Funneling Spontaneous Emission into Waveguides via Epsilon-Near-Zero Metamaterials

In this work, we discuss the use of epsilon-near-zero (ENZ) metamaterials to efficiently couple light radiated by a dipolar source to an in-plane waveguide. We exploit both enhanced and directional emission provided by ENZ metamaterials to optimize the injection of light into the waveguide by tuning the metal fill factor. We show that a net increase in intensity injected into the waveguide with respect to the total power radiated by the isolated dipole can be achieved in experimentally feasible conditions. We think the proposed system may open up new opportunities for several optical applications and integrated technologies, especially for those limited by outcoupling efficiency and emission rate.

Evaluation of Different EEG Source Localization Methods Using Testing Localization Errors

The ideas underlying the quantitative localization of the sources of the EEG review within the brain along with the current and emerging approaches to the problem. The ideas mentioned consist of distributed and dipolar source models and head models ranging from the spherical to the more realistic based on the boundary and finite elements. The forward and inverse problems in electroencephalography will debate. The inverse problem has non-uniqueness property in nature. More precisely, different combinations of sources can produce similar potential fields occur on the head. In contrast, the forward problem does have a unique solution. The forward problem calculates the potential field at the scalp from known source locations, source strengths and conductivity in the head, and it can be used to solve the inverse problem. In the final part of this paper, we compare the performance of three well–known EEG source localization techniques which applied to the underdetermined (distributed) source localization of the inverse problem. These techniques consist of LORETA, WMN and MN, which comparing by testing localization error.

Neuroplastic alterations in brain responses to painful visceral stimulations reflects individual neuropathic symptoms in diabetes mellitus patients

Background/aimsAbnormal visceral sensory function in diabetes mellitus (DM) leads to neuronal changes in the enteric, peripheral and/or central nervous system (CNS). To explore the role of diabetic autonomic neuropathy (DAN) in patients with long-standing DM, we investigated psychophysical responses and neuronal activity recorded as evoked brain potentials (EPs) and dipolar source modelling.MethodsFifteen healthy volunteers and 14 type-1 DM patients with DAN were assessed with a symptom score index characterizing upper GI abnormalities. Multi-channel (62) electroencephalography was recorded during painful electrical stimulation of the lower oesophagus. Brain activity to painful stimulations was modelled by use of Brain Electrical Source Analysis (BESA).ResultsDiabetic patients had higher stimulus intensities to evoke painful sensation (P<0.001), longer latencies of N2 and P2 components (both P<0.001), lower amplitudes of P1–N2 and N2–P2 complexes (P<0.001; P = 0.02). Inverse modelling of brain sources showed deeper bilateral insular dipolar source localization (P = 0.002). Symptom score index was negatively correlated to the depth of insular activity (P = 0.004) and positively correlated to insular dipole strength (P = 0.03).ConclusionDM patients show neuroplastic changes in the central nervous system. The role of abnormal insular processing may explain the development and persistence of upper GI-symptoms related to DAN. This enhanced understanding of DAN may have clinical and therapeutical implications.

A Consistency Test of Thickness and Loading Noise Codes Using Ffowcs Williams and Hawkings Equation

The thickness noise predicted by the Ffowcs Williams and Hawkings (FW&H) equation depends on the normal velocity which is very sensitive to the meshing size. Isom showed that in far field a monopolar source is equivalent to a dipolar source induced by a uniform distribution of the load on the entire moving surface. The main objective of this paper is to determine a specific expression of Isom's thickness noise in time and frequency domains for subsonic fans. The scope of the proposed expression of Isom's thickness noise is to define a benchmark test of consistency for thickness and loading noise codes in both time and frequency domains for subsonic fans when using the free field solution of FW&H's equation.