1,720,984 research outputs found
Late neogene laminated and opal-rich facies from the Mediterranean region: Geochemical evidence for mechanisms of formation
No full textThe mechanisms for the formation of laminated and opal-rich sediments from southern Italy (Bianco and Vrica) and southern Sicily (Gela) are investigated using a geochemical approach. The Vrica laminates are relatively rich in organic carbon while the Gela laminites are not. Carbon/nitrogen ratios, carbon isotopic composition and lipid content of the organic matter at Vrica indicate that the laminates represent periods of increased input of terrestrial organic matter and enhanced preservation. Based on oxygen isotopic studies of planktonic foraminifera, a basin stratification model is presented to explain the formation of laminites at both Vrica and Gela. Biogenic silica and carbonate content, and the carbon isotopic composition of benthic foraminifera suggest that the Bianco diatomites represent periods of increased productivity. The isotopic composition of planktonic foraminifera from Bianco indicates that the increased productivity was a result of basin eutrophication brought on by continental runoff. The low organic carbon content of the Bianco diatomites is attributed to continuous bottom water ventilation. The results of laminites studies indicate that they are not always rich in organic matter, as generally assumed. Moreover the formation of organic-rich laminites can be the result of enhanced preservation, not increased productivity. Results from Bianco indicate that preservation plays a primary role in controlling the organic carbon content of sediments. © 1988
Chronology of the pleistocene oxygen isotope record: 0–1.88 m.y. B.P
No full textDetailed oxygen isotope records from various ocean basins and representing the last 1.88 m.y. are correlated using nannofossil biostratigraphy and paleomagnetic stratigraphy. These correlations establish the global nature of oxygen isotope stages 23 through 63 in the early Pleistocene to latest Pliocene. A composite isotope record for the last 1.88 m.y. reveals that the mid-Pleistocene change in climate regime was a complicated response that lasted from approximately 0.9 to 0.6 Ma and not a simple shift from one climate mode to another. The proposed chronology for the extended isotope stages provides a chronostratigraphic framework for detailed studies of paleoceanographic processes in the early Pleistocene and paves the way for application of oxygen isotope stratigraphy to early Pleistocene deep-sea and continental margin drilled sections. © 198
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
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
Pliocene-Pleistocene Stable Isotope Record for Ocean Drilling Program Site 653, Tyrrhenian Basin: Implications for the Paleoenvironmental History of the Mediterranean Sea
No full textPlanktonic foraminiferal oxygen and carbon isotope analyses from Tyrrhenian Sea Ocean Drilling Program (ODP) Site 653 provide a continuous record of the Pliocene-Pleistocene paleoceanographic history of the Mediterranean. Long-term trends in oxygen isotopes primarily reflect changes in global climatic conditions, with a more local or regional signal superimposed on this record. In contrast to most open-ocean results, the early Pliocene δ18O record of Site 653 exhibits high-amplitude fluctuations indicative of very unstable climatic conditions in this region. Another unique aspect of this Mediterranean δ18O record is the pronounced cooling at the Pliocene/Pleistocene boundary
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