Sentence:  The <WSD>deep</WSD> concave gradient employed ( fig. 2 ) was obtained with a nine chambered gradient elution device ( `` Varigrad '' , reference ( 8 ) ) and has been described elsewhere . 
Meaning of the word marked with <WSD> tags:  having great spatial extension or penetration downward or inward from an outer surface or backward or laterally or outward from a center; sometimes used in combination