What made you want to look up negative valence? Please tell us where you read or heard it (including the quote, if possible).
WBS is nothing but Work Breakdown Structure. It is mainly used in Project System (PS) module. Tcode: CJ20N. For any project defined we must have atleast one WBS. Within this WBS we can have networks. Networks are nothing but the series of activities. Material are used to perform the activities.
LTs are used to guide the physician along with the history and physical examination, in the diagnosis and management of a number of liver diseases. A problem in relying on these biochemical tests is that they are indirect measurements from the blood, of what is happening in the liver.