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111.
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
112.
<正>Terrestrial plants and insects currently account for the majority of the Earth's biodiversity,and approximately half of insect species are herbivores.Thus,insects and plants share ancient associations that date back more than 400 Myr.However,investigations of their past interactions are at the preliminary stages in Western Europe.Herein,we present the first results of our study of various feeding damage based on a dataset of nearly 3500 examined plant specimens from the Lower Miocene of the Lagerstatte Bilina Mine in the Most Basin, Czech Republic.This site provides a unique view of the Neogene freshwater ecosystems.It has long been studied by scientists working in different branches of sedimentology,paleobotany,and paleozoology.The fossils are preserved in three characteristic horizons overlaying the coal seam(Clayey Superseam Horizon,Delta Sandy Horizon,and Lake Clayey Horizon),reflecting paleoenvironmental changes in a short time period of development The trace fossils are classified as functional feeding groups or"guilds",without searching for a direct cause or a recent analog host relation.Approximately 23%of specimens of dicotyledonous plant leaves were found to be damaged and associated with some leaf"morphotypes".Deciduous plant-host taxa,and those with a chartaceous texture typical of riparian habitats,were frequently damaged,such as Populus,recorded with two species Populus zaddachii and Populus populina(57.9%and 31%herbivory levels,respectively),followed by Acer,Alnus,and Carya,averaging almost 30%of damaged leaves/leaflets.There has been evidence of 60 damage types(DT) representing all functional feeding groups recorded at the Bilina Mine,including 12 types of leaf mines and 16 gall- type DT.In total,Lower Miocene of the Lagerstatte Bilina Mine exhibits a high level of external foliage feeding types(23.7%),and a low level of more specialized DT,such as galls(43%)and leaf mines(1%).A broader comparison based on DT of the main sedimentary environments shows significance supporting different biomes by frequency of damage levels and DT diversities. 相似文献
113.
Multiple sources for mineralizing fluids in the Charmitan gold(-tungsten) mineralization (Uzbekistan) 总被引:1,自引:0,他引:1
Torsten Graupner Samuel Niedermann Dieter Rhede Ulf Kempe Reimar Seltmann C. Terry Williams Reiner Klemd 《Mineralium Deposita》2010,45(7):667-682
Mineral assemblages present within the Charmitan gold(-tungsten) quartz-vein mineralization have been investigated for their
cathodoluminescence behaviour, chemical composition and noble gas isotope systematics. This inventory of methods allows for
the first time a systematic reconstruction of the paragenetic relationships of quartz, scheelite, sulphides and native gold
within the gold mineralization at Charmitan and provides the basis to utilise noble gas data in the discussion of sources
and evolution of ore-forming fluids. The vein quartz is classified into four generations based on microscopic and cathodoluminescence
investigations. Quartz I shows intense brittle deformation as associated scheelite I. Undeformed scheelite II overgrows scheelite
I and has lower light rare earth element and higher intermediate rare earth element contents as well as higher strontium concentrations.
Scheelite II is associated with the economic gold mineralization and formed during re-crystallisation and re-precipitation
of material which was partly re-mobilised from early scheelite I during infiltration of gold-bearing fluids. Early stage native
gold inclusions are often associated with stage 2 sulphides, scheelite II and bismuth tellurides and contain Ag (3.6–24.4 wt.%),
Hg (≤1.0 wt.%) and Bi (≤0.2 wt.%). Later stage electrum grains occur in association with stage 3 sulphides and sulphosalts
and contain Hg (<0.8 wt.%) and elevated Sb concentrations (up to 3.0 wt.%). Noble gas isotope data (3He/4He: 0.2-0.4 Ra) for hydrothermal ore fluids trapped in the gold-related sulphides and sulphosalts (stage 2 pyrite and arsenopyrite;
stage 3 pyrite, sphalerite, galena and lead sulphosalts) suggest that diverse fluid sources were involved in the formation
of the Charmitan gold deposit. These data are indicative of a small, but significant input of fluids from external, deep-seated
(mantle and possibly lower crust) sources. A decrease in the input of mantle helium and an increasing role of crustal helium
from early to later stages of the mineralization is suggested by the measured 3He/4He and 40Ar*/4He ratios. Sulphides from ore veins in meta-sedimentary rocks contain higher portions of meteoric fluids than those in intrusive
rock types as indicated by their lower 3He/36Ar ratios. The 3He/36Ar ratios in the meta-sedimentary rocks agree well with ratios typical of gold mineralizations in the Tien Shan gold province
completely hosted by meta-sedimentary sequences, indicating intense fluid-wall rock interaction. 相似文献
114.
Michael J. Rycroft Anna Odzimek Neil F. Arnold Martin Füllekrug Andrzej Kuak Torsten Neubert 《Journal of Atmospheric and Solar》2007,69(17-18):2485
Several processes acting below, in and above thunderstorms and in electrified shower clouds drive upward currents which close through the global atmospheric electric circuit. These are all simulated in a novel way using the software package PSpice. A moderate negative cloud-to-ground lightning discharge from the base of a thunderstorm increases the ionospheric potential above the thundercloud by 0.0013%. Assuming the ionosphere to be an equipotential surface, this discharge increases the current flowing in the global circuit and the fair-weather electric field also by 0.0013%. A moderate positive cloud-to-ground lightning discharge from the bottom of a thunderstorm decreases the ionospheric potential by 0.014%. Such a discharge may trigger a sprite, causing the ionospheric potential to decrease by . The time scales for the recovery of the ionospheric potential are shown to be , which is of the same order as the CR time constant for the global circuit. Knowing the global average rate of lightning discharges, it is found that negative cloud-to-ground discharges increase the ionospheric potential by only 4%, and that positive cloud-to-ground discharges reduce it by 3%. Thus, overall, lightning contributes only 1%—an almost insignificant proportion—to maintaining the high potential of the ionosphere. It is concluded that the net upward current to the ionosphere due to lightning is only . Further, it is concluded that conduction and convection currents associated with “batteries” within thunderclouds and electrified shower clouds contribute essentially equally ( each) to maintaining the ionospheric potential. 相似文献
115.
Extinct isotope heterogeneities in the mantles of Earth and Mars: Implications for mantle stirring rates 下载免费PDF全文
Heterogeneities in terrestrial samples for 182W/183W and 142Nd/144Nd are only preserved in Hadean and Archean rocks while heterogeneities in 129Xe/130Xe and 136Xe/130Xe persist to very young mantle‐derived rocks. In contrast, meteorites from Mars show that the Martian mantle preserves heterogeneities in 182W/183W and 142Nd/144Nd up to the present. As a consequence of the probable “deep magma ocean” core formation process, we assume that the Earth and Mars both had a very early two‐mantle‐reservoir structure with different initial extinct nuclide isotopic compositions (different 182W/183W, 142Nd/144Nd, 129Xe/130Xe, 136Xe/130Xe ratios). Based on this assumption, we developed a simple stochastic model to trace the evolution of a mantle with two initially distinct layers for the extinct isotopes and its development into a heterogeneous mantle by convective mixing and stretching of these two layers. Using the extinct isotope system 182Hf‐182W, we find that the mantles of Earth and Mars exhibit substantially different mixing or stirring rates. This is consistent with Mars having cooled faster than the Earth due to its smaller size, resulting in less efficient mantle mixing for Mars. Moreover, the mantle stirring rate obtained for Earth using 182Hf‐182W is consistent with the mantle stirring rate of ~500 Myr constrained by the long‐lived isotope system, 87Rb‐87Sr and 147Sm‐143Nd. The apparent absence of 182W/183W isotopic heterogeneity in modern terrestrial rocks is attributed to very active mantle stirring which reduced the 182W/183W isotopic heterogeneity to a relatively small scale (~83 m for a mantle stirring rate of 500 Myr) compared to the common sampling scale of terrestrial basalts (~30 or 100 km). Our results also support the “deep magma ocean” core formation model as being applicable to both Mars and Earth. 相似文献
116.
Nejib JEMMALI Fouad SOUISSI Torsten W. VENNEMANN Emmanuel John M. CARRANZA 《Resource Geology》2011,61(4):367-383
The Jebel Ressas Pb–Zn deposits in North‐Eastern Tunisia occur mainly as open‐space fillings (lodes, tectonic breccia cements) in bioclastic limestones of the Upper Jurassic Ressas Formation and along the contact of this formation with Triassic rocks. The galena–sphalerite association and their alteration products (cerussite, hemimorphite, hydrozincite) are set within a calcite gangue. The Triassic rocks exhibit enrichments in trace metals, namely Pb, Co and Cd enrichment in clays and Pb, Zn, Cd, Co and Cr enrichment in carbonates, suggesting that the Triassic rocks have interacted with the ore‐bearing fluids associated with the Jebel Ressas Pb–Zn deposits. The δ18O content of calcite associated with the Pb–Zn mineralization suggests that it is likely to have precipitated from a fluid that was in equilibrium with the Triassic dolostones. The δ34S values in galenas from the Pb–Zn deposits range from ?1.5 to +11.4‰, with an average of 5.9‰ and standard deviation of 3.9‰. These data imply mixing of thermochemically‐reduced heavy sulfur carried in geothermal‐ and fault‐stress‐driven deep‐seated source fluid with bacterially‐reduced light sulfur carried in topography‐driven meteoric fluid. Lead isotope ratios in galenas from the Pb–Zn deposits are homogenous and indicate a single upper crustal source of base‐metals for these deposits. Synthesis of the geochemical data with geological data suggests that the base‐metal mineralization at Jebel Ressas was formed during the Serravallian–Tortonian (or Middle–Late Miocene) Alpine compressional tectonics. 相似文献
117.
Vertical deformations from homogeneously processed GRACE and global GPS long-term series 总被引:3,自引:1,他引:2
Volker Tesmer Peter Steigenberger Tonie van Dam Torsten Mayer-Gürr 《Journal of Geodesy》2011,85(5):291-310
Temporal variations in the geographic distribution of surface mass cause surface displacements. Surface displacements derived
from GRACE gravity field coefficient time series also should be observed in GPS coordinate time series, if both time series
are sufficiently free of systematic errors. A successful validation can be an important contribution to climate change research,
as the biggest contributors to mass variability in the system Earth include the movement of oceanic, atmospheric, and continental
water and ice. In our analysis, we find that if the signals are larger than their precision, both geodetic sensor systems
see common signals for almost all the 115 stations surveyed. Almost 80% of the stations have their signal WRMS decreased,
when we subtract monthly GRACE surface displacements from those observed by GPS data. Almost all other stations are on ocean
islands or small peninsulas, where the physically expected loading signals are very small. For a fair comparison, the data
(79 months from September 2002 to April 2009) had to be treated appropriately: the GPS data were completely reprocessed with
state-of-the-art models. We used an objective cluster analysis to identify and eliminate stations, where local effects or
technical artifacts dominated the signals. In addition, it was necessary for both sets of results to be expressed in equivalent
reference frames, meaning that net translations between the GPS and GRACE data sets had to be treated adequately. These data
sets are then compared and statistically analyzed: we determine the stability (precision) of GRACE-derived, monthly vertical
deformation data to be ~1.2 mm, using the data from three GRACE processing centers. We statistically analyze the mean annual
signals, computed from the GPS and GRACE series. There is a detailed discussion of the results for five overall representative
stations, in order to help the reader to link the displayed criteria of similarity to real data. A series of tests were performed
with the goal of explaining the remaining GPS–GRACE residuals. 相似文献
118.
The stable carbon and oxygen isotope compositions of fossil ostracods are powerful tools to estimate past environmental and climatic conditions. The basis for such interpretations is that the calcite of the valves reflects the isotopic composition of water and its temperature of formation. However, calcite of ostracods is known not to form in isotopic equilibrium with water and different species may have different offsets from inorganic precipitates of calcite formed under the same conditions. To estimate the fractionation during ostracod valve calcification, the oxygen and carbon isotope compositions of 15 species living in Lake Geneva were related to their autoecology and the environmental parameters measured during their growth. The results indicate that: (1) Oxygen isotope fractionation is similar for all species of Candoninae with an enrichment in 18O of more than 3‰ relative to equilibrium values for inorganic calcite. Oxygen isotope fractionation for Cytheroidea is less discriminative relative to the heavy oxygen, with enrichments in 18O for these species of 1.7 to 2.3‰. Oxygen isotope fractionations for Cyprididae are in-between those of Candoninae and Cytheroidea. The difference in oxygen isotope fractionation between ostracods and inorganic calcite has been interpreted as resulting from a vital effect. (2) Comparison with previous work suggests that oxygen isotope fractionation may depend on the total and relative ion content of water. (3) Carbon isotope compositions of ostracod valves are generally in equilibrium with DIC. The specimens’ δ13C values are mainly controlled by seasonal variations in δ13CDIC of bottom water or variation thereof in sediment pore water. (4) Incomplete valve calcification has an effect on carbon and oxygen isotope compositions of ostracod valves. Preferential incorporation of at the beginning of valve calcification may explain this effect. (5) Results presented here as well as results from synthetic carbonate growth indicate that different growth rates or low pH within the calcification site cannot be the cause of oxygen isotope ‘vital effects’ in ostracods. Two mechanisms that might enrich the 18O of ostracod valves are deprotonation of that may also contribute to valve calcification, and effects comparable to salt effects with high concentrations of Ca and/or Mg within the calcification site that may also cause a higher temperature dependency of oxygen isotope fractionation. 相似文献
119.
Rare earth elements (REE), while not essential for the physiologic functions of animals, are ingested and incorporated in ppb concentrations in bones and teeth. Nd isotope compositions of modern bones of animals from isotopically distinct habitats demonstrate that the 143Nd/144Nd of the apatite can be used as a fingerprint for bedrock geology or ambient water mass. This potentially allows the provenance and migration of extant vertebrates to be traced, similar to the use of Sr isotopes. Although REE may be enriched by up to 5 orders of magnitude during diagenesis and recrystallization of bone apatite, in vivo143Nd/144Nd may be preserved in the inner cortex of fossil bones or enamel. However, tracking the provenance of ancient or extinct vertebrates is possible only for well-preserved archeological and paleontological skeletal remains with in vivo-like Nd contents at the ppb-level. Intra-bone and -tooth REE analysis can be used to screen for appropriate areas. Large intra-bone Nd concentration gradients of 101-103 are often measured. Nd concentrations in the inner bone cortex increase over timescales of millions of years, while bone rims may be enriched over millenial timescales. Nevertheless, εNd values are often similar within one εNd unit within a single bone. Larger intra-bone differences in specimens may either reflect a partial preservation of in vivo values or changing εNd values of the diagenetic fluid during fossilization. However, most fossil specimens and the outer rims of bones will record taphonomic 143Nd/144Nd incorporated post mortem during diagenesis. Unlike REE patterns, 143Nd/144Nd are not biased by fractionation processes during REE-uptake into the apatite crystal lattice, hence the εNd value is an important tracer for taphonomy and reworking. Bones and teeth from autochthonous fossil assemblages have small variations of ±1 εNd unit only. In contrast, fossil bones and teeth from over 20 different marine and terrestrial fossil sites have a total range of εNd values from -13.0 to 4.9 (n = 80), often matching the composition of the embedding sediment. This implies that the surrounding sediment is the source of Nd in the fossil bones and that the specimens of this study seem not to have been reworked. Differences in εNd values between skeletal remains and embedding sediment may either indicate reworking of fossils and/or a REE-uptake from a diagenetic fluid with non-sediment derived εNd values. The latter often applies to fossil shark teeth, which may preserve paleo-seawater values. Complementary to εNd values, 87Sr/86Sr can help to further constrain the fossil provenance and reworking. 相似文献
120.
Joshua P. Townsend Yun-Yuan Chang Xiaoting Lou Miguel Merino Scott J. Kirklin Jeff W. Doak Ahmed Issa Chris Wolverton Sergey N. Tkachev Przemyslaw Dera Steven D. Jacobsen 《Physics and Chemistry of Minerals》2013,40(5):447-453
At ambient conditions, witherite is the stable form of BaCO3 and has the aragonite structure with space group Pmcn. Above ~10 GPa, BaCO3 adopts a post-aragonite structure with space group Pmmn. High-pressure and high-temperature synchrotron X-ray diffraction experiments were used to study the stability and equation of state of post-aragonite BaCO3, which remained stable to the highest experimental P–T conditions of 150 GPa and 2,000 K. We obtained a bulk modulus K 0 = 88(2) GPa with $K'$ = 4.8(3) and V 0 = 128.1(5) Å3 using a third-order Birch-Murnaghan fit to the 300 K experimental data. We also carried out density functional theory (DFT) calculations of enthalpy (H) of two structures of BaCO3 relative to the enthalpy of the post-aragonite phase. In agreement with previous studies and the current experiments, the calculations show aragonite to post-aragonite phase transitions at ~8 GPa. We also tested a potential high-pressure post–post-aragonite structure (space group C222 1 ) featuring four-fold coordination of oxygen around carbon. In agreement with previous DFT studies, ΔH between the C222 1 structure and post-aragonite (Pmmn) decreases with pressure, but the Pmmn structure remains energetically favorable to pressures greater than 200 GPa. We conclude that post–post-aragonite phase transformations of carbonates do not follow systematic trends observed for post-aragonite transitions governed solely by the ionic radii of their metal cations. 相似文献