1,721,161 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
Calcio-carbonatite melts and metasomatism in the mantle beneath Mt. Vulture (Southern Italy)
No full textAt Mt. Vulture volcano (Basilicata, Italy) calcite globules (5–150 μm) are hosted by silicate glass pools or veins cross-cutting
amphibole-bearing, or more common spinel-bearing mantle xenoliths and xenocrysts. The carbonate globules are rounded or
elongated and are composed of a mosaic of 2–20 μm crystals, with varying optical orientation. These features are consistent with formation from a quenched calciocarbonatite melt. Where in contact with carbonate amphibole has reacted to form fassaitic
pyroxene. Some of these globules contain liquid/gaseous CO2 bubbles and sulphide inclusions, and are pierced by quench
microphenocrysts of silicate phases. The carbonate composition varies from calcite to Mg-calcite (3.8–5.0 wt.% MgO) both within
the carbonate globules and from globule to globule. Trace element contents of the carbonate, determined by LAICPMS, are similar to those of carbonatites worldwide including ΣREE up to 123 ppm. The Sr–Nd isotope ratios of the xenolith carbonate are similar to the extrusive carbonatite and silicate rocks of Mt. Vulture testifying to derivation from the same mantle source. Formation of immiscibile silicate–carbonatite liquids within mantle xenoliths occurred via disequilibrium immiscibility during their exhumation
The carbonate fraction in carbonatitic Italian lamprophyres
No full textAlkaline and ultramafic lamprophyres represent the majority of pre-Pleistocene alkaline mafic magmatic activity in Italy and have been described from several localities. The age of magmatism ranges from Triassic to Lower Oligocene. Some contain appreciable amounts of carbonate. The primary carbonate of the Italian carbonatitic lamprophyres is mainly Sr- or Mn-rich calcite that occurs mostly as immiscible ocelli or as groundmass. Its textural occurrence, composition, and relationship with co-precipitating silicate phases is taken as evidence of an igneous origin. Low BaO and REE contents in the carbonate are explained by early crystallization of essential mica and subordinate apatite. Whole rock analyses and isotopic data (Rukhlov, A.S., Bell, K., Vichi, G., Stoppa, F., submitted for publication. The heterogeneous deep mantle: the Sr, Pb and Nd isotopic evidence from Early Cretaceous alkaline lamprophyres of Southern Tuscany, Italy. Lithos.) suggest a mantle origin for these rocks and rule out contamination in either high or low pressure regimes. The bulk compositions of the carbonatitic lamprophyres have high HFSE / LILE and LREE / HREE ratios and although the abundances of these elements are generally lower than for carbonatites s.s., they are comparable with the abundances in other ‘carbonate-free’ Italian lamprophyres and Italian carbonatites, suggesting similar mantle sources. Moreover, the age of the Italian lamprophyres, ranging from Middle Triassic to Lower Oligocene, is much greater than the Pleistocene age of Italian carbonatites and indicates that the source remained similar over a long time span
Potassic glass and calcite carbonatite in lapilli from extrusive carbonatites at Rangwa Caldera Complex, Kenya
No full textThe ~16 Ma Rangwa Caldera Complex, part of the large Kisingiri nephelinite-carbonatite volcano, Homa Bay District, western Kenya (0º34'S; 34º09'E) contains carbonatitic lapilli and ash tuffs, agglomerate and tuffisite, and a number of intrusive calcite carbonatites. A detailed petrographic and electron microprobe study has been performed on 20 fresh samples from the collection at The Natural History Museum, London. Most of the juvenile lapilli and ash particles are either predominantly composed of devitrified silicate glass (now biotite/phlogopite but probably also originally potassic silicate) or calcite carbonatite, which suggests that two molten liquids were erupted simultaneously. Some 10 mm-diameter lapilli contain quench-textured calcite crystals set in devitrified glass. They are interpreted as having crystallized from a molten silicate-carbonate melt at, or very near, the surface. The extrusive carbonate is mostly composed of calcite, consistent with intrusive calcite compositions at Rangwa. Other key minerals are magnetite, two types of mica (magnesian-biotite phenocrysts and phlogopite xenocrysts) and fluorapatite. The pyroclastic rocks contain many calcite carbonatite clasts, and fragments of calcite, aegirine and diopside, fluorapatite, magnetite, plus some phlogopite, titanite, K-feldspar, fenite and glimmerite; ijolite lithics are rare. Thus, there is no evidence for a cognate nephelinitic (ijolitic) or melilitic magma nor evidence for a direct relationship with the nephelinites of the Kisingiri volcano. Two hypotheses are discussed. A rising silicate and K-rich carbonatite liquid may have evolved towards a carbonate-rich K-silicate liquid after crystallization of calcite, phlogopite, apatite and magnetite. Preservation of the potassic component may be rare, with a more usual scenario being that potassic component separates as fenitizing fluids. The alternative is that the silicate component is remobilized fenite, formed from country rock that was mobilized by supercritical K-rich, fenitizing fluids associated with the carbonatite. Both scenarios require generation of a K-rich carbonatite magma, probably from a carbonated phlogopite-rich metasomatized mantle
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
Wall, F, VX25486
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/423584Surname: WALL. Given Name(s) or Initials: F. Military Service Number or Last Known Location: VX25486. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 35505.250099
Item: [2016.0049.55845] "Wall, F, VX25486
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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