Polarization-insensitive multifunctional reconfigurable band-notched absorber with wideband switchable absorption properties utilizing Galinstan.

A dual-polarized multifunctional reconfigurable band-notched absorber (MRBNA) based on Galinstan is presented in this paper. The proposed MRBNA comprises a liquid metal transmission/reflection switchable layer (LM-T/RSL) and a wideband band-notched absorber (BNA). The MRBNA represents a paradigm shift in adaptive electromagnetic (EM) solutions, offering unprecedented wideband switching capabilities between superior band-notched absorption and full-band reflection states.

Inductive Frequency-Coded Sensor for Non-Destructive Structural Strain Monitoring of Composite Materials.

Structural composite materials have gained significant appeal because of their ability to be customized for specific mechanical qualities for various applications, including avionics, wind turbines, transportation, and medical equipment. Therefore, there is a growing demand for effective and non-invasive structural health monitoring (SHM) devices to supervise the integrity of materials. This work introduces a novel sensor design, consisting of three spiral resonators optimized to operate at distinct frequencies and excited by a feeding strip line, capable of performing non-destructive structural strain monitoring via frequency coding.

Open-Ended Coaxial Probe for Effective Reconstruction of Biopsy-Excised Tissues' Dielectric Properties.

Dielectric characterization is extremely promising in medical contexts because it offers insights into the electromagnetic properties of biological tissues for the diagnosis of tumor diseases. This study introduces a promising approach to improve accuracy in the dielectric characterization of millimeter-sized biopsies based on the use of a customized electromagnetic characterization system by adopting a coated open-ended coaxial probe. Our approach aims to accelerate biopsy analysis without sample manipulation.

Dielectric Characterization of Breast Biopsied Tissues as Pre-Pathological Aid in Early Cancer Detection: A Blinded Feasibility Study.

Dielectric characterization has significant potential in several medical applications, providing valuable insights into the electromagnetic properties of biological tissues for disease diagnosis, treatment planning, and monitoring of therapeutic interventions. This work presents the use of a custom-designed electromagnetic characterization system, based on an open-ended coaxial probe, for discriminating between benign and malignant breast tissues in a clinical setting. The probe's development involved a well-balanced compromise between physical feasibility and its combined use with a reconstruction algorithm known as the virtual transmission line model (VTLM).

Analysis and design of holographic magnetic metasurfaces in the very near field for sensing applications at quasi-static regime.

In this paper, we present a novel low-frequency sensing solution based on the manipulation of the near-field distribution by employing a passive holographic magnetic metasurface, excited by an active RF coil placed in its reactive region. In particular, the sensing capability is based on the interaction between the magnetic field distribution produced by the radiating system and the magneto-dielectric inhomogeneities eventually present within the material under test. We first start from conceiving the geometrical set-up of the metasurface and its driving RF coil, adopting a low operative frequency (specifically 3 MHz) to consider a quasi-static regime and able to increase the penetration depth within the sample.

Spatial filtering magnetic metasurface for misalignment robustness enhancement in wireless power transfer applications.

In this paper, we present the design of spatial filtering magnetic metasurfaces to overcome the efficiency decay arising in misaligned resonant inductive Wireless Power Transfer systems. At first, we describe the analytical framework for the control of currents flowing on a finite-size metasurface, avoiding classical truncation effects on the periphery and opportunely manipulating, at the same time, the spatial magnetic field distribution produced by the closely placed RF driving coil. In order to validate the theoretical approach, we conceive a numerical test case consisting of a WPT system operating at 12 MHz.

Shaping and Focusing Magnetic Field in the Human Body: State-of-the Art and Promising Technologies.

In recent years, the usage of radio frequency magnetic fields for biomedical applications has increased exponentially. Several diagnostic and therapeutic methodologies exploit this physical entity such as, for instance, magnetic resonance imaging, hyperthermia with magnetic nanoparticles and transcranial magnetic stimulation. Within this framework, the magnetic field focusing and shaping, at different depths inside the tissue, emerges as one of the most important challenges from a technological point of view, since it is highly desirable for improving the effectiveness of clinical methodologies.

Magnetic metasurfaces properties in the near field regions.

In this paper, we present a general equivalent-circuit interpretation of finite magnetic metasurfaces interacting with an arbitrary arrangement of RF coils operating in near-field regime. The developed model allows to derive a physical interpretation of the interactions between the metasurface and the surrounding RF coils, both transmitting and receiving. Indeed, especially for near-field applications, the metasurface presence modifies the behavior of each RF coil differently, due to the specific reciprocal interactions.

Improved dual-polarized wideband multifunctional switchable absorber/reflector based on active frequency selective surfaces.

An improved dual-polarized multifunctional switchable absorber/reflector with both wideband absorbing and wideband reflecting characteristics is presented in this paper. The proposed structure consists of three parts including a top-layer active frequency selective surface (AFSS) structure, a bottom-layer metal sheet and an air spacer in between. The polarization stability is satisfied by deploying the super-element topology, which contains four similar unitary elements arranged in a 2 × 2 matrix form.

Numerical and Workbench Design of 2.35 T Double-Tuned (¹H/²³Na) Nested RF Birdcage Coils Suitable for Animal Size MRI.

The birdcage Radio Frequency (RF) coil is one of the most used configurations in Magnetic Resonance Imaging (MRI) scanners for the detection of the proton (H) signal over a large homogeneous volume. More recently, birdcage RF coils have been successfully used also in the field of X-nuclei MRI, where the signal of a second nucleus (e.g.

Design of Distributed Spiral Resonators for the Decoupling of MRI Double-Tuned RF Coils.

Objective: A systematic analytical approach to design Spiral Resonators (SRs), acting as distributed magnetic traps (DMTs), for the decoupling of concentric Double-Tuned (DT) RF coils suitable for Ultra-High Field (7 T) MRI is presented.

Methods: The design is based on small planar SRs placed in between the two RF loops (used for signal detection of the two nuclei of interest). We developed a general framework based on a fully analytical approach to estimate the mutual coupling between the RF coils and to provide design guidelines for the geometry and number of SRs to be employed.

Optimal Design of Miniaturized Reflecting Metasurfaces for Ultra-Wideband and Angularly Stable Polarization Conversion.

An ultra-wideband linear polarization converter based on a reflecting metasurface is presented. The polarizer is composed by a periodic arrangement of miniaturized metallic elements printed on a grounded dielectric substrate. In order to achieve broadband polarization converting properties, the metasurface is optimized by employing a genetic algorithm (GA) which imposes the minimization of the amplitude of the co-polar reflection coefficient over a wide frequency band.

Wideband Scattering Diffusion by using Diffraction of Periodic Surfaces and Optimized Unit Cell Geometries.

A methodology to obtain wideband scattering diffusion based on periodic artificial surfaces is presented. The proposed surfaces provide scattering towards multiple propagation directions across an extremely wide frequency band. They comprise unit cells with an optimized geometry and arranged in a periodic lattice characterized by a repetition period larger than one wavelength which induces the excitation of multiple Floquet harmonics.

Evaluation of 3D radio-frequency electromagnetic fields for any matching and coupling conditions by the use of basis functions.

A procedure for evaluating radio-frequency electromagnetic fields in anatomical human models for any matching and coupling conditions is introduced. The procedure resorts to the extraction of basis functions: such basis functions, which represent the fields produced by each individual port without any residual coupling, are derived through an algebraic procedure which uses the S parameter matrix and the fields calculated in one (only) full-wave simulation. The basis functions are then used as building-blocks for calculating the fields for any other S parameter matrix.

Investigation of maximum local specific absorption rate in 7 T magnetic resonance with respect to load size by use of electromagnetic simulations.

Local specific absorption rate (SAR) evaluation in ultra high field (UHF) magnetic resonance (MR) systems is a major concern. In fact, at UHF, radiofrequency (RF) field inhomogeneity generates hot-spots that could cause localized tissue heating. Unfortunately, local SAR measurements are not available in present MR systems; thus, electromagnetic simulations must be performed for RF fields and SAR analysis.

Ultra-broad and sharp-transition bandpass terahertz filters by hybridizing multiple resonances mode in monolithic metamaterials.

We present three monolithic metamaterial-based THz bandpass filters, the skewed circular slot rings, meandered slots and Jerusalem cross slots, to fit in the THz gap. These THz bandpass filters are comprised of a metal-dielectric-metal (MDM) structure that supports multiple resonances of electric dipole, magnetic dipole, and standing-wave-like modes. By exciting and further hybridizing these individual resonance modes, we demonstrate excellent performance of broad bandwidth and sharp band-edge transition beyond conventional bandpass filters.

Non-thermal effects of 2.45 GHz microwaves on spindle assembly, mitotic cells and viability of Chinese hamster V-79 cells.

The production of mitotic spindle disturbances and activation of the apoptosis pathway in V79 Chinese hamster cells by continuous 2.45 GHz microwaves exposure were studied, in order to investigate possible non-thermal cell damage. We demonstrated that microwave (MW) exposure at the water resonance frequency was able to induce alteration of the mitotic apparatus and apoptosis as a function of the applied power densities (5 and 10mW/cm(2)), together with a moderate reduction in the rate of cell division.