1,720,957 research outputs found
[Digital radiography of the thorax with selenium detector. Clinical results and optimization potential of the technique]
No full textINTRODUCTION: We compared the image quality of the chest radiograph obtained with a digital selenium detector and with a conventional system and investigated the possible improvements in the digital technique resulting from kilovoltage (kV) lowering, antiscattering grid addition and image format reduction.
MATERIAL AND METHODS: 150 subjects in the first series were submitted to posteroanterior chest radiography with both the selenium and the conventional systems. Image quality was compared by giving a score to the depiction of anatominal and pathologic findings. Thirty-two and 31 subjects from two other series were submitted to two digital chest radiographs each: the former at high (150) and low (90) kV, and the latter at 150 kV with the antiscattering grid and at 90 kV without the grid. Comparisons were made by choosing the better of the two images of each subjects. A score was given to the depiction quality of several difficult-to-detect findings in full-size and small-size format digital images obtained in another series of 27 subjects.
RESULTS: As for anatomical detailing, digital selenium images were of much better quality than conventional images: the mean scores given by 3 observers to digital images (5.32; 5.55; 6.68) are higher than those given to the corresponding conventional images (4.49; 5.02; 5.81) and the difference is statistically significant (p < 0.001 in all cases). The advantage of digital over conventional images is also significant with reference to diagnostic confidence in the identification of pathologic findings (p < 0.001; p < 0.005; p < 0.01), but to a lessere extent (mean scores: 3.98; 4.22; 3.60 for the digital system, versus 3.43; 3.69; 3.38 for the conventional system). The digital images acquired at lower kV (90 kV) were much more frequently chosen by the two observes (87.5% and 96.8% of cases) than the images acquired at 150 kV; the entry dose at lower energies (91 muGy using an anthropomorphic phantom) is not significantly higher than the dose given at 150 kV (85 muGy). No significant difference was found in the two observers' choice between the digital images taken at 90 kV without antiscattering grid and those taken at 150 kV with the grid, the former being preferred in 38.7% and 58% of cases. The level of diagnostic confidence in the detailing of difficult-to-detect findings was slightly higher in full-size digital images (mean scores: 5.33 and 6.77) than in small-size ones (4.88 and 5.96).
DISCUSSION AND CONCLUSIONS: Digital selenium images always exibit better quality than conventional images: the difference is very marked relative to anatomical detailing and not so striking, though still significant, in showing pathologic findings. Digital selenium image quality can be improved relative to the manufacturer's guidelines (150 kV exposure with no grid), by lowering the kV and adding the antiscattering grid, without increasing patient exposure too much. Digital image format reduction allows cost containment without affecting diagnostic reliability
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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