Galaxy clusters and microwave background anisotropy

Previous estimates of the microwave background anisotropies produced by freely falling spherical clusters are discussed. These estimates are based on the Swiss-Cheese and Tolman-Bondi models. It is proved that these models give only upper limits to the anisotropies produced by the observed galaxy clusters. By using spherically symmetric codes including pressureless matter and a hot baryonic gas, new upper limits are obtained. The contributions of the hot gas and the pressureless component to the total anisotropy are compared. The effects produced by the pressure are proved to be negligible; hence, estimations of the cluster anisotropies based on N-body simulations are hereafter justified. After the phenomenon of violent relaxation, any realistic rich cluster can only produce small anisotropies with amplitudes of order $10^{-7}$. During the rapid process of violent relaxation, the anisotropies produced by nonlinear clusters are expected to range in the interval $(10^{-6},10^{-5})$. The angular scales of these anisotropies are discussed.Comment: 31 pages, 3 postscript figures, accepted MNRA

Learning from observations of the microwave background at small angular scales

In this paper, we focus our attention on the following question: How well can we recover the power spectrum of the cosmic microwave background from the maps of a given experiment?. Each experiment is described by a a pixelization scale, a beam size, a noise level and a sky coverage. We use accurate numerical simulations of the microwave sky and a cold dark matter model for structure formation in the universe. Angular scales smaller than those of previous simulations are included. The spectrum obtained from the simulated maps is appropriately compared with the theoretical one. Relative deviations between these spectra are estimated. Various contributions to these deviations are analyzed. The method used for spectra comparisons is discussed.Comment: 15 pages (LATEX), 2 postcript figures, accepted in Ap

Cantemos a coro: An anthology of choral music from Latin America

This project presents an anthology of choral music, with examples from periods from the colonial time to the present. It includes notes about each composer's life and the historical context in which the works were created, and explains some of the most striking features of the music. The anthology is organized in three main sections. The first one covers music --- mostly sacred music---composed during the colonial era, from the 17th to 19th centuries. The second group includes choral music composed after most countries gained their independence from Spain; most of this music is secular. The third group features contemporary compositions written after the 1980s, as well as works inspired by Latin American folklore. The anthology includes scores for music that is in the public domain and songs for which permission to reproduce has been granted, as well as a list of contacts and publishing houses that carry the music. Concert program samples are provided

Brote de dermatofilosis en bovinos del altiplano de Jujuy, Argentina

Se describe un brote de dermatofilosis (Dermatophilus congolensis) en bovinos de la puna de Jujuy. El cuadro se presentó en un rodeo bovino criollo nativo, durante la estación lluviosa en el verano climático de la región. Los animales afectados presentaron dermatitis exudativa proliferativa no pruriginosa con formación de costras, afectando el espacio interdigital de los cuatro miembros, y en forma severa y localmente extensiva en los miembros posteriores y el interior de las fosas nasales. El diagnóstico se realizó en base a la presentación clínica, la identificación del agente causal en frotis obtenido del material dérmico, y las características epidemiológicas, considerando que los factores climáticos y las condiciones de manejo favorecieron la presentación de la enfermeda

Not a true copy. Processes of stigmatization in the photographic narrative of media coverage

En este trabajo se presentan los principales hallazgos de un estudio que releva e interpreta los discursos e imágenes sobre las violencias en el espacio escolar en los periódicos de la ciudad de La Plata de Argentina. Focalizamos sobre las narrativas fotográficas de las coberturas de los diarios El Día, Hoy, Extra y Diagonales de la ciudad de La Plata, del período 1993-2011. El objetivo fue acercarnos a los efectos de las imágenes difundidas por los medios gráficos elegidos, tomando como documentos el espesor material de las fotografías. Se buscaron continuidades en la serie de imágenes seleccionadas, en el propósito de advertir fuerzas en tensión. El enfoque metodológico es cualitativo y la interpretación de los datos se llevó a cabo mediante el análisis socioeducativo del discurso. Entre los resultados obtenidos se destaca que las imágenes destacan la oposición dualista entre víctima y victimario y construyen de forma diferenciada cada polo del par. Así también, se presenta a los jóvenes de sectores socialmente desfavorecidos como la cara de la inseguridad y de la violencia en el espacio escolar. Esta investigación amplía la base empírica con la que pensar y discutir las representaciones en los medios de comunicación, y cómo a través de las fotografías se sostienen núcleos de sentido común.In this article, the main findings of a study are presented which reveals and interprets the discourses and images about violence in school ambience in the newspapers of the city of La Plata in Argentina. We focus on the photographic narratives in the news coverage by El Día, Hoy, Extra, and Diagonales from the city of La Plata, between 1993 and 2011. The objective was to address the effects of the images disseminated by the printed media chosen, taking the material thickness of the photographs as documents. Continuities were searched in the series of images selected, with the purpose of finding forces in tension. The methodological approach is qualitative and the interpretation of the data was conducted by the socio-educative analysis of the discourse. The results obtained highlight the images which stress the dualist opposition between the victim and the perpetrator as this depicts each pole of the pair in a different manner. In addition, youths from socially deprived sectors are presented as the very face of insecurity and violence in school ambience. This investigation broadens the empirical basis to review and discuss the representations in the media, and how the cores of common-sense are retained through the photographs

Methods for Estimating Fluxes and Absorptions of Faint X-ray Sources

X-ray sources with very few counts can be identified with low-noise X-ray detectors such as ACIS onboard the Chandra X-ray Observatory. These sources are often too faint for parametric spectral modeling using well-established methods such as fitting with XSPEC. We discuss the estimation of apparent and intrinsic broad-band X-ray fluxes and soft X-ray absorption from gas along the line of sight to these sources, using nonparametric methods. Apparent flux is estimated from the ratio of the source count rate to the instrumental effective area averaged over the chosen band. Absorption, intrinsic flux, and errors on these quantities are estimated from comparison of source photometric quantities with those of high S/N spectra that were simulated using spectral models characteristic of the class of astrophysical sources under study. The concept of this method is similar to the long-standing use of color-magnitude diagrams in optical and infrared astronomy, with X-ray median energy replacing color index and X-ray source counts replacing magnitude. Our nonparametric method is tested against the apparent spectra of 2000 faint sources in the Chandra observation of the rich young stellar cluster in the M17 HII region. We show that the intrinsic X-ray properties can be determined with little bias and reasonable accuracy using these observable photometric quantities without employing often uncertain and time-consuming methods of non-linear parametric spectral modeling. Our method is calibrated for thermal spectra characteristic of stars in young stellar clusters, but recalibration should be possible for some other classes of faint X-ray sources such as extragalactic AGN.Comment: Accepted for publication in The Astrophysical Journal. 39 pages, 15 figure