Search

One of the main problems in cardiovascular surgery is the lack of functionally reliable small-diameter (no more than 4 mm) vascular grafts required for coronary artery bypass grafting and peripheral artery and vein bypass grafting. The purpose of this work is the development of a composite biopolymer porous tubular matrix (CPTB matrix) 2 and 4 mm in diameter with adjustable resorption time and physicomechanical properties close to native blood vessels of the same diameter. The specimens of CPTB matrices with a diameter of 2 and 4 mm were produced by means of electrospinning from poly(hydroxybutyrate-co-hydroxyvalerate) and gelatin solution in hexafluoroisopropanol. The matrix structure was stabilized by treatment with glutaraldehyde (HA) vapor. It was demonstrated that the best specimen in terms of structure, physicomechanical properties, and resorption rate is the matrix obtained with the ratio of poly(hydroxybutyrate-co-hydroxyvalerate) : gelatin equal to 1 : 2 v/v in the solution and additionally crosslinked in HA vapor for 48 h. The detected slight cytotoxicity of the CBPT matrices developed is easily eliminated by treatment with an aqueous solution containing a set of amino acids. Decreasing the diameter of the substrate rod from 4 to 2 mm is accompanied by small changes in the surface structure and the physicomechanical properties of the CPTB matrix.

This paper presents the results of the study of the domain structure of barium titanate crystals in a wide temperature range including the Curie point (TC) using the polarization-optical method in the reflected light and the force microscopy of the piezoelectric response. It is shown that a new a–c domain structure forms during cyclic heating of the crystal above TCand subsequent cooling to the ferroelectric phase. The role of uncompensated charges appeared on the crystal surface during the phase transition and their influence on the formation of the domain structure during cooling are discussed.

A comparative study of the morphology and piezoelectric response of island and continuous perovskite thin PZT films deposited on a platinized silicon substrate Si/SiO2/TiO2/Pt was carried out. It was shown that the self-polarization value of micron-size island films was about 1.4 times higher than that of continuous films. It is assumed that the difference is due to the relaxation of tensile mechanical stresses caused by silicon substrate at the island periphery.