Attenuation of Rayleigh waves due to three-dimensional surface roughness: A comprehensive numerical evaluation.

The phenomenon of Rayleigh wave attenuation due to surface roughness has been well studied theoretically in the literature. Three scattering regimes describing it have been identified-the Rayleigh (long wavelength), stochastic (medium wavelength), and geometric (short wavelength)-with the attenuation coefficient exhibiting a different behavior in each. Here, in an extension to our previous work, we gain further insight with regard to the existing theory, in three dimensions, using finite element (FE) modeling, under a unified approach, where the same FE modeling techniques are used regardless of the scattering regime. We demonstrate good agreement between our FE results and the theory in all scattering regimes. Additionally, following this demonstration, we extend the results to cases that lie outside the limits of validity of the theory.

Attenuation of Rayleigh waves due to surface roughness.

Rayleigh waves are well known to attenuate due to scattering when they propagate over a rough surface. Theoretical investigations have derived analytical expressions linking the attenuation coefficient to statistical surface roughness parameters, namely, the surface's root mean squared height and correlation length and the Rayleigh wave's wavenumber. In the literature, three scattering regimes have been identified-the geometric (short wavelength), stochastic (short to medium wavelength), and Rayleigh (long wavelength) regimes. This study uses a high-fidelity two-dimensional finite element (FE) modelling scheme to validate existing predictions and provide a unified approach to studying the problem of Rayleigh wave scattering from rough surfaces as the same model can be used to obtain attenuation values regardless of the scattering regime. In the Rayleigh and stochastic regimes, very good agreement is found between the theory and FE results both in terms of the absolute attenuation values and for asymptotic power relationships. In the geometric regime, power relationships are obtained through a combination of dimensional analysis and FE simulations. The results here also provide useful insight into verifying the three-dimensional theory because the method used for its derivation is analogous.

Radiotherapy for tumors of the mediastinum - state of the art.

Mediastinal tumors encompass a diverse range of malignancies, originating within or spreading to the mediastinum. The administration of radiotherapy within the anatomical confines of the mediastinum presents unique challenges owing to the close proximity of critical organs, including the heart, lungs, esophagus, and spinal cord. However, recent progress in imaging techniques, treatment modalities, and our understanding of tumor biology has significantly contributed to the development of effective and safe therapeutic strategies for mediastinal diseases. This review article aims to explore the latest innovations in radiotherapy and their practical applications in the management of mediastinal tumors, with a primary focus on lymphomas, thymomas, and thymic carcinomas. By examining these advancements, we seek to provide valuable insights into the current state of the art in radiotherapy for mediastinal malignancies, ultimately fostering improved patient outcomes and clinical decision-making.

Fatigue state characterisation of steel pipes using ultrasonic shear waves.

The phenomenon of the reduction in the propagation speed of an ultrasonic wave when it travels through a fatigue zone has been well studied in the literature. Additionally, it has been established that shear waves are more severely affected by the presence of such a zone, compared with longitudinal waves. Our study utilises these phenomena to develop a method able to characterise the fatigue state of steel pipes. Initially, the existing theory regarding the increased sensitivity of shear waves to the presence of fatigue is validated through measuring and comparing the change in propagation speed of both longitudinal and bulk shear waves on flat geometries, at different fatigue states. The comparison is achieved with the aid of ultrasonic speed C-scans of both longitudinal and shear waves, with the latter now being obtainable through our implementation of advances in Electromagnetic Acoustic Transducers (EMAT) technology. EMATs have not been traditionally used for producing C-scans, and their ability do to so with adequate repeatability is demonstrated here; we show that shear wave scanning with EMATs now provides a possibility for inspection of fatigue damage on the inner surface of pressure-containing components in the nuclear power industry. We find that the change in ultrasonic wave speed is amplified when shear waves are used, with the magnitude of this amplification agreeing well with the theory. Following the verification of the theory, the use of EMATs allowed us to tailor the shear wave scanning method to pipe geometries, where C-scans with conventional piezoelectric transducers would not have been possible, with the results successfully revealing the presence of fatigue zones.

Risk evaluation in adult congenital heart surgery: analysis of the Society of Thoracic Surgeons Congenital Heart Surgery Database risk models on data from the European Congenital Heart Surgeons Association Congenital Database.

OBJECTIVES: We sought to evaluate the predictive power of the Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) mortality score and the adult congenital heart surgery (ACHS) mortality score for the adults undergoing congenital heart operations entered into the European Congenital Heart Surgeons Association (ECHSA) database. METHODS: The data set comprised 17 662 major operations performed between 1997 and 2019, on patients 18 years of age or older, in European centres participating in the ECHSA database. Each operation was assigned a STAT mortality score and category and an ACHS mortality score. Operative mortality was based on the 30-day status and on the status at hospital discharge. The discriminatory power of the STAT and ACHS scores was assessed using the area under the receiver operating characteristic curve (c-index). RESULTS: A total of 17 214 (97.46%) operations were assigned ACHS scores. The 3 most frequent primary procedures were closure of the atrial septal defect (19.0%), aortic valve replacement (8.8%) and non-valve-sparing aortic root replacement (6.1%). Operative mortality for ACHS-coded operations was 2.07%. The procedures with the highest mortality were atrial septal defect creation/enlargement (19.0%), lung transplantation (18.8%) and heart transplantation (18.2%). A total of 17 638 (99.86%) operations were assigned a STAT score and category. The operative mortality for STAT-coded operations was 2.27%. The c-index for mortality was 0.720 for the STAT mortality score and 0.701 for the ACHS score. CONCLUSIONS: The ACHS mortality score and the STAT mortality score reached similar, moderate predictive power in adult patients undergoing congenital heart surgery in ECHSA database.

Higher Programmatic Volume in Neonatal Heart Surgery Is Associated With Lower Early Mortality.

BACKGROUND: The early results of congenital heart surgery in neonates remain a challenge. We sought to determine the nature of the association between annual center volume of neonatal cardiac surgery and operative mortality using a multicenter cohort. METHODS: The dataset consists of 27,556 neonatal procedures performed between 1999 and 2015 in 90 centers participating in the European Congenital Heart Surgeons Association database. Centers with mean annual volume load of six or more that submitted data for at least 3 consecutive years were included. World Bank annual gross national index per capita was utilized as an indicator of temporal national affluence. Multilevel logistic regression was used to create a model including the significant risk factors and to calculate odds ratios for operative mortality. Iterative modeling of the dataset incrementally excluding centers with lower annual caseload was used to identify the relationship between annual volume and mortality. RESULTS: In the model thus calculated including The Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) mortality score, operative weight and age, noncardiac genetic anomalies, and annual volume of operations were independent risk factors for operative mortality in the analysis of the entire cohort. In the model containing these variables, annual gross national index and year of surgery were not significantly associated with mortality. In the iterative process, annual volume ceased to be a risk factor when units operating on fewer than 60 neonates annually were excluded. CONCLUSIONS: In neonatal congenital heart surgery, the risk of operative death decreased with the increase of volume load. The cutoff point in this cohort was a mean annual volume of 60 neonatal operations per year.