1,720,989 research outputs found
Cardiovascular and ventilatory control during exercise in chronic heart failure: role of muscle reflexes
No full textDuring exercise nervous signals are generated by stimulation of mechanically (muscle mechanoreflex) and chemically (muscle metaboreflex) sensitive skeletal muscle receptors. These receptors and their associated afferent fibres are sensitive to muscle work and reflexively adjust the haemodynamic, ventilatory and circulatory responses during physical effort. Thus the muscle reflex is essential in achieving normal responses to exercise in healthy subjects. In chronic heart failure, characterised by exercise intolerance with early occurrence of dyspnea or fatigue, peripheral muscle abnormalities (i.e. muscle atrophy, decreased peripheral blood flow, fibre-type transformation, and reduced oxidative capacity) trigger an exaggerated muscle reflex. This abnormality has recently been implicated in the genesis of the disabling symptoms. We review the role of the muscle reflex in regulating the cardiovascular and the ventilatory systems during exercise in both healthy and diseased condition
Hydroxytyrosol but not resveratrol ingestion induced an acute increment of post exercise blood flow in brachial artery
No full textThe aim of this study was to test if previous ingestion of compounds containing resveratrol or hydroxytyrosol, followed by an exhausting hand grip exercise, could induce an acute post-exercise increase in brachial blood flow. Six healthy subjects (three males and three females, 35 ± 7 years), 60 minutes after ingestion of a capsule containing 200 mg of resveratrol or 30 ml of extra virgin olive oil enriched with tyrosol, oleuropein and hydroxytyrosol, performed a hand grip exercise equal to half of their maximum strength until they were no longer able to express the same force (2-day interval between tests). The nonparametric Wilcoxon signed rank test was used for statistical evaluations. Brachial artery blood flow (Fba) and both blood velocity (Vba) and artery diameter (Dba) were assessed immediately after exercise cessation by means of colour Doppler ultrasound. After ingestion of the oil mixture the post-exercise value of Fba median was 2.4 times higher than that after ingestion of the resveratrol compound (P = 0.03), and also the Vba median concerning the hydroxytyrosol was 1.9 times higher than that of the resveratrol (P = 0.03). Both functional foods did not lead to a significant difference in the Dba medians. These results indicate that hydroxytyrosol, but not resveratrol, may be an effective adjuvant of recreational or agonistic, long-lasting sports performances, thanks to the powerful blood flow increment which can be obtained as soon as one hour from its oral intake
Hemodynamic responses to metaboreflex activation: Insights from spinal cord-injured humans
No full textThis investigation was conducted to study the hemodynamic consequences of spinal cord injury (SCI) during post-exercise muscle metaboreflex activation in SCI subjects. The hemodynamic response to metaboreflex recruitment was assessed in ten SCI patients and nine healthy controls (CTL) by means of impedance cardiography. The main results were (1) the metaboreflex-induced blood pressure rise was blunted in SCI subjects compared with normals, (2) the CTL group achieved the blood pressure response via cardiac output increase, while the SCI subjects could not use this mechanism, (3) the CTL group was able to enhance stroke volume and ventricular filling rate in response to the metaboreflex, whereas the SCI group could not. It was concluded that in healthy individuals, the hemodynamic response to the metaboreflex is an integrated phenomenon that depends mainly on a flow-mediated mechanism, whereas in SCI individuals the reduced venous return impairs this mechanism
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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