Constructivismo y enseñanza de las ciencias : aplicación al estudio de la nutrición humana en Educación Secundaria Obligatoria.

Aplicación de los planteamientos del aprendizaje constructivista a la enseñanza de la nutrición humana en la enseñanza obligatoria, centrada en tres aspectos: diagnóstico de los conocimientos previos, elaboración de una propuesta de enseñanza sobre éste tema y análisis de su incidencia en el cambio conceptual de los alumnos. Plantear alternativas tendentes a la mejora de la práctica educativa, aportando algunas reflexiones relativas a la utilización del constructivismo como modelo para la enseñanza y el aprendizaje de las ciencias en los niveles obligatorios. El autor plantea cuatro hipótesis de trabajo con cuatro diseños para su contrastación y cuatro muestras diferentes. La población utilizada para realizar la exploración corresponde a aquellos niveles escolares en los que se aborda el estudio de la nutrición (sexto y octavo de EGB y primero y segundo de BUP), complementados, en algunos casos, con grupos de alumnos de Magisterio (ciencias). Elaboración de un amplio marco teórico en el que se abordan las cuestiones referidas a las bases teóricas del constructivismo y la forma en la que se contempla la enseñanza de la nutrición en el currículo de la enseñanza obligatoria; después se plantean las hipótesis de trabajo y la metodología seguida para su contrastación (instrumentos de recogida de información, entrevistas, cuestionarios, mapas conceptuales, posters, cuadernos de trabajo, informes, etc.). Recogida de información a través de distintas fases; ensayo previo, cuestionario inicial, estudio piloto y cuestionario definitivo; categorización de las respuestas; establecimiento de resultados y conclusiones. 1. La metodología empleada para explorar las concepciones de los alumnos ha resultado efectiva, particularmente para detectar esquemas y modelos conceptuales; 2. Las concepciones de los alumnos se organizan según diversos grados de articulación: concepciones puntuales, esquemas conceptuales y modelos conceptuales; 3. La enseñanza habitual no consigue que la mayoría de los alumnos lleven a cabo un aprendizaje adecuado de los conocimientos científicos objeto de estudio, predominando, la elaboración de concepciones puntuales, esquemas y modelos conceptuales que no se conrresponden con dicho conocimiento; 4. Los resultados obtenidos muestran que, en cada uno de los niveles explorados, el porcentaje de concepciones correctas es muy reducido; 5. La enseñanza basada en el modelo constructivista contribuye favorablemente a que una amplia mayoría de alumnos logre el aprendizaje de los aspectos básicos de la nutrición y construya modelos conceptuales adecuados desde el punto de vista científico; 6. El tipo de aprendizaje realizado con los alumnos, implica un proceso de modificación de los conocimientos previos que, según los casos, consisten en su reestructuración parcial o total; 7. La enseñanza basada en el constructivismo produce aprendizajes que se muestran estables a corto y medio plazo, aprendizaje de mayor calidad, influye positivamente en el interés de los estudiantes hacia las clases de ciencias; 8. La propuesta didáctica desarrollada contiene diversos elementos que favorecen el aprendizaje significativo de los aspectos fundamentales de la nutrición humana; 9. El estudio de la nutrición humana en octavo de EGB requiere el establecimiento de un nivel de diferenciación conceptual elemental y la adopción de un enfoque globalizador de la enseñanza; 10. En el contexto educativo actual, resulta viable el desarrollo de propuestas de enseñanza basadas en el constructivismo. En la medida en que la investigación se vaya consolidando, el constructivismo podrá constituirse como nuevo modelo de enseñanza, capaz de dar solución a muchos de los problemas que, en la actualidad, plantea la enseñanza-aprendizaje de las ciencias.

Motivaci??n y creatividad en la preadolescencia

Ofrecer un amplio bagaje de did??ctica de la educaci??n art??stica, englobando los temas de: motivaci??n, creatividad y preadolescencia partiendo de experiencias reales a trav??s del taller de expresi??n pl??stica. Realizar un abordaje de la adolescencia dentro del proceso de evoluci??n pl??stica del ni??o. Presentar una serie de objetivos que han de guiar la formaci??n art??stica del adolescente. Analizar las metodolog??as aplicadas a la ense??anza de las artes pl??sticas. Demostrar la aplicabilidad a un grupo de ni??os de una metodolog??a para el desarrollo de la expresi??n pl??stica basada fundamentalmente en el est??mulo . Grupo de ni??os entre los ocho y los trece a??os. Estudio longitudinal a trav??s de cuatro a??os desde 1984 hasta 1988. Se presentan una serie de propuestas de trabajo que son la estructura del estudio. Se realiza un an??lisis individualizado de cada ejecuci??n atendiendo a los criterios: ocupaci??n del campo gr??fico, texturas, utilizaci??n plena del color y sus matices, originalidad, an??lisis de elementos, influencias y estereotipos. Los ni??os preadolescentes que integraron los grupos de trabajo han mejorado sus modos de expresi??n gr??fica y pl??stica, con una mayor producci??n y calidad est??tica, sin interrumpir su desarrollo evolutivo, mejorando su nivel anal??tico y sincr??tico y, a la vez, prepar??ndose para un futuro aprendizaje de las artes.

En defensa del agua: campaña contra la privatización en Perú

El mismo gobierno que no pudo privatizar las empresas de electricidad de Arequipa en el 2002, por la enérgica resistencia de la población, y que registra los niveles de aprobación ciudadana más bajos de la historia, viene preparando ahora la privatización del agua potable. Alentado por instituciones internacionales como el Banco Mundial y el BID, que son quienes ponen los fondos para realizar interminables estudios que invariablemente demuestran la necesidad de hacer inversiones formidables que, por supuesto los Estados no pueden desarrollar, y de brindar el dinero para preparar la empresas para sus futuros propietarios privados. Nadie parece estar consciente del inmenso capital social que implican los sistemas de agua y saneamiento existentes; la cantidad de conexiones con que cuentan las ciudades grandes que se convierten en potenciales mercados cautivos de los inversionistas privados y en fuente segura de financiamiento de sus gastos; la capacidad técnica del país; y el valor de la fuentes de extracción del recurso. Como si todo esto fuera nada, los gobiernos, congresos y municipios, se proponen hacer concesiones a cargo de promesas de inversión y modernización.

Procesos: revista ecuatoriana de historia. 3 (SOLO LIBROS/Reseñas)

Presenta las reseñas de los siguientes libros: PILAR PONCE LEIVA, (INTRODUCCIÓN Y TRANSCRIPCIÓN), RELACIONES HISTÓRICO GEOGRÁFICAS DE LA AUDIENCIA DE QUITO(SIGLOS XVI-XIX), FUENTES PARA LA HISTORIA ANDINA, QUITO, MARKA-ABYA YALA, 1992, 666 PP. -- ENRIQUE AYALA MORA, EDIT., NUEVA HISTORIA. DEL ECUADOR), VOL. 12, ENSAYOS GENERALES I, QUITO, CORPORACIÓN EDITORA NACIONAL-GRI]ALBO, 1992. -- LORETO REBOLLEDO, COMUNIDAD y RESISTENCIA. EL CASO DE LUMBISÍ EN LA COLONIA, FLACSO-ABYA YALA, 1992, 321 PP. -- BERNARD LAVALLÉ, QUITO ET LA CRISE DE L'ALCABALA (1580-1600), PARÍS, CNRS, 1992, 213 PP.

Effects of host plant drought stress on the performance of the bird cherry-oat aphid, Rhopalosiphum padi (L.): a mechanistic analysis

1. The growth (increase in height and leaf number) of four grass species was reduced by a -0.5 MPa drought stress, but the performance of an associated herbivore, Rhopalosiphum padi (L.), was not affected consistently. The intrinsic rate of increase of R. padi was reduced by drought stress on three grass species, including Dactylis glomerata (L.), but was unaffected on Arrhenatherum elatius (L.). Therefore, there is no general relationship in the effect of plant drought on an insect herbivore, even among closely related host plant species. 2. Drought stress increased the quality of plant phloem sap, as indicated by increased sieve element osmotic pressure and essential amino acid concentrations. Thus, diet quality could not account for the reduced performance of R. padi under drought stress. The concentration of essential amino acids in the phloem of well-watered A. elatius was, however, lower than that of well-watered D. glomerata, correlating with the decreased performance of aphids on well-watered A. elatius. 3. There were no differences in aphid feeding duration between watering treatments or plant species but sap ingestion rates were reduced significantly under drought stress. 4. Using the measure of dietary amino acid concentrations and the estimate of sap ingestion, the essential amino acid flux through aphids was calculated. Compared with the flux through aphids feeding on well-watered D. glomerata, there was a reduction in aphids feeding on drought-stressed D. glomerata and drought-stressed A. elatius due to lower sap ingestion rates. The flux through aphids on well-watered A. elatius was also reduced due to low phloem essential amino acid concentrations. Thus, the performance of an aphid is correlated with the availability and accessibility of essential amino acids.

What is poverty? A diachronic exploration of the discourse on poverty from the 1970s to the 2000s

Poverty is central to the concept of development. However, the relevance given to particular aspects of poverty has changed over the years and with it the manner in which poverty has been represented. The following paper explores how concepts of poverty within the 'poverty discourse' have altered over a 30-year period. A diachronic analysis is performed to explore changes in the topical and thematic composition of the definitions, in addition to the manner in which poverty has been 'framed'. The results illustrated that poverty was variably framed across the decades ranging from a 'neutral' fact to a highly contested state with little agreement over causes and consequences. Nevertheless, the relational analysis revealed the de-problematization of poverty over time. The finding has clear implications for development praxis: poverty needs to be 'attacked', but the root causes, at least from a discursive perspective, may be ignored.

Neonatal mortality in puppies due to bacteremia by Streptococcus dysgalactiae subsp dysgalactiae

We report a case of bacteremia in puppies caused by Streptococcus dysgalactiae subsp. dysgalactiae. Identification was achieved by phenotypic and molecular genetic methods. This is the first report of the recovery of S. dysgalactiae subsp. dysgalactiae from dogs.

Synthesis of FimH receptor-active manno-oligosaccharides by reverse hydrolysis using alpha-mannosidases from Penicillium citrinum, Aspergillus phoenicis and almond

Recombinant Penicillium citrinum alpha-1,2-mannosidase, expressed in Aspergillus oryzae, was employed to carry out regioselective synthesis of alpha-D-mannopyranosyl-(1-->2)-D-mannose. Yields (w/w) of 16.68% disaccharide, 3.07% trisaccharide and 0.48% tetrasaccharide were obtained, with alpha1-->2 linkages present at 98.5% of the total linkages formed. Non-specific alpha-mannosidase from almond was highly efficient in reverse hydrolysis and oligosaccharide yields of 45-50% were achieved. The products of the almond mannosidase were a mixture of disaccharides (30.75%, w/w), trisaccharides (12.26%, w/w) and tetrasaccharides (1.89%, w/w) with 1-->2, 1-->3 and 1-->6 isomers. alpha-1,2-linkage specific mannosidase from P. citrinum and alpha-1,6-linkage-specific mannosidase from Aspergillus phoenicis were used in combination to hydrolyse the respective linkages from the mixture of isomers, resulting in alpha-D-mannopyranosyl-(1-->3)-D-mannose in 86.4% purity. The synthesised oligosaccharides can potentially inhibit the adhesion of pathogens by acting as 'decoys' of receptors of type-1 fimbriae carried by enterobacteria.

How active gaze informs the hand in sequential pointing movements

Visual information is vital for fast and accurate hand movements. It has been demonstrated that allowing free eye movements results in greater accuracy than when the eyes maintain centrally fixed. Three explanations as to why free gaze improves accuracy are: shifting gaze to a target allows visual feedback in guiding the hand to the target (feedback loop), shifting gaze generates ocular-proprioception which can be used to update a movement (feedback-feedforward), or efference copy could be used to direct hand movements (feedforward). In this experiment we used a double-step task and manipulated the utility of ocular-proprioceptive feedback from eye to head position by removing the second target during the saccade. We confirm the advantage of free gaze for sequential movements with a double-step pointing task and document eye-hand lead times of approximately 200 ms for both initial movements and secondary movements. The observation that participants move gaze well ahead of the current hand target dismisses foveal feedback as a major contribution. We argue for a feedforward model based on eye movement efference as the major factor in enabling accurate hand movements. The results with the double-step target task also suggest the need for some buffering of efference and ocular-proprioceptive signals to cope with the situation where the eye has moved to a location ahead of the current target for the hand movement. We estimate that this buffer period may range between 120 and 200 ms without significant impact on hand movement accuracy.

Probing the effect of allylic substitution on cyclic ammonium ylid rearrangements

The [2,3]-sigmatropic rearrangement of tetrahydropyridine-derived ammonium ylids is a valuable method for the preparation of substituted pyrrolidine carboxylates. The presence of an allylic substituent does not intrinsically reduce the yield of rearrangements, and the diastereoselectivity of rearrangement is related to the structure of the diazo reactant. The method represents a very rapid means of accessing complex pyrrolidines, as shown by preparation of a precursor to the core of lactacystin.

Effects of n-3 fatty acids on postprandial triacylglycerol and hormone concentrations in normal subjects

The present study reports results from two investigations to determine effects of a 6-week period of moderate n-3 fatty acid supplementation (2.7 g/d) on fasting and on postprandial triacylglycerol and metabolic hormone concentrations in response to standard test meals. In the first study postprandial responses were followed for 210 min after an early morning test meal challenge; in the second study responses to an evening test meal were followed during the evening and overnight for a total period of 12 h. In both studies postprandial triacylglycerol responses to the test meals were significantly reduced after compared with before fish-oil supplementation. In the second study the triacylglycerol peak response seen between 200 and 400 min in subjects studied before supplementation with fish oils was almost completely absent in the same subjects after 6 weeks of n-3 fatty acid supplementation. Analysis of fasting concentrations of metabolites and hormones was carried out on the combined data from the two studies. There were no significant differences in total, low-density-lipoprotein- or high-density-lipoprotein-cholesterol concentrations during fish-oil supplementation, although there was considerable individual variation in cholesterol responses to the supplement. Concentrations of Apo-B and Apo-A1 were unchanged during supplementation with fish oils. Fasting and early morning postprandial GIP concentrations were lower in subjects taking fish oils, possibly due to acute effects of fish-oil capsules taken on the evening before the studies. In both studies fasting insulin and glucose and postprandial insulin concentrations remained unchanged following fish-oil supplementation. The results do not support the view that triacylglycerol-lowering effects of n-3 fatty acids are due to modulation of insulin secretion mediated via the enteroinsular axis. Further studies are required to determine the precise mechanism by which fish oils reduce both fasting and postprandial triacylglycerol concentrations.

Molecular systematics of the Cactaceae

Bayesian, maximum-likelihood, and maximum-parsimony phylogenies, constructed using nucleotide sequences from the plastid gene region trnK-matK, are employed to investigate relationships within the Cactaceae. These phylogenies sample 666 plants representing 532 of the 1438 species recognized in the family. All four subfamilies, all nine tribes, and 69% of currently recognized genera of Cactaceae are sampled. We found strong support for three of the four currently recognized subfamilies, although relationships between subfamilies were not well defined. Major clades recovered within the largest subfamilies, Opuntioideae and Cactoideae, are reviewed; only three of the nine currently accepted tribes delimited within these subfamilies, the Cacteae, Rhipsalideae, and Opuntieae, are monophyletic, although the Opuntieae were recovered in only the Bayesian and maximum-likelihood analyses, not in the maximum-parsimony analysis, and more data are needed to reveal the status of the Cylindropuntieae, which may yet be monophyletic. Of the 42 genera with more than one exemplar in our study, only 17 were monophyletic; 14 of these genera were from subfamily Cactoideae and three from subfamily Opuntioideae. We present a synopsis of the status of the currently recognized genera

A note on estimating market–based minimum capital risk requirements: a multivariate GARCH approach

Internal risk management models of the kind popularized by J. P. Morgan are now used widely by the world’s most sophisticated financial institutions as a means of measuring risk. Using the returns on three of the most popular futures contracts on the London International Financial Futures Exchange, in this paper we investigate the possibility of using multivariate generalized autoregressive conditional heteroscedasticity (GARCH) models for the calculation of minimum capital risk requirements (MCRRs). We propose a method for the estimation of the value at risk of a portfolio based on a multivariate GARCH model. We find that the consideration of the correlation between the contracts can lead to more accurate, and therefore more appropriate, MCRRs compared with the values obtained from a univariate approach to the problem.