1,721,268 research outputs found
Electrochemical treatment of water containing Microcystis aeruginosa in a fixed bed reactor with three-dimensional conductive diamond anodes
No full textAn electrochemical treatment was investigated to remove Microcystis aeruginosa from water. A fixed bed reactor in flow was tested, which was equipped with electrodes constituted by stacks of grids electrically connected in parallel, with the electric field parallel to the fluid flow. Conductive diamond were used as anodes, platinised Ti as cathode. Electrolyses were performed in continuous and in batch recirculated mode with flow rates corresponding to Re from 10 to 160, current densities in the range 10–60 A m−2 and Cl− concentrations up to 600 g m−3. The absorbance of chlorophyll-a pigment and the concentration of products and by-products of electrolysis were measured. In continuous experiments without algae in the inlet stream, total oxidants concentrations as equivalent Cl2, of about 0.7 g Cl2 m−3 were measured; the maximum values were obtained at Re = 10 and i = 25 A m−2, with values strongly dependent on the concentration of Cl−. The highest algae inactivation was obtained under the operative conditions of maximum generation of oxidants; in the presence of microalgae the oxidants concentrations were generally below the detection limit. Results indicated that most of the bulk oxidants electrogenerated is constituted by active chlorine. The prevailing mechanism of M. aeruginosa inactivation is the disinfection by bulk oxidants. The experimental data were quantitatively interpreted through a simple plug flow model, in which the axial dispersion accounts for the non-ideal flow behaviour of the system; the model was successfully used to simulate the performances of the reactor in the single-stack configuration used for the experiments and in multi-stack configurations
Kinetic of electrochemical removal of microcystis aeruginosa from natural waters with DSA and BDD anodes.
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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
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
Electrochemical removal of microalgae with an integrated electrolysis-microbial fuel cell closed-loop system
Full text linkUncontrolled algal growth in water systems causes a number of serious issues that range from unpleasant odours and tastes to eutrophication. In this work, we propose for the first time to integrate an electrolysis process with the microbial fuel cell (MFC) technology as a sustainable way to treat algal contamination in water systems. Removal of chlorophyll-a by electrolysis was investigated in a fixed bed electrochemical reactor. The effect that operative parameters, such as current density and hydrodynamics, have on the process was analysed by using Chlorella vulgaris as a model of microalgae. Based on these results, a combined closed-loop system was developed in which the electrolysis unit was coupled with a cascade of miniature single chambered air-cathode MFCs. The electrolysis of C. vulgaris was performed under an applied current density of 25 A m−2 and for Reynolds equal to 13. The treated water was fed into a cascade of MFCs for further treatment and energy generation. The effect of the electrode surface area and of the number of MFCs in the cascade on both algae removal efficiency and power output was investigated. It resulted that the greater the active area of the electrodes in the MFCs, and the larger the number of fuel cells, the better the performance of the stack. The integrated system led to a 20% of reduction on the electrical energy requirement of the electrochemical reactor, giving the best results when the electrode surface area of the MFCs in the cascade was 0.32 cm2. Our approach provides a sustainable alternative to current algal removal systems that not only is chemical-free but also aims to be energy-neutral, thus reducing the large amount of energy that current water treatments require
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