1,721,036 research outputs found
A high-resolution environmental and climate record of change in the Holocene sediments of Windermere, UK
No full textThe Holocene (11,750 Yrs. B.P. – present day) provides valuable examples of climate change in response to natural and anthropogenic forcing, by which future forecasting models can be validated. However, reliable climate and environmental observations rarely extend beyond the past 200 years. In this case proxy-based reconstructions can extend the record further. The sediments and water of Windermere, NW England, have been studied since the 1930s. These studies show the potential of the sediments to create a record of environment and climate change which extends from the Pleistocene to the present day. It’s location in the NE Atlantic region means it is ideally suited to record changes in climate and environment which are affected by globally important systems such as the North Atlantic Oscillation, Atlantic sea surface temperatures and the North Atlantic Currents. This thesis aims to firstly provide preliminary results of a multiproxy study of the whole Holocene sediment sequence from Windermere’s North Basin. A combination of organic, geochemical, and sediment microfabric analysis complemented by a chironomid inferred mean July temperature and pollen community reconstruction show the potential for the Holocene sediments of Windermere to record major climate events such as the 4.2 k. Yrs. B.P. cooling event. More detailed analysis has identified mass transport deposits (MTDs) in the early Holocene, likely caused by seismic instability induced by isostatic readjustment following deglaciation. The sediments of Windermere have also been impacted by anthropogenic activities since at least the beginning of the industrial revolution. However, the full impact of this activity is as yet unknown. With this in mind this thesis aims to provide a detailed history of anthropogenic impacts on the water column and sediments. Using gravity cores collected from Windermere in 2014 this thesis presents a novel combination of techniques to relate microscopic sediment fabric features to lake-basin scale processes. Together microfabric and geochemical methods enabled the identification of MTDs which, despite bioturbational mixing, can be dated to 1979 and 1979-1980 respectively. The timing of these features make a likely trigger the 4.7 ML 1979 Carlisle earthquake. Slope failure was likely to be the result of preconditioning principally by increased sediment in-wash as a result of anthropogenic activities. This study constitutes the first evidence of seismic activity-induced MTDs preserved in lake sediments in the UK and is published in the Journal of the Geological Society of London. Further to this, this study presents the results of a multi-method organic- and geochemical, and sediment fabric analysis, applied to reconstruct the history of eutrophication and pollution in Windermere. Eutrophication developed in the late 19th and earliest 20th centuries and is marked by changes in the sediment microfabric, organic chemistry and geochemistry. Δ13C values show increased lake productivity is coeval with Pb, Zn, Cu, Hg, and As enrichment. Δ15N values in the South Basin sediment correlate with Zn, Hg and Cu, suggesting a major source of pollution to be from human sewage or farm runoff marked by isotopically heavy nitrate. In peak eutrophic conditions, a strongly reducing environment promoted Fe dissolution and the formation of anglesite-barite mineralisation, hitherto undescribed in lake sediments. Partial recovery is shown to occur after 1980 across both basins, but elevated δ15N in the South Basin shows the continued impacts of sewage discharge. Results also show elevated concentrations of Mn, Fe, Ba, and As in the surficial sediment. Scanning Electron Microscope (SEM)-led methods additionally identified preserved diatom algae seasonal blooms, some of which may be matched with bloom occurrence record from Windermere. Millimetre-scale laminations of Fe and Mn minerals are also further analysed from the surface and pre-eutrophication intervals, and are shown to record seasonal cycles of lake ventilation. Results also show tight coupling of Fe and P, which indicates the potential redox-driven release of P to the water column with implications for lake eutrophication. This study highlights the power of microstratigraphic techniques in the recognition and characterisation of event layers in sediments where bioturbative disruption has occurred<br/
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
Investigations into the operational effectiveness of hybrid laminar flow control aircraft
Full text linkHybrid Laminar Flow Control (HLFC) is an active drag reduction technique that
permits extended laminar flow on an aircraft surface at chord Reynolds numbers
normally associated with turbulent flow. The operational effectiveness of HLFC
aircraft relates to the probability of a partial or complete loss of laminar flow. Four
factors were considered: (1) Ice particles in cirrus clouds; (2) Insect contamination; (3)
Mechanical failure; and (4) Damage to the suction surfaces.
Two computer programs capable of determining the required fuel for a given
mission profile have been developed for aircraft in the classes of the B757-200 and the
A330-200. The programs were validated against published payload-range data, and
modified to emulate the installation of a HLFC system, by incorporating changes to the
drag polar, Specific Fuel Consumption (SFC) and Operating Empty Weight (OEW).
Sensitivity studies were conducted. The results permit estimates to be determined of the
trip fuel reduction of HLFC aircraft compared to equivalent turbulent aircraft.
A conceptual design of a HLFC system has been developed for the reference
aircraft. A SFC penalty of 1.6% was determined for the B757-200 class aircraft (range:
3272nm, payload: 19147kg) and 2.1% for the A330-200 class aircraft (range: 5980nm,
payload: 24035kg) for a system capable of reducing the drag by approximately 14%.
The installed system weight represents 2.0% and 1.6% of the OEW for the B757-200
and A330-200 classes of aircraft respectively. The reduction in trip fuel, compared to
the turbulent baseline vehicles, was estimated to be 7.4% for these conditions. To
obtain the greatest benefit for a HLFC aircraft, the fuel planning must consider the
probable time-in-cloud that will result in a loss of laminar flow. An optimised fuel
planning approach, which requires a forecast of en route cirrus cloud, has been
estimated to further reduce the trip fuel for long-range missions by 2.5 - 3.8%
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