1,721,039 research outputs found
Energy Transfer Tailoring in Conjugated Molecular Thin Films
No full textIn α-sexithienyl (T6) molecular thin films the spectral features of photoluminescence can be correlated to precise structural topologies and the nature of photoluminescence can be controlled. AFM images show that the topological features of T6 films evolve progressively from 2D to 3D structures with film thickness. It is shown that coalescence between different domains results in photoluminescence spectra that are dominated by the aggregate emission. The Figure shows the photoluminescence spectra of submonolayer and lamellae architectures
Cationic cyclometallated iridium (iii) complexes
No full textOver the past two decades dramatic advances have been achieved in the field of organic electroluminescent devices, for display and lighting applications. A recent development in this field involves the use of ionic transition metal complexes (iTMCs) that have shown the possibility to fabricate single layer electroluminescent devices, named Organic Light-emitting Electrochemical Cells (OLECs) [1]. This type of device represents an interesting possible alternative to the more investigated organic light- emitting diodes (OLEDs). In OLECs, the charged complexes support all three processes of charge injection, charge transport and emissive recombination. Therefore, no additional layers are needed in the device and the emissive layer can be solution processed, which makes industrial manufacturing easier. At the moment, the most common cationic complexes are based on iridium, ruthenium, osmium, platinum, and copper [2]. Here we present a study on the use of three different cationic iridium(III) complexes [3,4] (Figure 1) in luminescent single layer devices in the presence and in the absence of an ionic liquid (IL).
The complex [Ir(ppy)2(5-CH3-1,10-phen)][PF6] (ppy = 2-phenylpyridine, phen = phenanthroline) reaches the most efficient results compared to the other ones. It has a very competitive brightness of 3040 cd/m2, obtained at 8V. The presence of IL lowers the turn-on time, and therefore, the operation voltage of the device at 3V. However, from the other side, the enhancement of the ions concentration into the film reduces the device lifetime t1/2, which is one of the main concern in light emitting devices.
1. J. Slinker, S. Bernhard, G. G. Malliaras et al., J. Mater. Chem., 17 (2007) 2976-2988.
2. L. De Cola, C. Bizzarri, M. Mydlak et al., Adv. Funct. Mater., 20 (2010) 1812–1820.
3. C. Dragonetti, D. Roberto, A. Valore et al., Inorg. Chem, 46 (2007) 8533-8547.
4. C. Dragonetti, D. Roberto, A. Valore et al., J.Phys. Chem. C, 113 (2009) 12517–12522
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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