Age and source material of the Kingash ultramafic-mafic massif,East Sayan

The REE distribution patterns and Nd whole-rock and mineral isotope ratios of the Kingash ultramafic-mafic massif enabled us to propose a multistage history for its evolution at 1410 and 875 Ma. These stages reflect the magmatic evolution of the Siberian paleocontinent margin during the Late Precambrian. The age of metamorphism of the massif during collision and accretion in the Early Paleozoic (∼500 Ma) was obtained based on a Sm-Nd mineral isochron from rheomorphic veined albitite. The Nd and Sr isotopic compositions of rocks from the Kingash massif suggest mantle sources for picritic and basic magmas, which are thought to have originated by mixing of different proportions of depleted (PREMA or DM) and enriched (EM) melts. The initial isotope ratios of the parental melts transformed during interaction with Sr-rich material from the host metasedimentary complexes.     

Observability of Single Neutron Stars at SRG/eROSITA

Astronomy Reports - A four-year sky survey with the use of the eROSITA telescope on board the Spektr-RG observatory with focusing optics will provide the best coverage in the soft (0.5–2 keV)...     

Studies of temperature effects of dust storms

We studied the temperature variations of the lower air layer caused by dust content using a dust storm in Dushanbe in November 2007 as an example. Quantitative estimates of air cooling and a decrease in the diurnal temperature difference due to a diminishing horizontal visibility range are given. Observations of air temperature variations due to the dust content of the atmosphere in an arid zone are presented. The critical value of aerosol concentration for toggling between the greenhouse and antigreenhouse effects is determined. The long-term effect of dust aerosol on climate is analyzed.     

Transport rate of drifting snow and the mean wind speed profile

Transport rates, measured by weighing snow blown into a filter fabric trap, were greater over hard snow or ice than for the same wind speed over soft, fresh snow surfaces. Analysis of wind speed profiles from nine blizzards showed that friction between moving particles and the surface was less, and particle speeds were greater over hard surfaces. Transport rates at a given wind speed increased rapidly as aerodynamic roughness decreased in the rough-smooth transition region. Bagnold's theory for bed load transport provided a useful framework for the analysis.     

A very large scale GIS-based groundwater flow model for the Nubian sandstone aquifer in Eastern Sahara (Egypt,northern Sudan and eastern Libya)

A three-dimensional GIS-based groundwater flow model for the Nubian Sandstone Aquifer in the eastern Sahara was developed and calibrated under steady-state and transient conditions. The model was used to simulate the response of the aquifer to climatic changes that occurred during the last 25,000 years. The simulation results indicated that the groundwater in this aquifer was formed by infiltration during the wet periods 20,000 and 5,000 years b.p. The recharge of groundwater due to regional groundwater flow from more humid areas in the south was excluded. It also indicates that the Nubian Aquifer System is a fossil aquifer, which had been in an unsteady state condition for the last 3,000 years.

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Resumen Fue desarrollado un modelo de flujo de agua subterránea en tres dimensiones, basado en un SIG, para el Acuífero Arenisca Nubian en el Sahara Oriental, el cual fue calibrado para condiciones de estado estacionario y transitorio. El modelo se usó para simular la respuesta del acuífero a los cambios climáticos que ocurrieron durante los últimos 25000 años. Los resultados de esta simulación indicaron que el agua subterránea en este acuífero, se formó por infiltración, durante los períodos húmedos que hubo hace 20000 y 5000 años, antes del presente. Fue excluida la recarga del acuífero debida a un flujo regional de agua subterránea proveniente de áreas con un clima más húmedo en el sur. El modelo también muestra, que el Sistema Acuífero Nubian es un acuífero fósil, el cual ha permanecido en una condición de estado no estacionario, durante los últimos tres mil años.

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Résumé Pour laquifère gréseux Nubien de Sahara -Est on a mis au points un modèle tridimensionnel, basé sur GIS. Le modèle a été calibré tant pour lécoulement stationnaire que pour lécoulement transitoire. On a simulé après la réponse de laquifère aux changements climatiques des derniers 25000 ans. Les résultats des simulations indiquent que la nappe a été rechargée par des infiltrations pendant une période humide qui sétend 5000 et 20000 ans, dès temps actuel. On na pas pris en compte la recharge de laquifère par la zone plus humide située dans sa partie sud. Le modèle indique aussi que leau de laquifère Nubien est une eau fossile qui a eu un écoulement transitoire pendant les derniers 3000 ans.

     

Bücher- und Zeitschriftenschau

Ohne Zusammenfassung     

Selenium in a shore bird,the dunlin,from the Dutch Waddenzee

The hypothesis that Se is secreted by birds via the preen gland or salt glands, thus contaminating the feathers, has been investigated. It is concluded that the feather vanes show indirectly in this way the birds' e?posure to Se. Therefore they can be used as an indicator tissue for this element.