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diffusion
Deutschland Expedition (1911-1912) also named the Second German Antarctic
Expedition, which went to the Weddell Sea led by W. Filchner. They attempted in vain to establish a base on the ice shelf. Valuable series of temperature
and salinity observations off the Atlantic coast of South America were made
by W. Brennecke on its way south.
Devonian ~geological time scale.
diagenesis post-depositional changes of sediments as a result of interacting
physical, chemical and biological processes.
diapause eggs resting or dormant eggs. ~resting stages.
diapir a flow structure resulting from the upward intrusion of a less dense rock
mass through overlying denser rock. Salt and shale are the most common
rocks involved in diapirs. Intrusive rocks can also form diapir-like features
but the term is usually restricted to plastic flow.
diarrhetic shellfish poisoning (DSP), a transitory gastro-intestinal disorder following consumption of shellfish contaminated by lipid-soluble toxins. The toxins
are concentrated mostly in the hepatopancreas of mollusks and their origin
has been traced to planktonic Dinoflagellata ingested by the filter-feeding
shellfish prior to the time of harvest. Members of the genus Dinophysis have
been identified as producers of these toxins. This kind of DSP has been
reported in several coastal areas worldwide. ~paralytic shellfish poisoning.
diatoms ~Bacillariophyta.
Dictyochophyceae ~silicoflagellates.
diel referring to events that occur with a 24-hour periodicity.
diffluence ~divergence.
diffusion the transport across a unit surface can be quantified by putting it proportional to the concentration gradient. The proportionality factor is called
the diffusion coefficient. For molecular transport processes the diffusion coefficient can be taken independently of the scale length of the transport, for turbulent transport the coefficient of eddy diffusion depends on the scale length.
This is the normal condition in ocean waters. In sediments where the interstitial diffusion at the other hand is molecular, it should be corrected for the hindrance by sediment particles (tortuosity). For substances sorbed to sediment
particles, the apparent diffusion coefficient can be calculated by dividing the
molecular diffusion coefficient (of the order of 510- 6 cm 2 S- I) by the distribu-
diffusion
Deutschland Expedition (1911-1912) also named the Second German Antarctic
Expedition, which went to the Weddell Sea led by W. Filchner. They attempted in vain to establish a base on the ice shelf. Valuable series of temperature
and salinity observations off the Atlantic coast of South America were made
by W. Brennecke on its way south.
Devonian ~geological time scale.
diagenesis post-depositional changes of sediments as a result of interacting
physical, chemical and biological processes.
diapause eggs resting or dormant eggs. ~resting stages.
diapir a flow structure resulting from the upward intrusion of a less dense rock
mass through overlying denser rock. Salt and shale are the most common
rocks involved in diapirs. Intrusive rocks can also form diapir-like features
but the term is usually restricted to plastic flow.
diarrhetic shellfish poisoning (DSP), a transitory gastro-intestinal disorder following consumption of shellfish contaminated by lipid-soluble toxins. The toxins
are concentrated mostly in the hepatopancreas of mollusks and their origin
has been traced to planktonic Dinoflagellata ingested by the filter-feeding
shellfish prior to the time of harvest. Members of the genus Dinophysis have
been identified as producers of these toxins. This kind of DSP has been
reported in several coastal areas worldwide. ~paralytic shellfish poisoning.
diatoms ~Bacillariophyta.
Dictyochophyceae ~silicoflagellates.
diel referring to events that occur with a 24-hour periodicity.
diffluence ~divergence.
diffusion the transport across a unit surface can be quantified by putting it proportional to the concentration gradient. The proportionality factor is called
the diffusion coefficient. For molecular transport processes the diffusion coefficient can be taken independently of the scale length of the transport, for turbulent transport the coefficient of eddy diffusion depends on the scale length.
This is the normal condition in ocean waters. In sediments where the interstitial diffusion at the other hand is molecular, it should be corrected for the hindrance by sediment particles (tortuosity). For substances sorbed to sediment
particles, the apparent diffusion coefficient can be calculated by dividing the
molecular diffusion coefficient (of the order of 510- 6 cm 2 S- I) by the distribu-