The long-standing model of pigment cell origins is implicitly based upon a progressive fate restriction model of neural crest development and postulates the existence of a partially restricted progenitor common to all pigment cell types (i.e., a chromatoblast) [38] .
Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride.
Sodium. Chemical element, symbol: Na, atomic number: 11 and atomic weight 22,9898. Itâs a soft metal, reactive and with a low melting point, with a relative density of 0,97 at 20ÂºC (68ÂºF). From the commercial point of view, sodium is the most important of all the alkaline metals.odium. Chemical element, symbol: Na, atomic number: 11 and atomic weight 22,9898. Itâs a soft metal, reactive and with a low melting point, with a relative density of 0,97 at 20ÂºC (68ÂºF). From the commercial point of view, sodium is the most important of all the alkaline metals.