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991.
T. Eisenbeiss M. Moualla M. Mugrauer T.O.B. Schmidt St. Raetz R. Neuhuser Ch. Ginski M.M. Hohle A. Koeltzsch C. Marka W. Rammo A. Reithe T. Roell M. Vako 《Astronomische Nachrichten》2009,330(5):439-458
We have performed deep, wide‐field imaging on a ∼0.4 deg2 field in the Pleiades (Melotte 22). The selected field was not yet target of a deep search for low mass stars and brown dwarfs. Our limiting magnitudes are R ∼ 22 mag and I ∼ 20 mag, sufficient to detect brown dwarf candidates down to 40 MJ. We found 197 objects, whose location in the (I, R – I) color magnitude diagram is consistent with the age and the distance of the Pleiades. Using CTK R and I as well as JHK photometry from our data and the 2MASS survey we were able to identify 7 new brown dwarf candidates. We present our data reduction technique, which enables us to resample, calibrate, and co‐add many images by just two steps. We estimate the interstellar extinction and the spectral type from our optical and the NIR data using a two‐dimensional χ2 fitting (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
St. Raetz M. Mugrauer T.O.B. Schmidt T. Roell T. Eisenbeiss M.M. Hohle N. Tetzlaff M. Vako A. Seifahrt Ch. Broeg J. Koppenhoefer R. Neuhuser 《Astronomische Nachrichten》2009,330(5):475-481
We report on observations of transit events of the transiting planets XO‐1b and TrES‐1 with a 25 cm telescope of the University Observatory Jena. With the transit timings for XO‐1b from all 50 available XO, SuperWASP, Transit Light Curve (TLC)‐Project‐ and Exoplanet Transit Database (ETD)‐data, including our own I ‐band photometry obtained in March 2007, we find that the orbital period is P = (3.941501 ± 0.000001) d, a slight change by ∼3 s compared to the previously published period. We present new ephemeris for this transiting planet. Furthermore, we present new R ‐band photometry of two transits of TrES‐1. With the help of all available transit times from literature this allows us to refine the estimate of the orbital period: P = (3.0300722 ± 0.0000002) d. Our observations will be useful for future investigations of timing variations caused by additional perturbing planets and/or stellar spots and/or moons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
993.
Jeremy R. Davies Richard A. Waters Mark Williams David Wilson David I. Schofield Jan A. Zalasiewicz 《Geological Journal》2009,44(3):322-340
The discovery of a previously unrecognized unconformity and of new faunas in the type Llandovery area underpins a revised correlation of Hirnantian strata in mid Wales. This has revealed the sedimentary and faunal events which affected the Lower Palaeozoic Welsh Basin during the global rise in sea level that followed the end‐Ordovician glacial maximum and has allowed their interpretation in the context of local and global influences. In peri‐basinal shelfal settings the onset of post‐glacial deepening is recorded by an unfossiliferous, transgressive shoreface sequence (Cwm Clyd Sandstone and Garth House formations) which rests unconformably on Rawtheyan rocks, deformed during an episode of pre‐Hirnantian tectonism. In the deep water facies of the basin centre, this same sequence boundary is now recognized as the contact between fine‐grained, re‐sedimented mudstones and an underlying regressive sequence of turbidite sandstones and conglomerates; it is at a level lower than previously cited and calls into question the established lithostratigraphy. In younger Hirnantian strata, graptolites associated with the newly recognized Ystradwalter Member (Chwefri Formation) demonstrate that this distal shelf unit correlates with the persculptus graptolite‐bearing Mottled Mudstone Member of the basinal succession. Together these members record an important macrofaunal recolonization of the Welsh Basin and mark a key event in the post‐glacial transgression. Further deepening saw the establishment of a stratified water column and the imposition of anoxic bottom water conditions across the basin floor. These post‐glacial Hirnantian events are consistent with the re‐establishment of connections between a silled Welsh Basin and the open Iapetus Ocean. However, a comparison with other areas suggests that each event records a separate deepening episode within a pulsed glacio‐eustatic transgression, while also reflecting changes in post‐glacial climate and patterns of oceanic circulation and associated biotic flux. British Geological Survey © NERC 2009. All rights reserved. 相似文献
994.
John Finn 《GeoJournal》2009,74(3):191-200
After more than three decades of isolation from the West and a paralyzing economic crisis in the early 1990s, Cuba is increasingly
globally active in both cultural and economic realms. In this paper I use Bourdieu’s (The fields of cultural production, 1993)
fields of cultural production as a general frame through with to inspect the commercialization of Cuban music. Through a case
study with Juan de Marcos Gonzalez, the creator of the Buena Vista Social Club, I explore the dialectical relationship of
music as an expression of cultural and a cultural asset, and at the same time a commodity for the international market. I
show that de Marcos uses his position between the international music industry and the local music scene in order to preserve
cultural authenticity and survive economically. In doing so he challenges the all-to-typical place of the artist in the contested
space of cultural production between the West and the Third World.
相似文献
John FinnEmail: |
995.
What are the origins of the soft X‐ray line emission from non‐AGN galaxies? XMM‐Newton RGS spectra of nearby non‐AGN galaxies (including starforming ones: M82, NGC 253, M51, M83, M61, NGC 4631, M94, NGC 2903, and the Antennae galaxies, as well as the inner bulge of M31) have been analyzed. In particular, the Kα triplet of O VII shows that the resonance line is typically weaker than the forbidden and/or inter‐combination lines. This suggests that a substantial fraction of the emission may not arise directly from optically thin thermal plasma, as commonly assumed, and may instead originate at its interface with neutral gas via charge exchange. This latter origin naturally explains the observed spatial correlation of the emission with various tracers of cool gas in some of the galaxies. However, alternative scenarios, such as the resonance scattering by the plasma and the relic photo‐ionization by AGNs in the recent past, cannot be ruled out, at least in some cases, and are being examined. Such X‐ray spectroscopic studies are important to the understanding of the relationship of the emission to various high‐energy feedback processes in galaxies (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
996.
R. Lallement 《Astronomische Nachrichten》2012,333(4):347-350
Charge‐transfer (CT) X‐ray emission may occur at interfaces between a partially neutral gas and gas possessing high ions, provided there is a relative motion between those two phases. The CTX surface brightness from distant objects must be taken into account if it is not far below other “classical” emission sources, especially the thermal emission from the hot phase. I discuss those conditions and potential spectroscopic or photometric diagnostics. I also mention potential indirect effects of the CT reactions by means of pickup ion production, acceleration and subsequent modification of interface and plasma properties (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
997.
998.
对二十四史及《清史稿》帝纪和天文志中的全部天象记录进行了整理和计算验证,发现其中历日朔闰与陈垣《二十史朔闰表》不合27例。汇集这样的例证,对于恢复中国古代完整的实行历表,是至关重要的。 相似文献
999.
Pouria Kourehpaz Carlos Molina Hutt Nasser A. Marafi Jeffrey W. Berman Marc O. Eberhard 《地震工程与结构动力学》2021,50(1):26-42
Studies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the intensity of earthquake ground motions within a period range of approximately 1–4 s, but the economic impacts of basin effects are uncertain. This paper estimates key economic indicators of seismic performance, expressed in terms of earthquake‐induced repair costs, using empirical and simulated seismic hazard characterizations that account for the effects of basins. The methodology used is general, but the estimates are made for a series of eight‐ to 24‐story residential reinforced concrete shear wall archetype buildings in Seattle, WA, whose design neglects basin effects. All buildings are designed to comply with code‐minimum requirements (i.e., reference archetypes), as well as a series of design enhancements, which include (a) increasing design forces, (b) decreasing drift limits, and (c) a combination of these strategies. As an additional reference point, a performance‐based design is also assessed. The performance of the archetype buildings is evaluated for the seismic hazard level in Seattle according to the 2018 National Seismic Hazard Model (2018 NSHM), which explicitly considers basin effects. Inclusion of basin effects results in an average threefold increase in annualized losses for all archetypes. Incorporating physics‐based ground motion simulations to represent the large‐magnitude Cascadia subduction interface earthquake contribution to the hazard results in a further increase of 22% relative to the 2018 NSHM. The most effective of the design strategies considered combines a 25% increase in strength with a reduction in drift limits to 1.5%. 相似文献
1000.
中国历史大疫的时空分布及其规律研究 总被引:8,自引:0,他引:8
文章从甲骨文、二十五史、十三经、古医书、笔记和杂录、地方志、类书中,获取了中国历史大疫385条(公元前13世纪至1911年)。进而,对385奈疫情的烈度进行定量分级,分析中国历史大疫的时间分布、空间分布,并提出了一些规律性见解:在历史上中国是大疫频繁发生的国家;3000多年大疫史上有两个活跃期(公元2~3世纪、16~19世纪),且有愈后愈多之势,从百年一遇,到数十年一遇、数年一遇;东部多,西部少,以长江中下游和黄河中下游地区为最甚;存在着灾害链,有旱—疫、涝—疫、饥—疫等10多种灾害链。 相似文献