Electromagnetic wave propagation in rain and polarization effects

This paper summarizes our study on microwave and millimeter-wave propagation in rain with special emphasis on the effects of polarization. Starting from a recount of our past findings, we will discuss developments with these and how they are connected with subsequent research

Towards functional noninvasive imaging of excitable tissues inside the human body using focused microwave radiometry

Focused microwave radiometry, aiming mainly in clinical applications at measuring temperature distributions inside the human body, may provide the capability of detecting electrical conductivity variations at microwave frequencies of excitable cell clusters, such as in the case of brain tissues. A novel microwave radiometric system, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed for the imaging of biological tissues via contactless measurements. The measurement is realized by placing the human head in the region of the first focus and collecting the radiation converged at the second by an almost Isotropic dipole antenna connected to a sensitive radiometer operating at 3.5 GHz. In order to compute the focusing properties of the ellipsoidal reflector, an accurate electromagnetic numerical analysis is developed using a semianalytical method. The experimental part of this study focuses on measurements of activation of the primary somatosensory (SI) brain area, elicited during the application of the cold pressor test, a standard experimental condition inducing pain. Analysis of the measured data from 16 healthy subjects suggests that this methodology may be able to pick up activation of the SI during the pain conditions as compared with the nonpainful control conditions. Future research is needed in order to elucidate all the interacting factors involved in the interpretation of the presented results. Finally, potential limitations to the generalization of our results and strategies to improve the system's response are discussed

An l-band low profile spiral mobile antenna: Design and realization

The design characteristic-s of a compact size spiral type antenna, suitable for satellite mobile communications are determined. Criteria used in designing the antenna are low profile shape, circular polarization, optimum radiation pattern for European latitudes and simplicity in construction. Several experimental results measured on a constructed prototype are shown, exhibiting a satisfactory behaviour of the radiation properties. Some suggestions are also given for further improvement of the antenna unit. © 1995 Taylor & Francis Group, LLC

Inversion of Simulated Evoked Potentials to Charge Distribution Inside the Human Brain Using an Algebraic Reconstruction Technique

An analytic method is presented to estimate the evolution of electrical charge distribution inside the human brain related to the evoked potentials observed on the head surface. A three-layered concentric spherical human head model is adopted to express the relation between the observed potentials on the head surface and the spatial charge distribution inside the brain. In this context an integral equation associated with the three-layered concentric head model Green’s function is employed. Assuming the electric potentials are measured on the head surface, the charge distributions inside the human brain are computed by solving an inverse problem. To this end the Green’s function integral equation is inverted by using an algebraic reconstruction technique widely employed in X-ray tomography imaging. The accuracy of the proposed technique is examined by employing computer simulations and by checking the self-consistency of the developed algorithm. © 1991 IEE

Motive related positivity: Decision-making during a prisoners' dilemma task

The neural mechanisms underlying decision-making to cooperate or defect were investigated using event-related potentials during an iterated computer Prisoner's Dilemma task, adapted to induce working memory operation. Event-related potentials from 64 leads of 22 participants were recorded during 90 trials and averaged depending on the condition of cooperation and defect. The P200 component of the event-related potentials provided evidence for activation differences between cooperation and defect. Cooperation elicited significantly increased P200 activation at parieto-occipital leads, while defect activated primarily the prefrontal electrodes. Functional mapping using Low Resolution Electromagnetic Tomography indicated that in the 150-180 ms time window Brodmann areas 19 (precuneus) and 17 (lingual gyrus), exhibited increased activation during cooperation, while Brodmann area 6 (precentral gyrus) exhibited increased activation when participants defected. In conclusion, the current study provides evidence that cooperation and defect elicit different brain activation at specific loci and within specific time windows. © 2013 Imperial College Press