1,720,969 research outputs found
Structure, distribution, and dynamics of epibiota on different typologies of coastal defence works
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Impact of recreational harvesting on assemblages in artificial rocky habitats
No full textMan-made structures have become ubiquitous features of coastal landscapes. These artificial habitats are popular recreation sites. Patterns and effects of recreational activities were investigated from 1999 to 2004 on coastal structures along 40 km of shoreline in the Emilia Romagna region (North Adriatic Sea, Italy). Four studies estimated the magnitude and frequency of exploitation by people, and established how human exploitation varied in space and time. A manipulative experiment involving the removal of mussels, mimicking the impact of human harvesting, was carried out to identify the effects of extensive mussel exploitation. Recreational exploitation was a major recurrent disturbance. Hundreds of people visited defence structures for recreational fishing and to harvest a variety of invertebrates to be used primarily as food. Human exploitation was most intense during the spring and summer but relatively unpredictable at scales of days and hours. Exploitation was homogeneous among different locations, despite marked differences in the accessibility of the structures. Visitors to the structures were mainly local people. Harvesting of mussels was particularly disruptive for the assemblages, leading to depletion of mussel beds, opening of unoccupied space, patchiness in the assemblages, and favouring the development of macroalgae. The main types of macroalgae were green and filamentous algae, which are a nuisance for beach tourism in the area, and the invasive species Codium fragile ssp. tomentosoides. Effective management of human access to artificial habitats is essential, since recreational exploitation influences the distribution and structure of their associated assemblages, ultimately affecting the native characteristics of the areas
Assemblages on human-made structures in the North Adriatic Sea
No full textThe aims of the present study were to map all human-made structures occurring along 40 km of the Emilia- Romagna coasts (Italy) and to explore how the distribution of colonising epibiota varied in relation to a number of selected key features of the structures. For each structure, several parameters were recorded, including: location, type of structure, size, shape, height, age, distance from shore, size of gaps between structural units, construction material and abundance of conspicuous species of intertidal epibiota. A total of 133 structures were identified and mapped: these were mainly groynes, breakwaters, sea walls, harbour structures and pontoon pilings. Most structures were built with natural calcareous rock, while concrete, wood and metal structures were less common. Other parameters, such as age, distance from shore, gap-size and length, were very variable. The composition and abundance of species varied in relation to location of the structures. Differences in the abundance of epibiota also occurred among different typologies of human- made structures, between landward and seaward sides of the breakwaters and among structures of different material. Other factors explained only a limited amount of variability in the data set
Effects of coastal defence structures on the distribution of hard-bottom species
No full textThe aims of the present study were: (1) to characterise the abundance of conspicuous, intertidal species associated to defence structures along the Italian shores of the North Adriatic Sea and (2) to identify the scales of discontinuity in the distribution of species. The study was carried out in May 2000 at 8 locations, from Trieste south to Ancona. Assemblages were dominated by mussels and ephemeral green algae. Filamentous algae and limpets were also frequent, but their abundance was variable among locations. The distribution of species was heterogeneous. At small (1 to 10s of m, distance among plots) and medium (10s to 100s of m, distance among sites) scales differences reflected variations in the relative abundance of species rather than composition. Conversely, differences in species composition were observed among locations, with a trend of increasing species richness from north to sout
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
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