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rift
Rhodophyceae class of the Rhodophyta.
Rhodophyta (red algae) phylum of the kingdom Protoctista. The multicellular algae
range in size from 1 mm to a few dm. Rhodophyta contain the pigments
phycocyanin, phycoerythrin and lutein, but no chlorophyll other than chlorophyll-a. They store starch outside their plastids. Zooids are completely absent
in rhodophytan life cycles. Red seaweeds live attached to rocks or sometimes
on brown seaweeds (Phaeophyta). Several genera produce the raw material for
agar-agar or carrageen. Porphyra is cultured for human food in Japanese
estuaries. Lithothamnion and some other genera encrust rocks and coral
reefs with their calcium carbonate reinforced bodies, or form loose nodules
on the seabed. Such nodules are harvested locally as soil fertilizer. Few fossils can be assigned unequivocally to the Rhodophyta, except the calcareous
species.
Rhynchocoela ~Nemertina.
rhythm periodicity in a biological context, rhythms are physiological or behavioral changes, recurrent on a regular time scale such as days or lunar
months. One cycle of changes is called a period. ~biological clock and lunar cycle.
ribonucleic acid ~RNA .
Richardson number Ri, named after the British physicist L.F. Richardson is a
nondimensional number that gives the turbulent state of a stratified flow. If
Ri is large, turbulence is suppressed by stability. Different types of Richardson
numbers are used. The gradient Richardson number gives the relation
between stabilizing buoyancy and destabilizing shear. The flux Richardson
number gives the relation between energy loss by buoyancy and energy production by shear. They differ by a factor that is the relation between the coefficients for the turbulent diffusion of mass and momentum. If the flow is
characterized by a typical vertical length scale L, velocity U and a reduced
gravity g', the Richardson number can be approximated by the bulk
Richardson number Ri = g'L/U2. In modeling stratified flow this number
should be equal in model and prototype.
richness ~diversity.
rift topographic depression of regional or global extent formed by appreciable
displacement along normal faults with roughly parallel strikes, and associated with earthquake and commonly volcanic activity. Rifts are an expression of tension in the earth's crust and may be precursors of mid-ocean ridges.
e.g., the Gulf of Aden, East-African rift system.
rift
Rhodophyceae class of the Rhodophyta.
Rhodophyta (red algae) phylum of the kingdom Protoctista. The multicellular algae
range in size from 1 mm to a few dm. Rhodophyta contain the pigments
phycocyanin, phycoerythrin and lutein, but no chlorophyll other than chlorophyll-a. They store starch outside their plastids. Zooids are completely absent
in rhodophytan life cycles. Red seaweeds live attached to rocks or sometimes
on brown seaweeds (Phaeophyta). Several genera produce the raw material for
agar-agar or carrageen. Porphyra is cultured for human food in Japanese
estuaries. Lithothamnion and some other genera encrust rocks and coral
reefs with their calcium carbonate reinforced bodies, or form loose nodules
on the seabed. Such nodules are harvested locally as soil fertilizer. Few fossils can be assigned unequivocally to the Rhodophyta, except the calcareous
species.
Rhynchocoela ~Nemertina.
rhythm periodicity in a biological context, rhythms are physiological or behavioral changes, recurrent on a regular time scale such as days or lunar
months. One cycle of changes is called a period. ~biological clock and lunar cycle.
ribonucleic acid ~RNA .
Richardson number Ri, named after the British physicist L.F. Richardson is a
nondimensional number that gives the turbulent state of a stratified flow. If
Ri is large, turbulence is suppressed by stability. Different types of Richardson
numbers are used. The gradient Richardson number gives the relation
between stabilizing buoyancy and destabilizing shear. The flux Richardson
number gives the relation between energy loss by buoyancy and energy production by shear. They differ by a factor that is the relation between the coefficients for the turbulent diffusion of mass and momentum. If the flow is
characterized by a typical vertical length scale L, velocity U and a reduced
gravity g', the Richardson number can be approximated by the bulk
Richardson number Ri = g'L/U2. In modeling stratified flow this number
should be equal in model and prototype.
richness ~diversity.
rift topographic depression of regional or global extent formed by appreciable
displacement along normal faults with roughly parallel strikes, and associated with earthquake and commonly volcanic activity. Rifts are an expression of tension in the earth's crust and may be precursors of mid-ocean ridges.
e.g., the Gulf of Aden, East-African rift system.