1,720,964 research outputs found
La variazione della velocità di picco del flusso aortico e del diametro della vena cava caudale: studio di due nuovi indici di volemia e il loro utilizzo come predittori di risposta ai fluidi in cani anestetizzati e ventilati meccanicamente
Full text linkAdministration of IV fluid to optimize volume status and prevent inadequate tissue perfusion is a perioperative major task for the anaesthetist. Early fluid resuscitation improves cardiac output in preload-dependent subjects, but excessive fluid load can worsen postoperative outcome. Many variables have been proposed to predict fluid responsiveness. Dynamic variables reflect the variation in preload induced by mechanical ventilation and are reliable predictors of volume expansion. Dynamic preload indices, such as systolic pressure variation (SPV), aortic flow peak velocity variation (∆Vpeak) and distensibility index of the caudal vena cava (CVCDI), are reliable indices for predicting fluid responsiveness in humans. This study aimed to investigate the ability of these indices to predict fluid response in healthy dogs undergoing general anaesthesia and mechanical ventilation. The study included 24 dogs. ∆Vpeak, CVCDI, and SPV were calculated before a volume expansion (5 mL/kg bolus of lactated Ringer’s solution). The aortic velocity time integral (VTI) was measured before and after the volume expansion as surrogate of stroke volume. Dogs were considered responders (group R, n = 9) when the VTI increase was ≥15% and non-responders (group NR, n = 15) when the increase was <15%. ∆Vpeak, CVCDI and SPV before volume expansion were higher in group R than in group NR (P = 0.0009, P = 0.0003, and P = 0.0271, respectively). Receiver operating characteristic (ROC) curves were plotted for the three indices. The areas under the ROC curves for SPV, ΔVpeak, and CVCDI were 0.91 (CI 0.73–0.99; P = 0.0001), 0.95 (CI 0.77–1; P = 0.0001), and 0.78 (CI 0.56–0.92; P = 0.015), respectively. The best cut-offs were 6.7% for SPV (sensitivity, 77.78%; specificity, 93.33%), 9.4% for ΔVpeak (sensitivity, 88.89%; specificity, 100%), and 24% for CVCDI (sensitivity, 77.78%; specificity, 73.33). In conclusion, ∆Vpeak, CVCDI, and SPV are reliable predictors of fluid responsiveness in dogs undergoing general anaesthesia and mechanical ventilation
Integrazione di indicatori per una caratterizzazione del policentrismo in alcune aree urbane in Italia
No full textIl lavoro attraverso l’uso di alcuni strumenti di statistica territoriale è un primo approccio alla costruzione di una metodologia che, partendo dai dati di copertura del suolo, permetta di oggettivare attraverso una misurazione i due diversi modelli della struttura dell’area metropolitana: monocentrica o policentrica.L’area metropolitana, infatti, pur necessitando e presentando una importante componente di quantità di popolazione, non è un fatto semplicemente insediativo, sono le funzioni strategiche e i flussi che surclassano la dimensione urbana e proiettano il sistema nel panorama globale. I sistemi locali dei grandi comuni sono realtà territoriali che inglobano quella parte di flussi definita dal pendolarismo, e la loro dimensione di popolazione suggerisce una divisione del lavoro e delle economie esterne di scala che presuppongono un orientamento di tipo metropolitano.
Nel lavoro sono riportati i primi risultati ottenuti che saranno oggetto di successive indagini e qualificazioni in quanto parte di un più ampio progetto di ricerca
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
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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