1,720,955 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
PRELIMINARY U-Pb LA-ICPMS ZIRCON ANALYSES FROM THE GOIAS COMPLEXES: SHRIMP COMPARISON AND INTRUSION AGE
No full textCana Brava, Niquelàndia and Barro Alto are three mafic-ultramafic layered intrusions (from N to S) which form a - 350 km, NNE-trend belt within the Brasilia Belt (Goiés state, Brazil). Presently, their intrusion ages and geologica! evolution are stili debated. The Niquelàndia and Barro Alto complexes are forrned by two main sequences: the upper sequence and the lower one. Some authors suggest that the two sequences represent two separate intrusions: the upper sequence would be a Mesoproterozoic intrusion at - 1.3 Ga, whereas the lower sequence a Neoproterozic one at - 790 Ma. According to this interpretation, the two sequences were re-crystallized by Neoproterozoic metamorphism and exhumed and juxtaposed during the Brazilian event of formation of the Gondwana continent. Another model suggests that the two sequences are part of the same intrusion, which occurred during the Neoproterozoic and was exhumed during the Brazilian event. New U-Pb SHRIMP-II zircon analyses were perforrned at the Universidade de Sào Paulo from samples from Cana Brava and Barro Alto, the two least-known complexes in order to clarify the sequence of events that led to their forrnation. Analyses were then replicated at the CIGS of the Università di Modena e Reggio Emilia using a X Series" quadrupole ICP-MS coupled with a New Wave UP-213 Nd:YAG laser ablation system. Zircons were sampled through a 40 micron spot (static mode), using a He flux of 0.6 l/min, with an energy density of - 6 J/cm2. Daily instrument calibration was perforrned with the NIST 610 standard, monitoring also the oxide production rate {232Th160/232Th << 0.01 %). Laser-induced elemental fractionation was corrected by repeated analyses of the standard zircon TEMORA2 (Black et al., 2004). A secondary reference materia! (zircon CZ3) was used to check the precision and accuracy of the corrections. Our LA-ICP-MS data are preliminary, but very promising being the accuracy of the measured ratio within the SHRIMP variability. We are currently working to improve the precision of our methodology, which however is now comparable with literature LA-ICP-MS data (propagated 2SE - 2-6%; Horstwood et al., 2008). Overall, the isotopic data of Cana Brava and Barro Alto complexes previde for a coeval Neoproterozoic intrusion age at - 790 Ma. These ages are consistent with those reported in literature for Niquelàndia. Mesoproterozoic ages, consistent with the forrnation age of the metavolcanic-metasedimentary sequence in magmatic contaci with the complexes, were found in inherited zircon cores. Our data clearly show that the Goiàs complexes are formed by single bodies intruded during the Neoproterozoic at -790 Ma and that the hypothesis of two separate intrusions juxtaposed by tectonic must
be discarded
THE LARGE LAYERED GOIAS COMPLEXES: NEW U-Pb ANO PRELIMINARY Lu-Hf IN SITU ZIRCON ANALYSES FROM BARRO ALTO AND CANA BRAVA
No full textThe large layered Goias complexes are three mafic-ultramafic layered intrusions which outcrop in a -350 km, NNE-trend bel! within the Brasilia Belt (centrai Brazil). Fom N lo S, they are: Cana Brava, Niquelllndia and Barro Alto. The intrusion age and geologica! hystory of these intrusions is stili presently debated. New U-Pb SHRIMP-II zircon analyses were perforrned in samples from Cana Brava and Barro Alto, the two poorest-known complexes among them, providing fora coeval Neoproterozoic intrusion age al -790 Ma of both complexes, consistent with literature ages for the Niquelandia complex. lnherited zircons with Mesoproterozoic ages are consistent with the formation age of the metavolcanic-metasedimentary sequences in magmatic contaci with these three complexes and suggest some degree of contamination of the complexes. This contamination in Niquelandia and Cana Brava is well known in the literature as revealed by bulk-rock Rb-Sr and Sm-Nd systematics. The two complexes show enrichment of the contamination in their gabbroic sequence with local enrichment where the crustal xenoliths are more abundant. Conversely, the upper pari of Niquelandia, mainly formed by anorthosite, is almost or totally uncontaminated. The Lu-Hf analyses on zircons from the Goiés complexes were perforrned during the instrument calibration of the Lu-Hf methodology al the laboratories of Centro lnterdipartimentale Grandi Strumenti al the Università di Modena e Reggio Emilia. The measurements were carried out using a Neptune MC-ICPMS coupled with a New Wave UP-213 laser ablation. The instrument was firstly calibrated on a standard solution and successively in situ analyses on complexes zircons were carried out together with CZ3 and TEMORA2 zircon standards. Mass bias and isobaric interference were corrected offiine using the lsotopeMaker free software of Zhang et al. (2015). Preliminary Lu-Hf in situ zircon data show negative EHf(t) values which are consistent with crustal contamination of the Barro Alto and Cana Brava parental melts as show by Rb-Sr and Sm-Nd in Cana Brava. The new Lu-Hf data, togheter with a review of literature data, show, for Barro Alto, a contamination similar to Niquelandia for the Rb-Sr and Sm-Nd systematics: zircons from the gabbroic sequence are contaminated, while zircons from the upper anorthosites are poorly contaminated. lnherited zircons commonly show positive EHf(t) values, which suggest mantle-derived melts for the magmatism of the metavolcanicmetasedimentary sequence
Geochemical variability in the greenstone belts of Goiàs (Brazil): the Hidrolina and Crixàs sequences
No full textThe greenstone belts of Crixás and Hidrolina of Goiás, Brazil, are dismembered components of the same body or of originally adjacent belts. Their tectono-metamorphic history and stratigraphy is similar, as well as their components (meta-komatiites, meta-basalts and felsic meta-volcanics). Chemically, they differ for the CaO and Al2O3 versus MgO trends and for the behavior of many incompatible and compatible trace elements (Cr, Ni, Ti, Sc, Y, Zr, P). The difference in the Ca and Al behavior, which is anomalous at Crixás, is tentatively attributed to an unconstrained igneous crystallization process. This process should imply the growth of clinopyroxene into an olivine-dominated crystal mush, and has acted at Crixás and not at Hidrolina. The difference in the trace element behavior has been mainly attributed to a compositional and modal heterogeneity of the mantle source, which was probably spinel-richer at Crixás than at Hidrolina
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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