1,721,020 research outputs found
An extended ultraviolet ring around the SB0 galaxy NGC 4262
No full textWe present Galaxy Ultraviolet Explorer (GALEX) satellite observations of the SB0 galaxy NGC 4262 where we detect an extended, outer ring studded with UV-bright knots surrounding the galaxy body. Such a structure, not visible at optical wavelengths, is coupled with a ring of atomic (HI) gas. We will show that both star-forming and HI rings surrounding this SB0 galaxy share the same radial distance from the galaxy center and spatial orientation. We also model the kinematics of the ring(s) and of the galaxy body. Their kinematics is not coupled with that of the galaxy stars. We suggest that NGC 4262 has undergone a major gas stripping event in the past that was the origin of the present "necklace" of UV-bright knots
New candidate EHB stars in the open cluster NGC 6791: Looking locally into the UV-upturn phenomenon
Full text linkRelying on U and B imagery at the Italian Telescopic, Nazionale Galileo (TNG), we report here the discovery of a sample of 13 new UV-bright post-HB candidate stars in the field of the Galactic open cluster NGC 6791. Owing to its super-solar metal content ([Fe/H] greater than or similar to 0.2 dex) and estimated age (t greater than or similar to 8 Gyr), this cluster represents the nearest and ideal stellar aggregate to match the distinctive properties of the evolved stellar populations possibly ruling the UV-upturn phenomenon in elliptical galaxies and bulges of spirals. Our ongoing spectroscopic follow-up of this unique UV-bright sample will allow us to assess - once cluster membership of the candidates is properly checked the real nature (e.g., sdB, sdO, AGB-manque or EHB stars) of these hot sources and their link with the ultraviolet excess emerging from low-mass, metal-rich evolutionary environments of external galaxies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
UB CCD Photometry of the Old, Metal-rich, Open Clusters NGC 6791, NGC 6819, and NGC 7142
Full text linkWe report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters NGC 6791, NGC 6819, and NGC 7142. With their super-solar metallicity and ages >~ 3-8 Gyr, these three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. Following a first discussion of NGC 6791 observations in an accompanying paper, here we complete our analysis, also presenting for NGC 6819 and NGC 7142 the first-ever U CCD photometry. The color-magnitude diagram of the three clusters is analyzed in detail, with special emphasis on the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function clearly points to a looser radial distribution of faint lower main sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as also observed in NGC 6791. Compared to a reference theoretical model for the Galaxy disk, the analysis of the stellar field along the line of sight of each cluster indicates that a more centrally concentrated thick disk, on a scale length shorter than ~2.8 kpc, might better reconcile the lower observed fraction of bright field stars and their white-dwarf progeny
A single cell but many different transcripts: A journey into the world of long non-coding RNAs
Full text linkIn late 2012 it was evidenced that most of the human genome is transcribed but only a small percentage of the transcripts are translated. This observation supported the importance of non-coding RNAs and it was confirmed in several organisms. The most abundant non-translated transcripts are long non-coding RNAs (lncRNAs). In contrast to protein-coding RNAs, they show a more cell-specific expression. To understand the function of lncRNAs, it is fundamental to investigate in which cells they are preferentially expressed and to detect their subcellular localization. Recent improvements of techniques that localize single RNA molecules in tissues like single-cell RNA sequencing and fluorescence amplification methods have given a considerable boost in the knowledge of the lncRNA functions. In recent years, single-cell transcription variability was associated with non-coding RNA expression, revealing this class of RNAs as important transcripts in the cell lineage specification. The purpose of this review is to collect updated information about lncRNA classification and new findings on their function derived from singlecell analysis. We also retained useful for all researchers to describe the methods available for singlecell analysis and the databases collecting single-cell and lncRNA data. Tables are included to schematize, describe, and compare exposed concepts
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