1,721,025 research outputs found
Relation of anodic and cathodic performance to pH variations in membraneless microbial fuel cells
No full textOne-compartment (membraneless) microbial fuel cells (MFCs) are effective tools to test new bio-technology at a laboratory level. More efforts in MFC design and materials are necessary to move from laboratory tests to real applications.
In such a context, this paper presents the experimental results that investigate pH variations of three single chamber and membraneless MFCs having positive and negative electrodes made of graphite-based materials without any addition of chemical catalysts. MFCs were built and operated with raw wastewater (inoculum) and sodium acetate as substrate. The progression of the power in the MFC and the relationship between performances and induced pH variation (from pH 6.7 to 10.2) will be discussed. A general connection between SEM images, chemical analyses, pH trends and reactions in the MFCs will be attempted, by connecting all processes with thermodynamic and chemical equilibria considerations
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
A novel microbial electrochemical sensor for on-line monitoring anaerobic biogradation processes
No full textIn anaerobic biodegradation systems, fermentative breakdown of monomers to volatile fatty acids (VFAs) and other simple and soluble metabolites happens with rapid kinetics. The monitoring of VFAs concentration in anaerobic digesters (AD) is crucial to prevent inhibition for organic overload and is usually performed manually by operators. The promptness of this response cannot be, thereby, immediate and preventing the inhibition of a digester might often be a question of few hours. The present work reports on an innovative type of Microbial Electrochemical Sensor (MES), integrated in AD with the purpose of on-line continuously monitor the microbial activity. Preliminary experiments were performed in lab-scale AD, fed in batch mode with four different types of fresh organic substrates. Real correlations between the electrical signal obtained by a MES and the concentrations of VFAs (as well as other physico-chemical parameters) were identified
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
PTFE effect on the electrocatalysis of the oxygen reduction reaction in membraneless microbial fuel cells
No full textInfiuence of PTFE in the external Gas Diffusion Layer (GDL) of open-air cathodes applied tomembranelessmicrobial fuel cells (MFCs) is investigated in thiswork. Electrochemicalmeasurements on cathodeswith different PTFE contents (200%, 100%, 80% and 60%)were carried out to characterize cathodic oxygen reduction reaction, to study the reaction kinetics. It is demonstrated that ORR is not under diffusion-limiting conditions in the tested systems. Based on cyclic voltammetry, an increase of the cathodic electrochemical active area took placewith the decrease of PTFE content. This was not directly related to MFC productivity, but to the cathode wettability and the biocathode development. Low electrodic interface resistances (from 1 to 1.5 Ω at the start, to near 0.1 Ω at day 61) indicated a negligible ohmic drop. A decrease of the Tafel slopes from120 to 80mV during productive periods of MFCs followed the biological activity in the whole MFC system. A high PTFE content in the cathode showed a detrimental effect on the MFC productivity, acting as an inhibitor of ORR electrocatalysis in the triple contact zone. The lowest PTFE content (60%) manifested mechanical instability of the cathode, together with the best performance
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
Performance explorations of single chamber microbial fuel cells by using various microelectrodes applied to biocathodes
No full textCorrelations among biofilm activity, chemistry and power production of membraneless, single chamber microbial fuel cells (MFC) were established using four microelectrodes. Each different (pH, redox, conductivity, S-2) microelectrode was assembled, calibrated and located close to the cathode. Power productivity of five MFCs was explained in terms of response of the microelectrodes. pH variation demonstrated that a proton gradient establishes within the cathodic biofilm, increasing acidity near the electrode. Conductivity increases inside the biofilm, proving low diffusion and increased ion concentration. Redox profiles provide a significant improvement to the understanding of the biochemical equilibria inside and outside the biofilm. Sulphide variations emphasize the role of the sulphur cycle in the MFC development. Diffusion hindrance seems the key-factor for the development of a biofilm and the establishment of a natural separation of the cell in cathodic and anodic compartments
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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