1,721,033 research outputs found
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
Validity of the cerebral blood flow thresholds for the diagnosis of acute brain ischemia in head trauma. A systematic review.
No full textBackground: Reduction of cerebral blood flow plays a crucial role in causing posttraumatic cerebral ischemia. However, the methodologic adequacy of studies from which currently used cerebral blood flow thresholds in traumatic brain injury have been derived has not been evaluated. Objective: To systematically evaluate the evidence available on cerebral blood flow thresholds and its methodologic adequacy in adults with traumatic brain injury. Methods: Included were primary studies on adults with traumatic brain injury in which cerebral blood flow thresholds were evaluated and reported, and follow-up brain computed tomography or magnetic resonance imaging was used as the gold standard for diagnosing the finally infarcted area.
Results: Among the 53 diagnostic studies identified, 31 did not report any threshold value, whereas 20 studies used thresholds derived from the literature, mainly animal or clinical studies on ischemic stroke. One study measured cerebral blood flow thresholds, but did not use accepted neuroradiological criteria for the diagnosis of posttraumatic cerebral ischemia. The remaining study fulfilled all methodologic inclusion criteria, but was restricted to 14 patients with severe traumatic brain injury and cerebral contusion. This study proposed a cerebral blood flow threshold of 15 mL/100 mL/min, with sensitivity and specificity of 43% and 95%, respectively. Conclusions: Cerebral blood flow thresholds for the diagnosis of posttraumatic cerebral ischemia are based on weak evidence, and cannot be recommende
Discriminating between brain infarct and reversible brain ischaemia in acute stroke patients: A systematic review.
No full textBackground and Purpose—Cerebral blood flow (CBF) reduction below critical thresholds discriminates between irreversible infarct core, penumbra, and benign oligemia (penumbra that recovers spontaneously). Thresholds are based on animal studies, and their diagnostic accuracy in humans has never been established. The purpose of this study was to assess the evidence available on CBF thresholds for infarct core and penumbra in adult stroke patients.
Methods—Electronic database searching using Medline, Embase and the Cochrane Library, crosschecking of references, and contact with experts and authors of primary studies was used. Studies on adult stroke patients were included if they compared CBF measurements with a diagnostic gold standard (follow-up brain CT/MRI), and reported CBF thresholds. Two reviewers independently extracted the data and assessed study quality.
Results—A meta-analysis could not be carried out because of insufficient data. The optimal reported CBF thresholds varied widely, from 14.1 to 35.0 and from 4.8 to 8.4 mL/100 g per minute for penumbra and infarct core, respectively.
Conclusions—The use of CBF thresholds in commercial software for imaging methods cannot be recommended without further evaluation. (Stroke. 2006;37:1334-1339.
Cerebral Blood Flow Thresholds in Acute Stroke Triage. Response to letters by Lee et al and Lev et al [5]
No full textA discussion about the methodology used for systematic review and meta-analysis of cerebral blood flow threshold in ischemic strok
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
Cerebral blood flow thresholds for cerebral ischemia in traumatic brain injury. A systematic review
No full textBACKGROUND:: Reduction of cerebral blood flow plays a crucial role in causing posttraumatic cerebral ischemia. However, the methodologic adequacy of studies from which currently used cerebral blood flow thresholds in traumatic brain injury have been derived has not been evaluated. OBJECTIVE:: To systematically evaluate the evidence available on cerebral blood flow thresholds and its methodologic adequacy in adults with traumatic brain injury. METHODS:: Included were primary studies on adults with traumatic brain injury in which cerebral blood flow thresholds were evaluated and reported, and follow-up brain computed tomography or magnetic resonance imaging was used as the gold standard for diagnosing the finally infarcted area. RESULTS:: Among the 53 diagnostic studies identified, 31 did not report any threshold value, whereas 20 studies used thresholds derived from the literature, mainly animal or clinical studies on ischemic stroke. One study measured cerebral blood flow thresholds, but did not use accepted neuroradiological criteria for the diagnosis of posttraumatic cerebral ischemia. The remaining study fulfilled all methodologic inclusion criteria, but was restricted to 14 patients with severe traumatic brain injury and cerebral contusion. This study proposed a cerebral blood flow threshold of 15 mL/100 mL/min, with sensitivity and specificity of 43% and 95%, respectively. CONCLUSIONS:: Cerebral blood flow thresholds for the diagnosis of posttraumatic cerebral ischemia are based on weak evidence, and cannot be recommended. © 2008 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins
Un’elegia dipinta.
No full textIl saggio interpreta la Pietà di Brera di Giovanni Bellini come dipinto di devozione umanistica, in stretto rapporto con la teoria dei generi poetici antichi
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
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