Person:
Muñoz San Martín, Sagrario

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First Name
Sagrario
Last Name
Muñoz San Martín
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Estructura de la Materia, Física Térmica y Electrónica
Area
Electromagnetismo
Identifiers
UCM identifierORCIDScopus Author IDDialnet ID

Search Results

Now showing 1 - 10 of 22
  • Publication
    Modelling the internal field distribution in human erythrocytes exposed to MW radiation
    (Elsevier Science SA, 2004-08) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Miranda Pantoja, José Miguel
    This paper studies the internal electric field distribution in human erythrocytes exposed to MW radiation. For this purpose, an erythrocyte cell model is exposed to linearly polarized electromagnetic (EM) plane waves of frequency 900 MHz and the electric field within the cell is calculated by using a finite element (FE) technique with adaptive meshing. The results obtained show the dependence of the induced electric field distribution on the main modelling parameters, i.e., the electrical properties (permittivity and conductivity) of the membrane and cytoplasm and the orientation of the cell with respect to the applied field. It is found that for certain orientations, the field amplification within the membrane of the erythrocyte shape cell can be higher than the one observed in an equivalent simple spheroidal geometry cell, commonly used in bioelectromagnetism. The present work shows that a better insight of the interaction of electromagnetic fields with basic biological structures is obtained when the most possible realistic cell shape is used. (C) 2004 Elsevier B.V. All rights reserved.
  • Publication
    Analysis of the electric field induced forces in erythrocyte membrane pores using a realistic cell model
    (IOP Publishing Ltd, 2006-12-07) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Miranda Pantoja, José Miguel
    We calculate the induced electric stress forces on transient hydrophobic pores in the membrane of an erythrocyte exposed to an electric field. For this purpose, we use a finite element numerical technique and a realistic shape for the biconcave erythrocyte represented by a set of parametric equations in terms of Jacobi elliptic functions. The results clearly show that the electrical forces on the base and sidewalls of the pore favour the opening of the pore. A comparison of the force densities obtained for an unstretched flat membrane and for the realistic erythrocyte model shows that the thinning and curvature of the membrane cannot be neglected. We also show that the pore deformation depends strongly on the orientation of the pore with respect to the external field, and in particular is very small when the field is tangent to the membrane surface.
  • Publication
    Caracterización y optimización de amplificadores de microondas mediante la técnica de las funciones descriptivas
    (Universidad Complutense de Madrid, Servicio de Publicaciones, 2002) Muñoz San Martín, Sagrario; Sebastián Franco, José Luís
    En este trabajo se aplica la técnica de las funciones descriptivas al análisis de circuitos no-lineales en régimen de gran seal como son los amplificadores de rf. Aunque esta técnica ya se ha aplicado a dispositivos activos de una puerta, (osciladores), la extensión de su empleo a dispositivos no-lineales multipuerta, (bit, mesfet y hemt), no se habia desarrollado debido en parte a la dificultad para obtener las propias funciones descriptivas, (admitancias dinámicas del dispositivo), y en parte a la gran complejidad matemática que supone la resolución simultanea del conjunto de ecuaciones no-lineales que representa al sistema. La determinación de las funciones descriptivas implica el desarrollo de un modelo de parámetros concentrados para el elemento activo. En este estudio se ha desarrollado un modelo preciso para mesfet, incluyendo incluso la dependencia con la polarización, y se ha reducido la complejidad matemática mediante hipótesis previas sobre las formas de onda y estados de operación del transistor que posteriormente han sido plenamente justificadas. La comprobación de los resultados obtenidos por la técnica de las funciones descriptivas se lleva a cabo mediante técnicas de simulación bien probadas y por los resultados experimentales obtenidos de los distintos amplificadores diseñados. La excelente concordancia demuestra que si bien es necesario a priori un conocimiento de las formas de onda, conocimiento obtenido a partir de medidas experimentales o del análisis de la acción de filtrado de las redes lineales del circuito, la aplicación de esta técnica a redes no-lineales multipuerta permite un análisis completo y general de este tipo de circuitos. El método propuesto permite sin excesiva complejidad matemática, una caracterización completa del amplificador incluyendo las formas de onda de las tensiones y corrientes, la síntesis de las impedancias de entrada y salida y el calculo de los principales parámetros característicos. Los resultados obtenidos confirman la capacidad de latecnica de las funciones descriptivas para analizar el sistema no-lineal a pesar de las limitaciones impuestas por las hipótesis de trabajo. Aunque existen otras técnicas de análisis de amplificadores de rf en el dominio del tiempo, dichos métodos no permiten, como lo hace la técnica de las funciones descriptivas, el análisis del circuito no-lineal en su totalidad y no proporcionan los parámetros necesarios para la síntesis y optimización de los circuitos de acoplo.
  • Publication
    Transmembrane voltage induced on altered erythrocyte shapes exposed to RF fields
    (Wiley-Liss, 2004-12) Muñoz San Martín, Sagrario; Sebastián Franco, José Luis; Sancho Ruíz, Miguel; Miranda Pantoja, José Miguel
    In this article, the transmembrane voltage induced on erythrocyte, codocyte, ovalocyte and spherocyte cell models exposed to a linearly polarised electromagnetic plane wave of frequency 1800 MHz is calculated. For this purpose, a finite element (FE) numerical technique with adaptive meshing is used. The results show that the value of the induced voltage on the original erythrocyte shape is higher than the one observed on the rest of the altered cell geometries studied. The erythrocyte shape and the membrane electric permittivity are shown to play a fundamental role on the values of the induced transmembrane voltage. Bioelectromagnetics 25:631-633, 2004. (C) 2004 Wiley-Liss, Inc.
  • Publication
    Internacionalización de las prácticas de laboratorio en las asignaturas del área de Electromagnetismo del grado de Ingeniería Electrónica
    (2018-10-15) Miranda Pantoja, José Miguel; Antoranz Canales, Pedro; Muñoz San Martín, Sagrario; Tejedor Álvarez, Luis Ángel; Sebastián Franco, José Luis; Díaz Gómez, Leonardo; Serna Galán, Julio; Herrera Fernández, Fernando; Villarín Rosales, Álvaro; Sánchez Ávila, Mario; Cereceda Arias, Marcos; Teba Baeza, Pedro Miguel; Fernández Rodríguez, Pablo; Oliver García, Clara
    En esta memoria se describen los resultados del proyecto num 122, "Internacionalización de las prácticas de laboratorio en las asignaturas del área de Electromagnetismo del grado de Ingeniería Electrónica". Se han realizado más de veinte vídeos divulgativos en ingles sobre las técnicas experimentales que se estudian en las asignaturas del Área de Electromagnetismo de la Ingeniería Electrónica de Comunicaciones. Estos vídeos se han cargado en un canal de Youtube, al que se puede acceder desde la página web www.ucm.es/elec.
  • Publication
    Erythrocyte rouleau formation under polarized electromagnetic fields
    (American Physical Society, 2005-09) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Miranda Pantoja, José Miguel; Álvarez Galindo, Gabriel
    We study the influence of an external electromagnetic field of 1.8 GHz in the formation or disaggregation of long rouleau of identical erythrocyte cells. In particular we calculate the variation of the transmembrane potential of an individual erythrocyte illuminated by the external field due to the presence of the neighboring erythrocytes in the rouleau, and compare the total electric energy of isolated cells with the total electric energy of the rouleau. We show that the polarization of the external electromagnetic field plays a fundamental role in the total energy variation of the cell system, and consequently in the formation or disaggregation of rouleau.
  • Publication
    Characterization of parasitics in microwave devices by comparing S and noise parameter measurements with two different on wafer calibration techniques
    (IEEE, 2001) Miranda Pantoja, José Miguel; Muñoz San Martín, Sagrario; Sebastián Franco, José Luis
    This paper presents a procedure for an accurate characterization of parasitic effects of terminal pads in microwave devices. This procedure is based on the measurement of S and Noise parameters of the device with two different sets of calibration standards, and simplifies the process of extracting the parasitic elements of the small signal equivalent circuit.
  • Publication
    Polarizability of shelled particles of arbitrary shape in lossy media with an application to hematic cells
    (American Physical Society, 2008-11) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Álvarez Galindo, Gabriel
    We show that within the dipole approximation the complex polarizability of shelled particles of arbitrary shape can be written as the volume of the particle times a weighted average of the electric field in the particle, with weights determined by the differences in permittivities between the shells and the external, possibly lossy media. To calculate the electric field we use an adaptive-mesh finite-element method which is very effective in handling the irregular domains, material inhomogeneities, and complex boundary conditions usually found in biophysical applications. After extensive tests with exactly solvable models, we apply the method to four types of hematic cells: platelets, T-lymphocytes, erythrocytes, and stomatocytes. Realistic shapes of erythrocytes and stomatocytes are generated by a parametrization in terms of Jacobi elliptic functions. Our results show, for example, that if the average polarizability is the main concern, a confocal ellipsoid may be used as a model for a normal erythrocyte, but not for a stomatocyte. A comparison with experimental electrorotation data shows quantitatively the effect of an accurate geometry in the derivation of electrical cell parameters from fittings of theoretical models to the experimental data.
  • Publication
    Dielectric characterization of bacterial cells using dielectrophoresis
    (Wiley-Liss, 2007-07) Sanchis, A.; Sancho Ruíz, Miguel; Martínez López, Genoveva; Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Miranda Pantoja, José Miguel
    Measurements of dielectrophoretic collection spectra of Escherichia coli and Staphylococcus aureus suspensions are used for obtaining dielectric characteristics of both types of bacteria. The experiments are interpreted using a numerical method that models the cells as compartmented spherical or rod-like particles. We show the usefulness of this simple method to extract significant information about the electrical properties of Gram-negative and -positive bacteria.
  • Publication
    Drain temperature dependence on ambient temperature for a cryogenic low noise C-band amplifier
    (IEEE, 1997) Muñoz San Martín, Sagrario; Sebastián Franco, José Luis; Miranda Pantoja, José Miguel
    A comparison between predicted and measured noise temperatures for cryogenic HEMT amplifiers is presented by using the Pospieszalski's noise model. A good agreement between predicted and measured amplifier's noise performance is obtained both at room and cryogenic temperatures. However, the predicted values overestimate noise temperature in the center part of the measured temperature range (50K - 230K). A parabolic dependence for the drain temperature with ambient temperature is proposed to obtain a better fitting to the experimental results.