Spatial clustering of interacting bugs: Levy flights versus Gaussian jumps

A biological competition model where the individuals of the same species perform a two-dimensional Markovian continuous-time random walk and undergo reproduction and death is studied. The competition is introduced through the assumption that the reproduction rate depends on the crowding in the neighborhood. The spatial dynamics corresponds either to normal diffusion characterized by Gaussian jumps or to superdiffusion characterized by L\'evy flights. It is observed that in both cases periodic patterns occur for appropriate parameters of the model, indicating that the general macroscopic collective behavior of the system is more strongly influenced by the competition for the resources than by the type of spatial dynamics. However, some differences arise that are discussed.Comment: This version incorporates in the text the correction published as an Erratum in Europhysics Letters (EPL) 95, 69902 (2011) [doi: 10.1209/0295-5075/95/69902

Discontinuidades estratigráficas en el Jurásico de Sierra Gorda (Subbético intnerno, Provincia de Granada)

En el Jurásico de la unidad de Sierra Gorda (Subbético interno, prov. Granada) se reconocen cinco discontinuidades estratigráficas:en el Carixiense, en la base del Dogger, en la base del Calloviense en la base del Oxfordense y en el Kimmeridgiense. En el sector septentrional de la unidad se detectan por superficies de omisión y hardgrounds, mientras que en el borde meridional muesitran gran desarrollo de diques neptúnicos

La sedimentación liásica en el sector central del Subbético medio: registro de la evolución de un rift intracontinental

Durante el Lias medio tuvo lugar el paso brusco de la sedimenta-ción carbonatada somera a la pelágica en la Zona Subbética, en relación con la evolución de un rift intracontinental. Se han podido delimitar cuatro etapas con sus sedimentos correspondientes: a) Etapa prerruptura (sedimentación marina somera). b) Inicio de la rup-tura (hardgrounds y paleokarst). c) Comienzo de la sedimentación hemipelágica (niveles de calizas  condensadas). d) Individualización del surco subbético (ritmita  calizas/margas)

Role of 5 α -dihydrotestosterone in testicular development of gilthead seabream following finasteride administration

In teleosts, spermatogenesis is regulated by pituitary gonadotropins and sex steroids. 5α-dihydrotestosterone (DHT), derived from testosterone (T) through the action of 5α-reductase, has recently been suggested to play a physiologically important role in some fish species. In this study, gilthead seabream, Sparus aurata L., males received an implant of 1μg T/g body mass (bm) or vehicle alone and, 7 days later, 1 mg finasteride (FIN, an inhibitor of 5α-reductase)/kg bm or vehicle. Serum levels of T, 11-ketotestosterone (11KT), DHT and 17β-estradiol (E2), and the mRNA levels of the main enzymes involved in their synthesis, were analysed. T promoted a transient increase in the serum levels of T, 11KT and E2 but a decrease in those of DHT at day 15 following T injection, in accordance with the up-regulation of mRNA levels of the enzymes involved in T transformation to 11KT (coding genes: cyp11b1 and hsd11b) and the down-regulation of mRNA levels of the enzyme responsible for T transformation to DHT (coding gene:srd5a). Interestingly, a similar effect was observed when FIN was in- jected. However, when fish were injected with T and FIN successively (T + FIN), control levels were not re-covered at the end of the experimental period (28 days). DHT seems to regulate E2 serum levels via the down-regulation of mRNA levels of aromatase (coding gene:cyp19a1a), which is needed for the transformation of T into E2. The testis histology, together with the proliferative rates recorded upon T, FIN or T + FIN treatment, suggests that DHT is involved in the onset of the meiotic phase of spermatogenesis.Versión del edito

Machine learning techniques to select Be star candidates. An application in the OGLE-IV Gaia south ecliptic pole field

Statistical pattern recognition methods have provided competitive solutions for variable star classification at a relatively low computational cost. In order to perform supervised classification, a set of features is proposed and used to train an automatic classification system. Quantities related to the magnitude density of the light curves and their Fourier coefficients have been chosen as features in previous studies. However, some of these features are not robust to the presence of outliers and the calculation of Fourier coefficients is computationally expensive for large data sets. We propose and evaluate the performance of a new robust set of features using supervised classifiers in order to look for new Be star candidates in the OGLE-IV Gaia south ecliptic pole field. We calculated the proposed set of features on six types of variable stars and on a set of Be star candidates reported in the literature. We evaluated the performance of these features using classification trees and random forests along with K-nearest neighbours, support vector machines, and gradient boosted trees methods. We tuned the classifiers with a 10-fold cross-validation and grid search. We validated the performance of the best classifier on a set of OGLE-IV light curves and applied this to find new Be star candidates. The random forest classifier outperformed the others. By using the random forest classifier and colour criteria we found 50 Be star candidates in the direction of the Gaia south ecliptic pole field, four of which have infrared colours consistent with Herbig Ae/Be stars. Supervised methods are very useful in order to obtain preliminary samples of variable stars extracted from large databases. As usual, the stars classified as Be stars candidates must be checked for the colours and spectroscopic characteristics expected for them

Winding number instability in the phase-turbulence regime of the Complex Ginzburg-Landau Equation

We give a statistical characterization of states with nonzero winding number in the Phase Turbulence (PT) regime of the one-dimensional Complex Ginzburg-Landau equation. We find that states with winding number larger than a critical one are unstable, in the sense that they decay to states with smaller winding number. The transition from Phase to Defect Turbulence is interpreted as an ergodicity breaking transition which occurs when the range of stable winding numbers vanishes. Asymptotically stable states which are not spatio-temporally chaotic are described within the PT regime of nonzero winding number.Comment: 4 pages,REVTeX, including 4 Figures. Latex (or postscript) version with figures available at http://formentor.uib.es/~montagne/textos/nupt

On the Excitation and Formation of Circumstellar Fullerenes

We compare and analyze the Spitzer mid-infrared spectrum of three fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds; Tc1, SMP SMC16, and SMP LMC56. The three planetary nebulae share many spectroscopic similarities. The strongest circumstellar emission bands correspond to the infrared active vibrational modes of the fullerene species C60 and little or no emission is present from Polycyclic Aromatic Hydrocarbons (PAHs). The strength of the fullerene bands in the three planetary nebulae is very similar, while the ratio of the [NeIII]15.5um/[NeII]12.8um fine structure lines, an indicator of the strength of the radiation field, is markedly different. This raises questions about their excitation mechanism and we compare the fullerene emission to fluorescent and thermal models. In addition, the spectra show other interesting and common features, most notably in the 6-9um region, where a broad plateau with substructure dominates the emission. These features have previously been associated with mixtures of aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this band, which is likely related to the fullerene formation mechanism, and compare it with modeled Hydrogenated Amorphous Carbon that present emission in this region.Comment: 13 pages, 2 tables, 7 figures, Accepted for publication in Ap