1,721,162 research outputs found
Microstructural study of nanocrystalline pure and doped tin dioxide to be used for resistive gas sensors
No full textNanocrystalline pure and doped SnO2 have been intensively studied for a long time to build resistive gas sensors. However, it is still useful to synthesize nanopowders with the smallest crystallite size to build devices. A modified gel-combustion method and a novel reactive oxidation process are proposed for nanopowders synthesis and results are compared. Materials have been characterized by XRD, Scherrer equation to evaluate the crystallite size; BET absorption to determine specific area and HRTEM to observe the crystallites (evaluating their mean size and distribution); defects and effect of calcination treatments are also considered. Previous studies have shown that if nano-SnO2 replaces the conventional microcrystalline-SnO2 to build resistive gas sensors, sensitivity increases (>30%) and the operation temperature considerably decreases. A heating and measuring system has been designed for achieving low power consumption and uses pulsed heating operation. This method of electrical control and measurement is operated intermittently, with "heating" and "readout" cycles (readout: signal of sensitive film).Fil: Bianchetti, Mario Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Arrieta, Cristian L.. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; ArgentinaFil: Walsoe, Noemi Elizabeth. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin
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
Endoscopic biliary self-expandable metallic stent in malignant biliary obstruction with or without sphincterotomy: systematic review and meta-analysis
Full text linkBackground and aim: To assess the rate of adverse events and the technical success rate of biliary stenting with or without EBS.
Methods: A literature search up to February 2017 was performed. Studies assessing adverse events (AEs) and technical success rates of stenting with or without EBS were considered.
Results: Seven studies (870 patients; 12 treatment arms) were included. Early AEs, i. e. those occurring within 30 days, were significantly lower in no-EBS vs. EBS-group (11 % vs . 20.1 %; OR: 0.36, 95 %CI: 0.13 - 1.00). Rates of post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis were not significantly different in the two groups (no-EBS vs . EBS: 6.1 % vs 5 %; OR: 1.33, 95 %CI: 0.68 - 2.59). The rate of bleeding was significantly lower in patients without EBS (no-EBS vs EBS: 0 % vs 5 %; OR: 0.12, 95 % CI: 0.03 - 0.45). Rates of cholangitis were significantly lower in patients without EBS (no-EBS vs . EBS: 3.3 % vs. 7.4 %; OR: 0.38, 95 %CI: 0.17 - 0.83). Both late AEs and mortality rates did not significantly differ between no-EBS and EBS patients (19.9 % vs. 18.9 %; OR: 0.93, 95 %CI: 0.56 - 1.53, and 2.5 % vs. 2.9 %; OR: 1.18, 95 %CI: 0.22 - 6.29, respectively). The technical success rate for stent insertion also did not differ (98 % vs. 97.6 %; OR: 1.05, 95 %CI: 0.42 - 2.63).
Conclusion: EBS seems to be associated, in the first 30 days after the procedure, with an increased risk of cholangitis and bleeding. No difference was observed in the rate of post-ERCP pancreatitis
Water-filled technique for therapeutic pancreato-biliary EUS in patients with surgically altered anatomy
Full text linkOne of the main challenges encountered by endosonographers is performing diagnostic and interventional pancreato-biliary endoscopic ultrasound (EUS) procedures in the presence of surgically altered upper gastrointestinal anatomy. We describe the water-filled technique (WFT) for EUS examination and treatment of the pancreato-biliary region in patients with surgically altered upper gastrointestinal anatomy. Using the WFT, the scope is advanced up to the gastro-jejunal anastomosis and, after placing the tip of the scope 2 cm beyond it, enlargement of the jejunal lumen is obtained by water instillation of the jejunal loop. An enlargement of more than 1.5 cm allows advancement of the tip of the scope under EUSguidance up to the duodenum, in a retrograde way. The WFT is useful for reaching the ampullary area and performing diagnostic and therapeutic EUS in patients with surgically altered anatomy. The technique is also reproducible and can be easily used by endoscopists who regularly perform EUS
Nanostructured ceramic materials: Applications in gas sensors and solid-oxide fuel cells
No full textTwo applications of nanostructured ceramic materials developed at CINSO in recent years are reviewed, including the synthesis and properties of these materials:(i)Application of nanostructured SnO2-based semiconductors for gas sensors, showing the increase of their sensitivity and the decrease of their operating temperature if the sensor is built with nanomaterials in comparison to sensors prepared with conventional microcrystalline materials. The sensing mechanism is discussed in order to explain the different behavior.(ii)Application of nanocrystalline ZrO2-CeO2 solid solutions as novel anodes for solid-oxide fuel cells operated using hydrocarbons as fuel. Other applications of nanoceramics in these devices, recently investigated at CINSO, are also discussed.Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Bianchetti, Mario Fidel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Cabezas, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; ArgentinaFil: Walsoe, Noemi Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; Argentin
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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