That's the Microgravity Rack Barrier protecting FIR (Fluids Integrated Rack) from disturbances while it's utilizing the Passive Rack Isolation System (PaRIS) during science ops.
Both CIR and FIR use PaRIS
which provides a non-rigid mechanical connection between the CIR [or
FIR] and ISS structure using eight spring-damper isolators and
Even though the ISS is a microgravity environment, there are still vibrations in the structure itself due to crew exercise and other payload or system operations performed nearby. PaRIS minimizes any vibration transference to the rack utilizing it.
FIR was originally designed with an Active Vibration Isolation System (ARIS), but was later converted to PaRIS as well.
Fun fact, astronaut Jack Fischer (2Fish) decided to print out an image of MC Hammer captioned "Stop: Science Time" whenever sensitive microgravity ops were being performed in CIR. Unfortunately no studies were performed on its effectiveness vs that of the Microgravity Rack Barrier.