Biomechanical characterization of the passive response of the thoracic aorta in chronic hypoxic newborn lambs using an evolutionary strategy.

The present study involves experiments and modelling aimed at characterizing the passive structural mechanical behavior of the chronic hypoxic lamb thoracic aorta, whose gestation, birth and postnatal period were carried at high altitude (3600 masl). To this end, the mechanical response was studied via tensile and pressurization tests. The tensile and pressurization tests measurements were used simultaneously to calibrate the material parameters of the Gasser-Holzapfel-Ogden (GHO) hyperelasctic anisotropic constitutive model through an analytical-numerical optimization procedure solved with an evolutionary strategy that guarantees a stable response of the model. The model and procedure of calibration adequately adjust to the material behavior in a wide deformation range with an appropriate physical description. The results of this study predict the mechanical response of the lamb thoracic aorta under generalized loading states like those that can occur in physiological conditions and/or in systemic arterial hypertension. Finally, the novel use of the evolutionary strategy, together with the set of experiments and tools used in this study, provide a robust alternative to validate biomechanical characterizations.

The Rare and Challenging Presentation of Gastric Cancer during Pregnancy: A Report of Three Cases.

Pregnancy-associated gastric cancer is extremely rare. In many cases, it is diagnosed at an advanced stage because the symptoms during pregnancy are generally overlooked. We report three cases of gastric cancer during pregnancy with various outcomes. The first case included a patient with stage IV gastric cancer who received palliative chemotherapy. This patient had a preterm birth and died 7 months after diagnosis. The second case received neoadjuvant chemotherapy during pregnancy and a total gastrectomy was performed after delivery. She then received adjuvant chemoradiotherapy. This patient developed pulmonary metastasis and died of recurrence 41 months after surgery. In the third case, a distal subtotal gastrectomy was performed at week 14 of pregnancy, with no complications. The patient received adjuvant chemoradiotherapy. She is currently without recurrence 14 months after surgery. In patients with pregnancy-associated gastric cancer, treatment decisions are predominantly influenced by clinical stage and gestational age at diagnosis.