1,720,971 research outputs found
Impatto delle microplastiche e loro funzione di carrier per contaminanti persistenti in specie ittiche del Mar Mediterraneo con diverse strategie alimentari
No full textThe presence of microplastics in the marine environment was first observed in the 1970s and growing scientific interest has revealed that these are widespread and ubiquitous in the marine environment: over 92% of all plastic objects in the oceans are microplastics. This PhD study aims to increase the knowledge about the impact, distribution and abundance of microplastics in fish species with different feeding habits in the Mediterranean Sea. Within the scope of this study is included the assessment of the levels of persistent contaminants (PBDEs, PCBs and FRs) in fish tissues and its possible correlation with the presence of microplastics.
A digestion method of organic matter was developed and validated in order to isolate and characterize the microplastics in the fish gastro-intestinal tracts. Mullus barbatus and Merluccius merluccius were tested and validated as small-scale bioindicators of plastic pollution in three different areas. Eight fish species from the same area (Ligurian Sea) were examined, all of them had ingested microplastics with different characteristics. The ingestion rates and numbers of particle per individual were significantly different between species. The species with the highest percentages of ingestion are Boops boops, with 36.8%, and Sardina pilchardus, with 34.8%.
The study of stable isotopes of nitrogen and carbon (δ15N and δ13C), has allowed to define the trophic level and identify the main food resources exploited by the species, highlighting an inverse correlation between the trophic level and the number of plastics per individual as well as a change in feeding strategies related with plastics presence for some species (Scomber scombrus e Trachurus trachurus).
The assessment of the levels of persistent contaminants (PBDEs, PCBs and FRs) in fish muscles has shown that, for some species and in relation to certain contaminants (total PCB and lower chlorinated PCB in Boops boops, Bde-183 in Engraulis encrasicolus), the presence of plastics is inversely correlated to the levels of pollutants measured. In all other cases, the chemicals analysed were found at same concentrations regardless of the presence/absence of microplastics. This highlighting the complexity of the issue and the necessity of target studies and standardised methodologies to clarify the role of plastics as a source of contaminants for edible fish species.
Overall, this research should be considered as a starting point for a future science-policy interface based on a full awareness of the issue of marine litter and for the achievement of a better state of conservation and protection of fish resources in Mediterranean Sea
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
Contamination of natural and cultured mussels (Mytilus galloprovincialis) from the northern Adriatic Sea by tributyltin and dibutyltin compounds
No full textThe levels of tributyltin (TBT) and dibutyltin (DBT) compounds were measured by gas
chromatography ion-trap mass spectrometry (GC–MS/MS) in natural and cultured mussels (Mytilus
galloprovincialis) from the northern Adriatic Sea in spring 2003. The highest (725 ng g−1 dry weight)
and lowest levels (198 ng g−1 dryweight) of butyltins (TBT+DBT)were found in nativemussels from
the Lagoon of Venice,with the higher values being detected in specimens collected next to a dockyard
and the lower values in specimens from a location characterized by strong water exchanges between
the lagoon and the Adriatic Sea. The two cultured samples exhibited intermediate concentrations,
with marine harvested samples being more contaminated than those from the lagoon.
Concentrations of TBT were higher than those of DBT for several reasons: the limited capability
of bivalves to metabolize TBT and their ability to accumulate it (with recent input of TBT into the
environment as TBT-based anti-fouling paints being the most important contributor of organotin
contamination in our study area); and higher lipophilicity of TBT than DBT. In order to find
correlations between organotin pollution and the state of nourishment of the mussels, the condition
index was also evaluated as the mass ratio of meat dry weight to shell dry weight. There was no
correlation between condition index and butyltin concentrations. These results indicate that condition
index could not give information about stress conditions, as the contamination level is probably too
low to cause significant reductions in mussel growth
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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