hey... I also got the skype interview invite. I think they will ask general questions based on your research experience/research interest, so you can prepare by going through your CV and SOP (or any document which contains concept of the work you've done). Since it is with the admission panel, you should look up the research of faculty you mentioned in your SOP so that you can communicate their overarching goals when requested upon. Hopefully it will go well... All the best! PS i applied to the chem bio training group...