Black hole spin and radio loudness in a Λ cold dark matter universe     

Claudia del P. Lagos  Nelson D. Padilla  Sofía A. Cora 《Monthly notices of the Royal Astronomical Society》2009,395(2):625-636

We use a combination of a cosmological N -body simulation of the concordance Λ cold dark matter paradigm and a semi-analytic model of galaxy formation to investigate the spin development of central supermassive black holes (BHs) and its relation to the BH host galaxy properties. In order to compute BH spins, we use the α model of Shakura & Sunyaev and consider the King et al. warped disc alignment criterion. The orientation of the accretion disc is inferred from the angular momentum of the source of accreted material, which bears a close relationship to the large-scale structure in the simulation. We find that the final BH spin depends almost exclusively on the accretion history and only weakly on the warped disc alignment. The main mechanisms of BH spin-up are found to be gas cooling processes and disc instabilities, a result that is only partially compatible with Monte Carlo models where the main spin-up mechanisms are major mergers and disc instabilities; the latter results are reproduced when implementing randomly oriented accretion discs in our model. Regarding the BH population, we find that more massive BHs, which are hosted by massive ellipticals, have higher spin values than less massive BHs, hosted by spiral galaxies. We analyse whether gas accretion rates and BH spins can be used as tracers of the radio loudness of active galactic nuclei (AGN). We find that the current observational indications of an increasing trend of radio-loud AGN fractions with stellar and BH mass can be easily obtained when placing lower limits on the BH spin, with a minimum influence from limits on the accretion rates; a model with random accretion disc orientations is unable to reproduce this trend. Our results favour a scenario where the BH spin is a key parameter to separate the radio-loud and radio-quiet galaxy populations.  相似文献   

The out of ecliptic distribution of interplanetary dust and its relation to other bodies in the solar system     

Ingrid Mann 《Earth, Moon, and Planets》1995,68(1-3):419-426

We discuss the out-of-ecliptic component of the interplanetary dust cloud and its relation to the other small bodies in the solar system. The determination of the mass loss of comets, so far is quite uncertain and doesn't allow a finite study of the mass input to the dust cloud. However it is shown, that the dust particles in the inner solar system, i.e. within the earth orbit are most probable produced from a collisional evolution of larger, meteoroid, fragments of cometary origin. A further component of interstellar dust is especially important in the outer solar system and perhaps for the collisional evolution of the small bodies.  相似文献   

Climate change and the effect of temperature backlashes causing frost damage in Picea abies     

Anna Maria Jnsson  Maj-Lena Linderson  Ingrid Stjernquist  Peter Schlyter  Lars Brring 《Global and Planetary Change》2004,44(1-4):195

In boreal and nemoboreal forests, tree frost hardiness is modified in reaction to cues from day length and temperature. The dehardening processes in Norway spruce, Picea abies, could be estimated to start when the daily mean temperature is above 5 °C for 5 days. Bud burst will occur approximately after 120–170 degree-days above 5 °C, dependent on genetic differences among provenances. A reduced cold hardiness level during autumn and spring and an advanced onset of bud burst are expected impacts of projected future global warming. The aim of this study was to test if this will increase the risk for frost damage caused by temperature backlashes. This was tested for Sweden by comparing output from the Hadley Centre regional climate model, HadRM3H, for the period 1961–1990 with future IPCC scenario SRES A2 and B2 for 2070–2099. Different indices for calculating the susceptibility to frost damage were used to assess changes in frost damage risk. The indices were based on: (1) the start of dehardening; (2) the severity of the temperature backlash; (3) the timing of bud burst; and (4) the cold hardiness level. The start of dehardening and bud burst were calculated to occur earlier all over the country, which is in line with the overall warming in both climate change scenarios. The frequency of temperature backlashes that may cause frost damage was calculated to increase in the southern part, an effect that became gradually less pronounced towards the north. The different timing of the onset of dehardening mainly caused this systematic latitudinal pattern. In the south, it occurs early in the year when the seasonal temperature progression is slow and large temperature variations occur. In the north, dehardening will occur closer to the spring equinox when the temperature progression is faster.  相似文献   

Distribution and sedimentation of radionuclides in the Barents Sea   总被引：1，自引：0，他引：1  

Foyn  Lars; Svaeren  Ingrid 《ICES Journal of Marine Science》1997,54(3):333-340

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Export Production in the Subarctic North Pacific over the Last 800 kyrs: No Evidence for Iron Fertilization?     

Stephanie S. Kienast  Ingrid L. Hendy  John Crusius  Tom F. Pedersen  Stephen E. Calvert 《Journal of Oceanography》2004,60(1):189-203

The subarctic North Pacific is a high nitrate-low chlorophyll (HNLC) region, where phytoplankton growth rates, especially those of diatoms, are enhanced when micronutrient Fe is added. Accordingly, it has been suggested that glacial Fe-laden dust might have increased primary production in this region. This paper reviews published palaeoceanographic records of export production over the last 800 kyrs from the open North Pacific (north of ∼35°N). We find different patterns of export production change over time in the various domains of the North Pacific (NW and NE subarctic gyres, the marginal seas and the transition zone). However, there is no compelling evidence for an overall increase in productivity during glacials in the subarctic region, challenging the paradigm that dust-born Fe fertilization of this region has contributed to the glacial draw down of atmospheric CO₂. Potential reasons for the lack of increased glacial export production include the possibility that Fe-fertilization rapidly drives the ecosystem towards limitation by another nutrient. This effect would have been exacerbated by an even more stable mixed layer compared to today. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Estimating the catching efficiency of a 2-m beam trawl for sampling epifauna by removal experiments   总被引：1，自引：0，他引：1  

Reiss  Henning; Kroncke  Ingrid; Ehrich  Siegfried 《ICES Journal of Marine Science》2006,63(8):1453-1464

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The quantifiable clinothem – types,shapes and geometric relationships in the Plio‐Pleistocene Giant Foresets Formation,Taranaki Basin,New Zealand          下载免费PDF全文

Ingrid Anell  Ivar Midtkandal 《Basin Research》2017,29(Z1):277-297

The understanding of how clinoforms develop is approached based on shape and dimensions, correlation between geometric parameters, and internal characteristics of clinothems bounded by clinoform surfaces in high‐resolution 2D seismic data from the Giant Foresets Formation, Taranaki Basin, offshore New Zealand. The study subdivides the observed clinothems to identify nine types: 1. Oblique 2. Tangential oblique 3. Tangential oblique chaotic 4. Sigmoidal symmetrical 5. Sigmoidal divergent 6. Sigmoidal chaotic 7. Asymmetrical top‐heavy 8. Asymmetrical bottom‐heavy 9. Complex. Accommodation is a dominant control on the type of clinothem that develops, whereby limited accommodation promotes clinothems with significant shelf‐edge advance and low trajectory angles, while increasing accommodation promotes higher trajectory angles and increased deposition on the shelf. Further variations in shape, slope and deposition are influenced by many factors of which sediment influx appears be a fundamental driver. Sigmoidal clinothems tend to show a strong relationship between their maximum thickness and average thickness, their overall slope and maximum foreset angle, along with a high correlation between average thickness and toe advance. This suggests that they distribute sediment in a manner that may be possible to predict and quantify. The increasing steepness of the foreset slope from bottom‐heavy to symmetrical to top‐heavy clinothems, respectively, is dominantly the result of decreasing sediment influx. The clinothems with the steepest slopes, along with chaotic clinothems, are associated with comparatively large toe advance suggesting a strong link between over‐steepened slopes and/or collapse, and processes promoting sediment deposition along the basin floor. Apart from toe advance, the two types of chaotic clinothems develop differently from each other, and from their assumed parent‐clinothem. Tangential oblique chaotic forms steepen, and shelf‐edge advance is limited, suggesting upper slope collapse. Sigmoidal chaotic clinothems have comparatively higher shelf‐edge advance, lower shelf‐edge trajectories and gentler slopes and profiles, suggesting different processes are responsible for their development and resulting shape.  相似文献   

Microbial and viral pathogens in freshwater: current research aspects studied in Germany     

Michael Seidel  Lars Jurzik  Ingrid Brettar  Manfred G. Höfle  Christian Griebler 《Environmental Earth Sciences》2016,75(20):1384

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Temporal dynamics and persistence of sponge assemblages in a Central Pacific atoll lagoon          下载免费PDF全文

Ingrid S.S Knapp  Gareth J. Williams  James J. Bell 《Marine Ecology》2016,37(5):1147-1153

Sponges are important components of coral reef fauna, although little is known of their temporal dynamics. Sponges dominate the lagoon system at Palmyra Atoll in the Central Pacific, which may not be its natural state. Here we examined the temporal variability and recruitment rates of these sponge assemblages to determine if they are stable and examined the evidence that a recent transition has occurred from a coral‐ to sponge‐dominated system. We found 24 sponge species in permanent quadrats in the lagoon between 2009 and 2011, and 11 species on our recruitment panels. The sponge assemblage composition and abundance did not vary significantly between years and appear stable. Many sponge recruits were found in both years that the panels were examined although higher rates were recorded in the second year of the study. While it seems very possible that a change to a sponge‐dominated lagoon is associated with declining environmental quality at Palmyra as a result of modifications over 70 years ago, without pre‐modification data on reef assemblage composition this remains speculative. Our observations of short‐term temporal stability in the sponge assemblages at Palmyra highlight the potential for sponge‐dominated reef states to be maintained in degraded reef environments that are seemingly unsuitable for coral survival.  相似文献   

Carbon dioxide and helium dissolved gases in groundwater at central Tenerife Island,Canary Islands: chemical and isotopic characterization     

Rayco Marrero-Diaz  Dina López  Nemesio M. Perez  Emilio Custodio  Hirochika Sumino  Gladys V. Melián  Eleazar Padrón  Pedro A. Hernandez  David Calvo  José Barrancos  Germán Padilla  Francesco Sortino 《Bulletin of Volcanology》2015,77(10):1-18

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