1,720,964 research outputs found
Synergy between Zeolite Framework and Encapsulated Sulfur for Enhanced Ion-Exchange Selectivity to Radioactive Cesium
No full textTo eliminate the radioisotope 137Cs+ from contaminated water, various inorganic ion-exchange materials have been developed. Many selective ion-exchange materials are relatively expensive and difficult to prepare, whereas conventional materials such as aluminosilicate zeolites lack ion-exchange selectivity in the presence of competing cations. Here, we report a simple but powerful strategy to significantly increase the Cs+ selectivity of conventional zeolites. We demonstrate that encapsulation of elemental sulfur in the micropores of zeolites (NaA, NaX, chabazite, and mordenite) via vacuum sublimation can remarkably increase the selectivity toward Cs+ in the presence of competing ions. It appears that the elemental sulfur does not provide additional adsorption sites for Cs+ ions but increases the ion-exchange selectivity toward Cs+ by providing additional interaction. Various analyses show that sulfur partially donates its electron to the ion-exchanged Cs+ cations in zeolites, indicating significant Lewis acid–base interaction. According to the hard soft acid base (HSAB) theory, the enhanced Cs+ ion-exchange selectivity can be explained by the fact that sulfur, a soft Lewis base, interacts more strongly with Cs+, which is a softer Lewis acid than other alkali and alkaline earth metal cations. Because of the high intrinsic Cs+ selectivity of bare zeolites and selectivity enhancement resulting from sulfur encapsulation, the sulfur-modified chabazite and mordenite showed highly promising Cs+ capture ability in the presence of various competing ions.
Enhanced remediation of radioactive soil via synergistic foam flotation-acid washing process in a single reactor
No full textThis study presents an integrated single-reactor system for the remediation of soil contaminated with cesium (Cs+) and cobalt (Co2*) by combining foam flotation and acid washing. Initially, foam flotation with cetyltrimethylammonium bromide (CTAB) selectively separated clay particles, which bound to CTAB via electrostatic interaction. Subsequently, soil washing using oxalic acid and CTAB effectively desorbed residual Cs+ and Co2* from the sand-sized fraction. Based on these results, we evaluated the applicability of the integrated foam flotation-soil washing process to the decontamination of Cs- and Co-soil. When treating an artificially contaminated soil containing 40.9 mg/kg of Cs+ and 34.9 mg/kg of Co2*, the fine particle flotation process alone lowered their concentrations to 26.8 and 23.3 mg/kg, respectively. Further in-situ acid treatment reduced Cs+ to 8.5 mg/ kg for (79.3 % removal) and Co2* to 1.3 mg/kg (96.2 % removal). These results demonstrate that the integrated single-reactor approach enables selective separation of fine particles and enhanced desorption of radionuclides. While this study serves as a proof-of-concept using artificially contaminated soil, it offers a practical and scalable solution, warranting further investigation on field-contaminated radioactive soil.
Removal of radioactive cesium from an aqueous solution via bioaccumulation by microalgae and magnetic separation
Get PDFWe evaluated the potential sequestration of cesium (Cs+) by microalgae under heterotrophic growth conditions in an attempt to ultimately develop a system for treatment of radioactive wastewater. Thus, we examined the effects of initial Cs+ concentration (100-500 mu M), pH (5-9), K+ and Na+ concentrations (0-20 mg/L), and different organic carbon sources (acetate, glycerol, glucose) on Cs+ removal. Our initial comparison of nine microalgae indicated that Desmodesmus armatus SCK had removed the most Cs+ under various environmental conditions. Addition of organic substrates significantly enhanced Cs+ uptake by D. armatus, even in the presence of a competitive cation (K+). We also applied magnetic nanoparticles coated with a cationic polymer (polyethylenimine) to separate Cs-137-containing microalgal biomass under a magnetic field. Our technique of combining bioaccumulation and magnetic separation successfully removed more than 90% of the radioactive Cs-137 from an aqueous medium. These results clearly demonstrate that the method described here is a promising bioremediation technique for treatment of radioactive liquid waste.
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
