1,720,961 research outputs found
Criticità e limiti dei metodi di screening immunochimici per la determinazione di sostanze psicotrope in lavoratori addetti a mansioni a rischio
No full textIl lavoro riporta i risultati di uno studio finalizzato alla valutazione delle performance analitiche di un test di screening on-site, scelto tra quelli commercialmente disponibili sulla base delle caratteristiche tecniche fornite dal costruttore. Il disegno sperimentale ha previsto per ciascuna delle sostanze stupefacenti tabulate dalla normativa (cocainici, oppiacei, metadone, amfetamina, metamfetamina, MDMA, buprenorfina, cannabinoidi) l’analisi in triplicato di tre campioni urinari, preparati a partire da urine di tre soggetti non dediti all’uso/abuso di sostanze stupefacenti, addizionate di volta in volta con uno degli otto analiti a tre livelli di concentrazione (una corrispondente al valore di cut-off tabulato e gli altri a concentrazioni superiori). In totale lo studio ha previsto l’analisi di N = 216 campioni (3urine x 3concentrazioni x 3replicati x 8droghe). Ciascun campione è stato successivamente quantificato mediante gas cromatografia/spettrometria di massa, utilizzata quale metodica di riferimento.
Le performance del test di screening sono state valutate in termini di sensibilità diagnostica (VP/(VP+FN) * 100), specificità (VN/(FP+VN) * 100) ed accuratezza ((VP+VN)/(VP+VN+FP+FN)*100).
Sulla base dei risultati ottenuti è possibile affermare che i risultati falsamente positivi all’analisi di screening ottenuta mediante utilizzo di dispositivi immunochimici è attribuibile i)alla non specificità per singolo analita dei test; ii)ad errori di esecuzione del test e/o di interpretazione del risultato da parte dell’analista; iii)alla scelta dei cut-off analitici, in tutti quei casi in cui la sostanza d’abuso è effettivamente presente nel campione esaminato, ma in concentrazione inferiore rispetto al del cut-off stabilito.
I problemi analitici connessi con l’esecuzione dei test di screening on-site e l’inaccuratezza delle determinazioni quando gli analiti siano presenti in concentrazioni prossime al cut-off, pongono nuovi interrogativi sulla veridicità delle percentuali di positività emerse, intorno all’1% contro un valore atteso tra il 3-5% (e calcolato sulla base della percentuale di lavoratori tra la popolazione dedita all’uso di sostanze stupefacenti)
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
La problematica dei falsi positivi nei test di screening utilizzati per gli accertamenti dell’abuso di sostanze stupefacenti in lavoratori addetti a mansioni a rischio
No full text"Le problematiche dei falsi positivi nei test di screening utilizzati per gli accertamenti dell'abuso di sostanze stupefacenti in lavoratori addetti a mansioni a rischio"
No full textDispelling 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
[Effects of pentobarbital on serum levels of LH and FSH, in normal conditions and after GnRH stimulation: preliminary report]
No full text
- …
