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1.
In the five last years, different structures (density excess 1) have been proposed as the direct cause of our infall toward the direction of Hydra—Centaurus with a velocity of 500 km s–1. The direct effect of the mentioned matter accumulations on the X-ray background (XRB) can be estimated as a function of the geometry of the structures and of the cosmological evolution of the sources emitting in the X-ray band (2–10 keV) for different universes (01). If the XRB comes mostly from AGNs with low luminosity (L
X
<1043 erg s–1 and, therefore, they will have a weak cosmological evolution) and we consider the difference between the intensities coming from both hemispheres (that oriented toward the direction of our motion and the opposite one) obtained by means of different satellites, we can conclude that some candidates are highly unlikely.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain 相似文献
2.
New classes of bulk carriers and general cargo vessels are becoming more specialized and larger. The trend towards containerizing cargo has spurred construction of the large cellular containership, the roll-on/roll-off vessel, and the barge carrying ship (LASH). Bulk vessels, especially tankers, have undergone tremendous increases in size until few of the newer ones can pass through the Suez Canal. Crews have not increased primarily because of greater use of shipboard automation devices. Few ports have sufficient water depths to accommodate supertankers, necessitating more off-loading at sea and construction of new deep water terminals. Japanese yards dominate world supership construction, with Scandinavian shipyards most important in Europe. Substantial supership construction is taking place in southern Europe and is an indication of the recent economic growth of Italy, Spain and Yugoslavia. Supership construction in Great Britain has declined relative to Scandinavian and Japanese production and that in the United States is of little significance worldwide. 相似文献
3.
Gravitationally lensed QSOs (GLQs) at 1≤z≤2 play a key role in understanding the cosmic evolution of the innermost parts of active galaxies (black holes, accretion
disks, coronas and internal jets), as well as the structure of galaxies at intermediate redshifts. With respect to studies
of normal QSOs, GLQ programmes have several advantages. For example, a monitoring of GLQs may lead to unambiguous detections
of intrinsic and extrinsic variations. Both kinds of variations can be used to discuss central engines in distant QSOs, and
mass distributions and compositions of lensing galaxies. In this context, UV data are of particular interest, since they correspond
to emissions from the immediate surroundings of the supermassive black hole. We describe some observation strategies to analyse
optically bright GLQs at z∼1.5, using ISSIS (CfS) on board World Space Observatory-Ultraviolet. 相似文献
4.
新疆希勒库都克铜钼矿区岩浆混合作用: 来自锆石U-Pb年代学的证据 总被引：7，自引：6，他引：1
新疆北部富蕴县内希勒库都克铜钼矿区的花岗闪长岩及其包体岩相学、矿物化学和岩石地球化学特征及野外地质特征显示其为岩浆混合作用的结果。本文获得花岗闪长岩及其中暗色微粒包体玄武安山玢岩、细粒辉长闪长岩锆石U-Pb年龄为326.8±2.1Ma、327.6±2.4Ma、329.3±2.3Ma,年龄值基本一致,这一结果从年代学角度为花岗闪长岩及其中暗色微粒包体的岩浆混合作用成因提供证据。偏酸性的花岗闪长质与偏基性玄武安山质岩浆混合作用形成了331.9±2.1Ma的安山玢岩脉。 相似文献
5.
R. Gil-Merino L. J. Goicoechea M. Serra-Ricart A. Oscoz D. Alcalde E. Mediavilla 《Monthly notices of the Royal Astronomical Society》2001,322(2):397-410
From optical R -band data of the double quasar QSO 0957+561A,B, we made two new difference light curves (with an overlap of about 330 d between the time-shifted light curve for the A image and the magnitude-shifted light curve for the B image). We observed noisy behaviours around the zero line and no short time-scale events (with a duration of months), where the term 'event' refers to a prominent feature that may be a result of microlensing or another source of variability. Only one event lasting two weeks and rising −33 mmag was found . Measured constraints on the possible microlensing variability can be used to obtain information on the granularity of the dark matter in the main lensing galaxy and the size of the source. In addition, one can also test the ability of the observational noise to cause the rms averages and the local features of the difference signals. We focused on this last issue. The combined photometries were related to a process consisting of an intrinsic signal plus a Gaussian observational noise. The intrinsic signal has been assumed to be either a smooth function (polynomial), a smooth function plus a stationary noise process, or a correlated stationary process . Using these three pictures without microlensing, we derived some models totally consistent with the observations. We finally discussed the sensitivity of our telescope (at Teide Observatory) to several classes of microlensing variability. 相似文献
6.
We are developing a web-based interactive software to simulate crowded-field imaging with ISSIS on board the future WSO-UV. This new tool is aimed to prepare WSO-UV/ISSIS proposals to observe multicomponent targets and dense fields. For a given combination of UV channel, filters and exposure time, the user creates a set of point-like and extended sources (source model). This source model produces a final image, which takes into account a pixelated field of view, a realistic conversion between physical flux and counts per second, the convolution with the expected point spread function, a sky background and noise fluctuations. The current version of the simulator is available at the Glendama website, and it allows users to specify all relevant parameters of each point-like or extended source, drag-and-drop sources by using a mouse or a fingertip/stylus on a touchscreen, change the frame size or the brightness scale, etc. 相似文献
7.
8.
Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (14C) and stable isotope (δ18O and δ13C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core 14C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the 14C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ18O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ13C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns. 相似文献
9.
Microlensing variability in FBQ 0951+2635: short-time-scale events or a long-time-scale fluctuation?
V. N. Shalyapin L. J. Goicoechea E. Koptelova B. P. Artamonov A. V. Sergeyev A. P. Zheleznyak T. A. Akhunov O. A. Burkhonov S. N. Nuritdinov A. Ullán 《Monthly notices of the Royal Astronomical Society》2009,397(4):1982-1989
We present and analyse new R -band frames of the gravitationally lensed double quasar FBQ 0951+2635. These images were obtained with the 1.5-m AZT-22 Telescope at Maidanak (Uzbekistan) during the 2001–2006 period. Previous results in the R band (1999–2001 period) and the new data allow us to discuss the dominant kind of microlensing variability in FBQ 0951+2635. The time evolution of the flux ratio A / B does not favour the continuous production of short-time-scale (∼months) flares in the faintest quasar component B (crossing the central region of the lensing galaxy). Instead of a rapid variability scenario, the observations are consistent with the existence of a long-time-scale fluctuation. The flux ratio shows a bump during the 2003–2004 period and a quasi-flat trend in more recent epochs. Apart from the global behaviour of A / B , we study the intra-year variability over the first semester of 2004, which is reasonably well sampled. Short-time-scale microlensing is not detected in that period. Additional data in the i band (from new i -band images taken in 2007 with the 2-m Liverpool Robotic Telescope at La Palma, Canary Islands) also indicate the absence of short-time-scale events in 2007. 相似文献
10.
青海锡铁山铅锌矿床硫同位素地球化学研究——深源与海水硫的混合 总被引：5，自引：0，他引：5
锡铁山铅锌矿床发育较为完整的喷流沉积系统,包括管道相、近喷口相、远端沉积相及各种喷流沉积岩,并有后期改造作用形成的脉状铅锌矿体。本文通过喷流沉积系统各部位硫化物硫同位素的分析,不同部位硫化物硫同位素组成不同,且规律性变化。以黄铁矿分析结果为例,网脉状石英钠长岩δ34S=+0.8‰,代表供给系统的硫化物脉2.95‰,非层状矿体4.48‰,层状矿体3.25‰,炭质片岩为+6.26‰,后期改造型铅锌矿脉为+2.93‰。代表管道相的网脉状石英钠长岩黄铁矿具有深源(幔源)的硫同位素组成,而矿体或大理岩上盘炭质片岩具有海水硫来源的特点。矿体的硫介于二者之间,更靠近炭质片岩的硫化物同位素组成,其来源可能更多受海水硫酸盐的制约,即锡铁山矿床硫具有混合来源性质,主要是海水硫酸盐的还原,部分来源于深部卤水的供给。硫的还原方式以生物细菌还原为主。层状矿体中硫同位素组成由早至晚δ34S逐渐降低,表明层状矿体成矿作用过程中,发生了生物成因的H2S的大量加入。 相似文献