Magnetic and conducting composites of cobalt ferrite nanorods in a polyaniline matrix

Composites of cobalt ferrite nanorods in a polyaniline matrix have been synthesized and characterized by electron microscopy observation, X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, electrical conductivity, and DC magnetization measurements. The composites were prepared using dodecylbenzenesulphonic acid both as a particle protector and as acid media. In the magnetic experiments, hysteresis loops were observed, revealing ferromagnetism for both particles and composites. The results indicate that the magnetic properties of the particles were preserved in the composites, and on the other hand, the conductivity was almost independent on the polymer/particle ratio. These composites are new materials that show easily tunable magnetic properties, and are expected to be candidates for applications such as microwave shields. POLYM. ENG. SCI., 60:597–606, 2020.Fil: García Saggion, Nicolás Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Antonel, Paula Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Molina, Fernando Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Scientific method applied to failure analysis on engineering components.

Trabajo presentado en el 13º International Congress of Science and Technology of Metallurgy of Materials, SAM - CONAMET 2013. Puerto Iguazú, Misiones. 2013Shank adapters or start bars are slim parts of hardened steel used in rock drilling hammers for the mining industry. This extreme type of work occasionally generates premature failures to the bar because of the heavy-duty working conditions.In the present case, we will analyze the study of a bar, which has fractured suddenly and prematurely near the center of the piece. We are looking for an accurate method to detect the causes responsible for the problem applying the Scientific Method as a strategic tool to perform each of the steps in an orderly manner, without risking possible solutions prematurely or discarding hypotheses that seem unlikely at first sight.It has been performed a detailed study including part design, material, and working conditions, considering all possible combinations of cause and effect that may influence the final result, and considering the same using a Pareto analysis.http://www.sciencedirect.com/science/article/pii/S2211812815000565Fil: Masriera, Lucio. Universidad Católica de Córdoba. Facultad de Ingeniería; ArgentinaFil: Fernández, Marcos. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Marani, Juan. Universidad Católica de Córdoba. Facultad de Ingeniería; ArgentinaFil: Antonel, Gianfranco. Universidad Católica de Córdoba. Facultad de Ingeniería; ArgentinaFil: Acosta, Claudio. Universidad Nacional de Córdoba. Facultad de Arquitectura, Urbanismo y Diseño; ArgentinaFil: Halabí, Jorge. Universidad Católica de Córdoba. Facultad de Ingeniería; ArgentinaOtras Ingeniería de los Materiale

Composites of Poly(3,4-ethylenedioxythiophene) and CoFe2O4 Nanoparticles: Composition Influence on Structural, Electrical, and Magnetic Properties

Composites of magnetic CoFe2O4 nanoparticles (MNP) in a poly(3,4-ethylenedioxythiophene) matrix at different ratios have been synthesized. Composites were characterized by electron microscopy, X-ray diffraction, thermal analysis, electrical conductivity, magnetization, and magnetoresistance studies. In the composites the MNP appear clustered, with an interparticle distance essentially constant, but where two regimes are distinguished for cluster separation: for high MNP concentrations an intercluster separation similar to the interparticle distance is found, while for low MNP contents the distance between clusters is larger than the interparticle separation. The electrical conductivity increases with polymer content, but being always far lower than general effective medium theory expectations. This indicates that the effect of MNP effect on polymer conduction is probably related to the generation of mechanical stress both by introducing additional scattering centers and by producing different arrangement of the polymer chains, compared with the pure PEDOT. The magnetization studies reveal the existence of the RKKY interaction, which couples ferromagnetically the MNP located in a cluster, while the dipolar interaction dominates the interaction between clusters. Magnetoresistance was studied for these composites, with a maximum value close to 0.7% at 0.7 T for the lowest polymer content. The magnetoresistance correlates very well with the reversible part of the magnetization, indicating that its possible origin should be associated with polymer mechanical deformation due to the magnetic-field-induced rotation of the MNP.Fil: Lanús Mendez Elizalde, Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Acha, Carlos Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Molina, Fernando Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Antonel, Paula Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin

Facilitadores y Obstaculizadores que Presentan las Familias de Acogimiento

Trabajo de Integración Final de las Prácticas Pre Profesionales del Contexto Jurídico de la Facultad de Psicología, Universidad Nacional de Córdoba, realizado en la Dirección de Fortalecimiento Familiar, de la Ciudad de Córdoba, en el año 2015. Objetivos: Los objetivos generales apuntaron a identificar los facilitadores u obstaculizadores que presentan las familias de acogimiento (FA) en relación al derecho a revinculación de niños, niñas y adolescentes (NNyA) bajo medida excepcional con su familia de origen, extensa o comunitaria (centro de vida); y determinar el rol del psicólogo en el programa Familias para Familias en relación a dicha revinculación. Metodología: Como técnicas de recolección de datos se utilizaron observación no participante, revisión de expedientes, y entrevistas a profesionales. La muestra estuvo conformada por casos de NNyA que ingresaron entre Junio 2014 y Junio 2015, que se encontraban en una FA, y que realizaban revinculación con algún miembro de su familia de origen, extensa o comunitaria, con el fin de lograr su restitución al centro de vida. Resultados y discusión: Los principales facilitadores que presentan las FA en relación a la revinculación de NNyA son la claridad en su función, y el cumplimiento de la misma; mientras que con respecto a los obstaculizadores, se destacaron el deseo de adopción, y los prejuicios hacia la familia de origen, los cuales influirían en la función de las FA. Respecto al rol del psicólogo/a, se destacó su importancia como quien sostiene, guía y acompaña a las FA, remarcando el trabajo interdisciplinario y en red

Evaluation of Management Routes for the Paldiski Sarcophagi

The necessity to develop the submarine fleet in Russia required constructing a special training base for the training of submarine crews. To this purpose two prototypes of nuclear power units, close analogous to those fitting out nuclear submarines were constructed and commissioned in the sixties on the Navy training centre's base located in Paldiski (Pakri peninsula, Estonia). In 1994, nuclear fuel was discharged from the reactors and transported to Russia while the reactors themselves were prepared for prolonged storage, prior to transfer of the Paldiski facilities to the ownership of the Estonian Republic. The Paldiski facilities are currently being dismantled with the exception of two sarcophagi made of concrete that are housing the two reactor compartments. The question of the future management of both sarcophagi is a key-issue in the cleaning up of the whole Paldiski site. Actually, three basic questions should answered: when should dismantling operations occur, how this should be done, and what could be the corresponding cost. Within the context of enlargement of the European Union, the Commission services (first Directorate-General for Environment and then Directorate-General for Enlargement) decided to support Estonia to respond to these three questions through a study contract that was awarded in 1999 to a TECHNICATOME/BNFL consortium. The work scope was made up of three distinct tasks: data collection regarding the nuclear reactors and enclosing compartments design, and the works carried in order to prepare the reactor compartments for long-term storage; drawing up dismantling strategies in order to reach the third decommissioning level defined by IAEA; and evaluation of these decommissioning options on the basis cost estimation and radiological impact evaluation, in view to recommend the best management route. This article gives the key stages and the conclusions of this study

The phytosanitary status of the National Collection of fruits and nuts of Afghanistan and the private Mother Stock Nurseries: a virus survey

The horticultural industry is a vital component of the agriculture sector of Afghanistan, the primary engine of the country’s recovering economy which engages approximately 80% of the working population. This sector was thriving in the 1970s, but is today incapable of competing in the international market. To recover and develop the horticulture of the country, the European Community (EC) supports the PHDP (Perennial Horticulture Development Project), to provide true to type/ecotype and healthy planting materials, and the Plant Biotechnology Laboratory, to ensure the health status of local germplasm. This laboratory started screening the health status of the Afghan Germplasm National Collections in order to ensure the multiplication of not only the best-selected varieties or ecotype, but also to avoid production and distribution of virus-infected trees. Inspection for symptoms and sample collection for viral diseases was carried out in all the National Collection fields, including cherry, pear, peach, plum, apricot, almond, apple, grape and citrus plants, located in different areas of the country. Stone fruit plants infected by Apple chlorotic leaf spot virus or Prunus necrotic ringspot virus have been identified in the National Collection experimental farms located in different provinces of Afghanistan. Moreover, many grape plants included in the National Collection located in Herat and Kandahar resulted infected by Grapevine fanleaf virus, but only few imported plants by Grapevine leafroll associated virus 1, Grapevine leafroll associated virus 3 or Grapevine virus A. Finally, in Jalalabad (Nangarhar province) citrus plants showing vein flecking, yellowing and plant decline symptoms were found to be infected by Citrus tristeza virus. Some of the identified viral isolates have been characterized molecularly, amplifying a fragment corresponding to the coat protein gene from a selection of positive samples. The presence of those viruses in different accessions of the national collection is of concern for Afghan horticulture. Implementation of the certification schemes is therefore necessary to quarantine the production and for the employment of virus-free propagating material

Magnetic and elastic anisotropy in magnetorheological elastomers using nickel-based nanoparticles and nanochains

Nickel (Ni) based nanoparticles and nanochains were incorporated as fillers in polydimethylsiloxane (PDMS) elastomers and then these mixtures were thermally cured in the presence of a uniform magnetic field. In this way, macroscopically structured-anisotropic PDMS-Ni based magnetorheological composites were obtained with the formation of pseudo-chains-like structures (referred as needles) oriented in the direction of the applied magnetic field when curing. Nanoparticles were synthesized at room temperature, under air ambient atmosphere (open air, atmospheric pressure) and then calcined at 400 °C (in air atmosphere also). The size distribution was obtained by fitting SAXS experiments with a polydisperse hard spheres model and a Schulz-Zimm distribution, obtaining a size distribution centered at (10.0 - 0.6) nm with polydispersivity given by sigma= (8.0 ± 0.2) nm. The SAXS, XRD and TEM experiments are consistent with single crystal nanoparticles of spherical shape (average particle diameter obtained by TEM: (12 ± 1) nm). Nickel-based nanochains (average diameter: 360 nm; average length: 3 mm, obtained by SEM; aspect ratio=length/diameter ~10) were obtained at 85 ºC and ambient atmosphere (open air, atmospheric pressure). The magnetic properties of Ni-based nanoparticles and nanochains at room temperature are compared and discussed in terms of surface and size effects. Both Ni-based nanoparticles and nanochains were used as fillers for obtaining the PDMS structured magnetorheological composites, observing the presence of oriented needles. Magnetization curves, ferromagnetic resonance spectra (FMR) and strain-stress curves of low filler´s loading composites (2% w/w of fillers) were determined as functions of the relative orientation respect to the needles. The results indicate that even at low loadings it is possible to obtain magnetorheological composites with anisotropic properties, with larger anisotropy when using nanochains. For instance, the magnetic remanence, the FMR-resonance field and the elastic response to compression are higher when measured parallel to the needles (about 30% with nanochains as fillers). Analogously, the elastic response is also anisotropic, with larger anisotropy when using nanochains as fillers. Therefore, all experiments performed confirm the high potential of nickel nanochains to induce anisotropic effects in magnetorheological materials.Fil: Landa, Romina Ailín. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Química Física de los Materiales del Medioambiente y Energía; Argentina;Fil: P Soledad Antonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Química Física de los Materiales del Medioambiente y Energía; Argentina;Fil: Mariano M. Ruiz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Química Física de los Materiales del Medioambiente y Energía; Argentina;Fil: Oscar E Pérez. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Industrias;Fil: Alejandro Butera. Comisión Nacional de Energía Atómica;Fil: Guillermo Jorge. Universidad Nacional de General Sarmiento;Fil: Cristiano L. P. Oliveira. Instituto de Física, Universidade De São Paulo; Brasil;Fil: Martín Negri. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Industrias

The physiological variability of channel density in hippocampal CA1 pyramidal cells and interneurons explored using a unified data-driven modeling workflow

Every neuron is part of a network, exerting its function by transforming multiple spatiotemporal synaptic input patterns into a single spiking output. This function is specified by the particular shape and passive electrical properties of the neuronal membrane, and the composition and spatial distribution of ion channels across its processes. For a variety of physiological or pathological reasons, the intrinsic input/output function may change during a neuron’s lifetime. This process results in high variability in the peak specific conductance of ion channels in individual neurons. The mechanisms responsible for this variability are not well understood, although there are clear indications from experiment and modeling that degeneracy and correlation among multiple channels may be involved. Here, we studied this issue in biophysical models of hippocampal CA1 pyramidal neurons and interneurons. Using a unified data-driven simulation workflow and starting from a set of experimental recordings and morphological reconstructions obtained from rats, we built and analyzed several ensembles of morphologically and biophysically accurate single cell models with intrinsic electrophysiological properties consistent with experimental findings. The results suggest that the set of conductances expressed in any given hippocampal neuron may be considered as belonging to two groups: one subset is responsible for the major characteristics of the firing behavior in each population and the other responsible for a robust degeneracy. Analysis of the model neurons suggests several experimentally testable predictions related to the combination and relative proportion of the different conductances that should be expressed on the membrane of different types of neurons for them to fulfill their role in the hippocampus circuitry

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