Significados institucionales de la demostración : implicaciones para la educación matemática

In this paper the following main features of the meaning of proof in different institutional contexts, logic and foundations of mathematics, professional mathematics, experimental sciences, daily life and teaching of mathematics are analysed.This analysis suggests that the study of the epistemological and didactical problems involved in the teaching of proof in school mathematics should be carried out within the most general framework of human argumentative practices. A possible explanation for some students' cognitive conflict and difficulties with mathematical proof is the fact that at the different teaching levels and various stages of personal mathematical activity, the institutional meanings of proof are intertwined

Análisis de la introducción de los números decimales en un libro de texto

El libro de texto constituye uno de los referentes básicos para la organización de un proceso de enseñanza. Consideramos que debe ser objeto de revisión permanente para evaluar su pertinencia disciplinar y didáctica, identificar aspectos potencialmente conflictivos, y promover su adecuación a la labor de enseñanza y aprendizaje. En este artículo presentamos un análisis de una lección de un texto de matemáticas para cuarto curso de primaria, con el propósito de determinar el grado de adecuación del mismo para la introducción de los números decimales en dicho nivel escolar. El análisis de la lección, basado en un referente teórico, construido a partir de resultados de investigaciones sobre la didáctica de los números decimales, permite reflexionar sobre un uso pertinente del libro de texto

Reliability and validity of a domain-specific last 7-d sedentary time questionnaire

Purpose: The objective of this study is to examine test-retest reliability, criterion validity, and absolute agreement of a self-report, last 7-d sedentary behavior questionnaire (SIT-Q-7d), which assesses total daily sedentary time as an aggregate of sitting/lying down in five domains (meals, transportation, occupation, nonoccupational screen time, and other sedentary time). Dutch (DQ) and English (EQ) versions of the questionnaire were examined. Methods: Fifty-one Flemish adults (ages 39.4 +/- 11.1 yr) wore a thigh accelerometer (activPAL3 (TM)) and simultaneously kept a domain log for 7 d. The DQ was subsequently completed twice (median test-retest interval: 3.3 wk). Thigh-acceleration sedentary time was log annotated to create comparable domain-specific and total sedentary time variables. Four hundred two English adults (ages 49.6 +/- 7.3 yr) wore a combined accelerometer and HR monitor (Actiheart (R)) for 6 d to objectively measure total sedentary time. The EQ was subsequently completed twice (median test-retest interval: 3.4 wk). In both samples, the questionnaire reference frame overlapped with the criterion measure administration period. All participants had five or more valid days of criterion data, including one or more weekend day. Results: Test-retest reliability (intraclass correlation coefficient (95% CI)) was fair to good for total sedentary time (DQ: 0.68 (0.50-0.81); EQ: 0.53 (0.44-0.62)) and poor to excellent for domain-specific sedentary time (DQ: from 0.36 (0.10-0.57) (meals) to 0.66 (0.46-0.79) (occupation); EQ: from 0.45 (0.35-0.54) (other sedentary time) to 0.76 (0.71-0.81) (meals)). For criterion validity (Spearman rho), significant correlations were found for total sedentary time (DQ: 0.52; EQ: 0.22; all P <0.001). Compared with domain-specific criterion variables (DQ), modest-to-strong correlations were found for domain-specific sedentary time (from 0.21 (meals) to 0.76 (P < 0.001) (screen time)). The questionnaire generally overestimated sedentary time compared with criterion measures. Conclusion: The SIT-Q-7d appears to be a useful tool for ranking individuals in large-scale observational studies examining total and domain-specific sitting

Análisis epistémico y cognitivo de tareas en la formación de profesores de matemáticas

En este trabajo proponemos una herramienta de análisis epistémico/cognitivo de tareas que contribuye al desarrollo de dos tipos de conocimiento matemático para la enseñanza: conocimiento especializado del contenido y conocimiento de los estudiantes. Aplicamos la herramienta al análisis de un problema de proporcionalidad y las soluciones dadas al mismo por un grupo de estudiantes de magisterio. Concluimos con la potencial utilidad de estos análisis para la formación de profesores

Galactosemia: genotipo y fenotipo de siete pacientes

Rev Neurol. 2004 Jun 16-30;38(12):1132-5. [Galactosemia: the genotype and phenotype of seven patients]. [Article in Spanish] Martins E, Teixeira J, Cardoso ML, Lima MR, Briones-Godino P, Barbot C. SourceUnidad de Metabolismo, Hospital de Niños Maria Pia, Oporto, Portugal. [email protected] Abstract INTRODUCTION: Despite early dietary therapy, many patients with galactosemia show a neurodegenerative disease specially evident in speech impairment and movement disorders. Magnetic resonance imaging of the brain, show cerebral white matter changes with hypomielinization bilateral and symetrical periventricular hypersignal in T2. PATIENTS AND METHODS: We presented clinical and neuroradiological data of seven children (3 to 12 years of age) with classical galactosemia. All had a typical presentation in neonatal period. Two children had normal development (10 and 12 years-old), four presented developmental delay (10, 7, 4 and 3 years-old), and one showed a dystonic cerebral palsy (kernicterus). RESULTS: The brain MRI showed the typical involvement of white matter, in five children, and basal ganglia abnormalities in the kernicterus patient. Three patients are homozygous for Q188R mutation and two are compound heterozygous. CONCLUSION: We found a positive correlation among developmental delay, white matter involvement and Q188R mutation

Estudio epistémico del número π: implicaciones didácticas

La realización de un estudio documental epistemológico de la evolución de pi, nos permitió reconstruir un referente global para este número. Concretamente hemos recuperado a lo largo de su construcción científica, tipos de situaciones problemas y sistemas de prácticas en que se pone en juego este objeto. Si bien el punto de partida fue la detección de problemas que hicieran emerger algún significado de pi, interesó estudiar las técnicas, los lenguajes, las entidades conceptuales, proposicionales y argumentativas puestas en juego en cada momento y circunstancia. Los sistemas de prácticas identificados por ese conjunto de objetos permitieron estudiar y describir, desde el punto de vista epistémico, como se configuran los mencionados objetos matemáticos y poner en descubierto la complejidad epistémica de pi. Así, la construcción de un referente global permitió describir tres etapas en las que se ponen de manifiesto que pi va asumiendo diferentes estatus y características, posibilitando dar respuesta a algunos interrogantes vinculados a la enseñanza

Seagrass debris as potential food source to enhance Holothuria arguinensis' growth in aquaculture

Holothuria arguinensis aquaculture started to be developed in 2014, being the first sea cucumber species from Europe. However, some aspects of its aquaculture biotechnology, such diets, need to be assessed. This work aimed to evaluate seagrass debris of Zostera noltii and Cymodocea nodosa as food source for broodstock maintenance in tanks, during breeding periods. The given feed rations per tank were calculated as the 30% of the total sea cucumber biomass in each tank and reviewed each week. Then, feed rations of seagrass and sediment were calculated from this value, according to the following percentages: 40% sediment, 15% Z. noltii, 40% Z. noltii, 15% C. nodosa and 40% C. nodosa. H. arguinensis growth, feeding rate and nutritional value were assessed under these diets. H. arguinensis fed with 40% of Z. noltii showed the highest growth (specific growth rate = 0.09 +/- 0.06%/day, absolute growth rate = 0.11 +/- 0.07 g/day) increasing their final weight in 5.86 +/- 3.57% in 57 days. However, the individuals fed with C. nodosa showed a negative growth. H. arguinensis showed a reduction in its feeding rate as the organic matter content in the diets increased. H. arguinensis did not show any important change on proximate composition, protein, lipid, mineral contents and fatty acids profile among the feeding groups, or in comparison with the individuals collected from wild habitat. Therefore, H. arguinensis could be fed with Z. noltii debris during tanks maintenance along breeding period, ensuring its growth and maintaining its nutritional profile.Fundacao para a Ciencia e a TecnologiaPortuguese Foundation for Science and TechnologyEuropean Commission [CCMAR/SC/BI/02/2016, FRH/BD/105541/2014, IF/00049/2012, IF/00998/2014, PTDC/MAR-BIO/5948/2014, PTDC/MAR/119363/2010, SFRH/BPD/70689/2010]http://creativecommons.org/licenses/by/4.0

Rodilla flotante: Revisión retrospectiva de 24 casos

Se realiza una evaluación retrospectiva de 24 pacientes tratados de fracturas ipsilaterales de fémur y tibia. Solo en 7 (29%) casos esta lesión no se acompañaba de otras lesiones asociadas. Los resultados se han evaluado según la escala modificada de Thorensen y cols. (1985). El tipo de fractura fue muy polimorfo. Se realizó tratamiento definitivo de ambos huesos en la urgencia en 5 casos, en 7 casos se hizo tratamiento definitivo en tibia y provisional del fémur, y en 12 casos el tratamiento de urgencias fue provisional para ambas fracturas. Los resultados finales fueron buenos en 16 casos (67%), regulares en 6 (25%) y malos en 2 (8%). La estancia media de estos pacientes disminuyó, cuando se hizo tratamiento definitivo en urgencias.A retrospective evaluation of 24 patients with "floating knee" was done. Only in 7 (29%) cases this lesion was not associated to other lesions. The results have been evaluated according to the modified scale of Thorensen et al. (1985). The fracture pattern was very variable. One stage surgical treatment was carried out in 5 cases, in 7 cases definitive treatment was applied to the tibia and provisionally to the femur, and in 12 cases the treatment made in the emergency was provisional for both fractures. The final results were good in 16 cases (67%), fair in 6 (25%) and bad in 2 (8%). The length of hospital stay decreased when definitive treatment was made at once

Niveles de algebrización de la actividad matemática escolar : implicaciones para la formación de maestros

El desarrollo del razonamiento algebraico elemental desde los primeros niveles educativos es un objetivo propuesto en diversas investigaciones y orientaciones curriculares. En consecuencia, es importante que el profesor de educación primaria conozca las características del razonamiento algebraico y sea capaz de seleccionar y elaborar tareas matemáticas adecuadas que permitan la progresiva introducción del razonamiento algebraico en la escuela primaria. En este trabajo, presentamos un modelo en el que se diferencian tres niveles de razonamiento algebraico elemental que puede utilizarse para reconocer características algebraicas en la resolución de tareas matemáticas. Presentamos el modelo junto con ejemplos de actividades matemáticas, clasificadas según los distintos niveles de algebrización. Estas actividades pueden ser usadas en la formación de profesores a fin de capacitarlos para el desarrollo del sentido algebraico en sus alumnos.Developing elementary algebraic thinking since the earliest levels of education is a goal proposed in different research works and curricular guidelines. Consequently, primary school teachers should know the characteristics of algebraic reasoning and be able to select and develop appropriate mathematical tasks that serve to gradually introduce algebraic reasoning in primary school. In this paper we present a model that distinguish three levels of elementary algebraic thinking and is useful in analyzing the algebraic features in solving mathematical tasks. We describe this model with examples of mathematical activities, classified according to the different levels of algebraization. These activities can be used in the education of teachers to prepare them to develop their students' algebraic sense