1,720,962 research outputs found
Surface ocean cooling in the Eocene North Atlantic coincides with declining atmospheric CO2
No full textThe Eocene (56–34 million years ago) is characterised by declining sea surface temperatures (SSTs) in the low latitudes (~4°C) and high southern latitudes (~8-11°C), in accord with decreasing CO2 estimates. However, in the mid-to-high northern latitudes there is no evidence for surface water cooling, suggesting thermal decoupling between northern and southern hemispheres and additional non-CO2 controls. To explore this further, we present a multi-proxy (Mg/Ca, δ18O, TEX86) SST record from Bass River in the western North Atlantic. Our compiled multi-proxy SST record confirms a net decline in SSTs (~4°C) between the early Eocene Climatic Optimum (53.3-49.1 Ma) and mid-Eocene (~44-41 Ma), supporting declining atmospheric CO2 as the primary mechanism of Eocene cooling. However, from the mid-Eocene onwards, east-west North Atlantic temperature gradients exhibit different trends, which we attribute to incursion of warmer waters into the eastern North Atlantic and inception of Northern Component Water across the early-middle Eocene transition
Geochemical signals in fossil planktonic foraminifera
Get PDFThe stable isotope and trace element geochemistry of planktonic foraminifera is commonly used to reconstruct palaeoclimatic and palaeoceanographic parameters across recent and deeper timescales. However, aspects of their ecology, such as photosymbiont presence, ontogenetic growth and depth habitats, are suggested to alter these proxy signatures. Ecologies are additionally thought to change through time, creating further complications. Therefore, constraining foraminiferal palaeoecology, particularly during epochs which aid us in understanding future climate, is vital, to validate any proxy signals obtained. Two such epochs are the Eocene and Miocene, characterised by temperatures and CO2 levels comparable to a future warmer world. Many species within these periods have unresolved palaeoecologies. This thesis investigates the palaeoecology of multiple Eocene and Miocene planktonic foraminiferal species (from sites with well-preserved specimens) with unresolved palaeoecologies, using δ 13C, δ 18O, Mg/Ca, Sr/Ca and B/Ca. Whole and intra–shell geochemistry is investigated, using a combination of isotope ratio mass spectrometry and high resolution analytical techniques (laser ablation inductively coupled plasma mass spectrometry, electron microprobe analysis). It is shown for the first time that intra-chamber and size-segregated trace element/Ca data do not vary between Eocene foraminiferal species with differing ecologies (except Globigerina cf. bulloides and Pseudohastigerina wilcoxensis). Eocene and Miocene species EMPA data exhibit intra-shell Mg heterogeneity between species with varying depth habitats and photosymbiotic partnerships. Combining EMPA data with size-segregated δ 13C data is shown to be beneficial in distinguishing photosymbiotic species. Lastly, size-segregated δ 13C data from the species Globigerinatheka index indicate that it is possible for planktonic foraminifera to facultatively host photosymbionts in response to unfavourable environmental conditions. Having constrained the ecologies of various Eocene species, discrepancies between their inorganic proxy data are revealed and discussed. Overall, this thesis amplifies the importance of disentangling foraminiferal palaeoecology before constructing long-term downcore records, to mitigate the issues which vital effects can create
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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