Glass-forming ability and soft magnetic properties of FeCoSiAlGaPCB amorphous alloys

The glass-forming ability of ( Fe x Co y B z C u ) 80 Si 3 Al 5 Ga 2 P 10 with x 5 5 – 70, y 5 0 – 63, z 5 5 – 12, and u 5 0 – 5 amorphous alloys has been analyzed in terms of the width of the supercooled liquid region, the reduced glass transition temperature, and the Vogel–Fulcher–Tammann parameters. Substitution of Fe by Co slightly decreases the glass-forming ability of the studied alloys. The value of the fragility parameter m is discussed in the frame of the general classification scheme of glass-forming liquids. The crystalline phases formed during the first crystallization step are identified. Magnetic moment at low and room temperature, Curie temperature, room temperature magnetostriction, and coercivity decrease with increasing Co content

Structural ordering and magnetic properties of arc-melted FeGa alloys

X-ray diffraction, Mössbauer spectrometry and magnetic properties have been performed on FeGa arc-melted binary alloys in order to study the compositional dependence of the structural ordering and magnetic properties of these alloys. The average magnetic hyperfine field at 300 K decreases with increasing Ga content as does the average magnetic moment per Fe atom and a linear dependence between both quantities is found for Ga content up to 20 at. %. The substitution of Fe by Ga atoms increases the lattice parameter and causes a change in the order of the crystal structure that has been modelled using a binomial distribution method. The effect of Ga atoms as near neighbours of Fe on the average magnetic hyperfine field is evaluate

What do the teachers think about the experimental activities in biology?

En este trabajo presentamos resultados acerca del estudio de las concepciones de profesores argentinos de Biología sobre las Actividades Experimentales (AE). Se buscó conceptualizar desde la epistemología, la relevancia histórico-epistemológica de articular la Biología funcional y la Biología evolutiva. El estudio se llevó a cabo desde una perspectiva cualitativa, con base en el análisis de contenido y empleando como técnica de recolección de información un cuestionario validado por expertos para indagar sobre las percepciones respecto a los núcleos temáticos considerados en las AE, los objetivos, las ventajas y las desventajas de dichas actividades. La encuesta se organizó en tres ejes y se distribuyó mediante la lista de correo de la Asociación de Docentes de Ciencias Biológicas de Argentina a profesores de nivel secundario. La muestra quedo conformada por cincuenta y seis profesores. Los resultados indican la predominancia de modelos tradicionales de enseñanza con una imagen clásica de las ciencias considerando a las AE como actividades necesarias para reforzar teoría con un corte empírico-inductivista. Un número considerable menciona obstáculos institucionales vinculados con la infraestructura disponible en los laboratorios y las condiciones laborales. Los núcleos temáticos preferidos fueron aquellos del campo de la Biología Funcional.In this work we present results about the study of the Argentinean Biology teachers' conceptions about the Experimental Activities (AE). We sought to conceptualize from epistemology, the historical-epistemological relevance of articulating Functional Biology and Evolutionary Biology. The study was carried out from a qualitative perspective, based on the content analysis and using a questionnaire validated by experts as a data collection technique to inquire about the perceptions regarding the thematic nuclei considered in the AEs, the objectives, the advantages and disadvantages of such activities. The survey was organized in three axes and was distributed through the mailing list of the Association of Teachers of Biological Sciences of Argentina to secondary level teachers. The sample was made up of fifty-six professors. The results indicate the predominance of traditional teaching models with a classical image of the sciences considering the EA as necessary activities to reinforce theory with an empirical-inductivist cut. A considerable number mention institutional obstacles linked to the infrastructure available in laboratories and working conditions. The preferred thematic nuclei were those from the field of Functional Biology.peerReviewe

Malignant hypertension and thrombopenia in renal transplant after switching from sirolimus to tacrolimus

Presentamos un caso clínico, hasta ahora no descrito, de paciente trasplantado renal que desarrolla hipertensión arterial maligna tras el cambio de sirolimus por tacrolimus. Además presentó trombopenia y anemia que como primera orientación podrían hacer pensar en un síndrome hemolítico urémico, pero la evolución del caso confirmó que todo fue debido a la hipertensión maligna.We report a case, undescribed until now, of a renal transplant patient who developed a malignant hypertension after change sirolimus by tacrolimus. Also presented thrombocytopenia and anemia as a first orientation could suggest a hemolytic uremic síndrome, but subsequent events confirmed that everythins was due to malignant hypertension

What do the teachers think about the experimental activities in biology?

En este trabajo presentamos resultados acerca del estudio de las concepciones de profesores argentinos de Biología sobre las Actividades Experimentales (AE). Se buscó conceptualizar desde la epistemología, la relevancia histórico-epistemológica de articular la Biología funcional y la Biología evolutiva. El estudio se llevó a cabo desde una perspectiva cualitativa, con base en el análisis de contenido y empleando como técnica de recolección de información un cuestionario validado por expertos para indagar sobre las percepciones respecto a los núcleos temáticos considerados en las AE, los objetivos, las ventajas y las desventajas de dichas actividades. La encuesta se organizó en tres ejes y se distribuyó mediante la lista de correo de la Asociación de Docentes de Ciencias Biológicas de Argentina a profesores de nivel secundario. La muestra quedo conformada por cincuenta y seis profesores. Los resultados indican la predominancia de modelos tradicionales de enseñanza con una imagen clásica de las ciencias considerando a las AE como actividades necesarias para reforzar teoría con un corte empírico-inductivista. Un número considerable menciona obstáculos institucionales vinculados con la infraestructura disponible en los laboratorios y las condiciones laborales. Los núcleos temáticos preferidos fueron aquellos del campo de la Biología Funcional.In this work we present results about the study of the Argentinean Biology teachers' conceptions about the Experimental Activities (AE). We sought to conceptualize from epistemology, the historical-epistemological relevance of articulating Functional Biology and Evolutionary Biology. The study was carried out from a qualitative perspective, based on the content analysis and using a questionnaire validated by experts as a data collection technique to inquire about the perceptions regarding the thematic nuclei considered in the AEs, the objectives, the advantages and disadvantages of such activities. The survey was organized in three axes and was distributed through the mailing list of the Association of Teachers of Biological Sciences of Argentina to secondary level teachers. The sample was made up of fifty-six professors. The results indicate the predominance of traditional teaching models with a classical image of the sciences considering the EA as necessary activities to reinforce theory with an empirical-inductivist cut. A considerable number mention institutional obstacles linked to the infrastructure available in laboratories and working conditions. The preferred thematic nuclei were those from the field of Functional Biology.peerReviewe

The magnetocaloric effect in soft magnetic amorphous alloys

The influence of different compositional modifications on the magnetic entropy change and refrigerant capacity of Finemet, Nanoperm, HiTperm, and bulk amorphous alloys is presented. For all the studied alloys, the field dependence of the magnetic entropy change exhibits a quadratic dependence in the paramagnetic regime, a linear dependence in the ferromagnetic temperature range, and a potential law with a field exponent 0.75 at the Curie temperature. This exponent can be explained using the critical exponents of the Curie transition. It is shown that for alloys of similar compositional series, the magnetic entropy change follows a master curve behaviorSpanish Government and EU-Feder, MAT 2004-04618PAI of Junta de Andaluci

Relationship between mechanical amorphization and boron integration during processing of FeNbB alloys

Fe75Nb10B15 alloys were prepared by mechanical alloying using different boron powders (crystalline B, commercial amorphous B, optimized amorphous B and intermetallic FeB) in the initial mixture, in order to study the boron incorporation into the Fe matrix and its influence on the amorphization of the alloys. Another composition with the same Fe/Nb ratio but whithout boron was prepared in order to differentiate between the influence of B and Nb in the evolution of microstucture and magnetic properties. Amorphization of samples was followed by X-ray diffraction and Mössbauer spectroscopy, concluding that only B-containing alloys develop an amorphous phase, while for the B-free alloy a supersaturated solid solution was observed as the final microstructure. Nb is rapidly incorporated into the matrix whereas remaining B inclusions are found at the end of the explored milling range for all B-containing samples. The amount of dissolved boron into the amorphous matrix was estimated from magnetic measurements, being the alloy prepared using FeB powder the one that most effectively dissolves this elemen