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Temuco, Chile

Carine J.,Casilla | Carine J.,University of Concepcion | Guzman R.,University of Concepcion | Guzman R.,University of the Frontier | And 2 more authors.
Optics and Lasers in Engineering

In this paper we present a new algorithm for determining surface activity by processing speckle pattern images recorded with a CCD camera. Surface activity can be produced by motility or small displacements among other causes, and is manifested as a change in the pattern recorded in the camera with reference to a static background pattern. This intensity variation is considered to be a small perturbation compared with the mean intensity. Based on a perturbative method we obtain an equation with which we can infer information about the dynamic behavior of the surface that generates the speckle pattern. We define an activity index based on our algorithm that can be easily compared with the outcomes from other algorithms. It is shown experimentally that this index evolves in time in the same way as the Inertia Moment method, however our algorithm is based on direct processing of speckle patterns without the need for other kinds of post-processes (like THSP and co-occurrence matrix), making it a viable real-time method. We also show how this algorithm compares with several other algorithms when applied to calibration experiments. From these results we conclude that our algorithm offer qualitative and quantitative advantages over current methods. © 2016 Elsevier Ltd. Source

Gratton R.G.,National institute for astrophysics | Villanova S.,Casilla | Lucatello S.,National institute for astrophysics | Sollima A.,National institute for astrophysics | And 4 more authors.
Astronomy and Astrophysics

It has been found that globular clusters host multiple stellar populations. In particular, in NGC 1851 the subgiant branch (SGB) can be divided into two components and the distribution of stars along the horizontal branch (HB) is multimodal. Various authors have found that NGC 1851 possibly has a spread in [Fe/H], but the relation between this spread and the division in the SGB is unknown. We obtained blue (3950-4600 A°) intermediate resolution (R ̃ 8000) spectra for 47 stars on the bright and 30 on the faint SGB of NGC 1851 (b-SGB and f-SGB, respectively). The spectra were analysed by comparing with synthetic spectra. The determination of the atmospheric parameters to extremely high internal accuracy allows small errors to be recovered when comparing different stars in the cluster, in spite of their faintness (V ̃ 19). Abundances were obtained for Fe, C, Ca, Cr, Sr, and Ba. We found that the b-SGB is slightly more metal-poor than the f-SGB, with [Fe/H] = -1.227 ± 0.009 and [Fe/H] = -1.162 ± 0.012, respectively. This implies that the f-SGB is only slightly older by ̃0.6 Gyr than the b-SGB if the total CNO abundance is constant. There are more C-normal stars in the b-SGB than in the f-SGB. This is consistent with what is found for HB stars, if b-SGB are the progenitors of red HB stars, and f-SGB those of blue HB ones. As previously found, the abundances of the n-capture elements Sr and Ba have a bimodal distribution, reflecting the separation between f-SGB (Sr and Ba-rich) and b-SGB stars (Sr and Ba-poor). In both groups, there is a clear correlation between [Sr/Fe] and [Ba/Fe], suggesting that there is a real spread in the abundances of n-capture elements. By looking at the distribution of SGB stars in the [C/H] versus (vs.) Teff diagram and in the [Ba/H] vs. [Sr/H] diagram, not a one-to-one relation is found among these quantities. There is some correlation between C and Ba abundances, while the same correlation for Sr is much more dubious. We identified six C-rich stars, which have a moderate overabundance of Sr and Ba and rather low N abundances. This group of stars might be the progenitors of those on the anomalous RGB in the (v, v - y) diagram. These results are discussed within different scenarios for the formation of NGC 1851. It is possible that the two populations originated in different regions of a inhomogeneous parent object. However, the striking similarity with M 22 calls for a similar evolution for these two clusters. Deriving reliable CNO abundances for the two sequences would be crucial. © ESO 2012. Source

Gargallo L.,Casilla | Miranda B.,Casilla | Alegria L.,Casilla | Leiva A.,Casilla | Radic D.,Casilla
Journal of Applied Polymer Science

The static and dynamic behavior of the Langmuir monolayers of poly(ester)s containing germanium and silicon in the main chain (Scheme 1) is reported. True monolayers are found for all the poly(ester)s studied. The isotherms of surface pressure versus surface area for poly(ester)s exhibit a behavior of the expanded-type monolayers and that of condensed-type monolayers. It was observed that the addition of an hydrophilic polymer such as poly(monomethyl itaconate) to the water subphase produces significant changes in the isotherm properties. The interfacial rheology of the poly(ester)s monolayers has also been studied by using Oscillatory Barrier Experiments in a low-frequency range. It was found that the elasticity and the dilational viscosity increase from diluted monolayers until a surface concentration about 20 Ã - 10-5 mg cm-2. The static and dynamic elasticities were found to be very similar for the poly(ester)s over the dilute range. It was possible to conclude that these poly(ester)s form extremely viscoelastic monolayers. © 2011 Wiley Periodicals, Inc. Source

We tested the amplification potential of 8 microsatellites initially described for Odontesthes perugiae and O. argentinensis in 3 species of Odontesthes and 4 species of Basilichthys. Most of the microsatellites amplified and showed polymorphism; thus they will be useful in genetic conservation plans for these species. Source

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