排序方式: 共有31条查询结果,搜索用时 15 毫秒
11.
Guillermo Gonzalez Chris Laws 《Monthly notices of the Royal Astronomical Society》2007,378(3):1141-1152
We present the results of detailed spectroscopic abundance analyses for 18 elements in 31 nearby stars with planets (SWPs). The resulting abundances are combined with other similar studies of nearby SWPs and compared to a sample of nearby stars without detected planets. We find some evidence for abundance differences between these two samples for Al, Si and Ti. Some of our results are in conflict with a recent study of SWPs in the SPOCS data base. We encourage continued study of the abundance patterns of SWPs to resolve these discrepancies. 相似文献
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A. C. Becker E. Agol N. M. Silvestri J. J. Bochanski C. Laws A. A. West G. Basri V. Belokurov D. M. Bramich J. M. Carpenter P. Challis K. R. Covey R. M. Cutri N. W. Evans M. Fellhauer A. Garg G. Gilmore P. Hewett P. Plavchan D. P. Schneider C. L. Slesnick S. Vidrih L. M. Walkowicz D. B. Zucker 《Monthly notices of the Royal Astronomical Society》2008,386(1):416-424
We report on Two-Micron All-Sky Survey (2MASS) J01542930+0053266, a faint eclipsing system composed of two M dwarfs. The variability of this system was originally discovered during a pilot study of the 2MASS Calibration Point Source Working Data base. Additional photometry from the Sloan Digital Sky Survey yields an eight-passband light curve from which we derive an orbital period of 2.639 0157 ± 0.000 0016 d. Spectroscopic followup confirms our photometric classification of the system, which is likely composed of M0 and M1 dwarfs. Radial velocity measurements allow us to derive the masses (M1 = 0.66 ± 0.03 M⊙ ; M2 = 0.62 ± 0.03 M⊙ ) and radii (R1 = 0.64 ± 0.08 R⊙ ; R2 = 0.61 ± 0.09 R⊙ ) of the components, which are consistent with empirical mass–radius relationships for low-mass stars in binary systems. We perform Monte Carlo simulations of the light curves which allow us to uncover complicated degeneracies between the system parameters. Both stars show evidence of Hα emission, something not common in early-type M dwarfs. This suggests that binarity may influence the magnetic activity properties of low-mass stars; activity in the binary may persist long after the dynamos in their isolated counterparts have decayed, yielding a new potential foreground of flaring activity for next generation variability surveys. 相似文献
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Pyritization of trace metals in estuarine sediments and the controlling factors: a case in Jiaojiang Estuary of Zhejiang Province,China 总被引:1,自引:0,他引:1
Siyuan Ye Edward A. Laws Qiang Wu Shaojun Zhong Xigui Ding Guangming Zhao Shaojun Gong 《Environmental Earth Sciences》2010,61(5):973-982
Three undisturbed sediment samples were collected from the intertidal zone of the Jiaojiang Estuary of Zhejiang Province,
China. The sediments were found to contain remarkably low concentrations of organic carbon (<0.6%) and acid volatile sulfide
(AVS) (<30 μmol g−1). The availability of these two substrates likely constrained sulfate reduction and pyritization of several trace metals,
respectively. This was especially true at one station where AVS concentrations in the upper 20 cm averaged less than 0.05 μmol g−1. Although the depth dependence of the degree of trace metal pyritization was generally consistent with expectations based
on redox conditions, depth profiles of reactive-metal and pyrite-metal concentrations in several cases revealed more complex
behavior and a positive correlation between reactive-metal concentrations and pore water metal concentrations. 相似文献
14.
A general mathematical model of balanced global isostasy is presented that describes the geometrical relationships among atmospheric, oceanic, lithospheric, and asthenospheric components relative to a fixed, external frame of reference in terms of 19 parameters of mass, density, area, and thickness in five basic equations and various corollaries. The model is applicable and necessary for evaluating lithospheric processes that operate on a global scale or that affect globally oriented parameters such as sea level, freeboard, and ocean basin depth. It also provides a means of testing the internal consistency of a given set of mass, density, volume, and area parameters relative to present crustal geometry by showing how well they combine to predict present continental free-board. With modification, the basic model can be used to examine more complex questions involving glacially induced sea level fluctuations and long-term crustal evolution resulting from differential energy flux to Earth, short-term modulation of heat flux from the asthenosphere, and long-term monotonic cooling. 相似文献
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Johan O. A. Robertsson Robert Laws Chris Chapman Jean-Pierre Vilotte Elise Delavaud 《Geophysical Journal International》2006,167(1):70-76
We compare three numerical methods to model the sea surface interaction in a marine seismic reflection experiment (the frequencies considered are in the band 10–100 Hz): the finite-difference method (FDM), the spectral element method (SEM) and the Kirchhoff method (KM). A plane wave is incident at angles of 0° and 30° with respect to the vertical on a rough Pierson–Moskowitz surface with 2 m significant wave height and the response is synthesized at 6, 10 and 50 m below the average height of the sea surface. All three methods display an excellent agreement for the main reflected arrival. The FDM and SEM also agree very well all through the scattered coda. The KM shows some discrepancies, particularly in terms of amplitudes. 相似文献
17.
Characterization of errors in vector wind retrievals from satellite-based polarimetric microwave radiometer measurements 总被引:2,自引:0,他引:2
Laws K.E. Lyzenga D.R. Wiberg D.M. Vesecky J.F. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(1):45-48
We present a method for evaluating characteristics of wind vector retrieval errors from polarimetric radiometer measurements. We focus on wind direction errors due to ambiguous solutions. 相似文献
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为研究辽河三角洲湿地的固碳能力,2010年5月在辽河三角洲双台子河口东侧的两个翅碱蓬湿地区域采取7个柱状样,通过对样品的化学分析测试,并利用210Pb测年法确定的沉积速率研究了土壤对碳的扣留速率,其结果表明:有机碳浓度分别与各营养元素浓度间有显著的正相关关系(p0.01),指示沉积物中的有机物质对营养元素有很强的富集能力,同时营养元素促进植物的生长,从而影响土壤碳的加积速率。研究区总碳浓度范围为10.5~14.6 g/kg,其中约83%为有机碳,其相应的土壤对总碳和有机碳扣留速率分别为98.02~260.37 g/m2/a(均值171.84 g/m2/a)和81.17~229.98 g/m2/a(均值141.29 g/m2/a)。本研究区,土壤对碳的扣留速率主要受土壤的沉积速率控制,并与高程有显著的相关关系(p0.01)。土壤对碳扣留机制的研究有助于加深对全球碳循的理解。 相似文献
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