A protein found in most cells, especially in muscle.
One of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form.

Any of a series of 15 radioactive metallic chemical elements with atomic numbers 89 (actinium) to 103 (lawrencium). Elements 89 to 95 occur in nature; the rest of the series are synthesized elements only. Actinides are grouped together because of their chemical similarities (for example, they are all bivalent), the properties differing only slightly with atomic number. The series is set out in a band in the periodic table of the elements, as are the lanthanides.

ETYM Greek aktis, aktin ray.
Rare radio-active element.
White, radioactive, metallic element, the first of the actinide series, symbol Ac, atomic number 89, atomic weight 227; it is a weak emitter of high-energy alpha particles.
Actinium occurs with uranium and radium in pitchblende and other ores, and can be synthesized by bombarding radium with neutrons. The longest-lived isotope, Ac-227, has a half-life of 21.8 years (all the other isotopes have very short half-lives). Actinium was discovered in 1899 by the French chemist André Debierne.
A radioactive element of the actinide series; found in uranium ores; SYN. Ac, atomic number 89.

Actinium
A radioactive element of the actinide series; found in uranium ores

ETYM Greek aktis, aktin ray.
Rare radio-active element.
White, radioactive, metallic element, the first of the actinide series, symbol Ac, atomic number 89, atomic weight 227; it is a weak emitter of high-energy alpha particles.
Actinium occurs with uranium and radium in pitchblende and other ores, and can be synthesized by bombarding radium with neutrons. The longest-lived isotope, Ac-227, has a half-life of 21.8 years (all the other isotopes have very short half-lives). Actinium was discovered in 1899 by the French chemist André Debierne.
A radioactive element of the actinide series; found in uranium ores; SYN. Ac, atomic number 89.

ETYM Greek aktis, aktin ray.
The property of radiation that enables it to produce photochemical effects.
Action of solar radiation causing chemical change. Property of solar radiation of causing chemical change.

ETYM Greek aktis, aktin ray + -lite.
A green mineral of the amphibole group; calcium magnesium iron silicate.

ETYM Greek aktis, aktin ray + -meter.
An instrument for measuring the intensity of radiation (usually by the photochemical effect).
Instrument for measuring incident radiation.
Instrument measuring heating power of the sun's rays; Photography, instrument for calculating exposure times.

Measuring the intensity of radiation (especially of the sun's rays).