1,720,980 research outputs found
Multifunctional Materials Based On Iron/iron Oxide-filled Carbon Nanotubes/natural Rubber Composites
No full textThis work describes the synthesis, characterization and study of properties of novel multifunctional composite materials obtained by natural-rubber latex and a special kind of multi-walled carbon nanotube (CNT), in which the cavities are filled by magnetic species. To prepare stable aqueous dispersions of CNTs, two approaches have been employed, based on a mixture of the surfactant sodium dodecyl sulfate or a previous treatment with a mixture of acid solutions. The composites have been characterized by infrared and Raman spectroscopy, X-ray micro-tomography, transmission and scanning electron microscopy, and atomic and magnetic force microscopy. A good adhesion between the CNTs and the polymer matrices was obtained. Several samples have been prepared containing different amounts of CNTs (from 0.01 to 10 wt.%), and the effect of carbon nanotubes in the electrical, mechanical, chemical and thermal properties of the composites was evaluated by thermogravimetric analysis, resistivity measurements, stress-strain mechanical tests and solvent sorption measurements. The occurrence of networks of CNTs in the polymeric matrices provided significant increases in all of these properties. Additionally, because of the species encapsulated in CNT, the composites exhibit magnetic behavior, confirmed by magnetic force microscopy. This approach results in novel multifunctional material with great potential for further applications. © 2012 Elsevier Ltd. All rights reserved.501246854695Rippel, M.M., Paula Leite, C.A., Galembeck, F., Elemental mapping in natural rubber latex films by electron energy loss spectroscopy associated with transmission electron microscopy (2002) Anal Chem, 74 (11), pp. 2541-2546Van Beilen, J.B., Poirier, Y., Establishment of new crops for the production of natural rubber (2007) Trends Biotechnol, 25 (11), pp. 522-529Cyr, D.R., (1991) Encyclopedia of Chemical Technology, , Wiley-Interscience New YorkBokobza, L., Chauvin, J.P., Reinforcement of natural rubber: Use of in situ generated silicas and nanofibres of sepiolite (2005) Polymer, 46 (12), pp. 4144-4151Valadares, L.F., Leite, C.A.P., Galembeck, F., Preparation of natural rubber-montmorillonite composite in aqueous medium: Evidence for polymer-platelet adhesion (2006) Polymer, 47 (2), pp. 672-678Rezende, C.A., Bragança, F.C., Doi, T.R., Lee, L.T., Galembeck, F., Boué, F., Natural rubber-clay composites: Mechanical and structural properties (2010) Polymer, 51 (16), pp. 3644-3652Angellier, H., Molina-Boisseau, S., Dufresne, A., Mechanical properties of waxy maize starch nanocrystal reinforced natural rubber (2005) Macromolecules, 38 (22), pp. 9161-9170Cai, H.H., Li, S.D., Tian, G.R., Wang, H.B., Wang, J.H., Reinforcement of natural rubber latex film by ultrafine calcium carbonate (2003) J Appl Polym Sci, 87 (6), pp. 982-985Karásek, L., Sumita, M., Characterization of dispersion state of filler and polymer-filler interactions in rubber-carbon black composites (1996) J Mater Sci, 31 (2), pp. 281-289Bokobza, L., Multiwall carbon nanotube elastomeric composites: A review (2007) Polymer, 48 (17), pp. 4907-4920Bhattacharyya, S., Sinturel, C., Bahloul, O., Saboungi, M.L., Thomas, S., Salvetat, J.-P., Improving reinforcement of natural rubber by networking of activated carbon nanotubes (2008) Carbon, 46 (7), pp. 1037-1045Zhan, Y., Wu, J., Xia, H., Yan, N., Fei, G., Yuan, G., Dispersion and exfoliation of graphene in rubber by an ultrasonically-assisted latex mixing and in situ reduction process (2011) Macromol Mater Eng, 7, pp. 590-602Moniruzzaman, M., Winey, K.I., Polymer composites containing carbon nanotubes (2006) Macromolecules, 39 (16), pp. 5194-5205Spitalsky, Z., Tasis, D., Papagelis, K., Galiotis, C., Carbon nanotube-polymer composites: Chemistry, processing, mechanical and electrical properties (2010) Prog Polym Sci, 35 (3), pp. 357-401Coleman, J.N., Khan, U., Gun'Ko, Y.K., Mechanical reinforcement of polymers using carbon nanotubes (2006) Adv Mater, 18 (6), pp. 689-706Grossiord, N., Loos, J., Koning, C.E., Strategies for dispersing carbon nanotubes in highly viscous polymers (2005) J Mater Chem, 15 (24), pp. 2349-2352Cai, D., Song, M., Latex technology as a simple route to improve the thermal conductivity of a carbon nanotube/polymer composite (2008) Carbon, 46 (15), pp. 2107-2112Grunlan, J., Mehrabi, A., Bannon, M., Bahr, J., Water-based single-walled-nanotube-filled polymer composite with an exceptionally low percolation threshold (2004) Adv Mater, 16 (2), pp. 150-153Peng, Z., Feng, C., Luo, Y., Li, Y., Kong, L.X., Self-assembled natural rubber/multi-walled carbon nanotube composites using latex compounding techniques (2010) Carbon, 48 (15), pp. 4497-4503Anand, K.A., Jose, T.S., Alex, R., Joseph, R., Natural rubber-carbon nanotube composites through latex compounding (2010) Int J Polym Mater, 59 (1), pp. 33-44Schnitzler, M.C., Oliveira, M.M., Ugarte, D., Zarbin, A.J.G., One-step route to iron oxide-filled carbon nanotubes and bucky-onions based on the pyrolysis of organometallic precursors (2003) Chem Phys Lett, 381 (56), pp. 541-548Moraes, R.A., Matos, C.F., Castro, E.G., Schreiner, W.H., Oliveira, M.M., Zarbin, A.J.G., The effect of different chemical treatments on the structure and stability of aqueous dispersion of iron- and iron oxide-filled multi-walled carbon nanotubes (2011) J Braz Chem Soc, 22 (11), pp. 2191-2201Nossol, E., Zarbin, A.J.G., A simple and innovative route to prepare a novel carbon nanotube/Prussian blue electrode and its utilization as a highly sensitive H 2O 2 amperometric sensor (2009) Adv Funct Mater, 19 (24), pp. 3980-3986Salvatierra, R.V., Oliveira, M.M., Zarbin, A.J.G., One-pot synthesis and processing of transparent, conducting, and freestanding carbon nanotubes/polyaniline composite films (2010) Chem Mater, 22, pp. 5222-5234Canestraro, C.D., Schnitzler, M.C., Zarbin, A.J.G., Da Luz, M.G.E., Roman, L.S., Carbon nanotubes based composites for photocurrent improvement (2006) Appl Surf Sci, 252 (15), pp. 5575-5578Oliveira, M.M., Zarbin, A.J.G., Carbon nanotubes decorated with both gold nanoparticles and polythiophene (2008) J Phys Chem C, 112 (48), pp. 18783-18786Nossol, E., Zarbin, A.J.G., Carbon paste electrodes made from novel carbonaceous materials: Preparation and electrochemical characterization (2008) Electrochim Acta, 54 (2), pp. 582-589Rippel, M.M., Leite, C.A.P., Lee, L.-T., Galembeck, F., Formation of calcium crystallites in dry natural rubber particles (2005) J Colloid Interf Sci, 288 (2), pp. 449-456Masenelli-Varlot, K., Chazeau, L., Gauthier, C., Bogner, A., Cavaillé, J.Y., The relationship between the electrical and mechanical properties of polymer-nanotube composites and their microstructure (2009) Compos Sci Technol, 69 (10), pp. 1533-1539Bokobza, L., Rapoport, O., Reinforcement of natural rubber (2002) J Appl Polym Sci, 85 (11), pp. 2301-2316Bokobza, L., Kolodziej, M., On the use of carbon nanotubes as reinforcing fillers for elastomeric materials (2006) Polym Int, 55 (9), pp. 1090-1098Broza, G., Piszczek, K., Schulte, K., Sterzynski, T., Composites of poly(vinyl chloride) with carbon nanotubes (CNT) (2007) Compos Sci Technol, 67 (5), pp. 890-894Bokobza, L., Rahmani, M., Belin, C., Bruneel, J.L., El Bounia, N.E., Blends of carbon blacks and multiwall carbon nanotubes as reinforcing fillers for hydrocarbon rubbers (2008) J Polym Sci Pol Phys, 46 (18), pp. 1939-1951Sui, G., Zhong, W.H., Yang, X.P., Yu, Y.H., Curing kinetics and mechanical behavior of natural rubber reinforced with pretreated carbon nanotubes (2008) Mater Sci Eng A, 485 (12), pp. 524-531Li, S.D., Yu, H.P., Peng, Z., Zhu, C.S., Li, P.S., Study on thermal degradation of sol and gel of natural rubber (2000) J Appl Polym Sci, 75 (11), pp. 1339-1344Menon, A.R.R., Pillai, C.K.S., Nando, G.B., Thermal degradation characteristics of natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid (1996) Polym Degrad Stabil, 52 (3), pp. 265-271Cornell, S.W., Koenig, J.L., Raman spectra of polyisoprene rubbers (1969) Macromolecules, 2 (5), pp. 546-549Li, N., Huang, Y., Du, F., He, X., Lin, X., Gao, H., Electromagnetic interference (EMI) shielding of single-walled carbon nanotube epoxy composites (2006) Nano Lett, 6 (6), pp. 1141-1145Jou, W.S., Cheng, H.Z., Hsu, C.F., The electromagnetic shielding effectiveness of carbon nanotubes polymer composites (2007) J Alloy Compd, 434-435, pp. 641-64
New Polyaniline/porous Glass Composite
No full textIn this work we report the preparation of a glass-polymer composite, obtained by the in situ oxidative polymerization of aniline, in the pores of Porous Vycor Glass (PVG). A piece of PVG was added to acid aniline solution. PVG adsorbs aniline via an ion-exchange process (H+ from PVG porous surface/C6H5NH3 +). The impregnated PVG was added to a (NH4)2S2O8 acid solution. The glass gradually went to dark green with the formation of polyaniline in its conducting form, the emeraldine salt. The counter-anions are the SiO- groups on the pores surface of the glass, as confirmed by 29Si-CP-MAS-NMR. Addition of the composite to an NH4OH solution leads do a change from dark green to dark blue (emeraldine base), and this process is reversible.8401/03/15107108Chinn, D., Dubow, J., Liess, M., Josowicz, M., Janata, J., (1995) Chem. Mater., 7, p. 1504Kanatzidis, M.G., (1990) Chem Eng. News, DEC.3, p. 36Wuang, W.S., Humphrey, B.D., MacDiarmid, A.G., (1986) J. Chem. Soc., Faraday Trans. 1, 82, p. 2385Geniès, E.M., Boyle, A., Lapkowski, M., Tsintavis, C., (1990) Synth. Met., 36, p. 139Enzel, P., Bein, T., (1989) J. Phys. Chem., 93, p. 6270(1979) Mater. Eng., 90, p. 92Maia, D.J., Zarbin, A.J.G., Alves, O.L., De Paoli, M.A., (1995) Adv. Mater., 7, p. 792Furukawa, Y., Hara, T., Hyodo, Y., Harada, I., (1986) Synth. Met., 16, p. 18
Polyaniline Intercalation In α-sn(hpo4)2.h2o
No full textIn this work we report the preparation of a inorganic-organic nanocomposite, obtained by the in situ oxidative polymerization of aniline inside the layers of α-Sn(HPO4)2.H2O (α-SnP). Two approaches were used to obtain the α-SnP/polyaniline nanocomposite. Firstly, hydrogen atoms of α-SnP were exchanged with Fe3+ cation to promote aniline polymerization. Secondly, aniline was intercalated in α-SnP and polymerization was performed by (NH4)2S2O8 solution. Both resulting material leads to formation of polyaniline in its conducting form, the emeraldine salt. The characterization results suggest the formation of linear polymer chains between the α-SnP layers.1021-312771278Geniès, E.M., Boyle, A., Lapkowski, M., Tsintavis, C., (1990) Synth. Met., 36, p. 139Enzel, P., Bein, T., (1989) J. Phys. Chem., 93, p. 6270Maia, D.J., Zarbin, A.J.G., Alves, O.L., De Paoli, M.-A., (1995) Adv. Mater., 7, p. 792Zarbin, A.J.G., De Paoli, M.-A., Alves, O.L., (1997) Synth. Met., 84, p. 107Maia, D.J., Alves, O.L., De Paoli, M.-A., (1997) Synth. Met., 90, p. 37Whittinghan, M.S., Jacobson, A.J., (1982) Intercalation Chemistry, p. 147. , Academic PressConstantino, U., Gasperoni, A., (1970) J. Chromatogr., 51, p. 289Furukawa, Y., Hara, T., Hyodo, Y., Harada, I., (1986) Synth. Met., 16, p. 189Geniès, E.M., Lapkowski, M., Penneau, J.F., (1988) J. Electroanal. Chem., 249, p. 9
Multifunctional And Environmentally Friendly Nanocomposites Between Natural Rubber And Graphene Or Graphene Oxide
No full textThis work describes a green route to multifunctional nanocomposite materials composed of natural rubber (NR) latex and graphene (rGO) or graphene oxide (GO). Aqueous solutions with different concentrations of GO and rGO (prepared with the surfactant cetyltrimethylammonium bromide - CTAB) were mixed with natural rubber latex under magnetic stirring followed by sonication. The slurries obtained after casting were dried in an oven in air at 70 °C for 24 h. The nanocomposites were characterized by TEM and SEM, AFM and KFM. The thermal, electrical and mechanical properties were evaluated using TGA, resistivity measurements (four-point) and DMA. Swelling tests were performed using three solvents with different polarities: xylene, isopropanol and water. The inclusion of filler networks in the polymeric matrices provided significant improvements in the electrical, chemical and mechanical properties, in comparison to the unfilled polymer. In addition, the nanocomposites proved to be biodegradable. © 2014 Elsevier Ltd. All rights reserved.78469479Chiu, C.W., Huang, T.K., Wang, Y.C., Alamani, B.G., Lin, J.J., Intercalation strategies in clay/polymer hybrids (2014) Prog Polym Sci, 39, pp. 443-485Huang, J.C., Carbon black filled conducting polymers and polymer blends (2002) Adv Polym Sci, 21, pp. 299-313Al-Saleh, M.H., Sundararaj, U., Review of the mechanical properties of carbon nanofiber/polymer composites (2011) Compos A, 42, pp. 2126-2142Rahmat, M., Hubert, P., Carbon nanotube-polymer interactions in nanocomposites: A review (2011) Compos Sci Technol, 72, pp. 72-84Sham, A.Y.W., Notley, S.M., A review of fundamental properties and applications of polymer-graphene hybrid materials (2013) Soft Matter, 9, pp. 6645-6653Liu, G., Neoh, K.G., Kang, E.T., Dispersible graphene oxide-polymer nanocomposites (2012) Polym-graphene Nanocompos, 26, p. 179Wang, Y., Ameer, G.A., Sheppard, B.J., Langer, R., A tough biodegradable elastomer (2002) Nat Biotechnol, 20, pp. 602-606Darder, M., Aranda, P., Ferrer, M.L., Gutiérrez, M.C., Del Monte, F., Ruiz-Hitzky, E., Progress in bionanocomposite and bioinspired foams (2011) Adv Mater, 23, pp. 5262-5267Rippel, M.M., Leite, C.A.P., Galembeck, F., Elemental mapping in natural rubber latex films by electron energy loss spectroscopy associated with transmission electron microscopy (2002) Anal Chem, 74, pp. 2541-2546Sadasivuni, K.K., Ponnamma, D., Thomas, S., Grohens, Y., Evolution from graphite to graphene elastomer composites (2013) Prog Polym Sci, , 10.1016/j.progpolymsci.2013.08.003Singh, V., Joung, D., Zhai, L., Das, S., Khondaker, S.I., Seal, S., Graphene based materials: Past, present and future (2011) Prog Mater Sci, 56, pp. 1178-1271Verdejo, R., Bernal, M.M., Romasanta, L.J., Lopez-Manchado, M.A., Graphene filled polymer nanocomposites (2011) J Mater Chem, 21, pp. 3301-3310Kim, H., Abdala, A.A., Macosko, C.W., Graphene/polymer nanocomposites (2010) Macromolecules, 43, pp. 6515-6530Koning, C., Grossiord, N., Hermant, M.C., (2012) Polymer Carbon Nanotube Composites: The Polymer Latex Concept, , Pan Stanford PubTkalya, E., Ghislandi, M., Alekseev, A., Koning, C., Loos, J., Latex-based concept for the preparation of graphene-based polymer nanocomposites (2010) J Mater Chem, 20, pp. 3035-3039Wu, J., Xing, W., Huang, G., Li, H., Tang, M., Wu, S., (2013) Polymer, 54, pp. 3314-3323Wu, S., Tang, Z., Guo, B., Zhang, L., Jia, D., Vulcanization kinetics of graphene/natural rubber nanocomposites (2013) RSC Adv, 3, pp. 443-485Domingues, S.H., Salvatierra, R.V., Oliveira, M.M., Zarbin, A.J.G., Transparent and conductive thin films of graphene/polyaniline nanocomposites prepared through interfacial polymerization (2011) Chem Commun, 47, pp. 2592-2594Park, S., Ruoff, R.S., Chemical methods for the production of graphenes (2009) Nat Nanotechnol, 4, pp. 217-224Rippel, M.M., Lee, L.T., Leite, C.A.P., Galembeck, F., Skim and cream natural rubber particles: Colloidal properties, coalescence and film formation (2003) J Colloid Interface Sci, 268, pp. 330-340Kim, J., Hong, S., Park, D., Shim, S., Water-borne graphene-derived conductive SBR prepared by latex heterocoagulation (2010) Macromol Res, 18, pp. 558-565Rippel, M.M., Leite, C.A.P., Lee, L.T., Galembeck, F., Formation of calcium crystallites in dry natural rubber particles (2005) J Colloid Interface Sci, 288, pp. 449-456Potts, J.R., Shankar, O., Du, L., Ruoff, R.S., Processing-morphology-property relationships and composite theory analysis of reduced graphene oxide/natural rubber nanocomposites (2012) Macromolecules, 45, pp. 6045-6055Valadares, L.F., Leite, C.A.P., Galembeck, F., Preparation of natural rubber-montmorillonite nanocomposite in aqueous medium: Evidence for polymer-platelet adhesion (2006) Polymer, 47, pp. 672-678Cassu, S.N., Felisberti, M.I., Comportamento dinâmico-mecânico e relaxações em polímeros e blendas poliméricas (2005) Quim Nova, 28, pp. 255-263Geethamma, V., Kalaprasad, G., Groeninckx, G., Thomas, S., Dynamic mechanical behavior of short coir fiber reinforced natural rubber composites (2005) Compos A, 36, pp. 1499-1506López-Manchado, M.A., Biagiotti, J., Valentini, L., Kenny, J.M., Dynamic mechanical and Raman spectroscopy studies on interaction between single-walled carbon nanotubes and natural rubber (2004) J Appl Polym Sci, 92, pp. 3394-3400Robertson, C.G., Rackaitis, M., Further consideration of viscoelastic two glass transition behavior of nanoparticle-filled polymers (2011) Macromolecules, 44, pp. 1177-1181Li, S.D., Yu, H.P., Peng, Z., Zhu, C.S., Li, P.S., Study on thermal degradation of sol and gel of natural rubber (2000) J Appl Polym Sci, 75, pp. 1339-1344Menon, A.R.R., Pillai, C.K.S., Nando, G.B., Thermal degradation characteristics of natural rubber vulcanizates modified with phosphorylated cashew nut shell liquid (1996) Polym Degrad Stab, 52, pp. 265-271Uskoković, V., Drofenik, M., Ban, I., The characterization of nanosized nickel-zinc ferrites synthesized within reverse micelles of CTAB/1-hexanol/water microemulsion (2004) J Magn Magn Mater, 274, pp. 294-302Zhan, Y., Lavorgna, M., Buonocore, G., Xia, H., Enhancing electrical conductivity of rubber composites by constructing interconnected network of self-assembled graphene with latex mixing (2012) J Mater Chem, 22, pp. 10464-10468Bokobza, L., Kolodziej, M., On the use of carbon nanotubes as reinforcing fillers for elastomeric materials (2006) Polym Int, 22, pp. 1090-1098Broza, G., Piszczek, K., Schulte, K., Sterzynski, T., Nanocomposites of poly(vinyl chloride) with carbon nanotubes (CNT) (2007) Compos Sci Technol, 67, pp. 890-894Bragança, F.C., Valadares, L.F., Leite, C.A.P., Galembeck, F., Counterion effect on the morphological and mechanical properties of polymer-clay nanocomposites prepared in an aqueous medium (2007) Chem Mater, 19, pp. 3334-3342Scherillo, G., Lavorgna, M., Buonocore, G.G., Zhan, Y.H., Xia, H.S., Mensitieri, G., Tailoring assembly of reduced graphene oxide nanosheets to control gas barrier properties of natural rubber 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Nanocomposites Glass/conductive Polymers
No full textWe report on the preparation and characterization of two glass/conducting polymer nanocomposites obtained by the in situ oxidative polymerization of pyrrole and aniline inside the pores of Porous Vycor Glass (PVG). Oxidative polymerization of pyrrole was done via Cu2+ cation impregnated in the PVG pores. The polymerization of aniline was undertaken by impregnating PVG with the monomer, followed by an acid solution of (NH4)2S2O8. These nanocomposites were characterized by diffuse reflectance FT infrared spectroscopy, UV-Vis-NIR absorption spectroscopy, thermogravimetric analysis, Raman spectroscopy, solid state 13C and 29Si CP-MAS-NMR, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and conductivity measurements. The results showed that both polymers are formed inside the PVG pores in their oxidized conductive state, with the Si-O- groups of the glass surface acting as counter-anions. The dimensions of the pores of the glass preclude cross-linking of the polymers, allowing only formations of linear chains. The results suggest the formation of polymeric wires in the bulk of the glass substrate. © 1999 Elsevier Science S.A. All rights reserved.993227235Genies, E.M., Lapkowiski, M., Santier, C., Vieil, E., (1987) Synth. Met., 18, p. 631Duek, E.A.R., De Paoli, M.-A., Mastragostino, M., (1992) Adv. Mater., 4, p. 287Bäuerle, P., (1993) Adv. Mater., 5, p. 879MacDiarmid, A.G., Yang, L.S., Huang, W.S., Humphrey, B.D., (1987) Synth. Met., 18, p. 393Kanatzidis, M.G., (1990) Chem. Eng. News, 3, p. 36Deshpande, M.V., Malnerkar, D.P., (1993) Prog. Polym. Sci., 18, p. 623Gustafsson, G., Cao, Y., Tracy, G.M., Klavetter, F., Colaneri, N., Heeger, A.J., (1992) Nature, 357, p. 477Parker, I.D., (1994) J. Appl. Phys., 75, p. 1656Roth, S., Graupner, W., (1993) Synth. Met., 55-57, p. 3623Martin, C.R., (1995) Acc. Chem. 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New Route For The Obtention Of Cadmium Antimony Oxide Semiconducting Ceramic Powders
No full textHere we describe a new route for the obtention of the non-stoichiometric compound Cd2Sb2O7-x, through the thermal decomposition of cadmium-exchanged crystalline antimonic acid (CAA/Cd). Cadmium-exchanged crystalline antimonic acid already has the pyrochlore-type structure, and it seems to us that the precursor structure plays an important role in the formation of the final product. This new synthetic route presents some advantages compared to the other methods mentioned: (i) The synthesis is carried out at lower temperatures and for reduced heating times;, (ii) The ceramic powders are obtained from only one precursor reagent, leading to a final product with great chemical and phase purities. It is important to note that the ion-exchanged modified host structures provide an interesting way to prepare oxide ceramics powders.13860760
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
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