1,720,956 research outputs found
A sensitive method for the determination of Sulfonamides in seawater samples by Solid Phase Extraction and UV–Visible spectrophotometry
No full textThe authors have developed a sensitive spectrophotometric method for determination of sulfonamide derivatives such as sulfanilamide (SAA), sulfadiazine (SDZ), sulfacetamide (SCT) sulfamethoxazole (SMX), sulfamerazine (SMR), sulfadimethoxine (SDX), sulfamethiazole (SMT) and Sulfathiazole (STZ). This method is based on the Bratton-Marshall reaction, which involves the diazotization of sulfonamides with sodium nitrite under acidic conditions, followed by coupling with N-(1-naphtyl) ethylenediamine dihydrochloride (NED) to form a pink colored compound. Therefore, the Bratton-Marshall method was modified by optimizing the reaction conditions, which allows us to determine a low concentration range of sulfonamides compared to the reported methods. The limits of detection and quantification obtained were 0.019–0.05 and 0.06–0.16 μg mL− 1, respectively. In comparison with other reported methods using different coupling agents, the proposed method was found to be the most simple and sensitive for sulfonamides determination. In this paper, the modified method was successfully employed for the determination of sulfonamides in drinking water, seawater and pharmaceutical and veterinary formulations. The purpose of this work is to optimize and develop a simple method for extraction and concentration of sulfonamides present as residues in seawater and their quantification with the recommended spectrophotometric method. Solid phase extraction (SPE) of sulfonamides from seawater samples was evaluated using Oasis HLB cartridges (3 mL, 540 mg). The recovery efficiency was investigated in the sulfonamides concentration range comprised between 0.19 and 126 ng mL− 1. The ease of use of this extraction method makes it very useful for routine laboratory work. © 2017 Elsevier B.V
Magnesium recovery from seawater desalination brines: a technical review
Full text linkExisting desalination technologies produce large amount of waste brines with higher salinity concentration than feed seawater, the disposal of which pose serious environmental problems. At the same time, waste brines represent a valuable source of strategic materials—such as magnesium—and therefore their valorization offers the opportunity to overtake both the environmental and the economic issues. Current needs are to identify gaps and challenges to recover secondary magnesium in order to bring recovery technologies closer to the market for potential commercial applications. In this technical review, the available methods for magnesium recovery from seawater desalination brines are described and compared in details, to provide the readers with a wide overview to better address their research efforts towards resources valorization, in accordance with the circular economy principles. Graphical abstract: [Figure not available: see fulltext.
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
Vanadium Recovery from Bayer Process Liquor Residue
No full textThe objective of this work is to develop a vanadium recovery process from a liquor residue of Bayer process. Vanadium finds application in strategic industrial sectors such as steel production and energy storage. The recognized importance of vanadium has pushed academic and industrial research towards the development of technologies for its recovery from different types of secondary sources. The developed process refers to a sodium fluorovanadate sludge from a spent Bayer liquor. The resulting filter cake was characterized to determine its composition and a vanadium recovery process was studied and optimized. This starts with a solubilization of the filter cake by water, followed by a precipitation step of aluminum through pH adjustment with sulfuric acid till 9.2. Vanadium is then recovered as ammonium metavanadate by precipitation with ammonium sulfate using a ratio (NH4)2SO4/salt cake = 2.25 w/w; the precipitate was calcined at T = 500°C to obtain vanadium as V2O5. The results showed an overall vanadium recovery of about 95%, with a purity > 99.6%. The innovative contribution here addressed is represented by the feasibility of producing high-purity V2O5 from the Bayer liquor through a relatively simple precipitation route
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
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