1,720,996 research outputs found
Origin and evolution fo the vasovagal syncope [Origine ed evoluzione della sincope vasovagale]
No full textLa sincope vasovagale (SVV) è caratterizzata da una diminuzione improvvisa della pressione arteriosa e da un rallentamento della frequenza cardiaca in rapporto, rispettivamente, ad un’inibizione transitoria del sistema simpatico e ad un aumento del tono vagale. Svariate evidenze suggeriscono che la SVV classica (emozionale od ortostatica) non sia una malattia ma una caratteristica dell’individuo. Appare pertanto interessante indagare i fattori che possono spiegare la sua origine e la sua evoluzione e a tal scopo abbiamo analizzato i dati offerti dalla letteratura sul riflesso vasovagale nell’uomo e negli animali.
Abbiamo identificato due processi che appaiono utili ai fini del presente studio: la bradicardia da paura/spavento negli animali ed il riflesso vasovagale in corso di shock emorragico, sia nell’uomo che negli animali. Quest’ultimo riconosce lo stesso trigger del riflesso vasovagale osservato nell’uomo durante stress ortostatico (prolungato ortostatismo, tilt test) e cioè un’ipovolemia toracica. Durante tale ipovolemia il riflesso vasovagale si manifesta con gli stessi meccanismi fisiologici nell’uomo e negli altri mammiferi (per lo meno nella sua componente efferente) e cioè un aumento del tono vagale ed una inibizione transitoria del sistema simpatico, preceduta da un’aumentata attività dello stesso sistema. Anche la SVV emozionale nell’uomo e la bradicardia da paura/spavento negli animali sembrano presentare gli stessi meccanismi fisiologici. Il riflesso vasovagale appare pertanto predisposto, con gli stessi meccanismi fisiologici, nei mammiferi, incluso l’uomo e negli altri vertebrati (uccelli, rettili, anfibi, pesci); ciò suggerisce un’origine evolutiva comune. Se tale riflesso è persistito milioni di anni attraverso il lungo percorso evolutivo dei vertebrati significa che svolge (o ha svolto in passato) una funzione utile; poiché interviene solo sporadicamente è altamente probabile che rappresenti un “meccanismo di difesa”. L’ipotesi più plausibile è un meccanismo di difesa per il cuore in un momento in cui tale organo lavora in condizioni molto sfavorevoli. Un rallentamento della frequenza cardiaca indotto dal riflesso vasovagale rappresenta un break benefico per la pompa cardiaca, riducendo il consumo di ossigeno e migliorando il riempimento diastolico e la perfusione coronarica
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
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
A Simplified, practical echocardiographic approach for 3-dimensional surfacing and quantitation of the left ventricle: clinical application in patients with abnormally shaped hearts
No full textThe goal of this study was to validate the quantitative accuracy of a system for 3-dimensional (3D) echocardiographic reconstruction of the left ventricle to assess its volume and function in human beings by using 3 apical views as a simplified technique to promote practical clinical application. End-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (EF) were obtained by 3D echocardiography in 50 patients with dilated or geometrically distorted left ventricles and compared with values from magnetic resonance imaging (20 consecutive patients), angiography (22 consecutive patients), and radionuclide imaging (8 consecutive patients). Three-dimensional results were also compared with 2-dimensional (2D) echocardiographic estimates. Three-dimensional left ventricular reconstruction provided values that correlated and agreed well with pooled data from the other techniques for EDV (y = 0.93x + 9.1, r = 0.95, standard error of the estimate [SEE] = 15.2 mL, mean difference = -0.5 ± 15.4 mL), ESV (y = 0.94x + 4.3, r = 0.96, SEE = 11.4 mL, mean difference = 0.4 ± 11.5 mL), and EF (y = 0.90x + 4.1, r = 0.92, SEE = 6.2%, mean difference = -0.9 ± 6.4%) (all mean differences not significant versus 0), with greater errors by 2D echocardiography. Intraobserver and interobserver variabilities of 3D echocardiography were less than 6% for EDV, ESV, and EF. The overall time for image acquisition and 3D reconstruction was 5 to 8 minutes. Although this 3D method uses only a small number of apical views, it accurately calculates EDV, ESV, and EF in patients with dilated and asymmetric left ventricles and is more accurate than 2D echocardiography. The flexible surface fit used to combine the 3 views provides a convenient visual output as well as quantitation. This simple and rapid 3D method has the potential to facilitate routine clinical applications that assess left ventricular function and changes that occur with remodeling
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