Source analysis of acoustic emissions in Aue granite cores under symmetric and asymmetric compressive loads   总被引：5，自引：0，他引：5  

Arno Zang  F. Christian Wagner  Sergei Stanchits  Georg Dresen  Reimer Andresen  & Mark A. Haidekker 《Geophysical Journal International》1998,135(3):1113-1130

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Comparison of Five Eulerian Air Pollution Forecasting Systems for the Summer of 1999 Using the German Ozone Monitoring Data     

Stefan Tilmes  JØrgen Brandt  Frode FlatØy  Robert Bergström  Johannes Flemming  Joakim Langner  Jesper H. Christensen  Lise M. Frohn  Øystein Hov  Ingo Jacobsen  Eberthard Reimer  Rainer Stern  Jörg Zimmermann 《Journal of Atmospheric Chemistry》2002,42(1):91-121

Eulerian state-of-the-art air pollution forecasting systems on the European scale are operated routinely by several countries in Europe. DWD and FUB, both Germany, NERI, Denmark, NILU, Norway, and SMHI, Sweden, operate some of these systems. To apply such modeling systems, e.g. for regulatory purposes according to new EU directives, an evaluation and comparison of the model systems is fundamental in order to assess their reliability. One step in this direction is presented in this study: The model forecasts from all five systems have been compared to measurements of ground level ozone in Germany. The outstanding point in this investigation is the availability of a huge amount of data – from forecasts by the different model systems and from observations. This allows for a thorough interpretation of the findings and assures the significance of the observed features. Data from more than 300 measurement stations for a 5-month period (May–September 1999) of the German monitoring networks have been used in this comparison. Different spatial and temporal statistical parameters were applied in the evaluation. Generally, it was found that the most comprehensive models gave the best results. However, the less comprehensive and computational cheaper models also produced good results. The extensive comparison made it possible to point out weak points in the different models and to describe the individual model behavior for a full summer period in a climatological sense. The comparison also gave valuable information for an assessment of individual measurement stations and complete monitoring networks in terms of the representativeness of the observation data.  相似文献   

Stratospheric ozone fluctuations and the evolution of skin pigmentation in man     

Anita Baker-Blocker 《Theoretical and Applied Climatology》1977,25(1):91-100

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The spontaneous fission rate of U-238 and fission track dating     

G.A Wagner  G.M Reimer  B.S Carpenter  H Faul  R Van Der Linden  R Gijbels 《Geochimica et cosmochimica acta》1975,39(9):1279-1286

The rate of spontaneous fission decay of uranium-238 (λ_f²³⁸) was determined in 4π-geometry by the fission track method. Uranium glasses of known age of manufacture were used. Spontaneous tracks have accumulated since the time of manufacture and induced tracks to determine the uranium content were produced by thermal neutron irradiations. Spontaneous tracks in all glasses were found to be partially annealed. By correcting for this annealing effect, a (λ_f²³⁸) = 8.7 ± 0.6 × 10^?17yr^?1 was obtained. Uncertainty in the neutron dose is the largest source of error.  相似文献   

The calculation of the net radiation flux     

R. de Jong  C. F. Shaykewich  A. Reimer 《Theoretical and Applied Climatology》1980,28(4):353-363

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Crystallization and welding variations in a widespread ignimbrite sheet; the Rattlesnake Tuff,eastern Oregon,USA     

Martin J. Streck  Anita L. Grunder 《Bulletin of Volcanology》1995,57(3):151-169

The 7.05 Ma Rattlesnake Tuff covers ca. 9000 km², but the reconstructed original coverage was between 30000 and 40000 km². Thicknesses are remarkably uniform, ranging between 15 and 30 m for the most complete sections. Only 13% of the area is covered with tuff thicker than 30 m, to a maximum of 70 m. The present day estimated tuff volume is 130 km³ and the reconstructed magma volume of the outflow is 280 km³ DRE (dense rock equivalent). The source area of the tuff is inferred to be in the western Harney Basin, near the center of the tuff distribution, based mainly on a radial exponential decrease in average pumice size, and is consistent with a general radial decrease in welding and degree of post-emplacement crystallization. Rheomorphic tuff is found to a radius of 40–60 km from the inferred source.Four facies of welding and four of post-emplacement crystallization are distinguishable. They are: non-welded, incipiently welded, partially welded and densely welded zones; and vapor phase, pervasively devitrified, spherulite and lithophysae zones. The vapor phase, pervasively devitrified and lithophysae zones are divided into macroscopically distinguishable subzones. At constant thickness (20±3 m), and over a distance of 1–3 km, nonrheomorphic sections can cary between two extremes: (a) entirely vitric sections grading from nonwelded to incipiently welded; and (b) highly zoned sections. Highly zoned sections have a basal non- to densely welded vitric tuff overlain by a spherulite zone that grades upward through a lithophysae-dominated zone to a zone of pervasive devitrification, which, in turn, is overlain by a zone of vapor-phase crystallization and is capped by partially welded vitric tuff. A three-dimensional welding and crystallization model has been developed based on integrating local and regional variations of 85 measured sections.Strong local variations are interpreted to be the result of threshold-governed welding and crystallization controlled by residence time above a critical temperature, which is achieved through differences in thickness and accumulation rate.  相似文献   

Mantle contribution to the evolution of Middle Tertiary silicic magmatism during early stages of extension: the Egan Range volcanic complex,east-central Nevada     

Todd C. Feeley  Anita L. Grunder 《Contributions to Mineralogy and Petrology》1991,106(2):154-169

The Egan Range volcanic complex lies 30 km northwest of Ely, on the edge of a highly extended domain in east-central Nevada. It consists mainly of lavas with subordinate tuffs and sedimentary rocks. The rocks are divided into three stratigraphic and lithologic groups that correlated with widespread middle Tertiary volcanic rocks associated with early stages of extension in the region. Volcanic rocks of the early group are predominantly two-pyroxene dacite and andesite lavas, all of which contain quenched, mafic inclusions and have compositions indicating they were derived by mixing between a contaminated mantle melt and a rhyodacitic crustal component. Rocks of the middle group are relatively homogeneous biotite, hornblende dacite and rhyodacite lavas. Elevated compatible and incompatible element concentrations and straight-line correlations of compositional data in the early and middle groups support a simple mixing model. Minor fractionation of clinopyroxene is required to explain some low Cr concentrations. Major element variations of the late group can be successfully modeled by crystal fractionation of observed phenocrysts accompanied by moderate assimilation of a crustal component to account for elevated Rb, Th, U, and light rare earth element concentrations. Rocks of all three groups appear to be related to a common primary magma type, the composition of which can be modeled from the mafic inclusions in the early group. Low Ni and Mg contents in the inclusions indicate that olivine was fractionated prior to their participation in mixing of early group magmas. Based on estimated volumes of volcanic rocks in the Egan Range volcanic complex and in the region, and on the petrologic models for each group, a significant amount of basalt must have been added to the crust during this middle Tertiary magmatic episode.  相似文献   

Homogenization and lowering of O/O in mid-crustal rocks during extension-related magmatism in eastern Nevada     

Anita L. Grunder  Stephen M. Wickham 《Earth and Planetary Science Letters》1991,107(2)

The oxygen isotope systematics of Tertiary volcanic rocks of east-central Nevada and of plutonic and metamorphic rocks of the Ruby Mountains-East Humboldt Range core complex provide complementary evidence for major¹⁸O-depletion and ¹⁸O/¹⁶O homogenization of mid-crustal rocks during metamorphism and magmatism. The δ¹⁸O value of crustal source material for silicic volcanic rocks decreased from between +9 and +11‰ to between +7 and +8‰ over 5 Ma. Mid-crustal metasedimentary and granitic rocks in the East Humboldt Range have δ¹⁸O values very similar to the volcanic rocks and values are lower and more homogeneous at deeper structural levels. Exchange with deep-seated mantle-derived igneous rocks, or fluids derived therefrom, is the most plausible¹⁸O-depletion mechanism. Intrusion of these mafic magmas promoted crustal melting and fluid migration. Homogenization of ¹⁸O/¹⁶O resulted from migration of high-temperature fluids and melts at mid-crustal levels, and was less effective at higher structural levels where the crust was dominated by less permeable carbonate rocks.  相似文献   

Regional soil-gas helium distribution of the Ely and Delta 1° × 2° quadrangles, Basin and Range Province     

G.M. Reimer  C.G. Bowles 《Journal of Geochemical Exploration》1990,38(1-2)

A reconnaissance soil-gas helium survey was made in the Ely, Nevada and Delta, Utah 1° × 2° quadrangles in the Basin and Range Province. Helium concentrations in 510 samples ranged from −147 to 441 ppb He with respect to ambient air. The median helium value for the study area was 36 ppb. Concentrations of more than 100 ppb He and less than −20 ppb He occur more commonly in the Ely quadrangle and are especially numerous in the western one-half of this quadrangle. Interpretation of the data reveals that the helium concentrations reflect the rock type, particularly the silicic volcanic occurrences, and the geological structure of the area created by crustal extension. The regional soil-gas helium distribution is important information to consider when interpreting anomalies from detailed surveys.  相似文献   

The marine polychaete Arenicola marina: its unusual arsenic compound pattern and its uptake of arsenate from seawater.     

Anita E Geiszinger  Walter Goessler  Kevin A Francesconi 《Marine environmental research》2002,53(1):37-50

Arsenic compounds in the marine polychaete Arenicola marina collected from Odense Fjord, Denmark were determined by HPLC-ICPMS. In contrast to most other marine animals, A. marina contained most of its water soluble arsenic as inorganic forms, arsenite (58%) and arsenate (16%), and arsenobetaine was present as a minor constituent (6%) only. Other arsenic compounds detected in A. marina were dimethylarsinate (4%), two arsenosugars (1 and 3%), tetramethylarsonium ion (1.5%), and arsenocholine (<1%). A new arsenobetaine -trimethylarsoniopropionate-previously only reported in fish, was also present at trace levels (<1%), and an unknown anionic arsenical (approximately 10%) remains unidentified. When A. marina was exposed in laboratory experiments to different concentrations of arsenate in seawater (10, 50. 100, 500 and 1000 microg As 1(-1)) the polychaetes accumulated arsenic in a dose dependent. non-linear manner. Most of the accumulated arsenic was biotransformed to arsenite and dimethylarsinate. with the remainder being accumulated as unchanged arsenate. None of the other arsenic compounds naturally present in A. marina increased in concentration following arsenate exposure.  相似文献