Refining it involves removing the outer layers, including the husk,bran and germ, leaving the inner white kernel.

VOA: standard.2010.06.25

Core electrons are all those electrons held in really tight with the nucleus in the inner shells, whereas the valence electrons are only those electrons that are in the outer-most shell, or at your highest value of n of the principal quantum number.

芯电子是那些,在内壳层被原子核束缚得非常紧的电子，而价电子只包括,最外层的电子，或者说主量子数，n，的值最大的那些电子。

麻省理工公开课 - 化学原理课程节选

When one imagines that a talent that great and a person with that much inner and outer beauty could have had obstacles simply because of the color of her skin, it makes me weep."

VOA: standard.2010.05.15