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The low-energy emulsification method Emulsion Inversion Point (EIP) was used to prepare O/W nano-emulsions in the W/potassium oleate-oleic acid-C(12)E(10)/hexadecane ionic system. This method had not practically been used in ionic systems up to now. The resulting droplet sizes, much smaller than those obtained with the high-energy emulsification methods, depend on the composition (formulation variables) and preparation variables (addition and mixing rate). Phase diagrams, rheology measurements, and experimental designs applied to nano-emulsion droplet sizes obtained were combined to study the formation of these nano-emulsions. To obtain small droplet sizes, it is necessary to cross a direct cubic liquid crystal phase along the emulsification path, and it is also crucial to remain in this phase long enough to incorporate all of the oil into the liquid crystal. When nano-emulsion forms, the oil is already intimately mixed with all of the components, and it only has to be redistributed. Results show that the smaller droplet sizes are obtained when the liquid crystal zone is wide and extends to high water content, because in this case, during the emulsification process, the system remains long enough in the liquid crystal phase to allow the incorporation of all of the oil. Around the optimal formulation variables, the liquid crystal zone crossed during emulsification is wide enough to incorporate all of the oil whatever mixing or stirring rate is used, and then the resulting droplet size is independent of preparation variables. However, when the composition is far from this optimum, the liquid crystal zone becomes narrower and the mixing of components controls the nano-emulsion formation. High agitation rates and/or low addition rates are required to ensure the dissolution of all of the oil into this phase.

En el presente trabajo se discute acerca de la construcción de la competencia lectora y se examinan las relaciones existentes entre dicha competencia y el aprendizaje. Se asume que una concepción amplia y compleja de la lectura tiene mayores posibilidades de lograr una plena alfabetización (social e individual) que una representación más restringida y simple. Esta –la concepción simple– tiende a considerar que leer es una habilidad que se adquiere en un periodo concreto de la vida y que se aplica indistintamente a diversos textos y situaciones. Contrariamente a esta postura, se argumenta que la apropiación y el uso de la lectura en las sociedades letradas se inician muy pronto y no se acaban nunca, pues siempre es posible profundizar en la competencia lectora. Esta posición conlleva aceptar los cambios profundos que, por el impacto de las diversas situaciones y usos de la lectura en las que las personas nos vemos implicadas, se producen en la forma de ser lector a lo largo de la vida. En estas situaciones, gracias al concurso de otros, se pueden aprender las estrategias que permiten ir más allá de la lectura superficial, y posibilitan una lectura profunda, crítica, capaz de transformar la información en conocimiento. Se revisan algunos datos proporcionados por estudios internacionales de evaluación, así como las conclusiones de trabajos de investigación, que en conjunto ponen de manifiesto que la enseñanza y el aprendizaje de esta forma de lectura es menos frecuente de lo que cabría desear. Se concluye argumentando la necesidad de proyectos sociales y de centro dirigidos a fomentarla.

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The production of written syntheses, which requires reading various sources and integrating information from these sources into one's own text, has been characterised as a potentially useful task for promoting constructive learning. This article describes research aimed at examining and characterising written syntheses and the processes involved in producing them.A case study was carried out of 45 students from four different educational levels (ranging from secondary school to university) performing synthesis tasks set by their teachers. An analysis was made of the synthesis tasks set and the syntheses produced, the prototypical procedures carried out at each educational level, and the quality of the written products.The results corroborate the view that producing syntheses is difficult even for university students with a high degree of reading and writing competence. They also show that the difficulty level of the texts and tasks set by the teachers is generally high and that this difficulty increases as students go up the educational ladder. It was found that the younger students adopted more sequential procedures, whereas more experienced students employed more recursive approaches. It was concluded that there is a need to teach students the epistemic uses of reading and writing.

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