Complex sleep apnea is the term used to describe a form of sleep disordered breathing in which repeated central apneas (>5/hour) persist or emerge when obstructive events are extinguished with positive airway pressure (PAP) and for which there is not a clear cause for the central apneas such as narcotics or systolic heart failure.
Giant covalent structures. Such as silicon dioxide, have extremely high melting points and low solubility in all solvents. They are non-volatile and conductivity depends on the availability of electrons in the valence shell (eg graphite). If all electrons are used in bonding they are insulators.ow melting points:- The bonds between molecules are very weak, especially when the molecules are small. It only requires a small quantity of heat energy to create enough molecular vibration to break the molecules attraction for one another and the solid melts.
Because the electrons in ionic solids are localized (in the ions) these solids tend to be stiff and brittle like covalent solids. As solids they do not conduct electricity (again because of the localize electrons).However, they do conduct electricity as liquids (or when dissolved in water) since then the ions can move.istortion away from this geometry can only occur through a breaking of covalent sigma bonds. As a result, the melting point of covalent solids is extremely high. They also tend to be extremely hard substances that will break into pieces rather than smoothly change shape. We say that they are stiff and brittle.