El juego-rey y la ciencia de los números

El ajedrez puede constituir un excelente recurso didáctico en el aula de matemáticas. El presente trabajo trata sobre algunas de las conexiones que se pueden establecer entre estas dos disciplinas, y sobre la posibilidad de plantear problemas matemáticos tomando como soporte el tablero y las piezas de ajedrez. Los contenidos de los problemas son muy variados, manejando diversas cuestiones -algebraicas, combinatorias, geométricas, cálculo de probabilidades, de lógica, etc.-, que resultan especialmente motivadoras por el carácter lúdico y manipulativo que posee el juego de los 64 escaques.

La reina Dido de Cartago y el primer problema isoperimétrico conocido

Se presenta el problema original de la Reina Dido y se hace un recuento de los intentos de solución del problema isoperimétrico a lo largo de muchos siglos.

Diversity of functional groups in the vegetation sandy seashore of the Grande, Anclitas and Caguamas Cays (Jardines de la Reina Archipelago, Cuba)

Sandy shores are known to be extreme ecosystems where the vegetation has evolved many morphological and physiological adaptations for its survival. With the aim of identify possible relationships between the vegetation´s functional diversity with abiotic factors and its corresponding quantification, we collected data on the abundance and richness of the sandy coast vegetation complex in Grande, Anclitas and Caguamas keys. Its flora is largely characterized by the dominance of hemicryptophytes and chamaephytes plants with nanophyllous leaves and displaying dispersal syndromes such as zoochory and anemochory. However, the functional groups´ richness, in the present study, varies from one key to another. Functional diversity is similar between the wet and dry seasons, and its spatial variation is influenced by the interplay of the set of abiotic factors herein studied.

A couple of embroiled sheets of Miguel Barnades Manaider and Esteban de Prado in the Herbaria of Real Colegio Alfonso XII of San Lorenzo de El Escorial (Madrid)

In this paper we present a couple of sheets of Umbelliferae that are preserved in the RCAXII herbaria. One of them, Selinum carvifolia, where collected in the Gredos Mountains by Miguel Barnades Mainader and was identified by his son Miguel Barnades Clarís. The other, Tragium flabellifolium, was collected in Mieres (Asturias) by Esteban de Prado and identified by Mariano La Gasca.

Rubén Darío's new unpublished and unknown documents: on La "Isla de Oro", the "Poema del Otoño" and the years of "Mundial"

This article studies and reproduces a group of documents that includes some hand-written and typed texts most likely authored by Rubén Darío, along with others where Darío’s authorship can be easily contested. These documents seem to have originated during the years of Mundial Magazine (1912-1914), and besides the interest for their probably unpublished nature, they also show the cooperation between Darío and his collaborators in the preparation of his original manuscripts right before being sent to the publishers.

"Bobok" y "Pedro Páramo", dos narraciones sobre muertos

El presente estudio realiza un análisis comparativo entre la novela del mexicano Juan Rulfo, Pedro Páramo (1955), y un cuento del escritor ruso Dostoievski que trata también el tema del Más allá, titulado Bobok (1873). Paralelamente, se trabaja con la posibilidad de que el relato ruso hubiese podido ser una más de las fuentes literarias de la novela mexicana, y se trata de determinar las posibles conexiones -directas o indirectas- entre las dos obras. Ambas son puestas en común por su género literario, y a partir de ahí se estudian los elementos constitutivos que tienen en común, sus afinidades y divergencias más llamativas.

Energy levels, radiative rates and electron impact excitation rates for transitions in H-like N VII, O VIII, F IX, Ne X and Na XI

We report calculations of energy levels, radiative rates and electron impact excitation rates for transitions in H-like N VII, O VIII, F IX, Ne X and Na XI. The general-purpose relativistic atomic structure package (grasp) is adopted for calculating energy levels and radiative rates, while the Dirac atomic R-matrix code (DARC) and the flexible atomic code (FAC) are used for determining the collision strengths and subsequently the excitation rates. Oscillator strengths, radiative rates and line strengths are listed for all E1, E2, M1 and M2 transitions among the lowest 25 levels of the above five ions. Collision strengths have been averaged over a Maxwellian velocity distribution, and the effective collision strengths so obtained are reported over a wide temperature range below 10(7) K. Additionally, lifetimes are also given for all the calculated energy levels of the above five ions.