1,721,010 research outputs found
Percutaneous Heart Valve Replacement: An Update
No full textValvular heart disease continues to be an important health care problem. Although surgical valve replacement remains the standard treatment, minimally invasive approaches for valve repair and replacement are becoming attractive alternatives among physicians and patients. In fact, percutaneous procedures can extend treatment to the increasing population of elderly patients with severe comorbidities who cannot withstand the stress of open heart surgery and to the younger patients at the early stage of valve disease, who are not treated until older ages to avoid multiple invasive surgeries. Feasibility of this technique has been shown in the first clinical experiences, and the early results are promising. However, it is clear that percutaneous valve replacement therapy is still at the early stage of development and requires enhanced implantation procedures and substantial design improvements as well as long-term follow-up to show the safety and effectiveness of this new treatment modality
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
Study of pulmonary vascularization in pulmonary atresia with ventricular septal defect in relation to deletion of chromosome 22
No full textA normal lung is supplied by a pulmonary artery branching from the pulmonary trunk. Major aorto-pulmonary collateral arteries (MAPCAs) are found in combination with various congenital heart malformations such as pulmonary atresia with ventricular septal defect (PA-VSD). Now that MAPCAs are used for unifocalization in patients with PA-VSD, the question arises as to whether the morphologic criteria of these collateral arteries could help to provide better results. We compared the morphology of the pulmonary vascular bed, the origin, course and connections of the MAPCAs in 40 consecutive infants with PA-VSD with or without 22q deletion (de122q11.2.). All underwent echocardiographic evaluation and catheterization. Identification of de122q11.2. was performed by FISH study. De122q11.2. was identified in 16 pts (40%); the presence of MAPCAs was significantly higher in patients with de122q11.2. (9/16 vs 3/24, p = 0.01). While complex morphology of MAPCAs, anastomoses with the central pulmonary artery outside the lung and absent ductus arteriosus were associated with de122q11.2, confluence of the pulmonary arteries was not a relevant phenotypic difference. The size of the right and left pulmonary arteries expressed as a standard deviation difference of the normal range for body surface area was -4.2 (quartiles - 3.1/-1.8) for PA-VSD with del22q11.2. and -2.6 (quartiles -5.3/-2.9) for PA- VSD without del22q11.2. (p = 0.02). The difference between measured and theoretical Nakata index was -373 ± 94 for PA-VSD with del22q11.2. vs. -245 ± 93 for PA-VSD without del22q11.2. (p = 0.0002). A specific pulmonary vascular bed phenotype could be defined in patients with PA-VSD with del22q11.2. deletion: MAPCAs with complex loop morphology and small but confluent central pulmonary arteries. These findings indicate a different timing of the faulty development pathway of the pulmonary vascular bed in patients with and without del22q11.2. This phenotype difference may help our understanding of maldevelopment and facilitate decisions concerning the suitability of these arteries for unifocalization procedures
A novel nanocomposite polymer for development of synthetic heart valve leaflets
No full textA novel nanocomposite polymer with a polycarbonate soft segment (PCU) and polyhedral oligomeric silsesquioxanes (POSS) nanoparticle (POSS-PCU) has been selected for a synthetic heart valve due to its superior biocompatibility and in vivo biostability. However, the development of synthetic heart valves from polymeric materials requires an understanding of the basic mechanical and surface properties of the polymer. In this study, the mechanical properties of POSS-PCU, including tensile strength, tear strength and hardness, were tested and compared to control (PCU). The surface property was analyzed using contact angle measurement and the resistance to platelet adhesion was also investigated. POSS-PCU (hardness 84 ± 0.8 Shore A) demonstrated significantly higher tensile strength 53.6 ± 3.4 and 55.9 ± 3.9 N mm-2 at 25 and 37 °C, respectively) than PCU (33.8 ± 2.1 and 28.8 ± 3.4 N mm-2 at 25 and 37 °C, respectively). Tensile strength and elongation at break of POSS-PCU was significantly higher than PCU at both 25 and 37 °C (P < 0.001). POSS-PCU showed a relatively low Young's modulus (25.9 ± 1.9 and 26.2 ± 2.0 N mm-2) which was significantly greater in comparison with control PCU (9.1 ± 0.9 and 8.4 ± 0.5 N mm-2) at 25 and 37 °C, respectively, with 100 μm thickness. There was no significant difference (P > 0.05) in tear strength between POSS-PCU and PCU at 25 °C. However, tear strength increased significantly (P < 0.001) (at 37 °C) as the thickness increased from 100 μm (51.0 ± 3.3 N mm-1) to 200 μm (63 ± 1.5 N mm-1). The surface of POSS-PCU was significantly less hydrophilic than that of PCU. © 2009 Acta Materialia Inc
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