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341.
A radioisotope energy-dispersive X-ray (EDX) system has been used on board the German research vessel “Valdivia” during an exploration expedition in the northern equatorial Pacific in 1973. The instrumentation used consisted of an X-ray detection system incorporating a 30 mm2 effective-area Si (Li) detector with a measured energy resolution of 195 eV for Mn Kα X-rays, standard nuclear electronics, a 1024-channel analyser and a data read-out unit. The X-ray spectra in the manganese-nodule samples were excited by a 30-mCi 238Pu source.The six elements Mn, Fe, Co, Ni, Cu and Zn were analysed on board. Precision values for the analyses were less than 3% for Mn, Fe, Ni, Cu and Zn and about 5% for Co. A total amount of 350 analyses was carried out during a one-month cruise.Average contents of 190 analysed whole manganese-nodule samples from all the sampling sites of the covered area were 23.3% Mn, 6.7% Fe, 0.23% Co, 1.16% Ni, 0.94% Cu and 0.10% Zn. The average content of the base metals expressed as the sum of the Co, Ni, Cu and Zn contents was 2.48%. A linear relationship between Mn and Ni in all analysed samples, including whole manganese-nodule samples, zones of manganese nodules and manganese crusts, was observed. The Mn/Ni ratio calculated by regression analysis was 23.0. Zonal variations of the chemical contents of the six elements in the manganese nodules were found. A size classification of the manganese nodules has been suggested. Geochemical correlations of Cu and Ni versus Mn/Fe in the investigated samples are given. 相似文献
342.
Friedrich Kiefer 《Aquatic Sciences - Research Across Boundaries》1963,25(1):40-48
Ohne Zusammenfassung
Herrn Prof. Dr. A. Remane, Kiel, zum 65. Geburtstag gewidmet. 相似文献
343.
344.
Bruno Merz Jana Friedrich Markus Disse Jochen Schwarz Johann G. Goldammer Jochen Wächter 《Natural Hazards》2006,38(1-2):3-20
The German Research Network for Natural Disasters (DFNK) linked 15 partners with scientific expertise in the field of natural
hazards. Main objectives were the development and provision of the scientific fundamentals for an advanced risk management
of important natural disasters in Germany, i.e., floods, earthquakes, storms and wildland fires. This included risk analyses,
the development of information systems for supporting disaster management, and recommendations for risk reduction measures.
This paper gives an overview of DFNK and summarises its experiences concerning multidisciplinarity and user-orientation. It
illustrates the concept of risk chains, causally linking the different processes from hazard to risk. The step from hazard
to risk requires interdisciplinary research teams. The experiences show that integrative concepts allow results not achievable
with mono-disciplinary approaches. Integrative approaches pave the way to harmonised safety considerations taking into account
the different hazards in a region within a common framework. User-orientation, policy advice and development of operational
tools are key issues of disaster research. The experiences of DFNK illustrate the limitations of a research network in bridging
the gap between research and application within rather short-term projects. Successful cooperation with users could be established
by those activities where, at the beginning of the project, a user was identified who had a strong interest in solving an
urgent problem. 相似文献
345.
Friedrich Lucassen Dieter Pudlo Gerhard Franz Rolf L. Romer Peter Dulski 《International Journal of Earth Sciences》2013,102(1):183-205
Chemical and Sr, Nd and Pb isotopic compositions of Late Cenozoic to Quaternary small-volume phonolite, trachyte and related mafic rocks from the Darfur volcanic province/NW-Sudan have been investigated. Isotope signatures indicate variable but minor crustal contributions. Some phonolitic and trachytic rocks show the same isotopic composition as their primitive mantle-derived parents, and no crustal contributions are visible in the trace element patterns of these samples. The magmatic evolution of the evolved rocks is dominated by crystal fractionation. The Si-undersaturated strongly alkaline phonolite and the Si-saturated mildly alkaline trachyte can be modelled by fractionation of basanite and basalt, respectively. The suite of basanite–basalt–phonolite–trachyte with characteristic isotope signatures from the Darfur volcanic province fits the compositional features of other Cenozoic intra-plate magmatism scattered in North and Central Africa (e.g., Tibesti, Maghreb, Cameroon line), which evolved on a lithosphere that was reworked or formed during the Neoproterozoic. 相似文献
346.
Friedrich HÖRZ 《Meteoritics & planetary science》2012,47(4):763-797
Abstract– Whether a target is penetrated or not during hypervelocity impact depends strongly on typical impactor dimensions (Dp) relative to the absolute target thickness (T). We have therefore conducted impact experiments in aluminum1100 and TeflonFEP targets that systematically varied Dp/T (=D*), ranging from genuine cratering events in thick targets (Dp << T) to the nondisruptive passage of the impactor through very thin films (Dp >> T). The objectives were to (1) delineate the transition from cratering to penetration events, (2) characterize the diameter of the penetration hole (Dh) as a function of D*, and (3) determine the threshold target thickness that yields Dh = Dp. We employed spherical soda‐lime glass (SLG) projectiles of Dp = 50–3175 μm at impact velocities (V) from 1 to 7 km s?1, and varied target thicknesses from microns to centimeters. The transition from cratering to penetration processes in thick targets forms a continuum in all morphologic aspects. The entrance side of the target resembles that of a standard crater even when the back of the target suffers substantial, physical perforations via spallation and plastic deformation. We thus suggest that the cratering‐to‐penetration transition does not occur when the target becomes physically perforated (i.e., at the “ballistic limit”), but when the shock pulse duration in the projectile (tp) is identical to that in the target (tt), i.e., tp = tt. This condition is readily calculated from equation‐of‐state data. As a consequence, in reconstructing impactor dimensions from observations of space‐exposed substrates, we recommend that crater size (Dc) be used for the case of tp < tt, and that penetration hole diameter (Dh) be used when tp > tt. The morphologic evolution of the penetration hole and its size also forms a continuum that strongly depends on both the scaled parameter D* and on V, but it is independent of the absolute scale. The condition of Dh = Dp is approached at D* > 50. The dependence of Dh on T and V, however, is very systematic. This has led to new and detailed calibration curves, permitting the reconstruction of Dp from the measurement of either crater diameter or penetration‐hole size in Al1100 and TeflonFEP targets of arbitrary thickness. We also placed witness plates behind penetrated targets to intercept the down‐range debris plume, which is generally a mixture of both target and impactor fragments and melts. These witness plates also reveal that the debris plume systematically and diagnostically depends on D*. Thick targets shed spall debris only, and target thickness must be less than crater depth (Tc) to allow projectile material on the witness plate. Concentric plume patterns, accented by characteristic “hole saw” rings, characterize penetrated Al‐targets at D* = 1–10, but they give way to distinctly radial geometries at D* = 10–20. Most of the target debris occupies the periphery of the plume, while the projectile fragments or melts reside in its central parts. The periphery of the plume is also typically more fine‐grained than its center. At D* > 50, the exit plume is dominated by solid projectile fragments that progressively coagulate and overlap with each other, giving rise to compound craters. The latter have irregular crater interiors on account of the heterogeneous mass distribution of a collisionally produced, aggregate impactor. Similarly, complex craters are observed on LDEF and Stardust and they are produced by aggregate cosmic‐dust particles containing large, dense components within a relatively low‐density, fine‐grained matrix. The witness‐plate observations can also be used to address the enigmatic clustering of impact sites observed on Stardust’s aerogel and aluminum surfaces. We suggest that this clustering is difficult to produce by the collision of particles from comet Wild 2 with the Stardust spacecraft, and that it is more likely due to particle disaggregation in the comet’s coma. 相似文献
347.
348.
F. Brngen G. Friedrich G. Lenk R. Richter N. B. Richter 《Astronomische Nachrichten》1970,292(3):103-106
In a field of 4 square degrees, including the southwestern part of M 31 18 blue starlike objects are found by a photometric statistics in U,B,V of all starlike objects in this field. With great probability 13 of them are OB stars of M 31. Their utmost distances from the nucleus of M 31 are 35…50 kpc. Three further objects are probably quasistellar objects. Two others are striking by their extraordinary position in the two-colour diagram and cannot be classified in a distinct category of objects. 相似文献