Comparing liquid homogeneous and multilayer phantoms for human body implantable antennas

We compare the performance of a ultrawideband implantable antenna when immersed in a liquid homogeneous phantom and in a multilayer phantom. The goal is to assess how good the simple liquid phantom is to represent the real body over a broad bandwidth. We evaluate not only the frequency-domain parameters – input reflection (s11) and transmission coefficients (s21) – but also the performance of the antenna in the time domain – pulse fidelity and window containing 90% of the pulse energy. The results show a good resemblance between both phantom results, suggesting that liquid homogeneous phantoms may be enough to test the performance of this type of antennas and potentially simplify the measurement setup.info:eu-repo/semantics/acceptedVersio

Systematic analysis of microwave breast imaging detection of different-sized malignant and benign tumors

Microwave Imaging (MWI) has been explored as an alternative to conventional breast tumor screening methods. It is acknowledged that benign and malignant tumors can be distinguishable by their architectural features: benign tumors are often round with well-defined margin, while malignant tumors have an ill-defined margin and are micro-lobulated or spiculated. We present a MWI-based systematic analysis of malignant and benign breast tumors of different sizes, to evaluate if its characteristics allow differentiating the images. To this end, we performed measurements on a dry MW setup, using a slot-based antenna in the 2–5 GHz frequency range to scan an anthropomorphic breast phantom. We placed inside eight malignant and benign tumors with 3, 4,… 10 mm average radius, one at a time. This study shows that both types of tumors can be detected, but not distinguishable only via MWI. Smaller tumors become harder to detect, the 3 mm tumor being unreliably caught.info:eu-repo/semantics/acceptedVersio

Webcam-based distance and surface estimation system for microwave imaging

One of the critical steps in Medical Microwave Imaging (MMWI) algorithms is the calculation of the distances between the antenna and the synthetical focal point, due to the different propagation velocities in the tissues and background medium. In fact, it has a major influence on the image accuracy. As a result, it is very important to have a priori information about the shape of the body part under examination. Here we propose a low cost optical system based on a single commercial webcam. We validate the new system by showing an application to breast imaging, where we reconstruct the scatterers inside the breast using the real and estimated shapes. The results show very good resemblance, thus proving the new system supplies a reliable estimation of the breast shape.info:eu-repo/semantics/publishedVersio

Antenna phase center and angular dispersion estimation using planar acquisition setup applied to microwave breast imaging

We propose a “near-field phase center” estimation technique based on planar acquisition setup. It requires a single antenna and an electrically small object to serve as target. The technique allows to estimate the phase center spatial coordinates, as well as its angular dispersion. This data is useful in microwave imaging applications where the antenna operate in near-field regime, such as medical applications (e.g. breast and head imaging). We demonstrate that for a commonly used Vivaldi antenna operating in the 2-5 GHz band, the angular dispersion of the pseudo phase center can be as high as 50 mm. Moreover, we show that incorporating this data in the signal processing algorithms improves the imaging results, by applying it to microwave breast imaging. We believe this type of antennacharacterization techniques will leverage the use of more informative imaging algorithms (e.g. truncated singular value decomposition), since they increase the accuracy of the distance calculations, thus improving the signal to noise ratio.info:eu-repo/semantics/acceptedVersio

Microwave breast imaging using a dry setup

This article demonstrates for the first time, both numerically and experimentally, the feasibility of radar-based microwave imaging of anthropomorphic heterogeneously dense breasts in prone position, requiring no immersion liquid. The dry, contactless approach greatly simplifies the setup, favors patient comfort, and further avoids lengthy sanitation procedures after each exam. We use a radar-type technique with the antennas distributed in cylindrical configuration around the breast phantom. The reflectivity map is reconstructed using a wave-migration algorithm in the frequency domain. This article presents new developed strategies to cope with the challenges of a dry setup, namely increased skin artifact due to the concomitant absence of matching liquid and nonuniform breast shape. We propose an iterative and adaptive algorithm based on singular value decomposition that effectively removes the skin backscattering under the abovementioned conditions. It is compatible with automatic processing, and computationally fast. One of its inputs is the breast three-dimensional surface information, and its distance to the antennas, all obtained automatically from a proposed low-cost procedure based on a webcam. The imaging method is reasonably resilient to the presence of fibroglandular tissues, and to uncertainties of tissue permittivity. Another tackled challenge is the miniaturization of the antenna in air, which is achieved with an optimized balanced antipodal Vivaldi of the same size as counterparts used in dense immersion liquids. Finally, all the building blocks are combined to demonstrate experimentally the overall dry system performance, with very good detection of the tumor at three different positions in the breast, even in low-contrast scenarios.info:eu-repo/semantics/acceptedVersio

Preliminary characterization of microwave backscattering of floating plastic

Microwaves (MW) may offer advantages over optical techniques for remote monitoring of marine litter. However, no systematic studies are found in the literature about microwave sensing of floating plastics. In order to assess the potential, we carried out two types of experiments and analysis. In one scenario we measured and characterized the MW backscatter of different densities of typical plastic bottles and jerry cans, floating in a small pool of static water. The results show a significant increase of litter response with litter density, thus demonstrating that floating plastic affects the MW backscattering of the water surface. In the second scenario, we assembled a setup to resemble a synthetic aperture radar system: a small container filled with water and floating plastic was linearly translated under a fixed antenna operating in monostatic mode; we have successfully reconstructed the energy backscattering map of the target. This preliminary work demonstrates that floating macro plastics do present a MW signature that may be relevant for remote monitoring of this type of marine pollution.info:eu-repo/semantics/acceptedVersio

Dynamic critical exponents of the Ising model with multispin interactions

We revisit the short-time dynamics of 2D Ising model with three spin interactions in one direction and estimate the critical exponents $z,$ $\theta,$ $\beta$ and $\nu$. Taking properly into account the symmetry of the Hamiltonian we obtain results completely different from those obtained by Wang et al.. For the dynamic exponent $z$ our result coincides with that of the 4-state Potts model in two dimensions. In addition, results for the static exponents $\nu$ and $\beta$ agree with previous estimates obtained from finite size scaling combined with conformal invariance. Finally, for the new dynamic exponent $\theta$ we find a negative and close to zero value, a result also expected for the 4-state Potts model according to Okano et al.Comment: 12 pages, 9 figures, corrected Abstract mistypes, corrected equation on page 4 (Parameter Q

Wrist-Worn RFID Antenna Printed on Additive Manufactured Flexible Substrate

We assess the feasibility of fabricating a flexible RFID wrist-worn antenna printed on a substrate manufactured using 3D-printing technology, as to enable full customization of the bracelet at low cost. Numerical results show adequate power transmission to the RFID chip. Also, the fabricated prototype shows enough flexibility to be bent around the wrist.info:eu-repo/semantics/acceptedVersio

A resource for sustainable management:<i>De novo</i> assembly and annotation of the liver transcriptome of the Atlantic chub mackerel, <i>Scomber colias</i>

Mackerels represent a valuable fishery worldwide. Their ample geographic distribution and capture levels make them an insightful model to address stock management strategies in the context of global changes. Yet, and despite recent impressive genome and transcriptome sequencing efforts from teleost species, available resources from the Scombridae family are comparatively scarce. Here, we generated the first high-quality de novo assembly of the liver transcriptome of the Atlantic chub mackerel (Scomber colias). Through the use of RNA-Seq Illumina technology, 111,124,228 clean reads were obtained for the liver transcriptome. De novo assembly resulted in 93,731 transcripts with an N50 of 1462 bp. This dataset provides an important insight into the context of fisheries management. Keywords: RNA-Seq, Scombridae, Stock management, Atlantic chub mackerel, Live