1,720,961 research outputs found
The Influence Of Na+ On The Anilinepropylsilica Xerogel Synthesis By Using The Flouride Nucleophilic Catalyst
No full textAnilinepropylsilica xerogel was obtained by using an appropriate organosilane and tetraethyl orthosilicate as precursor reagents. The gelation was carried out using HF and NaF as catalysts. The presence of Na+ (when NaF was used) resulted in a decrease in the final organic content of the materials. This effect was interpreted as an inhibition of the organosilane polycondensation possibly due to the Na+ interaction with the SiO- groups of the hydrolyzed organosilane. The presence of Na+ also results in morphological changes in the xerogels.2812173177Levy, D., Esquivias, L., (1995) Adv. Mater., 7, p. 120Corriu, R.J.P., Leclercq, D., (1996) Angew Chem. Int. Ed. Engl., 35, p. 1420Loy, D.A., Shea, K.J., (1995) Chem. Rev., 95, p. 1431Schubert, U., Hüsing, N., Lorenz, A., (1995) Chem. Mater., 7, p. 2010Aznar, A.J., Sanz, J., Ruizhitzky, E., (1992) Colloid Polym. Sci., 270, p. 165Cerveau, G., Corriu, R.J.P., Fischmeister-Lepeytre, C., (1999) J. Mater. Chem., 9, p. 1149Pedroso, M.A.S., Dias, M.L., Azuma, C., Mothé, C.G., (2000) Colloid Polym. Sci., 278, p. 1180Ogasawara, T., Izawa, K., Hattori, N., Okabayashi, H., O'Connor, C.J., (2000) Colloid Polym. Sci., 278, p. 293Collinson, M.M., (1999) Crit. Rev. Anal. Chem., 29, p. 289Pavan, F.A., Franken, L., Moreira, C.A., Costa, T.M.H., Benvenutti, E.V., Gushikem, Y., (2001) J. Colloid Interface Sci., 241, p. 143Pavan, F.A., Hoffmann, H.S., Gushikem, Y., Costa, T.M.H., Benvenutti, E.V., (2002) Mater. Lett., , (in press)Feng, P., Xia, Y., Feng, J., Bu, X., Stucky, G.D., (1997) Chem. Commun., p. 949Bernards, T.N.M., Van Bommel, M.J., Jansen, J.A.J., (1998) J. Sol-Gel. Sci. Technol., 13, p. 749Wijnen, P.W.J.G., Beelen, T.P.M., Rummens, K.P.J., Saeijs, H.C.P.L., Haan, J.W., van de Ven, L.J.M., van Santen, R.A., (1991) J. Colloid Interface Sci., 145, p. 17Arriagada, F.J., Osseo-Asare, K., (1995) J. Colloid Interface Sci., 170, p. 8Guo, X., Ding, W., Wang, X., Yan, Q., (2001) Chem. Commun., p. 709Pavan, F.A., Gobbi, S.A., Costa, T.M.H., Benvenutti, E.V., (2002) J. Therm. Anal. Calorim., 68, p. 199. , (2002)Prouzet, E., Pinnavaia, T.J., (1997) Angew. Chem. Int. Ed. Engl., 36, p. 516Pavan, F.A., Leal, S., Costa, T.M.H., Benvenutti, E.V., Gushikem, Y., (2002) J. Sol-Gel. Sci. Technol., 23, p. 129Foschiera, J.L., Pizzolato, T.M., Benvenutti, E.V., (2001) J. Braz. Chem. Soc., 12, p. 159Brunauer, S., Emmett, P.H., Teller, E., (1938) J. Am. Chem. Soc., 60, p. 309Sing, K.S.W., Everett, D.H., Haul, R.A.W., Moscou, L., Pierotti, R.A., Rouquérol, J., Siemieniewska, T., (1985) Pure Appl. Chem., 57, p. 603Barret, E.P., Joyner, L.G., Halenda, P.P., (1951) J. Am. Chem. Soc., 73, p. 373Nielsen, S.B., Masella, M., Kebarle, P., (1999) J. Phys. Chem. A., 103, p. 9891Tsurusawa, T., Iwata, S., (1999) J. Phys. Chem. A., 103, p. 6134Hoyau, S., Norrman, K., Ohanessian, G., (1999) J. Am. Chem. Soc., 121, p. 8864Sonnefeld, J., (1996) Colloid Polym. Sci., 274, p. 1137Brinker, C.J., Scherer, G.W., (1990) Sol-gel Science, , Academic, Londo
Anisotropic Self-organization Of Hybrid Silica Based Xerogels Containing Bridged Positively Charged 1,4-diazoniabicycle[2.2.2]octane Chloride Group
No full textAnisotropic self-organized hybrid silica based xerogels were obtained. The ordered structure was imposed by the double charged 1,4-diazoniabicycle[2.2.2]octane chloride group bonded in a bridged way. This was confirmed by the presence of well defined X-ray diffraction peaks corresponding to an interplanar distance with the same length estimated for the organic bridged groups. The material was characterized by elemental analysis using CHN technique and the chloride ion was analyzed by a potentiometric titration. 13C and 29Si CP MAS solid state NMR spectroscopy and thermogravimetric analysis were also performed. The material that can be obtained in the form of powders and transparent monoliths or films, is thermally stable up to 260 °C and the samples with high organic content presented birefringence properties. © 2007 Elsevier Inc. All rights reserved.318196102Schubert, U., Gao, Y., Kogler, F.R., (2007) Prog. 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Colloid Interface Sci., 263, p. 688Passos, C.G., Ribaski, F.S., Simon, N.M., Santos, A.A., Vaghetti, J.C.P., Benvenutti, E.V., Lima, E.C., (2006) J. Colloid Interface Sci., 302, p. 396Walcarius, A., (2001) Chem. Mater., 13, p. 3351Price, P.M., Macquarrie, D.J., (2000) J. Chem. Soc. Dalton Trans., 2, p. 101Ford, D.M., Simanek, E.E., Shantz, D.F., (2005) Nanotechnology, 16, pp. S458Costa, T.M.H., Hoffmann, H.S., Benvenutti, E.V., Stefani, V., Gallas, M.R., (2005) Opt. Mater., 27, p. 1819Serwadczak, M., Ubbenhorst, M.W., Kucharski, S., (2006) J. Sol-Gel Sci. Technol., 40, p. 39Shea, K.J., Loy, D.A., (2001) Acc. Chem. Res., 34, p. 707Loy, D.A., Shea, K.J., (2001) Chem. Mater., 13, p. 3306Ben, F., Boury, B., Corriu, R.J.P., Strat, V.L., (2000) Chem. Mater., 12, p. 3249Boury, B., Ben, F., Corriu, R.J.P., Delord, P., Nobili, M., (2002) Chem. Mater., 14, p. 730Muramatsu, H., Corriu, R.J.P., Boury, B., (2003) J. Am. Chem. 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Structure And Property Studies Of Hybrid Xerogels Containing Bridged Positively Charged 1,4-diazoniabicycle[2.2.2]octane Dichloride
No full textThe compound di-3-n-propyltrimethoxysilane (1,4-diazoniabicycle[2.2.2] octane) dichloride, [(MeO)3Si(CH2)3N +(CH2CH2)3N+(CH 2)3Si(OME)3]Cl2 was obtained and was used as a precursor reagent to obtain hybrid xerogels where the organic molecule was bonded to a silica framework by reacting the ends of both sides of the precursor reagent. That is, both Si(OME)3 groups react with tetraethylorthosilicate (TEOS) by hydrolysis-condensation reactions. The resulting hybrid xerogels with variable C/Si mole ratios were prepared and analyzed and their textural characteristics determined. The samples prepared presented micropores with diameter 1.5 nm, the chain length of which matched with the estimated length of the organic bridging group. The charged organic bridging groups allow the immobilization of hexacyanoferrate ions by an ion exchange process. The electron transfer process of the hexacyanoferrate anionic complex confined in the pores of the matrices was studied by cyclovoltammetry. © 2005 Elsevier Inc. All rights reserved.2971244250Schottner, G., (2001) Chem. Mater., 13, p. 3422Yang, H.-H., Zhang, S.-Q., Yang, W., Chen, X.-L., Zhuang, Z.-X., Xu, J.-G., Wang, X.-R., (2004) J. Am. Chem. Soc., 126, p. 4054Shchipunov, Y.A., (2003) J. Colloid Interface Sci., 268, p. 68Scott, B.J., Wirnsberger, G., Stucky, G.D., (2001) Chem. Mater., 13, p. 3140Martínez, Y., Retuert, J., Yazdani-Pedram, M., Colfen, H., (2004) Polymer, 45, p. 3257Phillips, S.H., Haddad, T.S., Tomczak, S.J., (2004) Curr. Opin. Solid State Mater. Sci., 8, p. 21Kickelbick, G., (2003) Prog. Polym. Sci., 28, p. 83Khoroshevskiy, Y., Korneev, S., Myerniy, S., Kholin, Y.V., Pavan, F.A., Schifino, J., Costa, T.M.H., Benvenutti, E.V., (2005) J. Colloid Interface Sci., 284, p. 424Arenas, L.T., Langaro, A., Gushikem, Y., Moro, C.C., Benvenutti, E.V., Costa, T.M.H., (2003) J. Sol-Gel Sci. Technol., 28, p. 51Splendorea, G., Benvenutti, E.V., Kholinc, Y.V., Gushikem, Y., (2005) J. Braz. Chem. Soc., 16, p. 147Arenas, L.T., Aguirre, T.A.S., Langaro, A., Gushikem, Y., Benvenutti, E.V., Costa, T.M.H., (2003) Polymer, 44, p. 5521Arenas, L.T., Vaghetti, J.C.P., Lima, E.C., Moro, C.C., Benvenutti, E.V., Costa, T.M.H., (2004) Mater. Lett., 58, p. 895Fernandes, J.R., Kubota, L.T., Gushikem, Y., Neto, G.O., (1993) Anal. Lett., 26, p. 2555Kogure, M., Ohya, H., Paterson, R., Hosaka, M., Kim, J.-J., McFadzean, S., (1997) J. Membr. Sci., 126, p. 161Gray, G.M., Hay, J.N., (2004) J. Sol-Gel. Sci. Technol., 31, p. 191Cuiming, W., Tongwen, X., Weihua, Y., (2003) J. Membr. Sci., 216, p. 269Lin, C.-L., Tien, P., Chau, L.-K., (2004) Electrochim. Acta, 49, p. 573Walcarius, A., Delacote, C., Sayen, S., (2004) Electrochim. Acta, 49, p. 3775Darder, M., Colilla, M., Lara, N., Ruiz-Hitzky, E., (2002) J. Mater. Chem., 12, p. 3660Cardoso, W.S., Francisco, M.S.P., Lucho, A.M.S., Gushikem, Y., (2004) Solid State Ionics, 167, p. 165Kubota, L.T., Gushikem, Y., (1993) J. Electroanal. Chem., 362, p. 219Liu, S.Q., Chen, H.Y., (2002) J. Electroanal. Chem., 528, p. 190Zaldivar, G.A.P., Gushikem, Y., Benvenutti, E.V., De Castro, S.C., Vasquez, A., (1994) Electrochim. Acta, 39, p. 33Foschiera, J.L., Pizzolato, T.M., Benvenutti, E.V., (2001) J. Braz. Chem. Soc., 12, p. 159Guinier, A., Fournet, G., (1955) Small-Angle Scattering of X-Ray, , Wiley New YorkGlatter, O., Kratky, O., (1982) Small-Angle X-Ray Scattering, , Academic Press LondonBarret, E.P., Joyner, L.G., Halenda, P.P., (1951) J. Am. Chem. Soc., 73, p. 373Brunauer, S., Emmett, P.H., Teller, E., (1938) J. Am. Chem. Soc., 60, p. 309Hou, S.S., Kuo, P.L., (2001) Polymer, 42, p. 9505Davis, M.E., Saldarriaga, C.J., (1988) Chem. Soc. Chem. Commun., p. 920Costa, T.M.H., Hoffmann, H.S., Benvenutti, E.V., Stefani, V., Gallas, M.R., (2005) Opt. Mater., 27, p. 1819Azolin, D.R., Moro, C.C., Costa, T.M.H., Benvenutti, E.V., (2004) J. Non-Cryst. Solids, 337, p. 201Takei, T., Chikazawa, M., Kanazawa, T., (1997) Colloid Polym. Sci., 275, p. 1156Shea, K.J., Loy, D.A., (2001) Chem. Mater., 13, p. 3306Muramatsu, H., Corriu, R.J.P., Boury, B., (2003) J. Am. Chem. Soc., 125, p. 854Boury, B., Ben, F., Corriu, R.J.P., Delord, P., Nobili, M., (2002) Chem. Mater., 14, p. 730Maniar, P.D., Navrotsky, A., Rabinovich, E.M., Ying, J.Y., Benziger, J.B., (1990) J. Non-Cryst. Solids, 124, p. 101Bard, A.J., Faulkner, L., (2000) Electrochemical Methods - Fundamentals and Applications, , Wiley New YorkMuelwyn-Hughes, E.A., (1961) Physical Chemistry, , Pergamon Londo
Gold Nanoparticle/charged Silsesquioxane Films Immobilized Onto Al/sio 2 Surface Applied On The Electrooxidation Of Nitrite
No full textIn this work, gold nanoparticles lower than 10 nm were prepared in an aqueous medium using two charged silsesquioxanes, the propylpyridinium chloride and propyl- 1-azonia-4-azabicyclo[2.2.2]octane chloride, as stabilizer agents which revealed to be water-soluble. This stabilization method is innovative allowing thin films containing gold nanoparticles to be obtained, and it was used for the first time in the preparation of carbon paste electrodes (CPEs). The charged silsesquioxanes were characterized by liquid 13C NMR. The gold nanoparticle/silsesquioxane systems were characterized by ultraviolet-visible spectroscopy (UV-Vis) and transmission electron microscopy. In sequence, they were immobilized on silica matrix coated with aluminum oxide. The resulting solid materials designated as Au-Py/AlSi and Au-Db/AlSi were characterized by infrared spectroscopy and N2 adsorption/desorption isotherms. 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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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