Libor Severa

Evaluation of shape variability of stallion sperm heads by means of image analysis and Fourier descriptors

This study quantified and evaluated the variability of sperm head shape for 10 different stallions. Sperm head shape characteristics including sperm head length to width ratio, position of the center of gravity, curvature, and degree of roundness were assessed and analysed from images using elliptic Fourier descriptors and inverse Fourier transformation. The first four principal components accounted for 88.46-92.33% of the total variance and provided a good summary of the overall data. In the case of the ejaculate with defective sperm heads the components accounted for 97.35-98.21% of variation. The study was able to quantitatively confirm that head length to width ratio, which contributed 48.63-53.48% and 71.30-73.34% to the total variance for normal and defective sperm, respectively, was the predominant determining parameter of sperm head shape. There were no statistical significant relationships between Fourier descriptors and values of sperm concentration and/or motility.

Determination of Hen’s Eggshell Elastic Properties under Quasistatic Compression

The elastic properties belong to key engineering properties of eggshell material. Their knowledge enables e.g. the evaluation of the eggshell strength which is the important parameter of the egg quality (Lin J. et al 1993, Carnarius et al., 1996, Boushy and Ratering, 1993, Rezac et al, 2000, Nirasawa et al. 1998, Nirasawa Picman and Pripil 1997). There are different experimental technique of the eggshell strength measurement see e.g. Bain (1997) for a review. One of them is the quasi — static compression test that corresponds to the loading of eggs during their packing. During this test, eggs are compressed between two parallel plates by a steadily increasing load until failure results. This procedure enables to determine the force and the shortening of the egg at the moment of failure. This force is affected by many factors as e.g. by the eggshell geometry (shape and thickness), by the velocity of loading and by many other factors which more or less cover the influence of the intrinsic material properties. The exact evaluation should lead to the values of stress and strain at the failure. These parameters may be easily obtained from test mentioned above if we use flat testing specimens. The eggs exhibit a more complicated shape but they may be considered as a shell of revolution. The evaluation of the eggshell strength thus must involve the following steps: experiment described above selection of the eggshell material model evaluation of the stress and strain in the eggshell at the moment of the eggshell failure