1,720,953 research outputs found
The use of synthetic zeolites in catalysis
No full textThis study reports on investigations into the use of synthetic zeolites in catalysis in an attempt to design catalyst systems which have size and shape selectivity. Zeolites have been widely used in petroleum refineries as acid catalysts. This has led to the field of study known as \shape selective catalysis\" since the product distribution is limited to those molecules which can pass through the zeolite channel. In this study zeolites have been used both as an acid catalyst for the cracking of hydrocarbons and as a catalyst support for a cationic palladium complex. n-Octane and 2-methylheptane were used in cracking reactions over zeolites HY HZSM-5 and their combinations. The two hydrocarbons were selected to discern the skeletal effect introduced by the structure of a molecule while the zeolites were chosen because of their common use in commercial catalytic cracking. Three ways of mixing the zeolites were employed by which the influence of each zeolite on a particular feedstock could be isolated:- i. Placing the bed of zeolite HY prior to that of zeolite HZSM-5. ii. Placing the bed of zeolite HZSM-5 prior to that of zeolite HY. iii. Mixing the two zeolites thoroughly. It was found that overall distributions of cracking products by carbon number from reaction of either paraffin on combinations of HY and HZSM-5 and from reaction of a mixture of the paraffins on either zeolite can be reasonably described by the addition of product distributions on individual catalysts and from individual paraffins weighted according to the relative amounts present. Ratios of branched to linear paraffins are much more strongly influenced by catalyst type and feedstock than the corresponding ratios for olefinic products. For reactions on catalyst mixtures distributions of the total products by carbon number correspond well to a summation o~ contributions on the individual catalysts. However a greater departure from prediction is seen for individual distributions of paraffins olefins and aromatics as well as for ratios of branched to linear paraffins showing that hydrogen transfer processes and isomerisation must occur. The addition of pentasil resulted in enrichment of the linear saturates at lower carbon number which is due to preferential cracking of linear paraffins over the branched isomers. The use of zeolite as a catalyst support was investigated by immobilising a cationic palladium complex [Pd(22'-bipy)i]2+ in NaY zeolite. Three immobilisation methods were investigated from which a model for location and distribution of the supported complex was proposed:- i. Prepared from [Pd(22'-bipy)i](N03)2 complex which was exchanged directly with the zeolite (method I). ii. Synthesised in-situ from Pd(22'-bipy)Cl2 complex which was exchanged with the zeolite in the presence of 22'-bipyridyl (method II). iii. Synthesised in-situ from [Pd(NH3)4]2+ which was exchanged with the zeolite. Free 22'-bipyridyl was then added to the cation-exchanged zeolite in solution to replace the ammine (method III). UV-visible atomic absorption and raman spectroscopies together with microprobe and elemental analyses were used to characterise the zeolite supported complexes. Attempts to directly ion-exchange [Pd(22'-bipy)i]2+ into the zeolite resulted in a maximum palladium loading of 0.62 wt% compared with a maximum loading of 8.97 wt% when [Pd(NH3)4]2+ was ion-exchanged into the zeolite. Efforts to obtain higher loadings of [Pd(22'-bipy)i]2+ by in-situ synthesis from Pd(22'-bipy)Cli and 22'-bipyridyl resulted in an increased maximum palladium loading to 1.15 wt%. Although a maximum Pd loading of 8.97 wt% could be obtained by ion-exchanging [Pd(NH3)4]2+ into the zeolite it was found that the [Pd(NH3)4]2+ could only be partially converted to [Pd(22'-bipy)i]2+. The inability to achieve 100% conversion using this method is probably due to the steric constraints within the smaller zeolite cages. The catalytic activity of the zeolite supported complexes was tested for dimerisation of ethene. It was found that the product distribution resulting from the supported complexes was similar to that obtained from the homogeneous system.
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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