1,720,953 research outputs found
Silica source-dependent synthesis of ferrierite : application in Cu 2+ removal from wastewater
Get PDFThesis (M.Sc. (Chemistry)) -- University of Limpopo, 2015This dissertation investigated the properties of ferrierite synthesised using different SiO2 sources under identical conditions. The SiO2 sources used were TEOS, water-glass, Aerosil 200 and Ludox LS-30. The synthesis procedure comprised preparation of a gel with molar composition: 20 Na2O : Al2O3 : 37 pyrrolidine : 66:5 SiO2 : 6:3 H2SO4 : 1460 H2O. This was followed by hydrothermal treatment at 160 oC in a stainless steel autoclave for 72 h. The solid products were characterised by XRD, SEM, NH3-TPD and BET techniques. The ferrierite prepared using sodium silicate was more crystalline than ferrierite zeolites synthesised using Ludox LS-30, Aerosil 200 and tetraethyl orthosilicate as SiO2 sources. An amorphous phase was produced when ferrierite was synthesised using unhydrolysed TEOS as a sole SiO2 source. The physicochemical properties of the materials were not only affected by the nature of the SiO2 source, but also some synthesis manipulations such as acid-hydrolysis and water-glass addition when TEOS was used as a primary silica source. There were improvements in the materials produced when the TEOS was pre-hydrolysed with HCl and also mixed with water-glass in equal proportions. The SEM images of ferrierite materials synthesised using water-glass and Ludox LS-30 were uniform. The water-glass-based materials were thin sheets, flake-like images and Ludox LS-30-based produced thin-plate-like morphologies. The micrograph of ferrierite synthesised using TEOS as the SiO2 source showed hexagonal-type morphology and aggregates of smaller particles. There were two types of shapes in the ferrierite synthesised using Aerosil 200 as the silica source, namely, octagonal prismatic and hexagonal type morphologies. An equimolar mixture of TEOS and water-glass showed octagonal prismatic shape with triangular faces along certain edges of the material. The NH3-TPD acid site distribution profiles showed two peaks of weak acid strength at low temperatures (≤ 350 oC) for the representative H-ferrierite investigated. The ferrierite materials synthesised using unhydrolysed TEOS and Ludox LS-30 as SiO2 sources, showed NH3 desorption peaks at higher temperatures (≥ 350 oC). These peaks correspond to ammonia eluted from strong acid sites. The BET surface area of ferrierite synthesised using water-glass was high, while the material synthesised using unhydrolysed TEOS had the lowest surface area. Novel crystal shapes, comprising octagonal prisms with additional triangular phases, were observed in ferrierite samples prepared by the use of TEOS/water-glass mixture as silica source.
The zeolitic materials prepared in this study were tested for the efficiency in the removal of Cu2+ from simulated wastewater, using a batch method. The effects of initial pH, initial concentration, contact time and adsorbent dose on Cu2+ adsorption were studied. All the materials showed maximum metal uptake efficiency at pH 5, and this pH was fixed in further studies involving other variables. It was observed that the metal uptake from aqueous solution increased with contact time and adsorbent dose. The Na-form of ferrierite synthesised using water-glass was the poorest Cu2+ adsorbent with respect to the four variables investigated (pH, contact time, adsorbent dose and initial metal ion concentration).
KEY CONCEPTS
Acidity, Adsorption, Ferrierite, Morphology, Silica source
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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