1,720,992 research outputs found
Slab stiffness control of trench motion: Insights from numerical models
No full textSubduction zones are not static features, but trenches retreat (roll back) or advance. Here, we
investigate the dominant dynamic controls on trench migration by means of two- and three-dimensional
numerical modeling of subduction. This investigation has been carried out by systematically varying the
geometrical and rheological model parameters. Our viscoplastic models illustrate that advancing style
subduction is promoted by a thick plate, a large viscosity ratio between plate and mantle, and a small
density contrast between plate and mantle or an intermediate width (w 1300 km). Advancing slabs
dissipate 45% to 50% of the energy in the system. Thin plates with relatively low viscosity or relatively
high density, or wide slabs (w 2300 km), on the other hand, promote subduction in the retreating style
(i.e., slab roll-back). The energy dissipated by a retreating slab is 35% to 40% of the total dissipated
energy. Most of the energy dissipation occurs in the mantle to accommodate the slab motion, whereas the
lithosphere dissipates the remaining part to bend and ‘‘unbend.’’ With a simple scaling law we illustrate
that this complex combination of model parameters influencing trench migration can be reduced to a single
one: plate stiffness. Stiffer slabs cause the trench to advance, whereas more flexible slabs lead to trench
retreat. The reason for this is that all slabs will bend into the subduction zone because of their low plastic
strength near the surface, but stiff slabs have more difficulty ‘‘unbending’’ at depth, when arriving at the
660-km discontinuity. Those bent slabs tend to cause the trench to advance. In a similar way, variation of
the viscoplasticity parameters in the plate may change the style of subduction: a low value of friction
coefficient weakens the plate and results in a retreating style, while higher values strengthen the plate and
promote the advancing subduction style. Given the fact that also on Earth the oldest (and therefore
probably stiffest) plates have the fastest advancing trenches, we hypothesize that the ability of slabs to
unbend after subduction forms the dominant control on trench migratio
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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