Publications by authors named "Pinchas D Einziger"

We present an analytical model for the optical emission of a two-dimensional source in a flexible organic light-emitting diode formation with arbitrary curvature. The formulation rigorously produces closed-form analytical expressions which clearly relate the emission pattern and the device configuration, in particular, the radius of curvature. We investigate the optical properties of a prototype model through the resultant expressions, revealing that the bending induces a dramatic enhancement of emission to large angles, allowing for large viewing angle and reduced total internal reflection losses.

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We present an analytical method for extracting the recombination zone location from emission patterns produced by organic LEDs (OLEDs). The method is based on derivation of the closed-form expressions for OLED-radiated power developed in previous work and formulation of the analytical relations between the emitter position and the pattern extrema. The results are confirmed to be in good agreement with reported optical measurements.

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Image reconstruction in electrical impedance tomography is, generally, an ill-posed nonlinear inverse problem. Regularization methods are widely used to ensure a stable solution. Herein, we present a case study, which uses a novel electrical impedance tomography method for reconstruction of layered biological tissues with piecewise continuous plane-stratified profiles.

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The reconstruction of layered biological tissues, via electrical impedance tomography, is carried out by utilizing two alternative linear transformations, namely, Legendre polynomial expansion and Fourier Bessel transform. Both transformations are performed on a recently proposed image series expansion scheme in conjunction with the WKB approximation. The resultant spectrum posses a crucially important locality feature, assigning analytically to each spectral image term a local impedance associated with a unique layer, and thereby leading to efficient and accurate novel reconstruction procedures.

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Ultrasound contrast agents (UCA), created originally for visualization and diagnostic purposes, recently have been suggested as efficient enhancers of ultrasonic power deposition in tissue. The ultrasonic energy absorption by the contrast agents, considered as problematic in diagnostic imaging, might have beneficial impact in therapeutic applications such as targeted hyperthermia-based or ablation treatments. Introduction of gas microbubbles into the tissue to be treated can improve the effectiveness of current treatments by limiting the temperature rise to the treated site and minimizing the damage to the surrounding healthy tissues.

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Herein, the well-known cable equation for nonmyelinated axon model is extended analytically for myelinated axon formulation. The myelinated membrane conductivity is represented via the Fourier series expansion. The classical cable equation is thereby modified into a linear second order ordinary differential equation with periodic coefficients, known as Hill's equation.

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The quasi-static electromagnetic field interaction with three-dimensional infinite-cylindrical cell is investigated for both intracellular (IPS) and extracellular (EPS) current point-source excitation. The induced transmembrane potential (TMP), expressed conventionally via Green's function, may alternatively be expanded into a faster-converging representation using a complex contour integration, consisting of an infinite-discrete set of exponentially decaying oscillating modes (corresponding to complex eigenvalues) and a continuous source-mode convolution integral. The dominant contributions for both the IPS and EPS problems are obtained in simple closed-form expressions, including well documented special mathematical functions.

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