Über das Vorkommen einiger Spurenmetalle in Blei-Zink-Erzen der ostalpinen Metallprovinz     

Erich Schroll 《Mineralogy and Petrology》1955,5(3):183-208

Zusammenfassung Die Spurenanalyse ostalpiner Bleiglanze und Zinkblenden ergibt unabhängig von minerogenetischen Faktoren regionale Unterschiede in der Mikroparagenese. Die Pb-Zn-führenden Erzvorkommen der Ostalpen werden in nachstehend angeführte Erzbezirke gegliedert (vgl. auch Abb. 8): Mit 10 Textabbildungen.  相似文献   

Untersuchungen zum Mechanismus von Blastesis und Syntexis in Phylliten und Hornfelsen des südwestlichen Fichtelgebirges     

Erich Dimroth 《Mineralogy and Petrology》1963,8(3):361-402

Ohne ZusammenfassungMit 14 Textabbildungen  相似文献   

Untersuchungen zum Mechanismus von Blastesis und Syntexis in Phylliten und Hornfelsen des südwestlichen Fichtelgebirges     

Erich Dimroth 《Mineralogy and Petrology》1963,8(4):475-522

Ohne ZusammenfassungMit 22 Textabbildungen  相似文献   

Numerical investigations of shear localization in a micro‐polar hypoplastic material     

Wenxiong Huang  Erich Bauer 《国际地质力学数值与分析法杂志》2003,27(4):325-352

In this paper a micro‐polar continuum approach is proposed to model the essential properties of cohesionless granular materials like sand. The model takes into account the influence of particle rotations, the mean grain size, the void ratio, the stresses and couple stresses. The constitutive equations for the stresses and couple stresses are incrementally non‐linear and based on the concept of hypoplasticity. For plane strain problems the implementation of the model in a finite element program is described. Numerical studies of the evolution of micro‐polar effects within a granular strip under plane shearing are presented. It is shown that the location and evolution of shear localization is strongly influenced by the initial state and the micro‐polar boundary conditions. For large shearing the state quantities tend towards a stationary state for which a certain coupling between the norm of the stress deviator and the norm of the couple stress tensor can be derived. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

The haze and methane distributions on Neptune from HST-STIS spectroscopy     

Erich Karkoschka  Martin G. Tomasko 《Icarus》2011,211(1):780-797

We analyzed a data cube of Neptune acquired with the Hubble STIS spectrograph on August 3, 2003. The data covered the full afternoon hemisphere at 0.1 arcsec spatial resolution between 300 and 1000 nm wavelength at 1 nm resolution. Navigation was accurate to 0.004 arcsec and 0.05 nm. We constrained the vertical aerosol structure with radiative transfer calculations. Ultraviolet data confirmed the presence of a stratospheric haze of optical depth 0.04 at 370 nm wavelength. Bright, discrete clouds, most abundant near latitudes −40° and 30°, had their top near the tropopause. They covered 1.7% of the observed disk if they were optically thick. The methane abundance above the cloud tops was 0.0026 and 0.0017 km-am for southern and northern clouds, respectively, identical to earlier observations by Sromovsky et al. (Sromovsky, L.A., Fry, P.M., Dowling, T.E., Baines, K.H., Limaye, S.S., [2001b]. Icarus 149, 459-488). Aside from these clouds, the upper troposphere was essentially clear. Below the 1.4-bar layer, a vertically uniform haze extended at least down to 10 bars with optical depth of 0.10-0.16/bar, depending on the latitude. Haze particles were bright at wavelengths above 600 nm, but darkened toward the ultraviolet, at the equator more so than at mid and high latitudes. A dark band near −60° latitude was caused by a 0.01 decrease of the single scattering albedo in the visible, which was close to unity. A comparison of methane and hydrogen absorptions contradicted the current view that methane is uniformly mixed in latitude and altitude below the ∼1.5-bar layer. The 0.04 ± 0.01 methane mixing ratio is only uniform at low latitudes. At high southern latitudes, it is depressed roughly between the 1.2 and 3.3-bar layers compared to low-latitude values. The maximum depression factor is ∼2.7 at 1.8 bars. We present models with 2° latitude sampling across the full sunlit globe that fit the observed reflectivities to 2.8% rms.  相似文献   

Neptune’s cloud and haze variations 1994-2008 from 500 HST-WFPC2 images     

Erich Karkoschka 《Icarus》2011,215(2):759-773

The analysis of all suitable images taken of Neptune with the Wide Field Planetary Camera 2 on the Hubble Space Telescope between 1994 and 2008 revealed the following results. The activity of discrete cloud features located near Neptune’s tropopause remained roughly constant within each year but changed significantly on the time scale of ∼5 years. Discrete clouds covered 1% of the disk on average, but more than 2% in 2002. The other ∼99% of the disk probed Neptune’s hazes at lower altitudes. At red and near-infrared wavelengths, two dark bands around −70° and 10° latitude were perfectly steady and originated in the upper two scale heights of the troposphere, either by decreased haze opacity or by an increased methane relative humidity. At blue wavelengths, a dark band between −60° and −30° latitude was most obvious during the early years, caused by dark aerosols below the 3-bar level with single scattering albedos reduced by ∼0.04, and this contrast was constant between 410 and 630 nm wavelength. The dark band decayed exponentially with a time constant of 5 ± 1 years, which can be explained by settling of the dark aerosols at a rate of 1 bar pressure difference per year. The other latitudes brightened with the same time constant but lower amplitudes. The only exception was a darkening event in the 15-30° latitude region between 1994 and 1996, which coincides with two dark spots observed in the same region during the same time period, the only dark spots seen since Voyager. The dark aerosols had a similar latitudinal distribution as the discrete clouds near the tropopause, although both were separated by four scale heights. Photometric analysis revealed a phase coefficient of 0.0028 ± 0.0010 mag/deg for the 0-2° phase-angle range observable from Earth. Neptune’s sub-Earth latitude varied by less than 3° throughout the observation period providing a data set with almost constant viewing geometry. The trends observed up to 2008 continued into 2010 based on images taken with the Wide Field Camera 3.  相似文献   

Neptune’s rotational period suggested by the extraordinary stability of two features     

Erich Karkoschka 《Icarus》2011,215(1):439-448

The interior rotation and motions in giant planets have generally been probed only at radio wavelengths from spacecraft near the planet, except for Jupiter’s radio emission detectable from Earth. Here I suggest that Neptune’s interior can be indirectly probed at visible wavelength by tracking 10 features that are connected with a stationary latitudinal speed pattern of 7 m/s amplitude. All 10 features remained aligned at the same longitude throughout the Voyager observation period in 1989. Two of them, the South Polar Wave and South Polar Feature, have been observed from Earth for ∼20 years, but their extraordinary rotational stability was never recognized. They probably pinpoint Neptune’s rotational period (15.9663 ± 0.0002 h), one of the largest improvements in 346 years of measuring the giant planets’ rotations. The previous best estimate of Neptune’s rotational period (16.108 ± 0.006 h) was based on Voyager 2 radio data (Lecacheux, A., Zarka, P., Desch, M.D., Evans, D.R. [1993]. Geophys. Res. Lett. 20, 2711-2714). The new result suggests an upward revision of the mass of Neptune’s core. This finding may also question the accepted value of Uranus’ rotational period. The first reliable wind measurements within 15° of Neptune’s South Pole, based on tracking four features in Voyager images, show a 300 m/s eastward jet peaking near 76° South, while the area within 4° of the South Pole seems to be rotationally locked to the interior. These new observations of the stationary features and winds could address the long-standing question about the depth of the atmospheric circulation and may allow some constraints on convection currents in Neptune’s interior.  相似文献   

The reflectivity spectrum and opposition effect of Titan's surface observed by Huygens' DISR spectrometers     

Erich Karkoschka  Stefan E. Schröder  Martin G. Tomasko  Horst Uwe Keller 《Planetary and Space Science》2012,60(1):342-355

We determined Titan's reflectivity spectrum near the Huygens' landing site from observations taken with the Descent Imager/Spectral Radiometer below 500 m altitude, in particular the downward-looking photometer and spectrometers. We distinguish signal coming from illumination by sunlight and the lamp onboard Huygens based on their different spectral signatures. For the sunlight data before landing, we find that spatial variations of Titan's reflectivity were only ～0.8%, aside from the phase angle dependence, indicating that the probed area within ～100 m of the landing site was very homogeneous. Only the very last spectrum taken before landing gave a 3% brighter reflectivity, which probably was caused by one bright cobble inside its footprint. The contrast of the cobble was higher at 900 nm wavelength than at 600 nm.For the data from lamp illumination, we confirm that the phase function of Titan's surface displays a strong opposition effect as found by Schröder and Keller (2009. Planetary and Space Science 57, 1963–1974). We extend the phase function to even smaller phase angles (0.02°), which are among the smallest phase angles observed in the solar system. We also confirm the reflectivity spectrum of the dark terrain near the Huygens' landing site between 900 and 1600 nm wavelength by Schröder and Keller (2008. Planetary and Space Science 56, 753–769), but extend the spectrum down to 435 nm wavelength. The reflectivity at zero phase angle peaks at 0.45±0.06 around 750 nm wavelength and drops down to roughly 0.2 at both spectral ends. Our reflectivity of 0.45 is much higher than all previously reported values because our observations probe lower phase angles than others. The spectrum is very smooth except for a known absorption feature longward of 1350 nm. We did not detect any significant variation of the spectral shape along the slit for exposures after landing, probing a 25×4 cm² area. However, the recorded spectral shape was slightly different for exposures before and after landing. This difference is similar to the spectral differences seen on scales of kilometers (Keller et al., 2008. Planetary and Space Science 56, 728–752), indicating that most observations may probe spatially variable contributions from two basic materials, such as a dark soil partially covered by bright cobbles.We used the methane absorption features to constrain the methane mixing ratio near the surface to 5.0±0.3%, in agreement with the 4.92±0.24% value measured in situ by Niemann et al. (2005. Nature 438, 779–784), but smaller than their revised value of 5.65±0.18% (Niemann et al., 2010. Journal of Geophysical Research 115, E12006). Our results were made possible by an in depth review of the calibration of the spectroscopic and photometric data.  相似文献   

A Light Portable Steam-driven Ice Drill Suitable for Drilling Holes in Ice and Firn     

Erich Heucke 《Geografiska Annaler: Series A, Physical Geography》1999,81(4):603-609

The purpose of this contribution is to explain the characteristics of a newly developed ice drill which is particularly geared to the needs of glaciologists. It is primarily designed for drilling holes for ablation stakes and for measuring water levels or temperatures in firn areas. Its distinguishing features are its light weight, making it easy to carry even over long distances, and the variety of tasks to which it can be adjusted. Furthermore, it is easy to operate even by one person.
Water is heated in a boiler by two gas flames to produce steam, which flows through an insulated hose to a nozzle. When the valve is opened the issuing steam condenses, and the heat released in the process melts the ice. The heater is constructed in such a way that it can easily be adapted to any form of gas supply locally available. It can be used for drilling in ice as well as in firn. The maximum drilling depth is 13 m in ice and 30 m in firn; hole diameters range from 25 to 45 mm. Mean drilling time is 16 min for 6 m, 35 min for 12 m in ice. The total weight is somewhat less than 16 kg, including all parts needed for drilling holes of 10 m in depth as well as the gas supply for one day. In recent years, devices of this type have been used successfully by scientists in various glaciated regions.  相似文献   

Intersteller masers: The influence of the geometrical shape on the radiation properties     

Erich Bettwieser 《Journal of Astrophysics and Astronomy》1981,2(2):187-199

The relation between the minimum and the maximum of the energy density of the microwave field is important in determining the internal physical conditions in a maser source and is directly connected with the size of the emission spot. This relation is investigated for models of homogeneous maser clouds for three different geometries: a thin tube, a thin disk and a sphere. For substantial degrees of saturation, an approximate analytical calculation scheme is presented. The radiation properties found satisfy the transfer and the rate equations well. As expected, the analysis supports the long standing view that the active medium is 10 to 100 times larger than the interferometer size. Here the real purpose is to provide some insight into the dependence of the radiation characteristics on the geometrical shape of the emission region. The luminosity is only slightly affected by the shape of the emitting region (for the same volume). However, the angular variation of the intensity and the peak intensity of the rays reflect sensitively on the geometrical shape.  相似文献