Mass loss from hot massive stars     

Joachim Puls  Jorick S. Vink  Francisco Najarro 《Astronomy and Astrophysics Review》2008,16(3-4):209-325

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Nature of sedimentary deposits in the western Makgadikgadi basin, Botswana     

Susan Ringrose  Bill Downey  Dane Genecke  Francis Sefe  Bernard Vink 《Journal of Arid Environments》1999,43(4):375

Quaternary sedimentation in the western Makgadikgadi basin of north central Botswana is evaluated on the basis of new evidence from satellite imagery and sedimentological analyses. Thematic Mapper imagery interpretation, combined with field evidence, has led to the identification of geomorphological features which are mainly composed of light grey calcareous sandstones (formerly calcretes) overlain by dark grey sands. The literature suggests that palaeolake Makgadikgadi I formed and developed intermittently after initial downwarping in the early–mid Pleistocene. The calcareous sandstones were formed when calcium carbonate precipitation took place in pre-existing Kalahari sands along the western shoreline of Makgadikgadi I. Field evidence, supported by X-ray diffraction and SEM analyses, indicates that CaCO₃precipitated mainly in marshy conditions around plant roots and stems and in association with bacteria in embayments along the lakeshore. The sandstones thickened and became partially indurated as a result of increasing palaeolake levels. Deposition was terminated by renewed tectonism which uplifted the shoreline zone relative to the lake basin, leading to falling palaeolake levels. Post-uplift reworking led to case hardening and pedogenic calcrete formation in the upper sections of the calcareous sandstones. Sedimentary conditions altered during the late Pleistocene. Extensive distributaries from the proto-Okavango system incised the shoreline ridge contributing to the filling of Makgadikgadi II. Satellite data suggest that the proto-Okavango rivers formed a series of fan deltas at this time along the western Makgadikgadi basin. Widespread dispersal of fluvial grey sands took place as a result of basin tilting which led to anastomosing channels flowing southward possibly around 18,000 B.P. These results, although preliminary in nature, augment previous geomorphological analyses by adding some detail in terms of depositional environments and by providing a tentative age and origin for the ubiquitous grey sands.  相似文献   

Korean East Coast wave predictions by means of ensemble Kalman filter data assimilation     

Sofia Caires  Jinah Kim  Jacco Groeneweg 《Ocean Dynamics》2018,68(11):1571-1592

To respond to the need for preventing offshore and coastal accidents, damage and flooding, a state-of-the-art coastal wave forecast system for the East Coast of Korea waters is being developed. Given that the quality of the input wind has been identified as the main factor influencing the quality of the wave results, the effectiveness of adjusting the wind fields by means of data assimilation using the ensemble Kalman filter technique has been explored. In this article the model setup, the data assimilation parameters and the validation of the predictions during stormy periods is described. The validation shows that the model is able to provide predictions of coastal waves fulfilling available benchmarks; especially, the data assimilation analysis and forecast predictions are judged to be of high quality.  相似文献   

Heavy metal transport in large river systems: heavy metal emissions and loads in the Rhine and Elbe river basins     

Rona Vink  Horst Behrendt 《水文研究》2002,16(16):3227-3244

Pollutant transport and management in the Rhine and Elbe basins is still of international concern, since certain target levels set by the international committees for protection of both rivers have not been reached. The analysis of the chain of emissions of point and diffuse sources to river loads will provide policy makers with a tool for effective management of river basins. The analysis of large river basins such as the Elbe and Rhine requires information on the spatial and temporal characteristics of both emissions and physical information of the entire river basin. In this paper, an analysis has been made of heavy metal emissions from various point and diffuse sources in the Rhine and Elbe drainage areas. Different point and diffuse pathways are considered in the model, such as inputs from industry, wastewater treatment plants, urban areas, erosion, groundwater, atmospheric deposition, tile drainage, and runoff. In most cases the measured heavy metal loads at monitoring stations are lower than the sum of the heavy metal emissions. This behaviour in large river systems can largely be explained by retention processes (e.g. sedimentation) and is dependent on the specific runoff of a catchment. Independent of the method used to estimate emissions, the source apportionment analysis of observed loads was used to determine the share of point and diffuse sources in the heavy metal load at a monitoring station by establishing a discharge dependency. The results from both the emission analysis and the source apportionment analysis of observed loads were compared and gave similar results. Between 51% (for Hg) and 74% (for Pb) of the total transport in the Elbe basin is supplied by inputs from diffuse sources. In the Rhine basin diffuse source inputs dominate the total transport and deliver more than 70% of the total transport. The diffuse hydrological pathways with the highest share are erosion and urban areas. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The Red Supergiant IRAS04553-6825 in the LMC     

Jacco Th. Van Loon 《Astrophysics and Space Science》1997,255(1-2):405-406

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Obscured asymptotic giant branch variables in the Large Magellanic Cloud and the period–luminosity relation     

Patricia A. Whitelock  Michael W. Feast  Jacco Th. van Loon  Albert A. Zijlstra 《Monthly notices of the Royal Astronomical Society》2003,342(1):86-104

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Reply to ‘Comment on: “Establishing the Late Pleistocene-Holocene sedimentation boundary in the southern North Sea using OSL dating of shallow continental shelf sediments” by L. Alappat,A. Vink,S. Tsukamoto,M. Frechen,Proceedings of the Geologists’ Association 121 (2010), 43–54’ by B. Mauz     

L. Alappat  M. Frechen  S. Tsukamoto  A. Vink 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(4):666-668

The major concerns in the correspondence of Mauz (2012) was the correction applied for the calculation of cosmic dose in response of changing sea level in the past and statistical parameters used as well as the selection of MAM. A better approach is discussed in this note for the calculation of cosmic dose over a variable time span of rising sea level with the help of established sea level curves in the area. The selection of MAM-3 for the estimation of final De's are discussed in the article. The comments by Mauz (2012) have been helpful in rectifying some confusions that might have arisen in the original article of Alappat et al. (2010). However, some comments were merely speculative in nature and made by ignoring the statements that have been clearly mentioned in the article. After addressing various concerns of Mauz (2012), the results show that the variation in the final age due to this is small and within the uncertainty for all the samples.  相似文献   

First results of the Central-East-South European Binary Star Study Group (CESEB)     

T. Hegedüs  J. Nuspl  N. Markova  H. Markov  H. Rovithis-Livaniou  I. Vince  J. Vinkó 《Astrophysics and Space Science》2006,304(1-4):51-53

Several eclipsing binary systems have been selected for combined spectral and photometric observations using the Bulgarian NAO 2 m telescope and several smaller telescopes located at various places in the CESE region. Preliminary results, based on a pilot study started in 2001, about radial velocity and light curve variations of the active W UMa system LS Del are presented here.  相似文献   

The X-ray properties of young radio-loud AGN     

Jacco Vink  Ignas Snellen  Karl-Heinz Mack  Richard Schilizzi 《Monthly notices of the Royal Astronomical Society》2006,367(3):928-936

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A polarimetric study of the B[e] star HD 45677     

M. Patel  R. D. Oudmaijer  J. S. Vink  J. C. Mottram  B. Davies 《Monthly notices of the Royal Astronomical Society》2006,373(4):1641-1647

We aim to characterize the current status of knowledge on the accuracy of open-cluster parameters such as the age, reddening and distance. These astrophysical quantities are often used to study the global characteristics of the Milky Way down to the very local stellar phenomena. In general, the errors of these quantities are neglected or set to some kind of heuristic standard value. We attempt to give some realistic estimates for the accuracy of available cluster parameters by using the independently derived values published in the literature. In total, 6437 individual estimates for 395 open clusters were used in our statistical analysis. We discuss the error sources depending on theoretical as well as observational methods and compare our results with those parameters listed in the widely used catalogue by Dias et al. In addition, we establish a list of 72 open clusters with the most accurate known parameters which should serve as a standard table in the future for testing isochrones and stellar models.  相似文献