1,721,039 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Sr–Nd isotope data of basement rocks from the northernmost argentine Precordillera and its implications for the early Paleozoic evolution of SW Gondwana margin
No full textThe Precordillera terrane (Cuyania) in western Argentina is commonly accepted as an exotic fragmentderived from Laurentia in the Early Paleozoic. Evidence supporting such an interpretation is manly basedon similarities in the sedimentary cover successions and their paleontological content. Little is knownabout the basement of the Precordillera terrane. Its isotopic characterization is essential to betterconstrain the present areal distribution of the terrane and it may provide more insight into the pre-rifting evolution of the Precordillera terrane along the Iapetan margin of Laurentia. We present newSr and Nd isotope data of pre-Late Ordovician meta-igneous rocks from the Río Bonete region in NWArgentina, interpreted as the northernmost extent of the Precordillera. The Nd systematics of the RíoBonete basement rocks including greenschists and metagabbros (εNd(470)¼þ2.14e 0.19;TDM¼0.99e1.2 Ga), a garnet-amphibolite (εNd(470)¼ 0.53;TDM¼1.32 Ga) and a quartz-phyllite (εNd(470)¼ 3.83;TDM¼1.55 Ga), are similar to other pre-Ordovician meta-igneous rocks from Sierra de Umango, Pie dePalo and the Ullum xenoliths, usually interpreted as the basement of the Precordillera terrane. Nd modelages around 1.2 Ga are also typical from the Mesoproterozoic Grenvillian basement of southern NorthAmerica, currently exposed in the Llano region. In addition, the greenschists and metagabbros show arobust correlation with the Late Neoproterozoic Catoctin volcanics in the central Appalachians. The Srisotope data (when not disturbed) also supports this novel interpretation and suggests the presence ofthe Blue Ridge rifting event in Precordillera. According to our interpretation, some lithotypes includedwithin the basement complex of the Río Bonete area belonged to the basement of the Precordilleraterrane supporting previous correlation between both regions.Fil: Martina, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Astini, Ricardo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Pimentel, Marcio. Universidade Do Brasilia. Instituto de Geociencias; Brasi
Variations on the Author
Get PDF“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
Get PDFWe 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
U-Pb LA-ICP-MS geochronology of detrital zircon grains from low-grade metasedimentary rocks (Neoproterozoic - Cambrian) of the Mojotoro Range, northwest Argentina
No full textThe first results of U–Pb detrital zircons were obtained in three lithostratigraphic units of the Puncoviscana Complex in NW Argentina: Chachapoyas, Alto de la Sierra and Guachos Formations. The Chachapoyas Formation has a maximum sedimentation age of 569 Ma and a minimum age of 533 Ma, based on the U–Pb age of an intrusive porphyry granitic. The Alto de la Sierra Formation, composed by sandstones and volcaniclastic rocks, has a maximum age of 543 Ma. A maximum age of 517 Ma is here reported for the deposition of the Guachos Formation, the youngest unit. The contact between the Chachapoyas and Guachos formations is by a tectonic relation, and it's probably coincident with a stratigraphic unconformity between them (unconformity Tilcara I). The Lizoite Formation is overlying by an unconformity (Tilcara II unconformity) the Puncoviscana Complex, and represents the basal unit of the Mesón Group. The provenance zircon data for that formation indicate a maximum depositional age of 513 Ma.Fil: Aparicio Gonzalez, Pamela Alejandra. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pimentel, Marcio. Universidade do Brasilia; BrasilFil: Hauser, Natalia. Universidade do Brasilia; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Moya, Maria Cristina. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
High resolution isotopic ages for the early Miocene "Patagoniense" transgression in Southwest Patagonia: Stratigraphic implications
Get PDFThe classical marine Patagoniense succession at Lago Argentino, southwestern Patagonia (Argentina), known as Estancia 25 de Mayo Formation, was dated by radiometric U-Pb on zircon grains from pyroclastic rocks and 87Sr/ 86Sr ratio on calcitic oyster shells. U-Pb data yielded an age of 19.14 Ma for the lower portion of the Patagoniense succession and 18.85 Ma for the lowermost part of the overlying Santa Cruz Formation. 87Sr/ 86Sr data yielded ages ranging from 20.05 Ma at the lower part and 19.1 Ma for the upper portion of the Estancia 25 de Mayo Formation, in good agreement with respect to the U-Pb results. Our results constrain the age of these beds entirely into the early Miocene Burdigalian stage, and locally into the Superpatagoniense stage. Correlation with other Patagoniense units in Santa Cruz, especially in the westernmost parts of the Austral Basin, reveals the existence of a shallow and extended sea, and lack of correlation with global sea-level highstands suggests a local Andean tectonic overprint as the cause of the sea level rise.Fil: Cuitiño, José Ignacio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geología. Cátedra de Sedimentologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pimentel, Marcio M.. Universidade Federal do Rio Grande do Sul; BrasilFil: Ventura Santos, Roberto. Universidade Do Brasilia. Instituto de Geociencias; BrasilFil: Scasso, Roberto Adrian. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Geología. Cátedra de Sedimentologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Mineralogical and geochemical characterization of a rare ultramafic lamprophyre in the Tandilia belt basement, Río de la Plata Craton, Argentina
Get PDFA metre-thick ultramafic lamprophyre dyke intrudes the basement of the andilia belt at the Sierra Alta de Vela, Argentina. A petrological and geochemical study of this rock and associated small dykes indicates a predominantly calc-alkaline trend. Phlogopite KeAr dating of the ultramafic lamprophyre gave a minimum age of 1928 +/- 54 Ma as a late event of the Transamazonian Orogeny, which is well represented in the basement of the Tandilia belt. An electron microprobe study indicates the presence of phlogopite,albite, chromite and Cr-rich phenocrysts and Cr-free microphenocrysts of diopside as primary minerals. Subsequent to deformation at the contacts with the wall rock, metasomatism generated strongly zoned amphibole (edenite, pargasite, Mg-hastingite and tremolite compositions) and andradite as well as chlorite, sericite, albite,apatite and calcite. The central zone of the lamprophyre is almost undeformed and exhibits some ocellar texture. Geochemical and isotopic signatures of the lamprophyre suggest that its magma source may have previously undergone incompatible element enrichment of the mantle source, representing the original precursor magma for the calc-alkaline dyke series of the Sierra Alta de Vela.Fil: Dristas, Jorge A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Geológico del Sur; ArgentinaFil: Martinez, Juan Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Instituto Geológico del Sur; ArgentinaFil: Massonne, Hans Joachim. Universität Stuttgart; AlemaniaFil: Pimentel, Marcio M.. Universidade Federal do Rio Grande do Sul; Brasi
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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