1,721,504 research outputs found
Synthesis and chemistry of novel bridged polyamines
No full textReaction of the bishydrazine 4,9-dimethyl-2,3,7,8-tetraazatetracyclo-[7.3.1.04,1206,10]trideca-1,6-diene with potassium carbonate in ethanol results in a base catalysed rearrangement to give a tetracyclic bisazoalkane. Photolysis of the bisazoalkane in either acetone or methanol affords a triasterane by a double extrusion of nitrogen. The azo groups in the bisazoalkane can be reduced to give the bishydrazine, 1,6-di-methyl-2,3,7,8-tetraazatetracyclo[7.3.1.04,1206,10] tridecane. Reductions of tetraacyl derivatives of this bishydrazine afford the tetramethyl and tetraethyl bishydrazines and differences in the conformations of these systems have been noted by the use of NMR and PE spectroscopy. The reductive cleavage of the hydrazine bonds in the above bishydrazine has been studied and in connection with this an investigation into the optimum conditions for the cleavage of a number of 1,2-diacyl substituted hydrazine derivatives has been carried out. As an extension of this work elaboration of the Diels-Alder adduct obtained from cyclopentadiene and diethyl azodicarboxylate affords oxidised products. The hydrazine bond in these systems can be reduced to give highly functionalised cyclopentadiamine derivatives. Reduction of the tetratrifluoroacetyl derivative of the above bishydrazine using aluminium amalgam gives a tetra(trifluoro-acetamido)bicyclo[3.3.1]nonane, although attempted hydrolysis of the trifluoroacetyl groups to give an unsubstituted tetraamine was unsuccessful. Reaction of the tetraacetyl derivative of the bishydrazine with borane successfully reduces the N-N bonds to give a tetraethyl tetraamine system. The chemistry of the bishydrazine and this tetraamine with aldehydes, ketones and acid derivatives has been investigated and a number of caged condensation products have been obtained. (D71545/87)</p
Towards Data-Driven Agent-Based Simulation: A Case Study of West Asian Urban Dynamics
No full textThis extended abstract discusses the challenges of obtaining
data for agent-based simulation in one case. Our motivation is to explore
the e↵ects of significant migrations upon urban dynamics. To date, we
have produced a theoretically-grounded spatial agent-based model, and
validated it with data in urban contexts without migration. Now, in
contexts with migration, upon moving from an abstracted model to a
data-grounded model, we encounter a number of challenges in extending
and validating the model. The majority of these challenges concern data
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
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