ResumenSe presenta el desarrollo de un metamaterial para estimar el índice de refracción en líquidos. El metamaterial se desarrolló insertando celdas cilíndricas en el plano de tierra de una línea microcinta, cintas estas que forman una estructura de brecha de banda electromagnética (electromagnetic bandgap, EBG). Dentro de las celdas se depositaron líquidos con índices de refracción estimados en el laboratorio. Se evaluaron los parámetros de dispersión S21 y S 11 mediante simulaciones electromagnéticas con modelos desarrollados, y de forma experimental, con prototipos fabricados. Se analizó la variación de la frecuencia central, el ancho de banda y el nivel de pérdidas por inserción de la brecha de frecuencias generada como respuesta a la variación del índice de refracción del material depositado dentro de las celdas. Los resultados obtenidos muestran que es posible estimar el índice de refracción de materiales monitoreando la frecuencia de resonancia o el nivel de pérdidas por inserción de la brecha generada. El metamaterial desarrollado es fácil de construir y su desempeño es adecuado en el rango de las microondas. © 2019. Acad. Colomb. Cienc. Ex. Fis. Nat. Palabras clave:Metamateriales; EBG; Índice de refracción. Application of metamaterials to estimate refractive indexes AbstractWe developed a metamaterial to estimate the refractive index in liquids by inserting cylindrical cells in the ground plane of a microstrip line, lines that form an electromagnetic bandgap (EBG) structure. We deposited inside the cells liquids with refractive indices estimated in the laboratory. The dispersion parameters S21 and S11 were evaluated by means of electromagnetic simulations with developed models and experimentally with manufactured prototypes. We analyzed the variation of center frequency, the bandwidth, and the level of losses by the variation of the refractive index of the material deposited inside the cells. Our results showed that it is possible to estimate the refractive index of materials by monitoring the resonance frequency or the level of insertion losses of the generated gap. The metamaterial developed is easy to build and its performance is adequate in the range of microwaves.
The analysis of the impact of the variation of the substrate and the geometric characteristics of the cells basic that make up a metamaterial, as well as their frequency response, bandwidth and insertion losses level of the bandgap generated, is presented. A metamaterial in microstrip transmission line technology was simulated and manufactured on two dielectric substrates with different relative permittivity index, introducing electromagnetic band gap structures (EBG) in the ground plane. Five geometrical shapes were selected for the cells of the EBG structure. The response of the metamaterial is analyzed on the characteristics of the band gap, varying the lattice constant, the size and the geometry of the cells (defects) and the substrate used. The results obtained show that this type of devices can be used to measure the properties of elements by detecting the change of the refractive index of the metamaterial, with frequency selectivity. The study of these parameters is critical for the applications of metamaterials in filters, sensors and actuators, among others.
Conventional doses of therapeutic ultrasound alter the mechanical behavior of ligament fibroblasts to improve the regenerative and remodeling stages of the wound healing process. Using a multidisciplinary approach, we applied ultrasound doses of 1.0 and 2.0 W/cm2 at 1 MHz frequency for five days on ligament fibroblasts. Atomic force microscopy showed a decrease in cell elastic modulus for both doses, but the treated cells were still viable based on flow cytometry. Finite element method analysis exhibited visible cytoskeleton displacements and decreased harmonics in treated cells. Colorimetric assay revealed increased cell proliferation, while scratch assay showed increased migration at low doses. An increase in collagen and fibronectin was detected by enzyme-linked immunoassay at high doses, and β-actin expression for both treatments was visualized through immunofluorescence imaging. Both doses of ultrasound altered the fibroblast mechanical properties due to cytoskeletal reorganization and enhanced the early and late stages of cell repair.
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