1,721,024 research outputs found
Evidences of Reverse Faults Within South Polar Layered Deposits in Promethei Lingula Region (Mars). A Possible Clue of Ice-Cap Migration?
No full text“Unconformity-Bounded” Units on Mars SPLD (Promethei Lingula): a First Step Towards Formal Stratigraphic Classification?
No full textNew Elements on Stratigraphy of South Polar Layered Deposits on Promethei Lingula Region and a Possible Structural Approach
No full textHints at diapirism in Arabia Terra craters, Mars
No full textArabia Terra is a region of Mars located at the boundary between the southern highlands and the northern lowlands
and classically dominated by heavily cratered terrain. Unlike the rest of the topographic dichotomy on the planet,
in Arabia Terra the elevation transition is very gentle, falling of 4 km over a distance of 2500 km (average
slope = 0.0016). Most of the impact craters within the region display a central bulge, bearing a well preserved
stratification and a wide range of smaller morphologies like pitted cones, mounds and knobs (Franchi et al. 2013).
Images acquired by HiRISE and CTX cameras on board MRO provided a comprehensive dataset in which also
these small features can be easily recognized. These are tens of meters of diameter and tens of meters high, and
many of them show an apical orifice. They are interpreted to have worked as pathways for subsurface fluid flow
(e.g. Pondrelli et al., 2011; Rossi et al., 2008). Indeed an active underground fluid flow activity in Arabia Terra It
has been recently hypothesized (e.g. Andrews-Hanna et al, 2011) , being crater central bulges a place of sulfate
precipitation, due to local water table emergence (e.g. Franchi et al., 2013).
To date, there is no clear explanation for occurrence of central bulges surrounded by prominent depressions in
Arabia craters. In addition, in Firsoff and Crommelin craters it is possible to recognize folds and outward dipping
strata on the central bulges and their surroundings. Interestingly, a few craters with a prominent bulged floor
elsewhere in Arabia Terra do not display stratification and are not explainable as impact related structures as their
expected pristine central peak derived by hydrocode modelling is 2km lower and one third the diameter than
the actual topography (Pozzobon et al., 2013). All these evidences are not consistent with a typical lacustrine
stratigraphic environment, whether interested by sulfate precipitation or not, and suggest active deformation after
or during bulge sequences deposition.
One or – more likely - multiple layers of sulfates below the shallower levels of Arabia Terra surface need, in our
opinion, to be hypothesized in order to explain all these contrasting observations. Indeed impact cratering on
such an evaporate bearing layered target might have provided the ideal conditions of faulting, interconnectivity of
evaporatic beds and lithostatic load release to allow diapirs ascent, In turn diapirism could have been responsible
for central bulging as testified by outward dipping strata on stratified bulges, broad un-stratified bulges and folding
(see Jackson and Vendeville, 1994 for typical salt tectonics). The depth of the fluid source calculated with a fractal
method (Pozzobon et al., 2013) using the position of the small widespread mounds within Firsoff and Crommelin
craters can give a hint of the average depth of the evaportic horizons (4 km).
As further developments we plan to test and quantify our model to take into account geological evidences, possible
kinematics, rheology and stratigraphic constrains
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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