The Kelvin-Voigt visco-elastic model involving a fractional-order time derivative for modelling torsional oscillations of a complex discrete biodynamical system.

Under external loads trees exhibit complex oscillatory behaviour: their canopies twist and band. The great complexity of this oscillatory behaviour consists to an important degree of torsional oscillations. Using a system of ordinary differential fractional-order equations, free and forced main eigen-modes of fractional-type torsional oscillations of a hybrid discrete biodynamical system of complex structures were done.

The effect of friction and impact angle on the spermatozoa-oocyte local contact dynamics.

Although a large proportion of biomolecules involved in spermatozoa-oocyte interaction has been discovered so far, many details of fertilization mechanism remain unknown. Both biochemical and biomechanical components exist in the fertilization process. Mammalian sperm evolved a ZP (zona pelucida) thrust reduction penetration strategy probably in response to the ZP resilient elasticity.

Influence of sperm impact angle on successful fertilization through mZP oscillatory spherical net model.

According to the available literature, penetrating sperm creates an oblique path trough Zona pellucida (ZP)--the most outer surface of oocytes. Considering fertilization process as an oscillatory phenomenon, the influence of sperm impact angle relative to the oscillatory behavior of mouse ZP is described by using the discrete continuum mechanical model in the form of a spherical net model. A parametric frequency analysis of oscillatory behavior of knot material particles in the mouse ZP (mZP) spherical net model is conducted by using generalized Lussajous curves.

Attitudes and motives of potential sperm donors in Serbia.

Background/aim: For curing infertility, sperm donors and their donations are important source of benefits for the society. Attitudes of sperm donors towards different recipient categories and relation with offspring become more important. The aim of our study was to explore sperm donation related attitudes and motives among potential sperm donors in Serbia.