1,720,959 research outputs found
Monitoring mosaic biotopes in a marine conservation zone by autonomous underwater vehicle
No full textThe extent of marine protected areas (MPAs) has increased dramatically in the last decade, and poses a major logistic challenge for conservation practitioners in terms of spatial extent and the multiplicity of habitats and biotopes that now require assessment. Here we demonstrate a single field method, photographic assessment by autonomous underwater vehicle (AUV) that enables the consistent description of multiple habitats, in our case including mosaics of rock and sediment. We describe a case study in the Greater Haig Fras marine conservation zone (Celtic Sea, NE Atlantic) where we distinguished seven biotopes, detected statistically significant variations in standing stocks, species density, species diversity, and faunal composition, and identified significant indicator species for each habitat. Our results demonstrate that AUV-based photography can produce robust data for ecological research and practical marine conservation. We note that standardizing to a minimum number of individuals per sampling unit, rather than to a fixed seafloor area, may be a valuable means of defining an ecologically appropriate sampling unit. Although representing a change in ‘standard practise’, we suggest that other users consider the potential benefits of this approach in their own conservation studies. The approach is broadly applicable in the marine environment, and has already been successfully implemented in deep-sea conservation and impact studies. It is clear that without a cost-effective methodology, applicable across habitats, it will be difficult to progress a coherent classification of biotopes, or to routinely assess their conservation status, in the rapidly expanding global extent of MPAs
Marine Geophysical Investigation of the Chain Fracture Zone in the Equatorial Atlantic From the PI‐LAB Experiment
Full text linkThe Chain Fracture Zone is a 300 km long transform fault that offsets the Mid Atlantic Ridge. We analysed new multibeam bathymetry, backscatter, gravity and magnetic data with 100 % multibeam bathymetric data over the active transform valley and adjacent spreading segments as part of the Passive Imaging of the Lithosphere Asthenosphere Boundary (PI‐LAB) Experiment. Analyses of these data sets allow us to determine the history and mode of crustal formation and the tectonic evolution of the transform system and adjacent ridges over the past 20 M.y. We model the total field magnetic anomaly to determine the age of the crust along the northern ridge segment to better establish the timing of the variations in the seafloor fabric and the tectonic‐magmatic history of the region. Within the active transform fault zone, we observe 4 distinct positive flower structures with several en échelon fault scarps visible in the backscatter data. We find up to ‐10 mGal residual Mantle Bouguer Anomaly in the region of the largest positive flower structure within the transform zone suggesting crustal thickening relative to the crustal thinning typically observed in fracture zones in the Atlantic. The extensional/compressional features observed in the Chain Transform are less pronounced than those observed further north in the Vema, St Paul and Romanche and may be due to local ridge segment adjustments
Eruptive hummocks: Building blocks of the upper ocean crust
No full textThe spreading axis at many slow-spreading mid-ocean ridges is marked by an axial volcanic ridge. In this study, we use a combination of high-resolution remote sensing methods to elucidate the detailed nature of volcanoes in such a ridge. We find that the “hummocks” described in previous sidescan sonar studies are dome- or cone-shaped edifices, 5–150 m high with diameters of 30–330 m. We estimate they form quickly, in single eruptions, each of which may produce several hummocks. Hummock collapse is common and hummocks of all heights are prone to failure. Collapses generally occur down the regional seafloor slope, suggesting control by local topography. Approximately 33% of hummocks lose ?40% of their volume by collapse, so ?12% of all material erupted on the axial volcanic ridge is rapidly converted to talus. The higher porosity of these deposits may increase average upper crustal porosity by several percent, contributing >0.5 km s?1 to seismic velocity decrease in the upper oceanic crust, and may be one of the dominant mechanisms for increasing porosity in upper slow-spreading oceanic crust
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
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