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The use of sodium birnessite as a curing agent for liquid polysulfide sealant
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Manganese (IV) oxide phases are widely used as curing agents for polysulfide sealants. The manganese based curing agents, however, do not give a reproducible cure and this results in material waste. As the market for insulating glass applications is increasing, efficient curing becomes more significant both commercially and environmentally. The research described in this portfolio focuses on using a laboratory synthesised manganese (IV) oxide phase, sodium birnessite, as a polysulfide curing agent. The synthesis and full characterisation of sodium birnessite is described and its curing ability measured in terms of the following properties of the cured polysulfide: rate of cure. surface condition, hardness build-up, stress-strain data, low and high temperature properties. and moisture transmission. The results obtained are compared with those of polysulfides cured with a good commercial product. Different concentrations of curing agents, and types and concentrations of accelerators, plasticisers and inert diluents were investigated to optimise the curing process, reduce material use and product wastage. Sodium birnessite is an active and reliable curing agent when used at half of the concentration of the commercial agent in the presence and absence of inert diluents. Diluted sodium birnessite (1: 1 with inert diluent) cures polysulfide to levels comparable in terms of stress-strain properties, moisture transmission rate, hardness, surface condition, low- and high- temperature properties, and degree of polysulfide cross linking to that achieved with commercial agent. The mechanism of the curing of polysulfide with sodium birnessite, as with all curing agents is conversion of mercaptan groups -S-H into disulfide linkages (-S-S-). Sodium birnessite is a mixed oxidation state compound and its synthesis results in the inclusion of Mn 2+ in addition to Mn 4+ ions in the manganese oxide based lattice. A rationale for the improved curing ability of sodium birnessite is presented. It is based on the ability of Mn 2+ to create vacancies in the Mn4+ sub-lattice thus increasing the mobility of the Mn4 in the structure and its transport to the surface of the curing agent where the oxidation reduction reaction responsible for the cure takes place.Financial support was obtained from Twinstar Chemicals Ltd, and the Engineering and Physical Sciences Research Council (EPSRC
Particle trapping and beaming using a 3D nanotip excited with a plasmonic vortex
Get PDFRecent advances in nanotechnology have prompted the need for tools to accurately and noninvasively manipulate individual nano-objects. Among the possible strategies, optical forces have been widely used to enable nano-optical tweezers capable of trapping or moving a specimen with unprecedented accuracy. Here, we propose an architecture consisting of a nanotip excited with a plasmonic vortex enabling effective dynamic control of nanoparticles in three dimensions. The structure illuminated by a beam with angular momentum can generate an optical field that can be used to manipulate single dielectric nanoparticles. We demonstrate that it is possible to stably trap or push the particle from specific points, thus enabling a new, to the best of our knowledge, platform for nanoparticle manipulation. (C) 2020 Optical Society of Americ
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
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