1,720,960 research outputs found
FIRST INTERFEROMETRIC IMAGES OF THE 36 GHz METHANOL MASERS IN THE DR21 COMPLEX
No full textClass I methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of class I masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other class I methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found in virtual overlap with class II 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W, we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that class I masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in class I masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them.National Science Foundation (U.S.) (Experiences for Undergraduates program)Smithsonian InstitutionAcademia Sinica (Beijing, China
An interferometric study of molecular emission around NGC 7538 at millimeter wavelengths
No full textETDs are only available to UIUC Users without author permissionU of I OnlyNGC 7538 is a visible H II region with an associated molecular cloud, situated in the Perseus arm of the Galaxy. A group of infrared sources, IRS 1, IRS 2, and IRS 3, is situated at the interface between the molecular cloud and the visible nebula. Maser emission from OH, H\sb2O, H\sb2CO, CH\sb3OH, and NH\sb3 has been detected toward IRS 1. In order to examine the model for the excitation of the formaldehyde (H\sb2CO) maser, proposed by Boland and de Jong (1981), interferometric observations of the cloud around IRS 1 have been made in the J = 1-0 transitions of HCN, HCO\sp{+}, and \sp{13}CO. The HCN and HCO\sp{+} maps show the presence of a cavity around IRS 1 which is not seen in the \sp{13}CO maps. Since HCN and HCO\sp{+} trace densities 10\sp5 cm\sp{-3}, the cavity indicates a lack of high density material around the H II region. Continuum observations at 88 GHz and 110 GHz result in a 2-component model for the H II region. There is a cool, extended component toward which all the masers are seen. The parameters calculated for this component, along with the H\sb2 densities (10\sp4 cm\sp{-3}) from the molecular observations, were put into the H\sb2CO master model. The results show that the H\sb2CO gas must be at a distance of 0.011 pc from the H II region for maximum inversion in the H\sb2CO transition and the abundance of H\sb2CO relative to H\sb2 must be 4 10\sp{-7}."The molecular observations also show that the molecular cloud is extremely clumpy. These clumps around IRS 1 could provide the varying densities required for the other masers observed in the region. The HCO\sp{+} results also indicate the presence of a high density molecular outflow which originates about 15"" south of IRS 1. The position angle of the outflow agrees with that of a CO outflow detected toward this source. The results imply that there may be another source powering the outflow which is situated south of IRS 1. The new source appears to be situated at the center of an elongated structure, also seen in HCO\sp{+}, which is oriented perpendicular to the direction of the outflow."Made available in DSpace on 2011-05-07T14:21:25Z (GMT). No. of bitstreams: 2
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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