F
FAB mass spectroscopy See fastatom bombardment mass spectroscopy.
face-centred cubic (f.c.c.) See
cubic crystal.
fac-isomer See isomerism.
FAD (Ûavin adenine dinucleotide) A
*coenzyme important in various biochemical reactions. It comprises a
phosphorylated vitamin B 2 (riboÛavin) molecule linked to the nucleotide adenine monophosphate
(AMP). FAD is usually tightly bound
to the enzyme forming a Ûavoprotein. It functions as a hydrogen acceptor in dehydrogenation reactions,
being reduced to FADH 2 . This in turn
is oxidized to FAD by the *electron
transport chain, thereby generating
ATP (two molecules of ATP per molecule of FADH 2 ).
Fahrenheit, Gabriel Daniel
(1686–1736) German physicist, who
became an instrument maker in Amsterdam. In 1714 he developed the
mercury-in-glass thermometer, and
devised a temperature scale to go
with it (see fahrenheit scale).
Fahrenheit scale A temperature
scale in which (by modern deÜnition)
the temperature of boiling water is
taken as 212 degrees and the temperature of melting ice as 32 degrees. It
was invented in 1714 by G. D.
*Fahrenheit, who set the zero at the
lowest temperature he knew how to
obtain in the laboratory (by mixing
ice and common salt) and took his
own body temperature as 96°F. The
scale is no longer in scientiÜc use. To
convert to the *Celsius scale the formula is C =5(F – 32)/9.
Fajan’s method See adsorption
indicator.
Fajans’ rules Rules indicating the
extent to which an ionic bond has covalent character caused by polarization of the ions. Covalent character is
more likely if:
(1) the charge of the ions is high;
(2) the positive ion is small or the
negative ion is large;
(3) the positive ion has an outer electron conÜguration that is not a noblegas conÜguration.
The rules were introduced by the
Polish-born US chemist Kasimir Fajans (1887–1975).
fall-out 1. (radioactive fall-out)
Radioactive particles deposited from
the atmosphere either from a nuclear explosion or from a nuclear accident. Local fall-out, within 250 km
of an explosion, falls within a few
hours of the explosion. Tropospheric
fall-out consists of Üne particles deposited all round the earth in the approximate latitude of the explosion
within about one week. Stratospheric
fall-out may fall anywhere on earth
over a period of years. The most dangerous radioactive isotopes in fall-out
are the Üssion fragments iodine–131
and strontium–90. Both can be taken
up by grazing animals and passed on
to human populations in milk, milk
products, and meat. Iodine–131 accumulates in the thyroid gland and
strontium–90 accumulates in bones.
2. (chemical fall-out) Hazardous
chemicals discharged into and subsequently released from the atmoswww.AzShimi.ir www.AzShimi.com
FAB mass spectroscopy See fastatom bombardment mass spectroscopy.
face-centred cubic (f.c.c.) See
cubic crystal.
fac-isomer See isomerism.
FAD (Ûavin adenine dinucleotide) A
*coenzyme important in various biochemical reactions. It comprises a
phosphorylated vitamin B 2 (riboÛavin) molecule linked to the nucleotide adenine monophosphate
(AMP). FAD is usually tightly bound
to the enzyme forming a Ûavoprotein. It functions as a hydrogen acceptor in dehydrogenation reactions,
being reduced to FADH 2 . This in turn
is oxidized to FAD by the *electron
transport chain, thereby generating
ATP (two molecules of ATP per molecule of FADH 2 ).
Fahrenheit, Gabriel Daniel
(1686–1736) German physicist, who
became an instrument maker in Amsterdam. In 1714 he developed the
mercury-in-glass thermometer, and
devised a temperature scale to go
with it (see fahrenheit scale).
Fahrenheit scale A temperature
scale in which (by modern deÜnition)
the temperature of boiling water is
taken as 212 degrees and the temperature of melting ice as 32 degrees. It
was invented in 1714 by G. D.
*Fahrenheit, who set the zero at the
lowest temperature he knew how to
obtain in the laboratory (by mixing
ice and common salt) and took his
own body temperature as 96°F. The
scale is no longer in scientiÜc use. To
convert to the *Celsius scale the formula is C =5(F – 32)/9.
Fajan’s method See adsorption
indicator.
Fajans’ rules Rules indicating the
extent to which an ionic bond has covalent character caused by polarization of the ions. Covalent character is
more likely if:
(1) the charge of the ions is high;
(2) the positive ion is small or the
negative ion is large;
(3) the positive ion has an outer electron conÜguration that is not a noblegas conÜguration.
The rules were introduced by the
Polish-born US chemist Kasimir Fajans (1887–1975).
fall-out 1. (radioactive fall-out)
Radioactive particles deposited from
the atmosphere either from a nuclear explosion or from a nuclear accident. Local fall-out, within 250 km
of an explosion, falls within a few
hours of the explosion. Tropospheric
fall-out consists of Üne particles deposited all round the earth in the approximate latitude of the explosion
within about one week. Stratospheric
fall-out may fall anywhere on earth
over a period of years. The most dangerous radioactive isotopes in fall-out
are the Üssion fragments iodine–131
and strontium–90. Both can be taken
up by grazing animals and passed on
to human populations in milk, milk
products, and meat. Iodine–131 accumulates in the thyroid gland and
strontium–90 accumulates in bones.
2. (chemical fall-out) Hazardous
chemicals discharged into and subsequently released from the atmoswww.AzShimi.ir www.AzShimi.com