Chiara Pelletti

Non-thermal effects of 2.45 GHz microwaves on spindle assembly, mitotic cells and viability of Chinese hamster V-79 cells

The production of mitotic spindle disturbances and activation of the apoptosis pathway in V79 Chinese hamster cells by continuous 2.45 GHz microwaves exposure were studied, in order to investigate possible non-thermal cell damage. We demonstrated that microwave (MW) exposure at the water resonance frequency was able to induce alteration of the mitotic apparatus and apoptosis as a function of the applied power densities (5 and 10mW/cm(2)), together with a moderate reduction in the rate of cell division. After an exposure time of 15 min the proportion of aberrant spindles and of apoptotic cells was significantly increased, while the mitotic index decreased as well, as compared to the untreated V79 cells. Additionally, in order to understand if the observed effects were due to RF exposure per se or to a thermal effect, V79 cells were also treated in thermostatic bath mimicking the same temperature increase recorded during microwave emission. The effect of temperature on the correct assembly of mitotic spindles was negligible up to 41°C, while apoptosis was induced only when the medium temperature achieved 40°C, thus exceeding the maximum value registered during MW exposure. We hypothesise that short-time MW exposures at the water resonance frequency cause, in V79 cells, reversible alterations of the mitotic spindle, this representing, in turn, a pro-apoptotic signal for the cell line.

Three-dimensional FSS elements with wide frequency and angular responses

In this paper, we describe a three-dimensional frequency-selective surface (FSS) element that generates a flat bandpass response over a wide band, as well as controllable low-pass angular response. The unit cell, which consists of a waveguide element with two connected cascaded radiating elements, exhibits a flat bandpass response over the frequency range 13 GHz to 24 GHz, i.e. a -3dB bandwidth (BW/f0) of 66.6%. We show that the angular response of the FSS can be controlled by changing its periodicity, which, in turn, determines the angle at which the first higher-order Floquet harmonic begins to propagate.

Analysis of Finite Conformal Frequency Selective Surfaces via the Characteristic Basis Function Method and Spectral Rotation Approaches

An efficient characteristic basis function (CBF)-based method is proposed to analyze conformal frequency selective surfaces (FSS) that are not amenable to analysis by using conventional numerical methods typically used to model infinite, planar, and doubly periodic FSSs. The technique begins by employing the CBFs to describe the currents induced on the elements. The reaction integrals needed to derive the reduced matrix elements are computed either in the spatial domain, or spectral domain, depending on the separation distance between the blocks, so as to make the process numerically efficient. The spectral domain integrals are evaluated by making use of the spectral rotation (SR) on the spectra of the CBFs to alleviate the computational burden to be associated with full three-dimensional (3-D) Fourier transform, which is required in the conventional spectral domain approach applied to nonplanar geometries. Numerical results from the new method have good agreement with the fully spatial characteristic basis function method (CBFM) and the conventional method of moments (MoM). However, the required central processing unit (CPU) time is greatly reduced.

A Computationally Efficient Technique for Prototyping Planar Antennas and Printed Circuits for Wireless Applications

In this paper, we present a novel procedure for an efficient and accurate electromagnetic simulation of microstrip circuits and printed antennas etched in layered media. The proposed approach, based on a new algorithm referred to herein as the equivalent medium approach (EMA), is applied for a rapid design of the preliminary desired circuit prototype. The illustrated technique yields reliable results and reduces the computational time in comparison with the conventional method of moments (MoM). Some examples that demonstrate the accuracy and the efficiency of the described procedure are included.

An Efficient Technique for the Evaluation of the Reduced Matrix in the Context of the CBFM for Layered Media

In this letter, we present a technique for an efficient evaluation of the reduced matrix in the context of the characteristic basis function method (CBFM) for the simulation of microstrip circuits printed on layered media. The underlying concept is to evaluate the off-diagonal terms of the reduced matrix, which vary much less rapidly then the diagonal ones, in the spectral domain, while the self-interactions are computed in the conventional way. Numerical examples are presented to demonstrate that the fill-time of the reduced matrix is reduced by working in the spectral domain, as compared to the spatial domain evaluation in the conventional CBFM, while maintaining the computational accuracy of the results. Furthermore, the efficiency of the present approach increases rapidly as the number of unknowns in each block is increased .

Signal processing approach to electromagnetic sub-wavelength imaging

In this paper, signal processing techniques are employed for electromagnetic sub-wavelength imaging. Three signal processing algorithms are investigated, including phase conjugation (PC), correlation method (CM) and maximum search and removal method (MSRM).

Volume Integral Equation Analysis of Thin Dielectric Sheet Using Sinusoidal Macro-Basis Functions

In this letter, we present an improvement over the conventional thin dielectric sheet (TDS) formulation for the analysis of thin dielectric sheets. Our focus is to address the problem of scattering from thin penetrable scatterers by developing a volumetric formulation based on the use of macro-basis functions. The electric fields produced by the source basis functions are derived directly, bypassing the summation of scalar and vector potentials. The latter results in a considerable time advantage in comparison to the conventional method of moments (MoM) solution of the volume electric field integral equation (V-EFIE), while the accuracy remains comparable. In contrast to the TDS formulation, both tangential and normal currents are employed so that problems with high and low permittivity, as well as those involving grazing incident angles, can be accurately analyzed. Several examples are reported that show excellent agreement with conventional techniques and demonstrate the effectiveness of the new approach.

Singularity-free approach for the evaluation of the matrix elements in the context of the method of moments based on the use of closed-form expressions for the fields radiated by the subdomain basis functions

The Method of Moments (MoM) is the most commonly used technique for solving the Electric Field Integral Equation (EFIE) formulated for problems involving electromagnetic scattering from metallic objects. This formulation entails the expansion of the unknown current on the surface of the scatterer in terms of known basis functions [1, 2]. A key issue in the MoM solution is the evaluation of the singular integrals, which can be performed both by numerical and semi-analytical techniques [3]. A commonly used approach is to apply the singularity-extraction techniques, which is based upon subtracting the singular terms from the kernel and integrating them analytically. In this work, we propose a new method for the above field calculation, which utilizes the analytical expression for the near fields radiated by an electrically small dipole. The proposed method is found to be well suited for mitigating the problem of singularities encountered in the process of field computation while constructing the MoM matrix.

Resolution Enhancement of Phase-Conjugating Lenses by Using Signal Processing Algorithms

In this letter, we show how we can improve the resolution capability of a phase-conjugating lens by employing a signal processing algorithm, namely the Minimum Residual Power Search Method (MRPSM), and we apply it for subwavelength imaging in the microwave regime by combining it with the well-known phase conjugation (PC) technique, which has been extensively used in the electromagnetics area for imaging purposes. We show that by using such a combination, we can achieve subwavelength resolution on the order of λ/10, even if the phase-conjugating lens or the measurement plane is located in the far-field region of the source. We describe the proposed algorithm in detail and study its ability to resolve at the subwavelength level, as well as its computational efficiency in a comparative manner.

A High-Order Characteristic Basis Function Algorithm for an Efficient Analysis of Printed Microwave Circuits and Antennas Etched on Layered Media

In this letter, we present a characteristic basis function method (CBFM) algorithm for an efficient “full-wave” analysis of printed microwave circuits and antennas etched on layered media. The main contribution of the proposed approach is a technique for the generation of the primary characteristic basis functions (PCBFs) in conjunction with the employment of high-order characteristic basis functions (CBFs), which enables us to implement a totally general decomposition scheme of the circuit under analysis. Numerical examples are presented to demonstrate the efficiency and the accuracy of the proposed approach.