Lithium isotope systematics of lavas from the Cook–Austral Islands: Constraints on the origin of HIMU mantle     

Lui-Heung Chan  John C. Lassiter  Erik H. Hauri  Stanley R. Hart  Jerzy Blusztajn 《Earth and Planetary Science Letters》2009,277(3-4):433-442

Radiogenic isotope variations in lavas from the Cook–Austral volcanic chain have delineated three distinct mantle sources: a HIMU component, a depleted component (DM), and an enriched component (EM). To better constrain the mantle sources for South Pacific hot spot volcanism, we determined lithium isotopic compositions of lavas from Raivavae, Rapa, Mangaia and Tubuai of the volcanic chain. The study includes whole rock and mineral analyses. In general, δ⁷Li of most olivines resemble bulk rock composition whereas clinopyroxenes are variably lighter. This implies that clinopyroxene is more susceptible to diffusion-induced fractionation, in agreement with previous studies. Olivine δ⁷Li values span a narrower range than whole rock values, and do not extend to the very heavy compositions previously reported in HIMU bulk lavas. This discrepancy likely reflects alteration of bulk lavas, and suggests that Li-isotope analyses of bulk lavas should be interpreted with caution. Olivines from HIMU lavas have heavy δ⁷Li values (up to 6.2‰), and extend beyond the range reported for fresh MORB. Correlations between Li-isotopes and radiogenic isotopes suggest that the heavy δ⁷Li values in HIMU olivines are a source characteristic and not the result of post-magmatic alteration. Although the Li-isotope composition of recycled, dehydrated oceanic crust is currently under debate, our results suggest that HIMU lavas derive from a source containing recycled dehydrated oceanic crust, and that the “heavy” Li-isotope signature of altered oceanic crust is partially preserved during passage through the subduction factory.  相似文献   

Adaptive Smoothing Method For Computer Derivation of K-Indices     

Krzysztof Nowo&#;y&#;ski  Tomasz Ernst  Jerzy Jankowski 《Geophysical Journal International》1991,104(1):85-93

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Orbit calculations near by the equilibrium points by a discrete mechanics method     

Jerzy Albrycht  Andrzej Marciniak 《Celestial Mechanics and Dynamical Astronomy》1981,24(4):391-405

Basic formulas of discrete mechanics in a rotating frame of references are obtained. Its application to several computer examples of orbits near by the equilibrium points of the Earth-Moon system are presented, and—for computational purposes—an algorithm is given.  相似文献   

Changes of acoustic emission and strain in hard coal during gas sorption–desorption cycles     

Zofia Majewska  Jerzy Zi&#x;tek 《International Journal of Coal Geology》2007,70(4):305-312

The cylindrical coal samples were subjected to three successive cycles of sorption–desorption processes of a single gas (CO₂, CH₄). Acoustic emission (AE) and strains were simultaneously recorded during the sorption and desorption processes.Tests were conducted on medium-rank coal from the Upper Silesia Basin, Poland. Follow-up tests for gas sorption–desorption consistently showed significant changes of AE characteristics for re-runs on the same sample. The AE level decreased in each successive test. The most spectacular differences were observed between AE generated during the first cycle of gas sorption and the subsequent cycle. This phenomenon could be due to structural changes in the coal taking place substantially on its first exposure to the sorbate. The AE results indicate, that each cycle of gas sorption–desorption was run on the same coal though with a somewhat different structure.In those tests, the swelling of coal by CO₂ or/and CH₄ was anisotropic (greater in the direction perpendicular to the bedding plane than parallel) in each cycle of the gas sorption–desorption process.  相似文献   

The Permian–Triassic boundary in the Central European Basin: magnetostratigraphic constraints     

Jerzy Nawrocki 《地学学报》2004,16(3):139-145

Some stratigraphic interpretations concerning correlation of the Permian–Triasssic transition beds from the Central European, Boreal and Tethyan Basins are inconsistent with the existing magnetostratigraphic data. In addition, the suggestion that the Permian–Triassic boundary is located in the lower part of the Calvörde Formation of the Central European Basin cannot be supported by magnetostratigraphic data. Results of magnetostratigraphic correlation show that in the Polish part of the Central European Basin the Permian–Triassic boundary is close to the boundary between the uppermost Zechstein and the Lower Buntsandstein. It is located within the reversed magnetozone ‘PZr1’ identified in the upper part of the Rewal Formation. In the German part of the Central European Basin the Permian–Triassic boundary can be located within the reversed magnetozone ‘zrz’ that covers most of the Bröckelschiefer. A higher stratigraphic location of this boundatry, i.e. inside the lowermost Buntsandstein, requires a reversed polarity record to be found within the basal Triassic normal polarity zone.  相似文献   

Poland's maritime economy in the-post WW II period     

Professor Dr. Jerzy Zaleski 《GeoJournal》1978,2(2):179-190

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A cloud model of active galactic nuclei: the iron Kα line diagnostics     

V. Karas  B. Czerny  A. Abrassart  M. A. Abramowicz 《Monthly notices of the Royal Astronomical Society》2000,318(2):547-560

The origin and the profile of the iron K α line from active galactic nuclei are studied. The model with a quasi-spherical distribution of clouds around a compact galactic nucleus is explored, in which the intrinsic spectral feature around 6–7 keV is substantially affected by Comptonization of primary X-rays. The predicted spectral profiles are influenced mainly by the motion of the clouds in the strong gravitational field of the centre, and by the orientation of the source with respect to the observer. The case of the Seyfert galaxy MCG–6-30-15 is examined in more detail and free parameters of the model are determined. A robust result is obtained: acceptable fits to the observed profile correspond to a spherical distribution of the clouds with strong self-obscuration effects and with a rather high value of ionization parameter. This is a different situation from that considered in the model of a cold illuminated disc. Nevertheless, geometrically flat (disc-type) configurations are not rejected.  相似文献   

Detached eclipsing binaries: analysis of BD–00° 3357     

W. Dimitrov  D. Kolev  P. Lig&#x;za  A. Schwarzenberg‐Czerny 《Astronomische Nachrichten》2006,327(9):899-904

Detached eclipsing binaries constitute potential accurate distance tracers. They are also useful as the test bench of stellar evolution. In BD–00° 3357 eclipses are partial and its orbital period is 1.^d4. Our combined spectroscopic and photometric solution yields secure parameters of this system. The model of the star was obtained using the Wilson‐Devinney method. As result we obtained a semi major axis of 7.65 R_⊙ and a mass ratio of 0.78. The derived masses and radii are M ₁ = 1.73 M_⊙,M ₂ = 1.34 M_⊙R ₁ = 1.78 R_⊙, R ₂ = 1.32 R_⊙, respectively. These values correspond to the slightly evolved F0 and F6.5 components, both slightly less than 1Gyr old. The distance of the star was estimated to be 310 ± 60 pc, and the corresponding photometric parallax is 3.24 ± 0.74 mas. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Magnetic flares in Active Galactic Nuclei: modeling the iron Kα line     

R. W. Goosmann  B. Czerny  M. Mouchet  V. Karas  M. Dov iak  G. Ponti  A. Ra&#x;ska  A.‐M. Dumont 《Astronomische Nachrichten》2006,327(10):977-980

The X‐ray spectra of Active Galactic Nuclei (AGN) are complex and vary rapidly in time as seen in recent observations. Magnetic flares above the accretion disk can account for the extreme variability of AGN. They also explain the observed iron Kα fluorescence lines. We present radiative transfer modeling of the X‐ray reflection due to emission from magnetic flares close to the marginally stable orbit. The hard X‐ray primary radiation coming from the flare source illuminates the accretion disk. A Compton reflection/reprocessed component coming from the disk surface is computed for different emission directions. We assume that the density structure remains adjusted to the hydrostatic equilibrium without external illumination because the flare duration is only a quarter‐orbit. The model takes into account the variations of the incident radiation across the hot spot underneath the flare source. The integrated spectrum seen by a distant observer is computed for flares at different orbital phases close to the marginally stable orbit of a Schwarzschild black hole and of a maximally rotating Kerr black hole. The calculations include relativistic and Doppler corrections of the spectra using a ray tracing technique. We explore the practical possibilities to map out the azimuthal irradiation pattern of the inner accretion disks and conclude that the next generation of X‐ray satellites should reveal this structure from iron Kα line profiles and X‐ray lightcurves. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

A deglaciation model of the Oberhasli,Switzerland          下载免费PDF全文

Christian Wirsig  Jerzy Zasadni  Susan Ivy‐Ochs  Marcus Christl  Florian Kober  Christian Schlüchter 《第四纪科学杂志》2016,31(1):46-59

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