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Nitrogen and carbon cycling in the South Atlantic Ocean: a stable isotope study along a 40°S transect (UK GEOTRACES)
No full textFixed N (nitrate, nitrite, and ammonium) is a limiting nutrient for photosynthesis in
the surface ocean. The rates and relative importance of N cycling processes,
however, are temporally and spatially complex, which hamper their direct
measurement and quantification. The South Atlantic subtropical front separates the
Atlantic Ocean and the subantarctic, an area which can elucidate information about
water masses both entering and leaving the basin. Through the GEOTRACES
programme, an oceanographic section across 40°S in the South Atlantic is used to
investigate biogeochemical cycling of nitrogen and carbon in this region.
Hydrographic data, in combination with the isotopic composition of nitrate (NO3-),
particulate organic carbon and particulate nitrogen (δ15NNO3, δ18ONO3, δ13CPOC,
δ15NPN), is used to provide integrative measurements for temporally and spatially
variable processes of the marine N-cycle and C-cycle.
A thorough examination of the stable isotope cycling of particulate and dissolved N
across the subtropical front is used to quantify the supply of fixed N to the mixed
layer. The relative importance of nitrate from the subsurface, N2 fixation, terrestrial
input and atmospheric deposition in supplying production is determined. Typically,
30-50% of the export flux in the subtropical water masses is sourced from N2 fixers
and up to 75% within the Brazil Current. This finding suggests that diazotrophs may
be abundant in the South West Atlantic providing a source of new N to this region.
To assess the basin scale N-cycling processes, the deep water masses were analysed
to reveal the origin and history of NO3-. Intermediate waters formed in the
subantarctic are enriched in δ15NNO3 and δ18ONO3 from partial utilisation by algae.
This enrichment in δ15NNO3 is not present in the subtropical North Atlantic or the
return flow of the North Atlantic Deep Water (NADW), which decreases from
~5.9‰ in the newly formed intermediate waters to ~4.8‰ in the NADW at 40°S.
The modification of isotopic signatures through the subtropical Atlantic can be
calculated as an incorporation of 26-36 Tg N yr-1 of newly fixed N from an isotopic
source of -1‰ (N2 fixation). The extent of N addition is higher than estimated rates
of N loss within the Atlantic and surpasses the amount of N deficit supplied to the
basin.
Fixed N inputs and losses through the global ocean are investigated by the
assessment of remineralised nitrate added to the ocean interior. A lower δ15N is
observed in Atlantic remineralised nitrate in comparison to the Pacific. The relative
importance of N2 fixation and pelagic denitrification within each ocean basin is
quantified and through this approach, N2 fixation rates are estimated at 92-116 Tg N
yr-1 in the Pacific and 24-32 Tg N yr-1 in the Indian Ocean. Combining Atlantic N2
fixation of ~32 Tg N yr-1 with Indo-Pacific, global N2 fixation rates can be estimated
at 142-184 Tg N yr-1. The high inputs in the Pacific suggest that excess P is the
dominant control on the success of N2 fixers. However, estimates of new N addition
to the Atlantic indicate other mechanisms such as the recycling efficiency of P and
supply of Fe to the surface ocean increase N2 fixation rates above this threshold.
The organic matter supplied to sediments is principally derived from phytoplankton
across the subtropical front. High organic content is associated with the productive
Brazil-Malvinas Confluence region where a diverse supply of nutrients sustains
elevated biomass. The Rio Plata outflow is characterised with high δ15NNO3 and
δ15NPN, suggesting denitrification processes occur in the estuary. A low δ13C source
associated with high Al concentrations is identified on the western slope, indicating a
supply of terrestrial derived C to the deep ocean. The fractionation of C uptake by
phytoplankton is assessed in subtropical and subantarctic waters. In the subantarctic,
CO2[aq] and growth rates determine the extent of C isotope fractionation. In this
region, low species diversity and a small range in cell size enable the fractionation
from CO2[aq] and growth rate to be expressed in phytoplankton. In subtropical water
masses a larger range of cell size is the principal determinant of C fractionation.
Increased surface area to volume is the main mechanism for increasing C uptake,
arguing against the use of δ13CPOC as a palaeoproxy. The low δ13CPOC and δ15NPN
observed in the subtropics (from C fractionation and N2 fixation) contrast the heavier
signatures in the subantarctic. These observations are propagated to the sediments,
wherein organic matter shifts are determined by changes in the subtropical front over
time. The results of this study have greatly improved knowledge of N and C cycling
within the South Atlantic, providing new insight into the cycling of these two
important elements in the surface and deep ocean, on a regional and global scale
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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