High cycle fatigue behavior of implant Ti-6Al-4V in air and simulated body fluid.

Ti-6Al-4V implants that function as artificial joints are usually subjected to long-term cyclic loading. To study long-term fatigue behaviors of implant Ti-6Al-4V in vitro and in vivo conditions exceeding 107 cycles, constant stress amplitude fatigue experiments were carried out at ultrasonic frequency (20 kHz) with two different surface conditions (ground and polished) in ambient air and in a simulated body fluid. The initiation mechanisms of fatigue cracks were investigated with scanning electron microscopy.

Can baseline magnetic resonance angiography (MRA) status become a foremost factor in selecting optimal acute stroke patients for recombinant tissue plasminogen activator (rt-PA) thrombolysis beyond 3 hours?

Objective: We investigated whether baseline vessel status evaluated by magnetic resonance angiography (MRA) can be the foremost factor to classify acute ischemic stroke patients into subgroups for thrombolytic therapy within 3-6 hours of symptom onset.

Methods: Acute ischemic stroke patients beyond 3 hours after symptom onset were examined by stroke magnetic resonance imaging (MRI) (diffusion- and perfusion-weighted imaging, and MRA) before and after thrombolysis treatment within 24-48 hours. Stroke MRI was used to classify acute ischemic stroke patients into subgroups and select optimal patients for thrombolytic treatment.