1,720,966 research outputs found
Speciation of Underivatized Organotin Compounds in Sediments by Gas Chromatography-triple Quadrupole Mass Spectrometry
Full text linkTributyltin is well recognized as an environmental endocrine disruptor and is listed as a priority substance that requires extended monitoring by the European Water Framework Directive (2000/60/EC). At the same time, due to their high pathogenicity, producing hormonal, immune, metabolic, and reproductive dysfunctions, other butyltin species (e.g. monobutyltin, dibutyltin, and tetrabutyltin) are consistently monitored in marine and freshwater aquatic ecosystems; the European Chemicals Agency classified these butyltin species as potential carcinogens and toxic substances for the human reproduction. Several analytical techniques, including gas chromatography and high-performance liquid chromatography, have been used to determine organotin species in aquatic ecosystems. Because of their chemical properties, organotin compounds are poorly stable upon temperature and are thus unsuited for direct analysis through capillary gas chromatography, which is usually performed after a derivatization step. The procedure described in this paper allowed the detection of underivatized chlorinated organotin compounds through gas chromatography-triple quadrupole mass spectrometry. Importantly, the obtained spectra of chlorinated monobutyltin and dibutyltin are herein presented and the fragmentation patterns are identified for the first time. The method was successfully applied to evaluate organotin compounds in sediments, providing the speciation of organotin species. Taking advantage of a simplified procedure of sample treatment, this study provided an innovative protocol for the gas chromatography/mass spectrometry of phenyl and butyl-substituted organotin compounds in contaminated sediments, capable of improving the efficiency of the conventional analysis of organotin compounds. © (2024), (Iranian Chemical Society). All rights reserved
Heavy metal accumulation capacity of Axinella damicornis (Esper, 1794) (Porifera, Demospongiae): a tool for bioremediation of polluted seawaters
Full text linkA wide range of contaminants are continuously introduced into the aquatic environment and among these, heavy metals constitute one of the most dangerous groups because of their persistent nature, toxicity, tendency to accumulate in organisms and more still, they are non-degradable. Marine organisms such as sponges represent target species for the monitoring of heavy metal contamination due their filtering activity. This study aims to evaluate the retention capacity of lead and cadmium by the sponge Axinella damicornis under laboratory conditions. The sponges were exposed for 144 h to seawaters artificially polluted with lead (Pb) and cadmium (Cd) separately and with a mixture of the two metals. The final goal of the experiments was to evaluate the metal uptake in the sponge body and efficiency of the sponge in removing the metals from seawater. In particular, the highest values of metal concentration in the sponges were recorded for Pb: this metal was found to be 6 times and 9 times more concentrated than Cd, respectively in the case of exposure to the single metal and to the combination of both metals. The metal concentrations found, especially for Pb, were much higher in A. damicornis than in other organisms investigated in the sea. Remarkable signs of stress and necrosis were recorded in the specimens when exposed to the combination of Pb and Cd, evidencing a synergistic effect of the metals mixture. This study paves adds knowledge on the contamination effects by heavy metals on the marine organisms and on the contribution from A. damicornis as efficient tool for bioremediation of polluted seawaters
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
The development of nano-structured printed electrochemical (bio)sensors for synergic approaches to environmental monitoring
No full textThe necessity to monitor the presence of toxic chemicals in the environment has become increasingly urgent during the last century. For this purpose, the emerging development of ad hoc designed electrochemical sensors for the selective and sensitive pollutants detection has attracted growing interest within the researchers’ attention. Indeed, it has been widely reported how the employment of electrochemical sensors allows for a reduction of the costs and the time required for the analysis with conventional techniques, as well as minimising the waste of reagents, resulting in a more environmentally-friendly approach. Basing on these features, electrochemical sensors play a noteworthy role within the scenario of environmental concerns, being particularly suitable for the planning of innovative and sustainable analytical monitoring programmes. Within the research work of my PhD studies, miniaturised electrochemical screen-printed sensors were developed, characterised and applied for the detection of two main categories of highly toxic and polluting chemicals: heavy metals and chemical warfare agents, which represent ones among the most worrying long-term threats for the environment and livings, because of their severe toxicity and
persistence in the environment. In order to tune the analytical performances of the herein developed sensors toward the detection of such substances, different nano-structured materials as well as different supports have been employed and combined with the versatile and cost-effective mass production of electrodes by using serigraphic and inkjet printing technologies. The overall approach of this research was focused on the development of synergic strategies to face environmental concerns. In detail, bismuth-based and Nafion-modified sensors, realised onto a flexible and transparent polyester support, were employed for the voltammetric detection of cadmium and lead ions in water
samples, as a more affordable and environmentally-friendly alternative to the conventional mercury based sensors. The electrochemical and analytical performances of these sensors upon storage and working conditions were evaluated, in order to improve the reliability of the heavy metal detection. In addition, such sensors were applied for the monitoring of heavy metal content in water environment, as well as biotic tissues, within remediation experiments carried out with filter-feeding organisms. In this way, the heavy metal uptake capability of the organism was examined and characterised, highlighting the high versatility and adaptability of the developed analytical tools for a variety of samples matrices. In a second part of the work, enzymatic inhibition paper-based sensors were realised for the detection of mustard agents, a class of toxic substances used as chemical weapons in the military field as well as in terrorist activities. The use of office and filter paper as support for serigraphic printing, coupled with the use of wax to realise hydrophobic patterns onto the paper sheets, allowed for the development of reagentless and wearable sensing tools for the real-time and on-site detection of this chemical risk. More precisely, the properties of paper were harnessed to integrate the reagents onto the sensor, as well as to allow for easy and safe disposal procedures of the sensors after the detection of these toxic chemicals (i.e. through incineration). The detection of mustard agents were performed by measuring their inhibitory activity toward choline oxidase enzyme, which was assessed through the amperometric measurement of the enzymatic by-product hydrogen peroxide. A Carbon Black/Prussian Blue nanocomposite was employed to enhance the electrochemical performances toward the reduction of hydrogen peroxide. Finally, another approach for the realisation of printed electrodes was investigated, by using inkjet printing technique and paper suitable for the realisation of electronic device as support with the aim to develop miniaturised fully-printed analytical devices, in which all the components, such as electroanalytical sensors, displays, and batteries, are integrated into the same support by printing. In detail, the electrochemical properties of a graphite-based inkjet-printed sensor were characterised by using ascorbic acid as a model analyte, and enhanced by the employment of Carbon Black nanoparticles as electrode modifier. These all-in-one devices pave the way for the improvement of the in-field applicability of printed electrochemical sensors, as well as for the decrease of costs, reagent consumption and waste material production
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
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
- …
