1,721,524 research outputs found
Ambipolar field-effect transistors based on solution processable blends of thieno[2,3-b]thiophene terthiophene polymer and methanofullerene.
No full textThe first direct experimental comparison between the hugely contrasting properties of PEDOT and the all-sulfur analogue PEDOT by analogy with well-defined EDTT-EDOT copolymers
No full textThe structures of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-ethylenedithiathiophene) (PEDTT) vary only in the substituent chalcogen atoms, yet the electronic properties of the materials are surprisingly dissimilar. The difference in electronic band gaps is approximately 0.8 eV and the polymers behave very differently upon p-doping. Two new terthiophenes have been synthesised using Negishi coupling methods. The X-ray crystal structures of EDOT-EDTT-EDOT (OSO) and EDTT-EDOT-EDTT (SOS) show strong intramolecular chalcogen-chalcogen contacts which are responsible for persistent conformers in solution and solid state, although significant interchain interactions should also influence the properties of the materials. SOS and OSO can be polymerised by electrochemical oxidation to give the corresponding, well-defined poly(terthiophenes) PSOS and POSO. Spectroelectrochemical studies on all four polymers reveal strong similarities between PEDTT and PSOS, and between PEDOT and POSO. Together with independent electrochemical and absorption studies, the results indicate that the unique properties of PEDOT are influenced more by conformational effects (intrachain S center dot center dot center dot O contacts) than substituent effects
Air-stable all-polymer field-effect transistors with organic electrodes
No full textOrganic transistors will be one of the basic components of future plastic electronic devices as they are a precondition for the manufacture of low-cost, integrated plastic circuits (IPCs). Thus investigations on all-polymer electronics devices, i.e. electronics without any silicon and metal constituents, are of growing interest. We report here our recent results on the fabrication of all-polymer organic field-effect transistors (OFETs) comprising conductive poly(ethylenedioxythiophene)-poly(styrene sulfonic acid) PEDOT/PSS systems as electrode material, regioregular poly(3-hexylthiophene) as semiconductor, as well as polymer substrates and dielectrics. All devices were manufactured under ambient conditions by means of spin-coating and standard lithographic techniques. OFET characteristics and simple shelf lifetime tests are reported and reveal an unexpected high device stability
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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