1,720,957 research outputs found
Ultrasonic instrument effects on different implant surfaces
Full text linkAim: From the literature we infer that efficient peri- implant debridment cleaning result is obteined using metal tips rather than plastic material tips. Plastic tips allow to alter, the least possible, fixture superficial properties or analized specimens. Aim of this study was to evaluate in vitro effects of ultrasonic instrumentation using Acteon Implant Protect® ultrasonic grade IV titanium tips on implant surface micro- and macro-topography.
Methods: Nine 6 mm diameter and 2,6 mm height titanium disks were used in this study, with 3 different kinds of surface: machined, laser-treated and sandblasted. Four 500x500 μm areas were selected on each surface. Each area was equidistant from the disk center and from the disk border. Each area was analized using a Talysurf CLI 1000® profilometer and captured with an optical microscope at 3x enlargement and with a scanning electron microscope at 100x and 300x enlargement. Successively thesurface of each titanium disk was instrumented for a total of 40 strokes by a single operator using Implant Protect® (Acteon®) ultrasonic tianium tip. The tip was angulated tangentially. Calibrations were performed with scales before the experiment, and the average pressure applied in this study was 30g. Back and forth movements were performed in the same direction for 40 times. For the Satelec® scaler a power setting 3/10 was set at 25 to 32 kHz. Instrumentation was achieved with a continuos water irrigation. Pictures were acquired again by optical microscope and scanning electron microscope. After instrumentation any contaminants were searched with SEM-EDX (Scanning Electron Microscope – Energy Dispersive X-ray spectrometry). All reserched values were subjected to statistical analysis.
Results: Each image acquired with optical microscope and with Scanning Electron Microscope reveals instrumentation signs with tested tips. Machined and sandblasted surfaces showed a significant Ra reduction (p value < 0,05). Only laser-treated surface showed scratch signs without substantial Ra reduction. Contaminants were not found with EDX analysis before specimen instrumentation and after instrumentation neither. Before instrumentation and after instrumentation sandblasted surface presented a considerable quantity of Al and O.
Conclusion: To be effective implant surface ultrasonic instrumentation has to be done with titanium tips, not whith plastic material tips. Nevertheless titanium tips instrumentation causes alterations of implant surface microtopography; in addition different implant surfaces undergo different kinds of structural alteration non-clinically definable
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
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