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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.

Over the years, we have seen how, thanks to experimentation on animal models, the foundations have been laid in the field of implantology. In most cases, studies related to the bone scale are carried out on the species that are most similar in their movements and behavior to humans. The femur has been selected as the reference bone for our test, selecting as animals to experiment with the goat breed, the bovine breed and the porcine breed for their similarity to the human body, obtaining specimens of the cortical part of the bone. Destructive bending tests will be carried out in the same way on each of the femur fragments of each animal. When interpreting the results, we will be guided by taking sections of the transverse and longitudinal part of the bone, performing the tests in both cases inside the femur, and once the results have been obtained, we will proceed to their subsequent evaluation. We relate the bone resistance of the samples to the effect of an oncological drug, Altan Zolendronic Acid 4 mg/ 100 ml solution for perfusion EFG, administered in cases of bone metastasis.

The study aims to characterize two alloys in order to evaluate if they can be used for medical applications, these alloys have the following compositions: A1 (93.2% Ti, 4% Fe, 2% Al, 0.8% V) and A2 (96.5% Ti, 3% Mn, 0.6% Al, 0.2% V). Information on the behavior of the samples was obtained, studying how the composition of the materials and the presence of iron or manganese has an effect on the corrosion resistance when submerging them in a Ringer Lactate solution after covering the samples in epoxy resin, polishing using carbide emery paper of progressive value of grith (800 to 2500) and a 0.1 alpha alumina suspension applied on a polishing cloth in order to obtain a mirror finish. The corrosion potential of the samples was analyzed in order to study how the phenomenon of corrosion occurs in each sample. In order to compare which one of the two materials posseses a better resistance to the effects of corrosion, studies of electrochemical impedance spectroscopy were performed for different values of potential. Images of the surfaces of the alloys after applying Kroll reactive were obtained through the use of a microscope in which 100 magnifications was applied in order to reveal the structure of the surface.

Potsherds from 7 Venezuelan islands have been studied using a two-fold magneto/dielectric technique in order to identify clay sources and characterize different stages of pottery craftsmanship. This is the first study of archeological material using this technique. Petrographic analyses appear to agree with the clusters of data identified in scatter plots of initial magnetic susceptibility versus saturation isothermal remanent magnetization (SIRM), and natural remanent magnetization (NRM). Thus, these magnetic parameters appear to be suitable for describing clay source characteristics. Effective magnetic grain sizes, investigated via stability analyses of SIRM and anystheretic remanent magnetization (ARM) upon alternating field (AF) demagnetization, and SIRM acquisition and AF demagnetization crossover plots, seem to be related to different steps of pottery craftsmanship, namely clay preparation, finishing and firing. Thermomagnetic curves might also provide valuable information about original firing conditions. A scatter plot of SIRMs intersections versus maximum current depolarization temperatures and average activation energies, shows a coarse correlation due perhaps to the fact that these rock magnetic and dielectric data are both associated to pore-related features.

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 ‰).

Abstract: We assessed the effect of salinity on plant growth and leaf expansion rates, as well as the leaf life span and the dynamics of leaf production and mortality in seedlings of Avicennia germinans L. grown at 0, 170, 430, 680, and 940 mol m−3 NaCl. The relative growth rates (RGR) after 27 weeks reached a maximum (10.4 mg g−1 d−1) in 170 mol m−3 NaCl and decreased by 47 and 44% in plants grown at 680 and 940 mol m−3 NaCl. The relative leaf expansion rate (RLER) was maximal at 170 mol m−3 NaCl (120 cm m−2 d−1) and decreased by 57 and 52% in plants grown at 680 and 940 mol m−3 NaCl, respectively. In the same manner as RGR and RLER, the leaf production (P) and leaf death (D) decreased in 81 and 67% when salinity increased from 170 to 940 mol m−3 NaCl, respectively. Since the decrease in P with salinity was more pronounced than the decrease in D, the net accumulation of leaves per plant decreased with salinity. Additionally, an evident increase in annual mortality rates (λ) and death probability was observed with salinity. Leaf half-life (t 0.5) was 425 days in plants grown at 0 mol m−3 NaCl, and decreased to 75 days at 940 mol m−3 NaCl. Thus, increasing salinity caused an increase in mortality rate whereas production of new leaves and leaf longevity decreased and, finally, the leaf area was reduced.

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.

This study assessed the effect of leaf age on construction cost (CC) in the mangrove species Avicennia germinans, Laguncularia racemosa, and Rhizophora manglegrowing in their natural habitat. Leaf osmolality values were species-specific, the highest in A. germinans(1 693 mmol kg−1) and the lowest in L. racemosa(1 270 mmol kg−1). In the three species, contents of chlorophyll (a+b) (Chla+b) and nitrogen (N) per unit of leaf area were maximal in adult leaves and tended to decline with age. Leaf mass to leaf area ratio (LMA) and ash content increased during leaf ageing. Similarly, as leaves aged, a significant increase in leaf construction cost per leaf area (CCa) was observed, while per leaf mass (CCm) it remained almost constant, suggesting a sustained production of leaf compounds as leaves became older. CC was positively correlated with LMA and heat of combustion (Hc) per leaf area, suggesting differences among species in the quantity and composition of expensive compounds. Leaf half lifetime (t0.5) showed contrasting values in the three mangrove species (60, 111, and 160 d in L. racemosa, R. mangle, and A. germinans, respectively). Overall, L. racemosawas the species with less expensive leaves to construct while leaves of A. germinansand R. manglehad the highest CCmand CCa, respectively. Leaf longevity was positively correlated with the ratio between CC and maximum photosynthetic rate (Pmax), clearly showing the existence of a balance between leaf costs and benefits.

AbstractA series of four tyrosine-derived polyarylates with different number of methylene groups in the backbone (y = 2, 4, 6 and 8) were studied by measuring thermally stimulated depolarization currents (TSDC). The low temperature TSDC spectra (80—240K) were analyzed at two different degrees of hydration to assess the effects of small amounts of water in the observed broad and complex β band. Higher temperature TSDC spectra (250 to 350 K) provided the α relaxation peaks associated with the glass transition temperature. The direct signal analysis (DSA) method allowed the decomposition of the complex peaks into elementary processes. The βicomponents result from localized motions of molecular segments of variable length molecules whose identities were established in a prior study of polycarbonates. The changes observed in the low and high temperature polarization with the number of backbone methylene groups were interpreted as a combination of flexibility and entanglement phenomena.

AbstractThe Thermally Stimulated Depolarization Currents (TSDC) technique was used to characterize a lithological contact in a sedimentary sequence (Cretaceous Northeastern, Venezuela). TSDC spectra in the temperature range from 77 to 240 K were obtained for samples collected near a contact identified in the field as that between Chimana (CH) and Querecual (QC) formations. Deconvolution of the complex spectra, by the Direct Signal Analysis (DSA) method, shows the presence of four overlapping peaks. Drying and rehydration treatments performed on these samples indicate that the dielectric peaks are associated with physisorbed moisture. TSDC results show a progressive change in the mean reorientation energy with the lithology for the four relaxations. In the same lithological zone where this variation is observed, NRM measurements indicate significant changes in remanent magnetization values. The results obtained suggest that TSDC technique can be used as sensitive and alternative means of characterizing lithologies and stratigraphic discontinuities in a sedimentary sequence.

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

Rock magnetic and dielectric studies have been conducted in sedimentary rocks close to a lithological contact (Chimana and Querecual formations) at the Pertigalete sedimentary sequence (Cretaceous northeastern Venezuela). Rock magnetic results suggest that the presence of secondary magnetic minerals has been conditioned by the transitional zone between Chimana and Querecual. In fact, this contact might have acted as a conduit for fluid circulation and a focus of chemical alteration on most of its adjacent strata. Some of the secondary magnetic minerals (e.g. magnetite) must be the outcome of the anoxic conditions that prevailed during times when the sedimentary basin reached its maximum temperatures when oil and gas were generated (Lower Miocene). Some others (e.g. hematite) are the likely byproduct of alteration dating from times when oxidizing conditions were dominant. The Thermally Stimulated Depolarization Current (TSDC) technique is used here to dielectrically characterize the same contact. The complex TSDC spectra obtained in the temperature range from 77 to 230 K for the samples studied, indicate a notable difference between the Chimana (CH) and Querecual (QC) samples. Drying and rehydration treatments performed on these samples show that the whole depolarization spectrum is mainly due to moisture trapped in the microporosity of the material. The broad spectra, separated by using Direct Signal Analysis, reveal the presence of four overlapping peaks. TSDC results indicate a progressive change in the mean re-orientation energy with the lithology for the four relaxations. This variation, due to the change in the environment seen by the water dipoles hydrogen-bonded to different sites in the material, is observed for the same lithologies where magnetic anomalies have been reported. Thus, rock magnetic analyses, combined with the TSDC technique, seem to serve as a sensitive and alternative means of characterizing lithologies and stratigraphic discontinuities in a sedimentary sequence.

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.

Abstract: The interpretation of the Mssbauer spectra of iron bearing chromites is still a matter of discussion. After a preliminary characterization by X-ray diffraction, electron microscopy and chemical analysis of Cuban natural chromites, a Mssbauer study and a detailed computation analysis were carried out. The studied samples show both types of iron cations (Fe3+ and Fe2+) in the octahedral and tetradral sites of the spinel structure. No ordered distribution, or charge transfer effects were detected. All the spectra were fitted using the same model, with consistent hyperfine parameters.

A series of tyrosine-derived polycarbonates with different lengths (2 ≤ n ≤ 8) for the alkyl ester pendent chain were studied by measuring thermally stimulated depolarization currents (TSDC). The observed spectra could be separated into three regions: the low-temperature zone with a broad, complex β band (80–240 K), the intermediate zone (250–300 K), and the high-temperature zone (300–400 K) with a sharp α peak. The application of direct signal analysis (DSA) to decompose the complex peaks into elementary processes led to the determination of the relaxation time distribution and temperature dependence of each process. The variation of the relaxation parameters as a function of the pendent chain length facilitated the tentative identification of the relaxation mechanisms responsible for the observed current peaks. It is proposed that as the temperature increases one observes, first, the individual motion of each polar group, then the concerted motion of the entire pendent chain, and, last, the movement of the polymer backbone. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1457–1466, 1997

Abstract: Physiological traits involved in leaf water relations were evaluated in Avicennia germinans (L.) L. seedlings growing at different salinities in the field. Analysis of pressure-volume (P-V) curves and sap osmometry were combined to evaluate osmotic adjustment and cell elasticity, and the contribution of accumulated inorganic ions to osmotic potential was estimated. Seedlings growing in soils with interstitial water salinity above that of normal sea water showed a modification of the relationship between water potential and relative water content. Thus, their leaf osmotic potential at maximum turgor (Ψπ( max )) and at zero turgor (Ψπ(0)) was 1.41 and 1.82 MPa lower respectively, than that of the seedlings from the low salinity site. Volumetric moduli of elasticity () were between 17 and 23 MPa. Thus, ɛ was about 6 MPa lower in high-salinity plants indicating that their cells were slightly more elastic. Ionic concentration analysis showed that Σ [anions] and Σ [cations] were higher in the high-salinity site (22–35%) while the water content per unit dry mass was only 12–17% lower. Reduction in water content was insufficient to explain the increase in ion concentration. Ion concentration explained 73 and 66% of the osmotic potential estimated by P-V curves for leaves from low- and high-salinity sites, respectively. In conclusion, this study provided evidence that leaves of A. germinans seedlings adapt to hypersaline soils by increasing solute concentration by 52% and cell elasticity by 26%. Both processes allow leaf water uptake and turgor maintenance over a large range of soil water potential.

Thermal-stimulated polarization and depolarization experiments with and without blocking electrodes are performed on a particular tyrosine-derived polyarylate: poly(DTH succinate). The high temperature region comprising the combined effects of the glass transition relaxation peak and the conduction through the sample is modeled. Conduction through the sample is described by a simple temperature relaxation model that, in the presence of blocking electrodes, gives rise to a charge redistribution peak. The analytical expression for this peak is found and, together with a convenient description for the glass transition relaxation peak the experimental data, is closely reproduced. An estimate of the dielectric constant can be obtained with the model proposed. For the sample used, the value is equal to 2.4. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 283–291, 1998

Thermal-stimulated polarization and depolarization experiments with blocking electrodes are performed on a particular tyrosine-derived polyarylate: poly(DTH succinate). Aging effects on this sample are observed for the glass transition relaxation peak and the charge redistribution peak originated by the conduction though the sample when blocking electrodes are present. The high temperature region where these peaks are present is modeled, and results are presented as a function of aging time. The model describes the experimental data to better than 1% for all the aging times. Contributions between the two peaks modeled are found to be constant and independent of aging. The glass transition temperature is constant within a fraction of a degree, and the shift of the maximum temperature of the spectrum is due to the charge redistribution peak. The results obtained suggest that the variation in shape of these peaks is originated by the change in the mobility of the polymeric chains, affecting in different manners the dipole orientation mechanism, as well as conduction through the sample. A simple logarithmic aging time dependence is found for most of the parameters used in the model. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 293–301, 1998