1,721,012 research outputs found
Photo And Electroluminescence Studies Of Poly(methyl Methacrylate-co-9- Anthryl Methyl Methacrylate)
No full textA series of poly(methyl methacrylate-co-9-anthryl methyl methacrylate) was prepared in which the anthryl groups were interspersed between each 2, 4, 10, 25 and 35 methyl methacrylate mers. The effect of the proximity of the chromophores in the photophysical properties was studied in dilute and concentrated conditions, showing that the association of anthryl groups giving rise to aggregates or excimers is strongly dependent of the chain conformations. The photophysical properties of cast-films of largely spaced copolymers are characterized by two decays: one of the isolated chromophore (longer decay rate and vibronically structured emission) and another of aggregated species (faster decay with some broadening of the red-edge of the emission band). Copolymers having the chromophores separated by two or four methyl methacrylate units presented the highest degree of association and were the only electroluminescent materials. The proximity of anthryl moieties and the conformation of the polymer chains are important factors governing excimeric-like emission and film properties of anthracene containing polymers used in technological applications. © 2003 Elsevier B.V. All rights reserved.2971-3177186Akcelrud, L., (2003) Prog. Polym. Sci., , Review on EL polymers with 500 referencesGarnier, F., Hajlaoui, R., Yassar, A., Srivastava, P., (1994) Science, 265, p. 1684Tessler, N., Denton, G.J., Friend, R.H., (1996) Nature, 382, p. 695Yu, G., Pakbaz, K., Heeger, A.J., (1994) Appl. Phys. Lett., 64, p. 3422Arias, A.C., Hümmelgen, I.A., Meneguzzi, A., Ferreira, C.A., (1997) Adv. Mater., 9, p. 972Paul, S., Halle, O., Einsiedel, H., Menges, B., Müllen, K., Knoll, W., Neher, S.M., (1996) Thin Solid Films, 288, p. 150Mitsuishi, M., Tanuma, T., Matsui, J., Chen, J., Miyashita, T., (2001) Langmuir, 17, p. 7449Ma, B.D., Aguiar, M., Freire, J.A., Hümmelgen, I.A., (2000) Adv. Mater., 12, p. 1063Hsu, J.W.P., Yan, M., Jedju, T.M., Rothberg, L.J., Hsieh, B.R., (1994) Phys. Rev. B, 49, p. 712Wu, M.W., Conwell, E., (1997) Phys. Rev. B, 56, p. 10060Samuel, I.D., Rumbles, G., Collison, C.J., (1995) Phys. Rev. B, 52, p. 11573Aguiar, M., Fugihara, M.C., Hummelgen, I.A., Peres, L.O., Garcia, J.R., Gruber, J., Akcelrud, L., (2002) J. Lumin., 96, p. 219Deus, J.F., Souza, G.P., Corradini, W.A., Atvars, T.D.Z., Akcelrud, L., in preparationDeus, J.F., Tavares, A.C., Lepienski, C.M., Akcelrud, L., Polymer, , submittedAguiar, M., Akcelrud, L., Pinto, M.R., Atvars, T.D.Z., Karasz, F.E., Saltiel, J., (2003) J. Photosci., 10, p. 149Prado, E.A., Yamaki, S.B., Atvars, T.D.Z., Zimerman, O.E., Weiss, R.G., (2000) J. Phys. Chem. B, 104, p. 5905Akcelrud, L., Gomes, A.S., (1978) J. Polym. Sci., Polym. Chem., 16, p. 2423Hu, B., Karasz, F.E., (1998) Chem. Phys., 227, p. 263Harwood, H.J., (1965) Angew. Chem. Intl. Ed., 4, p. 394Kamat, P.V., (1987) Anal. Chem., 59, p. 1636Atvars, T.D.Z., Dorado, A.P., Pierola, I.F., (1997) Polym. Network Blends, 7, p. 111Birks, J.B., (1970) Photophysics of Aromatic Molecules, , New York: Wiley-InterscienceChandross, E., Ferguson, J., (1966) J. Chem. Phys., 45, p. 3554Lin, Z., Pryadarsky, S., Bartko, A., Waldeck, D.H., (1997) J. Photochem. Photobiol. a, 110, p. 131McVey, J.F., Shold, D.M., Yang, N.C., (1976) J. Chem. Phys., 65, p. 3375De Schryver, F.C., Demeyer, K., Huybrets, J., Bouas-Laurent, H., Castelan, A., (1982) J. Photochem., 20, p. 341Yamamoto, S., Grellmann, K., Weller, A., (1980) Chem. Phys. Lett., 70, p. 241Hayashi, T., Mataga, N., Sakata, Y., Misumi, S., Morita, M., Tanaka, J., (1976) J. Am. Chem. Soc., 98, p. 5910Ng, D., Guillet, J.E., (1982) Macromolecules, 15, p. 724Hargreaves, J.S., Webber, S.E., (1984) Macromolecules, 17, p. 235Tazuke, S., Hayashi, N., (1978) Polym. J., 10, p. 443Bai, F., Chang, C.H., Webber, S.E., (1986) Macromolecules, 19, p. 2484Soutar, I., Swanson, L., Guillet, J.E., Takahashi, Y., (1991) Macromolecules, 24, p. 2815Aguiar, M., Karasz, F.E., Akcelrud, L., (1995) Macromolecules, 28, p. 4598Aguiar, M., Hu, B., Karasz, F.E., Akcelrud, L., (1996) Macromolecules, 29, p. 316
Light Emitting Mechanisms In An Alternated Fluorene Edot Copolymer - A Theoretical And Photophysical Study
No full textThe synthesis and photophysical characterization of a PPV type copolymer containing a fluorene derivative alternated with ethylenedioxythiophene units, poly[2,5-(3,4-ethylenedioxythiophene)-alt-(9,9′-dihexil-2,7-fluorene)] (LaPPS32) are presented and discussed. The photophysical studies along with theoretical simulation demonstrated that the main factor responsible for the polymer behavior is the progressive conformational twisting upon addition of each repeating unit to the polymer chain, together with intra- and intermolecular energy transfer processes. The main electroluminescence parameters are also discussed in connection with the photophysical behavior. © 2012 Elsevier B.V. All rights reserved.134670677Stéphan, O., Tran-Van, F., Chevrot, C., (2002) Synth. Met., 131, p. 31Akcelrud, L., (2003) Prog. Polym. Sci., 28 (6), p. 875Wu, W.C., Liu, C.L., Chen, W.C., (2006) Polymer, 47, p. 527Bundgaard, E., Krebs, F.C., (2007) Sol. Energy Mater. Sol. 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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
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
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