Abstract: A pop-up greeting card presenting a media item to a recipient, comprising two card panels integrally formed with a pop-up element secured between the card panels, forming a three-dimensional configuration with an elongated slot through which the free end of a presentation support element periscopes when the pop-up greeting card is opened. A media item, such as a CD or mini CD, is inserted in the presentation support element such that the media item protrudes at least partially through the elongated pop-up slot when the front surfaces of the card panels are brought together, and is extended through the pop-up slot by the presentation support element when the recipient opens the greeting card. The media item is presented to a recipient of the pop-up greeting card when the card panels are moved apart, as the greeting card is opened.

Abstract: A total counterflow heat exchanger comprising a system of partitions dividing an interior chamber into a series of channels which coincide with the path of a duct through that interior chamber. A substance at one temperature is passed through the duct, and a substance at a second temperature is passed through the channels, thereby creating a temperature differential gradient over which thermal energy is transfered from one substance to the other as the substances flow through the heat exchanger. The arrangement of the partitions permits a substance to pass back and forth through the channels in the heat exchanger along the same path as the duct, so that while the substance may flow through the heat exchanger at the same net rate as if the partitions were not present, the length of the heat exchange gradient may be increased many times, therefore enhancing the efficiency of the gradient and the heat exchanger.