1,721,034 research outputs found
The effect of shape and size distribution of abrasive particles on the volume loss of enamel using micro-abrasion
No full textWear of enamel during tooth brushing is a complex phenomenon with many variables affecting the level of loss. Toothpastes contain angular abrasive particles at a concentration of 12%–15% v/v abrasive designed to remove biofilm and extrinsic stains that also have the potential to harm the tooth enamel resulting in wear. Toothpastes contain multi-modal particles in the size range of 4μm–12μm. The aim of this paper is to develop an understanding of the relationship between the combined effects of particle shape, size, size distribution and load on the volume loss of enamel under abrasive testing. Micro-abrasion testing using a Nylon ball, to simulate the toothbrush, was undertaken on hydrated bovine enamel disks using volume concentrations of 5% – 20% v/v alumina and silica. Post experimental surface analysis was performed to analyse the wear scar morphology and groove analysis. The synergistic effects were calculated of bimodal particles vs. mono sized particles. Mono-sized particles as compared to bimodal, appeared to give the best outcome and least wear of enamel. A positive synergy existed for the alumina and silica bimodal tests, indicating the bimodal particle distribution was causing more wear than the mono-sized particles. The mechanism of material removal was a combination of crushing and fracture of the enamel prisms (rods), followed by micro-chipping and removal of enamel. The magnitude and the distribution of the particle sizes is the most dominant factor in determining the levels of wear, with smaller particles and narrow distributions of the particle size reducing the magnitude of wear. The shape of the particles is also a major factor influencing wear, with the spherical tests generating lower wear rates than the angular tests.<br/
Evolution of wear on enamel caused by tooth brushing with abrasive toothpaste slurries
No full textMaintaining good oral hygiene is vital to a healthy body and aesthetically attractive smile. Regular tooth brushing prevents cavities, tooth decay and gum disease which if left, can lead to serious health problems. However, cleaning your teeth comes with a drawback. Toothpastes contain abrasive particles, which in combination with the toothbrush, have the potential to wear tooth enamel. To optimise the cleaning efficiency of teeth and minimise the enamel wear it is essential to understand the science behind the tooth/toothpaste/toothbrush interface. An integrated approach is employed in this study to investigate the tribology of brushing, examining the friction and wear evolution. A reciprocating tribometer was modified to enable a toothbrush head to reciprocate against a bovine enamel disk to simulate the tooth brushing action, with a constant feed of either an abrasive free or a silica or alumina containing toothpaste slurry to the contact. The evolution of the friction with time during the brushing simulation as well as the changes in the enamel surface roughness were determined. The alumina slurry resulted in higher friction, increased wear depth and an increased roughening of the enamel surface compared to the silica slurries, with all abrasives causing 2 body grooving to the enamel surface. The spherical silica provided both the lowest friction and material loss of the slurries tested. The abrasive free slurry caused no wear or surface roughening but exhibited the highest friction during brushing
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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