Aetiology And Management Of Primary Amenorrhoea.

Background: Amenorrhoea is absence of menstruation. It could be primary, if menstruation has not occurred by the age of 16 years in the presence of normal growth and secondary sexual characters or by the age of 14 years in the absence of secondary sexual characters. It is secondary if periods have not occurred for six months.

Resonance frequencies of a spherical aluminum shell subject to static internal pressure.

Measurements of the vibrational response of a spherical aluminum shell subject to changes in the interior pressure clearly demonstrate that resonance frequencies shift higher as the pressure is increased. The frequency shift appears to be smaller for longitudinal modes than for bending wave modes. The magnitude of frequency shift is comparable to analytical predictions made for thin cylindrical shells.