Significant coercivity enhancement at low temperatures in magnetically oriented cobalt ferrite nanoparticles

The present work describes a synthesis and characterization strategy employed to study the magnetic anisotropic properties of a diluted nanoparticulate system. The system under analysis is composed of monodisperse and highly crystalline 16 nm Co0.5Fe2.5O4 nanoparticles (NPs), homogenously dispersed in 1-octadecene. Owing to the liquid nature of the matrix at room temperature, the relative orientation of the nanoparticle easy axis can be controlled by an external magnetic field, enabling us to measure how the magnetic properties are modified by the alignment of the particles within the sample. In turn, by employing this strategy, we have found a significant hardness and squareness enhancement of the hysteresis loop in the magnetically oriented system, with the coercive field reaching a value as high as 30.2 kOe at low temperatures. In addition, the magnetic behavior associated with the system under study was supported by additional magnetic measurements, which were ascribed to different events expected to take place throughout the sample characterization, such as the melting process of the 1-octadecene matrix or the NP relaxation under the Brownian mechanism at high temperatures.Fil: Tancredi, Pablo. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Rivas Rojas, Patricia Carolina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Moscoso Londoño, Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Muraca, Diego. Universidade Estadual de Campinas; BrasilFil: Knobel, Marcelo. Universidade Estadual de Campinas; BrasilFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; Argentin

Strategies to tailor the architecture of dual Ag/Fe-oxide nano-heterocrystals—interfacial and morphology effects on the magnetic behavior

Bifunctional nanostructured architectures have shown appealing properties, since a single entity can combine the diverse properties of its individual constituents. Particularly, by growing Fe-oxide domains over Ag nanoparticles, the plasmonic and superparamagnetic properties can be combined in a single particle. Beyond the multifunctionality of this system, there are several properties that emerge from intrinsic factors, such as: interface and/or morphology. In this study, we present the synthesis protocols to obtain two sets of heterocrystals, each one with different morphology: dimer and flower-like. In addition, the magnetization behavior of these hybrid nano-heterocrystals is investigated and discussed. These nanomaterials were built by a seed assisted heterogeneous nucleation process, carried out in organic solvents of high boiling point, using the same batch of silver nanoparticles with a mean size of 6 nm as seeds, and tuning the electron-donor capacity of the reaction environment at the thermal decomposition of the iron precursor. Ag/Fe3O4 heterocrystals with dimer and flower-like morphologies were obtained. The synthesis protocols for generating these types of nanomaterials are discussed step-by-step. Structural and morphological properties were determined by transmission electron microscopy, x-ray diffraction and x-ray absorption fine structure. DC magnetization results suggest that the silver/magnetite coupling generates an increase of the blocking temperature in comparison to those obtained from pure magnetite. This behavior could be linked to a possible increase in the magnetic anisotropy produced by an additional disorder at the Ag–Fe3O4 interface. The higher interface area of the Ag/Fe3O4 heterocrystals with flower-like architecture leads to a higher blocking temperature and a stronger magnetic anisotropy. These results are supported by AC susceptibility data.Fil: Tancredi Gentili, Pablo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Sólidos Amorfos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; ArgentinaFil: Moscoso Londoño, Oscar. Universidad Autónoma de Manizales; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade Estadual de Campinas; BrasilFil: Rivas Rojas, Patricia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física. Laboratorio de Sólidos Amorfos; ArgentinaFil: Wolff, U.. Leibniz Institute for Solid State and Materials Research; AlemaniaFil: Socolovsky, Leandro Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Tecnológica Nacional. Facultad Regional Santa Cruz. Centro de Investigaciones y Transferencia de Santa Cruz. Universidad Nacional de la Patagonia Austral. Centro de Investigaciones y Transferencia de Santa Cruz; ArgentinaFil: Knobel, M.. Universidade Estadual de Campinas; BrasilFil: Muraca, D.. Universidade Estadual de Campinas; Brasi

Fine zircon (ZrSiO4) powder mechanical activation, a Perturbed Angular Correlation (PAC) analysis

By means of Perturbed Angular Correlation (PAC) analysis the resulting phases during mechano-chemical activation process on zircon (ZrSiO4) commercial fine powder (D50 ≅ 0.8 µm) were accurately identified and characterized. A high energy planetary mill was employed with 850 rpm up to 120 min. The phenomenological macroscopic confirmation of the structural change and mechanical activation consisted in an important enhancement of the sintering behavior of the treated fine zircon powders. Three different well known zircon phases were identified and quantified as a function of the milling time: a fully crystalline phase, an aperiodic phase and a distorted phase. A decrease in the first two phases was accompanied by the appearance of the third one; finally, at long term treatments, a partial dissociation was observed. Particularly the resulting zirconium oxide is a highly distorted one. The results were discussed together with those obtained using XRD, SEM and laser scattering. The XRD only showed the partial dissociation of zircon and failed in the differentiation of its nanoconfigurations observed by PAC. The milling of this hard material can be optimized through the performed characterization strategy.Centro de Tecnología de Recursos Minerales y CerámicaInstituto de Física La PlataFacultad de Ciencias Agrarias y ForestalesConsejo Nacional de Investigaciones Científicas y Técnica

Fine zircon (ZrSiO4) powder mechanical activation, a Perturbed Angular Correlation (PAC) analysis

By means of Perturbed Angular Correlation (PAC) analysis the resulting phases during mechano-chemical activation process on zircon (ZrSiO4) commercial fine powder (D50 ≅ 0.8 µm) were accurately identified and characterized. A high energy planetary mill was employed with 850 rpm up to 120 min. The phenomenological macroscopic confirmation of the structural change and mechanical activation consisted in an important enhancement of the sintering behavior of the treated fine zircon powders. Three different well known zircon phases were identified and quantified as a function of the milling time: a fully crystalline phase, an aperiodic phase and a distorted phase. A decrease in the first two phases was accompanied by the appearance of the third one; finally, at long term treatments, a partial dissociation was observed. Particularly the resulting zirconium oxide is a highly distorted one. The results were discussed together with those obtained using XRD, SEM and laser scattering. The XRD only showed the partial dissociation of zircon and failed in the differentiation of its nanoconfigurations observed by PAC. The milling of this hard material can be optimized through the performed characterization strategy.Centro de Tecnología de Recursos Minerales y CerámicaInstituto de Física La PlataFacultad de Ciencias Agrarias y ForestalesConsejo Nacional de Investigaciones Científicas y Técnica

Fine zircon (ZrSiO4) powder mechanical activation, a Perturbed Angular Correlation (PAC) analysis

By means of Perturbed Angular Correlation (PAC) analysis the resulting phases during mechano-chemical activation process on zircon (ZrSiO4) commercial fine powder (D50 ≅ 0.8 µm) were accurately identified and characterized. A high energy planetary mill was employed with 850 rpm up to 120 min. The phenomenological macroscopic confirmation of the structural change and mechanical activation consisted in an important enhancement of the sintering behavior of the treated fine zircon powders. Three different well known zircon phases were identified and quantified as a function of the milling time: a fully crystalline phase, an aperiodic phase and a distorted phase. A decrease in the first two phases was accompanied by the appearance of the third one; finally, at long term treatments, a partial dissociation was observed. Particularly the resulting zirconium oxide is a highly distorted one. The results were discussed together with those obtained using XRD, SEM and laser scattering. The XRD only showed the partial dissociation of zircon and failed in the differentiation of its nanoconfigurations observed by PAC. The milling of this hard material can be optimized through the performed characterization strategy.Centro de Tecnología de Recursos Minerales y CerámicaInstituto de Física La PlataFacultad de Ciencias Agrarias y ForestalesConsejo Nacional de Investigaciones Científicas y Técnica

Formando educadores en el sur de Colombia : Investigación educativa en licenciatura en educación infantil.

Este libro ofrece al lector reflexión continua de los retos de la universidad en la formación de licenciados para la transformación y emancipación de Colombia hacia la construcción de paz, revela las realidades socio críticas del XXI en los programas académicos de licenciados y visualiza las niñeces como sujetos políticos y sociales, logrando un despliegue significativo de metodologías pertinentes para la formación de maestros en Colombia y Latinoamérica

Formando educadores en el sur de Colombia : Investigación educativa en licenciatura en educación infantil.

Este libro ofrece al lector reflexión continua de los retos de la universidad en la formación de licenciados para la transformación y emancipación de Colombia hacia la construcción de paz, revela las realidades socio críticas del XXI en los programas académicos de licenciados y visualiza las niñeces como sujetos políticos y sociales, logrando un despliegue significativo de metodologías pertinentes para la formación de maestros en Colombia y Latinoamérica

Caminando en la ruta sentipensante: configuración de experiencias pedagógicas nivel inicial

494 páginasEste texto es realizado en el contexto del Plan de Desarrollo 2016 – 2020, “Bogotá mejor para todos”, en el que se señala: Bogotá es entendida como una ciudad educadora, en la que todos los ciudadanos son agentes educadores y todos los espacios pueden ser escenarios pedagógicos para el aprendizaje. Una ciudad educadora tiene como centro el conocimiento e inspira aprendizaje, formas y lenguajes para reconocernos, para reencontrarnos; los espacios para el aprendizaje son entendidos como espacios para la vida, en los que se posibilita la investigación y la innovación para vivir mejor, para reinventarnos como ciudad, una ciudad mejor para todos. Los dieciocho textos aquí presentados, fruto del acompañamiento pedagógico realizado por el IDEP en 2019, son base y referente para seguir aportando en la configuración y consolidación de comunidades de saber y práctica pedagógica de la ciudad, así como en la conformación de colectivos y redes de maestros. Son la evidencia de un potente trabajo de acompañamiento a experiencias de nivel inicial, caracterizadas por contar con ideas o avances para problematizar, estructurar, fundamentar, elaborar estrategias y un plan de acción

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries(1,2). However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world(3) and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health(4,5). However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol-which is a marker of cardiovascular riskchanged from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million-4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.Peer reviewe