1,721,024 research outputs found
Observations about surface behaviour of the great white shark Carcharodon carcharias (L.) in presence of passive preys at Dyer Island (Southafrica)
Full text linkDuring 4 study expeditions in SouthAfrica, performed in 2000, 2003, 2004 and 2005, observations about surface predatory behaviour of the Great White Shark in presence of passive preys were made. Observations were carried out by Unlimited Shark Diving boats and by cage diving around Dyer Island, about 5 miles far from Gansbaai. During the 27 observation days were identified 78 different specimens, that exhibited 8 different behaviours. The Great White Shark population observed around Dyer island
shows a greater variety of behaviours than the population studied along the California coasts
Addressing conservation measures through fine-tuned species distribution models for an Italian endangered endemic anuran
Full text linkClimate and land cover changes are the two most important stressors causing the decline of amphibians' populations worldwide. Within the Mediterranean area, one of the global biodiversity hotspots, the endemic Italian yellow-bellied toad (Bombina pachypus) suffered the same fate, as the decreases and local extinctions proved over time. Since the need to preserve this Apennine endemic species is evident, we take advantage of a novel approach combining climate-based ecological niche models and post-modelling GIS techniques (i.e., the weighted overlay framework) to produce finer species distribution models for B. pachypus. In doing so, we coupled climate variables with topographic-, hydrologic-, and habitat-related predictors, sharpening the potential species' distribution at its whole range scale. Our findings show a latitudinal subdivision in predicted suitability: Central Apennines populations are expected to suffer more than the Northern ones, with considerable potential future losses of genetic diversity. On the contrary, Southern Apennines' suitability is predicted to remain stable over time, preserving the vast di-versity. When assessing the coverage that protected areas offer to the locations of suitable habitats for B. pachypus, the protected sites of the Central Apennines result in slightly less suitable con-servation areas than those in the Northern and Southern Apennines. The overall protected areas coverage is currently low (similar to 20%) and predicted in the future to narrow towards medium suit-ability values, except in Southern Apennines, where an increase is inferred. In light of our spatially-explicit results, we suggest that a national-scale conservation strategy should consider different management options according to the sub-territories that our analyses highlighted. Our coupled "weighted modelling - spatialised genetic inference" approach permits us to support different conservation policies at all spatial scales, capitalising on relatively few input data. Also, in-depth spatial analyses should be performed to support effective protection strategies and management for the conservation stakeholders
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
Bloom fitoplanctonici e presenza stagionale di squalo balena (rhincodon typus) lungo la costa di gibuti – golfo di Aden
No full textDuring a 5 days research expedition performed in January, some observations on a whale shark population were performed. Just 7 specimens have been observed and identified. This number of sharks is lower than that observed in previous reports in the same period for similar research efforts. Recent remote sensing studies showed summer phytoplanktonic bloom higher than in autumn, but no sharks have been recorded suggesting that the quantity of phytoplankton could be not linked with the presence of the whale sharks
Surface behaviour of bait-attracted white sharks at Dyer Island (South Africa)
No full textSix research expeditions were conducted at Dyer Island to observe the surface behaviour of white sharks in the presence of bait. Observations were made from a commercial cage-diving boat. We observed 140 white sharks that exhibited 9 different types of behaviour: parading, bait following, visual inspection, breach, tail slap, tail stand, spy hop, repetitive aerial gaping, and head-up vertical emerging. Breach and tail slap were most often performed by male sharks, and tail slap and tail stand were more often performed by mature animals. The ethogram consisted of an average of 20 behavioural units, with a significant transitional pattern from bait follow to parading and from parading to bait follow. The individual surface behaviour of white sharks is not a simple stimulus-response reflex, but rather a complex tactical situation in which animals show plastic responses. Many aspects of white shark surface behaviour resemble those of other predator species that spend time at the surface
Social interactions among bait-attracted white sharks at Dyer Island (South Africa)
No full textThe goal of this preliminary research was to provide an ethogram of social interactions among white sharks at Dyer Island's Nature Reserve (Gansbaai, South Africa) in the presence of bait. Eighty-three social interactions were observed, both from a boat and from a cage. Seven different interaction types were recognized: swim by; follow give way; follow; parallel swimming; give way; splash fights; and piggybacking. The preliminary data analysis did not reveal any significant relationship between the behavioural patterns and the sex of the sharks, but a strong correlation between behavioural patterns and the size of the animals was found. The observed displays were more often performed by animals of the same length than by animals of different size
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
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