Calcium phosphate-titanium composites for articulating surfaces of load-bearing implants.

Calcium phosphate (CaP)-titanium (Ti) composites were processed using a commercial laser engineered net shaping (LENS™) machine to increase wear resistance of articulating surfaces of load-bearing implants. Such composites could be used to cover the surface of titanium implants and potentially increase the lifetime of a joint replacement. It was hypothesized that adding calcium phosphate to commercially pure titanium (CP-Ti) and Ti6Al4V alloy via laser processing would decrease the material loss when subjected to wear. This added protection would be due to the in situ formation of a CaP tribofilm. Different amounts of CaP were mixed by weight with pure Ti and Ti6Al4V powders. The mixed powders were then made into cylindrical samples using a commercial LENS™-750 system. Microstructures were observed and it was found the CaP had integrated into the titanium metal matrix. Compression test revealed that CaP significantly increased the 0.2% offset yield strength as well as the ultimate compressive strength of CP-Ti. It was found that the addition of CaP to pure titanium reduced the material loss and increased wear resistance. This was due to the formation of CaP tribofilm on the articulating surface. The in situ formed tribofilm also lowered the coefficient of friction and acted as a solid lubricant between the two interacting metal surfaces. Overall, CaP addition to Ti and its alloy Ti6Al4V show an effective way to minimize wear induced damage due to the formation of in situ tribofilm at the articulating surface, a strategy that can be utilized in various biomedical devices.

Aerobic exercise enhances cognitive flexibility.

INTRODUCTION: Physical activity is believed to prevent cognitive decline and may enhance frontal lobe activity. METHODS: Subjects were 91 healthy adults enrolled in a wellness center. Over a 10 week intervention, controls were aerobically active 0-2 days per week. Half the intervention group was active 3-4 days/week and half 5-7 days/week. Outcome measures included memory, mental speed, reaction time, attention, and cognitive flexibility. RESULTS: Neurocognitive data were analyzed by repeated measures comparing minimal aerobic exercise (the control group) to moderate aerobic exercise (3-4 days/week), and to high aerobic exercise (5-7 days/week). Initial analyses noted significant improvements in mental speed (p = .03), attention (p = .047), and cognitive flexibility (p = .002). After controlling for age, gender, education, and changes in psychomotor speed, only cognitive flexibility still showed significant improvements (p = .02). CONCLUSION: Over a 10 week period, increasing frequency of aerobic activity was shown to be associated with enhanced cognitive performance, in particular cognitive flexibility, a measure of executive function.