Compositos elaborados con resina de reciclo y fibras de desecho: propiedades mecánicas y evaluación de la constante dieléctrica

Se presentan los efectos de la radiación gamma en las propiedades fisicoquímicas y dieléctricas de materiales compuestos de resina de poliéster de desecho y de celulosa de reciclo de envases de Tetra Pak. Se modifican las propiedades fisicoquímicas de resina poliéster de desecho y de la celulosa de reciclo de envases de Tetra Pak, con lo cual es posible obtener un material compuesto con incremento en las propiedades mecánicas y estudio de la constante dieléctrica

Massive star formation in Wolf-Rayet galaxies. IV: Colours, chemical composition analysis and metallicity-luminosity relations

(Abridged) We performed a multiwavelength analysis of a sample of starburst galaxies that show the presence of a substantial population of very young massive (WR) stars. Here we present the global analysis of the derived photometric and chemical properties. We compare optical/NIR colours and the physical properties (reddening coefficient, equivalent widths of the emission and underlying absorption lines, ionization degree, electron density, and electron temperature) and chemical properties with previous observations and galaxy evolution models. Attending to their absolute B-magnitude many of them are not dwarf galaxies, but they should be during their quiescent phase. We found that both C(Hb) and Wabs increase with increasing metallicity. We detected a high N/O ratio in objects showing strong WR features. The ejecta of the WR stars may be the origin of the N enrichment in these galaxies. We compared the abundances provided by the direct method with those obtained using empirical calibrations, finding that (i) the Pilyugin method is the best suitable empirical calibration, (ii) the relations between the oxygen abundance and the N2 or the O3N2 parameters provided by Pettini & Pagel (2004) give acceptable results for objects with 12+log(O/H)>8.0, and (iii) the results provided by empirical calibrations based on photoionization models are systematically 0.2-0.3 dex higher than the values derived from the direct method. The O and N abundances and the N/O ratios are related to the optical/NIR luminosity; the dispersion is consequence of the differences in the star-formation histories. Galaxies with redder colours tend to have higher oxygen and nitrogen abundances. Our detailed analysis is fundamental to understand the nature of galaxies showing strong starbursts, as well as to know their star formation history and the relationships with the environment.Comment: 30 pages, 22 figures, accepted to A&A. Updated with the final version

Curriculum reform based on the development of scientific competences: controversies in teachers’ opinions

This paper examines certain controversies among a group of secondary education science teachers with regard to the teacher’s role and his/her professional environment, their views being gathered following a training programme aimed at introducing a key competences approach into the Spanish science curriculum. During the programme they were required to design, implement, and assess their own teaching unit for developing students’ scientific competences by means of context-based learning. At the end of the programme a representative group of teachers were selected to take part in a focus group in which they discussed the training received and its transferability to the classroom. Their statements were then analysed and categorised in order to identify factors associated with their professional environment (at the level of both school and the wider education system) and the implications they had for classroom practice. The present study focuses on those aspects which generated controversy among the teachers, specifically as regards whether they were seen as facilitating or as an obstacle to the teaching of science via a competence-based approach. The issues of controversy related to the following topics: the approach to teaching, the content to be taught, the views of and coordination with colleagues, the utility of contexts and the need for reflection on one’s own practice. The paper concludes by considering potential reasons for these issues of controversy and the implications they have for a competence-based approach to teaching.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.I+D Excelencia project EDU2013-41952-

Divesting power

We study alternative market power mitigation measures in a model where a dominant producer faces a competitive fringe with the same cost structure. We characterise the asset divestment by the dominant firm which achieves the greatest reduction in prices. This divestment entails the sale of marginal assets whose cost range encompasses the post-divestment price. A divestment of this type can be several times more effective in reducing prices than divestments of baseload (or low-cost) assets. We also establish that financial contracts (modeled as Virtual Power Plant schemes) are at best equivalent to baseload divestments in terms of consumer welfare.Divestments; Virtual power plants; contracts; market power; electricity; antitrust remedies;

The distribution of Mexico's public spending on education

Research shows that education has played a crucial role in raising levels of earnings and that returns to education in Mexico have increased, particularly in higher education and in the upper tail of the conditional earnings distribution. The authors examine patterns of public spending on education in the face of further increases in earnings inequality. They analyze the incidence of benefits using two sets of data: data on unit costs per student by state and by education level, and data from surveys on household income and spending. Among their findings: Nationally, the poorest income groups get most of the national and state subsidy for primary education. At higher education levels the poor get progressively smaller subsidies. For all Mexico, government spending on primary education is very progressive. In lower secondary education it is neutral. And in upper secondary education it benefits mainly the middle and upper classes. Tertiary education is strongly regressive, benefiting mainly the richest deciles and mainly in urban areas. But those government patterns vary by region. In the central region average total spending is more uniformly distributed than the national pattern. In the northern region the subsidy is progressive. Primary education is neutral and higher levels of instruction are moderately regressive. In the central region primary schooling is very progressive, while lower secondary schooling is almost neutral. Upper secondary and tertiary instruction strongly benefit the richest income deciles. In the southern region basic (primary and lower secondary) education is very progressive, upper secondary education is neutral, and tertiary education is highly regressive. In Mexico City all levels of education except primary are stronglyregressive. The authors show that public spending at the tertiary level is more regressive than household spending. So much of public spending on tertiary education favors non-poor families in urban areas that to reallocate the spending so that poor students have a chance to participate would require developing credit markets for higher education. The government's role should be to help overcome market failures in the financial sector, which limit the availability of long-term financing for higher education. These failures can be corrected through student loan programs or means-tested financial aid and scholarship programs. Such programs are rarely devoid of subsidy but are preferable to the direct, cost-free provision of services because the subsidy is targeted more closely to the source of market failure.Curriculum&Instruction,Decentralization,Primary Education,Teaching and Learning,Environmental Economics&Policies,Curriculum&Instruction,Teaching and Learning,Primary Education,Gender and Education,Health Monitoring&Evaluation