1,721,104 research outputs found
Study Of Copolymer Composed By Polyacetylene And Polyazine
No full textThe polyacetylene was investigated by us showing the presence of conductive states in the Fermi level caused by a disordered distribution of defects of soliton type. Also we have shown that the polyazine polymer presents conductive characteristics through defects of the bipolaron type for orderly and disordered systems. The aim of this investigation is to verify whether the copolymer from polyacetylene and polyazine can be found on the metallic regime. For the calculations of this system we used semiempirical methods for the optimization of the geometry. Our results indicate that, when we take of charge from the structure, the bipolaron type of defect is formed on the copolymer.1011365366Lavarda, F.C., Dos Santos, M.C., Galvão, D.S., (1994) B.Laks,Phys. Rev. B, 49, p. 979Del Nero, J., Laks, B., (1997) Synth. Met., 84, p. 423Del Nero, J., Laks, B., (1997) Synth. Met., 84, p. 869Abdalla Araujo, A., Del Nero, J., Laks, B., to be publishe
"Theoretical and empirical approaches to phonotactics and morphonotactics ". Special Issue of Language Sciences 46 (2014)
No full textEffect Of Bipolaron Type Of Defect On The Polyacetylene-polycarbonitrile Copolymer
No full textIn the present work we report a theoretical study on the effect of the presence of conformational defects like bipolaron on the electronic properties of polyacetylene-polycarbonitrile copolymers. Negative Factor Counting and inverse iteraction techniques have been used to evaluate densities of states and wave functions, respectively. Our results show a finite density of state at the Fermi energy for high concentration defect. This fact, together with the extention of the highest occupied molecular orbital (HOMO) state, indicate the possibility to have the copolymer in the metallic regime.8401/03/15869870Su, W.P., (1983) Solid State Commun., 47, p. 947Mele, E.J., Rice, M.J., (1981) Phys. Rev. B, 23, p. 5397Galvão, D.S., Dos Santos, D.A., Laks, B., Melo, C.P., Caldas, M.J., (1989) Phys. Rev. Letter, 63, p. 786Lavarda, F.C., Dos Santos, D.A., Galvão, D.S., Laks, B., (1991) Chem.Phys., 155, p. 1Lavarda, F.C., Dos Santos, M.C., Galvão, D.S., Laks, B., (1994) Phys. Rev. B, 49, p. 979Aldissi, R., (1984) Synthetic Met., 9, p. 131Wöhrle, D., (1971) Makromol. Chem., 22, p. 1969Wöhrle, D., (1974) Makromol. Chem., 175, p. 1751Springborg, M., (1991) Synth. Met., 41, p. 4393Karpfen, A., (1979) Chem. Phys. Lett., 64, p. 299Brédas, J.L., Thémans, B., André, J.M., (1983) J.Chem.Phys., 78, p. 6137Dewar, M.J.S., Zoebisch, E.G., Healy, E.F., Stewart, J.J.P., (1975) J.Amer.Chem. Soc., 107, p. 3902Dewar, M.J.S., Thiel, W., (1967) J. Amer. Chem. Soc., 99, p. 4899Clementi, E., Raimondi, D.L., (1963) J.Chem.Phys., 39, p. 139
"Theoretical and empirical approaches to phonotactics and morphonotactics ". Special Issue of Language Sciences 46 (2014)
No full textElectronic Structure Of Polycarbonitrile: The Role Of Polaron-type Defects
No full textIn this work we report the electronic structure of polycarbonitrile, a conjugate polymer generated from polyacetylene by replacing every second CH unit by a single N atom, in the presence of defects like polarons. The negative factor counting method was used in a tight-binding parameterization and geometrical data were from Austin model 1 (AM1) calculations. A comparative study of the ordered and disordered distribution of defects is presented. © 1997 Elsevier Science B.V.39402/03/15209214Chiang, C.K., Fincher, C.R., Park, Y.W., Heeger, A.J., Shirakawa, H., Louis, E.J., Gau, S.C., MacDiarmid, A.G., (1977) Phys. Rev. Lett., 39, p. 1098Galvão, D.S., Dos Santos, D.A., Laks, B., Melo, C.P., Caldas, M.J., (1989) Phys. Rev. Lett., 63, p. 786Lavarda, F.C., Dos Santos, D.A., Galvão, D.S., Laks, B., (1991) Chem. Phys., 155, p. 1Lavarda, F.C., Dos Santos, M.C., Galvão, D.S., Laks, B., (1994) Phys. Rev. B, 49, p. 979Wöhrle, D., (1971) Tetrahedron Lett., 22, p. 1969Wöhrle, D., (1974) Makromol. Chem., 175, p. 1751Springborg, M., (1991) Synth. Methods, 41, p. 4393Karpfen, A., (1979) Chem, Phys. Lett., 64, p. 299Brédas, J.L., Thémans, B., André, J.M., (1983) J. Chem. Phys., 78, p. 6137Albert, I.D.L., Ramaseska, S., Das, P.K., (1991) Phys. Rev. B, 43, p. 7013Dewar, M.J.S., Zoebisch, E.G., Healy, E.F., Stewart, J.J.P., (1975) J. Am. Chem. Soc., 107, p. 3902Dewar, M.J.S., Thiel, W., (1967) J. Am. Chem. Soc., 99, p. 4899Hoffman, R., (1963) J. Chem. Phys., 39, p. 1397Clementi, E., Raimondi, D.L., (1963) J. Chem. Phys., 38, p. 2826Dan, P., (1960) Proc. R. Soc. London, Ser. A, 254, p. 507Seel, M., (1973) Chem, Phys., 43, p. 103Wilkinson, J.H., (1965) The Algebrate Eigenvalue Problem, p. 633. , Clarendon Press, Oxfor
French liaison and the lexical repository
No full textIn this paper we propose a frequency analysis of French liaison that focuses on the liaison environments attested in the PFC database. The results of the analysis show the existence of a significant relationship (statistically interpreted as a power-law distribution) according to which a very restricted set of liaison environments has very high frequency of occurrence in the corpus and is substantially untouched by phonological and sociolinguistic variation, while a large “periphery” of infrequent uses appears to show significant aspects of style- and speaker-dependent variation. The study therefore demonstrates the importance of basing any variationist analysis on very large data sample, such as those provided by contemporary, well-reasoned linguistic corpora
Electronic Structure Investigation Of Biosensor Polymer
No full textWe report a theoretical study of the ground, excited and ionic states of 3-methyl pyrrole-4-carboxilic acid (MPC) oligomers and related compounds which present conformational defects. Our results reveal the existence of differentiated electronic behavior for MPC with relation to oligopyrrole derivatives. These electronic features might explain why MPC works properly as a biosensor for cytochrome C while no voltametric response is observed for unsubstituted poly(pyrrole). © 2002 Elsevier Science B.V. All rights reserved.2101/03/15461466Naarmann, H., (1990) Appl. Conduct. Polym., 81Friend, R., (1991) Nature, 352, p. 377Ouerghi, O., Senillou, A., Jaffrezic-Renault, N., Martelet, C., Ben Ouada, H., Cosnier, S., (2001) J. Elecroanal. Chem., 501, p. 62Alizadeh, N., Mahmodian, M., (2000) Electroanalysis, 12, p. 509Costello, B.P.J.D., Evans, P., Guernion, N., Ratcliffe, N.M., Sivanand, P.S., Teare, G.C., (2000) Synth. Met., 114, p. 181Cosnier, S., (2000) Appl. Biochem. Biotech., 89, p. 127Yamada, K., Kume, Y., Tabe, H., (1998) Jap. J. Appl. Phys., 37, p. 5798Vidal, J.C., Garcia, E., Castillo, J.R., (1999) Sens. Actuators, B-Chem., 57, p. 219Ryder, K.S., Schweiger, L.F., Glidle, A., Cooper, J.M., (2000) J. Mater. Chem., 10, p. 1785Swann, M.J., Glidle, A., Gadegaard, N., Cui, L., Barker, J.R., Cooper, J.M., (2000) Physica B, 276, p. 357Chen, Y., Imrie, C.T., Cooper, J.M., Glidle, A., Morris, D.G., Ryder, K.S., (1998) Polym. Int., 47, p. 43Griffith, A., Glidle, A., Beamson, G., Cooper, J.M., (1997) J. Phys. Chem. B, 101, p. 2092Ryder, K.S., Morris, D.G., Cooper, J.M., (1995) J. Chem. Soc.-Chem. Commun., 14, p. 1471Cooper, J.M., Morris, D.G., Ryder, K.S., (1995) J. Chem. Soc.-Chem. Commun., 6, p. 697Garnier, F., Kori-Youssoufi, H., Srivastava, P., Yassar, A., (1994) J. Am. Chem. Soc., 116, p. 143Schuhmann, W., (1991) Synth. Met., 41, p. 429Eddowes, M.J., Hill, H.A.O., (1977) J. Chem. Soc. Chem. Commun., 771, p. 364Eddowes, M.J., (1987) Biosensors, 3, p. 1Eddowes, M.J., (1987) Sens. Actuator, 11, p. 265Eddowes, M.J., Pedley, D.G., Webb, B.C., (1985) Sens. Actuator, 7, p. 233Barker, P.D., Gleria, K.Di., Hill, H.A.O., Lowe, V.J., (1990) Eur. J. Biochem., 190, p. 171Kudera, M., Aitken, A., Jiang, L., Kaneko, S., Hill, H.A.O., Dobson, P.J., Leigh, P.A., McIntire, W.S., (2000) J. Electroanal. Chem., 495, p. 36Lancaster R.E., Jr., Werf, C.A.V., (1958) J. Org. Chem., 23, p. 1208Ge, H., Asraf, S.A., Gilmore, K.J., Too, C.O., Wallace, G.G., (1992) J. Electroanal. Chem., 340, p. 41Dewar, M.J.S., Zoebisch, E.G., Healy, E.F., Stewart, J.P., (1985) J. Am. Chem. Soc., 107, p. 3902Dewar, M.J.S., Thiel, W., (1977) J. Am. Chem. Soc., 99, p. 4899Stewart, J.J.P., (1989) J. Comp. Chem., 10, p. 209MOPAC Program Version 6 (QCEP 455)Ridley, J., Zerner, M.C., (1973) Theor. Chim. Acta, 32, p. 111Ridley, J., Zerner, M.C., (1976) Theor. Chim. Acta, 42, p. 223Bacon, A.D., Zerner, M.C., (1979) Theor. Chim. Acta, 53, p. 21Head, J.D., Zerner, M.C., (1985) Chem. Phys. Lett., 122, p. 264Head, J.D., Zerner, M.C., (1986) Chem. Phys. Lett., 131, p. 359Anderson, W.P., Edwards, W.D., Zerner, M.C., (1986) Inorg. Chem., 25, p. 2728Edwards, W.D., Zerner, M.C., (1987) Theor. Chim. Acta, 72, p. 347Del Nero, J., Laks, B., (1999) Synth. Met., 101, p. 440Del Nero, J., Laks, B., (1999) Synth. Met., 101, p. 379Doretto, R.L., Del Nero, J., Laks, B., (1999) Synth. Met., 101, p. 178Del Nero, J., De Melo, C.P., (2001) Synth. Met., 121, p. 1741Del Nero, J., Galvao, D.S., Laks, B., in preparatio
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
High-temperature Superconductivity In Graphite-sulfur Composites: Theoretical Analysis
No full textRecently superconductivity in graphite-sulfur composites was experimentally observed. In this work we have analyzed the electronic structure changes associated with the presence of sulfur atoms in one and two dimensional graphite layers. We have considered ordered and disordered sulfur atoms distributions in many configurations. The density of states (DOS) of these structures were obtained using the negative factor counting (NFC) technique coupled to a tight-binding Hamiltonian (Hückel type). Our results indicate that the incorporation of sulfur atoms at edge graphite layers (changing their global geometric curvature and increasing the DOS at the Fermi level) might be in the origin of the graphite superconductivity.689127132Da Silva, R.R., Tores, J.H.S., Kopelevich, Y., (2001) Phys. Rev. Lett., 87, pp. 147001-147011González, J., Guinea, F., Vozmediano, M.A.H., (2001) Phys. Rev. B, 63, p. 134421Nagamatsu, J., Nakagawa, N., Muranaka, T., Zenitani, Y., Akimitsu, J., (2001) Nature (London), 410, p. 63Dean, P., Martin, J.L., (1960) Proc. Roy. Soc., A259, p. 409Ladik, J., Seel, M., Otto, P., Bakhshi, A.K., (1986) Chem. Phys., 108, p. 203Galvão, D.S., Dos Santos, D.A., Laks, B., De Melo, C.P., Caldas, M.J., (1989) Phys. Rev. Lett., 63, p. 786Lavarda, F.C., Dos Santos, M.C., Galvão, D.S., Laks, B., (1994) Phys. Rev. Lett., 73, p. 1267Galvão, D.S., Laks, B., Da Silva, R.R., Torres, J.H.S., Kopelevich, Y., to be publishe
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