1,721,017 research outputs found
Multiproxy approach to the stydy of Croce della Moggiona cold seep-carbonates (Northern Apennines)
No full textSeep-carbonates are described in both the present day marine environments and in the sedimentary record of ancient basins. They are the result of microbially-mediated processes that occur on the seafloor where hydrocarbon-rich fluids are seeping. These carbonate bodies have received considerable attention in the international scientific community because they may provide a clue to investigate the origin and the composition of the fluids from which they have precipitated. In the Northern Apennine foredeep, seep-carbonates are concentrated in pelitic successions from different settings. Seep carbonates occur in large turbiditic bodies (Mt. Cervarola and Marnoso-arenacea Formations) and in slope hemipelagites (Vicchio and Verghereto Marls, and Ghioli di letto mudstones).In this study we present evidence for a long time of hydrocarbon seepage during the Middle Miocene in the form of newly discovered occurrences of carbonate bodies and concretions. About ninety authigenic carbonate bodies occur in the examined Fosso Riconi outcrop. Carbonates are irregularly scattered, both laterally and vertically, and have irregular shapes and geometries, varying from stratiform to amygdaloid, lenticular bodies and pinnacles. The thickness vary from 50 dm to 7-8 m, with lateral extension ranging from 1 to 3 m. Carbonate lithologies consist of marly limestones and calcareous marls. The lateral conctact with host sediments varies from sharp to transitional and interfingering. The marly limestone, calcareous marl lithologies are typically associated with abundant fossil remains, mainly consisting of thick recrystallized closed shells and moulds of lucinid and vesicomyid-like clams and rare and small gastropod shells. Lucinids and vesicomyids are infaunal ad semi-infaunal bivalves living in cold-seep areas and sustained by mutual symbiosis with sulphide-oxidizing bacteria. The authigenic carbonate mineralogy is dominated by low Mg-calcite, ankerite, and dolomite. Petrographic observations show complex facies relationships, as indicative of different stages in seep-carbonates growth. Stable isotope analyses of these nodules show depleted δ13C values which are consistent with the formation of carbonates in a cold-seep setting. Thus, the Fosso Riconi carbonates exhibit numerous characteristics (mineralogy, sedimentary fabrics, fossil assemblages) found at modern and ancient hydrocarbon seeps.The objectives of this contribution are to investigate the nature and source of the fluids associated with Fosso Riconi carbonate precipitation and to delineate an evolutionary model of the formation and development of these seep-carbonates.We suggest that examined seep-carbonates may be a consequence of episodes of varying fluid-venting rates
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
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
Molecular Fossil Inventory in Microbial Carbonates and Sponges of the Deep Fore Reef of Mayotte and MohÉli, Comoro Islands
No full textDispelling 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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