Search

Purpose: to identify new functional parameters that may help in the early primary open angle glaucoma (POAG) diagnosis.

"In the context of BCI-driven electrical stimulation for tremor suppression, a model of the upper limb is presented. The model simulates arm behaviour in terms of nerve recruitment and muscle contraction when current pulses are applied on the skin surface. Tests with array electrodes show that. the proposed arm model is a good tool for selecting the suitable electrode design and stimulation parameters for an effective muscle contraction."

In this contribution, we present the design of cylindrical electromagnetic cloaks working at optical frequencies, making use of layered structures of plasmonic and non-plasmonic materials. The simulated results confirm the validity of the proposed approach and show a rather broad-band behavior of the cloaking device., Comment: 2 pages, 2 figures, submitted to EOS Topical Meeting on Nanophotonics, Photonic Crystals and Metamaterials - TOM 3 - 2008

Echinoderm Mutable Collagenous Tissues (MCTs) undergo nervously mediated, drastic and reversible changes in their passive mechanical properties. MCT mutability is involved in autotomy, posture maintenance and motility, and, as a consequence, it influences all aspects of echinoderm biology (nutrition, reproduction, habitat selection, self-defense and predatory behavior) representing a key-factor for the ecological success of the phylum. Besides this, MCT performance represents a topic of remarkable interest for many different applied fields. A biomimetic research route looks at MCTs as a source of inspiration for the development of smart and innovative biomaterials with great potential for in vitro and in vivo applications when controlled and reversible plasticization and/or stiffening of the extracellular matrix is required. The MIMESIS (Marine Invertebrate Models & Engineered Substrates for Innovative bio-Scaffolds) project has been developed within this scientific context. The selected echinoderm model is the common sea urchin Paracentrotus lividus. This project is based on a multidisciplinary approach combining functional biology with biomaterial engineering. A brief review of recent morphological, biomolecular, biomechanical and biochemical results on P. lividus MCTs are here presented in a biotechnological perspective, taking into account also a promising application regarding the use of MCT-derived substrata for cell culture studies.

We numerically demonstrate that properly designed plasmonic covers can be used to enhance the performance of near-field scanning optical microscopy (NSOM) systems based on the employment of apertureless metallic tip probes. The covering material, exhibiting a near-zero value of the real permittivity at the working frequency, is designed in such a way to dramatically reduce the undesired scattering due to the strongly plasmonic behavior of the tip. Though the light scattering by the tip end is necessary for the correct operation of NSOMs, the additional scattering due to the whole probe affects the signal-to-noise ratio and thus the resolution of the acquired image. By covering the whole probe but not the very tip, we show that unwanted scattering can be effectively reduced. A realistic setup, working at mid-IR frequencies and employing silicon carbide covers, has been designed and simulated to confirm the effectiveness of the proposed approach.

Here we extend the plasmonic cloaking technique to irregularly shaped objects with anisotropic scattering response. The scattering-cancellation approach to cloaking [A. Alu and N. Engheta, Phys. Rev. E 72, 016623 (2005)] has been extensively applied in the past to symmetrical geometries and canonical shapes. However, recent papers have raised some doubts concerning the fact that its use may not be as effective when dealing with strongly anisotropic and noncanonical geometries. Our goal here is to extend the plasmonic cloaking technique to irregular obstacles and to show that proper cloak design may provide a significant and uniform scattering reduction, independent of angle of incidence, position, and polarization of the illumination. We investigate how the volumetric effect of scattering cancellation provided by plasmonic media may drastically suppress the scattering for these irregular geometries independent of the illumination angle, and we shed some light on the physical mechanisms and the design rules at the basis of this cloaking technique when applied to objects whose scattering properties are dependent upon polarization and angle of incidence.

In this contribution, we practically show the use of “antiphase” plasmonic scatterers to effectively reduce the scattering cross-section of a cylindrical dielectric object in the visible regime. By properly distributing a set of silver rods around a cylindrical inner core of silica, we demonstrate through a set of full-wave simulations the possibility to obtain a sensible reduction of the scattering phenomenon, achieving a condition of transparency for the structure.

In this contribution, we present the employment of a Genetic Algorithm (GA) based procedure to retrieve the effective permittivity and permeability of planar metamaterial samples. The approach used here is the same of standard Transmission/Reflection (TR) techniques, consisting in extrapolating the sample properties by inversion of its scattering coefficients. The proposed procedure makes use of parametric models for describing the inherently dispersive behavior of the involved materials. This approach eliminates the anomalous behavior of most of the commonly used inversion techniques, providing a consistent representation of the material in the working frequency range. The transition to bulk effective parameters is also investigated determining a proper sample thickness assuring the validation of the homogenization procedure.

In this paper, we present the theoretical analysis and the design of cylindrical multilayered electromagnetic cloaks based on the scattering cancellation technique. We propose at first the analysis and the design of bi-layered cylindrical shells, made of homogenous and isotropic metamaterials, in order to effectively reduce the scattered field from a dielectric cylindrical object. The single shell and the bi-layered shell cases are compared in terms of scattering reduction and loss effects. The comparison shows that the bi-layered configuration exhibits superior performances. The scattering cancellation approach, is, then, extended to the case of generic multilayered cylindrical shells, considering again homogeneous and isotropic metamaterials. The employment of the proposed technique to the case of cloaking devices working at multiple frequencies is also envisaged and discussed. Finally, some practical layouts of cylindrical electromagnetic cloaks working at optical frequencies are also proposed. In these configurations, the homogenous and isotropic metamaterials are replaced by their actual counterparts, obtained using alternating stacked plasmonic and non-plasmonic layers. The theoretical formulation and the design approaches presented throughout the paper are validated through proper full-wave numerical simulations.

In this letter, we present the theoretical analysis and the design principles of electromagnetic cloaking devices working at optical frequencies. The cloaking approach is based on the scattering cancellation principle. The robustness of the cloaking devices is also discussed, proposing a proper figure of merit and validating the design through a set of full-wave numerical simulations. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2713–2717, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24718

In this paper, we present the design of cylindrical and spherical electromagnetic cloaks working at visible frequencies. The cloak design is based on the employment of layered structures consisting of alternating plasmonic and non-plasmonic materials and exhibiting the collective behavior of an effective epsilon-near-zero material at optical frequencies. The design of a cylindrical cloak to hide cylindrical objects is firstly presented. Two alternative layouts are proposed and both magnetic and non-magnetic objects are considered. Then, the design of spherical cloaks is also presented. The full-wave simulations presented throughout the paper confirm the validity of the proposed setup, and show how this technique can be used to reduce the observability of cylindrical and spherical objects. The effect of the losses is also considered.

Date of Conference: 27-31 Oct. 2008 Conference name: 38th European Microwave Conference, 2008 This paper is focussed on the miniaturization and characterization of semi-lumped resonators, of interest for the synthesis of metamaterial-based structures such as metamaterial transmission lines, frequency selective surfaces, absorbers, and radiating elements, among others. The particles consist on metallic patterns etched on a dielectric and are inspired on the split ring resonator, SRR (that is, the formerly resonant particle used for the synthesis of left handed metamaterials). The different strategies for miniaturization are discussed and examples are given. It is shown that by using two metallic levels connected through vias it is possible to achieve very small electrical size for the particles (namely, below λ/100, where λ is the wavelength in the considered substrate at resonance). A method to determine the electrical parameters of the resonators in metamaterial transmission line configurations is also presented, and the possibility to determine the characteristics of the isolated particles is discussed. Finally, examples of application of this technique are presented. This work is of interest for the synthesis of effective media metamaterials based on resonant elements. © 2008 EuMA.

The authors present the design of a multi-functional dipole antenna based on the employment of artificial magnetic metamaterials. A regular dipole antenna is placed in front of a metamaterial slab, whose effective permeability is described through the Lorentz dispersion model. Since the electromagnetic behaviour of the layer changes with the frequency, the dipole antenna may work in different operation modes. Specifically, around the resonant frequency of the effective permeability, the slab acts as an artificial magnetic conductor, while, when the effective permeability is close to zero, it behaves as a spatial filter allowing, for a given polarisation, the transmission of only a few angular components around the broadside. The proposed design is shown to be robust to the variations of the main electrical and geometrical parameters of the metamaterial slab and suitable for an actual implementation through real-life magnetic inclusions. Interesting applications of such an antenna can be found in radio base stations of mobile communication systems and in multi-functional radiators mounted in complex platforms, where space occupancy and electromagnetic interference between different sources have to be minimised.

In this paper, we present the design of an electromagnetic cloaking device working for both transverse electric (TE) and transverse magnetic (TM) polarizations. The theoretical approach to cloaking used here is inspired by the one presented by Alù and Engheta (2005 Phys. Rev. E 72 016623) for TM polarization. The case of TE polarization is firstly considered and, then, an actual inclusion-based cloak for TE polarization is also designed. In such a case, the cloak is made of a mu-near-zero (MNZ) metamaterial, as the dual counterpart of the epsilon-near-zero (ENZ) material that can be used for purely dielectric objects. The operation and the robustness of the cloaking device for the TE polarization is deeply investigated through a complete set of full-wave numerical simulations. Finally, the design and an application of a cloak operating for both TE and TM polarizations employing both magnetic inclusions and the parallel plate medium already used by Silveirinha et al (Phys. Rev. E 75 036603) are presented.