For Arhu's experiment, assuming he survived the fight, one of the guys there will be guarding downstairs in the barracks; go talk to him.
The diary doesn't currently lead to any new conversation options.
you can put things in a spoiler by placing tags around the text, as following (with an extra space by each bracket, so they stay in plain text):
[ spoiler ]text to be hidden[ /spoiler ]
becomes, without the spaces
