Novos materiais à base de niobato de bismuto para armazenamento de energia elétrica

O desenvolvimento de novos materiais, que permitam a redução das dimensões de componentes eletrónicos, tem sido objeto de investigação. Os cerâmicos dielétricos à base de bismuto têm sido extensivamente estudados com este objetivo, em particular o niobato de bismuto (BiNbO4). A primeira tentativa de melhorar as propriedades elétricas do BiNbO4 ocorreu em 1992, com a adição de óxidos. Este trabalho consiste na melhoria das propriedades dos cerâmicos de niobato de bismuto, usando a substituição de iões de bismuto por iões ferro e európio. Para investigar a inclusão de ferro e európio em cerâmicos de BiNbO4, (Bi1-xFex)NbO4 e (Bi1-yEuy)NbO4, as amostras foram preparadas utilizando o método sol-gel. Como a substituição dos iões de bismuto por iões de ferro foi bem sucedida, compósitos de BiNbO4-FeNbO4 foram preparados pelo método de reação do estado sólido, usando como precursores o BiNbO4 e o FeNbO4 produzidos pelo método sol-gel. A estrutura das amostras preparadas foi estudada por difração de raios X e espectroscopia de Raman e a morfologia por microscopia eletrónica de varrimento. As propriedades dielétricas foram estudadas, na gama das micro-ondas, utilizando o método da cavidade ressonante, e na gama da radiofrequências, com a técnica de espectroscopia de impedância. À frequência de 100 kHz, a amostra que apresenta as propriedades dielétricas mais promissoras pertence ao sistema (Bi1-xFex)NbO4, com x = 0.25, tratada termicamente a 1100 °C, que apresenta os valores de 166, 0.37 e 0.0022 para a constante dielétrica, perdas dielétricas e tangente de perdas, respetivamente. À frequência de 2.7 GHz, é a amostra de BiNbO4, sem qualquer substituição, tratada termicamente a 650 °C, que apresenta as propriedades dielétricas mais vantajosas, com os valores de 5, 0.01 e 0.002 para a constante dielétrica, perdas dielétricas e tangente de perdas, respetivamente. Apesar dos valores da constante dielétrica não serem particularmente elevados, salienta-se o facto das perdas dielétricas manterem valores bastante reduzidos.The development of new materials, that allow the reduction of size of electronic components, has been in the scope of the researchers. The bismuth-based dielectric ceramics are extensively studied for this propose, in particular the bismuth niobate (BiNbO4). The first attempt to improve the electric properties of BiNbO4 occurred in 1992, with the addition of oxides. This work focus in the improvement of bismuth niobate ceramics using the substitution of bismuth ions by iron and europium ions. To investigate the inclusion of iron and europium in BiNbO4 ceramics, (Bi1-xFex)NbO4 and (Bi1-yEuy)NbO4, samples were prepared using the sol-gel method. Since the substitution of bismuth ions by iron ions was successful, composites of BiNbO4-FeNbO4 were prepared by the solid state reaction method, using as precursors the BiNbO4 and FeNbO4 produced by the sol-gel method. The structure of the prepared samples was studied by X-ray diffraction and Raman spectroscopy and the morphology by scanning electron microscopy. The dielectric properties were studied, in the microwave frequency range, using the resonant cavity method, and in the radio frequency range, with the impedance spectroscopy technique. At the frequency of 100 kHz, the sample with the most promising dielectric properties belongs to the system (Bi1-xFex)NbO4, with x = 0.25, thermally treated at 1100 °C, which has the values of 166, 0.37 and 0.0022 for the dielectric constant, dielectric losses and loss tangent, respectively. At the frequency of 2.7 GHz, it is the sample of BiNbO4, without any substitution, thermally treated at 650 °C, which presents the most advantageous dielectric properties, with values of 5, 0.01 and 0.002 for the dielectric constant, dielectric losses and loss tangent, respectively. Although the values of the dielectric constant are not particularly high, it should be noted that the dielectric losses remain very low.Programa Doutoral em Engenharia Físic

Propriedades eléctricas de polímeros para aplicações industriais na banda das microondas

Mestrado em Física AplicadaO presente trabalho pretende contribuir para o desenvolvimento de uma metodologia a adoptar, no sentido de resolver um problema concreto no âmbito da optimização das propriedades eléctricas de polímeros para aplicações na banda das microondas. Foram testados vários polímeros (ABS, PBT e PP) com diferentes concentrações de cargas condutoras de “negro de fumo”. Pretende-se moldar as propriedades eléctricas daqueles materiais de modo a obter um valor mais elevado de ε’, sem aumentar demasiadamente ε’’. Com estas características podem ser aplicados como absorventes de radiação electromagnética nos fornos de microondas e como lentes em antenas dieléctricas. Construíram-se e testaram-se várias cavidades ressonantes, onde foram efectuadas medidas de transmissão. Utilizando o método das pequenas perturbações, calcularam-se os valores da permitividade complexa dos vários materiais. Aplicaram-se diferentes leis de mistura para modelar os resultados experimentais obtidos. Finalmente, concluiu-se que o politereftalato de butileno (PBT) com 2 % de cargas de “negro de fumo” é o material adequado para aquelas aplicações.The present work is a contribution to the development of a methodology to optimize the electrical properties of polymers for applications at microwave frequencies. Several polymers (ABS, PBT, PP) were studied, with different concentrations of conducting charges of carbon black. We pretended to tune the electrical properties of the materials, in order to enhance ε’, without increasing ε’’ too much. With these characteristics they can be used as electromagnetic radiation absorbers in microwave ovens as well as dielectric lenses in antennas. We have designed and tested several resonant cavities, where we made the transmition measurements. Using the small perturbation method, we calculated the complex permittivity of the materials. We used different mixture laws to fit the experimental results. Finally, we concluded that PBT with 2 % of carbon black particles is the adequate material for these kind of applications

Dielectric Properties of Bismuth Niobate Ceramics

The development of new dielectric materials that allow the reduction of size and weight of electronic components has been in the scope of the researchers. The bismuth-based dielectric ceramics are extensively studied for this purpose, namely, the bismuth niobate (BiNbO4). The first attempt to improve BiNbO4 occurred in 1992 when Kagata reported the microwave dielectric properties of bismuth niobate doped with the addition of oxides. This chapter will present a brief review of the several attempts that have been carried out to enhance the dielectric properties of BiNbO4 by modifying their structure through addition, doping, or atom(s) substitution. This manuscript focuses on a case study that involves bismuth substitution by europium ions. To investigate the inclusion of europium in BiNbO4 ceramics, (Bi1–xEux)NbO4 samples were prepared using the sol-gel method, in particular, the citrate route. The structure of the prepared samples was studied by X-ray diffraction (XRD) and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). The dielectric properties were studied, in the microwave frequency range (MW), using the resonant cavity method, and in the radio frequency range (RF), with the impedance spectroscopy technique

Suplementación de vacas de cría

Una amplia región del Noroeste rionegrino y Sudoeste pampeano se encuentra con estados muy degradados de sus pastizales naturales, por lo cual su oferta forrajera es escasa a nula (Figura 1).Si bien a la fecha los/as productores/as ante la limitante de pasto han tomado varias de las medidas recomendadas, como por ejemplo, el destete, la clasificación de los vientres en producción (por tacto y boqueo) y disminución de la carga animal, en algunos casos resultarán insuficientes para el mantenimiento de las vacas de crías que aún deben superar el invierno con una mala condición corporal (Figura 2). Ante la situación desde las Agencias de Extensión Rural de Río Colorado,Guatraché y General Acha brindamos algunas recomendaciones y orientaciones para la suplementación de las vacas de cría, entendiendo que en cada campo se pueden presentar condiciones particulares y que no hay recomendaciones que se ajunten a todas las situaciones.EEA Alto ValleFil: Devesa, Antonia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Alto Valle. Agencia de Extensión Rural Río Colorado; ArgentinaFil: Angolani, Daniel Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural General Acha; ArgentinaFil: Paredes, Silvia Susana. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural Guatrache; ArgentinaFil: Lehr, Fernando Javier. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Anguil. Agencia De Extensión Rural Guatrache; Argentin

Condición corporal en rodeos de cría

En las explotaciones agropecuarias que se dedican a la actividad ganadera de cría, el 65% de los ingresos proviene de la producción de terneros por hectárea y por año; el ingreso restante se origina por la venta de las vacas de refugo (gordas o conserva), las vaquillonas sobrantes de los reemplazos y toros de descarte. De allí que, de todas las variables que afectan a la productividad física y económica de la cría bovina, el porcentaje de vacas que desteta cada año un ternero es la de mayor significación. Para lograr un ternero por año debemos conseguir la preñez de la vaca poco tiempo después del parto. Del total de 365 días, en promedio 283 corresponden al periodo de gestación, de modo que para cumplir nuestro objetivo la vaca debe preñarse en el lapso de 82 días. Muchas pueden ser las causas de falta de preñez (por ejemplo, sanitarias); sin embargo, en la mayoría de los casos están asociadas a nutrición inapropiada y pobre condición corporal (CC). La estimación de la Condición Corporal es una herramienta sencilla que permite anticiparse a las situaciones de déficit nutricional y realizar acciones para mejorar los índices de preñez del rodeo.EEA Alto ValleFil: Devesa, Antonia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Alto Valle. Agencia de Extensión Rural Río Colorado; ArgentinaFil: Angolani, Daniel Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural General Acha; ArgentinaFil: Paredes, Silvia Susana. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural Guatrache; ArgentinaFil: Lehr, Fernando Javier. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Anguil. Agencia De Extensión Rural Guatrache; Argentin

Additive manufactured stoneware fired in microwave furnace

In the context of ceramic manufacturing, additive manufacturing or 3D printing creates new opportunities and perspectives, allowing the fabrication of parts with complex shapes, which by traditional means would be impossible to produce or would be very expensive [1]. This is the case for dinnerware and artworks (stoneware, porcelain and clay-based products). After piece forming, the greenware is gas or electrically fired at high temperatures to achieve its mechanical strength and aesthetic properties. These conventional firing processes usually require long processing times, in the present case taking 10 h to reach temperatures around 1200 °C [2]. In the search for faster firing processes, small size and cup shaped 3D printed stoneware pieces were fired using microwave radiation as the energy source. As microwave radiation has the potential to penetrate the material to be sintered, volumetric heating can be achieved, and faster firing processes are possible to implement without cracks formation and other thermal related defects. Pieces were fired in 10% of the conventional manufacturing time in a six magnetrons (energy sources) microwave furnace [3]. The microwave, the electrically-fast-fired and conventionally-fired pieces are presented in Figure 1. The conventionally-fired pieces are seen as reference samples. Temperature was controlled through a calibrated pyrometer [3], and using Process Temperature Control Rings (PTCR) the temperature of the pieces of (1207 ± 15) °C was determined. An error of only 1.25% was calculated between the temperature measured by the pyrometer and the PTCR in the piece where the pyrometer is measuring the temperature. The PTCR elements give a better representation of the real heating process at its location, concomitantly of each piece when they are placed inside it. The results show that microwave-fast-fired pieces present comparable mechanical strength to the references (10 h electrically fired) and to the electrically fast-fired pieces (41, 46 and 34 (N/mm2), respectively), and present aesthetic features closer to the reference ones. Porosity quantification does not fully agree with the mechanical strength of the pieces, of ~5% for electrically fast-fired, ~9% for the references and ~4% for microwave-fired ones. Overall, microwave heating can be used as an alternative stoneware firing technology, without compromising its quality and features with gains in the manufacturing time. Another advantage attributed to microwave heating is the reduction in the firing temperature, as claimed by the literature [4,5]. However, this possibility still requires confirmation in 3D-printed stoneware.publishe

Alimentación: Monitoreo de heces

El monitoreo de las heces es una técnica sencilla que se utiliza para evaluar el efecto de la alimentación en los animales y determinar si es necesario corregir sobre la marcha el déficit o exceso de nutrientes. Las observaciones se pueden realizar en cualquier lugar del campo, pero es importante que se realicen sobre heces frescas. Hay tres aspectos a observar al realizar la lectura de heces: el color, la forma y la consistencia. A continuación, se presenta una clasificación en cinco categorías para utilizar de guía (la misma fue realizada por Bavera y Peñafort en el 2006). Es importante señalar que estas divisiones no son tajantes, sino que pueden pre-sentarse muchos casos intermedios entre dos categorías debido a la variación en la composición de los pastos en distintas zonas, sales totales del agua de bebida, épocas, clima y manejo.EEA Alto ValleFil: Devesa, Antonia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Alto Valle. Agencia De Extensión Rural Río Colorado; ArgentinaFil: Angolani, Daniel Hugo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural General Acha; ArgentinaFil: Paredes, Silvia Susana.Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural Guatrache; ArgentinaFil: Lehr, Fernando Javier. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia De Extensión Rural Guatrache; ArgentinaFil: Distel, Roberto Alejandro. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-ω auto-Abs in children

We found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-alpha 2 in 10 patients: IFN-alpha 2 only in three, IFN-alpha 2 plus IFN-omega in five, and IFN-alpha 2, IFN-omega plus IFN-beta in two; IFN-omega only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-alpha 2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-omega in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-alpha 2 only (OR [95% CI] = 67.6 [5.7-9,196.6]) than for auto-Abs neutralizing IFN-. only (OR [95% CI] = 2.6 [1.2-5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6-35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1-9.6]) of IFN-omega and/or IFN-alpha 2

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements