Perturbed Angular Correlation Studies in SrTi0₃ Single Crystals

The quadrupole hyperfine interactions of ^111Cd/^111 probe nuclei in single-crystalline SrTiO₃ perovskite samples were investigated using Perturbed Angular Correlation spectroscopy. Three electric field gradients were detected and their fractions and hyperfine parameters were measured in the temperature range from 26 to 700 K. The fraction f₀ having a vanishing quadrupole frequency, as expected for ^111Cd on substitutional sites in a cubic lattice, starts to develop around 300 K and reaches 100% at 700 K. Two well-defined EFG's having closely lying quadrupole frequencies and asymmetry parameters of ω_(Q1) = 49.1(3) Mrad/s, η_(1) = 0.10(2) and ω_(Q2) = 51 8(3) Mrad/s, η_(2)= 0.12(2), at room temperature, were identified in the temperature range from 250 to 530 K, and their (100) orientation in the lattice was determined. They are associated with electronic defects at the probe atoms

Mapeo de Actores y Necesidades de Información Agroclimática en los Cultivos de Maíz y Frijol en sitios piloto - Colombia

Este trabajo presenta los resultados del mapeo de actores y necesidades de información agroclimática en los cultivos transitorios de seguridad alimentaria: maíz y frijol arbustivo en sitios piloto en Colombia. A través del mapeo de los actores que transmiten información a los agricultores, la confianza en la información proporcionada, y las necesidades de información para la toma de decisiones, logramos entender el ancho espectro de problemas y prioridades a tomar en cuenta en la producción de estos cultivos, y proponer soluciones útiles, relevantes, confiables, sostenibles y aplicables. Con este enfoque, se llevaron a cabo 27 entrevistas semi-estructuradas con informantes clave y 12 grupos focales con un total de 151 agricultores en los departamentos de Córdoba y Santander. Los resultados evidencian que una de las prioridades de los agricultores es recibir información agroclimática confiable a escala local, que permita tomar mejores decisiones de siembra, variedades, insumos y manejo de suelos y cultivos ante eventos de variabilidad climática. Se evidencia una desconfianza en las instituciones oficiales que transmiten información climática y un sentimiento difuso de falta de interés de las instituciones hacia los pequeños agricultores. Los agricultores se endeudan para lograr producir fríjol arbustivo y maíz o subsidian la producción por otros cultivos, mientras el acceso a un seguro agrícola es limitado. El formato preferido para recibir información climática es a través de mensajes de texto (celular) y mensajes en la radio local. Grupos de interacción presencial o virtual entre agricultores y expertos parecen una alternativa útil y confiable para recibir y compartir información en tiempo real. Sin embargo, los agricultores están interesados en adoptar el manejo agrícola tras un pronóstico si: a) la información es local, b) proviene de una fuente considerada confiable como expertos u otros agricultores, c) se transmite en el momento adecuado para la toma de decisiones y d) si sus efectos son medibles, verificables y validados, por ejemplo, a través de resultados de pilotos o parcelas experimentales en dos años consecutivos. ENGLISH This working paper presents the results of the mapping of actors and of agroclimatic information needs in pilot sites in Colombia for two annual crops, fundamental for food security: maize and bush beans. The mapping of the actors that transmit information to farmers, the confidence the latter have in the information provided, and their information needs for decision-making, allows us to understand the broad spectrum of issues and priorities to be taken into account in the production of these crops, and suggest solutions that are useful, relevant, reliable, sustainable and applicable. Under this assumption, we conducted 27 semi-structured interviews with key informants and 12 focus groups with a total of 151 farmers in the departments of Córdoba and Santander. Results show that one of the priorities of farmers is to receive reliable local agroclimatic information that enables them to take decisions on planting, varieties, inputs, soil and crop management, that address climate variability. We find a generalized distrust of official institutions that transmit weather information, and a feeling that institutions are not interested in smallholders. Farmers resort to indebtedness to produce beans and maize, or subsidize production with cash crops, while access to agricultural insurance is limited. The format preferred to receive weather information is text messages (phone) and information through the local radio. The creation of groups of farmers and experts who interact in person or virtually seem a useful and reliable alternative to receive and share information in real time. However, farmers are only interested in adopting farm management changes after a forecast if: a) the information is local, b) the information is given by a trusted source such as experts or other farmers, c) the information is transmitted at the right time for decision-making d) the effects of taking these decisions are measurable, verifiable and validated, for example, through pilots or results from experimental plots in two consecutive years

Sensitivity Analysis and Potential Uses of a Novel Gamma Interferon Release Assay for Diagnosis of Tuberculosis

Sputum smears for acid-fast bacilli (AFB) are the primary methods for diagnosis of tuberculosis (TB) in many countries. The tuberculin skin test (TST) is the primary method for diagnosis of latent TB infection (LTBI) worldwide. The poor sensitivity of the former and the poor specificity of the latter warrant the development of new tests and strategies to enhance diagnostic capabilities. We evaluated the sensitivity of an “in-tube” gamma interferon release assay (IGRA) using TB-specific antigens in comparison to the TST and the sputum smear for AFB in TB cases in South Africa. The sensitivity of the IGRA for TB was considered a surrogate of sensitivity in LTBI. Among 154 patients with a positive culture for Mycobacterium tuberculosis, the sensitivity of the IGRA for the diagnosis of TB varied by clinical subgroup from 64% to 82%, that of the TST varied from 85% to 94%, and that of two sputum smears for AFB varied from 35% to 53%. The sensitivity of the IGRA in human immunodeficiency virus (HIV)-infected TB cases was 81%. HIV-infected TB patients were significantly more likely to have indeterminate IGRA results and produced quantitatively less gamma interferon in response to TB-specific antigens than HIV-negative TB patients. The overall sensitivity of the TST in all TB cases was higher than that of the IGRA (90% versus 76%, respectively). The combined sensitivities of the TST plus IGRA and TST plus a single sputum smear were 96% and 93%, respectively. The TST combined with IGRA or with a single sputum smear may have a role in excluding the diagnosis of TB in some settings

Magneto-resistive coefficient enhancement observed around Verwey-like transition on spinel ferrites XFe₂O₄ (X = Mn, Zn)

Manganese and Zinc ferrites were prepared by solid state reaction. The resulting powders were pressed into pellets and heat treated at 1100 ⁰C. The samples were characterized by using X-ray diffraction, pure phases of zinc ferrite (ZnFe²O₄) and manganese ferrite (MnFe₂O₄) were obtained. Scanning electron microscopy images showed a good contact between particles. A drop of electrical resistance was found in both samples, MnFe₂O₄ and ZnFe₂O₄, with values going from 2750 to 130 Ω and from 1100 to 55 Ω, respectively. Transition temperatures were determined to be Tv = 225 K for MnFe₂O₄ and Tv = 130 K for ZnFe₂O₄. Magnetoresistance measurements were carried out in the temperature range where R showed the transition, defined as the Verwey-like transition temperature range, ∆Tv. No magnetoresistive effect was observed out of it. The magnetoresistive coefficient (MRC) observed at ∆Tv reached its maximum values of 1.1% for MnFe₂O₄ and 6.68% for ZnFe₂O₄. The differences between MRC values are related to the divalent metal element used. Finally, the magnetoresistive response indicates that the electrical transition observed is strongly influencing the magnetoresistance; where the underlying responsible for this behavior could be a charge reordering occurring at the Verwey-like transition temperature

Structural and magnetic characterization of oleic acid and oleylamine-capped gold nanoparticles

In this work the study of oleic acid and oleylamine-capped gold nanoparticles is presented. The structural characterization of the sample shows 6.7 nm gold nanoparticles with a narrow size distribution. The experimental optical absorption spectrum has a maximum at 2.35 eV. The calculated optical absorption spectrum is shifted and narrower than the experimental one, indicating that the oleic acid and oleylamine do not merely passivate the metallic nanoparticles but modify its electronic structure. These gold nanoparticles show in addition a kind of magnetic order similar to other organic passivated gold nanoparticles as thiol-capped gold nanoparticles. Although the magnetic interactions seem to be weaker than in thiol-capped ones, the magnetic behavior looks similar to that, i.e., an invariant temperature dependence of the magnetization from 5 to 300 K and a noticeable coercive field. We analyze the influence of the organic layer bonding the nanoparticles on the magnetic behavior

Structural, electronic, and hyperfine properties of pure and Ta-doped m-ZrO₂

A combination of experiments and ab initio quantum-mechanical calculations has been applied to examine electronic, structural, and hyperfine interactions in pure and Ta-doped zirconium dioxide in its monoclinic phase (m-ZrO₂). From the theoretical point of view, the full-potential linear augmented plane wave plus local orbital (APW + lo) method was applied to treat the electronic structure of the doped system including the atomic relaxations introduced by the impurities in the host in a fully self-consistent way using a supercell approach. Different charge states of the Ta impurity were considered in the study and its effects on the electronic, structural, and hyperfine properties are discussed. Our results suggest that two different charge states coexist in Ta-doped m-ZrO₂. Further, ab initio calculations predict that depending on the impurity charge state, a sizeable magnetic moment can be induced at the Ta-probe site. This prediction is confirmed by a new analysis of experimental data

Información agro-climática local, confiable y oportuna, una necesidad de los agricultores colombianos

Conocer información climática relevante hacia el futuro a través de las predicciones climáticas, no es suficiente para apoyar la toma de decisiones de los agricultores. Es necesario buscar alternativas de manejo agrícola para adaptarse a las condiciones climáticas e implementar mecanismos eficaces y sostenibles, bajo un marco de comunicación efectiva con el agricultor (Jones, 2003; Pulwarty et al., 2003). En América Latina son pocas las iniciativas relacionadas con predicción agroclimática. Por lo anterior, el proyecto “Servicios agroclimáticos e información de seguridad alimentaria para una mejor toma de decisiones – AgroClimas” busca apoyar a los actores del sector privado y público de Colombia, Guatemala y Honduras para implementar y usar herramientas de gestión del riesgo agro-climático, validadas y ajustadas a las necesidades de los usuarios finales. Esta nota presenta los resultados del mapeo de actores y necesidades de información agroclimática en cultivos de seguridad alimentaria (maíz y frijol arbustivo), en sitios piloto del proyecto en Colombia. El trabajo se basa en el supuesto que, mapeando los actores que transmiten información de clima, de precios, financiera y agronómica a los agricultores, conociendo la confianza en la información proporcionada, identificando las necesidades de información y los formatos preferidos para recibir información que apoye la toma de decisiones productivas, se pueden proponer soluciones útiles, relevantes, confiables, sostenibles y aplicables

Latin America ClimateSmart Villages AR4D sites: 2016 Inventory

Inventory of CSA practices in Latin America’s ClimateSmart Villages