Authors:F. Fraga, V. Soto, E. Rodríguez-Núñez, J. Martínez-Ageitos and V. Rodríguez
The study of the cure reaction of the epoxy
network diglycidyl ether of bisphenol A with amantidine is a useful tool to
characterize the industrial behaviour of this material. The total enthalpy
of reaction, the glass transition temperature and the partial enthalpies at
different cured temperatures have been determined using differential scanning
calorimetry in dynamic and isothermal mode. Two models, one based on chemical
kinetics and the other accounting for diffusion were used and compared with
experimental data. It can be seen that the inclusion of a diffusion factor
in the kinetic model is negligible.
Authors:B. Hermosillo-Nuñez, F. Rodríguez-Zaragoza, M. Ortiz, C. Galván-Villa, A. Cupul-Magaña and E. Ríos-Jara
The spatial distribution and abundance of the seven most abundant species of echinoderms (Diadema mexicanum, Centrostephanus coronatus, Eucidaris thouarsii, Isostichopus fuscus, Pharia pyramidatus, Phataria unifascialis and Acanthaster ellisii) were evaluated in coral communities of Isla Isabel National Park (Mexico). Biological (corals and other benthic groups) and physical (rocks and boulders) structural elements of the habitat were evaluated to determine their relationship to these species. Our results show that species composition and abundance varied among sampling sites and between seasons. Also were obtained significant differences in the echinoderm assemblage among sites across seasons. Similar results were detected for the environmental variables related to benthic habitat structure. D. mexicanum, P. unifascialis, E. thouarsii and C. coronatus were the main contributors to the species abundance and distribution in Isla Isabel. Most echinoderm species were positively related to the coverage of different coral species, algae and various types of benthic organisms as well as to physical benthic variables. These outcomes suggest that the spatial distribution and abundance of these echinoderms are explained by the habitat structure, which should be used to design conservation and management strategies for coral communities.
Authors:F. Fraga, V. Soto, J. Blanco-Méndez, A. Luzardo-Alvarez, E. Rodríguez-Núñez, J. Martínez-Ageitos and M. Pérez
Knowledge of the the kinetic study of chitosan/genipin
allow to know the different effects that time and temperature have on the
cure reaction of the material.
The total enthalpy of reaction,
the glass transition temperature and the partial enthalpies have been determined
using DSC in dynamic mode. Two models, one based on chemical kinetics and
the other accounting for diffusion were used. The incorporation of the diffusion
factor in the second model allowed for the cure kinetics to be predicted the
whole range of conversion.