1,721,156 research outputs found
Synthesis and modification of pamam dendrimers as histone replacement molecules
No full textThe primary objective of this work was to synthesise and structurally modify a series of PAMAM dendrimers with a view to investigating and controlling their complexation with, and compaction of, DNA. The Introduction gives an overview to the origins of polymer and dendrimer science, and describes the synthetic approaches and resulting properties of dendrimers together with their impact on biological systems. The preparation of poly(amidoamine) (PAMAM) dendrimers utilising a number of different core materials are reported and characterised in Chapter 2. The conformational motion of the dendritic branches has been studied using 1H spin-lattice relaxation time experiments, and the results have been compared for the differently cored materials. Chapter 3 examines the modification of the dendrimer surfaces with acetyl, poly(ethylene glycol) and fluorescent groups and reports the results of a study of how the degree of DNA condensation affects gene expression by analysing dendrimer-DNA compaction using linear dichroism, dynamic light scattering and competitive binding of ethidium. Experiments designed to investigate modified dendrimer-lipid interactions are also discussed and the results of these are compared to molecular dynamic simulations. The synthesis of novel small molecules based around L-histidine and photo-responsive azobenzene, and the use of these to modify the surface of 4th and 5th generation PAMAM dendrimers is reported in Chapters 4 and 5 respectively. There follows a final chapter containing detailed descriptions of the synthetic procedures and characterisation for each of the compounds studied and the experimental methods used for exploring their behaviou
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
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