Anomalous Fe II spectral effects and high H I Lyα temperature in gas blobs near η Carinae     

S. Johansson  V. S. Letokhov 《Astronomy Letters》2004,30(1):58-63

We consider the origin of the anomalously high intensity of the ultraviolet Fe II λλ2507/2509 Å lines observed with high spatial and spectral resolutions from gas blobs (GBs) near η Carinae. This rare effect in stellar spectra is attributable to a combination of several factors: (1) the high hydrogen density(>10⁸ cm^?3) that ensures the blockingof the Lyman continuum by GBs and, accordingly, the formation of a cold H I region with completely ionized Fe atoms; (2) the small distance between the GBs and the central star that ensures a high (>8000–10000 K) Lyα H spectral temperature, which photoexcites Fe II selectively; and (3) the population of Fe II levels and, accordingly, the opening of a stimulated emission channel, which together with spontaneous transitions creates a radiative cycle where a single Fe II ion can multiply absorb Lyα emission.  相似文献   

Reconstructing floodplain sedimentation rates from heavy metal profiles by inverse modelling     

Hans Middelkoop 《水文研究》2002,16(1):47-64

The embanked floodplains of the lower River Rhine in the Netherlands contain large amounts of heavy metals, which is a result of many years deposition of contaminated overbank sediments. Depending on local sedimentation rates and changing pollution trends in the past, the metal pollution varies greatly between different floodplain sections as well as vertically within the floodplain soil profiles. Maximum metal concentrations in floodplain soils vary from 30 to 130 mg/kg for Cu, from 70 to 490 mg/kg for Pb and from 170 to 1450 mg/kg for Zn. In the present study these metals were used as a tracer to reconstruct sedimentation rates at 28 sites on the lower River Rhine floodplains. The temporal trend in pollution of the lower River Rhine over the past 150 years was reconstructed on the basis of metal concentrations in sediments from small ponds within the floodplain area. Using a one‐dimensional sedimentation model, average sedimentation rates over the past century were determined using an inverse modelling calibration procedure. The advantage of this method is that it uses information over an entire profile, it requires only a limited number of samples, it accounts for post‐depositional redistribution of the metals, and it provides quantitative estimates of the precision of the sedimentation rates obtained. Estimated sedimentation rates vary between about 0·2 mm/year and 15 mm/year. The lowest metal concentrations are found in the distal parts of floodplain sections with low flooding frequencies and where average sedimentation rates have been less than about 5 mm/year. The largest metal accumulations occur in low‐lying floodplain sections where average sedimentation rates have been more than 10 mm/year. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Der Basaltstock des Weilberges im Siebengebirge     

Hans Cloos 《International Journal of Earth Sciences》1948,35(1):33-35

Ohne Zusammenfassung  相似文献   

Preface     

Walter Fernandez  Hans J. Haubold 《Earth, Moon, and Planets》1993,63(2):iii-iii

  相似文献   

Drought variability in eastern Mongolian Plateau and its linkages to the large-scale climate forcing   总被引：1，自引：0，他引：1  

Guang Bao  Yu Liu  Na Liu  Hans W. Linderholm 《Climate Dynamics》2015,44(3-4):717-733

  相似文献   

On Solar-Wind Electron Heating at Large Solar Distances     

Igor V. Chashei  Hans J. Fahr 《Solar physics》2014,289(4):1359-1370

We study the temperature of electrons advected with the solar wind to large solar distances far beyond 1 AU. Almost nothing is known about the thermodynamics of these electrons from in-situ plasma observations at these distances, and usually it is tacitly assumed that electrons, due to adiabatic behaviour and vanishing heat conduction, rapidly cool off to very low temperatures at larger distances. In this article we show, however, that electrons on their way to large distances undergo non-adiabatic interactions with travelling shocks and solar-wind bulk-velocity jumps and thereby are appreciably heated. Examining this heating process on an average statistical basis, we find that solar-wind electrons first cool down to a temperature minimum, which depending on the occurrence frequency of bulk velocity jumps is located between 3 and 6 AU, but beyond this the lowest electron temperature again starts to increase with increasing solar distance, finally achieving temperatures of about 7×10⁴ K to 7×10⁵ K at the location of the termination shock. Hence these electrons are unexpectedly shown to play an important dynamical role in structuring this shock and in determining the downstream plasma properties.  相似文献   

Der geologische Lehrstuhl an der Universität Neuenburg in der Schweiz     

Hans Cloos 《International Journal of Earth Sciences》1941,32(3):389-393

Ohne Zusammenfassung  相似文献   

Tektonische Probleme am Nordrand des Harzes     

Hans Cloos 《International Journal of Earth Sciences》1916,7(7-8):314-329

Ohne ZusammenfassungVgl.Cloos, Eine neue Störungsform, (8).  相似文献   

A three-dimensional model study on processes of stratification and de-stratification in the Limfjord     

Richard Hofmeister  Hans Burchard  Karsten Bolding 《Continental Shelf Research》2009,29(11-12):1515-1524

Investigations on stratifying and de-stratifying processes in the Limfjord in Denmark, stretching from the North Sea at the western end to the Kattegat at the eastern end, were carried out. The forcing of the Limfjord is dominated by mean sea surface elevation and salinity gradients, diffuse freshwater supply, as well as episodic saline inflow events from the North Sea boundary. The physical regime of the Limfjord switches periodically from stratified to mixed conditions. In order to investigate the complexity of the system, a realistic three-dimensional high-resolution numerical model study was conducted for the year 2003. The results are based on, and compared to, available field data. A central subject of this study is the anomaly of potential energy as a measure for stratification. The stratifying and de-stratifying processes are identified as contributing terms in a dynamic equation for the potential energy anomaly. The comparison of model results and observations shows that the model has the capability of reproducing the observed physical regimes. Changes in the simulated stratification turn out to be a complex interaction of differential advection, heating and turbulent mixing in the central Limfjord.  相似文献   

Über das Gleitvermögen der Glimmer     

Hans Seifert 《Contributions to Mineralogy and Petrology》1948,1(4):486-504

Ohne Zusammenfassung  相似文献