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This paper presents an analytical and numerical investigation of the radiation features of an interesting class of electromagnetic bandgap (EBG) structures excited by an electric line source. The radiation from two-dimensional (2-D) lattices made with lossless dielectric cylinders, typically optimized by using the Bloch analysis of the corresponding 2-D photonic crystals, are originally investigated in terms of leaky waves. A thorough modal analysis of open waveguides, composed by a finite number of periodic chains of circular dielectric rods, is presented that shows a multiplicity of bound and leaky modes. Two radiation windows are identified and the relevant directive features are described in terms of properly excited dominant leaky modes. The possible excitation of higher order leaky modes and guided modes has been carefully considered, by also capturing the relevant residue contributions in a nonspectral representation of the excited fields. The final results on radiated fields by realistic truncated structures, obtained by ad-hoc software as well as full-wave EM simulators, are in excellent agreement with those predicted by the proposed leaky-wave approach.

A resonant-cavity antenna is implemented assembling on an open-ended rectangular waveguide a wideband electromagnetic band gap (EBG), designed as a multilayer. Two different implementations of the multilayer are proposed, labeled as Cases A and B. As to Case A, a high-permittivity layer is embedded between two slabs of low permittivity, whereas a single layer of low permittivity, surrounded by two high-permittivity slabs, is employed in Case B. Successful performances of the broadband behavior are also dependent on the side length of the EBG, that is truncated to small footprints, with an effect of high sidelobe level (SLL). Therefore, grid layouts with nonuniform air holes are proposed for in-plane realization of the dielectric slabs. Their effect in the EBG superstrate is a nonuniform spatial reflectivity, that reduces the SLL keeping a good wideband response. In the EBG manufacturing, both numerically controlled machining techniques and 3-D printing have been employed. 3-D printing has been used for the low permittivity layers, realized in the polylactic acid (PLA) filament, allowing more flexibility in the fabrication of the grid slabs to custom layouts. Results of two antenna prototypes assembling the EBGs, with the parameters of Cases-A and -B and grid layout, to the waveguide source are reported.

The use of Ground Penetrating Radar (GPR) as a non-destructive technique for the localization and imaging of buried targets is nowadays widely used in the fields of civil engineering, archeology, and geology. In traditional GPR applications, the transmitting antenna is placed in air, whereas targets are embedded in a background of different permittivity, which may be given by a soil or a construction material. However, the GPR architecture can be also applied to the case of targets located in air but hidden from the illumination field radiated by the transmitting antenna by a dielectric discontinuity, as in the case of the Through-the-Wall (TW) radar applications, where targets inside a building interior must be localized and imaged [1]. In this work, a commercial GPR equipment is employed to perform an experimental campaign on a TW scene, where two targets of different reflectivity, i.e., a metallic cylinder and a wooden bar, are located behind a masonry wall in a laboratory environment. To increase the information on the scattered fields, the scanning of the transmitting and receiving antennas is performed in a fully multi-bistatic manner, through a multi-view and multi-illumination mode, along a horizontal line parallel to the wall, and keeping the antennas in direct contact with it. The transmitting antenna is a transducer emitting a pulsed signal, with frequency centered at 1 GHz. The imaging of the buried targets has been performed through a novel two-step inverse-scattering technique, that is based on a regularization scheme developed in the framework of variable exponent Lebesgue spaces [2], [3]. In particular, the norm exponent function is directly built from the available data through an initial processing of the data, based on a beamforming approach or on a truncated singular value decomposition (TSVD) technique [4]. The whole frequency spectrum of the measured data is exploited, as the scattered field from the pulsed signals is extracted on a set of frequencies through a Fast Fourier Transform. The proposed approach, applied to the measured data, shows good reconstruction capabilities and a reduction of artifacts. [1] M. G. Amin, Ed., Through-the-Wall Radar Imaging. Boca Raton, FL: CRC Press, 2011.[2] C. Estatico, A. Fedeli, M. Pastorino, and A. Randazzo, ‘Quantitative microwave imaging method in Lebesgue spaces with nonconstant exponents’, IEEE Trans. Antennas Propag., vol. 66, no. 12, pp. 7282–7294, Dec. 2018.[3] A. Randazzo, C. Ponti A. Fedeli, C. Estatico, P. D’Atanasio, M. Pastorino, G. Schettini, ‘A two-step inverse-scattering technique in variable-exponent Lebesgue spaces for through-the-wall microwave imaging: Experimental results’, IEEE Trans. Geosci. Remote Sens., vol. 59, no. 9, pp. 7189–7200, Sep. 2021.[4] A. Randazzo, C. Ponti, A. Fedeli, C. Estatico, P. D’Atanasio, M. Pastorino, G. Schettini, ‘A Through-the-Wall Imaging Approach Based on a TSVD/Variable-Exponent Lebesgue-Space Method’, Remote Sens., vol. 13, 17 pp., 2021.

A comparative study of the directive radiation obtained from two kinds of 2-D photonic crystal structures excited by an electric source is presented in this letter. These structures consist of a stack of periodic chains of dielectric cylinders in free space or of circular voids in dielectric media. On the basis of an in-depth description of the physical phenomena underlying the Bloch transverse-electric modal field configurations of such structures, a set of design rules to achieve highly directive leaky-wave radiation is obtained. An analysis of the two types of structures shows that it is preferable to consider holey lattices to achieve more directive radiation, obtained by the excitation of a weakly attenuated fundamental leaky mode. Indeed, radiators consisting of an integer number of periodic chains of voids drilled in a dielectric medium over a metal plate show directivity at broadside approximately 6 dB higher than in the dielectric cylinder case. This class of holey lattices can be used to design highly directive leaky-wave antennas, with significant advantages of easy manufacturing, design simplicity, and low complexity.

In this paper we present an accurate analytical solution of the scattering of a plane-wave by dielectric cylinders placed above a multilayered medium. An analytical approach is used to solve the scattered field by the cylinders in each medium through expansions into cylindrical waves, expressed through plane-wave spectra. The multilayer models a biological tissue consisting of skin, fat and muscle covered by a cotton textile. Several numerical examples are presented considering the electrical parameters of the biological and textile tissues at the millimeter frequency range (24 GHz). The results show that it is possible to obtain an intensification of the electric field in the underlying tissues in case of TM polarization of the incident wave, finding an interesting application for the charging of implantable or wearable devices.

Skin contact is one of the most common exposure routes to graphene-based materials (GBMs) during their small-scale and industrial production or their use in technological applications. Nevertheless, toxic effects in humans by cutaneous exposure to GBMs remain largely unexplored, despite skin contact to other related materials has been associated with adverse effects. Hence, this in vivo study was carried out to evaluate the cutaneous effects of two GBMs, focusing on skin sensitization as a possible adverse outcome. Skin sensitization by few-layer graphene (FLG) and graphene oxide (GO) was evaluated following the Organization for Economic Cooperation and Development (OECD) guideline 442B (Local Lymph Node Assay; LLNA) measuring the proliferation of auricular lymph node cells during the induction phase of skin sensitization. Groups of four female CBA/JN mice (8-12 weeks) were daily exposed to FLG or GO through the dorsal skin of each ear (0.4-40 mg/mL, equal to 0.01-1.00 mg/ear) for 3 consecutive days, and proliferation of auricular lymph node cells was evaluated 3 days after the last treatment. During this period, no clinical signs of toxicity and no alterations in body weight and food or water consumptions were observed. In addition, no ear erythema or edema were recorded as signs of irritation or inflammation. Bromo-deoxyuridine (BrdU) incorporation in proliferating lymphocytes from ear lymph nodes (stimulation indexes

Palytoxin (PLTX) is a highly toxic polyether identified in various marine organisms, such as

In this paper, we present an analytical solution based on the Cylindrical Wave Approach to study the interaction of a plane-wave with cylindrical objects, either dielectric or conducting, placed above a semi-infinite lossy medium. The effects of focusing of the electromagnetic field by the array of scatterers is investigated. The analytical approach is validated by a comparison with a commercial software. Some numerical examples are presented, considering both TM and TE polarization of the incident wave in the millimeter frequency range at 24 GHz. Interesting applications are in the modelling of the scattered field by objects above a biological tissues, in the presence of wereable or implantable antennas sources.

An approach to study the scattering of a pulsed and spatially nonuniform field, by a set of dielectric cylinders, is presented. Cylinders are embedded in a semi-infinite medium and source field is impinging from an outside region. Source field is expressed through its space and time spectra, and solution is developed with the frequency-domain Cylindrical Wave Approach, applied to a discretized spectrum of monochromatic plane-wave sources, with amplitude belonging to a Gaussian waveform. Time-domain dependence of the scattered field is reconstructed through an inverse Fast Fourier Transform. The method has interesting applications in the modelling of the scattering by inclusions, like small vessels or fibers, in biological tissues, for the diagnostic at THz and optical frequencies. Simulated radargrams provided useful information on the physical properties of the targets, and data useful for the understanding the image formation.

In this work, an inverse-scattering technique for through-the-wall imaging is presented and validated against experimental data. The inverse-scattering scheme is developed in variable-exponent Lebesgue spaces, where a delay-and-sum beamforming approach is preliminary applied to build the exponent function. Measurements are collected as time-domain data in a laboratory environment, under a multi-illumination and multi-view approach. Processing of the data is performed in the frequency-domain, by application of the Fast Fourier Transform, and extracting the scattered fields at several frequencies in order to improve the reconstruction capabilities. The obtained results confirm the successful imaging of both high- and low-reflectivity targets in the inspected scenario.

This letter shows that the position of a source inside an electromagnetic bandgap material determines how the emission is shaped and focused. Two degenerate electromagnetic configurations, allowed by a square lattice at a given frequency, can be selectively excited by placing the feeding point in specific locations within the building block of the periodic structure. In this way, the radiated energy can be directed toward defined focusing directions, without need to change the lattice and its dispersion diagram. A practical application, where embedded emitters selectively drive single lattice modes, is presented, showing that such a mechanism may open the way to important uses in the microwave domain, e.g., for cell splitting, smart antennas, and multiple-input-multiple-output technology, as well as in terahertz communications and optical applications.

A hybrid inversion scheme for through-the-wall imaging is proposed in this paper. The approach is based on a linearized model of the inverse-scattering problem, employing the Green’s function developed for a layered background. The reconstruction is obtained by means of a Landweber-like iterative method performing a regularization in the framework of variable-exponent Lebesgue spaces. Thanks to the non-conventional geometrical properties of such spaces, it is possible to enhance the reconstruction capabilities, e.g., by promoting sparseness and reducing over-smoothing. The exponent function defining the specific space adopted in the inversion procedure is adaptively obtained directly from the measured data, through a truncated-singular value decomposition method. In this way, it is possible to precompute and reuse in both steps, for a given scenario, all the matrices necessary in the inversion process, thus leading to a computationally efficient solving strategy. The effectiveness of the approach is evaluated by using experimental data obtained with a commercial GPR apparatus employing a pulsed source field. A fast Fourier transform is applied to the time-domain measurements to extract frequency-domain data at a set of frequencies in the source spectrum, which are fed in input to the imaging scheme. Very good reconstruction capabilities are obtained both with a single metallic target, as well as in a challenging two targets layout including both a metallic object and a low-permittivity target.

The scattering of a far-field source by perfectly conducting targets above a semi-infinite lossy medium is studied. An analytical solution is applied to the electromagnetic scattering problem with the Cylindrical Wave Approach. Interaction of a plane-wave field with the cylindrical targets is expressed through expansions into cylindrical waves, and a spectral approach is used to deal with the interaction of the scattered field and the interface. The method allows modelling the interaction of an external source with a biological medium, in the presence of external metallic objects. In the numerical examples, the electrical parameters of a muscle are used to model the biological tissue. Application to cases of interest for the total field transmitted in the muscle is investigated for both TM and TE polarization states. Penetration of the electromagnetic field is evaluated, both at the ISM frequency of 2.4 GHz and in the millimeter frequency range at 28 GHz.

A novel two-step inverse-scattering technique is proposed for through-the-wall microwave imaging. The approach is based on a regularization scheme developed in the framework of variable-exponent Lebesgue spaces, which enhances the quality of the reconstruction by properly tuning the exponent function that defines the adopted norm. Such a function is built directly from the available data by using a beamforming technique based on a delay-and-sum scheme. After an initial numerical assessment, the approach is validated against experimental measurements in a laboratory environment, with targets placed behind a brick wall. Measured data are collected in time domain by scanning the transmitting and receiving antennas in a multi-illumination and multi-view arrangement. The processing of experimental data is performed in the frequency domain, where data at multiple frequencies are extracted by a Fast Fourier Transform (FFT) and simultaneously processed by the imaging algorithm. The obtained imaging results confirm the good reconstruction capabilities of the developed inverse-scattering scheme in the case of both metallic and low-contrast targets.

This paper presents an overview of our analytical and numerical methods to design radiative structures based on photonic crystals by means of leaky-wave theory. In particular, we present several parametric studies to justify the choice of the design parameters. Based on these studies, we show how it is possible to design highly directive devices in which the radiation can be described by a properly excited dominant leaky mode. The proposed design procedure can be easily extended to a wide class of structures, leading to the construction of sensors and antennas with high radiation efficiency and directivity.

International audience; In the frame of graphene-based material (GBM) hazard characterization, particular attention should be given to the cutaneous effects. Hence, this study investigates if HaCaT skin keratinocytes exposed to high concentrations of few-layer graphene (FLG) or partially dehydrated graphene oxide (d-GO) for a short time can recover from the cytotoxic insult, measured by means of cell viability, mitochondrial damage and oxidative stress, after GBM removal from the cell medium. When compared to 24 or 72 h continuous exposure, recovery experiments suggest that the cytotoxicity induced by 24 h exposure to GBM is only partially recovered after 48 h culture in GBM-free medium. This partial recovery, higher for FLG as compared to GO, is not mediated by autophagy and could be the consequence of GBM internalization into cells. The ability of GBMs to be internalized inside keratinocytes together with the partial reversibility of the cellular damage is important in assessing the risk associated with skin exposure to GBM-containing devices.

The imaging of dielectric targets hidden behind a wall is addressed in this paper. An analytical solver for a fast and accurate computation of the forward scattered field by the targets is proposed, which takes into account all the interactions of the electromagnetic field with the interfaces of the wall. Furthermore, an inversion procedure able to address the full underlying non-linear inverse scattering problem is introduced. This technique exploits a regularizing scheme in Lebesgue spaces in order to reconstruct an image of the hidden targets. Preliminary numerical results are provided in order to initially assess the capabilities of the developed solvers.

Through-wall imaging is an application field in which microwaves play an important role, thanks to their ability of penetrating inside building materials. In this framework, the aim of this paper is twofold. On the one hand, it presents an analytical forward model able to effectively describe the scattering phenomena by fully taking into account all the reflection and transmission effects due to the wall. On the other hand, a new inversion procedure, able to address the full underlying non-linear inverse scattering problem, is introduced. Some numerical results aimed at validating the two approaches are shown.

In this work, a prototype of microwave imaging system for through-the-wall monitoring is presented. The system can operate remotely, as well as by using antennas directly in contact with the wall. For the remote modality, ad-hoc wide-band antennas have been designed and integrated into an efficient measurement system, able to acquire the scattered-field data. Such measurements are processed by a novel hybrid inversion procedure able to create an image of the inspected scenario. For the proximity modality, a Bessel beam launcher is specifically designed, realized and tested to provide a focused near-field with enhanced penetration capabilities. Preliminary results are provided for assessing the capabilities of the system.

Electromagnetic Band-Gap (EBG) media, working right above the band-gap can shape the radiation of a simple emitter embedded in their periodic structures. In this region of the dispersion diagram, degenerate lattice modes can be selectively excited with a proper positioning of the primary sources. This paper presents the design of an antenna that exploits such physical mechanism, which is potentially attractive at mm-waves since it relies on dielectric structures. An antenna fed by two sources and based on a square lattice of dielectric cylinders is presented. For the first time, the dependences of radiation properties on some geometrical parameters are investigated before moving to a final realistic design.

Electromagnetic modelling of ground penetrating radar applications to the survey of buried targets is a fundamental step in the interpretation of measured data from experimental campaigns. When pulsed source fields are employed, such a modelling is commonly performed through time-domain numerical techniques. The cylindrical wave approach is proposed here to solve the scattering of a pulsed field by circular cross-section cylinders buried in a semi-infinite medium. The field radiated field by a transmitting antenna is modelled using a line-current source. Theoretical solution is developed on a semi-analytical basis, through a spectral approach. Time and space spectra are employed to derive the scattered fields, and the final space&ndash, time dependence is found through an inverse Fourier Transform. The proposed approach allows an accurate modelling of a wide class of ground penetrating radar problems that are commonly simulated through two-dimensional layouts.

Besides inhalation, skin contact may be considered one of the most relevant exposure routes to graphene-based materials (GBMs). However, very few data on the cutaneous toxicity of these materials are available, so far. This study is focused on skin irritation potential of a panel of GBMs: few-layer graphene (FLG), exfoliated by ball milling of graphite, FLG exfoliated by ultrasonication using sodium dodecyl sulfate (FLG-SDS) or sodium dodecylbenzenesulfonate (FLG-SDBS), CVD-graphene, obtained by chemical vapor deposition, graphene oxide (GO) and reduced GO (rGO). Skin irritation was assessed using the SkinEthic™ Reconstructed human Epidermis (RhE), following the Organisation for Economic Co-operation and Development (OECD) Test Guideline (TG) 439. Even though not validated for nanomaterials, the OCED TG 439 turned out to be applicable also for GBM testing, since no interference with the methylthiazolyldiphenyl-tetrazolium bromide (MTT) reduction, used as a final readout, was found. Furthermore, direct epidermal exposure to powdered GBMs mimics the actual human exposure, avoiding interference by the cell culture medium (protein corona formation). Only GBMs prepared with irritant surfactants (FLG-SDS and FLG-SDBS), but not the others, reduced RhE viability at levels lower than those predicting skin irritation (≤50%), suggesting irritant properties. This result was further confirmed by measuring cytokine (IL-1α, IL-6 and IL-8) release by GBM-treated RhE and by histological analysis as additional readouts to implement the guideline. On the whole, these results demonstrate that GBMs prepared with non-irritant exfoliation agents do not induce skin irritation after a single acute exposure.

Mode filters, based on oversized rectangular waveguides with periodic symmetrical junctions, are addressed through analytical models under a small coupling approximation to explain the physical mechanisms of their behavior, and provide guidelines for their design. In the junctions, which are partially filled with a lossy dielectric, both propagating and evanescent modes play a role. Filter parameters are studied with respect to their impact on the excitation, propagation, and absorption of such modes in the junctions. Particular attention is paid to practical choices a designer has to face in real applications. The performance of single versus multiple lengthwise slots with the same total length is compared, and high-power matters such as voltage and thermal breakdown are discussed. A novel junction with two absorbing layers is proposed to help designers in maximizing absorption, while fulfilling thermal constraints.

The pulsed scattering by buried perfectly conducting cylinders is solved with the cylindrical wave approach. The source of the scattering problem is a wideband excitation from a plane-wave source field. A spectral approach is employed, expressing the electric field as a superposition of monochromatic contribution. Time-domain response is found through the inverse Fourier transform on the spectra relevant to each field contributions. Numerical implementation of the method turns out to be very accurate. The technique has important applications in the simulation of the scenarios of embedded objects within remote sensing techniques. Results are plotted to simulate both A-scan and B-scan plots typical of ground penetrating radar measurements. The method has been validated through a comparison with a numerical technique available in the literature.

The emission of radiators can be shaped by means of electromagnetic bandgap (EBG) materials exploiting proper Bloch waves supported by the lattice rather than its bandgaps. So far, such a method has relied only on the dispersion diagram of the periodic structure, i.e., on the eigenvalues of the lattice, neglecting the particular configuration of the associated eigenfunction. This paper explores the radiation mechanism under a novel viewpoint, which is mostly focused on the electric field pattern of lattice modes, allowing a deeper understanding of the underlying physics. Such an approach is profitably used here to improve the performance of antennas based on different Bloch waves by reducing spurious lattice modes. Geometrical configurations coupled to a line source are provided with little adjustments, getting EBGs to work at a frequency where they had no bandgap originally. As a proof-of-concept of the proposed perspectives, a compact antenna using a cheap low-permittivity dielectric is conceived, fabricated, and successfully tested.

An overview of the cylindrical wave approach in the modeling of through-wall radar problems with targets hidden behind a dielectric wall is reported. The cylindrical wave approach is a technique for the solution of the two-dimensional scattering by buried circular cross-section cylinders in a semi-analytical way, through expansion of the scattered fields into cylindrical waves. In a through-wall radar application, the scattering environment is made by a dielectric layer between two semi-infinite half-spaces filled by air. For this layout, two possible implementations of the cylindrical wave approach have been developed in the case of plane-wave excitation. The first was an iterative scheme with multiple-reflection scattered fields, and the second was a fast and non-iterative solution, through suitable basis functions (i.e., reflected and transmitted cylindrical waves). Such waves take into account all the interactions of the source field with the interfaces bounding the dielectric layers and the targets. The non-iterative approach was also extended for excitation from the radiated field by a line source. A final system was derived for the computation of the scattered field by PEC or dielectric targets. Numerical results show the potentialities of the cylindrical wave approach in the modeling of through-wall radar, in particular in the evaluation of the scattered fields by human targets in a building’s interior, modeled with a two-dimensional approach.

This paper addresses the beam shaping by means of Electromagnetic Band Gap (EBG) materials operating at the edge of the forbidden band, i.e., where some lattice modes can propagate. Unlike classical resonator antennas, where the primary source is located in a cavity made of a ground plane and an EBG working in the band gap, 'lattice mode' antennas embed the primary source in the periodic structure. Owing to this feature, the position of the source inside the unit cell of the periodic structure comes out to play a pivotal role in shaping the radiation outside the EBG because it determines which lattice modes are excited and to which extent. This mechanism is exploited here to attain two different radiation patterns through the same dielectric EBG structure by placing two primary sources in different positions. Such positions allow each source to excite one out of two degenerate lattice modes and to be almost invisible to the other one, thus entailing a good decoupling between feeding antennas despite their proximity.

IFI16, member of the IFN-inducible PYHIN-200 gene family, modulates proliferation, survival and differentiation of different cell lineages. In particular, IFI16 expression, which is regulated during the differentiation of B cells, was recently studied in B-CLL as well. Here, we compared IFI16 expression in several lymphomas including Burkitt lymphoma, diffuse large B-cell lymphoma, follicular lymphoma, marginal zone lymphoma and mantle cell lymphoma with respect to normal cell counterparts. We observed that IFI16 expression was significantly deregulated only in mantle cell lymphoma (p < 0.05). Notably, IFI16 was associated with the expression of genes involved in interferon response, cell cycle, cell death and proliferation and, interestingly, lipid and glucose metabolism, suggesting that IFI16 deregulation might be associated with relevant changes in cell biology. In our group of mantle cell lymphoma samples a correlation between patient survival and IFI16 expression was not detected even though mantle cell lymphoma prognosis is known to be associated with cell proliferation. Altogether, these results suggest a complex relationship between IFI16 expression and MCL which needs to be analyzed in further studies., Molecular biology; Cell biology; Biochemistry; Oncology; Pathology; Cancer research; Mantle cell lymphoma; Immunohistochemistry; IFI16; Proliferation; Gene expression

A method for solving forward scattering problems in through-the-wall applications with multilayered walls is presented. Targets are perfectly conducting cylindrical scatterers, with circular cross section, hidden by the wall. The technique is developed in the frequency domain, and it employs expansions of the scattered fields by the targets through cylindrical waves as basis functions. Numerical results allow to solve the scattering problem in large domains, with a semi-analytical technique.