Electromagnetic radiation produced by avalanches in the magnetization reversal of Mn12-Acetate

Electromagnetic radiation produced by avalanches in the magnetization reversal of Mn12-Acetate has been measured. Short bursts of radiation have been detected, with intensity significantly exceeding the intensity of the black-body radiation from the sample. The model based upon superradiance from inversely populated spin levels has been suggested

Time-Series BVI Photometry for the Globular Cluster NGC 6981 (M72)

We present new BVI photometry of the globular cluster NGC 6981 (M72), based mostly on ground-based CCD archive images. We present a new color-magnitude diagram (CMD) that reaches almost four magnitudes below the turn-off level. We performed new derivations of metallicity and morphological parameters of the evolved sequences, in good agreement with previous authors, obtaining a value of [Fe/H] ~ -1.50 in the new UVES scale. We also identify the cluster's blue straggler population. Comparing the radial distribution of these stars with the red giant branch population, we find that the blue stragglers are more centrally concentrated, as found in previous studies of blue stragglers in globular clusters. Taking advantage of the large field of view covered by our study, we analyzed the surface density profile of the cluster, finding extratidal main sequence stars out to r ~ 14.1 arcmin or about twice the tidal radius. We speculate that this may be due to tidal disruption in the course of M72's orbit, in which case tidal tails associated with the cluster may exist. We also take a fresh look at the variable stars in the cluster, recovering all previous known variables, including three SX Phoenicis stars, and adding three previously unknown RR Lyrae (1 c-type and 2 ab-type) to the total census. Finally, comparing our CMD with unpublished data for M3 (NGC 5272), a cluster with similar metallicity and horizontal branch morphology, we found that both objects are essentially coeval.Comment: Accepted for publication in A

NGC 5694: another foster son of the Galactic Halo

We present the results of the analysis of high-resolution spectra obtained with UVES-FLAMES@VLT for six red giant branch stars in the outer-halo metal-poor ([Fe/H]I=-1.98 and [Fe/H]II=-1.83) Galactic globular cluster NGC 5694, which has been suggested as a possible incomer by Lee et al. (2006) based on the anomalous chemical composition of a single cluster giant. We obtain accurate abundances for a large number of elements and we find that: (a) the six target stars have the same chemical composition within the uncertainties, except for Na and Al; (b) the average cluster abundance of \alpha\ elements (with the only exception of Si) is nearly solar, at odds with typical halo stars and globular clusters of similar metallicity; (c) Y, Ba, La and Eu abundances are also significantly lower than in Galactic field stars and star clusters of similar metallicity. Hence we confirm the Lee et al. classification of NGC 5694 as a cluster of extra-galactic origin. We provide the first insight on the Na-O and Mg-Al anti-correlations in this cluster: all the considered stars have very similar abundance ratios for these elements, except one that has significantly lower [Na/Fe] and [Al/Fe] ratios, suggesting that some degree of early self-enrichment has occurred also in this cluster.Comment: Accepted for publication by MNRAS. 15 pages, 8 figures, 4 table

Kinematics of a globular cluster with an extended profile: NGC5694

We present a study of the kinematics of the remote globular cluster NGC5694 based on GIRAFFE@VLT medium resolution spectra. A sample of 165 individual stars selected to lie on the Red Giant Branch in the cluster Color Magnitude Diagram was considered. Using radial velocity and metallicity from Calcium triplet, we were able to select 83 bona-fide cluster members. The addition of six previously known members leads to a total sample of 89 cluster giants with typical uncertainties <1.0 km/s in their radial velocity estimates. The sample covers a wide range of projected distances from the cluster center, from ~0.2 arcmin to 6.5 arcmin = 23 half-light radii (r_h). We find only very weak rotation, as typical of metal-poor globular clusters. The velocity dispersion gently declines from a central value of sigma=6.1 km/s to sigma = 2.5 km/s at ~2 arcmin = 7.1= r_h, then it remainins flat out to the next (and last) measured point of the dispersion profile, at ~4 arcmin = 14.0 r_h, at odds with the predictions of isotropic King models. We show that both isotropic single-mass non-collisional models and multi-mass anisotropic models can reproduce the observed surface brightness and velocity dispersion profiles.Comment: Accepted for publication by MNRAS. Pdflatex, 10 pages, 10 figure

Scaling and regeneration of self-organized patterns

Biological patterns generated during development and regeneration often scale with organism size. Some organisms, e.g., flatworms, can regenerate a rescaled body plan from tissue fragments of varying sizes. Inspired by these examples, we introduce a generalization of Turing patterns that is self-organized and self-scaling. A feedback loop involving diffusing expander molecules regulates the reaction rates of a Turing system, thereby adjusting pattern length scales proportional to system size. Our model captures essential features of body plan regeneration in flatworms as observed in experiments.Comment: 5 pages, 3 color figure

A generalized permutation entropy for noisy dynamics and random processes

Permutation entropy measures the complexity of a deterministic time series via a data symbolic quantization consisting of rank vectors called ordinal patterns or simply permutations. Reasons for the increasing popularity of this entropy in time series analysis include that (i) it converges to the Kolmogorov–Sinai entropy of the underlying dynamics in the limit of ever longer permutations and (ii) its computation dispenses with generating and ad hoc partitions. However, permutation entropy diverges when the number of allowed permutations grows super-exponentially with their length, as happens when time series are output by dynamical systems with observational or dynamical noise or purely random processes. In this paper, we propose a generalized permutation entropy, belonging to the class of group entropies, that is finite in that situation, which is actually the one found in practice. The theoretical results are illustrated numerically by random processes with short- and long-term dependencies, as well as by noisy deterministic signals

Nota sobre la presencia de minerales arcillosos de transformación en facies evaporíticas del Bundsandstein superior de Sierra Calderona (Ibérica suroriental, Valencia)

En lutitas de la facies Rot, en la Cordillera Ibérica, zona sudoriental, se ha determinado la presencia de interestratificados (14c,-14m,), que denotan el carácter evaporítico de estas facies