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.
GIANT COVALENT STRUCTURES This page decribes the structures of giant covalent substances like diamond, graphite and silicon dioxide (silicon(IV) oxide), and relates those structures to the physical properties of the substances.n diamond, each carbon shares electrons with four other carbon atoms-forming four single bonds. In the diagram some carbon atoms only seem to be forming two bonds (or even one bond), but that's not really the case. We are only showing a small bit of the whole structure.