Doping of inorganic materials in microreactors – preparation of Zn doped Fe₃O₄ nanoparticles

Microreactor systems are now used more and more for the continuous production of metal nanoparticles and metal oxide nanoparticles owing to the controllability of the particle size, an important property in many applications. Here, for the first time, we used microreactors to prepare metal oxide nanoparticles with controlled and varying metal stoichiometry. We prepared and characterised Zn-substituted Fe₃O₄ nanoparticles with linear increase of Zn content (ZnxFe₃−xO₄ with 0 ≤ x ≤ 0.48), which causes linear increases in properties such as the saturation magnetization, relative to pure Fe₃O₄. The methodology is simple and low cost and has great potential to be adapted to the targeted doping of a vast array of other inorganic materials, allowing greater control on the chemical stoichiometry for nanoparticles prepared in microreactors

Effect of inorganic ions on pyrite catalyzed Fenton reaction

© 2018, Avestia Publishing. Industrial wastewaters contain not only organic pollutants but also considerable amounts of inorganic ions that may affect the efficiency of wastewater remediation processes. Thus, it is important to study the influence of such ions in the respective chemical reactions. Here we performed Fenton reactions for the decolourization of Rhodamine B dye using the naturally occurring mineral pyrite (FeS2) as heterogeneous catalyst in presence of different inorganic ions that are typically present in wastewater. Additionally, the effect of milling time of the pyrite powder on the performance of the heterogeneous Fenton reaction has also been investigated

The costs of preventing and treating chagas disease in Colombia

Background: The objective of this study is to report the costs of Chagas disease in Colombia, in terms of vector disease control programmes and the costs of providing care to chronic Chagas disease patients with cardiomyopathy. Methods: Data were collected from Colombia in 2004. A retrospective review of costs for vector control programmes carried out in rural areas included 3,084 houses surveyed for infestation with triatomine bugs and 3,305 houses sprayed with insecticide. A total of 63 patient records from 3 different hospitals were selected for a retrospective review of resource use. Consensus methodology with local experts was used to estimate care seeking behaviour and to complement observed data on utilisation. Findings: The mean cost per house per entomological survey was $4.4 (in US$ of 2004), whereas the mean cost of spraying a house with insecticide was $27. The main cost driver of spraying was the price of the insecticide, which varied greatly. Treatment of a chronic Chagas disease patient costs between$46.4 and $7,981 per year in Colombia, depending on severity and the level of care used. Combining cost and utilisation estimates the expected cost of treatment per patient-year is$1,028, whereas lifetime costs averaged $11,619 per patient. Chronic Chagas disease patients have limited access to healthcare, with an estimated 22% of patients never seeking care. Conclusion: Chagas disease is a preventable condition that affects mostly poor populations living in rural areas. The mean costs of surveying houses for infestation and spraying infested houses were low in comparison to other studies and in line with treatment costs. Care seeking behaviour and the type of insurance affiliation seem to play a role in the facilities and type of care that patients use, thus raising concerns about equitable access to care. Preventing Chagas disease in Colombia would be cost-effective and could contribute to prevent inequalities in health and healthcare.Wellcome Trus

Fortalecimiento organizacional del departamento de recursos humanos de la compañía Naturisa S.A

En la actualidad la compañía Naturisa S.A. ubicada en la ciudad de Guayaquil ha tenido una baja en su productividad en el año anterior y en los primeros meses del año presente, debido que su personal no cumple con el desempeño que se necesita en las diferentes áreas de la compañía. Lo cual se ha visto reflejada en la disminución de sus ventas. Se establece en un estudio de factibilidad donde se muestra los estados financieros del año anterior de la compañía para demostrar su productividad que es afectada por la relación de su personal por lo que se deberá realizar cambios necesarios  según se obtuvo en las encuestas realizadas a sus empleados, para mejorar el desempeño de estos, así se obtendrá un incremento en su productividad, se efectuó proyecciones de los estados financieros a 4 años con esto se podrá indicar los resultados que se obtendrán con las mejoras a realizar sobre las necesidades de la compañía. Se obtendrá un préstamo en la Corporación Financiera Nacional para realizar las implementaciones como son ofrecer capacitaciones, integraciones, para todo el personal de la compañía y la contratación de un psicólogo con esto permitirá ayudar los empleados y brindar motivación a los mismos. En el análisis económico se ha proyectado la rentabilidad que tendrá la compañía con el fortalecimiento del departamento de recursos humanos, se obtuvo un Van de 13.077,24 y un Tir de 55% lo que nos indica el ingreso que se obtendrá, con las proyecciones a largo plazo que refleja un resultado que beneficiará a la compañía

Effect of Mn and Ba Codoping on a Magnetic Spin Cycloid of Multiferroic Bismuth Ferrite Nanoparticles

International audienceBismuth ferrite (BFO) is the drosophila of research in multiferroic materials due to its simultaneous magnetic and electric ordering at room temperature. The unfortunate detail is its antiferromagnetic ordering, which practically cancels magnetization and magnetoelectric coupling of the crystals. To induce finite coupling, dopants have been introduced with a certain success so far. Nanoparticles (NPs) can additionally constrain the formation of the magnetic cycloid in BFO due to size confinement. Doping nanoparticles can thus potentially provide a sizeable magnetization of BFO, making applications in computer memories and hyperthermia cancer treatment feasible. We show that the codoping of BFO NPs by Ba and Mn balances the electrochemical equilibrium, reduces the particle size, and shifts the magnetic phase transition to lower temperatures. The ferroelectric properties are retained and the remanent magnetization is increased by 1 order of magnitude: Bi0.95Ba0.05Fe0.95Mn0.05O3 possesses a remanent magnetization of 0.277 Am2/kg. Our Mössbauer studies reveal that two effects drive this increase: partial destruction of the spin cycloid due to Mn and increased spin canting due to Ba doping inducing local stress fields. This dopant combination and particular concentration improve the effective magnetization value exceptionally well

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Work of numerous research groups has shown different outcomes of studies of the transition from the ferroelectric α-phase to the high temperature β-phase of the multiferroic, magnetoelectric perovskite Bismuth Ferrite (BiFeO3 or BFO). Using the perturbed angular correlation (PAC) method with 111mCd as the probe nucleus, the α to β phase transition was characterized. The phase transition temperature, the change of the crystal structure, and its parameters were supervised with measurements at different temperatures using a six detector PAC setup to observe the γ−γ decay of the 111mCd probe nucleus. The temperature dependence of the hyperfine parameters shows a change in coordination of the probe ion, which substitutes for the bismuth site, forecasting the phase transition to β-BFO by either increasing disorder or formation of a polytype transition structure. A visible drop of the quadrupole frequency ω0 at a temperature of about Tc≈820∘C indicates the α−β phase transition. For a given crystal symmetry, the DFT-calculations yield a specific local symmetry and electric field gradient value of the probe ion. The Pbnm (β-BFO) crystal symmetry yields calculated local electric field gradients, which very well match our experimental results. The assumption of other crystal symmetries results in significantly different computed local environments not corresponding to the experiment

Strong magnetoelectric coupling at an atomic nonmagnetic electromagnetic probe in bismuth ferrite

Isolated nonmagnetic substitutional defect ions experience huge coupled electric magnetic interaction in the single-phase multiferroic BiFeO3. In the ferroelectric state above the magnetic Néel temperature TN, the electric environment generates a single symmetric electric field gradient (EFG) parallel to the electric polarization direction. Below TN, a distinct magnetic interaction arises, monitored by the probe nuclei via their magnetic moment. Two magnetic environments arise, given by the relative angle of the local magnetic moment within its easy magnetic plane with respect to the EFG orientation. The angle between field gradient orientation and magnetic field direction is the most stable fitting parameter. The magnetic interaction concomitantly increases the EFG dramatically which reflects an outstandingly large local magnetoelectric coupling. In the set of best fits, two different electric environments form concurrently with two distinctly different local magnetic fields. The magnetic ordering in BiFeO3 thus completely distorts the electric environment of the nonmagnetic probe nucleus. The implications for the local effect of dopants in BiFeO3 are discussed. A third probe environment arising independent of temperature is identified and associated with an iron vacancy.ISSN:1098-0121ISSN:0163-1829ISSN:1550-235XISSN:0556-2805ISSN:2469-9969ISSN:1095-3795ISSN:2469-995

Phase transitions, screening and dielectric response of CsPbBr3

Cesium–lead–bromide (CsPbBr3) is the simplest all inorganic halide perovskite. It serves as a reference material for understanding the exceptional solar cell properties of the organic–inorganic hybrid halide perovskites and is itself discussed as an alternative absorber material. Broadband dielectric spectroscopy has proven to yield an in depth understanding of charge screening mechanisms in the halide solar cell absorbers based on methylammonium and modifications hereof. For a deeper understanding of charge carrier screening, we have investigated CsPbBr3 across wide temperature (120 K–450 K) and frequency ranges. Besides the two known phase transitions at 403 K and 361 K, the dielectric data show another anomaly around 220 K, which can be interpreted as another phase transition. XRD and EPR studies confirm the presence of this anomaly, but Raman scattering spectra do not show any lattice anomalies in the vicinity of 220 K. This additional anomaly is of first order character (different transition temperatures upon cooling and heating) but hardly influences the lattice dynamics. Our broadband dielectric investigations of CsPbBr3 display the same microwave limit permittivity as for MAPbX3 (3r z 30, X ¼ Cl, Br, I, MA ¼ CH3NH3 +) but do not afford a second permittivity relaxation up to this frequency. Our prior assignment of the second contribution in the methylammonium compounds being due to the relaxation dynamics of the methylammonium ion as a dipole is herewith proven. Nevertheless, CsPbBr3 shows large charge carrier screening up to very high frequencies which can still play a vital role in charge carrier dynamics and exciton behaviour in this material as well.publishe

Reply to the comment on “Phase transitions, screening and dielectric response of CsPbBr3” by Š. Svirskas, S. Balčiūnas, M. Šimėnas, G. Usevičius, M. Kinka, M. Velička, D. Kubicki, M. E. Castillo, A. Karabanov, V. V. Shvartsman, M. R. Soares, V. Šablinskas, A. N. Salak, D. C. Lupascu and J. Banys, J. Mater. Chem. A, 2020, 8, 14015

In this reply, we address the concerns that were raised about our paper on CsPbBr3 single crystals. M. Szafranski criticized the dielectric and DSC data in our original paper claiming that they were a ´ ffected by the experimental artefacts or poor quality of the investigated single crystals, as his DSC and dielectric data did not show any low temperature anomalies in CsPbBr3. We argue in this reply that our main conclusions were not made based on the DSC and dielectric experiments. Here, we emphasize the importance of other experiments like EPR and XRD that were performed to understand if there are any structural transformations of CsPbBr3 at low temperatures. We believe that M. Szafranski did not take ´ into account all the discussion that was presented in our original paper. We hope to clear the doubts in this reply.publishe