Migraciones internas hacia la Región Metropolitana de Santiago de Chile: una comparación con planteamientos teóricos

The orientations of migrations movement pattems in Chile are analyzed, with special reference to the causes of the demographic growth of the Greater Santiago Area. On the one hand, these are related to the degree of attraction that the area still has within the country, and on the other, with a predominant nonselective emigrant typology. It was determinate, in a communal level of resolution, the impact of the regional migrations movements in the city growth, by means of the identification of the 1980's immigrant profile. The results indicate that the influx from other regions is definitely less significant than the intra-regional movements in the same period. Spatial interaction reveals a strong relationship with the central regions of the country, as well as a diffuse destiny pattem central - penpheral within the metropolis. Associated attributes indicate a ves, selective movement trend that stands out in the wealthier communes. The results identify a behavioral pattem already analyzed in an urbanization paradigm for Latin America. The Metropolitan Region of Santiago has lost the historical polarizing role of movements. Nevertheless, the tendency to the agglomeration continues, in a new functional hierarchic framework: the dynamism of the mid size cities.Se analiza la orientación de los movimientos migratorios en Chile, los cuales estan implícitos en el debate actual sobre las causas del crecimiento demográfico del Gran Santiago. En este se resalta, por un lado, la atracción que puede continuar presentando la metrópolis y por otro, una tipología de inmigrante poco selectiva. Se determina y evalúa, con una resolución espacial comunal, el impacto de los movimientos migratorios regionales en el crecimiento de la ciudad, identificando el perfil que caracteriza al inmigrante hacia fines de la década de los 80. Los resultados muestran que el aporte poblacional desderegiones, en términos cuantitativos, resulta ser menos significativo que los movimientos intraurbanos registrados en el mismo período. La interacción espacial, se manifiesta en una fuerte asociación con las regiones centrales del país y un patrón de destino metropolitano difuso, centro-periferia. Se trata de una migración selectiva, que se manifiesta con particular fuerza en las comunas de mayor status socioeconómico. Corresponde a un modelo de comportamiento ya encontrado para Latinoamérica y sistematizado en un paradigma de la urbanización. La Región Metropolitana de Santiago ha perdido peso en surol histórico, polarizador de movimientos; sin embargo, prosigue la tendencia a la aglomeración, en el marco de una nueva jerarquía funcional: el dinamismo experimentado por las ciudades intermedias

Optical Turbulence Measurements and Models for Mount John University Observatory

Site measurements were collected at Mount John University Observatory in 2005 and 2007 using a purpose-built scintillation detection and ranging system. $C_n^2(h)$ profiling indicates a weak layer located at 12 - 14 km above sea level and strong low altitude turbulence extending up to 5 km. During calm weather conditions, an additional layer was detected at 6 - 8 km above sea level. $V(h)$ profiling suggests that tropopause layer velocities are nominally 12 - 30 m/s, and near-ground velocities range between 2 -- 20 m/s, dependent on weather. Little seasonal variation was detected in either $C_n^2(h)$ and $V(h)$ profiles. The average coherence length, $r_0$, was found to be $7 \pm 1$ cm for the full profile at a wavelength of 589 nm. The average isoplanatic angle, $\theta_0$, was $1.0 \pm 0.1$ arcsec. The mean turbulence altitude, $\bar{h_0}$, was found to be $2.0\pm0.7$ km above sea level. No average in the Greenwood frequency, $f_G$, could be established due to the gaps present in the \vw\s profiles obtained. A modified Hufnagel-Valley model was developed to describe the $C_n^2(h)$ profiles at Mount John, which estimates $r_0$ at 6 cm and $\theta_0$ at 0.9 arcsec. A series of $V(h)$ models were developed, based on the Greenwood wind model with an additional peak located at low altitudes. Using the $C_n^2(h)$ model and the suggested $V(h)$ model for moderate ground wind speeds, $f_G$ is estimated at 79 Hz.Comment: 14 pages; accepted for publication in PAS

Variables psicosociales del consumo de cánnabis en adolescentes

Objetivo. Profundizar en el conocimiento de aquellas variables psicosociales que pueden ejercer una función mediadora en el consumo de cánnabis de los adolescentes.Material y métodos. Se ha utilizado una muestra de 2.401 sujetos de 2º y 3º de la ESO, con una media de edad de 13,96 años, realizándose un análisis comparativo entre los tres grupos en los que se ha dividido la misma: No consumo; Alguna vez y Último Mes.Resultados. Desde un análisis global de los datos es el grupo de consumidores del último mes quien mantiene unas actitudes más favorables, una intención mayor de consumo y una baja percepción de riesgo frente al mismo. Se confirma la importancia del grupo de iguales como variable mediadora del propio consumo, así como la influencia del contexto familiar y se observa como la relación con el entorno familiar y educativo empeora a medida que aumenta la utilización de esta sustancia.Conclusiones. Es necesario intervenir lo antes posible y hacerlo con la puesta en marcha de estrategias diferenciadas, dependiendo de las características del grupo con el que se va a trabajar. Las medidas preventivas que se lleven a cabo deberán enmarcarse dentro de una política más amplia de actuación, que permita contrarrestar la información sesgada que la población esta recibiendo sobre el cánnabis y que podría explicar parte del descenso en la percepción de riesgo asociado al consumo de esta sustancia

Astronomical Site Ranking Based on Tropospheric Wind Statistics

We present comprehensive and reliable statistics of high altitude wind speeds and the tropospheric flows at the location of five important astronomical observatories. Statistical analysis exclusively of high altitude winds point to La Palma as the most suitable site for adaptive optics, with a mean value of 22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have found a clear annual periodicity of high altitude winds for the five sites in study. We have also explored the connection of high to low altitude atmospheric winds as a first approach of the linear relationship between the average velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001). We may conclude that high and low altitude winds show good linear relationships at the five selected sites. The highest correlation coefficients correspond to Paranal and San Pedro Martir, while La Palma and La Silla show similar high to low altitude wind connection. Mauna Kea shows the smallest degree of correlation, which suggests a weaker linear relationship. Our results support the idea of high altitude winds as a parameter for rank astronomical sites in terms of their suitability for adaptive optics, although we have no evidence for adopting the same linear coefficient at different sites. The final value of this linear coefficient at a particular site could drastically change the interpretation of high altitude wind speeds as a direct parameter for site characterization.Comment: 18 pages, 5 figures. Accepted in MNRA

Optical turbulence vertical distribution with standard and high resolution at Mt. Graham

A characterization of the optical turbulence vertical distribution (Cn2 profiles) and all the main integrated astroclimatic parameters derived from the Cn2 and the wind speed profiles above the site of the Large Binocular Telescope (Mt. Graham, Arizona, US) is presented. The statistic includes measurements related to 43 nights done with a Generalized Scidar (GS) used in standard configuration with a vertical resolution Delta(H)~1 km on the whole 20 km and with the new technique (HVR-GS) in the first kilometer. The latter achieves a resolution Delta(H)~20-30 m in this region of the atmosphere. Measurements done in different periods of the year permit us to provide a seasonal variation analysis of the Cn2. A discretized distribution of Cn2 useful for the Ground Layer Adaptive Optics (GLAO) simulations is provided and a specific analysis for the LBT Laser Guide Star system ARGOS (running in GLAO configuration) case is done including the calculation of the 'gray zones' for J, H and K bands. Mt. Graham confirms to be an excellent site with median values of the seeing without dome contribution epsilon = 0.72", the isoplanatic angle theta0 = 2.5" and the wavefront coherence time tau0= 4.8 msec. We find that the optical turbulence vertical distribution decreases in a much sharper way than what has been believed so far in proximity of the ground above astronomical sites. We find that 50% of the whole turbulence develops in the first 80+/-15 m from the ground. We finally prove that the error in the normalization of the scintillation that has been recently put in evidence in the principle of the GS technique, affects these measurements with an absolutely negligible quantity (0.04").Comment: 11 figures. MNRAS, accepte

Bolometric correction and spectral energy distribution of cool stars in Galactic clusters

We have investigated the relevant trend of the bolometric correction (BC) at the cool-temperature regime of red giant stars and its possible dependence on stellar metallicity. Our analysis relies on a wide sample of optical-infrared spectroscopic observations, along the 3500A-2.5micron wavelength range, for a grid of 92 red giant stars in five (3 globular + 2 open) Galactic clusters, along the -2.2<[Fe/H]<+0.4 metallicity range. Bolometric magnitudes have been found within an internal accuracy of a few percent. Making use of our new database, we provide a set of fitting functions for the V and K BC vs. Teff and broad-band colors, valid over the interval 3300K<Teff<5000K, especially suited for Red Giants. No evident drift of both BC(V) and BC(K) with [Fe/H] is found. Things may be different, however, for the B-band correction, given a clear (B-V) vs. [Fe/H] correlation in place for our data, with metal-poor stars displaying a "bluer" (B-V) with respect to the metal-rich sample, for fixed Teff. Our empirical bolometric scale supports the conclusion that (a) BC(K) from the most recent studies are reliable within <0.1 mag over the whole color/temperature range considered in this paper, and (b) the same conclusion apply to BC(V) only for stars warmer than ~3800K. At cooler temperatures the agreement is less general, and MARCS models are the only ones providing a satisfactory match to observations.Comment: 18 pages with 12 color figures and 12 tables. To appear in the MNRAS. Full spectral catalog of stars available at http://www.bo.astro.it/~eps/home.htm

Lucky Imaging Adaptive Optics of the brown dwarf binary GJ569Bab

The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high precision astrometry and differential photometry in the optical is investigated by conducting observations of the close 0\farcs1 brown dwarf binary GJ569Bab. We took 50000 $I$-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which exhibits an $I$-band magnitude of $7.78\pm0.03$. The AO+LI observations at WHT were able to resolve the binary system GJ569Bab located at 4\farcs 92 \pm 0\farcs05 from GJ569A. We measure a separation of $98.4 \pm 1.1$ mas and $I$-band magnitudes of $13.86 \pm 0.03$ and $14.48 \pm 0.03$ and $I-J$ colors of 2.72$\pm$0.08 and 2.83$\pm$0.08 for the Ba and Bb components, respectively. Our study rules out the presence of any other companion to GJ569A down to magnitude I$\sim$ 17 at distances larger than 1\arcsec. The $I-J$ colors measured are consistent with M8.5-M9 spectral types for the Ba and Bb components. The available dynamical, photometric and spectroscopic data are consistent with a binary system with Ba being slightly (10-20%) more massive than Bb. We obtain new orbital parameters which are in good agreement with those in the literature.Comment: 13 pages, 9 figures, 7 tables, in press in MNRA

Atmospheric optical-turbulence at Roque de los Muchachos Observatory: database and recalibration of the generalized-SCIDAR data

We present the largest database so far of atmospheric optical-turbulence profiles (197035 individual CN2(h)) for an astronomical site, the Roque de los Muchachos Observatory (La Palma, Spain). This C2 (h) database was obtained through generalized-SCIDAR observations at the 1 meter Jacobus Kapteyn telescope from Febrary 2004 to August 2009, obtaining useful data for 211 nights. The overestimation of the turbulence strength induced during the generalized SCIDAR data processing has been analyzed for the different observational configurations. All the individual C2 (h) have been recalibrated to compensate the introduced errors during data treatment following (Avila & Cuevas 2009). Comparing results from profiles before and after the recalibration, we analyze its impact on the calculation of relevant parameters for adaptive optics.Comment: 8 pages, 3 figures, MNRAS accepte

First results of site testing program at Mt. Shatdzhatmaz in 2007 - 2009

We present the first results of the site testing performed at Mt.~Shatdzhatmaz at Northern Caucasus, where the new Sternberg astronomical institute 2.5-m telescope will be installed. An automatic site monitor instrumentation and functionality are described together with the methods of measurement of the basic astroclimate and weather parameters. The clear night sky time derived on the basis of 2006 -- 2009 data amounts to 1340 hours per year. Principle attention is given to the measurement of the optical turbulence altitude distribution which is the most important characteristic affecting optical telescopes performance. For the period from November 2007 to October 2009 more than 85\,000 turbulence profiles were collected using the combined MASS/DIMM instrument. The statistical properties of turbulent atmosphere above the summit are derived and the median values for seeing $\beta_0 = 0.93$~arcsec and free-atmosphere seeing $\beta_{free} = 0.51$~arcsec are determined. Together with the estimations of isoplanatic angle $\theta_0 = 2.07$~arcsec and time constant \tau_0 = 2.58 \mbox{ ms}, these are the first representative results obtained for Russian sites which are necessary for development of modern astronomical observation techniques like adaptive optics.Comment: Accepted for publication in MNRAS, 17 pages, 15 figure