1,721,002 research outputs found
Environmental signals of Pliocene-Pleistocene climatic changes in Central Europe: insights from the mineral magnetic record of the Heidelberg Basin sedimentary infill (Germany)
No full textThe entrance of Earth's climate into the present icehouse state during a time of rapid temperature decline in the late Pliocene was intensively investigated during the past decade. Even though it is well documented in marine archives, detailed reconstruction of the Pliocene-Pleistocene climatic evolution of central Europe is hampered by a general lack of data. The work presented here is based on sedimentary material from drill cores obtained at three sites within the Heidelberg Basin (Germany). The scientific relevance of this unique archive was discovered only in the last decade. The hundreds of metres thick sequences of mainly fluvial sediments record the evolution of the environment and climatic conditions during the late Pliocene and the entire Pleistocene of western central Europe. In our present study, we implement unpublished mineral magnetic S-ratio data and new evidence from X-ray analysis into two previously completed studies on the magnetic polarity stratigraphy and the magnetic mineralogy of the Pliocene to Pleistocene sediments of the Heidelberg Basin. The total set of data enable distinction of environmental and climatic processes, and unveil details on the climatic conditions of continental Europe during this period. We demonstrate the dominance of an Mediterranean type to subtropical type climate during the Pliocene. Cyclic variations in the groundwater table in the Rhine flood plain resulted in redox fluctuations, which led to the decomposition of the primary detrital mineral assemblage. Authigenic Fe oxides, particularly haematite, formed during dry periods. A rapid transition into cooler and moister conditions occurred at the end of the Pliocene, as indicated by the persistence of Fe sulphides, especially greigite. A high groundwater table and the associated reducing conditions have largely persisted to the present day. We show that the rapid transition from warm to cooler and moister climatic conditions in central Europe during the final Pliocene is a regional response to the intensification of Northern Hemisphere glaciation (iNHG). This work supplements existing knowledge of the climatic evolution of central Europe during the Pliocene-Pleistocene transition by data from a region from which little data has been available. A sideglance to climatic archives elsewhere in the Northern Hemisphere (e.g., North Atlantic Ocean, Chinese Loess Plateau, Russian arctic) is used to show the coincidence of the iNHG events in quite different environmental regimes
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
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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