A Be star with a low nitrogen abundance in the SMC cluster NGC330

High- resolution UVES/ VLT spectra of B 12, an extreme pole- on Be star in the SMC cluster NGC 330, have been analysed using non-LTE model atmospheres to obtain its chemical composition relative to the SMC standard star AV304. We find a general underabundance of metals which can be understood in terms of an extra contribution to the stellar continuum due to emission from a disk which we estimate to be at the similar to 25% level. When this is corrected for, the nitrogen abundance for B12 shows no evidence of enhancement by rotational mixing as has been found in other non-Be B-type stars in NGC 330, and is inconsistent with evolutionary models which include the effects of rotational mixing. A second Be star, NGC330-B 17, is also shown to have no detectable nitrogen lines. Possible explanations for the lack of rotational mixing in these rapidly rotating stars are discussed, one promising solution being the possibility that magnetic fields might inhibit rotational mixing.

Escape times for rigid Brownian rotators in a bistable potential from the time evolution of the Green function and the characteristic time of the probability evolution

The greatest relaxation time for an assembly of three- dimensional rigid rotators in an axially symmetric bistable potential is obtained exactly in terms of continued fractions as a sum of the zero frequency decay functions (averages of the Legendre polynomials) of the system. This is accomplished by studying the entire time evolution of the Green function (transition probability) by expanding the time dependent distribution as a Fourier series and proceeding to the zero frequency limit of the Laplace transform of that distribution. The procedure is entirely analogous to the calculation of the characteristic time of the probability evolution (the integral of the configuration space probability density function with respect to the position co-ordinate) for a particle undergoing translational diffusion in a potential; a concept originally used by Malakhov and Pankratov (Physica A 229 (1996) 109). This procedure allowed them to obtain exact solutions of the Kramers one-dimensional translational escape rate problem for piecewise parabolic potentials. The solution was accomplished by posing the problem in terms of the appropriate Sturm-Liouville equation which could be solved in terms of the parabolic cylinder functions. The method (as applied to rotational problems and posed in terms of recurrence relations for the decay functions, i.e., the Brinkman approach c.f. Blomberg, Physica A 86 (1977) 49, as opposed to the Sturm-Liouville one) demonstrates clearly that the greatest relaxation time unlike the integral relaxation time which is governed by a single decay function (albeit coupled to all the others in non-linear fashion via the underlying recurrence relation) is governed by a sum of decay functions. The method is easily generalized to multidimensional state spaces by matrix continued fraction methods allowing one to treat non-axially symmetric potentials, where the distribution function is governed by two state variables. (C) 2001 Elsevier Science B.V. All rights reserved.

El Buen Vivir como alternativa al desarrollo. Algunas reflexiones económicas y no tan económicas

El texto parte de una crítica a cómo los países colonizadores han usado los fantasmas del “desarrollo” y del “progreso” para dominar a los que consideraban países “atrasados”. En el debate del post-desarrollismo se recoge el Buen Vivir como una alternativa al desarrollo, no como una alternativa de desarrollo. El Buen vivir como practicas vivenciales de resistencia al colonialismo, y como una categoría central de los pueblos indígenas, pero no como una visión única. Su importancia toma cuerpo en varias Constituciones por que los límites bio-físicos de la naturaleza están siendo superados. Por esto es necesaria una nueva economía que respete los “derechos de la naturaleza”. Se relatan los diversos componentes que esta nueva economía puede tener para una transición paciente hacia el Buen Vivir.

Density functional/Monte Carlo study of ring-opening polymerization

Density functional calculations of the structure, potential energy surface and reactivity for organic systems closely related to bisphenol-A-polycarbonate (BPA-PC) provide the basis for a model describing the ring-opening polymerization of its cyclic oligomers by nucleophilic molecules. Monte Carlo simulations using this model show a strong tendency to polymerize that is increased by increasing density and temperature, and is greater in 3D than in 2D. Entropy in the distribution of inter-particle bonds is the driving force for chain formation. (C) 2002 Elsevier Science B.V. All rights reserved.

Anisotropic optical properties of arrays of gold nanorods embedded in alumina

A series of thin films comprising gold nanorods embedded in an alumina matrix have been fabricated with lengths ranging from 75 to 330 nm. Their optical properties, expressed in terms of extinction - In(T), where T is optical transmittance, have been measured as a function of wavelength, rod length, angle of incidence, and incident polarization state. The results are compared to a Maxwell-Garnett based theory modified to take into account the strongly anisotropic nature of the medium. Transverse and longitudinal plasmon resonances are observed. The interaction between the nanorods leads to the splitting of the longitudinal resonance with the longer-wavelength resonance being forbidden for direct optical observations. The shorter-wavelength resonance related to the symmetric coupling between longitudinal plasma excitations in the nanorods depends on rod length, polarization state, and angle of incidence of the probing light. The impact of electron confinement on the optical properties of the gold rods is also seen and may be incorporated into the Maxwell-Garnett theory by restricting the mean free path of the conduction electrons to produce excellent agreement between observations and the complete theory. Annealing experiments that modify the physical structure of the gold confirm this conclusion.

Non-agrocultural co-peratives and economy transformation in Cuba: politic processes and strategies

Contribution of co-operatives has been demonstrated since the 1970s as the main development line in agricultural production in Cuba. In contrast, there has been a late recognition of urban co-operatives, even if the need of transformations based on the realization of property in different territorial scenarios had been identified. The article analyses the reform processes launched since the first decade of the 21st century focusing on the nature of the initiatives fostering formation and promotion of nonagricultural co-operatives including follow up of their performance. The potential and limitations of the recent experiences are examined in order to reflect on the organizational processes and transformations from the point of view of their members. To conclude, some questions are posed about whether these co-operatives are capable of avoiding the impact of earlier employment circumstances and of developing strategies aimed at reinforcing voluntary membership and autonomy on which they are founded.

Cooperativism, entrepreneurship and economic development: a linking theoretical model

Cooperatives, as a kind of firms, are considered by many scholars as an remarkable alternative for overcoming the economic crisis started in 2008. Besides, there are other scholars which pointed out the important role that these firms play in the regional economic development. Nevertheless, when one examines the economic literature on cooperatives, it is detected that this kind of firms is mainly studied starting from the point of view of their own characteristics and particularities of participation and solidarity. In this sense, following a different analysis framework, this article proposes a theoretical model in order to explain the behavior of cooperatives based on the entrepreneurship theory with the aim of increasing the knowledge about this kind of firms and, more specifically, their contribution to regional economic development.

Determining factors of the innovative behavior of cooperatives: an analysis of the case of Castilla y León

Cooperatives have a long historical experience in the Spanish economy and have demonstrated their ability to compete against traditional firms in the market. To maintain this capability, while taking advantage of the competitive advantages associated with their idiosyncrasies as social economy enterprises, they should take into consideration that the economy is increasingly globalized and increasingly knowledge-based, especially with regards to technological content. As a consequence, the innovative capacity appears to be a key aspect in order to be able to challenge competitors. This article characterizes the innovative behavior of cooperatives in the region of Castile and Leon and analyses the internal and external factors affecting their innovative performance, based on data from a survey of 581 cooperatives. The results of the empirical analysis, which is performed by multivariate binary logistic regression on various types of innovation, lead us to identify the size of the organizations, the existence of planning, the R & D activities and the human capital as the main determining factors.

Reading of audiovisual productions of contemporary art in art education

This article focuses on the reading of audiovisual productions of contemporary art as a creative process, seeking to analyse which effects of meaning the articulations between the visual and sound systems produce, and the meaning that children give to then. It describes a video art, identifying the languages that compose it and the relationships that link them. Such reading exercise had as corpus of analysis the Chair video art, by Masaru Ozaki, and counted with the theoretical and methodological support of the discourse semiotics, especially with studies on assembly procedures that articulate visual and auditory languages. Also, it presents a focal study with the meanings that a group of children gave to the video art. The findings indicate the importance of including the reading of audiovisual productions of contemporary art at school through the problematization of effects of meaning produced by the interrelation between different languages. And they suggest some subsidies that allow teachers from different areas of knowledge to reflect about the visuality in their pedagogical practice; the choice of the audiovisual materials taken to the classroom and other ways of seeing these texts edited.

El razonamiento moral como elemento constitutivo de la competencia ética: dilemas reales e hipotéticos en profesores de educación secundaria en México

El objetivo del presente texto es la indagación del razonamiento moral en los profesores de secundaria como un elemento de la competencia ética. Se realizó con dilemas morales hipotéticos (analizados y probados previamente para su validación y cuya fiabilidad se obtuvo a través del alfa de Cronbach) y con dilemas reales. Se aplicó a 264 profesores, miembros de la comunidad académica de la Escuela Normal Superior de Michoacán, México. Se analizó a través del programa estadístico Aquad 6. Entre los descubrimientos se encuentra una presencia mayoritaria de conflictos entre las normas éticas interpersonales con las normas de conformidad social y con las normas institucionales particulares. También que la justicia y la protección contra daños a los alumnos son valores presentes en los dilemas reales y una prevalencia en el razonamiento convencional de los profesores

¡Abre los ojos! Un proyecto de mejora educativa para la prevención de drogas en adolescentes

La Educación para la Salud (EpS) es un tema transversal del currículo que adolece de propuestas didácticas novedosas para la intervención pedagógica. El objetivo del trabajo que se presenta es poner en marcha un plan de mejora para la prevención de drogadicciones en adolescentes. Para ello, se ha trabajado con un total de 142 estudiantes de 3º de Educación Secundaria Obligatoria (ESO) con edades comprendidas entre los 14 y los 16 años que cursan estudios en el Instituto “Francisco Salzillo” de la localidad de Alcantarilla (Murcia). Concretamente, este artículo da luz al Proyecto ¡Abre los ojos!, que forma parte del Plan de Acción Tutorial (PAT) y del Plan de Mejora para la Prevención de Drogas (PMPD) propuesto desde el Departamento de Orientación. Se exponen ad hoc las actividades implementadas durante las 3 sesiones trabajadas con cada uno de los 6 grupos-clase escolarizados en este nivel. Haciendo uso de la reflexión-acción, el alumnado ha desarrollado una conciencia crítica acerca de los riesgos que entraña para la salud el consumo de drogas. Asimismo, mediante la técnica de grupos de discusión los discentes han realizado un interesante debate cuyas ideas han sido organizadas en torno a tres aspectos clave: causas por las que se empieza a consumir, cómo evitar caer en las drogas, y alternativas de ocio y tiempo libre para una vida saludable. Finalmente, se especifica la necesidad de abordar tareas de prevención en los centros educativos así como de facilitar información y de resolver las inquietudes de los jóvenes acerca de esta temática.