N-body models of rotating globular clusters     

A. Ernst  P. Glaschke  J. Fiestas  A. Just  R. Spurzem 《Monthly notices of the Royal Astronomical Society》2007,377(2):465-479

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Thixotropie und Fließeigenschaften feinkörniger Böden     

Ernst Ackermann 《International Journal of Earth Sciences》1948,36(1):10-29

Ohne ZusammenfassungVortrag auf der Mitgliederversammlung der Geologischen Vereinigung April 1947. - Manuskript erhalten Frühjahr 1947. Die Schriftleitung.  相似文献   

A New Ectasian Event of Basitic Magmatism in the Southern Siberian Craton     

Gladkochub  D. P.  Donskaya  T. V.  Ernst  R. E.  Hamilton  M. A.  Mazukabzov  A. M.  Pisarevsky  S. A.  Kamo  S. 《Doklady Earth Sciences》2019,486(1):507-511

Doklady Earth Sciences - On the basis of U–Pb dating of zircon and baddeleyite from gabbro–dolerite of the Goloustnaya dyke swarm (southern margin of the Siberian Craton), the age of...  相似文献   

Pressure-dependent Production Efficiency of an Enhanced Geothermal System (EGS): Stimulation Results and Implications for Hydraulic Fracture Treatments     

Günter Zimmermann  Torsten Tischner  Björn Legarth  Ernst Huenges 《Pure and Applied Geophysics》2009,166(5-7):1089-1106

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Seismicity in the outer rise offshore southern Chile: Indication of fluid effects in crust and mantle   总被引：1，自引：0，他引：1  

Frederik J. Tilmann  Ingo Grevemeyer  Ernst R. Flueh  Torsten Dahm  Jürgen Goßler 《Earth and Planetary Science Letters》2008,269(1-2):41-55

We examine the micro-earthquake seismicity recorded by two temporary arrays of ocean bottom seismometers on the outer rise offshore southern Chile on young oceanic plate of ages 14 Ma and 6 Ma, respectively. The arrays were in operation from December 2004–January 2005 and consisted of 17 instruments and 12 instruments, respectively. Approximately 10 locatable events per day were recorded by each of the arrays. The catalogue, which is complete for magnitudes above 1.2–1.5, is characterized by a high b value, i.e., a high ratio of small to large events, and the data set is remarkable in that a large proportion of the events form clusters whose members show a high degree of waveform similarity. The largest cluster thus identified consisted of 27 similar events (average inter-event correlation coefficient > 0.8 for a 9.5 s window), and waveform similarity persists far into the coda. Inter-event spacing is irregular, but very short waiting times of a few minutes are far more common than expected from a Poisson distribution. Seismicity with these features (high b value, large number of similar events with short waiting times) is typical of swarm activity, which, based on empirical evidence and theoretical considerations, is generally thought to be driven by fluid pressure variations. Because no pronounced outer rise bulge exists on the very young plate in the study region, it is unlikely that melt is accessible from decompression melting or opening of cracks. A fluid source related to processes at the nearby ridge is conceivable for the younger segment but less likely for the older one. We infer that the fluid source could be seawater, which enters through fractures in the crust. Most of the similar-earthquake clusters are within the crust, but some of them locate significantly below the Moho. If our interpretation is correct, this implies that water is present within the mantle. Hydration of the mantle is also indicated by a decrease of P_n velocities below the outer rise seen on a refraction profile through one of the arrays [Contreras-Reyes, E., Grevemeyer, I., Flueh, E.R., Scherwath, M., Heesemann, M., 2007. Alteration of the subducting oceanic lithosphere at the southern central Chile trench-outer rise. Geochem., Geophys. Geosyst. 8, Q07003.]. The deepest events within the array on the 6 Ma old plate occur where the temperature reaches 500–600 °C, consistent with the value observed for large intraplate earthquakes within the mantle (650 °C), suggesting that the maximum temperature at which these fluid-mediated micro-earthquakes can occur is similar or identical to that of large earthquakes.  相似文献   

Microseismicity induced during fluid-injection: A case study from the geothermal site at Groß Schönebeck,North German Basin   总被引：1，自引：1，他引：0  

Grzegorz Kwiatek  Marco Bohnhoff  Georg Dresen  Ali Schulze  Thomas Schulte  Günter Zimmermann  Ernst Huenges 《Acta Geophysica》2010,58(6):995-1020

The technical feasibility of geothermal power production in a low enthalpy environment will be investigated in the geothermal site at Groß Schönebeck, North German Basin, where a borehole doublet was completed in 2007. In order to complete the Enhanced Geothermal System, three massive hydraulic stimulations were performed. A seismic network was deployed including a single 3-component downhole seismic sensor at only 500 m distance to the injection point. Injection rates reached up to 9 m³/min and the maximum injection well-head pressure was as high as ～60 MPa. A total of 80 very small (?1.8 < M _W < ?1.0) induced seismic events were detected. The hypocenters were determined for 29 events. The events show a strong spatial and temporal clustering and a maximum seismicity rate of 22 events per day. Spectral parameters were estimated from the downhole seismometer and related to those from other types of induced seismicity. The majority of events occurred towards the end of stimulation phases indicating a similar behavior as observed at similar treatments in crystalline environments but in our case at a smaller level of seismic activity and at lower magnitudes.  相似文献   

Elektronenmikroskopische Untersuchung von Nadeleisenerzooiden in Pulverpräparaten und Dünnschnitten     

Prof. Dr. Otto Ernst Radczewski  Dr. Paula Schneiderhöhn 《Contributions to Mineralogy and Petrology》1962,8(5):349-353

Zusammenfassung Elektronenmikroskopische Untersuchungen isolierter Nadeleisenerzooide in Ultradünnschnitten und Pulverpräparaten zeigen; daß das Nadeleisenerz hier in Form sechsseitiger rhombischer Blättchen (Durchmesser in der Größenordnung von 100–300 Å) vorliegt. Dünnschnittbilder lassen eine lageweise Anordnung der Blättchen im Ooid erkennen.  相似文献   

Trace-element concentrations in single circumstellar silicon carbide grains from the Murchison meteorite     

Sachiko Amari  Peter Hoppe  Ernst Zinner  Roy S. Lewis 《Meteoritics & planetary science》1995,30(6):679-693

Abstract— Concentrations of the trace elements Mg, Al, Ca, Ti, V, Fe, Sr, Y, Zr, Ba and Ce were determined by ion microprobe mass spectrometry in 60 individual silicon carbide (SiC) grains (in addition, Nb and Nd were determined in 20 of them), from separate KJH (size range 3.4–5.9 μm) of the Murchison carbonaceous meteorite, whose C-, N- and Si-isotopic compositions have been measured before (Hoppe et al., 1994) and provide evidence that these grains are of stellar origin. The selected SiC grains represent all previously recognized subgroups: mainstream (20 < ¹²C/¹³C < 120; 200 < ¹⁴N/¹⁵N; Si isotopes on slope 1.34 line), grains A (¹²C/¹³C < 3.5), grains B (3.5 < ¹²C/¹³C < 10), grains X (¹⁵N excesses, large ²⁸Si excesses) and grains Y (150 < ¹²C/¹³C < 260; Si isotopes on slope 0.35 line). Data on these grains are compared with measurements on fine-grained SiC fractions. Trace-element patterns reflect both the condensation behavior of individual elements and the source composition of the stellar atmospheres. A detailed discussion of the condensation of trace elements in SiC from C-rich stellar atmospheres is given in a companion paper by Lodders and Fegley (1995). Elements such as Mg, Al, Ca, Fe and Sr are depleted because their compounds are more volatile than SiC. Elements whose compounds are believed to be more refractory than SiC can also be depleted due to condensation and removal prior to SiC condensation. Among the refractory elements, however, the heavy elements from Y to Ce (and Nd) are systematically enriched relative to Ti and V, indicating enrichments by up to a factor of 14 of the s-process elements relative to elements lighter than Fe. Such enrichments are expected if N-type carbon stars (thermally pulsing AGB stars) are the main source of circumstellar SiC grains. Large grains are less enriched than small grains, possibly because they are from different AGB stars. The trace-element patterns of subgroups such as groups A and B and grains X can at least qualitatively be understood if grains A and B come from J-type carbon stars (known to be lacking in s-process enhancements shown by N-type carbon stars) or carbon stars that had not experienced much dredge-up of He-shell material and if grains X come from supernovae. However, a remaining puzzle is how stars become carbon stars without much accompanying dredge-up of s-process elements.  相似文献   

Comets and the formation of planets     

Ernst J. Öpik 《Astrophysics and Space Science》1973,21(2):307-398

A morphological study of the physical and dynamical processes of planet formation is presented, with emphasis on the intermediary role of comet nuclei. Although guided by a particular model of the evolution of the pre-planetary solar nebula, implying the freezing-out of hydrogen in the region of the giant planets, the derivations and conclusions are of wider import, applicable to other cosmogonic models as well as to certain phases of star formation. The items evaluated physically, dynamically, or statistically comprise: (1) the total number mass of comets in Oort's cloud; (2) a re-evaluation of the diameters and masses of cometary nuclei; (3) the processes of nucleation from gravitational and Boltzmann instabilities of gaseous media to agglomerations of particulate matter as conditioned by inbuilt angular momentum; (4) the statistical-dynamical conditions and time scales of orbital interaction of comets with the planets and the consequences of disintegration.A consistent model proposes the formation of comets and planets in pre-planetary rings of the residual solar nebula, with subsequent ejection, chiefly by Jupiter, of the comets to Oort's sphere. Screening by absorbing matter is not only probable, but necessary to protect the comets from dis-integration during the process of ejection.Paper dedicated to Prof. H. C. Urey on the occasion of his 80th birthday on 29 April, 1973.This work has been currently supported by grants from the National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland.  相似文献   

Direkte Berechnung der Ionenradien in Alkalihalogeniden aus der Lichtbrechung bzw. Molrefraktion und dem Ionenabstand     

Ernst Kordes 《Mineralogy and Petrology》1962,8(1):13-23

Zusammenfassung Es wird gezeigt, daß man allein aus der Lichtbrechung und dem Ionenabstand (bzw. über die Molrefraktion) die Ionenradien in Alkalihalogeniden berechnen kann, ohne daß hierzu die Kenntnis irgendeines Ionenradius erforderlich ist. Die neu angegebenen Gleichungen enthalten nur physikalisch eindeutig definierte Größen und keinerlei empirische Konstanten.Die vermittels dieser Gleichungen aus Salzpaaren von Alkalihalogeniden mit gemeinsamem Anion aus Ionenabstand und Lichtbrechung berechneten Ionenradien stimmen gut mit den vonV. M. Goldschmidt subtraktiv (mit r=1·33 Å für F^–) order vonL. Pauling halbtheoretisch erhaltenen Ionenradien überein.Herrn Prof.K. H. Scheumann zum 80. Geburtstag gewidmet.  相似文献