Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Numerical simulation of wave propagation in cracked shafts

The presence of crack-like defects in mechanical and structural elements produces failures during their service life that in some cases can be catastrophic. The increasingly importance of problems related with safety and costs derived from these catastrophic failures, have pushed the researchers in the field of damage detection, to look for and develop methods for the detection and identification of defects. The presence of cracks in rotating mechanical elements, such as shafts, is especially dangerous due to the fatigue effect generated by the work in bending and torsion together with the motion in rotation. In this work, the wave propagation in a cracked shaft due to an initial compression dynamic load has been numerically analyzed as the first step to establish a non-destructive method for the detection and identification of cracks using a dynamic test. Cracks with increasingly depths have been considered and studied. The same model has been submitted to an initial velocity. The results obtained in this work would allow the development of an on-line method for damage detection and identification for cracked mechanical elements using an easy and portable dynamic testing device

Elliptical Crack Identification in a Nonrotating Shaft

It is known that fatigue cracks are one of the most important problems of the mechanical components, since their propagation can cause severe loss, both personal and economic. So, it is essential to know deeply the behavior of the cracked element to have tools that allow predicting the breakage before it happens. The shafts are elements that are specially affected by the described problem, because they are subjected to alternative compression and tension stresses. This work presents, firstly, an analytical expression that allows determining the first four natural frequencies of bending vibration of a nonrotating cracked shaft, assumed as an Euler–Bernoulli beam, with circular cross section under pinned-pinned conditions, taking into account the elliptical shape of the crack. Second, once the direct problem is known, the inverse problem is approached. Genetic Algorithm technique has been used to estimate the crack parameters assuming known the natural frequencies of the cracked shaft

Estudio del factor de intensidad de tensiones para fisuras anulares incipientes abiertas contenidas en un eje sometido a flexión

The appearance of cracks in rotating machine elements such as shafts is one of the main causes of failure and even breakage of this machinery. Most studies on cracked shafts focus on straight or semi-elliptical cracks, when in fact cracks can also occur with a circumferential or annular front. In this work, a 3D numerical model has been developed by means of the Finite Element Method (FEM) that allows an exhaustive study of the Stress Intensity Factor at different points of the front of an annular crack contained in a shaft subjected to bending, as a function of the crack size and its eccentricity. Incipient cracks have been considered as the most dangerous for the integrity of the mechanical component.La aparición de fisuras en elementos de máquinas rotatorias como son los ejes es una de las principales causas que abocan al fallo e incluso a la rotura de esta maquinaria. La mayoría de los estudios sobre ejes fisurados se centran en fisuras de forma recta o semielíptica, cuando en realidad las fisuras se pueden presentar también con un frente circunferencial o anular. En este trabajo se ha desarrollado un modelo numérico 3D mediante el Método de los Elementos Finitos (MEF) que permite realizar un estudio exhaustivo del Factor de Intensidad de Tensiones en los diferentes puntos del frente de una fisura anular contenida en un eje sometido a flexión, en función del tamaño de la fisura y de su excentricidad. Se han considerado fisuras incipientes por ser las más peligrosas para la integridad del componente mecánico

Stress Intensity Factor equations for incipient transverse external annular eccentric cracks contained in a shaft under bending

One of the most common failures in rotating machines is the apparition and propagation of fatigue cracks in one of its main elements: the shafts. These cracks can cause catastrophic failures and lead to costly maintenance or repair processes. Most of the studies in relation to cracks contained in shafts have focused on straight or elliptical transverse cracks. However, although it is less common, the shaft breaks also occur with cracks whose fronts are approximately circumferential, that are more difficult to analyze. These cracks are transverse with circular shape that extend over a complete circumference and that have a certain eccentricity. This work presents the equations that provide the value of the Stress Intensity Factor (SIF) of an incipient crack with circumferential shape contained in a shaft subjected to bending, along the front, as a function of the characteristics of the crack, size and eccentricity. For this, an exhaustive numerical study has been carried out, using the Finite Element Method (FEM), to determine the SIF value along the circumferential front for different sizes and eccentricities of the annular crack