1,720,960 research outputs found
A late glacial-Holocene record of Southern Hemisphere westerly wind dynamics from the Falkland Islands, South Atlantic
No full textThe Southern Hemisphere westerly wind belt (SHWW) is a major feature of Southern Hemisphere, midlatitude climate that is closely linked with the sequestration and release of CO2 in the Southern Ocean. Past changes in the strength and position of this wind belt are poorly resolved, particularly across the Pleistocene-Holocene transition, a time period associated with fluctuations in atmospheric temperatures and CO2 levels. We used dust geochemistry, particle size measurements, and paleoecological analyses from a peat sequence in the Falkland Islands, South Atlantic Ocean, to describe changes in the SHWW between 16.0 and 6.5 ka (thousands of years before CE 1950). Wind strength was low at ~51°S before and during the Antarctic Cold Reversal (ACR, 14.9–13.0 ka), intensified between 13.1 and 12.1 ka as atmospheric temperatures increased, and then weakened, reaching a minimum between 12.1 and 10.9 ka during the Early Holocene thermal maximum. Northwesterly air masses became more dominant from 12.0 to 10.2 ka, and wind strength remained low until our record was affected by a storm surge or tsunami ca. 7.8 ka. These data indicate a southward shift in the latitude of the SHWW, from north of 51°S prior to and during the ACR, at ~51°S before the onset of the Holocene, and south of 51°S during the early Holocene thermal maximum. This pattern suggests that the latitude of the SHWW was coupled with atmospheric temperatures through the Pleistocene-Holocene transition
Modern and Paleoecological Perspectives on a Terrestrial-Marine Linkage in the Falkland Islands
Full text linkThe Falkland Islands are a biodiversity hotspot in the South Atlantic Ocean, with some of the world’s most important populations of seabirds and seals. The impact of climate change on these marine populations and their coastal breeding habitat in the Falklands is unknown. Coastal grasslands of Poa flabellata (tussac grass) form critical breeding habitat for wildlife, but have been heavily degraded by the introduction of livestock in the 17th century. This dissertation investigates the impacts of global change (climate change, grazing) on P. flabellata and its sensitivity to the fecal nutrient subsidies provided by marine wildlife. Chapter 1 provides the first multi-proxy reconstruction of past environmental change to understand how marine animals breeding in the Falklands responded to climate change over the past 14,000 years. At ~5,000 years ago, seabird and/or seal populations reached higher levels than the previous 9,000 years at Surf Bay, East Falkland Island. Fires were present throughout the past 14,000 years, but fire activity was highest when marine-derived nutrient input into the coastal grasslands from seabirds and/or seals increased. The increase in marine-derived nutrients and fire coincided with an increase in grasses, as well as the onset of neoglaciation. This reconstruction suggests that the Falklands are a refuge for seabirds and/or seals during cold periods in the past, and that marine-derived nutrients are important for improving coastal grasslands. It remains unknown whether tussac grass or other grasses species responded to changes in marine-derived nutrient input in our paleoecological reconstruction. Thus, in Chapter 2, I found that phytoliths and not pollen of modern native grass species are useful in distinguishing tussac grass from other species, supporting future investigations of the response of tussac grasslands to global change. Chapter 3 examines the potential for P. flabellata, which forms extensive peat records, as a new paleoclimate proxy in the South Atlantic where other archives for paleoclimate reconstructions (i.e. tree ring records and ice cores) are absent. Through a year-long modern calibration study, I found that tussac grass tissues record inter-seasonal environmental changes in temperature and humidity, though not precipitation source. Thus, this study warrants the use of tussac grass peat records to fill in a significant gap in our knowledge of paleoclimate in the South Atlantic Ocean. Chapter 4 provides an assessment of the impact of modern and historic grazing on soils and plants in the ecologically important coastal tussac grasslands. After release from grazing, tussac grasslands recovered rapidly, and marine-derived nutrient subsidies may be critical to improve restoration efforts. Overall, this work suggests that the terrestrial-marine linkage in the Falkland Island is sensitive to both climate change and land use change
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
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