carboxyl radical (COOH)
râdikâl-e karboksil (#)
Fr.: radical carboxyl
Chem.: The -COOH group, regarded as the essential and characteristic constituent of organic acids.
Fr.: radical cyano
A diatomic chemical radical composed of carbon and nitrogen atoms. The triple bonds of C to H leave one electron available, which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.
Fr.: radical libre
A chemical radical that can exist independently from atoms or group of atoms.
rišé (#), rišegi (#), rišâl
1) Math.: The indicated root of a quantity, as denoted by an expression written under
the → radical sign.
M.E., from L.L. radicalis "of or having roots," from → radix "root."
Fr.: axe radical
Of two circles, the straight line containing all points P such that the lengths of the tangents from P to the two circles are equal.
nešâne-ye rišâl, ~ rišegi
Fr.: signe radical
The symbol √ placed before a number or quantity to indicate the extraction of the square root. The value of a higher (the n-th) root is indicated by a raised positive digit (n) in front of the symbol, as in 3√ (cube root). The first known occurrence of this symbol was in the book Die Cross, published in 1525, by the German mathematician Christoff Rudolff.