1,721,043 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
Long-Term Hemodynamic Performance of the Aortic Valve After David I: An Echocardiographic Study
No full textDespite optimal hemodynamics at rest, the performance of the aortic valve under stress conditions long after David I procedure is still debated. From 2001-2014, 73 patients underwent reimplantation with David I technique. Aortic valve function of 13 patients (age 61.2 ± 8.72) with a follow-up of at least 5 years (6.3 ± 0.9 years) was assessed at exercise echocardiographic stress test on a stationary cycle. Patients who had undergone concomitant procedure, with recurrent aortic insufficiency or mitral valve incompetence, were excluded. In all, 8 healthy volunteers served as controls. Transvalvular gradients progressively increased during the steps in both groups (P-within < 0.001), being higher in David patients (P-between < 0.001), but never reaching a clinical significance (David Peak gradient 23.8 ± 9.3 mmHg; Mean gradient 13.2 ± 5.1 mmHg). Effective orifice area (EOA) and EOA index did not change during the test in David patients, whereas Controls showed a progressive increase of functional valve area to a peak at 50 W (Controls EOA 4.0 ± 0.5 cm(2); EOA index 2.0 ± 0.3 cm(2)/m(2)). In conclusion, David I procedure ensures good hemodynamics during high-flow conditions at long-term follow-up. The reimplantation of the functional aortic annulus inside a rigid tube determines a paradoxical reduction of functional aortic valve area, secondary to the increased stroke volume, without any clinically relevant increase in transvalvular gradients. These data confirm the reliability of David I in the long term, even under physical stress conditions
Midterm follow-up of the reimplantation technique in patients with relatively normal annulus: is David I still a clinically valid option?
No full textOBJECTIVE: The aim of this study was to evaluate the midterm results of the reimplantation technique with a straight tubular graft in patients with aortic root aneurysms with or without aortic insufficiency.
METHODS: From February 2002 to November 2012, 51 consecutive patients underwent the David I valve-sparing aortic procedure for aortic root aneurysm; the mean age was 59.9±12.3 years. Nine patients (17.6%) had a bicuspid aortic valve. Patients were followed prospectively for 4.78±3.60 years (median, 5 years). Operative results, survival, freedom from redo aortic surgery and from recurrent aortic insufficiency greater than 2+ were assessed.
RESULTS: No in-hospital mortality was recorded. In 5 cases, adjunctive procedures on the aortic valve were needed to achieve good leaflet coaptation. Aortic regurgitation was significantly lower at discharge (2.3±1.0 vs 0.3±0.5; P<.001). There were 5 postoperative deaths, all noncardiac related. Survival was 91.0%±4.4% at 5 years; freedom from redo aortic surgery was 96.8%±3.2% and freedom from recurrent aortic insufficiency greater than 2+ was 96.8%±3.2%. The outcomes in patients with repaired bicuspid aortic valves showed no significant differences compared to the outcomes in patients with repaired tricuspid valves.
CONCLUSIONS: The reimplantation procedure using a straight tube is a safe and reproducible valve-sparing technique that can achieve no in-hospital mortality and durable midterm results, either in bicuspid or tricuspid valves. Further studies are needed to assess the behavior of repaired valves under physical stress at long-term follow-up
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
- …
