Three-dimensional Ising model confined in low-porosity aerogels: a Monte Carlo study

The influence of correlated impurities on the critical behaviour of the 3D Ising model is studied using Monte Carlo simulations. Spins are confined into the pores of simulated aerogels (diffusion limited cluster-cluster aggregation) in order to study the effect of quenched disorder on the critical behaviour of this magnetic system. Finite size scaling is used to estimate critical couplings and exponents. Long-range correlated disorder does not affect critical behavior. Asymptotic exponents differ from those of the pure 3D Ising model (3DIS), but it is impossible, with our precision, to distinguish them from the randomly diluted Ising model (RDIS).Comment: 10 pages, 10 figures. Submitted to Physical Review

The relationship of telomere length to baseline corticosterone levels in nestlings of an altricial passerine bird in natural populations

Indexación: Web of Science; Scopus.Background: Environmental stressors increase the secretion of glucocorticoids that in turn can shorten telomeres via oxidative damage. Modification of telomere length, as a result of adversity faced early in life, can modify an individual's phenotype. Studies in captivity have suggested a relationship between glucocorticoids and telomere length in developing individuals, however less is known about that relationship in natural populations. Methods: In order to evaluate the effect of early environmental stressors on telomere length in natural populations, we compared baseline corticosterone (CORT) levels and telomere length in nestlings of the same age. We collected blood samples for hormone assay and telomere determination from two geographically distinct populations of the Thorn-tailed Rayadito (Aphrastura spinicauda) that differed in brood size; nestlings body mass and primary productivity. Within each population we used path analysis to evaluate the relationship between brood size, body mass, baseline CORT and telomere length. Results: Within each distinct population, path coefficients showed a positive relationship between brood size and baseline CORT and a strong and negative correlation between baseline CORT and telomere length. In general, nestlings that presented higher baseline CORT levels tended to present shorter telomeres. When comparing populations it was the low latitude population that presented higher levels of baseline CORT and shorter telomere length. Conclusions: Taken together our results reveal the importance of the condition experienced early in life in affecting telomere length, and the relevance of integrative studies carried out in natural conditions.https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-016-0133-

El efecto competitivo de las importaciones recientes en México

Uno de los beneficios esperados de un proceso de liberalización y apertura comercial es la imposición de restricciones al poder de fijación de precios que tienen los monopolios o los oligopolios internos. Es decir, la disminución de las barreras arancelarias y el desmantelamiento de las no tarifarias, como permisos de importación y precios oficiales de importación, y su sustitución por aranceles, puede aumentar la competencia efectiva y la potencial que enfrentan los productores locales. Algunos autores (Esposito y Esposito, 1971) sugieren incluso que la liberalización comercial puede ser utilizada para disminuir las presiones inflacionarias de los bienes manufactureros locales, gracias al efecto competitivo que debe ser mayor en las industrias más concentradas (De Rosa y Goldstein, 1981). El comportamiento competitivo de la industria local es reforzado también por los consumidores. En efecto, una apertura comercial modificará la estructura de sus preferencias, y cuando éstas se desplacen hacia los productos importados, la elasticidad-precio de la demanda de los bienes nacionales tiende a menos infinito y en consecuencia el precio interno debe tender a su costo marginal (Zeelemberg, 1986).

Evaluacion del efecto de Spinosad, Bacillus thuringiensis subsp. tenebrionis y nematodos entomopatogenicos sobre la pulguilla de la papa Epitrix yanazara Bechyne 1959 (Coleoptera: Chrysomelidae) en papa (Solanum tuberosum).

En el Perú, la “pulguilla de la papa”, Epitrix yanazara Bechyné se presenta como uno de los problemas potenciales de plagas en el cultivo de papa en ciertas localidades de la región andina y cuando no se utilizan aplicaciones de insecticidas para el control del gorgojo de los Andes. Esta plaga si no se controla ocasiona serios daños en la reducción del rendimiento del cultivo. Actualmente, el método de control más efectivo utilizado es el uso de insecticidas químicos. En la búsqueda de métodos alternativos para el control de E. yanazara, que sean más amigables con el medio ambiente y con la salud humana, se planteó el objetivo del presente trabajo: evaluar el efecto de un insecticida biológico (Bacillus thuringiensis subsp. tenebrionis (Btt)), un insecticida derivado de bacterias (spinosad) y nematodos entomopatógenos (NEPs). Los tratamientos utilizaron como testigo al insecticida piretroide betaciflutrin y un control absoluto (sin ningún tratamiento). Se evaluó el efecto contra adultos y larvas en un periodo de 7 y 30 días respectivamente, bajo condiciones de laboratorio. Además, se determinó la DL50, el TL50 y el potencial de propagación de Alcázar1, usando 6 concentraciones de NEPs (0, 1, 2, 4, 8 y 16 JIs/larva). Inicialmente, en la prueba con adultos, la mortalidad obtenida con betaciflutrin fue significativamente más alta (55.75%) que los demás tratamientos, sin embargo al final de la prueba no se encontraron diferencias significativas entre los tratamientos spinosad y betaciflutrin (89.25% y 95% de mortalidad respectivamente), mientras que Btt fue el menos tóxico (33.5%). De igual forma, sucedió en el ensayo con larvas, donde la mortalidad obtenida con spinosad y betaciflutrin fue la más alta al finalizar el ensayo (98.75% y 100%) que lo obtenido con Btt (56.25%). Además, con 9 aislamientos de NEPs, pertenecientes a la zona de sierra, se realizó la prueba de patogenicidad sobre el tercer estadío larval de E. yanazara durante un periodo de 15 días, siendo el aislamiento denominado Alcázar1 (Heterorhabditis sp.) el más virulento (90% de mortalidad). La DL50 para un periodo de 8 días fue de 5.92 JIs/ larva, el TL50 usando una dosis de 8 JIs/larva fue de 7.09 dias y el potencial de propagación más alto se obtuvo con la dosis de 16 JIs/larva (1242 JIs). Finalmente, los resultados muestran el alto potencial de spinosad, con un modo de acción ligeramente más lento que el insecticida comercial, así como el alto potencial del aislamiento Alcázar1 (Heterorhabditis sp.) como agentes de control biológico de E. yanazara

High resolution spectroscopic analysis of seven giants in the bulge globular cluster NGC 6723

Globular clusters associated with the Galactic bulge are important tracers of stellar populations in the inner Galaxy. High resolution analysis of stars in these clusters allows us to characterize them in terms of kinematics, metallicity, and individual abundances, and to compare these fingerprints with those characterizing field populations. We present iron and element ratios for seven red giant stars in the globular cluster NGC~6723, based on high resolution spectroscopy. High resolution spectra ($R\sim48~000$) of seven K giants belonging to NGC 6723 were obtained with the FEROS spectrograph at the MPG/ESO 2.2m telescope. Photospheric parameters were derived from $\sim130$ FeI and FeII transitions. Abundance ratios were obtained from line-to-line spectrum synthesis calculations on clean selected features. An intermediate metallicity of [Fe/H]$=-0.98\pm0.08$ dex and a heliocentric radial velocity of $v_{hel}=-96.6\pm1.3~km s^{-1}$ were found for NGC 6723. Alpha-element abundances present enhancements of $[O/Fe]=0.29\pm0.18$ dex, $[Mg/Fe]=0.23\pm0.10$ dex, $[Si/Fe]=0.36\pm0.05$ dex, and $[Ca/Fe]=0.30\pm0.07$ dex. Similar overabundance is found for the iron-peak Ti with $[Ti/Fe]=0.24\pm0.09$ dex. Odd-Z elements Na and Al present abundances of $[Na/Fe]=0.00\pm0.21$ dex and $[Al/Fe]=0.31\pm0.21$ dex, respectively. Finally, the s-element Ba is also enhanced by $[Ba/Fe]=0.22\pm0.21$ dex. The enhancement levels of NGC 6723 are comparable to those of other metal-intermediate bulge globular clusters. In turn, these enhancement levels are compatible with the abundance profiles displayed by bulge field stars at that metallicity. This hints at a possible similar chemical evolution with globular clusters and the metal-poor of the bulge going through an early prompt chemical enrichment

Estudios sobre las Rubiáceas de México, L

Abstract The new Guettarda species of Oaxaca (Mexico) is related to G. foliacea Standl. of a distribution from Tabasco and Chiapas to Panama, but differs by having long acuminate and falcate leaves with lineolate quaternary nerves on the abaxial surface, inflorescences with very short ovate and glabrous bracteoles and much shorter flowers with 8–9 mm long corolla tube

Lensing by Kerr Black Holes. II: Analytical Study of Quasi-Equatorial Lensing Observables

In this second paper, we develop an analytical theory of quasi-equatorial lensing by Kerr black holes. In this setting we solve perturbatively our general lens equation with displacement given in Paper I, going beyond weak-deflection Kerr lensing to third order in our expansion parameter epsilon, which is the ratio of the angular gravitational radius to the angular Einstein radius. We obtain new formulas and results for the bending angle, image positions, image magnifications, total unsigned magnification, and centroid, all to third order in epsilon and including the displacement. New results on the time delay between images are also given to second order in epsilon, again including displacement. For all lensing observables we show that the displacement begins to appear only at second order in epsilon. When there is no spin, we obtain new results on the lensing observables for Schwarzschild lensing with displacement.Comment: 23 pages; final published versio

Variation in fine-scale genetic structure and local dispersal patterns between peripheral populations of a South American passerine bird

Indexación: Scopus.The distribution of suitable habitat influences natal and breeding dispersal at small spatial scales, resulting in strong microgeographic genetic structure. Although environmental variation can promote interpopulation differences in dispersal behavior and local spatial patterns, the effects of distinct ecological conditions on within-species variation in dispersal strategies and in fine-scale genetic structure remain poorly understood. We studied local dispersal and fine-scale genetic structure in the thorn-tailed rayadito (Aphrastura spinicauda), a South American bird that breeds along a wide latitudinal gradient. We combine capture-mark-recapture data from eight breeding seasons and molecular genetics to compare two peripheral populations with contrasting environments in Chile: Navarino Island, a continuous and low density habitat, and Fray Jorge National Park, a fragmented, densely populated and more stressful environment. Natal dispersal showed no sex bias in Navarino but was female-biased in the more dense population in Fray Jorge. In the latter, male movements were restricted, and some birds seemed to skip breeding in their first year, suggesting habitat saturation. Breeding dispersal was limited in both populations, with males being more philopatric than females. Spatial genetic autocorrelation analyzes using 13 polymorphic microsatellite loci confirmed the observed dispersal patterns: a fine-scale genetic structure was only detectable for males in Fray Jorge for distances up to 450 m. Furthermore, two-dimensional autocorrelation analyzes and estimates of genetic relatedness indicated that related males tended to be spatially clustered in this population. Our study shows evidence for context-dependent variation in natal dispersal and corresponding local genetic structure in peripheral populations of this bird. It seems likely that the costs of dispersal are higher in the fragmented and higher density environment in Fray Jorge, particularly for males. The observed differences in microgeographic genetic structure for rayaditos might reflect the genetic consequences of population-specific responses to contrasting environmental pressures near the range limits of its distribution.http://onlinelibrary.wiley.com/doi/10.1002/ece3.3342/epd

Homogeneous metallicities and radial velocities for Galactic globular clusters. II. New CaT metallicities for 28 distant and reddened globular clusters

Although the globular clusters in the Milky Way have been studied for a long time, a significant fraction of them lack homogeneous metallicity and radial velocity measurements. In an earlier paper we presented the first part of a project to obtain metallicities and radial velocities of Galactic globular clusters from multiobject spectroscopy of their member stars using the ESO Very Large Telescope. In this paper we add metallicities and radial velocities for a new sample of 28 globular clusters, including in particular globular clusters in the MW halo and the Galactic bulge. Together with our previous results, this study brings the number of globular clusters with homogeneous measurements to $\sim 69$ \% of those listed in the W. Harris' catalogue. As in our previous work, we have used the CaII triplet lines to derive metallicities and radial velocities. For most of the clusters in this study, this is the first analysis based on spectroscopy of individual member stars. The metallicities derived from the CaII triplet are then compared to the results of our parallel study based on spectral fitting in the optical region and the implications for different calibrations of the CaII triplet line strengths are discussed. We also comment on some interesting clusters and investigate the presence of an abundance spread in the globular clusters here. A hint of a possible intrinsic spread is found for NGC 6256, which therefore appears to be a good candidate for further study.Comment: 13 pages, 9 figures, accepted for publication in Astronomy and Astrophysic