Dislocation substructure of mantle-derived olivine as revealed by selective chemical etching and transmission electron microscopy     

Stephen H. Kirby  Mary W. Wegner 《Physics and Chemistry of Minerals》1978,3(4):309-330

Cleaved and mechanically polished surfaces of olivine from peridotite xenoliths from San Carlos, Arizona, were chemically etched using the techniques of Wegner and Christie (1974). Dislocation etch pits are produced on all surface orientations and they tend to be preferentially aligned along the traces of subgrain boundaries, which are approximately parallel to (100), (010), and (001). Shallow channels were also produced on (010) surfaces and represent dislocations near the surface that are etched out along their lengths. The dislocation etch channel loops are often concentric, and emanate from (100) subgrain boundaries, which suggests that dislocation sources are in the boundaries. Data on subgrain misorientation and dislocation line orientation and arguments based on subgrain boundary energy minimization are used to characterize the dislocation structures of the subgrain boundaries. (010) subgrain boundaries are of the twist type, composed of networks of [100] and [001] screw dislocations. Both (100) and (001) subgrain boundaries are tilt walls composed of arrays of edge dislocation with Burgers vectors b=[100] and [001], respectively. The inferred slip systems are {001} 〈100〉, {100} 〈001〉, and {010} 〈100〉 in order of diminishing importance. Exploratory transmission electron microscopy is in accord with these identifications. The flow stresses associated with the development of the subgrain structure are estimated from the densities of free dislocations and from the subgrain dimensions. Inferred stresses range from 35 to 75 bars using the free dislocation densities and 20 to 100 bars using the subgrain sizes.  相似文献   

Chemical etching of amphiboles and pyroxenes     

M. W. Wegner  J. M. Christie 《Physics and Chemistry of Minerals》1985,12(2):86-89

Chemical etching of defect structures in pyroxenes and amphiboles has been investigated. Many features, such as very thin (～1 micrometer) exsolution lamellae not observed by transmission optical microscopy of thin sections, have been observed in reflected light after chemical etching of cleaved or polished crystal surfaces. A new feature in the microstructure of pyroxenes, not previously reported in the literature, has been revealed by one of the etchants.  相似文献   

Neuere Veröffentlichungen     

Gerd Wegner 《Ocean Dynamics》1990,43(6):333-334

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Eurasian Arctic shelf hydrography: Exchange and residence time of southern Laptev Sea waters     

D. Bauch  I. Dmitrenko  S. Kirillov  C. Wegner  J. Hlemann  S. Pivovarov  L. Timokhov  H. Kassens 《Continental Shelf Research》2009,29(15):1815-1820

The hydrography of the Laptev Sea is significantly influenced by river water and sea-ice processes, which are highly variable over the annual cycle. Despite of an estuarine structure the inner and outer shelf regions are decoupled at times as documented by the stability of a warm intermediate layer formed during summer below the Lena River plume. We demonstrate that a remnant of this warm layer is preserved below the fast ice until the end of winter, while only slightly farther to the north, offshore of the landfast ice in the polynya region, the pycnocline is eroded and no signature of this layer is found. The warm intermediate layer (WIL) formed during summer can be used as tracer for Laptev Sea shelf waters throughout the winter. Thereby, residence times of southern Laptev Sea waters can be estimated to be at least from summer to the end of winter/spring of the following year.  相似文献   

The peculiar motions of early-type galaxies in two distant regions – VII. Peculiar velocities and bulk motions     

Matthew Colless  R. P. Saglia  David Burstein  Roger L. Davies  Robert K. McMahan  Jr    Gary Wegner 《Monthly notices of the Royal Astronomical Society》2001,321(2):277-305

We present peculiar velocities for 85 clusters of galaxies in two large volumes at distances between 6000 and 15 000 km s⁻¹ in the directions of Hercules–Corona Borealis and Perseus–Pisces–Cetus (the EFAR sample). These velocities are based on Fundamental Plane (FP) distance estimates for early-type galaxies in each cluster. We fit the FP using a maximum likelihood algorithm which accounts for both selection effects and measurement errors, and yields FP parameters with smaller bias and variance than other fitting procedures. We obtain a best-fitting FP with coefficients consistent with the best existing determinations. We measure the bulk motions of the sample volumes using the 50 clusters with the best-determined peculiar velocities. We find that the bulk motions in both regions are small, and consistent with zero at about the 5 per cent level. The EFAR results are in agreement with the small bulk motions found by Dale et al. on similar scales, but are inconsistent with pure dipole motions having the large amplitudes found by Lauer & Postman and Hudson et al. The alignment of the EFAR sample with the Lauer & Postman dipole produces a strong rejection of a large-amplitude bulk motion in that direction, but the rejection of the Hudson et al. result is less certain because their dipole lies at a large angle to the main axis of the EFAR sample. We employ a window function covariance analysis to make a detailed comparison of the EFAR peculiar velocities with the predictions of standard cosmological models. We find that the bulk motion of our sample is consistent with most cosmological models that approximately reproduce the shape and normalization of the observed galaxy power spectrum. We conclude that existing measurements of large-scale bulk motions provide no significant evidence against standard models for the formation of structure.  相似文献   

Observations of persistent pattern in the temperature field related to the North Atlantic Current     

Dr. Eberhard Fahrbach  Gerd Wegner 《Ocean Dynamics》1987,40(4):141-155

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Intrinsic colour indices of Be stars obtained from 2MASS photometry     

W. Wegner 《Astronomische Nachrichten》2015,336(2):159-167

This paper is based on 2MASS photometry (J H K_s magnitudes) of 1172 Be stars. The observed mean intrinsic colours have been derived with aid of two‐colour diagrams for Be stars of luminosity classes Ie‐IIe, IIIe and IVe‐Ve. The obtained results are the first determinations of their intrinsic colours in the astronomical literature. The smoothed infrared colours are compared with those obtained for “normal” B stars. Several two‐colour diagrams and plots of observed and smoothed intrinsic colour versus spectral type of luminosity classes Ie‐IIe, IIIe and IVe‐Ve are presented. Generally the determined infrared intrinsic colours of Be stars (V – J)₀, (V – H)₀, and (V – K_s)_o differ substantially from those of “normal” B stars. It is found that the intrinsic colours of B stars are generally bluer than Be stars of corresponding spectral type and luminosity class. The mean absolute visual magnitude M_v of 528 Be stars for luminosity classes Iae, Ibe‐Iabe, IIe, IIIe and IVe‐Ve is derived from HIPPARCOS parallaxes. The M_v calibration is compared with the existing ones. The Be stars are generally brighter than “normal” B stars of corresponding spectral types. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Instellar extinction curves originated in single clouds     

J. Krelowski  W. Wegner 《Astronomische Nachrichten》1989,310(4):281-287

In der Arbeit wird gezeigt, daß zwischen den Extinktionskurven heller, relativ gering entfernter Sterne große Unterschiede bestehen, die mögficherweise dadurch verursacht werden, daß nur eine interstellare Wolke mit spezifischen Eigenschaften die Extinction verursacht. Die Unterschiede betreffen sowohl den Verlauf der Extinktionskurve als auch den R-Wen. Die Unterschiede in den Extinktionskurven sind korreliert mit den Inten-sitatsverhaltnissen der diffusen interstellaren Banden bei 578 nm und 579,7 nm. Es wird geschlußfolgert, daß sich die physikalischen Eigenschaften einzelner interstellarer Wolken stark voneinander unterscheiden und die aus den Spektren stark verfärbter Sterne gewonnenen Extinktionskurven nur einen schlecht spezifizierbaren Mittelwert der Verhältnisse in den Einzelwolken darstellen. Die abgeleiteten individuellen Extinktionskurven sollten mit theoretischen oder aus Laborexperimenten abgeleiteten Kurven verglichen werden.  相似文献