1,720,970 research outputs found
Aspects of reproductive biology of Mediterranean amberjack (Seriola dumerilii Risso, 1810): gonadal development.
No full textWild Seriola dumerilii juveniles (77.3 +_ 23 g total body weight, 17.4 f 1.8 cm standard length; 2-3 months of age), were caught in the Eolian Island and reared in floating cages for a 14 months period. Gonads were collected routineously and submitted to histological and histochemical analysis to study the type and timing of gonadal differentiation and development. The histological examination shows that sex differentiation is clearly expressed in juveniles 23-25.5 cm long, 4-5 months old. A "differentiated" development was detected, as sexes early differentiate into female or male. In both sexes, anatomical and cytological differentiation proceed in parallel. Gonadal differentiation is completely achieved by the end of the first year of age. Within this period also cytological differentiation was completed in reared males, whereas females do not show the secondary growth phase oocytes. These findings agree with the previous data on wild S. dumerilii caught in natural environment. Comparing data reported by other Authors, gonadal development seems to be linked to fish size more than to age. Gonadal development in cage-reared fish was continuous and no pathological or degenerative signs were histologically observed. From an aquaculture perspective cage rearing conditions, being similar to the natural ones, seem to be suitable to correctly develop and manage broodstock in captivit
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
Modelling biogeochemical fluxes across a Mediterranean fish cage farm
Full text linkAn integrated approach is described for modelling interactions between off-shore fish cages and biogeochemical fluxes of carbon (C), nitrogen (N) and phosphorus (P). Two individual- based population dynamic models for European seabass Dicentrarchus labrax and gilthead seabream Sparus aurata were coupled with a Lagrangian deposition and a benthic degradation model. The individual models explicitly take into account the effects of water temperature and feed availability on fish growth. The integrated model was tested at a Mediterranean fish farm where a comprehensive set of in situ environmental and husbandry data was available. Tests were performed to compare the predicted and observed total organic carbon (TOC) concentrations in surface sediment under and near fish cages. At a local scale, the model output simulated the spatial
distribution of 4 biogeochemical indicators, namely: TOC concentrations, C fluxes towards the seabed and C:N and C:P ratios. These allowed the most impacted areas and more extended areas of intermediate organic enrichment to be identified. The model was also used for estimating the
mass balance of C, N and P, in order to determine the potential cumulative effects of multiple fish farms in the same area. The C, N and P fluxes among feed, fish and environment were calculated for each fish species over 24 mo of farm activity. The results showed that the amount of dissolved N directly released into the water column in inorganic form (ammonia/urea) was comparable to that deposited on the seafloor in particulate form as uneaten feed and faeces. A larger fraction of
P (about 65%) was released as faeces. Results from the integrated model yielded useful information for assessing the sustainability of an area for aquaculture activities that could be used to provide a scientific rationale for fish farm development in new areas
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
Inorganic nitrogen control in wastewater treatment ponds from an acquaculture hatchery (Orbetello, Italy): denitrification versus Ulva uptake
No full textInorganic nitrogen control in wastewater treatment ponds from a fish farm (Orbetello, Italy): Denitrification versus Ulva uptake
No full textThe aim of this study was to quantify the N removal efficiency of an Ulva-based phytotreatment system receiving wastewaters
from a land-based fish farm (Orbetello, Italy), to identify the main biogeochemical pathways involved and to provide basic guidelines
for treatment implementation and management. Fluxes of O2 and nutrients in bare and in Ulva colonised sediments were
assessed by light/dark core incubations; denitrification by the isotope pairing technique and Ulva growth by in situ incubation of
macroalgal disks in cages. O2 and nutrient budgets were estimated as sum of individual processes and further verified by 24-h investigations
of overall inlet and outlet loads. Ulva uptake (up to 7.8 mmol N m2 h1) represented a net sink for water column and
regenerated NHþ
4 whilst N removal via denitrification (10–170 lmol N m2 h1) accounted for a small percentage of inorganic nitrogen
load (<5%). Laboratory experiments demonstrated a high potential for denitrification (over 800 lMNm2 h1) indicating that
N loss could be enhanced. The control of Ulva standing stocks by optimised harvesting of surplus biomass may represent an effective
strategy to maximise DIN removal and could result in the assimilation of 50% of produced inorganic nitrogen
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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