1,721,022 research outputs found
Proving lightning role in the evolution of life. Comment on "Lightning-triggered electroporation and electrofusion as possible contributors to natural horizontal gene transfer" by Tadej Kotnik.
No full text[No abstract available
NUOVE APPLICAZIONI DI CAMPI ELETTRICI PULSATI IN MEDICINA
No full textGLI IMPULSI DI CAMPO ELETTRICO ULTRABREVI SONO UNA DELLE NUOVE FRONTIERE DELLA RICERCA BIO-ELETTROMAGNETICA. LE APPLICAZIONI MEDICALI POSSONO INTERESSARE LA TERAPIA DEL CANCRO, LA DEFIBRILLAZIONE, LA CURA DI MALATTIE NEURODEGENERATIV
Quantitative Assessment of Dielectric Parameters for Membrane Lipid Bi-Layers from RF Permittivity Measurements
No full textIn this article, we propose and validate theoretical and experimental methods to quantitatively assess the Debye dielectric model of membrane lipid bi-layers. This consists of two steps: permittivity measurements of biological solutions (liposomes), and estimation of the model parameters by inverse application of the Effective Medium Theory. The measurements are conducted in the frequency domain between 100 MHz and 2 GHz using a modified coaxial connector, at the temperatures of 27 and 30 degrees C. Estimations have been performed using a three-layered model based on the Maxwell-Wagner formulation. Debye parameters (mean value standard error) found from fitting experimental data are: epsilon(s) = 11.69 +/- 0.09, epsilon(infinity) = 4.00 +/- 0.07, f(relax) = 179.85 +/- 6.20 MHz and epsilon(s) = (1.1 +/- 0.1) x 10(-7) S/m. This model can be used in microdosimetric studies aiming to precisely determine the E-field distribution in a biological target down to the single cell level. In this context the use of an accurate membrane dielectric model, valid through a wide frequency range, is particularly appropriate. Bioelectromagnetics 30:286-298, 2009. (C) 2009 Wiley-Liss. Inc
Microdosimetry for ultrashort electric pulses: A literature review
No full textA review of the electromagnetic (EM) approaches used for electric (E) field and transmembrane potential (TMP) evaluation (i.e. microdosimetry) on cells exposed to ultra short-pulsed E fields (usPEF) is presented in this paper. The literature classification is provided on the basis of the EM solution type (i.e. analytical, numerical) and of the analyzed biological target (i.e. single cell, clusters). Moreover, for each EM approach, dielectric modeling of cell compartments is described as well as the various cell shapes employed and pulses characteristics. The EM solutions coupling with biophysical models as those used for membrane electroporation is also discussed. © 2012 IEEE
A Microwave Microdosimetric Study on Blood Cells: Estimation of Cell Membrane Permittivity and Parametric EM Analysis
No full textIn the study of the interaction of RF and MW fields with biological systems particular attention has been recently devoted to microdosimetric research. In this paper a microdosimetric study on erythrocytes is proposed. Facing this topic, two fundamental steps are needed: the set tip of a proper membrane dielectric model valid up to the RF and MW range, and the set up of an appropriate EM solution on the cell environment. Concerning the first point, an accurate estimation of the membrane dielectric model and of its uncertainty has been performed, from permittivity measurements of erythrocytes solutions. Focusing on the second point, a quasi-static EM analysis solving the Laplace equation has been chosen. An analytical approach has been applied on simplified spherical cell geometry, while a numerical solver has been used for erythrocyte shaped cell. In this context the fundamental role of the dielectric membrane modeling on results reliability has been highlighted
Non-phase transition magnetic-responsive liposomes controlled by low intensity magnetic stimuli
No full textControllable release from high-transition temperature magnetoliposomes by low-level magnetic stimulation
No full textHigh-transition temperature liposomes with embedded coated magnetite nanoparticles were prepared using the thin lipid film hydration method in order to obtain magnetoliposomes not sensitive to temperature increase (at least up to 50 degrees C). Accordingly, drug can be released from such magnetoliposomes using a low-level electromagnetic field as triggering agent, while no delivery would be obtained with temperature increase within the physiological acceptable range. The hypothesized release mechanism involves mechanical stress of the liposome membrane due to nanoparticles oscillations and it is investigated by means of a numerical model evaluated using multiphysics simulations. The carrier content was repetitively released by switching on and off a 20 kHz, 60 A/m magnetic field. The results indicated high reproducibility of cycle-to-cycle release induced by the magnetic-impelled motions driving to the destabilization of the bilayer rather than the liposome phase transition or the destruction of the liposome structur
Dielectric spectroscopy of blood cells suspensions: Study on geometrical structure of biological cells
No full textA promising procedure combining dielectric spectroscopy of red blood cells and an inverse application of an Effective Medium Theory (EMT) has been realized to prove the plausibility to obtain cells morphological information. This theoretical-experimental methodology could be the basis for an accurate and simple tool in diagnosis and research activity, especially when cell morphological alterations are a prime indicator of illness as in all hematopoietic pathologies. © 2006 IEEE
Microdosimetric Study for Nanosecond Pulsed Electric Fields on a Cell Circuit Model with Nucleus
No full textRecently, scientific interest in electric pulses, always more intense and shorter and able to induce biological effects on both plasma and nuclear membranes, has greatly increased. Hence, microdosimetric models that include internal organelles like the nucleus have assumed increasing importance. In this work, a circuit model of the cell including the nucleus is proposed, which accounts for the dielectric dispersion of all cell compartments. The setup of the dielectric model of the nucleus is of fundamental importance in determining the transmembrane potential (TMP) induced on the nuclear membrane; here, this is demonstrated by comparing results for three different sets of nuclear dielectric properties present in the literature. The results have been compared, even including or disregarding the dielectric dispersion of the nucleus. The main differences have been found when using pulses shorter than 10 ns. This is due to the fact that the high spectral components of the shortest pulses are differently taken into account by the nuclear membrane transfer functions computed with and without nuclear dielectric dispersion. The shortest pulses are also the most effective in porating the intracellular structures, as confirmed by the time courses of the TMP calculated across the plasma and nuclear membranes. We show how dispersive nucleus models are unavoidable when dealing with pulses shorter than 10 ns because of the large spectral contents arriving above 100 MHz, i.e., over the typical relaxation frequencies of the dipolar mechanism of the molecules constituting the nuclear membrane and the subcellular cell compartments
An Over-Moded TEM Cell System for in Vivo Exposure at 2.45 GHz
No full textA TEM cell designed to operate at 900 MHz for exposing small-restrained animals (e.g. mice) has been theoretically, numerically and experimentally characterized at 2.45 GHz, which is the central frequency of the WiFi protocol. This study aims at evaluating the influence of higher order modes on the field homogeneity. The results demonstrate the superposition of a tolerable standing wave, due to reflections at the cell terminations, and a slight beat wave due to the interference between different modes. Nevertheless, the final outcome is that the system can still be efficiently used to expose small animals in specific WiFi channels, provided they are properly placed in correspondence to the maxima of the electric field along the guide length
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