The growing interest in biodegradable scaffolds for bone regeneration created a need to investigate new materials suitable for scaffold formation. Poly(lactic acid) (PLA) is a polymer commonly used in biomedical engineering, e.g. in tissue engineering as a biodegradable material. However, the mechanical behavior of PLA along its degradation time is still not explored well. For this reason, the mechanical properties of PLA scaffolds affected by incubation in physiological medium needs to be investigated to show the potential of PLA to be used as a material for biodegradable scaffold formation. The purpose of this research is to determine the mechanical properties of PLA scaffolds before and after incubation, and to apply constitutive material models for further behavior prediction. Two sets of PLA scaffolds were printed by the 3D printer “Prusa i3 MK3S” and sterilized by ultraviolet light and ethanol solution. The first set of specimens was incubated in DMEM (Dulbecco’s Modified Eagle Medium) for 60, 120, and 180 days maintaining 36.5 °C temperature. The mechanical properties of the scaffolds were determined after performing the compression test in the “Mecmesin MultiTest 2.5-i” testing stand with a force applied at two different speed modes. The obtained data was curve fitted with the hyperelastic material models for a model suitability study. The second set of specimens was incubated in PBS (Phosphate Buffered Saline) for 20 weeks and used in a polymer degradation study. The obtained results show that the mechanical properties of PLA scaffolds do not decrease during incubation in physiological medium for a predicted new bone tissue formation period, though hydrolysis starts at the very beginning and increases with time. PLA as a material seems to be suitable for the use in bone tissue engineering as it allows to form biocompatible and biodegradable scaffolds with high mechanical strength, required for effective tissue formation.

This article investigates the influence of different solvents on the mechanical properties of biocompatible and biodegradable polycaprolactone (PCL) scaffolds. During the research, using electrospinning technology, 27 samples of polycaprolactone nanofibers exposed to different solvents were produced. A tensile test was performed on the produced nanofiber samples, and the nanofiber mechanical properties, yield strength, elastic modulus, and elastic elongation were calculated, and load–displacement and stress–strain dependence diagrams were compared from the obtained results. The strongest nanofiber was singled out, and its mechanical properties were compared with those of biological tissues and its application in tissue engineering. The structure was determined using a scanning electron microscope, and the structures of nanofibers exposed to different solvents were compared. After calculating the influence of different solvents on the mechanical properties of the nanofibers, the strongest structure was identified, PCL and chloroform, which has an elastic modulus of 9.86 MPa and a yield strength of 1.11 ± 0.32 MPa. The type of solvent used in the production of the solution affects the homogeneity of the fibre and the shape of the filaments. In solvents with lower viscosity, the fibre filaments are more homogeneous and more evenly distributed.

A method for the preliminary processing of MRI images of the heart that allows for the elimination of fluctuation and impulse noise from useful signals is proposed. These types of noise are due to the regular geometric structure of the photoelectric elements of the MRI scanner matrix and the structure of the signal transmission channel. The aim of this work is to develop a comprehensive mathematical model for eliminating noise in the signal of an MRI scanner. In this work, mathematical models of linear and median filtering of impulse noise, fluctuation, and geometric noise are implemented. The mathematical models consist of the combined use of linear and median filters for recording MRI images of the heart. In the experiments, real MRI images of the heart from six patients with different diseases were used after noise was added to them. We were able to eliminate the impulse noise, geometric noise, and fluctuation noise in the MRI images by applying our filtering techniques. The filtering technique not only removed the noise, but also increased the contrast of the cancerous volumetric heterogeneous formations in the heart region.

BACKGROUND: In this paper a method is proposed to evaluate the heart’s coronary vessels’ status based on the elimination of large coronary branches from IR-thermal image. This method makes it possible to determine nutrient cardiac blood circulation b

In this paper, the energy characteristics of the charge circuits of a supercapacitor (nonlinear capacitor) and an equivalent linear capacitor from a DC voltage source, which is a lithium-ion battery for such energy storage devices, are analyzed. It is established under what conditions the losses of electricity in the charge circuits of linear and equivalent nonlinear capacitors from the DC voltage source are reduced. The influence of final and initial voltages on similar terminals and capacitance terminals on similar energy losses is analyzed. The regularities of increasing the energy transfer coefficient in the circuits of the aperiodic charge of supercapacitors and equivalent linear capacitors from a DC voltage source (battery) with increasing initial voltages at the capacitor terminals are determined.