1,720,986 research outputs found
Effects of global climate change on on fisheries in trasimeno Lake (central Italy), with special reference to the Carassius spp. invasion. and possible management strategies
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Indici di struttura ed accrescimento standard per la trota fario Salmo (trutta) trutta L. in Italia centrale
No full textAnalysis of the biological features of the goldfish Carassius auratus auratus (Linnaeus, 1758) in Lake Trasimeno (Umbria, Italy) with a view to drawing up plans for population control.
No full textThe growth and reproductive biology of the invasive goldfi sh Carassius auratus auratus were
studied in Lake Trasimeno, central Italy. The results of the research revealed that the population is made up
of eight age-classes. The sex ratio proved to be extremely unbalanced (1 : 19 in favour of females). Growth
can be deemed rapid, the von Bertalanffy growth in length function being TL = 43.019{1-e(-0.272(t+0.162) )} for
the total sample and ’ = 2.702. No sexual dimorphism in growth was observed. Back-calculation analysis
suggested the existence of an inverse Lee phenomenon among 1 year-old specimens. The reproductive period
covers a broad time-span, from March to June. In females, sexual maturity is reached after the second winter
of life (2+ age-class); however, a small percentage (7.55%) of females is able to reproduce at the age of 1 year.
Most of the males attained sexual maturity in the fi rst year (60.61%). The reproductive investment of the
females is high; the relationship between SL and the number of eggs was Ne = 0.0041 SL4.368. Fecundity varied
from 286 to 219104 eggs, with an average relative fecundity of 103 ± 5 eggs g-1; the mean diameter of the
eggs was 1.27 ± 0.01 mm. The reproductive investment of the females was not homogeneous across the ageclasses;
in addition to absolute fecundity, relative fecundity and egg diameter were seen to increase with the
size of the specimens
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
Fish community of the river Tiber basin (Umbria-Italy): temporal changes and possible threats to native biodiversity
No full textThe introduction of exotic fish species in the river Tiber basin has probably caused a
serious alteration of original faunal composition. The purpose of this research was to
assess the changes occurred over time in the state of the fish communities with particular
reference to the reduction of local communities of endemic species. The study area
comprised 68 watercourses of the Umbrian portion of the River Tiber basin; the analyses
were carried out using the data of the Regional Fish Map of 1st and 2nd level and the 1st
update, respectively collected during the periods between the 1990–1996, 2000–2006 and
2007–2014, in 125 sampling stations. The results show a progressive alteration of the fish
communities’ structure, as confirmed by the appearance in recent times of new alien
species. A total of 40 species was found, only 14 native. The qualitative change of the
fish communities appear to be closely related to the longitudinal gradient of the river.
The results shows that particularly in the downstream reaches, the combined action of
pollution and introduction of exotic species resulted in a gradual decrease in the
indigenous component of fish communities. The information collected are the indispensable
premise for taking the necessary strategies for conservation of endangered species
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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