Diseño y construcción de un teslámetro digital embebido para la caracterización magnética de materiales

We present the design, construction and validation of an embedded digital teslameter, intended for use in experiments of magnetic materials characterization by inductive and static methods. The teslameter consists of a planar type Hall effect transducer THS119, with differential output and adjustable measuring range, an INA129P instrumentation amplifier with adjustable gain, a microcontroller PIC16F873A with ADC converter of 10-bits for digital processing, data storage and data transfer to the computer via serial port; and a liquid crystal display to visualize the measurements. The system is adaptable to magnetic field transducers with single or differential output and with different measuring ranges; is sensitive to changes in the intensity and the polarity of the applied magnetic field and has an effective sensitivity of 5.0 mV/mT and uncertainty of 0.5−3T for the THS119 Hall effect transducer. The prototype teslameter was compared with a commercial teslameter PHYWE 13610.90.PACS: 84.30.-r, 85.40.-e, 85.75.-dSe presenta el diseño, construcción y validación de un teslámetro digital embebido, para uso en experimentos de caracterización magnética de materiales por métodos inductivos y estáticos. El teslámetro se compone de un transductor de efecto Hall THS119 de tipo planar, con salida diferencial y ajustable a diferentes rangos de medida, un amplificador de instrumentación INA129P con ganancia ajustable y un microcontrolador PIC16F873A con convertidor ADC de 10 bits para el procesamiento digital de los datos, visualización de las medidas en una pantalla de cristal líquido, almacenamiento y transferencia de los datos al computador vía puerto serie. El sistema es adaptable a transductores de campo magnético con salida simple o diferencial y con diferentes rangos de medida; es sensible a cambios en la intensidad y la polaridad del campo magnético aplicado y cuenta con una sensibilidad efectiva de 5,0 V/T e incertidumbre de 0.5 10−3T para el transductor de efecto Hall THS119. El prototipo desarrollado fue comparado con un teslámetro comercial PHYWE 13610.90. PACS: 84.30.-r, 85.40.-e, 85.75.-

Simulation and parameterization by the finite element method of a C Shape Delectromagnet for application in the characterization of magnetic properties of materials

This article presents the simulation, parameterization and optimization of an electromagnet with the C–shaped configuration, intended for the study of magnetic properties of materials -- The electromagnet studied consists of a C-shaped yoke, which provides self–shielding for minimizing losses of magnetic flux density, two poles of high magnetic permeability and power coils wound on the poles -- The main physical variable studied was the static magnetic flux density in a column within the gap between the poles, with 4cm2 of square cross section and a length of 5cm, seeking a suitable set of parameters that allow us to achieve a uniform magnetic flux density of 1x104 Gaussor values above this in the column, when the system operates at room temperature and with a current consumption not exceeding 5A -- By means of a magnetostatic analysis by the finite element method, the magnetic flux density and the distribution of the magnetic field lines were visualized and quantified -- From the results obtained by simulating an initial configuration of electromagnet, a structural optimization of the geometry of the adjustable caps for the ends of the poles was performed -- The magnetic permeability effect of the soft magnetic materials used in the poles system, such as low–carbon steel (0.08% C), Permalloy (45% Ni, 54.7% Fe) and Mumetal (21.2% Fe, 78.5% Ni), was also evaluated -- The intensity and uniformity of the magnetic field in the gap showed a high dependence with the factors described above -- The magnetic field achieved in the column was uniform and its magnitude ranged between 1.5x104 Gauss and 1.9x104 Gauss according to the material of the pole used, with the possibility of increasing the magnetic field by choosing a suitable geometry of the cap, introducing a cooling system for the coils and adjusting the spacing between the poles -- This makes the device a versatile and scalable tool to generate the magnetic field necessary to perform magnetic characterization of materials by techniques such as vibrating sample magnetometry (VSM), Hall-effect, Kerr-effect magnetometry, among others -- Additionally, a CAD design of the modules of the electromagnet is presented in order to facilitate the construction and scaling of the physical devic

The impact of COVID-19 on the well-being and cognition of older adults living in the United States and Latin America.

In the COVID-19 pandemic, older adults from vulnerable ethnoracial groups are at high risk of infection, hospitalization, and death. We aimed to explore the pandemic's impact on the well-being and cognition of older adults living in the United States (US), Argentina, Chile, Mexico, and Peru. 1,608 (646 White, 852 Latino, 77 Black, 33 Asian; 72% female) individuals from the US and four Latin American countries aged ≥ 55 years completed an online survey regarding well-being and cognition during the pandemic between May and September 2020. Outcome variables (pandemic impact, discrimination, loneliness, purpose of life, subjective cognitive concerns) were compared across four US ethnoracial groups and older adults living in Argentina, Chile, Mexico, and Peru. Mean age for all participants was 66.7 ( = 7.7) years and mean education was 15.4 ( = 2.7) years. Compared to Whites, Latinos living in the US reported greater economic impact ( < .001,  = .031); while Blacks reported experiencing discrimination more often ( < .001,  = .050). Blacks and Latinos reported more positive coping ( < .001,  = 040). Compared to Latinos living in the US, Latinos in Chile, Mexico, and Peru reported greater pandemic impact, Latinos in Mexico and Peru reported more positive coping, Latinos in Argentina, Mexico, and Peru had greater economic impact, and Latinos in Argentina, Chile, and Peru reported less discrimination. The COVID-19 pandemic has differentially impacted the well-being of older ethnically diverse individuals in the US and Latin America. Future studies should examine how mediators like income and coping skills modify the pandemic's impact. Massachusetts General Hospital Department of Psychiatry