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.
Typography: Kerning, Leading and Tracking. Kerning and Leading are ways to manipulate the spacing between characters. Spatial manipulation in type can be a very important tool. Some fonts need to have individual characters adjusted to help create better readability and a more aesthetically pleasing layout.