1,720,979 research outputs found
State of stress and stress rotations: Quantifying the role of surface topography and subsurface density contrasts in magmatic rift zones (Eastern Rift, Africa)
Full text linkIn rift settings, the crustal stress field is dominated by extension, which leads to rift-parallel topography and basin alignments. However in some continental rift systems, some observables of the orientation of principal stresses show substantial deviations from these patterns. Such stress field rotations are currently poorly understood and could reflect the critical role of rift magmatism in the creation of topography, the plate state-of-stress, and volcanic and tectonic processes. Yet the role of magma intrusions, crustal thinning, and rift basin and flank topography on rift zone stress field rotations remain poorly quantified. The seismically- and volcanically-active Magadi-Natron-Manyara region of the East African Rift shows a 60 degrees local stress field rotation with respect to regional extension. Here, we test the hypothesis that such rotation is due to the cumulative effects of surface and subsurface loads (lateral subsurface density contrasts). We use analytical and calibrated numerical models of magmatic rift zones to simulate lithospheric deformation in the presence of magma bodies, crustal thinning, and topography to quantify their effect on intrusions and fault kinematics in a rift setting. Our 3D static models of a weakly extended rift suggest that surface topography influences shallow stress localization, whereas subsurface density contrasts play a larger role in lower crustal stress localization. Both patterns suggest a preferred region for melt storage beneath the rift valley. We show that the interaction between topography, crustal thinning, extension, and a pressurized magma reservoir could generate principal stress orientations consistent with the local stress rotation observed from earthquake focal mechanisms. Our results demonstrate how rift topography and the geometry of crustal thinning can guide magmatism and strain localization, highlighting the need for a three-dimensional treatment of rift kinematics
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
InSAR Applied to the Study of Active Volcanic and Seismic Areas in Africa
Full text linkTwo active volcanic areas situated in immature portions of the East African Rift System
(EARS): the Lake Kivu (Dem. Rep. of Congo) and Lake Natron (Tanzania) regions,
which are located in the western and eastern branch, respectively, are still poorly known.
Both areas indeed lack of ground-based networks, due to security problems or difficult
field accessibility. The Lake Kivu area includes two volcanoes erupting frequently: the
Nyamulagira and Nyiragongo volcanoes. The SAR database covering these volcanoes in-
cludes data from JERS, ERS-1&2, ENVISAT, ALOS, RADARSAT-1&2 satellites back
from year 1996. SAR Interferometry (InSAR) is thus applied to study the ground de-
formations. MT-InSAR approaches, such as the ”‘StaMPS”’ method, are used to give
us new complementary information to better constrain the previous established eruption
models, or gain new insights on eruptions missed by the conventional InSAR, as well as
on magmatic and tectonic activity. When enough constrains are available, the ground
displacements are modeled using a 3D-Mixed Boundary Elements Method combined with
a neighborhood algorithm. Hence, the 1996, 2002, 2004 and 2010 eruptions of Nyamu-
lagira are modeled. The modeling results, coupled with the StaMPS MT-InSAR results,
bring new insights concerning the magma plumbing system of this poorly known volcano
and its eruptive mechanisms. The collapse of the eastern flank of Nyamulagira, along the
NNW-trend fractures network linking Nyamulagira and Nyiragongo volcanoes, can also
be identified. InSAR also captures the ground displacements associated with the January
2002 Nyiragongo eruption. The modeling of this major event evidences a deep magma
intrusion beneath the Lake Kivu. Such intrusions should be taken into account for hazard
assessment. The magma could indeed finds its way to the Lake Kivu floor, as evidenced by
the presence of several old phreato-magmatic cones, and causes a lake overturn. The low
dikes overpressures found in the North Kivu and Lake Natron areas indicate that, although
the rift is considered as immature, the rift extension is driven by the supply of magma from
depth, rather than by the tectonics. A new criterion to identify the rifting stage is found to
be the stress state. In the southern part of the rift, tectonic activity dominates, indicating
that the tectonics is probably driving the rift opening there
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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