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Numerical analysis of deformation and flow in the proximal area of the urethra

Rudyk R., Malinowski M., Mackiewicz A., Bedzinski R., Noszczyk-Nowak A., Skonieczna J., Madej J. P.

International Journal of Applied Mechanics and Engineering

2020

Vol. 25, no. 2

130--141

Pathological conditions of a male urethra, including fibrosis, have a mechanical background along the entire length of the urethra. They may be caused by excessive deformation of the urethra locally or globally. The condition of prolonged overload causes abnormal tissue remodelling and, consequently, the formation of a thick layer of scar tissue differentiated from the connective tissue of the urethra. This tissue, which has higher mechanical properties, is not highly deformable and therefore, causes a decrease in the diameter of the urethra, which results in conditions that disturb the natural flow of urine. In this paper, it was decided to determine the deformation conditions in the proximal part of the urethra. The study was conducted in three main stages. Transverse sections of the animal urethral tissues were prepared in order to examine mechanical properties and perform histological examinations. On the basis of these examinations, material models which fitted best for the experimental results were sought. Material constants of the Mooney-Rivlin material model with the best fit ratio were determined for further research. On the basis of histological photographs, a geometrical and numerical model of the urethra was developed. The urethra was tested in a flat state of deformation. The strain and stress fields of the Caucha tensor were examined. The methodology of testing the dynamics of the urine flow in the highly deformable urethra was proposed. This is important for the analysis of the influence of at excessive pressure on pathological tissue remodelling leading to fibrosis.

Element content of Scots pine (Pinus sylvestris L.) stands of different densities

Skonieczna J., Małek S., Polowy K., Węgiel A.

Drewno : prace naukowe, doniesienia, komunikaty

2014

vol. 57, nr 192

77--87

Modern forestry management should be based on the principle of sustainability. In order to preserve habitat productivity, the amount of nutrients removed from the environment along with forestry products must be taken into consideration. This study shows the exact concentrations of chemical elements in different tree parts of Scots pine, growing on poor soils in north-western Poland. The observed values were compared to the values found in literature. In addition, the relationship between the concentrations of elements and stem diameter or stand density was researched. The highest concentration of chemical elements was observed in the needles (C, N, P, K, Mg, S, Mn, Na, Fe) and the lowest (C, N, P, S, Cu, Na, Ni, Pb, Zn, Fe) in the stem wood. Most of the macronutrients (P, K, Ca, Mg and S) reached optimal values, with the exception of N showing a deficiency, especially in the needles. The relationship between the content of elements and DBH or stand density was rather weak, and in both cases, negative.