Caro’s acid See peroxosulphuric(vi) acid.
carotene A member of a class of
*carotenoid pigments. Examples are
β-carotene and lycopene, which colour carrot roots and ripe tomato
fruits respectively. α- and β-carotene
yield vitamin A when they are broken down during animal digestion.
carotenoid Any of a group of yellow, orange, red, or brown plant pigments chemically related to terpenes.
Carotenoids are responsible for the
characteristic colour of many plant
organs, such as ripe tomatoes, carrots, and autumn leaves. They also
absorb light energy and pass this on
to chlorophyll molecules in the lightdependent reactions of photosynthesis.
Carothers, Wallace Hume
(1896–1937) US industrial chemist,
who joined the Du Pont company
where he worked on polymers. In
1931 he produced *neoprene, a synthetic rubber. His greatest success
came in 1935 with the discovery of
the polyamide that came to be
known as *nylon. Carothers, who
suffered from depression, committed
suicide.
carrageenan A naturally occurring
polysaccharide isolated from red
algae. The polymer is composed of dgalactose units, many of which are
sulphated. K-carrageenan is a gelling
agent with uses similar to those of
*agar.
carrier gas The gas that carries the
sample in *gas chromatography.
carrier molecule 1. A molecule
that plays a role in transporting electrons through the *electron transport chain. Carrier molecules are
usually proteins bound to a nonprotein group; they can undergo oxidation and reduction relatively easily,
thus allowing electrons to Ûow
through the system. 2. A lipidsoluble molecule that can bind to
lipid-insoluble molecules and transport them across membranes. Carrier
molecules have speciÜc sites that interact with the molecules they transport. Several different molecules may
compete for transport by the same
carrier.
Carr–Purcell–Meiboom–Gill sequence See cpmg sequence.
CARS (coherent anti-Stokes Raman
spectroscopy) A form of Raman spectroscopy (see raman effect) enabling
the intensity of Raman transitions to
be increased. In this technique two
laser beams with different frequencies pass through a sample producing
electromagnetic radiation of several
frequencies. It is possible to adjust
the frequency of the lasers so that
one of the frequencies corresponds
to that of a Stokes line from the sample and the coherent emission has
the frequency of the anti-Stokes line
with a high intensity. CARS enables
Raman spectra to be obtained even
in the presence of other radiation.
One application of CARS is to obtain
Raman spectra from bodies in Ûames.
Using this technique temperatures in
different parts of the Ûame can be estimated from the intensity of the
transitions.
cascade liqueÜer An apparatus
for liquefying a gas of low *critical
temperature. Another gas, already
below its critical temperature, is
liquiÜed and evaporated at a reduced
pressure in order to cool the Ürst gas
to below its critical temperature. In
practice a series of steps is often
used, each step enabling the critical
temperature of the next gas to be
reached.
cascade process Any process that
takes place in a number of steps, usu105
cascade process
c
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carotene A member of a class of
*carotenoid pigments. Examples are
β-carotene and lycopene, which colour carrot roots and ripe tomato
fruits respectively. α- and β-carotene
yield vitamin A when they are broken down during animal digestion.
carotenoid Any of a group of yellow, orange, red, or brown plant pigments chemically related to terpenes.
Carotenoids are responsible for the
characteristic colour of many plant
organs, such as ripe tomatoes, carrots, and autumn leaves. They also
absorb light energy and pass this on
to chlorophyll molecules in the lightdependent reactions of photosynthesis.
Carothers, Wallace Hume
(1896–1937) US industrial chemist,
who joined the Du Pont company
where he worked on polymers. In
1931 he produced *neoprene, a synthetic rubber. His greatest success
came in 1935 with the discovery of
the polyamide that came to be
known as *nylon. Carothers, who
suffered from depression, committed
suicide.
carrageenan A naturally occurring
polysaccharide isolated from red
algae. The polymer is composed of dgalactose units, many of which are
sulphated. K-carrageenan is a gelling
agent with uses similar to those of
*agar.
carrier gas The gas that carries the
sample in *gas chromatography.
carrier molecule 1. A molecule
that plays a role in transporting electrons through the *electron transport chain. Carrier molecules are
usually proteins bound to a nonprotein group; they can undergo oxidation and reduction relatively easily,
thus allowing electrons to Ûow
through the system. 2. A lipidsoluble molecule that can bind to
lipid-insoluble molecules and transport them across membranes. Carrier
molecules have speciÜc sites that interact with the molecules they transport. Several different molecules may
compete for transport by the same
carrier.
Carr–Purcell–Meiboom–Gill sequence See cpmg sequence.
CARS (coherent anti-Stokes Raman
spectroscopy) A form of Raman spectroscopy (see raman effect) enabling
the intensity of Raman transitions to
be increased. In this technique two
laser beams with different frequencies pass through a sample producing
electromagnetic radiation of several
frequencies. It is possible to adjust
the frequency of the lasers so that
one of the frequencies corresponds
to that of a Stokes line from the sample and the coherent emission has
the frequency of the anti-Stokes line
with a high intensity. CARS enables
Raman spectra to be obtained even
in the presence of other radiation.
One application of CARS is to obtain
Raman spectra from bodies in Ûames.
Using this technique temperatures in
different parts of the Ûame can be estimated from the intensity of the
transitions.
cascade liqueÜer An apparatus
for liquefying a gas of low *critical
temperature. Another gas, already
below its critical temperature, is
liquiÜed and evaporated at a reduced
pressure in order to cool the Ürst gas
to below its critical temperature. In
practice a series of steps is often
used, each step enabling the critical
temperature of the next gas to be
reached.
cascade process Any process that
takes place in a number of steps, usu105
cascade process
c
www.AzShimi.ir www.AzShimi.com