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The species Eunica tatila(Herrich-Schäffer) is present in the Neotropical region and comprises three subspecies. In Mexico, only one subspecies is reported: E. t. tatila(Herrich-Schäffer). The Yucatan Peninsula, in southeastern Mexico, is located in a transitional geographical position, between southern Florida, the West Indies and Central America. It is part of a transitional region, important for the dispersion of insects from southern Florida via Cuba and the Yucatan Peninsula. Considering the possibility of the overlapping and delimitation of described subspecies, we sampled different populations in the Yucatan Peninsula to possibly assign a subspecies name and evaluate the magnitude of sexual dimorphism. We collected 591 individuals (♀284, ♂307) in conserved areas. The study of male genitalia led to the identification of Eunica tatila tatilista(Kaye) as a subspecies; however, hypandrium structure and wing pattern analysis suggest a mix of E. t. tatilaand E. t. tatilistacharacteristics. The analysis of sexual dimorphism provided evidence of more complex wing morphs for females, with 12 patterns instead of four as previously described. Our results demonstrate the complexity of characterizing E. tatilaand suggest that the Yucatan Peninsula is a transitional zone for subspecies of some butterflies.

We analysed plant growth, ion accumulation, leaf water relations, and gas exchange of Avicennia germinans(L.) L. subjected to a long-term, controlled salinity gradient from 0 to 55 ‰. Growth and leaf area were affected by salinity higher than 10 ‰. As salinity increased, the predawn leaf water potential (Ψw) and leaf osmotic potential (Ψs) decreased. Leaf Ψwwas at least −0.32 MPa lower than the Ψwof solution. Na+and K+ions explained about 78 % of decrease in Ψs. K+tissue water concentration decreased by more than 60 % in all salinity treatments as compared with those grown at 0 ‰. Inversely, Na+concentration in tissue water increased with nutrient solution salinity. The maximum net photosynthetic rate (PN) and stomatal conductance (gs) decreased by 68 and 82 %, respectively, as salinity increased from 0 to 55 ‰; the intercellular CO2concentration (Ci) followed the same trend. The PNas a function of Cishowed that both the initial linear slope and upper plateau of the PNvs. Cicurve were markedly affected by high salinity (40 and 55 ‰).

This study assessed the effects of salinity and drought upon leaf construction (CC) and maintenance (MC) costs in Avicennia germinansgrowing under contrasting soil salinities in the field. Additionally, an analysis of leaf chemical composition was carried out to determine the underlying reasons for possible variation in CC. With the increase of external salinity, leaf osmotic potential (ψs) declined and a significant negative correlation was found between both variables. Changes in average CC were about 15 % when ψschanged by 85 %. Despite this, leaf ash-free heat of combustion per unit of leaf dry mass remained relatively constant at 21.3 ± 0.9 kJ g−1in all conditions. The estimated maximum and minimum CC for the synthesis of protein present in leaves increased significantly with total leaf CC. Conversely, the estimated CC for lipid synthesis shows a tendency to decrease with total leaf CC. Under conditions of high salinity, ash content increased by 78 % compared to that of leaves collected at low salinity. It is concluded that undergoing changes in proteins and lipids (expensive) and ash (cheap) explain the changes in CC under contrasting salinities. Additionally, the average MC remained almost constant at moderate salinity and declined by 6 % under hyper-saline conditions. Thus, differences in CC and MC with salinity are explained in part by changes in the chemical composition of different compound fractions.This study assessed the effects of salinity and drought upon leaf construction (CC) and maintenance (MC) costs in Avicennia germinansgrowing under contrasting soil salinities in the field. Additionally, an analysis of leaf chemical composition was carried out to determine the underlying reasons for possible variation in CC. With the increase of external salinity, leaf osmotic potential (ψs) declined and a significant negative correlation was found between both variables. Changes in average CC were about 15 % when ψschanged by 85 %. Despite this, leaf ash-free heat of combustion per unit of leaf dry mass remained relatively constant at 21.3 ± 0.9 kJ g−1in all conditions. The estimated maximum and minimum CC for the synthesis of protein present in leaves increased significantly with total leaf CC. Conversely, the estimated CC for lipid synthesis shows a tendency to decrease with total leaf CC. Under conditions of high salinity, ash content increased by 78 % compared to that of leaves collected at low salinity. It is concluded that undergoing changes in proteins and lipids (expensive) and ash (cheap) explain the changes in CC under contrasting salinities. Additionally, the average MC remained almost constant at moderate salinity and declined by 6 % under hyper-saline conditions. Thus, differences in CC and MC with salinity are explained in part by changes in the chemical composition of different compound fractions.

Thermal-stimulated polarization and depolarization experiments without blocking electrodes are performed on tyrosine-derived polyarylates with different backbone lengths. The experiments on the different samples are carried out using the same thermal history throughout the entire characterization process. The high-temperature current rise caused by the conductivity of the samples is studied with a simple model that utilizes an approximation of the Williams–Landel–Ferry (WLF) relaxation time. The conductivity data is well reproduced except for temperatures well below the glass-transition temperature and for small currents. The glass-transition peak is modeled with a phenomenological expression valid near Tg, which is able to describe the glass relaxation with a minimum number of parameters. The conduction and the glass-transition relaxation are studied versus the structural changes for the different samples. It is found that the conductivity and the glass-transition temperature shift to lower temperatures as the methylene groups in the backbone increase. Furthermore, if the experimental data is presented as a function of the reduced temperature, the shape of the glass-transition relaxation for the different samples is independent of the polymer backbone length. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3504–3511, 1999

The combined results obtained by ionic thermal currents (ITC) and electron paramagnetic resonance (EPR) techniques on CaF2 double-doped either with Gd+Lu or Gd+Sm are presented here. In both systems a fraction of the Gd ions are observed in tetragonal and cubic sites. The Gd+Lu systems shows a very weak ITC spectrum in contrast to the Gd+Sm samples which present at least eight peaks of dipolar origin. The differences observed are accounted for by the existence in one case of an hexamer structure from the lowest Lu doping level and in the second case by the scavenging of F-i by clusters of increasing size with the Sm concentration. The experimental results confirm the predictions from HADES simulations that take into account the ion size effects.