An impact model of Newton’s law of gravitation     

Klaus Wilhelm  Horst Wilhelm  Bhola N. Dwivedi 《Astrophysics and Space Science》2013,343(1):135-144

The far-reaching gravitational force—in the approximation of Newton’s law of gravitation—is described by a heuristic model with hypothetical massless particles propagating at the speed of light in vacuum and transferring momentum and energy between physical entities through interactions on a local basis. The model has some similarities with the impact theory presented by Nicolas Fatio de Duillier to the Royal Society in 1690. Objections raised against this idea are dispelled by invoking the Special Theory of Relativity, considering non-local interactions, and replacing the shielding concept by a secular mass increase of massive bodies. Some consequences and applications of the model are discussed.  相似文献   

Ejection behavior characteristics in experimental cratering in sandstone targets     

Frank SOMMER  Fiona REISER  Anja DUFRESNE  Michael H. POELCHAU  Tobias HOERTH  Alex DEUTSCH  Thomas KENKMANN  Klaus THOMA 《Meteoritics & planetary science》2013,48(1):33-49

Abstract– Within the frame of the MEMIN research unit (Multidisciplinary Experimental and Numerical Impact Research Network), impact experiments on sandstone targets were carried out to systematically study the influence of projectile mass, velocity, and target water saturation on the cratering and ejection processes. The projectiles were accelerated with two‐stage light‐gas guns (Ernst‐Mach‐Institute) onto fine‐grained targets (Seeberger sandstone) with about 23% porosity. Collection of the ejecta on custom‐designed catchers allowed determination of particle shape, size distribution, ejection angle, and microstructures. Mapping of the ejecta imprints on the catcher surface enabled linking of the different patterns to ejection stages observed on high‐speed videos. The increase in projectile mass from 0.067 to 7.1 g correlates with an increase in the total ejected mass; ejecta angles, however, are similar in range for all experiments. The increase in projectile velocity from 2.5 to 5.1 km s^?1 correlates with a total ejecta mass increase as well as in an increase in comminution efficiency, and a widening of the ejecta cone. A higher degree of water saturation of the target yields an increase in total ejecta mass up to 400% with respect to dry targets, higher ejecta velocity, and a steeper cone. These data, in turn, suggest that the reduced impedance contrast between the quartz grains of the target and the pores plays a primary role in the ejecta mass increase, while vaporization of water determines the ejecta behavior concerning ejecta velocity and particle distribution.  相似文献   

World space observatory-ultraviolet among UV missions of the coming years     

Boris Shustov  Mikhail Sachkov  Ana I. Gómez?de?Castro  Klaus Werner  Norbert Kappelmann  Alexander Moisheev 《Astrophysics and Space Science》2011,335(1):273-282

Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity imaging and high/low resolution spectroscopy from the middle of the decade.  相似文献   

Geochemical characteristics and Sr–Nd–Hf isotope compositions of mantle xenoliths and host basalts from Assab, Eritrea: implications for the composition and thermal structure of the lithosphere beneath the Afar Depression     

Mengist Teklay  Erik E. Scherer  Klaus Mezger  Leonid Danyushevsky 《Contributions to Mineralogy and Petrology》2010,159(5):731-751

The Afar Depression offers a rare opportunity to study the geodynamic evolution of a rift system from continental rifting to sea floor spreading. This study presents geochemical data for crustal and mantle xenoliths and their alkaline host basalts from the region. The basalts have enriched REE patterns, OIB-like trace element characteristics, and a limited range in isotopic composition (⁸⁷Sr/⁸⁶Sr = 0.70336–0.70356, ε _Nd = +6.6 to +7.0, and ε _Hf = +10.0 to +10.7). In terms of trace elements and Sr–Nd isotopes, they are similar to basalts from the Hanish and Zubair islands in the southern Red Sea and are thus interpreted to be melts from the Afar mantle. The gabbroic crustal xenoliths vary widely in isotope composition (⁸⁷Sr/⁸⁶Sr = 0.70437–0.70791, ε _Nd = −8.1 to +2.5, and ε _Hf = −10.5 to +4.9), and their trace element characteristics match those of Neoproterozoic rocks from the Arabian–Nubian Shield and modern arc rocks, suggesting that the lower crust beneath the Afar Depression contains Neoproterozoic mafic igneous rocks. Ultramafic mantle xenoliths from Assab contain primary assemblages of fresh ol + opx + cpx + sp ± pl, with no alteration or hydrous minerals. They equilibrated at 870–1,040°C and follow a steep geothermal gradient consistent with the tectonic environment of the Afar Depression. The systematic variations in major and trace elements among the Assab mantle xenoliths together with their isotopic compositions suggest that these rocks are not mantle residues but rather series of layered cumulate sills that crystallized from a relatively enriched picritic melt related to the Afar plume that was emplaced before the eruption of the host basalts.  相似文献   

Age constraints on faulting and fault reactivation: a multi-chronological approach   总被引：2，自引：0，他引：2  

Wolfgang Siebel  Horst P. Hann  Martin Danišík  Cosmas K. Shang  Christoph Berthold  Johann Rohrmüller  Klaus Wemmer  Noreen J. Evans 《International Journal of Earth Sciences》2010,99(6):1187-1197

Movement within the Earth’s upper crust is commonly accommodated by faults or shear zones, ranging in scale from micro-displacements to regional tectonic lineaments. Since faults are active on different time scales and can be repeatedly reactivated, their displacement chronology is difficult to reconstruct. This study represents a multi-geochronological approach to unravel the evolution of an intracontinental fault zone locality along the Danube Fault, central Europe. At the investigated fault locality, ancient motion has produced a cataclastic deformation zone in which the cataclastic material was subjected to hydrothermal alteration and K-feldspar was almost completely replaced by illite and other phyllosilicates. Five different geochronological techniques (zircon Pb-evaporation, K–Ar and Rb–Sr illite, apatite fission track and fluorite (U-Th)/He) have been applied to explore the temporal fault activity. The upper time limit for initiation of faulting is constrained by the crystallization age of the primary rock type (known as “Kristallgranit”) at 325 ± 7 Ma, whereas the K–Ar and Rb–Sr ages of two illite fractions <2 μm (266–255 Ma) are interpreted to date fluid infiltration events during the final stage of the cataclastic deformation period. During this time, the “Kristallgranit” was already at or near the Earth’s surface as indicated by the sedimentary record and thermal modelling results of apatite fission track data. (U–Th)/He thermochronology of two single fluorite grains from a fluorite–quartz vein within the fault zone yield Cretaceous ages that clearly postdate their Late-Variscan mineralization age. We propose that later reactivation of the fault caused loss of helium in the fluorites. This assertion is supported by geological evidence, i.e. offsets of Jurassic and Cretaceous sediments along the fault and apatite fission track thermal modelling results are consistent with the prevalence of elevated temperatures (50–80°C) in the fault zone during the Cretaceous.  相似文献   

GGR Biennial Review: Reference Materials in Geoanalytical and Environmental Research – Review for 2008 and 2009     

Klaus Peter Jochum  Jacinta Enzweiler  Regina Mertz-Kraus  Xiaohong Wang 《Geostandards and Geoanalytical Research》2010,34(4):353-385

This review gives an overview of the literature on reference materials of geochemical and environmental interest for the two-year period 2008–2009. Reference materials play an increasingly important role in all fields of geoanalytical research. This is demonstrated by the large number of publications containing data on reference materials. Although many reference materials exist, there is still a great need for certified samples, so-called delta zero materials for stable isotopic work and homogeneous microanalytical reference materials. This review focuses on six topics: developments of certification processes of reference materials mainly postulated in ISO guidelines and the IAG protocol, new developments of the GeoReM database, investigations of powdered rock reference materials, Chinese reference materials published in Chinese journals, microanalytical reference materials and isotopic reference materials.  相似文献   

2002年和2003年夏季波弗特海海冰叶绿素a和小型生物的研究     

张庆  唐学玺  刘子琳  GRADINGER Rolf  MEINERS Klaus 《海洋学报》2007,29(1):170-180

海冰在极地海洋中是个较为独特的生境,海冰卤道系统中的光照强度、温度、盐度和生存空间随着季节更替发生显著变化[1].春天,在北极新冰和多年冰的底部冰藻旺发,随后浮游植物生产力上升[2,3].  相似文献   

A. BEER (Ed.): Vistas in Astronomy. Volume 15. Perganion Press,Oxford, New York,Toronto, Sidney,Braunschweig, 1973. VII + 192 Seiten,Preis E 9.00     

Klaus Frilae 《Astronomische Nachrichten》1975,296(1):46-47

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PATRICK MOORE: The Planet Neptun. Elis Horwood Ltd., Chichester; John Wiley & Sons,New York—Chichester—Brisbane—Toronto, 1988. 144 Seiten,Preis: £ 19,95. ISBN 0-7458-0606     

Klaus Fritze 《Astronomische Nachrichten》1989,310(6):444-444

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S. Böhme et al. (eds.): Astronomy and Astrophysics Abstracs. Volume 34. Literature 1983, Part 2. Published for Astronomi- sches Rechen-Institut by Springer-Verlag,Berlin-Heidelberg- New York-Tokyo. 1984. × + 921 Seitcn,Preis DM 148.-. ISBN 3-540-13485-9. ISBN 0-387-13485-9     

Klaus Frilze 《Astronomische Nachrichten》1985,306(4):261-262

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