1,720,993 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
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
Sigh: tool to determine the respiratory viscoelastic properties.
No full textOBJECTIVE:
In mechanically ventilated patients a high fraction of the pressure can be dissipated to overcome the viscoelastic components of the respiratory system. Recently it was demonstrated that sigh improved oxygenation in mechanically ventilated ARDS patients. We evaluated if, in acute lung injury (ALI) patients, the sigh can be used to measure the respiratory viscoelastic properties.
METHODS:
Ten consecutive normal subjects undergoing general anaesthesia for minor abdominal surgery and ten ALI patients admitted to the ICU, were studied. Three sighs were administered every minute during the measurement period. The viscoelastic constants (E2, R2 and tau2) were determined by (i) a series of end-inflation airway occlusions (multiple breath method, MBM) and (ii) fitting the time course of the slow decay in pressure during end inspiratory pause of the sigh (sigh method, SM). The results were compared by means of the limits of agreement as modified for small sample sizes.
RESULTS:
Viscoelastic parameters were similar to those obtained in other studies. In normal subjects the mean differences (+/- SEM) of tau2, R2, and E2 given by the SM and the MBM were 0 +/- 0.04 s, 0.37 +/- 0.20 cmH2O L(-1) s, and 0.21 +/- 0.26 cmH2O L(-1), respectively. The mean differences (+/- SEM) of tau2, R2, and E2 in ALI patients were 0.02 +/- 0.02 s, 0.45 +/- 0.31 cmH2O L(-1) s, 0.34 +/- 0.36 cmH2O L(-1), respectively. No lack of agreement could be detected between the two methods in all variables in normal subjects and ALI patients.
CONCLUSIONS:
The long inflation time characteristic of the sigh allowed the determination of the viscoelastic constants by means of a simpler and faster method. Moreover it does not require very small tidal volumes, which can increase reabsorption atelectasis in ALI patients and can improve alveolar recruitment and oxygenation in these patients
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
Effects of mechanical load on flow, volume and pressure delivered by high-frequency percussive ventilation.
No full textHigh-frequency percussive ventilation (HFPV) has proved its unique efficacy in the treatment of acute respiratory distress, when conventional mechanical ventilation (CMV) has demonstrated a limited response. We analysed flow (V(dot)), volume (V) and airway pressure (Paw) during ventilation of a single-compartment mechanical lung simulator, in which resistance (R) and elastance (E) values were modified, while maintaining the selected ventilatory settings of the HFPV device. These signals reveal the physical effect of the imposed loads on the output of the ventilatory device, secondary to constant (millisecond by millisecond) alterations in pulmonary dynamics. V(dot), V and Paw values depended fundamentally on the value of R, but their shapes were modified by R and E. Although peak Paw increased 70.3% in relation to control value, mean Paw augmented solely 36.5% under the same circumstances (maximum of 9.4 cm H2O). Finally, a mechanism for washing gas out of the lung was suggested
Mechanical loads modulate tidal volume and lung washout during high-frequency percussive ventilation.
No full textHigh-frequency percussive ventilation (HFPV) has been proved useful in patients with acute respiratory distress syndrome. However, its physiological mechanisms are still poorly understood. The aim of this work is to evaluate the effects of mechanical loading on the tidal volume and lung washout during HFPV. For this purpose a single-compartment mechanical lung simulator, which allows the combination of three elastic and four resistive loads (E and R, respectively), underwent HFPV with constant ventilator settings. With increasing E and decreasing R the tidal volume/cumulative oscillated gas volume ratio fell, while the duration of end-inspiratory plateau/inspiratory time increased. Indeed, an inverse linear relationship was found between these two ratios. Peak and mean pressure in the model decreased linearly with increasing pulsatile volume, the latter to a lesser extent. In conclusion, elastic or resistive loading modulates the mechanical characteristics of the HFPV device but in such a way that washout volume and time allowed for diffusive ventilation vary agonisticall
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