An apparatus for treating atrial fibrillation or atrial tachycardia comprises means for dynamically steering or selecting two or more current vector paths sequentially or simultaneously for defibrillation to change the transmembrane potential in the left and right atria sufficiently to halt AF or AT. The method comprises contacting the alkane distillation bottoms stream in the liquid phase with a phosphine or a phosphine-functionalized support, and recovering a treated alkane distillation bottoms stream having a reduced methyl iodide content. The second station has a first baseband transceiver and a second baseband transceiver for respectively communicating packets according to the first and the second version communication standards. A time-limit-based invalidation process, wherein a cache entry can be associated with a time limit, and the time-limit-based invalidation process sends a signal to the cache coordinator to invalidate a cache entry whose time limit has expired. The vanes are aerodynamically shaped to redirect wind-blown rain and snow away from the vent and are configured to block the migration of rain and snow through the vent.