Multi-Color Photometry of the Galactic Globular Cluster M75 = NGC 6864. A New Sensitive Metallicity Indicator and the Position of the Horizontal Branch in UV

We carry out and analyze new multi-color photometry of the Galactic globular cluster (GC) M75 in UBVI and focus on the brighter sequences of the color- magnitude diagram (CMD), with particular emphasis on their location in U-based CMD. Specifically, we study the level both of the horizontal (HB) and red giant branches (RGB) relative to the main-sequence turnoff (TO) in the U magnitude. Along with the presented photometry of M75, we use our collection of photometric data on GCs belonging to the metal-poor range, [Fe/H]zw<-1.1 dex, obtained from observations with different equipment, but calibrated by standard stars situated in the observed cluster fields. We confirm our earlier finding, and extend it to a larger magnitude range.We demonstrate that DeltaU_{TO}^{BHB} expressing the difference in U magnitude between the TO point and the level of the blue HB, near its red boundary, of the metal-poor GCs observed with the EMMI camera of the NTT/ESO telescope is about 0.4-0.5 mag smaller as compared to GCs observed with the 100" telescope and 1.3 m Warsaw telescope of the Las Campanas Observatory. At the same time, Delta U_{TO}^{RGB}, the difference in U magnitude between the TO and RGB inflection (brightest) points, does not show such an apparent dependence on the characteristics of U filters used, but it depends on cluster metallicity. We have shown, for the first time, the dependence of the parameter DeltaU_{TO}^{RGB} on [Fe/H] and have estimated its analytical expression, by assuming a linear relation between the parameter and metallicity. Its slope, Delta U_{TO}^{RGB}/Delta [Fe/H]~1.2 mag/dex, is approx. a factor of two steeper than that of the dependence of the RGB bump position in the V magnitude on metallicity. The asymptotic giant branch (AGB) clump and features of the RGB luminosity function (LF) of M75 are also discussed.Comment: 9 pages, 7 figures, accepted for publication in A&

Strong radial segregation between sub-populations of evolutionary homogeneous stars in the Galactic globular cluster NGC 6752

We investigate the new and still poorly studied matter of so-called multiple stellar populations (MSPs) in Galactic globular clusters (GGCs). Studying MSPs and their accumulated data can shed more light on the formation and evolution of GGCs and other closely related fundamental problems. We focus on the strong relation between the radial distribution of evolutionary homogeneous stars and their U-based photometric characteristics in the nearby GGC NGC 6752 and compare this with a similar relation we found in NGC 3201 and NGC 1261. We use our new multi-color photometry in a fairly wide field of NGC 6752, with particular emphasis on the U band and our recent and already published photometry made in NGC 3201 and NGC 1261. We found and report here for the first time a strong difference in the radial distribution between the sub-populations of red giant branch (RGB) stars that are bluer and redder in color U-B, as well as between sub-giant branch (SGB) stars brighter and fainter in the U-magnitude in NGC 6752. Moreover, the fainter SGB and redder RGB stars are similarly much more centrally concentrated than their respective brighter and bluer counterparts. Virtually the same applies to NGC 3201. We find evidence in NGC 6752 as in NGC 3201 that a dramatic change in the proportion of the two sub-populations of SGB and RGB stars occurs at a radial distance close to the half-mass radius, R_h, of the cluster. These results are the first detections of the radial trend of the particular photometric properties of stellar populations in GGCs. They imply a radial dependence of the main characteristics of the stellar populations in these GGCs, primarily of the abundance, and (indirectly) presumably of the kinematics.Comment: 5 pages, 5 figures, accepted for publication in Astronomy and Astrophysics (Letters

Evidence of the inhomogeneity of the stellar population in the differentially reddened globular cluster NGC 3201

We report on evidence of the inhomogeneity (multiplicity) of the stellar population in the Galactic globular cluster (GC) NGC 3201, which is irregularly reddened across its face. We carried out a more detailed and careful analysis of our recently published new multi-color photometry in a wide field of the cluster with particular emphasis on the U band. Using the photometric data corrected for differential reddening, we found for the first time two key signs of the inhomogeneity in the cluster's stellar population and of its radial variation in the GC. These are (1) an obvious trend in the color-position diagram, based on the (U-B) color-index, of red giant branch (RGB) stars, which shows that the farther from the cluster's center, the bluer on average the (U-B) color of the stars is; and (2) the dependence of the radial distribution of sub-giant branch (SGB) stars in the cluster on their U magnitude, where brighter stars are less centrally concentrated than their fainter counterparts at a confidence level varying between 99.2% and 99.9% depending on the color-index used to select the stars. The same effects were recently found by us in the GC NGC 1261. However, contrary to NGC 1261, we are not able to unambiguously suggest which of the sub-populations of SGB/RGB stars can be the progenitor of blue and red horizontal branch stars of the cluster. Apart from M4, NGC 3201 is another GC very probably with an inhomogeneous stellar population, which has essentially lower mass than the most massive Galactic GCs where multiple stellar populations were unambiguously detected for the first timeComment: 5 pages, 4 figure

Multi-color photometry in wide field of the Galactic globular cluster NGC 3201

Aims. This paper aims at further studying one of the nearby Galactic globular clusters (GCs), NGC 3201. It is known to experience notable irregular variability of reddening across its face. By relying on our previous studies and findings and by developing them, we focus on the brighter sequences of the color-magnitude diagram (CMD) and on the cluster's characteristics. Methods. We carried out and analyzed new multi-color photometry of NGC 3201 in UBVI reaching below the turnoff point in all passbands in a fairly large cluster field, about 14\arcmin \times 14 \arcmin. To achieve more reliable results and conclusions, we reduced the negative impact of the irregularly varying reddening and contamination by field stars. Results. With this aim we first estimated mean reddening in different zones of the studied cluster field and then took its variations into account, by reducing them to the same level. We estimated metallicity of NGC 3201 using a new metallicity indicator related to U-based CMDs, recently proposed by us. We find [Fe/H]$_{ZW} = -1.54 \pm 0.12$ dex, which falls between extreme estimates of the cluster's metallicity obtained using different methods or indicators. Also, the location of the RGB bump on the branch corresponds to [Fe/H]$_{ZW} = -1.46 \pm 0.15$ dex. We isolate 73 probable blue straggler (BS) candidates, the largest population found in NGC 3201 so far. They are more centrally concentrated than the lower red giants at the 99.2% level. Their position in the two-color diagram assumes that presumably none of them belongs to BSa of collisional origin. The luminosity function (LF) of the RGB and its features in the low part of the branch are examined and discussed. We also resolve some of the contradictory results of previous publications

Coccidias intestinales en caninos de la comuna de San Miguel, Región Metropolitana, Chile

El objetivo de este estudio fue determinar la prevalencia de las coccidias en caninos urbanos de la Comuna de San Miguel (Región Metropolitana). Para ello se analizaron 480 muestras de excrementos mediante la técnica de flotación en solución de azúcar, identificándose además los huevos de helmintos que pudiesen estar presentes. Para estudiar la presencia de Crvptosporidium en perros sanos y diarreicos, se obtuvieron 144 muestras adicionales. Estas fueron estudiadas mediante la técnica de tinción de frotis fecales con Ziehl–Neelsen modificado.La prevalencia de infección por coccidias en los 480 caninos fue de 16,3%, no observándose diferencias en cuanto a edad o sexo de los animales (p > 0,05). Sarcocystis fue el género que se presentó con mayor frecuencia (11,3%), seguido de isosporas de tamaño intermedio (I. ohioensis, I. burrowsi, I. neorivolta) y en menor proporción I. canis (1,9%) e I. bahiensis (0,4%). Tanto en los perros sanos como diarreicos, no se detectaron ooquistes de Cryptosporidium.La mitad de los perros examinados (50,2%) presentó algún tipo de parasitismo, siendo los helmintos de mayor frecuencia (32,7%) que los protozoos (6,6%). Infecciones mixtas se encontraron en 52 casos (10,8%). Los helmintos más frecuentes fueron Trichuris vulpis (29,8%), Toxocara canis (12,3%) y anquilostomídeos (10,8%).Palabras claves: coccidiosis, perros, infección intestinal.AbstractIn order to establish the prevalence of intestinal coccidial infections in dogs, 480 faecal samples were collected from an urban area, and examined through a sugar flotation technique. Oocysts as well as helminths eggs were identified and recorded. Cryptosporidium oocysts were studied in 144 faecal samples, additionally collected for this purpose, half from diarrheic and the other half from health_y, dogs. A modified Ziehl–Neelsen technique was used.Coccidial infections were found in 16.3% of the dogs, being Sarcocystis the most prevalent genus (11.3%) folloxved by, median size isospora (3.8%) (I. ohioensis, I. burrowsi, I. neorivolta) and I. canis (1.9%). I. bahiensis was the least found (0.4%). No significant diferences of coccidial infections were detected with regard to age or sex (p > 0.05). Cryptosporidium oocvsts were not found in the,faecal smears from normal or diarrheic dogs. Half of the 480 dogs examined (50.2%) was recorded as infected with intestinal parasitos. Helminths were more prevalent (32.7%) than protozoa (6.6%). Dogs with mixed infections numbered 52 (10.8%). Among the helminths, Trichuris vulpis was most frequently found (29.9%), followed by Toxocara canis (12.3%) and hookworms (10.8%).Key words: coccidiosis, dogs, intestinal infection

Instrumentos de la política antiinflacionaria del Banco Central

Tesis (Ingeniero Comercial)A medida que se ha observado mayor desarrollo en el sistema financiero, mayor integración de Chile a los mercados financieros internacionales y menor inflación, el Banco Central se ha visto en la obligación de mejorar tanto sus herramientas de política monetaria como los indicadores del estado de la economia. En la política monetaria existen diversas teorías que vinculan algunas variables independientes, tales como la base monetaria, con otras variables intermedias, como la oferta de dinero, las reservas bancarias, las tasas de interés, el tipo de cambio, el nivel de precios, el producto nacional nominal o real, etc. En cuanto al control que tendría la autoridad sobre las variables independientes, éste requiere que se le den las condiciones institucionales, estructurales y técnicas que permitan regular los desequilibrios monetarios. Además se hace necesario definir ciertas condiciones de implementación de la política, relativa a la definición de los agregados monetarios, a los mecanismos de transmisión sobre las demás variables económicas y los plazos de ajuste entre los momentos en que se implementan las políticas y se # manifiestan sus resultadost Durante los Últimos diez años la política monetaria por el Banco Central ha tenido como objetivo influir sobre las tasas de interés de mercado, política fundamentada en el impacto que éstas ejercen sobre el ritmo de crecimiento sobre el gasto agregado, con el objetivo final de lograr la estabilidad de los precios de la economia. El desarrollo del Seminario de Tesis comienza con el capítulo 1, el cual aborda el tema de la autonomía del Banco Central, tomando como referencia la Ley Orgánica del Banco Central y perspectivas del Fondo Monetario Internacional para mostrar la conveniencia de que esta institución sea independiente del Estado. Por otro lado, se muestran las operaciones cuasi-fiscales que tienen gran importancia en el déficit del Banco Central, que en la actualidad aún proyecta. En el capítulo 11, se describen los objetivos y operaciones de acción de los Bancos Centrales, que permiten implementar la política monetaria. El capitulo III, se refiere a la política monetaria y a los instrumentos que utiliza el Instituto Emisor para manejar los equilibrios macroeconómicos y especialmente controlar la política antitinflacionaria. Por otra parte, el capítulo IV abarca el tema del control de la cantidad de dinero por parte del Banco Central vía base monetaria y vía tasa de interés, destacando que el país utiliza una política monetaria de tasa. Por último, el capítulo V describe detalladamente la evolución de la política ' antiinflacionaria y las variables macroeconómicas entre los años 1984 - 1997. Aquí se mencionan las distintas crisis que sufrió el país durante este período y las políticas de ajuste llevadas a cabo para corregirlas