Electrum is a metal alloy mainly consisting of gold, silver and traces of some other metals. This naturally occurring alloy has a long history of being used for making coins, vessels and also for coatings. It was referred to as âgoldâ or âwhite goldâ by ancient Greeks.
In Interstitial defect, atom occupies the interstitial space of the lattice structure of solid crystal. In Substitutional defect, the foreign atom occupies only the lattice site of a crystalline solid. Interstitial defect may occur by the atoms of either same solid (called self-interstitial) or foreign material. Substitutional defect is always caused by foreign atoms.
atrial septal defect see atrial septal defect. filling defect an interruption in the contour of the inner surface of stomach or intestine revealed by radiography, indicating excess tissue or substance on or in the wall of the organ. neural tube defect see neural tube defect. septal defect a defect in the cardiac septum resulting in an abnormal communication between opposite chambers of the heart. Common types are aortic septal defect, atrial septal defect, and ventricular septal defect. See also congenital heart defect.