1,721,218 research outputs found
Bioaccumulation, Biodistribution, Toxicology and Biomonitoring of Organofluorine Compounds in Aquatic Organisms
Full text linkThis review is a survey of recent advances in studies concerning the impact of poly- and perfluorinated organic compounds in aquatic organisms. After a brief introduction on poly- and perfluorinated compounds (PFCs) features, an overview of recent monitoring studies is reported illustrating ranges of recorded concentrations in water, sediments, and species. Besides presenting general concepts defining bioaccumulative potential and its indicators, the biodistribution of PFCs is described taking in consideration different tissues/organs of the investigated species as well as differences between studies in the wild or under controlled laboratory conditions. The potential use of species as bioindicators for biomonitoring studies are discussed and data are summarized in a table reporting the number of monitored PFCs and their total concentration as a function of investigated species. Moreover, biomolecular effects on taxonomically different species are illustrated. In the final paragraph, main findings have been summarized and possible solutions to environmental threats posed by PFCs in the aquatic environment are discussed
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
Spatial and temporal dynamics of microbial communities in an aquifer contaminated by chlorinated solvents
No full textChlorinated solvents are widely spread, recalcitrant environmental pollutants. In contaminated aquifers, they are generally biodegraded by OrganoHalide Respiring Bacteria (OHRB) that reduce them in the anaerobic dehalorespiration process. However, aerobic direct and cometabolic oxidative processes can also co-exist. In order to define the microbial composition of an aquifer chronically and heavily contaminated by chlorinated solvents, never microbiologically characterized before, here we studied the groundwater autochthonous microbial communities and monitored their changes over time. The main chlorinated contaminant detected in the aquifer is 1,2-dichloroethane (1,2-DCA), whose concentrations undergo high fluctuations over time and have exceeded one gram per liter. Groundwater samples were collected from eight piezometers placed in the study area and were analyzed for microbial diversity by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and for taxonomic profiling by 16S rRNA gene metagenomic sequencing. Autochthonous microbial communities were unexpectedly characterized by very high alpha and beta diversity. Among the identified taxa, chemolithotrophic, methylotrophic, sulphate-reducing and sulfur-oxidizing bacteria were revealed, while the relative abundance of known dechlorinating anaerobic and aerobic bacteria was very low. However, a large part of most groundwater communities was made up of unclassified taxa. Groundwater from the most 1,2-DCA contaminated area was sampled in three moments over two years and 16S rRNA gene Illumina sequencing was applied on metagenomic DNA from each sampling event. The microbial characterization revealed a reduction in bacterial diversity and an enrichment in Helicobacteraceae and Desulfuromonadaceae families over time. The presence of the dehalorespiring genera Dehalococcoides, Dehalogenimonas and Desulfuromonas was also PCR detected using phylogenetic biomarkers. In conclusion, the low relative abundance of known anaerobic or aerobic dechlorinating taxa suggests a poor intrinsic biodegradation potential, consistent with the deep and chronic contamination at the site. However, this limited dechlorinating potential of groundwater could be exploited in bioremediation interventions, if properly biostimulated
Recent development in fluorinated antibiotics
No full textThis chapter presents the most recent results in the development of fluorinated antibioticsby taking into consideration modern challenges of multidrug-resistant pathogens. After a brief introduction on the direct and indirect effects of fluorine and fluorinated moieties in regulating biological activity, the chapter is developed in three main subsections discussing the two major classes of fluorinated antibiotics, fluoroquinolones and oxazolidinones, plus an overview of recent research on the antibiotic activity of fluorinated analogs of tetracyclines, peptidomimetics, triazoles, and nucleosides. Discussed aspects include: (1) Synthesis and challenges posed by the introduction of fluorinated moieties in specific positions of the main scaffold; (2) mechanism of action and structure–activity relationships in which the introduction or modification of fluorinated substituent is crucial to control efficacy; and (3) resistance mechanisms and solutions to treat resistant pathogens
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
Controlled uptake of PFOA in adult specimens of Paracentrotus lividus and evaluation of gene expression in their gonads and embryos
Full text linkPerfluorooctanoic acid (PFOA) has been largely used in the manufacturing industry but a few years ago it turned out to be a dangerous pollutant which is now of concern for terrestrial and aquatic environments. Here, we investigated the bioaccumulation of PFOA in the sea urchin Paracentrotus lividus after exposure to different concentrations of the pollutant for 28 days. We observed rapid uptake of PFOA in the coelomic fluid collected weekly during the exposure period and high bioaccumulation in gonads at the end of the experiment. Interestingly, animals were also able to fast depurate when relocated to a clean environment. In addition, to assess the effect of PFOA on sea urchins' physiological pathways, we analysed the expression profile of some marker genes both in the gonads and in the embryos obtained from parents exposed to PFOA. Our results suggest that PFOA is a persistent, bioaccumulative compound that adversely affects the health of the exposed organisms and their offspring by causing significant changes in the expression of some key target genes and the occurrence of developmental anomalies in the embryos
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