1,720,984 research outputs found
Adsorption of radioactive metals by strongly magnetic iron sulfide nanoparticles produced by sulfate-reducing bacteria
No full textThe adsorption of a number of radioactive ions from solution by a strongly magnetic iron sulfide material was studied. The material was produced by sulfate-reducing bacteria in a novel bioreactor. The uptake was rapid and loading on the adsorbent was high due to the high surface area of the adsorbent and because many of the ions were chemisorbed. The structural properties were examined with high-resolution imaging and electron diffraction by transmission electron microscopy. The adsorbent surface area was determined to be 400-5OOm(2)/g by adsorption of heavy metals, the magnetic properties, neutron scattering, and transmission electron microscopy. The adsorption of a number of radionuclides was examined at considerably lower concentration than in previous work with these adsorbent materials. A number of ions studied are of interest to the nuclear industry, particularly the pertechnetate ion (TcO4-). Tc-99 is a radionuclide thought to determine the long-term environmental impact of the nuclear fuel cycle because of its long half-life and because it occurs normally in the form of the highly soluble pertechnetate ion, which can enter the food chain. This bacteria-generated iron sulfide may provide a suitable matrix for the long-term safe storage of the pertechnetate ion. Also, because of the prevalence of the anaerobic sulfate-reducing bacteria worldwide and, in particular, in sediments, the release of radioactive heavy metals or toxic heavy metals into the environment could be engineered so that they are immobilized by sulfate-reducing bacteria or the adsorbents that they produce and removed from the food chai
Structural and magnetic studies on heavy-metal-adsorbing iron sulphide nanoparticles produced by sulphate-reducing bacteria
No full textIn previous and in work to be published, it has been shown that iron sulphide material, produced by sulphate-reducing bacteria (SRB), is an excellent adsorbent for a wide range of heavy metals. The material adsorbs between 100 and 400 mg g?1 and residual levels in solutions can be of the order of pg per litre. Further, strongly magnetic forms of this material can now be produced which can be effectively and cheaply removed from suspension together with the adsorbate by magnetic separation. This paper examines the structure of weakly magnetic and strongly magnetic iron sulphide material produced by SRB with a view to increasing the understanding of its adsorbent and the magnetic properties. The structural properties have been examined using high-resolution imaging and electron diffraction in a transmission electron microscope (TEM), the measurements of magnetisation versus field and temperature, extended X-ray absorption fine-structure (EXAFS) spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy and neutron diffraction. Before drying the surface area of both the weakly magnetic and the strongly magnetic iron sulphide is of the order of 400–500 m2 g?1 as revealed by the magnetic properties, neutron scattering and the adsorption of a number of heavy metals. After freeze-drying the surface area falls to between 18 and 19 m2 g?1. The initial inocula came from a semi-saline source and when fed with nutrient containing Fe2+ and Fe3+ produced a weakly magnetic iron sulphide (Watson et al., Minerals Eng. 8 (1995) 1097) and a few % of a more strongly magnetic material. Further work using a novel method (Keller-Besrest, Collin, J. Solid State Chem. 84 (1990) 211) produced a strongly magnetic iron sulphide material. EXAFS and XANES spectroscopy revealed (Keller-Besrest and Collin, 1990) that the weakly magnetic iron sulphide material had the Ni–As structure in which the Fe is tetrahedrally coordinated with the composition Fe1?xS. The strongly magnetic iron sulphide was composed of some greigite (Fe3S4) and mackinawite (Fe1+xS), however, the bulk of the material at room temperature probably consists of disordered greigite and mackinawite. The weakly magnetic and strongly magnetic iron sulphide are good adsorbents for heavy metals and halogenated hydrocarbons
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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