Usable? No.
I'm not sure if theres some piece of information thats trying to be portrayed here (other than quantity of dissertations per major) but as a browser, it's pretty useless. It employs mystery meat nav heavily, mostly because you have to hover over a dissertation to view any info about it. Imagine finding a paper you liked, and then going back 15 minutes later to try and find it.
If there is some data thats trying to be shown its not clear to me what it is. Some of the inner circles are in columns which seem to indicate correlation, but I cant figure out if thats accurate or not. For instance, if I click on philosphy, I see a dot in the direction of Food Research, and when I hover over that dot I see a thesis about "Practical reasoning and the varieties of agency".
What is trying to be portrayed here?