Volumen 19, Números 1 y 2
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Ítem Niveles de radioactividad en tres regiones de Costa Rica(2011-02-15 00:00:00) Mora Rodríguez, PatriciaThe establishment of the first radioactivity levels of natural radiation was carried out during the period 1991 to 1994 in three different regions of Costa Rica. The radionuclides studied belong to different soil types related to each selected region. Utilizing low level counting techniques the specific activity of the natural radioactive chains 238U daughters, 232Th and the element 40K were measured for a total of 120 samples during this period. The amount of 137Cs, as fall out radionuclide, was also studied. The average national values in Bqkg-1 measured for 238U were 11.66 for 214Bi, 34.42 for 226Ra and 10.73 for 214Pb, for 232Th daughters were 4.08 for 208Tl, 9.65 for 212Bi and 7.62 for 228Ac. The specific activity values for 40K 95.14 Bqkg-1 and for 137Cs was 2.38 Bqkg-1. It is found that Costa Rica is not highly natural radioactive country and that the values for 137Cs are well below international reported values.Ítem Historia del campo geomagnético de Costa Rica(2011-02-15 00:00:00) Páez Portuguez, Jorge Eduardo; Jiménez, M.; Leandro, GermanThe study of the geomagnetic field began with the publication of the book De Magnete (1600) of Sir William Gilbert (1504-1603). By influence of Sir Edmund Halley the British Marine is obligated to make measurements of the declination of the magnetic field wherever theirs ships go. Thus, Sir Edward Belcher measured it at the Cocos Island on board of The British ship Sulphur on 3 of april 1838, it gave a value of 8°23`49`` East. At the end of last century and at the beginning of this one, Henri Pittier did a sort of measurements of the magnetic declination of Costa Rica, thus allowing the publications of the first isogonic chart of Costa Rica for the year 1901.But it is not until 1965 when Gutiérrez Braun published a more actualized isogonic chart. In 1978 G. Leandro and J. Páez did the more sustained effort to get a detailed data of the magnetic field of Costa Rica, allowing the chart of 1978, actualized afterward by G. Leandro in 1984.Ítem Acerca de si pudo o no ser el universo anisotrótipico(2011-02-15 00:00:00) Alvarado Marín, Rodrigo EduardoThe theoretical and experimetnal problem concerning the origin and formations of the universe is establish in this paper, specially by developing some theories that try to explain this phenomena, and also to settle the reasons why the universe could have been anisotropic and homogeneous at the very beginning, envolving in time later on in what we see today. Besides some other posibilities are studied in order to avoid the singularyty at the beginning of the universe. Some exact solutions are obtained by autoconsistency with the Einstein equations utilizing for that purpose different types of interactions among the spinor and the scalar fields, with and without matter.Ítem Álgebras-MV artinianas y noetherianas(2011-02-14 00:00:00) Belluce, L. P.Estudiamos álgebras-MV que satisfacen las condiciones de cadena ascendente o de cadena descendente por ideales. Por ejemplo, si un álgebra es artiana, entonces tiene un número finito de ideales primos y minimales. También demostramos que el conjunto de ideales implicativos de un álgebra-MV satisface ambas condiciones de cadena si esta álgebra, módulo su radical, es noetheriana. Otros resultados relacionan las condiciones de cadea con la propiedad de ser semi-local.Ítem Aplicación de las técnicas de punto fijo(2011-02-15 00:00:00) Azofeifa Z., Carlos E.This article will develop a computacional procedure for approximating a fixed point of continuos functions of the simplex into itself using the Brouwer`theorem. We also shows the different applications of the theory of fixed point in the economic area.Ítem Punto fijo una teoría interdisciplinaria(2011-02-15 00:00:00) Azofeifa Z., Carlos E.We show a survey of the theory of the fixed point by commenting the most important theorems and their applications in the mathematical fields as well as in other disciplines: economy, theory of games and optimization. We mention the different definitions of functions of contraction. The applications of Brouwer`s Theorem are also given, futhermore we recommend the adecuate bibliography for each case.