1,720,961 research outputs found
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
High temperature emplacement of the Cerro Galán and Toconquis Group ignimbrites (Puna plateau, NW Argentina) determined by TRM analyses.
No full textEstimates of pyroclastic flow emplacement. temperatures in the Cerro Galán ignimbrite and Toconquis. Group ignimbrites were determined using thermal. remanent magnetization of lithic clasts embedded within. the deposits. These ignimbrites belong to the Cerro. Galán volcanic system, one of the largest calderas in the. world, in the Puna plateau, NW Argentina. Temperature. estimates for the 2.08-Ma Cerro Galán ignimbrite are. retrieved from 40 sites in 14 localities (176 measured. clasts), distributed at different distances from the caldera. and different stratigraphic heights. Additionally, temperature. estimates were obtained from 27 sample sites (125. measured clasts) from seven ignimbrite units forming. the older Toconquis Group (5.60–4.51 Ma), mainly. outcropping along a type section at Rio Las Pitas, Vega. Real Grande. The paleomagnetic data obtained by. progressive thermal demagnetization show that the clasts. of the Cerro Galán ignimbrite have one single magnetic. component, oriented close to the expected geomagnetic. field at the time of emplacement. Results show therefore. that most of the clasts acquired a new magnetization. oriented parallel to the magnetic field at the moment of. the ignimbrite deposition, suggesting that the clasts were. heated up to or above the highest blocking temperature. (Tb) of the magnetic minerals (Tb=580°C for magnetite;. Tb=600–630°C for hematite). We obtained similar emplacement. temperature estimations for six out of the seven. volcanic units belonging to the Toconquis Group, with the. exception of one unit (Lower Merihuaca), where we found. two distinct magnetic components. The estimation of. emplacement temperatures in this latter case is constrained. at 580–610°C, which are lower than the other ignimbrites.. These estimations are also in agreement with the lowest. pre-eruptive magma temperatures calculated for the. same unit (i.e., 790°C; hornblende–plagioclase thermometer;. Folkes et al. 2011b). We conclude that the Cerro Galán. ignimbrite and Toconquis Group ignimbrites were emplaced. at temperatures equal to or higher than 620°C, except for. Lower Merihuaca unit emplaced at lower temperatures. The. homogeneity of high temperatures from proximal to distal. facies in the Cerro Galán ignimbrite provides constraints for. the emplacement model, marked by a relatively low eruption. column, low levels of turbulence, air entrainment, surface–. water interaction, and a high level of topographic confinement,. all ensuring minimal heat loss
Columnar jointing in vapor phase altered Cerro Galan Ignimbrite, Paycuqui, Argentina
No full textAbstract Columnar jointing is thought to occur primarily
in lavas and welded pyroclastic flow deposits. However, the
non-welded Cerro Galán Ignimbrite at Paycuqui, Argentina,
contains well-developed columnar joints that are instead
due to high-temperature vapor-phase alteration of the
deposit, where devitrification and vapor-phase crystalliza-
tion have increased the density and cohesion of the upper
half of the section. Thermal remanent magnetization
analyses of entrained lithic clasts indicate high emplace-
ment temperatures, above 630°C, but the lack of welding
textures indicates temperatures below the glass transition
temperature. In order to remain below the glass transition at
630°C, the minimum cooling rate prior to deposition was
3.0 10–8.5 102°C/min (depending on the experimental
data used for comparison). Alternatively, if the deposit was
emplaced above the glass transition temperature, conduc-
tive cooling alone was insufficient to prevent welding.
Crack patterns (average, 4.5 sides to each polygon) and
column diameters (average, 75 cm) are consistent with
relatively rapid cooling, where advective heat loss due to
vapor fluxing increases cooling over simple conductive
heat transfer. The presence of regularly spaced, complex
radiating joint patterns is consistent with fumarolic gas rise,
where volatiles originated in the valley-confined drainage
system below. Joint spacing is a proxy for cooling rates and
is controlled by depositional thickness/valley width. We
suggest that the formation of joints in high-temperature,
non-welded deposits is aided by the presence of underlying
external water, where vapor transfer causes crystallization
in pore spaces, densifies the deposit, and helps prevent
welding
The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types
No full textAbstract The 2.08-Ma Cerro Galán Ignimbrite (CGI)
represents a >630-km3 dense rock equivalent (VEI 8)
eruption from the long-lived Cerro Galán magma system
(∼6 Ma). It is a crystal-rich (35–60%), pumice (<10%
generally) and lithic-poor (<5% generally) rhyodacitic
ignimbrite, lacking a preceding plinian fallout deposit.
The CGI is preserved up to 80 km from the structural
margins of the caldera, but almost certainly was deposited
up to 100 km from the caldera in some places. Only one
emplacement unit is preserved in proximal to medial
settings and in most distal settings, suggesting constant
flow conditions, but where the pyroclastic flow moved into
a palaeotopography of substantial valleys and ridges, it
interacted with valley walls, resulting in flow instabilities
that generated multiple depositional units, often separated
by pyroclastic surge deposits. The CGI preserves a
widespread sub-horizontal fabric, defined by aligned
elongate pumice and lithic clasts, and minerals (e.g. biotite).
A sub-horizontal anisotropy of magnetic susceptibility
fabric is defined by minute magnetic minerals in all
localities where it has been analysed. The CGI is poor in
both vent-derived (‘accessory’) lithics and locally derived
lithics from the ground surface (‘accidental’) lithics.
Locally derived lithics are small (<20 cm) and were not
transported far from source points. All data suggest that the
pyroclastic flow system producing the CGI was character-
ised throughout by high sedimentation rates, resulting from
high particle concentration and suppressed turbulence at the
depositional boundary layer, despite being a low aspect
ratio ignimbrite. Based on these features, we question
whether high velocity and momentum are necessary to
account for extensive flow mobility. It is proposed that the
CGI was deposited by a pyroclastic flow system that
developed a substantial, high particle concentration granu-
lar under-flow, which flowed with suppressed turbulence.
High particle concentration and fine-ash content hindered
gas loss and maintained flow mobility. In order to explain
the contemporaneous maintenance of high particle concen-
tration, high sedimentation rate at the depositional bound-
ary layer and a high level of mobility, it is also proposed
that the flow(s) was continuously supplied at a high mass
feeding rate. It is also proposed that internal gas pressure
within the flow, directed downwards onto the substrate over
which the flow was passing, reduced the friction between
the flow and the substrate and also enhanced its mobility.
The pervasive sub-horizontal fabric of aligned pumice,
lithic and even biotite crystals indicates a consistent
horizontal shear force existed during transport and deposi-
tion in the basal granular flow, consistent with the existence
of a laminar, shearing, granular flow regime during the final
stages of transport and deposition
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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