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Nuclear Activity in Circumnuclear Ring Galaxies

International Journal of Astronomy and Astrophysics 2016年第3期6卷 219-235页

作者： maría P. Agüero Rubén J. Díaz Horacio Dottori observatorio Astronómico de Córdoba UNCand CONICET Córdoba Argentina ICATE CONICET San Juan Argentina Gemini observatory La Serena Chile Instituto de Física UFRGS Porto Alegre Brazil

We have analyzed the frequency and properties of the nuclear activity in a sample of galaxies with circumnuclear rings and spirals (CNRs), compiled from published data. From the properties of this sample a typical circumnuclear ring can be characterized as having a median radius of 0.7 kpc (mean 0.8 kpc, rms 0.4 kpc), located at a spiral Sa/Sb galaxy (75% of the hosts), with a bar (44% weak, 37% strong bars). The sample includes 73 emission line rings, 12 dust rings and 9 stellar rings. The sample was compared with a carefully matched control sample of galaxies with very similar global properties but without detected circumnuclear rings. We discuss the relevance of the results in regard to the AGN feeding processes and present the following results: 1) bright companion galaxies seem not to be important for the appearance of CNRs, which appear to be more related to intrinsic properties of the host galaxies or to minor merger processes;2) the proportion of weak bars in galaxies with a CNR is higher than expected;3) the incidence of Seyfert (Sy) activity coeval with CNRs is significantly larger than the rate expected from the morphological distribution of the host galaxies;4) the rate of Sy 2 to Sy 1 type galaxies with CNRs is about three times larger than the expected ratio for galaxies without CNRs and is opposite to that predicted by the geometric paradigm of the classical unified model for AGNs, although it does support the hypothesis that Sy 2 activity is linked to circumnuclear star formation. The possible selection effects of the sample are discussed, and we conclude that the detected trends are strong enough to justify high quality observations of as large as possible set of galaxies with circumnuclear rings and their matched control samples.

关键词： Galaxies Spiral Nuclei Structure Dynamics Active

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Yield models for predicting aboveground ectomycorrhizal fungal productivity in Pinus sylvestris and Pinus pinaster stands of northern Spain

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Forest Ecosystems 2019年第4期6卷 414-426页

作者： mar.ola Sánchez-González Sergio de-Miguel Pablo martin-Pinto Fernando martínez-Pe?a maría Pasalodos-Tato Juan Andrés oria-de-Rueda Juan martínez de Aragón Isabel Ca?ellas José Antonio Bonet Spanish National Institute for Agricultural and Food Research and Technology (INIA)

Background: Predictive models shed light on aboveground fungal yield dynamics and can assist decision-making in forestry by integrating this valuable non-wood forest product into forest management planning. However, the currently existing models are based on rather local data and, thus, there is a lack of predictive tools to monitor mushroom yields on larger ***: This work presents the first empirical models for predicting the annual yields of ectomycorrhizal mushrooms and related ecosystem services in Pinus sylvestris and Pinus pinaster stands in northern Spain, using a long-term dataset suitable to account for the combined effect of meteorological conditions and stand *** were fitted for the following groups of fungi separately: all ectomycorrhizal mushrooms, edible mushrooms and marketed mushrooms. our results show the influence of the weather variables(mainly precipitation) on mushroom yields as well as the relevance of the basal area of the forest stand that follows a right-skewed unimodal curve with maximum predicted yields at stand basal areas of 30–40 m2·***: These models are the first empirical models for predicting the annual yields of ectomycorrhizal mushrooms in Pinus sylvestris and Pinus pinaster stands in northern Spain, being of the highest resolution developed to date and enable predictions of mushrooms productivity by taking into account weather conditions and forests’ location, composition and structure.

关键词： Mushrooms Fungi Non-wood forest products Mixed models Hurdle models

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周星驰小传(英文)

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大学英语 2005年第2期 32-33,54页

作者： mar Pollard 孙三军

Stephen Chow was born in Hong Kong in 1962 and grew up in Shanghai, along with three sisters. He developed an early fascination1 with martial arts2 Kung Fu star Bruce Lee3 and while still in school took three months o... 详细信息

关键词：大学英语注释读物人物传记影视明星

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