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Title: The ultraviolet morphology of evolved populations
Author: Arnez-Prado, A.H.
Gonzalez-Ortiz, L.J.
Aranda-García, F.J.
Jasso-Gastinel, C.F.
Issue Date: 2012
Abstract: Semicontinuous seeded emulsion copolymerizations, using 5 different types of feeding profiles of comonomers (styrene/butyl acrylate, S/BA) were carried out, to vary in a gradual manner the composition of the copolymer chains formed throughout the reactions (gradient composition copolymer, GCC). For comparison, equivalent core-shell type polymeric materials were synthesized in two stages (T-S). In all reactions, the S/BA global mass ratio was: 70/30. To estimate the weight composition distribution (WCD) of the copolymer chains, the cumulative styrene content in the polymer mass was followed throughout the reaction ( 1H-NMR). Average molecular weights were determined using SEC. The differences in mechanical performance were established, carrying out a mechanodynamic (DMA), and mechanostatic characterization (stress-strain at several temperatures and, Izod testing). The area under the loss modulus curve (LA) was correlated with Izod impact strength, showing the damping superiority of the GCCs over the T-S material. At all tested temperatures (between 25 and 70 °C), the GCC materials exhibited yielding and plastic deformation, while the T-S material presented brittle fracture in that temperature interval. The WCDs were used to elucidate the differences in mechanical behaviour among GCC materials. The feeding profile variation in combination with the WCD analysis represents a novel methodology to produce tailor made copolymers. " ARKAT-USA, Inc.",,,,,,,,,"","",,,,,,,,"E-Polymers",,,,,,"Scopus
WOS",,,,,,,,,,,,"The variation of comonomers feeding profile to design the distribution of chains composition for the optimization of the mechanical properties in copolymer systems",,"Article" "47088","123456789/35008",,"Chávez, M., Instituto Nacional de Astrofísica, óptica y Electrónica (INAOE), Luis Enrique Erro 1, Tonantzintla, Cholula, Puebla C.P. 72840, Mexico, Instituto de Astronomia y Meteorología, Universidad de Guadalajara, Av. Vallarta 2602, Col. Arcos Vallarta, Guadalajara C.P. 44130, Mexico",,"Chavez, M.",,"2009",,"In this paper I present a summary of the recent investigations we have developed at the Stellar Atmospheres and Populations Research Group (GrAPEs-for its designation in Spanish) at INAOE and collaborators in Italy. These investigations have aimed at providing updated stellar tools for the analysis of the UV spectra of a variety of stellar aggregates, mainly evolved ones. The sequence of material here presented roughly corresponds to the steps we have identified as mandatory to properly establish the applicability of synthetic populations in the analyses of observational data of globular clusters and more complex aged aggregates. The sequence is composed of four main stages, namely, (a) the creation of a theoretical stellar data base that we have called UVBLUE, (b) the comparison of such data base with observational stellar data, (c) the calculation of a set of synthetic spectral energy distributions (SEDs) of simple stellar populations (SSPs) and their validation through a comparison with observations of a sample of galactic globular clusters (GGCs), (d) construction of models for dating local ellipticals and distant red-envelope galaxies. Most of the work relies on the analysis of absorption line spectroscopic indices. The global results are more than satisfactory in the sense that theoretical indices closely follow the overall trends with chemical composition depicted by their empirical counterparts (stars and GGCs). " 2008 Springer Science+Business Media B.V.
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