1,721,018 research outputs found
Introduced and cryptogenic marine and estuarine species of South Africa
No full textThe introduction history, systematics, transport vectors and distribution patterns of 85 introduced and 39 cryptogenic marine or estuarine animals and plants of South Africa are presented. This represents an addition of 93 species compared with previous lists. Taxa covered include protists, dinoflagellates, sponges, cnidarians, annelids, crustaceans, pycnogonids, insects, molluscs, brachiopods, bryozoans, echinoderms, ascidians, fish, algae and higher plants. For each species a justification motivating its inclusion as an introduction into South African shores or its cryptogenic status, is provided. Challenges associated with this type of inventory work are explored and major patterns of bioinvasion within the region are summarized briefly
Revealing the scale of marine bioinvasions in developing regions: a South African re-assessment
No full textAs recently as 2009 the number of introductions recorded for South Africa comprised 22 marine and estuarine species. This review aims to reassess the diversity and scale of introduced marine and estuarine species in the region. Accurate taxonomic and systematic work, broad review of historical records and new sampling surveys across selected marine habitats conducted by a team of local and international experts has effectively revealed the presence of previously misidentified, overlooked, or new introductions. A total of 86 introduced and 39 cryptogenic species are recognized, increasing known numbers four and twofold respectively within 1 year, although the current assessment is far from fully comprehensive. Additional species were revealed within the historic literature (76%), from surveys conducted post-2005 (11%) and following taxonomic resolution (13%). Temporal analyses confirmed discovery rates were increasing over time. Ship fouling and ballast water were the dominant vector pathways, accounting for 48 and 38% respectively. Spatial analyses revealed patterns of bioinvasion to be significantly higher on the west coast compared to the other coastal regions. Overall, 53% of introductions were concentrated within harbour areas with only 4 open-coast invaders detected at present. Introduced species found in the cool and warm-temperate provinces of the west and south coast mainly originated from the northern hemisphere (65%). In contrast, introductions located in the sub-tropical and tropical provinces of the east coast mainly originated from the southern hemisphere (18%), with the remaining 17% of introduced species being of unknown origin. The research approach described has proven pivotal, contributing massively toward revealing the true scale and patterns of bioinvasion for a developing region within a relatively short period of time
Marine alien species of South Africa – status and impacts
No full textThe current status of marine alien species along the South African coast is reviewed and the ecological and economic impacts of these invasions are discussed. In all, 10 confirmed extant alien and 22 cryptogenic species are recorded from the region. All 10 alien species support well-established populations and the majority of these remain restricted in distribution to sheltered bays, estuaries and harbours. Only one species, the Mediterranean mussel Mytilus galloprovincialis, has spread extensively along the coast and caused significant ecological impacts. These include the competitive displacement of indigenous species and a dramatic increase in intertidal mussel biomass. These changes have also increased available habitat for many infaunal species and resulted in enhanced food supply for intertidal predators. Considerable economic benefits have also resulted from this invasion because M. galloprovincialis forms the basis of the South African mussel culture industry
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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