A match coefficient approach for damage imaging in structural components by ultrasonic synthetic aperture focus

Ultrasonic Synthetic Aperture Focus (SAF) techniques are commonly used to image structural defects. In this paper, a variation of SAF based on ideas borrowed from Matched Field Processing (MFP) is evaluated to reduce artifacts and sidelobes of the resulting images. In particular, instead of considering the full RF ultrasonic waveforms for the SAF time backpropagation, only selected features from the waveforms are utilized to form a “data vector” and a “replica” (expected) vector of MFP. These vectors are adaptive for the pair of transmitter-receiver and the focus point. The image is created as a matched filter between these two vectors. Experimental results are shown for an isotropic and homogenous metallic plate with simulated defects, probed by six piezoelectric patches used as receivers or transmitters

Leprosy-like cutaneous presentation of Histoplasma capsulatum infection in an African HIV+ patient

Histoplasma capsulatum is an opportunistic dimorphic fungus responsible for most often self-limiting or flu-like infections but potentially lethal in immunocompromised hosts. Histoplasmosis is rare in Europe. We reported a case of disseminated histoplasmosis in an African HIV patient with a leprosy-like primary cutaneous presentation and involvement of lungs, brain, limphnodes and eye. The therapy with liposomial B amphotericin and itraconazole led to a prompt resolution of the symptoms

Mediterranean visceral leishmaniasis in immunocompetent children. Report of two cases relapsed after specific therapy

Visceral leishmaniasis (VL) is endemic in areas bordering the Mediterranean Sea (Spain, Italy, France, Greece, Morocco, Tunisia) where it is caused by Leishmania infantum and is transmitted by the bite of a hematophagous sandfly belonging to Phlebotomus spp.; the dog constitutes the main reservoir of infection. Two cases of VL in immunocompetent children are described. Both patients lived in endemic areas for leishmaniasis (Sicily) and at admission were febrile, pale and had splenomegaly. In both patients anti-leishmania antibodies were present and a definitive diagnosis was confirmed by demonstration of leishmania parasites by microscopy or polymerase chain reaction (PCR) in the bone marrow aspirates. The use of PCR performed on peripheral blood has been reported to be highly sensitive for the diagnosis and follow-up of children with VL. One patient was treated with N-dimethylglucamine, Glucantim, the other one with liposomal Amphotericin B (AmBisome). Both had symptomatic relapses 3 months later, and recovered following re-treatment with AmBisome administered intravenously at a dosage of 3 mg/Kg for ten consecutive days. The patients were monitored for one year after treatment was complete

Nonlinear guided wave propagation in prestressed plates

The measurement of stress in a structure presents considerable interest in many fields of engineering. In this paper, the diagnostic potential of nonlinear elastic guided waves in a prestressed plate is investigated. To do so, an analytical model is formulated accounting for different aspects involved in the phenomenon. The fact that the initial strains can be finite is considered using the Green Lagrange strain tensor, and initial and final configurations are not merged, as it would be assumed in the infinitesimal strain theory. Moreover, an appropriate third-order expression of the strain energy of the hyperelastic body is adopted to account for the material nonlinearities. The model obtained enables to investigate both the linearized case, which gives the variation of phase and group velocity as a function of the initial stress, and the nonlinear case, involving second-harmonic generation as a function of the initial state of stress. The analysis is limited to Rayleigh-Lamb waves propagating in a plate. Three cases of initial prestress are considered, including prestress in the direction of the wave propagation, prestress orthogonal to the direction of wave propagation, and plane isotropic stress

Non-destructive evaluation of prestress in plates by nonlinear guided waves

This paper investigates the diagnostic potential of guided Rayleigh-Lamb waves in a homogeneous, elastic, isotropic prestressed plate in the light of the finite strain theory. This theory accounts for the fact that strains are not infinitesimal and involves the use of the Green Lagrange strain tensor. Since the strains are not infinitesimal, an appropriate expression of the strain energy must be adopted. Three different states of prestress are considered: uniaxial stress in the direction of the wave propagation, uniaxial stress orthogonal to the direction of wave propagation, and quasi-isotropic stress state. Two different approximations of the model are considered, that is first and second-order. The first-order approximation provides linearized equations of motion enabling to investigate the variation of group velocity as a function of the initial state of prestress. The second-order approximation is used to develop an analysis of the secondary wave field based on the perturbation approach and accounting for synchronicity requirements. This enables to define quantitative relations between the amplitude of the nonlinearity-driven second-harmonic plate wave and the state of prestress. These relations can be used to evaluate, nondestructively, the level of prestress in plate-like structures