Relationships Between Saline Ground Water Soil, and Leaf Tissue Composition of the Phreatophyte Mezquite     

F. L. García-Carreño  E. Troyo-Diéguez  J. L. Ochoa 《Ground water》1992,30(5):676-682

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Is dark matter created in the gravitation field of galaxies?     

V. Majerník 《Astrophysics and Space Science》1996,240(1):133-139

Using the heuristic arguments of quantum physics we describe a new mechanism of the creation of short-living particles from the virtual ones in a stationary gravitation field. The mass of these particles is a function of the intensity of gravitation field. We suppose that the particles created in the gravitation field form a part of the non-baryonic dark matter. Having the intensity of gravitation field in a galaxy we can calculate the density of dark matter created in it by the vacuum quantum fluctuation. We calculate the distribution of this dark matter in a model galaxy and show that its total mass is comparable with the visible mass of the galaxy.  相似文献   

Interactions and the Evolution of Cluster Galaxies     

R. Vílchez-Gómex  G. A. Bruzual  R. Pelló  R. Domínguez 《Astrophysics and Space Science》2001,276(2-4):757-764

We have developed model predictions for the morphological distribution of cluster galaxies as a function of the cluster-centric distance and the local galaxy density, using a semi-analytical code. This code allows us to obtain magnitudes and colours for cluster galaxies at different redshifts, and thus to study in detail the evolution of the colour–magnitude relation of specific distant clusters. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Prediction of Stellar Atmospheric Parameters using Instance-Based Machine Learning and Genetic Algorithms   总被引：1，自引：0，他引：1  

J. Federico Ramírez  Olac Fuentes  Ravi K. Gulati 《Experimental Astronomy》2001,12(3):163-178

In this article we present a method for the automated prediction of stellar atmospheric parameters from spectral indices. This method uses a genetic algorithm (GA) for the selection of relevant spectral indices and prototypical stars and predicts their properties, using the k-nearest neighbors method (KNN). We have applied the method to predict the effective temperature, surface gravity, metallicity, luminosity class and spectral class of stars from spectral indices. Our experimental results show that the feature selection performed by the genetic algorithm reduces the running time of KNN up to 92%, and the predictive accuracy error up to 35%. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The expansive nondecelerative universe     

Vladimír Skalský 《Astrophysics and Space Science》1993,201(1):3-14

(a) Hubble's discovery of the expansion of the Universe makes it possible to choose unambiguously from the models described by Friedmann's equations of universe dynamics. (b) From the present temperature of the cosmic microwave background radiation, the specific entropy in the matter era and the model properties of the expansive nondecelerative universe, we can determine the present parameters of our Universe with deviations smaller than 2.2%.  相似文献   

Testing the consistency of the Starburst scenario for active galactic nuclei     

María Luisa García Vargas  Angeles Díaz  Roberto Terlevich  Elena Terlevich 《Astrophysics and Space Science》1993,205(1):77-84

In the frame of the Starburst Model, we show that the evolution of a massive stellar cluster in a high metallicity environment can reproduce the observed emission-line spectrum and the UV-optical Spectral Energy Distribution of the Seyfert 2 galaxies and LINERs. We apply the results of our models to three objects: NGC 5506, NGC 5643 and Mk 348.  相似文献   

Optical and near-infrared observations of the microquasar V4641 Sgr during the 1999 September outburst     

S. Chaty  P. A. Charles  J. Martí  I. F. Mirabel  L. F. Rodríguez  T. Shahbaz 《Monthly notices of the Royal Astronomical Society》2003,343(1):169-174

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Beam Mode Expansion of Corrugated Conical Horns with Phase Correcting Lens: Application to Radioastronomy Receivers     

E. García  L. De Haro  C. O'Sullivan  G. Cahill  J. A. López Fernández  F. Tercero  B. Galocha  J. L. Besada 《Experimental Astronomy》2003,15(3):173-193

A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME). Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

On the self-consistency of evolutionary synthesis models     

Miguel Cerviño 《Astrophysics and Space Science》2003,284(2):897-900

Evolutionary synthesis models have been used to study the physical properties of unresolved populations in a wide range of scenarios. Unfortunately, their self-consistency is difficult to test and there are some theoretical open questions without an answer: (1) The change of the homology relations assumed in the computation of isochrones due to the effect of stellar winds (or rotation) and the discontinuities in the stellar evolution are not considered. (2) There is no consensus about how the isochrones must be integrated. (3) The discreteness of the stellar populations (that produce an intrinsic statistical dispersion) usually are not taken into account, and model results are interpreted in a deterministic way instead of a statistical one. The objective of this contribution is to present some inconsistencies in the computation and some cautions in the application of the results of such codes. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Astronomical Site Testing in Northwest of Argentina     

Pablo Recabarren  Pablo Recabarren  Mirta Mosconi  Hernán Muriel  Hernán Muriel  Diego García Lambas  Diego García Lambas  Marc Sarazin  Riccardo Giovanelli 《Astrophysics and Space Science》2004,290(3-4):409-413

We present the preliminary results of the astronomical site testing, which the group IATE of the OAC is developing in northwest of Argentine in collaboration with ESO and the Department of Astronomy of Cornell University. We show the results, which we have obtained from the analysis of GOES 8 satellite images in the 10.7 μm band, which allowed us to configurate a map of clear sky regions in an area between 23° and 28° S, and 66° 30′ and 69° W. We also comment logistical and tectonic aspects, and discuss next steps to follow in the research.  相似文献