Transcranial Doppler (TCD), first described in 1982 [1], is a noninvasive ultrasound (US) study that involves the use of a low-frequency (â¤2 MHz) transducer probe to insonate the basal cerebral arteries through relatively thin bone windows.
Details. as.character and is.character are generic: you can write methods to handle specific classes of objects, see InternalMethods. Further, for as.character the default method calls as.vector, so dispatch is first on methods for as.character and then for methods for as.vector.
Important Characterization Terms. 1  A round character has many traits, some of which may even be contradictory--a very complex individual. In A Pair of Two Tickets, Jing-Mei is a round, dynamic character. 2  Flat characters have only a single or very few traits.