1,721,025 research outputs found
Stability and chemical equilibrium of amphibole in calc-alkaline magmas: an overview, new thermobarometric formulations and application to subduction-related volcanoes
No full textThis work focuses on a rigorous analysis of the
physical–chemical, compositional and textural relationships
of amphibole stability and the development of new
thermobarometric formulations for amphibole-bearing calcalkaline
products of subduction-related systems. Literature
experimental results (550–1,120C, \1,200 MPa, -1 B
DNNO B ?5), H2O–CO2 solubility models, a multitude of
amphibole-bearing calc-alkaline products (whole-rocks and
glasses, representing 38 volcanoes worldwide), crustal and
high-P (1–3 GPa) mantle amphibole compositions have
been used. Calcic amphiboles of basalt-rhyolite volcanic
products display tschermakitic pargasite (37%), magnesiohastingsite (32%) and magnesiohornblende (31%) compositions with aluminium number (i.e. Al# = [6]Al/
AlT) B 0.21. A few volcanic amphiboles (*1%) show high
Al# ([0.21) and are inferred to represent xenocrysts of
crustal or mantle materials. Most experimental results on
calc-alkaline suites have been found to be unsuitable for
using in thermobarometric calibrations due to the high Al#
([0.21) of amphiboles and high Al2O3/SiO2 ratios of the
coexisting melts. The pre-eruptive crystallization of consistent
amphiboles is confined to relatively narrow physical–
chemical ranges, next to their dehydration curves. The
widespread occurrence of amphiboles with dehydration
(breakdown) rims made of anhydrous phases and/or glass,
related to sub-volcanic processes such as magma mixing
and/or slow ascent during extrusion, confirms that crystal
destabilization occurs with relatively low T–P shifts. At the
stability curves, the variance of the system decreases so that
amphibole composition and physical–chemical conditions
are strictly linked to each other. This allowed us to retrieve
some empirical thermobarometric formulations which work
independently with different compositional components
(i.e. Si*, AlT, Mg*, [6]Al*) of a single phase (amphibole),
and are therefore easily applicable to all types of calcalkaline
volcanic products (including hybrid andesites). The
Si*-sensitive thermometer and the fO2–Mg* equation
account for accuracies of ±22C (rest) and 0.4 log units
(maximum error), respectively. The uncertainties of the
AlT-sensitive barometer increase with pressure and
decrease with temperature. Near the P–T stability curve, the
error is\11% whereas for crystal-rich (porphyritic index
i.e. PI[35%) and lower-T magmas, the uncertainty
increases up to 24%, consistent with depth uncertainties of
0.4 km, at 90 MPa (*3.4 km), and 7.9 km, at 800 MPa
(*30 km), respectively. For magnesiohornblendes, the
[6]Al*-sensitive hygrometer has an accuracy of 0.4 wt%
(rest) whereas for magnesiohastingsite and tschermakitic
pargasite species, H2Omelt uncertainties can be as high as
15% relative. The thermobarometric results obtained with
the application of these equations to calc-alkaline amphibole-
bearing products were finally, and successfully,
crosschecked on several subduction-related volcanoes,
through complementary methodologies such as pre-eruptive
seismicity (volcano-tectonic earthquake locations and frequency),
seismic tomography, Fe–Ti oxides, amphibole–
plagioclase, plagioclase–liquid equilibria thermobarometry
and melt inclusion studies. A user-friendly spreadsheet (i.e. AMP-TB.xls) to calculate the physical–chemical conditions
of amphibole crystallization is also provided
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
Determinazioni chimiche, fisiche e biologiche su alcuni campioni di mucillagine e sulle acque circostanti le masse mucillaginose comparse nel Mare Adriatico nell’estate 1997
No full textDispelling 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
- …
