, limited frequency preservation, reduced climate sensitivity, and large-scale constraints. 相似文献
140.
S. L. Bräuer K. Kranzler N. Goodson D. Murphy H. M. Simon A. M. Baptista B. M. Tebo 《Estuaries and Coasts》2013,36(5):1073-1083
Dark CO2 fixation has been shown to rival the importance of oxygenic photosynthesis in the global carbon cycle, especially in stratified environments, such as salt wedge estuaries. We investigated this process in the Columbia River estuary using a variety of techniques including functional gene cloning of cbbL (the large subunit of form I RuBisCO), quantitative real-time PCR (qPCR) estimations of cbbL abundance, and analyses of stimulated 14C-bicarbonate assimilation. A diversity of red-type cbbL genes were retrieved from clone libraries, with 28 unique operational taxonomic units determined from 60 sequences. The majority of the sequences formed two clusters that were distinct from the major clusters typically found in soil environments, revealing the presence of a unique community of autotrophic or facultatively autotrophic/mixotrophic microorganisms in the Columbia River estuary. qPCR estimates indicated that roughly 0.03–0.15 % of the microbial population harbored the cbbL gene, with greater numbers of total bacteria and cbbL gene copies found in the estuarine turbidity maxima (ETM) compared to non-ETM events. In vitro incubations with radiolabeled bicarbonate indicated maximum stimulation by thiosulfate and also suggested that a diversity of other potential electron donors may stimulate CO2 fixation, including nitrite, ammonium, and Mn(II). Taken together, these results highlight the diversity of the microbial metabolic strategies employed and emphasize the importance of dark CO2 fixation in the dynamic waters of the Columbia River estuary despite the abundance of organic material. 相似文献