The effect of cochlear implant insertion technique on post-operative neural response telemetry and impedance in paediatric patients.

OBJECTIVE: This study aimed to compare neural response telemetry and impedance between the round window and cochleostomy approaches for cochlear implantation. METHODS: In this case-control study, 64 patients aged less than 3.5 years underwent cochlear implantation via the round window or cochleostomy approach. Post-operative neural response telemetry and impedance were measured. RESULTS: The impedance measurements at electrodes 1, 11 and 22 showed no significant differences between the two groups three months after implantation (p = 0.90, p = 0.08 and p = 0.37, respectively). Similar results were observed six months after implantation (p = 0.71, p = 0.65 and p = 0.70, respectively). There was no significant difference in neural response telemetry between the two groups after three months. The neural response telemetry of electrode 1 in the cochleostomy group (171.26 ± 19.81 µV) was significantly higher in comparison with that of electrode 1 in the round window group (161.97 ± 12.71 µV) after six months (p = 0.03). The neural response telemetry values for electrodes 11 and 22 did not show any significant difference after six months (p = 0.14 and p = 0.48, respectively). CONCLUSION: Both approaches provide equal stimulation of the cochlear nerve and impedance.

Modeling and analysis of optical properties of a gold nanoring based on electric and magnetic dipoles.

The optical behavior of a plane-wave excited gold nanoring (NR), originated from localized surface plasmon resonance is modeled by two coupled electric- and magnetic-point dipoles. Considering the extinction cross-section spectrum, it is found that the electric-dipole effect is dominant in comparison with the magnetic-dipole effect although the magnetic-dipole signature is observable in the near-field response of the NR. In addition, the far-field electromagnetic radiation pattern of the NR verifies the corresponding radiation pattern of the point dipoles. The numerical simulation near-field results are in agreement with the proposed electric- and magnetic-dipole theory.

Strong optical interaction of two adjacent rectangular nanoholes in a gold film.

The strong near-field optical interaction between two adjacent nanoholes milled in a gold film is investigated. A single nanohole is modeled as a magnetic dipole described by the simple relation between the magnetic- and electric-polarization in electromagnetic theory. To elucidate the role of the electric and magnetic fields in near-field characteristics of a nanohole illuminated by an optical plane-wave, the normalized electric and magnetic power amplitudes are accordingly introduced. This is extended to model the strong optical interaction of the two adjacent nanoholes in the near-field regime, leading to the magnetic coupled-dipole approximation (MCDA). It is shown that the optical transmission spectrum of the nanostructure may exhibit hybridized resonant peaks, depending on the configuration or the polarization. Compared to the known effects in the optical properties of a pair of metal nanoparticles for which the electric-field of the incident light is crucial, here it is illustrated that the magnetic-field of the incident light plays the dominant role in defining the optical properties of the complement structure. Thus, the strength of the interaction of the two adjacent nanoholes and the resulting hybridized plasmon resonances are strongly depends on the magnetic-field orientation in respect to the pair axis as well as on the separating distance of the nanoholes. The theoretical findings are supported by the electromagnetic computations.