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A large reactor for performing dielectric barrier discharges (DBD) experiments at atmospheric pressure (AP) has been built and tested. The area of electrodes is more than 40 times greater than that of a small DBD cell, in which we have perfected a method formeasuring Eg, the energy dissipated per cycle of the applied a.c. high voltage, Va( f). This methodology has been successfully applied to plasma polymerization experiments on the larger system, using volatile organic precursors (dopants) at ‰ concentrations in 10 standard liters per minute of argon (Ar). We measured Δ Eg, the energy difference with and without dopant, for Va( f) ∼ 3 kVrms (20 ≤ f ≤ 40 kHz). From Δ Eg we then derived Etot/ N, the energy per molecule, and observed surprisingly good agreement with data published in the literature relating to low-pressure (LP) plasmas. [ABSTRACT FROM AUTHOR]

Assessing the performance of electrical impedance tomography (EIT) systems usually requires a phantom for validation, calibration, or comparison purposes. This paper describes a resistive mesh phantom to assess the performance of EIT systems while taking into account cabling stray effects similar to in vivo conditions. This phantom is built with 340 precision resistors on a printed circuit board representing a 2-D circular homogeneous medium. It also integrates equivalent electrical models of the Ag/AgCl electrode impedances. The parameters of the electrode models were fitted from impedance curves measured with an impedance analyzer. The technique used to build the phantom is general and applicable to phantoms of arbitrary shape and conductivity distribution. We describe three performance indicators that can be measured with our phantom for every measurement of an EIT data frame: SNR, accuracy, and modeling accuracy. These performance indicators were evaluated on our EIT system under different frame rates and applied current intensities. The performance indicators are dependent on frame rate, operating frequency, applied current intensity, measurement strategy, and intermodulation distortion when performing simultaneous measurements at several frequencies. These parameter values should, therefore, always be specified when reporting performance indicators to better appreciate their significance. [ABSTRACT FROM AUTHOR]

Finite element modeling of the skin is useful to study the electrical properties of cutaneous tissues and gain a better understanding of the current distribution within the skin. Such an epithelial finite element model comprises extremely thin structures like cellular membranes, nuclear membranes, and the extracellular fluid. Meshing such narrow spaces considerably increases the number of elements leading to longer computing time. This also greatly reduces the number of epithelial cells that can be assembled before reaching computing limitations. To avoid the problem of meshing extremely narrow spaces while unnecessarily increasing the number of elements, we present a new hybrid modeling approach to develop a 3-D finite element model of the skin. This skin model comprises all skin layers, different lesion types, and a complete electrode model. It is used to analyze the complex electrical behavior of normal and malignant skin tissues. The current distribution within this model is also simulated to assess the depth of field achievable by an electrical impedance tomography system at different operating frequencies. [ABSTRACT FROM AUTHOR]

Completely or partially disconnected electrodes are a fairly common occurrence in many electrical impedance tomography (EIT) clinical applications. Several factors can contribute to electrode disconnection: patient movement, perspiration, manipulations by clinical staff, and defective electrode leads or electronics. By corrupting several measurements, faulty electrodes introduce significant image artifacts. In order to properly manage faulty electrodes, it is necessary to: 1) account for invalid data in image reconstruction algorithms and 2) automatically detect faulty electrodes. This paper presents a two-part approach for real-time management of faulty electrodes based on the principle of voltage-current reciprocity. The first part allows accounting for faulty electrodes in EIT image reconstruction without apriori knowledge of which electrodes are at fault. The method properly weights each measurement according to its compliance with the principle of voltage-current reciprocity. Results show that the algorithm is able to automatically determine the valid portion of the data and use it to calculate high-quality images. The second part of the approach allows automatic real-time detection of at least one faulty electrode with 100% sensitivity and two faulty electrodes with 80% sensitivity enabling the clinical staff to fix the problem as soon as possible to minimize data loss. [ABSTRACT FROM AUTHOR]