GLOSSARY - Archaeological Chemistry - page 501

nuclear reaction A reaction that involves changes in the nuclei of atoms , such as decay

and fission .
nuclear reactor A device in which nuclear reactions can be initiated, maintained, and

controlled.
nuclear transformation A radioactive decay process whereby the isotope of an element
is transformed into an isotope of another element.
nuclear transmutation See nuclear transformation .
nucleic acid A class of complex biogenic substances comprising two basic types:
ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), both consisting of very
large molecules , among the largest known.
nucleon A nuclear particle , either a proton or a neutron .
nucleoside In nucleic acids , a base bound to a sugar ; see nucleotide .
nucleotide The basic unit from which nucleic acids are built up; it consists of a
nitrogenous base , a phosphate group , and a sugar molecule ( deoxyribose in DNA and
ribose in RNA ).
nucleus (1) The central part of an atom that consists mainly of neutrons and protons
and makes up nearly all of the atom's mass; (2) the site of a living cell that con-
tains chromatin , where RNA is synthesized and DNA is replicated .
nuclide An isotope ; an atom with a particular combination of protons and neutrons
in its nucleus.
nugget A lump of native metal , such as gold, silver, or copper, uncombined with
other elements .
numerical date See absolute date .
nut gall See gall .
nutrient A chemical element , compound , or food required by a living organism to
live, grow, or reproduce.
obsidian A black or dark volcanic glass that is formed when lava cools so rapidly
that crystals do not have time to grow.
obsidian hydration dating See dating, obsidian hydration .
ocher A yellow, red, or brown earthy mineral composed of hydrated ferric oxide.
OCR dating Abbreviation for oxidizable carbon ratio dating .
OES Acronym for optical emission spectrometry.
oil A liquid lipid .
oil, drying An oil , such as linseed oil , which, when exposed to air, is oxidized and
hardens (“dries”), forming a tough solid.
oil, nondrying An oil that neither is oxidized nor hardens when exposed to air.
oil tanning See tanning, oil .
onyx A banded type of agate that incorporates straight, parallel layers of different
colors.
onyx marble See oriental alabaster .