A constant contact side bearing assembly configured for insertion into a walled receptacle provided on an upper surface of a railcar bolster. The aircraft may include at least one lift fan assembly coupled to its housing and including a gearbox and at least one lift fan. The first computer analyzes the first data and generates a second data. The amount of cobalt used may be from about 1,800 ppm to about 6,000 ppm, with respect to the total weight of the liquid in the reaction medium, and the weight ratio of cobalt to manganese may be from about 40 to about 400. Some methods are directed to ablating tribiculated atrial wall tissue to treat atrial fibrillation.