After talking to Three Dog, exit the Galaxy News Radio and head to Rivet City through the Farragut West Station.
Once you've reached Rivet City, you will encounter Harkness, one of the Rivet's security guards. You will have to convince him to let you in.
After talking to Harkness, head to the Stairwell.
Once you're inside, head inside the Science Lab.
After entering the Science Lab, talk to Doctor Li about James' location.
After talking to Doctor Li, head to the Jefferson Memorial and search for Dad (James).
Once you've reached the Jefferson Memorial, head inside the Museum and Gift Shop.
The place will be full of Super Mutants, so try to avoid them as much as you can.
After dealing with the Super Mutants, head inside the Jefferson Memorial Rotunda and look for James.
You will find some Journal Entries on one of the machines found inside the Rotunda, take them and listen to the 10th Entry. The 10th Jurnal Entry will indicate where had James headed from the Jefferson Memorial.
After exiting the Jefferson Museum and Gift Shop, head to Smith Casey's Garage and gain access to Vaul 112.
Once you're inside Smith Casey's garage, head to the back room behind the desk and activate the switch located on the wall and head downstairs.
Enter Vault 112.
After entering Vault 112, you will encounter a Robobrain that will give you a Vault 112 Jumpsuit.
Enter the Tranquility Lounger. This will bring the Scientific Pursuits quest to an end.