1,720,970 research outputs found
Assessment of qualitative tests
No full textFor qualitative (2-class) tests, which provide binary (yes/no) information, the correctness of specimen classification remains the most important criterion for performance evaluation. However, a more informative picture emerges from the relationship between percentage of positive results and analyte concentration, which allows some inherent test characteristics to be derived (the positive/negative discrimination concentration and the "grey zone" around it). The information content of evaluation approaches is decidedly improved by the availability of numerical results (counts per minute, absorbance) in most situations of clinical interest. The concentration/response functions underlying the quality of individual tests may thus be derived and compared, and laboratory staff given a more objective criterion to judge individual performance. Examples are drawn from the authors' experience in running external quality assessment programs for tests for infectivity markers
Quattro anni di esperienza nel controllo di qualità dei test immunometrici per HBsAg e anti-HBs in Italia
No full textGoing 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
Interlaboratory quality control of immunometric assays of HBsAg and anti-HBs in Italian laboratories: a two-year experience
No full textAn interlaboratory quality control for the immunometric tests of HBsAg and anti-HBs has been initiated in Italy in 1985. Participants (153 laboratories at present) are periodically supplied with sets of unknown serA for each analyte. The assay results are returned as both positive/negative classification and digital response. Limitedly to a 40-laboratory group, from the latter data quantitative estimates are obtained through interpolation on a 'hidden' calibration curve included in the control sets. Periodical reports containing the results of statistical elaboration of data are distributed to participants (both total results and results subgrouped according to the commercial kits). The analysis of qualitative control data collected so far indicates that misclassifications are relatively frequent in the low-positive ranges, i.e. 18% for HBsAg tests (0.25-0.50 U PEI/ml) and 30% for anti-HBs tests (6.5 15 mU WHO/ml). A progressive decrease is observed in the higher-concentrations (0.2% for both HBsAg concentrations ≥ 2 U/ml and anti-HBs concentrations ≥ 60 mU/ml), while ca 2.5% false positives occur in both assays. Some differences emerge as for the classification ability of individual kits. The quantitative evaluation evidences in both cases a moderate variability (10-40% CV, depending on kind and concentration of analyte) and a good between-kit agreement of estimates
Programma CNR di controllo di qualità tra laboratori per le misure di indicatori dell'epatite virale B: risultati della valutazione della sensibilità di rilevazione dell'HBsAg nel siero
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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
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
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