Las complicadas relaciones entre la Didáctica y las Didácticas : La construcción metodológica en la enseñanza de la gimnasia

En el presente trabajo relatamos la labor de indagación que desde hace tres años venimos realizando un equipo de profesores (un profesor de Educación Física y dos profesoras de Ciencias de la Educación) del instituto de Educación Superior Tandil. A partir de la necesidad de articular interdisciplinariamente empezamos a estudiar las relaciones entre la Didáctica General y las Didácticas de las Prácticas Gimnásticas. Asumimos que los vínculos entre estas disciplinas están basados en una cooperación constructiva, pero a medida que fuimos avanzando en el análisis de posibles articulaciones surgieron algunas tensiones, problematizaciones y sobre todo la necesidad de producir nuevos conocimientos. Tal es el caso del tema que nos ocupa en la actualidad y que se refiere específicamente a la categoría de construcción metodológica. Focalizando su estudio puntualmente en el caso de la enseñanza de gimnasia, surgieron como interrogantes y líneas de problematización las siguientes cuestiones. Si pensamos que en la gimnasia - en tanto deporte cerrado y no como práctica pedagógica - existe una ejecución motora con una técnica única ¿Implica esto asumir su enseñanza por medio de un único método? o ¿Es posible pensar en una construcción metodológica? De existir una construcción metodológica: ¿Sobre cuál de sus componentes habría que poner mayor énfasis? Sobre algunas de las respuestas a estos lineamientos trata el presente trabaj

Chemical and morphological surface modification of epoxy based thermosets

Recently developed low fluorine containing polymers are advanced materials which confer advantageous properties to surfaces at a lower cost than conventional fluoropolymers (like PTFE), and are also more easily processable. Fluoropolymer surfaces are characterized by a low surface energy, high oleo and hydrophobicity, low coefficients of friction, among many other properties. This makes them desired materials in microelectronics, antifogging, antifouling and medical applications, to name a few. Fluorinated compounds are not easily coupled with macromolecules or com-mon organic systems, and great efforts are made to compatibilize fluorinated species with hydrocarbon polymers. In this work, two chemical routes were explored in order to incorporate perfluorinated alkyl chains in an epoxy-amine based thermoset. On one side, a perfluoroalkyl thiolated molecule was used as a stabilizing ligand for silver nanoparti-cles, which were incorporated in the matrix polymer. On the other hand, fluorinated chains containing epoxy function-alities, were used as the matrix modifier. In the first case, fluorinated chains covering the nanoparticles, were mixed with the matrix, while in the second case, the fluoroalkyl chains were chemically linked to the network. Fluorine migration to the air-polymer interface was confirmed by X-Ray photoelectron spectroscopy (XPS). The ma-terials hydrophobicity was then studied in terms of their contact angle with water (CA), as a function of the surface composition and the topography. Scanning electron microscopy (SEM) and atomic force microscopy (AFM), operated in moderate and light tapping modes, were used to morphologically describe the surfaces. An exhaustive surface analy-sis was made in order to explain the different hydrophobicity grades found.Fil: Penoff, Marcela Elisabeth. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Oyanguren, Patricia Angelica. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Schreiner, Wido.Fil: Montemartini, Pablo Ezequiel. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentin

An artificial neural network (ANN) model for predicting water absorption of nanoclay-epoxy composites

Glass fiber reinforced epoxy (GFRE) composite materials are prone to suffer from water absorption due to their heterogeneous structure. The main process governing water absorption is diffusion of water molecules through the epoxy matrix. However, hydrolytic degradation may also take place during components service life specially due high temperatures. In order to mitigate the effects of the water diffusive processes in the deterioration of in-service behavior of epoxy matrix composites, the use of chemically modified nanoclays as an additive has been proposed and studied in previous works [1]. In this work, an Artificial Neural Network (ANN) model was developed for better understanding and predicting the influence of modified and unmodified bentonite addition on the water absorption behavior of epoxy-anhydride systems. An excellent correlation between model and experimental data was found. The ANN model allowed the identification of critical points like the precise temperature at which a particular system?s water uptake goes beyond a predefined threshold, or which system will resist an immersion longer than a particular time.Fil: Capiel, Guillermina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Arrosio, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Montemartini, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Morán, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Las complicadas relaciones entre la didáctica y las didácticas: la construcción metodológica en la enseñanza de la gimnasia

En el presente trabajo relatamos la labor de indagación que desde hace tres años venimos realizando un equipo de profesores (un profesor de Educación Física y dos profesoras de Ciencias de la Educación) del instituto de Educación Superior Tandil. A partir de la necesidad de articular interdisciplinariamente empezamos a estudiar las relaciones entre la Didáctica General y las Didácticas de las Prácticas Gimnásticas. Asumimos que los vínculos entre estas disciplinas están basados en una cooperación constructiva, pero a medida que fuimos avanzando en el análisis de posibles articulaciones surgieron algunas tensiones, problematizaciones y sobre todo la necesidad de producir nuevos conocimientos. Tal es el caso del tema que nos ocupa en la actualidad y que se refiere específicamente a la categoría de ¨construcción metodológica¨. Focalizando su estudio puntualmente en el caso de la enseñanza de gimnasia, surgieron como interrogantes y líneas de problematización las siguientes cuestiones. Si pensamos que en la gimnasia – en tanto deporte cerrado y no como práctica pedagógica - existe una ejecución motora con una técnica única ¿Implica esto asumir su enseñanza por medio de un único método? o ¿Es posible pensar en una construcción metodológica? De existir una construcción metodológica: ¿Sobre cuál de sus componentes habría que poner mayor énfasis? Sobre algunas de las respuestas a estos lineamientos trata el presente trabajo.Departamento de Educación Físic

Beta-endorphins during coronary angioplasty in patients with silent or symptomatic myocardial ischemia

AbstractObjectives. The aims of this study were to correlate betaendorphin plasma levels and anginal pin in patients with ischemia induced by percutaneous transluminal coronary angioplasty and to detect eventual endorphin variations during balloon occlusion.Background. The opioid system appears involved in the absence of pain occurring in silent myocardial ischemia.Methods. Beta-endorphin plasma levels were measured 24 h before, just before, during and after coronary angioplasty (performed on the left anterior descending artery) in 53 men with documented coronary artery disease and exercise-induced myocardial ischemia.Results. Group 1 (33 patients) reported symptoms; group 2 (20 patients) was asymptomatic during angioplasty. In these patients, the prevalence of exercise-induced silent ischemia was 57%. The occurrence of angina during exercise or angioplasty was related to the frequency of angina during daily life when patients were subgrouped. The severity and distribution of coronary artery disease did not differ between the two groups. During angioplasty, the number of balloon inflations and the Inflation time and pressure were similar in symptomatic and asymptomatic patients. In each group, no short-term variability of baseline betaendorphin plasma levels was observed during 2 consecutive days. Corresponding beta-endorphin plasma levels (at baseline and during and after angioplasty) were significantly in Group 2. During balloon occlusion, the levels decreased significantly in the symptomatic group at the onset of angina but remained stable in the asymptomatic group.Conclusions. Methodologic variables and the severity of coronary artery disease did not influence the presence of symptoms during angioplasty-induced ischemia. Beta-endorphin plasma levels were higher and more stable in patients with silent ischemia during angioplasty, suggesting that opiate levels and their variation during ischemia are associated with individual attitude toward anginal pain

Nutritional status and airflow obstruction: two independent contributors to CO diffusing capacity impairment in COPD

Background. The association between weight loss and Chronic Obstructive Pulmonary Disease (COPD) has been recognised from many years. Based on the evidence that nutritional status reflects metabolic disturbances in COPD, the relationship between body mass index (BMI), severity of airflow obstruction and CO diffusing capacity (DLCO), that is the functional hallmark of emphysema, is relevant to the management of COPD phenotypes. Methods. We reviewed 104 patients with COPD (82 males), aged 66±9 years (mean±SD). Height averaged 165±8 cm, weight 71±16 Kg, FEV1 50±18 (% of predicted), RV 169±49%, and DLCO 56±26%. Multiple linear regression was performed using BMI, FEV1 and RV, as explanatory variables for DLCO. Patients were also classified into four groups according to BMI ≤ 18.5 (low), > 18.5 and ≤ 25 (ideal), > 25 and ≤ 30 (overweight), > 30 (obese), and post-bronchodilator FEV1 < 50%. Using this categorisation, a two-factor analysis of variance, testing for interaction and main effects (BMI and FEV1) was performed as confirmatory analysis for the association between BMI (kg/m2), FEV1% and DLCO%. Results. FEV1 and BMI were significantly and independently associated to DLCO according to the equation: DLCO = -18.32 + 0.65·FEV1 + 1.59·BMI (R2 = 0.40, p<0.0001). The contribution of RV % to DLCO % was largely non-significant (p=0.16). A close relationship was found between BMI (kg/m2) and DLCO %, for all of the four BMI groups segregated by post-bronchodilator FEV1%, (p<.0001). No interaction was found between these two factors (p=0.30). Conclusion. Nutritional status as assessed by BMI contributes substantially to impairment of DLCO independently of the severity of airflow obstruction. This data confirms the association between emphysematous process and weight loss in advanced COPD, independent of the airflow obstruction severity

Leishmania Mitochondrial Peroxiredoxin Plays a Crucial Peroxidase-Unrelated Role during Infection: Insight into Its Novel Chaperone Activity

Two-cysteine peroxiredoxins are ubiquitous peroxidases that play various functions in cells. In Leishmania and related trypanosomatids, which lack catalase and selenium-glutathione peroxidases, the discovery of this family of enzymes provided the molecular basis for peroxide removal in these organisms. In this report the functional relevance of one of such enzymes, the mitochondrial 2-Cys peroxiredoxin (mTXNPx), was investigated along the Leishmania infantum life cycle. mTXNPx null mutants (mtxnpx−) produced by a gene replacement strategy, while indistinguishable from wild type promastigotes, were found unable to thrive in a murine model of infection. Unexpectedly, however, the avirulent phenotype of mtxnpx− was not due to lack of the peroxidase activity of mTXNPx as these behaved like controls when exposed to oxidants added exogenously or generated by macrophages during phagocytosis ex vivo. In line with this, mtxnpx− were also avirulent when inoculated into murine hosts unable to mount an effective oxidative phagocyte response (B6.p47phox−/− and B6.RAG2−/− IFN-γ−/− mice). Definitive conclusion that the peroxidase activity of mTXNPx is not required for parasite survival in mice was obtained by showing that a peroxidase-inactive version of this protein was competent in rescuing the non-infective phenotype of mtxnpx−. A novel function is thus proposed for mTXNPx, that of a molecular chaperone, which may explain the impaired infectivity of the null mutants. This premise is based on the observation that the enzyme is able to suppress the thermal aggregation of citrate synthase in vitro. Also, mtxnpx− were more sensitive than controls to a temperature shift from 25°C to 37°C, a phenotype reminiscent of organisms lacking specific chaperone genes. Collectively, the findings reported here change the paradigm which regards all trypanosomatid 2-Cys peroxiredoxins as peroxide-eliminating devices. Moreover, they demonstrate, for the first time, that these 2-Cys peroxiredoxins can be determinant for pathogenicity independently of their peroxidase activity

Branched-chain and aromatic amino acid catabolism into aroma volatiles in Cucumis melo L. fruit

The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty acids, carotenoids, amino acids, and terpenes. Although amino acids are known precursors of aroma compounds in the plant kingdom, the initial steps in the catabolism of amino acids into aroma volatiles have received little attention. Incubation of melon fruit cubes with amino acids and α-keto acids led to the enhanced formation of aroma compounds bearing the side chain of the exogenous amino or keto acid supplied. Moreover, L-[13C6]phenylalanine was also incorporated into aromatic volatile compounds. Amino acid transaminase activities extracted from the flesh of mature melon fruits converted L-isoleucine, L-leucine, L-valine, L-methionine, or L-phenylalanine into their respective α-keto acids, utilizing α-ketoglutarate as the amine acceptor. Two novel genes were isolated and characterized (CmArAT1 and CmBCAT1) encoding 45.6 kDa and 42.7 kDa proteins, respectively, that displayed aromatic and branched-chain amino acid transaminase activities, respectively, when expressed in Escherichia coli. The expression of CmBCAT1 and CmArAT1 was low in vegetative tissues, but increased in flesh and rind tissues during fruit ripening. In addition, ripe fruits of climacteric aromatic cultivars generally showed high expression of CmBCAT1 and CmArAT1 in contrast to non-climacteric non-aromatic fruits. The results presented here indicate that in melon fruit tissues, the catabolism of amino acids into aroma volatiles can initiate through a transamination mechanism, rather than decarboxylation or direct aldehyde synthesis, as has been demonstrated in other plants

Role of Δ1-Pyrroline-5-Carboxylate Dehydrogenase Supports Mitochondrial Metabolism and Host-Cell Invasion ofTrypanosoma cruzi

Proline is crucial for energizing critical events throughout the life cycle of Trypanosoma cruzi, the etiological agent of Chagas disease. The proline breakdown pathway consists of two oxidation steps, both of which producereducing equivalents as follows: the conversion of proline to Δ1-pyrroline-5-carboxylate (P5C), and the subsequent conversion of P5C to glutamate. We have identified and characterized the Δ1-pyrroline-5-carboxylate dehydrogenase from T. cruzi (TcP5CDH) and report here on how this enzyme contributes to a central metabolic pathway in this parasite. Size-exclusionchromatography, two-dimensional gel electrophoresis, and small angle x-ray scattering analysis of TcP5CDH revealed an oligomericstate composed of two subunits of six protomers. TcP5CDH was found to complement a yeast strain deficient in PUT2 activity,confirming the enzyme's functional role; and the biochemical parameters (Km, kcat, and kcat/Km) of the recombinant TcP5CDH were determined, exhibiting values comparable with those from T. cruzi lysates. In addition, TcP5CDH exhibited mitochondrial staining during the main stages of the T. cruzi life cycle. mRNA and enzymatic activity levels indicated the up-regulation (6-fold change) of TcP5CDH during the infectivestages of the parasite. The participation of P5C as an energy source was also demonstrated. Overall, we propose that thisenzymatic step is crucial for the viability of both replicative and infective forms of T. cruzi