so 'a' would name a local variable, but $a would be a locking full-empty variable. this structure was badly preserved but did not appear to have a stairway. it then goes on to describe black holes, which remains the topic of focus in the last part of the book. in her career as 14-time national champ, she broke 6 world records. they have presented custom belts every year since. this type of pollution is very challenging to manage given that the original source(s) may be difficult to identify. the overall form of the tree can vary from upright to weeping. 