Perhaps you should try some spelling variations:
ppm decrease » _ decrease (Expand Search), nn decrease (Expand Search), pa decreased (Expand Search)
na decrease » nn decrease (Expand Search), pa decreased (Expand Search), la decreased (Expand Search)
n decrease » nn decrease (Expand Search), _ decrease (Expand Search), _ decreased (Expand Search)
a decrease » _ decrease (Expand Search), _ decreased (Expand Search), _ decreases (Expand Search)
50 ppm » 5 ppm (Expand Search)
50 na » 50 ns (Expand Search), 50 ng (Expand Search), 50 n (Expand Search)

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( 50 ppm decrease ) OR ((( 50 na decrease ) OR ( 50 ((n decrease) OR (a decrease)) ))))~".
• Adding a wildcard symbol may retrieve word variants: (( 50 ppm decrease ) OR ((( 50 na decrease ) OR ( 50 ((n decrease) OR (a decrease)) ))))*.