Piezoelectric transducer design optimization

To respond to the design of a torsion sensor into mechanical ultrasonic tissue applications, it is necessary to use FEM Finite Element Models. Through a simplified analytical model of torsion transducer, we determine the resonant frequency for a torque transducer ultrasonic waves. It is computationally validated. More specifically the idea is to refine and optimize the design to be applied to the detection of preterm birth identifying changes in the consistency of the cervical tissue through the shear modulus measurements. Therefore, a model with a disk transmitter and a ring receiver for easy accessibility was performed and sensitivity analysis to find the range of optimal design values with this application was calculated. Therefore, it is neces- sary to optimize the piezoelectric transducer model design regarding two types of parameters. On one hand the design parameters, and on the other hand the model parameters that characterize the specimen. The forward problem is obtained by performing a three-dimensional finite element simulation. The experimental measurements are simulated by adding a gaussian noise as a percentage of the RMS of the numerically predicted signals. In addition, a semi-analytical estimate of the probability of detection (POD) is developed to provide a rational criterion to optimize the experimental design.Para responder al diseño de un sensor de torsión con aplicaciones a la mecánica tisular ultrasónica, es necesario el uso de modelos de elementos finitos FEM como procedimiento directo. A través de un modelo simplificado de análisis de transductor de torsión, se determina la frecuencia de resonancia que se valida computacionalmente. Más específicamente, la idea es refinar y optimizar el diseño que debe aplicarse a la detección de parto prematuro identificar los cambios en la consistencia del tejido del cuello uterino a través de medidas del módulo G . Por lo tanto, se elige un modelo con un disco transmisor y un anillo receptor para facilitar la accesibilidad en el diseño y se realizó un análisis de sensibilidad para encontrar el rango de valores óptimos con esta aplicación. Para optimizar el diseño del modelo del transductor piezoeléctrico con respecto a dos tipos de parámetros. Por un lado los parámetros de diseño, y por otra parte los parámetros del modelo que caracterizan la muestra. Las medi- ciones experimentales se simulan mediante la adición de un ruido gaussiano como un porcentaje de la RMS de las señales predichas numéricamente. Además, una estimación semi-analítica de la probabilidad de detección (POD) se ha desarrollado para proporcionar un criterio racional para optimizar el diseño experimental.Universidad de Granada. Departamento de Mecánica de Estructuras e Ingeniería Hidráulica. Máster Universitario en Estructuras, curso 2011-2012Este trabajo a sido financiado por el Ministerio de Educación a través de Dpi2010-1706

Viscoelastic Biomarkers of Ex Vivo Liver Samples via TorsionalWave Elastography

We thank the Department of Electronics and Computer Technology of the University of Granada for assistance with the electronic system of the torsional wave sensor.The clinical ultrasound community demands mechanisms to obtain the viscoelastic biomarkers of soft tissue in order to quantify the tissue condition and to be able to track its consistency. Torsional Wave Elastography (TWE) is an emerging technique proposed for interrogating soft tissue mechanical viscoelastic constants. Torsional waves are a particular configuration of shear waves, which propagate asymmetrically in-depth and are radially transmitted by a disc and received by a ring. This configuration is shown to be particularly efficient in minimizing spurious p-waves components and is sensitive to mechanical constants, especially in cylinder-shaped organs. The objective of this work was to validate (TWE) technique against Shear Wave Elasticity Imaging (SWEI) technique through the determination of shear wave velocity, shear moduli, and viscosity of ex vivo chicken liver samples and tissue mimicking hydrogel phantoms. The results of shear moduli for ex vivo liver tissue vary 1.69–4.0kPa using TWE technique and 1.32–4.48kPa using SWEI technique for a range of frequencies from 200 to 800Hz. Kelvin–Voigt viscoelastic parameters reported values of μ = 1.51kPa and η = 0.54Pa·s using TWE and μ = 1.02kPa and η = 0.63Pa·s using SWEI. Preliminary results show that the proposed technique successfully allows reconstructing shear wave velocity, shear moduli, and viscosity mechanical biomarkers from the propagated torsional wave, establishing a proof of principle and warranting further studies.This research was funded by the Ministry of Education grant numbers DPI2017-83859-R, DPI2014-51870-R, and UNGR15-CE-3664; Ministry of Health grant numbers DTS15/00093 and PI16/00339 Carlos III Instituto de Salud y Fondos Feder; and Junta de Andalucía grant numbers, PI-0107-2017 and PIN-0030-2017. Juan de la Cierva Incorporación IJC2018-037167-I

Numerical Modelling of Magnetic Nanoparticle Behavior in an Alternating Magnetic Field Based on Multiphysics Coupling

In magnetic nanoparticle hyperthermia, the magnetic nanoparticles (MNPs) start oscilla- tions when they are exposed to an alternating magnetic field, which may generate ultra- sound waves. These resulting oscillations of nanoparticles can lead to the movement of drug carrier liposomes. In this study, a multiphysics coupling model of magnetic nanoparticle behavior in an alternating magnetic field was developed, implementing solid mechanics compliance parameters and piezomagnetic coupling matrices. A detailed sensitivity study was conducted to to examine the effects of size and elastic modulus of MNPs, distribution and distance between two MNPs, elasticity and viscosity of the glycerol medium and mesh element sizes on the output displacement signals of MNPs. The results indicated that mag- netic nanoparticles undergo some displacements when they are exposed to an alternating magnetic field. These oscillations may generate ultrasound waves, though the amount of displacement for each nanoparticle is negligibly small. It is expected that aggregated nanoparticles result in much higher oscillations.Ministry of Science and Innovation, Spain grant numbers PID2019-106947RA-C2FEDER EQC2018-004508-

Damage prediction via nonlinear ultrasound: A micro-mechanical approach

Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.ultras.2018.10.009. All results obtained within the paper can be reproduced using formulae provided.Nonlinear constitutive mechanical parameters, predominantly governed by micro-damage, interact with ultrasound to generate harmonics that are not present in the excitation. In principle, this phenomenon therefore permits early stage damage identification if these higher harmonics can be measured. To understand the underlying mechanism of harmonic generation, a nonlinear micro-mechanical approach is proposed here, that relates a distribution of clapping micro-cracks to the measurable macroscopic acoustic nonlinearity by representing the crack as an effective inclusion with Landau type nonlinearity at small strain. The clapping mechanism inside each micro-crack is represented by a Taylor expansion of the stress-strain constitutive law, whereby nonlinear terms arise. The micro-cracks are considered distributed in a macroscopic medium and the effective nonlinearity parameter associated with compression is determined via a nonlinear Mori-Tanaka homogenization theory. Relationships are thus obtained between the measurable acoustic nonlinearity and the Landau-type nonlinearity. The framework developed therefore yields links with nonlinear ultrasound, where the dependency of measurable acoustic nonlinearity is, under certain hypotheses, formally related to the density of micro-cracks and the bulk material properties.The authors acknowledge the Spanish Ministerio de Economía y Competitividad for project DPI2014-51870-R and Junta de Andalucía for projects P11-CTS-8089 and GGI3000IDIB. Melchor is grateful to the University of Manchester for funding via the Engineering and Physical Science Research Council (EPSRC) grant reference EP/I01912X/1. Parnell is grateful to the EPSRC for his research fellowship (EP/L018039/1)

Torsional wave elastography to assess the mechanical properties of the cornea

Corneal mechanical changes are believed to occur before any visible structural alterations observed during routine clinical evaluation. This study proposed developing an elastography technique based on torsional waves (TWE) adapted to the specificities of the cornea. By measuring the displacements in the propagation plane perpendicular to the axis of the emitter, the effect of guided waves in platelike media was proven negligible. Ex vivo experiments were carried out on porcine corneal samples considering a group of control and one group of alkali burn treatment ( NH 4OH) that modified the mechanical properties. Phase speed was recovered as a function of intraocular pressure (IOP), and a Kelvin-Voigt rheological model was fitted to the dispersion curves to estimate viscoelastic parameters. A comparison with uniaxial tensile testing with thin-walled assumptions was also performed. Both shear elasticity and viscosity correlated positively with IOP, being the elasticity lower and the viscosity higher for the treated group. The viscoelastic parameters ranged from 21.33 to 63.17 kPa, and from 2.82 to 5.30 Pa s, for shear elasticity and viscosity, respectively. As far as the authors know, no other investigations have studied this mechanical plane under low strain ratios, typical of dynamic elastography in corneal tissue. TWE reflected mechanical properties changes after treatment, showing a high potential for clinical diagnosis due to its rapid performance time and paving the way for future in vivo studies.Ministerio de Educacion, Cultura y Deporte Grant DPI2017-83859-R DPI2014-51870-R UNGR15-CE-3664 EQC2018-004508-PSpanish Government DTS15/00093 PI16/00339Instituto de Salud Carlos III y Fondos FederJunta de Andalucia PI-0107-2017 PIN-0030-2017 IE2017-5537MCIN/AEI - European Social Fund "Investing in your future" PRE2018-086085Consejeria de economia, conocimiento, empresas y universidad SOMM17/6109/UGR B-TEP-026- IE2017-5537 P18-RT-1653European Commission SOMM17/6109/UGR B-TEP-026- IE2017-5537 P18-RT-165

Lysozyme crystallization in hydrogel media under ultrasound irradiation

Sonocrystallization implies the application of ultrasound radiation to control the nucleation and crystal growth depending on the actuation time and intensity. Its application allows to induce nucleation at lower supersaturations than required under standard conditions. Although extended in inorganic and organic crystallization, it has been scarcely explored in protein crystallization. Now, that industrial protein crystallization is gaining momentum, the interest on new ways to control protein nucleation and crystal growth is advancing. In this work we present the development of a novel ultrasound bioreactor to study its influence on protein crystallization in agarose gel. Gel media minimize convention currents and sedimentation, favoring a more homogeneous and stable conditions to study the effect of an externally generated low energy ultrasonic irradiation on protein crystallization avoiding other undesired effects such as temperature increase, introduction of surfaces which induce nucleation, destructive cavitation phenomena, etc. In-depth statistical analysis of the results has shown that the impact of ultrasound in gel media on crystal size populations are statistically significant and reproducible.MCIN/AEI PID2020-118498GB-I00 PID2020-116261GB-I00 PID2020-115372RB-I00 MCIN/AEI/FEDER "Una manera de hacer Europa", Spain PID2019-106947RA-C22FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades (Spain) A-FQM-340-UGR20 P18-FR-3533 P18-RT-1653 BTEP-026-UGR1

Estimación de los efectos redistributivos y de las ganancias en bienestar social derivados de la progresividad del IRPF en las Comunidades Autonómas del territorio de Régimen Común

RESUMEN. En este artículo, en primer lugar, exponemos las principales características de los registros administrativos de la información fiscal sobre la tributación efectiva del IRPF agrupada por tramos de base imponible gravada media, procedente de la Dirección General de Informática Tributaria de la Agencia Tributaria. En segundo lugar, siguiendo la metodología expuesta por Kakwani y Podder (1976), estimamos, para cada Comunidad Autónoma del Territorio de Régimen Común, curvas de Lorenz y de concentración y los correspondientes índices de desigualdad asociados. A continuación, y siguiendo a Creedy (1996), estimamos para cada Comunidad Autónoma las ganancias en bienestar social asociadas a la progresividad del IRPF. Por último, presentamos los valores estimados de progresividad del IRPF, capacidad redistributiva y ganancias en bienestar social, para cada Comunidad Autónoma, analizando brevemente sus características y evolución.ABSTRACT. This work first examines the main characteristics of the administrative tax records on effective income tax payment grouped by taxable income bands, provided by the Tax Authority’s General Directorate for Tax Information Technology. Secondly, following the methodology set out by Kakwani and Podder (1976), we estimate Lorentz and concentration curves and the corresponding indices of associated inequality for each of Spain’s Autonomous Regions. Subsequently, and based on Creedy (1996), we estimate the gains in social welfare associated to income tax progressiveness for each Autonomous Region. Finally, we present the estimated values of income tax progressiveness, redistribution capacity and gains in social welfare for each Autonomous Region, briefly analysing their characteristics and evolution

Biomechanical Finite Element Method Model of the Proximal Carpal Row and Experimental Validation

This research was funded by the Ministry of Education Grants DPI2017-83859-R, EQC2018-004508-P, and UNGR15-CE-3664; Ministry of Health Grants DTS15/00093 and PI16/00339; and Junta de Andalucia Grants, B-TEP-026-UGR18, IE2017-5537, P18-RT-1653, PI-0107-2017, and PIN-0030-2017.The Finite Element Method (FEM) models are valuable tools to create an idea of the behavior of any structure. The complexity of the joints, materials, attachment areas, and boundary conditions is an open issue in biomechanics that needs to be addressed. Scapholunate instability is the leading cause of wrist pain and disability among patients of all ages. It is needed a better understanding of pathomechanics to develop new effective treatments. Previous models have emulated joints like the ankle or the knee but there are few about the wrist joint. The elaboration of realistic computational models of the carpus can give critical information to biomedical research and surgery to develop new surgical reconstructions. Hence, a 3D model of the proximal carpal row has been created through DICOM images, making a reduced wrist model. The materials, contacts, and ligaments definition were made via open-source software to extract results and carry on a reference comparison. Thus, considering the limitations that a reduced model could carry on (unbalanced forces and torques), the stresses that result in the scapholunate interosseous ligament (SLIL) lead us to a bones relative displacement, which support the kinematics hypothesis in the literature as the distal carpal row moves as a rigid solid with the capitate bone. Also, experimental testing is performed, successfully validating the linear strength values of the scapholunate ligament from the literature.Ministry of Education Grants DPI2017-83859-R EQC2018-004508-P UNGR15-CE-3664Ministry of Health Grants DTS15/00093 PI16/00339Junta de Andalucia B-TEP-026-UGR18 IE2017-5537 P18-RT-1653 PI-0107-2017 PIN-0030-201

Lung Ultrasound, Clinical and Analytic Scoring Systems as Prognostic Tools in SARS-CoV-2 Pneumonia: A Validating Cohort

At the moment, several COVID-19 scoring systems have been developed. It is necessary to determine which one better predicts a poor outcome of the disease. We conducted a single-center prospective cohort study to validate four COVID-19 prognosis scores in adult patients with confirmed infection at ward. These are National Early Warning Score (NEWS) 2, Lung Ultrasound Score (LUS), COVID-19 Worsening Score (COWS), and Spanish Society of Infectious Diseases and Clinical Microbiology score (SEIMC Score). Our outcomes were the combined variable “poor outcome” (noninvasive mechanical ventilation, intubation, intensive care unit admission, and death at 28 days) and death at 28 days. Scores were analysed using univariate logistic regression models, receiver operating characteristic curves, and areas under the curve. Eighty-one patients were included, from which 21 had a poor outcome, and 9 died. We found a statistically significant correlation between poor outcome and NEWS2, LUS > 15, and COWS. Death at 28 days was statistically correlated with NEWS2 and SEIMC Score although COWS also performs well. NEWS2, LUS, and COWS accurately predict poor outcome; and NEWS2, SEIMC Score, and COWS are useful for anticipating death at 28 days. Lung ultrasound is a diagnostic tool that should be included in COVID-19 patients evaluation