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251.
Thermoluminescence dating of sediments in the Warsaw laboratory is based on blue-to-green emission. The ‘partial bleach + regeneration’ method is proposed for dating sediments which have not been completely bleached at the time of burial. Correct TL ages are reported for sediments covering organic deposits of the Eemian Interglacial and also for glacial sediments of Würm and Riss age. We obtained good results for dating till using the partial bleach + regeneration method. The TL zeroing in till is explained by the ‘rubbing’ or compression of grains beneath the glacier and by the freeze-thaw activity occurring during glacial transport and deglaciation. 相似文献
252.
Marek Súľovský Vladimír Falťan Hana Skokanová Marek Havlíček František Petrovič 《自然地理学》2013,34(5):470-488
AbstractThe influence of abiotic conditions on land-use development since the nineteenth century is assessed in case studies from the Czech and Slovak Carpathians. Hypotheses claim that significant land-use changes have occurred, but without pronounced differences because of similar abiotic conditions in the case studies. Abiotic conditions are expressed by physiotopes, which contain information on georelief, lithology, and soil. Our results indicate a high rate of land-use change in both case studies, and a detailed analysis of changes in two sequential periods reveals significant differences in five of the six periods compared in these case studies. Areas along state border seem to be more affected by anthropogenic changes as the proportion of plots with stable land use was only 25.7% in the Czech area (Starý Hrozenkov, Vápenice, and Vy?kovec) compared to 47.6% in the Slovak area (Lietavská Svinná-Babkov). Repeated land-use changes occurred mostly in valley floors and adjacent slopes. Land-use changes in the study areas are only partly explained by the abiotic conditions in physiotope and morphometric attributes, as shown by multiple correspondence analysis. The crucial difference in land use is in different settlement structures, which reflect differences in historical development. 相似文献
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The galactic black hole binary systems give an observational template showing how the accretion flow changes as a function
of increasing mass accretion rate, or L/LEdd. These data can be synthesised with theoretical models of the accretion flow to give a coherent picture of accretion in strong
gravity, in which the major hard-soft spectral transition is triggered by a change in the nature and geometry of the inner
accretion flow from a hot, optically thin plasma to a cool, optically thick accretion disc. However, a straightforward application
of these models to AGN gives clear discrepancies in overall spectral shape. Either the underlying accretion model is wrong,
despite its success in describing the Galactic systems and/or there is additional physics which breaks the simple scaling
from stellar to supermassive black holes. 相似文献
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Several new times of minimum light recorded with photoelectric or CCD means have been gathered for the eccentric eclipsing
binary V889 Aql (P = 11.1 days, e = 0.37). Its O–C diagram is presented, and improved elements of the apsidal motion and the light-time effect (LITE) are given. We found a
long apsidal motion period of about 24 400 ± 2400 years and a period of the third body of about 52 ± 2 years. 相似文献
259.
Jeanette Gladstone Chris Done Marek Gierliski 《Monthly notices of the Royal Astronomical Society》2007,378(1):13-22
We systematically analyse all the available X-ray spectra of disc accreting neutron stars (atolls and millisecond pulsars) from the RXTE data base. We show that while all these have similar spectral evolution as a function of mass accretion rate, there are also subtle differences. There are two different types of hard/soft transition, those where the spectrum softens at all energies, leading to a diagonal track on a colour–colour diagram, and those where only the higher energy spectrum softens, giving a vertical track. The luminosity at which the transition occurs is correlated with this spectral behaviour, with the vertical transition at L / L Edd ∼ 0.02 while the diagonal one is at ∼0.1. Superimposed on this is the well-known hysteresis effect, but we show that classic, large-scale hysteresis occurs only in the outbursting sources, indicating that its origin is in the dramatic rate of change of mass accretion rate during the disc instability. We show that the long-term mass accretion rate correlates with the transition behaviour, and speculate that this is due to the magnetic field being able to emerge from the neutron star surface for low average mass accretion rates. While this is not strong enough to collimate the flow except in the millisecond pulsars, its presence may affect the inner accretion flow by changing the properties of the jet. 相似文献
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