Doppler ultrasound is a type of ultrasound that depends on the Doppler Effect, a change in the wave's frequency, which can occur from the motion of a reflector, such a red blood cell. We experience the Doppler Effect when, for example, an ambulance approaches us, passes and then drives away.
Definition of PLACODERM. : any of a class (Placodermi) of extinct chiefly Devonian fishes with an armor of bony plates and primitive jaw structures.ADVERTISEMENT. New Latin Placodermi, ultimately from GK plak-, plax + derma skin â more at derm-. any of a class (Placodermi) of extinct chiefly Devonian fishes with an armor of bony plates and primitive jaw structures. ADVERTISEMENT.
The Placozoa are an animal phylum, a primitive form of invertebrate. They are the simplest in structure of all metazoa. The Placozoa is usually considered to have only one species, Trichoplax adhaerens, but there is enough genetic diversity that it is possible that there are multiple, morphologically similar species. Although they were first discovered in 1883, a common name does not exist for the taxon.