Effect of the Ti-6Al-4V alloy specimens crystal lattice curvature within surface layers on fatigue failure mechanisms

In the present work the role of the crystal lattice curvature in fatigue failure of Ti-6Al-4V alloy specimens was discussed. The effect of the specimens ultrasonic treatment and further electrolytic hydrogenation on their fatigue properties was revealed. It was found that the crystal lattice curvature resulted in the fatigue durability increase due to a grain boundary sliding at the boundaries of strongly dispersed phases as well as the decrease one by reason of the brittle intermetallic phase of Ti3Al precipitation or the stabilization by hydrogen of the strong BCC ß phase depending on the Ti-6Al-4V specimens structure and phase composition

Long-term neurodevelopmental outcome and exercise capacity after corrective surgery for tetralogy of Fallot or ventricular septal defect in infancy.

BACKGROUND: The purpose of this prospective study was to assess whether neurodevelopmental status and exercise capacity of children 5 to 10 years after corrective surgery for tetralogy of Fallot or ventricular septal defect in infancy was different compared with normal children and influenced by the preoperative condition of hypoxemia or cardiac insufficiency. METHODS: Forty unselected children, 20 with tetralogy of Fallot and hypoxemia and 20 with ventricular septal defect and cardiac insufficiency, operated on with combined deep hypothermic circulatory arrest and low flow cardiopulmonary bypass at a mean age of 0.7 +/- 0.3 years (mean +/- SD), underwent, at mean age 7.4 +/- 1.6 years, standardized evaluation of neurologic status, gross motor function, intelligence, academic achievement, language, and exercise capacity. Results were compared between the groups and related to preoperative, perioperative, and postoperative status and management. RESULTS: Rate of mild neurologic dysfunction was increased compared with normal children, but not different between the groups. Exercise capacity and socioeconomic status were not different compared with normal children and between the groups. Compared with the normal population, motor function, formal intelligence, academic achievement, and expressive and receptive language were significantly reduced (p < 0.01 to p < 0.001) in the whole group and in the subgroups, except for normal intelligence in ventricular septal defect patients. Motor dysfunction was significantly higher in the Fallot group compared with the ventricular septal defect group (p < 0.01) and correlated with neurologic dysfunction, lower intelligence, and reduced expressive language (p < 0.05 each). Reduced New York Heart Association functional class was correlated with lower exercise capacity and longer duration of cardiopulmonary bypass (p < 0.05 each). Reduced socioeconomic status significantly influenced dysfunction in formal intelligence (p < 0.01) and academic achievement (p < 0.05). Preoperative risk factors such as prenatal hypoxia, perinatal asphyxia, and preterm birth, factors of perioperative management such as cardiac arrest, lowest nasopharyngeal temperature, and age at surgery, and postoperative risk factors as postoperative cardiocirculatory insufficiency and duration of mechanical ventilation were not different between the groups and had no influence on outcome. Degree of hypoxemia in Fallot patients and degree of cardiac insufficiency in ventricular septal defect patients did not influence the outcome within the subgroups. CONCLUSIONS: Children with preoperative hypoxemia in infancy are at higher risk for motor dysfunction than children with cardiac insufficiency. Corrective surgery in infancy for tetralogy of Fallot or ventricular septal defect with combined circulatory arrest and low flow bypass is associated with reduced neurodevelopmental outcome, but not with reduced exercise capacity in childhood. In our experience, the general risk of long-term neurodevelopmental impairment is related to unfavorable effects of the global perioperative management. Socioeconomic status influences cognitive capabilities