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171.
Sebastian Heinz Andrea Merloni Tiziana Di Matteo Rashid Sunyaev 《Astrophysics and Space Science》2005,300(1-3):15-21
The scale invariance model (Heinz, S. and Sunyaev, R.A.: 2003, MNRAS 343, L59) can be used to derive robust scaling relations between the radio luminosity from accreting black holes and the black
hole mass and accretion rate. These relations agree well with the recently found “fundamental plane” of black hole activity
(Merloni, A., Heinz, S. and Di Matteo, T.: 2003, MNRAS 345, 1057). This relation provides a new, powerful tool for the comparison of jets from black holes of different masses and accretion
rates. The regression coefficients of this relation contain information about the nature of the X-ray emission mechanism driving
the correlation. We argue that X-ray synchrotron emission from the base of the jets is unlikely to be the dominant contribution
to the X-ray spectrum in most of the sources. 相似文献
172.
Christopher S. Reynolds † Sebastian Heinz Mitchell C. Begelman 《Monthly notices of the Royal Astronomical Society》2002,332(2):271-282
We present a numerical investigation of dead, or relic, radio galaxies and the environmental impact that radio galaxy activity has on the host galaxy or galaxy cluster. We perform axisymmetric hydrodynamical calculations of light, supersonic, back-to-back jets propagating in a β -model galaxy/cluster atmosphere. We then shut down the jet activity and let the resulting structure evolve passively. The dead source undergoes an initial phase of pressure driven expansion until it achieves pressure equilibrium with its surroundings. Thereafter, buoyancy forces drive the evolution and lead to the formation of two oppositely directed plumes that float high into the galaxy/cluster atmosphere. These plumes entrain a significant amount of low entropy material from the galaxy/cluster core and lift it high into the atmosphere. An important result is that a large fraction (at least half) of the energy injected by the jet activity is thermalized in the interstellar medium (ISM)/intracluster medium (ICM) core. The whole ISM/ICM atmosphere inflates in order to regain hydrostatic equilibrium. This inflation is mediated by an approximately spherical disturbance which propagates into the atmosphere at the sound speed. The fact that such a large fraction of the injected energy is thermalized suggests that radio galaxies may have an important role in the overall energy budget of rich ISM/ICM atmospheres. In particular, they may act as a strong and highly time-dependent source of negative feedback for galaxy/cluster cooling flows. 相似文献
173.
Using pressure fields classified by the SANDRA algorithm, this study investigates the changes in the relationship between North Atlantic/European sea level pressure (SLP) and gridded European winter (DJF) temperature and precipitation back to 1750. Important changes in the frequency of the SLP clusters are found, though none of them indicating significant long-term trends. However, for the majority of the SLP clusters a tendency toward overall warmer and partly wetter winter conditions is found, most pronounced over the last decades. This suggests important within-type variations, i.e. the temperature and precipitation fields related to a particular SLP pattern change their characteristics over time. Using a decomposition scheme we find for temperature and precipitation that within-type-related variations dominate over those due to changed frequencies of the SLP clusters: Approximately 70% (60%) of European winter temperature (precipitation) variations can be explained by within-type changes, most strongly expressed over Eastern Europe and Scandinavia. This indicates that the current European winter warming cannot be explained by changed frequencies of the SLP patterns alone, but to a larger degree by changed characteristics of the patterns themselves. Potential sources of within-type variations are discussed. 相似文献
174.
Hedman JE Rüdel H Gercken J Bergek S Strand J Quack M Appelberg M Förlin L Tuvikene A Bignert A 《Marine pollution bulletin》2011,62(10):2015-2029
The implementation of the EU Marine Strategy Framework Directive necessitates the development of common criteria and methodological standards for marine environmental monitoring and assessment across Europe. Eelpout (Zoarces viviparus) is proposed as a key indicator organism in the Baltic and North Sea regions. This benthic fish species is widely used in ecotoxicological studies and as a bioindicator of local pollution due to its stationary behavior. Eelpout is included in the environmental monitoring program of several Baltic States, covering both chemical and biological effects measurements, and samples have been archived in environmental specimen banks for >15 years. A method for evaluating the frequency of larval aberrations has been suggested as a standardized assessment tool. The large scientific knowledge-base and considerable experience of long-term chemical and biological effects monitoring and specimen banking, make eelpout a suitable species for the assessment of Good Environmental Status in the Baltic and North Seas. 相似文献
175.
Jan-Hendrik May Jana Zech Frank Preusser Jaime Argollo Heinz Veit 《Quaternary Research》2011,76(1):106-118
Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating (14C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29-25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20-18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~ 17-16 ka, followed by several smaller readvances until ~ 10-11 ka, and complete deglaciation at the end of the Early Holocene. 相似文献
176.
177.
The exact closed-form mathematical solution for Schwarzschild black-hole fed by the Cosmic Micro-wave Background Radiance (CMBR) is obtained analytically. This unique solution holds for both growth (evolution) and decay, which are bifurcated by the critical initial mass, which depends on the temperature of CMBR. Results are presented to illustrate this solution in terms of decay/growth of black-hole, and the variation of rate of growth/decay with CMBR. 相似文献
178.
Raymond Jonckheere Daniel Heinz Bradley R. Hacker David Rafaja Lothar Ratschbacher 《地学学报》2019,31(3):263-270
This contribution reports Raman radiation damage measurements of zircons from the Kontinentale Tiefbohrung, on the western border of the Bohemian Massif. The mean wavenumbers (ω3) and widths (Γ3) of the ν3(SiO4) Raman band are constant down to 3 km, decrease (ω3) resp. increase (Γ3) between 3 and 5 km, and are again constant between 5 and 7 km. Uniform high Γ3 values associated with ω3 values close to those of undamaged zircon between 5 and 7 km are interpreted as due to residual damage predating the exhumation of the Bohemian Massif. A superimposed post‐exhumation signal indicates full damage retention down to 3 km depth, partial annealing between 3 and 5 km, and zero retention at greater depth. An attempt to calculate radiation damage ages gives results of a meaningful order of magnitude but also exposes difficulties associated with dating basement samples with complex damage accumulation and annealing histories. 相似文献
179.
To reduce the complexity and save computation time, an isotropic and a scalar dispersion model are explored and compared to the anisotropic advection/dispersion model to study the interstitial flow in a stream and lake sediment induced by a periodic pressure wave. In these systems, the solute transport is controlled by the ratio (R = a/(LS)) of the pressure wave steepness (a/L) to the stream slope (S), and the dispersivity ratio (λ = αL/L) that measures the longitudinal dispersivity (αL) relative to the pressure wave length (L). Through a series of numerical experiments, the conclusion is reached that a scalar dispersion model can be applied with satisfactory results for advection-dominated transport, i.e. when R ? 0.1 and λ ? 0.01, or λ ? 0.0001, i.e. Peclet number (Pe) ? 10000; an isotropic dispersion model can be applied when R ? 10 or λ ? 0.001, and the full anisotropic advection/dispersion model has to be applied when R > 10 and λ > 0.001. 相似文献
180.
Bernhard Aichner Heinz Wilkes Ulrike Herzschuh Steffen Mischke Chengjun Zhang 《Journal of Paleolimnology》2010,43(4):873-899
A sediment core from Lake Koucha (eastern Tibetan Plateau) was investigated using organic biomarkers and their stable carbon
isotope signatures. The correlation between TOC content, total amount of aquatic macrophyte-derived n-alkanes (e.g. nC23) and δ13C values of TOC and nC23 indicates that Lake Koucha was macrophyte-dominated before 8 cal ka BP. Shortly after the lake turned from a saline to a
freshwater system at 7.2 cal ka BP, a variety of algal and bacterial markers such as hopanoids and isoprenoids emerged, of
which phytane, pentamethylicosene (PMI), moretene and diploptene are particularly abundant. Phytane and PMI show different
isotopic signals (≈−18 and ≈−28‰, respectively), which indicates that they originated from different sources. Phytane may
have been derived from cyanobacteria, while methanogenic archaea may be the source of PMI. The isotopic depletion of diploptene
and moretene (≈−60‰) indicates the presence of methanotrophs. After 6.1 cal ka BP, the saturated C20 highly branched isoprenoid (HBI) became the dominant constituent of the aliphatic hydrocarbon fraction. Such dominance has
rarely been reported in lacustrine environments, and indicates a strong presence of algae (most likely diatoms) or cyanobacteria.
At 4.7 cal ka BP, the appearance of an unsaturated C25 HBI, which is a specific biomarker for diatoms, was noted. Furthermore, the level of nC17-alkane was observed to increase in abundance in the uppermost two samples. These results suggest that the lake was phytoplankton-dominated
during the last 6.1 ka. Relatively low biomarker concentrations and δ13C values at 6.0, 3.1 and 1.8 cal ka BP indicate the occurrence of cool periods, which is in agreement with inferences from
other locations on the Tibetan Plateau. The δ13C values of nC23 range from −23.5 to −12.6‰, with high values at the peak of macrophyte abundance at ca. 11 cal ka BP and at the phytoplankton
maximum between ca 6.1 and 2.8 cal ka BP. Thus, aquatic macrophyte-derived mid-chain n-alkanes have been found to be excellent indicators of carbon-limiting conditions, which lead to the assimilation of isotopically-enriched
carbon species. The limitation of carbon sources could be a localized phenomenon occurring in dense plant stands (as in the
older section of the core), or it may be induced by high primary productivity (as in the younger section). Since the δ13C value of the inorganic carbon source may vary, the offset between the δ13C values of nC23 and TIC could serve as a more precise proxy for carbon-limiting conditions in lacustrine environments, which could in turn
be interpreted with respect to lacustrine paleo-productivity. 相似文献