1,720,955 research outputs found
Spatial and temporal variations of the food web structure in a dynamic water-level lake.
No full textThe effects of water-level variations on the structural organization of a detritus source food web were studied in the littoral zone of Lake Trasimeno (C Italy). Dry leaf-packs of Phragmites australis were used, a detritus food source. The web structure changes both temporally and spatially with the initial depths of the leaf-packs in water (0, -10, -35, -50 cm). In winter (submersion season), there was a very complex detritus source web with: 1) high values of connectivity (number of taxonomical units per connectance), 2) more polyphagous predators than monophagous ones and 3) high number of competitive horizontal links. In the dry season, a minimal structure of the source web is characterized by the opposite relationships. The structure of the source web is also influenced by the permanence of detritus source in water, the bathymetrical declivity, and the ontogenetic niche shift of many aquatic insects. The space-time elasticity of the structural organization of the source web could represent a stabilizing property. -from Author
NUMERICAL VARIATION IN 3 COEXISTING MACRODETRITIVORE SPECIES (PROASELLUS-COXALIS, PLANORBARIUS-CORNEUS AND BITHYNIA-TENTACULATA) UNDER DIFFERENT LEVELS OF VERTICAL FORCES IN AQUATIC MICROCOSMS
No full textLaboratory experiments were conducted to assess the impact of both top-down and bottom-up forces on simplified macrodetritivore guilds. Three macrodetritivore species of Lake Albano (central Italy) were used: Proasellus coxalis, an isopod, and Planorbarius corneus and Bithynia tentaculata, two snails. They were stocked at the ratio of 32:160:164 individuals in each of 24 aquaria. The simplified guilds were governed by different vertical pressures. Three types of top-down (predation) pressures, viz. (i) absence of predators, (ii) high density of the predator Erpobdella octoculata, a leech, (iii) high density of Erpobdella and Gambusia affinis, a fish, and two types of bottom-up pressures, viz. high and low leaf-detritus availability, were employed. The effects of vertical forces were determined by the numerical variation in the survivors of each species and the ratio between the survivors of the three species of macrodetritivores. A quantitative index of the daily top-down force (TDF) was computed. The results showed that the three coexisting macrodetritivore species were sensitive to vertical pressures. When increasing the top-down pressure in aquaria with high detritus availability, the guild response was non-linear: (i) in absence of predators, the percentage of the survivors of the three macrodetritivore species was the highest; (ii) the presence of Erpobdella reduced the macrodetritivore abundance and (iii) the set of aquaria with coexisting Erpobdella and Gambusia significantly increased the number of survivors of the three macrodetritivore species when compared top aquaria with Erpobdella. On the contrary, in aquaria with low detritus availability, the increase of the top-down pressure caused no significant variation in the number of surviving species
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
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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