Numerical modelling of osteocyte growth on different bone tissue scaffolds.

The most common solution for the regeneration or replacement of damaged bones is the implantation of prostheses comprising ceramic or metallic materials. However, these implants are known to cause problems such as post-operative infections, collapse of the prosthesis, and lack of osseointegration. Consequently, bone tissue engineering was established because of the limitations of such implants. Osteogenic implants offer promising solutions for bone regeneration; however, three-dimensional scaffolds should be used as supportive structures. It is challenging to correctly design these structures and their compositions or properties to provide a microenvironment that promotes tissue regeneration and expedites bone formation. Computational fluid dynamics can be used to model the main phenomena that occur in bioreactors, such as cell metabolism, nutrient transport, and cell culture growth, or to model the influence of several key mechanisms related to the fluid medium, in particular, the wall shear stress. In this work, a new numerical bone cell growth model was developed, which considered the oxygen and nutrient consumption as well as the wall shear stress effect on cell proliferation. The model was implemented using 35 three-dimensional scaffolds of different porosities, and the effect of the main geometrical parameters involved in each scaffold type was analysed. The porosity plays an important role, however, a similar porosity did not guarantee similar shear stress or cell growth among the scaffolds. Randomised trabecular scaffolds, that more closely resembled trabecular bone, showed the highest cell growth values, so these are the best candidates for cell growth in a bioreactor.

Glottis effects on the cough clearance process simulated with a CFD dynamic mesh and Eulerian wall film model.

In this study, we have reproduced the cough clearance process with an Eulerian wall film model. The simulated domain is based on realistic geometry from the literature, which has been improved by adding the glottis and epiglottis. The vocal fold movement has been included due to the dynamic mesh method, considering different abduction and adduction angles and velocities. The proposed methodology captures the deformation of the flexible tissue, considers non-Newtonian properties for the mucus, and enables us to reproduce a single cough or a cough epoch. The cough efficiency (CE) has been used to quantify the overall performance of the cough, considering many different boundary conditions, for the analysis of the glottis effect. It was observed that a viscous shear force is the main mechanism in the cough clearance process, while the glottis closure time and the epiglottis position do not have a significant effect on the CE. The cough assistance devices improve the CE, and the enhancement rate grows logarithmically with the operating pressure. The cough can achieve an effective mucus clearance process, even with a fixed glottis. Nevertheless, the glottis closure substantially improves the CE results.

Valor predictivo de cáncer de los exámenes preoperatorios en el nódulo tiroideo: primera parte: estudio clínico / Predictive value for cancer of preoperative tests in thyroid nodule: first part: clinical study

Se analiza en una serie de 231 nódulos tiroideos operados el valor predictivo de cáncer de datos clínicos y de exámenes complementarios concluyéndose que los únicos con significación estadística son el nódulo único, el crecimiento rápido y la citología por punción positiva o de sospecha

Valor predictivo de cáncer de los exámenes preoperatorios en el nódulo tiroideo: segunda parte: desarrollo de un modelo predictivo / Predictive value for cancer of preoperative tests in thyroid nodule: second part: development of a predictive model

Habiendo identificado previamente por análisis de 231 pacientes operados tres factores de riesgo significativos en la predicción de hallazgo de un carcinoma diferenciado de tiroides: nódulo único, crecimiento rápido y citología por punción positiva o de sospecha, se logró determinar: diferencias significativas en la incidencia de carcinoma diferenciado de tiroides según estuviera ausente (6,66 por ciento) o presente por lo menos un factor de riesgo (25,37 por ciento; X2: 5,16, p 0,0125). A su vez aumento significativo de incidencia de carcinoma tiroideo de acuerdo al número de factores de riesgo presentes (1:13,97 por ciento vs. 2:31,57 por ciento, X2:8,25, p<0,005)y 2 vs.3:61,54 por ciento; X2:4,5, p<0,05-en ambos casos luego de corrección de Bonferroni. Desarrollo de un modelo matemático predictivo de riesgo de ocurrencia de carcinoma diferenciado de tiroides, de acuerdo al número de factores de riesgo y mediante análisis de regresión logística, por el momento sujeto a ulterior validación prospectiva