1,720,964 research outputs found
Boundary processes and neodymium cycling along the Pacific margin of West Antarctica
Full text linkNeodymium (Nd) isotopes have been utilized as a tracer of water mass source in the modern ocean and in palaeoceanographic studies, though the oceanic cycling of Nd is not yet fully constrained. Recent studies have highlighted the importance of processes that occur near the seawater – sediment interface in altering the Nd isotopic composition of bottom waters. The two major observed processes “boundary exchange” and “benthic flux” have been suggested as playing an important role in setting water mass compositions, however, more studies are needed to constrain their chemical mechanism and the extent to which these processes set the composition of deep waters. The Antarctic continental margin is an important place to study these processes because Antarctic-sourced waters dominate the Southern Ocean and ventilate the global deep ocean. This study is the first to measure and compare seawater, porewater and sediment data from along the margin of Antarctica to examine the nature of potential boundary processes. We show that a process similar to boundary exchange seems to be occurring within porewaters, modifying porewater chemistry by shifting its Nd isotopic ratios to more radiogenic values without significantly increasing the concentration of dissolved Nd. We hypothesize that this shift results from partial dissolution of radiogenic detrital particles, such as smectite, amphibole and/or volcanic glass, while re-scavenging maintains low Nd concentrations. We infer the existence of benthic flux of porewaters to deep waters by examining chemical gradients in porewaters and show that it is much lower on the Antarctic Margin compared to other studies. Benthic flux appears to be slightly enhanced along the Antarctic Peninsula than in the Bellingshausen Sea due to partial degradation of organic matter and associated dissolution of Fe-Mn oxyhydroxides. Taken together, boundary processes do not significantly change the Nd isotopic composition of Antarctic margin seawater because while the porewaters have an altered Nd isotopic composition the Nd concentration of these porewaters is low compared to other settings
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
Reversible scavenging and advection – Resolving the neodymium paradox in the South Atlantic
Full text linkSignificant gaps in our understanding of the oceanic cycling of neodymium (Nd) and the other rare earth elements (REEs) remain despite decades of research. One important observation which has not been adequately explained is that the concentration of dissolved Nd typically increases with depth, similar to nutrient profiles, while Nd isotopes appear to reflect conservative water mass mixing in the intermediate and deep ocean; this has been termed the “Nd paradox”. Here we present a detailed study of the dissolved Nd isotopic composition across a section at 40°S in the South Atlantic, collected by UK GEOTRACES cruise (section GA10). The South Atlantic represents a natural laboratory for our understanding of spatial controls on ocean geochemistry, because of the large variability of inputs, spatial differences in particulate cycling, and horizontal advection and mixing at depth between major northern- and southern-sourced water masses. This variability has also made the South Atlantic a critical region subject to intense investigations that aim at reconstructing past changes in ocean processes, such as changes in biological productivity and deep ocean circulation. Our Nd isotope results from the GA10 section provide observational data show the signal of water mass mixing and reversible scavenging. In the surface ocean (0–600 m), Nd isotopic compositions are distinct between different surface ocean currents and spatially can be tied to various continental sources. In the intermediate ocean (600–2500 m), the vertical Nd isotope distribution exhibits distinct signals of different water masses by horizontal advection, including upper North Atlantic Deep Water and Antarctic Intermediate Water formed in the Atlantic Ocean or the Indian Ocean. The Nd isotope distribution also reflects influence of reversible scavenging that smears the signals downwards in the water column (i.e., offset to more radiogenic values). In the deep ocean below 2500 m, Nd isotope distribution largely follows conservative water mass mixing model. Nd concentration in the deep ocean, however, deviates from conservative mixing and increases constantly with depth. We also observe that Nd isotopes appear to be shifted towards the composition of overlying water masses. These observations suggest that reversible scavenging of Nd onto organic and other types of particles is a major vertical process throughout the water column. We also suggest that this process can resolve the “Nd paradox” of decoupling of Nd concentration and isotopic composition due to mixing dynamics. Because abyssal water masses already have a high Nd concentration, a given amount of Nd added from the vertical process has less of an effect on Nd isotopic compositions in deep water masses than it does for intermediate water masses which have comparatively low Nd concentration
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
