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21.
22.
Rainer Altherr Manfred Schliestedt Martin Okrusch Eberhard Seidel Hans Kreuzer Wilhelm Harre Heinz Lenz Immo Wendt Günther A. Wagner 《Contributions to Mineralogy and Petrology》1979,70(3):245-255
Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K-Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite+quartz+3T phengite, and omphacite+garnet +3T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote+2M
1 phengite.K-Ar and Rb-Sr dates on phengites (predominantly 3T) of the best preserved high P/itTmetamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high P/T metamorphism. Phengites (2M
1+3T) of less preserved high P/T assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb-Sr dates. The higher K-Ar dates are interpreted as being elevated by excess argon.K-Ar and Rb-Sr ages on 2M
1 phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks. 相似文献
23.
Wilhelm Meyer Johannes Stets Paul Wurster 《International Journal of Earth Sciences》1974,63(3):1113-1132
The last products of the pleistocene Laach volcano (Eifel, about 40 kms SW of Bonn, Germany) are grey tuffs. Outcrops in the rim show characteristic cross-bedding in these tuffs. It is in discussion whether these structures are produced by wind or by phreato-magmatic outbursts. At all larger outcrops in the rim we measured numerous depositional elements of the tuffs, and analyzed their geometrical structure. So we are able to reconstruct shape, structure and orientation of dunes in the tuffs. They show transport vectors in centrifugal orientation, radially to the vent. The dunes are orientated concentrically to the vent, we intruduce the term “concentrical dune” for this dune type. This points out that the dunes in the Laach tuffs are of volcanic origin. But our geometrical results give no authorization to assume phreato-magmatic processes during the activity of the Laach volcano. We think that the grey Laach tuffs are no base surge deposits, but products of gas-rich eruptions in the phase of decreasing volcanic energy. 相似文献
24.
Wilhelm Wenz 《International Journal of Earth Sciences》1914,5(5-6):321-346
Ohne Zusammenfassung 相似文献
25.
Measuring and forecasting recruitment are central to the understanding and management of fish stocks. Kainge et al. (2013) studied the effect of spawning stock size and environmental fluctuations on the recruitment levels of the Cape hake Merluccius capensis in Namibia. However, their study contains some flaws that undermine the conclusion that Cape hake recruitment is under the influence of upwelling in summer. Until those flaws are properly addressed, this conclusion, in our view, should be treated with caution. 相似文献
26.
K. Wilhelm 《Astronomische Nachrichten》2010,331(5):502-511
Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measurements of spectral radiances with high spectral and spatial resolutions as well as spectral irradiances yield detailed information on temperatures, electron densities, bulk and turbulent motions, element abundances of plasma structures in various regions of the solar atmosphere – from the photosphere to the outer corona and the solar wind. The particular requirements for helioseismology and magnetic‐field observations will not be covered in any depth in this review. Calibration by a laboratory standard is necessary, but not sufficient, because an adequate radiometric stability can only be achieved together with a stringent cleanliness concept that rules out a contamination of the optical system and the detectors as much as possible. In addition, there is a need for calibration monitoring through inter‐calibration and other means (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
27.
Katharina Marquardt Elena Petrishcheva Rainer Abart Emmanuel Gardés Richard Wirth Ralf Dohmen Hans-Werner Becker Wilhelm Heinrich 《Physics and Chemistry of Minerals》2010,37(10):751-760
In this study, we address volume diffusion of ytterbium in yttrium aluminum garnet (YAG) using thin-film single crystal diffusion
couples. We employ analytical transmission electron microscopy (ATEM) as a tool for combined microstructural and microchemical
analysis and compare the results to Rutherford backscattering (RBS) analysis. Given the high spatial resolution of the method,
we focus on microstructural changes of the thin-film diffusant source during the diffusion anneal. We evaluate the potential
influence of the associated changes in its transport properties on the evolution of concentration profiles in the single crystal
substrate. This approach allows us to test the reliability of determination of volume diffusion coefficients from thin-film
diffusion experiments. We found that for the chosen experimental setting, the influence of thin-film re-crystallization is
small when compared with the experimental uncertainty and good estimates for the volume diffusion coefficients of Yb in YAG
can be obtained using standard assumptions. Both Yb-concentration profiles analyzed with ATEM and with RBS give similar results.
At 1,450°C and 1 bar, we infer log D
Yb (m2/s) values of −19.37 ± 0.07 (TEM) and −19.84 ± 0.02 (RBS). Although the change in thin-film transport properties associated
with successive crystallization during the diffusion anneal does not play a major role for our experimental setup, this effect
cannot generally be ignored. 相似文献
28.
Counteracting urban climate change: adaptation measures and their effect on thermal comfort 总被引:1,自引:1,他引:0
Nicole Müller Wilhelm Kuttler Andreas-Bent Barlag 《Theoretical and Applied Climatology》2014,115(1-2):243-257
Cities represent thermal load areas compared with their surrounding environments. Due to climate change, summer heat events will increase. Therefore, mitigation and adaptation are needed. In this study, meteorological measurements in various local climate zones were performed to demonstrate the influence of evaporation surfaces and other factors on thermal comfort, as determined by the physiologically equivalent temperature (PET). Furthermore, a quantification of the thermal effects of several adaptation measures and varying meteorological parameters was made using model simulations (ENVI-met) in an inner-city neighborhood (Oberhausen, Germany). The results show that the most effective adaptation measure was increased wind speed (maximal 15 K PET reduction). Moreover, vegetation areas show greater PET reductions by the combination of shading and evapotranspiration than water surfaces. The creation of park areas with sufficient water supply and tall, isolated, shade-providing trees that allow for adequate ventilation can be recommended for planning. 相似文献
29.
W. Curdt D. Germerott K. Wilhelm U. Schühle L. Teriaca D. Innes K. Bocchialini P. Lemaire 《Solar physics》2014,289(6):2345-2376
We have released an archive of all observational data of the VUV spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on SOHO that have been acquired until now. The operational phase started with ‘first light’ observations on 27 January 1996 and will end in 2014. Future data will be added to the archive when they become available. The archive consists of a set of raw data (Level 0) and a set of data that are processed and calibrated to the best knowledge we have today (Level 1). This communication describes step by step the data acquisition and processing that has been applied in an automated manner to build the archive. It summarizes the expertise and insights into the scientific use of SUMER spectra that has accumulated over the years. It also indicates possibilities for further enhancement of the data quality. With this article we intend to convey our own understanding of the instrument performance to the scientific community and to introduce the new, standard FITS-format database. 相似文献
30.
A humic acid extracted from a peat was easily hydrolysed by 6N HCl after oxidation with peracetic acid. The proportion of amino-acids in the hydrolysate was high (11,7 g of aminoacids per 100 g of humic acid), when the proportion of NH3 was relatively low. 17 aminoacids were identified and titrated. On the opposite, a humic acid with the same origin, which was not oxidised with peracetic acid, gave less amino-acids on hydrolysis, but tenfold more NH3, which is probably produced by partial decomposition of the amino-acids. 相似文献