Ultrastructure of porcine pericardium and aortic valve tissues, devitalized with cryogenic and irradiation exposures - N. V. Repin; L. N. Marchenko; T. P. Govorukha; I. P. Mikhajlova; A. A. Manchenko; B. P. Sandomirskij (Problems of cryobiology and cryomedicine, 2015)