Design of a Remote, Multi-Range Conductivity Sensor.

So far, research on remote conductivity detection has primarily focused on large conductivities. This paper examines the entire conductivity range, proposing a method that can be adapted to the desired application. The optimization procedure for the different regions is presented and discussed. Specific interest is given to the low-conductivity range, below 10 S/m, which covers human body tissues. This could lead to applications in body imaging, especially for induction tomography. Conductivities below 12.5 S/m are extracted experimentally with an error below 10%.

Tailoring the dispersion characteristics in planar arrays of discrete and coalesced split ring resonators.

In this report, the coupling and dispersion characteristics of discrete and coalesced square resonators was investigated in the MHz regime. Resonators with one and three gaps were considered. When the resonators are not in direct contact, the number of gaps has little effect upon the total coupling, which is negative. When the resonators are connected so that they share one side, the coupling can change drastically depending on the number of gaps. In particular, when the shared side has a gap, the total coupling coefficient switches to positive values, making it possible for forward travelling waves to propagate on arrays. Experimental, numerical and analytical data verify this behaviour.

Switchable unidirectional waves on mono- and diatomic metamaterials.

We demonstrate switchable unidirectional propagation of slow waves of coupling within a metamaterial array of strongly coupled elements. We predict theoretically and verify experimentally that the direction of propagation of magnetoinductive waves for any chosen excitation pattern is dictated by the dispersion relations, with forward and backward waves propagating in opposite directions along a chain of meta-atoms. We further prove that the same fundamental phenomenon of direction selectivity due to the forward/backward wave nature is not limited to magnetoinductive waves: we predict analytically and verify numerically the same selective unidirectional signal propagation occurring in nanostructured metamaterial arrays with purely electric coupling. Generalising our method of unidirectional waveguiding to a diatomic magnetoinductive array featuring both forward-wave and backward-wave dispersion branches, switchable unidirectional signal propagation is achieved with distinct frequency bands with opposite directions of signal propagation. Finally, by expanding our technique of selective unidirectional waveguiding to a 2D metasurface, a selective directional control of waves in two dimensions is demonstrated opening up possibilities for directional wireless signal transfer via magnetoinductive surfaces. The observed phenomenon is analogous to polarisation-controlled near-field interference for unidirectional guiding of surface plasmon-polaritons.

Plasmonic excitations in metallic nanoparticles: resonances, dispersion characteristics and near-field patterns.

Metamaterials acquire their functionality from the structuring of the small building blocks, "artificial atoms". Our paper provides a study of the resonant behaviour for a variety of metallic nanoparticles in the region of hundreds of THz. Resonant modes for nanorods of rectangular cross section are investigated numerically for different types of excitation and the set of resonant frequencies (fundamental and higher order) are determined for rods of various length. From that the dispersion relationship for surface plasmon-polaritons propagating along the rod is deduced. We analyse resonant-mode near-field distribution of the electric field, including the field lines, to emphasise the underlying physics. Resonant frequencies are also found and field distributions analysed when the rods are combined to form particles of L, U and O shapes. The similarities and differences between those particles, both in the values and in the number of resonances, are discussed. The results of this study may aid the design of nanostructured metamaterials with required properties in the IR and optical domain.

Pulse delay and propagation through subwavelength metallic slits.

The transmission properties of a 2D metallic grating are investigated at optical wavelengths for an incident Gaussian pulse having pulse widths from 100 fs to 10 ps. The slits in the grating are subwavelength which can nevertheless allow significant transmission in the narrow wavelength regions where the so-called surface plasmon polariton (SPP) and waveguide mode resonances occur. The solution is obtained for each spectral component of the pulse by using the rigorous coupled wave approach and then the temporally varying output pulse is reconstructed by the standard method of taking an inverse Fourier transform. The delay of the pulse and the output pulse widths are determined by taking the first and second order moments of the Poynting vector with respect to time. It is shown that the time delay may be significant, as much as 256 fs for a pulse width of 200 fs for the SPP resonance but quite small (32 fs) for the waveguide mode resonance. The focus of the work is on demonstrating how the pulse delay evolves as the pulse propagates in the half-space beyond the grating. It is shown that the distance over which the time delay develops is much larger than the actual longitudinal dimension of the grating structure and it is approximately the same distance over which the stored energy and the vortices of the Poynting vector extend.

Arterial complications following cardiac catheterization in children less than 10 kg.

We sought to determine if a higher dose of heparin would reduce arterial complications in patients weighing 10 kg or less undergoing cardiac catheterization to investigate congenital heart disease. Sixty patients were given either 100 (group A) or 150 (group B) IU x kg(-1) of heparin in a double-blinded randomized manner. Initial arterial access was established using a 4F cannula in all patients. Mean activated clotting time measured 20 minutes following heparin administration was significantly lower in group A than in group B (199 versus 251 seconds). Only 3 out of 60 patients (5%) required treatment for loss of femoral pulse. The age, weight, activated clotting time, length of catheterization procedure, time taken to establish arterial access, and the duration of arterial cannulation were comparable between the groups. Weight under 4 kg, age under 1 month, and cannula size larger than 4F were identified as independent risk factors for the development of arterial complications. Arterial access using a 4F cannula is a safe procedure in children weighing 10 kg or less. The incidence of significant arterial complications is low, and they do not appear to be preventable by a higher dose of heparin.