84 joins adjacent disks 54 with bolts rivets welds threads splines tapers snap fits or other means the coupling 84 may also be integrally formed with each of the adjacent disks 82 not shown the cooling air 38 is pumped radially outward against the couplings 84 by the rotation of the disks 54 apertures 86 in the couplings 84 direct the cooling air 38 into rim cavities 88 the apertures may be circular holes slots or other forms and are typically evenly distributed cirumferentially about the coupling 84 the apertures 86 are sized to allow the appropriate cooling air 38 volume to enter the rim cavity 88 the cooling air 38 inside the rim cavity 88 is maintained at a higher pressure than the combustion gases 24 in the annular duct 40 under all engine operating conditions the higher pressure cooling air 38 prevents combustion gas 24 ingestion into the rim cavities 88 and provides cooling for the blade 50 to vane 52 interface a portion of the cooling air 38 is directed axially rearward through a plurality of slots 90 disposed between the blade roots 56 and the disk 54 this portion of cooling air 38 reduces the temperature of the blade root 56 to disk 54 interface before being directed axially rearward to a downstream rim cavity 88 another portion of the cooling.