In a high-efficiency encoder which performs motion-compensation prediction, an intra-field is set every n fields. Each impingement chamber is connected to the central impingement cavity by a number of metering and impingement holes to supply cooling air and a number of cooling air exit holes to discharge the cooling air out the sides of the four edges. A distal edge of the annulus section is generally parabolic and extends from one of the commissure attachment features to an adjacent one of the commissure attachment features, with the middle of the parabola being closest to the inflow end of the stent body. A gradient of solvent concentration relative to hydrocarbon concentration is formed through the internals which act as multiple stages of separation. When the viewing user later requests presentation of newsfeed stories, the user device retrieves the set of newsfeed stories and presents, to the viewing user, stories from the set according to the presentation order.