Contrasted abyssal basalt liquidus trends: evidence for mantle major element heterogeneity     

W.B. Bryan  H.J.B. Dick 《Earth and Planetary Science Letters》1982,58(1):15-26

Natural submarine basalt glasses define liquidus trends which may be summarized as curvilinear regression lines in the normative plagioclase-pyroxene-olivine ternary. Individual basalt suites separated in time or space may differ in major element composition; these differences translate into systematic differences in normative plagioclase, leading to efficient discrimination of individual trends in this ternary. Comparison of two contrasted sets of trends to available experimental and petrographic data confirms the similarity of the natural basalt trends to those predicted by 1-atm experiments, in general agreement with earlier studies based on whole-rock data. These contasted liquidus trends are believed to reflect major element heterogeneity and varying degrees of melting of the mantle source. This major element heterogeneity is not simply correlated with heterogeneity in incompatible trace elements, and like incompatible trace element heterogeneity, there is growing evidence that it may vary abruptly in space and time. The existence of these compositionally contrasted basalt suites must be considered in petrogenetic modelling; specifically, they will introduce scatter in most generalized variation diagrams, and will increase the likelihood of “misfits” in fractionation calculations utilizing parent and residual compositions drawn from different suites.  相似文献   

Exploring the geophysical and socio-economic determinants of land cover changes in Eastern Mau forest reserve and Lake Nakuru drainage basin,Kenya     

Kennedy Were  Øystein B. Dick  Bal R. Singh 《GeoJournal》2014,79(6):775-790

Understanding the linkages between the biogeophysical and socio-economic processes that operate at different spatial and temporal scales is important for land cover change mitigation. This study analysed several factors that explained the forest-shrubland conversions, grassland conversions and cropland expansions in Lake Nakuru drainage basin and Eastern Mau forest reserve in Kenya from 1985 to 2011. Logistic regression models were developed using a combination of remote sensing-based land cover data, and geographical information systems-based geophysical and socio-economic data (i.e., temperature, rainfall, elevation, slope, aspect, topographic wetness, curvature, soil pH, soil cation exchange capacity (CEC), population density and distance to road, river and town). The results were varied; for example, in the period 1985–2000, forest-shrubland conversions were linked to distance to road), distance to town, soil pH, soil CEC, rainfall, topographic wetness, curvature and aspect. The same factors, in addition to slope and distance to river, also determined the likelihood of forest-shrubland conversions in the period 2000–2011. Overall, significance of the determining factors varied depending on time and nature of land cover change. For example, topographical factors influenced grassland conversions in the period 1985–2000, while soil-related factors did not. But in the period 2000–2011, the converse was true. Therefore, policies for restoration, conservation and sustainable management of critical ecosystems (e.g., forests) should be spatially targeted and time-specific. These results broaden our knowledge of land cover dynamics in this locality, and provide a base for effective environmental policy formulation, planning and management.  相似文献   

A. H. BATTEN: Resolute and Undertaking Characters: The Lives of WILHELM and OTTO STRUVE. (Astrophysics and Space Science Library,Vol. 139). Dordrecht,Boston, Lancaster,Tokyo: D. Reidel Publishing Company, 1988. 259 S., 76 Fotos, 7 Zeichnungen. Preis 130,-Dfl. ISBN 90-277-2652-3     

W. R. Dick 《Astronomische Nachrichten》1989,310(4):346-347

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H. PIEPER (Hrsg.): Briefwechsel zwischen Alexander von Humboldt und C. G. Jacob Jacobi. (Beiträge zur Alexander-von-Humboldt-Forschung,Bd. 11). Berlin: Akademie-Verlag, 1987. 307 S., 4 Tafeln. Preis 58,- M. ISBN 3-05-000240-9     

W. R. Dick 《Astronomische Nachrichten》1990,311(1):84-84

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Bestimmung absoluter Eigenbewegungen in einem KSZ-Feld mit zwei Astrographen     

W. R. Dick 《Astronomische Nachrichten》1985,306(2):91-96

In the field No. 153 of the KSZ program relative proper motions of 144 stars up to 15^m.0 are presented as well as parameters for the reduction to absolute with reference to 6 galaxies. The external error of one proper motion is 0.014″/y. It is shown that in a small field the statistical method for the estimation of the magnitude error is not able to give significant results due to the variance of the proper motion. It is concluded that in practice the long focus and the wide angle astrographs of the Main Observatory of the Ukrainian Academy of Science in Kiev can be combined for the derivation of proper motions.  相似文献   

GUNTER D. KOTH : Kosmos Astronomiegeschichte. Astronomen,Instru-mente. Entdeckungen. (Kosmos,Gesellschaft der Naturfreunde). Stuttgart: Franckh'sche Verlagsbuchhandlung. W. Keller & Co. 1987. 192 S 38 Fotos. 43 Zeichnungen. Preis 48. DM. ISBN 3-440-05800-X     

W. R. Dick 《Astronomische Nachrichten》1989,310(2):177-178

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