Profiling Voids Embedded in a Slab by a Non-Linear Model

In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data.     

Second-order iterative approach to inverse scattering: numerical results

We introduce an iterative algorithm for the reconstruction of dielectric profile functions from scattered field data, in which each step corresponds to the solution of a quadratic inversion problem. This means that, at each iteration, we perform a second-order approximation of the scattering operator connecting the unknown profile to the data about a reference profile function. This procedure is then compared with a linear iterative inversion algorithm, and it is pointed out that, within a prescribed class of profile functions, the linear iterative inversion does not converge to the actual solution, whereas the proposed approach does. This feature can be explained by reference not only to the improved approximation provided by the addition of a further term for profile functions of a larger norm but also to the different classes of functions that can be reconstructed by either the linear or the quadratic model. Numerical examples of profile reconstruction in the scalar two-dimensional geometry, with far-zone scattered field data at a fixed frequency, confirm the theoretical analysis.     

Landsliding in seismic areas: the case of the Acquara-Vadoncello landslide (southern Italy)

On 29 December 1993, a slump-earthflow was activated in the outskirts of Senerchia (southern Italy) in a locality named "Vadoncello". Mass movement has been active until the time of writing, at a variable rate. Maximum velocity was reached during 1995, when a seismic sequence of low magnitude (maximum 3.6) was recorded. The landslide evolution was studied considering both the characteristics of seismic activity and slope stability conditions. The results of the analyses showed that the role of seismic action in triggering mass movement is uncertain, although it cannot be excluded. Slope behaviour is more likely to have been controlled by morphological and hydrogeological factors and their modifications, which could also have been responsible for the vulnerability of the slope. In conclusion, the mass movement observed in 1995, triggered by the possible contribution of low magnitude shocks repeated at short intervals, determined new and more stable equilibrium conditions in the slope.     

Regulatory Noncoding and Predicted Pathogenic Coding Variants of CCR5 Predispose to Severe COVID-19

Genome-wide association studies (GWAS) found locus 3p21.31 associated with severe COVID-19. CCR5 resides at the same locus and, given its known biological role in other infection diseases, we investigated if common noncoding and rare coding variants, affecting CCR5, can predispose to severe COVID-19. We combined single nucleotide polymorphisms (SNPs) that met the suggestive significance level (P ≤ 1 × 10⁻⁵) at the 3p21.31 locus in public GWAS datasets (6406 COVID-19 hospitalized patients and 902,088 controls) with gene expression data from 208 lung tissues, Hi-C, and Chip-seq data. Through whole exome sequencing (WES), we explored rare coding variants in 147 severe COVID-19 patients. We identified three SNPs (rs9845542, rs12639314, and rs35951367) associated with severe COVID-19 whose risk alleles correlated with low CCR5 expression in lung tissues. The rs35951367 resided in a CTFC binding site that interacts with CCR5 gene in lung tissues and was confirmed to be associated with severe COVID-19 in two independent datasets. We also identified a rare coding variant (rs34418657) associated with the risk of developing severe COVID-19. Our results suggest a biological role of CCR5 in the progression of COVID-19 as common and rare genetic variants can increase the risk of developing severe COVID-19 by affecting the functions of CCR5.     

Far-field pattern determination from the near-field amplitude ontwo surfaces

The possibility of determining the far field of radiating systems by measuring only the near-field amplitude is investigated. The main difficulties of the problem are examined in some detail and a new near-field/far-field transformation technique is developed, based on the measurement of the near-field amplitude over two surfaces surrounding the antenna under test. The accuracy of the far-field reconstruction results are related both to the distance between such surfaces and to some a priori information concerning the near-field phase and/or the radiating system. The information on the radiating system allows relaxation of the need for any information on the near-field phase provided that the distance between the measurement surfaces is high enough. Conversely, the knowledge of a more or less corrupted near-field phase allows reduction of such distances without affecting the accuracy of the far-field reconstruction. Numerical examples validating the effectiveness of the developed algorithm are provided for the planar scanning case     

Medical treatment of heart failure at a tertiary hospital of S?o Paulo]

The clinical hemostatic effect of tranexamic acid mouthwash after oral surgery was evaluated in 47 patients receiving oral anticoagulant therapy. Surgery was performed after the anticoagulant medication was reduced in 15 patients (control group) and with no change in anticoagulant therapy in 32 patients (test group). The only statistical difference between the two treatment groups at baseline was the level of anticoagulation, which was significantly higher in the test group. There was no significant difference between the two treatment groups in the incidence of bleeding after oral surgery. The results indicated that a combination of local antifibrinolytic therapy and a local hemostatic agent is effective in preventing postoperative bleeding after oral surgery in patients treated with anticoagulants.     

Global convergence of phase retrieval by quadratic approach

The reliability of two different implementations of a quadratic phase retrieval approach to the problem of determining the far field of a radiating system from only square amplitude information on the near field zone is studied. The first implementation exploits square amplitude data over two scanning surfaces. The second one exploits the square amplitude of the voltages received by two different probes moving over a single scanning surface. It is pointed out how the diversity between the two scanning surface data or the two probes gives rise to "cancellation effects" which help in avoiding the local minima problem. Numerical examples are shown to discuss the global convergence properties of the two algorithms.     

Experimental validation of a PO-based shape reconstruction algorithm

The effectiveness of a linear inverse scattering algorithm for the shape reconstruction of perfectly conducting objects is experimentally validated by processing measured data. The data are collected via an automatic system for free-space measurements under reflection mode geometry. The amplitude and phase of the scattered field is measured in a multistatic and multifrequency configuration for different locations (views) of the transmitting antenna. The reliability of the measurement setup is shown by a comparison with simulated data. No a priori knowledge of the shape of the scatterers is assumed. The results of inversions of experimental data collected under single-view illumination agree well with those of inversions of synthetic data, so showing the robustness of the algorithm.     

Reflector antenna fields--An exact aperture-like approach

A new computational approach is presented which allows fast analysis of radiation from large reflector antennas. For an aperture a Fourier transform (FT) relationship does exist between far-field and aperture distribution. Accordingly, the far field can be exactly reconstructed from the knowledge of approximately one sample per lobe (Shannon-Whittaker theorem applied at Nyquist rate). The finite reflector curvature introduces an extra factor in the radiation integral so that the radiation integral is no longer a FT. In order to overcome this difficulty a new pseudosampling expansion, which explicitly takes into account the extra factor, is developed. For parabolic reflector the sampling functions are related to the Fresnel integrals, and the far field can be exactly reconstructed in terms of aperture far-field samples, which can be computed using the fast Fourier transform (FFT). Numerical computations and error analysis show the excellent performance of the method, which can be generalized to deal with arbitrary reflector surfaces and near-field evaluation.