J. Martin

Local deterministic string-to-string transductions arise in natural language processing (NLP) tasks such as letter-to-sound translation or pronunciation modeling. This class of transductions is a simple generalization of morphisms of free monoids; learning local transductions is essentially the same as inference of certain monoid morphisms. However, learning even a highly restricted class of morphisms, the so-called fine morphisms, leads to intractable problems: deciding whether a hypothesized fine morphism is consistent with observations is an NP-complete problem; and maximizing classification accuracy of the even smaller class of alphabetic substitution morphisms is APX-hard. These theoretical results provide some justification for using the kinds of heuristics that are commonly used for this learning task.

Both the physiological and the pathological morphogenetic processes that we can meet in embryogenesis, neogenesis and degenerative dysgenesis present common features: they are ruled by three different kinds of mechanisms, one related to cell migration, the second to cell differentiation and the third to cell proliferation. We deal here with an application to the cambial growth which essentially involves the third type of mechanism.Woody plants produce secondary tissue (secondary xylem and phloem) from a meristematic tissue called vascular cambium, responsible for the radial growth of a tree. This paper focuses on the formation of secondary xylem, considered in two dimensions in a cross-section framework. A new discrete modelling approach is used, based on the cellular scale, in order to attain a more accurate understanding of how the elementary microscopic behaviour of each cell takes part in the macroscopic morphogenesis. The mathematical model essentially uses an occurrence method simulating the main features of radial growth with simple geometric rules, such as Thom's division rule (Thom,1972)to account for the cell proliferation. The study applies to concrete instances in which the changes made in the geometrical cellular patterns of the vascular cambium clearly affect the shape of the tree, as in Pinus radiata (D. Don.).

El Tratado de la Unión Europea firmado en Maastricht en 1992 introdujo cambios revolucionarios en las competencias de la Comunidad, pues, por vez primera, se admite que la acción de la Comunidad implicará «una contribución a una enseñanza y a una formación de calidad, así como el desarrollo de las culturas de los Estados miembros». La evolución de esta nueva situación no ha sido satisfactoria por los problemas de fondo de la Unión Europea y por las dificultades que hoy entraña toda acción verdaderamente educativa. El artículo analiza los intentos que se realizaron a partir del 1992 para introducir una profunda dimensión europea de la educación, con las implicaciones axiológicas que ello comporta, y cómo estos intentos se encontraron ante diversos obstáculos poderosos que les han reducido a un estado de hibernación. A partir de fines del 1999 se consolida una nueva tendencia funcionalista en la política de la educación europea, que ha sido refinada en estos dos años, encontrándonos ahora, por mucho que sean limitados sus horizontes, ante unas pautas de trabajo que pienso serán beneficiosas para introducir mayores cotas de racionalidad en la política educativa de los Estados miembros.