1,720,974 research outputs found
On the timing of retreat of the Loch Lomond (‘Younger Dryas’) Readvance icefield in the SW Scottish Highlands and its wider significance
Get PDFIt has long been assumed that the last glacier expansion in the Scottish Highlands, the Loch Lomond Readvance (LLR), resulted from a cold reversal that was broadly coeval with the ‘Younger Dryas’ episode. This view has recently been challenged, with the suggestion that glacier ice had disappeared from Rannoch Moor, one of the main ice accumulation centres in the SW Scottish Highlands, by as early as 12.5 ka, i.e. within the first half of the ‘Younger Dryas’. Here we present new radiocarbon, tephrostratigraphical and pollen-stratigraphical evidence from one of the key sites on Rannoch Moor, the results of an experiment designed to test this hypothesis. Our results not only contradict that concept, but are fully compatible with other evidence from the SW Scottish Highlands that suggests that the LLR glaciers in this area continued to expand until towards the end of the ‘Younger Dryas’ period, and may have persisted in some places after the onset of the Holocene. We consider the possible reasons for this marked divergence in chronology, a matter that is crucial to resolve because the precise timing of the demise of the LLR glaciers has important palaeoclimatic and other implications. In the wider context, we also draw attention to problems with the general use of the term ‘Younger Dryas’ and why we regard the Greenland stratotype unit and term ‘Greenland Stadial 1’ (GS-1) a more secure stratigraphic comparator
Environmental variability in response to abrupt climatic change during the Last Glacial–Interglacial Transition (16–8 cal ka BP): evidence from Mainland, Orkney
No full textThe Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene
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
Developing a refined tephrostratigraphy for Scotland, and constraining abrupt climatic oscillations of the Last Glacial-Interglacial Transition (ca 16-8 ka BP) using high resolution tephrochronologies
Get PDFUnderstanding the abrupt climatic oscillations that characterised the Last Glacial to Interglacial Transition (LGIT, ca. 16-8 ka) requires an ability to precisely correlate the archives within which such transitions are recorded. One way in which to scrutinise the timing of abrupt events in the LGIT is tephrochronology, a technique which exploits the isochronous potential of tephra horizons derived from the geologically ‘instantaneous’ settlement of volcanic ash. In NW Europe, macro- and crypto-tephra layers of varying age and provenance have become increasing utilised as a means to correlate palaeoclimate records, and to test the spatial and temporal synchronicity of key climatic transitions. At present, however, tephrostratigraphies in NW Europe are limited by: 1) the number of horizons that have robust chronological constraint, and 2) our abilities to trace these tephras across multiple sites. As a result, the potential of generating continental-scale tephra lattices is greatly restricted, and a spatial disparity in the number and type of tephras has emerged. It is hypothesised that part of this disparity may relate to the resolution at which sequences are studied and the inconsistent manner in which methodologies are applied. In order to test this hypothesis, five terrestrial basins from western Scotland were examined in detail for tephra content. Four of the sites were examined contiguously at high resolutions, whilst the fifth was examined using traditional ‘scan and resample’ strategies. Three new tephras for the LGIT are identified, and several existing tephras previously unknown in the British Isles were also detected. The results from this tephrostratigraphic study suggest that the series of eruptive episodes impacting Northern Britain through the LGIT is richer than appreciated hitherto. Results also indicate that tephras may have been missed in previous tephrostratigraphic investigations due to: 1) incomplete stratigraphic refinement, 2) a propensity to focus on tephras of greatest concentration, and 3) a conflation of horizons.Using the high-resolution site-tephrostratigraphies, a composite tephrochronological age model was developed. The purpose of this exercise was to establish whether age models constructed exclusively from tephra horizons could provide a viable means to constrain abrupt climatic oscillations in sites which traditionally are difficult to date e.g. carbonate basins. The resulting age model achieves centennial-decadal scale precision through the early Holocene, and is used to accurately constrain the first record incidence of the 10.3 ka event in the British Isles. This study emphasises the importance of contiguous high resolution refinement, and demonstrates that this approach is essential if the true tephrostratigraphic complexity of NW Europe is to be fully understood, and if tephras are to be used successfully in constraining abrupt climatic events.<br/
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
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