1,720,978 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
Cytoprotective effect of acetyl-L-carnitine evidenced by analysis of gene expression in the rat brain
No full textAcetyl-L-carnitine (ALC), the acetyl ester of L-carnitine, is a naturally occurring substance that when administered at supraphysiological concentrations is neuroprotective. ALC plays an essential role in intermediary and mitochondrial metabolism. It has also neurotrophic and antioxidant actions. ALC has demonstrated efficacy and high tolerability in the treatment of neuropathies of various etiologies, and it is a molecule of considerable interest for its clinical application in various neural disorders, such as Alzheimer's disease and painful neuropathies, although little is known regarding the effects of ALC on gene expression. Suppression subtractive hybridization methodology was used for the generation of subtracted complementary DNA libraries and the subsequent identification of differentially expressed transcripts in the rat brain after a chronic ALC treatment. In the present paper, we provide evidences for the up-regulation of the expression of prostaglandin D(2) synthase, brain-specific Na(+)-dependent inorganic phosphate transporter, and cytochrome b oxidase, bc1 complex induced in the rat brain by ALC. On the contrary, ALC treatment down-regulates the expression of the gene of ferritin-H. Altogether, these results suggest that ALC might play a cytoprotective role against various brain stressors
Effects of Catechin on cerebral arteriole vasomotion in spontaneously hypertensive rats
No full textStudies in humans have found consumption of certain flavanoid-containing foods to be associated with improvement in endothelial function and with reduction in blood pressure. In particular, catechin, a natural phenol contained in cocoa and green tea, appears to play a crucial role in the prevention of cardiovascular diseases reducing the systemic arterial blood pressure. The aim of the present study was to in vivo investigate the effects of oral administration of catechin on pial arteriolar rhythmic diameter changes in SHR in comparison with normotensive rats. Catechin was orally administered to SHR for 2 months at the dosage of 30 mg/kg b.w. The pial microcirculation was visualized by fluorescence microscopy. The vessel diameter and rhythmic variations in diameter were evaluated with computer-assisted method. Moreover, the pial arterioles were classified by Strahler scheme in five orders. On 30 min of recordings was performed the Spectral analysis in order to evaluate different frequency components: the first two in the ranges 0.005-0.0095 Hz and 0.0095-0.021 Hz (endothelial activity), the second in the range 0.021-0.052 Hz (neurogenic activity), the third in the range 0.052-0.145 Hz (myogenic activity), finally, the fourth and the fifth in the ranges 0.145-0.6 Hz (respiratory activity) and 0.6-3.0 Hz (heart beat), respectively. The data indicate that SHR treated with catechin presented an increase in the amplitude frequency components related to endothelial activity that in untreated SHR were markedly reduced. In conclusion, the catechin treatment induces the recovery of endothelial activity in SHR where this frequency component was seriously compromised compared to normotensive rats
Recenti acquisizioni sui meccanismi cellulari e molecolari dei processi di apprendimento
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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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