Magnetoestratigrafía en sedimentos del cenozoico tardío de la localidad de Villa Cacique, provincia de Buenos Aires

La presente contribución se refiere a una sucesión sedimentaria del Cenozoico tardío expuesta en la localidad de Villa Cacique (37° 41’ 19.70” S y 59° 21’ 46.78” W). Las muestras paleomagnéticas se obtuvieron de una sección de 9.10 m de potencia integrada por las formaciones Barker y Las Animas. Una interpretación preliminar permite suponer que las muestras extraídas de la formación Las Animas pertenecen al cron Brunhes (< 0.78 Ma) y que las muestras extraídas de la formación Barker pertenecen al cron Matuyama (0.78 – 2.588 Ma).The present contribution refers to a Late Cenozoic sedimentary sequence exposed in the locality of Villa Cacique (37° 41’ 19.70” S. y 59° 21’ 46.78” W.). Paleomagnetic samples were collected from a section of 9.10 m that was assigned to the Barker and Las Animas formations. A preliminary interpretation of results allows us to consider that the samples collected from Las Animas formation correspond to the Brunhes chron (< 0.78 Ma) while the samples of the Barker formation correspond to the Matuyama chron (0.78 - 2.588 Ma).Fil: Gómez Samus, Mauro Leandro. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bidegain, Juan Carlos. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata; Argentin

Magnetostratigraphy in the Vela and Barker Formations, Tandil, Buenos Aires Province, Argentina

La presente contribución se refiere a una sucesión sedimentaria del Cenozoico tardío expuesta en la localidad de María Ignacia, Argentina. Las muestras paleomagnéticas se obtuvieron de una sección asignada principalmente a las Formaciones Vela y Barker. El análisis de los datos paleomagnéticos indica que la Formación Vela es de polaridad normal, y se atribuye, con seguridad, al Cron Brunhes (< 0,781Ma). La porción expuesta de la Formación Barker es, en cambio, de polaridad inversa y puede ser asignada al Cron Gilbert (3,596 – 6,033 Ma). Los estudios magnetoestratigráficos constituyen una vía apropiada para conocer la edad de la Formación Barker ya que se carece de dataciones radiométricas y de registros bioestratigráficos hasta el presente. Los parámetros de magnetismo de rocas indican diferencias entre las unidades estudiadas. Se estudiarán exhaustivamente en futuras contribuciones con el fin de poder realizar interpretaciones de las condiciones paleo-ambientales en el lapso de tiempo considerado.The present contribution refers to paleomagnetic studies carried out in a late Cenozoic sedimentary sequence exposed in the locality of María Ignacia, Argentina. Paleomagnetic samples were collected from a section assigned mainly to the Vela Formation (the youngest) and the Barker Formation (the oldest). The analysis of Paleomagnetic data indicates that the Vela Formation presents samples of normal polarity while the Barker Formation presents samples of reverse polarity. A preliminary interpretation allows us to assign the samples of normal polarity to the Brunhes Normal Polarity Chron (< 0.781 Ma) while the reverse polarity samples might be assigned to the Gilbert Reverse Polarity Chron (3.596 – 6.033 Ma). Magnetostratigraphic studies provide a suitable way for estimate the age of the Barker Formation, since there are a lack of radiometric datable materials and fossils remains up to now. The rock magnetic parameters indicate difference between geological units; such behavior will be studied carefully in future contributions for estimating the paleoenvironmental conditions during the considered time span.Fil: Gómez Samus, Mauro Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bidegain, Juan Carlos. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin

The outskirts of globular clusters as modified gravity probes

In the context of theories of gravity modified to account for the observed dynamics of galactic systems without the need to invoke the existence of dark matter, a prediction often appears regarding low acceleration systems: wherever $a$ falls below $a_{0}$ one should expect a transition from the classical to the modified gravity regime.This modified gravity regime will be characterised by equilibrium velocities which become independent of distance, and which scale with the fourth root of the total baryonic mass, $V^{4} \propto M$. The two above conditions are the well known flat rotation curves and Tully-Fisher relations of the galactic regime. Recently however, a similar phenomenology has been hinted at, at the outskirts of Galactic globular clusters, precisely in the region where $a<a_{0}$. Radial profiles of the projected velocity dispersion have been observed to stop decreasing along Keplerian expectations, and to level off at constant values beyond the radii where $a<a_{0}$. We have constructed gravitational equilibrium dynamical models for a number of globular clusters for which the above gravitational anomaly has been reported, using a modified Newtonian force law which yields equilibrium velocities equivalent to MOND. We find models can be easily constructed having an inner Newtonian region and an outer modified gravity regime, which reproduce all observational constraints, surface brightness profiles, total masses and line of sight velocity dispersion profiles. Through the use of detailed single stellar population models tuned individually to each of the globular clusters in question, we derive estimates of the total masses for these systems. Interestingly, we find that the asymptotic values of the velocity dispersion profiles are consistent with scaling with the fourth root of the total masses, as expected under modified gravity scenarios.Comment: Accepted in ApJ, 13 pages, 7 figure

Наслідки та оцінка результатів аграрної реформи в Україні

У статті проаналізовані наслідки аграрної реформи в Україні та надана оцінка їх результатів. Визначені подальші напрями аграрних трансформацій. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/29491В статье проанализированы последствия аграрной реформы в Украине и подана оценка их результатов. Определены дальнейшие направления аграрных трансформаций. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/29491In the article analysed the consequences of agrarian reform in Ukraine and given estimation of their results. Determined further directions of agrarian transformations. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2949

A high resolution, multi-epoch spectral atlas of peculiar stars including RAVE, GAIA and HERMES wavelength ranges

We present an Echelle+CCD, high S/N, high resolution (R = 20\,000) spectroscopic atlas of 108 well-known objects representative of the most common types of peculiar and variable stars. The wavelength interval extends from 4600 to 9400 Ang, and includes the RAVE, Gaia and HERMES wavelength ranges. Multi-epoch spectra are provided for the majority of observed stars. A total of 425 spectra of peculiar stars are presented, which have been collected during 56 observing nights between November 1998 and August 2002. The spectra are given in FITS format and heliocentric wavelengths, with accurate subtraction of both the sky background and the scattered light. Auxiliary material useful for custom applications (telluric dividers, spectro-photometric stars, flat-field tracings) is also provided. The atlas aims to provide a homogeneous database of the spectral appearance of stellar peculiarities, a tool useful both for classification purposes and inter-comparison studies. It could also serve the planning for and training of automated classification algorithms designed for RAVE, Gaia, HERMES and other large scale spectral surveys. The spectrum of XX Oph is discussed in some detail as an example of the content of the present atlas.Comment: AJ in press (issue 140:6 December 2010

EM Cygni: a study of its eclipse timings

EM Cygni is a Z Cam-subtype eclipsing dwarf nova. Its orbital period variations were reported in the past but the results were in conflict to each other while other studies allowed the possibility of no period variation. In this study we report accurate new times of minima of this eclipsing binary and update its O-C diagram. We also estimate the mass transfer rate in EM Cygni system and conclude that the mass transfer is far from the critical value. The mass transfer rate determined from the eclipse timings is in agreement with the spectroscopically determined value.Comment: 5 pages, 4 figures, accepted for publication in Astronomische Nahrichte