Search results for "post"
showing 10 items of 6213 documents
Metallocenes and post-metallocenes immobilized on ionic liquid-modified silica as catalysts for polymerization of ethylene
2014
Abstract The supported ionic liquid (SIL) strategy was used for the first time to metallocene and post-metallocene heterogeneous catalysts for olefin polymerization. The metal complexes: Cp2TiCl2, Cp2ZrCl2, FI–Ti, and Sal–Ti were immobilized in the 1-(3-triethoxysilyl)propyl-3-methylimidazolium alkylchloroaluminate ionic liquid, anchored on the surface of the mesoporous amorphous silica. The SIL systems were characterized by FTIR, 29Si NMR, N2 adsorption, EA, AAS, TG, and SEM techniques. The developed supported catalytic systems were found to be active in the ethylene polymerization and produce the polyethylene of various properties.
Transition metal complexes of tetradentate and bidentate Schiff bases as catalysts for ethylene polymerization: Effect of transition metal and cocata…
2009
This article compares catalytic performance of ethylene polymerization in similar polymerization conditions of transition metal complexes having two ligands [O,N] (phenoxy-imine) and having one tetradentate ligand [O,N,N,O] (salphen or salen). It is shown that the activity of both complex types as well as the product properties depend in the same way on the type of central metal in the complex and on the cocatalyst used. Although the type of ligand has some effect on the catalyst activity, yet it does not control the properties of the obtained products. The vanadium and zirconium complexes, irrespective of the cocatalyst used, yield linear polyethylene with high molecular weight (a few hund…
Effect of immobilization of titanocene catalyst in aralkyl imidazolium chloroaluminate media on performance of biphasic ethylene polymerization and p…
2012
1-(2-Phenylethyl)-3-methylimidazolium and 1-benzyl-3-methylimidazolium chloroaluminates, [Ph-C2mim][AlCl4] and [Bzlmim][AlCl4], were applied as media of the Cp2TiCl2 catalyst for biphasic ethylene polymerization. The studied aralkyl ionic liquids ensure greater stability of the catalyst at higher temperatures and more regular morphology of the produced polyethylene than analogous 1-n-alkyl-3-methylimidazolium chloroaluminates. The alkylaluminium compound participates in the termination reaction of the polymer chain. The catalyst is stable and enables recycling of the ionic liquid phase in the consecutive polymerization reactions. The [Ph-C2mim][AlCl4] ionic liquid and AlEt2Cl alkylaluminium…
Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO2 ionic liquid system
2015
Polyethylene of fibrous morphology was obtained using Cp2VCl2 and VCl2(salenCl2) catalysts activated by AlEt2Cl and AlEtCl2 and heterogenized on a supported ionic liquid system prepared with SiO2 and 1-(3-triethoxysilyl)propyl-3-methylimidazolium chloroaluminate. The fibre length ranges from 15 to 60 µm, depending on the reaction conditions. The polyethylene is characterized by a high molecular weight ((1.1–2.4) × 106 g mol−1) and a narrow molecular weight distribution (1.4–2.5). It is a linear polymer, properly without branching. The DSC method reveals characteristic changes in melting temperature and crystallinity degree between the first and second scan heating cycles (141 °C and 136 °C,…
Ejercicios de caligrafía teatral para escribir una escena imprevisible y disconforme. Rodrigo García (1987-1997) = Theatrical calligraphy exercises t…
2016
<p style="font-weight: normal; page-break-inside: avoid; widows: 136;" lang="es-ES" align="JUSTIFY"> </p><p>Una etapa bastante desatendida en la trayectoria de Rodrigo García comprende desde su llegada a España hasta su incipiente proyección internacional. A partir de documentos de ese periodo, este estudio revisa sus primeras reflexiones teatrales, las diversas estrategias aplicadas a su escritura y puesta en escena, así como los referentes interdisciplinares que han ido conformando su universo escénico<strong>.</strong></p><p style="font-weight: normal; page-break-inside: avoid; widows: 136;" lang="es-ES" align="JUSTIFY"> </p><p style="f…
Sociologia e urbanistica, dalle diseguaglianze agli spazi condivisi
2011
Poichè nuove società, geografie ed economie riconfigurano città e territori attuali, il contributo auspica un ritorno concreto al binomio urbanistica/sociologia affinchè le forme spaziali pianificate traducano concretamente le questioni di giustizia ed equità richieste dall’abitare contemporaneo. Poichè nuove società, geografie ed economie riconfigurano città e territori attuali, il contributo auspica un ritorno concreto allo storico binomio urbanistica/sociologia, affinchè le forme spaziali pianificate traducano concretamente le questioni di giustizia ed equità richieste dall’abitare contemporaneo. Nello specifico viene proposta l'applicazione - anche a contesti urbani - della Post Occupan…
Applicazioni della Spettroscopia nel vicino infrarosso (fNIRS) e della Mirror Therapy per la riabilitazione dell’arto superiore in pazienti post-stor…
2021
L’ictus cerebrale negli ultimi 20 anni registra un aumento della sua incidenza sulla popolazione italiana, conseguente anche ad un aumento dell’è demografica media. L’ictus determina un’ampia gamma di deficit funzionali che possono essere recuperati con un progetto riabilitativo mirato ed anche rimanere in parte o in toto permanenti. Negli ultimi anni è stato affermato che l’approccio multidisciplinare sembra essere necessario per contribuire ad un recupero funzionale del paziente in tempi brevi. Cercando di garantire al paziente, quanto più possibile, la restituzione di una vita quanto più autonoma possibile, nell’espletamento delle attività di base di vita quotidiana. Lo scopo dell’interv…
Enabling environments for equity, access and quality education post-2015 : Lessons from South Africa and Tanzania
2016
In this paper we seek to contribute to the post-2015 education agenda by shifting the focus from considerations of what education goals and targets should be to a people-centred exploration of enabling environments, within and beyond education, for equity, access and quality. Theoretically, the paper draws on the capabilities approach. Empirically, we present data from two independent qualitative studies conducted in South Africa (n = 40) and Tanzania (n = 10) with university students who accessed higher education despite trends of low participation for their social class and/or gender. The paper highlights the importance of taking account of both instrumental and intrinsic values of educat…
Post-Keynesian Principles of Economic Policy
2006
Duality-invariant dispersion relations for electromagnetic and gravitational waves at Planck scales
2012
In this paper we explore some mathematical aspects of a duality-invariant Einstein-Planck relation on electromagnetic waves and gravitational waves at a Planckian scale. We explore a generalized version of Maxwell's equations leading to the proposed duality-invariant dispersion relation for electromagnetic waves. We also study the analogous aspects of duality in a post-Newtonian description of gravitational waves.