None we know of
Arkady Stepanov, Russes(Aркадии Стеланов), invented the Stepanov Transformer and all of a sudden, it disappeared. Arkady makes an appearance in one of, of all people, Roman Karnaukhov's demonstration Videos! See Below. I have assumed he is working for Steho Energy. Which is where Roman went also.
The face of the person below, you can see in the above videos also, but find out more here also, I believe this may be Arkady's brother, but I am not sure.
Loosley translated, the heading is: 100 watts of free energy from Germany
Germany is where Arthur Tränkle (Steho Energy) and his company is based, along with Roman Karnaukhov (Akula)
At nine seconds into the below video you can also see Arkady Stepanov recruting Roman Karnaukhov (Akula)