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Larisa A. Yakovina Yakiv V. Pavlenko Carlos Abia 《Astrophysics and Space Science》2003,288(3):279-286
Lithium abundances in the atmospheres of the super Li-rich C-giants WZ Cas and WX Cyg are derived by the spectral synthesis
technique using the Li I resonance line at λ670.8 nm and three subordinate lines at λλ 812.6, 610.4 and 497.2 nm. The differences
between the Li abundances derived from the λ670.8 nm line and the λλ 497.2, 812.6 nm lines do not exceed ±0.5 dex. The lithium
line at λ610.4 nm provides typically lower abundances than the resonance line (by ≈ 1 dex). The mean LTE and NLTE Li abundances
from three Li I lines (excluding λ610.4 nm) are 4.7, 4.9 for WZ Cas, and 4.6, 4.8 for WX Cyg, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
43.
韩玲 《地球科学与环境学报》2003,25(1):74-75
提出了一种基于格网DEM的粗差检测及剔除方法,其基本思想是对每个表面上的点,在坡度上,高程或突变量引起的形状不连续,可能被怀疑有误差,通过坡度上每个点,应用坡度逼近或改变量来计算,考虑坡度变化的相对值,并以这些相对值计算一个统计值为判断该点合法性的阈值,使计算结果更为可靠。 相似文献
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The Cycladic blueschist belt in the central Aegean Sea has experienced high‐pressure (HP) metamorphism during collisional processes between the Apulian microplate and Eurasia. The general geological and tectonometamorphic framework is well documented, but one aspect which is yet not sufficiently explored is the importance of HP mélanges which occur within volcano‐sedimentary successions. Unresolved issues concern the range in magmatic and metamorphic ages recorded by mélange blocks and the significance of eventual pre‐Eocene HP metamorphism. These aspects are here addressed in a U‐Pb zircon study focusing on the block–matrix association exposed on the island of Syros. Two gneisses from a tectonic slab of this mélange, consisting of an interlayered felsic gneiss‐glaucophanite sequence, yielded zircon 206Pb/238U ages of 240.1 ± 4.1 and 245.3 ± 4.9 Ma, respectively, similar to Triassic ages determined on zircon in meta‐volcanic rocks from structurally coherent sequences elsewhere in the Cyclades. This strongly suggests that parts of these successions have been incorporated in the mélanges and provides the first geochronological evidence that the provenance of mélange blocks/slabs is neither restricted to a single source nor confined to fragments of oceanic lithosphere. Zircon from a jadeitite and associated alteration zones (omphacitite, glaucophanite and chlorite‐actinolite rock) all yielded identical 206Pb/238U ages of c. 80 Ma. Similar Cretaceous U‐Pb zircon ages previously reported for mélange blocks have been interpreted by different authors to reflect magmatic or metamorphic ages. The present study adds a further argument in favour of the view that zircon formed newly in some rock types at c. 80 Ma, due to hydrothermal or metasomatic processes in a subduction zone environment, and supports the interpretation that the Cycladic blueschist belt records both Cretaceous and Eocene HP episodes and not only a single Tertiary HP event. 相似文献
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We consider the effects of projection, internal absorption, and gas-or stellar-velocity dispersion on the measured rotation curves of galaxies with edge-on disks. Axisymmetric disk models clearly show that the rotational velocity in the inner galaxy is highly underestimated. As a result, an extended portion that imitates nearly rigid rotation appears. At galactocentric distances where the absorption is low (i.e., it does not exceed 0.3–0.5m kpc?1), the line profiles can have two peaks, and a rotation curve with minimum distortions can be obtained by estimating the position of the peak that corresponds to a higher rotational velocity. However, the high-velocity peak disappears in high-absorption regions and the actual shape of the rotation curve cannot be reproduced from line-of-sight velocity estimates. In general, the optical rotation curves for edge-on galaxies are of little use in reconstructing the mass distribution in the inner regions, particularly for galaxies with a steep velocity gradient in the central region. In this case, estimating the rotation velocities for outer (transparent) disk regions yields correct results. 相似文献
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DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHEHEXIREGION,CHINA肖洪浪,高前兆,李福兴DEVELOPMENTSTRATEGIESOFWATERANDLANDRESOURCESINTHE... 相似文献