1,721,199 research outputs found
Star formation in the bright rimmed globule IC 1396N
No full textWe report mm-wave multiline and continuum observations of IC 1396N, a conspicuous bright, rimmed globule excited by the O6.5 star HD 206267 in the Cep OB2 association. Single-dish high resolution observations in CO and CS lines reveal the cometary structure of the globule with unprecedented detail. The globule head contains a dense core of 0.2 pc, whereas the tail, pointing away from the exciting star, has a total length of 0.8 pc. Two high velocity bipolar outflows have been identified in the CO maps: the first one is located around the position of a strong IRAS source in the head of the globule, and the second one, which was previously unknown, is located in the northern region. The outflows emerge from high density clumps which exhibit strong line emission of CS, HCO+, and DCO+. Within these clumps, the sources driving the outflows have been identified thanks to mm-wave continuum observations. The globule head harbors two YSOs separated by about 104 AU. SiO line observations of the central outflow unveals a highly collimated structure with four clumps of sizes <=0.1 pc, which are located along the outflow axis and suggest episodic events in the mass loss process from the central star. Kinetic temperatures of ~ 50-100 K and hydrogen densities of fews 106 cm-3 have been estimated in the shocked regions traced by the strong SiO emission. The jet is also exposed to view by the means of interferometric HCO+ observations that confirms that it is very narrow (<=0.02 pc wide). The detection of blue- and redshifted CO emission along the globule rim suggests that IC 1396N is in a transient phase, undergoing one of the expansions or compressions predicted by theoretical models describing the evolution of cometary globules. Moreover, the CO data, together with near IR observations reported elsewhere, indicate that the star forming process is occurring also in the northern part of IC 1396N, at 0.5 pc from the central CS peak. The present observations provide evidence that several star-forming sites can develop even in a moderately massive globule like IC 1396N
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
Modeling the Continuum Emission from the Circumstellar Environment of Herbig Ae/Be Stars
No full textThis paper discusses a model for the continuum emission of the Herbig Ae/Be stars in the light of an updated set of observational data spanning 5 orders of magnitude in wavelength and including the low-resolution spectra
obtained with the Short Wavelength Spectrometer and Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The model is used to reproduce the continuum emission of the 36 Herbig Ae/Be stars
included in the list by The and coworkers and observed by ISO. The circumstellar matter responsible for the observed spectral energy distributions has been investigated by comparing the set of the observations with the
model spectra computed for different possible distributions of circumstellar matter. Cases have been considered with the circumstellar regions partially evacuated along the polar axis by the action of the stellar wind, a phenomenon that is quite common in these pre–main-sequence objects. The inclusion of the polar cavities indirectly allows geometries in which a small-scale disklike structure around the central star is present. The
possible coexistence of two different density profiles, in the inner and the outer region of the envelope, respectively, has been also considered. The comparison of the computed models with the observed spectral energy
distributions selects the parameter values in such a way that the larger dust grains are preferentially associated with the later spectral types. We find that 17 objects are reasonably fitted, eight of which with a purely spherical
model and the remaining nine with the inclusion of the polar cavities. For 10 further objects the fit is worse, and for the remaining nine, almost all associated to IR companions, our model is clearly inappropriate. A linear relationship is suggested between the logarithm of the initial density n0 and the exponent p of the power law adopted for the circumstellar density distribution
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
